Recently, voids in solder joints has been a hot topic of discussion within the electronics manufacturing industry. The main interest stems from the impact that these voids have on the long term reliability of solder joints. But, not all solder joints voids are the same. In this paper, various types of voids found in solder joints will be described. These include: Macrovoids, also called process voids, which are the most widely known and studied voids in the literature; Planar Microvoids, also called champagne voids, which are mainly observed when soldering to certain types of surface finishes; Shrinkage Voids, also called sink holes, which are more common to lead-free Sn-Ag-Cu(SAC) solders than tin-lead solders, Micro Via voids, which are caused by vias in PCB lands; Pin hole voids, which are initially seen on the un-soldered PCB lands, and Intermetallic Compound (IMC) voids which generally occur within the IMC formed between two metals that have different diffusion rates within each other. Each category of Voids in Solder Joints will be described, their known root causes explained, ways of minimizing or even eliminating them will be listed, and the commonly understood effects of these voids on solder joint reliability will be discussed.
Key Words: Voids, PCB, IMC, Lead-free, BGA, solder joint