Attenuation characteristics of microstrip transmission lines on alumina substrates up to 50GHz are discussed. The lines under test came from three different manufacturers, each of whom used different processes to realise the transmission lines. Two of the manufacturers used silver (Ag) paste, whereas the process of one of the manufacturers was copper (Cu) based. Each manufacturer used identical alumina substrates and identical test pattern files so that the measured attenuation properties reflected manufacturer’s capability to fabricate microstrips and the quality of the metal system used. Measurements showed that the attenuation of copper microstrips was slightly lower than that of the silver microstrips, but the difference was small. Measured attenuation (S21) of about 50Ω microstrips was approximately 0.5db/cm at 30GHz and 0.8dB/cm at 50GHz, respectively. The loss coefficient, αt, of about 0.035dB/mm at 40GHz was obtained for the Cu microstrips. Such an attenuation is reasonable for many practical applications in the microwave and millimetre wave regions.
This paper presents the results of a research program set up to evaluate atomic layer deposition (ALD) conformal coatings as a method of mitigating the growth of tin whiskers from printed circuit board assemblies. The effect of ALD coating process variables on the ability of the coating to mitigate whisker growth were evaluated. Scanning electron microscopy and optical microscopy were used to evaluate both the size and distribution of tin whiskers and the coating/whisker interactions. Results show that the ALD process can achieve significant reductions in whisker growth and thus offers considerable potential as a reworkable whisker mitigation strategy. The effect of ALD layer thickness on whisker formation was also investigated. Studies indicate that thermal exposure during ALD processing may contribute significantly to the observed whisker mitigation.
Micronas test chip MAS 7812 has been used to assess the reliability of a number of different packages, associated materials and chip passivations as well as sane assembly houses. The test device has been earlier found to give sufficient coverage of the most important failure mechanisms in plastic encapsulated and wire bonded IC's.Reliability of Finlux TAB-package has been evaluated in environmental tests. The encapsulated devices were subjected after ageing to tmprature cycling, condition -55 C to +125 C 100 cycles. Pressure cooker tests followed at 125 C and 85 % RH.The shape of the p d openings in final passivation were studied. Four different padopening structures were selected for this work and also the b w size and type were varied. The bunp layers were Ti-W (N, O)/Au. W h attention has been paid to the design of the final passivation and pad-areas to inprove the reliability.
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