WO2013170648A1 - 一种压敏电阻器及制造方法 - Google Patents

一种压敏电阻器及制造方法 Download PDF

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Publication number
WO2013170648A1
WO2013170648A1 PCT/CN2013/072343 CN2013072343W WO2013170648A1 WO 2013170648 A1 WO2013170648 A1 WO 2013170648A1 CN 2013072343 W CN2013072343 W CN 2013072343W WO 2013170648 A1 WO2013170648 A1 WO 2013170648A1
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Prior art keywords
varistor
chip
silicone rubber
electrode
wrapping layer
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PCT/CN2013/072343
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English (en)
French (fr)
Inventor
李炬
彭冬梅
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成都铁达电子有限责任公司
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Publication of WO2013170648A1 publication Critical patent/WO2013170648A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/02—Housing; Enclosing; Embedding; Filling the housing or enclosure
    • H01C1/024—Housing; Enclosing; Embedding; Filling the housing or enclosure the housing or enclosure being hermetically sealed
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/10—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material voltage responsive, i.e. varistors
    • H01C7/102—Varistor boundary, e.g. surface layers

Definitions

  • the present invention relates to a piezoresistor and a method of fabricating the same. Background technique
  • the varistor is a voltage-limiting protection device that utilizes the nonlinear characteristics of the varistor.
  • the varistor can clamp the voltage to a relatively fixed voltage value. Therefore, the protection of the latter circuit is realized, and it is widely used in various electronic devices.
  • the main component of the varistor is a varistor chip, which is a semiconductor ceramic containing zinc oxide as a main component, adding a metal oxide such as cerium oxide or cobalt oxide, sintered at a high temperature of about liocrc, and then in a ceramic body.
  • the electrode is placed on the upper surface and the metal lead is connected, and finally the outer casing of the resistor chip is packaged with an insulating case.
  • the insulating shell of the varistor mainly functions as an insulating and protecting varistor chip. Since the metal lead spliced on the electrode needs to pass through the insulating shell, a gap is left between the metal lead and the insulating shell; The sealing effect is not the main purpose of the design.
  • the outer casing cannot seal the varistor chip well, resulting in the actual working environment, especially in the wet work.
  • the water vapor in the air enters the varistor through the gap on the insulating case and is attached to the varistor chip.
  • the article uses a high-quality epoxy encapsulation material to form a densely packed encapsulation layer outside the varistor chip, effectively protecting the varistor from moisture.
  • the epoxy encapsulating material selected is usually epoxy resin.
  • a phenolic epoxy resin is wrapped on the outside of the varistor chip to form an epoxy resin encapsulant after curing.
  • the cured epoxy resin has good physical and chemical properties, and has good dielectric properties and changes. Low shrinkage, good dimensional stability, high hardness, stability to alkali and most solvents, so the use of epoxy resin as the varistor envelope can not only block the infiltration of moisture in the atmosphere, but also It can electrically insulate and protect the chip from damage during transportation and use.
  • the encapsulation layer after the curing of the powdered epoxy resin is not perfect, and there are many defects of micropores in the interior. If the micropores pass through, a channel of moisture intrusion is formed, thereby affecting the product. Moisture resistance.
  • the cured epoxy resin encapsulant has a small set shrinkage, good dimensional stability, high hardness, no adhesion to the pressure sensitive ceramic chip, and the cured epoxy encapsulant and pressure sensitive layer.
  • the coefficient of thermal expansion between the resistor chip and the metal lead is inconsistent, so when the ambient temperature changes cyclically, micro-cracks are formed between them, and the moisture in the atmosphere will enter the crack from the root of the metal lead or the defect channel of the encapsulation layer under capillary action. And accumulate there, the varistor chip is damp, which seriously affects the reliability of the product, especially the use of the varistor in a humid environment.
  • the production method of the varistor using the powder epoxy resin curing as the insulating encapsulation layer is as follows: First, the lead wire is spliced on the varistor chip, and then the galvanic lead is coated on the varistor chip and the lead wire with an organic solvent. After the cleaning, the solution is dried at 12CTC for 2 hours. After cooling, the varistor chip and the root of the lead are coated with powder epoxy resin, and finally cured at a temperature of 15 CTC for 1 hour to obtain a varistor. .
  • the chip In the manufacturing method of the varistor, the chip easily re-adsorbs the water vapor in the air during the cooling process, especially in the hot summer, which seriously affects the drying effect, so After the varistor chip with the lead wire is dried at 120 ° C for 2 hours, the powder epoxy resin should be coated as soon as possible. Otherwise, the defective product produced by the varistor due to the leakage current will be unqualified. Significantly increased, the rate of batch unqualified products in severe cases even exceeds 10% (normally, the rate of batch unqualified products is less than 1%). In order to avoid this loss, in the production, especially in the hot summer months, a batch of products must be divided into several small batches. Although the method of using such a small batch production reduces the failure rate of the product, it also leads to low utilization rate of the production equipment, a decrease in output, an increase in energy consumption, and difficulty in management. Summary of the invention
  • the object of the present invention is to overcome the degradation of the product performance of the prior art varistor due to poor moisture resistance, and to ensure the drying effect of the varistor chip during the production process, it is necessary to set a separate drying step and dry it. After the sequel, it is necessary to carry out the next step in time, resulting in a lack of high utilization rate of production equipment, low output, high energy consumption, and difficulty in management, and a varistor and a manufacturing method are provided.
