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DELAMINATION FAILURE IN PLASTIC IC PACKAGES DISASSEMBLED FROM SCRAPPED PRINTED CIRCUIT BOARDS

DELAMINATION FAILURE IN PLASTIC IC PACKAGES DISASSEMBLED FROM SCRAPPED PRINTED CIRCUIT BOARDS,Xiaoyu Ding,Dong Xiang,Xueping Liu,Jiping Yang

DELAMINATION FAILURE IN PLASTIC IC PACKAGES DISASSEMBLED FROM SCRAPPED PRINTED CIRCUIT BOARDS  
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Recycling of scrapped or rejected printed circuit boards (PCBs) becomes desirable due to environmental and legislative reasons. Many components on scrapped or rejected PCBs are still functional and usable so that the reuse of those components has a great ecological and economical benefit. In order to reuse those components, it is necessary to disassemble them from PCBs without doing any damage to them. To date, highly effective PCB disassembly methods almost solely depend on high temperature to melt solder. However, this kind of disassembly process may weaken, and even destroy the reliability of components because of intense thermal shock. In this paper, the delamination in plastic IC packages, which is a serious component failure mode caused by high-temperature disassembly process, is discussed. Firstly, PCBs are disassembled under different parameters using a pilot disassembly apparatus. After disassembly, plastic IC components are examined by ultrasound scanning to check their internal qualities. Results show that plastic IC components are easy to delaminate during high temperature disassembly and delamination is more serious under higher heating rates. Then the delamination reasons are analyzed, and possible countermeasures, which include prebaking PCBs and controlling heating rate, are proposed to improve disassembly process. After that, this paper discusses some unique characteristics of baking PCBs, which are not the same as baking process in SMT. Then a Finite Element Analysis (FEA) diffusion model is built to study moisture desorption behavior in plastic packages at different baking condition, and an baking experiment is performed. Finally, in order to controlling heating rate during disassembly, a new automatic PCB disassembly cell is developed. A contrasting experiment using this system is conducted to prove the efficiency of improved disassembly process. Results reveal that identical components that are found delaminated in prime experiments do not delaminate again under improved process. This paper concludes that proper parameters of pre-baking and disassembly process could decrease delamination of plastic IC packages greatly, hence they have high benefit to ensure reliability and reusability of plastic IC components disassembled from scrapped or rejected PCBs.
Published in 2008.
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