Polymers Lasers En

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Polymers & Lasers

Laser Application Center


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PerformancePolymersLaser Application Center


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Contents

Introduction.

High Performance Polymers from Evonik


Laser Technolgy

What is laser radiation?

Types of Laser

Solid-State Lasers

Semiconductor Lasers

Gaslaser

Other Types of Laser

Polymers and Lasers

Requirements

Factors Inuencing Laser-Welding of Plastics

Optical Properties of Plastics

Transmission Spectra

Laser-Marking

Factors Impacting Laser-Marking

Laser-Marking Non-Transparent Plastics.

Marking Lasers

Lettering and Contrast on Non-Transparent Plastics

Laser-Marking of Transparent Plastics

Laser-Marking by NIR Absorbers

2D Laser-Marking of Transparent Plastics

3D Sub-Surface Laser-Engraving of Transparent Plastics

Basics of 3D Sub-Surface Laser-Engraving

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3D Sub-Surface Laser-Engraving of Transparent Plastics

3D Laser for Sub-Surface Engraving

Advantages of Laser-Sensitive, Transparent,

Colorless Plastics.

Advantages of Laser-Marking .

Laser-Welding of Plastics.

Degrees of Difculty in Laser-Welding..

The Laser-Welding Process.

Weld Seam Quality.

Factors affecting weld seam quality in thermoplastics..

Laser-Welding Processes..

Contour Welding...

Simultaneous Welding..

Quasi Simultaneous Welding...

Mask Welding....

Application Areas..

Advantages.

Laser-Structuring...

Laser-Sintering....

Requirements on Laser-Processable Molding Compounds.

Application Proles Laser-Marking....

Application Proles Laser-Welding.

Requirements on Laser-Workable Molding Compounds.

Requirements Prole Laser-Structuring.

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Laser Additives....

Additives for Non-Transparent Molding Compounds..

Additives for (Highly) Transparent, Colorless Molding Compounds.

Laser-Processable Molding Compounds ..

VESTODUR..................................................................................

VESTORAN..................................................................................

TROGAMID.................................................................................

VESTAMID...................................................................................

VESTAKEEP.................................................................................

Laser-Processable Seminished Products ...

EUROPLEX...................................................................................

PLEXIGLAS..................................................................................

Environmental Aspects..

Emissions....

Recycling.

Quality...

Future Prospects .

Classes of Lasers .

DIN EN 60825-1 Classication...

Literature and Sources...

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Performance Polymers

Application possibilities for laser systemsused in processing plastics are virtuallyunlimited. Fast, exible, and precise, laser

technology is more cost efcient thanconventional processes; moreover, thisadvanced technology brings innovativeideas to rapid implementation and addsyears to the life of processed materials.

Where products are marked with bar-codes, contour sharpness is important, asis contrast. Only if the marking stands outclearly from the material surface can it becorrectly read by a bar code scanner andprocessed further.

The miniaturization of components andtheir increasingly complex geometriesrequire welds of such neness that con-ventional welding processes can obtainthem only with great difculty, if at all.The laser-welding process, on the otherhand, makes it possible to do even three-dimensional welding in a single workstep.In the manufacture of sensors for medicalengineering, the laser can produce the -nest welds in the most conned of spaces.The conventional manufacture of three-

dimensional circuit substrates dependson product-specic tools for creating the

printed circuit structure on the compo-nent, which severely limits the exibilityof the processes when designs are chan-

ged. Further miniaturizing printed circuitstructures on MID components requiresadditional time and cost. Using specialmolding compounds in conjunction withthe appropriate laser-structuring techno-logy offers a exible and cost-effectivealternative.

In design studies, modeling, and even invery small-scale production, parts are stilloften produced manually because the highcost of tools rules out the fabrication ofinjection-molded parts. Laser-sintering

offers an economical alternative here. Theparts need only be developed on a CADsystem and then constructed as hardwarein a subsequent rapid prototyping process.

The scope of application of plastics de-pends strongly on their material proper-ties and their compatibility with the laserwavelengths used in the various systems.Not all of the currently used thermoplas-tics absorb laser beams equally well. Butthanks to special additives developed

and patented by Evoniks PerformancePolymers and Inorganic Materials Business

Units, our molding compounds can be ad-justed for use in an extremely wide rangeof applications.

The components made from thesemolding compounds ensure good laserweldability of two transparent materialsand, for laser-marking, dark lettering ofthe highest quality, even for highly trans-parent and colorless plastics. Moreover,the High-Performance Polymers BusinessLine offers various black and dark-coloredproducts that can be laser-marked to givelight-on-dark images with good contrast.

For the selection of a suitable laser-pro-

cessable material, the requirements prolefor the molded part must be known. Thefollowing table of laser-processablemolding compounds from our high-performance polymers product range willhelp you draw up a short list of suitablematerials. We recommend that youconsult us as your knowledgeable partnerbefore beginning a new project. Our LaserApplication Center has the skills to selectthe molding compounds that are optimalfor you, and to identify fast and economic-

al processing options when these materi-als are used.

Introduction

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Laser Sintering

Laser Printing Laser Engraving Laser Welding Laser Direct Structuring

IndustrialPartners:Laser Technologies

Customers:Problems

Applications

High PerformancePolymers:Polymer Materials

Solution Provider

The Laser Application Center of High Performance Polymers offers support in the use of lasers with polymers, in the form of:

comprehensive advice, state-of-the-art technology, and

quality testing

Polymers & Lasers

The Laser Application Center supports you in choo-sing materials for all relevant laser processes.You are welcome to try out the following laser appli-cations at the Center:

Laser-marking (2D and 3D) Laser-welding Laser-sintering Laser-structuring

Quality

In our testing and analytical laboratories, we canperform a wide range of tests on lasered and un-lasered materials to check and safeguard our highquality standards. These include

transmission measurements, haze, scanning electron microscopy (SEM), transmission electron microscopy (TEM), light microscopy, and

tensile testing

as well as many other physical and chemical tests.

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Laser Technology

What is laser radiation?

The word laser is an acronym for Light Amplicationby Stimulated Emission of Radiation, and describesa physical process leading to the production of laserradiation.

In the rst step, atoms1)of a laser medium (the activemedium) are excited by supplying them with energy,a process known as pumping (see diagram). Theactive medium may be a liquid, solid, or gas.

end mirror front mirror(totally reflecting) (partly transparent)

optical resonator

Fig. 1: Structure of a laser

coherence: the waves possess a constant phase difference; they are temporally and spatially coherent; monochromatic light: laser radiation has exactly one wavelength; low divergence: lasers emit bundled, almost parallel radiation.

1)These may be atoms, molecules, or ions; for the sake of brevity they will be referred to in the following as atoms

laser pumping energy

Depending on the active medium, the energy can besupplied by electrical gas discharges, ash lamps, anapplied voltage, or another laser. The excited atomsemit photons (light particles), thereby returning tothe non-excited state. If these light particles collidewith other atoms in the excited state, the latter alsoemit light particles of the same wavelength, phase,and direction as the incident light particles. This pro-cess, known as stimulated emission, is what occursin an optical resonator.

The resonator may be, for example, a (gas-lled) tubeor a solid (such as ruby, or a semiconductor), at bothends of which a mirror reects the radiation. Thistherefore traverses the active medium many times,stimulating further atoms to give up their light par-ticles on each pass. One of the two mirrors is partly

transparent, so that part of the radiation can emergefrom the tube.Laser radiation differs essentially from radiationemitted by conventional radiation sources, such asincandescent lamps, in the following ways:

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monochromatic (a single color) luminous power of the order of mW to MW spatially and temporally coherent directional laser beam radiation good bundling (focusing) of the beam

white light, emitting a broad spectrum luminous power of the order of mW to W not coherent omnidirectional radiation

IR

Fig. 2: Normal light Fig. 3: Laser light

light source prism spectrumUV

In practice, this means that laser beams can be strongly bundled and easily focused on the smallest spaces. This property is exploitedin every CD player, for example, to read out the microscopically small structures on the CD. On the other hand, laser beams alsoallow enormous energies to be bundled at a single point, for example, for very precise cutting, marking, or welding of materials.

