Thermal characterisation and heat transfer analysis of a wire bond chip-on-board package

Electronic packaging trends in chip-on-board (COB) technologies are desirable because of the benefits of miniaturisation and low-cost manufacturability. Wire-bond COB packaging is commonly employed in low-cost multichip module (MCM) applications because of its simplicity in design and manufacturability. However, these applications are usually used in low-end performance electronics products, which are not subjected to high power cycling and environmental thermal cycling loads. The potential for using wire-bond COB packages in more demanding loading conditions can be realistically employed by rational and systematic thermomechanical design and design of experiments (DOE) in reliability tests. In the automotive industry, under-the-hood electronic systems are subjected to both power cycling and environmental loads and consequently the reliability of such products must be designed and tested for reliability under more demanding thermal load conditions which can accelerate the wear-out failure. In this paper, a wire-bond COB package with calibrated thermal chip (PST4) provided by Delco Electronics was analysed. The package consists of five different materials: the silicon chip, die-attach adhesive, wire-bond, glob-top encapsulant and FR-4 board