應用應變規於印刷電路板熱翹曲量測技術開發

Developing Strain Gauge Technology for the Measurement of PCB Warpage

張照緯(Chai-Wei Chang)

指導教授 ： 黃乾怡

國立臺北科技大學/管理學院/工業工程與管理系碩士班/碩士(2014年)

摘要

印刷電路板(Printed Circuit Board; PCB)為包含FR-4、綠漆和銅的複合材料板，在經過迴焊製程受熱時，因不同材料間熱膨脹係數(Coefficient of Thermal Expansion; CTE)的不匹配，造成其膨脹程度不同。但PCB各材料又緊密貼合，而形成熱翹曲(Warpage)之現象，可能造成枕頭效應 (Head on Pillow)及空焊(Open)等後續製程不良風險。
本研究旨在利用三軸式應變規量測技術，建構低成本且精準的PCB熱翹曲量測方法，可應用於PCB乘載元件高度差距甚大時，並適用迴焊製程中助焊劑揮發環境下，仍能精準地量測PCB翹曲量。研究考量迴焊溫度等製程參數，以PCB裸板及PCB產品為研究對象，分別評估或驗證該量測技術應用於迴焊製程前、中、後等階段及PCB特性之可行性。本研究規劃並執行常溫裸板、高溫裸板及迴焊後實板等三階段實驗建構應變規量測PCB熱翹曲方法，並驗證或評估其可行性。首先，常溫裸板實驗結果顯示，應變規測得應變值所推估PCB翹曲曲率與應用力學推導曲率匹配，表示應變規可有效量測PCB於室溫環境下變形。其次，在高溫裸板實驗中發現，由於應變規量測應變範圍甚小且過於靈敏，故僅可應用於量測PCB處於無震動靜止環境下熱變形。此外，迴焊後實板實驗結果顯示，應變值推估曲率與雷射3D量測計算曲率一致，表示本研究開發之應變規量測技術可有效量測已上件PCB受熱後產生的變形。

關鍵字

應變規 ； 印刷電路板 ； 熱膨脹係數 ； 翹曲 ； 陰影疊紋技術

並列摘要

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.

並列關鍵字

Strain Gauge ； PCB ； CTE ； Warpage ； Shadow Moire

參考文獻

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