  • the varistor and the manufacturing method of the invention effectively prevent the water vapor in the air from entering the varistor, have good moisture resistance, and improve the varistor in use, especially in a high humidity environment.
  • the reliability of use but also has good insulation strength and mechanical strength; and, reduces the energy consumption in the production process, improves the utilization rate of production equipment and the production efficiency of the product, and also reduces the difficulty of production management.
  • the present invention provides the following technical solutions:
  • a varistor comprising a varistor chip, a silicone rubber encapsulation layer, an insulating encapsulation layer, an electrode and an electrode lead, the varistor chip being encapsulated in a silicone rubber encapsulation layer, the silicone rubber wrap
  • the sealing layer is encapsulated in the insulating encapsulation layer, and an electrode is disposed on each side of the varistor chip, and an electrode lead is disposed on the electrode through the silicone rubber encapsulation layer and the insulating encapsulation layer to the insulating package. The outside of the seal.
  • the varistor chip is first packaged together with the electrode lead in a silicone rubber encapsulation layer, and then encapsulated inside the insulating encapsulation layer together with the silicone rubber encapsulation layer.
  • the silicone rubber encapsulating layer is preferably coated on the surface of the varistor chip with a room temperature curing one-component silicone rubber, and after curing, forms a wrap layer with good moisture and electrical insulation properties, and powdered epoxy. Compared with the encapsulation layer formed by curing the resin, the internal defects are less and the texture is more compact. At the same time, since the silicone rubber encapsulation layer can be firmly bonded to the varistor chip and the electrode lead, it has good plasticity.
  • the silicone rubber encapsulation layer can change with the same, so that no micro-cracks are formed between the contact faces. , does not provide conditions for the intrusion and accumulation of water vapor, effectively preventing the varistor chip from being deteriorated by moisture.
  • the production method of the varistor of the invention is:
  • one electrode is disposed on each side of the varistor chip, and one electrode lead is respectively connected to the electrode;
  • the epoxy resin was cured at a temperature of 15 CTC for 1 hour, and after curing, an insulating encapsulant layer was formed to obtain a varistor finished product.
  • the step (1) is connected to the electrode and
  • the auxiliary agent used in the electrode lead is not a no-cleaning aid, and is disposed on the varistor chip and the lead when the splicing lead is cleaned with an organic solvent between the step (1) and the step (2).
  • a step of a helping aid if the step (1) is connected to the electrode and The auxiliary agent used in the electrode lead is not a no-cleaning aid, and is disposed on the varistor chip and the lead when the splicing lead is cleaned with an organic solvent between the step (1) and the step (2).
  • the varistor chip Due to the nature of the silicone rubber itself, it is necessary to absorb water during the curing process to participate in the curing. Therefore, it is not necessary to separately set the varistor chip drying step in the production process, gp, and the varistor chip is coated with silicone rubber and connected. During the curing process, the water molecules adsorbed on the surface of the varistor chip are taken away by the silicone rubber coating and participate in the curing reaction of the silicone rubber encapsulation layer. Therefore, the curing process is also a drying process. After the curing process is finished, the surface of the varistor chip has been wrapped by a dense silicone rubber encapsulation layer and is no longer in contact with air. The varistor chip in this state will not be placed after the long-term placement. The product quality has any influence, realizing the mass production of the product, especially the mass production under the hot and humid environment in summer, which improves the utilization rate of the production equipment and the production efficiency of the product, and also reduces the difficulty of production management.
  • the thickness of the silicone rubber encapsulation layer is 0. 01 ⁇ lmm.
  • the insulating encapsulating layer is an epoxy resin encapsulating layer formed by sealing a layer of a powdery epoxy resin outside the silicone rubber encapsulating layer and curing.
  • the cured epoxy resin encapsulant has good physical and chemical properties, and has good dielectric properties, small variable shrinkage, high hardness and stability to alkali and most solvents. Therefore, epoxy resin is used as pressure sensitive.
  • the insulating encapsulant of the resistor blocks the infiltration of moisture into the varistor in the atmosphere, and also acts as an electrical insulator and protects the varistor chip and the silicone rubber encapsulant during transport and use.
  • the varistor of the invention adopts moisture absorption during curing, and has good plasticity and toughness after curing, and has compact texture, few defects, and can be firmly bonded with the varistor chip and the electrode lead.
  • the silicone rubber acts as a wrap layer for the varistor chip, so that in the production of the varistor, there is no need to separately set the varistor chip drying step, gp, the varistor chip is coated with silicone rubber and the subsequent curing During the process, water molecules adsorbed on the surface of the varistor chip are taken away by the silicone rubber coating and participate in the curing reaction of the silicone rubber encapsulation layer. Therefore, the curing process is also a drying process.
