Thermistor flat plate type packaging structure and packaging method thereof

Abstract

The invention discloses a thermistor flat plate type packaging structure and a packaging method thereof, and relates to the field of energy storage and electric vehicles, the thermistor flat plate type packaging structure comprises a thermistor chip, the thermistor chip is welded on an electric wire, a packaging head is formed after first epoxy resin is coated and cured, and then the packaging head is fixed in a substrate through second epoxy resin. According to the invention, the substrate, the thermistor chip and the wire are arranged, and the copper substrate is directly connected to the aluminum bar, so that the influence of external air temperature on the temperature sensor is avoided, the temperature of the battery pack can be directly measured, and the temperature measurement accuracy of the temperature sensor is effectively improved; the temperature sensor is connected to the aluminum bar, the aluminum bar is directly connected with the battery, and the battery temperature is measured more accurately; the substrate adopts copper nickel plating, and the response time is shortened through good heat conduction of copper; epoxy resin is coated outside the thermistor chip, so that the voltage resistance grade of the product is increased; a large contact surface is formed between the substrate and the aluminum bar, so that the heat conduction efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the fields of energy storage and electric vehicles, and particularly to a flat package structure of a thermistor and its packaging method. Background Art

[0002] In the fields of energy storage and electric vehicles, temperature sensors are used to monitor the temperatures of energy storage battery packs and power batteries to ensure the stable performance of battery packs.

[0003] The performance of temperature sensors is reflected in temperature measurement and control accuracy. At present, new energy electric vehicles and various energy storage power stations in China are developing rapidly, and the functional stability of batteries is particularly crucial. Therefore, it is necessary to develop a sensor that can monitor the temperature of battery packs at any time to track the real-time temperature of the battery and regulate and compensate to ensure the long-term normal operation of the battery.

[0004] Most existing temperature sensors are installed on the surface of cooling water pipes, and the temperature is confirmed by detecting the cooling water. The installation method is a pipe wall envelopment mode, and the direct measurement point is the outer wall of the pipe. Due to the influence of the ambient temperature, the ambient temperature difference is large in summer and winter, and it is difficult to ensure the temperature measurement accuracy through compensation and calibration. Therefore, there is an urgent need to develop a sensor with high detection accuracy that can directly detect the temperature of the battery pack. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that most existing temperature sensors are installed on the surface of cooling water pipes, and the temperature is confirmed by detecting the cooling water. The installation method is a pipe wall envelopment mode, and the direct measurement point is the outer wall of the pipe. Due to the influence of the ambient temperature, the ambient temperature difference is large in summer and winter, and it is difficult to ensure the temperature measurement accuracy through compensation and calibration. The present invention provides a flat package structure of a thermistor and its packaging method.

[0006] To achieve the above purpose, the present invention provides the following technical solution: a flat package structure of a thermistor, including a thermistor chip, the thermistor chip is welded to a wire, and after being cured by coating with a first epoxy resin to form a package head, the package head is fixed in a substrate by a second epoxy resin.

