Pb soldering to Pb free finishes Views: 2569

Pb soldering to Pb free finishes			floydf	10/02/09
Pb soldering to Pb free finishes			gplume	10/01/09
Pb soldering to Pb free finishes			davef	10/02/09
	Pb soldering to Pb free finishes		smt_guy	10/05/09
		Pb soldering to Pb free finishes	kudamarani08	10/15/09

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Date: October 02, 2009 11:23 AM
Author: floydf  
Subject: Pb soldering to Pb free finishes


> Does anyone out there have experience soldering
> with Pb solder (Sn 63 or Sn 62) to SAC 305 coated
> PCB lands (about 50um) or Sn-Cu plated lands
> (about 10um). I know soldering Pb free (Sac based
> soler) to Pb/Sn coated lands is a no-no, but was
> waondering what the pitfalls were going the other
> way. We are trying to convert bare circuits to Pb
> free, yet be able to use either SAC solder or Sn
> 63 (or Sn 62) for some lagacy projects where
> changing solder alloy is out of the question.
> What should we look out for?

We had a problem putting regular solder on unleaded pads. The finish looked grainy and it didn't fillet well. I found that making the profile so that it is at the max allowable temperature and dwell gives the unleaded a chance to diffuse into the leaded paste.

(http://www.smtnet.com/distributed_forums/Index.cfm?CFApp=8&Message_ID=60034)

Date: October 01, 2009 04:56 PM
Author: gplume  
Subject: Pb soldering to Pb free finishes

Does anyone out there have experience soldering with Pb solder (Sn 63 or Sn 62) to SAC 305 coated PCB lands (about 50um) or Sn-Cu plated lands (about 10um). I know soldering Pb free (Sac based soler) to Pb/Sn coated lands is a no-no, but was waondering what the pitfalls were going the other way. We are trying to convert bare circuits to Pb free, yet be able to use either SAC solder or Sn 63 (or Sn 62) for some lagacy projects where changing solder alloy is out of the question. What should we look out for?

(http://www.smtnet.com/distributed_forums/Index.cfm?CFApp=8&Message_ID=60033)

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Date: October 02, 2009 02:52 PM
Author: davef  
Subject: Pb soldering to Pb free finishes


If you know "soldering Pb free (Sac based soler) to Pb/Sn coated lands is a no-no," why would soldering with Pb/Sn to Pb-free coated lands be different? If you are going to do this, follow the advice of an earlier poster who recommended higher peak soldering temperature [~230*C] than you would use for leaded assembly.

(http://www.smtnet.com/distributed_forums/Index.cfm?CFApp=8&Message_ID=60037)

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Date: October 05, 2009 06:53 PM
Author: smt_guy  
Subject: Pb soldering to Pb free finishes


this is what they call hybrid soldering....i missed the discussion at the IPC Show in Chicago...

Can someone with hybrid soldering idea share some?


thanks

(http://www.smtnet.com/distributed_forums/Index.cfm?CFApp=8&Message_ID=60054)

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Date: October 15, 2009 09:00 AM
Author: kudamarani08  
Subject: Pb soldering to Pb free finishes


This may help...http://www.numonyx.com/Documents/WhitePapers/WP_Soldering_Compatibility.pdf

(http://www.smtnet.com/distributed_forums/Index.cfm?CFApp=8&Message_ID=60116)