Humidity affects the resistance properties of alloys, and moisture-proof selection and application strategies
Date：2025-12-09
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Humidity is an important environmental factor that affects the stability of alloy resistance performance, especially in high humidity environments. Water vapor may penetrate through packaging gaps, cause material oxidation or electrochemical corrosion, leading to resistance drift, insulation performance degradation, and even circuit failure. This article will systematically analyze the specific impact mechanism of humidity on alloy resistance, provide a full process moisture-proof method from product selection to application protection, and introduce the resource advantages of Shenzhen Shunhai Technology Co., Ltd. as the core agent, as well as the service characteristics of Huanian Mall as a professional online procurement platform.
1、 The specific effect of humidity on alloy resistance
1. Resistance drift and decreased accuracy
Although the core materials of alloy resistors, such as manganese copper and constantan alloys, have strong chemical stability, long-term exposure to high humidity environments (relative humidity>80%) can cause water vapor to react with trace impurities remaining on the surface of the resistor, forming an oxide film or electrolyte layer, resulting in increased contact resistance. At the same time, micro gaps may appear at the welding interface between the electrode and the resistor due to water vapor erosion, causing slow drift in resistance. According to the industry testing standard (IPC-TM-650 2.6.3.7), after 1000 hours of testing in an 85 ℃/85% RH environment, the resistance drift rate of ordinary alloy resistors can reach over ± 2%, far exceeding the precision circuit requirement of ± 0.1% accuracy range.
2. Deterioration of insulation performance and increase in leakage current
The packaging materials of alloy resistors, such as epoxy resin and plastic substrates, will absorb moisture and expand under high humidity, resulting in a decrease in insulation resistance. For example, alloy resistors used in high-voltage circuits may produce significant leakage currents, interfere with signal transmission, and even pose safety hazards if the insulation resistance drops from the initial 1000M Ω to below 100M Ω. In humid and salty environments (such as coastal areas), ions in water vapor can accelerate the aging of insulation layers and shorten the service life of resistors.
3. Electrode corrosion and solder joint failure
The electrodes of alloy resistors are usually made of materials such as silver and copper. Under the combined action of high humidity, oxygen, sulfides, etc., electrochemical corrosion is prone to occur: silver electrodes may generate silver sulfide (Ag ₂ S), leading to an increase in electrode resistance; Copper electrodes will oxidize to form copper oxide (CuO), causing poor contact at solder joints. When severe, corrosion products may spread to the resistor, causing circuit breakers, which is particularly common in industrial wet workshops, outdoor communication equipment, and other scenarios.
(Suggest inserting a chart: Correlation chart between humidity and alloy resistance performance, with the horizontal axis representing relative humidity (%) and the vertical axis representing resistance drift rate (%) and insulation resistance (M Ω), respectively, to visually display the trends of their changes)
2、 Moisture prevention methods for alloy resistors
1. Product selection: Priority should be given to moisture-proof enhanced alloy resistors
Packaging type: Metal shell fully sealed packaging (such as TO-220, bolt type) or glass glaze sealed alloy resistors are selected. This type of packaging can isolate more than 99% of water vapor penetration and is suitable for extreme environments with relative humidity greater than 90% (such as underground mines and marine equipment).
Material optimization: Choose products with nickel or gold plating on the electrode surface. Nickel and gold have better corrosion resistance than silver and copper, and can reduce the electrode corrosion rate by more than 60%; The resistor is treated with passivation (such as forming an oxide film) to enhance its resistance to water vapor erosion.
2. Application protection: Strengthen circuit level moisture-proof measures
Coating with Three proof Paint: After the PCB board is soldered, acrylic or silicone rubber three proof paint is sprayed on the alloy resistor and surrounding solder joints to form a protective film with a thickness of 50-100 μ m, which can effectively block water vapor and pollutants. Pay attention to selecting high-temperature resistant models to avoid affecting the heat dissipation of resistors.
Environmental control: Place silicone desiccants (50-100g per cubic meter of space) inside the device casing, or integrate small dehumidification modules (such as Peltier effect dehumidifiers) to control the relative humidity of the working environment within the ideal range of 30% -60%.
Layout design: When laying out PCBs, keep alloy resistors away from heat dissipation holes and areas where condensation water is prone to accumulate (such as under power modules). If necessary, add water blocking ribs or protective covers to reduce the probability of direct contact with water vapor.
3. Process assurance: Standardize production and storage processes
Storage conditions: Alloy resistors should be stored in a dry cabinet (relative humidity ≤ 50%) to avoid outdoor stacking; After opening, the product should be used up within 48 hours. Unused products should be sealed and placed in a drying cabinet to prevent moisture absorption.
Welding process: Control the temperature zone curve during reflow soldering to avoid microcracks in the packaging material caused by high temperatures; Clean after welding to remove residual flux (residual flux has strong moisture absorption and is prone to corrosion).
summary
The influence of humidity on alloy resistance needs to be addressed from multiple dimensions, including selection, protection, and process, and choosing professional suppliers and procurement channels is key. As electronic devices expand into complex environments, moisture-proof alloy resistors will develop towards higher moisture resistance levels (such as 100% humidity resistance) and smaller packaging. It is recommended that enterprises leverage the original factory resources and technical support of Shunhai Technology to efficiently purchase compatible products through Huanian Mall, ensuring the long-term stable operation of circuits in humid environments.
