Analysis of dynamic behavior of solder reflow by solder ball test

A dynamic model for evaluating the reflow characteristics of solder pastes is developed. The model is based on a solder paste - solder ball test (IPC-TM-650 2.4.43). The process of this test can be divided into four sequent stages: solvent effusion and volatilization, solder paste pattern shrinkage, solder ball shrinkage, and stabilization. Another bubbling stage is separated alone, because it occurs erratically. All these stages are associated with defects and their possible reasons are described and discussed. It is found that the shrinking behavior and bubbling process are two key points in the reflow process. Fast and stable shrinking, and exhaustive escaping of bubbles, are helpful to reduce the reflow defects.