  • the surface of the varistor chip has been wrapped by a dense silicone rubber encapsulation layer and is no longer in contact with air.
  • the varistor chip in this state will not be placed after the long-term placement.
  • the product quality has any influence, realizing the mass production of the product, especially the mass production under the hot and humid environment in summer, improving the utilization rate of the production equipment and the production efficiency of the product, and also reducing the difficulty of production management; In the middle, the infiltration of water vapor in the atmospheric environment is blocked, and the electrical parameters of the varistor due to the moisture of the varistor chip are effectively prevented from being reduced or even scrapped.
  • the varistor of the present invention since silicone rubber is used as a wrap layer for the internal varistor chip of the varistor, since the cured silicone rubber is too soft, it cannot protect itself and the internal varistor chip from the mechanical damage. Therefore, an epoxy resin having good physical and chemical properties after curing, and having good dielectric properties, small variable shrinkage, high hardness, and stability to alkali and most solvents is sealed on the outside of the silicone rubber encapsulation layer. Wrapped, the epoxy encapsulation layer protects the varistor chip and the silicone rubber encapsulation layer from mechanical damage during transportation and use, and further improves the electrical insulation and moisture resistance of the varistor.
  • the varistor of the invention effectively prevents the water vapor in the air from entering the varistor, has good moisture resistance, and improves the varistor in use, especially in a humid environment. Reliability in use, and good insulation strength and mechanical strength;
  • the varistor of the present invention is hardly affected by ambient temperature and humidity during production Loud, there is no need to separately set the varistor chip drying step, which realizes mass production of the product, especially in the hot and humid environment in summer, which improves the utilization rate of the production equipment and the production efficiency of the product. Reduced the difficulty of production management.
  • FIG. 1 is a schematic structural view of a varistor of the present invention
  • FIG. 2 is a schematic view showing the connection of a varistor chip and an electrode lead of the present invention
  • FIG. 3 is a schematic view of the varistor of the present invention
  • Fig. 5 is a comparison chart of the humidity test data of the varistor and the conventional varistor of the present invention. Marked in the figure: 1- varistor chip, 2-silicone rubber encapsulation layer, 3-insulating encapsulation layer, 4-electrode lead, 5-electrode, a- varistor voltage change rate curve of varistor of the present invention , b-traditional varistor varistor voltage change rate curve.
  • an electrode 5 is disposed on each side of the varistor chip 1, and an electrode lead 4 is respectively attached to the electrode 5, and then coated with the organic solvent to clean the splicing lead 4
  • the auxiliary agent on the chip 1 and the lead 4 (if the auxiliary agent is a no-cleaning auxiliary agent, no cleaning is required), and after drying, the varistor chip 1, the electrode 5 and the electrode lead 4 are coated.
  • the one-component silicone rubber is cured at room temperature, and is naturally allowed to stand for more than 4 hours in the room. When curing, the room temperature curing single-component silicone rubber absorbs moisture on the roots of the varistor chip 1, the electrode 5 and the electrode lead 4, so that the interior is obtained after curing.
  • the silicone rubber encapsulation layer 2 Drying the silicone rubber encapsulation layer 2, finally coating a layer of powdered epoxy resin on the silicone rubber encapsulation layer 2 and the electrode lead 4, curing the epoxy resin at a temperature of 15 CTC for 1 hour, and forming after curing
  • the insulating wrap layer 3 is obtained to obtain a varistor finished product as shown in FIG.
  • the varistor chip and the lead root are sealed by silicone rubber, and the silicone rubber encapsulation layer 2 is cured. Since the silicone rubber absorbs water molecules to participate in the reaction during curing, it is necessary to absorb water during the curing process.
  • the outermost insulating encapsulation layer 3 is made of epoxy resin, has good electrical insulation properties and high strength and hardness, and can protect the inner silicone rubber encapsulation layer 2, varistor chip 1 And the electrode 5 is not mechanically damaged, and at the same time prevents moisture in the air from entering the varistor chip 1;
  • the thermal expansion coefficients of the insulating encapsulation layer 3, the varistor chip 1, the electrode 5, and the electrode lead 4 are inconsistent, resulting in the formation of micro-cracks between the contact faces, but in the insulating encapsulation layer 3 and pressure sensitive
  • the structure of the conventional varistor is as shown in FIG. 4, one electrode 5 is respectively disposed on both sides of the varistor chip 1, and one electrode lead 4 is respectively connected to the electrode 5, and then the splicing lead is cleaned with an organic solvent.
  • the auxiliary agent applied to the varistor chip 1 and the lead 4 if the auxiliary agent is a no-cleaning auxiliary agent, no cleaning is required
  • the temperature is dried at 12 CTC for 2 hours, and the temperature is lowered.
  • the varistor chip and the root of the lead are coated with a powder epoxy resin, and finally cured at a temperature of 15 CTC for 1 hour to obtain an epoxy resin encapsulant layer 3, thereby obtaining a varistor.
