Issue link: https://iconnect007.uberflip.com/i/1529411
88 PCB007 MAGAZINE I NOVEMBER 2024 Ultra high density interconnect (UHDI) has many forms, structures, and alternatives, so capturing all the variations and reducing them to design rules has required some depar- tures from traditional IPC design standards. In this column, I'll be discussing the IPC UHDI design guidelines and standards. What Drives Yields? e fundamental question is: "Do you need HDI or microvias?" IPC-2315, Design Guide for High Density Interconnects and Microvias, helps answer that question by providing wir- ing demand estimates. If HDI is required (or desired), the document walks you through Yields March to Design Rules the design process: selection of critical HDI dielectrics from IPC-4104, Specification for High Density Interconnect (HDI) and Micro- via Materials; selection of blind and buried via structures; and selection of design rules. e design rules and structures in the stan- dard are arranged in increasing degrees of com- plexity, starting with a single build-up layer of microvias and drilled through-holes through- out the entire structure. is is a Type I struc- ture. Type II is a single HDI layer over a two- sided or multilayer core. erefore, it has bur- ied vias. e next section introduces varia- tions in the structure by allowing stacked vias, variable depth vias, and conductive paste vias. Happy's Tech Talk #35 Feature Column by Happy Holden, I-CONNECT007