Issue link: https://iconnect007.uberflip.com/i/1284035
SEPTEMBER 2020 I SMT007 MAGAZINE 111 responding to microvia failures. Again, Auer reinforced the IPC microvia warning that tra- ditional inspection techniques utilizing ther- mally stressed micro-sections and light micro- scope alone are no longer an effective quality assurance tool for detecting microvia-to-target plating failures. Kevin Kusiak Speaking with many years' experience of reli- ability testing and failure analysis, Kevin Kusiak, electronics engineering senior staff at Lockheed Martin Space Systems, gave a comprehensive pre- sentation on "Microvia Reliability Testing Utiliz- ing D-Coupons to Understand Best Design Prac- tices." This session detailed a project Kusiak is leading to design and test coupons, which will give LMS insight to best practice design vari- ables of PCBs utilizing microvias. The test vehicle will be: • Multiple via structures of varying microvia diameters across 54 different D-coupons • 37 coupons for plated hole evaluation through micro-sectioning and SEM-FIB analysis • Four peel strength coupons with embedded microvias • 5-, 6-, and 7-mil diameter; 0-, 5-, 10-, 15-, and 20-mil pitch (center to center) • Fabricated by two different vendors recording bath parameters during the processing of panels He also explained the IPC-TM-650 2.6.27 reflow cycle, 12x reflows at 260°C using OM testing followed by IPC-TM-650 2.6.7.2 100 thermal shock from -55–205°C and failure cri- teria, and the via failure mode that will be observed as an open or measurable resistance change at or near the peak temperature. Marc Carter Marc Carter, president and owner of Aeromarc LLC, as well as an I-Connect007 columnist, addressed "Stacked Micro- via/ Weak Interface Reli- ability Study Project." For over a year, a commit- ted group of companies and individuals has been developing a reliability modeling study. This study combines empirical confirmation structures and testing protocols with advanced reliability simulation in a three- phase, three-year iterative study (simulate, test, refine, and repeat). The goal is to pro- vide an urgently needed enabler of greater miniaturization in the form of increased com- plexity "stacked microvias" currently limited by an incomplete understanding of the forces and mechanisms (click here for background information). While several company-specific studies have generated excellent proprietary data, these do little to benefit the wider industry. In part, this project aims to begin to raise the capability level and understanding of those in the elec- tronics manufacturing supply chain for high- reliability, critical applications not privy to the proprietary studies. The mutually agreed test vehicle is charac- terized by: • 12-layer high-Td laminate with three build-up layers of various stacked and staggered microvias over buried TH vias fabricated by shop A vs. shop B • Microvia formation methods of mechanically drilled vs. laser-ablated (UV/CO 2 /UV) • Alternative metallization of direct metallization vs. electroless copper • 17 different D structured coupons • Reflow simulation of eutectic (230°C vs. lead-free 260°C) • Analysis by test lab A vs. test lab B