JP6203136B2 - Protective element, manufacturing method thereof, and dissipative flux for protective element - Google Patents

Description

  The present invention relates to a protective element composed of a heat-resistant insulating substrate having a soluble refractory metal material and a pattern electrode directly bonded to the refractory metal material, a method for manufacturing the same, and a dissipative flux for the protective element.

  In recent years, with the rapid spread of small electronic devices such as mobile devices, small and thin protective elements mounted on a protection circuit for a power supply to be mounted are used. For example, a surface-mounting protection element is preferably used for the protection circuit of the secondary battery pack. These protective elements detect abnormal conditions such as overheating and overvoltage caused by overcurrent of the protected device, or respond to abnormal overheating of the ambient temperature to activate the fuse and shut off the electric circuit under specified conditions. There is a non-recoverable protection element. In order to ensure the safety of the device, the protection element generates heat by causing the resistance element to generate heat by a signal current when an abnormality occurring in the device is detected, and the fuse element made of a fusible alloy material is blown by the generated heat. Or the fuse element can be blown by an overcurrent to interrupt the circuit. For example, as described in Patent Document 1 and Patent Document 2, there is a protective element in which a resistance element that generates heat when an abnormality occurs is provided on an insulating substrate such as a ceramic substrate.

  These protective elements are made of a fusible alloy having a high melting temperature such as a high-temperature solder material so that the protective element is not melted by secondary soldering such as reflow mounting by the customer after the product is shipped. However, the fuse element itself is assembled by being joined to the pattern electrode of the insulating substrate by reflow soldering in the manufacturing process of the protective element. Therefore, in order to prevent the fuse element from melting in the conventional reflow process for manufacturing the protective element, the fuse element is exclusively used with a solder paste having a melting temperature lower than that of the fuse element at a reflow temperature lower than the solid phase temperature of the fuse element. It was necessary to join the pattern electrode. Even when solder paste is not used, as in Patent Document 2, a low melting point solder layer is laminated on a high temperature solder high melting point base material of the fuse element body, and the low melting point solder layer is melted and bonded to the pattern electrode. It was. Therefore, the conventional protection element is joined via the low melting point solder layer between the fuse element and the pattern electrode of the insulating substrate.

Japanese Patent Application Laid-Open No. 07-153367 JP 2013-239405 A

  However, particularly in the case of a very small protective element, the influence of the low melting point solder material used for joining the high temperature solder material of the fuse element to the pattern electrode has become non-negligible. When the low melting point component increases in the fuse element, the fusing temperature fluctuates greatly, which adversely affects the operation accuracy, which is not preferable for the protection element. In addition, conventional reflow bonding uses an organic flux containing solid components such as rosin, so the flux component is discharged to the bonding interface between the fuse element, which has become lighter and lighter and lighter, and the pattern electrode on the insulating substrate. This may cause a void and cause variations in internal resistance and bonding strength. Moreover, since it has a flux residue, there existed a fault, such as a washing | cleaning process becoming essential in the post-process of a reflow process. The conventional liquid flux used for joining the fuse elements remains in a trace amount even if the solid component such as rosin is reduced by adjusting the solvent ratio so as to be a low residue and contaminates the periphery of the pattern electrode. Furthermore, since the conventional flux contains an activator component such as a hardly volatile organic acid or a high boiling point amine, if it is left on the pattern electrode or the insulating substrate, it is left between the pattern electrodes of the Ag sintered body. Ion migration occurs and causes insulation failure.

  The present invention has been proposed in order to solve the above-mentioned problems. In a protective element for an electric / electronic circuit, a predetermined fuse element is used, and a low melting point is formed at a joint interface between the fuse element and the pattern electrode. A protection element characterized by having no metal, and a method for manufacturing the protection element, without forming a low melting point alloy layer that adversely affects the fusing temperature and operation accuracy on the fuse element, An object of the present invention is to provide a protective element manufacturing method that does not leave a caustic flux residue and does not require a cleaning step, and a protective element dissipative flux.

