Conformal Coating VEWebinar2016 - Vision Engineering · Conformal Coating Customer Specification...

Register on line for the next webinar at http://www.visioneng.com/electronics-academy-webinar-series

Conformal Coating Inspection & Coating Faults

Bob Willis

Electronics Academy Webinar Presenter

Your Delegate Webinar Control Panel

Open and close your panelFull screen view

Submit text questionsduring or at the end

Welcome to the Vision EngineeringElectronics Academy Webinar whichwill start at 2.30pmUK Time


FREEElectronics Academy Webinar Series

The Electronics Academy Webinar Series takes an in‐depth look at the issuesaffecting PCB/SMT assembly and the challenges of achieving Zero DefectManufacture. Understand the common causes of solder joint failure and learn howto identify and rectify process defects – improving quality and reducing costs

Learn expert tips to identify quality issuesUnderstand the common causes of process failuresA convenient and quick way to update your skills

In the future have access to a video library of online training sessions

Electronics Academy Webinar Series

Crimp Connector Inspection & Quality ControlThursday 15th September 2.30pm

Printed Circuit Board Inspection & Quality ControlWednesday 12th October 2.30pm

Inspection of Conductive Adhesive JointsThursday 10th November 2.30pm

Future webinars may cover

Solder paste and stencil inspection

Component inspection and recognition

Microsection inspection

Inspection of underfill and staked components

Destructive solder joint assessment and inspection

Register on line at http://www.visioneng.com/electronics‐academy‐webinar‐series


Bob Willis

Bob Willis has been involved with the introduction and implementa tion of lead‐free process technology for the last sevenyears. He received A SOLDERTEC/Tin Technology Global Lead‐Free Award for his contribution to the industry, helpingimplementation of the technology. Bob has been a monthly contributor to Global SMT magazine for the last s ix years. He wasresponsible for co‐ordination and introduction of the Firs t series of hands‐on lead‐free tra ining workshops in Europe for

Cookson Electronics during 1999‐2001. These events were run in France, Italy and the UK and involved lead‐free theory,hands‐on paste printing, reflow, wave and hand soldering exercises. Each non commercia l event provided the firstopportunity for engineers to get f irs t hand experience in the use of lead‐free production processes and money ra ised fromthe events was presented to local charity. More recently he co‐ordina ted the SMART Group Lead‐Free Hands On Experienceat Nepcon E lectronics 2003. This gave the opportunity for over 150 engineers to process four different PCB solder f inishes,with two different lead‐free pastes through convection and vapour phase reflow. He a lso organised Lead‐Free Experience 2, 3

+ 4 in 2004‐2006.

He has also run training workshops with research groups like ITTF, SINTEF, NPL & IVF in Europe. Bob has organised and runthree lead‐free production lines a t interna tional exhibitions Productronica, Hanover Fair and Nepcon E lectronics in Germanyand England to provide an ins ight to the practical use of lead‐free soldering on BGA Ball Grid Array, CSP Chip Scale Package,

0210 chip and through hole intrusive ref low connectors. This resulted inmany technical papers being published in Germany,USA and the United Kingdom. Bob also defined the process and ass isted with the set‐up and running of the f irs t SimultaneousDouble Sided Lead‐Free Reflow process using tin/silver/copper for reflow of through hole and surface mount products.Bob also had the pleasure of contributing a small section to the first Lead‐F ree Soldering text book “Environment ‐ FriendlyElectronics: Lead‐Free Technology” written by Jennie Hwang in 2001. The section provided examples of the type of lead‐freedefects companies may experience in production. Further illus trations of lead‐free joints have been featured in here most

recent publication “Implementing Lead‐Free Electronics” 2005. He has helped produce booklets on x‐ray inspection and lead‐free defects with DAGE Industries, Balver Zinn and SMART Group

Mr Willis led the SMART Group Lead‐Free Miss ion to Japan and with this team produced a report and organised severalconference presentations on their f indings. The miss ion was supported by the DTI and vis ited many companies in Japan as

well as presenting a seminar in Tokyo at the British Embassy to over 60 technologists and seniormanagers of many of Japansleading producers. Bob was respons ible for the Lead‐F ree Assembly & Soldering "CookBook" CD‐ROM concept in 1999, theworld’s firs t interactive training resource. He implemented the concept and produced the interactive CD in partnership withthe National Physical Laboratory (NPL), drawing on the many resources available in the industry including valuable work fromNPL and the DTI. This incorporated many interviews with leading engineers involved with lead‐free research and processintroduction; the CD‐ROM is now in its 3rd edition.

