Hi Gregg,
Lead-free plated leaded components are backward compatible, i.e. they can be used in a leaded process. When you have BGAs with SAC solder spheres that have to be reflowed with SnPb paste, then you run into the unknown (special processes, reflow profile, reliability concerns and so on). Leaded components have been available with LF surface finishes (matt Sn, or reflowed Sn or Ni under plating and so on) for quite a while now, and are being soldered with no problems with SnPb paste

The way I see it is, BGA components and SnPb finish components are 2 gates to switch over from a leaded assembly to a LF assembly. SAC BGA components ideally require SAC solderpaste, but you cannot also transition to a LF paste till you have SnPb surface finish components (which are not yet available in LF format) present on the board due to maximum temperature concerns.

Hope I managed to answer your question without further confusing you......

Amol Kane
M.S (Industrial Eng.)
Process Engineer
Harvard Custom Manufacturing 
941 Route 38  Owego, NY 13827
Phone: (607) 687-7669 x349
[log in to unmask]

 -----Original Message-----
From:   TechNet [mailto:[log in to unmask]]  On Behalf Of Gregg A. Owens
Sent:   Tuesday, May 02, 2006 1:26 PM
To:     [log in to unmask]
Subject:        [TN] Mixing Lead-free Plated Parts with Leaded Solder

Dear Technetters:

 

One of my students have asked a good question. Can one take lead-free plated
parts (likely Sn100) and solder using Sn63 without any significant
metallurgical concerns? I believe this issue was previously discussed but
can't find it in the archives. 

 

Your thoughts appreciated. 

 

Gregg Owens, MIT

Manufacturing Technology Training Center, Inc.

 

 


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