JP4429624B2 - Battery protection circuit and secondary battery using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery protection circuit for a rechargeable secondary battery that supplies power to a portable information terminal such as a mobile phone or an electronic notebook, and a secondary battery using the same.
[0002]
[Prior art]
In recent years, electronic devices, particularly portable information terminals such as mobile phones, notebook personal computers equipped with wireless communication functions, and personal information terminals, have been rapidly reduced in size and weight. A battery for supplying power is used for these portable information terminals. As this battery, a rechargeable secondary battery is used. And along with the miniaturization and weight reduction of such portable information terminals, there is a strong demand for miniaturization and weight reduction of secondary batteries used therein.
[0003]
The secondary battery has a battery body including a battery core that is a power generation element, electrode terminals that are electrically connected to the battery core, and an exterior member that houses the battery core. The electrode terminal electrically connected to the battery core has a positive electrode terminal and a negative electrode terminal, and is led out of the exterior member. A protective circuit for preventing an overcurrent or an overvoltage from being applied to the battery core is connected to either the positive terminal or the negative terminal. In addition to the protection circuit, a PTC (Positive Temperature Coefficient) element is provided to further protect the battery from overcurrent, overcharge, and short circuit. The PTC element increases the electric current value flowing through the PTC element and increases the electrical resistance as the temperature rises, thereby suppressing the current flowing through the battery core, thereby reducing the battery current caused by overcurrent, overcharge, and short circuit. Reduces temperature rise. After the battery body, the protection circuit, and the PTC element are electrically connected as described above, they are housed in a case to form a secondary battery (battery pack).
[0004]
A general PTC element is configured by providing a foil made of Ni (nickel) foil or Ni / Cu (nickel / copper) foil on both opposing surfaces of a PTC material. Each foil sandwiching the PTC material functions as an electrode of the PTC material. Of the foils constituting the PTC element, the Ni extraction electrode is soldered to the foil on the upper side of the PTC material. This extraction electrode functions as an extraction electrode for the PTC element. On the other hand, Cu electrodes are formed by soldering on the lower surface of the foil on the lower side of the PTC material, that is, on the circuit board. This functions as an extraction electrode on the circuit board side of the PTC element. That is, a PTC element is configured by sandwiching a PTC material from above and below, and a sandwich structure is formed in which the upper and lower foils of this PTC element are further taken out and sandwiched by electrodes (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
International Publication No. 99/060637
[0006]
[Problems to be solved by the invention]
As described above, the PTC element is an element that increases the electric resistance as the temperature rises by detecting the temperature rise of the battery or the temperature rise of the surrounding environment caused by application of overcurrent or overvoltage. . However, the accuracy and reliability of temperature detection of PTC elements vary due to fluctuations in internal impedance.
[0007]
The PTC element is classified into a surface mounting type and a lead type according to the mounting type. The surface mount type is mounted directly on the circuit board coated with cream solder together with chip resistors, chip capacitors, etc., and the circuit board is passed through a high-temperature reflow bath to melt the cream solder and mount it on the circuit board. PTC element to be used. The lead type is a PTC element in which a lead that is electrically connected to the battery core or the protection circuit board is connected to the extraction electrode of the PTC element by spot welding, ultrasonic welding, or solder bonding.
[0008]
A surface-mounting type PTC element requires a smaller mounting space than a lead-type PTC element, and thus is preferable as an element applied to a secondary battery for a portable information terminal, which is becoming smaller, thinner, and lighter. . However, when the surface mount type PTC element is mounted on a circuit board, the impedance of the PTC material constituting the PTC element is significantly increased because it is exposed to a high temperature environment in a reflow bath in a high temperature atmosphere. There is a demerit that current efficiency decreases. A portable information terminal receives operating power from a battery body via a protection circuit and a PTC element, but a PTC element whose impedance has increased by reflow processing is interposed between the battery body and the terminal load A loss of power consumption occurs in the PTC element. As a result, there arises a problem that the continuous call time / continuous standby time of the terminal is shortened. For these reasons, the lead type is mainly selected as the PTC element applied to the secondary battery of the portable information terminal.
[0009]
However, the lead type PTC element is connected to the lead electrode of the PTC element and the lead by spot welding, ultrasonic welding, or soldering, so that the manufacturing process is increased and the manufacturing process becomes complicated, so that the manufacturing quality may not be ensured. . In addition, there is a problem that the reliability of the battery is lowered due to a problem that a joint portion between the lead and the extraction electrode is detached due to a mechanical external force acting by dropping the terminal. Furthermore, since the lead type combines a plurality of leads to join the PTC element take-out electrode, the battery, and the protection circuit, it requires a relatively large mounting space and is not suitable for reducing the size of the secondary battery.
