Experimental and numerical investigation of flow and thermal effects on flexible printed circuit board

The desire of flexibility, compact, lightweight and low cost in current electronic device increases the application of flexible printed circuit board (FPCB). However, FPCB would encounter significant deflection and stress under operating condition (thermal factor) with air flow cooling system as compared to rigid printed circuit board (RPCB). Therefore, present study aims to investigate the effects of airflow rate and heat on FPCB attached with a ball grid array (BGA) package using experimental and numerical method. In this present study, the simulation was carried out by using FLUENT and ABAQUS, coupled in real time by Mesh-based Parallel Code Coupling Interface (MpCCI) where flow and thermal effects were coupled simultaneously. The experiments were conducted in a wind tunnel with the BGA package on the FPCB. Low discrepancy between simulation and experimental results indicated that the proposed numerical simulation method is proven to be reliable and sufficient to study the FPCB with thermal and flow effects which has not been established by previous researchers. The findings also showed that the Reynolds number and heat have significant effects on FPCB's deflection and stress. Therefore, it is important to include thermal effect when dealing with FPCB under flow environment. The outcomes of this paper can be a guideline to the FPCB industries.     

激光工作参数对铜蒸气激光器振荡—放大链最佳延时影响的实验研究

本文研究了氖气压、输入电压、管壁温度和放电管气氛对铜蒸气激光器振荡—放大链最佳延时的影响。结果表明,激光工作参数对黄光影响较大。当激光工作参数改变时,最佳延时相对于最大放大区(10ns)有较大的变化。     

热与随机振动对车载电路板的影响研究

研究汽车在行驶中发动机发热与振动两者共同作用对车载电路板组件产生的影响。运用有限元软件ANSYS对发动机模块电路板建模,温度场热应力分析,将应力结果导入模态分析和随机振动分析中,再比较电路板在常温与受热后的模态与随机振动结果。结果发现,电路板受热后固有频率提高,且其刚度增大,电路板变形减小。此外,该电路板组件应力最大点的统计应力值在第8阶频率下达到最大,且较常温相比,电路板受热后的功率谱曲线整体有所后移。通过随机疲劳计算,在热与振动影响下,该电路板结构满足疲劳要求。     

基于红外温度序列的电路板故障诊断研究

电路板红外温度序列包含了丰富的故障类别信息,充分利用其局部与全局特征可以提高电路板故障诊断的准确率。为此,文中提出了一种由特征提取网络(Features Extraction Network,FEN)与关系学习网络(Relationship Learning Network,RLN)并行构成的可综合利用温度序列局部特征及特征间关系的电路板故障诊断模型。其中,FEN基于多尺度膨胀卷积(Multi-scale Dilated CNN,MDCNN)残差结构搭建,可在不增加训练参数的前提下构建多层次感受野,学习温度序列不同范围的空间特征;RLN基于嵌入长短期记忆网络的注意力机制(Long Short-Term Memory hybridized with Attention,LSTMwAtt)结构搭建,通过控制温度序列信息传递来学习特征重要性并分配权重,挖掘不同位置特征间的相关性。实验结果显示,所提模型在两个自建电路板温度序列测试数据集上的诊断性能优于同类型的FCN、MFCN、LSTM和LSTM-FCN,故障诊断准确率分别达到91.15%和96.27%,可实现对电路板故障的高准确率诊断。     

Experimental and numerical approach on junction temperature of high-power LED

The understanding of thermal resistance and junction temperature is important in the area of designing efficient, long-lasting high-power Light Emitting Diodes (LEDs) and diode stacks. This paper developed a systematic evaluating program for investigating the effect of location and thickness on the thermal resistance and junction temperature of LED on an aluminum substrate. Structure function measurements were implemented by Thermal Transient Tester (T3ster) and Integrating Sphere on LED placed on an aluminum plate. The temperature distribution of LED was analyzed to understand the relationship between thermal resistance and location of the LED on the aluminum base. Meantime, to evaluate the validity of the test, the simulation is developed by considering structure properties. The simulation curve basically has a similarity with the experimental curve in the overall. It implies that the evaluating method can provide guidance in understanding thermal reliability of LED lamps and designing thermal management techniques.     

