THE SOLDERABILITY EVALUATION OF SURFACE MOUNT COMPONENTS THROUGH THE USE OF WETTING BALANCE ANALYSIS

Abstract

Solderability is an important concern in the surface mount assembly of Printed Circuit Boards (PCBs). It impacts assembly reliability and yield. The solderability requirement of the components and boards used in surface mount PCB assembly is critical since the solder joint needs to provide both the electrical and the mechanical connections. The advent of ultrafine pitch components has only helped to increase the importance of solderability in surface mount assembly. Solderability evaluation for surface mount components and the identification and study of factors that influence it are of primary importance in the surface mount assembly of PCBs. The wetting balance can provide a quantitative investigation of solderability through measurement of wetting speed and the wetting force. It has been used for the solderability testing of through hole components. The use of the wetting balance apparatus for the testing of surface mount components raised several concerns. Some modifications were made to simplify the testing operations, to enhance the precision of the wetting balance apparatus and to enable the collection of more accurate data. The preliminary experiments explored the nature of the wetting balance test and helped identify a standardized process that could provide valid conclusions. A set of validated test parameters and a standardized set of test procedures that could be used to perform the incoming solderability testing of surface mount components were established. While the test procedures used in this research were a derivative of the IPC ANSI J-STD-002 standard, changes were made based upon the experience gained through the test schedule and the results and inferences obtained through preliminary experiments. Various types of mass reflow surface mount components were measured by their relative solderability. The solderability of tape automated bonding components with various plating metallurgy and coating thicknesses was also tested. The specific testing parameters used, the test procedures adopted, the data collected and the inferences made are presented in this paper.