  • the varistor chip 1 is easy to re-adsorb the water vapor in the air during the cooling process, especially in the hot summer, the effect of the drying process is seriously affected, so the splicing After the varistor chip 1 of the lead 4 is dried at a high temperature of 12 CTC for 2 hours, the powder epoxy resin needs to be coated as soon as possible. Otherwise, the defective product produced by the varistor due to the leakage current is greatly increased. In severe cases, the rate of batch unqualified products is even more than 10% (normally, the rate of batch unqualified products is less than 1%).
  • the varistor due to the defects of many micropores in the epoxy encapsulating layer 3 after the epoxy resin is cured, if the micropores pass through, a channel of moisture intrusion is formed, thereby affecting the product. Moisture resistance.
  • the cured epoxy encapsulant layer 3 has a small shrinkage rate and product size.
  • the varistor of the present invention and a conventional varistor were placed in an environment having a temperature of 40 ⁇ 2 ° C and a relative humidity of more than 95% for 3000 hours, and electrical parameters were tested every 500 hours and recorded.
  • the varistor voltage change rate (AVlmA/VlmA) X 100% was calculated separately, and the moisture resistance of the varistor was measured by the varistor voltage change rate.
  • the varistor voltage of the varistor is lower than 90% before the test, that is, the voltage of the varistor If the rate of change of the sensitive voltage is greater than 10%, the product is judged to be ineffective.
  • the varistor voltage change rate of the obtained varistor of the present invention and the varistor voltage change rate data of the conventional varistor are plotted as shown in Fig. 5.
  • the varistor of the present invention Comparing the varistor voltage change rate curve a of the varistor of the present invention shown in FIG. 5 with the varistor voltage change rate curve b of the conventional varistor, it can be seen that the varistor of the present invention is in a short time. Compared with traditional varistor, it has good moisture