Modeling Of The Dust Ingression And The Investigation Of The Simulation Test Method

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.