Tomohisa Ohta

FLIP-CHIP INTERCONNECTION TO VARIOUS SUBSTRATES USING ANISOTROPIC CONDUCTIVE ADHESIVE FILMS

Flip-chip interconnection to various substrates using ACF was investigated. It was demonstrated that the interconnection resistance of the joints made between gold bumps of the chip and Ni/Au coated pads on FR-4 boards was lower than 10 mΩ depending upon the kinds of conducting particles, although the interconnection was due to the mechanical contact between conducting particles and conductor surfaces. The current–voltage characteristics of the interconnection exhibited an ohmic behavior up to currents of 2000 mA per bump. In attaching bumpless chips to various substrates, the interconnection resistance strongly depended on the kinds of conducting particles and substrates. It was demonstrated that Ni particles were favorable for making good electrical contacts between Al pads of the bumpless chip and substrate electrodes. It was also demonstrated that low interconnection resistance in the range of 2 mΩ to 7 mΩ was obtained as well as with bumped chips, when FR-4 boards with Ni/Au bumped pads were used as substrates for interconnecting bumpless chips.

Adhesion properties of electron-beam cured oligomers for pressure-sensitive-adhesives

Abstract The properties of non-solvent pressure-sensitive-adhesives of the cured oligomers were studied with relation to their structure. Two types of liquid oligomers having certain double bonds, namely the side-chain and telechelic types, were employed for the test. The telechelic pure oligomer was cured in lower concentration of double bonds than the side-chain oligomer. Peel strength of the oligomers was almost the same. In the addition of mercapto-functional chain transfer agent, however, the telechelic type resulted in remarkably better peel strength compared with the side-chain. Thus, it is suggested that, in the case of the telechelic oligomer, the polymerizing or crosslinking by ene-thiol addition occurs effectively, and the adhesives indicate rubberlike elasticity.

PEEL BEHAVIOR OF PRESSURE-SENSITIVE ADHESIVES

Studies on the dependence of the peel strength on the rate of separation have shown that the peel behavior is influenced greatly by the interfacial interaction. The introduction of carboxyl groups in the surface of an adhesive resulted in the high peel strength at the wide range of rates and varied the shape of the whole curve; whereas the effect of carboxyl groups was diminished by the addition of a small amount of surface active agent sufficient for monolayer formation at the adhesive-adherend interface.

Ultra-Precision Machining of Dies for Microlens Arrays Using a Diamond Cutting Tool

Patterning of numerous microlenses on a surface improves the optical performance of components such as liquid crystal displays. A cutting method using a diamond tool is examined to fabricate a molding die that employs arbitrary array patterns to mold millions of microlenses. The present paper investigates machining of microlenses on the order of 2 kHz, using a piezo-actuated micro cutting unit and a synchronous control system of the cutting unit with an NC controller. Experiments using this system revealed that it is possible to machine a large number of microlenses on a molding die with high precision.