Wiring Board Materials Research Articles

Technological Trends in High-Frequency Low-Loss Printed Wiring Board Materials for Information and Communication Systems

Technological Trends in High-Frequency Low-Loss Printed Wiring Board Materials for Information and Communication Systems

Applicability of Different Bio-based Polymers for Wiring Boards

The paper gives a review of experiments for the application of biodegradable, sustainable polymers as a wiring board material. In the paper two different biobased materials and the standard PCB materials FR4 and FR2 were compared. The investigations refer to mechanical, electrical performance, surface quality the flammability and applicability for Polymer Thick Film Technology (PTFT) of the biobased material. The biobased materials are polylactic acid (PLA) mixed with different contents of cellulose acetate (CA) or flame retardant zinc pyrophosphate (ZnPP) and polyurethane (PU) with CA. The results show that the addition of CA to the polymers leads to a change of different properties for PLA and to a significant change in mechanical properties for PU. The use of ZnPP in PLA shows major improvements regarding the flammability of the polymer. The properties of the samples are in the same order of magnitude as the properties of FR2.

Reliability testing for microvias in printed wire boards

PurposeThe purpose of this paper is to identify and expand upon the understanding of the reliability of high density interconnect (HDI) technologies containing multi‐level microvia interconnections with 2, 3 or 4 stacked and staggered configured structures.Design/methodology/approachMicrovia testing was performed with interconnect stress testing (IST) using a modified methodology documented in the IPC test methods manual TM650, Method 2.6.26, titled DC current induced thermal cycle test. The IST coupon designs utilize mathematical modeling, in combination with prior experience in the fields of printed wiring board (PWB) processing, chemistry, materials and statistics, to improve the sensitivity of testing.FindingsSingle and 2 stack microvias are generally the most robust type of copper interconnection used in HDI applications, 3 stack and 4 stack require greater discipline to assure product reliability. Ranking the inherent reliability of 3 stack and 4 stack structures to other interconnects like plated through holes, blind, or buried vias, may need to be reconsidered in future reliability test programs.Research limitations/implicationsThis work was focused on the reliability of bare board and does not address failure modes associated with the additional stresses applied to the microvia structures created by the devices and their associated solder joints formed during surface mount assembly and rework operations.Originality/valueThis paper was written to improve the understanding of various aspects of design and their influence on reliability for stacked and staggered microvia structures. The design function must understand the physical construction as a critical influence on microvia reliability that should be taken into consideration in parallel with the electrical requirements.

Integrated microfluidic components on a printed wiring board platform

Advancements in printed wiring board (PWB) materials and processes have enabled the PWB to become an ideal low cost/high volume fabrication vehicle for integrated Micro-Electro-Mechanical Systems (MEMS). It is especially applicable for single-use microfluidic devices with electrochemical detection sensors, since detection and signal processing can be integrated on a single low cost platform. To showcase the PWB as a platform for MEMS applications, a MEMS microfluidic system for DNA amplification and detection has been developed using PWB materials and processes. PWB, embedded passives (EP), and high-density interconnect (HDI) technologies have been utilized to fabricate these microfluidic structures following processes analogous to those for fabricating silicon MEMS. Several functional blocks, such as heating and sensing elements, together with electrical circuitries have been demonstrated.

Evaluation of Dielectric Properties of Printed Wiring Board Materials by Using a Microstrip-ring and Strip-line Ring Resonator Methods

In this article, the opportunities to apply microstrip and strip-line ring resonator methods for evaluating the performance of the PWB materials are discussed. The study consists of an evaluation of the effects of frequency, temperature, and moisture absorption on the dielectric properties of the PWB. The study is carried out mainly in the frequency range from 1 GHz to 10 GHZ that includes ally typical electronic and wireless consumer products. An experimental research for the study is carried out mainly using different FR-4 type materials due to the principal use of FR-4 in mass production

Dielectric characterization of printed wiring board materials using ring resonator techniques: a comparison of calculation models

Ring resonator structures are widely used to characterize the frequency and temperature dependence of the relative permittivity and loss tangent of printed wiring board materials. Several theoretical models for the ring resonator structures have been presented since the first ring resonator application. In this paper, the theoretical models of the ring resonator structure are adapted for calculating the relative permittivity of low-loss and high-loss printed wiring board materials at frequency range from 250 MHz to 10.0 GHz. In addition, a review of the characterization of the loss tangent using the ring resonator is presented. The review also provides information about differences of the results due to different approximation used for conductor losses of the microstrip line. The research presented in this paper is based on an experimental research with several different microstrip and strip line ring resonator structures. The results of this study provide useful information about applying the ring resonator method for measuring the relative permittivity and loss tangent of dielectric substrates

Effects of conductor surface condition on signal integrity

The evolution of digital electronic systems to ever‐faster pulse rise times has placed increased demands on printed wiring board (PWB) materials. Signal loss associated with dielectric materials has driven development and commercialization of cost‐effective low loss laminate materials. In order to provide a better understanding of conductor material and surface finish choices, efforts have been made to quantify the impacts of these factors on loss. An alternative test approach has been identified which provides a measure of conductor performance, decoupled from both system geometry and the influence of laminate material.

