【作者】 王东；

【导师】 许良军；

【作者基本信息】 北京邮电大学 ， 机械电子工程， 2011， 博士

【摘要】 尘土污染导致的性能退化是信号连接器的主要失效原因之一。我国由于尘土污染严重,电子/电器设备中的连接器抗污染能力弱,导致故障频发,直接影响设备整体性能及可靠性。但是目前在国际范围内尚无有效的测试评估方法,其中合理的尘土进入电子/电器设备的分析模型及实验模拟方法的建立是重要的环节。本论文从系统研究的角度,对此进行了分析和研究。论文在分析研究的基础上,提出了评估电子/电器设备中的连接器抗尘土污染能力的思路：将尘土进入、尘土聚集到接触区域的实验和尘土颗粒在接触区域造成故障的模拟实验相结合,即随机实验、概率分析与确定性的故障实验结合。建立评估体系,将长期依赖于经验和现象分析的尘土影响测试上升为有理论指导测试。该评估体系及模拟系统的建立依赖于两方面的研究：尘土进入电子/电器设备分析模型研究与尘土对接触可靠性的影响研究。本文重点是对前者的研究,同时对后者做了初步的分析。论文主要的内容和结论如下：1通过有限元分析及实验,对影响尘土进入的因素(外界气流、电子/电器设备密封结构、动态环境因素、电效应、热效应等)进行研究,得到了各自的影响形式、评价指标及参数范围。结果表明：外界气流、密封结构及动态环境是影响尘土进入的主导因素,电及热的影响较弱,在模拟及评估中可忽略。2确定了尘土进入电子/电器设备的模式：空气中的尘土颗粒,一部分由于密封结构及外界气流引起的设备内外气压差直接随气流进入,另一部分在其自身重力和气流拖曳力作用下沉积在表面。电子/电器设备在使用过程中受动态环境影响,当外界激励频率达到一定程度,沉积在表面的颗粒惯性力大于摩擦力,颗粒在其初始位置附近做微幅振动,从而逐渐通过密封间隙进入并向内部扩散。其数学表达式为：Qdi=QdKp+QdKgKv。3提出了尘土进入实验模拟系统的设计方案,该实验模拟系统具备模拟外界气流及动态环境这两大主导因素综合影响的能力。通过气-固两相流模型计算,分析得到了在水平循环模式下,粒径5μm-200-μm的尘土颗粒在该实验箱内,当气流流速达到15m/s以上,循环效率将超过75%。在垂直循环模式下,底部漏斗形管壁与水平线之间的夹角应大于17度,这样有利于沉积在管壁上的尘土颗粒在重力作用下进入循环管道。对于振动载物台系统,以路面不平度功率谱密度作为激励信号。4进行了尘土引起电接触失效的概率实验,结果符合正态分布,但是该模型存在局限性,并不反映尘土存在条件下的主要失效模式。在微动与粘接综合作用下,尘土聚集并附着或嵌入到接触表面,从而造成接触界面脱开是尘土引起电接触故障的主要表现形式之一。从微动聚集的角度,通过理论推导得到尘土堆积物的体积V服从对数正态分布,故电连接器的寿命符合对数正态分布。基于失效机理研究结果,将尘土影响分为两大类：直接影响与间接影响,其中共五个子类：断路、接触电阻升高、阻抗变化、加速腐蚀失效、加速微动失效。更多还原

【Abstract】 It is known that dust contamination is one of the factors causing electric contact failures. However, dust test normally used for the reliability evaluation of electric/electronic devices including connectors could hardly reflect the contact failure due to the complexity of the problem. In this paper, for improving dust test method and evaluating method, the investigation was performed.It needs to note that both ingression and contact behavior should be involved in dust test system for evaluating the reliability of electric/electronic devices and connectors. As one part of this test method research, modeling of dust ingression was established. The research works and obtained conclusions are as follows:1 Many factors such as air flowing, structure, electro/thermo characteristic of electric/electronic devices, and dynamic environments may affect the dust ingression. Air flowing, structure densification and dynamic environment effects are the leading factors on dust ingression of mobile phone. Thermal and electro effects can be ignored.2 The pattern of dust ingression:some dusts in the air are blowed into the electric/electronic devices because of the differential pressure; the other dusts are deposited on the devices surface. Since the frequency of dynamic environment increase, it is able to produce acceleration. Therefore, the dust deposited on the electronic devices surface can be easily moved. The movement between the dust and the electric/electronic device is an attempt to make the dust ingression. The mathematic model of dust ingression is shown as Qdi=QdKp+QdKgKv.3 The dust ingression test equipment which these leading factors and their combined effects can be simulated was presented. It divides into four parts:dust injection value, dust circulatory/recycling system, control system and random vibration object stage. The dust distribution in the chamber induced by the air flowing and the transform function of the vibration stage are the two core issues for this research. The discrete phase model was established to compute the dust circulator/recycling efficiency in the chamber. The horizontal circulator/recycling efficiency of dust particles (5μm～200μm) is above 75% when the air velocity is larger than 15m/s. The vertical model shows there is a critical angle which could cause the particle sliding down to the recycling. The criticalθ=170. The effects of random road surface roughness when the mobile phone using in a vehicles is one exterior vibration source example. The power spectral density of road surface roughness can be used in this simulation dust chamber.4 Reliability models of dust effects on electric contact were established. The mathematic model of failure rate was got from the curve fitting of experimental results.The failure mode was analyzed based on dust effect on the electric contact feature. There are two groups including five parts.更多还原