Heating film integrated with temperature monitoring function and preparation method thereof
By integrating a PTC carbon paste sensing circuit onto the heating film, the high cost and space occupation issues of heating film temperature monitoring in existing technologies are solved, achieving efficient and reliable temperature monitoring and improving the safety and integration of the battery system.
Patent Information
- Application Number
- CN202511458087.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-13
- Publication Date
- 2025-11-11
AI Technical Summary
Existing lithium-ion power battery heating film temperature monitoring solutions are costly, have complex assembly processes, and occupy a lot of space. Furthermore, single-point NTC sensors cannot fully perceive the temperature distribution, posing safety hazards.
PTC carbon paste is directly coated onto the heating film substrate to form an integrated sensing circuit structure that is insulated from the heating circuit. Temperature monitoring is achieved by monitoring changes in PTC resistance, simplifying the processing flow and reducing costs and space requirements.
It integrates heating and temperature measurement functions, improving production efficiency and reliability, reducing costs, enhancing safety, and adapting to the lightweight and highly integrated design of battery systems.
Smart Images
Figure CN120935876A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power battery technology, specifically to a heating film with integrated temperature monitoring function and its preparation method. Background Technology
[0002] In the thermal management system of lithium-ion power batteries, in order to improve battery activity and ensure charging efficiency and discharge power in low-temperature environments, a flexible electric heating film is usually attached to the surface of the battery module or individual cells for active heating. In this process, real-time and accurate monitoring of the heating film temperature is crucial. It is not only the key to achieving precise temperature control and improving energy efficiency, but also the core safety barrier to prevent the heating film from overheating and avoid battery thermal runaway.
[0003] Currently, the mainstream solution in the industry is to use independent negative temperature coefficient thermistors (NTCs) as temperature sensors. This solution typically involves fixing the packaged NTC probe to a non-uniformly heated area on the surface of the heating film using highly thermally conductive adhesives or mechanical clips, and then using the temperature at that single point to approximate the working status of the entire heating film.
[0004] However, this traditional solution has revealed many inherent defects in the demanding and rigorous application scenario of power batteries.
[0005] First, a single power battery pack often requires the deployment of multiple heating films and corresponding NTCs. Independent NTC sensors, wiring harnesses, and connectors significantly increase material costs and wiring harness complexity. At the same time, they occupy valuable space within the high-energy-density battery pack, which contradicts the design goals of lightweight and highly integrated systems.
[0006] Secondly, on automated or semi-automated production lines for battery packs, the addition of dispensing, bonding, and fixing processes for each NTC reduces production efficiency and introduces risks related to process consistency due to variations in adhesive layer thickness and curing degree. More seriously, under the vibration, impact, and thermal cycling conditions encountered during long-term vehicle operation, the bonding interface between the NTC and the heating film is prone to aging and cracking, leading to temperature measurement failure and posing a significant safety hazard.
[0007] Finally, a single-point NTC cannot fully detect the temperature distribution on the surface of the heating film, making it difficult to identify hot spots caused by poor adhesion, local short circuits, or other reasons. This undetectable localized overheating could potentially trigger battery thermal runaway, failing to meet the highest level of safety warning requirements for power battery systems.
[0008] Therefore, for heating applications of lithium-ion power batteries, there is an urgent need to develop an integrated, highly reliable, low-cost, and more comprehensive heating film temperature monitoring solution. Summary of the Invention
[0009] The present invention aims to provide a heating film with integrated temperature monitoring function and its preparation method, so as to solve the problems of high cost, complex assembly process and large space occupation of the NTC used in the temperature monitoring of heating films in the prior art.
[0010] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a heating film with integrated temperature monitoring function, comprising the following steps: Etching: Etching thermal circuitry onto a substrate; Coating: PTC carbon paste is coated onto the substrate according to the set sensing circuit structure and connected to the internal copper core, and the sensing circuit structure is insulated from the heating circuit. Insulation layer hot pressing: The insulating film is attached to the insulating area of the substrate and placed in a hot press. After hot pressing for a predetermined time under set temperature and pressure, it is removed.
