Test Circuit Board Research Articles

Quantifying squeeze film damping in four-leaf clover-coupled micro-resonators: A comprehensive study under variable vacuum degrees

The squeeze film effect has a significant impact on the performance of micro-resonators when utilizing the electrostatic excitation and capacitive detection technique, due to the narrow air gaps present. It becomes the most critical damping effect that needs to be addressed. However, when micro-resonators are encapsulated in vacuum or rarefied air, squeeze film damping analysis can become considerably complex due to high-quality factors. In this study, we systematically investigate the squeeze film damping of a widely-used four-leaf clover-coupled micro-resonator under different vacuum degrees. The characteristic frequencies of micro-resonators are determined by applying the principle of mode superposition. Subsequently, the energy transfer theory is utilized to derive the theoretical formula for the quality factor caused by squeeze film damping, for varying levels of vacuum. Finite element analysis is then conducted to simulate the characteristic behavior and squeeze film damping of the resonator, confirming the accuracy of the proposed theory. In the experiment, a novel four-leaf silicon micro-resonator is fabricated using bulk anisotropic wet etching and other micromachining technologies. An experimental platform is established to study the squeeze film damping of the micro-resonator under various vacuum degrees, where the micro-resonator is excited electrostatically and detected capacitively. The frequency response and quality factor of the resonator under different vacuum degrees are measured using a house-made modal test circuit board. The experimental results demonstrate excellent agreement with the theoretical and simulated results, indicating that the proposed method can be a reliable and precise guide for understanding the squeeze film damping effect in advance, once the primary model of a micro-resonator has been designed.

Radiation-hard performance research of front-end electronics for fusion diagnostic by Gamma Irradiation Experiment

In the environment of a fusion reactor, electronic systems are subjected to various influences including vibration, electromagnetic pulses, as well as irradiation from neutrons and gamma rays. Diagnostics systems on fusion reactors can accumulate radiation doses to a level where issues such as signal attenuation and system interruption can occur. Additionally, maintenance of electronic systems during fusion reactor experiments is often not feasible. Therefore, assessing the radiation tolerance of electronic systems used in fusion reactors is of paramount importance. To validate the radiation resistance of front-end electronics and cable in various diagnostic systems, a test circuit board was designed. This board integrates a variety of commonly used amplification chips and power supply chips to assess their performance in the environment of a fusion reactor. The experiment selected three different types of cables commonly used in fusion reactors for separate testing, to assess their parameter changes before and after irradiation experiments. Gamma Irradiation Experiments were conducted using a cobalt-60 (Co-60) radiation source at the Irradiation Center of Nanjing University of Aeronautics and Astronautics. The test circuit board was exposed to continuous gamma irradiation at two test points, with dose rates of 6 Gy/min and 1 Gy/min, respectively, for a total of 6.5 h, Data from the irradiation experiments were collected and analyzed. The results show that under continuous gamma irradiation, CJ7805 and AMS1117–5 chips stopped working at 586 Gy and 776 Gy, respectively. The output of the LT1175I5 chip dropped from -5 V to -1 V at 447 Gy. Apart from the radiation-resistant power supply chips, the output of other power supply chips slightly decreased. The signal reference of the charge amplifier dropped at 741 Gy but then slowly rose again, and the signal amplitude decreased at 900 Gy. The signal reference of the current amplification circuit remained unchanged, with a slight decrease in amplitude. The signal reference of the voltage amplifier exhibited jitter, with no change in amplitude. The experiment provides valuable data support for the radiation-resistant design of electronic systems in the environment of a nuclear fusion reactor.

Failure patterns of solder joints identified through lifetime vibration tests

ABSTRACT A method for non-destructively tracking the integrity of flip chip solder joints through life is investigated in this paper. An industry standard double-sided PCB was designed and manufactured with 14 flip chips to assess the failure patterns of each flip chip and each solder joint in lifetime vibration tests. Two configurations of PCB finish were tested, Electro Nickel Immersion Gold (ENIG) and Hot Air Surface Levelled lead (Pb HASL) using automotive industry manufacturing processes and quality standards. A random vibration test over a frequency range 10 Hz to 1000 Hz was specified by automotive engineers to replicate vibrations typically found on road vehicles. This vibration profile was applied to test circuit board assemblies (CBA) for 4-minute intervals until failure of all chips. At each interval test boards were extensively scanned by an acoustic micro-imaging (AMI) microscope to non-destructively measure parameters of solder joints. This enabled tracking of mechanical joint connection through-life. Methods were developed to process the large number of acoustic images of each solder joint and form metrics to evaluate solder joint integrity. Results from AMI show that the solder joints exhibit three distinct zones as they age: crack initiation, crack propagation and then failure.