Find out more at:[email protected]

Bob Willis currently operates a training and consultancy business based in England. Bob is a member of the SMART Technical Committee.Although a specialist for companies implementing Surface Mount Technology Mr Willis provides training and consultancy in most areas ofelectronic manufacture. He has worked with the GEC Technical Directorate as Surface Mount Co-Coordinator for both the Marconi and GECgroup of companies and prior to that he was Senior Process Control Engineer with Marconi Communication Systems, where he had workedsince his apprenticeship. Following his time with GEC he became Technical Director of an electronics contract manufacturing companywhere he formed a successful training and consultancy division.

As a process engineer, he was involved in all aspects of electronic production and assembly involved in setting up production processes andevaluating materials; this also involved obtaining company approval on a wide range of Marconi's processes and products including printedcircuit board manufacture. During the period with Marconi, experience was gained in methods and equipment for environmental testing ofcomponents, printed boards and assemblies with an interest developed in many areas of defect analysis. Over the last 15 years he hasbeen involved in all aspects of surface mounted assembly, both at production and quality level and during that time has been involved intraining staff and other engineers in many aspects of modern production.

Over the past few years Mr. Willis has travelled in the United States, Japan, China, New Zealand, Australia and the Far East looking atareas of electronics and lecturing on electronic assembly. Mr. Willis was presented with the Paul Eisler award by the IMF (Institute of MetalFinishing) for the best technical paper during their technical programmes. He has conducted SMT Training programs for Texas Instrumentsand is currently course leader for Reflow and Wave Soldering Workshops in the United Kingdom. Mr Willis is an IEE Registered Trainer andhas been responsible for training courses run by the PCIF originally one of Europe's largest printed circuit associations. Bob has conductedworkshops with all the major organisations and exhibition organisers World Wide and is known for being an entertaining presenter and theonly presenter to use unique process video clips during his workshops to demonstrate each point made. Bob has written two book which arefree to download on line, Design & Assembly with Pin In Hole Intrusive Reflow & Package On Package Design, Assembly andInspection

Mr. Willis was Chairman of the SMART Group, European Surface Mount Trade Association from 1990-94 and has been elected HonoraryLife President and currently holds the position of SMART Group Technical Director, he also works on BSI Standards Working Parties. He isa Fellow of the Insti tute Circuit Technology, an NVQ Assessor, Member of the Institute of Quality Assurance and Society of EnvironmentalTest Engineers. Bob Willis currently writes regular features for AMT Ireland, Asian Electronics Engineer and Circuits Assembly the USmagazine. He also is responsible for writing each of the SMART Group Charity Technology reports, which are sold in Europe and Americaby the SMTA to raise money for worthy causes. Bob ran the SMART Group PPM Monitoring Project in the United Kingdom supported by theDepartment of Trade and Industry. He was coordinator of the LEADOUT Project for SMART Group. LEADOUT was one of the largest EUfunded projects, currently he is coordinating European projects TestPEP, uBGA and ChipCheck

In September 2015 Bob voted the Best Speaker at SMTA International Conference in Chicago

Find out more at:[email protected]


What is a Conformal Coating?

IPC says ……………………………

Conformal coating is defined as a thin, transparent, polymeric coating that is applied to the surface of a printed

circuit assembly to provide protection from the end-use environment. Typical coating thickness ranges from 12.5um

(0.49mil) to 200um (7.9mil).


Coating Material Options

Reference from IPC 830

Coating Material Type Designation Thicknessum

ThicknessThou

Acrylic resin AR 30-130 1-5

Polyurethane resin UR 30-130 1-5

Epoxy resin ER 30-130 1-5

Silicon resin SR 50-210 2-8

Fluorocarbon resin FC 25-125 1-5

Paraxylylene (Parylene) XY 10-50 0.5-2

Books and SpecificationsIPC HDBK 830IPC 830CMIL-I-46058DEF STD 59/47IEC 61086NASA 8739-1

Gen3Systems coating guide www.gen3systems.com

HumiSeal booklets www.humiseal.comIntroduction to conformal coatingsSelection criteria for the use of conformal coatings


Books and Specifications

Conformal Coatings for Electronics Applications

Author Manfred Suppa

Published by Werner Peters

Conformal Coating Application



Video clip from interactiv e training CD-ROM and hands on training w orkshop






Vacuum Deposition

Coating service offered by Para Tech Coating & SCH in Europe


Vacuum Deposition

Parylene coating does not normally have a UV trace to aid inspection but this is now availbale fromsome suppliers. The images above show with and without a UV inspection source. This is a benefit asmany people including your instructor finds it difficult to see the coating unless as test strip or spot isadded on a waste area of the board

Vacuum Deposition


Conformal Coating Process Steps

Clean the board assembly ?Mask selected areas

Coat one side of the assemblyAllow board to dry or flip the assembly

Coat side two of the assembly

Possible inspection and touch-up stepHold board assembly, pre-cure or solvent flash off

Cure assemblyFinal Inspection

Examples of dip, brush and spray coating coverage during inspection

Manual Optical Inspection



Examples of dip, brush and spray coating coverage during inspection

Coated Printed Boards – Where & How?

