Rediscovering Multilayer Rigid-Flex with Z-interconnect Technology

摘要

Rigid-flex allows designers to replace multiple substratesinterconnected with connectors, wires, and ribbon cables witha single package offering improved performance, reliability,and a potential cost-effective solution. However, processingand materials selection is critical in order to achieve highquality multilayer, rigid-flex structures. To date, there is notechnology available which can economically produce highdensity multilayer rigid-flex with rigid or flex originatingfrom any layer in the stack. In the present study, a novelstrategy allowing for multi-layer rigid flex structures isreported. Specifically, metal-to-metal z-axis electricalinterconnection among the flexible and rigid elements duringlamination to form a single package rigid-flex structure isdescribed. Conductive joints are formed during laminationusing an electrically conductive adhesive (ECA). As a result,structures can be fabricated with multiple flexible elements atany arbitrary layer. Recent development work on flex joiningusing different pre-pregs is highlighted, particularly withrespect to their integration in laminate chip carrier substrates,and the reliability of the joints formed between the rigid andflex surfaces. A variety of rigid-flex structures werefabricated, with 1 to 3 flex layers laminated into printedwiring board substrates. Photographs and optical microscopywere used to investigate the joining, bending, and failuremechanism. Several classes of flexible materials, includingpolyimides, PTFE, liquid crystal polymer (LCP), have beenused to develop high-performance rigid-flex packages. Rigidflexpackages with embedded passives and actives are alsobeing investigated.