压力约束模式下热超声倒装键合的试验

在采用压力约束模式夹持倒装芯片的条件下，实现了热超声倒装键合。通过观测键合过程中的输入超声功率、工具末端和芯片的振幅变化情况，研究了压力约束模式下不同键合参数对键合过程和键合强度的影响规律。试验结果表明：在这种约束模式下，键合力和功率对键合强度具有重要的影响；键合力对金凸点的变形是决定性的；键合强度与输入的超声能量总量有关，过小和过大的超声能量都不能形成好的键合强度，高强度的键合并不需要大的超声功率输入，键合过程中能量主要耗散于工具／芯片间相对运动导致的摩擦做功，并造成了芯片和工具的磨损。

Study on Thermosonic Flip Chip Bonding under Pressure Constraint Pattern

Thermosonic flip chip bonding was realized under the pressure constraint pattern of flip chip. The input ultrasonic power, vibration amplitudes of flip chip and tool tip during bonding process were recorded. The effects of bonding parameters on bonding strength were studied, and related conclusions had been obtained. Firstly, in this chip constraint pattern, the bonding strength is mainly effected by the bonding force and ultrasonic power, and decided by the total energy consumed on bonding interface. Secondly, large ultrasonic power is not necessary for high bonding strength because most energy is consumed by the friction of tool and chip interface, which causes the abrasion of flip chip back and tool tip. Thirdly, the deformation of bumps is chiefly caused by bonding force.