Low-temperature, organics-free sintering of nanoporous copper for reliable, high-temperature and high-power die-attach interconnections
Conference
Mohan, K, Shahane, N, Raj, PM et al. (2017). Low-temperature, organics-free sintering of nanoporous copper for reliable, high-temperature and high-power die-attach interconnections
. 3083-3090. 10.1109/APEC.2017.7931137
Mohan, K, Shahane, N, Raj, PM et al. (2017). Low-temperature, organics-free sintering of nanoporous copper for reliable, high-temperature and high-power die-attach interconnections
. 3083-3090. 10.1109/APEC.2017.7931137
A novel die-attach joining technique based on low-temperature film sintering of nanoporous Cu is demonstrated. Nanoporous Cu films are proposed as a low-cost replacement of nano-sintering pastes with the following benefits: (i) synthesis by electrochemical dealloying, compatible with standard lithography processes; (ii) no organic content to minimize risks of voiding and corrosion; and (iii) controllable physical properties post sintering through tailorable initial nanostructure and morphology. As a first proof-of-concept, thin films of nanoporous Cu with 25-50nm feature size and ∼60% relative density were synthesized by dealloying of Cu-Si films. The nanoporous Cu films were then sintered on bulk Cu metallizations at temperatures of 200-250°C for 5-15min with an applied pressure of 6-9MPa, in reducing atmosphere. A maximum shear strength of 4.2kgf was achieved and analysis of the fracture profiles showed failure through the sintered joints, confirming strong metallurgical bonding to bulk Cu. Cross-sections of joints formed at 200°C and 250°C-15min observed by SEM showed relative density as high as 85%, achieved for the first time with sintered copper.