Comparative investigation on numerical de-embedding techniques forequivalent circuit modeling of lumped and distributed microstripcircuits

A so-called "short-open calibration" (SOC) technique is applied together with two existing numerical de-embedding techniques for equivalent circuit modeling of microstrip circuits based on a full-wave method-of-moments (MoM) algorithm. A stub-loaded microstrip line discontinuity with both electrically short (lumped) and long (distributed) stub lengths is extensively studied in terms of its Z-matrix circuit model. Our obtained results show that the SOC scheme allows an accurate calibration of all the potential error terms out of the core circuit network, thereby avoiding numerical noise-related behaviors regardless of either lumped or distributed circuits, which are nevertheless observed for the two existing techniques     

Effect of temperature on elastic properties of woven-glass epoxy composites for printed circuit board applications

The effect of temperature on the elastic properties of woven-glass epoxy substrates for printed circuit board applications was investigated. Three common commercially pressed boards (1080, 2116, and 7628 woven-glass fabrics and FR4 epoxy) were used for this study. The elastic properties were identified by means of a combined theoretical and experimental vibration method. Vibration experiments were performed under reduced air pressure to reduce the influence of mass, stiffness, and damping of the surrounding air and inside an environmental chamber with varying temperature and constant humidity. Above the glass-transition temperature (Tg) of the epoxy, the in-plane shear moduli (G₁₂) were decreased by 33–37% and the out-of-plane shear moduli (G₁₃, G₂₃) were decreased by 48%, whereas the Young’s moduli in the warp (E₁) and fill (E₂) directions were much less affected.     

Experimental investigation of the temperature dependence of GaAsFET equivalent circuits

Accurate 13-element temperature-dependent RF equivalent circuits have been extracted from on-wafer S-parameter measurements of ion implanted and epitaxially grown recess-gate MESFETs and HEMTs at many biases for temperatures from -70 to +110°C. The variations in each equivalent circuit element are expressed by a linear function of temperature. The temperature coefficients are bias- and technology-dependent. These data can be used to predict RF circuit performance variations with temperature. It is used to deduce the temperature dependence of physical factors such as electron mobilities and saturated velocities and the Schottky-barrier height     

雷诺数对超声速气膜气动光学效应影响的实验研究

受到风洞实验能力的限制,高速飞行器气动光学效应实验很难与其实际飞行情况完全一致。雷诺数作为重要的相似准则数,在经典流体力学风洞实验中应用广泛,研究其对于气动光学效应的影响,对于建立气动光学相似准则具有重要意义。基于定理对可能影响气动光学效应的变量进行分析,证明了雷诺数是影响气动光学效应的一个相似准则数;通过创新性设计变雷诺数实验装置,可以实现喷流单位雷诺数在106~108 m-1范围内变化。通过选取八个典型的雷诺数,并利用BOS-WS（BOS-based Wavefront Sensor）技术测量了对应状态的光程差,通过函数拟合的方法得到了光程差的均方根值与雷诺数之间的幂函数关系式。通过对不同孔径下的测量结果进行对比和归一化处理可以发现,对于二维超声速气膜而言,观察孔径尺寸并不会对获取的规律产生影响。     

NBTI: Experimental investigation,physical modelling,circuit aging simulations and verification

