4. Millimeter-Wave Chip-on-Board Integration and Packaging

A form of chip-on-board integration and packaging is being applied to millimeter-wave electronics to bring it into the low-cost, high-volume arena. This chapter gives some pointers on how low cost is achieved and then discusses the particular problems of millimeter-wave circuit performance. These problems have to do with interconnect lengths, encapsulant effects, shielding effectiveness, and cavity resonances. Also discussed are issues with thermal expansion mismatch and environmental control. What then follows is a description of the low-cost chip-on-board method for millimeter-wave integration and the means by which it overcomes the various millimeter-wave-specific problems. This solution combines existing surface-mount PC board technology with the highly-automated die attachment and wire bonding operations used in the plastic packaging industry and places bare millimeter-wave chips in environmentally protected air cavities. Examples of millimeter-wave products utilizing this technology are described, and some price points are given.