Because lasers are used for a wide range of different purposes, they differ also in their structure. The wavelengths range from the farinfrared (IR) region through visible light to the ultraviolet (UV) region (see Fig. 4).

Fig. 4: The electromagnetic spectrum

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Types of Laser

Lasers are categorized and named according to the type of the optically active material used; they may be gas, solid, or liquid (or dye)lasers (Fig. 5).

Fig.5: Typical lasers and their wavelengths

Lasers can also be classied according to whether they radiate continuously (cw (continuous wave) lasers, Fig. 6) or operate in apulsed mode. Lasers radiating for a period exceeding 0.25 s are known as continuous wave lasers. Pulsed lasers emit radiation pulsesat regular intervals; the duration of these pulses may range from a few femtoseconds to 0.25 seconds (Fig. 7).

Fig. 6: Continuous wave (cw) laser Fig. 7: Pulsed laser

Time(t) Time (t)

Power(P)

Power(P)

PL

T

tP

PS

Pm

PL= laser power (W) PS= peak power (W) Pm= mean power (W)T = pulse period tp= pulse duration

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Solid-State Lasers

The rst working laser was a ruby laser, made fromruby (chromium-doped corundum), developed byMaiman in the year1960.Solid-state laser materials are commonly made bydoping a crystalline solid host with ions provide therequired energy states. Embedded in the host mate-rial, these ions form the actual active medium. Theirorbitals do not participate in chemical bonding. Thecarrier material (host crystal or glass) therefore hasonly a small inuence on the properties of the ions.

Solid-state lasers are distinguished according to thetype and form of the host material and the dopedelements.

Examples of host or carrier materials

Glass (in the form of rods or fiber lasers) Advantage: simple to produce, even in large

dimensions Disadvantages: low thermal conductivity,

low strengthAl2O3(corundum, sapphire; e.g., ruby laser

(chromium doped), titanium:sapphire laser) Advantages: high thermal conductivity,

high strength Disadvantages: relatively high absorption;

expensiveYAG (yttrium aluminum garnet laser: seeNd:YAG laser), doped with Nd, Er, Yb

Advantages: high thermal conductivity,high strength, low absorption

Disadvantage: expensiveYttrium vanadate (YVO

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), doped with Nd

Examples of Doping Materials

The doping material in the first ever laser, theruby laser (694.3 nm, red), was chromium. Be-cause of its low efficiency it is now rarely used.Neodymium, is used in the most important com-mercial solid-state lasers, Nd:YAG at 1064 nm(infrared) and double frequency at 532 (green).Nd:glass and Nd:YLF are also possible.Ytterbium, allows high efficiency (>50%) in la-

ser operation, but needs narrow-band pumpingwith laser diodes (940 nm). The most importantmaterial with this dopant is the Yb:YAG laser, forexample, highly doped as a thin disk laser with awavelength of 1030 nm.Titanium; an important mode-coupled solid-sta-te laser is the titanium:sapphire laser, 670-1100nm (red-infrared), which due to broadbandamplification is suitable for pulses in the fs range.Erbium, 3 m, pumping with diode laser at 980nm; known as the eye-safe laser, this is used forlaser range finders and in medicine.

Types of Active Media

Rod lasersMicrocrystal lasersSlab lasersFiber lasersThin disk lasers

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Semiconductor Lasers

In semiconductor lasers, the active medium is the dif-fusion zone of the charge carriers in a p-n transition1)of a semiconductor crystal. The optical resonator canbe formed here by the end faces of the semiconduc-tor crystal, because the high refractive index of thecrystal results in high reectivity.Laser diodes are directly electrically pumped lasers.The power of laser diodes lies between < 1W and10W. The beam quality declines with increasingpower.

A number of individual diodes can be assembled sideby side on a single narrow chip (approx. 0.1 x 1 x 10mm). These bars, as they are known, can supplymore than 50 watts if mounted on a heat sink, withthe individual diodes electrically connected in paral-lel. The mounted bar is also known as a submount.By coupling a number of bars or submounts in a stack,outputs in the kW range can be achieved, with corres-pondingly poor beam quality. By the use of different(normally up to 3) wavelengths and polarizationdirections, up to 6 stacks can be optically added withlow losses and without deterioration of beam quality.

For optical pumping of solid-state lasers by laser dio-des, the pump wavelength must be matched exactlyand wavelength coupling is therefore not possible.However, the diode lasers need not be combined hereinto beams with high power densit y.

Diode lasers with wavelengths in the range of approx.800 nm to 1000 nm are now, in addition to Nd:YAGlasers (1064 nm), the most important industrial lasersfor processing of plastics.

Other semiconductor lasers include:

optically pumped semiconductor lasers, inclu-ding semiconductor thin disk lasers,quantum cascade lasers,surface-emitting lasers (VCSEL) (optically aswell as electrically pumped), andtunable lasers (tunable laser source, TLS) withadjustable wavelength.

Gas LasersIn gas lasers the active medium is gaseous. Gas lasersare usually electrically pumped by a gas discharge inthe active medium itself.The most important gas lasers used in the processingof polymers are:

the carbon dioxide (CO 2) laser, with wavelengthapprox. 10.6 m (mid-infrared), an importantindustrial laser for cutting and marking, andthe excimer laser, for example, KrF (248 nm),

XeF (351-353 nm), ArF (193 nm), XeCl (308nm), and F2(157 nm), for marking and nedrilling; all these are ultraviolet.

Other Types of Laser

Other types of lasers include, for example, dye lasers,color center lasers, and free-electron lasers (FEL).

1)p-n (positive-negative) transitionis the boundary layer between a p-conducting and an n-conducting region in a semiconductor. The strong concentration gra-dient of the carriers at the boundary layer causes some holes to diffuse from the p- to the n-conducting layer, and some electrons in the reverse direction, where theythen recombine with the respective carriers.

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Polymers and Lasers

If plastics are used for laser-welding, the material-specific properties of the various types of plastics must be taken into particularconsideration.

Thermoplastics, whether amorphous or semicrystalline, are easily fusible and have a fusion temperature range above which theydecompose (Fig. 9).

In addition to morphology, fillers, such as glass fibers, also affect welding properties.

Additives

Ultra violet Infrared

Electronic excitation

400 nm 700 nm

Vibronic excitation

Nd:YAG

1064 nm

Nd:YAG/SHG

532 nm

Visible region

CO210.6 m

Diode laser

808, 940, 980 nm

AbsorptionPolymer

Additives



400 nm 700 nm

Vibronic excitation

Nd:YAG

1064 nm

Nd:YAG/SHG

532 nm

Visible region

CO210.6 m

Diode laser

808, 940, 980 nm

AbsorptionAdditivesAdditives



400 nm 700 nm

Vibronic excitation

Nd:YAG

1064 nm

Nd:YAG/SHG

532 nm

Visible region

CO210.6 m

Diode laser

808, 940, 980 nm

AbsorptionPolymer

Fig. 8: Light absorption of polymers and laser wavelengths

Requirements

Virtually any plastic can be laser processed, but material- and process-specic restrictions must be taken into account.

Plastics do not absorb laser radiation in the region extending from the near ultraviolet to the near infrared. Conversion of laser ener-gy into heat (of fusion) is therefore possible only if the polymer has been appropriately laser sensitized by addition of an additive.

In the absence of laser additives, therefore, polymers can be processed only in far ultraviolet light, for example, with excimer lasers,and in far infrared light, for example, with CO2lasers (Fig. 8).

