JP2004363630A - Packaging method of protective element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the response of operation, widen the latitude of fuse element for selecting material, and reduce the manufacturing cost, when a protection element, in which a fuse element is arranged on a substrate, is packaged. <P>SOLUTION: A protection element 1, in which a fuse element 4 is arranged across electrodes 3a, 3b and 3c on a substrate 2 is packaged at the temperature which is lower than the liquid phase point but is higher than the solid phase point of the fuse element 4 of the protective element 1. As the protective element 1, an element having a difference of 5°C or larger between the liquid phase and the solid phase points is used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for mounting a protection element in which a fuse element is provided on a substrate.

  As a chip-shaped current fuse, a protection element in which a fuse element is provided on a substrate is known. Further, such a protection element provided with a heating element close to a fuse element is also used for an overvoltage prevention device (Patent Documents 1 and 2).

  FIGS. 2B and 2C are a plan view and a cross-sectional view of such a protection element 1o. In this protection element 1o, electrodes 3a, 3b, and 3c are provided on a substrate 2, and a solder foil is provided as a fuse element 4 so as to bridge the electrodes 3a, 3b, and 3c. A heating element 7 is provided on the lower surface of the electrode 3b via an insulating layer 8. The heating element 7 is electrically heated from the electrode 3o through the wirings 3x and 3y.

  In the manufacturing process of the protection element 1o, after the wirings 3x, 3y, the heating element 7, the insulating layer 8, and the electrodes 3a, 3b, 3c are formed on the substrate 2, as shown in FIG. Solder paste 5 is applied on 3a, 3b, and 3c, and fuse element 4 is mounted thereon, and a cover (not shown) is further provided as necessary. The protection element 1o thus obtained is usually heated and mounted on a base circuit board using a technique such as reflow or soldering.

  Therefore, as a constituent material of the fuse element 4, in order to prevent the fuse element 4 from being blown out at the time of mounting the protection element 1 o, a solid point higher than the mounting temperature of the protection element 1 o, particularly, the maximum temperature reached at the time of mounting, Those having a high solidus point and an even higher liquidus point are used. As a constituent material of the solder paste 5, a material having a liquidus point at least equal to or higher than the temperature at the time of heating and mounting is selected. For example, when the mounting temperature of the protection element 1o on the circuit board is 250 ° C., the solder paste 5 of the protection element 1o has a liquidus point of 250 ° C. or higher. Those whose points are higher than the liquidus point of the solder paste 5 are used.

Japanese Patent No. 2792433 JP-A-8-161990

  When the above-described protection element 1o is used as a protection device for a device to be protected, when an error occurs in the device to be protected, an overcurrent flows through the fuse element 4 and the fuse element 4 is blown, or the wires 3x and 3y from the electrode 3o are disconnected. The heating element 7 is energized and heated, and the heat blows the fuse element 4. However, since the liquid phase point of the fuse element 4 is high, there is a problem that the time from the start of the temperature rise of the fuse element 4 to the fusing is long, and the operation response as a protection element is slow. Also, since it takes time until the fuse element 4 is blown, the mounting portion of the protection element 1o on the base circuit board is melted before the fuse element 4 is blown, and the protection element 1o is displaced from the base circuit board or is mounted around the base circuit board. There is also a problem that a defect is caused in parts, board wiring, and the like.

  Furthermore, providing the above-mentioned relationship between the liquid phase point and the solid phase point of the solder paste 5 and the fuse element 4 of the protection element 1o also has a problem that the room for material selection is narrowed and the cost is increased. Particularly, in order to improve the operation response, even if the solid point of the fuse element 4 is set to be slightly higher than the mounting temperature by approaching the mounting temperature of the protection element 1o, a suitable fuse having such a solid point is used. Finding element materials is difficult.

  The present invention is intended to solve the above-described problems of the related art. In a protection element in which a fuse element is provided on a substrate, the operation response is improved, and the range of material selection for the fuse element is expanded. It is intended to reduce manufacturing costs.

