In this paper, porous micron sliver bump arrays composed of nano-Ag particles are deposited on DBC substrates by the PLD technique to replace the traditional solder bumps, and they are applied to the connection between Si chips and DBC substrates. The results show that, by adopting stainless steel mask, Ag bump arrays with feature sizes of 500 μm and 300 μm can be deposited with a height of 60 μm and morphology of circular truncated cone, and the top diameters of two kinds of bumps are 330 μm and 100 μm, respectively. Under the thermo-compression bonding parameter of 250 ℃-2 MPa-10 min, metallurgical connections form at the upper and lower interfaces of Ag bumps with the metallized layer. The Ag bumps are transfered into a porous network structure, in which the porosity of the edge area is about 42% and that of the central area is 22%. The shear strengths of chip-DBC joints with 500 μm and 300 μm feature size Ag bump arrays are 14 MPa and 12 MPa, respectively. The joint fracture mainly occurs at the interface between the sintered Ag bumps and the chip or DBC substrate. This paper proves that it is feasible to replace the traditional solder bumps with porous micron silver bumps in the integrated circuit chip package, but it is still necessary to improve the morphology of bumps from the aspects of mask materials and PLD technology.
Yongchao Wu, Jintao Hu, Wei Guo, Lei Liu, Hui Kang, Peng Peng. Ultrafast Laser Patterning Deposition of Micron Sliver Bumps for Chip Bonding Application[J]. Chinese Journal of Lasers, 2022, 49(2): 0202002