KR20040043687A - method of positive temperature coefficient electrical device for surface mounting - Google Patents

Abstract

PURPOSE: A method is provided to simplify manufacturing procedures by forming an electrode connection path in the positive temperature coefficient(PTC) device. CONSTITUTION: A method comprises a step of preparing a PTC device(30) having two conductive wires(21,22) spaced apart from each other in the PTC device, wherein conductive wires have certain parts exposed to the outside; a step of forming conductive layers on the top and bottom surfaces of the PTC device in such a manner that the conductive layers are electrically connected to the conductive wires; and a step of forming electrically separated first and second electrodes(41,42) by forming non-conductive gaps in the conductive layers.

Description

Method of manufacturing a positive temperature coefficient electrical device for surface mounting

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a surface mount type constant temperature coefficient electrical apparatus, and more particularly, to a surface mount type constant temperature coefficient electrical apparatus mounted on a printed circuit board and serving to protect a circuit.

The resistivity of many conductive materials is known to vary with temperature. Generally referred to as a thermistor, it is classified into a negative temperature coefficient (NTC), which increases resistance as temperature increases, and a positive temperature coefficient (PTC), which increases resistance as temperature increases.

PTC materials are made of a variety of materials, but crystalline polymers are particularly effective that allow electrically conducting electricity by dispersing conductive particles therein. Polymers having such properties include polyethylene, polypropylene, and polyolefins such as ethylene / propylene copolymers.

The PTC material is used as a device for suppressing overcurrent in a circuit board because it has a property of rapidly increasing electric resistance at a specific temperature as described above. For example, under normal operating conditions, the temperature of the load and the PTC device is in equilibrium by being kept below the critical or switching temperature of the PTC device. However, if a short circuit or a power surge occurs in the circuit, a large amount of power is lost in the PTC device and the PTC device becomes unstable. The increased power dissipation results in very high resistance and temperature of the PTC device, but as the resistance and temperature of the PTC device increase, the current flowing through the circuit decreases, protecting other devices. In other words, since the PTC device has a function of reducing the current passing through the device to a safe and relatively low value when heated to a critical temperature range, it is widely used in circuit boards as a resettable fuse.

The PTC thermistor having such properties generally includes a PTC device that is switched between a pair of laminator electrodes. In addition, in order to connect the device to other electrical elements, a terminal is provided and mounted on a printed circuit board.

Referring to FIG. 1, U.S. Patent No. 58,589797 drills through-holes 51 in a PTC sheet laminated on both sides of the PTC element 17 with metal foils 13 and 15, and the front surface of the sheet. The inside of the hole was plated 52 to connect upper and lower metal foils, for example, upper and lower electrodes, and then etched to separate the electrodes. In the present invention, the through hole is used as an electrical connection passage of the upper and lower electrodes.

In addition, referring to FIG. 2, US Pat. No. 5,843,84391 forms a long slit in place of a hole in a PTC sheet, and connects the upper and lower electrodes by plating 150 the entire surface including the slit cross section. Thereafter, the upper and lower electrodes are separated by etching, and a solder resist 120 and a solder plating 180 are applied to form both electrodes. The present invention is characterized by using a slit as an electrical connection passage of the upper and lower electrodes, instead of the hole, unlike the US patent.

Meanwhile, as another conventional example, U.S. Patent No. US5699607 shown in FIG. 3 forms a long slit in a PTC sheet, first applies a solder resist 120 to the entire surface of the sheet including the slit cross section, and gaps in a portion of the solder resist. 130 is formed to expose the metal foil of the PTC sheet, for example, the electrode 90, and then plated at both ends. The present invention is characterized in that, unlike the above two inventions, a portion of the solder resist applied first is removed without etching the electrode and the plated layer is connected to the electrode of the PTC sheet. That is, since the effective area of the PTC device is large because it is not connected to the hole of the first invention or the slit of the second invention, the feature is that it is large.

