KR20030042980A - Polymer fuse having ptc characteristics and method of making the same - Google Patents

Abstract

PURPOSE: A polymer fuse is provided to be capable of reducing a consumed power amount needed to heat a solder by joining a conductive polymer having a PTC characteristic and a metal electrode by high frequency heating. CONSTITUTION: A conductive polymer(12) is prepared to have a positive temperature coefficient(PTC). Metal electrodes(14) are attached on both sides of the conductive polymer. A lead wire(16) is disposed on the metal electrodes and is connected to an external electronic device. A solder is disposed between the metal electrode and the lead wire. The solder connects the metal electrode and the lead wire through high frequency heating by induction current.

Description

Polymer fuse having PTC characteristics and manufacturing method thereof {POLYMER FUSE HAVING PTC CHARACTERISTICS AND METHOD OF MAKING THE SAME}

The present invention relates to a polymer fuse, and more particularly, to a polymer fuse having a PTC characteristic in which a conductive polymer having a PTC (Positive Temperature Coefficient) characteristic and a metal electrode are stably bonded by high frequency heating, and a method of manufacturing the same.

In general, a fuse refers to a kind of automotive circuit breaker used to prevent overcurrent from flowing in a line. Conventionally, a fuse is a type of a fuse that melts itself by heat generated by a current and breaks an electric wire. Recently, a fuse using a PTC (Positive Temperature Coefficient) polymer having a property in which electrical resistance increases rapidly with temperature rise is used. Is also used.

The PTC polymer has a sufficiently low resistivity at room temperature, so the current flow in the circuit is maintained in a normal state. However, when a high current flows in the circuit due to a short circuit or the like, the high current flows into the PTC polymer. Since heat is generated, the temperature of the PTC polymer is increased, and the resistivity is increased, the PTC characteristic is expressed and no current flows, thereby protecting the circuit. In addition, the PTC polymer ensures normal current flow since the temperature of the device decreases when the current becomes normal, thereby lowering the resistivity again. Therefore, the polymer fuse using the PTC polymer has the advantage that it can be repeatedly used because there is no consumption of certain components such as disconnection of the wire.

There are many different types and shapes of PTC polymers applied to fuses, one of which has a lead wire connected to the device to be protected. Soldering, commonly called soldering, is used as a method of joining the lead wires. Soldering is an indispensable bonding method for manufacturing electronic devices. The soldering material is used to solder the base material without melting the base material.

Soldering distinguishes between the melting point of the commonly used lead higher or lower than 450 ℃, and the use of lead that does not melt at a higher temperature than this is called hard soldering or brazing, and the lower melting point of lead is used. This is called soft soldering or soldering. In general, soldering applied to a fuse uses soldering having a melting point of less than 450 ° C., and uses a method of joining the solder by spreading the solder through the narrow gap between metal surfaces.

A typical solder is solder, an alloy of lead-tin. The more tin, the more expensive it is. Lead solders other than solder include lead-tin-zinc alloys, lead-cadmium, and zinc-cadmium lead, which are bonded together, and lead-tin-bismuth solders having lower melting points are also used.

At this time, in order to solder, the temperature of the solder must rise above the melting point, and various methods such as the iron method, the deposition method, the wave method, and the reflow method are used according to the heating method of the solder. The most widely used soldering of dual electronics is the reflow method. The reflow soldering device uses a variety of methods such as using IR (infrared rays), hot air, and various kinds of light. The method using the heating continuous furnace is suitable for continuous production because many components can be soldered in a batch.

However, in general, since the PTC polymer has a limit in recovering again after the electrical resistance increases with increasing temperature, its resistance increases after soldering for mounting the lead wire. In addition, since the reflow method has a relatively long heating time, the degradation of the PTC polymer is further increased, which may cause a failure of the fuse or a deterioration of the performance of the electric device using the fuse.

The present invention was devised to solve the above problems, and by stably joining a conductive electrode and a metal electrode having a PTC (Positive Temperature Coefficient) characteristic by high frequency heating to reduce the power consumption required for solder heating and shorten the process time It is an object of the present invention to provide a polymer fuse having PTC properties.

Still another object of the present invention is to provide a method of manufacturing a polymer fuse having the PTC characteristics as described above.

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 showing a polymer fuse having PTC properties according to the present invention.

2 is a perspective view showing a heating apparatus used for solder heating of a polymer fuse according to the present invention;

<Explanation of symbols for the main parts of the drawings>

10. Polymer fuse 12. PTFE polymer 14. Metal electrode

16.lead wire 18.solder 20.heater

In order to achieve the above object, a polymer fuse having a PTC characteristic according to the present invention is a conductive polymer having a PTC characteristic, a metal electrode attached to both surfaces of the conductive polymer, a lead disposed on the metal electrode and connected to an external electric device. And a solder disposed between the metal electrode and the lead wire, wherein the solder bonds the metal electrode and the lead wire to each other by high frequency heating by an induction current.

Preferably, the high frequency of heating the solder has the conditions of the output voltage 350 ~ 400Hz and the frequency 350 ~ 450V.

