JP2007280807A - Fuse and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small or very small fuse, along with its manufacturing method, which is excellent in instantaneous blown nature and is suitable as a printed board mounting type fuse. <P>SOLUTION: The fuse is provided with a porous resin film comprising a plurality of through holes running in thickness direction from one surface to the other surface, a fuse layer formed on the inner surface of each through hole, a connection conductor which is provided at least on one surface of the porous resin film and connects the fuse layers in series or in parallel, and two electrodes that are provided at both ends of the porous resin film and connected to two fuse layers, through the connection conductor, closest to both ends among the fuse layers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a small-sized or ultra-small fuse suitable for mounting on a printed circuit board and a method for manufacturing the same, and more particularly, a small-sized or ultra-small fuse suitable for surface mounting and exhibiting a fast-blow type fusing characteristic. It relates to the manufacturing method.

  Current exceeding the allowable limit of electronic equipment is called overcurrent. Although electronic devices are designed not to generate overcurrent, there is always a danger of overcurrent flowing in when troubles such as circuit component failures, short circuit accidents, mixed accidents, and incorrect wiring occur. The fuse is an overcurrent protection element that is used to cut off a power source by fusing when a current larger than an allowable current flows through the electronic device. The fuse includes a fusible body (fuse element), and when an abnormal overcurrent flows through the circuit, the fusible body melts due to Joule heat generated by the flowing current and interrupts the current. The fuse is also used for checking during the production or completion of electronic components.

  In recent years, electronic devices have been miniaturized, and resistors, capacitors, semiconductors, and mechanical components have all been mounted on printed boards. For this reason, a small fuse is also disposed in an electronic circuit configured on a printed circuit board. Known fuses for protecting electronic equipment include tube fuses, through-hole fuses with lead terminals for board mounting, chip fuses for surface mounting, and the like.

  Fuses placed in electronic devices are required to have the ability to safely and reliably cut off current in the event of a short circuit accident, etc., and in the normal operation of electronic devices, they never end up and endure long-term use Sex is also required. In particular, a fuse mounted on a printed circuit board has a characteristic that a fusible body quickly melts and cuts off the current when a current exceeding the rated capacity flows due to a short-circuit accident or incorrect wiring. In addition to having characteristics (pulse resistance) that can withstand transient overcurrent such as inrush current that flows at start-up, it is required to be small and / or thin.

  Printed circuit board mounted fuses used for secondary circuit protection of electronic equipment include tube fuses with a structure in which fusible metal wires are stretched in a ceramic hollow body, and fusible bodies formed on heat-resistant substrates. A typical example is a thin film type chip fuse having a structure in which a thin film pattern is sealed with a heat resistant resin. Tube fuses are limited in size and thickness due to structural limitations. The thin film chip fuse has no heat insulation space around the fusible body, so the fusing characteristics are easily affected by the ambient temperature, and the minimum fusing current tends to increase.

  Japanese Patent Application Laid-Open No. 11-224590 (Patent Document 1) proposes a micro fuse having a structure in which a plurality of through holes are provided in an insulator and a fuse layer is formed on the inner surface of the through holes. Similarly, in JP-A-2002-42632 (Patent Document 2), a plurality of through holes are provided in an insulator, a fuse layer is formed on the inner surface of each through hole, and the shape and number of through holes, the hole diameter, There has been proposed an ultra-small fuse having a desired fusing characteristic by changing a hole interval or the like. Patent Document 2 also shows a micro fuse having a desired fusing characteristic by filling an insulating resin into a through hole in which a fuse layer is formed.

  Since the micro fuse disclosed in Patent Documents 1 and 2 has a fuse layer in the through hole, the fused fuse is not re-welded, and the number and shape of the through holes are adjusted to adjust the predetermined size. Fuses with a rated current and a rated voltage of 1 mm can be obtained, and further, downsizing and thinning are possible.

  However, since the micro fuses disclosed in Patent Documents 1 and 2 are manufactured using a normal insulating substrate as an insulator, even if Joule heat is generated due to an overcurrent flowing in the fuse layer. The insulator in contact with the fuse layer loses heat, and the fuse layer tends to be blown out later. If the heat generated in the fuse layer is easily dispersed through the insulator, the fuse is difficult to blow in a low current region, and the minimum fusing current is increased. When the fusing time in the high current region is the same, a fuse having a large minimum fusing current tends to have a reduced pulse resistance.

