电子封装金属微凸点制备技术研究进展

起着电互连、热传递和机械支撑等重要作用的金属微凸点是基于面积阵列封装的关键。以球栅阵列封装（Ball Grid Array Packaging, BGA）、芯片尺度封装（Chip Scale Packaging, CSP）以及倒装芯片封装（Flip Chip Packaging, FCP）为代表的面积阵列封装形式凭借硅片利用率高、互连路径短、信号传输延时短以及寄生参数小等优点迅速成为当今中高端芯片封装领域的主流。然而,不同应用领域的微凸点具有尺寸跨度大、材料范围广的特点,很难有一种技术能实现全尺寸范围内不同材料金属微凸点的制备。文中综述了当前主流的微凸点制备技术,包括每种技术的优缺点及其适用范围、常见微凸点材料等,最后对当下微凸点制备技术的发展趋势进行了展望。     

球化介质对球栅阵列封装钎焊球质量的影响

以63Sn37Pb焊丝为原料,分别以花生油、硅油、机油、蓖麻油为球化介质,利用切丝重熔法在球化温度为320℃下制备了球栅阵列封装(BGA)焊球,研究了不同球化介质对焊球真球度、表面质量及含氧量的影响。结果表明:当球化介质为花生油时,焊球的真球度最高,为98.89%,表面质量最好,且含氧量最低,为0.027%(质量分数);花生油的球化效果最好,蓖麻油次之,硅油和机油的最差。     

复合量程微加速度计封装热应力的研究

贴片胶的选择和贴片工艺对MEMS封装器件的可靠性和有效性影响很大.针对贴片胶固化时热效应的影响,分析复合量程微加速度计封装热应力产生的机理.从贴片胶的材料特性出发,分析贴片胶的厚度、杨式模量及热膨胀系数对硅芯片所受到封装热应力的影响.并通过有限元仿真分析,确定了适合复合量程加速度计封装的贴片胶材料及使用厚度,并用拉曼光谱仪对封装后的应力进行了测试,结果显示应力较小,封装效果良好.     

线切割机加工集成电路TAB微孔模具

随着半导体零件的轻、小、廉价的快速发展,加工企业正在谋求新的加工技术。BGA（球栅阵列组件）封装元件,因CSP（末端填料封装元件）的问世,对槽孔间距和槽孔直径的要求越来越小。     

BGA植球机三维计算机辅助模块化设计

球栅阵列(BGA)封装能很好地满足IC芯片引脚数越来越多、IC尺寸越来越小的要求,成为新的IC封装技术主流。分析BGA植球机的工艺过程和工作原理,完成该设备的机械部分设计。在对BGA全自动植球机进行运动仿真后,可以确定各个机构运动正常。所设计的STAR-04Z型BGA全自动植球机产品样机能够满足市场的功能需求。     

结构封装式光纤Bragg光栅温度补偿研究

光纤Bragg光栅的中心反射波长λB会随温度的变化而漂移,影响其在波分复用及压力测量等方面的应用.本文通过对石英和有机玻璃两种热膨胀系数不同的材料进行合理的结构设计,提出了一种无源温度补偿装置,探讨了施加预应力对光纤Bragg光栅补偿效果的影响,并对单面封装和双面封装的补偿效果进行了对比研究.该装置在-19℃～60℃的温度范围内,中心反射波长仅漂移0.035nm,温度稳定性大约提高了20倍.     

BGA连接器植球工艺研究

球栅阵列（Ball Grid Array,BGA）封装具有体积小、引脚密度高、信号完整性和散热性能佳等优点，因而广泛应用于大规模集成电路的封装领域。植球工艺作为BGA封装（连接器）生产中的关键工艺会直接影响器件与电路的性能及可靠性，现从植球工艺路线、BGA连接器设计要求、植球工艺参数及关键技术、试验及检测要求等几个方面，阐述了影响BGA连接器植球工艺实现的各种因素，借以提高BGA连接器产品的可靠性及稳定性。     

红外加热技术在BGA返修焊接中心的应用

在大规模集成芯片中以BGA(球栅阵列)封装的IC芯片被广泛使用。而在贴片焊接中返修工作始终是整个生产环节中的一个重要组成部分。多年来SMT的返修系统几乎是热风系统一统天下,然而在实际使用中,尤其是在对BGA、CSP先进封装器件电路板的返修过程中,热风返修系统却暴露出很多明显的缺点。为解决有关技术问题,采取红外加热技术克服热风返修系统存在的缺点,提高BGA返修的成功率,同时也降低了使用费用。本文详细介绍了在BGA返修设备中由传统的热风焊接方式,发展到红外加热控制形式及其控制原理。     

