underfill crack meaning in Chinese

底部填充裂缝

Zhang liji ( material physics and chemistry ) directed by professor xie xiaoming this paper is intended to solve problems for those who are designing , using pbgas . failure mechanism , as well as cycles to failure of two groups of pbga samples ( with / without underfill ) for thermal cycling conditions in the range of - 40 ~ 125 , were presented . the experiment shows that solder ball in the samples without underfill cracked after 500 times cycle , no crack was found in the underfilled samples even after 2700 cycles
通过一系列的实验，得到以下实验结果： ?在本论文设定的温度循环条件下，未充胶pbga样品的热疲劳品寿命在500周左右，充胶样品的焊点寿命高于2700周； ?对于未充胶器件，中心距( dnp )是决定焊点应力、应变大小的最主要因素，裂纹总是从中心距较大处萌生并向中心处扩展； ?温度循环的过程中焊盘附近焊料组织明显粗化。