Alcohol clean, plasma clean with an aggressive cycle, dam around the part with removeable mask, dry by baking for 24 hours at 80C, then fill the area with a globtop or other die encapsulant.  We have excellent results with Hysol FP4470, but that has a large lot size associated with it.  FP4650   is available in small quantities, but is slightly more viscous, so we haven't tried it because we have some very high resolution features.  Probably would work for you though.

http://bondingsource.com/products-services/epoxy-quick-fact-sheet

http://www.bondingsource.com/techdata/Loctite-FP%204650.pdf

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Laroche
Sent: Thursday, April 25, 2013 8:47 AM
To: [log in to unmask]
Subject: [TN] tamper proofing electronic assembly

Good morning,

One of our customer has requested, for security purposes, that we assemble their board in such a way to make the removal of the microprocessor impossible without damaging it.  The component is a 64 pin LQFP.  The design is already completed and this requirement came afterwards.

Our approach so far has been to add a material over the part and on the leads prior to conformal coating.  All the materials we have used to this point have been peeled away when heating the component.

Is this something that some of you have been requested before?  How have you managed to do this?

thanks for your feedback,

Eric



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