[in Japanese]

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[in Japanese]

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It is necessary to prepare the formation of the metal film on the insulation resin, during the build-up process. Conventionally, to achieve the adhesion between deposited metal and insulation resin, resin surface are roughed with a strong oxidant such as the chromic acid and permanganate. However, these oxidation agents are hazardous to the environment, and require a special effluent treatment. Accordingly, in this study, photo-oxidation using UV irradiation with titanium oxide (anatase form) is examined. the functional groups were introduced on the insulation resin by applying this technique. In addition, conductive Cu film without blister were formed by the electroless copper plating.

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[in Japanese]

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We examined the copper electroplating by using the additives and controlling the current waveform in a low copper concentration bath for the through-holes and via-holes. In the initial stage, copper electroplating at high current density was effective to a bottom-up filling for the via-holes and the through-holes plating. Moreover, the adsorption behavior of various additives were evaluated by the QCM method. As the results, a large amount of PEG was adsorbed on the substrate under the coexistence of Cl^-, compared with Cl^--free.

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The copper foil crystals have been found to grow with lateral growth of macrosteps on the (100) surface of the f.c.c. structure. The copper foil crystals with geratin additive have the (111) orientation and have triangular pyramidal morphology. With chloride only and geratin and chloride, the crystals have (110) orientation and pyramidal morphology. Both of these crystals grow with the lateral growth of macrosteps on the (100) surface. The cross sections and the surface roughness have been successfully explained by our proposed crystal growth mechanism of macrostep lateral growth on the (100) surfaces and the crystal orientations of (111) and (110).

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High uniformity of electrodeposit can be obtained with small height hump located at the cathode surroundings. Less than 1.0% uniformity was able to achieved with numerical computation of current density. This uniformity can be achieved by partial insulation coverage on the hump. The uniformity is related to the coverage ratio and hump height.

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In present work, we investigated about the effects of colloidal cobalt hydroxide and pH in the solution on the internal strain in cobalt deposits and on the surface morphology and crystal structure. The internal strain was measured using strain gauge mounted on the reverse side of 0.6 mm thick copper electrode, of which size was 8 mm wide and 25 mm long. A part of hydrogen codeposited with cobalt was spontaneously released from the deposits during electroplating, which caused the change in the structure from fcc to hcp and might result in the development of great tensile strain in the deposits. Using the PR electrolysis condition of i(c)= −6.0 A/dm², i(a)= +2.0 A/dm² and T(c)=T(a)=0.5 s in plating bath of pH 1.6, the tensile strain was reduced to 40% of that electroplated under DC electrolysis of −2.0 A/dm².

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This paper describes the phosphorus distribution and content in the electroplating and electroless nickel films at both the initial stages and following steady state of deposition conditions. From the results of EPMA, GDOES, AES and ESCA measurements, it was found that phosphorus contents in the deposited films at the initial stages indicate higher values than the following steady state deposition. The highest phosphorus content in the films was obtained from the citric acid bath among the tested complexing agents. The P rich layer around 20 to 40 nm in thickness calculating by the AES sputtering rate is produced at the initial stages of deposition and this layer is always staid at the surface of the deposited film along with the advancement of deposition reaction.

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[in Japanese]

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[in Japanese]

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The requirement of electroless Au plating solution has been increased with miniaturization of printed circuit boards and downsizing of electronic devices and the solutions are expected to be cyanide-free from the viewpoint of worldwide environmental protection. We have developed a cyanide-free immersion type electroless gold plating solution using alkylphosphine as a complexing agent. Tris(3-Hydroxypropyl) phosphine(T3HPP) was used as a complexing agent and thiourea was added in the solution. The optimum bath composition of cyanide-free immersion type Au plating solution was 0.01mol/l Au, 0.015mol/l T3HPP, 0.20mol/l thiourea and 0.07mol/l potassium dihydrogenphosphate. The addition of some additive such compounds as 1,2,3-benzotriazole, mercaptobenzothiazole, and catechol was also effective to stabilize the solution and to prevent dissolution of Cu from substrates. Deposition rate of gold was 0.06μm/30min from the immersion type solution at the bath temperature of 80°C and pH value of 7.0. The solution provides so good stability and the gold films obtained from above solutions showed high performance of pull strength of solder ball.

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Resin Coated Foil (RCF) for thinner multilayer boards (MLBs) need not only high heat resistance, low CTE and low dielectric constant but also to satisfy layer thickness, uniformity and filling up inner layer pattern in laminate process. Press cycle (heating ratio, temperature profile, pressure etc.) in laminate process was determined through trial and error in the past. We applied Quality Engineering to optimize the laminate condition of the RCF with effectiveness and concreteness.

