Force monitoring tool to monitor mold cleanliness in a transfer molding machine

• Main Author: Ho, John Thiam Yong.
• Other Authors: Yu Ching Man, Simon
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Manufacturing::Product design
• Online Access: http://hdl.handle.net/10356/39653
• Institution: Nanyang Technological University

Mold cavity cleanliness has always been a major productivity issue in any type of molding processes because it affects the functionality, surface finish and/or quality of the end product, especially for transfer molding of electronic packages where too much ejection force due to sticky molds will damage the delicate and thin electronic package. The use of mold release agents in the molding compound and during the mold cleaning process only served to prolong the cleanliness of the mold cavity; it does not completely eliminate the issue of the sticky molding compound residue buildup in the mold cavities. Thus, periodic and time consuming manual cleaning of the mold cavities is required; causing significant downtime and productivity loss. The residue buildup is the main cause of excessive ejection forces on the molded part. This project attempted to measure and monitors the ejection forces experienced by an electronic package in a transfer molding machine after consecutive molding cycles. This was accomplished by designing and building a force measurement tool to indirectly measure and record the ejection force. The recorded data had been analyzed offline and the changes of the ejection force with deteriorating mold cleanliness had been observed. The design of the force measurement tool followed the process of the conceptual design phase, embodiment design phase, detailed design phase and finally the testing and evaluation phase. The force measurement tool had been successfully tested and evaluated. Evaluation results of the ejection forces showed an increasing ejection force reading with deteriorating mold cleanliness simulated by molding a few cycles and then leaving the mold cavity idle for 16 hours without performing any cleaning procedures. Thus, letting the molding compound residues and the remaining wax coating from mold release agents on the mold cavities to dry up and accelerate the deterioration of mold cleanliness. During the testing and evaluation phase which lasted four consecutive days, the increased ejection forces which was expected and detected when mold cleanliness deteriorated showed that the force measurement tool was able to accomplish what it was designed to do. After the functionality of the force measurement tool was validated, more ejection force data spanning 5 hours was collected to study the changes in ejection forces during a real production run. From the collected data, an estimation of the durability (in no. of molding cycles) of the effectiveness of the wax coating applied to the mold cavities during the cleaning treatment was obtained.