  According to the present invention, an insulating substrate, a plurality of pattern electrodes provided on the insulating substrate, and a predetermined fuse element electrically connected to the pattern electrode, the fuse element is made of a soluble refractory metal material, There is provided a protective element characterized by not having a low melting point metal material having a melting temperature lower than the melting temperature of the high melting point metal material and a low melting point alloy layer derived from the low melting point metal material at the joining interface with . The refractory metal material of the fuse element and the predetermined pattern electrode are directly diffused and joined without using another metal material therebetween. Therefore, there is no low melting point metal material or low melting point alloy layer that adversely affects the fusing temperature and operation accuracy at the junction interface between the fuse element and the pattern electrode, so the fusing temperature, operation accuracy and internal resistance value of the protective element are stabilized. , Reducing defective bonding and preventing the protective element from malfunctioning below a desired temperature. As the fuse element, it is particularly preferable to use a soluble alloy material having a temperature difference between the solidus temperature and the liquidus temperature of 5 ° C. or more and less than 100 ° C. The protection element according to the present invention may be provided with a resistance heating element on the insulating substrate so that the fuse element can be forcibly blown by heating as necessary.

  According to another aspect of the present invention, in a method of manufacturing a protection element comprising an insulating substrate, a plurality of pattern electrodes provided on the insulating substrate, and a fuse element electrically connected to the pattern electrode, the fuse element and the pattern electrode The electrical connection with the substrate includes a preparation step for preparing an insulating substrate, a bonding flux applying step for applying a dissipative flux to the insulating substrate or the fuse element, a mounting step for mounting the fuse element on a predetermined pattern electrode of the insulating substrate, and a fuse element. There is provided a method for manufacturing a protective element comprising a reflow process in which an insulating substrate equipped with a substrate is passed through a reducing reflow furnace adjusted to a reducing gas atmosphere to join a fuse element and a pattern electrode. .

  The dissipative flux according to the present invention covers the periphery of the fuse element with a liquid phase until the joining is completed, and dissolves and concentrates the reducing gas component activated at a high temperature to exhibit an appropriate reducing property. Since this dissipative flux is completely evaporated in the reflow process after the bonding is completed, there is an advantage that a flux residue does not remain and a cleaning process is unnecessary. Moreover, since there is no activator component left, there is no worry of corroding the metal material. In the reflow process, the furnace temperature is adjusted so that the effective temperature around the joint is higher than the solid phase temperature of the fuse element and lower than the liquid phase temperature in a high temperature reducing gas atmosphere. If the effective temperature of the reflow process is equal to or lower than the solid phase temperature of the refractory metal material used for the fuse element, the fuse element does not melt at all, so that the bonding does not work well and the bonding strength, electrical resistance value, etc. are deteriorated. In addition, when the effective temperature exceeds the liquid phase temperature of the fuse element, the fuse element is completely melted and spheroidized due to its surface tension, and the shape of the fuse element cannot be maintained, so that the protection element cannot be assembled. . Further, when the temperature of the reducing gas is less than 300 ° C., the reducing gas has a relatively low reducing activity, and the temperature of the reducing gas is preferably 300 ° C. or higher. Therefore, it is particularly preferable that at least the peak temperature in the reflow process is an ambient temperature of 300 ° C. or higher at which the reducing gas is sufficiently activated, and the effective temperature around the junction heated in the reducing gas atmosphere is the fuse element. It is preferable to adjust the conveyance speed, the number of conveyance, the conveyance jig and the like so that the solid phase temperature is not lower than the liquid phase temperature and not higher than the liquid phase temperature. When joining with reducing gas only without using dissipative flux, mass transfer such as diffusion of reducing gas into the metal oxide solid existing on the surface of the fuse element and discharge of reduction products is a gas phase. The reaction is slow, the reaction rate is extremely slow, and it takes a long time to complete the joining, which is not practical.

  In the protective element according to the present invention, the refractory metal material of the fuse element and the predetermined pattern electrode are directly interdiffused and joined without using another metal material therebetween. Since there is no low melting point metal material or low melting point alloy layer that adversely affects the fusing temperature and operation accuracy at the junction interface between the fuse element and the pattern electrode, the fusing temperature, operation accuracy and internal resistance value of the protective element are stabilized, Reduces bonding failure and prevents the protective element from malfunctioning below the desired temperature

  The protection element manufacturing method according to the present invention dissolves and concentrates the reducing gas activated at the working temperature by the dissipative flux, and the dissipative flux acts as a medium for dissolving and removing oxides on the surface of the fuse element. And facilitates the mass transfer of the pattern electrode and significantly promotes the diffusion bonding reaction. Since this dissipative flux works as an active medium for a certain period of time, it completely evaporates in a reflow furnace, leaving no residue, so that the cleaning step can be omitted. After the flux is dissipated, the metal material of the protective element can be protected from high-temperature oxidation by the reducing gas atmosphere.

