Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


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Sn62Pb36Ag2 | 30 November, 2010

1.) Are there any industry white papers written that document any advantages in running this alloy? From what I've read, this alloy was formulated to prevent leaching of silver for silver-bearing component terminations.

2.) Are there any concerns with rework/touchup using regular Sn63 on a solder joint that is comprised of Sn62Pb36Ag2?

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Sn62Pb36Ag2 | 30 November, 2010

62/36/2 is used often in thickfilm hybrid circuits where Pd/Ag conductors are used. The idea is that you saturate the joint with the 2% silver and thus help eliminate the leaching of the silver from the hybrid circuit pads or the component. We mix the 63/37 and 62/36/2 alloys when reworking and have never had any problems. I have never heard anyone say it was harmful or have read any papers stating such.

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Sn62Pb36Ag2 | 2 December, 2010

Several years ago we acquired a plant that uses this alloy in their solder paste. I don't know why they chose it in the first place since they've never run hybrid circuits. They do rework with regular SnPb wire. I haven't heard of any issues, and we're in the high reliability market.

Note that some BGA suppliers (eg. Motorola/Freescale) were using this as a ball alloy. We used millions of them with 63/37 paste and they survived >2000 cycles of -40/+150C thermal cycling.

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