Why do you prefer immersion Silver over immersion Tin?

-----Original Message-----
From: Guy Ramsey [mailto:[log in to unmask]]
Sent: Wednesday, October 03, 2001 7:07 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG v Immersion Ag


Be aware that the wetting forces are lower and wetting too is slower on ENIG
than with HASL or Immersion Silver, or for that matter bare copper. This is
because you are soldering to nickle, not copper. Make sure that the time
above liquidus is long enough and the that temperature under the BGA is hot
enough. You should be able to solder  to the ENIG.
Our experience with Immersion Silver has been positive. I prefer it over
Immersion Tin.

But I do not have data to answer your other questions.
Guy Ramsey
Senior Lab Technician / Instructor


E-Mail: [log in to unmask] <mailto:[log in to unmask]>
Ph: (610) 362-1200 x107
Fax: (610) 362-1290



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kirsch, Clif
Sent: Tuesday, October 02, 2001 4:45 PM
To: [log in to unmask]
Subject: [TN] ENIG v Immersion Ag


We are running into solderability issues with ENIG boards, especially under
dense (500+ pins) BGA devices. Once the BGA is removed some of the pads
indicate they did not / will not wet.

Does anyone have experience with immersion silver finished boards from a
reliability and NEBS compliant standpoint? Also are there surface resistance
issues for test pads that are not reflowed with solder?

Clif Kirsch
Mfg Eng

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