SMT炉后晶体管类元件无铅焊点的自动光学检测算法

基于3CCD彩色相机和3色(红、绿、蓝)LED阵列环形结构光源获取的无铅焊点图像,其图像的颜色分布反映焊点的三维特征.通过分析晶体管类元件的无铅焊点图像,提取出无铅焊点的区域特征、数字特征和逻辑特征;在这些特征的基础上,设计了一种检测炉后晶体管类元件无铅焊点的自动光学检测(AOI)算法.该算法提取的特征较全面地反映了无铅焊点的信息,适用于表面贴装技术(SMT)炉后晶体管类元件无铅焊点的检测.结果表明,此算法可有效地检测多锡、少锡、无锡、假焊、偏移、桥接、缺件等晶体管类元件常见的无铅焊点缺陷.

Abstract：

The color distribution of lead-free solder joint image, which is acquired by a 3-color (red, green, and blue) hemispherical LED arrays light resource and a 3-CCD color camera, can express the 3 dimensional shape of the solder joint. The region features, digital features and logical features are extracted from the solder joint image. Base on these features, an automatic optical inspection (AOI) algorithm for transistor lead-free solder joints is presented. The features obtained in the algorithm reflect the shape information of the lead-free solder joint properly, which can be applied to inspect the quality of the transistor lead-free solder joints in surface mounted technology (SMT). The experiment and analysis results show that the proposed method can effectively identify the lead-free solder joint defects of the transistor, such as surplus solder, lacking solder, no solder, riseudo solder, shift, bridging and component absent.     

少缺陷样本的PCB焊点智能检测方法

随着印刷电路板组装技术向高密度化和"零缺陷"方向发展,市场对自动光学检测系统的要求也向高准确率、智能化发展.而传统自动光学检测系统的检测算法不仅需要进行复杂的设置,而且需要大量不同类型的样本进行训练以提高系统的泛化性能,但在电路板组装过程中,有缺陷的样本难以获得.针对此类问题,提出了一种适应少缺陷样本的智能检测方法.首先对焊点图像的一系列特征进行了提取;然后介绍了一种基于统计方法的自动阈值设置方法;最后建立了用于进行焊点分类的BP神经网络.结果表明,方法具有较高的准确率.     

激光再流焊焊接速度对SOP器件焊点力学性能的影响

分别采用半导体激光再流焊与红外再流焊方法钎焊SOP器件,研究了激光焊焊接速度对其焊点抗拉强度的影响,并对焊点断口形貌进行了分析.结果表明,在激光再流焊条件下,激光焊焊接速度对SOP器件焊点的抗拉强度有显著的影响,而Sn-Pb焊点的力学性能对焊接速度的敏感度低于Sn-Ag-Cu无铅焊点,且存在一个最佳焊接速度.通过SEM观察发现,焊接速度相对慢时,断口有浅显韧窝和微孔,焊点断裂类型为微孔聚合型断裂;速度过快时,断口有较多的韧窝群,并且局部区域还有台阶,焊点断裂类型为韧窝型断裂和解理型断裂;焊接速度适中时,断口韧窝大且深,焊点断裂类型为韧性断裂.     

数控机床检测元件故障诊断及维修实例

位置检测元件是数控机床的重要组成部分,检测元件采用直接或间接的方法将数控机床的执行机构或工作台等设备的速度和位移检测出来,并发出反馈信号,与数控系统发出的信号指令相比较,构成闭环(半闭环)系统,补偿执行机构的位置误差,从而提高数控机床加工精度.本文作者阐述了数控机床检测元件的日常维护及注意事项,总结了位置检测元件常见的故障,并介绍了维修实例.     