However, the above-mentioned prior arts all disclose a laminated PTC sheet in which metal foils are laminated on upper and lower surfaces of the PTC element. Therefore, in order to connect the upper and lower electrodes, a space for connecting both electrodes, for example, a through hole or a slit, is required. In addition, a process of separating the electrodes through a process such as etching to move the electrode of the PTC sheet electrically connected to one side with the through hole or slit for mounting the both electrodes on the printed circuit board to one side is essential. Because it must be included, there was a problem that the process is complicated and the productivity is lowered.

The present invention was devised to solve the above problems. In the PTC electrical apparatus, the connection paths of the upper and lower electrodes are not formed in a separate space but are inserted into the PTC element to simplify the process, thereby increasing productivity. Compared to the unit size, unlike the conventional invention, since the conductive material having a large surface area is inserted thereinto, the effective area of the PTC device is increased, thereby providing a surface mount type constant temperature coefficient electric device and a method of manufacturing the same. Its purpose is to.

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 cross-sectional view of a PTC electrical apparatus as one conventional embodiment.

2 is a cross-sectional view of a PTC electrical apparatus as one conventional embodiment.

3 is a cross-sectional view of a PTC electrical apparatus as one conventional embodiment.

4 is a cross-sectional view of a PTC electrical apparatus according to a preferred embodiment of the present invention.

5 is a schematic view showing an apparatus for manufacturing a PTC device used in an embodiment of the present invention.

6 to 10 are views illustrating a manufacturing process of a PTC electric device according to a preferred embodiment of the present invention.

<Brief description of the main references in the drawings>

10..PTC electrical devices 21, 22..conductive lead 30..PTC elements

40, 41, 42. Electrode 45. Non-conductive gap 50. Insulator

60.Solder layer

In order to achieve the above object, the method of manufacturing a surface mounted PTC electrical apparatus according to the present invention includes (a) two conductive conductors spaced apart from each other, and a portion of the conductive conductor is exposed to the outside. (B) forming a conductive layer electrically connected to the two conductive wires on the upper and lower surfaces of the PTC device; and (c) forming a non-conductive gap in the conductive layer, respectively, to form a first electrically separated layer. Forming an electrode and a second electrode.

Preferably, the PTC electrical apparatus further includes forming an insulating layer in the non-conductive gap, and forming a solder layer that surrounds the first electrode and the second electrode, respectively, and is electrically separated by the insulating layer. Include.

According to another aspect of the present invention, a method of manufacturing a surface-mount PTC electrical device is (a) preparing a PTC device having two conductive wires spaced apart therein, and part of the conductive wires are exposed to the outside. (b) forming a conductive layer electrically connected to the two conductive wire exposed portions on upper and lower surfaces of the PTC device, and (c) forming a non-conductive gap in the conductive layer, respectively, to electrically separate the first electrode. And forming a second electrode and (d) cutting the PTC device in a vertical direction of the conductive lead to form a plurality of PTC devices.

Preferably, the present PTC electrical device comprises the steps of forming an insulating layer in the non-conductive gap after step (c), surrounding the first electrode and the second electrode, and being electrically separated by the insulating layer. Forming a solder layer further comprises.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

4 is a cross-sectional view of a PTC electric device manufactured according to an embodiment of the present invention, in which the PTC electric device 10 includes a PTC element 30 having two conductive wires 21 and 22 therein. A first electrode 41 and a second electrode 42 formed on upper and lower surfaces of the PTC device 30 and electrically connected to respective conductive wires, an insulator 50 for insulating the electrode, and the PTC device; And a solder layer 60 for improving connectivity with the printed circuit board.

6 to 10 show a process for manufacturing the above PTC electrical apparatus. Referring to FIG. 6, in order to manufacture the device, first, a PTC device 30 having two conductive wires 21 and 22 embedded therein is prepared.

