A thermistor

Abstract

The application provides a thermistor. The thermistor wraps a thermistor body in a glass shell, and adopts a special signal lead wire to extend into the glass shell to connect electrodes of the thermistor. The signal lead wire has a nickel-iron wire core, a copper plating layer, a connecting layer and a gold plating layer from inside to outside. The connecting layer is a nickel plating layer or a nickel alloy plating layer. The above thermistor can comprehensively protect the thermistor body from damage in a humid and corrosive environment, and can ensure that the signal lead wire and the glass shell have similar temperature expansion coefficients, and can isolate water vapor through the inert gold plating layer on the outer layer to inhibit copper ion migration of the copper plating layer for signal transmission. In addition, the cooperation of the gold plating layer and the connecting layer can prevent the electric signal of the thermistor from being disturbed by the electromagnetic environment during transmission, and effectively improve the transmission quality of the signal. The thermistor provided by the application has the advantages of moisture resistance, corrosion resistance, high working reliability and anti-electromagnetic environment interference.

Description

Technical Field

[0001] The technical solution of this application relates to the field of electronic component packaging, specifically to a moisture-resistant and high-temperature-resistant thermistor. Background Technology

[0002] With the increasing demands for temperature control in industries such as automotive, HVAC, and home appliances, corresponding requirements have been placed on the accuracy, sensitivity, and environmental adaptability of temperature measurement products. Temperature measurement products include thermistors, thermocouples, and infrared sensors. Among these, thermistors are widely used in various devices due to their low cost and small size. However, despite these advantages, thermistors suffer significant reductions in measurement accuracy and lifespan when used in high-temperature and humid (high-temperature water vapor), acidic corrosive environments, and complex electromagnetic environments.

[0003] Currently, single-ended glass-encapsulated NTC thermistors use nickel-iron alloy copper-clad materials as the lead material. Copper is a relatively reactive metal element; under humid conditions and with electrical current, copper ion migration will occur in the thermistor leads, causing the NTC thermistor to fail in temperature measurement and control.

[0004] The copper migration process generally includes the following steps: When the copper plating on the outer layer of the thermistor leads is exposed to a humid environment and energized, under the influence of the humid environment and electric field, the copper undergoes an oxidation reaction, losing electrons and transforming into copper ions (Cu). 2+ Simultaneously, water molecules ionize to generate hydrogen ions (H+). + ) and hydroxide ions (OH) - Driven by an electric field, copper ions migrate through a moist insulating medium (such as residual flux, contaminants, or tiny gaps in the package) towards the cathode (a conductor with a lower potential). During this migration, these copper ions combine with hydroxide ions to form unstable conductive substances. When the copper ions reach the cathode and gain electrons, they are reduced to metallic copper and deposited. Over time, these deposits grow, eventually forming tree-like copper dendrites between the two electrode leads, causing a micro-short circuit. This reduces the resistance of the thermistor or causes a direct short circuit, leading to temperature measurement failure. Summary of the Invention

[0005] To address the shortcomings of existing thermistors in temperature measurement under high temperature, humidity, and complex electromagnetic interference environments, this application provides a thermistor that is resistant to electromagnetic interference, moisture, and corrosion. This thermistor not only completely isolates moisture from the copper layer and effectively suppresses copper ion migration generated by the copper-plated material on the surface of the nickel-iron alloy wire core, but also has excellent electromagnetic interference resistance, making it suitable for high-precision temperature measurement in temperature control systems operating in humid, corrosive, and complex electromagnetic environments.

[0006] The thermistor provided in this application structurally includes: a thermistor body, a glass shell, and signal leads. The thermistor body is housed inside and enclosed by the glass shell. The signal leads extend into the glass shell and connect to the signal electrodes of the thermistor. From the inside out, the signal leads sequentially comprise a nickel-iron wire core, a copper plating layer, a connecting layer, and a gold plating layer. The connecting layer is a nickel plating layer or a nickel alloy plating layer.

