(In order to achieve functional integration of high performance and miniaturization in microelectronic devices and allied subsystems (viz. Digital signal processors, Motherboards, Microcontrollers, etc.), one needs High Density Interconnect (HDI) technology; which offers competitive advantages in size and cost reduction. This can be realized by adopting appropriate packaging technology, which includes an application dependant combination of Photoimageable Thick Film Circuits (new generation Hybrid Microelectronic circuits or HMCs), Microvias, Ball Grid Arrays and a host of new generation materials. Conventional HMCs using classical Thick film pastes have limitation for high frequency operation (~250MHz), difficulties in fabricating buried resistors and cannot produce line and via dimensions of less than ~250µm in production.
Photoimageable Thick Film Materials – a combination of classical thick film processing and photoresist technology – offer much improved line/space (50/50µm) and via resolutions (<100µm) quite comparable to relatively cumbersome thin film technology at a lower cost with proven reliability and production capabilities of standard thick film materials. Photoimaging is a process of several steps that together realizes metal interconnection pattern, to be formed on surface of substrate using photon energy (e.g. Ultra Violet).
Microwave circuits are fabricated by interconnecting variety of passive circuit elements together with active devices. Characteristics such high electrical conductivity, fine-line and space resolution, well defined conductor edges, nearly vertical walls and smooth upper surfaces are essential for achieving low losses in microwave structures at frequencies above 1GHz.
C-MET, Pune has developed photoimageable silver and gold pastes with line/space resolution of 50/50µm with a fired thickness of 7-9 µm and a sheet resistance of <6mO/? & 13mO/?, respectively, photoimageable dielectric paste with via resolution ~100µm and dielectric constant ~5 and photodefinable gold paste with line/space resolution of 50/50µm and sheet resistance of 13mO/? under a project partially funded by Dept. of Information Technology.
The following pictures present some result of C-MET’s photoimagable and definable pastes: