JP2005129352A - Thermal fuse with resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal fuse with resistance in which small size and low cost are realized by selection of the material and components used and simplification of assembly structure in a protection circuit in which a resistance heating element and a thermal fuse element are mounted and arranged on an insulating substrate. <P>SOLUTION: This is the thermal fuse with resistance in which a protection circuit is formed by mutually placing close by and arranging in space a resistance heating element of a chip resistor 8 and a thermal fuse element 10 on one side of a glass epoxy substrate 1, and by fixing by solder at the electrode part of wiring patterns 3-6 of the glass epoxy substrate 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention uses a resistance temperature fuse in which a resistance heating element and a temperature fuse element having an operating temperature of a predetermined temperature are mounted on an insulating substrate, and in particular, uses an insulating substrate having low thermal conductivity and a chip type component. The present invention relates to a temperature fuse with a resistance for a protective circuit suitable for downsizing and low cost by reducing the mounting arrangement interval at the time of soldering.

Generally, the temperature fuse is a protective element that is activated by an abnormal temperature rise around the device environment, such as excessive heat generation caused by an overcurrent of the protected device. On the other hand, as shown in Patent Document 1, the fuse resistor detects an abnormal signal generated in the device, and generates a resistance heat by this signal to operate the current fuse, and constitutes a protection circuit including a detection / control circuit. . As a main power source for portable information terminals, a high-density energy lithium ion secondary battery having excellent storage characteristics and liquid leakage resistance is used, and a protection circuit for a fuse resistor is used to ensure safety. For example, as shown in Patent Document 2, a secondary battery is provided with a double protection circuit of a return type and a non-reset type in order to prevent overcharge and overdischarge, and the battery voltage exceeds a predetermined set voltage. Highly safe protection with a resettable protection circuit that cuts off the charging current and a non-recoverable protection circuit that blows the thermal fuse when the battery voltage rises abnormally when the resettable protection circuit does not operate for some reason Configure the device. The thermal fuse used in the non-recoverable protection circuit is composed of two fusible fuse elements connected in series between the charger and the battery, and a resistance of a heating element that is thermally coupled to these fuse elements. Built-in thermal fuse. The heating element is configured to operate with an on signal of a voltage detection circuit that detects the battery voltage and outputs an on signal when the battery voltage exceeds a set value. As described in Non-Patent Document 1, for example, a resistance built-in thermal fuse used in such a protection circuit includes a low melting point alloy fuse element mounted on the front surface side of an insulating ceramic substrate and a resistance formed in a thin film on the back surface side. And is incorporated as a non-recoverable protection circuit for the secondary battery described above, and when an abnormality such as overcharging is detected, heat is generated by energizing the fuse element and the thermal coupling resistor to force The fuse element is blown to break the circuit. The protection circuit is configured by mounting a built-in resistor thermal fuse on the printed circuit board of the motherboard together with a dedicated control IC including a switching element such as a MOSFET that controls charging / discharging. It is installed side by side.
JP-A-7-153367 JP 10-56742 A NEC Technical Report vol. 53No. 10pp93-96

  In the above-described fuse resistor, the heating element and the current fuse are integrally coupled via an insulating layer, which is accompanied by structural complexity and troublesome manufacturing work with respect to the interposed insulating layer. That is, since the heating element and the current fuse are integrated, the cutoff characteristic is greatly affected by the structure of the insulating layer, and strict manufacturing control is required to avoid this. On the other hand, with a built-in resistor thermal fuse in which a single or two fuse elements are mounted on one side using a ceramic substrate and a thin film resistor is formed on the other side, it is interposed in the same manner as the protection circuit for the fuse resistor described above. The manufacturing process is inevitably complicated on the processing surface due to the formation of heat generating elements on the ceramic substrate. In addition, since an expensive ceramic material is used for the insulating substrate, the cost is increased, and due to the influence of the thermal conductivity of the substrate, the required mounting area is widened as a countermeasure for the soldering process. Therefore, the conventional protection circuit is disadvantageous for application to portable information devices and the like that are required to be reduced in size and cost. In addition, in order to increase the temperature detection sensitivity of the thermal fuse and operate it with high accuracy, it is desirable to mount it close to active elements that may cause abnormal overheating, but there is also a problem in workability in handling. Has occurred.