残余应力对混合组装BGA热循环可靠性影响

研究混装球栅阵列(Ball grid array,BGA)回流焊后产生的残余应力对热循环寿命产生影响。根据Sn63Pb37/Sn3.0Ag0.5Cu均匀混装BGA封装实体,建立有铅和混装BGA封装体ANSYS有限元模型。通过加载不同峰值温度(220~265℃)和不同降温速度(1~6℃/s)的回流温度曲线后,得到BGA封装体焊点残余应力、应变。随后选取峰值温度243℃、降温速度3℃/s条件下的回流焊后BGA封装体模型施加热循环载荷,根据修正Coffin-Manson方程预测焊点寿命。研究结果表明:回流焊中降温速度对焊后应力占主导因素,应力降温速度的增加逐渐由27.9 MPa增加到32.5 MPa,而峰值温度对焊后应变影响明显;热循环分析中BGA焊球左上角区域始终处于高应力应变状态,均匀混装BGA寿命稍低于SnPb焊点BGA;回流焊工艺后进行热循环加载结果表明残余应力对Sn63Pb37/Sn3.0Ag0.5C均匀混装BGA寿命影响不大。     

基于自组装成品率的球栅阵列焊点工艺参数分析

为了提高球栅阵列焊点封装器件的自组装成品率,研究了焊点体积偏差率及焊盘直径对器件自组装成品率的影响。考虑封装器件的温度翘曲变形、焊点体积的不可避免的制造误差及焊点位置的随机性,分析了器件自组装过程。通过求解不同体积焊点的形态,得到了不同体积焊点的液桥刚度曲线。基于不同体积焊点的液桥刚度曲线,仿真分析了焊点体积偏差率及焊盘直径对器件自组装成品率的影响。结果表明,焊点体积偏差率及焊盘直径的减小会增大焊点液桥刚度曲线的公共范围,从而提高器件的自组装成品率。     

塑料薄膜热收缩率测试方法

塑料薄膜是一种重要的商品软包装材料,其热收缩性对于商品包装的美观性有重要影响。适当的热收缩性可使包装紧凑,避免不平衡收缩导致薄膜产生褶皱。介绍了薄膜热收缩率的定义和标准规定的测量方法,介绍了目前常用的几种薄膜热收缩率测量仪器及其工作原理,总结了这些测试方法的优缺点,并提出一种新的测试方法。其思想可为后续的薄膜热收缩率测试方法研究提供指导。     

Evaluation of thermal deformation in electronic packages

Thermal deformation in an electronic package due to thermal strain mismatch is investigated. The warpage and the in-plane deformation of the package after encapsulation is analyzed using the laminated plate theory. An exact solution for the thermal deformation of an electronic package with circular shape is derived. Theoretical results are presented on the effects of the layer geometries and material properties on the thermal deformation. Several applications of the exact solution to electronic packaging product development are illustrated. The applications include lead on chip package, encapsulated chip on board and chip on substrate.     

Analysis of thermal conductivity in HI-LEDs lighting materials

The present study devised a measurement system to estimate the thermal conductivity of electronic product materials, especially in HILEDs lighting materials, exhibiting distinct thermal characteristics by conducting thermal performance experiments and theoretical analyses. First, steady-state conduction analysis with thermal resistance method was investigated on three composite material substrates of unknown heat conduction coefficients through a substrate material named Bakelite of low thermal conductivity revealing stable quality. Second, one-dimension semi-infinite transient conduction analysis was utilized to investigate metal materials with high thermal conductivities. Results showed that the Bakelite experimental module was verified for 62.5 % of the original wattages, which closest to the thermal conductivity 0.233 W/m-K of the Bakelite. And these composite materials M1, M2 and M3 composed of polymer and epoxy were 1.311, 0.844 and 2.403 W/m-K, respectively. The thermal performance experiments were investigated and the results have proved the correctness of the theoretical model. According to the experimental results, calculating the temperature value of the metal materials comprising cotton insulation and the transient analysis, this study determined the temperature error to be less 20 %. Consequently, a transient measurement system and method for metal materials with high heat conduction coefficients was established. Finally, the results of this work are the useful thermal conductivity method to facilitate rapid analysis in the future.

     

Experimental investigation of transient and thermal effects on lubricated non‐conformal contacts

In this work, thermal and transient effects on non‐conformal lubricated contacts are investigated through experimental analyses. Experiments between a ball and a plane surface of a disc are described. Friction coefficients and film thicknesses are measured (the film thickness only for the glass‐on‐steel contact). A paraffin base mineral oil is used as a lubricant. First experiments are carried out under steady‐state conditions. To include effects due to different thermal properties of contacting materials, a steel‐on‐steel and a glass‐on‐steel contact with different slide‐to‐roll ratios are tested. If the contacting materials have different thermal properties, as in the case of a glass‐on‐steel contact, thermal effects like the temperature–viscosity wedge action could clearly be shown. It is found that the friction coefficients are influenced by the slide‐to‐roll ratio and the thermal properties of the contacting materials. Under transient conditions, the entraining velocity is varied with a sinusoidal law. Squeeze effects explain ‘loops’ of friction and film thickness found also in previous works. The formation of friction loops is related to the measured film thickness differences. However, also under non‐steady‐state conditions, thermal effects, like the temperature–viscosity wedge action, influence the friction coefficients. Copyright © 2007 John Wiley & Sons, Ltd.     

