Novel approach to copper sintering using surface enhanced brass micro flakes for microelectronics packaging
Copper pastes suitable for low temperature and low pressure die-attach bonding were developed to enable sintering at 275 °C under N2 atmosphere. First, brass flakes were treated with HCl to selectively etch Zn and to realize enhanced surface modifications on the flakes. Then, polyethylene glycol was added as binder to the modified flakes due to its reducing effects on copper oxides and its property to prevent agglomeration. Shear strength of ca. 50 MPa was achieved while sintering with 10 MPa bonding pressure thereby providing suitable, easy and low-cost sintering pastes for microelectronics packaging applications.