BGA封装FPGA焊点失效故障诊断系统设计

针对BGA(Ball Grid Array)封装FPGA(Field Programmable Gate Array)焊接点连接失效的故障诊断问题,提出了一种故障检测系统设计方案;该方案分别从焊点级、芯片级和系统级故障诊断3个层次构建故障检测系统;方案基于Altera公司的DE2硬件平台构建单个焊点健康信息提取IP核;针对芯片焊点众多,难以全部监控的问题采用Canary故障检测法监测4个角落的敏感焊点的健康信息;敏感焊点的健康信息经菊花链式通信链路实现了不同FPGA芯片之间的信息互联,完成整个系统的焊点健康信息整合。     

基于变换矩阵的BGA X-ray图像倾斜识别

针对基于X-Ray的焊球阵列封装(BGA)焊接缺陷检测中,现有的图像处理算法无法有效处理PCB意外倾斜的问题,提出了一种自动判断BGA焊点X射线图像倾斜程度并进行校正的方法。首先根据BGA焊点阵列排布的特性恢复出原始图像中的结构信息,然后使用广义逆矩阵求解出理想正视图像与实际倾斜图像之间的变换矩阵,最后对倾斜图像进行逆变换以得到理想正视图像,并使用变换矩阵估计出PCB的倾斜程度。实验针对正视与倾斜的BGA焊点的X射线图像,运用所提方法,准确判别出图像的倾斜程度,并进行了校正。此方法既可以作为一种图像质量评价算法,在BGA X-Ray缺陷检测中判断图像是否为需要的正视图像;也可以作为一种图像自动校正算法,提升基于X射线的自动检测系统的适应性。     

基于变换矩阵的BGA X-ray图像倾斜识别及校正方法

针对基于X-Ray的焊球阵列封装(BGA)焊接缺陷检测中,现有的图像处理算法无法有效处理PCB意外倾斜的问题,提出了一种自动判断BGA焊点X射线图像倾斜程度并进行校正的方法。首先根据BGA焊点阵列排布的特性恢复出原始图像中的结构信息,然后使用广义逆矩阵求解出理想正视图像与实际倾斜图像之间的变换矩阵,最后对倾斜图像进行逆变换以得到理想正视图像,并使用变换矩阵估计出PCB的倾斜程度。实验针对正视与倾斜的BGA焊点的X射线图像,运用所提方法,准确判别出图像的倾斜程度,并进行了校正。此方法既可以作为一种图像质量评价算法,在BGA X-Ray缺陷检测中判断图像是否为需要的正视图像;也可以作为一种图像自动校正算法,提升基于X射线的自动检测系统的适应性。     

微电路FPGA的γ电离总剂量效应与加固技术

 讨论了Actel公司的FPGA芯片A1280XL在有偏置和无偏置条件下的γ电离总剂量效应,试验结果表明偏置条件对FPGA芯片电离总剂量效应有较大影响,在有偏置下FPGA芯片A1280XL失效阈最小,为12.16 Gy(Si);无偏置时FPGA失效阈最大,为33.2 Gy(Si)。对芯片内部结构进行了辐射效应分析,并提出一些加固方法提高器件的抗总剂量能力,如电路设计中采用冗余技术来实现对故障的检测和隔离,以及选取适当的屏蔽材料对器件进行屏蔽。     

基于双目视觉的车身焊点定位误差补偿研究

在应用机器人对车身点焊质量检测过程中,其焊点的定位精度受到点焊作业质量以及车身制造误差等因素的影响,导致实际焊点与设计值并不重合.针对传统示教无法对焊点定位进行实时补偿的问题,提出基于双目视觉引导机器人的焊点定位策略,并构建基于改进粒子群算法优化的支持向量机回归误差补偿模型,对定位结果进行补偿.在机器人末端安装双目传感...     

