Richard, Assuming you are using a leaded component and not a BGA with
SAC balls for the moment, a normal tin;lead profile should be adequate
to provide a good connection between the component and the pad.  There
is not enough SAC solder present on the leads to cause much of a change
in the alloy during reflow.

However, there are two schools of thought concerning the SAC Balls and
tin-lead paste.  One says that the combination does not make good
connections, the other says it is OK.  However, both agree that it is
necessary to increase the reflow temperatures to cause the SAC solder to
melt in order to form a bond.  If the SAC ball does not melt there will
not be a good connection for the component using just melted tin-lead
solder.

Tin-Lead reflow temperatures are good enough for Lead Free lead
finishes.
SAC reflow temperatures are necessary to form acceptable solder
connections for SAC BGA balls.



mark
Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave |
Westminster, CO 80234  USA |

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Richard D. Krug
Sent: Wednesday, March 02, 2011 7:31 AM
To: [log in to unmask]
Subject: [TN] Recommended Reflow Peak Temperature Using Sn63Pb37 Solder
and SAC305 Finished Component Leads?

What should the peak reflow temperature be when using Sn63Pb37 solder
paste when some component lead finishes are now an undefined Pb-free
finish?  Based on comments from the component manufacturer, I suspect a
SAC alloy.  

Can I solder to SAC solder or do I need to reflow the lead finish?  

Dick Krug, CSMTPE
SMT Process Engineer
Sparton Corporation
30167 Power Line Road
Brooksville, FL  34602-8299
p (352) 540-4012  (Internal Ext. 2012)
[log in to unmask]

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