METHOD OF FORMING FILM DEPOSITED ON PRINTED WIRING BOARD FOR MOUNTING ELECTRONIC DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a printed wiring board mounting electronic devices which can be used for a long period. SOLUTION: This film is one for joining the copper electrode 5 of a printed wiring board 1 with the copper electrode 4 of an electronic device 2 mounted on this printed wiring board 1. The junction layer 3 to join the above copper electrodes 4 and 5 with each other is made of a single layer which is heat- treated after application of solder paste having non-Pb Sn for its main component and has a Cu3Sn layer for its main component, and besides this junction layer 3 is 10-30μm thick.