[0007] A packaging method for a flat package of a thermistor is as follows: Step 1: Weld the thermistor chip and the wire. Use a wire stripper to strip the insulating layer at the end of the wire to expose about 3 - 5 mm of copper core. Clean the oxide on the surface of the solder feet of the thermistor chip. Fix the pins of the thermistor chip with tweezers. The tip of the soldering iron touches both the pins of the thermistor chip and the copper core of the wire at the same time. Wait for both to be evenly heated. Touch the solder wire gently to the soldering point. After the molten solder naturally wraps the pins and the copper core, remove the soldering iron. Avoid shaking. Immediately use a radiator clip to clamp the root of the pin to accelerate heat dissipation and prevent heat from conducting to the chip body. Step 2: After welding, apply the first epoxy resin and heat it for curing. Thoroughly clean the surface of the thermistor chip with alcohol or isopropyl alcohol to remove oxides, grease, and dust impurities. Perform plasma treatment on the lead or electrode area to enhance the adhesion of the epoxy resin. Preheat the thermistor chip in an environment of 60 - 80°C for 10 - 15 minutes to reduce the thermal stress during coating and improve the fluidity of the resin. Immerse the chip vertically into the epoxy resin liquid and slowly lift it (speed ≤ 5 cm / min) to ensure uniform coverage and no dripping. Cure it at 60 - 80°C for 1 - 2 hours to make the resin take an initial shape; raise the temperature to 120 - 150°C and maintain it for 4 - 6 hours to ensure complete cross-linking; after natural cooling to room temperature, age it in an 80°C oven for 24 hours to eliminate internal stress. Step 3: Fill the inner cavity of the substrate with the second epoxy resin. Remove the oil stain, oxide, and impurities on the surface of the substrate. Mechanical grinding or chemical cleaning can be used to ensure the bonding strength between the second epoxy resin and the substrate. Preheat the substrate to 40 - 80°C to reduce the viscosity of the second epoxy resin and accelerate capillary flow; remove air bubbles through a vacuum environment to avoid porosity defects after filling; utilize the capillary effect to evenly fill the internal gaps of the substrate with the resin. Step 4: Insert the thermistor chip into the substrate and heat it for curing again. Insert the sealing head into the position where the second epoxy resin is filled in the substrate. Adopt gradient temperature rise and segmented curing to improve the cross-linking density and thermal stability; after curing, cool it naturally or perform annealing treatment to reduce the deformation or cracking of the substrate caused by thermal stress. Step 5: Install it on the aluminum bar. Drill holes in the aluminum bar and the substrate in advance, and use T-bolts in combination with flange nuts or slider nuts plus hexagon socket head cap screws for fastening. The aluminum bar is directly connected to the battery.

[0008] As a further scheme of the present invention: in the above Step 1, the thermistor chip is an NTC negative temperature coefficient thermistor.

[0009] As a further scheme of the present invention: in the above Step 2, the first epoxy resin is prepared by mixing the main agent, diluent, and curing agent according to the ratio of 70:20:30. Weigh the active diluent (such as HK-66 or AGE), mix the diluent with the epoxy resin, stir until it is uniformly transparent, add the curing agent (such as amine or anhydride), and continue stirring to ensure sufficient reaction.

[0010] As a further scheme of the present invention: in the above Step 3, the second epoxy resin is prepared by mixing the main agent, diluent, and curing agent according to the ratio of 70:20:30. Slowly add the diluent (acetone or ethyl acetate) to the epoxy resin, stir until it is uniform, add the curing agent and stir (such as amine or anhydride), pay attention to the evaporation rate to avoid generating bubbles, let it stand for defoaming and then use it. Heat it if necessary to accelerate evaporation.

[0011] As a further solution of the present invention: in the third step, the substrate is generally copper or aluminum.

[0012] As a further solution of the present invention: in the fourth step, the filling amount of the second epoxy resin needs to fill the substrate, and grooves for filling the second epoxy resin are provided on the substrate.

[0013] As a further solution of the present invention: in the fifth step, the substrate is installed on the aluminum bar, pre-machined matching mounting holes are provided on the aluminum bar and the substrate, the hole positions correspond to the connector specifications, and anti-loosening bolts are used to pass through the reserved hole positions of the substrate and fix it to the aluminum bar, used in conjunction with insulating washers.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. By setting the substrate, the thermistor chip and the wire, and directly connecting the copper substrate to the aluminum bar, the influence of the external temperature on the temperature sensor is avoided, the temperature of the battery pack can be directly measured, and the temperature measurement accuracy of the temperature sensor is effectively improved; 2. The temperature sensor is connected to the aluminum bar, and the aluminum bar is directly connected to the battery, so the measurement of the battery temperature is more accurate; 3. The substrate is made of copper-nickel plating, and the good heat conduction of copper is used to reduce the response time; 4. The thermistor chip is coated with epoxy resin to increase the withstand voltage level of the product; 5. There is a large contact surface between the substrate and the aluminum bar, increasing the heat conduction efficiency. Description of the Drawings

[0015] Figure 1 It is a schematic structural view of the thermistor of the present invention; Figure 2 It is a schematic view of the encapsulation components of the present invention; Figure 3 It is a schematic structural view of the substrate of the present invention; Figure 4 It is a side view of the substrate of the present invention.

