Solder alloys, solder paste, printed circuit boards and electronic control devices

Abstract

[Topic] This invention provides a solder alloy, solder paste, electronic circuit board, and electronic control device that possess both heat fatigue resistance and impact resistance. [Solution] The solder alloy of this invention comprises Ag, Cu, Bi, Ni, and Co, with the remainder being Sn. The content of Ag is 2.5% by mass to 4.0% by mass, the content of Cu is 0.6% by mass to 0.75% by mass, the content of Bi is 2.0% by mass to 4.5% by mass, the content of Ni is 0.01% by mass or more, the content of Co is 0.01% by mass or more, and the total content of Ni and Co is 0.05% by mass or less, satisfying the following formula (1). 13≦58.046+(-4.238×Ag)+(-11.371×Cu)+(-4.145×Bi)≦33 (1) (wherein the element symbols in the above formula (1) represent the content (mass%) of each element in the solder alloy).

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