Low-Temperature Copper Bonding Strategy with Graphene Interlayer.
ACS nano(2018)
摘要
The reliability of lead-free Cu bonding technology is often limited by high bonding temperature and perpetual growth of intermetallic compounds between Sn solder and Cu substrate. Here, we report a low-bonding-temperature and highly-reliable Cu bonding strategy with the use of graphene as an interlayer. By integrating nanoscale graphene/Cu composite on the Cu substrate prior to thermocompression bonding, we observe a macro-scale phenomenon where reliable Sn-Cu joints can be fabricated at a bonding temperature as low as 150 ºC. During the bonding process, nanoscale features are replicated in the Sn solder by the Cu nanocone array morphology. Compared to microscale Sn, nanoscale Sn is mechanically weaker and thus can distribute on the Cu substrate at a much lower temperature. Furthermore, insertion of a graphene interlayer, which is of one-atomic-thick, can successfully retard the intermetallic compounds growth and preserves high bonding yield, following a 96h of aging, as confirmed through SEM and shear strength analyses. Our graphene-based Cu bonding strategy demonstrated in this work is highly reliable, cost-effective, environmentally friendly, representing a much closer step towards industrial applications.
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关键词
integrated circuit packaging,copper interconnects,tin solder,copper nanocone array,graphene
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