It is the protection element 10 which concerns on this invention, (a) shows the top view which cut | disconnected the cover body along the dd line of (b), (b) followed the DD line of (a). Sectional drawing is shown, (c) shows the bottom view. It is the protection element 20 which concerns on this invention, (a) shows the top view which cut | disconnected the cover body along the dd line of (b), (b) followed the DD line of (a). Sectional drawing is shown, (c) shows the bottom view. It is the protection element 30 which concerns on this invention, (a) shows the top view which cut | disconnected the cover body along the dd line of (b), (b) followed the DD line of (a). Sectional drawing is shown, (c) shows the bottom view. The flowchart of the manufacturing process of the protection element which concerns on this invention is shown.

  As shown in FIG. 1, the protection element 10 according to the present invention includes an insulating substrate 11, a plurality of pattern electrodes 12 provided on the surface of the insulating substrate 11, and at least one fuse element 13 electrically connected to the pattern electrode 12. And an operating flux applied to the surface of the fuse element 13, and a lid 14 that covers the operating flux and the upper portion of the fuse element 13. The fuse element 13 has a solidus temperature of 250 ° C. or more and a liquidus temperature. Using a high melting point metal material of less than 400 ° C., the fuse element 13 and the pattern electrode 12 are directly joined without using another metal material having a lower melting temperature, such as a low melting point solder material. And The refractory metal material used for the fuse element 13 is not particularly limited, but is 94.5Pb-5.5Ag (solidus 304 ° C., liquidus 365 ° C), 95Pb-5Sn (solidus 300 ° C, liquidus 314). ° C), 90Pb-8Sn-2Ag (solidus 290 ° C, liquidus 320 ° C), 86Pb-14Sn (solidus 255 ° C, liquidus 289 ° C), 85.5Pb-14.5Sn (solidus) High temperature solder materials such as 251 ° C. and liquidus 288 ° C. can be suitably used. The insulating substrate 11 of the protective element is made of a heat-resistant insulating substrate such as a glass epoxy substrate, a BT (Bismaleimide Triazine) substrate, a Teflon (registered trademark) substrate, a ceramic substrate, a glass substrate, etc. A resistance heating element may be provided as necessary. The resistance heating element is provided with an insulating coating as necessary. In the case where the resistance heating element is not provided, the central electrode of the pattern electrodes 22 and 32 connected to the fuse elements 23 and 33 in FIG. 2 or 3 may be omitted. The operating flux is a coating flux of solid or semi-solid paste applied on the fuse element 13 after bonding the fuse element 13 to the insulating substrate 11, and is applied to guarantee the fuse operation of the protective element. Therefore, it is different from the dissipative flux for bonding. The lid body 14 only needs to cover the upper portions of the insulating substrate 11 and the fuse element 13 to ensure a desired cavity space, and does not limit the shape and material. For example, a dome-shaped resin film material, a plastic material, a ceramic material, or the like can be suitably used for the lid body 14. In the protection element of the present invention, the wiring means for electrically connecting the pattern electrodes on the upper and lower surfaces of the insulating substrate is, for example, a conductor through hole that penetrates the insulating substrate, or a half through that is formed on the end surface by breaking the conductor through hole in half. Surface wiring by holes or planar electrode patterns can be used.

  As shown in the manufacturing process flow of FIG. 4, the protection element manufacturing method according to the present invention includes an insulating substrate, a plurality of pattern electrodes provided on the insulating substrate, and a refractory metal material electrically connected to the pattern electrodes. In the manufacturing method of the protection element including the fuse element, the electrical connection to the pattern electrode of the fuse element includes a substrate preparation step 41 for preparing an insulating substrate, and a flux applying step 42 for applying a dissipative flux to the insulating substrate or the fuse element. And an alloy mounting step 43 for mounting the fuse element on a predetermined pattern electrode of the insulating substrate, and a reduction in which the insulating substrate mounting the fuse element is adjusted to a reducing gas atmosphere or a mixed atmosphere of a reducing gas and an inert gas. Reflow process 44 in which the fuse element and the pattern electrode are joined by passing through a reflow reflow furnace Method for producing a protective element characterized by Ranaru is provided. After the reflow process 44, an operation flux application process 45 for applying an operation flux to the fuse element mounted on the insulating substrate, a cap mounting process 46 for covering the insulating substrate with a cap covering the operation flux film and the fuse element, and insulating the cap. The protective element of the present invention is manufactured through a resin coating process 47 for applying a curable resin to bond the substrate, a resin curing process 48 for curing the applied curable resin, and the like.

