when can't the unleaded soldering of Sn- Zn be used?

[carteman]

"The developing item about the sealing and packing technique by unleaded soldering at low temperature" started by the Japanese Electronics Sealing Association and the manufacturers in August, 2000 public their research results. Though some topics need still to solve, the relevant personage said that these results have already met the practical level currently.
In "the developing item about the sealing and packing technique by unleaded soldering at low temperature", the soldering that can be ......
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