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SN/PB soldering with gold plated pcb


SN/PB soldering with gold plated pcb | 23 April, 2005


Is there a solder paste alloy espacially done to solder components on a pcb gold plated ???

I am using the AIM 297DX SN63/PB37 no clean and i had a comments from my customer telling me that i am not using the right alloy.

Personally i never herd about a special alloy for this kind of plating. If i am in the field please bring me back!!

Thank's for your answers guys

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SN/PB soldering with gold plated pcb | 24 April, 2005

We're not sure what your customer is talking about either.

Gold and tin form an intermetallic compound [IMC] that can cause poor solder connections. To minimize the potential of a problem, keep gold to less than 3 percent of the metal. [Search the fine SMTnet Archives for more]

In the old days, there was a belief, but no proof, that Sn62Pb36Ag2 solder would "scavange" the gold. We never figured-out what "scavange" means. With Sn63Pb37 and gold, the connection looks duller than some other connections. It's possible that the normally shinier Ag2 connections would counter balance the dullness caused by the gold.

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SN/PB soldering with gold plated pcb | 25 April, 2005

I wonder if yor customer means wrong "flux"?

Your not solderng to gold. Your soldering to Nickle. The gold is disolved and dispersed. Your joint strength comes from the SnNi intermetalic.

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SN/PB soldering with gold plated pcb | 26 April, 2005

I have found that Sn62 solder gives better strength and leach resistance when soldering to gold surfaces. The gold needs to be at least 5 to 10 micro inches thick to prevent nickel oxidation but if over 25 micro inches will cause brittleness. I have a sample of Sn62 no clean paste I can send to you if you write me direct at Regards, Den

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SN/PB soldering with gold plated pcb | 26 April, 2005

Sounds to me like they are thinking since they have a gold board that it must be processed lead free. This kind of thing is happening all over since OEMs are starting to think about pb free and sending their purchasing and engineering to these seminars and hear that the finish of boards will need to be changed from HASL and all of the other stuff. Now they think that if they have any pb free finishes that they have to be pb free. Our oldest customer just asked us about how we were going to segregate the new components that "now are lead free" from those with lead. They were somewhat surprised when we told them that they have been using many pb free components from day one of their products over the last 7 yrs. a little siver in the paste does make them shinier as mentioned but I have seen no statistical difference in the solder joint performance itself between Sn 63 and Sn 62 they just look better.

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