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The interface delamination of waste plastic chip will seriously affect the value of their recycling reuse; therefore, it has been a hot issue in recycling researches of Waste Electrical and Electronic Equipment (WEEE). Based on the exponential cohesion theory, this paper has researched chip delamination and established the Cohesive Zone Model (CZM) of delamination crack for chip interface, as well as proposed a method which combined the experiment of crack surface observation and the simulation of fracture mechanics. By employing this method, the CZM parameters of waste plastic chip interface have been obtained. Based on the CZM, the simulation of waste plastic chip interface delamination has been made, and its results showed that: temperature and humidity factors have a significant impact on the chip delamination. At last, the disassembly experiments of Waste Printed Circuit Boards (WPCB) have been made under different disassembly technology, and the delamination rate of resulting chips has been calculated. Then this paper has analyzed the influence rule of different disassembly conditions on the chip delamination and verified the correctness of chip delamination simulation results, as well as proposed an optimized disassembly technology of WPCB for reducing plastic chip’s delamination. Introduction With the rapid development of world economy, a large number of Waste Electrical and Electronic Equipment (WEEE) appeared each year, and caused tremendous pressure to the environment, then the recycling of WEEE has become a major issues causing social attention. Countries all around the world have issued corresponding bill about WEEE processing . For example, the WEEE Directive issued by European Union in 2003 cleared rules for ten classes of recovery and regeneration utilization of WEEE. Printed Circuit Board (PCB) is the important material for classification processing after dismantling the WEEE, "the National Hazardous Waste List" of China clearly stipulates that PCB components are T-class hazardous wastes. Therefore, studying the recycling method is of great significance. Component reuse is an effective method to achieve the high value recycling of Waste Printed Circuit Boards (WPCB), and is the current hot research spot. Study shows that the design life of components is 5 hours, while the average service life of WEEE in developed country is only 20000 hours. According to the Bathtub Curve theory of components invalidation, the component is in the optimal period of quality, and has high reuse value . Guo Xiuying et al. researched the reusability of waste plastic chip through experimental method in 2009, then put forward that the qualified rate can be up to 98% as long as the recycling way of waste plastic chip is reasonable and normative, and it could make very high reuse value. The delamination damage of waste plastic chip is a common problem which influences chips’ reuse value and reliability, so the research of chip interface delamination has been the core content in the waste plastic chip reusability study. Aiming at the interface delamination fracture problems of waste plastic chip, the exponential Cohesive Zone Model (CZM) was used to analyze delamination crack of two phase interface in chip interior, and the chip interface delamination was analyzed by adopting finite element simulation method with the CZM as a guide. Finally, the simulation results were verified to be International Power, Electronics and Materials Engineering Conference (IPEMEC 2015) © 2015. The authors Published by Atlantis Press 720 effective through the WPCB disassembly experiment, and concrete countermeasures of WPCB disassembly technology to reduce the chip delamination were put forward. The Cohesive Zone Model Traditional interface delamination fracture research was conducted using fracture mechanics simulation method, thus it needed to set the preset crack in simulation model. Due to the position and size of preset crack were set subjectively, it often brought great influence on the accuracy of calculation results . In addition, we can also use the cohesion theory to describe the fracture behavior of material. The crack formation and extension phenomenon is analyzed with the tension displacement law of cohesion theory, and it doesn't need preset crack in simulation process, so this is very suitable for the fracture problems of fixed crack propagation path. The delamination phenomenon of plastic chip mainly occurs in the interface between different materials, and the crack formation and extension path is relatively stationary. Therefore, the cohesion theory method was adopted to study the delamination fracture problems of plastic chip in this paper. In the delamination fracture process of plastic chip, a transition zone generates in the interface between two phase materials. This paper used the edge-opened crack as example to study the fracture process, as shown in Fig.1(a). There is a transition zone between the original interface and free surface in the tensile fracture zone, which is called cohesive zone. The mechanical properties of material in cohesive zone are different from other interfaces of plastic chip. For the mechanical properties of cohesive zone, it is described with the tension displacement law. Among numerous cohesion models, the tension displacement law of exponential CZM most conforms to the Van Der Waals force form, and gets high accuracy to solve the problems of composite interface fracture [7, . So the exponential CZM was adopted to study the interface delamination fracture problems of plastic chip in this paper. Fig.1 Cohesive zone of plastic chip delamination interface The cohesive zone of delamination crack in plastic chip is shown in Fig.1(b), making an analysis of one point in the cohesive zone, the received tension of the point can be decomposed to a normal tension Pn which is perpendicular to the interface and a tangential tension Pt which is parallel to the interface. The interface’s fracture displacement δ can be also decomposed to a normal displacement δn and a tangential displacement δt. The relation between the fracture energy φ(δ) of exponential CZM and the interface’s fracture displacement δ is shown in Eq.1.

Research Based on Cohesive Zone Model for Interface Delamination of Waste Plastic Chip