# Research on the Mechanism and Dynamic Characteristics of Intermitt Failure of Electrical Connectors
## 1 Introduction  
With the rapid development of modern industry, laser technology plays an increasingly important role in the fields of material processing [1, 2, 3], medical treatment [4], sensing technology [5], optical communication [6], military applications, and aerospace [7]. As a high-energy light source that converts electrical energy into light energy, the stability and reliability of lasers are crucial to ensure the performance of the entire system. However, lasers are exposed to harsh conditions such as high temperatures, high voltages, and strong currents during operation, which can lead to damage to laser optics, electrical failures, thermal management problems, and mechanical failures [8]. Intermittent failures of electrical connectors in lasers increase significantly with increasing usage time [9, 10]. An intermittent failure (IF) is defined as a failure of an item for a limited period of time, following which the item recovers its ability to perform its tasks without being subjected to any external corrective action [11]. As a kind of intermittent failures, electrical connection intermittent failures may induce false alarms of built-in test (BIT) system [12]. Electrical connection components mainly consist of electrical connector, solder joint, pin and so on. This paper mainly discusses the intermittent failure mechanism of electrical connector. Intermittent failures of each electrical connector will cause operation risk, or, more seriously, a catastrophic accident [13, 14]. For the purpose of isolating an intermittent failure, many experts and scholars have carried out relevant studies, which are mainly focused on modeling intermittent failure. Considering the randomness of intermittent failure, a certain number of statistical modelsof intermittent failure are proposed. To summarize these statistical models [15, 16, 17, 18, 19, 20, 21], the intermittent failures are modeled as a random event with a probability of state transition. Through experimental research, the intermittent failures are found to be closely related to environmental stress. Then, the intermittent failures are modeled as random events with a conditional state transition probability [22], and the intermittent failures' transfer to fault-free state or permanent fault (PF) state needs to consider the effect of environmental stress [21, 23]. By applying these statistical models, the ability to diagnose intermittent failure is improved. However, the validity and accuracy of the statistical model relies on a large number of intermittent failure sample data that are difficult to obtain; therefore, most intermittent failures are still difficult to diagnose and isolate. To improve the ability to diagnose intermittent failure, the intermittent failures must be modeled as a deterministic event instead of a random event. However, there are few research studies on the intermittent failure mechanism as it is difficult to model an intermittent failure as a deterministic event. Thus, the mechanism of intermittent failure is a key issue that should be studied urgently. This paper mainly discusses the mechanism and dynamic characteristics of intermittent failure of electrical connectors. Among many parameters of electrical connectors, contact resistance is an important parameter that reflects the performance of electrical contact [24, 25, 26]. Hence, the studies on electrical connector intermittent failure can be concentrated on contact resistance. Compared with other factors, the fretting has the greatest influence on electrical connectors' contact performance [27]. It is widely acknowledged that fretting is a form of relative sliding with no more than 125 microns of amplitude, and it is the main cause behind the increase in contact resistance. Many research studies on contact resistance have been conducted through experiments [28, 29, 30, 31]. Also, many contact resistance models have been developed, including the Holm model, the Malucci model, and the Grossmann model [32]. Those models performed well in modeling static contact resistance.