Bon giorno,
My response is late, been in Rome for some days, 35 Centigrades and polluted city air, could study the wetting of sweat very well. If it were not for the watching police, I had jumped into Fontana di Trevi.
Very interesting to see the answers on solder wetting. We have a Multicore WB, but it's abandoned, been placed in a corner and never asked for. The reason is that we could not find a person that got enough in love and married the machine and who promised to be a good husband for decades. With different operators we got too much variations of parameters.
If inspecting just a few items per day, I think Bev's recipe is working, but if you have hundreds and hundreds of samples to test, I ask myself if not WB is necessary to use. At least if you have a WB enthusiast and someone who can use statistics.
We have found that better than a machine or any dip pots or whatever, is a person who KNOWS about soldering. Even if samples are WB tested from a lot of 100,000 chip caps, and that sample looks nice, we know that there can still be soldering trouble. When you get soldering problems in the line, the root cause must be found in hours. A person who KNOWS about soldering use to have that ability. Usually, those guys are greyhaired gentlemen with shit under the nails despite a PhD grade, and with no take-overs. Two of the guys at our company left big holes when they withdraw. There are a few left, don't see how we will manage the time they too leave. Knowing a lot about soldering is not on the hit list.....
For those who are interested in KNOWING about soldering and wetting, I recommend this book:
"The Mechanisms of Solder Alloy Wetting and Spreading" written by Frederick G. Yost, F.Michael Hosking and Darrel R. Frear. Sandia Lab guys. ISBN-0-442-01752-9 Van Nostrand Reinhold, 115 Fifth Avenue, New York,
NY 10003.
300 pages about wetting and only wetting!
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Luigi Cantagallo [mailto:[log in to unmask]]
Sent: Wednesday, May 25, 2005 2:00 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [TN] Wetting balance
Hello Technetters,
I have questions about wetting balance.
We intend to use a wetting balance not to accept/reject supplied SMD's
(Our
SMD's are 1 to 5 years old) but to minimize the risk of solderability
defects in production (Low volume, SnPb technology).
So we don't apply J-STD-002D criterium but we try to find them to
corroborate wetting balance and production results.
On some tests (Wetting balance calibrated and in order, same type of flux,
same alloy) on same component lots, we have not a perfect correspondence
between wetting balance and visual inspections results in production
(Vapor
phase soldering). One of the case is "Good at the solderability
test/Defect
in production" and this one is the most risky.
Somebody have experience with that kind of problem?
What actions have you made ?
Thanks for answers.
Best regards,
CANTAGALLO Luigi
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