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Conformal Coat Quality issues

Conformal Coat Quality issues. Update of November 3, 2004. Thorough Visual Inspection Done. Have done a very careful inspection of about 300 boards. Virtually all have some problems. All are documented in a spreadsheet

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Conformal Coat Quality issues

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  1. Conformal Coat Quality issues Update of November 3, 2004

  2. Thorough Visual Inspection Done • Have done a very careful inspection of about 300 boards. Virtually all have some problems. All are documented in a spreadsheet • About 50 have virtually no CC on the sides of many components. Most have no CC near the encapsulant including on a few solder pads. • Most have CC lifting on the top or sides of some components. Locations are documented. • A few have a visible contaminant. • A few have small gold nodules in the grounding screw holes. • A few have CC problems near the screw holes • Many have CC in the connectors.

  3. Plans to fix production problems • Production at Teledyne is shut down while process changes are devised to reduce these problems on future boards. • Not the topic of this meeting, but • Will spray CC from multiple directions • Consider adding cleaning steps so CC will bond better • Learn to mask the connectors better

  4. Lifting Tests • Have thermal cycled 5 board 200 times. Lifting did not get worse. • Have vacuum cycled 4 boards 3 times. Lifting did not get worse. (See separate report).

  5. Proposed Action Plan • no CC on the sides of many components and near the encapsulant. • Fix by cleaning and applying coating with a brush. • CC lifting. • Leave as is • Visible contaminant. • Judge by size and location whether to leave or remove and recoat • A few have small gold nodules in the grounding screw holes. • Fix by scraping off. This will leave a non-gold plated spot in the hole, but it is the head of the screw that makes the electrical contact. • A few have CC problems near the screw holes • Fix because they are few and it is easy. • Many have CC in the connectors. • Fix by carefully removing loose CC.

  6. CC lifting risk analysis • Vacuum and thermal tests indicate it won’t get worse. • Purpose of CC is to keep conductive contaminants from shorting between 2 metal things. It will do this even though it has lifted a bit. • Using tweezers to remove CC from these tiny components and then recoating them is more likely to cause a problem than fix a problem.

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