Indium (In) Bump Bonds
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**Superconducting Materials**

 

Superconducting 3D Integration for Scalable Processors

**Tc = 3.4 K**

 

Indium (In) Bump Bonds
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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