Evaluation on Die Cracking due to Handling Damage in FBGA DDP for Memory Device using Handling Impact Test

摘要

Dual Die Package (DDP) is widely used as a memory package to achieve high density and consists of two, thin, stacked dies. The thinner and the larger the die, the more probability of die cracking due to mishandling. The outbreak of die crack during mass production is a deathblow in the development of a package. The product with a die crack is difficult to screen out from mass products because the crack is so fine that it cannot be detected by non-destructive inspection such as visual inspection, SAT and X-ray. Therefore, a robust structure and material against die cracking are required and a test method to evaluate the handling impact reliability is also needed. In this study, the handling impact test method, which led to the revision of the package handling process, was newly devised and proposed. In constructing it, an upper jig similar to a picking tool was manufactured, and a stainless steel plate was placed on the bending fixture to reflect the effect of the spring bumper at the picking tool. The picking impulse was controlled by the displacement of upper jig. Die cracking was detected by the electrical function test and verified visually by chemical etching. These detection and verification methods showed that the handling impact reliability is greatly influenced by the die size, the stacking structure and the elastic modulus of the adhesive between the 1st and 2nd die. A reliability criterion for handling damage prepared based on field experience. The handling impact test was useful for quantifying the handling impact reliability and understanding factors related to it, and the test enabled us to develop FBGA DDP satisfying the criterion of handling damage.