Die-attach for high-temperature applications using fineplacer-pressure-sintering (FPS)

A new joining technique called “Fineplacer-Pressure-Sintering” (FPS) for die-attach of small electronic components (e.g. LEDs and photodiodes) is described. Using a modified Flip Chip Bonder, bare dies could be bonded onto substrates with high positioning accuracy. For the FPS process a 50 tons press, which is conventionally used for pressure sintering, is no longer required. Very high average shear strengths (63 MPa) were achieved on molybdenum substrates (metallization: Ni/Au). With the help of silver powder of micro-to-nanometre grain size the electrical and mechanical properties of the compound layer could be further increased. The bond strength of metalized GaN-LEDs on Al₂O₃ substrates with a Ti/Pd/Au metallization is twice as high as with standard micro-powder and the process temperature could be reduced to 200°C. Finally the applicability of FPS was demonstrated by an optoelectronic module consisting of two commercial InGaN-LEDs and GaP-photodiodes on a metalized Al₂O₃ substrate. Successful function was found with prototype modules at temperatures up to 250°C.