PCB&PCBA-PTH失效原因分析

介绍了一个典型的印刷电路板(PCB)失效原因分析的案例。该PCB经过波峰焊后因油墨塞孔导致孔壁断裂而失效。分析结果表明:孔壁镀层中存在的柱状结晶及镀层空洞削弱了孔铜镀层的延展性及抗拉强度,这是导致在随后的焊接工艺过程中承受不住相对较大的膨胀应力而发生孔铜镀层断裂失效的主要原因;PCB本身相对较大的膨胀系数也是导致孔铜断裂的原因之一。     

电镀铜孪晶形成原因及对产品质量的影响

介绍PCB电镀铜过程中,铜孪晶产生的机理、图像及表现,并结合PCB在电镀铜实际生产过程中如何预防铜孪晶的产生,防止PCB板在客户端SMT高温焊接时或后期使用过程中,因铜孪晶问题导致PCB孔铜断裂发生失效的致命缺陷产生。     

孔化过程中过孔塞孔现象的探究

在PCB制作过程中，塞孔现象会导致孔无铜、孔铜偏薄缺陷，直接影响到PCB的电气功能，这是一直困扰PCB制作的顽疾。塞孔现象目前没有成熟的检测工具，使塞孔现象在过程控制中容易被忽略，最终使PCB报废或将不良品流入到客户端。孔铜偏薄现象在客户端使用时，受热拉伸导致孔铜断裂形成开路，引起客户投诉。本文主要讲述塞孔缺陷的危害性、导致塞孔的原因分析及过程控制。     

关于厚板镀厚铜要求的电镀探讨与实践

文章讨论了厚铜箔PCB板镀铜和图形电镀铜的生产制作工艺，指出厚铜箔PCB普遍存在的孔铜厚度不均匀和一般厚度偏低的解决途径和操作方案。     

国内印制电路板产品失效现状与改进

对本实验室2019—2022年承接的国内印制电路板（PCB）制造商及相关用户委托的失效案例开展统计，发现PCB自身质量异常已成为引起印制电路板组装（PCBA）失效的最主要问题。进一步对PCB总体失效模式与失效原因分布、不同排名PCB企业失效案例数量分布、军用PCB失效模式分布及民用PCB失效模式分布等进行分析，发现导通失效、可焊性不良、分层爆板和绝缘失效是PCB行业最为常见的4大失效模式。生产制程缺陷是造成PCB失效的最主要原因（69%）；内资排前100名企业失效案例数量合计占比为48%，失效模式分布与整个PCB行业一致；军用PCB与民用PCB失效模式分布存在差异，军用PCB和民用PCB第一大失效模式分别为导通失效（49%）和可焊性不良（25%）。最后结合行业的失效问题现状，提出了改进建议。     

PCB失效分析技术与典型案例

由于PCB高密度的发展趋势以及无铅与无卤的环保要求,越来越多的PCB出现了润湿不良、爆板、分层、CAF等等各种失效问题。本文首先介绍针对PCB在使用过程中的这些失效的分析技术,包括扫描电镜与能谱、光电子能谱、切片、热分析以及傅立叶红外光谱分析等。然后结合PCB的典型失效分析案例,介绍这些分析技术在实际案例中的应用。PCB失效机理与原因的获得将有利于将来对PCB的质量控制,从而避免类似问题的再度发生。     

PCB的腐蚀失效及其分析

通过一个电子辞典用PCB腐蚀失效的分析案例,介绍了PCB的失效现象、分析过程和分析技术．阐述了其失效机理,并提出了相应的改进措施。     

液晶电视CAF失效实例分析和预防

电子产品大量使用印制电路板(PCB),在潮湿环境下使用时易产生导电性阳极丝失效,影响电子产品可靠性。通过对多起液晶电视机电路板CAF失效实例的测试、分析,总结出导电性阳极丝失效(即CAF失效)首先发生在具有固定直流偏压的高阻抗电路中,同时分析了CAF失效高发的现象与盐雾之间的关联性,通过对比说明了PCB设计、装配工艺、PCB选材对CAF预防的不同效果,指出了选择抗CAF的PCB材料的重要性,并给出了两种在线监测电路的设计方案。     

