Chemical Substrate Treatment for Improved Pressureless Silver Sintering Adhesion of Power Electronics Dies

We investigated a method for increasing the adhesion of pressureless-sintered silver die attach layers to common copper surfaces using sulfuric acid. Surfaces of DCB-, AMB substrates, and oxygen-free copper lead frames were cleaned and etched with different sulfuric acid-based solutions. Dummy chips were sintered to the treated substrates and changes in adhesion were evaluated by shear tests. Visual inspection of the fracture surfaces after shear testing shows adhesive failure at the substrate-to-sintered layer interface. Yet, increases in mean shear strength from 30 MPa to up to 117 MPa were achieved with a standard deviation reduction from 9.3 MPa to 3.6 MPa, respectively.