Failure mechanisms of boards in a thin wafer level chip scale package
Failure mechanisms of boards in a thin wafer level chip scale package
复制标题
薄晶圆级芯片级封装中电路板的失效机制
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
L. Nguyen
中科院分区：
文献类型：
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作者：
Pavan Rajmane;Hassaan Ahmad Khan;A. Doiphode;Unique Rahangdale;D. Agonafer;A. Lohia;S. Kummerl;L. Nguyen
已经进行了各种研究来研究不同板厚度对BGA封装的热机械可靠性的影响。晶圆级芯片规模封装（WLCSP）也在这方面进行了研究，以确定PCB构建厚度对焊点可靠性的影响[1]。研究清楚地表明，较薄的印刷电路板（PCB）导致BGA焊点的热机械疲劳寿命较长。随着文献和过去的趋势支持更薄的电路板的想法，制造商选择通过减少PCB的厚度来提高封装的可靠性。通过减小各个层的厚度并保持总层数恒定，厚度从1 mm减小到0.7mm。当经受热循环时，观察到0.7mm板比1 mm板更早失效。由于WLCSP的这种行为与过去的趋势形成鲜明对比，因此需要进行广泛的研究，以确定和理解0.7 mm板中故障的过早物理学/故障的因果关系。在本文中，努力了解的机制，这是造成早期失败的薄板。通过对1 mm和0.7mm板的材料表征，研究了板中芯层、铜层和铜层的数量和厚度的影响。此外，还提出了一种设计优化帐户，以提高这种封装的热机械可靠性。
Various studies have been conducted to study the effect of varying board thickness on thermo-mechanical reliability of BGA packages. Wafer level chip scale packages (WLCSP) have also been studied in this regard to determine the effect of PCB build-up thickness on the solder joint reliability [1]. The studies clearly demonstrate that the thinner Printed Circuit Boards (PCBs) result in longer thermo-mechanical fatigue life of solder joints for BGA. With the literature and past trends supporting the idea of thinner boards, manufacturer opted to move forward by decreasing the thickness of their PCBs to improve the reliability of their packages. The thickness was reduced from 1mm to 0.7mm by decreasing the thicknesses of individual layers and keeping the total number of layers constant. When subjected to thermal cycling, it was observed that 0.7mm board was failing earlier than the 1mm board. Since this behavior of a WLCSP contrasts with the past trends, it required extensive study to determine and understand the pre-mature physics of failure/causality of failure in 0.7mm board. In this paper, an effort is made to understand the mechanism which is causing an early failure in the thinner board. The effect of number & thicknesses of core layers, prepregs and Cu layers in the board has been studied through material characterization of both 1mm and 0.7mm boards. Further, a design optimization account has also been presented to improve the thermo-mechanical reliability of this package.