FR4 Board Research Articles

Investigation of copper plated-through-holes in glass fiber reinforced epoxy substrates using AC impedance spectroscopy

AC impedance spectroscopy was used to investigate copper plated-through-holes (PTH) in glass fiber reinforced epoxy substrates (FR4) at different stages of temperature-humidity-bias driven electrochemical migration failure. The test vehicles consisted of PTHs arranged in an alternate anode and cathode configuration in FR4 boards. The test vehicles were subjected to accelerated stress testing [130 °C, 85 % relative humidity (RH) and 100 V DC] to initiate a specific sub-surface electrochemical failure mode referred to as conductive anodic filament (CAF) formation. The test vehicle variations included a control with no exposure, test vehicle with electrical insulation failure (resistance change to 1 MΩ during the test) and test vehicle with initiation of CAF to compare the impedance characteristics at different stages of electrochemical migration failure. AC impedance measurements were carried out on the test vehicle variations at ambient and in an in situ humidity chamber as a function of RH at 14–85 %. The prior exposure condition of the test vehicles was found to have a strong effect on the impedance characteristics at different RH values. The accelerated testing results and impedance characteristics of the PTHs in epoxy-glass fiber substrates are discussed.

이층 기판용 3 dB 커플러

가장 많이 쓰이는 FR4 이층 기판을 사용하여 3 dB 커플러를 설계하고 제작하였다. 커플러 일부의 겹치는 면적을 키워서 커플링을 증가시키고 대역폭을 증가시키는 구조를 제안하였다. 설계를 위한 주요 파라미터 값들을 여러 조건에 따라 도시하였고, 시뮬레이션과 측정을 통해 검증하였다. 제작된 커플러의 크기는 <TEX>$30{\times}14mm^2$</TEX>이고, 중심 주파수 2.5 GHz 에서 0.6 dB의 삽입 손실과 <TEX>$90.5^{\circ}$</TEX>의 위상차를 측정으로부터 얻었다. 측정된 삽입 손실 <TEX>$3.6{\pm}0.5dB$</TEX>에 대한 주파수 범위는 1.72 GHz에서 3.08 GHz이다. 제안한 커플러는 기존의 랭 커플러와 유사한 성능을 보였고, 와이어 본딩 공정이 필요 없어 추가 비용이 들지 않고 도선의 폭과 간격이 넓어서 제작이 용이하다. A 3 dB coupler has been designed and implemented using the most commonly used double-sided FR4 boards. The coupling and the bandwidth of the coupler are enhanced with the enlarged overlapped area of the coupler. Major design parameters are plotted as a design guide and the parameters are verified by simulation and measurement. The size of the manufactured coupler is <TEX>$30{\times}14mm^2$</TEX>. Its measured insertion loss and phase difference are 0.6 dB and <TEX>$90.5^{\circ}$</TEX> at center frequency of 2.5 GHz, respectively. The operating frequency range is 1.72 GHz to 3.08 GHz for <TEX>$3.6{\pm}0.5dB$</TEX> insertion loss. The coupler has the performance similar to that of conventional Lange coupler, and implementation of the coupler is easy and cheap with wide metal width and spacing and no additional wire bonding process.

Finite Element Analysis and Experiment Validation of Highly Reliable Silicon and Glass Interposers-to-Printed Wiring Board SMT Interconnections

Interposers that support high input/output density are becoming critical for system miniaturization and high performance. Silicon and glass are emerging as the primary candidates for such high-density interposers, due to their outstanding dimensional stability, which enables layer-to-layer wiring with small vias. However, silicon and glass have very low coefficient of thermal expansion (CTE), 3–8 ${\rm ppm}/^{\circ}{\rm C}$ , compared with organic printed wiring board (PWB), which has a CTE of 12–18 ${\rm ppm}/^{\circ}{\rm C}$ . The large CTE mismatch between interposer and board raises reliability concern with the ball grid array interconnections. In this paper, compliant dielectric build-up layers laminated on silicon and glass interposers are explored as stress buffers to reduce the strain accumulated in solder interconnections. Finite element method was used to analyze the thermo-mechanical reliability of the interconnections, and predict the fatigue life of solder joints. Three types of low-CTE interposer materials were studied, low-CTE glass (3 ${\rm ppm}/^{\circ}{\rm C}$ ), high-CTE glass (8 ${\rm ppm}/^{\circ}{\rm C}$ ), and silicon (2.7 ${\rm ppm}/^{\circ}{\rm C}$ ). Test vehicles with the above three interposers at a size of 7.2 mm $\times\,$ 7.2 mm with 25- $\mu{\rm m}$ -thick polymer stress buffers laminated on both sides were fabricated, and assembled on organic FR-4 boards using Sn96.5Ag3Cu0.5 solder. The reliability of the solder interconnections, with the three different test vehicles, was studied using thermal cycling test from ${-}{40}^{\circ}{\rm C}$ to 125 $^{\circ}{\rm C}$ . The high-CTE glass sample was observed to survive 1800 thermal cycles before the first failure was detected in one of the corner joints. Experimental results of fatigue life of interconnections agreed well with finite element modeling results, and reliable interconnections between low-CTE interposer and organic PWB using stress buffers were demonstrated. Based on the validated model, parametric study was conducted to explore the influence of geometry and material properties of interposer on the thermo-mechanical reliability of the solder interconnections, as a guideline for interconnection design of similar interposers.