  Specifically, in Patent Document 2, when the hole diameter of the through hole forming the fuse layer is small and the number of holes is large, the heat generated in the fuse layer is dispersed and easily dissipated. Fuse is less likely to blow, and the minimum fusing current is increased. Therefore, in order to obtain a fuse with a low minimum fusing current and excellent pulse resistance, a method with a large hole diameter and a reduced number of holes should be adopted. Teaches. However, such a method restricts the design freedom of a micro fuse that exhibits a desired rated breaking capacity.

  In Patent Document 2, if a method of filling an insulating resin in a through hole in which a fuse layer is formed, each fuse layer is more likely to dissipate heat than a case where the through hole is left hollow. It is stated that the fusing time in the basin can be extended. However, the method of filling the through hole with the insulating resin has a problem that the processing is complicated and the quick disconnection of the fuse is further deteriorated.

JP 11-224590 A JP 2002-42632 A

  An object of the present invention is to provide a small or ultra-small fuse that is excellent in quick disconnection and suitable as a printed circuit board mounting type fuse, and a method for manufacturing the same. Another object of the present invention is to provide a fuse excellent in heat resistance, low outgas resistance, and high frequency characteristics in addition to being excellent in quick disconnection, and a method for manufacturing the same.

  As a result of diligent research to solve the above problems, the present inventors have not made a conventional method of forming a through hole in an insulating substrate and forming a fuse layer on the inner surface thereof, but heat resistance such as porous fluororesin. With the method of forming a through-hole in a porous resin film with excellent insulation and forming a fuse layer on the inner surface, Joule heat generated by overcurrent flowing in the fuse layer becomes difficult to dissipate and quick-breaking It was found that an excellent fuse can be obtained.

  Since the fuse of the present invention uses a highly heat-insulating porous resin film as a base material, the release of Joule heat generated in the fuse layer due to overcurrent is suppressed. According to the fuse of the present invention, the hole diameter, the number of holes, the hole interval, the thickness of the fuse layer, and the like can be arbitrarily designed according to desired fusing characteristics. When a fluororesin film such as a porous polytetrafluoroethylene film is used as the porous resin film, a fuse excellent in heat resistance, low outgas resistance, high frequency characteristics, and the like can be obtained. The fuse of the present invention has excellent pulse resistance in addition to excellent quick disconnection. The fuse of the present invention can be miniaturized and thinned by using a thin porous resin film, and is suitable for mounting on a printed circuit board. The present invention has been completed based on these findings.

  According to the present invention, a porous resin film in which a through hole is provided in the thickness direction from one surface to the other surface, a fuse layer formed on the inner surface of the through hole, and both ends of the porous resin film A fuse is provided that includes two electrodes provided and connected to opposite ends of the fuse layer, respectively.

  According to the present invention, (a) a porous resin film provided with a plurality of through holes in the thickness direction from one surface to the other surface, (b) a fuse layer formed on the inner surface of each through hole, (c ) A connecting conductor provided on at least one surface of the porous resin film and connecting the fuse layers in series or in parallel with each other; and (d) provided on both ends of the porous resin film, There is provided a fuse having two electrodes respectively connected to two fuse layers closest to both end portions thereof via a connecting conductor.

  Further, according to the present invention, the step I of forming a through hole in the thickness direction of the porous resin film from one surface to the other surface, the step II of forming a fuse layer on the inner surface of each through hole, and the porous There is provided a method for manufacturing a fuse including a step III in which two electrodes connected to both ends of the fuse layer are disposed at both ends of the resin film, respectively.

  Furthermore, according to the present invention, Step 1 for forming a plurality of through holes in the thickness direction of the porous resin film from one surface to the other surface, Step 2 for forming a fuse layer on the inner surface of each through hole, Forming a connecting conductor for connecting the fuse layers in series or in parallel to each other on at least one surface of the porous resin film; and at both ends of the porous resin film, at both end portions of the fuse layers A method for manufacturing a fuse is provided, which includes a step 4 of disposing two electrodes respectively connected to two fuse layers close to each other via a connecting conductor.

  According to the present invention, by using a porous resin film instead of a conventional insulating substrate as an insulator, it is possible to provide a fuse having excellent quick disconnection characteristics when an overcurrent flows. By using a fluororesin film such as a porous polytetrafluoroethylene film obtained by a stretching method as the porous resin film, a fuse having excellent heat resistance, low outgas resistance, and high frequency characteristics can be obtained. The fuse of the present invention can be easily reduced in size and thickness.

