A Study Of The Preparation And Properties Of High-temperature Joint With Porous Copper As Interlayer

As the trend of miniaturization and multi-function continued,microelectronic devices became highly compact and integrated.As a result,the current density,and therefore the inevitable waste heat generation,of these microelectronic devices increased continuously.For power electronics using the wide-bandgap semiconductors,the operating temperatures were constantly over 200 ?,and occasionally even reaching 600 ?,which required a new generation of hightemperature interconnecting materials.In this thesis,dealloying is employed to fabricate nanoporous copper sheets.By changing the etching temperature,the optimum preparation parameters of nanoporous copper sheets are determined.Then the Cu-NPC-Cu joints are manufactured by thermocompression using the as-dealloyed nanoporous copper as interlayer.We characterize the interface morphology of the bonding joints.The connection mechanism of the nanoporous copper and the Cu substrate and the densification principle of NPC are discussed.In order to investigate the bonding quality of nanoporous copper joints,this paper tests the electrical,thermal conductivity and mechanical properties of the joints.We characterize the fracture after the shear test and analyzes the fracture location and mode of the joints.Finally,morphology,densified structure as well as the mechanical properties changes of the Cu-NPC-Cu joints after aging at 150 ? are characterized in order to analyze the reason of organization and property changes of the joints after aging.After lots of experiments,we found that the nanoporous copper with uniform ligament-channel structure can be fabricated using Cu40Al60 alloy as precursor.The alloy were dealloyed in 1.6 M HCl solution under 80 ?.The connection of nanoporous copper and Cu substrate could be obtained under 260 ? with pressure of 10 MPa maintained for 5 min.Sintering reaction occurs on the surface of NPC and Cu substrate in order to form interconnection while the NPC ligaments form a dense structure under pressure.According to the characterization of the properties of the joints,the shear strength of the joint was 22.10 MPa and the resistivity was 9.65 ??·cm.The thermal conductivity was 144.30 W·m-1K-1,139.63 W·m-1K-1 and 104.37 W·m-1K-1 respectively at 30 ?,150 ? and 300 ?.After aging,there were no new defects or cracks formed in the microstructure of the joints.The densified porous structure was stable during high-temperature service,and the Vickers hardness characterization showed that the thermal-coarsening reaction continues during the aging process.The shear strength of the aged joints was also larger than as-bonded one.In summary,this paper found a new high-temperature interconnection material was fabricated.The Cu-Cu joints which were bonded under low temperature bonding could serve at high temperature.This high-temperature joint has excellent electrical,thermal,mechanical properties and the interconnection structure and shear strength of the joints can maintain stable during aging.