Lifetime test of multilayer printed wiring boards

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Pinkola János Dr.
Department of Electronics Technology

My task is delamination testing of multilayer printed wiring boards. During the manufacturing process after the inner layers have been developed the printed wiring boards go through a surface treatment processes. The first is the temperation process, which is important because of the copper surface treatment before the Multibond process. The Multibond is a chemical procession to treat the surface of the copper before the pressing of the layers. Now the temperation process at Eurocircuits Ltd. takes 4 hours. My search trended to shorten the time this process takes. For this purpose I designed multilayer printed wiring boards especially for these tests from two stocks (PCL370; IS400). I subjected the test boards to various environmental tests. Mostly I used Highly Accelerated Stress Test (HAST), thermal shock test and the combination of them. On the test boards which made from PCL370 stock have been delaminated after 260 hours in the HAST chamber and 4 cycles in the thermal shock chamber. Unlike the expectations, the delamination is not inversely proportional with the temperation time. Mostly the test boards, which have been temperated for 2-3 hours were the bests from the aspect of delamination. Meanwhile the IS400 boards did not delaminate. Therefore I continued the tests. The boards spent another 170 hours in the HAST chamber and 22 cycles in the Thermal shock chamber. In both cases I performed the tests alternately. From the HAST chamber I took out the test boards in warm and wet condition out and put them into the cold chamber of the Thermal shock machine. This was important because the water diffuses among the layers of the multilayer board on high pressure. When the water becomes frozen, it can bend apart the layers. Despite these test the IS400 boards did not delaminate. According to my tests by this material there is no significant importance of the temperation time. I think my goal was achieved, because the examinations were successful.


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