Research Of Electronic Products’Nickel Release Theory, Test And Evalustion Criterion

Connector is an important constituent of the electrical engineering, electronics and telecommunications equipment. It provides guarantee for efficient energy and signal transmission. Anticorrosive plating on connector contacts is adopted widely in recent time in order to guarantee the stability of the connector. Nickel and its alloys have good mechanical and anticorrosive properties, and they are important metal materials, widely used in producing mobile phones, digital music players, digital cameras and other electronic products. However, in recent years research shows that the nickel is an allergic metal. Nickel plating is corroded by sweat and then releases nickel ions because of human skin long-term in contact with the nickel products or nickel products. After that nickel ions can go into skin through the pores and sebaceous glands, causing skin allergies. In view of this, the nickel plating safety of electronic products is an important topic which the electronic industry faces. This topic researches the electronic products’ nickel release theory, test method and the evaluation criterion, providing the basis for electronic product safety design.This topic simulates the actual usage of electronic products by using artificial sweat. Selected samples are made of nickel though different processing technology to research the influence of different processing technology on nickel release. At the start stage of corrosion, the surface of the samples is oxidized by oxygen containing in artificial sweat, and the passivation film is formed. Nickel-oxide (NiO) is the outermost layer of passivation film. As P-type semiconductor, it is able to adsorption free chlorine ion and lactic acid in artificial sweat ions, making sample weight. In the middle stage of corrosion, with aggressive anion adsorption, passivation film gradually breaks and pits. Nickel ions go into the artificial sweat, when artificial sweat’s nickel release rate reaches maximum and the pH value increases as well. Nickel ions released into the artificial sweat reacts with lactic acid root, producing complex lactic acid nickel. Because of the passivation membrane rupturing and dissolving, hydroxyl’s rate in the solution increases quickly. It causes the nickel combine, generated from artificial sweat lactic acid and nickel ions, precipitating and adsorbing on the sample surface. As a result, samples put on weight again.Respectively, detect directly or indirectly the nickel release quantity of samples soaked in the artificial sweat by using quality-loss-method, plating-thickness-method and spectrum-analysis-method. On this basis, the relationship between corrosion time and nickel release quantity’s curve of the sample is concluded. Comparing nickel release quantity per unit area curve and nickel release rate per unit area curve tested by three methods, find the results appearing differences in the soaking phase. In weight-loss-method and spectral-analysis-method, nickel release results deviate largely in the start stage of soaking. In the end stage of soaking, some samples appear weight gain. Nickel-plating in the start stage of nickel release test, data of plating-thickness-method and spectral-analysis-method is closed. As the nickel release test goes into the middle stage, the samples’nickel release rate per unit area reached the maximum and the curve tested by two test methods reverses separation. Comparison nickel release of different samples tested by the same test method, find that release quantity of nickel-plating is always less than pure-nickel-piece after the same soaking time. In additional, the shapes of the curves are roughly same, suggesting that nickel-plating is more anticorrosive than pure-nickel-piece.At the same time, the metallographic analysis and SEM energy spectrum analysis is used, having the aid of surface elements of samples after artificial sweat soaked to analysis. After all, the corrosion theory of nickel release is improved, and the suitable method with nickel release evaluation standard of electronic product is fund out. The nickel release quantities tested by three different methods all exceed EN1811:1998standard. According to the data and analysis results, plating-thickness-method can accurately measure the nickel release quantity of the electronic product. In the start stage spectral-analysis-method can accurately test nickel release quantity of the electronic product. In the end stage, because of the artificial sweat pH value increasing, complex accumulation of lactic acid nickel falls back to the sample surface, causing released nickel rate getting down. So spectral-analysis-method is not suitable for testing nickel release quantity of electronic products in a long soaking time. Due to the previous sample passivation layer adsorption of anionic, complex accumulation of lactic acid nickel falls back, weight-loss-method also can’t accurately measure samples’quality loss, cann’t be used to test nickel release quantity of electronic products.