CO2

10.6 m

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Polymers

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Factors Inuencing Laser-Welding of Plastics

Crosslinked plastics of the thermoset and elastomer class (except for thermoplastic elastomers, TPE/TPU) are not fusible. They aretherefore not suitable for laser-welding. They can, however, be used for laser-marking.

Fig. 9: Fusion and softening ranges of plastics

Fusion/softening ranges Decomposition temperature

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Optical Properties of Plastics

When a laser beam strikes a plane interface between two media with different refractive indices, it is partly reected at the interfaceand partly absorbed on penetration, the remaining radiation then being transmitted. The proportion in which these effects occurdepends on the material properties of the obstacle; the sum of all radiations is always 100%.

Reflektion

Transmission

Kunststoff

Laserstrahl

Absorbtion

Reflektion

Transmission

Kunststoff

Laserstrahl

Absorbtion

Reflektion

Transmission

Kunststoff

Laserstrahl

Absorbtion

Reflektion

Transmission

Kunststoff

Laserstrahl

Absorbtion

Reflektion

Transmission

Kunststoff

Laserstrahl

Absorbtion

Laser beam Reection

Plastic

Transmission

Fig. 10: Optical properties of plastics

AbsorptionAbsorption (from the Latin absorptio) occurs whenpower from the light beam is transferred to theplastic. The absorbed fraction of the light is generallyconverted into heat, but may also be lost throughscattering at defects (air, etc.) in the structure of the

material (Fig. 10).

Polymers do not absorb laser radiation in the regionfrom the ultraviolet to the infrared. Conversion oflaser energy into heat (of fusion) is therefore possibleonly if the polymer has been laser sensitized byaddition of an appropriate additive (Fig. 8).

ReectionReection (from the Latin reectere, to bend back,or turn) occurs when, for example, electromagneticwaves are bounced back from a surface (Fig. 10).

The ratios of the refractive indices and absorptioncoefcients of the plastics determine the intensities

of reection and transmission. For reection, thefollowing simple law (for plane surfaces) applies: theangle of incidence () of the light beam equals theangle of reection ().

Scattering

Scattering of electromagnetic waves occurs mainlyat defects in the structure of materials, caused by, forexample, poor distribution of additives, bubbles (airpockets), etc.

HazeHaze is the scattered component of the transmittedlight in transparent plastics. Low haze values therefo-re indicate high transparency.

TransmissionTransmission (from the Latin trans(through) and

mittere(send)) is a measure of the transparency ofa medium to, for example, electromagnetic waves(light, etc.) (Fig. 10).

in

ex

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Transmission Spectra

Fig. 12:Transmission spectrum ofnanomodied TROGAMID CX7323

Fig. 11:Transmission spectrum ofnanomodied PMMA

TransmittanceIn optics, transmittance is the proportion of the incident radiationor light ux that completely penetrates a transparent component.The transmittance is dened as the quotient of the radiant uxof the emergent (transmitted) light beam (ex) and that of theincident beam (in).

= ex/in

The transmittance depends on, among other factors, thewavelength and therefore the frequency of the electromagneticradiation, that is, on the color of the light, and on the angle of

incidence of the wave.

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Laser-Marking

The range of potential applications for laser systemsin the marking of plastics is virtually unlimited. Fast,exible, and precise, laser technology is more eco-nomical than the conventional printing and injectionmolding processes; moreover, this advanced techno-logy guarantees the durability and contour sharpnessof the marking.For marking products with a barcode or data matrixcode, contrast is important, as is contour sharpness;only when the marking stands out clearly from thematerial surface can it be correctly read by the barcode scanner and processed further.

The contrast and contour sharpness of laser markings

depend on the material properties of the plastics usedand their compatibility with the various laser systemsand their wavelengths. Not all of the commonly usedthermoplastics absorb laser beams equally well, andthis can negatively impact the contrast or suppress italtogether.

Marking plastics in the UV, visible, and IR rangesis possible either directly or with the use of laseradditives.Because the Nd:YAG laser (1064 nm, Fig. 13) isthe most commonly used in practice, most molding

compounds for laser-marking are now formulated forthe wavelength of this laser. Exceptionally high con-trast is achieved when the materials contain specialadditives developed and patented by Evoniks HighPerformance Polymers Business Line. Laser additivesdesigned specially for transparent plastics have alsobeen developed by the companys Inorganic Materi-als Business Unit.In non-transparent plastics, these laser additivesensure dark markings of the highest quality on almostall light-colored formulations, irrespective of thepigmentation of the plastic and even for in-house

Fig. 13:Nd:YAG marking laser1064 nm (from Baasel-Lasertechnik)

coloring by customers. Additionally, the High Perfor-mance Polymers Business Line offers various dark-colored and black products that can be laser-markedin light colors with good contrast.

Highly transparent plastics from Evonik that containlaser additives are distinguished by their absolutecolorlessness and very low haze. In this case also,the lettering is of the highest quality, with very goodcontrast.

To choose an appropriate laser-markable material,you must know the requirements prole for the partto be marked.

Factors Impacting Laser-Marking

The markability of a plastic depends only on its ma-terial properties and any laser additive used. Markingeffects such as color change, foaming, and carboni-zation depend on the reciprocal effects of materialproperties and laser wavelength. The characteristicscrucially important for high-quality marking arehomogeneity of the molding compound, excellentdistribution of the laser additive, and appropriateselection of laser parameters.

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Writing laser

The writing laser offers exibilit y. The laser beam isdeected in the x- and y-directions by two computercontrolled galvanometer mirrors, and is focused witha lens on the part to be marked. An area of appro-ximately 10 x 10 cm can be marked at any requiredpoint. It is possible to provide every single part in aproduction line with an individual marking, such as aserial number.

Mask Laser

The mask laser is not as exible as the writing laser,but is considerably faster. The laser beam, a fewsquare centimeters in area, passes through a lens,imaging a mask on the part to be marked. This processallows up to 200 markings per second.

Dot-Matrix-Process

In the dot matrix process, a laser beam is chopped by a rotating mirror. By movement of the part to be marked, a marking consistingof a number of individual points is produced, in the same manner as on an inkjet printer. This process represents a special form oflaser-marking of plastics because it can be used for only a few thermoplastics.

The Dot-Matrix-Process is suitable for batch date marking at high speed. The size of the marking is restricted, however, and marking

is possible only with moved parts.

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Laser-Marking Non-Transparent Plastics

Marking Lasers

Fig. 14:Writing laser

Fig.15:Mask laser

Deection unit forthe x direction

CAD-SYSTEM

Deection mirror

Deection unit forthe y direction

Lens

Workpiece

Laser

Mask

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Lettering and Contrast onNon-Transparent Plastics

The staining depth and foaming height can be deter-mined from light microscopic images of thin sections(Fig. 16, 17, and 18). The staining depth [a] shouldbe at least 100 m, and the foaming height [b] shouldbe as low as possible. The most important parametercharacterizing the marking is the legibility, which canbe quantied in terms of contrast; this can be deter-mined using a luminance meter.

Fig. 16: Contrast without additive Fig. 17: Contrast with additive

Surface prole of the letter E with the same laserenergy

Fig. 19:No additive; high

foaming height

Fig. 20:Low foaming height

achieved by use of anadditive

Fig. 18: Characterization of laser-marking byevaluation of staining depth (a) and foamingheight (b)

To eliminate gloss angle effects, the measurementpoint is illuminated by an integrating sphere with aluminosity of 200 lux. The luminances of the back-ground (BL) and characters (CL) are determined,and the contrast C is dened by the ratio BL/CL. TheGS-VWSG7 test standards of the Employers LiabilityInsurance Association specify that for characters onkey caps C must be > 3.

