Development of crack-less and deformation-resistant electroplated Ni/electroless Ni/Pt/Ag metallization layers for Ag-sintered joint during a harsh thermal shock

Abstract

Aiming for a suitable die-attached substrate for Ag-sintered joint technology during harsh operating environment, three surface finishes of sputtered Ti/Ag- layers, electroless Ni-/Pt-/Ag- layers, and electroplated Ni-/electroless Ni-/Pt-/Ag- layers were developed to directly bond copper (DBC) substrates, denoted as Ti/Ag, ENPA, and E-ENPA, respectively. The effect of the metallization layers by three deposition technologies on the Ag joint structures was systematically investigated during an extreme thermal shock test (TST) ranging from −50 to 250 °C. The mechanical behaviors and interface evolution considerably varied depending on the metallization layer used. Both ENPA and E-ENPA substrates provided a more robust initial shear strength of approximately 60 MPa. More importantly, both metallization layers were productive in restraining interfacial deformation owing to the effect of the thick Ni plating. A better performance was derived from the electroplated Ni in E-ENPA metallization with crack-less and deformation-resistant, because of electroplated Ni possessed a suitable hardness and toughness, thus the optimal stress-relaxation capability. This study provides insights to the properties of Ag-sintered joints on three metallization layers, where the metallization, mainly by electroplating, exhibited superior reliability beyond that of sputtered and electroless depositions in both strength and microstructure maintenance.

Keywords

• Ag-sinter joint
• Coating technology
• Thermal shock test
• Deformation-resistant
• Interface evolution