I totally agree with George. Better to have to rework BGAs on IAg board than on ENIG, for example. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Monday, August 25, 2008 2:15 PM To: [log in to unmask] Subject: Re: [TN] ENIG White paper 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. 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