KR20060025839A - Electrical device having ptc conductive polymer - Google Patents

Abstract

The present invention relates to an electrical device comprising a PTC conductive polymer sheet and first and second electrodes in physical contact with opposite sides of the conductive polymer sheet. The first and second electrodes include a plurality of protrusions protruding from the surface, the surface roughness (Rz) of the electrode by 1 to 20㎛, the average width (Rw) of the 0.5 to 2 times the surface roughness Rz, and the average spacing Rg between adjacent protrusions is 0.5 to 2 times the surface roughness Rz. In addition, the thickness of the conductive polymer sheet is preferably at least five times the surface roughness (Rz).

PTC, Surface Roughness, Average Width, Average Spacing

Description

ELECTRICAL DEVICE HAVING PTC CONDUCTIVE POLYMER}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a perspective view of a PTC electric apparatus according to a preferred embodiment of the present invention.

2 is a cross-sectional view of an electrode applied to the apparatus of FIG. 1.

The present invention relates to an electrical device including a PTC (Positive Temperature Coefficient) conductive polymer, and more particularly, to a light and short PTC electric device having excellent bonding force between a conductive polymer and an electrode and no breakdown at the time of bonding. .

Electrical devices comprising PTC conductive polymers are well known. The conductive polymer is a conductive filler dispersed in the organic polymer and exhibits PTC characteristics. The PTC characteristic means that the electrical resistance rapidly increases in a narrow temperature range, and the polymer material having the PTC characteristic is applied to a constant temperature wire, an overcurrent protection device, a circuit protection device, and a heater.

Such conductive polymers are mechanically and chemically bonded to at least one or more electrodes in an electrical device, which is usually a metal plate. Examples of such devices are described in US Pat. Nos. 4,426,633 (Taylor), 4,689,475 (Matthiesen), 4,800,253 (Kleiner et al), 4,857,880 (Au et al), 4,907,340 (Fang et al), and 4,426,633 Fang et al.

The adhesion between the metal electrode and the polymer can be largely divided into mechanical and chemical adhesion. In order to improve the mechanical adhesion, a manufacturing process that can suppress the separation between the metal sheet and the polymer by increasing the surface roughness of the metal sheet is performed. need.

U.S. Patent Nos. 4,689,475 and 4,800,253 use metal plates having fine surface roughness as electrodes to increase adhesion to conductive polymers. In particular, US Pat. No. 4,689,475 limits the height and width of the protrusions formed on the surface of the electrode to an appropriate size in order to increase the bonding force with the polymer. In addition, US Pat. No. 4,800,253 uses a metal sheet having a fine surface roughness including a macronodule formed by a plurality of micronodules as an electrode.

In addition, US Pat. No. 5,874,885 uses a metal plate consisting of a base layer, an intermediate layer and a surface layer as an electrode in contact with a conductive polymer.

As electronic devices become lighter and shorter in recent years, the size of PTC devices is also decreasing. As such, in order to reduce the size of the PTC device, the thickness of the conductive polymer sheet interposed between the electrodes must be set to be thin. If the thickness of the conductive polymer sheet is thin, a protrusion such as nodule or irregularity formed on the surface of the opposing electrode may come into contact with or come into contact with each other, which may cause breakdown. .

In addition, when the size of the nodule or irregularity is set smaller as the thickness of the conductive polymer sheet becomes thinner, the mechanical bonding force between the electrode and the conductive polymer is lowered.

Therefore, it is necessary to appropriately adjust the thickness of the conductive polymer suitable for the PTC device applied to the light and thin element and the height, width, and spacing of the nodule or irregularity formed on the surface of the electrode.

However, none of the above patents suggests optimum values for the protrusion height, width and spacing of the protrusions that can be easily and sufficiently secured to a relatively thin conductive polymer without breakdown and air gaps. I'm not doing it.

The present invention was devised to solve the above problems, and an object of the present invention is to increase the mechanical bonding force between a relatively thin conductive polymer and an electrode without an air gap without causing a breakdown problem. To provide roughness of the electrode surface.                         

To achieve the above object, an electrical apparatus according to one aspect of the present invention includes a PTC conductive polymer sheet and first and second electrodes in physical contact with opposite surfaces of the conductive polymer sheet.