[0011] Meanwhile, this solution also provides a heating film with integrated temperature monitoring function, applied to the above-mentioned method for preparing a heating film with integrated temperature monitoring function, including a flexible insulating substrate, on which a heating circuit layer is etched; a sensing circuit structure is also provided on the substrate, the sensing circuit structure is coated with PTC carbon paste and is insulated from the heating circuit layer; the sensing circuit structure includes multiple parallel N PTC temperature sensing points.
[0012] The principles and advantages of this scheme are: This innovative solution utilizes a functional paste with a positive temperature coefficient effect. By directly integrating the PTC sensor with the heating film, the sensing circuit structure and the heating circuit are integrated and manufactured on the same flexible substrate in a single, unified manner. By monitoring the resistance (or current / voltage) change of the PTC sensing circuit itself, the overall and local temperature state of the heating film can be directly and in real time reflected, thereby achieving the fusion of heating and temperature measurement functions.
[0013] Not all PTC pastes are suitable for co-firing with carbon pastes and silver pastes commonly used in heating films. It is necessary to solve the matching problems of different pastes in terms of hot-pressing temperature, adhesion, and coefficient of thermal expansion to ensure strong bonding, stable performance, and no mutual interference between functional layers. Furthermore, accurately extracting the weak resistance signal caused solely by temperature changes from the PTC sensor network "surrounded" by a powerful heating current is a significant technical challenge. The real-time interference of the heating condition on temperature measurement must be overcome.
[0014] In existing technologies, when facing the problem of temperature measurement reliability, the conventional approach is to improve the NTC bonding process or choose a more expensive sensor—a linear approach. This solution, however, breaks away from the conventional thinking that an independent sensor must be added. Instead, it seeks answers from the materials themselves and the basic structure, proposing a technical concept that allows the heating film to sense temperature itself. Furthermore, it utilizes the characteristics of PTC material and combines it with a specific circuit network design to solve the signal interference problem.
[0015] Based on this, this solution innovatively applies functional PTC paste as a material integrating structure and function in the manufacturing of heating films, transforming it from a passively heating component into an actively sensing circuit structure. Simultaneously, by setting up regional monitoring and reference areas, and utilizing the hardware itself to cancel common-mode signals (overall heating), the problem of interference from overall heating to local temperature measurement is cleverly solved, enabling simultaneous global temperature measurement and local overheat warning on a single component.
[0016] Furthermore, this solution greatly simplifies the complex sensing system. Compared to the traditional NTC chip bonding process, this solution only requires three steps to complete the manufacturing process. It eliminates the need for processes such as hole drilling and sealant application, as well as the need for separate production, transportation, and assembly of additional NTC chips. It also eliminates the need for additional circuit structures. While simplifying the overall structure, it reduces the processing steps and costs, lowers the overall footprint, and increases the stability and reliability of the overall structure. Attached Figure Description
[0017] Figure 1 This is a schematic flowchart of a method for preparing a heating film with integrated temperature monitoring function according to the present invention. Figure 2 This is a schematic diagram of the structure of a heating film with integrated temperature monitoring function according to the present invention.
[0018] In the attached diagram: 1. Substrate; 2. Heating circuit; 3. Sensing circuit structure; 4. PTC temperature sensing point; 5. Copper core. Detailed Implementation
[0019] The following detailed description illustrates the specific implementation method: Example 1 This embodiment describes a method for preparing a heating film with integrated temperature monitoring function. By directly integrating a PTC with the heating film and processing it through coating, the material is directly coated inside and connected to the copper core 5 during production. This simplifies the structure and processing flow, improves overall space utilization and lightweight performance, and reduces manufacturing costs.
[0020] In this embodiment, as shown in the appendix Figure 1 As shown, it includes the following steps: S1, Etching.
[0021] Etch thermal circuitry onto the substrate.
[0022] In this embodiment, a drawing with a heating circuit pattern and a sensing circuit structure is first designed based on thermal field simulation. A copper-clad laminate substrate is selected, which is a flexible substrate on which a thin copper foil is laminated. A photosensitive material is covered on the copper foil, and the drawing with the heating circuit pattern is attached to the substrate 1. The heating circuit is etched onto the substrate through an etching process to create a metal circuit pattern that serves as a resistive heating element.
[0023] S2, coating.
[0024] The PTC carbon paste is coated onto the substrate according to the set sensing circuit structure and connected to the internal copper core 5. The sensing circuit structure 3 is insulated from the heating circuit 2.
