lead-free wave

Dr. Lee, For lead-free wave soldering, we are recommended to use SnCu0.7, why not 0.8 or more ?? Since SnCu0.7 has eutectic melting point at 227 deg C, does it mean with more Cu or less Cu, the melting point will be higher ??

Also, in lead soldering, we usually will want to screen out Cu, as this will affect wave soldering quality, I think it is due to melting point goes up.... but how abt SnCu0.7 environment? Doesn't that make it easier to have higher Cu content as time pass ??

Pls advise.

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