[0010]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a secondary battery provided with a PTC element mounted on a protective circuit board without passing through a reflow bath.
[0011]
[Means for Solving the Problems]
The battery protection circuit according to the present invention includes a circuit board that is mounted with a current amount control circuit that controls the amount of current flowing through the secondary battery, and that can be bent with a flexible material. A pair of charging terminals electrically connected to an external charging device of the terminal body through a circuit of the terminal body, and charging of one of the pair of charging terminals formed on the circuit board. The circuit board that is electrically connected to any one of a positive terminal and a negative terminal of the secondary battery and overlaps the first pattern when the circuit board is bent. After the step of mounting the second pattern formed at a predetermined position on the circuit board and the current amount control circuit on the circuit board, it is applied to either the first pattern or the second pattern. The first pattern and the second pattern are fixed and electrically connected in a state in which the first pattern and the second pattern are overlapped, and positive resistance that increases electric resistance in response to a temperature rise And a resistance material having a temperature coefficient.
[0012]
The secondary battery according to the present invention includes a battery core serving as a power generation element, a housing member that houses the battery core, a positive electrode that is electrically connected to the battery core and led out of the housing member And a battery main body having electrode terminals for the negative electrode and a current amount control circuit for controlling the amount of current flowing through the battery main body, and a circuit board formed so as to be bendable with a flexible material, this circuit A pair of charging terminals formed on the circuit board and electrically connectable to an external charging device of the terminal body via a circuit of the terminal body; one of the pair of charging terminals formed on the circuit board; The first pattern connected to the charging terminal, electrically connected to one of the positive electrode terminal and the negative electrode terminal of the battery body, and overlapped with the first pattern when the circuit board is bent. A second pattern formed at a predetermined position on the circuit board, and applied to any one of the first pattern and the second pattern after the step of mounting the current amount control circuit on the circuit board. The first pattern and the second pattern are fixed and electrically connected in a state where the first pattern and the second pattern are overlapped, and the electric resistance is increased in response to a temperature rise. And a battery protection circuit having a resistance material having a positive temperature coefficient.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Hereinafter, a protection circuit including a surface-mounting type PTC element and a configuration of a secondary battery using the protection circuit will be described according to Embodiment 1 of the present invention. FIG. 1 is an exploded perspective view showing the structure of the secondary battery in an exploded state. In FIG. 1, the secondary battery 1 is configured by being housed in cases 5 a and 5 b after a battery body 2, a protection circuit 3, and a PTC element 4 are electrically connected. The battery body 2 includes an electrode terminal that is electrically connected to a battery core that is a power generation element, and an exterior member that houses the battery core. The electrode terminals are the positive electrode terminal 6 and the negative electrode terminal 7 shown in FIG. 1, and are electrically connected to the battery core and led out of the exterior member. 1 shows a case where the battery body 1 is a buttercup type polymer battery.
[0014]
The protection circuit 3 is a current amount control circuit that prevents an overcurrent or an overvoltage from being applied to the battery body 1, and overcharges, overdischarges a circuit board that is foldable with a flexible material. Various ICs for overcurrent protection, chips, resistors, capacitors and the like are mounted. The protection circuit operates as a circuit that performs overdischarge protection, overcurrent protection, and overcharge protection. In particular, the voltage detector performs overcharge, overcurrent, and overdischarge detection. The various circuits mounted on the circuit board operate as a current amount control circuit that controls the amount of current flowing through the battery body 2. The protection circuit 3 is fixed so as to cover the surface of the base 8 made of a material containing glass fiber such as an epoxy resin, and various ICs and chips for controlling current and voltage, as well as external devices and electricity. It is composed of a flexible substrate 9 on which a pattern or the like for obtaining a normal conduction is mounted. In FIG. 1, charging terminals 10 and 11 that are in contact with terminals inside the portable information terminal, and electrode connection terminals 12 and 13 for connecting the protection circuit 3 and the battery body 2 are shown on the flexible substrate 9. The PTC element 4 is not shown in FIG. 1 because it is provided on the back side of the protection circuit 3 shown in FIG.
[0015]
The battery body 2, the protection circuit 3, and the PTC element 4 are electrically connected and then housed in the case 5. The case 5 includes an upper case 5a and a lower case 5b. The lower case 5b is a case facing the portable information terminal side with the secondary battery 1 attached to the portable information terminal. Terminal windows 14 and 15 are formed in the lower case 5b. The charging terminals 10 and 11 of the protection circuit 3 and the connector on the portable information terminal side are brought into electrical contact with each other through the terminal windows 14 and 15 to supply power from the secondary battery 1 to the portable information terminal or The secondary battery 1 is charged from the external charging device.
