I must have missed something.  If you are using a eutectic SnPb solder allowy that melts at 183C why would you thnk it won't wet a Sn termination unitl the temperature gets to the Sn melting temperature of 232C?  If one used that logic I guess you would have to say that SnPb sodler will not wet copper until the temperature gets to the copper melting temperature of 1083C.  However, we know copper boards can be soldered using typical surface mount reflow temperatures of 200-220C.  Solder doesn't have to melt the termination surface finish, it needs to be able to "wet" the finish.  I think that means it needs to dissolve part of the surrface finish and chemically bond with the material (i.e. form an intermetallic.  My guess (based on my metallurgist frients in my old company) is that if you are using a eutectic SnPb solder to solder a Sn plated components the melting temperature would probably increasebercause some Sn would dissolve in the solder moving you away from the eutectic composition but my other guess is that the change would be so slight you'd never know there was a change 



-----Original Message----- 

From: Earl Moon [mailto:[log in to unmask]] 

Sent: Wed 8/14/2002 6:44 PM 

To: [log in to unmask] 

Cc: 

Subject: Re: [TN] Pb free components soldered with Sn/Pb







Scott, 



Not being trite, try it. 



Earl 



----- Original Message ----- 

From: "Scott Lefebvre" <[log in to unmask]> 

To: <[log in to unmask]> 

Sent: Wednesday, August 14, 2002 2:34 PM 

Subject: [TN] Pb free components soldered with Sn/Pb 





I am currently still using the standard HASL for our board finish and Sn/Pb 

solder paste.  We have currently purchase a new chip component (0603) that 

has 100% Sn finish on it's terminations. 



I would like to know if I should have any concerns using the existing solder 

profile.  Will the Sn/Pb solder paste lower the melting point of the lead 

termination on the component.  It is my understanding the component 

termination will not start to wet until 232 degrees C.  Any input in this 

matter would be greatly appreciated. 



Thanks in advance. 



Scott Lefebvre 

> *  [log in to unmask] 

> 

> 

> 



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