AN ADHESIVE SELECTION ADVISER FOR PCB ASSEMBLY USING SURFACE-MOUNT TECHNOLOGY

The interrelationships that exist in the manufacturing processes associated with the surface mount manufacture of printed circuit boards (PCBs) are complex and varied. Proper understanding of the relationships between the variables in a surface mount technology (SMT) process are critical for achieving effective process control and high yields. One aspect of the complex relationship is the selection and dispensing of adhesives for the wave soldering of surface mount components on a PCB. The quantitative and repeatable dispensing of adhesive dots is critical to providing adequate process control for attaching components including chip resistors, capacitors, and small outline type transistors to the wave solder side of a PCB. Variables that need to be considered include facility temperature, humidify, size and types of components used on the PCB, adhesive properties, type of dispenser used, curing requirements, and the soldering time and temperature. A knowledge-based approach which considers these relationships is described. Developed in PROLOG, this stand alone adhesive selection advisor is capable of guiding the user in the selection of the proper adhesive, and providing dispenser related information. The factors considered include facility temperature, material property requirements, productivity measures including yield, and the process used to dispense the adhesive. The system also functions as a database for adhesive related properties and as an on-line installation and maintenance manual for the adhesive dispenser. Twenty-one different commerically available adhesives and two types of dispensers (air over and positive displacement) have been considered in this research.