[0016]
FIG. 2 is a perspective view showing the structure of the battery main body 2 and the protection circuit 3 constituting the secondary battery 1 shown in FIG. In FIG. 2, the same reference numerals as those shown in FIG. In FIG. 2, the protection circuit 3 shown in FIG. 1 is shown in an inverted state, and it is shown that a conductive polymer 16 that is a PTC material is formed on the flexible substrate 9 of the protection circuit 3. Yes. A first pattern 17 is formed on the flexible substrate 9 of the protection circuit 3. The first pattern 17 is connected to the charging terminal 11 out of the pair of charging terminals 10 and 11. The other charging terminal 10 is connected to the electrode connection terminal 12. The electrode connection terminal 12 is electrically connected to the negative electrode terminal 7 of the battery body 2. A second pattern 18 is formed on the flexible substrate 9 of the protection circuit 3. The second pattern 18 is connected to the electrode connection terminal 13, and is electrically connected to the positive electrode terminal 6 of the battery body 2 through the electrode connection terminal 13. The conductive polymer 16 is provided on the first pattern 17.
[0017]
The conductive polymer 16 is a material having a positive temperature coefficient that increases the electrical resistance in response to a temperature rise, and contains carbon. The conductive polymer 16 exhibits a low resistance value at room temperature because carbon dispersed in the polymer forms an infinite number of conductive paths. On the other hand, when the temperature of the conductive polymer 16 rises due to an increase in the ambient temperature or the occurrence of a short circuit, the conductive polymer 16 is thermally expanded and the conductive path formed by the carbon is cut, so that a high resistance value is obtained. Indicates. The conductive polymer 16 is a highly viscous liquid substance when applied to the first pattern 17 on the flexible substrate 9, but has a property of becoming a solid over time.
[0018]
Utilizing such a property, the conductive polymer 16 is applied on the first pattern 17 after the reflow process is performed, and the applied conductive polymer 16 is sandwiched between the second patterns 18. Thus, the PTC element is formed integrally with the protection circuit 3. That is, in forming the protection circuit 3, first, cream solder is applied on a circuit pattern for establishing electrical continuity with an external device formed on the flexible substrate 9, and then a current, Various ICs, chips, resistors, and capacitors for voltage control are arranged and subjected to reflow processing. When the reflow process is performed, the cream solder on the circuit pattern is melted by the high temperature atmosphere in the reflow tank, and various ICs, chips, resistors, capacitors, and the like are mounted in a predetermined pattern. A conductive polymer 16 is applied on the first pattern 17 formed on the flexible substrate 9 for the protection circuit 3 after such reflow treatment.
[0019]
When the conductive polymer 16 was applied on the first pattern 17, the flexible substrate 9 on which the second pattern 18 was formed was bent on the first pattern 17 side and applied on the first pattern 17. The conductive polymer 16 and the second pattern 18 are brought into contact with each other. The conductive polymer 16 becomes a solid after a predetermined time in contact with the second pattern 18, and fixes the second pattern 18. FIG. 3 shows a state in which the conductive polymer 16 on the first pattern 17 is sandwiched between the second patterns 18. Reference numeral 19 in FIG. 3 denotes a portion (referred to as a bent portion) where the flexible substrate 9 is bent at a position where the second pattern 18 is provided. The second pattern 18 is formed on the back side of the bent portion 9 with the conductive polymer 16. In contact with.
[0020]
FIG. 4 is a cross-sectional view showing a BB cross section on the protection circuit 3 shown in FIG. In FIG. 4, the flexible substrate 9 is bent so that the second pattern 18 is brought into contact with the conductive polymer 16 applied on the first pattern 17, and the first pattern 17, the conductive polymer 16, and the second pattern 18 are contacted. Are shown being electrically connected. As described above, the first pattern 17 is electrically connected to the charging terminal 11, and the second pattern 18 is electrically connected to the electrode connection terminal 13. Since the electrode connection terminal 13 is connected to the positive electrode terminal 6 of the battery body 2, when the first pattern 17, the conductive polymer 16, and the second pattern 18 are electrically connected, the charging terminal 11 -first Pattern 17-conductive polymer 16-second pattern 18-the positive electrode of the battery is electrically conductive. As described above, according to FIG. 4, the flexible substrate 9 on which the second pattern 18 is formed is bent toward the first pattern 17 and is electrically connected to the conductive pattern 16.