Disc Monopole Antenna with Ring Patches and Meandered Feeder for Radio Frequency Energy Harvesting

In this paper, a new wideband antenna with meandered feed line is presented which can be used in radio frequency (RF) energy harvesting. The proposed antenna is designed on 36 by 56.5 mm<SUP>2</SUP> FR4 board with thickness of 1.6 mm and dielectric permittivity constant and tangent loss of 4.3 and 0.025, respectively. It consists of circular disc antenna, two ring patches and three rectangular slots on the ground plane as well as a meandered feed line. Although any RF signal could be useful from energy harvesting point of view, the proposed antenna shows a wideband frequency range from 1.59 to 6.62 GHz and 7.44 GHz to 8 GHz in reference to -10dB return loss or better for wideband applications.

Design of High Sensitivity Radiofrequency Energy Harvesters Dedicated to Low-Power Applications

The Radiofrequency (RF) energy harvesting is a widespread technique to extend the lifetime of devices in low power applications such as Wireless Sensor Networks (WSNs). This paper presents the comparison between a n-stage traditional CMOS voltage multiplier and a n-stage voltage multiplier using bulk biasing to overcome the threshold voltage drop. The two rectifiers operate at 900 MHz ISM band and are prototyped using a standard CMOS 130 nm process. The rectifier circuits were placed into a quad flat no leads (QFN) package and mounted on a standard FR4 board with commercially available devices. The bulk-biased rectifier achieves a significant increase in power efficiency and low voltage-drop. Loaded by a 400 kΩ resistor, typically 3.6 μW/1.2 V, the power efficiency reaches 58%, which is an improvement of about 50% compared with the traditional circuit. Concerning the RF energy harvesters, they are able to deliver an output voltage of 1 V at approximately 900 MHz requiring an available input power of –25.5 dBm and –23 dBm using the bulk-biased and traditional architectures, respectively. Furthermore, the harvesters operate at 3 meters delivering an output power of 1 μW when a power source radiates 19 and 20.5 dBm EIRP, for bulk-biased and traditional circuit, respectively.

A 12.4-mW 4.5-Gb/s Receiver With Majority-Voting 1-Tap Speculative DFE in 0.13- $\mu\hbox{m}$ CMOS

This brief presents a majority-voting 1-tap speculative decision-feedback equalization (DFE) architecture wherein the current-mode-logic (CML) selector after the slicers is replaced with a CML majority voter with two instead of three transistors in the stack, thereby resulting in improved speed and increased voltage headroom (or lower supply voltage operation). Compared with the traditional CML selector, the majority voter shows around 50% delay reduction at the same bias conditions and 25% reduction in supply. A receiver with the proposed majority-voting DFE is implemented in 0.13- μm CMOS process. With the DFE enabled, the receiver is able to equalize a 20-in channel over an FR4 board with 22-dB Nyquist loss at 4.5 Gb/s. The whole receiver core occupies 0.14 mm2 and consumes 12.4 mW.

Comments on “A novel technique in simplifying the fabrication process and improving the reflection coefficient of the linear polarized radial line slot array (LP-RLSA) antennas”

Concerning the subject paper [1] and theory therein about “how the FR4 board reduces the reflection coefficient”, apparently, the authors (and even the referees) are unaware of the basics of the pr...

