With the development trend of miniaturization and lightweight of electronic equipment, the size requirements for components are becoming smaller and smaller. Therefore, the demand for high precision NTC thermistor chip developed by EXSENSE Electronics Technology Co., Ltd. is also increasing. Due to the requirements of PCB board for temperature protection, temperature monitoring, temperature controlling of thermistor chip are very high, so the production of a high-precision and high-reliability NTC chip can better meet the needs of customers. EXSENSE Electronics introduces a Cr-Ni-Au electrode NTC chip, which has good electrical performance, high reliability and high precision.
The thickness of metal layer of CR-Ni-Au electrode NTC chip should be moderate, which can not be too thick or too thin. Too thick will increase the cost; If the transition layer - chromium layer is too thin, the combination between the composite electrode and the thermal-sensitive ceramic substrate will be affected; If the barrier layer - nickel layer is too thin, which can not play the role of block; If the gold layer, which acts as a welding layer and protective layer, is too thin, it can easily cause external damage to the barrier layer, then affect the reliability of the product. Therefore, the thickness of each electrode layer is generally 0.2 μm chromium layer, 0.4 μm nickel layer and 0.1 μm gold layer. The appropriate thickness of each metal layer can make the electrical performance and reliability of the product reach the best, and effectively control the material cost.
The printing method of Cr-Ni-Au electrode is vacuum sputtering method. Compared with the silk-screen printing method, vacuum sputtering method has the following beneficial effects on the preparation of each metal layer:
First, the sputtering process is carried out in the vacuum sputtering coating equipment, which will not pollute the environment and has high cleanliness, to ensure that the surface cleaning will not be polluted twice;
Second, it saves the complicated preparation work of silk-screen printing and can be put into use immediately after sputtering in vacuum sputtering equipment;
Third, the thickness of the metal layer obtained by vacuum sputtering can reach less than 1% of the thickness of the silk-screen printing, which is saving material and the composite electrode and thermal-sensitive ceramic substrate can be closely fit, there will be no skin or burr in the process of cutting basically;
Fourth, vacuum sputtering process is easy to control, the coating area of obtained metal layer is large and uniform coverage, the combination with thermal-sensitive ceramic substrate is firm, the surface is very dense, which can effectively prevent external erosion, so that the product can really achieve high precision, high reliability;
Fifth, there is no process of drying and electrode layer sintering, which can avoid air pollution due to discharge of harmful gases, environmental protection advantages are prominent.
The prepared Cr-Ni-Au electrode NTC chip is compared with the traditional NTC thermistor chip for performance comparison testing, and the following table data can be obtained:
From the data in the table, the resistance value and B value of the traditional NTC thermistor chip are dispersed, with low precision; The change rate large of aging and thermal shock is also large, with low reliability. The resistance value and B value of Cr-Ni-Au electrode NTC chip are very concentrated, and the change rate of aging and thermal shock is very small, which really achieves high precision and high reliability.