IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1546580
78 I-CONNECT007 MAGAZINE I SEPTEMBER 2026 Defining Density Needs Industry veteran Happy Holden once explained the interrelationship between component packaging, SMT assembly, and printed wiring boards: • Assembly complexity: A measure of the dif- ficulty to assemble surface mounted compo- nents, measured in parts per square inch and leads per square inch. • Component packaging: The degree of so- phistication of a component, measured by its average leads (I/Os) per part. • Printed wiring board density: The amount of density (or complexity) of a PCB as measured by the average length of traces per square inch of that board, including all signal layers. The metric is inches per square inch. Wiring density is defined as the amount of elec- trical interconnection routed within a given board or IC substrate footprint. The greater the wiring density, the smaller the footprint. This allows for miniaturization of the package and board. Microvias used in HDI and UHDI designs increase density and functionality, while reducing layer counts and the overall footprint. Where are we today? It wasn't too long ago that the industry was thrilled to get down to 50-micron lines and spaces and 100-micron blind vias. Today, with advanced packaging, heterogeneous integration and the use of chiplets, 15– 20-micron lines and spaces, and 45–60-micron diameter blind vias are at the leading edge. Major advances in photolithography, metallization, and etching process, laser via formation, unique registration systems, and online process controls have enabled T RO U B L E I N YO U R TA N K Figure 1: Blind via defects. (Source: Happy Holden)