| 摘要 |
PURPOSE:To increase the joining strength of a through hole part and to reduce the electric resistance by allowing the titled soldering paste to contain plural solder grains, plural metallic grains and flux and using a part of the plural metallic grains having a higher melting point than that of the solder grains. CONSTITUTION:A hole 5 for a through hole is pierced on a laminated body 1 having conductive layers 3 and 4 with an insulating layer 2 between. Soldering paste mixing the solder grains 6A, metallic grains 7 and flux 8 is applied or filled in the hole 5 by the screen printing, etc. After being preheated at the temperature under a melting point of solder, the soldering paste is reflowed at the higher temperature and cooled and solidified. By this method, a solder block 6 in which the metallic grains 7 are dispersed is formed. The volume ratio of the metallic grains to the solder grains is 0.005<= the metallic grains/(the metallic grains+the solder grains) <= 0.67 and the grain diameter of the metallic grain is <=150mum and the metallic grains are the copper grains and material having the flux, by weight ratio, >=5% of the solder grains and the grain diameter of the solder grain <= 150mum is mixed to form the paste.
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