复杂背景下X射线BGA焊点气泡检测

基于全局阈值分割的焊点气泡提取不准确,且当焊点被遮挡造成的气泡提取困难时,导致球栅阵列(ball grid array,BGA)焊点气泡检测困难. 针对这些复杂背景下BGA焊点气泡的X射线缺陷检测问题,采用阈值分割、焊点圆度、焊点面积等标准提取未被遮挡的焊点,并提出了一种交互式射线轮廓提取方法完成被遮挡焊点轮廓的提取. 针对焊点气泡的特点,提出基于灰度形态学、直方图拉伸、模糊增强、BLOB分析综合处理的焊点气泡检测方法. 对比试验研究结果表明,该算法对复杂背景下BGA焊点气泡检测有较高准确率.     

检测元件在数控机床中的故障诊断与维修

位置检测元件是数控机床的重要组成部分,检测元件采用直接或间接的方法将数控机床的执行机构或工作台等设备的速度和位移检测出来,并发出反馈信号,与数控系统发出的信号指令相比较,构成闭环(半闭环)系统,补偿执行机构的位置误差,从而提高数控机床加工精度.阐述了数控机床检测元件的日常维护及注意事项,通过长期实践总结积累了位置检测元件常见的故障及维修实例.     

数控机床检测元件故障诊断及维修实例

位置检测元件是数控机床的重要组成部分,检测元件采用直接或间接的方法将数控机床的执行机构或工作台等设备的速度和位移检测出来,并发出反馈信号,与数控系统发出的信号指令相比较,构成闭环(半闭环)系统,补偿执行机构的位置误差,从而提高数控机床加工精度.本文阐述了数控机床检测元件的日常维护及注意事项,通过长期实践总结积累了位置检测元件常见的故障及维修实例.     

铝合金点焊焊点超声回波信号特征与熔核直径测量方法

对铝合金点焊焊点进行了超声检测,分析了焊点各区域的超声回波信号特征,并用MATLAB设计了点焊焊点熔核直径的计算程序.该程序可通过两种方法来计算焊点熔核直径,一种是对超声A扫描信号处理,另一种是对B扫描图像进行处理.最后,将计算所得的焊点熔核直径值和熔核直径实测值对比.结果表明,采用超声回波信号法测量焊点熔核直径是可行...     

射线检测图像中焊缝和缺陷的提取方法

针对射线检测图像中焊缝和缺陷难于准确检测提取问题,基于逐级局部化处理,提出了一种实用的检测方法.方法充分利用了图像本身已包含的信息,首先通过条带区域特征检测确定焊缝区域在原始图像中的大致位置,然后通过列灰度波形分析确定焊缝边界和缺陷所在的局部区域,并粗分标记区域类型为非裂纹类和裂纹类,最后分别采用基于分水岭变换和Bea...     

薄板点焊超声检测信号特征分析与缺陷识别

运用低碳钢薄板点焊超声检测有限元仿真模型,对气孔、压痕过深、熔核过小、脱焊等四种缺陷类型的点焊检测超声仿真信号进行快速傅里叶变换得到其频谱图,并采用统计学方法分别提取了超声信号时域和频域特征值.通过分析超声在不同缺陷焊点内部的传播规律,以及特征值的变化规律,总结了点焊缺陷类型的识别方法.利用该方法对大量点焊试样超声检测试验信号进行缺陷识别并与金相试验结果对比分析. 结果表明,综合分析超声检测信号时域和频域特征值规律,能够有效地识别点焊缺陷类型.     

基于Anand模型SnAgCu-X焊点疲劳寿命预测

Anand模型采用有限元法模拟WLCSP器件Sn3.8Ag0.7Cu-X（Ce，Fe）无铅焊点在热循环载荷条件下的应力-应变响应，借助蠕变应变疲劳寿命预测模型SnAgCu，SnAgCuCe，SnAgCuFe焊点疲劳寿命.结果表明，在服役器件整体器件出现明显的变形现象，电路板翘曲严重.从中心到拐角焊点变形-应力-应变逐渐增加，芯片下拐角焊点成为整个结构潜在的危险区域.通过计算WLCSP器件SnAgCu、SnAgCuCe和SnAgCuFe三种焊点的疲劳寿命，证实了SnAgCuCe和SnAgCuFe焊点寿命明显高于SnAgCu焊点，证明了在SnAgCu中添加一定量的铈和铁可以显著提高SnAgCu焊点的使用寿命，分析结果为新型无铅钎料的研发提供理论支撑.     

