BGA, CSP and FLIP CHIP

摘要

It has been understood for many years why flip chip devices need to be underfilled. Traditional large ball grid array (BGA) devices are only underfilled on rare occasions when the device will be used in critical applications, such as flight computers. There has been debate for a number of years on the need to underfill chip scale packages (CSPs). Most package manufacturers try to design their CSPs so they do not require underfill. However, in practice, an underfilled CSP has greater reliability than one that is not underfilled. Many manufacturers underfill CSPs when the parts are used in portable electronic applications that users often drop. When product testing shows that a device needs to be underfilled, the next step is to determine the most appropriate underfill process. This article discusses the differences in flip chip, CSP and BGA device underfills and reviews when and where to use each process.