Work instructions should state where the conformal coating should be applied to the surface of theboard. It should also state where the coating should not be applied. There may also be some specificareas coating could be which does not impact the quality of the product

BGA

+

BGA

CSP

CSP


Conformal Coating Customer Specification

A.3 Conformal Coating

The areas around the crystal oscillator and the battery-backup circuit on the TCP/IP Development Board have had the Dow Corning silicone-based 1-2620 conformal coating applied. The conformally coated areas are shown in Figure A-3. The conformal coating protects these high-impedance circuitsfrom the effects of moisture and contamination

Figure A-3. TCP/IP Development Board Areas Receiv ing Conformal Coating

Any components in the conformally coated area may be replaced using standard soldering procedures for surface-mounted components. A newconformal coating should then be applied to offer continuing protection against the effects of moisture and contaminants. For more information onconformal coatings, refer to Technical Note 303, Conformal Coatings

Reference www.rabbit.com

Inspection & Quality ControlInspect sample boards under UV lighting for completecoating coverage. Check areas of the board after removal ofany masking for any local lifting or contamination. Thecoating should be compared with any work instructions,alternatively a golden coated board assembly should beavailable for reference



1K


Simple hand held UV light source for sample inspection away from a dedicated inspection area. Typicalinspection system for coated boards with built in UV light source supplied by Vision Engineering


Automated Inspection under UV

Example of coating inspection results from YESTech showing small area of delamination/peelingfrom the printed circuit board surface. Other AOI suppliers are offering this type of capability

Webinar Survey Questions

What conformal coating do you use?

What is your main reason for coating?

What is your most common coating problem?


Coating Inspection References

Coating Cracking

Poor Adhesion Cracking

Bubbles/FisheyesCoating Drain/Build Up

ContaminationBubbles Gassing

Coating Inspection References

Coating Measling Coating ContaminationExcess Thickness & Bubbles

Coating Flaking from SurfaceCoating Dewetting Coating Contamination


IPC 610F Inspection Criteria

IPC 610F Inspection Criteria


NASA STD 8739 Visual Criteria

NASA STD 8739 Visual Criteria


Available to download online search for NASA Workmanship Standard

Inspection & Quality ControlSimple process control checks can be a valuable tool duringconformal coating. Check the wet coating thickness on thesurface of the board after application

Using a wet depth gauge check the coating in two or threeareas on a sample board. Ideally check more than onesample in the batch. Record the reading, location, materialand process parameters for future reference


Coating Thickness Assessment

Placing the gauge on the surface of the board will indicate the thickness of the coating based on the coatingcontacting the measurement surfaces and a visual inspection under UV light. Example images taken by thepresenter during a workshop at Henkel Technologies. Remember that there will be little marks in the coatingleft so make sure inspection are aware of this to avoid unnecessary rejects

Coating Thickness Assessment

Coating thickness measuring equipment available at www.conformalcoating.co.uk

0.007”


The surface of a solder mask does have an impact on successfulapplication and cure. Many coating suppliers recommend a minimumsurface energy around 35.0 dyne/cm

Assembly processes may change the surface energy and cause thecoating to have poor adhesion or poor wetting during application andcure. It is very uncommon for customer specifications to quote soldermask types of surface energy reading, unless they have had aproblem in the past. Please discuss this point with your supplier,there are other surface mount related benefits of havingconsistent solder mask coatings

Assessment of the PCB Surface

Assessment of the PCB Surface

Surface of the printed board may impact the conformal coating adhesion. Methods of test todetermine the surface tension include surface energy measurement, dye pens and sessile drop test


Adhesion Testing (Tape Test)

Tape testing is all about the bond to the base material, normally solder mask and not necessarily a test of the coatingmaterial’s performance.Differentsolder masks formulation may give varying results ASTM D3359

Adhesion Testing (Tape Test)

Special hand tool supplied by Sheenhas 6 blades with 1mm separationreference number tool 750/1


Cleanliness Monitoring

0.1 ug/cm2


0.1 ug/cm2



0.5 ug/cm2


1.1 ug/cm2

1 – 1.5ug/cm2 of equivalent sodium salt solution


Material Viscosity Control

Control of materials using ZAHN viscosity flow cups. The cup is immersed into the coating and then withdrawn, the time taken for the fluid to drain through the hole in the bottom of the cup is then timed to establish the viscosity and the need forsolvent additions.

Colour change of the coating could be used as a reference for the coating ageing in the tank

Material Viscosity Control

All material suppliers will provide instructions on the procedure to be used for test and the toleranceand corrective action to change the solids content of the coating material


Inspection & Quality ControlCoating a blank test board prior to running production orusing a proprietary matrix test card is the best way ofchecking spray process parameters are consistent. The testboard or card can be inspected with a UV light for coatingdefinition, overspray or coating runs.