  For example, a protective element comprising an insulating substrate made of alumina, a plurality of pattern electrodes made of Ag, Ag—Pt alloy, etc. provided on the insulating substrate, and a refractory metal fuse element electrically connected to the pattern electrode. In the manufacturing method, the electrical connection of the fuse element to the pattern electrode includes a substrate preparation step 41 for preparing an insulating substrate, a flux applying step 42 for applying the dissipative flux of the present invention to the insulating substrate or the fuse element, and a fuse element. An alloy mounting step 43 for mounting a metal element on a predetermined pattern electrode of an insulating substrate, and an insulating substrate on which a fuse element is mounted are made of hydrogen gas or a mixed gas of hydrogen gas and nitrogen gas with a hydrogen gas concentration adjusted to 74% or more. In a reducing gas atmosphere, the effective temperature (joint ambient temperature) is higher than the solid phase temperature of the fuse element. It consists of a reflow process 44 in which a fuse element and a pattern electrode are joined by passing through a reducing reflow furnace whose temperature is adjusted to be equal to or lower than the phase temperature. After the reflow process 44, the fuse element mounted on the insulating substrate is operated. An operation flux application process 45 for applying a flux, a cap mounting process 46 for covering the insulating substrate with a cap that covers the operation flux application film and the fuse element, and a resin application for applying a photocurable resin to bond the cap and the insulating substrate. The protective element is manufactured through step 47, a resin curing step 48 in which UV is cured by irradiating the applied resin with ultraviolet rays. The resin applied to the resin application step 47 may be any curable resin having adhesiveness, and can be replaced with, for example, a thermosetting resin such as an epoxy resin instead of the photocurable resin. The thermosetting resin is cured by normal temperature or heating in the resin curing step 48. The upper limit of the resin curing temperature is set to a temperature that does not adversely affect the components including the fuse element.

  The reducing gas used for manufacturing the protective element according to the present invention is made of hydrogen gas, and the inert gas is made of nitrogen gas or rare gas. In the reducing reflow furnace, the furnace temperature is adjusted so that the effective temperature around the joint in the reducing gas atmosphere is not less than the solid phase temperature of the fuse element and not more than the liquid phase temperature. Particularly preferably, the reducing gas atmosphere temperature of the furnace, for example, the circulating temperature of the reducing gas (at least the peak temperature of the reflow) is set to 300 ° C. or more at which the reducing gas is sufficiently activated. The dissipative flux works as a medium that dissolves and concentrates the reducing gas activated at the working temperature and also dissolves and removes oxides on the surface of the fuse element, facilitating mass transfer between the fuse element and the pattern electrode, and diffusion bonding reaction. Remarkably promotes. At the same time, the dissipative flux absorbs the heat of vaporization associated with the breaking of hydrogen bonds from the surroundings while the flux liquid wets and covers the bonding site, so that the fuse element is not overheated. Since this dissipative flux works as an active medium for a certain period of time, it completely evaporates in a reflow furnace, leaving no residue, so that the cleaning step can be omitted. After the flux is dissipated, the protective material metal material is protected from high-temperature oxidation by a reducing gas atmosphere.

