Transcript 下載/瀏覽
Reporter : 黃一軒 Advisor : 莊承鑫 老師 Institute of Mechanical Engineering Southern Taiwan University, Tainan Taiwan 1 Outline • Motivation • Simulation Design and Boundary conditions • Results and Discussions - Influence of cap on PWB’s thermal deformation - Influence of adhesive material and thickness • What is Buffer Layer? - Discussion on buffer layer effect • Conclusions 2 (a) COB (Chip on Board) Motivation Advantage: Cost down , Small size , Simple design , etc. Shortcomings : molding difficult. (b) SMT (Surface Mount Technology) Solder paste printing ↓ Pick and Place machine ↓ Solder paste printing Reflow(260 ℃) ↓ Complete Pick and Place Automation. machine Advantage: Shortcomings : Reflow temperature is Reflow higher. ECM MEMS Microphone 3 What is problem of MEMS Microphone ? E Adhesive CTE Soft Cap PWB 260℃ Rigid Cap effect PWB PWB effect Chip High temperature Heating of chip from SMT. 4 Simulation Design and Boundary conditions 300 Temperature (oC) 250 200 150 100 50 0 0 Hinge Sliding end 50 100 150 200 250 300 350 400 Time (sec) Heating process Sliding end Total element : 810002000 Simulation Cases 5 Material properties 2025D > 3140RTV DA6501 Metal Cap > PWB > LCP Cap LCP Cap > PWB > Metal Cap 3140RTV DA6501 > 2025D 6 Results and Discussions 7 Buffering effect Low E Buffering effect High E No Buffering effect 8 Conclusions According to the simulations result when the adhesive thickness at 30um is at the minimum of stress and deformation on the diaphragm . A low Young’s modulus adhesive materials, such as 3140RTV and DA6501, effectively isolates the silicon chip with less influence of thermal deformation from bottom PWB as the buffer layer effect. However, the thickness of soft adhesive needs to be controlled in a low level to prevent the thermal stress in the diaphragm rising with thickness. 9 Thank you for your attention 10