Surface Profiles of Printed Ag Nanoparticle Paste and Their Implication on the Quality of Sintered Joints

This paper is concerned with the surface profiles of printed Ag nanoparticle paste and their implication on the quality of sintered joints. The effect of the surface morphology of the printed Ag paste on the quality of the sintered joints has been investigated using two types of experiments. In the first type of experiment, voids, densification and uniformity of the sintered joints and impact of the non-flat printed paste with the spikes and valleys on dummy Si devices were examined. In the second type of experiment, real Si diode attach samples using both the printed paste larger than the device and the printed paste exactly the same size as the device were prepared, and the surface morphology of the printed paste on the reliability of these samples are analysed in the paper. It clearly showed that the spikes and valleys in the printed paste led to larger voids and increased non-uniformity within the sintered Ag joints; they also resulted in broken device in the joints consisting of two dummy Si devices under an average pressure of 15 MPa. The Si diode attachments prepared using the printed Ag pastes with spikes and valleys under the diodes also exhibited faster degradation rate and poorer reliability during thermal cycling test between -55 °C and 190 °C.