Flexible Printed Circuit Research Articles

The Possibilities of Silicon as Flexible Printed Circuit Board (Biochips): An interface between electronics and non-electronic World

The ubiquitous microprocessor has dramatically increased the world’s data processing capacity. The limiting factor in expanding computer analysis and control for clinical and biotechnological applications is the interface between electronics and the non-electronic world. Emerging applications in a number of areas are expanding the need for chemical sensing. For example, there is a trend in clinical testing away from use of centralized laboratory facilities and toward testing which can be done quickly in physician, office. The monitoring of biological fluids for illicit drugs or for hazardous chemicals, particularly when there is workplace exposure, is increasingly important. Monitoring of biological fluids for illicit drugs or for hazardous chemicals, particularly when there is workplace exposure, is increasingly important. Monitoring of toxic substances in industrial effluents in the environment is becoming a priority. White analytical instrument and laboratory procedures are available for collecting the data required data, these approaches are often unacceptably expensive or slow. Availability of low-cost, portable, direct-reading instrument could have an impact on data collection comparable to the effect that microprocessor have had on data processing. Due to its dependence on instrumentation, analysis chemistry has long benefited from advances in electronics. For example ion selective electrodes (ISEs) became practical early in the 20th century when vacuum tubes provided high input-impedance instrumentation, and the solid-state operational amplifier now pervades chemical instrumentation. Sensors and actuators bridge this boundary, transducing physical and chemical conditions electronic signals, or using electronic signals to bring about a physical or chemical change. In this paper, the focus is on fabrication technique for flexible silicon cables, which can be used In biotechnology as bio sensor (thin membrane), complete PCB (Printed circuit board) for interfacing components on a biochip, and in hearing aid equipment. The experiment carried out in clean rooms of class 100, as part of research in (nano tools) at Microelectronic center, Technical University of Denmark.

809 携帯電話カール曲げフレキシブル基板の疲労寿命予測

809 携帯電話カール曲げフレキシブル基板の疲労寿命予測

Development of an Array-Type Flexible Tactile Sensor Using PVDF and Flexible Circuitry

This paper represents the development of an array-type flexible tactile sensor using PVDF(polyvinylidene fluoride) film and flexible circuitry. The tactile sensor which has <TEX>$8{\times}8$</TEX> taxels is made by using PVDF film and FPC(flexible printed circuit) technique. Experimental results on static and dynamic properties are obtained by applying arbitrary forces and frequencies generated by the shaker. In the static characteristics, the threshold and the linearity of the sensor are investigated. Also dynamic response of the sensor subjected to the variable frequencies is examined. The signals of a contact force to the tactile sensor are sensed and processed in the DSP system in which the signals are digitalized and filtered. Finally, the signals are integrated for taking the force profile. The processed signals of the outputs of the sensor are visualized on a personal computer, the shape and force distribution of the contacted object are obtained using two and three-dimensional image in real time. The reasonable performance for the detection of contact state is verified through the experiment.

Design and characteristics of a newly developed cavity-up plastic and ceramic laminated thin BGA package

The key requirements for a package are high electric and thermal performance, thinness, light weight, small size or high assembly density, and low cost. Plastic packages are superior in terms of electrical performance and cost whereas highly thermally conductive ceramic packages are superior in terms of thermal performance, weight, and size. However, these conventional plastic or ceramic packages cannot simultaneously satisfy all the requirements A new cavity-up plastic and ceramic laminated package (PCLP) has been developed that not only has superior electrical and thermal characteristics simultaneously without a heat sink, but also a thin profile and small size and is cost-effective. For example, the frequency range applicable to the PCLP exceeds 500 MHz, the maximum power dissipation is 4 W under natural convection, and the thickness is less than 2 mm. The PCLP is composed of two substrates: an electrically conductive plastic substrate and thermally conductive ceramic substrate. The plastic substrate, made of liquid crystal polymer (LCP) and copper, forms a flexible printed circuit (FPC). LCP is a suitable material since it has low water absorption, low dielectric constant, and low dielectric loss. The ceramic substrate is cofired tungsten-metallized aluminum nitride (AlN). It has high thermal conductivity and its coefficient of thermal expansion (CTE) is close to that of silicon. The AlN substrate also supports mechanically both the FPC and the semiconductor chip. The package is made using simple processes: both FPC and AIN substrate are single insulation layers; interconnection technologies are simple, for example, screened bump interconnection and lamination; and a conventional pattern formation is used, for example, screen printing. The measured electrical resistance is 450 m/spl Omega/ (line length 14.7 mm, width=50 /spl mu/m), which was about 1/10 of that for a simple ceramic cofired package of the same dimensions with a tungsten conductor. The measured thermal resistance is 10.8/spl deg/C/W under natural convection without a heat sink. In this paper the PCLP's design concept, configuration and performance characteristics are reported.

