Study on vacuum brazing of glass to kovar® alloy with Cu-Ni-Sn-P

A vacuum brazing process of borosilicate glass to Kovar®alloy was carried out at 943-973 K using Cu-Ni-Sn-P brazing alloy. The shear strength was tested after vacuum brazing, and the microstructural evaluation of the glass-to-metal brazed joints was performed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that the maximum shear strength of the brazed joint was 1.6 MPa when the brazing temperature was 953 K and the brazing time was 10 min. The fracture location of the brazed joint was near the side of the glass. Many microcracks occurred along the interface of the glass, and then extended to the center of the interface. Cu ₃P and Ni ₂P intermetallic compounds, α-Cu, and Cu _xSn _y, layer form at the interface of the brazed joint. The compounds Cu ₃P and Ni ₂P are harmful for the strength of the brazed joint.