Did you ever compare immersion silver with immersion white Tin? What are the
inherent problems of
immersion Silver? Is there a problem with Sulfur corrosion or migration? How
about cost compared to immersion Tin?
-----Original Message-----
From: Wenger, George M (George) [mailto:[log in to unmask]]
Sent: Wednesday, October 03, 2001 8:39 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG v Immersion Ag
Clif,
When you indicate that "Once the BGA is removed some of the pads
indicate they did not / will not wet", what do you mean? How was the BGA
removed (mechanically or thermally with a repair tool?) What did the
problem pads look like (were they still covered with gold or was the pad a
dull gray or black color?). Did you print solder paste on the pads before
placing and reflowing the BGA?
The answers to the above would be help assessment of the problem. If I had
to guess off the top of my head you might be experiencing a brittle fracture
like the "Black Pad" problem rather than a soldering problem.
As for immersion silver (IAg) Lucent's been in volume production with IAg
boards since 1997. It is our surface finish of choice.
Regards,
George
George M. Wenger (609) 639-3210 [log in to unmask]
Celiant
Route 569 Carter Road PO Box 900
Hopewell, NJ 08525 Princeton, NJ 08542-0900
-----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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