Abstract: Disassembling end-of-life printed circuit boards (PCBs) and reusing the high-value electronic components is an effective way of recycling. During the disassembly process, the quality of components is easily to reduce if the process is inappropriate. A common defect which usually arises in the disassembly process is interfacial delamination within plastic-encapsulated integrated circuits (ICs). The IC delamination is mainly caused by excessive high temperature. Therefore, research of the temperature field of the PCB and the heating strategy is necessary. A peak-temperature principle and a ramp-rate principle are proposed to meet the purpose of heating, i.e. melting the solder sufficiently and avoiding the IC delamination. The peak-temperature principle requires the peak temperature of the PCB should be as low as possible on the premise of melting the solder sufficiently; the ramp-rate principle requires that the ramp-up should be fast at first, and slow when the temperature is approaching the peak temperature. Then a thermal model of PCB heated in multiple temperature zones successively with hot air is built. Combined with this model, a heating strategy is proposed based on the temperature-field uniformity to achieve the temperature profile which conforms to the two heating principles. An experiment is conducted using an independently-developed disassembly machine for end-of-life PCBs to validate the heating strategy. The experimental results show: The PCB temperature field with the fast-then-slow (FTS) ramp from the heating strategy is more uniform than the temperature field with the ramp-to-spike (RTS) which is usually used in reflow process; their component disassembly rate is very close to each other; compared with the RTS ramp, the delamination fraction caused by the disassembly process is 80% lower with the FTS ramp; and thus the proposed heating strategy can effectively reduce IC delamination during the disassembly process.

Key words: end-of-life printed circuit board;recycle;reuse;disassembly;temperature profile