Patent ID: 9010617
Filing Date: 2015-04-21
Classification: H01L

Abstract:
1. A method comprising: heating a plurality of solder bumps consisting essentially of silver (Ag) and tin (Sn) between a first workpiece and a second workpiece to a melted state; during a period of time all of the plurality of solder bumps are molten, cooling the plurality of solder bumps at a first cooling rate; between a first time point a first one of the plurality of solder bumps starts to solidify and a second time point all of the plurality of solder bumps finish solidification, cooling the plurality of solder bumps at a second cooling rate, wherein the second cooling rate occurs within a temperature range between 200° C. and 220° C.; and after the step of cooling the plurality of solder bumps at the second cooling rate, adjusting a cooling rate of the plurality of solder bumps to a third cooling rate lower than the second cooling rate, wherein the third cooling rate takes effect after the plurality of solder bumps reaches a temperature lower than 200° C., and wherein the third cooling rate is lower than the second cooling rate by a difference greater than about 0.5° C./second.