PCB Layout Influence on the Reversibility of Planar Soldered PCB-to-PCB Interconnections

Abstract

Power electronics converters rely on a wide range of physical implementation architectures. PCB-to-PCB interconnections are widely used to interconnect mother and daughter boards for control, driver, and IPEM implementation, and can take several technological forms such as pins, screws, press-fit or soldering. These interconnections must meet traditional requirements such as cost, efficiency and power density, as well as emerging ones such as environmental impact and ease of disassembly. This article analyses two approaches for soldered planar PCB-to-PCB interconnections. Unlike BGA assemblies with small devices and many contacts, in power electronics these interconnections are used to assemble large components or subsystems such as custom passive devices, auxiliary power supplies and control boards, typically with a limited number of pads. Because solder joints are usually located between stacked PCBs, access for repair and rework can be difficult. Experiments were conducted to assess how PCB layout design can enable repair and replacement of daughterboards, by controlling heat transfer between pads through copper traces. Thermal behavior, electrical resistance and mechanical strength were evaluated for different layout patterns. In particular, the influence of the amount and location of copper inertia on heat transfer along copper traces is highlighted. A manual solder/desolder cycle was successfully demonstrated, and design guidelines for reworkable PCB-to-PCB interconnections are discussed.