  Therefore, the present invention eliminates the above-mentioned conventional drawbacks and presents an improved mounting structure for a thermal fuse on an equipment circuit component, thereby increasing the cost associated with the material used for the protection circuit and the complexity of the assembly work. The purpose is to provide a new and improved thermal fuse with resistance that solves the above-mentioned problems while reducing costs by focusing on the selection of general-purpose members and the simplification of the assembly structure. It is.

  According to the present invention, an insulating substrate on which a wiring pattern having an electrode portion and a through hole is formed, and a temperature heater that operates at a predetermined temperature with a resistance heating element in an arrangement space close to each other on one side of the insulating substrate. There is provided a thermal fuse with resistance, which includes a thermal element and a thermal fuse element and a lead member soldered to a predetermined pattern electrode portion, respectively. In particular, the insulating substrate is made of a material with a relatively low thermal conductivity. For example, a general-purpose glass epoxy (glass fiber impregnated with epoxy) or phenol resin is used as a printed board with low thermal conductivity characteristics. The device can be soldered by high-density mounting, miniaturized and integrated, and low cost is achieved by using inexpensive materials and simplification work. In addition, chip-type component resistance heating elements and thermal fuse elements are used for the mounting parts, and the thermal fuse elements are used with a low-melting-point alloy fusible material hermetically sealed with an insulating package as required, resulting in resistance values. It is possible to construct a protection circuit having a small size. The temperature fuse element can be a low-melting-point fusible alloy-type temperature fuse or a temperature-sensitive pellet-type temperature fuse. You can also

  According to the temperature fuse with resistance of the present invention, a general-purpose glass epoxy resin substrate has a thermal conductivity of about two orders of magnitude smaller than that of a conventional ceramic substrate or metal lead terminal, so there is no need to mount it by soldering. Therefore, the mounting density is increased and the mounting substrate itself can be reduced in size and size. In addition, in the mass production process, a large number of components are separated by a method of separating a large number of component circuits from a single sheet, thereby simplifying and improving the efficiency of the manufacturing and assembling process. In addition, since it is a temperature fuse with resistance of a printed wiring structure that is completed by assembling work using a general-purpose automatic mounting machine, a non-recoverable protection device can be provided at a low cost with a simplified structure, which is highly practical. Further, the use of the chip component has an advantage that the resistance value of the lead wire segment can be cut by so-called leadlessing, so that the total resistance value of the protection circuit can be lowered, thereby extending the runtime of the battery.

  The thermal fuse with resistance of the present invention uses a large number of insulating substrates so that a plurality of thermal fuses can be processed at the same time, and is suitable for mass production. Individually, there is provided a thermal fuse with a resistance for a protection circuit having a unit unit size of 5 × 12 mm and a thickness of 1.6 mm or less. A plurality of such units are manufactured at the same time by making V-cuts or perforations on the insulating substrate. In a specific configuration, a thermal fuse element and a resistance heating element are soldered to the electrode part of the wiring pattern on the same surface of an insulating resin substrate, for example, a glass epoxy substrate having an electrode part with a through hole and a wiring pattern, and necessary. The part is covered with a solder resist. Each wiring pattern is processed by a well-known printed circuit board manufacturing method, and is subjected to 18 μm through-hole plating in addition to 35 μm copper foil, and masking and etching are performed. In particular, the solder resist covering the circuit component mounting position provides good bonding between the circuit component to be mounted and the glass epoxy substrate, and helps to prevent falling off. The protection circuit as a feature of the present invention includes a chip resistor as a resistance heating element that is fixed by soldering at an electrode portion of a wiring pattern according to a design standard in consideration of heat transfer during resistance heating, and a temperature fuse having a predetermined operating temperature. An element is mounted, and these mounted parts are preferably hermetically sealed with an epoxy resin after soldering of the mounted parts to prevent falling off the board.

