OPTIMIZATION OF ADHESIVE DEPOSITION FOR MIXED TECHNOLOGY PCB ASSEMBLY
Author: Lisa Rielly Company: State University of New York Date Published: 4/28/1997
Surface Mount International
Abstract: Adhesive deposits are used in mixed technology Printed Circuit Board (PCB) assembly to hold (passive) surface mount components in place on the bottom side of the board during the wave soldering operation. The presence of the adhesive allows for the formation of effective solder joints for both through-hole and surface mount components through wave soldering. The need to deposit adhesive adds to the complexity of the PCB assembly process. An effective process is essential to ensure the proper deposition of adhesive without creating adverse effects such as insufficient adhesive resulting in the possibility of components falling off before/during wave soldering or excessive adhesive resulting in poor solder connections. The adhesive deposition process considered m this research was syringe dispensing. In an effort to improve the accuracy of both the volume and the position of adhesive deposits, thereby increasing the quality of the overall process and product, this technology was extensively studied. The primary objective of this research was to ‘optimize’ the adhesive deposition process used at a PCB assembly facility. To accomplish this, several sub-objectives were determined and fulfilled. First, it was necessary to ‘optimize’ the current machinery used at the facility. To do so, it was necessary to study and quantify the current adhesive dispensing capabilities through the establishment and study of a ‘base case’. The ‘base case’ allowed for parameters of the process to be determined as well as time to understand improve and thus stabilize the use of the adhesive material used. The information gathered from the ‘base case’ was then used to develop a systematic ‘Design of Experiments’(DOE) based strategy to ‘optimize’ the machinery currently used at the facility. Observation of the adhesive deposition process revealed that the independent variables of the process could be divided into machine and program variables. The effects of these variables upon one another was studied. The adhesive dot height and diameter were measured. These dimensions were used to estimate the volume of an adhesive deposit.