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We demonstrate a 4.8-μV rms noise microelectrode array (MEA) based on the complementary-metal-oxide-semiconductor active-pixel-sensors readout technique with disaggregated differential amplifier implementation. The circuit elements of the differential amplifier are divided into a readout pixel, a reference pixel, and a column circuit. This disaggregation contributes to the small area of the readout pixel, which is less than 81 μm 2 . We observed neuron signals around 100 μV with 432 electrodes in a fabricated prototype chip. The implementation has technological feasibility of up to 12-μm-pitch electrode density and 6,912 readout channels for high-spatial resolution mapping of neuron network activity.

A chip size package (CSP) and fine pitch ball grid array (FBGA) are increasing by becoming the focal point of attention in semiconductor field. A reel-to-reel consecutive manufacturing process has been developed by the authors for a tape-based substrate consisting of multi conductive wiring layers (minimum four layers) with ball grid allay connections. This substrate, compared to those presently in use, is (a) thin (150-200um for four layers) and low weight;(b) applicable to many pin counts; (c) makes possible fine conductive wiring and insulating layers with high accuracy in layer thickness and (d) facilitates the control of characteristic impedance.Interlayer connection technology is key to multiconductive wiring layer structures, which may have effect primarily on substrate reliability. In the present study, a copper deposited plating process was used in conjunction with W-laser drilling so as to produce very small via-holes in diameter 40-5Oum as interlayer connections. The reliability of interconnections was confiied for via-holes with diameter 40-5Oum under the condtion of lOOOcycle thermal shocks of -65C/+150C a gaseous phase. Filled viahole formation without interior voids was found to take place in the plating process.Minute stacked via-hole formation was noted to provide a substrate with high density pin counts. The substrate structure was designed with consideration electromagnetic transmission characteristics by computer simulation. The present substrate meets recent requirements for GHz order signal transmission.

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