基于OMAPL138和FPGA构架的PC104主板检测系统

为了对PC104主板进行自动检测,分析了PC104主板工作原理及其总线时序,提出了一种基于ARM+FPGA的嵌入式检测系统的设计方案;该方案采用德州仪器(TI)双核架构的高性能芯片OMAPL138中的ARM核来实现检测系统的应用管理,DSP核实现数据的处理,并利用FPGA技术来实时采集PC104总线数据;检测系统在Linux操作系统下,通过人机交互方式实现了PC104主板的各种功能的自动检测;实验结果显示该检测快速可靠,为PC104主板的自动检测提供了一种有效的方法。     

面向电容式微机械超声换能器器件的32通道收发 电路设计与测试*

针对以电容式微机械超声换能器(CMUT)阵列为探头的超声成像系统,设计了一种兼具现场可编程门阵列(FPGA)控制、脉冲驱动以及微弱电流信号检测功能的电路。利用FPGA产生64路控制信号,控制脉冲信号的频率、脉冲个数、占空比等参数;脉冲电路在FPGA以及直流电压的控制下,产生32路脉冲信号;接收电路通过跨阻放大结构实现32路电流信号检测;32通道收发电路利用脉冲产生芯片内自带的T/R开关进行高压隔离。通过搭建测试平台,对收发电路功能及一致性进行测试,并连接CMUT进行自发自收测试。测试结果表明,32通道收发电路具有良好的一致性,电路可以实现基于CMUT阵列的32通道超声信号的发射,检测回波信号,并对CMUT器件的带宽进行测试。电路具有功能完善,结构稳定的优点,为基于CMUT阵列的超声成像系统的应用提供了硬件支持。     

基于单幅图像的集成电路引脚共面性检测方法

集成电路(IC)芯片引脚的共面性检测是确保其贴装质量的关键。基于单幅图像提出一种IC引脚共面性检测方法。首先,基于单目视觉系统建立相机、光源和被测表面的关系模型;其次,给出发光二极管(LED)环形结构光源的光强标定方法,并通过实验确定被测IC引脚材质的相关参数;然后,基于建立的光强与图像灰度的关系模型给出高度信息的求解方法;最后,基于高度信息还原IC引脚及其焊点的表面三维形貌。实验结果表明,本文方法检测IC芯片引脚及其焊点的实验结果与实际测量结果相比,其高度测量误差小于±0.08 mm,相对误差为-2.6%,验证了本文方法的有效性。     

一种FPGA芯片在射频干扰下的失效机理

研究了一种Xilinx公司FPGA芯片XC7A200T-2FBG676在射频干扰下的失效机理。通过对该FPGA内核供电引脚注入射频干扰发现,某些频率下,随着干扰强度的增大,FPGA会依次出现三种不同类型的失效,分别为该FPGA的内核失效、I/O失效和配置失效。测试分析和HSPICE仿真表明,内核失效是由于BRAM的逻辑层抗扰性差所致,I/O失效是由于射频干扰下输入/输出信号的同时失真所致,配置失效则是由于配置系统读取错误的配置使能信号所致。研究可为该FPGA芯片或者系统电磁兼容设计以及该FPGA抗扰性检测方案的制定提供指导。     

基于FPGA的电力电子变换器的精仿真研究

在电力电子仿真领域,基于现场可编程门阵列(FPGA)高速并行运算的特点,为了达到实时效果,对系统模型通常采用较为方便的建模。提出了使用FPGA对Boost变换器进行复杂建模以及算法研究。基于这一思想,首先对boost变换器进行建模以及算法研究;其次完成基于FPGA的Boost变换器的建模并利用XILINX的ML605开发板进行仿真实验,将仿真波形与MATLAB进行对比,证实了在一定误差范围内,基于FPGA复杂建模仿真的有效性及准确性。     

Microfocus X-ray printed circuit board inspection system

In order to solve the problem of digital radiography for printed circuit board (PCB) defect inspection, a new inspection system for PCB defect inspection with high resolution X-ray is proposed and implemented in this paper. The influence of the focus size of X-ray source on imaging formation is analyzed to get the best geometrical magnification. Moreover, the relationship between the resolution of intensifier and geometrical magnification is presented by analyzing the performance of MCP-X intensifier, which results in calculating the comprehensive resolution of this system. The experiment result indicates that the measurements on defect character is achieved by inspection software, and the defect analysis accuracy on ball grid array (BGA) solder joint of circuit board achieves minimum resolution of 0.03 mm. As a result, this system succeeds in implementing invisible solder joint defect inspection on BGA.     