  The present inventors, in a protective element having a fuse element provided on a substrate, in order to prevent the fuse element from being blown when mounting the protective element, the liquid phase point as a constituent material of the fuse element, If the temperature is higher than the mounting temperature of the protection element, the solidus point does not necessarily have to be higher than the mounting temperature.In other words, even if the solidus point is lower than the mounting temperature, if the liquidus point is higher than the mounting temperature, The fuse element does not completely retain the original shape, but does not melt, so that it has been found that the function as the fuse element is maintained, and the present invention has been completed.

  That is, the present invention provides a method for mounting a protection element in which a protection element in which a fuse element is provided on an electrode on a substrate is mounted at a temperature lower than the liquidus point of the fuse element of the protection element and equal to or higher than the solidus point. provide.

  According to the present invention, when a protection element having a fuse element provided on a substrate is mounted on a circuit board such as an overvoltage protection device, the solid-state point of the fuse element is set lower than in the conventional example. Can be improved. In addition, this makes it possible to expand the range of material selection for the fuse element and reduce the manufacturing cost. Furthermore, when a protection element is used so that the fuse element is heated by a separate heater and blows when the device to be protected is abnormal, the influence of heat on peripheral components other than the fuse element of the protection element is reduced, and the reliability of mounting is reduced. Performance can be improved.

  In addition, since the solid point of the fuse element is set at a temperature equal to or lower than the mounting temperature, the fuse element is in a reflow state during mounting. Therefore, the fuse element can be provided on the electrode without using the solder paste. Therefore, the manufacturing cost can be reduced by reducing the material, simplifying the manufacturing parameters, and the like, and the yield can be improved.

  Hereinafter, the protection element of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or equivalent components.

  In the protection element of the present invention, a fuse element is provided on an electrode on a substrate, and the shape and arrangement of each substrate, electrode, and fuse element itself are not particularly limited. Therefore, the protection element of the present invention may be configured as a chip-shaped current fuse in which a fuse element is provided on an electrode on a substrate, and a heating element may be provided close to the fuse element and used for an overvoltage prevention device. You may comprise as a protection element. For example, the arrangement can be the same as that of the conventional protection element 1o described with reference to FIG.

  The constituent materials of the substrate and the electrode are not particularly limited and can be the same as those of the conventional protection element.However, for the fuse element, the liquidus point is higher than the mounting temperature expected for the protection element, Preferably, the temperature is higher than the highest temperature at the time of mounting. Further, a solid phase point whose temperature is equal to or lower than the mounting temperature, preferably equal to or lower than the highest temperature at the time of mounting is used. As a result, the range of selection of the constituent material of the fuse element can be greatly expanded. Also, since the fuse element starts to be melted at the time of mounting, the fuse element can be satisfactorily mounted on the electrode without using a solder paste between the electrode and the fuse element. For example, as shown in FIG. 1A, only flux 6 such as rosin is applied on electrodes 3a, 3b and 3c instead of solder paste, as shown in FIGS. 1B and 1C. Thus, the fuse element 4 can be satisfactorily joined to the electrodes 3a, 3b, 3c, and the protection element 1 can be obtained. Therefore, the manufacturing cost of the protection element 1 can be reduced. Further, when a solder foil having a specific composition is mounted as a fuse element 4 via a solder paste, the solder foil may be melted at the time of reflow. However, when the solder paste is not used, such a problem also occurs. Can be eliminated.

  The difference between the liquidus point and the solidus point of the fuse element 4 is preferably 5 ° C. or more, more preferably 10 ° C. or more. If the difference between the liquidus point and the solidus point is less than 5 ° C., it is not possible to cope with variations in mounting temperature generally occurring, and the fuse element may be blown. If such a variation can be eliminated, the fusing of the fuse element due to a small difference between the liquidus point and the solidus point will not be a problem. However, in order to eliminate such variation, it is necessary to manufacture the fuse element 4. It is not preferable because the conditions must be very strict. Further, if the liquidus point of the fuse element 4 is higher than the maximum temperature at the time of mounting by 50 ° C. or more, the operation response of the protection element 1 is undesirably slow.

