Use of microwave technology for rapid cure of chip-on-board glob top encapsulants

Chip-On-Board (COB) is widely utilized in manufacturing electronic packages for automotive, computers and other electronic components. Glob top encaps ulation is used to protect semiconductor chips and bonded wires from advers e environment to increase the long-term reliability of COB assemblies. Howe ver, the current manufacturing practice normally involves a two to four-hou r long curing step to cure glob top encapsulants. Variable Frequency technology was specifically developed to apply microwave energy to the rapid cure of various advanced materials, while not interfer ing with metallic components or electronic circuitry. VFM curing of COB glo b top encapsulants has been performed with a wide range of encapsulants fro m various vendors. Key materials properties were measured after VFM curing and were compared to that of thermally cured samples. In general, VFM drama tically shortened the cycle time and provided the same cure quality as conv entional thermal cure. This study reports that VFM curing of COB encapsulants is a rapid, selectiv e and reliable process. Main results are: 1. The nominal VFM curing cycle i s 15 minutes or less as compared to a two-hour nominal thermal cure cycle, 2. No specific modification of encapsulants chemistry is necessary for VFM curing, 3. Glob top encapsulants cured by VFM yielded equivalent extent of cure, Tg and CTE properties as compared to those of convection oven cured s amples, 4. VFM has no adverse impact on functionality of the electronic com ponents. VFM processing has therefore been demonstrated as an attractive al ternative to conventional thermal manufacturing.