Processins Technology of High Density Interconnection Bumps

封装是实现个人电脑、手机等电子设备小型化的主要技术。凸点是不可缺少的互连方式。根据电流分布，讨论了这些凸起的形状演化机理。1当Peclet数为1.31时，凸起形状与光致抗蚀角有关，传质受扩散控制。传质集中在阴极角。负的光致抗蚀剂角度为0，阻止了这种传质并降低了阴极角的电流密度。当Peclet数为1407时，传质受对流控制。涡流形成于阴极角的上缘和下缘。当Pe=73.11时，两个涡旋开始合并为一个涡旋；当Pe=44500时，形成一个大的单涡。这种大的单涡增大了阴极中心处的电流。3.分析了大长宽比空腔中扩散控制时的电流分布。长径比越大，电流分布越对称，峰值越大。空腔外部的对流不会引起空腔内部的波动。4对于CSP，高深宽比的凸起，随着阴极放置角度的增大，凸起的下缘增大。由于阴极处的自然对流，在腔体外部形成了一个大漩涡。涡流再次流入空腔并与凸块下缘相撞。5带凸起的凸块形状与添加剂和应用-凸起在周围环境中捕获更多数量的导电粒子，提高电学性能。添加亚硒酸是有效的，该添加剂可以用Wagner数和二次电流分布来解释。

Packaging is the main technology to miniaturize the electronics devices such as personal computer and celler phone. Bump is indispensable interconnection method. The shape evolution mechanism of these bumps has been discussed based on the current distribution.1 Bump shapes with photo resist angle The mass transfer is controlled by diffusion for the Peclet number of 1.31. The mass transfer is concentrated at the cathode corner. The negative photo resist angle, 0, prevents this mass transfer and decrease current density at the cathode corner. The mass transfer is controlled by convection for the Peclet number of 1407. The vortices form both at upper and lower edge of the cathode corners. The negative 0 enlarges the vortices and decreases the current at the cathode corners.2 Bump shapes at high Peclet numbers The two vortices start to merge into one for Pe=73 11. A large single vortex form for P=44500. This large single vortex increases the current at the cathode center.3 Bump shapes with high aspect ratio The current distribution at diffusion control is analyzed with high aspect ratio cavity. The current distribution becomes symmetric with a sharp peak for larger aspect ratio. The convection outside of the cavity does not stir their inside.4 High aspect ratio bumps for CSP The lower edge of bump enlarges with increase of cathode placement angle for the cavity of 1.0 aspect ratio. A large vortex forms outside of the cavity because of the natural convection at the cathode. The vortex again flows into the cavity and collides with the bump lower edge.5 Bump shapes with additive and the application -The bumps with hump on the surroundings traps more number of conductive particles and increase the electric properties. An additive of selenic acid is effective and this additive can be explained by the Wagner number and secondary current distribution.