The literal answer to your question from a soldering point of view is that
the silver dissolves in molten solder whereas tin fuses, but I don't think
this is the issue.

In either case the coating is assimilated into the solder, therefore you are
soldering to the copper underneath, and it is the quality of this which
effects the result. Clearly the copper was unsolderable at the time of
applying the coating, or has become unsolderable because the coating was
applied in such a way as not to provide sufficient protection to the copper
from the time of application to your using the boards.


Kind Regards

Mike Fenner

Applications Engineer, European Operations
Indium Corporation
 T: + 44 1908 580 400
M: + 44 7810 526 317
 F: + 44 1908 580 411
 E: [log in to unmask]
W: www.indium.com
Leadfree: www.Pb-Free.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jack C. Olson
Sent: Friday, August 02, 2002 7:23 PM
To: [log in to unmask]
Subject: [TN] ASSY: Immersion Silver vs. Tin


Greetings,

A situation has come up that is beyond my experience.

We sent some Immersion Silver boards to an assembly
vendor and recieved an email saying:

"We are progressing on your boards. The bad news is
that the white tin flash used on the pads is awful.
The solder is reflowing irregularly, if at all.
We suspect that we'll have to touch every joint on
every part to make a good connection."

So my question to the group is:
Is there a difference from an assembly process point of view
between tin and silver?

I'm hoping the root problem is related to their assumption
that our silver boards were tin, but I don't know enough
about it.

Thanks in advance for any clues....

Jack

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