As shown in FIG. 1, the thermal fuse with resistance of the present invention has wiring patterns 3, 4 and 5 having electrode portions A, B and C with through holes on a glass epoxy substrate 1 in which glass fiber is impregnated with epoxy resin. A wiring pattern 6 for connection on the substrate is formed, and a solder resist 7 is coated on a necessary portion to be insulated. The wiring patterns of the copper foil land include the wiring patterns 3 and 4 that become the main operation circuit and the wiring patterns 5 and 6 that become the sub-control circuit. The chip resistor 8 and the thermal fuse element 10 are heated between these wiring patterns. Are closely spaced and soldered together to maintain a mechanical connection. Soldering can be performed by reflow processing, and automation is applied in most processes. Here, the chip resistor 8 is disposed with its resistance surface facing the glass epoxy substrate, and is sealed and fixed with an epoxy resin after soldering. As the thermal fuse element 10, an element having an operating temperature of 134 ± 5 ° C. in which a low melting point soluble alloy is ceramic packaged is used. The electrode portions A, B, and C of the wiring patterns 3, 4, and 5 are connected to an external circuit as terminals on the back surface side through the respective conductive through holes. The focus of the present invention is that the thermal conductivity of an insulating resin such as a glass epoxy substrate is much smaller than that of a general ceramic substrate, whereby the resistance heating element 9 and the thermal fuse element 10 are narrow on one side of the glass epoxy substrate 1. It is possible to reduce the man-hours and costs by improving the work efficiency by using an automatic mounter for mounting while reducing the size and mounting in space. Specifically, the thermal conductivity of these substrate materials is 8.4 × 10 ⁻⁴ (Cal / cm · sec · ° C.) for glass epoxy and 5.0 × 10 ⁻² (Cal / cm · sec for alumina ceramic).・ ℃), which is almost two orders of magnitude different. The specific heat of each material is about 0.2 (Cal / g · ° C), but the amount of heat required to raise the same volume by 1 ° C is lower for glass epoxy with a lower specific gravity. Less. Therefore, the present invention provides a small-sized and low-cost thermal fuse with resistance by selecting a general-purpose glass epoxy substrate as a printed circuit board and simplifying the mounting on one side, thereby reducing the cost of using materials and reducing the number of steps for mounting components. The

  The said embodiment concerning this invention provides the protection circuit suitable for the charging / discharging control circuit for battery packs, and the thermal fuse element 10 is comprised from the two division parts 12 and 13. FIG. Conventionally, it is known that the temperature fuse of the main operation circuit of the protection circuit is divided into two and the heating resistance of the sub-control circuit is connected to the center thereof. In this embodiment, as shown in the wiring diagram of FIG. Using this technique, the fuse element 10 is composed of divided portions 12 and 13 connected in series, and electrode portions A and B with through holes at both ends thereof are used as terminals of the main operation circuit. Then, a chip resistor 8 is arranged between the intermediate connection point of the divided portions 12 and 13 and the electrode portion C with through hole, and a resistance temperature fuse having a protection circuit with the electrode portion C as a terminal of the sub-control circuit is formed. provide.

As a modification in the case where the thermal fuse element is composed of divided parts, in another embodiment shown in FIG. 3, the thermal fuse element 11 is composed of first and second thermal fuse parts 14 and 15, and the first temperature A resistance thermal fuse is provided in which the fuse portion 14 is connected to the main operating circuit, and the second temperature fuse portion 15 and the resistance heating element 9 are connected to the sub-control circuit to form a protection circuit. For example, the first thermal fuse portion 14 of the thermal fuse element 11 is connected between the main operation circuits xy, and the second thermal fuse portion 15 is connected in series with the resistance heating element 9 between the sub control circuits yz. Arranged connected to. In this case, the fusing temperature is the first thermal fuse portion 14.
Is set lower than the second temperature fuse portion 14, and the resistance heating element 9 during overheating is protected by the operation of the second temperature fuse portion 15 to improve safety. That is, when the abnormal voltage is detected between the sub-control circuits yz including the resistance heating element 9 and the resistance heating element 9 is energized by the signal to cause self-heating, the first temperature fuse portion 14 is given priority. , And then the second thermal fuse portion 15 is blown to provide a non-recoverable protective device that also cuts off the sub-control circuit.

