Gimme a few days, Bob,
think we have MUCH in common, maybe you have seen my issues earlier in this
forum under 'SuperBGA problem'. Among the 560 balls on each BGA, it happens
that one or two give no electrical connection, until knocking the BGA gently
on his head: how are you mrBGA, may I have a line to room 456?... We used
Fluorescent moldings, SEM, FTIR, TOFSIMS and other stuff in this detective
work. Found it more complicated than anyone had thought of. Compressed but
not making contact...seen it too. Mebbe we can stumble on crutches
together, not funny to be alone with such problems.
cu later
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: bbarr [mailto:[log in to unmask]]
Sent: den 15 november 2000 15:45
To: [log in to unmask]
Subject: [TN] BGA Soldering Problem
I have a PBGA357 that is exhibiting a strange (to me) soldering condition.
Two to three balls (not necessarily adjacent, but usually along an edge) do
not appear to be wetting to the solder paste on the land. This is what it
looks like after reflow: The paste on the land has reflowed to a mound, the
ball on the BGA is compressed in shape but not wetted to the mound on the
land (so the ball must have reached reflow temperature to get compressed.) A
clear line of demarcation between the compressed ball and the mound of
solder on the land is visible. The component fails in test, but sometimes
pressing on it can get it to work. In most cases the balls on either side of
the one not wetted look fine. Process is OA flux with convection reflow.
Profile run several months ago with thermocouples imbedded in one center
ball and one edge ball showed max. temp. of 217 (center) and 220 (edge)
degrees C with time above 183 of 56 seconds. Max slope is 2 (center) and 2.8
(edge) degrees C. I am going to go run a verification profile, but in the
mean time your thoughts are much appreciated.
Bob
Robert Barr
Manufacturing Engineering
Formation, Inc.
Voice: 856-234-5020 x3035
Fax: 856-234-6679
email: [log in to unmask]
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