飞行器FPGA检测点优化设置方法

,针对诱发宇宙空间环境下航空航天飞行器工作异常和故障的FPGA单粒子效应,分析了FPGA电路的特点,从空间和时间维度上,提出基于“运算单元 存储器/触发器”进行FPGA电路层次模块的划分;结合节点所在位置的重要性、节点与其它节点的关联程度以及节点本身的单粒子软错误翻转概率,提出了重要度分析模型,从而建立基于重要度排序的对测试点设置优化方法。测试实验表明,该方法是一种可行的检测点优化设置方法。     

Research on the fault diagnosis technology of intermittent connection failure belonging to FPGA solder-joints in BGA package

A new method to detect intermittent faults in FPGA (field programmable gate array) of BGA (ball grid array) packages is presented. Inject proper current into measured IO port via sensor circuit, the intermittent faults will arouse impedance of the solder-joint to change intermittently, the voltage of solder-joint will also change intermittently, the fault information can be obtained through regulating the voltage signal. Compared with current monitoring method based on degradation model, this scheme is more reliable and accurate. It can prevent the catastrophic faults caused by failure of the FPGA solder-joints effectively, as well as economize the maintenance cost.     

一种改进的球栅阵列封装焊点射线图像阈值分割算法

球栅阵列封装焊点的射线图像具有信噪比差、背景不均匀等特点,故传统的阈值分割方法无法将目标焊点与背景图像很好的分割.本文通过对球栅阵列封装焊点射线图像直方图的分析,利用了自适应维纳滤波对阈值分割前的图像进行了预处理.根据图像的差异来调整该滤波器的参量,对局部差异大的地方进行小的平滑操作,对局部差异小的地方进行大的平滑操作.在最大类间方差法的基础上,对分割后的图像进行了进一步的分析并提出了改进的二次分割方法.改进的方法为并不直接通过OTSU法进行二值化处理来去除背景,而是在阈值分割得到的两个灰度级内通过计算中值和统计最大灰度像素的方法得到了更优化的阈值,使得去除背景后的焊点图像整体更加清晰和均匀.在背景灰度级内寻找了一个合适的灰度级作为处理后的灰度图像新背景,实验证明该方法明显改进了传统最大类间方差法对球栅阵列封装焊点射线图像的阈值分割效果.     

倒装芯片塑料球栅阵列封装器件在外应力下的失效机理

倒装芯片塑料球栅阵列(FC-PBGA)封装形式独特而被广泛应用, 分析研究其在实际应用过程中, 在高温、电、水汽等多种综合环境应力条件作用下的失效机理对提高其应用可靠性有重要意义. 本文对0.13 μm 6层铜布线工艺的FC-PBGA FPGA器件, 通过暴露器件在以高温回流焊过程中的热-机械应力为主的综合外应力作用下的失效模式, 分析与失效模式相对应的失效机理. 研究结果表明, FC-PBGA器件组装时的内外温差及高温回流焊安装过程中所产生的热-机械应力是导致失效的根本原因, 在该应力作用下, 芯片上的焊球会发生再熔融、桥接相邻焊球致器件短路失效; 芯片与基板之间的填充料会发生裂缝分层、倒装芯片焊球开裂/脱落致器件开路失效; 芯片内部的铜/低k互连结构的完整性受损伤而影响FC-PBGA器件的使用寿命.     