Process parameters like solids content, temperature, nozzletype, nozzle speed, height and pressure should be recordedfor reference or checked against the work instructions

Inspection of Coatings & Methods

Test sheets are used when setting up a spray/dispense application system provided by Nordson. After machine setup thedefinition of the coating, width of the coating and any drips can easily be seen under UV light. Example images taken by thepresenter during a conformal coating workshop atHenkel Technologies


Inspection of Coatings & Methods

Inspection & Quality ControlMeasuring the dry coating can be performed on a test labelapplied to the surface of a board prior to coating. Thethickness of the dry label can be recorded, subtracting thethickness of the label provides the coating thickness in thatlocation. The label can be retained for future reference andis ideal for engineers to review during process audits.

Digital thickness measuring systems are available for loggingdata for SPC. Alternatively optical microscopes with ameasuring capability can be used on dry deposits


Calibration of Measurement System

Inspection & Quality Control

Labels used for coating thickness checks after curing.The labels provide a reference to the coating thickness.The heightof the coating to the surface of the solder mask could be measured after the label is removed again leaving a reference

Removable labels


Thickness Measurement of Parylene

Spectrometer Sample film & print out

Video clips from hands on workshops run at Speedline Technology in Reading

Detailed Microsection Inspection

Example joints and component after coating without cleaning, the roughly prepared microsectionshows a coating thickness of around 30um. Normally the coating would be between 15-30um


Coating Thickness with Microsection Assessment

Microsections after coating board assemblies showing the coating thickness variation

Inspection & Quality ControlWith care sample coated boards can be examined quickly aftercoating using a UV light on a conveyor and touched up. Care needsto be taken to avoid contamination and disturbance of the coating.Surface contamination with hairs, fibres or other particulate can be aproblem with a delay before curing


Drying Oven/Cabinet/Enclosure

The majority of conformal coatings have a hold time associated as part of the process prior to curing at an elevatedtemperature. This allows solvent to flash off/evaporate from the coating and prevent skinning on the surface and voids in thecoating. The hold time is dependent on the coating and the thickness of that coating. Having a dedicated cabinet is goodpractice as it allows some extraction and reduces surface contamination prior to drying

UV cure materials normally do not have a hold associated with a standard process

Inspection & Quality ControlWhen coated boards are cured in a convection or IR oventhe temperature profile must be established based on thematerial supplier’s recommendations. The profile must alsobe considered in relation to the coating thickness.

Temperature profiling procedures should follow thetechniques used for reflow soldering with the correctattachment of thermocouples. Attempts to speed up thecuring process is a common causes of failure


Conformal Coating Temperature Profile

Temperature Profiling for Curing

Examples of coated boards after coating cure, also examples with too faster cure cycle welloutside of the supplier recommendations for the ideal profile


Drying Oven/Cabinet/EnclosureExamples of bubbles in a coating betweenterminations or pads and leads. The bubblesdo burst if they reach the surface before thecoating cures

Alternative industry criteria for these bubblescould be based on the size of the bubbleand visible coating of the leads between thebubble. The minimum coating thickness forthe product must visible on the leads

Conformal Coating UV Inline Cure

In line curing systems can use a mesh belt or pin transfer systems depending on the type of coatingmethod and materials used in the production process. The UV system should be regularly checked forthe lamp performance with a UV light profiler as the output from the lamps will change over time. Therelative output in selected positions on inline or batch systems should be checked and mapped


Inspection & Quality ControlProducing a coated reference sample with each batch of boards wasin the passed required under certain contracts, it is possible but verycostly. In the US this is sometimes referred to as a witness sample.

An alternative, where boards are produced as a panel the wasteareas of could be retained as a reference, provided they arerepresentative of production

Guide to Conformal Coating & Cleaning Defects

Free to download from the SMART Group www.smartgroup.org


Electronics Academy Webinar Series

Crimp Connector Inspection & Quality ControlThursday 15th September 2.30pm

Printed Circuit Board Inspection & Quality ControlWednesday 12th October 2.30pm

Inspection of Conductive Adhesive JointsThursday 10th November 2.30pm

Future webinars may cover

Solder paste and stencil inspection

Component inspection and recognition

Microsection inspection

Inspection of underfill and staked components

Destructive solder joint assessment and inspection

Register on line at http://www.visioneng.com/electronics‐academy‐webinar‐series

Conformal Coating VEWebinar2016 - Vision Engineering · Conformal Coating Customer Specification...

Documents

Transcript of Conformal Coating VEWebinar2016 - Vision Engineering · Conformal Coating Customer Specification...