Si
3N
4/Si
3N
4 joint was made using Cu
66Ti
34, Cu
50Ti
50 and Cu
43Ti
57 amorphous filler metals, where pressureless sintered Si
3N
4 was used. The joining strength of Si
3N
4 joint was measured by fracture shear testing, and the joining mechanism was investigated by microstructure observation with SEM, and elements analyses at the joint interface with EDX and EPMA. The results obtained are summarized as follows.
(1) The molten Cu-Ti alloys containing 20 at% Ti or more exhibit the equilibrium contact angle of about 8°, and are applicable to the filler metal for joining of Si3N4.
(2) The joining strength of Si
3N
4 using Cu
66Ti
34 filler is higher than that of Si
3N
4 using other Cu-Ti fillers at any brazing temperature except for brazing temperature of 1273 K. Thus, the joining strength of Si
3N
4 with Cu
66Ti
34 filler shows the maximum value of 313.8 MPa at brazing temperature of 1323 K. At the brazing temperature of 1373 K, Si
3N
4 joint with Cu
50Ti
50 filler shows the maximum value of 176.5 MPa at brazing time of 1.8 ks, and gradually decreases with longer brazing lime, and to 19.6 MPa at brazing time of 7.2 ks. The elevated temperature fracture shear strength of Si
3N
4 joint brazed at 1373 K for 1.8 ks using Cu
50Ti
50 filler increases to 199.1 MPa at 373 K, and gradually decreases to 105.9 MPa at 973 K.
(3) During brazing Ti in molten Cu
50Ti
50 filler reacts with Si
3N
4 by the following reactions. Si
3N
4(s) +4Ti(1)=4TiN(s)+3Si(s), and Si
3N
4(s)+9Ti(1)=4TiN(s)Ti
5Si
3(s). TiN at the interface between Si
3N
4 and the filler, Ti
5Si
3, and Cu-Si phase at the central part of the filler are formed. The activation energy for growth of TiN at the joining interface is 206.3 kJ/mol, and the growth of TiN is dominated by the diffusion of N in TiN. The silicon content of the Cu-Ti phase increases about 7 at%Si to about 20 at%Si with increasing the brazing temperature.
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