A Differential Split-Type Pressure Sensor for High-Temperature Applications

This study proposes a split-type pressure sensor based on differential capacitance that can be applied to in-situ accurate pressure testing in high-temperature environments. The sensor is mainly composed of a high-temperature resistant chip and a high-temperature resistant encapsulation structure. The chip is made of a ceramic substrate and presents a differential capacitance structure that can withstand high temperatures and effectively restrain the temperature drift. The encapsulation presents a split-type structure, in which the chip and the test circuit board are placed at the front and back ends of the sensor, respectively. Therefore, the front end of the sensor can work in the high-temperature area for in-situ testing, while the back-end temperature remains below 60°C all the time, which ensures normal operation of the circuit board. Finally, the test results show that the pressure sensor's temperature drift coefficient is only 6.6% within the temperature range of 25°C-400°C. The sensor's sensitivity can reach 9.27 mV/kPa and the maximum repeatability error is less than 2.2% at 400°C, which shows that the proposed sensor has a higher working temperature and higher precision than the existing pressure sensors.

Characteristics of a novel thermal-induced epoxy shape memory polymer for smart device applications

With the increasing demand for the application of electronic technology, high performance, multi-function and intelligent control have been the main developing trend of smart material. In this paper, a novel thermal-induced epoxy shape memory polymer (ESMP) is developed and utilized as substrate material for smart flexible electronic device. Owing to the advantage of thermal-induced ESMP, circuit substrate can be rigid-flexible controllable at different working temperature. Firstly, the ESMP samples are prepared and then the mechanical and shape memory characteristics are studied respectively. Secondly, the mechanical behaviors are analysed based on thin plate deflection theory and finite element simulation software on the engineering application. Meanwhile, corresponding experimental tests are designed and performed to corroborate the theory and simulation results. At last, ESMP based test circuit board is designed and manufactured. The electrical signals under large deformation are also measured and compared with typical circuit board. The results show that the prepared ESMP, as a smart material, has good reliability, flexibility and great application prospects in the field of intelligent devices.

Acoustic Detection of Cracks and Delamination in Multilayer Ceramic Capacitors

Multilayer ceramic capacitors (MLCC) are the most widely used capacitor type in the electronics industry. However, the brittle ceramic dielectric makes MLCCs prone to mechanical damage. Manufacturing defects or damage during board assembly may cause a capacitor to prematurely fail during its operational life. Here, we demonstrate the fast and non-destructive acoustic screening of MLCCs. Soldered 2220-sized MLCCs were subjected to ac voltage frequency sweeps, causing them to vibrate mechanically. Acoustic responses of the capacitors were measured before and after subjecting the test circuit board to severe bending. The results show that the cracks and delaminations caused by bending induce characteristic changes in the capacitors’ acoustic response. A support vector machine classifier was trained to successfully detect damaged capacitors based on their acoustic response.

Signal demodulation research of a frequency output resonant gyroscope based on instantaneous frequency analysis

Signal demodulation method of a frequency output resonant gyroscope is studied in this study. It has been a major problem of frequency micro gyroscopes. The detection elements of frequency gyroscopes are two double-ended tuning forks (DETF). The vibratory response of DETF is a periodic signal modulated by both amplitude and frequency. According to the characteristic that the amplitude and frequency of the gyro signal vary continuously with time, the signal demodulation algorithm is designed based on instantaneous frequency analysis. Hilbert transform is used to solve the instantaneous frequency. The algorithm is programmed in digital signal processor (DSP) and a test circuit board is made. Experimental test demonstrates that the demodulation circuit has a high precision and linearity, and the correlation coefficient between input signals and demodulation results achieves as much as 0.99999998. The demodulation method is proved to be feasible. This study provides a new train of thought for the study of the signal demodulation method of frequency micro gyroscopes and brings a new direction for the signal analysis of resonant sensors.

