JP2004006524A - Cob module equipped with temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the necessity of potting a silicone resin. <P>SOLUTION: COB modules (10, 10A), in each of which a plurality of bare chips are directly mounted on a circuit board (20), are each provided with a protection IC chip (12) for protecting a secondary battery (40); a switching IC chip (14) which is under the on/off control of the protection IC chip, being incorporated with a transistor, and serves as a heat generating source; and a temperature sensor element (TH). The plurality of bare chips are entirely coated with a mold resin (16) in a state that the heat generating source and the temperature sensor element are put apart from each other at a given distance (L). The temperature sensor element may be a thermistor (TH) or a temperature sensor IC chip. The mold resin desirably is composed of a resin having a high heat-transmitting property. The COB module (10) equipped with a temperature sensor may be arranged, being in contact with one side surface of the secondary battery. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a COB (Chip on Board) module in which a plurality of bare chips are directly mounted on a circuit board, and more particularly to a COB module used as a secondary battery protection circuit for protecting a rechargeable secondary battery.
[0002]
[Prior art]
The secondary battery protection circuit to which the present invention is applied is used for a secondary battery unit including a secondary battery such as a lithium ion battery, and detects an overcharge state, an overdischarge state, and an overcurrent state of the secondary battery. Then, the protection operation corresponding to each is performed to protect the secondary battery.
[0003]
There are various types of secondary batteries such as nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ion batteries. When charging a secondary battery, it is necessary to use a charger suitable for that type. Among various types of secondary batteries, lithium ion batteries are vulnerable to overdischarge and overcharge. For this reason, in the secondary battery protection circuit of the battery unit including the lithium ion battery, a detection device that detects an overdischarge state and an overcharge state of the lithium ion battery is indispensable. The secondary battery protection circuit further requires a detection device for detecting an overcurrent state.
[0004]
Speaking of overcharging, when a lithium-ion battery is charged by a charger, the battery voltage continues to rise even after the battery has been fully charged. When the battery is overcharged, the battery may be damaged due to an increase in internal stress of the battery, or a short circuit between the electrodes may occur due to deposition of lithium metal. For this reason, the lithium ion battery is charged with a constant current and a constant voltage. Also, the control voltage for constant voltage charging must not exceed the rating of the lithium ion battery. However, if the charger malfunctions or is erroneously charged by a charger for another type of secondary battery, the battery voltage may exceed the rated voltage of the lithium ion battery. In such a case, the function of interrupting the charging current so that the battery voltage does not exceed the maximum rating of the lithium ion battery is the overcharge protection function.
[0005]
Speaking of overdischarge, a nickel-cadmium battery and a nickel-hydrogen battery have a reduced battery capacity unless they are used until the battery capacity reaches zero and then charged. In other words, a nickel-cadmium battery or a nickel-hydrogen battery has a reduced battery capacity when used repeatedly by shallow discharge / charge. Such an effect is called a memory effect. On the other hand, a lithium-ion battery has no memory effect and is ideal as a secondary battery. However, on the other hand, if the battery voltage falls below a predetermined value due to excessive discharge, the constituent materials of the lithium ion battery may be deteriorated and the battery life may be shortened. For this reason, the function of interrupting the discharge current when the battery voltage drops below a predetermined value is the overdischarge protection function.
[0006]
Next, regarding overcurrent, when storing or carrying a lithium-ion battery, some kind of metal may accidentally short-circuit the + and-terminals of the lithium-ion battery, or the connected equipment may fail. If a short circuit occurs, a large current may flow. Therefore, the function of detecting the current value in the secondary battery protection circuit and interrupting the discharge current is the overcurrent protection function.
[0007]
In any of the above protection functions, a protection operation is performed by detecting a voltage or a current.
[0008]
By the way, conventionally, a protection IC component which is a discrete product is used as the above-described secondary battery protection circuit. This protection IC component constitutes a battery pack together with the secondary battery. Here, the portion of the battery pack excluding the secondary battery is referred to as a battery module.
