Formation and Change of AuSn4 Compounds at Interface Between PBGA Solder Ball and Au/Ni/Cu Metallization During Laser and Infrared Reflow Soldering
FORMATION AND CHANGE OF AuSn4 COMPOUNDS AT INTERFACE BETWEEN PBGA SOLDER BALL AND Au／Ni／Cu METALLIZATION DURING LASER AND INFRA-RED REFLOW SOLDERING

Interactions between 63Sn37Pb solder and PBGA metallization (Au/Ni/Cu) during laser and infrared reflow soldering were studied. During laser reflow soldering process, a thin layer of AuSn_4 was observed at the interface of the solder bumps, its morphology was strongly dependent on the laser reflow power and heating time. The solder bumps formed by the first laser reflow was reflowed again to form the solder joints. The AuSn_4 compounds formed in the first laser reflow process dissolved into the bulk solder after the secondary infrared reflow process. The needle-like AuSn_4 changed into rod- like, and distributed inside the solder near the solder/pad interface.