With the pitch of parts getting tighter and the pin count of BGAs going up, there is a need to get as much routing as possible into very dense areas of the board. HDI helps many people accomplish that, by allowing a much larger number of signals to escape the BGAs. However, there are a few specific things that one needs to understand about the technology in order to use it successfully. We will discuss when and why to make the jump to HDI, some issues that need special attention, and getting the fabricator involved early in the design process. Then we will cover a few manufacturing issues, and go over some things that can cause microvias to fail.