In addition, the lead wire may be bonded only to a part of the metal electrode, and the conductive polymer contains high density polyethylene (HDPE), low density polyethylene (LDPE) and a peroxide crosslinking agent, and 30 to 60% by weight of carbon black is preferably added.

Further, the metal electrode is preferably made of a thin film of electrolytic or electroless plating on nickel plated foil, nickel rolled foil or copper plated foil, and the lead wire is also preferably nickel or nickel alloy.

According to another aspect of the invention, the step of attaching a metal electrode on both surfaces of the conductive polymer having a PTC characteristic, placing a solder on the metal electrode and placing the lead wire thereon, and high frequency heating by induction current There is provided a method of manufacturing a polymer fuse having a PTC characteristic comprising the step of heating the solder to bond the metal electrode and the lead wire.

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 specification and claims should not be construed as having a conventional or dictionary meaning, 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.

1 is a view showing the configuration of a polymer fuse having a PTC characteristic according to the present invention. Referring to the drawings, the polymer fuse 10 of the present invention includes a conductive polymer 12 having PTC characteristics, and metal electrodes 14 are attached to both surfaces of the conductive polymer 12, respectively. In addition, a lead wire 16 electrically connected to an external electric device is disposed on each metal electrode 14, and a solder 18 for bonding them between the metal electrode 14 and the lead wire 16. Is placed. At this time, the solder 18 is melted by high frequency heating to bond the metal electrode 14 and the lead wire 16 to each other.

The polymer fuse 10 has a length of about 5 ~ 50mm, is manufactured to have a thickness of about 0.5 ~ 5mm, in addition to that can be variously modified as necessary.

In more detail, the conductive polymer 12 having the PTC characteristic serves to block when an excessive current is applied to the fuse due to a sudden increase in resistance at a specific temperature. Any type of conductive polymer 12 may be used, for example, 30-40 w% high density polyethylene (HDPE), 20-40 w% low density polyethylene (LDPE) and 10-30 w% ethylene-acrylic-acid An organic polymer containing a polyolefin component consisting of (EAA) or ethylene-vinyl-acetate (EVA) and 20-30% by weight of modified high density polyethylene or modified low density polyethylene modified with a maleic anhydride compound can be used. The thermal stability can also be improved by adding a peroxide crosslinking agent to (12).

In addition, 30-60 w% of carbon black is added to this conductive polymer 12. Such carbon black is a conductive particle, and serves to help the PTC polymer to be conductive. The conductive polymer 12 may be energized by the carbon black to ensure a daily current flow. When the temperature rises due to overcurrent, the polymer expands and the conductive paths between the carbon black particles are blocked to block the current.

The metal electrode 14 is bonded to both surfaces of the conductive polymer 12 in the form of a thin film. As the metal electrode 14, a nickel plated film, a nickel rolled foil, a copper plated foil, or the like may be used, and it is preferable to have a thin film form in which electrolytic or electroless plating is applied thereto. The metal electrode 14 has a thickness of about 15 ~ 50 ~ m, of course, can be applied to other ranges as needed.

The lead wire 16 serves to electrically connect the conductive polymer 12, which performs the overcurrent blocking function of the fuse, to the electric device by the PTC characteristic. For this purpose, a pair of lead wires 16 are respectively bonded to the metal electrodes 14 attached to both surfaces of the conductive polymer 12. In this case, each lead wire 16 may be bonded to the entire surface of the metal electrode 14, but may be bonded only to a part of the metal electrode 14. For example, as shown in FIG. 1, the lead wires 16 attached to the upper and lower surfaces of the conductive polymer 12 may be bonded to be biased in opposite directions. In this case, the amount of the solder 18 used to join the metal electrode 14 and the lead wire 16 can be reduced, and in particular, the damage of the conductive polymer 12 that can occur during the bonding process can be greatly reduced. have.

Nickel or a nickel alloy may be used as the lead wire 16 and is configured to have a thickness of approximately 0.1 to 0.2 mm.

The solder 18 is used to join the metal electrodes 14 and the lead wires 16 to each other, and uses solder having a melting point of less than 450 ° C. The solder 18 can be of any kind, commonly referred to as solder, but using a binary solder containing only tin (Sn) and lead (Pb), or zinc (Zn), cadmium (Cd) Preference is given to adding additives such as).

In the present invention, a high frequency heating method is used to join the metal electrode 14 and the lead wire 16. Generally, the method of electrically heating an object includes resistance heating, arc heating, beam heating, and high frequency heating. A method of heating a double object by applying a high frequency electric field or a magnetic field is generally called high frequency heating.

High frequency heating is a method of heating an object in a strong high frequency electromagnetic field, also called a radio heater. The high frequency heating is divided into dielectric heating and induction heating according to the heating principle. Double dielectric heating is based on the principle that the heating element itself generates heat when the insulator is placed in the high frequency electric field.Induction heating is caused by the eddy currents generated in the good conductor by placing the electric good in the high frequency magnetic field. It is based on the principle of self-heating due to loss or hysteresis loss. In the present invention, since the object to be heated is a conductor, induction heating using hysteresis loss due to induction current is used.

