An anti-stiction coating with a self-assembled monolayer (SAM) was investigated for ohmic contact micro-electro-mechanical system (MEMS) switches with low-load contacts. SAMs of thiophenol (TP) or 2-naphthalenethiol (2-NT) were coated on Au samples with variations in surface roughness to investigate the effects of the surface asperities on the adhesion force. The adhesion force was measured using a silicon tipless cantilever in the relative humidity range of 10 to 85% for the SAM coated samples and compared with those for the Au and SiO₂ sample surfaces. The adhesion force measurements indicate that the TP and 2-NT coatings can prevent a liquid meniscus from forming on the device surfaces due to their hydrophobic character caused by the protruding aromatic group. In addition, it was confirmed that these coatings could reduce van der Waals forces more than the Au coating. Based on these results, SAMs of TP and 2-NT have excellent potential as anti-stiction coatings for MEMS switch contacts.

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For VIA hole drilling into printed-wiring boards using a CO₂ laser, one of the critical issues is some insufficient electrical conduction by the thin layer of residual resin, so-called “smear,” on the inner circuits after the drilling. In general, smear over 2 μm thick cannot be removed by a chemical etching process. In this study, a novel in-situ process monitoring technology for laser drilling was developed to overcome this issue. During the laser drilling process, the amount of smear can be estimated by detecting the light emission generated from the reductive reaction of copper oxide on the inner circuits. Depending on the thickness of the smear, the number of laser pulses is controlled to keep it below 2 μm. This technology enables a VIA hole drilling system with high reliability.

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Various bandpass filters using stub resonators have been proposed to realize attenuation poles near the desired passband. However, designers have had to set the location of the attenuation poles by trial and error so as to use the attenuation pole effectively.
In this paper, we propose and design bandpass filters using stub resonators in order to decide the location of the attenuation poles and the sidelobe level in the stopband near the passband by using the elliptic function characteristic. The effectiveness of the designed filters is evaluated by circuit simulation, electromagnetic simulation, and experiment. We have also confirmed the realization of the sidelobe level in the stopband near the passband that is larger than the basic elliptic function characteristic by the appropriate choice of first and third resonators.

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We have adopted an electroless Ni/Pd/Au plating for the surface finishing of package substrates which ensure the same Au wire bonding reliability and high impact resistance as the conventional electrolytic Ni/Au finishing at the solder-ball joint. To utilize future substrates having fine wiring spaces of less than 20 μm, we investigated the minimum thickness of the electroless Ni film ensuring impact resistance by means of the high-speed solder ball shear test method. We found that the minimum electroless Ni film thickness is 1 μm with a Sn–3Ag–0.5Cu solder ball after heat (seven times 252°C peak N2 reflow or 1,000 h@150°C in air). We also found that the formations of voids and the grain miniaturization of intermetallic compound (IMC) near the interface of the ball-pad and the solder were the causes of brittle fracture which is the same failure mode in the drop test of mobile equipment.

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An attempt has been made to develop laser sintering incorporated with ink-jet printing of metal nanoparticles. To attain a bulk-like functional-film structure with a Ag-nanoparticle (5 nm in average diameter) paste, we have clarified that preheating is necessary to reduce solvents in the paste before laser sintering, that sintering is to be started from the substrate using a continuous-wave, near-infrared laser beam with low-absorbance of the paste, and that atmospheric sintering without oxygen or argon atmosphere enables the nanoparticles to separate from the organic dispersant. Regarding minute wiring on a polyimide substrate, a high interface-adhesion induced by molecular-level mechanical-locking as well as a low specific resistance of 4.8 μΩ·cm were obtained. In terms of wire-bond-pad formation on a Cu leadframe, a multistep printing process made it possible to form a 2–3 μm thick, φ 100 μm flat pad near the lead apex. Pull tests reveal that the wire bondability of the laser-sintered Ag pads is as good as that of electroplated ones.

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