The PTC device 30 is composed of a polymer having conductive particles electrically dispersed therein and having a PTC property. As the polymer, polyethylene, polypropylene, ethylene / propylene polymer, or the like may be employed, and the conductive particles may be carbon black or other metal particles. In addition, the conductive conductors 21 and 22 employ copper or copper alloy having good conductivity. In this case, the thickness, shape, and spacing of the conductive wires may vary according to a user's request. Preferably, the conductive wires such as round, irregularities, and the like having a large surface area of the conductive wires are preferably used to facilitate adhesion with the PTC material.

The PTC element 30 is manufactured by the extruder shown in FIG. Looking at the process, the polymer material of the PTC element is introduced into the extrudate inlet 1 in a molten state and is transferred to one side of the extruder head 3 through the transfer unit (2). On the other hand, the conductive wire 4 to be extruded is introduced into the head 3 to the other side of the head 3. The PTC polymer and the conductive lead introduced into the head are pressurized while passing through the head where the cross-sectional area gradually decreases as it proceeds to the discharge die 5, thereby increasing the mutual adhesive force, and forming the die 5 in the form of the PTC element 6. Extruded in the form of a PTC element while being discharged to).

The cross section of the PTC element 30 manufactured as above is shown in FIG. A portion of two conductive wires 21 and 22 is exposed on upper and lower surfaces of the PTC device. In order to expose a part of the conductive lead during the extrusion process, it is preferable to manufacture the shape of the discharge die 5 in such a manner that the conductive wire is exposed from the beginning. Otherwise, the PTC element having the conductive lead inserted therein may be used. It is also possible to add a post process of fabricating a predetermined thickness and polishing a portion of the conductive lead exposed on the surface of the fabricated PTC device. Polishing is carried out mechanically or chemically so that it can be cut to the required thickness.

A conductive layer 40 is formed on the upper and lower surfaces of the PTC device 10 having the conductive wires 21 and 22 inserted therein as shown in FIG. 7. The conductive layer 40 may be formed using a non-electrolytic or electroplating process. Alternatively, the conductive layer 40 may be formed by compressing a metal foil with a PTC device or by bonding a metal foil to a PTC device with a conductive adhesive. have. At this time, as the conductive layer material usable, copper, gold, silver or an alloy thereof may be employed.

When the conductive layer 40 is formed, a non-conductive gap 45 is formed on one side of the conductive layer as shown in FIG. 8 to form the first electrode 41 and the second electrode 42. Although the position of the non-conductive gap 45 is possible in any part of the conductive layer, it is preferable that the non-conductive gap 45 is formed to have a vertical symmetry. For example, in FIG. 8, although the non-conductive gap 45 is installed adjacent to the embedded conductive wire, the same function is performed even if formed in the center. The nonconductive gap 45 is formed by etching. The etching may employ both general dry and wet etching processes, and does not show etching processes such as a mask for etching, photoresist coating, exposure, development, and resist removal on the drawings.

Here, referring to the PTC device structure shown in FIG. 8, the conductive wires 21 and 22 are spaced apart from each other inside the PTC device, and the conductive wires 21 and 22 at this time are partially disposed on upper and lower surfaces of the PTC device 30. Is exposed. In addition, the conductive layer 40 formed on the upper and lower surfaces of the PTC element 30 is electrically connected to the exposed portions of the conductive conductors 21 and 22. In addition, a nonconductive gap 45 is formed in the conductive layer by etching, and a plurality of conductive layers 40a, 40b, 40c, and 40d are separated by the nonconductive gap. Accordingly, the conductive wire 21, the conductive layer 40a, and the conductive layer 40c form the first electrode 41, and the conductive wire 22, the conductive layer 40b, and the conductive layer 40d are formed. This second electrode 42 is formed.

According to the present invention, the non-conductive gap 45 between the first electrode 41 and the second electrode 42 is preferably filled with an insulator 50. The reason for this is that by interposing an insulating material, a short circuit caused by a bridge which may occur when the PTC electric device is mounted on a printed board can be prevented. Preferably, referring to FIG. 9, the insulator 50 is formed to surround the non-conductive gap 45 and a part of the first electrode 41 and the second electrode 42. Non-conductive materials such as ceramics, solder masks and the like can be employed, and solder masks are particularly preferred.

