Low Stress Die Attach by Low Temperature Transient Liquid Phase Bonding

A process called Low Temperature Transient Liquid Phase (LTTLP) bonding can allow components to be solder attached in the 60-1WC (140-320T) temperature range but not remelt until a much higher temperature. Stress is minimized by bonding at a low temperature and the component could be operated at or above the bonding temperature. This paper presents research on LTTLP bonding of silver, gold, and copper. Sixteen solders with melting temperatures between 30° (85°F and 15TC (315T) were studied. Bond formation for each alloy on the three metals was studied by measuring the bond remelting temperature and its development time. Some mechanical shear strength data was also collected. The use of LTTLP bonding for die attach could be particularly advantageous for fragile or temperature sensitive components which require a good electrically and thermally conductive bond.