  The dissipative flux used for the production of the protective element according to the present invention is a polyol having a carbon number of 2 or more (also referred to as a polyhydric alcohol) or a partial alcohol ether derivative, a partial carboxylic acid ester derivative of a polyol leaving at least two hydroxyl groups, A partial phenyl ether derivative is used as an active ingredient. These active ingredients preferably have a boiling point of 140 to 240 ° C. For example, ethylene glycol, polyethylene glycols, propylene glycol, polypropylene glycols, copolymers of ethylene glycol and propylene glycol, glycerin, pentaerythritol or its mono- or dialcohol ethers, trimethylolpropane, dimethylpentanediol, etc. are suitable. It is. A bulking agent may be added to this for the purpose of evaporation adjustment or dilution, if necessary. This extender comprises mono- or polyalkylene glycol alkyl ether or mono- or polyalkylene glycol phenyl ether or mono- or polyalkylene glycol carboxylic acid ester or higher alcohol or terpene alcohol having a boiling point of 240 ° C. or lower and its derivatives. Available. The addition amount of the extender is preferably 0 to 80% by mass. When bonding is attempted using only high-temperature reducing gas without using this dissipative flux, the oxide layer present on the bulk surface of the fuse element and pattern electrode is removed only by gas phase catalytic reduction. Therefore, it takes several hours to several tens of hours for joining, and is extremely inefficient and difficult to industrially use.

  The dissipative flux of the present invention reacts with active hydrogen under high-temperature hydrogen reflow conditions and exhibits moderate reducibility. Although the detailed activation mechanism is still unclear, the proton of hydrogen gas in equilibrium with proton and hydride at high temperature reacts with the active component polyols and the alcoholic hydroxyl group of the extender to form a reducing alkyl. It is considered that the remaining reducing hydride, which becomes oxonium ions, is dissolved and concentrated in the polyol medium to catalytically remove and remove the metal oxides present on the surface of the fuse element. Since polyols (polyhydric alcohols) remove water molecules adsorbed on metal surfaces and water vapor in the atmosphere by dissolving and absorbing them in hydrogen-bonded clusters, they also function as desiccants to remove moisture that is harmful by hydrogen reflow. . This dissipative flux is a reflow furnace adjusted so that the effective temperature is not less than the solid phase temperature of the fuse element and not more than the liquid phase temperature, without causing the fuse element made of a refractory metal material to completely melt, The components can be efficiently concentrated in the polyol liquid phase of the dissipative flux, and the oxide film on the surface of the fuse element and the pattern electrode can be catalytically reduced to be removed, and the dissipative flux of the present invention is a reflow process. Since it completely evaporates at 44, no flux residue is produced and no cleaning is required. The effective temperature around the joint heated in a reducing gas atmosphere is that of the refractory metal material used for the fuse element (for example, high-temperature solder material containing 85 mass% or more of Pb such as 85 mass% Pb and the remaining Sn alloy). If the temperature is lower than the solid phase temperature, the fuse element is not melted at all, so that the bonding is not performed well and the bonding strength, the electric resistance value, etc. are deteriorated. When the effective temperature exceeds the liquidus temperature of the refractory metal material that constitutes the fuse element, the fuse element becomes completely molten and spheroidizes due to its surface tension, making it impossible to maintain the shape of the fuse element. Can not be assembled. In addition, when the reflow peak temperature is less than 300 ° C., the activation of the hydrogen gas is insufficient, so that the reaction component between the dissipative flux component and the active hydrogen is not sufficiently generated. The reducing action on the coating is slow. On the other hand, high-temperature active hydrogen alone is also reducible, but when it reacts with solid-state metal oxides using only hydrogen gas without using a dissipative flux, the medium flux liquid does not intervene. The metal oxide cannot be quickly dissolved and removed in the polyol of the medium by chelate coordination like the nium ion, and since there is no catalytic effect on the gas alone, the bonding speed becomes extremely slow.

  The dissipative flux of the present invention is composed only of a high-boiling-point polyol which is an active ingredient, and if necessary, an alkylene glycol half ester such as ethylene glycol monophenyl ether or a terpene alcohol such as α-terpineol. Inclusive broad alcohols may be further added as extenders. The bulking agents polyhydric alcohol alkyl derivatives and higher alcohols cut the hydrogen-bonded clusters between the high-boiling polyol molecules appropriately, thus facilitating evaporation drying of the dissipative flux and adjusting the residence time of the flux liquid phase. It works to improve sex.

  As shown in FIG. 1, the protective element 10 of Example 1 according to the present invention includes an alumina / ceramic insulating substrate 11, a plurality of Ag alloy pattern electrodes 12 provided on the upper and lower surfaces of the insulating substrate 11, and an insulating substrate. 11, a fuse element 13 electrically connected to the pattern electrode 12 on the top surface, an operation flux (not shown) applied to the surface of the fuse element 13, and a lid made of liquid crystal polymer that covers the top of the fuse element 13 and is fixed to the insulating substrate 11. The fuse element 13 is made of high-temperature solder of 86Pb-14Sn (solid phase line 255 ° C., liquidus line 289 ° C.), and does not involve any other solder material having a melting temperature lower than this, The pattern electrode 12 was directly joined.