  The porous resin film used in the present invention is formed from an electrically insulating synthetic resin, and is preferably excellent in heat resistance from the viewpoint of the use atmosphere and durability of the fuse. Examples of the synthetic resin for forming the porous resin film include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA). , Fluorine resins such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride copolymer, ethylene / tetrafluoroethylene copolymer; polyimide, polyamideimide, polyamide, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polysulfone Engineering plastics such as polyethersulfone and liquid crystal polymer.

  Among these synthetic resins, fluororesins are preferable from the viewpoints of heat resistance, processability, mechanical characteristics, dielectric characteristics, and the like, and polytetrafluoroethylene (PTFE) is preferable from the viewpoints of heat resistance, high frequency characteristics, and outgas resistance. Is particularly preferred.

  Examples of a method for producing a porous resin film made of a synthetic resin include a pore making method, a phase separation method, a solvent extraction method, a stretching method, and a laser irradiation method. Among these, the stretching method is preferable in that the average pore diameter and the porosity can be easily controlled. By forming a porous resin film using a synthetic resin, elasticity can be given in the film thickness direction, and the dielectric constant can be further lowered.

  The porous resin film used as the base film of the fuse preferably has a porosity of about 20 to 80%. The porous resin film preferably has an average pore diameter of 10 μm or less or a bubble point of 2 kPa or more. From the viewpoint of making fine through-holes, the average pore diameter is preferably 5 μm or less, and more preferably 1 μm or less. The lower limit value of the average pore diameter is about 0.05 μm. The bubble point of the porous resin film is preferably 5 kPa or more, more preferably 10 kPa or more. The upper limit of the bubble point is about 300 kPa, but is not limited to this.

  The film thickness of the porous resin film can be appropriately selected according to the purpose of use and location of the fuse, but is usually 20 to 3000 μm, preferably 50 to 2500 μm, more preferably 100 to 2000 μm. The thickness of the porous resin film includes regions of a film (less than 250 μm) and a sheet (250 μm or more). The porous resin film may be a single layer or a multilayer. For example, a porous PTFE film obtained by a stretching method can be made into a porous PTFE film having a desired film thickness by thermally fusing layers between layers by heating and pressing.

  Among the porous resin films, porous polytetrafluoroethylene films (stretched porous PTFE films) obtained by the stretching method have heat resistance, workability, mechanical properties, dielectric properties, high frequency properties, outgas resistance, etc. Since it is easy to obtain a porous resin film having an excellent and uniform pore size distribution, it is the most excellent material as a base film of a fuse. The stretched porous PTFE membrane has a microstructure composed of a large number of fibrils and nodes, and a conductive metal such as plating particles can be easily attached to the fibrils.

  The expanded porous PTFE membrane used in the present invention can be produced, for example, by the method described in Japanese Examined Patent Publication No. 42-13560. First, a liquid lubricant is mixed with the unsintered powder of PTFE and extruded into a tube shape or a plate shape by ram extrusion. When a thin sheet is desired, the plate is rolled by a rolling roll. After the extrusion rolling process, the liquid lubricant is removed from the extruded product or the rolled product as necessary. When the extruded product or rolled product thus obtained is stretched at least in a uniaxial direction, unsintered stretched porous PTFE is obtained in the form of a film. An unsintered stretched porous PTFE membrane is heated to a temperature of 327 ° C. or higher, which is the melting point of PTFE, while being fixed so that shrinkage does not occur. A porous PTFE membrane is obtained. When the stretched porous PTFE membrane has a tube shape, a flat membrane can be obtained by cutting the tube.

  The stretched porous PTFE membrane has a microstructure composed of very thin fibrils formed by PTFE and nodes connected to each other by the fibrils, and this microstructure forms a porous structure.

  In order to use the porous resin film as the base film of the fuse, a through hole penetrating in the thickness direction is formed from one surface of the porous resin film to the other surface, and then the porous structure on the inner surface of the through hole A conductive metal is attached to the resin portion (for example, fibrils) to impart conductivity in the film thickness direction. In general, the conductive metal can be attached by a method in which plating particles are attached to the resin portion of the porous structure on the inner surface of the through hole by electroless plating or a combination of electroless plating and electroplating.

