Horiba Instruments (S) Pte Ltd

Content

Introduction

Important instrumental considerations

Applications

Measurement process

Static light scattering

Introduction

Static light scattering (SLS) or more commonly known as laser scattering/diffraction is used for the size determination of micron to submicron particles. The laser diffraction technique for the determination of particle size distribution is based on the phenomenon that particles scatter light in all directions with an intensity pattern that is dependent on particle size (and shape).

Introduction

• Analytical range generally from 10 nm to a few mm

• Powders, suspensions, emulsions, creams and pastes are possible

• Dry and wet measurement systems are available

• Possible to have de-agglomeration mechanism in dry and wet systems

• The whole measurement process can be completed in < 1 minute

• Uses Mie theory (needs refractive index) or Fraunhofer approximation (no need refractive index)

• Equivalent spherical diameter is obtained

• Volume based distribution

• ISO 13320:2009 Particle size analysis – Laser diffraction methods

Static light scattering

Requirements

Assumptions

Characteristics

Theory

Characteristics

• Particles suspended in a fluid • RI difference between particle and fluid

• Large particle • Small/low angle scattering

• Large signal/intensity

• Small particle • Big/high angle scattering

• Small signal/intensity

• Scattering pattern • Symmetrical on the axis of incident light

• Light wavelength dependent

• Particle size dependent

• Particle shape dependent

Characteristics

The figure below shows the effect of size on the scattering pattern detected at different angles. Note that the scattering intensity at the front of a particle (close to 0 degree) is always the highest and bigger particle scatters more intensely as compared to a smaller one.

Characteristics

Characteristics

Why you need two light sources of different wavelengths?

Theory

• Mie • Rigorous solution valid for all sizes of spherical particles

• Requires optical propety (RI) to be known for both sample and dispersant

• Fraunhofer • Approximation for large particles (~> 50 micron) or

opaque particles

• Optical property (RI) is not necessary

• Limited to forward (low angle) scattering

Theory

“Big particle”

Theory

“Small particle”

Assumptions

All particles are spherical and optically homogeneous.

If particles are not spherical, then the scattering pattern obtained is used to calculate the equivalent spherical diameter for the particles.

Requirements

1. Sample dispersion in a fluid (liquid or air) is necessary.

2. Sample cannot dissolve or react with the fluid it is dispersed in.

3. There must be a difference in refractive index of the sample and the fluid.

4. Particle concentration cannot be too high (multiple scattering) or low (low signal).

5. Refractive index of the sample and fluid should be known, especially for small particles.

Requirements

Information obtained from ISO 13320:2009 Reflected

Refracted

Absorbed and

Reradiated

Diffracted

Real Index (degree of refraction) Imaginary Index (absorption of light within particle)

Requirements

Information obtained from ISO 13320:2009

Requirements

Information obtained from ISO 13320:2009

Measurement process

Static/laser light scattering measurement process

• Sample is dispersed in a fluid (liquid or air) in a cell

• Monochromatic light source(s) illuminate(s) the cell

• The light scattered by the particles, at various angles, is measured by multi-element detectors

• The scattering pattern is used to calculate the particle size distribution

Measurement process

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Important instrumental considerations

1. Light source Number of light source(s) (2 is optimal)

Wavelength(s) (Long & short)

State of technology (solid state vs gas laser)

2. Detection system Number of detectors (> is better but not necessary best)

Detector angular coverage (> is better)

3. Sampling mechanism Circulation system (centrifugal vs peristaltic)

Dispersion system (ultrasonic probe vs bath)

4. Performance specifications Accuracy (compared to traceable standard)

Repeatability (< is better)

Important instrumental considerations

5. Maintenance requirements Cell removable mechanism

Pumping tubing replacement (?)

Important instrumental considerations

Images are obtained from the internet and are copyright of respective owners

Important instrumental considerations

Scattering patterns

for 0.05 and 0.07

micron particles with

650 nm laser and 405

nm LED

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180 o

270 o

Important instrumental considerations

Images obtained from the internet.

Important instrumental considerations

Images obtained from the Cole Parmer website

Important instrumental considerations

Important instrumental considerations

Applications

CMP slurry

Pigment ink

CMP slurry

What is a CMP process?

CMP or chemical mechanical planarization is a process used by semiconductor manufacturers to make wafers flat and smooth using specially formulated abrasive suspensions

http://www.horiba.com/semiconductor/products/processes/semicond

uctor-process/cmp-process/

CMP slurry

http://www.horiba.com/scientific/products/particle-characterization/applications/cmp/ Images from https://www.crystec.com/alpovere.htm

CMP slurry

What is a CMP slurry?

CMP slurry is a special chemical formulation that has abrasive particles with a specific (narrow) size range and pH value. The abrasive particles can be silica, alumina, ceria, titania, diamond, etc.

A silica CMP slurry normally has a high pH value that has a certain weight % of silica abrasives. The alkaline solution helps to soften/etch the silicon wafer surface while the abrasive particles remove material from the surface through mechanical action.

CMP slurry

An example of a silica CMP slurry

http://www.fujimico.com/catalog/Chemical%20Mechanical%20Planarization/33

CMP slurry

A certain CMP slurry particle size specification

CMP slurry

Particle size measurements needed by:

CMP slurry producers to control their product quality

End users to confirm specification before use and periodic check to ensure consistent performance

CMP slurry

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Silica CMP slurry

CMP slurry

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Diamond CMP slurry

Pigment ink

What are pigments?

Industrially, a pigment is any finely divided insoluble black, white or colored solid material, a major function of which is to improve the appearance of or give color to the medium in which it is to be used.

Image and information obtained from BASF website: https://www.dispersions-

pigments.basf.com/portal/basf/ien/dt.jsp?setCursor=1_561069

Pigment ink

Table obtained from BASF website: https://www.dispersions-

pigments.basf.com/portal/basf/ien/dt.jsp?setCursor=1_561069

Types of pigments

Pigment ink

What are pigment inks?

Pigment inks are complex liquid dispersions of pigments, binding agent and additives. A binding agent is normally a plastic resin. Additives commonly consist of anti-foam, waxes, extenders, pH-controllers and surfactants. Pigment inks can be solvent based or aqueous based.

Pigment ink

Why do you need to know particle size and distribution for pigment inks?

Pigment ink

Particle size and distribution for pigment inks

Pigment ink

C I pigment blue 15

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Pigment ink

C I pigment blue 15:3

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Danke

Gracias

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