[0007] To prevent the thermistor body from being damaged by moisture or corrosive substances, preferably, the glass shell is softened and cooled by high-temperature sintering to achieve a tight connection with the signal leads.

[0008] The glass casing, made of chip packaging glass, can protect the thermistor body in high-temperature, humid, and corrosive environments. The signal leads, through a gold-plated layer added to the outer layer of the nickel-iron wire core via a connecting layer, not only ensure that the thermal expansion coefficient of the signal leads is close to that of the packaging glass casing, but more importantly, it eliminates the phenomenon of "copper ion migration" and improves moisture resistance and corrosion resistance. The connecting layer is set as a nickel-plated layer or a nickel alloy-plated layer, not only because nickel or nickel alloys can effectively connect copper and gold, but also because they have excellent electromagnetic shielding capabilities. The gold plating layer and the connecting layer together form a double shield against external electromagnetic signals. Therefore, the thermistor provided in this application is very suitable for high-precision temperature measurement in high-temperature, humid, and complex electromagnetic environments.

[0009] Preferably, the cross-sectional area of ​​the nickel-iron wire core accounts for more than 50% of the total cross-sectional area of ​​the signal lead.

[0010] In some embodiments, the thermistor body is an NTC thermistor, which has two signal electrodes formed by coating electrode paste on two opposing surfaces of a ceramic body. Preferably, the signal lead includes a straight section and a bent section, one end of the bent section is connected to the signal electrode, and the other end of the bent section is connected to the straight section.

[0011] Furthermore, the signal lead has a circular or square cross-section, and the connecting layer is a nickel-iron alloy plating layer. Preferably, the thickness of the connecting layer is [missing information]. The thickness of the gold plating layer is .

[0012] The thermistor package provided in this application can effectively suppress local short circuits caused by copper ion migration in the thermistor signal leads in humid environments, while ensuring that the temperature coefficients of the glass shell and the signal pins are close within the temperature measurement range. The thermistor provided in this application has advantages such as moisture resistance, corrosion resistance, and good electromagnetic interference immunity, making it particularly suitable for long-term operation and accurate temperature measurement in humid, corrosive, and complex electromagnetic interference environments. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a thermistor package provided in this application in one embodiment.

[0015] Figure 2 This is a schematic diagram of the cross-section of the signal lead in the thermistor package provided in this application. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0017] like Figure 1 In the illustrated embodiment, the thermistor provided in this application includes: a thermistor body 1, a glass housing 3, and signal leads 2. The thermistor body 1 is disposed inside and enclosed by the glass housing 3. Those skilled in the art will understand that the glass housing 3 should be made of chip-package-grade glass, and this will not be elaborated further here.

[0018] The signal lead 2 extends into the glass housing 3 and is connected to the signal electrode of the thermistor body 1.

[0019] Preferably, the glass housing 3 is sintered at high temperature, softened, and then cooled to achieve a tight connection with the signal lead 2. This ensures that there are no gaps at the connection between the glass housing 3 and the signal lead 2, completely isolating the thermistor body 1 from moisture and corrosive environments.

[0020] like Figure 2As shown, the signal lead 2, from the inside out, has a nickel-iron wire core 21, a copper plating layer 22, a connecting layer 23, and a gold plating layer 24. The connecting layer 23 is a nickel plating layer or a nickel alloy plating layer. The nickel-iron wire core 21 itself is not used for signal transmission, but rather to ensure that the overall thermal expansion coefficient of the signal lead 2 is close to that of the glass shell 3, guaranteeing that no gaps or cracks form between the signal lead 2 and the glass shell 3 when the thermistor is used for temperature measurement in high-temperature and humid environments. If the copper plating layer 22, used to transmit the electrical signal output by the thermistor body 1, is exposed or encapsulated with adhesive wire, it is difficult to completely isolate moisture, especially in high-temperature and humid environments where moisture is difficult to prevent from entering the surface of the copper plating layer 22; often, copper ion migration occurs, causing the thermistor to experience a partial short circuit and fail. Therefore, in this application, the signal lead 2 has an inert metal plating layer—a gold plating layer 24—plated on the outer layer of the copper plating layer 22 through the connecting layer 23. Gold plating is a typical inert metal and is not easily hydrolyzed or ionized. Therefore, adding a gold plating layer can effectively isolate water vapor without causing ion migration or deposition.

