Lead free SAC solder paste on Sn63 HASL PCBs

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In switching to lead free processing, we find ourselves havi... - Jan 06, 2015 by Jack Lucas

The assumption that a HASL Sn63 PCB can be soldered with SAC... - Jan 07, 2015 by eezday

We switched our PCB's to 170Tg over 10 years ago, so we're p... - Jan 07, 2015 by Jack Lucas

Jack Lucas

#73300

Lead free SAC solder paste on Sn63 HASL PCBs | 6 January, 2015

In switching to lead free processing, we find ourselves having over 400 PCB part numbers with Sn63 HASL finish. And there is no hope of quickly purging inventory and getting our drawings changed to call out a lead free finish. I want to avoid having to run 2 SMT processes, requiring 2 ovens.

Question: If you accept, as I do, that BGA's with SAC balls can be reliably soldered with Sn63 solder paste, so long as you reach relative total mixture of alloys (≥230°C for ≥1 Min), does it follow that Sn63 HASL PCB's can be reliably soldered with SAC solder paste, so long as relatively total alloy mixing occurs?

NOTE: I am not trying to make RoHS compliant assemblies; just want to avoid a 2nd oven during our transition period to a total lead free shop.

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eezday

#73302

Lead free SAC solder paste on Sn63 HASL PCBs | 7 January, 2015

The assumption that a HASL Sn63 PCB can be soldered with SAC solder paste is likely a bad one. The board itself is likely FR4 which can be damaged by lead free temperatures. The HASL finish isn't an issue from the perspective of it's makeup and actually any trace amount of lead added to an otherwise lead free solder joint will improve reliability.

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Jack Lucas

#73303

Lead free SAC solder paste on Sn63 HASL PCBs | 7 January, 2015

We switched our PCB's to 170Tg over 10 years ago, so we're probably good to go on the temperature aspect. Thanks for the opinion on the added lead content.

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