Influence of Different Packaging and Footprint Technique for Microwave Absorptive Bessel Filter's Performance

摘要

In present day's ultra high speed data transmission environment, passive filters play a very important and critical function to achieve high-end system performance, especially in Microwave frequency ranges of 10 GHz or higher. Excellent electrical specification such as accurate -3dB cutofffrequency bandwidth, stable group delay, along with VSWR characteristics are very important parameters for system performance. Filters mechanical specification is similarly important, if not more. Products need not only be in certain size to fit in the board but also needs to be complement with other components. As available space in PCB become miniature for each component, filters footprint as well as via position need to be in certain ways to optimize board space and performance. Packaging material and packaging techniques play significant role to be ease of mass production as well. While some manufacturers like "Wirebonding" packaging, some like "Through Via", and "Ball Grid Array" is the packaging choice of some manufacturers. Component vendors need to have capability to change component design space, as the system designers' demandfor their choice offootprint and packaging environment. Moreover, these stringent mechanical specifications cannot compromise the electrical specification. To realize the effect of different packaging technique, we extensively studied several packaging techniques for Bessel filters with -3dB cutoff frequencies of 7 GHz to 10 GHz. We explored "stud bump ball grid array", "wirebonding", and "landgrid array " footprint packaging. We modeled different packaging technique and incorporated that into simulation to design the filter. We successfully manufacture surface mount filters with three different footprint packaging. We explored the influence of each packaging technique for electrical performance. We studied the hidden parasitic introduction from each packaging style and the detrimental effect of these to electrical performance, especially for frequency of 7 GHz to 10 GHz. We showed the advantages and disadvantages of all three kind ofpackaging technology in respect of electrical as well as mechanical specification.