[0016] In the figure: 1. Thermistor chip; 2. First epoxy resin; 3. Wire; 4. Substrate; 5. Second epoxy resin. Detailed Embodiments

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

[0018] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "joined", "set" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The following describes the embodiments according to the overall structure of the present invention.

[0019] Please refer to Figures 1 to 4 , in the embodiment of the present invention, a flat package structure of a thermistor includes a thermistor chip 1. The thermistor chip 1 is welded to a wire 3, and after being coated and cured with a first epoxy resin 2 to form a head seal, the head seal is fixed in a substrate 4 through a second epoxy resin 5.

[0020] A flat package method for a thermistor is as follows: Step 1: Weld the thermistor chip 1 and the wire 3. Use a wire stripper to strip the insulating layer at the end of the wire 3 to expose about 3 - 5 mm of copper core. Clean the oxide on the surface of the solder pad of the thermistor chip 1. Fix the pin of the thermistor chip 1 with tweezers. The tip of the soldering iron touches the pin of the thermistor chip 1 and the copper core of the wire 3 at the same time. Wait for both to be evenly heated. Touch the solder wire gently to the soldering point. After the molten solder naturally wraps the pin and the copper core, remove the soldering iron. Avoid shaking. Immediately use a radiator clip to clamp the root of the pin to accelerate heat dissipation and prevent heat from conducting to the chip body. Step 2: After welding, apply the first epoxy resin 2 and heat it for curing. Thoroughly clean the surface of the thermistor chip 1 with alcohol or isopropyl alcohol to remove oxides, grease, and dust impurities. Perform plasma treatment on the lead or electrode area to enhance the adhesion of the epoxy resin. Preheat the thermistor chip 1 in an environment of 60 - 80°C for 10 - 15 minutes to reduce the thermal stress during coating and improve the resin fluidity. Vertically immerse the chip into the epoxy resin liquid and slowly lift it (speed ≤ 5 cm / min) to ensure uniform coverage and no sagging. Cure it at 60 - 80°C for 1 - 2 hours to make the resin initially formed; raise the temperature to 120 - 150°C and maintain it for 4 - 6 hours to ensure complete cross-linking; after natural cooling to room temperature, age it in an 80°C oven for 24 hours to eliminate internal stress; Step 3: Fill the inner cavity of the substrate 4 with the second epoxy resin 5. Remove the oil stain, oxide, and impurities on the surface of the substrate 4, which can be done by mechanical grinding or chemical cleaning, to ensure the bonding strength between the second epoxy resin 5 and the substrate 4. Preheat the substrate 4 to 40 - 80°C to reduce the viscosity of the second epoxy resin 5 and accelerate capillary flow; exclude air bubbles through a vacuum environment to avoid pore defects after filling; utilize capillary action to make the resin uniformly fill the internal gap of the substrate 4; Step 4: Insert the thermistor chip 1 into the substrate 4 and then heat it for curing. Insert the sealing head into the position where the second epoxy resin 5 is filled in the substrate 4, and use gradient temperature rise for segmented curing to improve the cross-linking density and thermal stability; after curing, cool it naturally or perform annealing treatment to reduce the deformation or cracking of the substrate 4 caused by thermal stress; Step 5: Install it on the aluminum bar. Drill holes in advance on the aluminum bar and the substrate 4, and use T-bolts in combination with flange nuts or slider nuts plus hexagon socket head cap screws for fastening. The aluminum bar is directly connected to the battery.