The first and second electrodes include a plurality of protrusions protruding from the surface, the surface roughness (Rz) is 1 ~ 20㎛ by these projections, the average width (Rw) is the surface roughness ( Rz) is 0.5 to 2 times, and the average spacing Rg between adjacent protrusions is 0.5 to 2 times the surface roughness Rz. In addition, the first and second electrodes comprise a base layer of a first metal having a microrough surface and a surface layer of a second metal coated with a uniform thickness on the base layer. Is characterized in that the chemical bonding force to the conductive polymer is relatively superior to the first metal. In addition, the thickness of the conductive polymer sheet is preferably at least five times the surface roughness (Rz).

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

As shown in Fig. 1, the electric device 1 of the present invention is characterized by a conductive polymer sheet 7 having PTC characteristics and a metal electrode 3, 5 plated with a metal having excellent compatibility with the polymer. Include. At this time, the conductive polymer 7 is preferably sandwiched between the metal electrodes (3, 5) sandwiched and fused.

The conductive polymer composition is obtained by mixing an organic polymer with a conductive filler, a crosslinking agent, an antioxidant, and the like. In this case, as the organic polymer, polyethylene, polypropylene or ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-butyl acrylate copolymer and the like may be used, and polyethylene is particularly preferable. .

As the conductive filler, nickel powder, gold powder, copper powder, silver plated copper powder, metal alloy powder, carbon black, carbon powder or graphite may be used, and carbon black is particularly preferable.

In addition, as shown in FIG. 2, the metal electrode includes a base layer 9 made of a first metal, and a second metal interposed between the base layer 9 and the conductive polymer 7 to be in direct contact with the conductive polymer. Surface layer 13. Copper, aluminum, zinc, nickel, and the like may be used as the first metal, and copper is particularly preferable. In addition, the second metal has better compatibility with the conductive polymer than the first metal, and serves as a diffusion barrier for preventing the base layer from contacting with the polymer and causing the polymer to degrade. Works. Nickel, zinc, etc. are all possible as said 2nd metal, but nickel is especially preferable.

A plurality of protrusions 11 are formed on the surface of the base layer 9 to increase the mechanical bonding force with the conductive polymer. The micro-roughness of this base layer is formed by an electrodeposition process. In addition, the surface layer 13 of the present invention is formed on the surface of the base layer 9 on which the plurality of protrusions 11 are formed to have a uniform thickness through electroplating or electroless plating. In particular, the nickel surface layer 13 is preferably made through electroless plating. In the case of electroless plating, the process is performed by degreasing, pickling, activation and sensitization, electroless nickel plating, and washing with water. The thickness of the surface layer 13 according to the present invention is preferably about 0.1 ~ 5㎛. As such, plating nickel with a uniform thickness on the surface of the base layer on which the protrusions are formed can prevent degradation of the conductive polymer and corrosion of the electrolytic copper foil caused by direct contact between the conductive polymer and the base layer. Further, as a result, the chemical bonding force with the conductive polymer 7 can be increased without spoiling the surface roughness of the base layer 9. At this time, when the thickness of the surface layer 13 is 0.1 μm or less, the corrosion prevention effect is inferior, and when the thickness is 5 μm or more, the surface roughness of the base layer 9 may be impaired, thereby decreasing the bonding strength.

The protrusions 11 must be artificially adjusted in size. When the conductive polymer sheet 7 is thin in thickness, sufficient mechanical coupling force is ensured without opposing protrusions contacting each other so that breakdown does not occur. The protrusion degree Rz and the average width Rw should be set so as to be possible.

In the above, the projections 11 include one or more floors higher than 3/4 of the minimum surface roughness Rz, and the lowest valley among the valleys lower than 1/4 of the surface roughness Rz located on one side of the floor. It consists of the part from the lower part of the valley lower than 1/4 of the surface roughness (Rz) located on the other side of the floor.

Surface roughness (Rz) is 1 ~ 20㎛ by the protrusions 11, the average width (Rw) (average width) is 0.5 to 2 times or more preferably 1 to 1.5 of the surface roughness (Rz) It is good to be double. In addition, the average width Rw means the shortest distance between two points where the center line X and the curved surface of the protrusion meet each other as shown in FIG. 2. The center line X refers to an imaginary line that is set such that the sum of squares of the deviations of the distances from the cross-sectional curve of the surface layer 13 is minimized. At this time, when the surface roughness Rz is 1 μm or less, the protrusions are not sufficiently inserted in the conductive polymer, and thus the mechanical bonding force is lowered. There is a problem that a gap (air-gap) occurs. In addition, when the average width Rw is 0.5 times or less of the surface roughness Rz, the projections are easily broken during the adhesion process of the polymer and the metal electrode, and when the average width Rw is 2 times or more, the projections are not easily inserted into the polymer. .

