Abstract
Alumina-based die attach and encapsulation for high-temperature (300oC to 500oC) electronic packaging were investigated. The alumina paste material comprises of aluminum dihydric phosphate as a binder and alumina powder as a filler with embedded nano aluminum nitride and nano-silica powders to promote its curing process, reduce its curing tension, and increase its bond shear strength. The chip-to-substrate bond strength was enhanced and met the MIL-STD-883 2019.9 requirements for die-attach assembly. Its encapsulation property was improved with fewer cracks compared to similar commercial ceramic encapsulants. The die-attach material and encapsulation properties tested at 500°C showed no defect or additional cracks. Thermal aging and thermal cycling were carried out on the samples. XPS analysis revealed a higher oxygen bonding percentage for the 10% nanosilica ceramic sample than the samples with no nano-silica. XRD peak broadening is largest for the 10% nano-silica ceramic which indicated smaller crystallite sizes. The smaller crystallite size for the 10% nanosilica sample introduces a larger microstrain to the alumina crystal structure. FTIR revealed the presence of alumina-silicate bonds on these samples with the largest amount present in the 10% nanosilica samples. Si-O and Al-O bonds were observed from FTIR on nanosilica samples especially the higher than 10% nanosilica samples. SEM and EDX results showed a uniform bond line for the 10% sample and uniform material distribution.
Nano Ag sintering on Cu substrate assisted by self-assembled monolayers for high-temperature electronics packaging
