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Tue, 2 May 2000 16:55:48 -0400 |
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Hello Technetters:
I've gone from the WS6536 100% world to IPC's 50% hole fill requirement.
Unfortunately, I have a .150" thick pcb (G10, with many layers of ground) that
must be waved in a selective soldering fixture, that is averaging about 33-50%
hole fill.
The customer is looking at the 50% hole fill spec, and touching up to meet this
requirement (also, they are touching up from the topside and cosmetically
getting 100% hole fill to make them feel happy).
To achieve the current hole fill, my topside temperature leaving the preheaters
is 270F and the bottom-side portions of the board that are exposed to the
preheaters and wave are at 320F (my normal range and that recommended by the OA
flux manufacturer is 180-220F topside).
Also, the speed is 60cm/min (2 f/m), which on my machine equals about a 3 second
dwell @ 482F.
I can get 50% hole fill if I max out my preheaters which gives me a top-side
temp of 320F and bottom-side temp of 370F. Running a board at these
temperatures just to meet a 50% hole fill requirement doesn't make sense.
My theory: if 50% of a .060" thick board (.030") is OK, then a 25% hole fill of
a .150" thick board (.0375") would also be OK.
Any thoughts???
Al Kreplick
Sr. Mfg. Eng.
Teradyne, Inc.
978-370-1726
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