Bryan,

It may be that you have some silicone liberating from under the heatsinks. This could be from any buffer compound or adhesive in use.

As you will know, nothing will stick to silicone and your problem may be even a mono-molecular layer over the surface of the assembly.

This could also explain why thermal cycling makes it worse, as even more is being liberated.

If you could please get me your mailing address, I will send you some more info for help.

Regards,
Graham Naisbitt

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  ----- Original Message ----- 
  From: Bryan Kerr 
  To: [log in to unmask] 
  Sent: Wednesday, July 07, 1999 9:39 PM
  Subject: [TN] Conformal Coating


  Hi all,
  Any experiences with Humiseal 1B73. I'm finding it tends to pull away easily from a solder resist surface, particularly on boards with heatsinks, along the edge of the heatsink profile. Thermal cycling makes it much worse. Any similar problems out there ?

  Bryan