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Conformal Coating



Conformal Coating | 12 December, 2002


Does anyone have any bright ideas with regards to masking a PLCC socket with via holes directly below the socket, prior to conformal coating ? We've tryed kapton tape and peelable masks but not with desirable results. Our coating process is a two dip process using an acrylic based coating.Any info would be appreciated .


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Conformal Coating | 13 December, 2002

Bright ideas??? Bright ideas!!! I got bright ideas. In order of decreasing luminosity: * Stop installing the socket, solder the PLCC to the board, dip the board. The socket is a waste of time and money. You never replace the PLCC in the field, anyhow. Even if you do, it�s not because the PLCC is bad, it�s because the socket / PLCC interconnect has degraded. * Keep the socket, insert the PLCC, dip the board. That will help keep the socket / PLCC interconnect from degrading. * Keep the socket, insert the PLCC, don�t dip the board. The socket / PLCC is probably your greatest source of environmental problems. So, protecting everything but the main problem is a waste of time and money. * Use rubber boots to cover the socket during coating. Source of ESD boots: Caplugs Protective Industries LLC 2150 Elmwood Ave Buffalo, NY 888-227-5847

Sorry. I know of only one source for ESD protected boots. Other reputable sources of boots that may be ESD protected are: * Kinnarney Rubber 450 Main St PO Box 37 Mantua, NJ 08051 856-468-1320 FAX 7438

* Dempsey Industries 802 N. 4th St Miamisburg, OH 45342 (937)-866-2345 Gary Pascoe * Shercon somewhere in CA * Harman 360 South St. Rochester, MI 810-651-4477 * StockCap St Louis MO 800-827-CAPS (2277) * MOCAP Plastic Products Group 10964 Lin-Valle Drive, St. Louis, MO 63123 800-633-6775 314-845-3100 Fax 487-8855

�IPC-HDBK-830, Guidelines for Design, Selection and Application of Conformal Coatings� says words to the effect of: A conformal coating may have several functions depending on the type of application. The most common are: * Inhibit current leakage and short circuit due to humidity and contamination from service environment. * Inhibit corrosion. * Improve fatigue life of solder joints to leadless packages. * Inhibit arcing, corona and St. Elmo�s Fire. * Provide mechanical support for small parts that cannot be secured by mechanical means, to prevent damages due to mechanical shock and vibration.

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Conformal Coating | 13 December, 2002


Sounds like a tough problem with those holes underneath.

I guess a tight fitted cap that can stand the process is the best idea. DaveF gave you more than a few sources for that alternative. They always send these samples in the mail to me. You are probably going to have to play with a few different cap designs to get a tight seal for each and every socket.

I am not sure if a modified dummy PLCC might also help to keep the contacts cleaner. Maybe a dual approach of a dummy and a cap.

I did think about dissolvable or popable potting type compounds to create a seal, yet that seems too exotic and more time consuming to design.

Good Luck

YiE, MA/NY DDave

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