Issue link: https://resources.pcb.cadence.com/i/1180282
High Density Interconnect October 2019 7 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. Working with HDI The design methodology of high-density interconnect (HDI) technology allows for greater wiring density, utilizing lines and spaces under 3 mils and microvias (holes less than 6 mils, capture pads less than 13.8 mils) leading to greater miniaturization and reduced package size. This section describes these key aspects of HDI requirements and the tool features supporting them, such as microvias, DRCs for same net and net-net conditions, unused inner-layer pad removal, rules for via tangency (vias touch but do not overlap) and stacking (coincident location of adjacent layer vias), and dynamic filleting. Microvias and Padstacks Microvias are a principal feature of HDI, defined by the IPC as vias whose diameter is less than 6 mils with capture pads less than 13.8 mils. Microvias set up the clearance matrix associated with the technology, such as microvia-to-microvia and microvia-to-core via spacing rules. Prior to 16.2, all non-standard vias (buried and blind) were categorized by the database object BB Via. Allegro PCB Editor lets you differentiate microvias from mechanically drilled blind and buried vias using the Microvia option on the Padstack Editor. Pad Usage Options ■ Microvia: Use on HDI boards where spacing rule sets differ between HDI and conventional blind and buried or core vias. The Microvia option can only be applied to a blind and buried via to represent mechanical drilled vias, such as the core via on an HDI design. The Spacing and Same Net Spacing Constraint domains of Constraint Manager support these two via types. ■ Allow Suppression of Unconnected Internal Pads: Enable to suppress unused inner layer pads, thereby making them unavailable for DRC, routing, and display, with the Suppress Unconnected Pads option on the Film Control tab of the Artwork Control Form, available by choosing Manufacturing – Artwork (film param command) or with dynamic unused pad suppression, available by choosing Setup – Cross Section (xsectioncommand). ■ Enable Antipads as Route Keepouts (ARK): Enable to use antipads associated with mechanical pins as an implicit route keepout area to reduce the need to draw keepout