resistance. With the increase of test time, the moisture resistance of traditional varistor drops sharply. When the test time is about 2000 hours, the varistor voltage of traditional varistor changes. The rate exceeds 10%, S, the varistor fails; and the varistor of the present invention has relatively stable and good moisture resistance during the test time.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermistors And Varistors (AREA)

Abstract

提供了一种压敏电阻器及制造方法。该压敏电阻器包括压敏电阻芯片（1）、硅橡胶裹封层（2）、绝缘裹封层（3）、电极（5）和电极引线（4），压敏电阻芯片（1）封裹在硅橡胶裹封层（2）内，硅橡胶裹封层（2）封裹于绝缘裹封层（3）内，压敏电阻芯片（1）两侧分别设置一个电极（5），电极（5）上分别设置一根电极引线（4）穿过硅橡胶裹封层（2）和绝缘裹封层（3）延伸到绝缘裹封层（3）外部。该压敏电阻器有效地避免了空气中水汽进入到压敏电阻器内部，有良好的防潮性能，提高了压敏电阻器在使用中，特别是在湿度大的环境中使用的可靠性，并且具有良好的绝缘强度和机械强度；并且，降低了产品生产过程中的能耗，提高了生产设备的利用率和产品的生产效率，也降低了生产管理难度。

Description

一种压敏电阻器及制造方法 技术领域 本发明涉及一种压敏电阻器及制造方法。 背景技术
压敏电阻器是一种限压型保护器件， 利用压敏电阻的非线性特性， 当过电 压出现在压敏电阻的两极间， 压敏电阻可以将电压钳位到一个相对固定的电压 值， 从而实现对后级电路的保护， 广泛应用于各种电子设备中。
压敏电阻器的主要构成部份为压敏电阻芯片， 是以氧化锌为主成份， 添加 氧化铋、 氧化钴等金属氧化物， 在约 liocrc高温下烧结而成的半导体陶瓷， 然 后在陶瓷体上设置电极并悍接金属引线， 最后在电阻芯片外部封装绝缘外壳制 成。 目前， 压敏电阻器的绝缘外壳主要是起绝缘和保护压敏电阻芯片的作用， 由于电极上悍接的金属引线需要穿过绝缘外壳， 会在金属引线与绝缘外壳间留 下间隙； 以及在设计时并未将密封效果作为主要的解决目的， 所以目前的压敏 电阻器产品中， 外壳不能良好的将压敏电阻芯片密封在内， 导致了在实际工作 环境下， 特别是在潮湿的工作环境下， 空气中的水汽会通过绝缘外壳上的间隙 进入到压敏电阻器内部， 附在压敏电阻芯片上。
2003年 《电子元件与材料》 第 7期， 论文 《ZnO压敏电阻器在稳态湿热试验 中的性能变化与分析》文章编号 1001-2028 ( 2003 ) 07-0049-02中， 对氧化锌压 敏电阻器在高温、 高湿和直流负荷作用下性能的稳定性和可靠性进行了试验， 试验结论为： 氧化锌压敏电阻器在经过稳态湿热试验后， 其性能参数均发生变 化， 表现形式是压敏电压的下降和漏电流的增大， 甚至出现报废。 为了解决该 问题， 文章提出两方面的建议： 优化压敏电阻芯片的材质和绝缘外壳的选择。 对于绝缘外壳的选择， 文章选用了优质的环氧包封材料， 使得在压敏电阻芯片 外形成结构致密的裹封层， 有效的保护了压敏电阻器不受湿气的侵入。 目前压 敏电阻器中， 选用的环氧包封材料通常为环氧树脂。 通常为压敏电阻芯片外裹 封一层粉末状的环氧树脂， 固化后形成环氧树脂裹封层， 固化后的环氧树脂具 有良好的物理、 化学性能， 并且介电性能良好、 变定收缩率小、 制品尺寸稳定 性好、 硬度高、 对碱及大部分溶剂稳定等优点， 所以采用环氧树脂作为压敏电 阻器的包封外壳不仅能够阻断大气环境中水汽的渗入， 而且还能起到电气绝缘 作用和保护芯片在运输和使用过程中免受损伤。
但是， 在实际发现， 粉末状环氧树脂固化后的裹封层并不完美， 其内部还 存在许多微孔构成的缺陷， 如果微孔之间贯通就会形成潮气侵入的通道， 从而 影响产品的防潮性能。 另外固化后的环氧树脂裹封层变定收缩率小、 制品尺寸 稳定性好、 硬度高、 与压敏陶瓷芯片之间没有粘接力， 并且固化后的环氧树脂 裹封层与压敏电阻芯片以及金属引线之间的热膨胀系数都不一致， 所以当环境 温度变化循环后， 之间会形成微裂隙， 大气中的水汽会在毛细作用下从金属引 线根部或裹封层的缺陷通道进入裂隙并积聚在那里， 使压敏电阻芯片受潮， 严 重的影响了产品的可靠性， 特别是限制了压敏电阻器在潮湿环境中的使用。
