Developing Strain Gauge Technology for the Measurement of PCB Warpage

• Main Authors: Chai-Wei Chang, 張照緯
• Other Authors: Chien-Yi Huang
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/54uy4z

碩士 === 國立臺北科技大學 === 工業工程與管理系碩士班 === 102 === Printed circuit board(PCB) is Composite materials, it consists of FR-4, Solder Mask and copper. Because of the Coefficient of thermal expansion(CTE) of each material in PCB are different and Close fit. When PCB in reflow oven with Surface Mount Technology (SMT) process, the degree of expansion of each material in PCB are different, it cause PCB warpage, and may cause soldering point open, head on pillow and etc. in subsequent process. This research develop a low-cost and to accurate measure PCB thermal warpage method with 3-Elements strain gauge. It can be applied to very large gap of height when PCB with component and the flux volatilize for reflow process. This research considering reflow temperature etc. process parameters, plan and administer bare board in the room temperature test, bare board in high temperature test and PCB product after reflow test, to assess or verify feasibility of the measurement techniques applied to three stage( reflow before, in the reflow, reflow after) and PCB characteristic with PCB bare board and PCB product. First, the bare board in the room temperature test result show that, the warpage curvature of strain estimate match with the warpage curvature of applied mechanics estimate, which means that the strain gauge can be effectively measured PCB warpage at room temperature. Second, the bare board high temperature in the test result show that, because of strain gause is and it measure area is small, it can only be applied to measure the PCB is under no thermal shock in high temperature environments. In addition, PCB product after reflow test result show that, the warpage curvature of strain estimate match with the warpage curvature of Three dimensional profilometer calculate, , which means that the strain gause measurement technique of this research developed can effectively measure the warpage of PCB product after reflow.