  As shown in FIG. 2, the protective element 20 of Example 2 according to the present invention includes an alumina / ceramic insulating substrate 21, a plurality of Ag alloy pattern electrodes 22 provided on the upper and lower surfaces of the insulating substrate 21, and a pattern. A resistance heating element 25 electrically connected to the electrode 22 and provided on the lower surface of the insulating substrate 21, a fuse element 23 electrically connected to the pattern electrode 22 on the upper surface of the insulating substrate 21, and an operating flux applied to the surface of the fuse element 23 (see FIG. And a lid 24 made of a liquid crystal polymer that covers the upper portion of the fuse element 23 and is fixed to the insulating substrate 21. The fuse element 23 is composed of 85.5Pb-14.5Sn (solid line 251 ° C., liquid It is made of high-temperature solder with a phase wire of 288 ° C. and directly joined to a predetermined pattern electrode 22 without using another solder material having a lower melting temperature.The pattern electrode 22 has a half through hole 26 of Ag alloy that electrically connects the pattern electrodes 22 on the upper and lower surfaces of the substrate. Although not shown in particular, the surface of the resistance heating element 25 is overglazed with a glass material.

  The protection element 30 of Example 3 according to the present invention is a modification of the protection element 20. As shown in FIG. 3, an insulating substrate 31 made of alumina / ceramics, a plurality of Ag alloy pattern electrodes 32 provided on the upper and lower surfaces of the insulating substrate 31, and electrically connected to the pattern electrode 32, provided on the upper surface of the insulating substrate 31. A resistance heating element 35; a fuse element 33 in contact with the resistance heating element 35 and electrically connected to the pattern electrode 32 on the upper surface of the insulating substrate 31; an operating flux (not shown) applied to the surface of the fuse element 33; And a lid 34 made of a liquid crystal polymer that covers the upper portion of the element 33 and is fixed to the insulating substrate 31. The fuse element 33 is made of high-temperature solder of 95Pb-5Sn (solid phase line 300 ° C., liquidus line 314 ° C.). Then, it was directly joined to the predetermined pattern electrode 32 without using another solder material having a lower melting temperature. The pattern electrode 32 has a half through hole 36 made of an Ag alloy that electrically connects the pattern electrodes 32 on the upper and lower surfaces of the substrate. Although not shown in particular, the surface of the resistance heating element 35 is overglazed with a glass material.

  The protective elements of Examples 1 to 3 are assembled by the method for manufacturing a protective element of the present invention shown in the flowchart of FIG. That is, a substrate preparation step 41 for preparing an insulating substrate in which a plurality of Ag pattern electrodes are appropriately provided with heating resistors, a dissipative property composed of 80% by mass of trimethylolpropane, and the balance of 2,4-diethyl-1,5-pentanediol. Flux application process 42 for applying flux 1 to an insulating substrate, alloy mounting process 43 for mounting a fuse element on a predetermined pattern electrode of the insulating substrate, and mixing an insulating substrate with a fuse element with hydrogen gas and nitrogen gas Using a reducing reflow furnace with a total length of 4 m adjusted to a hydrogen gas concentration of 75% in a gas atmosphere, a first preheating zone with a furnace temperature of 310 ° C., a second preheating zone with a furnace temperature of 315 ° C., and a main heating with a furnace temperature of 395 ° C. A reflow process 4 in which a fuse element and a pattern electrode are joined by passing through a zone and a cooling zone at a temperature of 295 ° C. for 45 minutes. Consisting of. After the reflow process 44, an operation flux application process 45 for applying an operation flux to the fuse element mounted on the insulating substrate, a cap mounting process 46 for covering the insulating substrate with a cap covering the operation flux coating film and the fuse element, The protective element is manufactured through a resin coating process 47 for applying a photocurable resin to adhere to the insulating substrate, and a resin curing process 48 for irradiating the applied resin with ultraviolet rays to UV cure.