目前， 采用粉末环氧树脂固化作为绝缘裹封层的压敏电阻生产方法是： 首 先在压敏电阻芯片上悍接引线， 然后用有机溶剂清洗悍接引线时涂在压敏电阻 芯片和引线上的助悍剂， 清洗完毕后放入 12CTC的温度下干燥 2个小时， 降温后 将压敏电阻芯片和引线根部涂裹粉末环氧树脂， 最后在 15CTC的温度下固化 1小 时得到压敏电阻器。 在该压敏电阻制造方法中， 芯片在降温过程中容易重新吸 附空气中的水汽， 特别是在湿热的夏季， 严重的影响了干燥歩骤的效果， 所以 悍接了引线的压敏电阻芯片在 120°C高温下干燥 2小时后， 需尽快涂裹粉末环氧 树脂， 否则， 生产的压敏电阻器由于漏电流不合格而产生的不合格产品就会大 幅增加， 严重情况下的批次不合格产品率甚至超过 10% (正常情况下的批次不合 格产品率在 1%以内）。 为了避免这种损失， 在生产中， 特别是在湿热的夏季， 必 须将一批次的产品分成若干个小批次生产。 采用这种小批次生产的方法虽然降 低了产品的不合格率， 但是， 也导致了生产设备的利用率不高、 产量下降、 能 耗增加、 管理难度大等。 发明内容
本发明的目的在于克服现有压敏电阻器由于防潮性能差而导致产品使用性 能下降， 以及生产过程中， 为了保证压敏电阻芯片的干燥效果， 需要设置单独 的干燥歩骤， 并在干燥歩骤后需要及时进行下一歩骤， 导致的生产设备利用率 不高、 产量低、 能耗高、 管理难度大等不足提供一种压敏电阻器及制造方法。 本发明的压敏电阻器及制造方法， 有效的避免了空气中水汽进入到压敏电阻器 内部， 有良好的防潮性能， 提高了压敏电阻器在使用中， 特别是在湿度大的环 境中使用的可靠性， 而且还具有良好的绝缘强度和机械强度； 并且， 降低了生 产过程中的能耗， 提高了生产设备的利用率和产品的生产效率， 也降低了生产 管理难度。
为了达到上述目的， 本发明提供了以下技术方案：
一种压敏电阻器， 包括压敏电阻芯片、 硅橡胶裹封层、 绝缘裹封层、 电极 和电极引线， 所述压敏电阻芯片封裹在硅橡胶裹封层内， 所述硅橡胶裹封层封 裹于绝缘裹封层内， 所述压敏电阻芯片两侧分别设置一个电极， 所述电极上分 别设置一根电极引线穿过硅橡胶裹封层和绝缘裹封层延伸到绝缘裹封层外部。 本发明的压敏电阻器， 先将压敏电阻芯片连同电极引线一起封裹在硅橡胶 裹封层内， 然后再连同硅橡胶裹封层一起封裹于绝缘裹封层内部。 所述的硅橡 胶裹封层优先采用常温固化单组分硅橡胶涂覆在压敏电阻芯片表面， 经过固化 后形成一层具有良好的防潮和电气绝缘性能的裹封层， 与粉末状环氧树脂固化 形成的裹封层相比， 其内部缺陷少， 质地也更加致密； 同时， 由于硅橡胶裹封 层能牢固地粘结在压敏电阻芯片和电极引线上， 而自身又具有良好的塑性和韧 性， 所以， 在内部压敏电阻芯片和外部绝缘裹封层因温度循环变化而体积发生 改变时， 硅橡胶裹封层都能够随同一起发生变化， 进而不会在接触面之间产生 微裂隙， 不为水汽提供侵入和积聚的条件， 有效地防止了压敏电阻芯片受潮劣 化。
本发明压敏电阻器的生产方法为：
( 1 )在压敏电阻芯片两侧分别设置一块电极， 并在所述电极上分别悍接一 根电极引线；
(2)在所述压敏电阻芯片、 电极和电极引线根部浸涂常温固化单组分硅橡 胶；
(3) 室内自然放置 4小时以上固化， 固化时常温固化单组分硅橡胶吸收所 述压敏电阻芯片、 电极和电极引线根部上的水份， 使得固化后得到内部干燥的 硅橡胶裹封层；
(4) 在所述硅橡胶裹封层和电极引线 4根部涂裹一层粉末状的环氧树脂；
(5)在 15CTC的温度下固化环氧树脂 1小时， 固化后形成绝缘裹封层， 得到 压敏电阻成品。
进一歩的， 所述压敏电阻器的生产方法中， 若所述歩骤 （1 ) 中悍接电极与 电极引线时采用的助悍剂不是免洗助悍剂， 则在所述歩骤 （1 ) 与歩骤 （2 ) 之 间设置用有机溶剂清洗悍接引线时涂在压敏电阻芯片和引线上的助悍剂的歩 骤；
由于硅橡胶本身的性质决定， 在固化过程中要吸收水份来参与固化， 因此 在生产中不需要单独的设置压敏电阻芯片干燥歩骤， gp， 在压敏电阻芯片涂覆 硅橡胶和接下来的固化过程中， 压敏电阻芯片表面吸附的水分子会被硅橡胶涂 层夺走并参与到硅橡胶裹封层的固化反应中。 所以， 固化过程同时也是一个干 燥过程。 固化过程结束后， 压敏电阻芯片表面已经被致密的硅橡胶裹封层包裹， 不再与空气接触， 这种状态下的压敏电阻芯片长时间放置后再进行下道歩骤也 不会对产品质量有任何影响， 实现了产品的大批量生产， 特别是夏季湿热的环 境条件下的大批量生产， 提高了生产设备的利用率和产品的生产效率， 也降低 了生产管理难度。
本发明的压敏电阻器中， 所述硅橡胶裹封层厚度为 0. 01〜lmm。
进一歩的， 所述硅橡胶裹封层厚度为0. 05〜0. 3111111。 本发明的压敏电阻器中， 所述绝缘裹封层是在硅橡胶裹封层外封裹一层粉 末状的环氧树脂， 固化后形成的环氧树脂裹封层。 固化后的环氧树脂裹封层具 有良好的物理、 化学性能， 并且介电性能良好、 变定收缩率小、 硬度高和对碱 及大部分溶剂稳定等优点， 所以采用环氧树脂作为压敏电阻的绝缘裹封层能够 阻断大气环境中水汽渗入压敏电阻器内部， 而且还能起到电气绝缘以及在运输 和使用过程中保护压敏电阻芯片和硅橡胶裹封层的作用。
