Effect of Free-standing Al/Ni Exothermic Film on Thermal Resistance of Reactively Bonded Solder Joint

Abstract

In this study, a free-standing Al/Ni exothermic multilayer is fabricated and used as a heat source for reactive soldering, instead of an Al/Ni film directly deposited on the solder layer. The free-standing film enables us to reduce not only cracking in the reacted NiAl layer but also voiding at the NiAl-solder interface. These positive effects have successfully resulted in the reduction in the thermal resistance of the joint. Electron probe microanalysis (EPMA) and electron backscattering diffraction (EBSD) analyses suggest that reducing the thermal resistance has been caused by mechanical strain originating from volume shrinkage induced by the Al/Ni exothermic reaction as well as heat conduction from the reactive film to the solder layer. The mechanism of reducing the number of voids is discussed in light of stress distribution during reactive bonding.

Mechanical Property Measurement of Micro/Nanoscale Materials for MEMS: A Review

“…Miyake et al [136] measured the thermal resistance of the Al/Ni bonded element by the thermoreflectance method. After several improvements toward a smaller number of voids and cracks by Kanetsuki et al [137][138][139], the thermal resistance decreased down to around 1.5 × 10 −6 m 2 KW −1 , which is considered as a low value, close to its theoretical value. Those outcomes suggest that the NiAl compound will work well as a structural material for not only MEMS packaging but also power device packaging if several technical issues, such as voids and cracks, could be overcome.…”

Laser-induced multiple points ignition test in Al/Ni exothermic reactive film for crack propagation control

“…Al/Ni multilayer film having the atomic ratio of 1:1 where the formation enthalpy of the NiAl alloy compound is maximum during the reaction process and the total film thickness is 30 μm is chosen throughout the experiments in this study. [27][28][29][30] The outermost layers on both sides are set to be Ni in consideration of the affinity to SnAg solder. 31) Bilayer thickness is set to range from 15 to 200 nm.…”

Influence of Zeta potential on pore arrangement in porous oxide particles produced using ultrasonic atomization method

“…Since no emission gases are generated during the reaction, the instantaneous bonding technique using the exothermic reactive functional material might contribute to solving earth environment problems if conventional current soldering technologies can be replaced with the new technique. [1][2][3][4][5] It can be expected that there are a lot of more desirable applications of the exothermic reactive film other than the instantaneous reactive bonding. However, its multilayered film structure might restrict finding the application.…”