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Laser-marking of transparent plastics has so far been restricted to colored thermoplastics; selective coupling inof the laser energy was not formerly possible in transparent plastics. The problem could be solved by the use ofsuitable additives or pigments, but at the cost of transparency and colorlessness. Evoniks technicians have nowovercome these difculties and have succeeded in extending the process also to transparent polymers.

Laser-Marking of Transparent Plastics

A technology has been successfully developed forlaser-marking transparent plastics, which are other-wise difcult or impossible to mark with lasers. Thisuses nanoscale metal oxides, which, on account of

their small particle size, do not scatter visible light butabsorb the wavelength of the laser in the near infra-red (NIR) region. Because the Nd:YAG laser (1,064nm) is most commonly used in practice, the additiveshave been formulated for the wavelength of this laser.The skill in the incorporation of the metal oxides liesin controlling their tendency to agglomeration anddispersing them as homogeneously as possible inthe polymer matrix. Only under these conditions canhigh-contrast markings with the highest resolutionand contour sharpness be obtained. These infraredabsorbers are dispersed in PLEXIGLAS(polymethyl

methacrylate, PMMA) and TROGAMID

, a transpa-

Laser-Marking by NIR Absorbers

Well-dispersed laser sensitive additive Aggregated laser-sensitive additive

rent polyamide, new compounding processes beingused for this purpose.If a laser beam now falls on themetal oxides, they absorb the energy and heat theirimmediate environment, which results in foaming

(by formation of gaseous degradation products in themicrometer region) or carbonization (degradationto carbon). The result is a locally conned change ofrefractive index, rendering the marking, such as aninscription, visible. The additives do not produce a co-lor change, but appear in a shade of gray ranging fromwhite to black, depending on the polymer and thechoice of laser parameters. In both PLEXIGLASandTROGAMID, markings can be obtained with layerthicknesses of less than 100 micrometers. Multilayerdesigns are also possible in which the laser-sensitivelayer is embedded between two transparent covering

layers.

Fig: 21

Dispersion of NIR absorber

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Fig. 22: Mechanism of laser-marking and sub-surfaceengraving by NIR absorbers

Focused laser beam

Nanoscale particles absorb in theNIR

Polymer foams

Polymer carbonizes

Change of refractive index orcarbonization makes the markingvisible

Use of nanoscale NIR ab-sorbers

in transparent polymers suchas PLEXIGLAS(PMMA)orTROGAMID (PA)

for laser-marking or sub-surface engraving

The possible elds of application of this new tech-nology for laser-marking (highly) transparentplastics are many and varied. Because the marking isforgery-proof and highly durable, it is suitable for, forexample, identity cards, barcodes, and pharmaceuti-cal packaging. Medical technology could also benetfrom this contactless process because, in contrast toother marking processes such as printing or milling,there are no impurities and no contamination withchemical compounds or abrasion particles.

Entirely different elds of application, such as perso-nalized art objects or inscriptions for ofce doors, arealso conceivable. Evonik is now stepping up furtherdevelopment in cooperation with customers.

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2D laser-marking of nanomodied polyamide or PMMA gives good contrast and excellent contour sharpness.

2D Laser-Marking of Transparent Plastics

unmodied TROGAMID

nanomodied TROGAMID

Fig. 24: Laser-marking of TROGAMID (PA)

unmodied PLEXIGLAS

nanomodied PLEXIGLAS

Fig. 23: 2D laser-marking of PLEXIGLAS (PMMA)

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3D Sub-Surface Laser-Engraving ofTransparent Plastics

For many years, lasers have been used for sub-surfaceengraving of glass to produce 2D or 3D motifs (e.g.,from CAD applications), logos, patterns, and photos.The amazing possibility also exists of imaging faceswith 3D face scanners to produce realistically andaccurately engraved 3D motifs in glass blocks. Thistechnology works because a 3D scanner can capturethe face of a person in seconds. This face scan isthen prepared for the laser process by special soft-ware, the photo being transformed into a dot cloud.The laser, normally a frequency-doubled Nd:YAGlaser (532 nm), burns hundreds of thousands of

pixels into the glass in just a few minutes, reproducingthe surface and the texture of the face, hair, eyes, andother features. A high-resolution 3D representationdemands optimal matching of software, laser unit(hardware), and material.

3D motifs can be laser-engraved in normal, com-mercially available acrylic glass, but resolution andbrilliance are signicantly poorer than in silicate glass.The poor quality of sub-surface laser engraving has sofar prevented the use of acrylic glass for this purpose.Evonik has now succeeded in developing a special

type of acrylic glass in which, just as in silicate glass,3D motifs of high quality can be laser-engraved (Fig.25). This is achieved by nanomodifying of highlytransparent plastics. The excellent dispersion neces-sary for the nanomodication is the basic prerequisitefor obtaining high transparency of the plastic and pro-ducing an image with high resolution and brilliance.

In principle acrylic glass, such as PLEXIGLASfromEvonik, offers many advantages over silicate glass,such as signicantly lower specic weight, easy mold-ability and mechanical workability (affording greaterdesign freedom), and higher resistance to breakage.It is well known that on improper handling or longstorage, microcracks in silicate glass can increase insize to the point of breakage. This does not occur inacrylic glass.

Moreover, acrylic glass, unlike silicate glass, is easilycolored, and permits signicantly greater laser pene-

tration depth (approx. 500 mm for PMMA), allowingsub-surface laser-engraving even of large objects.

In nanomodied acrylic glass, very high resolution isachieved. Sub-surface laser-engraving of unmodi-ed acrylic glass results in optically and mechanicallyobjectionable microcracks; in nanomodied acrylicglass, on the other hand, well-dened points areproduced, as is clearly seen in the dot cloud of Fig. 26.

If at rst sight this technique appears to serve no morethan a decorative purpose, it has potential for impro-

ving the visual aesthetics of transparent plastics, as inarchitectural applications. The possibility of engra-ving high-resolution 3D motifs in components existsnot only for acrylic glass but also for other highlytransparent materials like TROGAMID(semicrystal-line polyamide).

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Production of a three-dimensional image with a CAD system or by stereo photography.

Basics of 3D Sub-Surface Laser-Engraving

Fig. 25: Laser-marking of PLEXIGLAS (PMMA)

The object from the CAD le must be transformed intoa dot cloud, in which process the x, y, and z coordinatesof each point are calculated and stored. In contrast tothe normal writing laser, the 3D laser can laser onlydiscrete points, but at very high speed.

Each individual point is then engraved into thetransparent polymer by a highly focused, frequencydoubled Nd:YAG laser (532 nm). For PMMA, thisprocess produces micro bubbles, while for PA the

plastic is carbonized (blackened).

Fig. 26: Dot cloud

25


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3D Laser for Sub-Surface Engraving

The 3D laser for sub-surface engraving offers highexibility in three- dimensional design. The laserbeam is deected in the x, y, and z directions by twocomputer controlled galvanometer mirrors, andfocused on the part to be marked by a (preferablyateld) lens. A eld of approximately 10 x 10 x 20cm can be marked at any desired point. Larger objectsmust be divided up (tiled) and composed in severalstages, as in a puzzle.

Fig. 27:3D laser for sub-surface engraving

PLEXIGLASwithoutadditive PLEXIGLASwithlaser additive PLEXIGLASwithoutadditive PLEXIGLASwithlaser additive

Fig. 28: 3D laser-marking of PLEXIGLAS (PMMA)

Microcracks

Microbubbles

26

CAD system

deection system for

the x direction

deection system for

the y direction

traverse path of the laser

head for the z direction

deection mirror

lens

laser

workpiece


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Sub-surface lasering in (highly) transparent, colorless, and laser-sensitive plastics allows forgery-proof labeling, forexample with serial numbers. Penetration depths of up to 500 nm can be attained in PMMA. Even deep lasered barcodesand data matrix codes can be read out without problems; only the penetration depth of the reader is important here.