  As the conductive metal, a metal generally used as a fuse material such as copper, tin, aluminum, solder, brass, gold, or silver can be used. In this way, a fuse layer (fuse element) is formed on the inner surface of the through hole. In order to obtain a fuse having desired interruption characteristics, it is preferable to employ a method in which a plurality of through holes are provided in a porous resin film and a fuse layer is formed on the inner surface of each through hole. Therefore, hereinafter, a method for forming a plurality of through holes will be mainly described. However, these methods can also be applied to the case of forming a single through hole.

  As a method for forming a single or a plurality of through holes in the thickness direction of the porous resin film, for example, a mechanical drilling method, a photoetching method, or at least one vibrator at the tip And a method of punching by applying ultrasonic energy by pressing the tip of the vibrator.

  In order to mechanically form the through-hole in the porous resin film, for example, a machining method such as a press process, a punching method, or a drill method can be employed. According to the machining method, for example, a through hole having a relatively large diameter of 100 μm or more, in many cases 200 μm or more, and further 300 μm or more can be formed at low cost. By selecting a processing tool such as a drill, a punch, or a drill, a through hole having a smaller diameter than the above can be formed.

  In order to form a through-hole in a porous resin film by a light ablation method, for example, the porous resin film is formed through a light shielding sheet (mask) having a plurality of independent light transmission portions (openings) in a predetermined pattern. By irradiating the surface of the resin film with light, a plurality of through holes can be formed. Light is transmitted through a plurality of openings of the light shielding sheet, and the irradiated portion of the laminate is etched to form a through hole. According to this method, for example, a through hole having a relatively small diameter of 10 to 200 μm, in many cases 15 to 150 μm, and further 20 to 100 μm can be formed. Examples of irradiation light in the photoablation method include synchrotron radiation light and laser light.

  In the ultrasonic method, a patterned through-hole can be formed by applying ultrasonic energy to the porous resin film using an ultrasonic head having at least one vibrator at the tip. Ultrasonic energy is applied only to the vicinity where the tip of the vibrator contacts, and the temperature rises locally due to the vibrational energy generated by the ultrasonic wave, and the resin is easily cut and removed to form a through hole.

  In forming the through-hole, a method of perforating the porous structure of the porous resin film by impregnating a soluble polymer such as polymethyl methacrylate or paraffin in a solution or in a molten state and solidifying it may be employed. This method is preferable because the porous structure of the inner wall of the through hole is easily retained. After drilling, the soluble polymer or paraffin can be removed by dissolving or melting.

  The shape of the opening of the through hole is arbitrary, such as a circle, an ellipse, a star, an octagon, a hexagon, a quadrangle, and a triangle, but in many cases, it is a circle. The diameter of the through hole can be reduced to 5 to 100 μm, and further to 5 to 30 μm in an application field where a small diameter through hole is suitable. On the other hand, in a field where a relatively large through-hole is suitable, the diameter of the through-hole can be increased to usually 50 to 3000 μm, in many cases 75 to 2000 μm, and further to 100 to 1500 μm. When the through hole is not circular, the above diameter means the maximum diameter (the length of the longest part of the opening). It is preferable to form a plurality of through holes in a predetermined pattern according to desired fusing characteristics and pulse resistance. The plurality of through holes may have the same diameter, but a plurality of through holes having different diameters may be combined.

  A specific example of the fuse of the present invention will be described with reference to FIG. FIG. 1 shows a porous resin film provided with a plurality of through holes in the thickness direction, a fuse layer formed on the inner surface of each through hole, a connecting conductor for connecting the fuse layers in parallel to each other, and the porous resin. It is a cross-sectional schematic diagram which shows an example of the fuse provided with the two electrodes provided in the both ends of the film | membrane.