[0021] In this embodiment: Compared with the prior art, for the existing battery pack detection means, they are all installed on the surface of the cooling water pipe, and the temperature situation is confirmed by detecting the cooling water, and the installation method is the pipe wall envelopment mode, and the direct measurement point is the outer wall of the pipe. This application optimizes this mode.

[0022] By directly connecting the copper substrate 4 to the aluminum bar, the influence of the external air temperature on the temperature sensor is avoided, the temperature of the battery pack can be directly measured, and the temperature measurement accuracy of the temperature sensor is effectively improved; The temperature sensor is connected to the aluminum bar, and the aluminum bar is directly connected to the battery, so the battery temperature can be measured more accurately; the substrate 4 is made of copper plated with nickel, and the good thermal conductivity of copper is used to reduce the response time; the thermistor chip 1 is coated with epoxy resin to increase the withstand voltage level of the product; there is a large contact surface between the substrate 4 and the aluminum bar to increase the heat conduction efficiency.

[0023] Please refer specifically to Figures 1 to 2 , in Step 1, the thermistor chip 1 is an NTC negative temperature coefficient thermistor.

[0024] In this embodiment: The NTC (Negative Temperature Coefficient) thermistor has a higher temperature sensitivity. The resistance temperature coefficient of the NTC is 10 - 100 times that of ordinary metal materials, capable of detecting tiny temperature changes, especially suitable for precision temperature measurement scenarios; it has a faster response speed. Its thermosensitive characteristic enables the response time to reach the millisecond level, which is several times faster than mechanical or optical sensors, and can provide real-time feedback on temperature mutations to activate the protection mechanism; it has a wider operating temperature range. A typical NTC can operate stably in the range of -40°C to +200°C, covering extreme cold start and full-load operating conditions, with better adaptability than ordinary thermistors; it has high precision and long-term stability. Through B-value calibration, an accuracy of ±0.5°C can be achieved, and the anti-aging and corrosion-resistant characteristics of the ceramic substrate enable its service life to reach more than 10 years.

[0025] Please refer specifically to Figures 1 to 2 , in step two, the first epoxy resin 2 is prepared by mixing the main agent, diluent, and curing agent in a ratio of 70:20:30. Weigh the reactive diluent (such as HK-66 or AGE), mix the diluent with the epoxy resin, stir until it is uniformly transparent, add the curing agent (such as amine or anhydride), and continue stirring to ensure sufficient reaction.

[0026] In this embodiment: The first epoxy resin 2 can effectively block the erosion of environmental factors such as moisture, dust, and chemical corrosive substances on the thermistor chip 1, prevent internal components from being affected by moisture, oxidation, or contamination, thereby improving environmental adaptability; its high mechanical strength can buffer external vibration or impact, reducing the risk of physical damage to the thermistor chip 1 caused by external forces; after encapsulation and curing, a stable protective layer is formed to prevent the thermistor chip 1 from deforming or shifting due to temperature changes or vibration, ensuring long-term measurement accuracy; the excellent high and low temperature resistance characteristics (-40°C - 150°C) of the first epoxy resin 2 can ensure the stable performance of the thermistor chip 1 in a hot and cold cycling environment; the cured first epoxy resin 2 has high insulation, avoiding the risk of circuit short-circuit or leakage, and at the same time reducing the influence of external electromagnetic interference on the signal.

[0027] Please refer specifically to Figures 1 to 2 , in step three, the second epoxy resin 5 is prepared by mixing the main agent, diluent, and curing agent in a ratio of 70:20:30. Slowly add the diluent (acetone or ethyl acetate) to the epoxy resin, stir until it is uniform, add the curing agent and stir (such as amine or anhydride), pay attention to the evaporation rate to avoid generating bubbles, let it stand for degassing before use, and heat it if necessary to accelerate evaporation.

