Conformal Coating Inspection Technical Bulletin Mar 09

     

 

Technical Bulletin Mar 09 Conformal Coating Inspection  

In the process of conformal coating, one of the most critical areas is conformal coating inspection. There are several purposes for coating inspection including the assessment of the conformal coating quality applied to the PCB. This assessment is measured against standards, whether internal, national or international, and the criteria defined in the standards of what is acceptable and unacceptable, ultimately help determine the long term reliability of the circuit board.

Conformal Coating Inspection and the International Standards With standards it’s important to distinguish between application and selection of coating, and qualification and manufacture of coating. Generally, the first is for the user of the conformal coating in production and the second is for the manufacturer of the conformal coating. The Interconnections & Packaging Conference (IPC) standards are very good for both these areas and their details can be found on www.ipc.org . For manufacturing conformal coating the standard IPC-CC-830B details the manufacturer’s requirements to self-certify the quality of their product. In the case of production the IPC A -610 standard is an ideal starting point. The IPC-A-610 gives some minor references which are of limited help except for specifying acceptance criteria. This standard also is a self-regulatory document.

IPC A 610 Acceptance Standards Summary Class 1, 2, 3 • Completely cured and homogeneous • Coating only in those areas where coating is required • Loss of adhesion adjacent to masking • No bridging of adjacent lands or conductive surfaces from: 1. loss of adhesion 2. voids or bubbles 3. de-wetting 4. cracks 5. ripples 6. fisheyes or orange peel • Foreign material does not violate minimum electrical clearance between components, lands or conductive surfaces • Coating is thin but still coats component / device edges These Acceptance criteria are taken from the IPC-A-610 standard. The references the IPC standard makes to the defects can be checked against the recent technical bulletins and FAQs on Conformal Coating Failure Mechanisms contained on the SCH website.

A conformal coated PCB under UVA ultraviolet light to aid inspection SCH Technologies is a Trading Name of SCH Services Limited  Newburgh Building, McLintock Way, Barnsley, South Yorkshire. S70 6BF    Tel: +44 (0)1226 297711 Fax: +44 (0)1226 297733  www.conformalcoating.co.uk 

Using these two information sources, this enables the acceptance criteria to be drawn up and a work instruction produced for conformal coating inspection.  

SCH Technologies are ISO9001 and ISO14001 certified

        IPC A  610 Defects Standards Summary Defect - Class 1, 2, 3

Automated Conformal Coating Inspection  

• Coating is not cured (exhibits tackiness) • Coating is not applied to required areas

It is now possible to automate the inspection process with the ACCIS Automated Conformal Coating Inspection System.

• Coating is on areas required to be free of coating • Any bridging of adjacent lands or conductive surfaces from: 7. loss of adhesion (mealing) 8. voids or bubbles 9. de-wetting 10. cracks 11. ripples 12. fisheyes or orange peel • Any foreign material that bridges lands or adjacent conductive surfaces, exposes circuitry or violates minimal electrical clearance between components, lands or conductive surfaces • Discolouration or loss of transparency • Coating wicking into connector housing

The ACCIS, developed by SCH, eliminates many of the problems associated with conformal coating inspection including • • • •

Operator error due to manual process Different standards between operators Time consuming process No traceable recording of inspection

Contact SCH for details or check the website.

• Coating wicking into mating surfaces These Acceptance criteria are taken from the IPCA-610 standard.

SCH Technologies offer

Mil-I-46058C

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Conformal coating Subcontract Services

Another standard often mentioned is Mil-I-46058C which is an old military standard from which the IPC committee developed the IPC-CC-830 standard and is related to materials.

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Global supply of Conformal Coating Application Equipment

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Humiseal Conformal Coatings

This standard is relevant where the conformal coating material must be qualified for military approval and placed on a Qualified Product List (QPL) which is constantly updated.

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Conformal Coating Training courses Consultation & troubleshooting PLEASE CHECK OUR WEBSITE FOR DETAILS

www.conformalcoating.co.uk

Future Bulletins •

Automated Conformal coating inspection. How effective is it?

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Conformal coating CTI (Comparative Tracking Index).

SCH Technologies is a Trading Name of SCH Services Limited  Newburgh Building, McLintock Way, Barnsley, South Yorkshire. S70 6BF    Tel: +44 (0)1226 297711 Fax: +44 (0)1226 297733  www.conformalcoating.co.uk 

SCH Technologies are ISO9001 and ISO14001 certified