150 u00b0 c to 63 hours this test would be equivalent to 30 years at projected operating conditions if a standard and simplistic assumption were correct that the rate of degradation doubles for every 10 u00b0 c rise in temperature the test showed no significant degradation occurring until near the end of the test period at the end of the test 100 of the bonds were still over 0 25 lb with an average of 0 70 lb when the test period was more than doubled to 135 hours 89 of the bonds still passed our criterion for initial peel strength by contrast when modules prepared using the conventional dip soldering techniques and a 96 tin 4 silver solder bath were subjected to the same test bond yield was stable at the beginning of the test but dropped to only 3 after 16 hours at 150 u00b0 c this example demonstrates the surprising and completely unexpected superior thermal stability of photovoltaic cell modules prepared in accordance with this invention compared to prior art modules based on these and other tests we conclude that photovoltaic cell modules prepared using the solder paste compositions of this invention will maintain their bond strength at a temperature of about 150 u00b0 c as much as 200 times longer than modules prepared using conventional dip soldering techniques and solder baths comprising approximately 96 tin 4 silver we have also explored the range of compositions providing best maintenance of.