Akihiko Happoya

Effects of Lignin Derivatives on Cross-Link Density and Dielectric Properties in the Epoxy-Based Insulating Materials for Printed Circuit Boards

Bio-plastics are made from renewable biomass sources. We focus on lignin and develop epoxy resins containing lignin derivatives. We describe the preparation and application of epoxy resin containing lignin as a matrix. Soda-lignin (SLG) is obtained from black liquor in a soda pulp process. First, we use a lignin manufacturing process in which a methanol extraction method enabled reduction in the molecular and hydroxyl equivalent weights of lignin and removal of SiO2 and cellulose. Second, we investigate the ratio of diglycidyl ether of bisphenol-A (DGEBA) and methanol extraction SLG (me-SLG). From the viewpoint of cross-linking density and dielectric properties, 100/84 phr in the DGEBA/me-SLG casting system is found to be preferable. Finally, we try to fabricate an insulating material made up of DGEBA/me-SLG for an aluminum-based printed circuit board, and it achieves standard values.

3D-integrated, low-height, small module design techniques for 4.48GHz, 560MHz-bandwidth TransferJet™ transceiver

A low-height, small module for 4.48GHz carrier frequency, 560MHz bandwidth transceiver has been designed employing 3D integration technology. An LSI integrated with RF and digital baseband circuits is embedded in an organic resin substrate of the module to achieve a small module size of 4.8mm × 4.8mm × 1.0mm. Since RF signals are degraded by parasitic capacitance associated with the low height and small footprint of the module, three design techniques are proposed in the paper. The module realizes the worlds smallest size, and achieves sufficient transmitter modulation accuracy and receiver sensitivity, which meet TransferJet™ standards.

Effects of Thermal Cycle Conditions on Thermal Fatigue Life of Substrate With Cu Through-Hole

The Cu through-hole is a structure of electroplated Cu thin film, which penetrates the substrate. Because of the mismatch of the thermal expansion coefficient between the Cu thin film and the substrate along the thickness direction, thermal strain occurs repeatedly at the Cu through-hole part with the variation of temperature. As a result, the thermal fatigue failure of Cu through-hole part is one of the failure modes of the substrate. In this study, the effects of thermal cycle conditions on the thermal fatigue life of the substrate with Cu through-hole were investigated by thermal cycle tests and Finite Element Method (FEM)-based analyses. Thermal cycle tests of the substrate with Cu through-hole were conducted under different thermal conditions. The effects of dwell time, temperature range and maximum temperature were investigated. Among these factors, the maximum temperature shows the greatest influence on the thermal fatigue life of Cu through-hole part. FEM-based thermal cycle analyses were also carried out to understand the effects of thermal cycle conditions. The glass cloth structures of the substrate should be considered in the analyses, because their rigid properties probably affect the generation of the failure at the through-hole part. In this study, glass cloth structures were modeled by taking advantage of a homogenization method. On the other hand, the inelastic constitutive model of the electroplated Cu thin film was introduced in the analyses in order to describe the creep deformation during the dwell process of thermal cycles. The inelastic strain range of the Cu through-hole during thermal cycles was calculated from the analysis results and the effectiveness of the Coffin-Manson law was evaluated. The results showed that the fatigue life prediction using the Coffin-Manson model was effective in the range of the same substrate thickness and the same maximum temperature. Additionally the influences of material model and material constants of epoxy resin were investigated to expand the range of application of the fatigue life prediction.Copyright

Ultrathin 4-layer flexible printed circuits (FPC) fabricated by molecular bonding technology

We have developed the ultrathin 4-layer flexible printed circuits (FPCs) with the thickness of 135 um. This 135 um ultrathin 4-layer FPC is made by the molecular bonding technology, by which the electroless plating (metallizing) can be directly applied to polyimide (PI) by using molecular junction agents. In this study, we show the fabrication procedures, the mechanism of direct copper plating, and the reliability verification of the ultrathin 4-layer FPC prototype.