SMT缺陷及防范措施概述.pptx

SMT defects and countermeasure SMT缺陷及防范措施 ;Identify SMT defects;Major contributor to defects缺陷的主要分布; Know the common defect 了解常见缺陷类型 Analysize the possible cause 分析可能的原因 Countermeasure for the defects 基于以上原因采取的对策 ;? Chip components standing on a terminal end (tombstoning). 片式元件末端翘起（墓碑）;Countermeasure/ 对策 Mechanism: Surface tension in component terminal is uneven in reflow. 原理:在回流过程中零件两末端的表面张力不均衡. 1. Component terminal heat distributed unevenly 零件两末端受热分布不均衡. Insufficient soak time: Reflow profile optimization. 保温区时间太短:优化回流曲线参数. 2. PCB Pad design issue (the pads distance is too big): improve PCB pad design. PCB焊盘设计问题(焊盘间距太大):改善PCB焊盘设计. ;Countermeasure/对策 3. Component terminal oxidization or contamination : Solderability test if necessary and RTV the defect material. 元件末端氧化或者受污染: 根据情况做可焊性实验并且退还缺陷物料. 4. Printing misalignment: adjust printing machine parameters. 丝印偏位: 校正丝印机的参数. 5. Placement misalignment: Optimize the PP machine parameters. 贴片偏位: 优化贴片机的参数. 6. Stencil aperture design issue: study and improve the aperture design. 钢网开孔的设计问题: 研究并且改善开孔设计. ;? A solder connection across conductors that was joined. 焊锡在导体间非正常连接. ? Solder has bridged to adjacent non-common conductor or component. 焊锡桥连到相邻的非导体或元件.;Countermeasure/对策 　1. Screen printing issue/丝印问题: a) Paste height out of UCL: Adjust the printer to control the paste height. 锡膏高度超出控制上线: 校正丝印机, 控制锡膏高度. b) Paste printing misalignment or bridging: Fine tune printing machine. /锡膏印刷偏位或者桥联: 优化丝印机. c) Icicle printing: Fine tune printing machine or change to lower viscosity paste. 丝印拉尖: 优化丝印机或者使用低粘性的锡膏. d) Solder paste collapse: change to higher viscosity paste./锡膏塌陷:使用高粘性的锡膏. e) Nonstandard stencil aperture opening : Study and improve the aperture./不标准的钢网开孔: 研究并改善???孔. ;Countermeasure/对策 2. Pick Placement/贴片 a) Component placing misalignment: Fine tune the PP machine . 元件贴片偏位: 优化贴片机的参数. b) High pre