  In other words, the temperature fuse element is divided into two, one is formed in the main operation circuit, and the other is formed in the sub-control circuit having the heat generating element, and the fusing temperature of the temperature fuse portion on the main operation circuit side is set to the sub-control circuit. It is set lower than the fusing temperature of the temperature fuse portion on the control circuit side, and the safety protection of the sub control circuit is realized by fusing. Thus, when a plurality of temperature fuse elements or fuse elements are used in a divided configuration, a protection circuit that operates safely and reliably is provided by protecting the circuit portion according to the difference in operating temperature.

  The protection circuit using the thermal fuse can be simplified and the cost can be reduced, and a general-purpose printed circuit board can be used and a soldering technique can be applied to expand the application field of the thermal fuse protection circuit.

It is the front (a) (b), side (c), and back view (d) of the thermal fuse with a resistance of the Example which concerns on this invention. It is a circuit diagram which similarly shows the wiring state of the Example of FIG. It is a circuit block diagram of the protection circuit of 2nd Example which is another embodiment of this invention.

Explanation of symbols

1 Glass epoxy board (insulating board)
3, 4 Wiring pattern to be the main operation circuit 5, 6 Wiring pattern to be the sub control circuit 7 Solder resist 8 Chip resistor 9 Resistance heating element 10, 11 Thermal fuse element 12, 13 Divided portion 14 First thermal fuse portion 15 Second Thermal fuse part A, B, C Electrode part with through hole

Claims (9)

A circuit in which a resistance heating element and a temperature fuse element having a predetermined operating temperature are arranged to maintain a thermal coupling state with each other through a wiring pattern formed on the same surface of an insulating substrate made of an insulating material having a low thermal conductivity. Configured thermal fuse with resistance. The insulating substrate is a material having low thermal conductivity, such as a glass epoxy substrate or a phenol resin substrate, and the resistance heating element and the thermal fuse element can be placed in a narrow space by soldering to each electrode portion of the wiring pattern. 2. The resistance thermal fuse according to claim 1, wherein a protective circuit is formed. 3. The resistance heating element according to claim 1, wherein the resistance heating element is a chip resistor, a resistance surface side thereof is in contact with the insulating substrate and soldered to the electrode portion, and the protection circuit is hermetically sealed with a resin material. Temperature fuse with resistance as described. The thermal fuse element is an alloy-type thermal fuse having an operating temperature of 134 ± 5 ° C. in which a low-melting-point fusible alloy is hermetically sealed with a ceramic cap, and is disposed in the space in close proximity to the chip resistor. Item 5. A thermal fuse with resistance according to item 3. The temperature fuse element is a temperature-sensitive pellet type temperature fuse having an operating temperature of 134 ± 5 ° C. in which a temperature-sensitive pellet is housed in a metal case and hermetically sealed, and is disposed in the vicinity of the chip resistor. The resistance thermal fuse according to claim 3, wherein The resistance heating element generates self-heating due to a current from a control element that detects an abnormal signal, and senses this heat generation to blow the temperature fuse element at the predetermined operating temperature to shut off a main operation circuit. 6. The temperature fuse with resistance according to claim 1, wherein the temperature fuse is provided with a protection circuit. The protection circuit is a charge / discharge control circuit for a battery pack, wherein the resistance heating element is self-heated by an abnormal voltage detected by the control circuit, and the thermal fuse element is blown at a predetermined operating temperature. The temperature fuse with resistance according to claim 6. The thermal fuse element includes a first fuse portion connected to the main operation circuit and a second fuse portion connected to the sub-control circuit. The operation temperature at which each fuse portion is melted is set to a different temperature, and the heat generation of the resistance heating element is performed. The temperature fuse with resistance according to claim 7, wherein the temperature fuse is operated at different timing. The operating temperature at which the first fuse portion is blown is set lower than the operating temperature at which the second fuse portion is blown, whereby the main operation circuit and the sub control circuit are sequentially turned off. Item 9. The temperature fuse with resistance according to Item 8.