  The constituent material of the fuse element 4 having such a liquidus point and a solidus point can be appropriately selected from known fuse element materials. For example, a solder foil made of Sn and Pb, general solder, or the like can be used. Can be. In this case, in order to make the fuse element 4 have a predetermined solid phase point and liquid phase point, the component ratio of the constituent materials may be adjusted. In particular, when a solder foil made of Sn and Pb is used, the liquidus point can be continuously adjusted by appropriately changing the ratio of Sn and Pb.

  Since the protection element of the present invention is configured as a protection element that can also be used for an overvoltage prevention device, not only a fuse element is provided on an electrode on a substrate, but also a heating element is provided in the vicinity of a fuse element. To make the element and the heating element close to each other means that the fuse element is placed on the heating element via an insulating layer as described in FIGS. 1 and 2 described above, Japanese Patent No. 2790433, and JP-A-8-161990. (Low melting point metal body), an embodiment in which fuse elements are stacked on a heating element without an insulating layer, as described in Japanese Patent Application No. 11-94385, JP-A-10-116549. As described in JP-A-10-116550, a heating element and a fuse element are arranged in a plane on a substrate. Shift also encompasses.

  For example, as shown in a protection element 1p shown in FIG. 3, a structure in which a heating element 7, an insulating layer 8, and a fuse element 4 made of a fuse material are sequentially stacked on a substrate 2 is formed by applying a resistive paste or the like. can do. In the figure, 3x and 3y are heating element electrodes, and 3a and 3b are fuse element electrodes. Reference numeral 9 denotes an inner sealing portion made of a solid flux or the like and sealing the fuse element 4 in order to prevent surface oxidation of the fuse element 4, and reference numeral 10 denotes a higher melting point or a higher softening point than the fuse element 4. This is an outer sealing portion that is made of a material having the following formula, and that prevents the melt from flowing out of the element when the fuse element 4 is blown.

  FIG. 4 is a circuit diagram of an overvoltage protection device using such a protection element 1p. In this circuit, terminals A1 and A2 are connected to electrode terminals of a device to be protected such as a lithium ion battery, and terminals B1 and B2 are connected to devices such as a charger used in connection with the device to be protected. The electrode terminals are connected. According to this overvoltage prevention device, when the charging of the lithium ion battery progresses and a reverse voltage equal to or higher than the breakdown voltage is applied to the zener diode D, the base current ib suddenly flows, thereby causing a large collector current ic to be generated by the heating element. , And the heating element 7 generates heat. This heat is transmitted to the fuse element 4 on the heating element 7, and the fuse element 4 is blown, thereby preventing an overvoltage from being applied to the terminals A1 and A2.

  FIG. 5 is a plan view (FIG. 5A) and a cross-sectional view (FIG. 5B) of a protection element 1q different from the protection element 1p of FIG. 3 described above. In this protection element 1q, two heating elements 7 are connected via an intermediate electrode 3z, and a fuse element 4 is provided thereon via an insulating layer 8.

  FIG. 6 is a circuit diagram of an overvoltage prevention device using such a protection element 1q. In the overvoltage protection device of the circuit of FIG. 4 described above, the power supply to the heating element 7 continues even after the fuse element 4 is blown by the overvoltage. However, according to the overvoltage protection device of the circuit of FIG. The fuse element 4 is blown at two locations 4a and 4b due to the heat generated by the heat source. After these blows, the power supply to the heating element 7 is completely cut off.

  The protection element 1r of FIG. 7 is also a protection element that can be used in the overvoltage protection device of the circuit of FIG. When the fuse element 4 is melted, the area of the electrodes 3a, 3b and the heating element 7 that are wetted by the melted fuse element is sufficiently increased when the fuse element 4 is melted. For simplicity, the insulating layer 8 on the heating element 7 is omitted. Since the insulating layer 8 on the heating element 7 is omitted, the operation time can be further reduced.

  Hereinafter, the present invention will be specifically described based on examples.

Examples 1 to 7
Using the solder foil and the solder paste shown in Table 1, the protection element shown in FIG. 1 without using the solder paste or the protection element shown in FIG. 2 using the solder paste was produced. In this case, an alumina substrate (3 mm × 5 mm) was used as the substrate 2, and the size of the solder foil was 0.15 mm (thickness) × 1.0 mm (width) × 4.2 mm (length).

