| 摘要 |
PROBLEM TO BE SOLVED: To enable reflow soldering in the atmosphere and improve paste storage life by coating a surface of solder powder with a coating film which is in a solid condition at a normal temperature and is vanished at solder melting temperature when it is heated by a reflow soldering process. SOLUTION: A globular solder powder 2 constituting a metal powder 1 for the solder paste is composed of a Sn-Zn system material, and its surface is coated with a coating film 3, namely N-methylacetamido CH3 CONHCH3 (the melting point 31 deg.C, the boiling point 206 deg.C) at the thichkness of about 0.1μm. The solder paste metal powder 1 is mixed with a proper solvent so as to manufacture a solder paste. Ethylene carbonate (CH2 O)2 CO, 2-acetylpyrrole C6 H7 NO, acetamido CH3 OONH2 and the like are used as the coating film 3. Sn-Ag system or Sn-Bi system materials(Sn-9Zn eutectic crystal, Sn-35Ag eutectic crystal, and Sn-58Bi eutectic crystal) can be used as the solder powder 2.
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