CREAM SOLDER AND METHOD OF SOLDERING ELECTRONIC PART

摘要

A cream solder obtained by kneading an Sn-Ag-Cu alloy together with a flux, wherein the Sn-Ag-Cu alloy comprises a mixture of a first powdery alloy and a second powdery alloy, the first powdery alloy is represented by an Sn-Ag phase diagram having a solid-liquid coexistence region and has a given silver amount which is larger than that in the eutectic composition (3.5 wt.% silver), and the second powdery alloy has a silver amount which is that in the eutectic composition (3.5 wt.% silver) or which is close to that in the eutectic composition and is smaller than that in the first powdery alloy. This cream solder is excellent in strength and thermal stability and has satisfactory bonding properties. It is based on an inexpensive Sn-Ag-Cu solder alloy. It is suitable for use as a high-temperature-side lead-free solder material conformable to temperature gradation bonding. Also provided is a method of soldering an electronic part.