Issue link: https://iconnect007.uberflip.com/i/1527613
18 DESIGN007 MAGAZINE I OCTOBER 2024 To accommodate new generations of high I/O semiconductor packaging, circuit board technology has undergone significant changes in both the fabrication process method and the criteria for base material selection. e reason behind these changes is the new high-function semiconductor package families that require more terminals than their predecessors and a significantly narrower terminal pitch. Interconnecting the very fine-pitch, high I/O semiconductors can dramatically affect the procedures used in both circuit board design and assembly processing. Implemen- tation of circuit boards with higher intercon- nect density, however, will enable the seam- less integration of high I/O semiconductor packages used in the more advanced electronic products. While a significant number of semi- conductor packages will have a moderate level of complexity (I/O and terminal pitch), others may have an excessively high I/O density. One solution for solving conductor routing road- blocks is to adopt blind via-in-land techniques Implementing HDI and UHDI Circuit Board Technology to transfer most of the interconnect responsi- bility to the circuit board's sub-surface layers typical of that illustrated in Figure 1. Adapting blind and buried microvia holes and furnishing pre-defined routing channels will help the circuit board designer to facili- tate efficient routing of these oen very fine- pitch, array terminal-configured semiconduc- tor packages. Planning for Sequential Build-up (SBU) Processing Sequential build-up processing offers a vari- ety of design options. Circuit board designers can choose sequential build-up using stacked microvias for layer-to-layer interconnect, or the staggered microvia, where via-holes are offset from one layer to the other. e SBU circuit board's complexity is ultimately deter- mined by component density, circuit intercon- nect density, the number of signal conductor layers, and the number of layers dedicated to power and ground. Designer's Notebook Feature Column by Vern Solberg, CONSULTANT Figure 1: HDI 3-4-3 build-up circuit board cross-section view.