RE: [TN] Silver Immersion right for fine pitch?
If you have fine pitch components plus the latest generation compliant pin sockets, like VHDM or Metral 3/4000, beware that the insertion would be harder. You cannot use lubricants with these assemblies either, so you need to have a controlled and repeatable, slow insertion processes. We are building a lot of these and our product engineer tells me that he can press in the same type of connector into half a dozen different finishes blindfolded and tell which one is silver! Other than that the finish is good for fine pitch. One needs to handle the boards with care - by the edges and with the use of gloves.
 
Regards,
 
Lakshmi
-----Original Message-----
From: Krmpotich, Mark [mailto:[log in to unmask]]
Sent: Thursday, September 25, 2003 4:33 PM
To: [log in to unmask]
Subject: Re: [TN] Silver Immersion right for fine pitch?

Bill,
We have just completed full analysis of converting our PCB's from IWT to Immersion Silver.
Benefits are: bettering soldering than IWT,  good for fine pitch components, Shelf life 12 Months
Downside:  Must change handling process - everybody now has to wear clean gloves and NO copy paper is allowed in the area.  Sulfides from finger prints and copy paper tarnish the silver and prevent soldering.

We have just started using it in our High Volume products that have fine pitch part less than 20 mil or under 1.0 mm pitch BGA.  Otherwise we use HASL.

If you do double Reflow with a Selective Wave process it will require a little more activation in the flux.

Our board buyers are saying that cost is the same as HASL, OSP and the rest.  But that maybe because we buy in large numbers.

Mark Krmpotich
DFx Engineer
World Wide Operations Technology
Scientific Atlanta
Tel: 770-236-5166
Fax: 770-236-4707
mailto:[log in to unmask]
http://www.scientificatlanta.com/


-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Thursday, September 25, 2003 4:08 PM
To: [log in to unmask]
Subject: [TN] Silver Immersion right for fine pitch?


Hi Technetters,

I have just attended a meeting of the IPC Designers Council where the
subject of finishes for PCB's came up and it was revealed that Silver
Immersion seems to have great benefits for assembly, shelf life,
solderability, rework, etc...

Can anyone give me their experiences with the process and its benefits and
down sides?  Have you personally used it, how long, what sort of problems
have you seen, what are the cost issues?

Best Regards,

Bill Brooks
"Politics is more difficult than Physics" - Albert Einstein

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