[0021] The bonding between gold and copper is poor. Introducing a nickel layer or nickel alloy layer as the bonding medium in the connecting layer 23 can improve the adhesion / bonding between the two. Furthermore, setting the connecting layer 23 as a nickel layer or nickel alloy layer can also shield external electromagnetic fields, preventing electromagnetic interference signals from interfering with the electrical signals transmitted in the copper layer. Additionally, since the coefficient of thermal expansion of nickel-iron material is close to that of the glass used for chip packaging, to ensure that the overall coefficient of thermal expansion of the signal lead 2 is close to that of the glass shell 3, preferably, the cross-sectional area of ​​the nickel-iron wire core accounts for more than 50% of the total cross-sectional area of ​​the signal lead.

[0022] It is evident that the thermistor body 1 can be either a positive temperature coefficient thermistor or an NTC (negative temperature coefficient) thermistor. Preferably, the thermistor body 1 is an NTC thermistor, with two signal electrodes formed by coating electrode paste on two opposing surfaces of its ceramic body. Accordingly, the signal lead includes a straight section and a bent section, one end of the bent section being connected to the signal electrode, and the other end of the bent section being connected to the straight section.

[0023] Furthermore, the signal lead 2 has a circular or square cross-section (flat conductor). Preferably, the connecting layer is a nickel-iron alloy plating layer. This further increases the cross-sectional area ratio of the nickel-iron material, which helps the coefficient of thermal expansion of the signal lead 2 to be closer to that of the glass shell 3. Preferably, the thickness of the connecting layer is... The thickness of the gold plating layer is .

[0024] The thermistor provided in this application not only effectively prevents copper (ion) migration and resists electromagnetic interference, but also effectively prevents the glass casing from cracking at the contact point with the signal leads within a relatively fast temperature change range. The thermistor has a simple structure and easy assembly process, making it suitable for accurate temperature measurement in humid, corrosive, and complex electromagnetic interference environments.

[0025] The above description is merely an embodiment of this application and is not intended to limit this application. For those skilled in the art, the technical solutions provided in this application can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A thermistor, characterized in that, The thermistor includes: a thermistor body, a glass shell, and signal leads; the thermistor body is placed inside and enclosed by the glass shell; the signal leads extend into the glass shell and connect to the signal electrodes of the thermistor body; the signal leads, from the inside out, have a nickel-iron wire core, a copper plating layer, a connecting layer, and a gold plating layer; the connecting layer is a nickel-iron alloy layer to increase the cross-sectional area of ​​the nickel-iron material; the cross-sectional area of ​​the nickel-iron wire core accounts for more than 50% of the total cross-sectional area of ​​the signal leads; the thickness of the connecting layer is... The thickness of the gold plating layer is .

2. The thermistor as described in claim 1, characterized in that, The glass shell is softened and cooled by high-temperature sintering to achieve a tight connection with the signal leads.

3. The thermistor as described in claim 1, characterized in that, The thermistor body is an NTC thermistor body, and its two signal electrodes are formed by coating electrode paste on the two opposite sides of the ceramic body.

4. The thermistor as described in claim 3, characterized in that, The signal lead includes a straight section and a bent section. One end of the bent section is connected to the signal electrode, and the other end of the bent section is connected to the straight section.

5. The thermistor as described in claim 1, characterized in that, The signal lead has a circular or square cross-section.

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