New design for a lead frame used for high pin counts and high-power LSI package

To meet the requirement of high speed driving LSI package with powerful output, combining flexible printed circuits (FPC) with the lead frame has been designed, and has been manufactured using TAB tape carriers by chemical etching. The back side plain metal laminated with high modulus adhesive allows for high speed wire bonding on it and used as electrical grounding and a heat spreader. The Au/Sn eutectic microsoldering method by heat press is applied for combining FPC and lead frame. The combining lead frame has some excellent characteristics. Electrical impedance of the lead can be easily controlled by the rearrangement of lead width, gaps, and dielectric insulation etc. The use of thin copper foil results in increasing pin count and narrow pitch lead frame. The heat spreading effect by plain metal with apparent thermal resistance is excellent. Insulation level of the dielectric is kept stable for a long time because of the selection of materials which has resistivity to electro-migration.

High-speed signal transmission at the front of a bookshelf packaging system

A front-connection technique using the front-side of the circuit board in rack systems configured like bookshelves is proposed to increase pin-counts for high-throughput switching modules (>20 Gb/s). This configuration technique was implemented using newly developed front connectors and flexible printed-circuit (FPC) cables that are both impedance-matched. This configuration enables the use of a new transmission route that meanders through every signal transmission line of every circuit board, backplane, and FPC cable. This route can extend the functional block size from the size of the circuit board to that of the unit, In a signal transmission experiment between circuit boards with this meander route passing through signal lines of an 18-cm-long FPC cable and over a distance of ten slots in the backplane, error-free (<10/sup -11/) signal transmission of 2/sup 23/-1 nonreturn-to-zero (NRZ) pseudo-random bit sequences (PRBS) at 622.08 Mb/s was obtained.

Dynamic Design Analysis of Looped Flexible Printed Circuit.

A new design process is developed for a flexible printed circuit (FPC) that picks up the head signals of a magnetic disk unit, and can optimize the FPC loop shape. The head can be positioned by consideration of dynamic reaction force of FPC. In the process the dynamic treatment of a FPC is regarded as a vibration structure. A calculation method is proposed equivalent bending rigidity (EI) of a complex FPC. The evaluated EI is further used to determine the influence of the dynamic reaction force. A dynamic FEM model and the servo model are used to determine the residual vibration force just after bang-bang seek. Evaluated dynamic reaction force agrees very well with the experimental data. It is clear that the dynamic reaction force is very similar to the shock spectrum of a single degree of freedom. The optimization of FPC jointed to carriage and base for both ends is achieved. The optimum shape is very close to semicircular.

Mechanism of electrical conduction through anisotropically conductive adhesive films

Anisotropically conductive adhesive films (ACFs) which had different amount of electrically conductive particle contents and insulating particle contents were offered for measurement of electrical resistance between electrically conductive glass substrates and flexible printed circuits (FPCs) connected by using these ACFs. As a result, the electrical resistance for samples using ACFs containing electrically conductive particles was proved to he low, and also that for samples using ACFs containing insulating particles or no particles was proved to be considerably lower than we had expected. On the other hand, after high temperature and high humidity treatment or temperature cycle treatment, the electrical resistance for samples using ACFs containing electrically conductive particles did not change so much, but that for samples using ACFs containing insulating particles or no particles changed significantly, that is, it increased remarkably. From these facts, we presumed that there were two kinds of electric current passing through ACFs: one passing through electrically conductive particles and the other not passing through them; the current passing through electrically conductive particles did not change so much even after high temperature and high humidity treatment or temperature cycle treatment, but the current not passing through electrically conductive particles significantly reduced after the treatment mentioned above. On the basis of the above result, the role of conductive particles in ACFs was considered.

Development of Biaxially Stretched Film for Flexible Printed Circuit Boards

A biaxially stretched film of BEK, a new engineering plastic with high heat resistance (T g: 181° C, T m: 364° C) and chemical resistance, was developed as a base film for flexible printed circuit boards. Its heat shrinkage percentage at 260° C and the coefficient of thermal expansion below T g were decreased to below 0.1%, and 3.3×10-5/° C, respectively. The process of determining stretching and heat setting conditions for film formation with a role stretcher and a tenter is reported.

磁気ディスク装置用ヘッドアームの熱変形低減

This paper describes a head-arm in which thermal deformation is eliminated for a large-capacity magnetic disk storage system. This study uses two methods: measurement by holographic interferometry and calculation by finite element method (FEM). The head-arm is a laminated structure composed of aluminum, adhesive and a flexible printed circuit (FPC). By inserting stainless steel in the adhesive layer, thermal deformation can be eliminated. When the stainless steel is 16 μm thick, thermal deformation is reduced to one third of the older head-arm. The stainless steel must be 22-26 μm thick for deformation in the head-arm to be completely eliminated. In addition, the influence of FPC and IC chips on the head-arm is investigated.

