April/May 2021

22 POWER MODULES www.vicorpower.com Issue 2 2021 Power Electronics Europe www.power-mag.com Innovating Power Module Packaging A system’s power delivery network or PDN is made up of passive and active components such as cables, connectors, AC-DC and DC-DC converters and regulators. As power levels increase to enable new features and the electrification of mechanical and hydraulic systems, PDN performance is becoming more critical, and in some cases, constraining end system capabilities because of PDN footprint, weight and power losses. Tom Curatolo, Director, Applications Engineering, Vicor, USA Power system design engineers are under increasing pressure to design a PDN that is small, lightweight and highly efficient, as this achievement can define a leadership product capable of delivering major end-system performance and competitive advantages for OEMs. Fourty years of innovation Understanding the importance of these power system design challenges and key PDN performance specifications drives Vicor to constantly innovate to stay on the forefront of power systems technology. To do so requires a major commitment to innovation on many levels. Five pillars of power innovation 1. Power delivery architectures 2. Power conversion topologies 3. Control systems 4. Components and materials 5. Power module packaging Each level has multiple dimensions, and each depends on the others. Together, the five levels of power innovation advance power module performance. Architecting the PDN is the first step for any power systems engineer and a great architecture can ultimately define overall performance. Architecture development involves asking questions critical to optimizing performance: When to convert, regulate and isolate? What voltages will be used and distributed within the PDN? Answers will vary according to need, but the modular elements of the solution are the same, leveraging high-frequency switching (power conversion) topologies enable reductions in passive and magnetic component values and hence their size, while innovative control systems such as zero-voltage and zero-current switching can significantly reduce power losses. Advanced materials for circuit boards, magnetics, semiconductors and passives enable reduced power losses and component sizes. However, all of this would have little impact if not for the constant innovation of power module packaging, which ultimately defines the power and current density. Power module packaging is a unique differentiator for Vicor and has been a core competency since the company’s inception. In 1984, the modular Brick DC- DC converter component, so called due to its form factor, was introduced with innovative attributes: Enabled a distributed power architecture High-efficiency quasi-resonant forward- converter topology A frequency-modulation (FM) control system with zero-current switching (ZCS) to reduce power loss With switching frequencies as high as 1 MHz, the physical size of the passive components and magnetics was significantly decreased, and the reduced power losses enabled a power module with breakthrough power density, which changed the power supply industry ` (Figure 1). Turning the corner from Bricks to VI Chip and ChiP packaging In 2008 Vicor introduced new innovations which enabled significant gains in power density over the Brick and advanced its power component design methodology for the power systems industry (Figure 2): 1. The Factorized Power Architecture (FPA™) 2. A new higher-frequency topology called a Sine Amplitude Converter (SAC™) 3. Zero-voltage switchin (ZVS) and zero- current switching (ZVC) 4. New packaging materials The new architecture, combined with the higher-frequency switching topology and control system ZVS and ZCS improvements, once again reduced power losses and enabled higher levels of power module integration that drove a new package development, the VI Chip. The package was a fully overmolded PCB assembly using a thermally-effcient molding compound incorporating specialized materials developed in conjuction with key suppliers. The module was manufactured in individual mold cavities and incorporated J-lead pins for surface-mounting on customer’s motherboards. The resulting family of new power modules offered breakthrough performance in powering sub-1 V high- current processors developed by IBM for its supercomputers and set the stage for Vicor 48 V-to-load leadership in the data center and AI processor markets a decade later. In 2015 further improvements in control systems, topologies, components and materials enabled the redesign of the VI Figure 1: From the early Brick which offered leadership density and efficiency to today’s ChiP, Vicor has driven significant advances for power systems engineers, particularly in the area of power density