Hi Eric - have you investigated the use of an epoxy based non-reworkable 
underfill material? It has been my experience that trying to remove this 
family of materials results in ginormous damage. But - you will need to 
test to make sure you don't cause solder joint issues for the LQFP 
component with its use. Also note that there is no such thing as a "make 
it impossible to remove without damaging it" as given enough time and 
techniques, any material can be removed carefully enough to not cause 
damage as reverse engineering is a science, not an art.

Dave Hillman
Rockwell Collins
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From:   Eric Laroche <[log in to unmask]>
To:     <[log in to unmask]>
Date:   04/25/2013 07:48 AM
Subject:        [TN] tamper proofing electronic assembly
Sent by:        TechNet <[log in to unmask]>



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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