Induction heating is generally used for melting, quenching, annealing, welding, brazing, forging, etc. of metal alloys, and for melting and purifying germanium and silicon in the semiconductor industry, and producing single crystals. At this time, as the frequency increases, the eddy current flows only on the surface of the conductor and does not penetrate into the inside of the conductor as the frequency increases. Therefore, a relatively low frequency is used when melting, and a relatively high frequency is used when heating only a surface such as metal quenching. use. This heating method has the advantage of being able to locally heat or melt a metal having high thermal conductivity.

When the high frequency heating method using the induced current as described above is applied to the solder 18 of the present invention, the lead wire 16 and the solder 18 can be effectively heated while minimizing the influence on the conductive polymer 12. It becomes possible. At this time, the state of the solder 18 is changed according to the characteristics of the high frequency, and the experiment of the frequency of the high frequency used for solder heating, the output voltage and the state of the heated solder, and the resistance value after the joining were conducted in various forms. The results are shown in Table 1 below.

Experiment number Frequency (Hz) Output voltage (V) Solder condition Resistance (Ωcm) One 250 300 Bad - 2 270 400 Bad 0.55 3 370 300 Bad 0.60 4 370 400 Good 0.67 5 370 450 Good 0.70 6 400 400 Good 0.69

In this case, the resistance means a resistance value at a room temperature of 25 ° C., and the lower the value, the more preferably 0.70 (Ω · cm) or less at room temperature. According to the experimental results, the high frequency required for the solder heating in the manufacturing process of the polymer fuse of the present invention can be obtained at the optimum frequency of 370Hz and the output voltage of 400V. In fact, in order to realize product characteristics of 0.70 (Ω · cm) or less at room temperature of 25 ℃, the high frequency used for solder heating is most preferably the frequency 350 ~ 400Hz, output voltage 350 ~ 450V.

Figure 2 shows a heating device 20 used for high frequency heating of solder in the manufacturing process of the polymer fuse of the present invention. Heating device 20 for high-frequency heating is composed of a pair of heating coils (22, 24), each heating coil (22, 24) is formed in the form of a U-loop in which one side is blocked and the other is parallel. In addition, the heating coils 22 and 24 are arranged to be spaced apart in parallel to each other, and power is applied to the solder 18 to be heated in a state located between the heating coils 22 and 24.

At this time, the interval a of the loops constituting the heating coils 22 and 24 is about 10 to 100 mm, and the interval b between each of the heating coils 22 and 24 is about 14,4 to 144 mm, It is preferable that it is about 3 times of space | interval (a).

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 is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

The polymer fuse having a PTC characteristic according to the present invention heats the solder for joining the metal electrode and the lead wire by a high frequency heating method using an induction current, thereby enabling selective heating of the heating target object. Therefore, when joining the metal electrode and the lead wire, only the lead wire and the solder portion which are the conductors are heated to reduce the degradation problem of the PTC polymer.

In addition, since the high frequency heating has a high energy density and a short heating time, the process time is short and the PTC polymer can be prevented from being deteriorated by heat. In addition, since local heating is performed for solder joints, there is an advantage in that energy efficiency is high and power consumption can be reduced.

Claims (10)

Conductive polymers having PTC properties; Metal electrodes attached to both surfaces of the conductive polymer; A lead wire disposed on the metal electrode and connected to an external electric device; And A solder disposed between the metal electrode and the lead wire, The solder is a polymer fuse having a PTC characteristic, characterized in that for bonding the metal electrode and the lead wire to each other by high frequency heating by induction current. The method of claim 1, The high frequency of heating the solder is a polymer fuse having a PTC characteristic, characterized in that having a condition of the output voltage 350 ~ 400Hz and frequency 350 ~ 450V. The method of claim 1, And the lead wire is bonded only to a part of the metal electrode. The method of claim 1, The conductive polymer includes a high density polyethylene (HDPE), low density polyethylene (LDPE) and a peroxide crosslinking agent, the polymer fuse having a PTFE characteristic, characterized in that 30 to 60% by weight of carbon black is added. The method of claim 1, The metal electrode is a polymer fuse having a PTC characteristic, characterized in that consisting of a thin film of electrolytic or electroless plating on nickel plated foil, nickel rolled foil or copper plated foil. The method of claim 1, The lead wire is a polymer fuse having a PTC characteristic, characterized in that the nickel or nickel alloy. Attaching metal electrodes to both surfaces of the conductive polymer having PTC properties; Disposing a solder on the metal electrode and placing a lead wire thereon; And And heating the solder through high frequency heating by an induction current to bond the metal electrode and the lead wire to each other. The method of claim 7, wherein The high frequency of heating the solder is a manufacturing method of a polymer fuse having a PTC characteristic, characterized in that having a condition of the output voltage 350 ~ 400Hz and frequency 350 ~ 450V. The method of claim 7, wherein The conductive polymer comprises a high density polyethylene (HDPE), low density polyethylene (LDPE) and a peroxide crosslinking agent, and 30 to 60% by weight of carbon black is added to the manufacturing method of a polymer fuse having a PTC characteristic. The method of claim 7, wherein And the lead wire is bonded only to a part of the metal electrode.