本发明的压敏电阻器， 采用了在固化时能吸收水汽， 并且固化后具有良好 的塑性和韧性以及质地紧密、 缺陷少、 能与压敏电阻芯片和电极引线牢固粘结 的硅橡胶作为压敏电阻芯片的裹封层， 使得压敏电阻器生产中， 不需要单独的 设置压敏电阻芯片干燥歩骤， gp， 在压敏电阻芯片涂覆硅橡胶和接下来的固化 过程中， 压敏电阻芯片表面吸附的水分子会被硅橡胶涂层夺走并参与到硅橡胶 裹封层的固化反应中。 所以， 固化过程同时也是一个干燥过程。 固化过程结束 后， 压敏电阻芯片表面已经被致密的硅橡胶裹封层包裹， 不再与空气接触， 这 种状态下的压敏电阻芯片长时间放置后再进行下道歩骤也不会对产品质量有任 何影响， 实现了产品的大批量生产， 特别是夏季湿热的环境条件下的大批量生 产， 提高了生产设备的利用率和产品的生产效率， 也降低了生产管理难度； 在 使用过程中， 阻断了大气环境中水汽的渗入， 有效的防止了压敏电阻器因为压 敏电阻芯片受潮而导致的电参数下降， 甚至报废的情况。
本发明的压敏电阻器， 由于采用硅橡胶作为压敏电阻器内部压敏电阻芯片 的裹封层， 由于固化后的硅橡胶过于柔软， 所以不能保护自身以及内部的压敏 电阻芯片免受机械损伤。 因此， 在硅橡胶裹封层外部采用固化后具有良好的物 理、 化学性能， 并且介电性能良好、 变定收缩率小、 硬度高和对碱及大部分溶 剂稳定等优点的环氧树脂进行封裹， 形成的环氧树脂裹封层保护了压敏电阻芯 片和硅橡胶裹封层在运输和使用过程中免受机械损伤， 并且进一歩的提高了压 敏电阻器的电气绝缘和防潮性能。
与现有技术相比， 本发明的有益效果为：
( 1 )本发明的压敏电阻器， 有效的避免了空气中水汽进入到压敏电阻器内 部， 有良好的防潮性能， 提高了压敏电阻器在使用过程中， 特别是在湿度大的 环境中的使用的可靠性， 并且具有良好的绝缘强度和机械强度；
( 2 ) 本发明的压敏电阻器， 在生产过程中， 几乎不受环境温度和湿度的影 响， 不需要单独的设置压敏电阻芯片干燥歩骤， 实现了产品的大批量生产， 特 别是夏季湿热的环境条件下的大批量生产， 提高了生产设备的利用率和产品的 生产效率， 也降低了生产管理难度。
附图说明： 图 1为本发明的压敏电阻器结构示意图； 图 2为本发明压敏电阻芯片与电极引线连接示意图； 图 3为本发明的压敏电阻器外形示意图； 图 4为传统压敏电阻器结构示意图； 图 5为本发明的压敏电阻器与传统压敏电阻器潮湿试验数据曲线对比图。 图中标记： 1-压敏电阻芯片， 2-硅橡胶裹封层，3-绝缘裹封层， 4-电极引线， 5-电极， a-本发明的压敏电阻器压敏电压变化率曲线， b-传统的压敏电阻器压 敏电压变化率曲线。 具体实施方式 下面结合试验例及具体实施方式对本发明作进一歩的详细描述。 但不应将 此理解为本发明上述主题的范围仅限于以下的实施例， 凡基于本发明内容所实 现的技术均属于本发明的范围。 实施例 本实施例为： 制造本发明的压敏电阻器。 如图 1和 2所示，在压敏电阻芯片 1两侧分别设置一块电极 5， 并在所述电 极 5上分别悍接一根电极引线 4，然后用有机溶剂清洗悍接引线 4时涂在压敏电 阻芯片 1和引线 4上的助悍剂 （若助悍剂为免清洗助悍剂， 则不需清洗）， 晾干 后在所述压敏电阻芯片 1、电极 5和电极引线 4根部涂覆常温固化单组分硅橡胶， 室内自然放置 4 小时以上固化， 固化时常温固化单组分硅橡胶吸收所述压敏电 阻芯片 1、 电极 5和电极引线 4根部上的水分， 使得固化后得到内部干燥的硅橡 胶裹封层 2，最后在所述硅橡胶裹封层 2和电极引线 4根部涂裹一层粉末状的环 氧树脂， 在 15CTC的温度下固化环氧树脂 1小时， 固化后形成绝缘裹封层 3， 得 到如图 3所示的压敏电阻成品。 在制造中， 采用硅橡胶封裹压敏电阻芯片和引线根部， 固化得到硅橡胶裹 封层 2， 由于硅橡胶在固化时要吸收水分子参与反应， 所以在固化过程中要吸收 水份来参与固化， 因此在生产中不需要单独的设置压敏电阻芯片 1的干燥歩骤， 即， 在压敏电阻芯片 1和引线 4根部上涂覆硅橡胶和接下来的固化过程中， 压 敏电阻芯片 1表面和引线 4根部吸附的水分子会被硅橡胶涂层夺走并参与到硅 橡胶裹封层 2的固化反应中。 固化过程结束后， 压敏电阻芯片 1表面已经被致 密的硅橡胶裹封层 2包裹， 不再与空气接触， 这种状态下的压敏电阻芯片 1长 时间放置后再进行下道歩骤也不会对产品质量有影响， 实现了产品的大批量生 产， 特别是夏季湿热的环境条件下的大批量生产， 提高了生产设备的利用率和 产品的生产效率， 也降低了生产管理难度； 在使用过程中， 阻断了大气环境中 水汽的渗入， 有效的防止了压敏电阻器因为压敏电阻芯片受潮而导致的电参数 下降， 甚至报废的情况。 在使用中， 最外层的绝缘裹封层 3采用环氧树脂制成， 具有良好的电气绝 缘性能和较高的强度和硬度， 能够保护内部的硅橡胶裹封层 2、 压敏电阻芯片 1 和电极 5不受机械损伤， 同时阻止了空气中水汽进入到压敏电阻器芯片上 1 ; 在 温度循环变化的环境下， 由于绝缘裹封层 3、 压敏电阻芯片 1、 电极 5和电极引 线 4热膨胀系数不一致， 导致在接触面之间形成微裂隙， 但是在绝缘裹封层 3 与压敏电阻芯片 1、 电极 5和电极引线 4的根部之间拥有一层柔软、致密并且具 有良好粘接性的硅橡胶裹封层 2， 能够牢固的粘结在压敏电阻芯片 1、 电极 5和 电极引线 4的根部上， 阻止了经绝缘裹封层 3渗入的水汽， 使压敏电阻芯片保 持干燥。 对比例：