沉锡PCB焊接失效分析方法介绍

根据多例沉锡焊接失效案例,对导致沉锡PCB焊接失效的原因进行了分析,并详细的介绍了多种沉锡PCB焊接失效分析方法。     

印制电路板分层起泡原因和分析方法概述

分层起泡是印制电路板（PCB）制造与装配中的一个常见问题,常见于焊接过程、偶尔见于PCB制程中;分层起泡涉及影响因素很多：板材来料、PCB加工、PCB装配加工、返工返修等。PCBA板件分层起泡的失效分析,对PCB制程预防及改善均有一定的参考意义。文章将对分层起泡的失效原因和分析方法进行讨论,以供参考、借鉴。     

PCB镀通孔疲劳寿命对设计参数的灵敏度分析

在PCB镀通孔疲劳寿命评估IPC模型的改进模型基础上,分析了镀通孔疲劳寿命对基板厚度与孔径之比(即厚径比l/r0)、基板厚度与镀层厚度之比(l/t)以及基板作用半径与孔半径之比(R/r0)的灵敏度。结果表明,镀通孔疲劳寿命对(l/r0)的灵敏度随(l/t)增大而减小;对(l/t)的灵敏度随(l/r0)增大而减小;而对(R/r0)的灵敏度则随(l/r0)增大而增大、随(l/t)增大而减小。最后,利用IPC的试验研究结果数据进行了验证。     

On thermo-mechanical reliability of plated-through-hole (PTH)

The mechanical properties of plated copper in plated-through-hole (PTH) were investigated experimentally by a thermo-mechanical analyzer, a nano-indenter, and an acoustic emission instrument. Coefficients of fatigue life prediction models for plated copper have been determined by different failure criteria. Afterwards thermal fatigue test of PTH at three different diameters were performed, and Weibull statistics was employed to evaluate the fatigue life of samples under different failure criteria. Finally, the strain variation of PTH during thermal cycle has been simulated by the finite element analysis (FEA) so as to predict its fatigue life by the selected models. From the comparison of the estimated fatigue life and its experimental results, it is found that the error can be minimized to be within 100%, provided that the drifting of electrical resistance by 20% is used as failure criteria and total strain amplitude is used as control variable in fatigue life prediction model. Based on these findings, design of PTH in printed circuit board (PCB) can be optimized by FEA. It is concluded that fatigue life of PTH will increase with lesser PCB layers, smaller depth-to-diameter ratio, higher PTH density and thicker plated copper.     

Determination of Acceleration Factor in Predicting the Field Life of Plated Through Holes From Thermal Stress Data

Accelerated thermal stress tests nowadays have widely been used in qualification and reliability assessment of printed wiring boards (PWBs). Predicting the field life of plated through holes (PTHs) from test data has been a primary goal of this type of testing. Understanding the PTH cycles to failure (CTF) versus temperature relationship and having a good estimate of acceleration factor (AF) not only expedites the data processing process but also helps in optimizing test conditions and minimizing the number of tests, and hence, reducing the test cost. In this paper, three different PTH CTF-temperature models, including an inverse power law (IPL) model, an IPC model, and an enhanced PTH fatigue-life prediction model, are discussed and evaluated in their effectiveness of determining acceleration factors for the purpose of PTH field life prediction under different test conditions. In addition, using the third model, AF influencing factors, including PTH geometric dimensions, PWB glass transition temperatures (Tg), and the temperature dependency of PWB material properties, are also discussed to provide information for accelerated test design in PWB qualification and reliability assessment.      

镀通孔制造过程中的失效机理与物理模型

镀通孔的可靠性与制造过程工艺参数有非常密切的关系。从钻孔、化学镀铜、电镀三个主要工艺入手,对目前制造过程镀通孔失效的机理与物理模型的研究现状进行总结。重点介绍了钻孔中分层、化学镀铜中的气泡缺陷、电镀中的镀层不均匀等缺陷产生的机理。并提出了需进一步研究的主要问题。     

印制电路板镀通孔制程可靠性问题与研究技术途径

影响镀通孔制程可靠性因素众多,关系复杂,需要一个有效的技术途径来研究该问题。文中总结了印制电路板镀通孔制程的各个加工步骤和工序的目的,以及制造过程中影响这些目的达成效果的影响因素。分析汇总了印制电路板镀通孔的各种失效模式和机理,及其对应的失效发生的部位和影响因素。在此基础上,明确了进行印制电路板镀通孔制程可靠性研究的技术途径,同时给出了实施这项研究的技术细节。     