基于田口法的CSP器件结构优化设计

为提高芯片尺寸封装(CSP)器件的焊点可靠性,基于田口法,采用Garofalo-Arrhenius稳态本构方程和有限元法,对CSP器件焊点热循环载荷下的应力应变分布进行有限元模拟. 考虑焊点材料、焊点高度、芯片厚度、基板厚度四个控制因素,借助田口法,采用正交表L9(34)安排试验,研究发现影响焊点可靠性的主要影响因素为焊点材料和焊点高度. 经过田口试验法优化得到的最佳方案组合为焊点材料Sn3.9Ag0.6Cu,焊点高度0.29 mm,芯片厚度0.1 mm,基板厚度0.17 mm. 该最优方案和原始设计方案相比,蠕变应变能密度降低65.4%,信噪比提高了9.22 dB. 结果表明,CSP器件焊点可靠性得到显著提高.     

FCBGA器件SnAgCu焊点的热冲击可靠性分析

采用有限元法和Garofalo-Arrheninus稳态本构方程,在热冲击条件下对倒装芯片球栅阵列封装（FCBGA）器件SnAgCu焊点的可靠性进行分析. 结果表明,Sn3.9Ag0.6Cu焊点的可靠性相对较高. 通过分析SnAgCu焊点的力学本构行为,发现焊点应力的最大值出现在焊点与芯片接触的阵列拐角处. 随着时间的推移,SnAgCu焊点的应力呈周期性变化. Sn3.9Ag0.6Cu的焊点应力和蠕变最小,Sn3.8Ag0.7Cu焊点应力和蠕变次之,Sn3.0Ag0.5Cu焊点应力和蠕变最大,与实际的FCBGA器件试验结果一致. 基于蠕变应变疲劳寿命预测方程预测三种SnAgCu焊点的疲劳寿命,发现Sn3.9Ag0.6Cu焊点的疲劳寿命比Sn3.0Ag0.5Cu和Sn3.8Ag0.7Cu焊点的疲劳寿命高.     

考虑定位误差的PCB焊点检测方法

定位误差会对AOI检测算法的性能产生影响.通过试验,定量研究了定位误差与误判率之间的关系.在现有AOI检测算法的基础上,提出在焊点统计学习阶段,通过对在位置、角度和尺度上存在定位误差的虚拟样本进行学习,使得系统能够学习到可能的定位误差.在评价AOI算法时,将定位误差考虑进来,定义了综合误判率作为AOI算法的性能评价方法...     

A novel approach for flip chip solder joint inspection based on pulsed phase thermography

Surface mount components have been extensively used in microelectronic packaging. However, it brings great challenge for defect inspection with the development of solder bumps towards ultra-fine pitch and high density. Traditional nondestructive detection methods are insufficient for solder joint assessment due to their own disadvantages. Therefore, it is necessary to explore new methods for solder joint inspection. A novel approach based on the pulsed phase thermography was investigated for identifying the defects of solder joints. In this approach, the test chip was stimulated by a thermal pulse, and the consequent transient response was captured by a commercial thermal imager. The spacial and temporal filtering techniques were adopted to improve the signal to noise ratio. The recorded thermograms were input to an improved median filter with a 5×5 mask, and the temperature evolution of each pixel was extracted and smoothed by the moving average operation. Then the temperature–time curve was fitted with an exponential function. To eliminate emissivity variations and heating non-uniformity, we converted the fitted temperature values in time domain to the phase information in frequency domain using the fast Fourier transform. In low frequency range, the phase–frequency curve of the defect area was differentiated from that of the sound area. The results demonstrate that this approach is effective for identification of the missing bumps, and can be used in the solder joint inspection in high density packaging.     

