LOW TEMPERATURE SYSTEM LEAD-FREE SOLDER COMPOSITION AND ELECTRONIC PARTS-PACKAGED STRUCTURE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide solder which is hardly changed in its structure in spite of long- time use at a high temperature and is capable of assuring joint boundary strength and is hardly oxidizable in spite of long-time use in flow soldering in the atmosphere.;SOLUTION: The strength at the joint boundary is assured in the case of the long- time use at the high temperature and the stability of the structure at the high temperature is assured by slightly adding Ni to Sn-Ag-Bi eutectic system solder. Ti is added in a slight amount to the structure, by which the Ti is dispersed and the texture is made finer and the coarsening of the texture at the high temperature is obstructed. The prevention of invasion to Cu and the improvement in the strength are excepted by slightly adding Cu to the solder. The embrittlement of the material is prevented and pliability is rendered by slightly adding In to the solder. The long-term use in the atmosphere is realized by the slight combined Ge and P for the purpose of oxidation prevention in the solder bath. The system of a high liquidus line temperature is selected and the apparent melting point is raised to the extent of not drastically changing the soldering temperature without the occurrence of a lift-off, by which the high temperature characteristic is assured.;COPYRIGHT: (C)2002,JPO