  Three through holes 20, 21, 22 are formed in the porous resin films 11, 12, 13, 14 (representing each part of one porous resin film), and the fuse layer 41, 42 and 43 are formed. In the example shown in FIG. 1, the fuse layer exists not only on the inner surface of the through hole but also on both surfaces of the porous resin film. Connection conductors 50 and 51 are arranged on both surfaces of the porous resin film in order to connect the fuse layers formed on the inner surfaces of the respective through holes in parallel. At one end of the porous resin film, the connection conductor 50 is connected to the upper end of the electrode 60 together with the fuse layer 40 present on one surface of the porous resin film. The lower end portion of the electrode 60 is not connected to the connecting conductor 51 and the fuse layer 45. On the other hand, at the other end of the porous resin film, the connection conductor 51 is connected to the lower end of the electrode 61 together with the fuse layer 48 present on the other surface of the porous resin film. The upper end portion of the electrode 61 is not connected to the connection conductor 50 and the fuse layer 44. The fuse is preferably protected by insulating heat resistant resins 70 and 71 such as epoxy resin. The two electrodes 60 and 61 are connected to a circuit component, for example.

  Another specific example of the fuse of the present invention will be described with reference to FIG. FIG. 2 shows a porous resin film provided with a plurality of through holes in the thickness direction, a fuse layer formed on the inner surface of each through hole, a connecting conductor for connecting each fuse layer in series, and the porous resin. It is a cross-sectional schematic diagram which shows an example of the fuse provided with the two electrodes provided in the both ends of the film | membrane.

  Three through holes 400, 401, 402 are provided in the porous resin films 201, 202, 203, 204 (representing each part of one porous resin film), and fuse layers 600, 601 are provided on the inner surfaces of the respective through holes. , 602 are formed. Connection conductors 700, 701, 702, and 703 for connecting the fuse layers of the respective through holes in series are formed on both surfaces of the porous resin film. Of the connection conductors, the connection conductor 700 formed on the upper surface of the porous resin film is connected to one electrode 800, and the connection conductor 703 formed on the lower surface of the porous resin film is the other electrode 801. And connected. The fuse is preferably protected by insulating heat resistant resins 900 and 901 such as epoxy resin. The two electrodes 800 and 801 are connected to a circuit component, for example.

  The fuse of the present invention includes a step 1 for forming a plurality of through holes in the thickness direction of the porous resin film from one surface to the other surface, a step 2 for forming a fuse layer on the inner surface of each through hole, and the porous resin. Step 3 of forming a connecting conductor for connecting each fuse layer in series or in parallel to each other on at least one surface of the film, and both ends of the porous resin film are closest to both ends of each fuse layer It can be manufactured by a manufacturing method including the step 4 of disposing two electrodes respectively connected to two fuse layers via connecting conductors.

  Specifically, the fuse shown in FIG. 1 can be manufactured by the process shown in FIG. 3, for example. A desired number of through holes are formed in the porous resin 10 (A1). FIG. 3 shows an example in which three through holes 20, 21, 22 are provided. In the cross-sectional view shown in A2, the porous resin film 10 is shown by the respective portions 11, 12, 13, and 14 divided by the through holes. However, the porous resin film 10 is an integral porous film except that the through holes are provided. There is no change in being a resin film.

  Plating catalysts 30 to 38 are attached to the surface including the inner surface of each through hole of the porous resin film (A3). At this time, a portion where no plating is formed can be masked in advance. For the mask, a method of attaching an arbitrary material such as the same kind of porous resin film, non-porous resin film, or adhesive tape can be used. If the mask is not applied when the plating catalyst is applied, unnecessary plating portions may be removed by a technique such as cutting or laser cutting after electroless plating. Further, electroless plating may be performed in a pattern by a photolithography technique.

  The porous resin film with the plating catalyst attached is electrolessly plated to form plating layers (fuse layers) 40 to 48 having a desired thickness (A4). The plating layer is also formed on the inner surface of each through-hole and the surface of the porous resin film. As the plating layer, a copper plating layer and / or a tin plating layer is preferable.

  Connection conductors 50 and 51 for connecting the fuse layers formed on the inner surfaces of the through holes in series are arranged on both surfaces of the porous resin film on which the fuse layers are formed (A5). As the connection conductor, a conductive metal film such as copper foil is used. The connecting conductors are disposed at necessary positions on both sides of the porous resin film, but may be formed in a predetermined pattern by photolithography. The connecting conductor can be fixed to both surfaces of the porous resin film by means such as conductive adhesive, thermal fusion, diffusion welding, pinning, and the like. If the electrodes 60 and 61 are attached to the porous resin film provided with the fuse layer prepared above and covered with protective films 70 and 71 such as epoxy resin as necessary, the fuse having the structure shown in FIG. 1 is obtained. It is done.

