KR100681394B1 - Thermistor bare chip and Method for making the same - Google Patents

Abstract

The thermistor bare chip according to the present invention comprises a ceramic body, a silver layer printed on opposite ends of the ceramic body, and a double electrode of a gold layer laminated on the silver layer by vapor deposition. In printing silver on the ceramic body and again depositing gold on it, manufacturing cost can be reduced by thinning the expensive gold layer and thickening the low-cost silver layer, securing a certain thickness with silver, and finally, precisely thicknessing with gold. In addition, it is possible to prevent the oxidation of the electrode surface by exposing the gold layer to the external environment, and by applying a silver paste to the ceramic body by printing method, the ceramic body and the silver layer are formed by using the glass particles contained in the silver paste. There is an advantage that can be tightly combined.

Thermistor, ceramic semiconductor, external electrode, surface oxidation, Au, Ag, thickness control

Description

Thermistor bare chip and Method for making the same             

1 is a perspective view illustrating a thermistor bare chip according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a final completed thermistor by applying the thermistor bare chip of FIG. 1. FIG.

3 is a flowchart illustrating a method of manufacturing a thermistor bare chip according to an embodiment of the present invention.

The present invention relates to a thermistor bare chip and a method of manufacturing the same. More specifically, the electrode to which the conductive lead is connected from the outside is formed by laminating different metals using different processes to prevent oxidation of the electrode by an external environment. The present invention relates to a thermistor bare chip and a method of manufacturing the same.

Thermistor acts as a sensor that senses temperature in electrical and electronic circuits because its electrical resistance changes with temperature, and is used mainly in products related to temperature control and temperature protection. Due to these characteristics, thermistors must maintain high precision and reliability, and must also withstand external environmental changes.

Referring to the structure of a general thermistor, a thermistor bare chip consisting of a ceramic semiconductor body having a characteristic of changing temperature as a change in electrical resistance and a pair of opposed electrodes formed on the surface of the body, and a pair of electrodes Each of the conductive leads and thermistor bare chips connected to each other, and a protective film surrounding and protecting a portion of the conductive leads.

The electrode of the thermistor bare chip was generally used either of gold or silver, and one of these was selected according to the purpose, and the electrode was formed by applying a screen printing method or the like to the opposite ends of the ceramic body in the form of paste. .

In more detail, the silver or gold particles and glass particles are mixed and mixed, a solvent such as toluene is mixed therein to prepare a liquid paste, and then it is applied to the ceramic body by printing.

Subsequently, the solvent is evaporated by drying at 140 ° C. for 20 minutes, and calcined at 650 ° C. for 60 minutes to melt the glass particles and bond them tightly to the ceramic body to form a layer of silver or gold as an electrode.

However, when forming the electrode by such a conventional printing method, there is a problem that it is difficult to adjust the thickness of the electrode made of silver or gold.

In the case of using silver separately, when using silver, the surface is oxidized by the moisture present in the air when the electrode is formed and left at room temperature in a continuous process or in a process atmosphere, thereby increasing the surface resistance. There is a problem in that a precision thermistor having a sensor function cannot be manufactured due to an increase in contact resistance at the time of joining.

Furthermore, in the protective film encapsulation process, which is the final process for manufacturing the thermistor, the silver electrode is oxidized by the high working temperature, thereby increasing the electrical resistance.

In addition, when soldering with the conductive lead, a leaching phenomenon occurs in which silver constituting the electrode comes to the solder by the lead (Pb) component of the solder, thereby causing a problem of contact failure.

In addition, when using gold, there is a problem that the manufacturing cost is excessively increased.

On the other hand, although the deposition method may be used by changing the coating method, there is a fatal weakness that the bonding between the electrode and the ceramic body to be formed is weak. In other words, since a target made of silver or gold is used instead of a silver or gold paste, a technology of melting glass through firing and bonding the ceramic body with a ceramic body cannot be applied.

Moreover, when connecting the conductive lead and the electrode, the thickness of the electrode is generally required to be 10 μm or more for the bonding force between the conductive lead and the electrode. Since the thickness is usually 5 μm or less, the thickness must be at least 10 μm. It is difficult to apply the thermistor electrode.

Accordingly, the present invention is proposed to solve the above-mentioned conventional problems, and an object of the present invention is to prevent the surface of the electrode from being oxidized by the external environment during the process or the process atmosphere and at the same time reduce the manufacturing cost. It is to provide thermistor bare chip.

Another object of the present invention is to provide a manufacturing method for manufacturing the thermistor bare chip.

Other objects and features of the present invention will be more clearly understood through the embodiments described below.

According to the present invention, the two materials, silver and gold, are appropriately applied to the printing method and the vapor deposition method to derive the advantages of the material and the method of the formation method to the maximum.

The thermistor bare chip according to the present invention includes a ceramic body, an electrode composed of a silver layer printed on opposite ends of the ceramic body, and a gold layer laminated on the silver layer by vapor deposition.

Preferably, the thickness of the silver layer is in the range of 10 to 30 μm, and the thickness of the gold layer is in the range of 0.5 to 4 μm.

