EP-0463826-A1: Sealing Glass and Electrically Conductive Formulation
This patent describes a glass sealing process that bonds semiconductor chips ("dies") to ceramic substrates, by firing at temperatures of less than 400° C. The sealing glass is composed primarily of an electrically conductive Silver paste, which can efficiently bond silicon semi-conductive devices to ceramic. Several trials were conducted to assess the strength of the paste's ceramic bonding, by heating a series of samples to different maximum temperatures that ranged from 300° to 420° C. Furthermore, these samples were heated to temperature at the uniform rate of 10° C per minute, and were held at maximum temperature for between 10 and 15 minutes. Results showed that while the strength of the bond was superior at a higher temperature, adequate bond strength was achieved at temperatures less than 400° C. A second experiment that follows the above process was conducted, except the composition was prepared and melted in a belt furnace at 900 C. for ~90 minutes. Results continued to show that a higher temperature increased the bond strength, and that sufficient bond strength was achieved at less than 400° C. This ultimately allows for the manufacturing of hermetic, insulating electrical seals.