Triple‐Band Cpw‐Fed Planar Monopole Antenna for Wlan/Wimax Application

A triple‐band planar monopole antenna is presented in this article. The antenna consists of three strips which correspond to operating frequency bands of 2.4, 3.5, and 5.8 GHz. The proposed antenna has been designed, simulated, and fabricated on 20 × 38 mm2 FR4 board. There is good agreement between simulation and measurement results in terms of return loss and radiation pattern. The proposed antenna provides measured −10 dB bandwidths of 200 MHz for the 2.4 GHz (from 2.36 to 2.56 GHz); 620 MHz for the 3.5 GHz (from 3.48 to 4.10 GHz); and 1.38 GHz for 5.8 GHz (from 5.65 to 7.03 GHz). Moreover, the antenna provides the measured gain of 4.73, 1.66, and 3.28 dBi for 2.4, 3.5, and 5.8 GHz, respectively. The radiation characteristics have proven that the proposed antenna seems to be a good potential candidate for WLAN/WiMAX applications. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2209–2214, 2013

WLAN System을 위한 U-slot 및 Short-pin 결합한 바람개비 모양의 이중대역(5.2/5.8GHz) 마이크로스트립 패치 안테나 설계 및 제작

본 논문에서는 IEEE 802.11 기반의 WLAN(5.2/5.8GHz)대역에서 동작하는 바람개비 모양의 마이크로스트립 패치 안테나를 설계 및 제작하였다. 안테나의 크기는 <TEX>$17.4{\times}17.4mm^2$</TEX>이며 FR-4 기판을 사용하였다. 이동성을 위해 소형화하였고, 바람개비 패치 모양에 U-slot 및 Short-pin을 삽입하여 이중대역 공진특성 및 적절한 대역폭을 만족하도록 하였다. 또한 단일 양면기판을 사용하였고, 시뮬레이션설계는 바람개비 모양과 U-slot 및 Short-pin의 위치 변화, 패치길이를 최적화하여 제작 및 측정하였다. 제작한 안테나의 대역폭(Return loss<-10dB)은 5.2~5.8GHz대역에서 695MHz의 대역폭을 얻었다. H면과 E면 방사패턴의 3-dB 빔폭이 각각 <TEX>$81.13^{\circ}$</TEX>, <TEX>$85.43^{\circ}$</TEX>로 넓은 빔폭을 얻었다. 또한 3.17~4.85dBi의 이득을 얻었다. In this paper, IEEE 802.11 based WLAN(5.2/5.8GHz) wideband Weathercock-shaped microstrip patch antenna was designed and manufactured. The antenna has a size of <TEX>$17.4{\times}17.4mm^2$</TEX> and utilized FR-4 board. The size was minimized for mobility, and Weathercock-shaped U-slot and short-pin was inserted to satisfy adequate bandwidth and double bandwidth resonance characteristics. In addition, the antenna incorporated single both-sided patch, and simulation design optimized the Weathercock-shaped, position of the U-slot and the short-pin, and the length of the patch for the measurement. The manufactured antenna achieved a bandwidth of 695MHz from 5.2~5.8GHz zone(Return loss<-10dB). Achieved a beam width of <TEX>$81.13^{\circ}$</TEX> and <TEX>$85.43^{\circ}$</TEX> for 3-dB beam width of H plane and E p;ane radiation pattern, there was 3.17~4.85dBi gain.

Compact Wide-Band Branch-Line Coupler with Meander Line, Cross, and Two-Step Stubs

Despite being widely used, branch-line couplers (BLC) still suffer from large size. This makes it difficult to incorporate BLC into miniature microwave devices. The work presented here is the design and implementation of a 3-dB reduced-size wide-band 3-branch-line coupler (3-BLC). By combining meander line, cross, and two-step stubs techniques, size reduction and bandwidth improvement is successfully achieved on 3-BLC design. The 3-BLC length was reduced along the horizontal branches using two-step reduction technique while the center vertical branch was reduced using cross stubs. A simple two-turn meander line is utilized at the two ends vertical branches of the coupler to obtain balanced length with the middle vertical branch. Hence, its width was optimized to maximize the coupler bandwidth. The 3-BLC was designed to operate at 2.45 GHz wireless local area network frequency band (IEEE 802.11 b/g) and fabricated on a 1.6 mm thick FR-4 board. The simulated and measured results are in very good agreement and show a fractional bandwidth of 50% and a sized reduction of 61.64% at the center of the frequency band. The proposed coupler design provides BLC that occupies less space, simple to implement, and wide-band BLC architecture with generic 3-BLC wide-band characteristics retained. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1810–1815, 2013

A novel COB structure with integrated multifunction

A novel COB (chip-on-board) structure with integrated multifunction is presented. The structure is prepared by laminating copper plate with FR4 board and then coating with a silver layer to offer high reflectivity and high conductivity. In comparison with MCPCB (aluminum) and ceramics (Al2O3) board, the substrate brings about 10% higher light extracting efficiency than aluminum board and 5% higher flux maintenance ratio than ceramics (Al2O3) board at 3000 h. With integrated multifunction, through an IC component driving high voltage serial LED chips, the COB can be directly connected to AC 110 V or 220 V power supply in lighting application.

