To improve the reliability of a multi-chip module (MCM) composed of two wafer process packages (WPPs) on a FR-4 base substrate, the structure of the MCM was optimized by finite element analysis (FEA) . The important reliability issue is chip cracking or solder-joint failure between the MCM and a motherboard caused by thermal stress. The FEA results showed that the thermal stresses in both the chips and the solder bumps are a function of the ratio of chip thickness (tc) and substrate thick-ness (ts), i.e., tc/ts, and ts. And then, it was concluded that the chip cracking can be prevented, and also the life of solder joints can be increased when tc/ts is decreased. Furthermore, it was confirmed that a MCM with low ratio of tc/ts is highly reliable under thermal-cycling test.

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Interfacial reaction between Sn-8Zn-3Bi solder and Cu pad has a significant effect on reliability of solder joints. However the effect of plating materials for Cu lead on the interfacial reaction behavior has not been cleared. In the present study, to clarifying this, Ag, Bi, Cu or Pb, which was the element of lead free plating for Cu lead, was added to Sn-8Zn-3Bi solder. These solders were reflowed on Cu substrate with varying reflow time and temperature. The reaction layer between solder and Cu, and the growth kinetics of the reaction layer were investigated both during the reflow processes and after high temperature exposure tests. The growth of the interfacial reaction layer using Ag added Sn-8Zn-3Bi solder was suppressed compared with the others solders.

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A control to reduce the warpage of LSI package is a critical issue to ensure good singulation, solder joint and its mechanical reliability in surface mount packaging. In this study, predicting methods of the ball grid array (BGA) warpage were investigated using a viscoelastic technology with introducing chemical shrinkage of mold compound. As a result, the package warpage was found to be well predictable in cooling process from molding temperature and heating process of reflow temperature under a precise warpage calculation corresponded to chemical shrinkage of mold compound. Thus, the warpage mechanism became clear through the parameter analysis of material properties. In order to obtain a minimum warpage for a material designing of mold compound, the following suggestion is supported; 1) To increase Tg, 2) To reduce modulus at high temperature.

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The influence of powder size in solder paste on the solder volume applied by paste printing has been examined. The applied solder volume increased with decreasing the average diameter of solder powder which are contained in the solder paste. The solder paste with fine solder powder easily caused a solder bridging failure between the electrodes for a fine pitch QFP after reflow soldering. The measurement value of the applied solder volume was good accordance with the approximate half of the calculated volume using the close-packed model in which the powder with the average diameter is close-packed in the opening space of the stencil.

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Design guidelines for air core coils in LTCC RF devices have been equivocal, because coils have the RF magnetic flux not only inside but also outside. In order to make a design rule for LTCC devices, the magnetic fields of coils and the influential traits from the adjoining components in the devices was analyzed. Consequently, the analysis results showed that the outside flux mainly exists within 200μm around the coil electrode and that the adjacent components make coil's impedance higher. The effects of the serial connection of air core coils with smaller number of turn on the self-resonance frequency were studied. The simulation results showed that the self-resonance frequency dose not shift higher.

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Recently, several Pb free solder are introduced on the electric appliance rapidly. But, for the co-existing of enough quality and short development L/T on the electric appliance, it become doubtful whether the existing reliability standard of heat cycle test based on the Sn-Pb solder can be used or not. Therefore, in this paper, in order to reconsider the existing standard, thermal fatigue simulation of Pb free solder with Anand model was carried out and the necessary and minimum heat cycle time for Pb free solder was calculated. In addition to that, the acceleration factors for several solders are compared. As a result of that, it became clear that the necessary and minimum heat cycle time for Pb free solder could be shortened than that of Sn-Pb solder and that the existing reliability standard based on Sn-Pb should be changed.

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The fluid micro electro mechanical system (fluid MEMS), which is composed of a micro pump, mixer, valve, reactor, sensor, and an electric circulate system on one chip, is proposed for an application of biotechnology or medical analysis. In this paper, the micro fluid pump, which was mounted on a flat chip, was developed and pumping function was evaluated by measurement of flow volume. The strong point of these fluid MEMS has a thin chamber, which possessed polymers as a filling, and a pumping function was given rise to a mechanical vibration by micro vibrator on the outer side of a chamber. A liquid sample, such as an electrolytic solution, blood, and a protein solution, was effectively flown by micro pumping system from entrance to exit of a chamber, of which flow volume was 10-560μL/min using a battery at 3V.

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