Thanks!
In the IPC-HDBK-001, I see a statement that when silver content rises over
2%, the silver-tin intermetallics will segregate upon cooling. So with an
immersion silver finish on the PCB sodler pads, and also silver in the
solder, it appears it might be a big mistake!(?) The application calling
for it has no silver finish components. In fact, they are gold! Now I have
to also do some research on silver and gold....hmmm...put some red and green
LEDs on there and it's my "Christmas" board...
Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, January 27, 2009 9:31 AM
To: TechNet E-Mail Forum; Kevin Glidden
Subject: Re: [TN] SnPbAg solder and Immersion Silver PCBs
Hi Kevin,
The main concern about the presence of Ag in solder joints is "Ag
embrittlement". Me personally, I've never seen any signs of it even in the
joints of components with a few microns (not microinches!!!!) thick layer of
Ag.
Now I'm eager to see what Dave Hillman will have to say about it :-)
------Original Message------
From: Kevin Glidden
Sender: TechNet
To: [log in to unmask]
ReplyTo: TechNet E-Mail Forum
ReplyTo: Kevin Glidden
Sent: Jan 27, 2009 08:35
Subject: [TN] SnPbAg solder and Immersion Silver PCBs
Morning all,
Question today about SnPbAg solder. We have always used Sn63Pb37 solder
alloy for all products, with exception of some high temp solders for special
cases. The lion's share of our PCBs are ImAg finish, 5 to 12 micro-inches,
per IPC-4553. In reading about SnPbAg solder, it appears to be recommended
for use on SMT components with thin (?) silver finishes. This is to prevent
the dissolution of the component lead into the solder joint. Drawbacks
appear to be only that the joint is not as shiny and reduced mobility of the
solder. Is it also considered good practive to use an SnPbAg alloy for
immersion silver PCBs for the same reasons? Any tech articles available on
this?
Thanks (again!)
Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.
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