HEAD – AND – PILLOW SMT FAILURE MODES

With the electronics manufacturing industry moving to lead free soldering and with Ball Grid Array (BGA) packages becoming thinner and having finer ball pitches, there is an increase in the incidences of a SMT non-wet type of defect known as head-and-pillow (HnP). This defect is hard to detect after SMT assembly and most likely will fail at the customer. There are a number of causes for this type of defect. They can be categorized into process issues, material issues, and design related issues. This paper will examine these different causes for the head-and-pillow non-wet defect after surface mount assembly and the mechanism to create this defect. The paper will also describe the critical factors that are affecting head-and-pillow. It will discuss how to identify the root cause and give potential solutions to prevent the defect and have a robust SMT assembly process.