本对比例为： 制造传统压敏电阻器。
传统压敏电阻器结构如图 4所示， 在压敏电阻芯片 1两侧分别设置一块电 极 5， 并在所述电极 5上分别悍接一根电极引线 4， 然后用有机溶剂清洗悍接引 线 4时涂在压敏电阻芯片 1和引线 4上的助悍剂 （若助悍剂为免清洗助悍剂， 则不需要清洗）， 清洗完毕后放入 12CTC的温度下干燥 2个小时， 降温后将压敏 电阻芯片和引线根部涂裹粉末环氧树脂，最后在 15CTC温度下固化 1小时得到环 氧树脂裹封层 3， 得到压敏电阻器。
在该压敏电阻器制造方法中， 因为压敏电阻芯片 1 在降温过程中是容易重 新吸附空气中的水汽而， 特别是在湿热的夏季， 严重的影响了干燥歩骤的效果， 所以悍接了引线 4的压敏电阻芯片 1在 12CTC高温下干燥 2小时后，需尽快涂裹 粉末环氧树脂， 否则， 生产的压敏电阻器由于漏电流不合格而产生的不合格产 品就会大幅增加， 严重情况下的批次不合格产品率甚至超过 10% (正常情况下的 批次不合格产品率在 1%以内）。
在该压敏电阻器使用过程中， 由于环氧树脂固化后的环氧树脂裹封层 3 内 部存在许多微孔构成的缺陷， 如果微孔之间贯通就会形成潮气侵入的通道， 从 而影响产品的防潮性能。 另外固化后的环氧裹封层 3 变定收缩率小、 制品尺寸 稳定性好、 硬度高、 与压敏电阻芯片 1 之间没有粘接力， 并且固化后的环氧树 脂裹封层 3与压敏电阻芯片 1以及引线 4之间的热膨胀系数都不一致， 所以当 环境温度变化循环后， 之间会形成微裂隙， 大气中的水汽会在毛细作用下从引 线 4根部或环氧树脂裹封层 3的缺陷通道进入裂隙并积聚在压敏电阻内部， 使 压敏电阻芯片 1 受潮， 严重的影响了产品的可靠性， 特别是限制了压敏电阻器 在潮湿环境中的使用。
将本发明的压敏电阻器与传统压敏电阻器在温度为 40±2°C，相对湿度大于 95%的环境中放置 3000小时， 每 500小时测试一次电参数并记录。 分别计算其 压敏电压变化率= ( AVlmA/VlmA) X 100%, 并记录， 以压敏电压变化率衡量压 敏电阻器的防潮性能。
根据美国国家标准 《浪涌保护器压敏电阻 IEEE 标准测试规范》 ANSI/IEEEC62. 33-1982， 规定压敏电阻器的压敏电压低于测试前的 90%为失效， 即压敏电阻的压敏电压变化率大于 10%, 则判定产品失效。
将得到的本发明的压敏电阻器的压敏电压变化率与传统压敏电阻器的压敏 电压变化率数据绘制如图 5所示的曲线图。
比较如图 5所示的本发明的压敏电阻器的压敏电压变化率曲线 a与传统压 敏电阻器的压敏电压变化率曲线 b， 可知， 在短时间内本发明的压敏电阻器与传 统压敏电阻器都有良好的防潮性能， 随着测试时间的增长， 传统压敏电阻器的 防潮性能急剧下降， 到测试时间为 2000小时左右的时候， 传统压敏电阻器压敏 电压变化率超过 10%, S , 压敏电阻器失效； 而本发明的压敏电阻器在测试时间 内都具有较稳定的并且良好的防潮性能。
通过实施例与对比例的比较， 可知， 本发明的压敏电阻器的防潮能力较传

Claims

权 利 要 求 书
1、 一种压敏电阻器， 包括压敏电阻芯片、 绝缘裹封层、 电极和电极引线， 所述 压敏电阻芯片两侧分别设置一个电极并封裹在绝缘裹封层内， 所述电极上各设 置一根引线并穿过所述的绝缘裹封层延伸到绝缘裹封层外部， 其特征在于， 所 述压敏电阻芯片与所述绝缘裹封层之间还设置有硅橡胶裹封层。
2、 如权利要求 1所述的一种压敏电阻器， 其特征在于， 所述绝缘裹封层为采用 环氧树脂固化制得。
3、 如权利要求 1或 2任意一项所述的一种压敏电阻器， 其特征在于， 所述硅橡 胶裹封层为采用常温固化单组分硅橡胶制得。
4、 如权利要求 1所述的一种压敏电阻器， 其特征在于， 所述硅橡胶裹封层厚度 为 0. 01〜： Lmm。
5、 如权利要求 4所述的一种压敏电阻器， 其特征在于， 所述硅橡胶裹封层厚度 为 0. 05〜0. 3mm
6、 一种制造权利要求 1所述的压敏电阻器的方法， 包含如下歩骤：
( 1 ) 悍接压敏电阻芯片引线；
( 2 ) 浸涂硅橡胶；
( 3 ) 固化硅橡胶；
( 4) 涂裹粉末环氧树脂；
( 5 ) 固化环氧树脂。
7、 如权利要求 6所述的方法， 其特征在于， 所述歩骤 （1 ) 和歩骤 （2 ) 之间还 设置有清洗除去助悍剂歩骤。
8、 如权利要求 7所述的方法， 其特征在于， 所述压敏电阻器制造方法歩骤 （2 ) (3)
(5)
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