[0009]
There is also known a battery module including a temperature sensor element such as a thermistor for detecting the temperature inside the battery pack. The temperature sensor element is connected to a charge control circuit of the charger. The charge control circuit is a circuit for controlling charging of the secondary battery, and is interposed between the AC adapter and the battery pack, and controls a charging current flowing from the AC adapter to the secondary battery in the battery pack. It is. A temperature detection signal indicating the temperature detected by the temperature sensor element is sent to the charge control circuit. In response to the temperature detection signal, the charge control circuit controls on / off of the charge control transistor.
[0010]
With reference to FIG. 1, a conventional battery module 10 'with a temperature sensor will be described. The battery module 10 'includes a positive battery terminal BH and a negative battery terminal BG to which a secondary battery (not shown) is connected, a positive terminal PH and a ground terminal (negative terminal) PG to which a load or a charger (not shown) is connected. , And a temperature detection output terminal TH.
[0011]
First and second transistors Q1 and Q2 are connected in series between a negative electrode battery connection terminal BG to which the cathode of the secondary battery is connected and a ground terminal PG. Each of the first and second transistors Q1 and Q2 is constituted by a field effect transistor. The first transistor Q1 operates as a discharge control switch, and the second transistor Q2 operates as a charge control switch.
[0012]
Battery module 10 'has protection IC component 12'. The protection IC component 12 'has a VDD terminal, a VSS terminal, a D terminal, a CO terminal, and a V- terminal. The VDD terminal is connected to a positive battery connection terminal BH and a positive terminal PH via a resistor R1 having a resistance value of 330Ω. The VSS terminal is connected to the negative battery connection terminal BG. A capacitor C1 having a capacitance of 0.1 μF is connected between the VDD terminal and the VSS terminal. The D terminal is connected to the gate of the first transistor Q1. The V- terminal is connected to the ground terminal PG via a resistor R2 having a resistance value of 1.0 kΩ, and is connected to the negative battery connection terminal BG via a capacitor C2 having a capacitance value of 0.1 μF. The CO terminal is connected to the gate of the second transistor Q2.
[0013]
As described above, the main functions of the protection IC component 12 'are the overdischarge protection function and the overcharge protection function. The protection IC components 12 'are an overdischarge control circuit (not shown) that performs an overdischarge protection function and an overcharge control circuit (not shown) that performs an overcharge protection function.
[0014]
It is assumed that a load is connected between the positive terminal PH and the negative terminal PG. An overdischarge detection threshold voltage Vth (od) is set in the overdischarge control circuit. That is, the over-discharge control circuit compares the battery voltage of the secondary battery with the over-discharge detection threshold voltage Vth (od), and when the battery voltage becomes lower than the over-discharge detection threshold voltage Vth (od). Judgment is made of discharge, and an overdischarge detection signal of a logic low level is output. When the overdischarge detection signal is supplied to the gate of the first transistor Q1, the first transistor Q1 turns off.
[0015]
Next, it is assumed that a charger described later is connected between the positive terminal PH and the negative terminal PG. When the battery voltage becomes higher than the overdischarge release voltage (Vth (od) + Vhy (od)) obtained by adding the overdischarge hysteresis voltage Vhy (od) to the overdischarge detection threshold voltage Vth (od), it becomes logic high. Outputs a level overdischarge protection release signal. When the overdischarge protection release signal is supplied to the gate of the first transistor Q1, the first transistor Q1 turns on.
[0016]
On the other hand, an overcharge detection threshold voltage Vth (oc) is set in the overcharge control circuit. In other words, the overcharge control circuit compares the battery voltage of the secondary battery with the overcharge detection threshold voltage Vth (oc), and when the battery voltage becomes higher than the overcharge detection threshold voltage Vth (oc), It determines that the battery is charged, and outputs an overcharge detection signal of a logic low level. When the overdischarge detection signal is supplied to the gate of the second transistor Q2, the second transistor Q2 turns off.
