Lead-free solder alloy, electronic circuit mounting board, and electronic control device

Abstract

Provided is a lead-free solder alloy, an electronic circuit mounting board, and an electronic control device. The lead-free alloy serves as a means for allowing the heating conditions during solderingto be the same as or less than that of Sn-3Ag-0.5Cu solder copper, for preventing cracks from spreading in solder joints even in harsh environments in which there are dramatic differences between hotand cold as well as vibration loads, and for preventing cracks from spreading in areas near the interface between a solder joint and the electrode of an electronic component even when creating solderjoints using an electronic component that has not been plated with Ni / Pd / Au or with Ni / Au. The lead-free solder alloy is characterized by comprising 2.5-4 mass% Ag, 0.6-0.75 mass% Cu, 2-6 mass% Bi, 0.01-0.04 mass% Ni, and 0.01-0.04 mass% Co, the remainder being Sn, where the total content of Ni and Co is no more than 0.05 mass%.

Description

technical field [0001] The invention relates to a lead-free solder alloy, an electronic circuit mounting substrate and an electronic control device. Background technique [0002] As a method of joining electronic components to conductor patterns formed on electronic circuit boards such as printed circuit boards and module boards, there is a soldering joining method using a solder alloy. Previously, lead was used for this solder alloy. However, since the use of lead is restricted by the RoHS Directive and the like from the viewpoint of environmental burden, soldering methods using so-called lead-free solder alloys that do not contain lead have become common in recent years. [0003] As such lead-free solder alloys, for example, Sn—Cu based, Sn—Ag—Cu based, Sn—Bi based, and Sn—Zn based solder alloys are known. Among them, Sn-3Ag-0.5Cu solder alloys are often used in consumer electronic devices used in televisions, mobile phones, and the like, and in-vehicle electronic device...

AI Technical Summary

Problems solved by technology

[0026] In addition, when using electronic components that are not Ni / Pd / Au plated or Ni / Au plated for soldering, Cu as an intermetallic compound near the aforementioned interface 3 The Sn layer grows remarkably in a convex-concave shape, so it is difficult to suppress the development of cracks near the interface

[0027] However, the above-mentioned patent documents neither propose a combination of the effect of suppressing the growth of cracks in the soldered joint and the suppression of the heating temperature during soldering, nor the suppression of the growth of cracks in the soldered joint with a small solder foot. and did not imply

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