[0021]
FIG. 5 is a perspective view showing a state in which the battery body 2 and the protection circuit 3 are electrically connected. In FIG. 5, the protection circuit 3 shown in FIG. 3 is placed in the inverted state, that is, at the end of the battery body 2 that is a butter-cube type polymer battery so that the charging terminals 10 and 11 face up. . The electrode connection terminal 12 of the protection circuit 3 is connected to the negative electrode terminal 7 of the battery body 2. On the other hand, the electrode connection terminal 13 of the protection circuit 3 is connected to the positive electrode terminal 6 of the battery body 2. The connection of the electrode connection terminal of the protection circuit 3 and the electrode terminal of the battery body 2 is performed using a technique such as spot welding, ultrasonic welding, or solder bonding. As described above, after the battery body 2 and the protection circuit 3 are electrically connected, they are housed in the cases 5a and 5b to form a secondary battery.
[0022]
As described above, according to the present invention, since the conductive polymer 16 is applied on the first pattern 17 after the reflow treatment, the PTC material (conductive polymer 16) is heated to a high temperature in the reflow bath. No more exposure. Therefore, it is possible to realize a surface mount type PTC element that prevents an increase in impedance of the PTC material due to exposure to a high temperature atmosphere in the reflow bath. Moreover, since the problem that the impedance of a PTC element increases by reflow processing can be solved, the loss of the power consumption in a PTC element can be suppressed, and the secondary battery with long use time by one charge can be obtained. That is, the continuous call time / continuous standby time of the terminal using the secondary battery can be increased.
[0023]
Further, according to the present invention, since the flexible substrate 9 on which the second pattern 18 is formed is bent and electrically connected to the conductive polymer 16, the first pattern 17 and the second pattern 18 are connected to the conductive polymer. It functions as 16 extraction electrodes. Therefore, the extraction electrode of the PTC material and the conductive polymer 16 in the above description can function as the extraction electrode of the PTC element.
[0024]
Further, since the flexible substrate 9 on which the second pattern 18 is formed is bent and electrically connected to the conductive pattern 16, the PTC element and the battery or the protection circuit and the lead are spot welded, ultrasonic welded, and soldered. And no need to connect. Therefore, since the mounting space is smaller than that of the lead type PTC element, it is suitable as an element applied to a secondary battery for a portable information terminal which is becoming smaller, thinner and lighter. In addition, there is an effect that it is possible to realize a highly reliable protection circuit and secondary battery against mechanical external force such as dropping.
[0025]
In the above description, as shown in FIG. 4, the flexible substrate 9 is bent so that the second pattern 18 is brought into contact with the conductive polymer 16 applied on the first pattern 17, so that the first pattern 17 and the conductive pattern are electrically connected. The conductive polymer 16 and the second pattern 18 were electrically connected, and the charging terminal 11 -the first pattern 17 -the conductive polymer 16 -the second pattern 18 -the battery was connected. However, even if the electrode terminal of the battery is directly connected to the conductive polymer 16 without using the second pattern 18 and the electrode connection terminal 13, it is possible to establish conduction between the charging terminal 11 and the battery.
[0026]
【The invention's effect】
According to the present invention, a current amount control circuit for controlling the amount of current flowing in the secondary battery is mounted, and a circuit board formed so as to be bendable with a flexible material, and formed on the circuit board. A pair of charging terminals that can be electrically connected to an external charging device of the terminal body through a circuit of the terminal body, and formed on the circuit board and connected to one charging terminal of the pair of charging terminals A predetermined pattern on the circuit board that is electrically connected to one of the positive terminal and the negative terminal of the secondary battery and overlaps the first pattern when the circuit board is bent. A second pattern formed at a position, and after the step of mounting the current amount control circuit on the circuit board, applied to either the first pattern or the second pattern; Patter The first pattern and the second pattern are fixed and electrically connected in a state where the second pattern and the second pattern are overlaid, and has a positive temperature coefficient that increases the electrical resistance in response to a temperature rise. Since the resistance material is provided, it is possible to realize a surface mount type PTC element that prevents an increase in impedance of the PTC material due to exposure to a high temperature atmosphere in the reflow bath. Further, it is not necessary to connect the PTC element and the battery or the protection circuit and the lead by spot welding, ultrasonic welding or soldering, and the protection circuit can be miniaturized.