Microstructure and Reliability Comparison of Different Pb-Free Alloys Used for Wave Soldering and Rework

This paper describes the results of an intensive microstructural and reliability study of pin-through-hole (PTH) and surface mount technology (SMT) components which were wave solder assembled using three groups of alloys: (1) near-eutectic Sn-Ag-Cu alloys such as SAC405 and SAC305, (2) low-Ag off-eutectic Pb-free alloys with an Ag content of about 1% and lower, and (3) eutectic Sn-Cu alloys with Ni and other additives. Both primary attach and reworked solder connections using solder fountain and hand rework were studied. The PTH connector types and SMT components were wave solder assembled on a test vehicle. Accelerated thermal cycling (ATC) was conducted at 0°C to 100°C for 6000 cycles. The difference in microstructures, intermetallic formation, Cu dissolution, grain coarsening, and crack formation is shown. The influence of the microstructure after assembly and rework on Weibull plot parameters and failure modes is described for 2512 resistors. Interconnect defects such as nonuniform phase distribution and void formation are discussed. The Sn-Cu-Ni- and Sn-Cu-Ag-Bi-based alloys tested in this study are recommended as potential suitable replacements for SAC305/405 in the wave solder process; no failure was detected up to 6000 cycles at 0°C to 100°C. Although SAC405 demonstrated better barrel fill and lower rate of crack propagation during ATC, after PTH rework, both of the alternative Pb-free alloys have a much lower Cu dissolution rate and definitely outperform SAC405 in ATC. SAC405 glue and wave resistors after primary attachment and rework demonstrate higher reliability than alternative alloys. Early failures relate to alternative alloy characteristics and should be considered for some applications.     

PTH制程的稳定性控制

简单介绍了碱性离子钯活化体系在PTH制程中的应用,通过正交试验优化PTH重要工艺参数。介绍了PTH常见故障及其排除方法,分析了多层线路板生产中去钻污段调整对化学沉铜过程的可能影响机理。阐述了PTH制程中去钻污对背光稳定性的贡献及传统PTH制程对高厚径比板件孔金属化过程的控制方向。     

清洗／调整剂CS-5-A中有机碱含量分析方法的建立

在PTH制程中,为了保证清洗／调整的效果,需要准确分析和保证清洗／调整剂中有机碱含量。通过选用合适的酸碱指示剂,对清洗／调整利CS-5-A中的有机碱含量的分析方法进行了探索,经过实验确定了一种可以对其中的有机碱含量进行精确分析的酸碱滴定方法,确保了CS-5-A的使用和维护性能。     

酸蚀法制作无环金属化孔/槽产品的技术开发与应用

随着电子产品技术发展与高密设计的需求,PCB板设计的密度越来越小,板厚径比也越来越高。为了便于层面布线和满足密Pitch元器件的安装,设计无环PTH孔/槽的PCB板也日趋增多。对于无环PTH孔/槽PCB板的外层图形转移,目前业界通常是采用碱性蚀刻的工艺运作,创造性开发了几种无环PTH孔/槽PCB板外层走酸蚀的特殊制作方法,突破了树脂塞孔或高厚径比无环PTH孔/槽的PCB板无法走碱蚀的局限,在确保产品品质的同时也缩短了外层制作流程和生产周期。     

层间粘接剂对刚挠板通孔可靠性的影响分析

在刚挠结合印制板中,层间不同粘接材料的热性能与镀层差异较大时,在热循环的条件下孔内镀层会发生疲劳断裂从而导致电性能缺陷。以两种典型的层间材料(不流动半固化片和纯胶片)为例,对影响PTH孔铜可靠性的材料特性因素方面进行探讨,首先采用一定的通孔应力应变模型理论分析通孔的应力分布,进而结合通孔的失效评估模型理论计算了不同材料下不同孔径的通孔的疲劳寿命,确定了不同介质材料下通孔的耐热循环性能;最后,通过冷热循环试验进行验证,对比出两种层间材料的差异,同时,通过对失效板件进行切片及SEM形貌分析,提出了PTH在热冲击下的失效原因和机理,获得了材料选择和性能对比的依据。