Improved Contacts in Glass-Encapsulated Capacitors

Ceramic chip capacitors hermetically sealed into glass sleeves are used extensively in the electronics industry. However, glass-encapsulated capacitors can loose contact at the termination lead wire. To improve the contact reliability, a brazing operation is suggested that coincides with the present sealing temperature of 720°C. For this purpose a nickel coating over the conventional termination and a braze paste for use in nitrogen was developed. It was found that an electroplated nickel coating and a braze paste consisting of "Incusil 15" were most satisfactory. However, the brazing operation increases the dissipation factor from 0.6 percent for conventional glass-encapsulated capacitors to about 1.8 percent for brazed and sealed capacitors. To test the contact reliability, the capacitors were temperature cycled between 30 and 210°C for up to 1000 times. In this test seven of the 36 conventional glass-encapsulated capacitors failed through loss of contact, whereas none of the 180 brazed and sealed capacitors failed. This result is a significant improvement in the contact reliability of glass-encapsulated capacitors.