Nanomodied PLEXIGLASnow provides a good alternative to marked and sub-surface engraved glass.

Fig. 29:The CERION C1 jet 3D laser

(from CERION)

To make colorless, (highly) transparent polymers laser-markable and sub-surface engravable, nanoscale laser absorbersare required with a very narrow particle-size distribution and highly homogeneous distribution of the nanoabsorbers.Only in this way can excellent high-resolution markings with good contrast be achieved. These nanoabsorbers can beadjusted for the laser wavelength required.For deep lasering, the surface of the object on the side where the laser beam penetrates is also required to be perfectlyplane. If, for example, the surface is waved on a macroscopic scale, the text obtained is also visibly wavy.

27

Application Fields of Laser-Sensitive, Transpa-rent, Colorless Plastics

Advantages of Laser-Sensitive, Transparent,Colorless Plastics


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Advantages of Laser-Marking

FastWriting speeds of up to 2000 mm/s or 200characters/s are possible.

FlexibleLayouts can be prepared and stored using standardCAD programs and can be retrieved in any desiredorder, thus allowing fast changes.

PreciseEven the smallest characters or symbols with verysmall line thicknesses can be accurately positioned

and are clearly legible.

CleanNo additives, and in particular no solvents, are requi-red.

ContactlessMarking is possible not only on smooth, uneven, andtextured surfaces and surfaces difcult to access, butalso through transparent covers.

Abrasion resistantPenetration depths of up to 200 m are possible,so that the marking is both abrasion-resistant andforgery-proof. This is particularly important in regardto product liability.

TransparentTo make colorless (highly) transparent polymers laserprocessable, nanoscale laser absorbers with verynarrow particle-size distribution are required. Onlyin this way can excellent weld seam quality and high-resolution markings with good contrast be achieved.These nanoabsorbers can be adjusted in accordancewith the required wavelength.

Resistant to chemicalsThe marking is resistant to cleaning agents, cos-metics, and perspiration with which it comes intocontact.

No pretreatment necessaryBecause there are no adhesion problems, surfaces canbe marked directly, without any special pretreatment.

Low operating costsParticularly for large runs, the process is highly costeffective. No additional materials are required, and

there are no cleaning and disposal costs for colorantsor chemicals. Labor costs are eliminated by integrati-on of marking into automatic production processes,and no storage of dies, masks, etc. is needed.

QualityThe process is characterized by a very high degree ofreproducibility.

Fig. 30: SEM micrograph line structure

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Laser-Welding of Plastics

Fig. 32: Welding matrix

good welded joint satisfactory welded joint poor welded joint

no welded joint no information available

29

transmitting

absorbing ABS

ABS/

PA

ASA

COC

MABS

PA12

PA612

PA6

PA6-3-T

PA

PACM12

PA66

PBT

PBT/

ASA

PC

PE-HD

PE-LD

PEEK

PES

PMMA

POM

PP

PPS

PPSU

PS

PSU

PTFE

SAN

TPE

ABS

ABS/PA

ASA

COC

MABS

PA12

PA 612

PA6

PA 6-3-T

PA PACM12

PA66

PBT

PBT/ASAPC

PE-HD

PE-LD

PEEK

PES

PMMA

POM

PP

PPS

PPSU

PS

PSU

PTFE

SAN

TPE

laser beam

weld seamabsorbingpolymer

transmittingpolymer

Fig. 31: Laser-welding(schematic representation)

Laser-welding of plastics consists in the bonding ofthermoplastics under heat and pressure.The bonded surfaces must be in the thermoplasticstate. Plastics that can be laser-welded with orwithout additives are listed in the table below.

The data in the table can vary, depending on the laser wavelength.


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Laser-welding of plastics is possible only with fusiblepolymers; in general, all amorphous and semicrystal-line thermoplastics, as well as thermoplastic elasto-mers (TPU) can be used. Elastomers and thermosets,on the other hand, are not suitable for laser-welding.The fusion temperature regions (Fig. 9) of the plasticparts to be bonded should overlap, and the meltsshould be mutually compatible. The laser-absorbentjoin partner should be able, possibly with the use ofan additive, to convert the laser energy into heat atthe wavelength used.

Degrees of Difculty inLaser-Welding

The degree of difculty in laser-welding dependson the laser transparency of the upper and the laserabsorption of the lower of the two join partners.The better the upper join partner transmits the laserenergy and the better the lower partner absorbs thisenergy, the easier is the welding process.

The requirements for the procedure increase in theorder black, colored, transparent, and white. Appli-cations with a black join partner as the absorber are

normally easy to realize or are already available

as standard solutions. Welding of colored plasticsrequires pigment combinations in laser-transparentand laser-absorbent form. Welding of light colored ortransparent plastics is possible by using laser-absor-bing high-performance additives.

difficult

moderate

easy

transparent/

black

black/

black

color 1/

black

color 1/

color 2

transparent/

transparent

white/

white

color 2 /

color 2

30

Fig. 33: Degrees of difculty in laser-welding


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Laser-welding of plastics is usually performed inthe overlap process. Two join partners are used, theseparation (bridged gap) of which should be lessthan 100 m. The upper join partner is a laser-trans-parent thermoplastic, selected according to the laserwavelength, which heats up very little, if at all, on thepassage of the laser beam. For a weld seam to be pro-duced, the second join partner must absorb the laserradiation. The absorbing medium can be, for examp-le, a laser-transparent thermoplastic doped with laseradditives (such as carbon black (approx. 0.3 wt%),metal oxides, or special dyes); alternatively, darkcolored thermoplastics may be used. When this sub-

stance absorbs energy it begins to fuse and transmitsits energy to the upper partner.

In order that the energy can actually be transmittedto the partner, the bridged gap should be < 100 m.The partners must be pressed together; otherwise asecure bond (weld) cannot be guaranteed, despitethe application of energy. The pressure required tojoin the plastic components should be applied as closeas possible to the weld; only in this way can the exter-nally applied compaction pressure cause the melts toblend and the plastic parts to weld to each other.

The Laser-Welding Process

Fig. 35: Stages of the laser-welding process

A B C D

laser

beam

join pressure

join pressure

non-absorbingplastic

absorbingplastic

Diode lasers are frequently used here because thebeam quality for this welding process does not usuallyneed to be exceedingly high.The laser passes through the upper join partner andis absorbed in the lower join partner (A). The laserenergy is converted into heat and a melt is formed(B). This now heats the upper join partner in the areaof the seam to the extent that the material here alsomelts (C). Due to the external compaction pressureon the two join partners the melt cannot escape, andthe parts are welded (D).

31

transmittingpolymer

absorbingpolymer

melt zone

laser beam

Fig. 34:Laser transmission welding of plastics


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Tool

Laser beamOptics

Weld Seam Quality

Factors affecting weld seam qualityin thermoplastics

A structured analysis of a production process is ne-cessary to understand it and develop it further. Everyproduction process is associated with a number ofparameters that affect the result of the process. Theresult in this case is the weld seam between two ther-moplastics. The parameters are of various kinds, andthe extent to which they impact the result also varies.The Ishikawa diagram is a useful tool for the structu-ring and analysis of a complex production process in

terms of its parameters (see also Fig.36).The main branch of the diagram represents the entireprocess of laser-welding of thermoplastics, the resultbeing the required quality of the joint.

The entire production process is inuenced by certainfactors that can be summarized under the heads:

tool (laser beam, laser radiation)machinepre- and post processesmaterialmethod, andpeople.

Some of these factors mutually inuence one ano-ther. The heads can be further divided into (functio-nal) subheads. The aim is to break down the structureto the extent that all the parameters directly affectingthe result of the process are contained in the diagram.For reasons of clarity, the Ishikawa diagram is shownhere only (roughly) to the rst level of the functionalsubheads.

