Low melting point SnBiIn-based micro-nanoparticles for high-density microbump bonding technology

As chip technology faces increasing difficulty and cost in development, scaling for integration density is slowing down. 3D integration technology has emerged as a solution to maintain computational performance in consumer electronics. The development of low melting point solder has become critical in order to broaden the temperature range in manufacturing processes. This paper achieves high-density bonding using low-melting-point SnBiIn-based micro-nanoparticles prepared through ultrasonication. Under the reflow condition of no applied pressure, 100 °C and 5 min, solder joints with complete intermetallic compounds can be achieved. The primary composition of this solder joint is Cu
6
(Sn, In)
5
. We also fabricated sandwich structure solder joints with a thickness of approximately 10 μm. The growth of Cu
6
(Sn, In)
5
at the interface increased with higher reflow temperatures and longer reflow times. The shear strength of the solder joint reached 33.26 MPa and exhibited distinct brittle fracture.