When the insulator 50 is interposed, the solder layer 60 is formed on the first electrode 41 and the second electrode 42, respectively. Preferably, the solder layer 60 surrounds the first electrode and the second electrode, and is electrically separated by the insulating layer. 10 illustrates a process of forming a solder layer 60 on a PTC device on which electrodes and insulators are formed. The solder layer 60 is formed to improve adhesion to a printed circuit board. As the solder composition, a mixture of tin and lead may be used, and a method of forming a solder layer may include a method such as electroplating or solder immersion.

In another manufacturing process of the present invention, it is possible to manufacture a PTC device using the extruder shown in FIG. For example, instead of manufacturing the PTC device by extruding the PTC devices one by one as in the above-described embodiment, after manufacturing the PTC device sheet continuously extending in the longitudinal direction of the conductive wire, the PTC device sheet is subjected to the conductive wire in a later step. The PTC device is manufactured by cutting by unit size in the orthogonal direction. For the process, the same method as in the above embodiment is employed, and thus a detailed description thereof is omitted.

As mentioned above, although this invention was demonstrated by the limited embodiment and drawing, this invention is not limited by this and is within the equal range of a common technical idea in the technical field to which this invention belongs, and a claim to be described below. Of course, various modifications and variations are possible.

The surface mount type PTC electric apparatus of the present invention can increase productivity by simplifying the process by inserting the upper and lower electrode connecting passages into the PTC element instead of forming them in a separate space, and comparing the present invention with a unit size. When the conductive material having a large surface area is inserted therein, the effective area of the PTC device is increased, thereby increasing the resistivity.

Claims (12)

In the surface-mount type constant temperature coefficient electrical device manufacturing method, (a) preparing a PTC device having two conductive wires spaced apart from each other and having a portion of the conductive wires exposed to the outside; (b) forming a conductive layer electrically connected to the two conductive wires on the upper and lower surfaces of the PTC device; and and (c) forming non-conductive gaps in the conductive layer to form first and second electrodes that are electrically separated from each other. The method of claim 1, Forming an insulating layer in the non-conductive gap; And wrapping the first electrode and the second electrode, respectively, and forming a solder layer electrically separated by the insulating layer. The method according to claim 1 or 2, Wherein said PTC device is made by extruding two conductive conductors and a molten PTC mixture. The method of claim 1, The conductive layer is formed by laminating or plating metal foils. The method of claim 1, The non-conductive gap is formed by etching. The method of claim 1, The step (a) is the step of extruding the molten PTC mixture and the two conductive wires, And polishing a portion of the conductive wire to expose the surface of the extruded PTC device. In the surface-mount type constant temperature coefficient electrical device manufacturing method, (a) preparing a PTC device having two conductive wires spaced apart from each other and having a portion of the conductive wires exposed to the outside; (b) forming a conductive layer on upper and lower surfaces of the PTC device to be electrically connected to the two conductive wire exposed portions; (c) forming non-conductive gaps in the conductive layer to form first and second electrodes that are electrically separated; and (d) cutting the PTC device in a vertical direction of the conductive wire to make a plurality of PTC devices. The method of claim 7, wherein after step (c), Forming an insulating layer in the non-conductive gap; And forming a solder layer surrounding the first electrode and the second electrode, the solder layer being electrically separated by the insulating layer. The method according to claim 7 or 8, Wherein said PTC device is made by extruding two conductive conductors and a molten PTC mixture. The method according to claim 7 or 8, The step (a) is the step of extruding the molten PTC mixture and the two conductive wires, And polishing a portion of the conductive wire to expose the surface of the extruded PTC device. The method of claim 7, wherein The conductive layer is formed by laminating or plating metal foils. The method of claim 7, wherein The non-conductive gap is formed by etching.