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We have developed two new types of Multi Layered Printed Circuit Board (MLPCB), have Inner Via Hole (IVH), whose insulating and adhesive layers are made from polyimides. The two types differ in the structure of IVH. Both of the structures are designed so as to improve the connection of printed conductive paste to copper circuit. In case of three layers MLPCB, curling and bending of each layer has not arisen before and after being stuck together. In addition, it is possible for each layer of the MLPCB to adhere to surface of another circuit board.

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In the LCD drive is using TAB (Tape Automated Bonding) package. As electronics packaging prefer to smaller and lighter. Now electronics packages attend to COF (Chip on Film) without flying lead structure. COF structure looks like a FPC (Flexible Printed Circuits). Generally, TAB is using liquid type resist for single side patterning. On the other, FPC is using DFR (Dry Film Resist) for double side patterning. We are already developed new type of DFR (7μm thickness. Resolution is L/S=5/5μm) for COF patterning technology in the subtractive process.

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LDI (Laser Direct Imager) is one of the mask-less exposure methods that has enough practicality and advantages to be used in exposure processes for manufacturing PCB. Thus, I briefly mentioned types of LDI by adopted light waves, its numbers of machines in the field, and its environment (especially resist which is one of the most important aspect of LDI). I also referred to advantages of LDI introduction, such as cost reduction, less lead time, and better positioning accuracy, and the influence of positioning accuracy on yield or AOI. In addition, I explained at which processes LDI can be used, and things to be taken into account when using LDI or calculating ROI.

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It is necessary to conquer various technical subject, such as development of material, electromagnetic field simulation technology, and near electromagnetic field measurement technology, in order to acquire the effective absorption characteristic in near electromagnetic field. In this announcement, it introduces about the example of examination of the effect of EM absorption material though [case/where EM absorption material has been arranged the inside of a case, and on a transmmision line, or the main part of a cellular phone] simulation technology (the FDTD method) or an experiment.

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This paper shows quantitative evaluation of coupling between an antenna outside a shield case and a line inside that for a portable telephone. The coupling is caused through the gaps between the ground plane and the shield case. The gaps can not be avoided because of manufacturing limit. Dependence of the coupling on the length of gaps, the position, the height of the strip line and the kind of the antenna is clarified and the methods to reduce the coupling are investigated.

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A lot of planar antennas are used for various electronic equipments made smaller, thinner and lighter. We have proposed to use a spiral slot antenna formed on a printed circuit board. This paper reports on improvements on the gain and side-lobe characteristics of the antenna. TLM method was used for analysis. From the analyses, we found that the maximum gain increased by about 3dB, and the side-lobe level was improved under −20dB, and as the thickness of the substrate decreased, the peak frequency of the gain increased.

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Software radio, which is functionalized by software, can deal with several communication systems by only one hardware system. We have proposed an equiangular spiral antenna, which can deal with circularly polarized wave, for software radio using several frequency bands. In this paper, an equiangular spiral antenna was evaluated by TLM analyses, and array antenna using the equiangular spiral antenna was investigated. As a result, the array antenna arranged with same direction, which was made the most of the unit antenna characteristics, performed well in the gain and axial ratio characteristics.

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[in Japanese]

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As processing speed and frequency of electronic equipment are higher, it is required that the EMC countermeasures may be executed in design process of mounting and packaging, and it is important that we have to evaluate the electromagnetic radiation from PCB strictly and obtain the effective techniques to suppress the EMI. We have evaluated and investigated the electromagnetic radiation from a via hole to electrically connect between two layers in a multi-layered PCB model. This paper investigates relation between the crosstalk and the electromagnetic radiation in the multi-layered PCB model with various shapes of via holes. As a result, it was found that the circle via hole was more effective than conventional slit via hole.

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Recently many printed wiring boards have buried parallel planes which supplies the ground and power voltage. In this study, experiments and Electromagnetic simulations were made to describe the characteristics of the resonance in a couple of non-rectangular parallel planes, which can be seen in a usual products. The field distributions of non-rectangular parallel planes were expanded with those of rectangular parallel planes. Using this method, we try to reduce a electromagnetic field in parallel planes at a resonance of non-rectangular shape.

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This report analyzes voltage distributions and resonant characteristics of the power-distribution planes in multilayer printed circuit boards (PCBs) responsible for high level radiated emissions. The analysis is achieved by two-dimensional circuit model with SPICE. To control the resonant characteristic, the radiation level can be reduced.

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Dominant source of the radiated emission from multi-layer PCBs, which have become widely used, is power-ground plane resonance. This paper describes that how the power-ground plane is excited and causes a large amount of emission, and what effects on the emission the power-ground plane structure has. As a result, symmetrical layer stack-up S-G-P-G-S board with edges of two ground planes connected confines resonant energy to the power-ground plane and significantly reduces the emission.