[0027]
The secondary battery according to the present invention includes a battery core serving as a power generation element, a housing member that houses the battery core, a positive electrode that is electrically connected to the battery core and led out of the housing member And a battery main body having electrode terminals for the negative electrode and a current amount control circuit for controlling the amount of current flowing through the battery main body, and a circuit board formed so as to be bendable with a flexible material, this circuit A pair of charging terminals formed on the circuit board and electrically connectable to an external charging device of the terminal body via a circuit of the terminal body; one of the pair of charging terminals formed on the circuit board; The first pattern connected to the charging terminal, electrically connected to one of the positive electrode terminal and the negative electrode terminal of the battery body, and overlapped with the first pattern when the circuit board is bent. A second pattern formed at a predetermined position on the circuit board, and applied to any one of the first pattern and the second pattern after the step of mounting the current amount control circuit on the circuit board. The first pattern and the second pattern are fixed and electrically connected in a state where the first pattern and the second pattern are overlapped, and the electric resistance is increased in response to a temperature rise. Since a battery protection circuit having a resistance material having a positive temperature coefficient is provided, it is possible to realize a surface mount type PTC element that prevents an increase in impedance of the PTC material due to exposure to a high temperature atmosphere in the reflow bath. . Accordingly, it is possible to obtain a secondary battery having a long use time by one charge. Further, it is not necessary to connect the PTC element and the battery or the protection circuit and the lead by spot welding, ultrasonic welding or soldering, and the secondary battery can be miniaturized.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a structure of a secondary battery according to Embodiment 1 of the present invention in an exploded state.
FIG. 2 is a perspective view showing the structure of a battery body 2 and a protection circuit 3 constituting the secondary battery 1 shown in FIG.
FIG. 3 is an enlarged perspective view showing the configuration of the protection circuit 3. FIG.
4 is a cross-sectional view showing a cross section of the protection circuit 3 shown in FIG. 3. FIG.
FIG. 5 is a perspective view showing a state in which a battery body and a protection circuit are electrically connected.
[Explanation of symbols]
1 secondary battery, 2 battery body, 3 protection circuit, 4 PTC element, 5 case,
6 positive terminal, 7 negative terminal, 8 substrate, 9 flexible substrate,
10 charging terminals, 11 charging terminals, 12 electrode connection terminals, 13 electrode connection terminals,
14 terminal window, 15 terminal window, 16 conductive polymer, 17 first pattern,
18 Second pattern, 19 A portion where the first pattern is bent.

Claims (4)

A circuit board that is mounted with a current amount control circuit that controls the amount of current flowing through the secondary battery and that can be bent with a flexible material;
Is formed on the circuit board, and an external charging device electrically connectable to a pair of charging terminals of the terminal body through the circuit of the end end of the body,
A first pattern formed on the circuit board and connected to one of the pair of charging terminals;
The second battery is electrically connected to either the positive electrode terminal or the negative electrode terminal of the secondary battery, and is formed at a predetermined position on the circuit board that overlaps the first pattern when the circuit board is bent. With patterns,
After the step of mounting the current amount control circuit on the circuit board, it was applied to either the first pattern or the second pattern, and the first pattern and the second pattern were superimposed. A resistance material having a positive temperature coefficient that increases electrical resistance in response to a temperature rise is provided in which the first pattern and the second pattern are fixed and electrically connected in a state. Battery protection circuit.   2. The battery according to claim 1, wherein the second pattern is formed at a position where a part of the circuit board protrudes so as to overlap the first pattern when folded to the circuit board side. Protection circuit.   The battery protection circuit according to claim 1, wherein the resistance material is a conductive polymer. A battery core serving as a power generation element, a housing member that houses the battery core, a battery that is electrically connected to the battery core and has electrode terminals for positive and negative electrodes led out of the housing member The body,
With the amount of current flowing through the battery body current control circuit are mounted, flexible foldably formed circuit board material, are formed on the circuit board, through the circuit of the end end of the body A pair of charging terminals electrically connectable to an external charging device of the terminal body, a first pattern formed on the circuit board and connected to one of the pair of charging terminals, the battery body A second pattern formed at a predetermined position on the circuit board that is electrically connected to any one of the positive electrode terminal and the negative electrode terminal and overlaps the first pattern when the circuit board is bent. After the step of mounting the current amount control circuit on the substrate, it is applied to either the first pattern or the second pattern, and the first pattern and the second pattern are overlaid. A battery protection circuit having a resistance material having a positive temperature coefficient that increases the electrical resistance in response to a temperature rise, wherein the first pattern and the second pattern are fixed and electrically connected in a state where A secondary battery characterized by being provided.

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