We are seeing problems with water getting into our hybrid ICs during
aqueous cleaning.  The substrate is made of alumina as well as the lid.
The substrate is 1.5 in. square.  The lid is 1.45 in square with a wall
thickness of .050 in and height of .105 in. At first we used Kyocera NC0150
B stage epoxy to attach the lid to the substrate.  What we found was cracks
in the epoxy.  We then tried RJR poly RJ4B, but failed because of leakage
problems during the leakage test (submerge the part in a liquid and look
for gas bubbles). We then tried RJ9F epoxy which started to have fine gas
bubbles all around the seal after 30 seconds.

     We started seeing problems with our Hybrid ICs shorting out internally
due to water getting into them during aqueous cleaning.  What we found is
that if we hand solder the parts on the board and then send the parts
through the aqueous cleaner (Westek Inline Triton IV ) the parts are fine.
If we sent the parts through a convection reflow process ( Heller 1500SN) ,
wait until the the board has cooled down, typically 5-10 min., then send
the parts through the aqueous cleaner we have leakage problems.  These
parts are fine pitch devices and hand soldering them is very time
consuming!  The parts are mountied on a .092, FR4 PCB approx. 12 in X 18
in. with surface mount and through hole connectors (paste-in-hole).

Does anyone have any ideas on the problem may be or a possible solution?
We would like to call out a leakage spec. for the part but I,m not sure
what the spec. needs to be to go through convection reflow and aqueous
cleaning, any ideas?  I would welcome any comments.  Thank you in advance.

Michael Forrester
LeCroy Corp.
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