Low temperature crack-less solder bonding technique using self-propagating exothermic nanolayers

Abstract

In this article, a new low temperature solder bonding technique using Al/Ni exothermic reactive film is described. Al/Ni reactive film is able to generate heat enough to melt SnAg solder film. During the reaction, the volume is definitely shrunk by 12% because of the changes in crystallographic structure and lattice constant. The volume shrinkage yields cracking in reacted NiAl. In this study we focus on the control of crack position and its propagation direction for realizing crack-less solder bonding using Al/Ni exothermic film. A multiple ignitions system to simultaneously start the reaction from several parts was developed. It was demonstrated that major cracks were produced at the portion where two reactions ran into each other. By changing reaction start point, Al/Ni film's thickness and the overlap width, crack-less solder bonding in 20mm-square silicon chips was achieved.

Fabrication of micron-sized Al/Ni tetrapod particles with self-propagating exothermic function

“…[9][10][11][12] By using Al=Ni multilayer films, we have so far succeeded in instant solder bonding of Si wafers, which can be used in hermetic packaging for microelectromechanical systems. [13][14][15] However, the multilayer films restrict applications because finely forming them to arbitral dimensions and shapes is technically difficult owing to the multilayered system made of two dissimilar materials. Two metallic materials typically have different etching characteristics.…”

Self-propagating explosive Al/Ni flakes fabricated by dual-source sputtering to mesh substrate

“…[9][10][11][12] By using Al/Ni films, we have so far succeeded in instant solder bonding of Si wafers, which is used for microelectromechanical systems hermetic package. [13][14][15] However, the multilayered films restrict applications because finely forming the films to arbitral dimensions and shapes is technically difficult due to multilayered structure made of two dissimilar materials. To explore various types of applications, fabricating micron-sized particles or flakes having exothermic reaction function is required.…”