I need to solder a BGA chip back onto a PCB which was originally attached using lead-free solder. Is it okay to use tin/lead solder to reattach the chip? I removed as much of the lead-free solder from the PCB pads as possible but they are still tinned with lead-free. Is it a good idea to tin the pads with the tin/lead solder first to ensure a better bond? And should I use Pb-free reflow temperatures (220° C) since there will be residual Pb-free solder on the pads?

 

I would have no problem with it, just not RoHS certified!
Max.

 

Let me rephrase, will using tin/lead solder to reattach a BGA chip that was originally attached using Pb-free cause any issues (cold joints, discontinuities, etc.) and what are some tips for ensuring a successful rework?

 

If it is any comfort I have found that lead/tin solder is a far better bond, the RoHS versions are a pain to use, IMO they both combine very easily when reworking.
Max.

 

No problem, but it won't act like the eutectic of 63% tin with 37% lead. Scroll down to the part describing "what happens if I have more than 62% tin:"

http://www.chemguide.co.uk/physical/phaseeqia/snpb.html

John

 

No problem, but it won't act like the eutectic of 63% tin with 37% lead.

I don't have enough experience to know the importance of having a eutectic mixture. My main concern is that everything becomes liquidus and my solder joints are solid. Don't mean to come off as rude, but can someone answer my specific questions (tinning pads, elevated temperature)?

 

No problem, but it won't act like the eutectic of 63% tin with 37% lead. Scroll down to the part describing "what happens if I have more than 62% tin:"

http://www.chemguide.co.uk/physical/phaseeqia/snpb.html

John

That's a very informative article. Thanks. So from what I've gathered, if I am going to use a SnPb solder, I should choose one with a lower Sn content since the Pb-free has a higher Sn content. Is this correct? If so, would something like Sn10Pb90 work better than Sn63Pb37?

 

Too much inappropriate contents, so deleted the inappropriate contents and closed the thread.

 

I closed it because there are some inappropriate contents, another moderator deleted the contents, I also hope the members could calm down, now someone said that he was interested in this, although he didn't see the inappropriate contents, now I reopen it, but if any inappropriate contents happen again then I or other moderators may close it again, I hope members could keep a good mood to discuss the technical problem, if have any argue only in technical, no personal, no emotional, thanks ...

 

The answer was given way back in post #2.
Hope the TS read it.

 

If it is any comfort I have found that lead/tin solder is a far better bond, the RoHS versions are a pain to use, IMO they both combine very easily when reworking.
Max.

That's the kind of answer I was looking for. Thanks Max!