Thermal resistance investigations on new leadframe-based LED packages and boards

In Solid State Lighting, thermal management is a key issue. Within the CSSL consortium, we have developed an advanced leadframe based LED package to reduce the thermal resistance of the component. Numerical simulations have been implemented using Ansys® software and thermal measurements have been carried out using the forward voltage method to derive the thermal resistance. The T3ster® transient thermal analysis has been used to determine the different thermal resistance contributions in the package and in the board, showing good correlation between experimental and simulation results. As a result, low thermal resistances of 5.5K/W have been obtained on our advanced leadframe based LED package and have been compared with the standard configuration of multiple Rebel LEDs on FR4 board.

A Parameters Optimization of the CO&lt;sub&gt;2&lt;/sub&gt; Laser Drilling Process for HDI Microvia Fabrication

The blind via holes formation by laser drilling is one of the key technologies for demanding high density interconnect printed circuit boards. In this paper , the drilling conditions of drilling the blind via holes and the quality of the drilled holes are examined using a CO2 laser source against the FR4 board without copper foil.We chose laser energy,pulse shot,pulse width and diameter of beam as the experimental parameter . The results showed that laser energy and beam diameter played a more important role on changing the blind vias’ diameter than pulse shot and pulse width .While the pulse shot and pulse width take more important role in changing the depth of vias.

Left-handed metamaterial structure incorporated with microstrip antenna

This article presents the design, simulation, and fabrication of a new planar left-handed metamaterial (LHM), which consist of a combination of a modified square rectangular split ring resonator and strip wire. Both structures are on the same plane. The structure is simulated and measured with the microstrip antenna operating at frequency 5.8 GHz. The LHM has been analyzed using Nicolson-Ross-Weir approach to obtain the negative permeability and permittivity at 5.8 GHz. The fabrication of the LHM is on FR-4 board substrate. From the simulation and measurement results, the gain of the microstrip antenna with LHM has increased by 4.0 dB. The return loss of the antenna with LHM is improved to 15.7 dB compare without LHM structure.

Design for reliability of solid state lighting systems

This work presents a methodology to design an SSL system for reliability. An LED lamp is thermally characterised and its model thermally simulated, indicating that the LED board (FR4 board with thermal vias, copper tracks and LED package) is the thermally most stressed part. Therefore, a thermo-mechanical analysis is performed from a detailed LED board model to study reliability and lifetime limits, using thermal boundary conditions deduced from the thermal simulation of the whole LED lamp. Based on this analysis the weakest spots are identified as the metal vias in the LED package and the interconnection area between the LED package and copper tracks on the FR4 board.

A Novel Technique in Simplifying the Fabrication Process and Improving the Reflection Coefficient of the Linear Polarized Radial Line Slot Array (LP-RLSA) Antennas

A novel technique in simplifying the fabrication process of LP-RLSA antenna as well as improving the reflection coefficient of LP-RLSA antenna is proposed in this paper. This technique utilizes a FR4 board added on the top of the normal LP-RLSA antenna. Theoretically, FR4 dielectric material is able to reduce antenna reflection coefficient since it produces the signal that has a different phase with the propagating signal within the antenna cavity. Moreover, by utilizing the copper part of the FR4 board as the radiating element, the fabrication process can be simplified since the antenna slots can be cut utilizing the simple low cost etching process. In this paper, the theory about how the utilization of the FR4 board can improve the reflection coefficient response is explained. The parameters that influence the capability of FR4 board in improving the reflection coefficient response are also discussed. A LP-RLSA antenna with FR4 board and a LP-RLSA antenna without FR4 board are designed and simulated at frequency of 5.8 GHz. The simulation result shows that the thickness and permittivity values of FR4 board influence the reflection coefficient response and the antenna gain. The best values of the permittivity and thickness of the FR4 board are 4.3 and 1.6, respectively. The simulation result shows that these values can improve antenna gain up to 2.45 dB. They can also improve reflection coefficient response significantly from –3 dB to –25 dB. It is discovered that the LP-RLSA with FR4 board also produces the beamsquint effect from –10° up to 10° from the boresight direction. The prototype of the designed antennas is fabricated and measured. The measurement and simulation results show that the LP-RLSA with FR4 board has a better gain and better reflection coefficient than the LP-RLSA without FR4 board, thus prove the concept of the novel technique.

