| Resistor is one of components commonly used in electronic equipments. In some special use, the resistor is required to resist high temperature and humidity and the varying ratio of resistance is very little. While the packaging paint used for resistors plays a critical role in the produce of resistors meeting performance required.Phenolic resin and epoxy resin is in common use in electronic packaging because of their excellent electrical properties. With simple curing system, just polymerizing of phenol and formaldehyde, phenolic resin becomes preferred material of paint for resistor. Resistor companies in our country mainly use phenolic resin paint made in our own country or imported at present. However, phenolic resin paint has some avoidless disadvantages, with toxicants released such as phenol and formaldehyde leading to pinholes in finished film when cured at high temperature. And the polymer of phenolic resin paint for resistor has bad tenacity, incapable of meeting requirements of high temperature and humidity resistance in special circumstances. In order to radically solve the intrinsic disadvantages of phenolic resin paint, a kind of paint in the paper, with properties of high temperature and humidity resistance and suitable for automated production line for mental film resistors, was first developed in a larruping way by hydroxy end capping silicone oil, epoxy resin, acid anhydride, diols, nano-SiO2 and so on.Activated hydroxy end capping silicone oil was used for modifying epoxy resin to prepare organic silicone epoxy resin with better tenacity, which solved the disadvantage of bad tenacity of epoxy resin polymer with high crosslink density. Latent curing system, composed of acid anhydride high temperature curing agent and diols accelerant, creatively solves the curing problem of epoxy resin paint for resistor, and combines long use at room temperature, with good property kept for at least six months, to fast curing in 2min at 170℃. Such paint has good property of high temperature and humidity resistance. The varying ratio of resistance is about 0.5‰, meeting indicator requirementΔR/R≤1.0‰, in high temperature resistance experiment. The least varying ratio of resistance is about 1.05‰, close to indicator requirementΔR/R≤1.0‰, in high humidity resistance experiment. The failure of high humidity resistance for resistor is attributed to part or complete damage of metal film on resistor by electrolytic oxidation corrosion. Nano-SiO2, with higher surface activity and tridimensional symmetrical structure, has a strong force with epoxy resin. Investigation on paint for resistor shows nano-SiO2 can catalyze the curing of epoxy resin paint, improve surface dry effect, make the paint polymer has good waterproof property and meet the indicator requirementΔR/R≤1.0‰in high humidity resistance experiment.Low-high-temperature curing process can improve the properties of epoxy resin polymer. Surface dry processes, such as 140℃/3min-170℃/4minn and 140℃/3min-170℃/2min-190℃/2min and so on, are first used to improve the property of high humidity resistance of resistor paint and achieve better results. Critical resistance 249K? resistor, experimenting using 250V limit voltage, and 2.2M? high resistance resistor with thinner film have more rigorous requirement of high humidity resistance of resistor paint. The design of epoxy resin paint for resistor, with two curing agents and dual accelerants system, creatively resolves the problem of high humidity resistance for the two particular kinds of resistors, the varying ratio of resistance meeting indicator requirement given in high humidity resistance experiment. Compared with phenolic resin paint made in our own country and imported from Japan, the epoxy resin paint developed by us has excellent property of high humidity resistance, and avoids the disadvantages resulted from the application of phenolic resin paint. Currently, the epoxy resin paint developed has passed experiment on the production line of resistor and having experimented on high humidity and temperature surroundings simulated resistance of paint for 240h and 2000h in Bejing company.
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