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Thu, 9 Oct 1997 03:28:07 -0500 |
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Address,
I have a recent lot (100 pieces) of assemblies with enough warp in the
longest edge to keep the assembly from plugging into the backplane.
As a flag, the warp should have been caught by operators following
Wave, but was not. I have a solution to ensure future assemblies are
not affected. I am also in the process of modifying the Wave fixture
for low mass assemblies and the Wave Process Flow Procedures.
There are three options I have come up with to (temporarily) fix the
warp problem, such that the field engineers can insert the assemblies.
OPTIONS:
1. Bake assemblies in oven at X temperature for X time with applied
weight; or
2. With the modified wave fixture, which ensures rigid stability in
all regions, re-solder assemblies via wave soldering; or
3. Run assemblies through the Convection Reflow Oven at X temp for X
time with the modified fixture holding the assembly in place
I have opted to go with Option 3 and would like to hear others
experience(s) or any other avenues of thought. I am thinking the
assemblies shall be run at a maximum of 220°C for 55secs max. (ramp up
temp/time is not included) at 1.12cm/sec using a Heller 1500 Reflow
Oven. My insanity is to bring the fab temperature as close to the
fabs Tg to minimize if not eliminate any Warp Memory. Granted, this
is another thermal excursion, but lets approach as if there are no
alternatives and components can withstand.
Thank you
John Gulley
Inet Inc.
Plano, TX 75075
972-578-3928
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