Relieving the Residual Stresses in Diamond/Copper Combination Using Y₂W₃O₁₂ NTE Particles Doped Ag-Based Filler Alloys
十月14, 2025
Relieving the Residual Stresses in Diamond/Copper Combination Using Y₂W₃O₁₂ NTE Particles Doped Ag-Based Filler Alloys
Objective
To reduce residual stresses in diamond/copper brazed joints by incorporating negative thermal expansion (NTE) Y₂W₃O₁₂ (YWO) particles into AgCuSnTi filler alloys for use in diamond microwave window fabrication.
Method
Base materials: CVD polycrystalline diamond (5×5×1 mm) and Cu (10×10×4 mm).
Filler: Ag–28Cu–10Sn–1Ti (wt%) + x vol% YWO (x = 0–5).
YWO particles were mixed by ball milling and joints were vacuum brazed at 750 °C for 10 min.
Characterizations: SEM/EDS, XRD, and Raman analysis for residual stress measurement.
Key Findings
| Parameter | Observation / Result |
|---|---|
| Filler composition (1 vol% YWO) | Formed phases: Ag(s,s), Cu(s,s), CuSn₃Ti₅, CuTi, and YWO particles. |
| Interface chemistry | Formation of TiO₂ + Ti₄Cu₂O double layers around YWO particles enhanced filler–particle bonding. |
| Residual stress | Reduced by 15.8–17 % compared with undoped filler. |
| Mechanical strength | Maximum shear strength = 253.7 MPa for 1 vol% YWO. |
| High YWO contents (3–5 vol%) | Aggregation defects weakened the bonding and reduced joint strength. |
Mechanism
YWO’s negative thermal expansion (CTE = −7 × 10⁻⁶ °C⁻¹) offsets the contraction of the metallic filler during cooling.
This balances thermal mismatch between diamond (low CTE) and copper (high CTE), thereby mitigating thermal stresses.
The interfacial oxide layers ensure chemical compatibility between YWO and the AgCuSnTi matrix.
Conclusions
Introducing a small amount (≈1 vol%) of Y₂W₃O₁₂ into AgCuSnTi filler effectively:
Relieves residual stresses by ~17 %.
Maintains strong metallurgical bonding.
Achieves near-optimal mechanical performance.
Excessive YWO (> 3 vol%) causes agglomeration and weakens the joint.
The approach provides a promising route for stress-relieved diamond–metal joints in high-power microwave and fusion applications
DIASEMI
Diamond semiconductor researching center
Fremont ,CA