In addition, the protrusions formed on the surface of the metal electrode according to the present invention should be spaced at regular intervals, for example, the average gap (Rg) between adjacent protrusions is 0.5 of the surface roughness (Rz). ~ 2 times is preferred, and more preferably 1 to 1.5 times the surface roughness (Rz).

Here, the average interval Rg means the shortest distance between two adjacent protrusions between the points where the curved surfaces of the protrusions meet with the center line X closest to each other.

When the average spacing Rg according to the present invention is 0.5 times or less of the surface roughness Rz, an air gap occurs during the bonding process of the polymer and the metal electrode, and when the average spacing Rg is 2 times or more, protrusion is performed. Due to the lack of support force, the bonding force between the polymer and the metal electrode is reduced.

In addition, the conductive polymer sheet 7 should have a thickness that exhibits sufficient PTC characteristics without breakdown due to the recent flow of electronic devices that are becoming thin and short. The thickness of the conductive polymer sheet 7 according to the present invention is preferably at least five times the surface roughness Rz.

Hereinafter, the present invention will be described in detail with reference to specific examples.

Example 1

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrode was manufactured by forming an electroless nickel plating layer having a thickness of 0.5 μm on the surface of the electrolytic copper foil by degreasing, pickling, activating and sensitizing, electroless nickel plating and washing with water. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 5 μm, and the average interval between adjacent protrusions is 5 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 2

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 10 μm, and the average interval between adjacent protrusions is 10 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 3

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 100 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrode was prepared by forming an electroless nickel plating layer having a thickness of 5 μm on the surface of the electrolytic copper foil by degreasing, pickling, activating and sensitizing, electroless nickel plating and washing with water. In this case, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 20 μm, and the average interval between adjacent protrusions is 20 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 4

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 100 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. Further, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 3 μm on the surface of the electrolytic copper foil to prepare an electrode. In this case, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 20 μm, and the average interval between adjacent protrusions is 5 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 5

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 100 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrode was manufactured by forming an electroless nickel plating layer having a thickness of 0.5 μm on the surface of the electrolytic copper foil by degreasing, pickling, activating and sensitizing, electroless nickel plating and washing with water. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 5 μm, and the average interval between adjacent protrusions is 20 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 6

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 100 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrode was prepared by forming an electroless nickel plating layer having a thickness of 0.1 μm on the surface of the electrolytic copper foil by degreasing, pickling, activating and sensitizing, electroless nickel plating and washing with water. In this case, the surface roughness Rz of the protrusions formed on the surface of the electrode is 1 μm, the average width is 1 μm, and the average interval between adjacent protrusions is 1 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Example 7

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 100 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrode was prepared by forming an electroless nickel plating layer having a thickness of 5 μm on the surface of the electrolytic copper foil by degreasing, pickling, activating and sensitizing, electroless nickel plating and washing with water. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 20 μm, the average width is 20 μm, and the average interval between adjacent protrusions is 20 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Comparative Example 1

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. In this case, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 3 μm, and the average interval between adjacent protrusions is 10 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Comparative Example 2

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. In this case, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 30 μm, and the average interval between adjacent protrusions is 10 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Comparative Example 3

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 10 μm, and the average interval between adjacent protrusions is 3 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Comparative Example 4

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 50 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 10 μm, and the average interval between adjacent protrusions is 30 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Comparative Example 5

Polyethylene and carbon black (100 phr) were mixed to prepare a PTC conductive polymer sheet having a thickness of 30 μm, a width of 5 mm, and a length of 10 mm. An electrolytic copper foil having a plurality of protrusions formed on its surface was prepared through electrolytic plating. In addition, the electrolytic copper foil was degreased, pickled, activated and sensitized, electroless nickel plated, and washed with water to form an electroless nickel plated layer having a thickness of 1 μm on the surface of the electrolytic copper foil to prepare an electrode. At this time, the surface roughness Rz of the protrusions formed on the surface of the electrode is 10 μm, the average width is 10 μm, and the average interval between adjacent protrusions is 10 μm. The electrode was welded to both sides of the conductive polymer sheet in the form of a sandwich to manufacture a PTC electrical apparatus as shown in FIG. 1.