  The fuse shown in FIG. 2 can be manufactured by the method shown in FIG. Mask layers 301 and 302 are disposed on both surfaces of the porous resin film 200 (B1). As the mask layer, the same kind of porous resin film or nonporous resin film can be used. In that case, the mask layer is laminated by thermocompression bonding to the surface of the porous resin film 200. An adhesive tape may be used as the mask layer.

  A plurality of through holes are formed in the laminate (B2). FIG. 4 shows an example in which three through holes 400, 401, and 402 are provided in the three-layer laminate. In the cross-sectional view shown in B2, the porous resin film 200 is shown by the respective portions 201, 202, 203, and 204 divided by the through holes. However, the porous resin film 200 is an integral porous film except that the through holes are provided. There is no change in being a resin film.

  The plating catalysts 500, 501, and 502 are adhered to the entire surface of the laminate having the through holes including the inner surface of the through holes (B3). Next, when the mask layers 301 and 302 are removed, a porous resin film in which the plating catalysts 500, 501, and 502 are attached only to the inner surfaces of the respective through holes is obtained (B4). When electroless plating is applied to the porous resin film, electroless plating layers (fuse layers) 600, 601, and 602 are formed only on the inner surfaces of the through holes (B5).

  Next, in order to connect the fuse layers of the respective through holes in series, connection conductors 700, 701, 702, and 703 are partially provided on both surfaces of the porous resin film (B6). In the cross-sectional view shown in B6, the fuse layer formed in each through-hole appears to be divided into left and right, but the fuse layer is formed in a cylindrical shape on the inner peripheral surface of each through-hole. By providing the conductor partially, each fuse layer can be connected in series. Of the connecting conductors, connecting conductors 700 and 703 are for connecting to two electrodes, respectively. The connecting conductor can be formed in a pattern according to the number of through holes and the arrangement state. If the electrodes 800 and 801 are attached to the porous resin film provided with the fuse layer prepared above and covered with a protective film 900 or 901 such as an epoxy resin as necessary, a fuse having the structure shown in FIG. 2 is obtained. It is done.

  Since the porous resin film can be finely processed, an ultra-small fuse can be manufactured. As described above, the thickness of the porous resin film can be arbitrarily selected from a thin one to a relatively thick one. As described above, the size and number of the through holes can be various diameters and numbers. The interval between the through holes is also arbitrary. The planar size and shape of the porous resin film are also arbitrary, and examples thereof include a 5 mm × 10 mm rectangle. The thickness of the fuse layer can be appropriately set according to desired fusing characteristics, but is usually about 1 to 10 μm, and in many cases about 2 to 5 μm.

  For the formation of the fuse layer, a technique such as through-hole plating can be employed. Specifically, it is preferable to employ an electroless plating method. Hereinafter, the method for forming the fuse layer will be described along the manufacturing process shown in FIG. 4, but the same technique can be applied to the manufacturing process shown in FIG. 3.

  In order to attach the plating catalyst (catalyst that promotes the reduction reaction of metal ions) to the surface of the laminate including the inner surface of the through hole, the laminate is immersed in a palladium-tin colloid catalyst application solution with sufficient stirring. That's fine. Using the catalyst remaining on the inner surface of the through hole, the conductive metal is selectively attached to the inner surface. Examples of the method for attaching the conductive metal include an electroless plating method, a sputtering method, and a conductive metal paste coating method. Among these, the electroless plating method is preferable.

  Before performing electroless plating, the catalyst (for example, palladium-tin) remaining on the inner surface of the through hole is activated. Specifically, by immersing in a commercially available organic acid salt or the like for activating the plating catalyst, tin is dissolved and the catalyst is activated. By immersing the porous resin film provided with the catalyst on the inner surface of the through hole in the electroless plating solution, the conductive metal (plating particles) can be deposited only on the inner surface of the through hole to which the catalyst is attached. By this method, a cylindrical fuse layer is formed.

  When using the stretched porous PTFE membrane, the plating particles are deposited so as to be entangled with the resin portion (mainly fibrils) exposed on the inner surface of the through-hole of the stretched porous PTFE membrane at first, so by controlling the plating time, The adhesion state of the conductive metal can be controlled. By setting an appropriate plating amount, a conductive metal layer is formed while maintaining a porous structure, and it is possible to provide elasticity in the film thickness direction as well as elasticity.

