In today's electronic devices, a variety of circuits and components typically reside on separate substrates. In particular, main logic boards (“MLBs”) commonly include a rigid printed circuit board (“PCB”) with major components such as processors, codecs, power management integrated circuits, and flash memory, among other things. Other system components such as displays, touchscreen, cameras, microphones, speakers and earpieces, antennas, external headphone and other connectors, battery, dome switches, daughter boards, and so forth, typically feed into the MLB via a polyimide flexible printed circuit board (“flex-PCB” or “flex”). The flex and MLB commonly are coupled together through one of a variety of interconnect methods inducting zero insertion force (“ZIF”), board-to-board (“B2B”), hand soldering, hot-bar soldering and anisotropic conductive film (“ACF”), for example. These interconnects consume a relatively large area on the surface of the MLB compared to other circuit elements, including passive components and integrated circuits (“ICs”).
Previous work has been undertaken to explore 3D circuit topologies using through mold via (TMV) modules. Generally, a module is a subsystem or group of circuit elements that share a common substrate. For the present purpose, a collection of components (active and/or passive) is soldered to a module substrate. The module may be potted or encapsulated with a resin to insulate the module components from external contact and to provide a rigid structure to the module. TMVS are created by a variety of techniques including drilling a hole through the resin to contact exposed metal circuits on the module substrate and filling the hole with solder or plating it with a metal. Alternatively, tall metal structures are embedded during potting that contact the substrate circuits on one end and are flush with the external surface of the resin on the other. In either case, a structure is formed with internal components and metal interconnects on both the substrate bottom and the resin surface. Circuits can pass up through the TMVs to other systems using passthrough connections. However, connection of a module to a flex using conventional techniques method (e.g., B2B, hand solder, etc.) incurs a height penalty (e.g., increases the height of the module) and may render the technology unsuitable for particular designs.