Test Example

(1) Peel Strength, (2) Resistance Characteristics according to PTC Thickness, and (3) PTC Thickness for Electrical Devices Prepared According to Examples 1-7 and Comparative Examples 1-5 Breakdown Voltage characteristics, (4) resistance characteristics after Humidity Aging Test according to PTC thickness, and (5) resistance characteristics after Solder heat withstand test according to PTC thickness were measured and the results are shown in Table 1 below. Illustrated in

At this time, the peel strength was measured by measuring the peak strength at the time of peeling by measuring the mechanical bonding force between the conductive polymer sheet and the electrode. The resistance of the PTC increases and decreases with the thickness of the conductive polymer sheet, thus dividing the measured resistance by the thickness of the conductive polymer sheet, thereby eliminating the dependency on the thickness of the conductive polymer sheet. In the breakdown voltage measurement, the physical properties were obtained by dividing the measured value by the thickness of the conductive polymer sheet, and the rising rate of the voltage during the measurement was 10 V / min. Humidity Aging Test is performed at 85 ℃, 9 5% RH (relative humidity) For 10,000 hr, the solder heat withstand test was performed for 10 sec at 210 ° C., and then the resistance was measured to express the value divided by the thickness of the conductive polymer sheet.

A (kgf) B (mΩ / mm) C (V / mm) D (mΩ / mm) E (mΩ / mm) Example 1 1.5 150 250 160 230 Example 2 1.6 140 270 140 210 Example 3 1.4 155 260 150 220 Example 4 1.4 155 270 160 230 Example 5 1.5 150 270 160 225 Example 6 1.4 160 310 150 250 Example 7 1.6 145 260 155 200 Comparative Example 1 1.5 150 250 250 260 Comparative Example 2 0.6 200 260 185 340 Comparative Example 3 1.4 160 270 165 400 Comparative Example 4 0.5 190 240 190 255 Comparative Example 5 1.5 155 120 160 230

[Here, A: peel strength (kgf), B: resistance / PTC thickness (mΩ / mm), C: breakdown voltage / PTC thickness (V / mm), D: resistance / PTC thickness (mΩ / after Humidity Aging Test) mm), E: Resistance after solder heat withstand test / PTC thickness (mΩ / mm)]

As can be seen from Table 1, Comparative Example 2 and Comparative Example 4 has a significantly lower peel strength and relatively high room temperature resistivity compared to the Examples of the present invention. In addition, the case of Comparative Example 5 is lower than the breakdown voltage (breakdown voltage) compared to the embodiment of the present invention. In addition, Comparative Example 1 can be confirmed that the specific resistance after the Humidity Aging test is higher than the embodiment of the present invention, Comparative Example 2 and Comparative Example 3 is higher than the embodiment of the present invention after the solder heat withstand test.

As described above, the electric device of the present invention has superior bonding force between the conductive polymer and the metal electrode, low interfacial resistance, suitable for corrosion prevention and air gap prevention as well as breakdown phenomenon, compared to the comparative device. Also prevents.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical spirit of the present invention and the following will be understood by those skilled in the art to which the present invention pertains. Various modifications and variations are possible, of course, within the scope of equivalents of the claims to be described.

The PTC electrical apparatus according to the present invention can increase the bonding force between the conductive polymer and the metal electrode and minimize the breakdown phenomenon while minimizing the thickness of the conductive polymer. In addition, the bonding of the conductive polymer and the metal electrode may have an excellent mechanical or chemical bonding force while preventing air gaps due to nodules or nonuniformities on the electrode surface.

Claims (6)

An electrical device comprising a PTC conductive polymer sheet and first and second electrodes in physical contact with opposite sides of the conductive polymer sheet, (A) the first and second electrodes comprise a plurality of protrusions protruding from the surface; (B) The protrusions have a surface roughness Rz of 1 to 20 μm, an average width of 0.5 to 2 times the surface roughness Rz, and an average gap between adjacent protrusions. 0.5 to 2 times the surface roughness Rz, (C) the first and second electrodes comprise a base layer of a first metal having a microrough surface and a surface layer of a second metal plated on the base layer with a uniform thickness; (D) the second metal has a relatively better chemical bonding force to the conductive polymer than the first metal; (E) The electric device, characterized in that the thickness of the conductive polymer sheet is at least five times the surface roughness (Rz). The method of claim 1, Wherein said first metal is copper and said second metal is nickel. The method of claim 2, And a base layer having a microrough surface is formed by an electrodeposition process, and the surface layer is formed by electroless plating. The method of claim 3, wherein Electrical apparatus characterized in that the average width (Rw) of the projections is 1 to 1.5 times the surface roughness (Rz). The method of claim 3, wherein The average distance (Rg) of the projections is characterized in that the electric device 1 ~ 1.5 times the surface roughness (Rz). The method of claim 3, wherein The thickness of the surface layer is an electric device, characterized in that 0.1 ~ 5㎛.

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