热超声倒装键合环状界面的形成

采用压力约束模式夹持倒装芯片,实现了热超声倒装键合,观察到环状的键合界面微观形貌,脊状撕裂棱以及表皮层碎片.采用有限元方法计算了键合界面应力、应力场的大小和分布在热超声倒装键合过程中的变化,从应力的角度揭示了环状界面的形成机理.研究结果表明,应力分布显示接触面边沿较其它位置更有利于去除表皮层、更有利于原子扩散形成键合强度,是形成环状界面的重要原因;振动的加载过程改变了应力和应力场的分布,使得应力分布进一步集中在振动位移决定的键合界面边沿位置,促进了环状界面的形成.

Formation of circle band interface of thermosonic flip chip bonding

The thermosonic flip chip bonding has been realized under the pressure constrain pattern of flip chip.Fragment of pad,circle band and ridge have been observed on the bonding interface.The ridge indicates high bonding strength,and fragment of pad indicates remove of interface surface,and the circle band indicates distribution of bonding strength.With the FEA tool,the value and distribution of stress were calculated under different bonding phases,and the formation theory of the circle band interface has been revealed on the term of stress.The edge of bonding interface has better stress conditions for surface remove and atom diffusion,which the primary factor for the formation of circle band interface.And the thermo-sonic vibration changed the distribution of stress and stress field,which caused the edge of bonding interface in better stress conditions,and promoted the formation of circle band interface.