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August 2008

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From:
"Wenger, George M." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wenger, George M.
Date:
Mon, 25 Aug 2008 15:14:36 -0400
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We've been using ImAg as our surface finish of choice for 
Paul,



We've been using ImAg as our surface finish of choice for over 10 years.

We don't eliminate the Ag tarnish.  As long as there are pollutants in

the environment the Ag will only tarnish again.  Many of the products we

sell wind up in telecommunications equipment in areas with high levels

of air pollutants and the exposed Ag surfaces do tarnish but they have

not cause any reliability issues or problems when components on our

products have worn-out or failed.  Repair of failed components on ImAg

boards is no more difficult than repair on other surface finishes.  You

need to remember the ImAg on pads and features is not very thick and it

dissolves into the solder joint and you wind up soldering to copper.

Therefore, repair on an ImAg board is just like repair of there boards

where the soldering is to copper (e.g., OSP or HASL). 



Regards,

George

George M. Wenger

Andrew Wireless Solutions

Senior Principal FMA / Reliability Engineer

40 Technology Drive, Warren, NJ 07059

(908) 546-4531 [Office]  (732) 309-8964 [Cell]

[log in to unmask]

 

-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Edwards

Sent: Monday, August 25, 2008 2:49 PM

To: [log in to unmask]

Subject: Re: [TN] ENIG White paper



Richard,



How do you eliminate the Ag tarnishing on completed PCAs? 



Paul



Paul Edwards

Surface Art Engineering



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.

Sent: Monday, August 25, 2008 6:25 AM

To: [log in to unmask]

Subject: Re: [TN] ENIG White paper



Dave,

You write as if you are not at all familiar with IAg, which is totally

understandable. However, IAg has been around in full production mode for

many years now, and is rapidly becoming the most-used finish in the

market. Do not confuse it with immersion tin finish, which has little or

no shelf life.

IAg-finished circuit boards have a recommended shelf or storage life of

about 1 year. However, if packaged properly in a hermetically sealed bag

with silver saver paper liners, and stored away from sulfates, it is

possible to use boards up to 5 years old or even longer with no issues

whatsoever. All you need to do is call out the packaging on the

fabrication drawing per IPC 4553.

I have soldered IAg boards that sat around exposed to the elements for

more than 4 years in previous lives, and they soldered up just fine, no

change in the DPMO.

Some of the bare boards we use here at GD are 34" by 40", 48 layers,

1/2" thick, cost is about $48,000 each. Their finish is IAg.

I have had a lot of experience with IAg over the past 10 years or so,

having seen at least 150,000 IAg boards assembled and soldered with

every type of component you can think of, and I have never experienced

any issues with them. I have experienced many, many issues with ENIG,

however, and that is the finish that would keep me up at night waiting

for the bomb to go off. There are many reliability issues associated

with ENIG such as black pad, brittle nickel, etc., etc, but just think

about the fact that you are soldering to nickel, which has a dissolution

rate about 50 times slower than copper.

Should you ever have a solderability issue with IAg, you can have the

fabricator rework the finish. If you have an issue with ENIG, the only

thing you can do is rework your scrap account.

However, you need to take the end-use environment into consideration

when you select a circuit board finish. ENIG (unfortunately) may be your

best choice. I would fully qualify just one assembly at a time, and I

would fully qualify it. For Space use, I would not suggest IAg.



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Connitt

Sent: Thursday, August 21, 2008 3:22 PM

To: [log in to unmask]

Subject: Re: [TN] ENIG White paper



Hi Werner,

Well, we seem to like to buy all the circuit boards for a production run

at one time which could be thousands and I worry about the special

handling. Some of the boards could end up being in stores for 9-12

months. We also have to do pretty comprehensive incoming inspection

which would keep me up at night wondering if the bare boards are being

handled (or not handled) correctly.. Setting of a time bomb of bad

boards.

Dave Connitt



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*

Sent: Thursday, August 21, 2008 3:10 PM

To: [log in to unmask]

Subject: Re: [TN] ENIG White paper



Hi Dave,

Why ENIG? Have you considered imAg?



Werner

Future workshops:

Reliability Issues with Lead-Free Soldering Processes, September 22,

Schaumburg Failure Mode and Root Cause Analyses Reliability (Fatigue,

Brittle Fracture, ENIG), September 22, Schaumburg Solder Joint

Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia Solder Joint

Reliability: Part 4, Oct. 17, Timisoara, Rumania Solder Joint

Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia







**************

It's only a deal if it's where you want to go. Find your travel deal

here.



(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)



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