(中國科學院 上海微系統(tǒng)與信息技術研究所
上海新代車輛技術有限公司，上海 200050)
摘 要: 對比了充膠和未充膠塑料封裝球柵陣列(PBGA)器件在-40℃～125℃溫度循環(huán)條件下的熱疲勞壽命，采用光學顯微鏡研究了失效樣品焊點的失效機制，并分析了充膠提高器件熱疲勞壽命的機制。實驗發(fā)現：底充膠可使PBGA樣品的壽命從500周提高到2000周以上，失效樣品裂紋最先萌生于最外側焊球中近硅芯片界面外邊緣處，界面處焊料組織粗化及界面脆性金屬間化合物Ni3Sn2和NiSn3相的生成均促使裂紋沿該界面從焊球邊緣向中心擴展。PBGA焊點界面處裂紋的萌生和擴展是該處應力應變集中、焊料組織粗化以及生成脆性金屬間化合物等各種金屬學和力學因素共同作用的結果。
關鍵字: 球柵陣列；可靠性；底充膠；晶粒粗化；金屬間化合物
grid array component
（Daimlerchrysler SIM Technology Co. Ltd, Shanghai Institute of
Microsystem and Information Technology, Chinese Academy of Science,
Shanghai 200050, China）
Abstract:Failure mechanism，as well as failure cycles of two groups of plastic ball grid array(PBGA) samples (with/without underfill) under thermal cycling conditions in the range of -40℃～125℃，were presented. The experiment results show that underfill can improve the thermal cycle life of PBGAs drastically，from 500 cycles to over 2000 cycles. Highly concentrated stress and strain induced by the mismatch of thermal expension coefficient between the BGA component and the printed circuit board，coarsened grain and two kinds of intermetallic com pounds (Ni3Sn2/NiSn3) which formed during reflow and thermal cycle and their negative effects on the reliability of solder joints were discussed. It is found that the initiation and propagation of micro-crack are caused by all the three factors above. The initiation of the crack and direction of its propagation were also presented.
Key words: BGA；reliability；underfill；coarsened grain； intermetallic compound
