Soldering investigations on biologically degradable circuit boards

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Supervisor:
Dr. Géczy Attila
Department of Electronics Technology

In these days environment pollution is one of the biggest problems of the society. In every part of our life we need to find eco-friendly solutions, in the way of living, and also in the manufacturing. Electronic devices are more and more needed in our daily life, but they create large amounts of electrical toxic waste. To protect the environment, reducing this waste is a serious problem. In my work I review two biodegradable materials: polilactid acid (PLA), and cellulose-acetate (CA). Those printed circuit boards, which are made of PLA and CA, are biodegradable, reducing the impact on the environment. Their main disadvantage compared to the usual FR4 PCB boards is the low melting temperatures. In my paper I write about those difficulties, which cause problems during production. I review the surface mount technology (SMT) and vapor phase soldering (VPS); the flexible heat transfer of VPS can compensate the problem of low melting temperature. My aim is to show the result of using SMT and VPS together on this biodegradable technology. There was former research on this topic at the Department of Electronics Technology, so using these results, and a new development I tried to optimize the quality of the soldered joints on these boards. This new development is an automatic sample holder inside the oven, which follows the adjusted profile with a low varience. I present different profile effects on the PLA and the CA subtrates. With the help of the novel sample holder I can have a look at the effect of low melting pointed solder paste on other heat profiles, so I can improve the quality of the reflowed solder. After this I evaluate the solder with optical and X-ray microscopy and choose the best heat profile. With this choosen profile I prepare soldered joints on CA substrate. The boards are prepared with and without pre-preg layer. I qualify these soldered joints with shear testing.

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