Effects of Extended Dwell Time on Thermal Fatigue Life of Ceramic Chip Resistors

The understanding of the effects of temperature cycling parameters, such as dwell and ramp times, mean cyclic temperature, and temperature range, on the fatigue life of solder interconnects is critical for qualification and reliability testing. After the solder achieves complete stress relaxation, a further increase in dwell time does not decrease the fatigue life of solder interconnects. Studies have shown that an increase in dwell time beyond a certain limit (10–20 minutes) has no effect on the fatigue life of eutectic tin-lead solder when cycled at peak cycle temperatures at or above 100°C. The duration of stress relaxation is longer in SnAgCu and SnCu solders than in eutectic tin-lead solder, resulting in higher creep damage accumulation and thereby reducing the fatigue life of solder interconnects. Experimental data for modeling of the effects of extended dwell time (beyond 60 minutes) on the temperature cycling reliability of tin-silver-copper solders is limited. In this study, forty 2512 ceramic chip resistors soldered onto an FR4 board using SAC105, SAC305, SN100C, and eutectic SnPb solders were subjected to temperature cycling tests with dwell time durations of 10 and 120 minutes, respectively. Resistors soldered on standard and narrow pads were compared to study the effects of pad size on thermal fatigue reliability. In eutectic SnPb-soldered narrow pad resistors, the increase in dwell time to 120 minutes did not change the cycles to failure. However, SnPb-soldered standard pad resistors showed a decrease in fatigue life with the increase in dwell time. For SAC105- and SAC305-soldered narrow and standard pad resistors, the 120-min dwell decreased the thermal fatigue life, compared to the 10-min dwell. The thermal fatigue life of SN100C-soldered narrow pad resistors increased when the dwell time was increased to 120 minutes, while that of the standard pad decreased. In the case of narrow pad resistors, extended dwell may be have annealed the SN100C solder, making it more robust to solder fatigue.

A Novel Dual-Band MIMO Antenna with Lower Correlation Coefficient

This paper demonstrates a novel dual-band operated MIMO antenna which consisted of planar monopole (main antenna) and 3D slot element (auxiliary antenna). The main antenna is printed on a 1.6 mm thick FR4 board, while the auxiliary antenna is fabricated with gold-coated copper. A lumped impedance network is applied to enhance matching effect at port1. From simulations by commercial software, it can be found that the proposed antenna is able to cover GSM800, GSM900 (lower band), and LTE/ WiMAX/WLAN (higher band) quite well. Good agreements between simulations and measurements are obtained. Corresponding measured results, antenna efficiency, peak gain, and radiation patterns, are presented at the same time. By equipping a passive decoupling element, the coupling power on the ground is radiated into free space, and great enhancement of isolation between antenna elements, especially for lower band, is achieved.

M‐shape surrounded with ring patch wideband monopole printed antenna

AbstractIn this article, a novel shape of a ring printed antenna is presented. Antenna is designed for wideband applications. There is an M‐shape patch inside the ring, which is optimized for wideband applications. The antenna operates between 2.05 and 6.85 GHz frequency bands. The measured bandwidth is about 107.87%. The proposed antenna has fabricated and tested. It has been fabricated on 30 × 51 mm2 FR4 board. A novel shape of ground plane has been used for increasing the bandwidth and removing some ripples in the result. The return loss results have been presented based on simulation and measurement. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 54:482–486, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26541

Branch line coupler using hybrid T‐model structure

AbstractA reduced size branch line coupler (BLC), which does not use bonding wires, lumped elements, or via holes, is reported in this article. The technique presented uses T‐model approach, which is a combination of low‐impedance and high‐impedance quarter wave transmission lines for realizing the proposed structure. The coupler's operating frequency bandwidth is between 2.1 and 2.67 GHz, and its size has been reduced by almost 75.31% compared with the conventional BLC. The S‐parameters and the phase difference between the output ports are simulated using CST microwave studio, and the simulation results have been compared with the measurements. The BLC has been designed to operate at 2.5 GHz and fabricated on flame resistance board (FR4 Board). The study shows that there is good agreement between the simulated and measured results. The proposed coupler has promising potentials for beam‐forming network applications such as butler matrix due to its smaller size. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:237–240, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26476