  The thickness of the resin part having a fine porous structure (for example, the thickness of the fibril of the stretched porous PTFE membrane) is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. The particle diameter of the conductive metal is preferably about 0.001 to 5 μm. The adhesion amount of the conductive metal can be appropriately set according to desired fusing characteristics. In many cases, the adhesion amount of the conductive metal is preferably about 0.01 to 4.0 g / ml, but is not limited thereto.

  The fuse layer produced as described above is preferably coated with a noble metal or a noble metal alloy in order to improve oxidation prevention and electrical contact. As the noble metal, palladium, rhodium, and gold are preferable from the viewpoint of low electric resistance. The thickness of the coating layer is preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.1 μm. For example, when the conductive part is coated with gold, a method of performing displacement gold plating after coating the conductive metal layer with nickel of about 8 nm is effective.

  When an expanded porous PTFE film is used as the porous resin film, a fuse layer having a structure in which conductive metal particles adhere to fibrils is formed on the inner surface of the through hole. When stress in the thickness direction is applied to the expanded porous PTFE film, the distance between the fibrils is reduced, so that the stress is relaxed and the structure of the fuse layer is maintained without being destroyed. Therefore, even if a compressive force is applied to the stretched porous PTFE film, the fuse layer hardly deteriorates.

  The electrode can be formed using a conductive metal generally used as an electrode material. In order to arrange the electrodes at both ends of the porous resin film, any method is adopted in which the ends of the U-shaped electrode are firmly adhered with a tool, pinned, or adhered with an adhesive. be able to.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.

[Example 1]
Both sides of an expanded porous PTFE membrane having a porosity (ASTM-D-792) of 60%, an average pore size of 0.1 μm, a bubble point (measured in accordance with ASTM-F-316-76 using isopropyl alcohol) of 150 kPa and a thickness of 800 μm. A stretched porous PTFE sheet having a porosity of 60%, an average pore diameter of 0.1 μm, and a thickness of 30 μm is overlapped and sandwiched between two stainless steel plates having a thickness of 3 mm. Heat-treated. After heating, it was quenched with water from the top of the stainless steel plate to obtain a laminate of porous PTFE membranes fused in three layers.

  The laminate obtained as described above was cut into 5 mm × 10 mm squares. This sample has a rotation speed of 100,000 / min and a feed speed of 0.01 mm / rev. The drill was operated under the conditions of the above, and eight through holes having a diameter of 300 μmφ were drilled at a pitch (hole interval) of 1 mm. Degrease treatment by immersing the laminated body with through-holes in ethanol for 1 minute to make it hydrophilic and then immersing it in Melplate PC-321 manufactured by Meltex Co., Ltd. diluted to 100 ml / L for 4 minutes at a temperature of 60 ° C. Went. Further, after immersing the laminate in 10% sulfuric acid for 1 minute, as a pre-dip, immersed in 0.8% hydrochloric acid for 2 minutes in a solution of Meltex Co., Ltd. Enplate PC-236 dissolved at a rate of 180 g / L. did.

  Further, the laminate was prepared by adding 150% of Enplate PC-236 manufactured by Meltex Co., Ltd. in an aqueous solution prepared by dissolving 3% of Enplate Activator 444 manufactured by Meltex Co., Ltd., 1% of Enplate Activator Additive, and 3% of hydrochloric acid. The catalyst particles were adhered to the surface of the laminate and the inner surface of the through hole by immersing in a solution dissolved at a ratio of L for 5 minutes. Next, the laminate was immersed in a 5% solution of Enplate PA-360 manufactured by Meltex Co., Ltd. for 5 minutes to activate the palladium catalyst nucleus. Thereafter, the first and third mask layers were peeled off to obtain a porous PTFE membrane in which catalytic palladium particles adhered only to the inner surface of the through hole.

  Meltex Co., Ltd. Melplate Cu-3000A, Melplate Cu-3000B, Melplate Cu-3000C, Melplate Cu-3000D are each 5%, and Melplate Cu-3000 Stabilizer is 0.1%. The above-mentioned expanded porous PTFE membrane was immersed in the electrolytic copper plating solution with sufficient air stirring, and only the inner surface of each through hole was made conductive with copper particles. The thickness of the plating layer was about 3 μm.