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In the recent years, electronic equipments are running with high speed and high frequency signal processing, and they are improved in several performances. However, unnecessary electromagnetic radiation from the equipment is increased by the spectral extension of signal component. Higher harmonics generated by LSIs propagate through power distribution line, and cause the electromagnetic interferences (EMIs). The power decoupling is desired to prevent the EMI without obstruction of power supply. In this paper, the power decoupling using a microstrip transmission line, which has various shapes of inner conductors, is investigated by TLM analyses. As a result, by devising the cross-sectional shape of the inner conductor, the decoupling characteristics was improved compared with the uniformly-thick inner conductor.

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[in Japanese]

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[in Japanese]

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Junctions are very important components for signal distribution. CPW junction is much affected on the transmission characteristics in order to divide the ground plane into two sections. In this paper, the transmission characteristics of CPW Tee junctions are investigated. From the measurements, we found that the transmission characteristics of Tee junction fell with a constant interval of frequency because of the path difference between two slots along both sides of signal conductor. And also, we found that the characteristics were improved by devising the shape and size of the slots.

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The characteristic impedance of the transmission line in high frequency domain was measured by TDR using sine wave. (calling “sine wave TDR method” here after.) The characteristic impedance value of 5m-long, 50Ω semi-rigid cable was measured almost as 50Ω by this method. On the other hand, that of the 28cm-long, 70Ω micro-strip line swung around 50Ω. As this cause it may be considered that the sine wave duration necessary for the measurement was not enough in case of 28cm line and It couldn’t be measured precisely by the visual observation. The characteristic impedance in the high frequency range could be measured by sine wave TDR method by using wide band width oscilloscope and high-speed switching IC in future.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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In soldering, because cooling speed depends on a design of assemblies and material properties of components, especially lead (42 alloy and Cu), the formation of defects in solidification will be influenced by those factors. In the present study, solidification process is analyzed by the in situ observation combined with solidification calculation. According to the simulation of solidification process, relationship between solidification process and the formation characteristics of solidification defects for a SOP lead (42 alloy and Cu) and Cu land can be clarified.

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[in Japanese]

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A few reliability evaluations indispensable for using Pb-free solder have not been investigated, especially the amount of data of joint reliability on Sn-Zn solder with Pb-free plated lead is less than other Pb-free solders. In this study, we measured pull strength for joint of Sn-8Zn-3Bi solder with various Pb-free plated leads and observed solder joints metallographically. And we suggest that the joint of Sn-Zn solder with Pb-free plated lead have sure reliability, which is higher than with Sn-Pb plated lead.

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[in Japanese]

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[in Japanese]

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Conductive adhesives are expected to be one of the alternatives to tin-read solders. However, conductive adhesives have not been understood yet on their thermal and mechanical properties In the present work, to build up the design basis of conductive adhesives, thermal and mechanical characteristics are analyzed in terms of the composite material theory. Cu-epoxy conductive adhesives are prepared and thermal conductivity and thermal expansion coefficient are measured, and those properties are analyzed with the rule of mixture.

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Electroplated hard gold is widely being used as a surface finish for electrical connectors and relays. However, relay contacts plated with hard gold have a service life often limited by the phenomenon of sticking. In order to understand the mechanism of sticking phenomena, several kinds of hard gold plated relays were prepared and adhesive force of these samples was measured. It was found that combinations of some plates showed little adhesive force. Based on the observations, the degree of the adhesive force are determined by surface morphology, hardness, and surface friction of the gold plates.

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Recently, an influence of electroless nickel plating-displacement gold plating process on solder joint strength have been studied. Generally, the present studies indicate the existence conditions of phosphorus after surface mounting. Therefore, we point out existence condition of phosphorus after electroless nickel plating and displacement gold plating. We studied the effects of phosphorus rich layer on solder joint strength. Major results are as follows. · The phosphorus rich layer is formed on electroless nickel plating. · The thickness of phosphorus rich layer does not rely on phosphorus contents type of electroless nickel plating film.· Displacement gold plating influences on the thickness of phosphorus rich layer.

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Microscopic properties of electroless tin-plating on copper were evaluated for hyperfine interconnections. Inter metallic compound (IMC) layers at interface between copper and tin were analyzed by SEM and XRD. The results showed the existence of η-Cu₆Sn₅ as plating. After storage at 150°C in 15min, both of η-Cu₆Sn₅ and ε-Cu₃Sn were confirmed. Moreover, η-Cu₆Sn₅ was confirmed at the initial interface by TEM and ED analysis. It was considered that the pure-tin-layer was thin because IMC layer was formed as electroless tin-plating on copper, especially, the thickness of pure-tin-layer after the pre-heating before the bonding. The mechanism of the diffusion and the optimization of bonding profile are to be studied in near future. This work was performed by ASET supported by NEDO.