  In Comparative Example 1, an attempt was made to produce a protective element in which other conditions were the same as in Example 1 without using a dissipative flux. That is, in Comparative Example 1, the same reflow furnace adjusted to the same working temperature in the same reducing gas atmosphere as in Example 1 was passed through, and the insulating substrate 11 was formed only in the reducing gas atmosphere without using a dissipative flux. This is an attempt to join the pattern electrode 12 and the fuse element 13 together.

  In Comparative Example 2, as an example of a conventional activation flux, an activation flux for soldering consisting of 85% by mass of a solvent ethylene glycol monobutyl ether, 13% by mass of an activator triethanolamine, and the balance consisting of diglycolic acid as an activator. An attempt was made to make a protective element using the same reflow conditions as in Example 1. That is, in Comparative Example 2, the same reflow furnace adjusted to the same working temperature in the same reducing gas atmosphere as in Example 1 using a conventional activation flux was passed through, and the pattern electrode 12 of the insulating substrate 11 and This is an attempt to join the fuse element 13.

  Table 1 shows the results of comparison of the internal resistance value and the dimensional stability of the fuse element, in which 10 protection elements of Examples 1 to 3 and 10 protection elements of Comparative Examples 1 and 2 were produced.

  The internal resistance values (fuse resistance values) of Example 1 to Example 3 are kept constant in size without fusing the fuse element by minimizing shrinkage and deformation caused by excessive melting of the fuse element material. Therefore, the variation in the electric resistance value can be reduced, and the electric resistance of the bonding portion is also low, indicating that the bonding state is extremely good. On the other hand, in Comparative Example 1 in which no dissipative flux was used, the fuse element material was not shrunk or melted, but the bondability was poor and the fuse element and the pattern electrode were so-called brazed joints that were insufficiently alloyed. Resistance value increases. Further, in Comparative Example 2 made using the conventional activation flux, the activation force of the flux becomes excessive, the fuse element is blown out, or the alloy dimensions are significantly shrunk or deformed due to melting, and the internal resistance value varies. Becomes very large.

  As the dissipative flux applicable to the present invention, in addition to the dissipative flux 1 described above, compositions such as the dissipative flux 2 or the dissipative flux 5 exemplified below can be suitably used. That is, the dissipative flux 2 is composed of 50% by mass of ethylene glycol and the balance being 2,5-dimethyl-2,5-hexanediol. The dissipative flux 3 is composed of 65% by mass of glycerin and the balance being 2,4-diethyl-1,5-pentanediol. The dissipative flux 4 is composed of 35% by mass of trimethylolpropane, 10% by mass of 2,5-dimethyl-2,5-hexanediol, and the balance is α-terpineol as an extender. The dissipative flux 5 is composed of 40% by mass of glycerin, 15% by mass of 2,4-diethyl-1,5-pentanediol, and the balance is diethylene glycol monophenyl ether as an extender.

  The present invention can be applied to a protection device for a secondary battery such as a battery pack or a protection device for a power supply circuit. The reducing gas of the present invention can be expected to have the same effect even when a very small amount of formic acid vapor is used instead of hydrogen gas.

10, 20, 30 ... protective element,
11, 21, 31 ... insulating substrate,
12, 22, 32 ... pattern electrodes,
13, 23, 33 ... fuse elements,
14, 24, 34 ... lid,
25, 35... Resistance heating element,
16, 26, 36 ... Half through hole,
41 ... substrate preparation process,
42 ... flux application process,
43 ... Alloy mounting process,
44 ... reflow process,
45 ... operation flux application process,
46: Cap mounting process,
47 ... Resin application process,
48 ... Resin curing step.

Claims (3)

An insulating substrate; a plurality of pattern electrodes provided on the insulating substrate; and a predetermined fuse element electrically connected to the pattern electrode, wherein the fuse elements are 94.5Pb-5.5Ag, 90Pb-8Sn-2Ag, A low melting point metal material comprising any one alloy material selected from the group of 86Pb-14Sn and 85.5Pb-14.5Sn, and having a melting temperature lower than the melting temperature of the fuse element at the bonding interface with the pattern electrode And a protective element having no low melting point alloy layer derived from the low melting point metal material.   The protective element according to claim 1, wherein a resistance heating element is provided on the insulating substrate. The protective element according to claim 1, wherein the insulating substrate, the pattern electrode, and the fuse element have no flux residue.

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