Design of Experiments Approach to Evaluating the Reliability of System-in-Package Assemblies

Abstract Reliability in microelectronic packaging has been, and will continue to be, a major concern that must be taken into account early in the design of a package. System-in-package (SiP) assemblies, as well as other high density packaging technologies, are being used in many system architectures in order to incorporate a high level of integration, reduce cost and fit on tighter next higher assembly (NHA) grid spacing. While these technologies are being adopted into system architectures, there is limited test data on the reliability of these packages in military applications. A better understanding of the impacts of design variables in a SiP assembly allows the design community to determine the most appropriate packaging solution for use in a given application. The term “system-in-package” covers a wide range of microelectronic packaging technologies. Microelectronic packaging technology is trending towards taking the SiP concept and incorporating a very high level of integration within as small of a footprint as possible. In many cases, a fan out design technique is used in order to utilize die with high density bump patterns and then use an interposer technology to increase the bump pitch to match pitches achievable on NHA board technologies. While increasing the packaging density appears beneficial in theory, its reliability becomes a risk as the complexity of the assembly increases and more interfaces are added. Mechanical and structural considerations must be taken into account when designing this type of assembly in order to limit the stresses observed in the assembly, especially when exposed to environmental conditions. This study will focus on traditional two dimensional (2D) integrated circuit (IC) designs. For the purposes of this study, a 2D IC package will be considered as multiple die attached to a SiP substrate via flip-chip bumps. These SiP assemblies will in turn be attached to a test circuit board via solder bumps, which are at a larger pitch relative to the flip-chip bump patterns. A daisy-chain circuit design was incorporated into the test board and die in order to evaluate the reliability of the assembly interconnects at various points throughout the assembly. Design variables such as underfill material, SiP substrate material and flip-chip bump density were incorporated into a design of experiments in order to evaluate their impact on the reliability of a SiP assembly. The materials selected for use in this testing allow for the evaluation of the impacts of coefficient of thermal expansion (CTE), modulus and other material properties on the reliability of a SiP assembly. Reliability of the assemblies was tested via temperature cycling and biased humidity testing. Successful reliability of each test was dictated by the continuity of the daisy chain circuits throughout testing, as well as a visual examination of the interconnects after test. Samples of each assembly design configuration were used in cross sectional analysis to further examine the effects of the reliability on the assembly. Material characterization techniques such as scanning electron microscopy (SEM) and focus ion beam scanning electron microscopy (FIB-SEM) were used, as necessary, to investigate failure modes. This paper will review a design of experiments study of SiP assemblies and present the results of reliability testing on various SiP assembly designs. Further study is suggested for the use of these results in developing and refining finite element models capable of accurately predicting failure modes in SiP assemblies.

PERFORMANCE EVALUATION OF GOLD (Au) WIRE AND RIBBON INTERCONNECTS IN HIGH FREQUENCY CIRCUITS

Abstract Gold (Au) wires and ribbons are widely being used in military and space applications of high frequency RF/microwave circuits. The purpose of this study is to examine the RF performance of different dimensions of Au wires & ribbons, which are typically bonded in cascade and parallel forms in the circuits operating microwave frequencies within 0–50 GHz. The second goal of this study is to establish a performance chart/handbook of Au wires, ribbons for high frequency circuit designers in order to show them which type of wire or ribbon as well as which type of interconnect form is suitable for their intended design. First, the test circuit board is manufactured by using chip & wire, epoxy attach method. The substrate material of used RF circuit materials is chosen as Alumina to minimize losses and the material of wires, ribbons are chosen as %99.99 pure Gold (Au). Au plated copper traces are used as conductive layers for optimal reliability and conductivity in the test circuit board. Automated thermosonic ball bonders are used for Au round wire bonds to reduce process errors. Manual parallel gap resistance welders and manual thermosonic wedge bonders are used for Au ribbons and always pay great attention to form the same length by using high magnification microscopes. The experiment conducted with the help of 0.7 mil, 1 mil round wires and 3×0.5 mil, 3×1 mil, 5×0.5 mil, 7×1 mil and 10×1 mil ribbons. Single bonds, parallel double bonds as well as V-type bonds, stitch over ball bonds are performed onto the circuit pads as interconnect types and forms. The RF tests (S11 return losses and S21 insertion loss) we performed showed that 0.7 mil and 1 mil round wires can be used in the frequency range of 0–20 GHz circuits. A better RF test result can be achieved if double parallel bonding method is used. For higher frequency range, 20 to 50 GHz, 3×0.5 mil, 3×1 mil, 7×1 mil and 10×1 mil ribbons should be used. On the other hand, the bare chip bonding pads and dimensions of transmission line conductive layer bond pads are limiting the usage of desired ribbon. Last but not least, a performance chart of RF wire/ribbon interconnects including a suggestion of bonding method with sustainable current load and shape is generated for design and application engineers who are dealing with high performance circuit efficiency.