[0017]
Assume again that a load is connected between the positive terminal PH and the negative terminal PG. If the battery voltage becomes lower than the overcharge recovery voltage (Vth (oc) -Vhy (oc)) obtained by subtracting the overcharge hysteresis voltage Vhy (oc) from the overcharge detection threshold voltage Vth (oc), The charge control circuit outputs a logic high level overcharge protection release signal. When the overcharge protection release signal is supplied to the gate of the second transistor Q2, the second transistor Q2 turns on.
[0018]
As shown in FIG. 1, the first transistor Q1 has a parasitic diode, and is connected such that the forward direction is the charging direction of the secondary battery. Therefore, even if the first transistor Q1 is turned off, charging can be performed by the parasitic diode. Similarly, the second transistor Q2 also has a parasitic diode, and is connected so that its forward direction is the discharge direction of the secondary battery. Therefore, even if the second transistor Q2 is turned off, discharge can be performed by the parasitic diode.
[0019]
Between the temperature detection output terminal TH and a ground terminal (negative terminal) PG, a thermistor TH having a resistance value of 68 kΩ acting as a temperature sensor element and a resistance value R3 having a resistance value of 120Ω are connected in parallel.
[0020]
FIG. 2 shows a layout of the battery module 10 ′ on the circuit board 20 ′. The circuit board 20 'has, for example, a rectangular shape with a length of 5 to 6 mm and a width of 30 mm. The first and second transistors Q1, Q2 are configured as a switch IC component 14 '. The protection IC component 12 ', the switch IC component 14', the thermistor TH, and the like are mounted on the circuit board 20 '.
[0021]
The switch IC component 14 'operates as a heat source. A thermistor TH is arranged close to the switch IC component 14 '. In order to thermally couple the switch IC component 14 'and the thermistor TH, a silicone resin 16' is potted so as to cover the switch IC component 14 'and the thermistor TH. Incidentally, the silicone resin 16 'is a resin having a high heat propagation property.
[0022]
Next, the charging control circuit 30 of the charger will be described with reference to FIG. The charging control circuit is interposed between an AC adapter (not shown) and the battery module 10 '(FIG. 1), and controls a charging current flowing from the AC adapter to the secondary battery.
[0023]
The charge control circuit (charge control IC) 30 has a VCC terminal, a CNT terminal, a CS terminal, a BAT terminal, a GND1 terminal, a GND2 terminal, and the like. The VCC terminal is connected to the AC adapter and to the emitter of the charge control transistor Q3. The CNT terminal is connected to the base of the charge control transistor Q3 via the resistor R5. The collector of the charge control transistor Q3 is connected to the CS terminal via the diode D. The current detection resistor R4 is connected between the CS terminal and the BAT terminal.
[0024]
The B + terminal is connected to the positive terminal PH of the battery module 10 ', and the B- terminal is connected to the negative terminal PG of the battery module 10'. The temperature detection output terminal TH of the thermistor TH is connected to the charge control circuit 30.
[0025]
During charging of the secondary battery by the charger, the temperature of the switch IC component 14 'rises. This temperature is detected by the thermistor TH, and the temperature detection signal is sent to the charge control circuit 30. When the temperature represented by the temperature detection signal becomes equal to or higher than a predetermined temperature, the charge control circuit 30 turns off the charge control transistor Q3.
[0026]
[Problems to be solved by the invention]
As described above, in the conventional battery module 10 ', the switch IC component 14' and the thermistor (temperature sensor element) TH need to be potted with the silicone resin 16 'in order to thermally couple them.
[0027]
Therefore, an object of the present invention is to provide a battery module that does not require potting of a silicone resin.
[0028]
[Means for Solving the Problems]
According to the present invention, a COB (Chip on Board) module (10, 10A) in which a plurality of bare chips are directly mounted on a circuit board (20), wherein at least one of the plurality of bare chips is a heat source (14), one of the bare chips is a temperature sensor element (TH, 18), and the heat source and the temperature sensor element are separated from each other by a predetermined distance (L, L '). Thus, a COB module with a temperature sensor is obtained, wherein the whole of the plurality of bare chips is coated with the mold resin (16).