[0028] In this embodiment: The encapsulation layer formed by the second epoxy resin 5 and the first epoxy resin 2 can buffer the damage to the thermistor chip 1 caused by external mechanical shocks, while the second epoxy resin 5 filled in the substrate 4 absorbs vibration energy, forming a double protection barrier to keep the connection structure stable in a dynamic environment; the filling material disperses stress through rigid support, reduces the risk of solder joint fatigue, and increases the connection strength by more than 5 times; after the second epoxy resin 5 cures, it fixes the relative positions of the thermistor chip 1 and the substrate 4, preventing deformation or displacement caused by temperature fluctuations or vibrations, and improving the long-term measurement accuracy; by removing the traditional welding layer and adopting an integrated filling design, the influence of high-temperature aging on the connection is reduced.

[0029] Please refer specifically to Figures 2 to 4 , in step three, the substrate 4 is generally made of copper or aluminum.

[0030] In this embodiment: The substrate 4 is made of copper or aluminum, has high thermal conductivity, and can quickly transfer heat for the thermistor chip 1 to detect; it has high mechanical strength and stability. The copper substrate 4 has strong resistance to mechanical stress, high chemical stability, and good oxidation resistance, and can withstand complex working conditions.

[0031] Please refer specifically to Figures 2 to 4 , in step four, the filling amount of the second epoxy resin 5 needs to fill the substrate 4, and the substrate 4 is provided with grooves for filling the second epoxy resin 5.

[0032] In this embodiment: The inner cavity of the substrate 4 is filled with the second epoxy resin 5. Remove the oil, oxides, and impurities on the surface of the substrate 4, and mechanical grinding or chemical cleaning can be used to ensure the bonding strength between the second epoxy resin 5 and the substrate 4. Preheat the substrate 4 to 40 - 80 °C to reduce the viscosity of the second epoxy resin 5 and accelerate capillary flow; remove air bubbles through a vacuum environment to avoid pore defects after filling; utilize capillary action to make the resin uniformly fill the internal gaps of the substrate 4.

[0033] Please refer specifically to Figures 2 to 4 , in step five, the substrate 4 is installed on the aluminum bar. Pre-machined matching mounting holes are provided on the aluminum bar and the substrate 4, and the hole positions correspond to the connector specifications. Use anti-loosening bolts to pass through the reserved hole positions of the substrate 4 and fix them to the aluminum bar, and use insulating gaskets in combination.

[0034] In this embodiment: The substrate 4 itself has excellent thermal conductivity, and the aluminum bar, as a conductor, can further conduct heat. The combination of the two can quickly conduct heat out of the battery pack for the thermistor chip 1 to detect. The high mechanical strength of the substrate 4 combined with the rigid structure of the aluminum bar can resist external shocks and vibrations, improving the stability of the connection; at the same time, by using anti-loosening bolts to pass through the reserved hole positions of the substrate 4 and fix them to the aluminum bar, and using insulating gaskets in combination, it is convenient for subsequent disassembly and maintenance operations.

[0035] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A thermistor flat package structure, comprising a thermistor chip (1), characterized in that, The thermistor chip (1) is welded to the wire (3), and after being coated and cured with the first epoxy resin (2), a sealing head is formed. Then, the sealing head is fixed in the substrate (4) with the second epoxy resin (5).

