It is very intriguing to design passive filters in a very small package, in the frequency domain of 10 GHz and above. Modeling the device footprint and correctly incorporate the model in the design work to design passive filter is key to successfully manufacture surface mount filter components that perform as expected, once they are mounted to the printed circuit board. This requires accurate correlation to the filter model and the measured first article component. In this work we studied footprint and it's influence in the final product. We developed filter design procedure using simulation software. We considered the impact of the parasitic of the input signal lines, printed circuit board's footprint parasitic, and filter's signal launch pad loss. We discussed an efficient way to design low pass passive filters in Ball Grid Array package; we optimized the design flow to manufacture filters. Then we designed and manufactured 12 GHz 9 th order absorptive low pass Bessel filter, whose size is 2.0 mm X 7.1 mm. We compared the measured data of the fabricated filter with the simulation results. We discussed the use of Coaxial Measurement Modules, which contains the filter with optimized design footprint.
Wireless telecommunication, broadcast and radar industries rely on high power transmission of the radio waves to reach subscribers or measure the environment. As the wireless revolution extends, component requirement in higher frequency, elevated operating power, smaller in size, and improved performance demands on resistive devices grow even more stringent. In this work, we extensively studied to improve the power handling capability of termination resistor while maintaining the smaller size. We optimized the energy transmission within the component and significantly improved the efficiency of energy transfer between the transmission lines and the terminations. We explored several innovative techniques to optimize thermal management. We applied new packaging techniques and developed termination resistors with optimum thermal management. We discussed several methods of improving power handling capability and reduction of thermal fatigue to the component’s structure by improving component packaging technology. Applying the packaging technology methods we significantly reduced the chance of solder cracking due to thermal fatigue. Employing novel techniques of heat transfer we appreciably increased power handling capability while keeping the product size as minimum. We constructed matching network using integrated microstrip line at the beginning of the resistor material. Considering required thermal performance, we designed and manufactured Pb free high power termination resistor. Several sizes of resistor are manufactured with rated power of 20 W and 100 W. Thermal profiles of the termination resistors illustrates the high power handling capability of the fabricated termination resistors.
Ever-rising pressure of improving frequency domain performance of RF and Microwave components to improve the signal integrity as well as to reduce component package size consistently challenge design engineers not only with signal integrity and size constraints, but also the power integrity and thermal constraints concurrently. To achieve excellent signal and power integrity performance for microwave frequency application, components need to have superior voltage standing wave ratio (VSWR) characteristics as well as outstanding power handling capability. Addition to the brilliant component performance, manufacturers need to achieve excellent fabrication yield performance to keep the project viable. Process engineers face many challenges on each fabrication steps, which could significantly degrade the fabrication yield. Few challenges could originate from material sets, while others could arise from the process variations. In this work, we extensively studied the influence of many different parameters that considerably diminish the fabrication yield performance. We analyzed different parameters to design RF and Microwave termination resistors using thin film materials. One of the essential parameters, which significantly reduce the fabrication yield, is the inconsistency of surface roughness throughout the wafer. We studied the variations of the thin film materials microstructure and the sensitivity of film resistivity in response to surface roughness inconsistency. We experimented anneal drift of the material and effects of the temperature compensation of resistor (TCR) due to substrate surface roughness and existence of powder contamination on the surface. We compared Lapped and As-Fired substrates roughness and researched the inconsistence roughness effects on the thin film material. We studied the deposition rate of sputtered copper over the life of the target, from machine to machine and across the pallet, and analyzed the effects on the thin film material component. We studied the moisture related long time drift based on electro migration effect and the temperature dependence drift based on the materials sheet resistance. We analyzed the alteration of current density due to thin film resistor trimming and yield loss due to resistor value tolerance and trim variation by studying the sensitivity of the resistor area variation through trimming process. By analyzing different fabrication factors and material parameter properties, we realized the fact that most sensitive parameter that degrades the process yield is the existence of inconsistent surface roughness throughout the substrate. Based on the research study, we developed high power RF and Microwave 50 ohm termination resistors with excellent fabrication process yield performance.
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