No, I didn't mean that at all.
From everything I have read Silver is preferable to Tin.
What I meant was, we sent some bare boards to an
assembly vendor and they assumed it was Tin when
it was really Silver, and for some reason they had severe
soldering problems. As soon as I told them they were
Silver they were building them with great results.
Shame on me for not asking more questions to learn
what they did differently, but I assumed they changed
the solder paste. (but I'm not sure about that).
I'm a layout guy and I don't know much about paste,
so I can't answer your question, sorry.
seeya,
Jack
Kitty Hines <[log in to unmask]>@IPC.ORG>
27Sep2002 12:23 PM
Please respond to "(Designers Council Forum)" <[log in to unmask]>;
Please respond to Kitty Hines <[log in to unmask]>
Sent by: DesignerCouncil <[log in to unmask]>
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Subject: Re: [DC] [pcdlist] Fine Pitch BGA board finish... HELP!
Retain Until: 10/27/2002 Retention Category: G90 - Information and Reports
Caterpillar Confidential: Green
Jack,
So, are you saying that the immersion silver didn't work as well as the
tin? We've just switched to using the silver recently. In your
experience, which solder paste works best with BGA's?
Thanks for you reply,
Kitty
Kitty Hines
CX2 Technologies
8330 S. Madison St., Ste. 15
Burr Ridge, IL 60521
(630) 323-6110 Ext. 336
(630) 323-5173 Fax
[log in to unmask]
-----Original Message-----
From: Jack C. Olson [mailto:[log in to unmask]]
Sent: Friday, September 27, 2002 9:47 AM
To: [log in to unmask]
Subject: Re: [DC] [pcdlist] Fine Pitch BGA board finish... HELP!
This might sound weird, but we just had a similar experience,
and the result was the finish was really immersion silver, not
white tin. The vendor switched solder-pastes or something and
the problem went away. Just a thought...
For this type of question you might get a lot more answers from
joining [log in to unmask], there are a lot of fab/assy vendors there
good luck,
Jack
p.s. Also, CircuiTree published a very good set of articles in the
last issue of "The Board Authority", vol4num1 called Assembly
and Solderability. You might try to get a back-issue at
http://www.circuitree.com/FILES/HTML/CT_board_authority_toc/0,4170,,00.h
tml
[log in to unmask]@freelists.org
26Sep2002 02:17 PM
Please respond to [log in to unmask]
Sent by: [log in to unmask]
To: [log in to unmask]
cc:
Subject: [pcdlist] Fine Pitch BGA board finish... HELP!
Retain Until: 10/26/2002 Retention Category: G90 - Information and
Reports
Caterpillar Confidential: Green
Hello All-
Just got a call from a good friend in big trouble. He's had a bunch of
VERY
expensive BGA assemblies built up with very poor yield. Military
application; designed and built outside. The boards have a 'white tin'
finish and appear to have soldered very poorly. I realize there are many
possible reasons for this, but it sounds like, from their analysis so
far,
the board finish is the problem. I don't know how long the boards were
on
the shelf before processing, and I won't say where they're from.
What are y'all using for board finish on 0.7 pitch BGA designs? Where do
you get your bareboards? What are the pros and cons of white tin vs.
nickel/gold?
Thanks in advance for your responses,
-Chris
P.S. Please excuse the double posting...
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