Abstract
Laser reflow soldering is of great importance in surface mount technology for the advantages of non-contact, local fast heating and cooling. Compared with Sn–Pb solder, lead-free solder has higher melting point and poorer wetability and becomes deterioration easily in the air. This undoubtedly brings new challenges for reflow soldering. In this paper fiber laser with high energy density was used to weld three microchips (QFP-44, SSOP-48, SOP-14) without solder at the parameter of 20 kHz repetition rate, 18 W in average power and 20 mm/s of the speed. The properties of micro-joints of laser welding without solder were analyzed including electric property test, X-ray nondestructive test, 45° pull test for tensile strength as well as SEM and EDS for fracture surface analyses. It shows the properties can meet the requirement of welding joint for microchips.
