Process challenges and solutions for single mold cap BGA assembly

This paper presents the process and equipment challenges faced with the introduction of single mold cap BGA assembly, with the main focus on End Of Line assembly processes. The design of the single mold cap without the stress relieve slots would subject the substrate to high warpage after the molding process. This high warpage may lead to handling and process issues at molding, ball attach, laser mark and package singulation processes respectively. Systematic study used in the molding process includes minimizing the coil set warpage at post mold cure (PMC) process with constrained PMC method and staging time. For the downstream processes, the approach lies mainly on improving the substrate handling from the equipment aspect. In addition, a new method of inspecting laser marked units at the post mark inspection was developed and implemented by means of a new inspection methodology. The resulted achievements are processibility readiness by resolving all issues pertaining to warpage, and ensuring that the quality of the product meet requirements despite the change from four panel mold cap to single mold cap in assembly process.