A facility for characterizing the steady-state and dynamic thermal performance of microelectromechanical system thermal switches

A facility to characterize microelectromechanical system (MEMS) thermal switches by measuring two pertinent figures of merit is described. The two figures of merit measured are the ratio of thermal resistance of the switch in the off and on states, Roff/Ron, and the time required to switch from the off to the on state, tauswitch. The facility consists of two pieces of equipment. A guard-heated calorimeter is used to measure heat transfer across the thermal switch under steady-state conditions. Measuring heat transfer across a thermal switch in both the off and on states then gives the thermal resistance ratio Roff/Ron. A thin-film radial heat-flux sensor is used to measure heat transfer across the thermal switch under dynamic conditions. Measuring heat transfer across a thermal switch as the switch changes from the off to the on state gives the thermal switching time tauswitch. The test facilities enable the control of the applied force on the thermal switch when the thermal switch is on, the thickness of the gas gap when the thermal switch is off, and the gas species and pressure in the thermal switch gas gap. The thermal performance of two MEMS thermal switches employing two different thermal contact materials, a polished silicon surface and an array of liquid-metal microdroplets, is characterized and compared.     

Formalism of thermal waves applied to the characterization of materials thermal effusivity

Thermal characterization of materials, especially civil engineering materials, in the way of non-destructive methods, are more and more widespread. In this article, we show an original point of view to describe the used method, the thermal waves, to obtain the thermal impedance of the studied system, using a specific sensor--a fluxmeter. The identification technique, based on a frequential approach, is optimized by applying a random input to the system. This kind of random heating is shown to provide a frequency range where the thermal effusivity is able to be identified and not correlated to another parameter. The strength of the method is also the determination of the contact resistance of the system, that allows to validate the identification process. Experimental results obtained from a sample with well-known thermal properties (polyvinyl chloride) are used to validate the proposed method.     

Effect of the cutting condition and the reinforcement phase on the thermal load of the workpiece when dry turning aluminum metal matrix composites

Aluminum metal matrix composites (Al-MMCs) are two-phase high-performance materials. The reinforcement of aluminum alloys enhances the properties of the composite material but leads to poor machinability. The required mechanical work for machining is mostly dissipated into heat. Considerable generated quantities of heat are therefore expected when machining Al-MMCs due to the poor machinability of these composite materials. The machine tool, the tool, and the workpiece are thus subjected to a thermal load, which decreases the accuracy of machining. The thermal load increases moreover when dry turning due to the missing heat convection through the cutting fluid. It is therefore necessary to investigate the effect of the reinforcement phase and the cutting condition used on the thermal load of the workpiece in dry turning. Therefore, composites with different reinforcement phases and the non-reinforced aluminum matrix were used as the workpiece materials. The reinforcement differs regarding the volume percent and the average size of the silicon carbide particulate reinforcements. The results revealed that the thermal load and the thermal expansion of the workpiece are significantly affected by the cutting condition used and the reinforcement phase. High cutting speeds and feeds and moderate depths of cut need to be used in order to decrease the thermal load of the workpiece. The Al-MMC workpieces are subjected to greater thermal loads than the workpieces of the non-reinforced alloy. However, better machining accuracies were achieved in dry turning the Al-MMCs.     

探头引线热损失对TPS法测量导热系数的影响

瞬态平面热源(Transient plane source,TPS)法是一种近年来发展起来的用于测量材料导热系数的方法.在测量过程中,加热功率受到探头引线传热的影响,进而会影响导热系数的测量准确度.针对这个问题,本文研究了测量过程中探头引线热损失对加热功率的影响,推导了热损失的数学计算公式,并提出了相应的修正模型.利用hot disk热常数分析仪对不同材料进行了一系列测量实验.实验结果表明引线热损失对测量的影响随着测量材料以及测试探头尺寸的不同而发生变化.当材料的导热系数大于0.2 W/(m·K)时,探头引线热损失的影响小于0.16％,可以忽略不计;但对于低导热系数材料的测量,对引线热损失进行补偿可以有效地提高导热系数的测量准确度.     

A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10(-1) to 10(5) Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.     

Effect of thermal treatment on acoustic characteristics of materials

Measured acoustic characteristics of some structural materials subjected to different types of thermal treatment are presented. Averaging of the ultrasonic waves’ phase when a probe’s dimensions and measurement base increase is observed.