Indium (In) Bump Bonds

Superconducting Materials

Superconducting 3D Integration for Scalable Processors

Tc = 3.4 K

Indium (In) Bump Bonds

Superconducting 3D Integration for Scalable Processors

Role in quantum circuits

Flip-chip indium bump bonds for 3D multi-chip quantum processor stacking

Why it matters

Indium is soft and ductile, making it ideal for superconducting bump bonds that connect

multiple quantum chips in a 3D flip-chip stack. This technique enables qubit chips and control chips to be connected with low-loss superconducting contacts, crucial for scaling beyond 100 qubits.

Key facts

  • Low melting point (157°C) — compatible with quantum chip processing

  • Soft metal: forms reliable superconducting bump bonds under low pressure

  • Superconducting at 3.4 K — well below qubit operating temperature (~15 mK)

  • Enables scalable 3D quantum processor stacking architectures

  • Supports 50–100 qubit multi-chip module workflows