High frequency electronic packaging and components : characterization, simulation, materials and processing

Sammanfattning: Electronic packaging continues to move towards improved performance and lower cost. Requirements of higher performance, reduced size, weight and cost of both high density interconnects and high frequency devices have led to the search for new materials, material combinations, methods, processes and production equipment. Efficient technologies for producing high density interconnects, circuits for high frequency applications but also integrated packaging solutions for electrical and optical interconnects are looked for. Of emerging interest are methods and materials for ultra low cost printing of active components such as diodes and transistors.Large area panel processing (LAP) and sequential build-up technologies, using an UV-excimer projection lithography equipment and a photo-patternable ORMOCER® dielectric, is presented. The novel large area processing equipment enables 5 ?m resolution patterning of surfaces up to a size of 610 mm x 610 mm. Large area panel processing enables miniaturized low cost & high performance electronics & photonics packaging. The advanced ORMOCER® dielectric and optical materials allow low temperature processing on low cost polymer substrates with low temperature stability such as FR4. Partitioning between cheap standard (lower) density interconnect in PCB substrates and high density interconnect in the upper thin film layers is possible in order to reduce the number of metal layers and arrive at an optimal performance cost ratio for specific applications.A demonstrator composed of four sequentially build-up dielectric layers have been deposited on a low cost FR4 epoxy substrate intended for high frequency applications. The dielectric layers consist of a photo-patternable ORMOCER® and the intermediate metal layers of sputtered Cu. The UV-patterning was performed with the LAP projection lithography equipment. The produced microstrip lines, ring resonators, vias, stacked capacitors and filters have been characterized at frequencies from 1 GHz to 40 GHz showing the potential of the new dielectric material for microwave applications.The investigation of the material properties were performed with a network analyzer where specially designed structures had been made for the characterization. Some of the measurements at high frequencies were also evaluated and compared with simulations. The measured results showed good agreement with the simulated response. The experimentally obtained high frequency properties of ?r ? 3.05 and tan(?) ? 0.024 at 10 GHz - 40 GHz would be sufficient for many applications.The dielectric properties of an electronics grade silicone elastomer have been investigated in the frequency intervals 0.1 Hz to 1 MHz and 7 GHz to 18 GHz. The low frequency measurements were performed with a dielectric spectrometer.The results are discussed in terms of performance and usefulness of the material in electronic packaging. The permittivity at room temperature in the frequency range 7 GHz - 18 GHz varied between 2.75 to 2.8 and the loss tangent between 0.018 to 0.033. The loss tangent in the GHz region at room temperature was considerably higher than in the Hz – MHz region most probably due to the activation of the inherent alpha relaxation in the material when reaching the GHz-range.A stepped impedance filter has been realized by changing the dielectric material, i.e. the permittivity instead of modifying the line width. It has been shown that the technology can offer alternatives to the standard approach and also that it is feasible to arrive at a denser packaging by combining low and high permittivity materials. The practical limit of the permittivity ratio is dependent on both available materials and on processability of these materials. The useful range of impedance ratios can be further increased by simultaneously using the ‘standard stepped impedance approach’ and the ‘variable dielectric approach’.A novel rectifying device has been realized by screen printing a silicon powder composite with the intention to use a low temperature low cost manufacturing method. Rectification at frequencies up to 1 MHz has been demonstrated but so far with a too high series resistance to be practically useful. With optimization of the device and composite concept, low temperature, ultra-low cost high speed printing of e.g. high frequency diodes on any substrate, may be viable.