flash芯片SMT焊点抗高g值冲击性能分析

电子产品中电路板与芯片之间的焊点尺寸越来越小,在机械震动冲击过程中,焊点连接处是最容易被损坏的部位,为了研究机械震动冲击时SMT焊点抗高g(重力加速度约为10 m/s2)值冲击性能,利用霍普金森杆(Hopkinson bar)激光干涉仪对两片未灌封的动态参数测试的核心存储flash芯片的SMT焊点进行了抗高g值冲击性能试验.结果表明,flash芯片SMT焊点在无多次冲击情况下,可以抗高达1.3×105g的冲击加速度,在累积冲击情况下,SMT焊点的抗冲击加速度幅值能力迅速减弱.     

无铅焊料制备的Y0.5Gd0.5Ba2Cu3O7-z涂层超导带材搭接接头的机电性能研究

由于单根Y0.5Gd0.5Ba2Cu3O7-z(YGdBCO)涂层超导带材的长度有限,因此在制造高温超导(HTS)器件时不可避免地需要接头。HTS设备的稳定运行在很大程度上取决于接头的品质,因为接头的机电性能通常低于母材。本研究应用Sn42Bi58焊料制作YGdBCO涂层超导带材搭接接头。与传统的Sn60Pb40焊料相比,无铅Sn42Bi58焊料对环境友好,且熔点降低了40℃,因此可在低于150℃的低温下进行焊接操作,有助于抑制超导带材在连接过程中的性能下降。通过测量自场和液氮温度下的电压-电流曲线,研究了加载压力,加压速度和搭接长度对YGdBCO接头临界电流,电阻和n值的影响。通过优化焊接技术,可在12.5 MPa的压强和50 N/s的加压速度下重复获得与母材临界电流相当的25 cm长的低阻接头,其电阻为4.35~5.58 nΩ。还对轴向拉伸作用下接头的力学行为进行了研究,单根带材和接头部分的临界轴向拉伸力分别为213和212 N。上述结果表明,与传统焊接技术相比,采用优化的无铅Sn42Bi58焊料制备低电阻、高拉伸特性的焊接接头的稳定性和重复性明显提升,为YGdBCO超导带材大规模运用的接头连接提供了一种有前景的选择。     

Design of a visual system for predicting SMT solder joint shape

A visual software system has been developed for predicting and analyzin g the shape of solder joints in surface mount technology (SMT). The formation of the solder joint is numerically simulated through Surface Evolver program and the calculation is automated with an additional controller. A preprocessor is developed in which process parameters determining the shape of solder joints can be input visually and transferred into Evolver program automatically. A postproces sor is built to analyze the global three-dimensional shape and cross-section profiles of solder fillets in multiple windows. Also, the application for predicting the solder joint shape of RC chip component is conducted with the PSJS system.     

High temperature reliability of lead-free solder joints in a flip chip assembly

The visco-plastic behaviour of solder joints of two models of a flip chip FC48D6.3C457DC mounted on a printed circuit board (PCB) via SnAgCu solder is investigated using Anand's model. While the bumps of one of the models are realistic with 6 μm thickness of intermetallic compound (IMC) at interconnects of solder and bond pads, the other are made up of conventional bumps without IMC at these interconnects. The solder bump profiles were created using a combination of analytical method and construction geometry. The assembled package on PCB was accelerated thermally cycled (ATC) using IEC standard 60749-25. It was found in the result of the simulation that IMC does not only impact solder joint reliability but also is a key factor of fatigue failure of solder joints. The IMC sandwiched between bond pad at chip side and solder bulk is the most critical and its interface with solder bulk is the most vulnerable site of damage. With reference to our results, it is proposed that non inclusion of IMC in solder joint models composed of Sn-based solder and metalized copper substrate is one of the major causes of the discrepancy on solder joint fatigue life predicted using finite element modelling and the one obtained through experimental investigation.