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首页> 外文会议>ASME international technical conference and exhibition on packaging and integration of electronic and photonic microsystems >IN-SITU MONITORING VIA SYNCHROTRON RADIATION LAM I NOG RAP HY OF THERMAL FATIGUE CRACKS AT DIE-ATTACHED JOINTS UNDER CYCLIC ENERGIZATION LOADING
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IN-SITU MONITORING VIA SYNCHROTRON RADIATION LAM I NOG RAP HY OF THERMAL FATIGUE CRACKS AT DIE-ATTACHED JOINTS UNDER CYCLIC ENERGIZATION LOADING

机译：循环激励载荷下通过模切接合点进行的热疲劳裂纹的现场疲劳监测

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Recently, due to the increasing heat density of printed circuit boards (PCBs), thermal fatigue damage in the joints has exerted a more significant influence on the reliability of electronic components. Accordingly, the development of a new nondestructive inspection technology is strongly desired by related industries. The authors have applied a synchrotron radiation X-ray micro-tomography system to the nondestructive observation of micro-cracks. However, the reconstruction of CT images is difficult for planar objects such as PCB substrates, due to insufficient X-ray transmission in the direction parallel to the substrates. In order to solve this problem, a synchrotron radiation laminography system was developed to relax size restrictions on the observation samples, and was applied to the three-dimensional nondestructive evaluation of several kinds of solder joints, which were loaded under accelerated thermal cyclic conditions via thermal shock tests. Moreover, the thermal fatigue crack propagation process that occurs under actual PCB energization loading conditions will differ from that under the usual acceleration test conditions. In this work, the possibility of in-situ monitoring of the thermal fatigue crack propagation process using the laminography system was investigated at die-attached joints subjected to cyclic energization loading, which is close to the actual usage conditions of PCBs. The optical system developed for use in the laminography system was constructed to provide a rotation stage with a tilt from the horizontally incident X-ray beam, and to obtain X-ray projection images via a beam monitor. In this manner, the X-ray beam is sufficiently transmitted through the planar specimen in all projections. The observed specimens included several die-attached joints, in which 3 mm square ceramic dies had been mounted on a 40 mm square FR-4 substrate using Sn-3.0wt%Ag-0.5wt%Cu solder. Consequently, the laminography system was successfully applied to the in-situ monitoring of thermal fatigue cracks that appeared in the solder layer under cyclic energization. This was possible because the laminography images obtained in the energization state have a quality that is equivalent to those obtained in a non-energized state, provided that the temperature distribution of the specimen is stable. In addition, the fatigue crack propagation process can be quantitatively evaluated by measuring the crack surface area and calculating the average crack propagation rate. However, in some cases, the appearance of thermal fatigue cracks was not observed in a solder layer that had been loaded by the accelerated thermal cycle test. This result strongly suggests that delamination occurred at the interface, which indicates that the corresponding fracture mode was significantly influenced by the type of thermal loading.
机译：近来，由于印刷电路板（PCB）的热密度增加，接头中的热疲劳损伤已对电子部件的可靠性产生了更大的影响。因此，相关行业强烈期望开发新的非破坏性检查技术。作者已将同步辐射X射线显微断层摄影系统应用于微裂纹的无损观察。然而，由于平行于基板的方向上的X射线透射不足，所以对于诸如PCB基板之类的平面物体而言，CT图像的重建是困难的。为了解决这个问题，开发了一种同步辐射薄层照相系统，以放宽对观察样品的尺寸限制，并将其应用于对几种焊点的三维无损评价，这些焊点在加速的热循环条件下通过热加载。冲击测试。此外，在实际的PCB通电负载条件下发生的热疲劳裂纹扩展过程将与通常的加速测试条件下的过程不同。在这项工作中，研究人员在经受周期性通电负荷的裸片连接点上，使用了X光照相系统对热疲劳裂纹扩展过程进行了现场监测，这接近于PCB的实际使用条件。被开发用于分层摄影系统的光学系统被构造为提供相对于水平入射X射线束倾斜的旋转平台，并通过束监视器获得X射线投影图像。以这种方式，X射线束在所有投影中都充分透射过平面样本。观察到的样品包括几个管芯连接点，其中使用Sn-3.0wt％Ag-0.5wt％Cu焊料将3mm方形陶瓷管芯安装在40mm见方的FR-4基板上。因此，薄层扫描系统已成功应用于循环通电下焊料层中出现的热疲劳裂纹的原位监测。这是可能的，因为只要样品的温度分布稳定，在通电状态下获得的层状图像的质量就等于在非通电状态下获得的层状图像的质量。另外，可以通过测量裂纹表面积并计算平均裂纹扩展速率来定量评估疲劳裂纹扩展过程。然而，在某些情况下，在通过加速热循环测试加载的焊料层中未观察到热疲劳裂纹的出现。该结果有力地表明在界面处发生了分层，这表明相应的断裂模式受热负荷类型的显着影响。

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