In addition, the gold layer may be deposited by either vacuum deposition or sputtering.

According to the present invention, the silver paste is printed on opposite ends of the ceramic body, the ceramic body on which the silver paste is printed is dried, the solvent is evaporated, the solvent is evaporated, and the silver body is fixed to the ceramic body by firing the ceramic body. After forming a silver layer, gold is deposited on the silver layer to prepare a thermistor bare chip.

Preferably, the glass particles mixed in the silver paste are melted and fixed to the ceramic body through firing.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a thermistor bare chip according to the present invention.

According to the present invention, the silver layer 20 is printed on both ends of the ceramic body 10, and the gold layer 30 is continuously deposited on the silver layer 20 to form a double layer electrode.

Preferably, the thickness of the silver layer 20 is in the range of 10 to 30 μm, and the thickness of the gold layer 30 is in the range of 0.5 to 4 μm.

Preferably, the silver layer 20 is formed by a printing method, the gold layer 30 is deposited by any one of vacuum deposition or sputtering.

By having such a structure, the layer directly exposed to the external environment is made of gold, and can be prevented from being oxidized by the external environment.

In addition, the thickness of the gold can be made thin by evaporation in a state where a constant thickness is secured with low-cost silver, thereby reducing manufacturing costs and precisely adjusting the final electrode thickness.

FIG. 2 is a perspective view illustrating a final completed thermistor by applying the thermistor bare chip of FIG. 1. FIG.

Conductive leads 50 are bonded to electrodes at both ends of the thermistor bare chip 1 having the structure of FIG. 1 and then encapsulated with a curable polymer or glass protective film 40 to fabricate a thermistor.

3 is a flowchart illustrating a method of manufacturing a thermistor bare chip according to an embodiment of the present invention.

First, silver paste is printed on opposite ends of the ceramic body (step S31). The silver paste is in a liquid state by mixing a solvent in a state in which silver particles and glass particles are mixed. The thickness printed initially can be about 30 micrometers, for example.

After printing the silver paste, the ceramic body is dried to evaporate the solvent (step S32). For example, drying is performed at 140 ° C. for about 20 minutes, whereby volatile components such as toluene are evaporated. As the solvent evaporates, the silver paste has a thickness of approximately 25 μm.

Subsequently, when the ceramic body in which the solvent is evaporated is calcined at about 650 ° C. for about 60 minutes (step S33), the glass particles mixed in the paste are melted and tightly combined with the ceramic body. That is, among the components of the silver paste, silver serves as a conductive material, and glass serves as an adhesive. As the glass particles melt, the layer made of silver has a thickness of about 18 μm.

Subsequently, gold is deposited on the silver layer by adjusting the thickness to about 2 μm (step S34). Vapor deposition may use either a sputtering method or a vacuum deposition method.

Therefore, it can be precisely adjusted to have a thickness of about 20㎛ as a whole, the manufacturing cost can be reduced by thinning the expensive gold layer and thickening the low-cost silver layer.

In addition, it is possible to prevent the oxidation of the surface by exposing the gold layer to the external environment, it is possible to bond firmly by allowing the silver paste to be printed on the ceramic body.

Although the above has been described with reference to the preferred embodiment of the present invention, it can be appropriately changed or modified by those skilled in the art without departing from the spirit of the present invention. It is natural that such changes or modifications fall within the scope of the present invention without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the claims described below.

As described above, the present invention has various advantages.

In printing silver on the ceramic body and depositing gold on it again, the expensive gold layer is thinned and the low cost silver layer is thickened to reduce the manufacturing cost. There is an advantage that can be adjusted.

In addition, it is possible to prevent the oxidation of the surface by exposing the gold layer to the external environment, there is an advantage that can be firmly bonded using the glass particles contained in the silver paste by applying the silver paste to the ceramic body by printing method. .

Claims (8)

In the thermistor bare chip electrically conductive lead is connected to both ends of the ceramic body, and encapsulated in a protective film, The thermistor bare chip, characterized in that the silver (Ag) layer is formed by the printing method on both ends of the ceramic body, the gold (Au) layer is laminated on the silver layer by the vapor deposition method. The thermistor bare chip of claim 1, wherein the thickness of the silver layer is in a range of 10 to 30 μm. The thermistor bare chip of claim 2, wherein the gold layer has a thickness in a range of 0.5 to 4 μm. The thermistor bare chip of claim 1, wherein the gold layer is deposited by either vacuum deposition or sputtering. Printing silver pastes on opposite ends of the ceramic body; Evaporating the solvent by drying the ceramic body on which the silver paste is printed; Firing the ceramic body in which the solvent is evaporated to fix the silver paste to the ceramic body to form a silver layer; And The method of manufacturing a thermistor bare chip comprising the step of depositing gold on the silver layer. 6. The method of claim 5, wherein the glass particles mixed with the silver paste are melted and fixed to the ceramic body through the firing. The method of claim 5, wherein the silver paste is printed so that the thickness of the silver layer is formed in a range of 10 to 30 ㎛. The method of claim 7, wherein the gold layer is deposited to have a thickness in a range of 0.5 to 4 μm.

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