Case Study | Copper Nanowire Interconnects: A More Flexible Solution for Shrinking Chip Connections

The electronics inside modern devices are getting more complex — and more tightly packed. One of the leading approaches to squeezing more performance out of chips is called heterogeneous integration: stacking different types of chips together into a single package.

It works well, but it creates a problem at the joints. The metal connections that hold stacked chips together are under constant stress as the device heats and cools, and as those connections get smaller, they become increasingly prone to cracking.

Researchers at Henan University of Technology and Huazhong University of Science and Technology (HUST) have published a new approach to solving this in the Journal of Advanced Joining Processes (doi:10.1016/j.jajp.2026.100386) — replacing conventional solder with arrays of copper nanowires that can flex rather than fracture.

Science Made Simple

When chips with different jobs are stacked into one package, the metal joints connecting them must cope with repeated heating and cooling. Different materials expand at different rates, and over time this stress causes conventional solder joints to crack or fatigue — eventually causing device failure.

This research replaces solid solder joints with bundles of ultrafine copper wires, each around 200 times thinner than a human hair. Because the bundle can flex slightly under stress rather than staying rigid, it absorbs movement rather than fracturing.
Think of the difference between a stiff metal bar and a bundle of threads: the threads bend without breaking. The result is a more durable connection better suited to the demands of modern, densely packed electronics.

Why Solder Is Struggling

Conventional solder has served the electronics industry well, but it has limits.
As chip connections shrink — some are now smaller than 20 micrometres across — the solder becomes increasingly brittle. The compounds that form at the joint interface grow proportionally larger relative to the joint itself, making fracture more likely under vibration or thermal stress. At the same time, gaps between connections are getting so small that the protective polymers typically used to cushion solder joints can no longer be dispensed effectively. The industry needs a structurally different solution.

Advent Materials at the Heart of the Process

To fabricate their nanowire interconnects, the Henan/HUST team used high-purity copper and tin sheet supplied by Advent Research Materials (99.98+% purity) as the source material for electroplating.
In a process like this — where metal is deposited wire by wire through nanoscale channels — the purity of the source material directly shapes the outcome. Impurities can disrupt the way metal ions distribute through the tiny pores of the template, affecting the crystal structure and consistency of the wires produced.

The team deposited copper into porous alumina templates using controlled electrical current, then dissolved away the template to leave free-standing arrays of copper nanowires. A key finding was that the electrical current used during deposition governs both the orientation of the crystal structure and the uniformity of wire height — both critical to how well the finished interconnect performs. Getting this right required precise, consistent source material.

A Joint That Flexes Rather Than Breaks

Once the copper nanowire arrays were prepared, the team bonded them to copper pads using a thin layer of tin — also electroplated — which melted under heat and pressure to form a strong, continuous joint. The finished interconnects were notably more flexible than conventional solder, with mechanical compliance orders of magnitude higher, while still delivering shear strength on a par with standard solder joints. In plain terms: they can absorb stress without sacrificing structural integrity.

Electrical performance was comparable to conventional solder interconnects, and estimated thermal conductivity was higher — a meaningful advantage in densely stacked chip configurations where heat management is a growing concern.

Holding Up Under Repeated Stress

The team subjected the interconnects to 2,000 bending cycles — repeated flexing at a tight radius — and monitored electrical performance throughout. No failures were recorded. Resistance remained stable across all cycles, indicating that the mechanical and electrical properties held up together under sustained, repeated deformation. The authors note that further testing under thermal cycling and real-world operating conditions is the next step before these interconnects could move toward production use.

A More Reliable Foundation for Next-Generation Electronics

This research is a strong example of how materials precision at the start of a process — in this case, the purity of the copper and tin used as electroplating anodes — feeds directly into the performance of the finished product.
For research teams working on next-generation chip interconnects, the work offers a clear, tested fabrication route and a compelling alternative to conventional solder. Advent Research Materials supplies high-purity copper and tin in the forms and specifications needed for exactly this kind of precision electrodeposition work.

Source: Li, Y., Chen, X., Ma, L., Lin, X., Wang, C., Li, Z., Liu, W., Tian, Y., & Wu, F. (2026). Formation mechanism and mechanical properties of compliant interconnects incorporating Cu nanowire arrays for heterogeneous integration. Journal of Advanced Joining Processes, 13, 100386. https://doi.org/10.1016/j.jajp.2026.100386