细间距倒装芯片互连过程中焊点界面金属间化合物的形成与演化

Evolution of interfacial intermetallic compound in small solder joint of fine pitch flip chip during reflow

关键词:  无铅焊料  金属间化合物  倒装芯片  界面反应

Key words:  lead-free solder  intermetallic compound  flip chip  interfacial reaction

摘要:

利用凸点间距为100μm,高度约为45μm,焊料成分为Sn-3.0Ag-0.5Cu(质量分数,%)(SAC305)的倒装芯片与树脂基板互连封装,研究芯片单侧凸点及芯片与BT基板焊点互连回流过程中界面金属间化合物(intermetalic compound,IMC)的形成和演化.结果表明,封装互连前,在芯片单侧镍焊盘界面上形成了长针状(Ni,Cu)₃Sn₄和薄层状Ni₃P,由于反应过程中焊料基体中Cu原子的大量消耗,没有形成典型的(Cu,Ni)₆Sn₅.封装互连过程中,由于大量Cu原子从铜界面扩散到镍界面,促使镍焊盘界面(Ni,Cu)₃Sn₄逐渐转化成(Cu,Ni)₆Sn₅,形貌由针状转变成短棒状,反应后(Cu,Ni)₆Sn₅成为主要IMC层;在铜焊盘界面上,形成了一层短棒状的(Cu,Ni)₆Sn₅,由于从镍焊盘界面扩散过来的Ni原子对Cu₃Sn生长的限制作用,反应后没有形成典型的Cu₃Sn.

Abstract:

Through the cyclic load-unload test of nano-indentation method,the effects of maximum load on cycling mechanics behavior for two kinds micro-solder joints of Sn-3.0Ag- 0.5Cu/Cu and Sn-0.3Ag-0.7Cu/Cu were investigated.The results indicated that the cycling F-h curves that before closed showed a hysteresis loop.The area of hysteresis loop and indentation residual depth of micro-soldered joints increased with the increase of the maximum load.The cumulative damage of microsoldered joints increased.When the maximum load was given, the area of hysteresis loop and increments of residual indentation depth decreased gradually with the loading time increasing.Indentation creep C of micro-soldered joints decreased with the increase of the maximum load.At the same time,indentation creep C of micro-soldered joints sharply decreased at first and then plateaued with the loading time increasing.Indentation creep C of Sn-3.0Ag-0.5Cu/Cu micro-soldered joint was less than that of Sn-0.3Ag-0.7Cu/Cu micro-soldered joint.