Copper Pattern Formation on Fluorocarbon Film by Single Shot of ArF Laser

ABSTRACTCopper nuclei have been photo-chemically patterned on the fluorocarbon film surface in copper sulfate atmosphere via the reticle with just one shot of the ArF laser. Previously, we have reported that it required more than 3, 000 shots of the ArF laser to substitute the Cu atoms on the fluorocarbon surface.Fluorocarbon is regarded as promising as a printed wiring board material in the high- frequency band. However, the fluorocarbon is chemically stable making it difficult to bond to copper foil. Generally, a copper foil is formed on the fluorocarbon surface by electroless plating with a catalyst core. In this method, however, the surface is made rough in pretreatment, which impairs its characteristics. Using the catalysts also causes differences in the dielectric constant, generating a high frequency noise. Thus, we demonstrated the direct formation of copper nuclei on the fluorocarbon surface photo-chemically by using the Xe2 excimer lamp and the ArF excimer laser.The sample surface was first irradiated by Xe2 excimer lamplight to ma ke it hydrophilic. The surface was then irradiated with circuit patterned ArF laser light in the presence of copper-sulfate (CuSO4) aqueous solution to substitute the Cu atom. The modified sample was immersed in the electroless plating solution at 60 degrees Celsius for 15 minutes, and the copper foil was locally formed on the areas exposed to light.

An accurate method for measuring the dielectric constant of printed wiring board materials

A new time‐domain reflectometry measurement method is described that provides accurate measurements of the average high‐frequency (0.1GHz ‐ 10GHz) dielectric constant of printed wiring board materials and is suitable for “factory floor” use. A parallel‐plate transmission line is used for the sample geometry. Only simple numerical processes are required to extract the characteristic impedance and dielectric constant of the sample from the acquired data. The long‐term measurement reproducibility and short‐term measurement repeatability of the method are described.

Evaluation of Potential Printed Wiring Board Materials: Thermoplastic Polyimide + Polymer Liquid Crystal Blends

ABSTRACTPolymer liquid crystals (PLCs) have potential applications as printed wiring board materials and in other aspects of plastic packaging. They have a number of desirable properties such as low moisture absorption, thermoplastic behavior, and low thermal expansivity. However, PLCs can have significant anisotropy in expansivity with negative expansivities in the drawing or molding direction and relatively low positive expansivities in the transverse directions. By incorporating PLCs into an engineering polymer (EP) matrix, in our case a thermoplastic polyimide (TPI), we expected to be able to control the expansivity of the resulting blend – thereby aiding in long-term service performance and reliability. Properties such as low moisture absorption, dimensional stability at elevated temperatures, good adhesion properties, and reworkability were also sought. In this paper, we report on our work to process a TPI/PLC blend and characterize the thermal properties of the blends.An amorphous TPI was chosen over a semicrystalline one because of a thermo-irreversible cold crystallization in the latter, causing undesirable changes in the morphology and poor adhesion to metals. Our evaluations of TPIs through thermally stimulated depolarization (TSD) and temperature-modulated differential scanning calorimetry (TMDSC) reveal sub-glass transition relaxations. We have investigated the selected semicrystalline TPI + PLC pair in the entire composition range, and concluded that the narrower range, up to 30 wt. % of the PLC, is sufficient for the achievement of our objectives. The glass transition temperature Tg = 240°C of the TPI determined by DSC is unaffected by variations of the PLC concentration. The cold crystallization temperature of the semicrystalline TPI decreases with increasing PLC concentration but upon formation of the LC-rich islands this effect becomes smaller. All the blends exhibit degradation onset temperature over 520°C. The thermal conductivity of the amorphous TPI + PLC blends varies as a function of the PLC concentration. The blends show very good film formability. The addition of the PLC improves the processability of the TPI. Thermomechanical analysis (TMA) reveals that the desired control of the expansivity of the blends is also achieved by varying the PLC concentration.

A fast and accurate method for measuring the dielectric constant of printed wiring board materials

A new time-domain-reflectometry measurement method is described that provides accurate measurements of the average high-frequency (0.1 GHz to 5 GHz) dielectric constant of printed wiring board (PWB) materials and that is suitable for factory-floor usage. A parallel-plate transmission line is used for the sample geometry. A model is developed that describes the electrical behavior of the transmission line thereby allowing the dielectric constant to be extracted from the observed signal. The data analysis and the sample preparation are both simple to accomplish.

基板材料 第９回 高周波回路用プリント配線板材料

基板材料 第９回 高周波回路用プリント配線板材料