For more than 10 years a major part of MOSFET reliability publications are dealing with (N)BTI. The degradation and recovery mechanism is still not fully understood (Grasser, 2014). New publications demonstrate incessantly the agile debate on this important transistor aging phenomenon.In this paper we want to illuminate four important subareas for the understanding of NBTI. First, we will discuss experimental investigations. Depending on the pursued goal of the measurements different set-ups are required to gain the desired information. To get meaningful statements regarding the median NBTI degradation of MOSFET with a relatively small number of test devices, e.g. for regular lifetime predictions, DUTs with larger active area are used. The relatively high number of defects within one transistor delivers stable (averaged) parameter shifts with a small number of DUTs. Relatively small area devices are the best choice to investigate the physical nature of the degradation and recovery mechanisms. The small number of defects within those devices enables to obtain and investigate the trapping and de-trapping of single charges. To investigate the NBTI impact on the parameter variability array structures with a higher number of devices under test (DUTs) are appropriate. The very fast and strong recovery behavior of NBTI has to be considered for the test structure design and for the measurement set-up.Based on the measurement results and gained knowledge we can refine the modelling of the degradation and recovery mechanism. We could improve the understanding of the temperature dependence and utilize this knowledge to reduce measurement efforts for model calibration for a circuit aging simulator (Pobegen and Grasser, 2013). An adequately accurate model at a manageable effort for characterization and implementation is a key factor for a successful integration of an aging simulator in the design flow. A correct modelling of the parameter recovery during circuit function is especially challenging.The last chapter introduces a new method to verify the NBTI model and the correct implementation into a circuit aging simulator with real hardware measurements. An arbitrary waveform generator is used to drive single transistors in identical operation modes with identical sequence and proportion of each single operating point as during real circuit operation. In this manner, the calculated drift for one transistor in a circuit can be compared with a measurement drift for a given stress pattern.     

光纤布拉格光栅温度传感增敏特性的实验研究

分别以铜、铝、有机玻璃、聚四氟乙烯为实验衬底材料,对采用片式粘敷封装技术的光纤布拉格光栅温度传感增敏特性进行了实验研究。研究结果表明,当对两侧尾纤有涂覆层的光纤布拉格光栅进行封装时,其温度灵敏系数分别是裸纤情况下的2.3倍、2.9倍、5.2倍、11.7倍。然而,粘敷材料在较高温度时显著的热膨胀会引起光纤包层与涂覆层发生一定的脱离,导致此时其实验结果重复性不甚理想。为了克服这种不利情况,对尾纤无涂覆层的光纤布拉格光栅进行了封装测试。在测试温度范围内,其反射波长随温度的变化始终呈现良好的线性关系,其温度灵敏系数分别提高到了3倍、3.4倍、9.2倍、12.6倍,测量结果重复性良好。研究结果为将来片式封装光纤布拉格光栅传感器的温度增敏特性的研究,提供了必要有益的数据支持和参考。     

Experimental investigation of the influence of laser intensity on the quality of Einstein-Podolsky-Rosen entangled photons

Using spontaneous parametric down conversion, polarization post selection and coincidence counting technique, the polarization Einstein-Podolsky-Rosen (EPR) entangled states are prepared. Experimental studies on the efficiency, contrast and fidelity with different pump laser intensities are performed systematically. The results show that the pump laser intensity distinctly influences the quality of entangled photons, especially the contrast and the fidelity. On the other hand, the pump efficiency of entangled photons is almost invariable, namely the entangled source brightness increases linearly with the increase of pump laser power.     

基于表面贴装工艺技术的印制板焊盘设计

伴随表面贴装技术的广泛运用,印刷电路板设计工艺变得越来越重要,焊盘设计要求也变得越来越高。本文针对焊盘设计存在的缺陷加以归纳并给出了较详细的改进措施。     

Surface property of passivation layer on integrated circuit chip and solder mask layer on printed circuit board

Adhesion of underfill to passivation layer on integrated circuit chip and solder mask layer on printed circuit board is critical to the reliability of an underfilled flip chip package. In this study, the surface properties of solder mask and four passivation materials: benzocyclobutene (BCB), polyimide (PI), silicon dioxide (SiO/sub 2/), and silicon nitride (SiN) were investigated. A combination of both wet and dry cleaning processes was very effective to remove contaminants from the surface. The element oxygen, introduced during O/sub 2/ plasma treatment or UV/O/sub 3/ treatment, led to the increase of the base component of surface tension. X-ray photoelectron spectroscopy (XPS) experiments confirmed the increase of oxygen concentration at the surface after UV/O/sub 3/ treatment. Wetting of underfill on passivation and solder mask was slightly improved at higher temperatures. Although UV/O/sub 3/ cleaning and O/sub 2/ plasma treatment significantly improved the wetting of underfill on passivation materials, they did not improve adhesion strength of epoxy underfill to passivation. Therefore, the wetting was not the controlling factor in adhesion of the system studied.     