  Subsequently, gold plating was performed in order to improve rust prevention and contact with circuit board electrodes. For the gold plating, a displacement gold plating method from nickel was adopted by the following method. A porous PTFE membrane with copper particles attached to the inner wall surface of the through hole is immersed as a pre-dip in Atotech's Activator Aurotech SIT Additive (80 ml / L) for 3 minutes, and then supplied with a catalyst. (125 ml / L), immersed in a bath solution of Atotech's Activator Aurotech SIT Additive (80 ml / L) for 1 minute, and further immersed in an Atotech Aurotech SIT post dip (25 ml / L) for 1 minute. Deposited on copper particles.

  Next, based on an electroless nickel plating solution built with sodium hypophosphite (20 g / L), trisodium citrate (40 g / L), ammonium borate (13 g / L), nickel sulfate (22 g / L). The membrane was immersed for 5 minutes and the copper particles were nickel coated. Subsequently, Meltex replacement gold plating solution [Melplate AU-6630A (200 ml / L), Melplate AU-6630B (100 ml / L), Melplate AU-6630C (20 ml / L), sodium gold sulfite aqueous solution (as gold In 1.0 g / L], the base film was immersed for 5 minutes to perform gold coating of conductive particles.

  In order to connect the through holes of the stretched porous PTFE membrane thus obtained in series, a copper foil was partially heat-sealed on both sides of the stretched porous PTFE membrane. Electrodes were placed on both ends of the stretched porous PTFE film and covered with an epoxy resin film to produce a fuse having the same structure as that shown in FIG. The fuse can exhibit a typical fast-blow type fusing characteristic.

  The fuse of the present invention can be used as a microminiature fuse suitable for mounting on a printed circuit board.

It is sectional drawing which shows an example in the fuse of this invention. It is sectional drawing which shows another example of the fuse of this invention. It is a flowchart which shows the manufacturing process of the fuse shown in FIG. FIG. 3 is a flowchart showing a manufacturing process of the fuse shown in FIG. 2.

Explanation of symbols

10: Porous resin layer 11-14: Each part 20-22 of porous resin layer: Through hole 30-38: Plating catalyst 40-48: Plating layer (fuse layer)
50, 51: Connection conductor 60, 61: Electrode 70, 71: Protective layer 200: Porous resin layer 301, 302: Mask layer 201-204: Each part of porous resin layer 400-402: Through hole 500-502: Plating catalyst 600 to 602: Plating layer (fuse layer)
700 to 703: Connection conductor 800, 801: Electrode 900, 901: Protective layer

Claims (9)

  A porous resin film having through-holes in the thickness direction from one surface to the other surface, a fuse layer formed on the inner surface of the through-hole, and a fuse layer provided at both ends of the porous resin film; A fuse with two electrodes connected to both ends of each.   (A) a porous resin film provided with a plurality of through holes in the thickness direction from one surface to the other surface, (b) a fuse layer formed on the inner surface of each through hole, and (c) the porous resin film A connecting conductor for connecting the fuse layers in series or in parallel to each other, and (d) provided at both ends of the porous resin film, at the most end of each fuse layer. A fuse having two electrodes respectively connected to two adjacent fuse layers via connecting conductors.   The fuse according to claim 1 or 2, wherein the porous resin film is a porous fluororesin film.   The fuse according to claim 3, wherein the porous fluororesin film is an expanded porous polytetrafluoroethylene film.   Step I for forming through holes in the thickness direction of the porous resin film from one surface to the other surface, Step II for forming a fuse layer on the inner surface of each through hole, and both ends of the porous resin film, A method for manufacturing a fuse, comprising a step III in which two electrodes connected to both ends of a fuse layer are arranged.   Step 1 for forming a plurality of through holes in the thickness direction of the porous resin film from one surface to the other surface, Step 2 for forming a fuse layer on the inner surface of each through hole, and at least one surface of the porous resin film Step 3 of forming a connecting conductor for connecting each fuse layer in series or in parallel with each other, and connecting to the two fuse layers closest to both ends of each fuse layer at both ends of the porous resin film A method for manufacturing a fuse, comprising the step 4 of disposing two electrodes to be connected to each other via a conductor.   The method according to claim 5 or 6, wherein, in the step II or 2, a fuse layer is formed on the inner surface of each through hole by plating.   The production method according to claim 5 or 6, wherein the porous resin film is a porous fluororesin film.   The production method according to claim 5 or 6, wherein the porous resin film is a stretched porous polytetrafluoroethylene film.

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