用于大面积芯片互连的纳米银膏无压烧结行为

Pressureless sintering behavior of nano-silver paste for large area chip interconnection

文中采用化学还原法制备出一种可以用于低温烧结的纳米银膏,通过对低温无压烧结纳米银焊点的组织结构、力学性能和失效模式进行了分析,系统地讨论了无压烧结焊点中烧结银组织的渐进性组织演变规律,获得了互连焊点尺寸对烧结银连接性能和可靠性的影响.在烧结温度250℃,保温时间1 h的条件下,焊点面积小于等于3 mm×3 mm时,无压烧结焊点强度可以达到70 MPa以上.随着尺寸的增加,焊点抗剪强度逐渐降低,但焊点尺寸为10 mm×10 mm时仍然保持20 MPa以上的抗剪强度.断面形貌表征结果显示,焊点面积越大,烧结银层塑性变形程度越低.所有尺寸焊点的断面形貌从中心到边缘处均存在渐进性的组织演变,边缘处均呈现剧烈的塑性变形.

A nano-silver paste which can be used in low temperature sintering was prepared by chemical reduction method. By analyzing the microstructure, mechanical properties and failure modes of pressureless low temperature sintered nano-silver joints, the gradual microstructure evolution of the pressureless sintered silver joints was systematically discussed, and the influence of joint size on the connection performance and reliability of sintered silver was obtained. By heating the joint to 250 ℃ with the sintering time of 1 hour, the shear strength of pressureless sintered joint reached 70 MPa or more when the joint area was less than or equal to 3 mm × 3 mm. As the joint area increased, the shear strength of the solder joint gradually decreased. However, when the solder joint size was 10 mm × 10 mm, the shear strength remained above 20 MPa. The fracture interface morphology showed that the larger the joint area, the lower the plastic deformation of the sintered silver. It was interesting that there was a gradual microstructure evolution from the center to the edge of the joints of all sizes, and violent plastic deformation occurred at the edges.