| abstract |
PURPOSE: To execute soldering at a low temperature, in which adhesive is not deteriorated by immersing pads on a substrate with eutectic alloy and executing solder plating or executing coating. n CONSTITUTION: Fitting is executed by the mutual operation of solder and eutectic alloy lower than the melting point of solder. Namely, coating is executed in a range with which solder balls 7 of the substrate are brought into contact by an alloy of 63% of tin and 37% of lead, and a chip 1 is arranged on the substrate. Then, the solder balls 7 are arranged with alloy pads 9. When the temperature of the device is raised to the melting point of the alloy by using a thermoid 10, pad alloy 9 becomes a melting state. Since the solder balls 7 have miscibility with respect to the melting alloy 9, the materials of the solder balls 7 melt into the melting alloy 9, a continuous change occurs in the composition of the melting mixture, and the melting point rises. When the compositor of the melting mixture becomes out of eutectic composition, the melting point reaches a temperature at which the melting mixture is solidified, and the junction is completed. Thus, the temperature by which fitting can be executed can be lowered. n COPYRIGHT: (C)1991,JPO |