Evaluation For the protection elements obtained in each of the examples and comparative examples, (a) oven heat resistance, (b) heater resistance, (c) fuse resistance, (d) 4W operation time, (e) 10A fusing time, Each was measured as follows. The results are shown in Tables 2 to 4.

  (a) Oven heat resistance: In order to prevent oxidation of the solder foil and to make the solder foil easy to melt, first, each protective element was covered with a flux. Note that no cap was provided on the protection element. Next, each protective element is placed in an oven (STH-120 manufactured by ESPEC) set to a predetermined temperature. After that, once the temperature inside the oven once again reaches the set temperature, it is left for 1 minute and removed from the oven. The melting and unfusing of the solder foil were confirmed by changing the temperature of the oven by + 5 ° C or -5 ° C, and the same operation was repeated. In this repetition, the temperature at which the solder foil was never blown was used as an index of heat resistance.

  (b) Heater resistance: The resistance value of the heater section was measured using a multimeter (ADVANTEST TR 6847).

  (c) Fuse resistance: The resistance value of the solder foil was measured using a multimeter (ADVANTEST TR 6847).

  (d) 4W operation time: In the case where 4W (power value) was applied to the heater to generate heat and the solder foil was blown off by the heat, the time required from the start of 4W application until the solder foil was blown was measured.

  (e) 10A fusing time: In the case where 10A was flowed into the solder foil and the solder foil was blown by self-heating of the solder foil, the time required from the start of 10A energization to the melting of the solder foil was measured.

  All of Examples 1 to 6 had good heat resistance and operation response.

  In particular, from Table 2, it can be seen that the oven heat resistance is better when the liquidus point of both the solder paste and the solder foil is higher.

  In the evaluation of the 4W operation time, the operation time of the protection element of Example 6 not using the solder paste was faster than that of Examples 1 to 5 using the solder paste. This is probably because the amount of solder that melts during operation and the amount of solder that wets the electrodes are small because the protection element of Example 6 does not use the solder paste.

  In the evaluation of the 10A fusing time, the protective element of Example 6 was blown on average 10 seconds faster than Comparative Example 1.

  INDUSTRIAL APPLICABILITY The mounting method of the present invention is useful as a method for mounting a protection element provided with a fuse element on a substrate on a circuit substrate such as an overvoltage prevention device.

It is explanatory drawing of the manufacturing process of the protection element of this invention. It is explanatory drawing of the manufacturing process of a protection element. It is the top view (the same figure (a)) and sectional drawing (the same figure (b)) of a protection element. It is a circuit diagram of an overvoltage prevention device. It is the top view (the same figure (a)) and sectional drawing (the same figure (b)) of a protection element. It is a circuit diagram of an overvoltage prevention device. It is the top view (the same figure (a)) and sectional drawing (the same figure (b)) of a protection element.

Explanation of reference numerals

1, 1o, 1p, 1q, 1r protection element,
2 substrates,
3a, 3b, 3c electrodes,
4 fuse elements,
5 Solder paste,
Reference Signs List 6 flux 7 heating element 8 insulating layer 9 inner sealing section 10 outer sealing section

Claims (7)

  A method for mounting a protection element, wherein a protection element having a fuse element provided on an electrode on a substrate is mounted at a temperature lower than a liquidus point of the fuse element of the protection element and higher than a solidus point.   The mounting method according to claim 1, wherein a difference between a liquid phase point and a solid phase point of the fuse element is 5 ° C or more.   3. The mounting method according to claim 1, wherein a liquidus point of the fuse element is higher than a maximum attainment temperature when the protection element is mounted, and a solidus point is equal to or lower than the maximum attainment temperature at the time of mounting the protection element.   The mounting method according to claim 3, wherein a difference between a liquidus point of the fuse element and a maximum attained temperature during mounting is less than 50 ° C. 5.   The mounting method according to claim 1, wherein the fuse element is a solder foil.   The mounting method according to claim 1, wherein the fuse element is provided on the electrode without using a solder paste. The mounting method according to any one of claims 1 to 6, wherein the heating element is arranged close to the fuse element in the protection element to be mounted.

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