Effect of ultrasonic vibration time on the Cu/Sn-Ag-Cu/Cu joint soldered by low-power-high-frequency ultrasonic-assisted reflow soldering

Techniques to improve solder joint reliability have been the recent research focus in the electronic packaging industry. In this study, Cu/SAC305/Cu solder joints were fabricated using a low-power high-frequency ultrasonic-assisted reflow soldering approach where non-ultrasonic-treated samples were served as control sample. The effect of ultrasonic vibration (USV) time (within 6 s) on the solder joint properties was characterized systematically. Results showed that the solder matrix microstructure was refined at 1.5 s of USV, but coarsen when the USV time reached 3 s and above. The solder matrix hardness increased when the solder matrix was refined, but decreased when the solder matrix coarsened. The interfacial intermetallic compound (IMC) layer thickness was found to decrease with increasing USV time, except for the USV-treated sample with 1.5 s. This is attributed to the insufficient USV time during the reflow stage and consequently accelerated the Cu dissolution at the joint interface during the post-ultrasonic reflow stage. All the USV-treated samples possessed higher shear strength than the control sample due to the USV-induced-degassing effect. The shear strength of the USV-treated sample with 6 s was the lowest among the USV-treated samples due to the formation of plate-like Ag₃Sn that may act as the crack initiation site.     

A general strategy of in-situ warpage characterization for solder attached packages with digital image correlation method

Recently, 3-D Digital Image Correlation (DIC) is widely applied to the reliability analysis of electronic packages, which particularly characterizes the in-situ deformation of ball grid array (BGA) packages. During the image correlation procedure, many parameters influence the accuracy and data integrity of measurement result. Facet (subset) size is the principal parameter and has been studied with much effort. However, the solder balls, which are built on the substrate surface, make the scenario different with the conventional 3-D DIC experiment for the planar samples. The undulant surface generates more obstacles for the successful image correlation. In order to summarize an effective solution of 3-D DIC measurement method for solder balls attached packages, camera angle, facet size and facet step are studied with different BGA packages and different stereoscopic camera systems to achieve the best correlation quality. Also, a novel surface treatment method is introduced to guarantee the surface speckles are generated uniformly on the fluctuant surface.     

高温超导带材Bi-2223/Ag的焊接接头电阻研究

针对高温超导带材Bi-2223/Ag的焊接问题进行了研究.利用ANSYS建立焊接接头电阻特性的有限元计算模型,仿真和计算分析了焊料材料、搭接长度和焊锡层厚度对接头电阻值的影响,并进行了实验验证.实验表明:可通过减少焊料厚度,增加焊接搭接长度来减少接头电阻,当焊接长度在2～5cm,焊料厚度为0.5mm时,Bi-2223/...     

Microstructure evolution and grain refinement of ultrasonic-assisted soldering joint by using Ni foam reinforced Sn composite solder

In this investigation, ultrasonic-assisted soldering at 260 °C in air produced high strength and high melting point Cu connections in 60 s using Ni foam reinforced Sn composite solder. Systematically examined were the microstructure, grain morphology, and shear strength of connections made with various porosities of Ni foam composite solders. Results shown that Ni foams as strengthening phases could reinforce Sn solder effectively. The addition of Ni foam accelerated the metallurgical reaction due to great amount of liquid/solid interfaces, and refined the intermetallic compounds (IMCs) grains by ultrasonic cavitation. The joints had different IMCs by using Ni foam with different porosity. Layered (Cu,Ni)₆Sn₅ and (Ni,Cu)₃Sn₄ phases both existed in Cu/Ni60-Sn/Cu joint while only (Cu,Ni)₆Sn₅ IMCs grew in Cu/Ni98-Sn/Cu joint. As ultrasonic time increasing, Ni skeletons were dissolved and the IMCs were peeled off from substrates and broken into small particles. And then, the IMCs gradually dissociated into refined particles and distributed homogeneously in the whole soldering seam under cavitation effects. Herein, the Cu/Ni60-Sn/Cu joint ultrasonically soldered for 60 s exhibited the highest shear strength of 86.9 MPa, as well as a high melting point about 800 ℃ for the solder seam composed of Ni skeletons and Ni-Cu-Sn IMCs. The characterization indicated that the shearing failure mainly occurred in the interlayer of the soldering seam. The homogeneous distributed granular IMCs and Ni skeletons hindered the crack propagation and improved the strength of Cu alloy joints.