Reliability Design of Conductive Adhesive Connection in Electronic Packages

各向异性导电胶膜（ACF）和导电树脂用于电子封装的导电胶连接，由于其易于小型化、低温制造、无铅等优点，预计将逐年增加。然而，目前胶粘连接的可靠性低于焊接连接，而焊接连接的可靠性技术已经很发达。发展电子封装粘接可靠性的评价与设计技术，对电子封装粘接技术的推广具有重要意义。倒装芯片通常与其他表面贴装设备一起使用，并使用焊点与电路板连接。在回流焊过程中，将电路板加热到150℃至200℃范围内进行预热，并达到峰值温度左右，范围为240℃至245℃。在焊料回流过程中，一些使用粘合剂连接的倒装芯片出现断裂或不连接的情况。在这项研究中，我们开发了一种使用ACF对焊料回流灵敏度测试的倒装芯片的新设计技术。首先对倒装芯片的扩散系数和亨利氏低系数进行了测量，然后对其吸湿过程进行了有限元分析，估算了倒装芯片在大气中吸湿后回流焊过程中产生的蒸汽压力。将由估算蒸汽压引起的倒装芯片假定裂纹周围的应力强度因子与ACF与组件材料（铝端、铜端或硅片）界面的分层韧性进行了比较。估计的焊料回流过程中引起脱层的临界吸收时间与实验结果吻合较好。

Conductive adhesive connection for electronic packaging using anisotropic conductive adhesive film (ACF) and conductive resin are expected to increase year after year due to its easiness for downsizing, manufacturing process under low temperature and including no lead and so on. However, the reliability of adhesive connection is currently lower than that of soldering which has the developed reliability technologies. Developing the evaluation and the design technique for the reliability of adhesively connected electronic packages is very important for the promotion of the adhesive connection technique for electronic packages.Flip chips are often used with other surface mount devices, and are connected with a circuit board using solder joints. During a solder reflow process, a circuit board is heated to the range from 150℃ to 200℃ for the pre-heating, and reached to the peak temperature around, the range from 240℃ to 245℃. During the solder reflow process, some flip chip using adhesive connection are broken or unconnected.In this study, we developed a new design technique for a flip chip using the ACF against the solder reflow sensitivity test. At first, the coefficient of diffusion, and Henry's low coefficient were measured, then the finite element analysis of the moisture absorption was performed to estimate the vapor pressure induced in a flip chip during solder reflow process after moisture absorption in an atmosphere. The stress intensity factors around assumed cracks in a flip chip caused by the estimated vapor pressure were compared with the delamination toughness of an interface between the ACF and the material of a component part (Aluminum terminal, Cu terminal or Si chip). Estimated critical absorption time that causes the delamination during the solder reflow process corresponds well with experimental result.