ADC evaluation boards design and test framework for LCLS-II precision receiver

In the low-level RF control field, ADC acquisition accuracy and noise set the boundary of our control ability, making it important to develop low-noise acquisition systems. From the design to test stage, all the noise terms should be understood and characterized. The specific need addressed here is the precision acquisition system for the second Linac Coherent Light Source (LCLS-II), led by SLAC National Accelerator Laboratory. Test circuit boards for the LTC2174 and AD9268 ADCs are designed and fabricated by LBNL. An ADC test framework based on FPGA evaluation board to assess performance has been developed. The ADC test framework includes both DSP (Digital Signal Processing) firmware and processing software. It is useful for low-level RF control and other synchronization projects. Investigating the clock jitter between two channels give us an understanding of that noise source. Working with the test framework, the raw ADC data are transferred to a computer through a Gigabit Ethernet interface. Then short-term error signal can be calculated based on a sine wave fit. By changing low-pass filter bandwidth, relative long-term performance can also be obtained. Amplitude jitter and differential phase jitter are the key issues for ADCs. This paper will report the test results for LTC2174 and AD9268 chips. The integral amplitude jitter is smaller than 0.003 %, and the integral phase noise is smaller than $$0.0015^{\circ }$$ (measured at 47 MHz RF, 100 MHz clock, bandwidth 1 Hz to 100 kHz) for both ADC chips.

Fabrication and Characterization of Vibration and Wind Energy Harvesters Using Multilayer Free-Standing Piezoelectric Thick Films

This article demonstrates the feasibility of fabricating energy harvesters based on piezoelectric cantilevers with a free-standing thick-film structure. Demonstrator devices have been designed, built, and evaluated in a range of mechanical coupling configurations to harvest energy from machinery vibrations and weak air flow. In terms of wideband vibration energy harvesters, arrays of the individual harvesters were assembled onto plastic test circuit boards integrated with diode bridge rectifiers. The harvesters were designed with different dimensions, and various tip masses were attached on the tip of the cantilevers to individually tune the resonant frequencies. The assembled harvesters were tested under harmonic vibration conditions. Great potential of harvesting vibration energy and broadening working bandwidth has been exhibited. In terms of the harvester for weak air flow, two individual cantilever devices were assembled on the chassis of a free-spinning fan. Permanent magnets were fixed on the blades of the fan as well as on the cantilevers. The device was tested in an open fluidic environment. The air flow was successfully transferred to axial oscillations, thus driving the cantilevers bending up and down. Possibilities of such devices being optimized to meet the requirements of real applications of self-powered wireless sensor networks can be foreseen.

Fabrication and Characterisation of Vibration and Wind Energy Harvesters Using Multi-layer Free-standing Piezoelectric Thick-films

This paper demonstrates the feasibility of fabricating energy harvesters based on piezoelectric cantilevers with a free-standing thick-film structure. Demonstrator devices have been designed, built and evaluated in a range of mechanical coupling configurations, in order to harvest energy from machinery vibrations and weak air flow. In terms of wideband vibration energy harvesters, arrays of the individual harvesters were assembled onto plastic test circuit boards integrated with diode bridge rectifiers. The harvesters were designed with different dimensions and various tip masses were attached on the tip of the cantilevers in order to individually tune the resonant frequencies. The assembled harvesters were tested under harmonic vibration conditions. Great potential of harvesting vibration energy and broadening working bandwidth has been exhibited. In terms of the harvester for weak air flow, two individual cantilever devices were assembled on the chassis of a free-spinning fan. Permanent magnets were fixed on the blades of the fan as well as the cantilevers. The device was tested in an open fluidic environments. The air flow has been successfully transferred to axial oscillations thus driving the cantilevers bending up and down. Possibilities of such devices being optimised to meet the requirements of real applications of self-powered wireless sensor networks can be foreseen.

