Ngk Spark Plug Company, Limited

Yosuke Kondo

Hajime Saiki

Kazuo Kimura

Mitsuo Shiraishi

In a resinous circuit board having a circuitized substrate having conductive layers therewithin, a plurality of pin pads formed on a rear surface of the substrate, and a plurality of pins, each pin having a tip end portion and a head portion and soldered to the pin pad in such a manner as to contact at the head portion to the pin pad. The head portion of the pin consists of a flange section which is larger in diameter than the tip end portion, and a part-spherical abutment section bulging from the flange section in the direction opposite to the tip end portion and brought into contact with the pin pad. The part-spherical abutment section is made of eutectic silver solder which is lower in melting point than solder such as Sn&mdash;Ag solder which is used for soldering the pin to the pin pad. Since the silver solder and soft solder are present between the flange section and the pin pad, they can release the stress applied to the pin, thus making it possible to increase the joining strength considerably. Further, the above structure can dispense with holes which are formed in the circuitized substrate and in which pins are press-fitted and fixed as in the prior art circuit board.

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Aichi, Japan

Yosuke Kondo