Seam quality

StrengthFastnessSeam widthHAZVisualappearance

Fig. 36: Factors impacting seam quality in laser-welding of thermoplastics (Ishikawa diagram)

Source: Russek, Dr. U.A.:SKZ Seminar, Laser-Welding of Plastics, Wrzburg, 2007

32

Pre- and post-process

Pre- and post- heat treatmentCoatingsAmbient conditionsProduction conditions

Machine

Traversing systemType and deection of beamClamping techniqueWorkpiece handling

Workpiece

MaterialGeometryTolerances

Seam accessibility

Method

Type of radiationEnergy input per unit lengthWeld path (with/without)

Post production

People

TrainingExperienceAlertness


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There are four different variants of laser-transmission welding:

contour welding,simultaneous welding,quasi simultaneous welding, andmask welding.

Laser-Welding Processes

Contour Welding

This method allows the use of low laser power. In

contour welding the laser beam traverses the entirejoin plane of the welding parts, so that relative move-ment of the laser beam and welding part is necessary.This can be achieved by means of a robot, by a traver-sing motion of the laser or the part to be welded. Oneadvantage here is that components with virtually anyseam structure can be welded. The welding process isalso very exible, and if the welding part is changed,the traversing movement can be rapidly adjusted forthe new weld geometry. This is currently the mostwidely used process.In the future, quasi simultaneous welding will

probably used for relatively small components andcontour welding for larger components.

Fig. 37:

Contour welding

Fig. 38:

Simultaneous welding

33

Simultaneous Welding

Simultaneous welding usually uses a diode laser

system. The laser beam simultaneously scans theentire joint plane and can heat it with one or morelaser pulses. No relative movement between the lasersystem and welding part is required.Simultaneous welding is highly advantageous forlarge runs because welding times can be reasonablyshort. A further advantage is the absence of mecha-nical components such as robot arms and scanners,which require maintenance. Like quasi simultaneouswelding, simultaneous welding also allows monito-ring of the process via the setting path; however, theneed to adjust the system for each welding part is a

disadvantage. The high laser power needed meansthat several diode lasers may be necessary. Moreover,the system cannot be modied, which means thatthe same laser cannot be used for slight changes ofgeometry of the weld seam, or if the componentsare changed. For reasons of cost, therefore, onlycomponents with simple seam geometries are weldedusing the simultaneous welding process.

Laser head

Laser beam

transmittingpolymer

weld seam

absorbingpolymer

Laser head

Laser beam

transmitting

polymer

weld seam

absorbingpolymer


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Quasi Simultaneous Welding

In quasi simultaneous welding, the laser beam isguided along the seam using scanner mirrors. There isno movement of either the laser or the join partners;instead, the laser beam is deected by the movingmirrors. Due to the high speed, the join surface canbe traversed several times per second so that, despitethe single-point energy source, the surface is heatedand plasticized almost simultaneously. Both the joinpartners are kept under pressure. The advantage ofthis process it can be used exibly, and components

with three-dimensional seams can also be welded.However, 3D welding is possible only within narrowlimits; in this case, a ateld lens must be used.

A further advantage of quasi simultaneous wel-ding is that higher path speeds are possible than forcontour welding. However, higher laser power isalso needed than for contour welding for the sameenergy input per unit length. A disadvantage is thatthe working space is restricted by the scanner, whichlimits the maximum geometry of the part. The quasisimultaneous welding process is used mainly for

two-dimensional seam geometries. In the future, thetechnique is expected to nd application for relativelysmall components, and contour welding for largercomponents.

Mask Welding

In this process, a metallic mask is placed betweenthe laser and the parts to be welded. A laser beamis moved across the mask. The mask has cut-outswherever welding is required. Areas adjacent to thejoin surface are covered by the mask. Mask weldingallows realization on components of very ne seamsthat may also lie very close together (< 100 mapart). Another important advantage of the processis the possibility of producing a variety of weld seamstructures on a single component simply by changing

the mask. The disadvantage is that at least one maskis necessary. Changes in the seam geometry requirethe production of a new mask, which results in lowexibility. The areas of application of mask weldinginclude microsystem engineering, electrical enginee-ring, sensors, and medical engineering.

Fig. 39:

Quasi simultaneous welding

Fig. 40

Mask welding

34

laser head

laser beam

transmittingpolymer

weld seam

absorbingpolymer

deecting mirror

transmittingpolymer

weld seam

absorbingpolymer

laser head

laser beam

mask

lens


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Application Areas

Laser-welding could replace almost all the classicalbonding techniques for plastics, such as adhesion,sealing technology, and ultrasound, vibration, mirrorand hot-gas welding.

The miniaturization of components and their incre-asingly complex geometries require weld seams ofa neness that could be achieved with conventionalwelding methods only with great difculty, if at all.Laser-welding offers the possibility of even three-

dimensional welds in a single workstep. In the pro-duction of sensors for medical engineering, the lasercan be used to produce the nest welds within a veryrestricted space.

The scope of application for plastics depends heavilyon the material properties and their compatibilitywith the laser wavelengths used in various systems.Not all of the currently used thermoplastics absorblaser beams equally well. Special additives developedand patented by Evonik can equip our molding com-pounds for a very wide range of applications.

Components made from these molding compoundsoffer the advantage of high-quality (transparent/transparent) laser-weldability even with highlytransparent and colorless plastics. The High Perfor-mance Polymers Business Line also offers a variety ofcolored products for non-transparent laser-welding.

Advantages

Advantages of using nanoscale laser absorbers

Colorless, (highly) transparent polymers can beprocessed using lasers. Excellent weld seam qualitiesare obtained thanks to the very narrow particle-sizedistribution of the nanoabsorbers. The nanoabsorberscan be adjusted for the laser wavelength.

Advantages over ultrasound, vibration, mirror, andhot-gas welding, sealing technology, and adhesion

No additional materials, such as adhesives, arenecessary. Processing is completely particle-free.No interfering microparticles, adhesive residues, orroughness are produced. Thermal and mechanicalstresses on the components are signicantly lower.Despite the usually shorter cycle times, the long-termstability and quality of the joints are superior, as arethe monitoring options. Lower costs for systems andtools are also an important consideration.

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Laser-Structuring

Increasing miniaturization of components requiresever ner and more accurate tools to produce nesurface structures. The laser, with resolutions of< 1/10 mm, is the ideal tool for such tasks, andsplendidly suited to producing the nest structures. Itcan remove material from plastic surfaces with greatprecision and selectivity.

Three-dimensional injection molded circuit substra-tes, or 3D MIDs (molded interconnect devices), openup a new dimension, in the true sense of the word,compared with conventional two-dimensional circuit

boards, because they offer a high degree of designfreedom. A new, laser-supported structuring process(the LDS process, from the company LPKF) for 3DMIDs considerably simplies the manufacturing

process. It allows, for example, antenna structuresto be directly and cost effectively integrated into thehousings of cell phones. Furthermore, sophisticatedmechatronic systems that integrate mechanical andelectrical properties can be realized for applications inautomotive construction and medical engineering.

36

Fig. 41: The LDS process, from LPKF

injection molding structuring metallizing

thermoplastic released metalnuclei

laser beam precipitated copper(track)


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Laser-Sintering

Selective laser-sintering (SLS) is a rapid prototypingprocess allowing layer-wise production of complexcomponents on the basis of CAD data. This dispenseswith the need for a molding tool. SLS is based on theprinciple of the layer-wise build-up of a structure byapplication of a polyamide 12 powder followed byselective heating by a laser beam, preferably from aCO2laser. In general, the process can be characte-rized as follows:

specication of a three-dimensional model in theform of CAD data

no use of molding toolsprocessing of material in powder formgenerative build-up. Molding occurs not byremoval of material, but by applying it.production by layer technologyany desired geometryno supporting structure necessary

Fig. 42:Intake manifold for LOTUS sports racing car


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Requirements on Laser-ProcessableMolding Compounds

Application ProlesLaser-Marking

Functional marking

Computer keyboardsvery good legibility; high abrasionresistance required, due to frequentuse

Barcodes on housing parts, electricalswitches, etc.

one-dimensional barcode two-dimensional data matrix

code Contrast and contour sharpness

are important for secure transmission of coded information.

