Eutectic Zn-Al Die Attachment for Higher Tj SiC Power Applications: Fabrication Method and Die Shear Strength Reliability

This paper comprehensively describes the fabrication method and shear strength reliability of a eutectic Zn-Al (m.p. = 382°C) attachment system, built by soldering SiC dice (2 × 2 mm2) onto Cu foil active-metal-brazed with a SiN ceramic plate. Four essential soldering conditions are presented and discussed for the formation of a strong and reproducible attachment. Die shear strength reliability data at Tj = 250°C are reported here for the first time. Storage tests at 250°C revealed that, after an initial slight decline, the die shear strength stayed virtually constant at a sufficient level (∼110 MPa) for at least 3,000 h. Thermal cycle test results indicated that the attachments can withstand thermal cycle stress for 3,000 cycles between −40°C and 250°C. The average die shear strength after 3,000 cycles was 18.5 MPa, a value that is three times higher than the IEC standard of 6.2 MPa specified in Document 60749-19.