Low-temperature bonding of laser diode chips using atmospheric-pressure plasma activation of flat topped Au stud bumps with smooth surfaces

Surface activation by atmospheric-pressure plasma has been used for low-temperature bonding of laser diode (LD) chips. Coined Au stud bumps with smooth surfaces (Ra: 1.3 nm) and Au thin film electrodes (Ra: 2.1 nm) of LD chips were activated by Ar+O
₂
or Ar+H
₂
atmospheric-pressure plasma for 30 s and bonded in ambient air at low-temperature (25-150°C). Bonding strength was high enough to exceed the strength requirement of MIL-STD-883F, method 2019 (×2). The measured results of light-current-voltage (L-I-V) characteristics of the LD chips indicated no degradation after bonding.