Experimental investigation of the temperature dependence of InAs-AlSb-GaSb Resonant Interband tunnel diodes

The temperature dependence of the current-voltage (I-V) characteristics of InAs-AlSb-GaSb resonant interband tunnel diodes (RITDs) has been investigated from 223 to 423 K. Several device structures were examined, with tunnel barrier thicknesses from 0.6 to 2.0 nm. For all barrier thicknesses, the peak current density (J/sub p/) decreases slightly as the temperature is increased, while the valley current density (J/sub v/) increases with temperature. We found that the temperature rate of change for the peak current density with temperature (/spl part/J/sub p///spl part/T) is nearly independent of barrier thickness, while J/sub v/ increases more rapidly for devices with thicker barriers. In addition, the peak voltage (V/sub p/) was found to be independent of temperature, regardless of barrier thickness. However, the valley voltage (V/sub v/) was observed to decrease with increasing temperature, with more rapid changes observed for RITDs with thicker barriers. Comparison of the temperature performance of RITDs with different barrier thicknesses shows that devices with thinner barriers have I-V characteristics that are less sensitive to temperature, as well as having larger peak and valley current density and voltage for the temperature range from 223 to 423 K. To our knowledge, this is the first report of the temperature dependence of the device characteristics of Sb-based RITDs as a function of barrier width.     

印制板阻焊塞孔加工技术实验研究

结合电路板阻焊塞孔工艺技术产品批产化,根据生产线现有设备的实际情况,解决阻焊塞孔印制板加工过程所遇到由于过孔阻焊塞孔不良（空洞及露铜等）而导致锡珠入孔,造成的短路异常风险隐患等各种工艺难题。采用此种工艺制作技术方法均可实现阻焊塞孔印制板产品的批量在线的加工。     

光纤双折射对光纤环保偏能力影响的实验研究

为了研究光纤双折射对陀螺光纤环保偏能力的影响,选用三种不同型号的光纤采用相同的绕制方法制作相同规格的光纤环.采用白光干涉仪测试光纤环的偏振耦合分布,并利用光纤环两端尾纤与白光干涉仪尾纤的熔点引起的偏振耦合干涉峰计算绕环光纤的双折射.通过不同光纤环测试结果的比较,分析绕环光纤双折射对光纤环保偏能力的影响.测试结果表明,三...     

On resonance and shielding of printed traces on a circuit board

A rigorous formulation in the spectral domain is used to investigate the radiation from unterminated traces printed on a circuit board in the frequency range from 30 MHz to 1 GHz. The effect of coupling among adjacent traces on the resonant frequencies and the shielding effectiveness of metallic coating on the plastic cover are analyzed. It is found that the radiation around resonant frequencies is critical to comply with the Federal Communications Commission (FCC) specifications and that an appropriate coating can resolve the problem     

The influence of temperature and humidity on printed wiring board surface finishes: Immersion tin vs organic azoles

Substitution of lead-free solders in electronic assemblies requires changes in the conventional Sn:Pb finishes on substrates and component leads to prevent contamination of the candidate lead-free solder. Options for solderability preservative coatings on the printed wiring board include organic (azole or rosin/resin based) films and tin-based plated metallic coatings. This paper compares the solderability performance and corrosion protection effectiveness of electroless tin coatings vs organic azole films after exposure to a series of humidity and thermal cycling conditions. The solderability of immersion tin is directly related to the tin oxide growth on the surface and is not affected by the formation of SnCu intermetallic phases as long as the intermetallic phase is underneath a protective Sn layer. Thin azole films decompose upon heating in the presence of oxygen and lead to solderability degradation. Evaluations of lead-free solder pastes for surface mount assembly applications indicate that immersion tin significantly improves the spreading of Sn:Ag and Sn:Bi alloys as compared to azole surface finishes.