Information markings

Name and address of producer/owner, etc.Equipment type/product data

Operating, setting, connection,safety, or installation instructions;test symbolsType of voltage supply/power ratingof electrical components orappliancesCircuit diagrams, scales, technicallabels

Decorations

Company logoColored symbols and patterns withtransfer lm, some directly applicable

Application ProlesLaser-Welding

Medical technology

SyringesHose/tube connectorsPharmaceuticals packagingPouches for liquidsIn-line ltersCatheter tipsBalloon cathetersSensors

Electrical Engineering

Miniature relay housingsDust- and water-tight housings forelectronic components

Requirements on Laser-Wor-kable Molding Compounds

Automotive engineering

Front headlamp casing with reectorRear lamp casing with reectorDust- and water-tight housings forelectronic componentsElectronic ignition key(remote control)

Requirements Prole

Laser-StructuringElectronics

Tracks for MIDs

Medical Engineering

Microne channels in biosensors

38


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Laser Additives

Additives for Non-Transparent Mol-ding Compounds

In addition to high contrast, adequate staining depthand a surface as smooth as possible are also required.The intensity of the color change reaction increaseswith the content of laser-sensitive pigment, but thepenetration depth of the laser radiation decreasessimultaneously. For a low content, the penetrationdepth is very high, but the expected contrast is toolow.

The contrast increases with increasing laserintensity.The staining depth is reduced with increasinglaser intensityThe foaming height (which is a measure of thequality of the surface) increases with increasingintensity; a smooth surface is desired.

For the same quality of marking, the surface does notfoam to the same extent when an additive is used, andis therefore more resistant to abrasion.To ensure excellent marking, we have taken these

effects into account in developing a laser additive thatdoes not affect the coloration.

Laser-welding requires high weld seam strength.This should ideally attain the strength of the weldedcomponents.For a good weld to be obtained, a laser-sensitiveadditive must be compounded into the absorbing joinpartner. The classic laser additive for this purposeis carbon black. If, however, the same coloration isrequired for the upper and lower join parts, colorpigments or metal oxides adjusted for the laserwavelength can be used.

If plastics are to be laser-structured at the surface, forexample, with CO2lasers, the use of additives is notabsolutely necessary. Special molding compoundsare required for production of three-dimensionalcircuit substrates with miniaturized track structures,for example, for insertion of MID components. Thelaser additive contained in these offers, after laser-structuring, the possibility of selective deposition ofcopper for the tracks.

Additives for (Highly) Transparent,Colorless Molding Compounds

With the special additives developed and patentedby the Inorganic Materials Business Unit of Evon-ik, our (highly) transparent and colorless moldingcompounds can be equipped for the most diverseapplications.The laser additive has practically no impact on thehaze of the plastics used. These molding compoundsare therefore also highly suitable for deep lasering ofmarkings or lasering of 3D CAD objects.

The laser additives ensure high-qualit y laser-weld-ability, even with colorless, transparent-transparentjoins.

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Laser-Processable Molding Compounds

40


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41


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Laser-Processable Seminished Products

1) = Produced by Nd:YAG laser (1064 nm)2) = Product with relatively high tracking resistance

HDT = Heat deection temperature, Method B, 0.45 Mpa HI = increased impact strengthC = Contrast, depends on the luminance of the color GF = glass ber contentLV = low viscosity P = plasticizedMV = medium viscosity CF = carbon ber contentHV = high viscosity FC = ller mix of equal parts of graphite, carbonbers, and PTFEFR = contains ame retardantN = no breakP = partial breakC = complete break

In addition to the compounds listed above, other variants, such as compounds of the VESTAMID E Series (PEBA), can be supplied in laser-processable form.

42


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Environmental Aspects

Emissions

In industrial laser systems, the small amounts of gase-ous decomposition products that can be generated bythe heat developed during laser-processing are drawnoff by exhaust systems. The high efciency achievedthrough the use of special additives in laser-pro-cessable molding compounds from Evonik makes theprocesses even more eco-friendly. The advantage isobvious: if the required contrast or fusion is achievedwith less laser energy, fewer decomposition productsare generated.

Recycling

All the laser-processable industrial plastics from Evo-nik listed here can be recycled without any problem.Sprues and unmarked moldings can be returneddirectly to the primary process as regrind. Only recy-cled materials from parts already marked should beused for a secondary application, due to their possiblediscoloration.

Quality

The High Performance Polymers Business Lineof Evonik is EN ISO 9001:2000 and ISO/TS16949:2002 certied, and therefore formallyrecognized as a reliable supplier.

Our products set high quality standards in the market.We offer you customized solutions specially tailoredto your requirements prole.

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Future Prospects

Wear resistance and protection against forgery areaspects that will promote the spread of laser-markingsystems. Whether for product liability or futurerecycling of nished parts, laser-inscribed quality-relevant or production data leave no doubt as to theorigin of a molding. Producer, production dates,machine numbers, and material batches can all beeasily recorded.

For very small part geometries, the compact datamatrix code (DMC) is the ideal solution; with theongoing miniaturization of components, this will

be the data code of the future. It encodes the data inthe matrix both horizontally and vertically, so thatthousands of items of information can be recorded onthe smallest surfaces. In addition it is possible to markdata in private mode, which can be read only with thecorrect access authorization.

The use of the laser-marking and data matrix codetechnologies on suitable materials from our productrange (see the tables on pages 40 to 42) allowsproduct identication with an extremely high degreeof security which practically eliminates the risk of

substitution errors.

Laser-welding of polymers is still a relatively new joi-ning technique. But in a number of sectors it is alreadywell on the way to replacing conventional joiningprocess such as ultrasound, vibration, mirror, and hot

gas welding, sealing technology, and adhesion.Compared with conventional methods, however,laser-welding currently involves signicantly higherinvestment costs.In medical engineering, a particle- and emission-freeworking environment is very important. Medicalsensors consist of components that are gettingincreasingly smaller, with complex joint geometries.The exibility and speed with which even compli-cated weld seams can be produced and high qualitystandards are the outstanding properties of the laser-welding process.

Similar observations apply for electrical engineering.Tiny housings for fully encapsulated miniature relaysand electronic components must be laser-weldedbecause only this method ensures clean processingwithout generating particles that interfere with themechanics or electronics.

In the automotive industry, headlamp and rear lampcasings are already being laser-welded. The partiallythree-dimensional geometries do not permit of anyother joining technique.

With the increasing use of plastics in automotive con-struction, new, fast, and exible joining techniquesare required that also meet the highest quality stan-dards. No other joining technique currently satisesthese requirements as well as laser-welding.

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Classes of Lasers

Laser devices are divided into classes depending on thebiological effects of the laser radiation. Specication ofthe limit values up to which no damage is expected isof major importance for nationally and internationallydened laser classes. In addition to the U.S. ANSI stan-dard, the International Commission on Non-IonizingRadiation Protection has published limit values in thespectral region between 400 and 1400 nm.

The limits are dened primarily in terms of thermalpower and non-ionizing radiation. Due to the opticalfocusing properties of the eye, the hazard increases

in the visible spectral range. In the invisible range,there is an adjacent region in which the eye is still wellfocused and transparent.

DIN EN 60825-1 ClassicationLasers are divided into equipment classes dependingon the hazard to humans. The DIN EN 60825-1 classi-cation is specied by the manufacturer. (The old DINVDI 0837 classication may no longer be used for newlasers.)