[0029]
In the COB module with temperature sensor (10, 10A), the temperature sensor element may be a thermistor (TH) or a temperature sensor IC chip (18). Further, it is desirable that the mold resin is made of a resin having a high heat transfer property. One of the plurality of bare chips is a protection IC chip (12) for protecting the secondary battery (40), and a switch IC including a transistor whose heat source is turned on / off by the protection IC chip. It may be a chip (14). Further, the COB module with a temperature sensor (10) may be arranged in a state of being in contact with one side surface of the secondary battery (40).
[0030]
The reference numerals in the parentheses are provided for facilitating the understanding of the present invention, are merely examples, and are not limited thereto.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0032]
A COB module (battery module) 10 with a temperature sensor according to the first embodiment of the present invention will be described with reference to FIG.
[0033]
As is well known in this technical field, COB (Chip on Board) refers to a form in which a bare chip is directly mounted on the circuit board 20. In the conventional battery module 10 ', a discrete product (IC component) is used as an IC, but in the battery module 10 of the present invention, a bare chip (IC chip) is used as the IC.
[0034]
For chip connection, wire bonding or flip chip mounting is used. Note that the connection relationship of the chip, the resistor, and the like is the same as in FIG.
[0035]
As shown in FIG. 4, a protection IC chip 12, a switch IC chip 14, resistors R1 to R3, capacitors C1 and C2, and a thermistor TH are mounted on a circuit board 20. The whole of these mounting chips is coated with a mold resin 16 having high heat propagation. The circuit board 20 has, for example, a rectangular shape with a length of 4 mm and a width of 30 mm. As the mold resin 16 having a high heat transmission property, for example, a mold resin mainly containing an epoxy resin and silicic anhydride can be used.
[0036]
The switch IC chip 14 and the thermistor TH are separated from each other by a predetermined distance L. Therefore, by changing the distance L, the degree of the influence of heat generated in the switch IC chip 14 can be changed. The separation distance L is, for example, 5 to 10 mm, but may be longer.
[0037]
In the conventional battery module 10 'with a temperature sensor, it was necessary to pot the silicone resin 16' to thermally couple the switch IC component 14 'and the thermistor TH. Since the plurality of bare chips mounted thereon are coated with the mold resin 16 having high heat propagation, it is not necessary to newly provide a thermal coupling means.
[0038]
FIG. 5 shows the heat generated by the switch IC chip 14 and the temperature change in the thermistor TH caused by the generated heat using the separation distance L as a parameter. 5A shows a temperature change of the switch IC chip 14, and FIG. 5B shows a temperature change in the thermistor TH using the separation distance L as a parameter. 5A and 5B, the vertical axis represents temperature, and the horizontal axis represents time t.
[0039]
As is clear from FIG. 5, the temperature of the thermistor TH rises rapidly and falls rapidly as the distance L decreases. On the other hand, as the distance L increases, the temperature of the thermistor TH gradually rises and gradually falls.
[0040]
In the first embodiment, like the conventional battery module with temperature sensor 10 'shown in FIGS. 1 and 2, when the temperature caused by the heat generated by the heat source rises to a predetermined temperature or more, The charging current for the secondary battery is cut off on the charger side. However, as described in the following embodiments, the discharge current and the charge current may be interrupted even in the battery module.
[0041]
Referring to FIG. 6, the COB module with a temperature sensor (battery module) 10A according to the second embodiment of the present invention has the same structure as the COB module shown in FIG. It has the same configuration as the module (battery module) 10.
[0042]
A predetermined terminal of the temperature sensor IC chip 18 is electrically connected to a predetermined terminal of the protection IC chip 12. The temperature sensor IC chip 18 is also coated with the mold resin 16 and, like the thermistor TH, detects the temperature of the battery module 10A caused by the switch IC chip 14 that is a heat source. The temperature sensor IC chip 18 and the switch IC chip 14 are separated from each other by a predetermined distance L '.
