Ceramic-to-metal bonding using rare-earth containing Sn-Bi solder

Area of Science:

• Materials Science
• Optoelectronics Engineering

Background:

• Miniaturization of optoelectronic devices requires efficient heat dissipation.
• Direct bonding of optical substrates to metal heat sinks is challenging without substrate metallization.

Purpose of the Study:

• To demonstrate direct bonding of glass to copper using rare earth (RE) element-doped tin-bismuth solder.
• To achieve high shear strength in solder joints at low temperatures (<200 °C).

Main Methods:

• Utilized Sn-58 wt% Bi solder doped with rare earth elements.
• Optimized reflow temperature, time, and used an inert gas atmosphere.
• Evaluated shear strength and failure morphology after thermal aging and cycling tests.

Main Results:

• Achieved highest shear strength in glass-copper joints using RE-doped solder without ultrasonic-assisted soldering.
• RE elements facilitated bonding to unmetallized glass.
• Solder joints showed minimal degradation at the interface after thermal stress.

Conclusions:

• RE-containing solder enables low-temperature direct bonding of unmetallized glass and ceramics to metals.
• This facilitates efficient heat dissipation in optoelectronic devices.
• Further optimization is needed for extreme working conditions.