Laser Class Description

Laser Classes

Fig. 43: Laser safety classes as dened in DIN EN 60825-1

*) Note on laser classes 2 and 2M: Scientic studies (at the FH in Cologne) have shown that the blink reex (which occurs within0.25 s; longer exposure damages the eye) occurred in less than 20 percent of the test subjects. The existence of the blink reex forprotecting the eye should not therefore be taken for granted. If laser radiation of class 2 or 2M enters the eye, the eyes should bedeliberately closed or immediately averted. It must also be noted that the bl ink reex occurs only with visible light. Laser radiation inthe infrared range, for example, does not cause blinking because the radiation is not detected by the eye. Special care must thereforebe exercised with invisible laser radiation.

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Literature and Sources

Bundesamt fr Arbeitsschutz und Arbeitsmedizin(BAuA): BAuA-Broschre Damit nichts ins Augegeht... - Schutz vor Laserstrahlung, 1. Auage.Dortmund, 2006.BAuA-Forschungsbericht Fb 985 berprfungder Laserklassizierung unter Bercksichtigung desLidschlussreexes

Berufsgenossenschaft der Feinmechanik und Elektro-technik (BGFE):

Die neuen Laserklassen Laserklassen nach DIN EN60825-1Unfallverhtungsvorschrift Laserstrahlung(BGV B2/VBG 93)

Bayerisches Laserzentrum (BLZ), Erlangen

BASF: Technische Information fr Experten 02/00 Laserstrahlschweien von Kunststoffen im Durch-strahlverfahren, Broschre, 2000

Becker/Braun: Kunststoff Handbuch (1 Die Kunst-

stoffe; 3/4 Polyamide), Hanser Verlag

Carl BAASEL Lasertechnik GmbH & Co. KG, Starn-berg: Laser zum Beschriften, Schneiden, Schweien,Mikrostrukturieren und Perforieren

CERION GmbH, Minden: Lasersysteme fr die 3D-Laserinnengravur

Dietel, C.: Laserstrahlbeschriften von Kunststoffen -eine bersicht, Vortrag BLZ, Mnchen, 2006

Donges, A.: Physikalische Grundlagen der Lasertech-

nik. 2. Auage. Hthig, Heidelberg 2000

Franck, A.: Kunststoff-Kompendium, Vogel Buchver-lag, 6. Auage 2006

Fraunhofer Institut fr Lasertechnik (ILT), Aachen

Gebert K.; Hopfner M..; Laserschweien von Kunst-stoffen, SKZ Vortrag, Wrzburg, 2004

Hnsch, D.: Die optischen Eigenschaften vonPolymeren und ihre Bedeutung fr das Durchstrahl-schweien mit Diodenlaser, Dissertation, Aachen,2001

Hillmann, R.: Kunststoffbeschriften mit Lasern un-terschiedlicher Wellenlnge, Vortrag BLZ, Mnchen,2006

Hopfner M.: Laserschweien von Kunststoffen, Vor-trag Allod Werkstoff GmbH, Burgbernheim, 2004

Klein, M.: Laser Beam Welding of Plastics in MicroTechnology, Dissertation, Kln, 2001

Klein, R.M.: Bearbeitung von Polymerwerkstoffen

mit infraroter Laserstrahlung, Dissertation, Aachen,1990

Kneubhl, F.K., Sigrist, M.W.: Laser, 6. Auage.Teubner (Teubner Studienbcher Physik), Wiesba-den 2005

Korte, J.: Laserschweien von Thermoplasten,Dissertation, Paderborn, 1998

Leitfaden Laserstrahlung, Fachverband fr Strah-lenschutz e.V.

Liebscher, J.: Beidseitig gleichzeitiges Laserstrahl-schweien von groformatigen 3D-Luftfahrtstruktu-ren, Fraunhofer Institut fr Werkstoff- und Strahl-technik (IWS), Dresden, 2005

46


47/48

LPKF Laser & Electronics AG, Garbsen/Erlangen:Lasersysteme/-verfahren fr die Laser-Direktstruk-turierung, Laserschweisysteme

Meyers Lexikon online 2.0

N.N : Einugren beim Schweiprozess, VortragSKZ, Wrzburg, 2006

N.N : Grundlagen Laser, SKZ, Wrzburg, 2006

N.N : Grundlagen Laserkunststoffschweien,Vortrag SKZ, Wrzburg, 2006

N.N : Kunststoff-Fgeverfahren, Vortrag, Wrzburg,2006

N.N.: Lasertechnik CD-ROM mit Bildern zur Vorle-sung Lasertechnik 1 und 2, Lehrstuhl fr Lasertech-nik, RWTH Aachen, 1998

N.N: Grundlagen Laser-Kunststoffschweien,

Vortrag BLZ, Erlangen, 2006

N.N: Kunststoff-Fgeverfahren, Vortrag BLZ, Erlan-gen, 2006

Oberbach , K.: Saechtling Kunststofftaschenbuch,28. Auage, Hanser Verlag 2001

Psentrup R.; Stier T.; Werkstoffe fr das Laser-schweien, SKZ Vortrag, Wrzburg, 2004

Potente, H.; Fiegler, G.: Technische Aspekte desLaserschweiens von Kunststoffen, SKZ Seminar,

Wrzburg, 2004

Potente, H.; Heil, M; Korte, J.: Laserschweien vonThermoplasten, Plastverarbeiter 46 (1995) 9

Russek, Dr. U.A. (Huf Tools GmbH, Velbert): Para-meternderungen beim Laserdurchstrahlschweienvon Thermoplasten und deren Auswirkungen auf dieSchweinaht, Vortrag SKZ, Wrzburg, 2007

Schulz J-E.: Material, Process and ComponentInvestigations at Laser Beam Welding of Polymers,Dissertation, Aachen, 2002

Siefert, M.; Renner, T.: Laser-adapted construction

for plastic welding, Kunststoffe 2/2004, 2004

Siegman, A.E.: Lasers; University Science Books,Mill Valley/CA 1986

Struve, B.: Laser, Grundlagen, Komponenten, Tech-nik, 11. Auage, Verlag Technik, Berlin 2001

TREFFERT GmbH & Co.KG, Bingen: Masterbatcheund Compounds mit Laseradditiven

William T.: Silfvast: Laser Fundamentals, 2. Auage,

Cambridge University Press, Cambridge 2004

Wolff, W.: Permanently Mark Highly TransparentPlastics, Kunststoffe plast europe 09/2005

Wolff, W.: 3D Laser Subsurface Engraving, Kunst-stoffe plast europe 12/2005

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This information and all technical andother advice are based on Evonikspresent knowledge and experience.However, Evonik assumes no liabilityfor such information or advice, includingthe extent to which such information oradvice may relate to third party intellectualproperty rights. Evonik reserves theright to make any changes to informationor advice at any time, without prior orsubsequent notice. EVONIK DISCLAIMSALL REPRESENTATIONS ANDWARRANTIES, WHETHER EXPRESSOR IMPLIED, AND SHALL HAVE NOLIABILITY FOR, MERCHANTABILITYOF THE PRODUCT OR ITS FITNESSFOR A PARTICULAR PURPOSE(EVEN IF EVONIK IS AWARE OF SUCHPURPOSE), OR OTHERWISE. EVONIKSHALL NOT BE RESPONSIBLE FORCONSEQUENTIAL, INDIRECT ORINCIDENTAL DAMAGES (INCLUDING

LOSS OF PROFITS) OF ANY KIND.It is the customers sole responsibilityto arrange for inspection and testingof all products by qualified experts.Reference to trade names used by othercompanies is neither a recommendationnor an endorsement of the correspondingproduct, and does not imply that similarproducts could not be used.

(July 2011)

Contact Person

Rainer Gring+ -rainer. [email protected]

Evonik Industries AG

High Performance PolymersPaul-Baumann-Str. Marl/Germany

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