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Multi layer Flexible Printed Circuit(FPC) with the flexible and the ultra thin structure (0.2mm for 4 layers) has been achieved with material technology, circuit patterning (L/S=50/50um), designing and multiple lamination. The Electrical connection between layers is achieved by creating thru holes or blind via holes. Therefore it is possible to have a multi-layer structure without having a thru hole that passes through all layers. Laser drilling technology is applied for via holes. The new adhesive material has been developed as of the insulation layer. This multi layer FPC can be handled in roll to roll through whole fabrication process by controlling the fluidity of the adhesive above.

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We can achieve multi-layer flexible printed circuit(FPC) with ultra-thin structure (0.25mm) and fine pitch (L/S=50/50um) in the case of 6layers. The multi-layer FPC is prepared by stacking the double layer FPC. The both sides of that are electrically connected with conventional plated thru hole (PTH). And International via holes connects the circuits on each double layer FPC in the stacking process with Pb-free solder via. Unlike the build-up method, wherein a substrate is created layer by layer, this method can laminate several layers at once. By simplifying the fabrication process, this technique can attain high yield, and thus it offers a high-productivity process.

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[in Japanese]

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In soldering of a surface mounted device, sometimes solder joint error may be occurred by the manufacture conditions; metal mask, cream solder printing, mounting, re-flow solder temperature, etc. There is nothing provably that presumed the manufacture conditions for controlling a solder joint error, although many causes or measures of soldering error which generated in the manufacture factory are reported. In this paper, “Manhattan phenomenon” is presumed by the Monte Carlo method, which took variation of manufacture conditions into consideration.

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We examined the joint strength of several Pb-free solder bumps, which are Sn-Ag-Cu alloys varied in content of Ag and/or Cu and formed on the Sn-plated Cu pad, by the bump pull test and the impact-shearing test (micro-shot test). The bump pull test showed that the Sn-3Ag-Cu bump is more brittle than the Sn-1Ag-Cu bump at the Cu-Sn intermetallic layer. The impact-shearing test(micro-shot test) showed that while the impact strength of the Sn-Ag-0.5Cu bump is superior to others, it is considerably lowered after aging at 125°C for 500 hours. The observations of the fracture surface and the cross-section revealed that the voids occurred at the interface between Cu and Cu-Sn intermetallic layer and grown up with Cu-Sn diffusion degrade the mechanical strength of the solder joints.

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We have developed a flip-chip bonding method for high-speed signal transmission for superconducting integrated circuit. We evaluated the flip-chip bonding method using Pb/In superconducting bumps by the experiments and simulations. Comparison of shear strength that controlled by different methods was carried out using a shear test. In the result, the shear strength was measured to be 0.865 kgf on the average by a method controlled the cylinder of the flip-chip bonding machine. And shear strengths of two methods controlled the servo were measured to be 0.795 kgf and 0.495 kgf, respectively. From these results, it was obtained that shear strength of a method controlled the cylinder was stronger than those of methods controlled the servo. The heat cycle characteristics of the flip-chip connection were evaluated by four terminal measurement in liquid He at 4.2 K. As a result, when a sample cooled down in liquid He at 50 times, the maximum supercurrent decreased from 1.8 A to 0.8 A. It is considered that the superconducting bump part deteriorated by the heat cycle. Characteristics of a scattering parameter in a microscopic bump were analyzed using an electromagnetic field analysis simulator with transmission line matrix (TLM) modeling method. We obtained that a S₂₁ parameter stayed in the decrease of 10% at 500 GHz. This result indicates a microscopic bump have a performance enough to transmit the high-speed signals.

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It has not been recognized as being adequate to employ a metal filled epoxy resin for RF signal application. That probably is because of inhomogenity with metal particles on those materials. In this work, we have prepared the co-planner transmission line made with our own silver filled epoxy resin. The transmission line characteristics up to 18GHz is measured by using a Vector Network Analyzer. We have evaluated and resulted a possibility to employ the silver filled epoxy resin for RF signal transmission up to 18GHz.

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Electrically conductive adhesives (ECA) have been expected as a solder replacement bonding material. However, its acknowledgement, application status and problems have not been known enough. Micro Bonding Technology Study Group at Japan Institute of Electronic Packaging held questionnaire survey twice to disclose these points. As the result, ECA has been used widely in the application where the merits of ECA were realized. On the other hand, it was revealed that the available information regarding the performances, evaluation methods etc. are limited, users were trying to evaluate or use ECA without enough knowledge. For promotion of ECA, a continuous organization for joint works and study by material suppliers, equipment manufacturers and users is required.

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