FPCを接着したアルミニウム積層板の熱変形解析(第2報)

This paper describes a method for eliminating thermal deformation on an aluminum laminated plate fixed to a flexible printed circuit (FPC) by adhesive. The objective of this study is to develop a head-arm for a magnetic disk storage system. Thermal deformation is calculated using the finite element method and the composite beam method. The deformation caused by temperature changes can be eliminated by making the equivalent thermal expansion coefficient of the FPC and that of the aluminum equal. Two methods for achieving this are investigated: controlling the volume of copper leaf in the FPC and controlling the volume of stainless steel inserted in the adhesive layer. The following results are found. The width ratio of copper leaf needed to eliminate thermal deformation is 0.50-0.55, and the necessary thickness of stainless steel is 10-15 μm. These results indicate that the insertion of stainless steel in the adhesive layer is the more appropriate method for application in the development of a new head-arm.

FPCを接着したアルミニウム積層板の熱変形解析 (第1報)

Analysis of thermal deformation on an aluminum laminated plate fixed to a flexible printed circuit (FPC) by adhesive leads to the development of a head-arm for a magnetic disk storage system. This work examines the establishment of a simple method for calculating thermal deformation. The efficacy of the composite beam method is investigated by comparing a measurement made by holographic interferometry and two calculations made by a finite element method, with the composite beam method. This research confirms the reliability of the calculation method using the equivalent characteristics of a simplified FPC. When the shearing deformation of an adhesive is neglected, the thermal deformation of an aluminum laminated plate can be easily calculated by using the composite beam method. When the Young's modulus of the FPC is small and the adhesive is thick, thermal deformation cannot be calculated using the composite beam method because of shearing deformation of the adhesive. It is possible to simplify the complicated shape of an FPC using the above two calculation methods.

Design Guidelines for Cost‐effective Manufacture of Flexible Printed Circuits (FPCs)

Several important factors are often neglected or forgotten by engineers and designers with respect to designing for cost‐effective manufacture of the different types of flexible printed circuits (FPCs). This paper discusses the various design features which influence the cost of FPC production, offers layout guidelines and considers the items affecting flexibility. Designing manufacturable products can lead to benefits such as reduced lead times, lower material costs, higher quality and increased yields.

X-Ray Photoacoustic Imaging of Surface and Subsurface Layers of Structured Materials

Surface and subsurface layers of structured materials were observed as the amplitude and phase images of X-ray photoacoustic signals. An X-ray beam from synchrotron radiation was narrowed with the use of a lead slit and allowed to irradiate the sample in the photoacoustic cell. A laminated sheet of aluminum and lead foils and a flexible print circuit board were used as samples. For the laminated sample, the empty space in the subsurface lead layer was clearly visualized in the images of both amplitude and phase delay. The results were compared with those of the photoacoustic measurement in the visible region. For the flexible print-circuit board, the printed copper strips were observed in both the amplitude and the phase images. The circuit pattern below the surface polymer layer was observed as signals with large phase delays.

Liquid Photoresist Techniques for Fine Pattern Flexible Printed Circuits

This paper presents a new roll‐to‐roll (R‐R) production system modified for fine line patterning of flexible printed circuits (FPCs) using the subtractive method. The R‐R system is especially suited to production of FPCs because the material used—copper‐clad laminate (CCU—can be handled as it is rolled. Consideration has been given to methods and materials in designing the machines. They are now operating successfully and are used in single‐sided flexible circuit manufacture. A liquid photosensitive etch resist and a collimated light source are recommended for the system and several factors necessary for achieving R‐R working conditions are discussed. Judging from the experimental results of these systems, using narrower width materials with chemical surface preparation is an effective technique for improving the yield rate. The selection of a liquid photoresist is not so common in the case of rigid printed circuit boards because of the difficulty of the coating process. On the other hand, in the case of flexible PCBs, it is successful not only in terms of resolution characteristics but also of productivity under several different types of coating conditions. It should be noted that use of the conventional subtractive method in the printed circuit field is still advantageous as some semiconductor technologies are applicable.

ＦＰＣの現状と展望 ＩＩＩ 製造

ＦＰＣの現状と展望 ＩＩＩ 製造

Disposable pudendal nerve stimulator: evaluation of the standard instrument and new device.

A disposable version of the pudendal nerve stimulator using flexible printed circuit (FPC) technology has been developed and manufactured in our department. Evaluation of this instrument against the standard is reported.

Observation of the Gold Plated Surface of Flexible Printed Circuits (FPC) by Electron Probe X-ray Micro-Analyzer (EPMA) .

Recently fine line Flexible Printed Circuits (FPC) are used in many applications such as Thermal Head Printers and Faximille. In these applications very precise control of plating thickness is required and leads us to difficult problem both in design and in measurment of plating thickness.The conventional β-ray method and Fluoro X-ray method are not sufficient to answer the above requirement. The Electron-Probe X-ray Micro Analyzer (EPMA) is recently developped surface measuring method which is especially suitable for these purposes.We applied this new technique to analyze the degrading problem in gold plated surface of FPC. Also the authors summarized the circuit resistivity effect on plating thickness control.