[0043]
The temperature detection signal detected by the temperature sensor IC chip 18 is supplied to the protection IC chip 12. In response to the temperature detection signal, the protection IC chip 12 controls on / off of the first or second transistor Q1, Q2 in the switch IC chip 14.
[0044]
In the second embodiment, the thermistor TH and the temperature sensor IC chip 18 are used as the temperature detecting means, but the thermistor TH may be omitted. That is, only the temperature sensor IC chip 18 may be used as the temperature detecting means.
[0045]
In the above-described embodiment, only the temperature caused by the switch IC chip 14, which is a heat source, is detected. However, as described later, by arranging the battery module according to the present invention in contact with the secondary battery, It is also possible to detect the temperature caused by the heat generated by the secondary battery.
[0046]
Referring to FIG. 7, in the third embodiment of the present invention, a COB module (battery module) 10 with a temperature sensor is arranged in contact with one side surface of secondary battery 40. In this case, the mold resin 16 of the battery module 10 is brought into contact with one side surface of the secondary battery 40. Further, the surface with which the battery module 10 is in contact may be any one of the four side surfaces of the secondary battery 40.
[0047]
Depending on the position of the battery module 10 with respect to the secondary battery 40, the way of transmitting heat (temperature) due to the heat generated by the secondary battery 40 also changes. Since the battery module 10 is smaller than the secondary battery 40, the battery module 10 has a greater degree of freedom in placing the battery module 10.
[0048]
As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described embodiments.
[0049]
【The invention's effect】
As apparent from the above description, according to the present invention, in a COB module in which a plurality of bare chips are mounted on a circuit board, a heat source and a temperature detecting element, which are bare chips, are coated with a mold resin. There is an advantage that there is no need to pot the silicone resin for thermal bonding as in the above.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a conventional battery module.
FIG. 2 is a schematic plan view showing a layout of the battery module shown in FIG. 1 on a circuit board.
FIG. 3 is a block diagram showing a charge control circuit of the charger.
FIG. 4 is a schematic plan view showing a layout on a circuit board of the COB module with a temperature sensor (battery module) according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating heat generated by a heat source and a change in temperature in a thermistor caused by the heat when the separation distance is used as a parameter.
FIG. 6 is a schematic plan view showing a layout on a circuit board of a COB module with a temperature sensor (battery module) according to a second embodiment of the present invention.
FIG. 7 is a schematic plan view showing a third embodiment of the present invention.
[Explanation of symbols]
10,10A COB module with temperature sensor (battery module)
12 Protection IC chip 14 Switch IC chip 16 Mold resin 18 Temperature sensor IC chip R1 to R3 Resistors C1, C2 Resistor TH Thermistors Q1, Q2 Transistors L, L 'Separation distance

Claims (6)

A COB (Chip on Board) module in which a plurality of bare chips are directly mounted on a circuit board,
At least one of the plurality of bare chips acts as a heat source,
One of the plurality of bare chips is a temperature sensor element,
A COB module with a temperature sensor, wherein the whole of the plurality of bare chips is coated with a mold resin in a state where the heat source and the temperature sensor element are separated from each other by a predetermined distance. The COB module with a temperature sensor according to claim 1, wherein the temperature sensor element is a thermistor. The COB module with a temperature sensor according to claim 1, wherein the temperature sensor element is a temperature sensor IC chip. The COB module with a temperature sensor according to claim 1, wherein the mold resin is made of a resin having a high heat transfer property. One of the plurality of bare chips is a protection IC chip for protecting a secondary battery, and the heat source is a switch IC chip including a transistor whose ON / OFF is controlled by the protection IC chip. A COB module with a temperature sensor according to claim 1. The COB module with a temperature sensor according to claim 5, wherein the COB module with a temperature sensor is arranged in a state of being in contact with one side surface of the secondary battery.

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