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When? How and What??



When? How and What?? | 22 August, 2000

Has there been a definite date for the total move over to lead free? Will it be 2004 or 2008. Also is there a direct replacement for leaded solder, I have read various articles on numerous alloys suggested for the switch, such as bismuth, tin, copper, silver etc, is there an ideal mix and balance suitable for generic PCA's.

Will the reflow properties be effected by the oven type, in particular will IR reflow ovens surfice, I have heard doubts about this and that only convection ovens are suitable. Is an inert atmosphere an essential process for reflow?.


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Dr. Ning-Cheng Lee


Re: When? How and What?? | 22 August, 2000

The European WEEE has issued a new (5th) version of its recommendations. In it they say that , on January 1st, 2004, they will review the status of the Pb-Free issue. There is currently NO DEADLINE for implementation.

As far as a direct replacement for the currently-popular 63%Sn37%Pb, YES. The industry is accepting a SnAgCu alloy as the primary option. The approximate chemistry is 95.5%SN 3.8%Ag 0.7%Cu - or equivalent ternary eutectic alloy. It melts at ~217C and should be reflowed at ~240-245C.

As far as oven type - YES, the type DOES MATTER. Some current forced air convection ovens may not be able to reach suitably-high temperatures. And, since new fluxes will be working at higher temperatures, current ovens could cause troubles due to inadequate heating efficiencies. Results will vary from oven to oven. I do not consider this to be a major long-term issue.

Currently, an inert atmosphere IS ESSENTIAL. This may not be true in the future, but it is very important for current Pb-Free solder pastes.

Thank you for these great questions! Dr. Lee

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