SU-E-T-158: Neutron Damage of Power Electronics Used during Image Guidance in Proton Therapy.

A series of measurements were performed in a clinical proton therapy beam to assess the sensitivity of silicon-based electronics in commercial x-ray generators to single event burnout from the secondary neutron background in proton therapy treatments. Failure rates were nondestructively measured in various metal oxide semiconductor field-effect transistors (MOSFETs) as a function of applied voltage using a dedicated test circuit board. Neutrons were produced by 230 MeV protons stopping in a brass beam target and high beam current was used to accelerate testing. Neutron fluences were measured by activation analysis of carbon and aluminum in both the test setup and in situ at the generator. Failure rates were determined by scaling results based on beam monitor output to the relevant neutron fluence rate. Current pulses from the test board clearly indicated the onset of single event burnout without destroying the MOSFET. The neutron fluence measured on the test board was 4.3 ± 0.8×106 n cm-2 MU-1 and this is consistent with previous measurements. The MOSFET failure rate decreased rapidly with a reduction in the applied voltage and is 20-30 times lower in higher-rated components at the same voltage. Under nominal operating conditions the estimated failure rate is tens of failures per year for a generator 6m from the treatment position. The sensitivity of x-ray generator power electronics to neutron-induced single-event burnout is significant and can affect the implementation of image-guided techniques for proton therapy. Strategies and system designs to mitigate this phenomenon are being investigated to help enable x-ray generators withstand the proton therapy environment. This research was supported by the NIH/NCI under grant number 6-PO1 CA 21239.

Using thermal image matter-element to design a circuit board fault diagnosis system

This paper presents a thermal image matter-element used to design a circuit board signal fault diagnosis system. When a circuit element presents faults the temperature distribution will skew. Therefore, extension theory is used to build several kinds of thermal image matter-element models with fault circuits. According to the matter-element and correlation function, the fault type in the testing circuit is detected by analyzing the correlation degree between the typical fault models and test circuit boards. This new method can attain fast fault determination and reduced manpower.

Circularly connected second-mode mechanical resonator chip for oscillator application

We have developed a novel circularly connected mechanical resonator with rotational symmetry. Its unit resonator design is based on a second-mode free-free beam resonator, suspended by four 1.2 μm narrow support beams. The resonator achieves high quality factors (>10,000) and higher transmissions (>−20 dB) simultaneously in 50 Ω measurement. The frequency range experimentally obtained was from 26 MHz to 195 MHz. The mechanical resonators are completely encapsulated into the cavity. The cavity is vacuumed in aluminum sputtering process and hermetically sealed by aluminum plugs. After the in-line encapsulation, it is possible to handle the proposed resonators as conventional IC chips. In addition, all of the fabrication steps were processed in the conventional CMOS technology. The characteristics of a 45 MHz oscillator were evaluated by using a test circuit board with our 45 MHz resonator chip. The phase noise performance at a 10 Hz offset from the carrier frequency was −40 dBc/Hz and a noise floor was observed at −150 dBc/Hz, demonstrating applicability for practical clock generator circuits.

BGA and CGA Solder Attachments: Results of Low‐acceleration Reliability Test and Analysis *

Highly accelerated tests, while capable of producing failures in short test durations, can cause significant damage and failure as a result of damage mechanisms and/or material behaviour not present in the actual use of electronic product. This is particularly true for surface mount solder attachments. The results of low‐acceleration reliability tests for the solder attachments of ball grid arrays (BGAs) and column grid arrays (CGAs) are reported in this paper. The tests were designed to mimic the thermal conditions of the use environment of the product, including internal power dissipation within the grid array components, as closely as practically possible. The test acceleration comes from two measures taken: (1) controlled reduced dwell times at the cyclic temperature extremes, thus allowing a higher cyclic frequency, and (2) a controlled increased CTE‐mismatch between the components and the test circuit board by an increase in the coefficient of thermal expansion (CTE) of the test circuit boards relative to the product cirucit boards. Control test vehicles with product‐like circuit board construction were also utilised. The results from the different test vehicle configurations are correlated and utilised to estimate the reliability of the product in the field.