2. A packaging method for a thermistor flat plate using the one in claim 1, characterized in that, The specific steps are as follows: Step 1: Weld the thermistor chip (1) and the wire (3). Use a wire stripper to remove the insulation layer at the end of the wire (3) to expose about 3 - 5 mm of copper core. Clean the oxide on the surface of the solder feet of the thermistor chip (1). Fix the pins of the thermistor chip (1) with tweezers. The tip of the soldering iron touches both the pins of the thermistor chip (1) and the copper core of the wire (3) simultaneously. Wait until both are evenly heated, then gently touch the solder wire to the soldering point. After the molten solder naturally wraps the pins and the copper core, remove the soldering iron. Avoid shaking and immediately use a heat sink clip to clamp the root of the pin to accelerate heat dissipation and prevent heat from conducting to the chip body; Step 2: Apply and heat - cure the first epoxy resin (2) after welding. Thoroughly clean the surface of the thermistor chip (1) with alcohol or isopropyl alcohol to remove oxides, grease, and dust impurities. Perform plasma treatment on the lead or electrode area to enhance the adhesion of the epoxy resin. Pre - heat the thermistor chip (1) in an environment of 60 - 80 °C for 10 - 15 minutes to reduce the thermal stress during coating and improve the fluidity of the resin. Immerse the chip vertically into the epoxy resin liquid and slowly lift it (speed ≤ 5 cm / min) to ensure uniform coverage and no dripping. Cure at 60 - 80 °C for 1 - 2 hours to make the resin initially take shape; raise the temperature to 120 - 150 °C and maintain for 4 - 6 hours to ensure complete cross - linking; after natural cooling to room temperature, age in an 80 °C oven for 24 hours to eliminate internal stress; Step 3: Fill the inner cavity of the substrate (4) with the second epoxy resin (5). Remove the oil stain, oxide, and impurities on the surface of the substrate (4), which can be achieved by mechanical grinding or chemical cleaning, to ensure the bonding strength between the second epoxy resin (5) and the substrate (4). Pre - heat the substrate (4) to 40 - 80 °C to reduce the viscosity of the second epoxy resin (5) and accelerate capillary flow; remove air bubbles through a vacuum environment to avoid pore defects after filling; utilize capillary action to make the resin evenly fill the internal gaps of the substrate (4); Step 4: Insert the thermistor chip (1) into the substrate (4) and then heat - cure it. Insert the sealing head into the position where the second epoxy resin (5) is filled in the substrate (4). Adopt gradient temperature rising and segmented curing to improve the cross - linking density and thermal stability; after curing, cool naturally or perform annealing treatment to reduce the deformation or cracking of the substrate (4) caused by thermal stress; Step 5: Install it on the aluminum bar. Drill holes in advance on the aluminum bar and the substrate (4), and use T - type bolts in combination with flange nuts or slider nuts plus hexagon socket head cap screws for fastening. The aluminum bar is directly connected to the battery.

3. A packaging method for a flat thermistor according to claim 2, characterized in that, In the above Step 1, the thermistor chip (1) is an NTC negative temperature coefficient thermistor.

4. A packaging method for a flat thermistor according to claim 2, characterized in that In the second step, the first epoxy resin (2) is prepared by mixing the main agent, diluent, and curing agent in a ratio of 70:20:

30. Weigh the reactive diluent (such as HK-66 or AGE), mix the diluent with the epoxy resin, stir until uniformly transparent, add the curing agent (such as amine or anhydride), and continue stirring to ensure full reaction.

5. A packaging method for a flat thermistor according to claim 2, characterized in that, In the third step, the second epoxy resin (5) is prepared by mixing the main agent, diluent, and curing agent in a ratio of 70:20:

30. Slowly add the diluent (acetone or ethyl acetate) to the epoxy resin, stir until uniform, add the curing agent and stir (such as amine or anhydride), pay attention to the evaporation rate to avoid generating bubbles, let it stand for degassing before use, and heat it if necessary to accelerate evaporation.

6. A packaging method for a flat thermistor according to claim 2, characterized in that, In the third step, the substrate (4) is generally made of copper or aluminum.

7. A packaging method for a flat thermistor according to claim 2, characterized in that In the fourth step, the filling amount of the second epoxy resin (5) needs to fill the substrate (4), and grooves for filling the second epoxy resin (5) are provided on the substrate (4).

8. A packaging method for a flat thermistor according to claim 2, characterized in that, In the fifth step, the substrate (4) is installed on the aluminum bar. Pre-processed matching installation holes are provided on the aluminum bar and the substrate (4), and the hole positions correspond to the specifications of the connectors. Use anti-loosening bolts to pass through the reserved hole positions of the substrate (4) to fix it to the aluminum bar, and use insulating gaskets in combination.

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