[0025] In this embodiment, the PTC carbon paste is a PTC paste with a positive temperature coefficient. During the coating process, using a pre-designed sensor circuit structure diagram, the PTC carbon paste is precisely printed onto the PI substrate using screen printing technology to form a temperature sensing network circuit. Silver paste is then printed at the locations where the PTC circuit requires connection terminals to serve as electrodes and leads.
[0026] In this embodiment, the sensing circuit structure 3 and the heating circuit 2 can be side by side or overlapped, depending on the circuit structure. When they overlap, an insulating dielectric layer needs to be printed between them to prevent short circuits.
[0027] In this embodiment, the sensing circuit structure 3 is coated on the substrate surface in the form of a distributed network pattern. As shown in the attached diagram... Figure 2 As shown, the distributed network graph consists of N parallel PTC temperature sensing points 4, and the multiple temperature sensing points are electrically connected in parallel to form a total sensing loop. In this embodiment, N∈[1,10].
[0028] Specifically, the sensing circuit structure 3 includes at least one main monitoring area (area A) and a reference area (area B) distributed on the substrate. Areas A and B use the same PTC paste and pattern design. In this embodiment, the main monitoring area is the central region of the heating film, which is typically the point with the greatest thermal inertia and is most prone to overheating; the reference area is the edge region of the heating film, where the heat dissipates fastest and the temperature is lowest. By combining and selecting to monitor these two areas, the approximate temperature gradient can be estimated, enabling monitoring of key areas.
[0029] In this embodiment, the sensing circuit structure 3 includes multiple independent sensing units, which are distributed in different partitions of the heating film and can be selectively addressed to measure the temperature of their respective areas.
[0030] In this embodiment, the resistance difference between region A and region B is monitored by a sensing unit. .once If the threshold is exceeded, an alarm is triggered immediately to determine localized overheating. Simultaneously, the resistance of area B is monitored and converted to a reference temperature. If the reference temperature also exceeds the absolute safety value, it indicates overall overheating, and an alarm is triggered accordingly. This addresses the interference of overall heating on localized monitoring, achieving highly reliable and safe integrated heating monitoring.
[0031] S3, Insulation layer hot pressing.
[0032] The insulating film is attached to the insulating area of the substrate and placed in a hot press. After hot pressing for a predetermined time at the set temperature and pressure, it is removed.
[0033] In this embodiment, a protective cover film (CVL) or printed insulating ink is applied to the entire structure to provide insulation, moisture protection, and mechanical protection. Specifically, during the hot pressing process of the insulating layer, a pre-made, solid insulating film (such as polyimide cover film, CVL) is bonded to the substrate to cover the area requiring insulation.
[0034] The semi-finished product is then placed in a hot press and processed at a set temperature, pressure, and time. In this embodiment, the hot pressing temperature, pressure, and time are set according to the characteristics of the selected PTC slurry. Hot pressing activates the heat-activated adhesive on the back of the overlay film, causing it to melt and form a strong bond with the underlying circuitry / substrate. Simultaneously, the pressure eliminates air between layers, ensuring a bubble-free, tight contact between each layer, thus guaranteeing reliable heat conduction and insulation.
[0035] In this embodiment, a current detection device is connected in series with the sensing circuit structure to determine the current temperature. By monitoring the magnitude of the current I, the current temperature can be directly calculated; the smaller the current value, the higher the temperature.
[0036] In existing technologies, independent temperature sensors (such as NTC chips) are physically attached to the surface of the heating film or specific points. This increases the size of the sensor and leads, and also requires additional assembly processes, additional fixing and insulation treatments, which reduces production efficiency and increases costs.
[0037] Furthermore, there are mechanical connection points between the sensor and the heating film. Long-term thermal expansion and contraction, as well as vibration, may lead to poor contact or detachment, causing temperature measurement failure or safety accidents. The sensor and its adhesive materials may also alter the local thermal conductivity characteristics of the heating film, resulting in measurement errors. Consequently, it becomes difficult to monitor the surface temperature of the heating film in real time, accurately, and reliably, making it difficult to meet the requirements for precise temperature control and safety protection.
[0038] Furthermore, a single sensor can typically only measure the temperature of a single "point," failing to fully reflect the temperature distribution across the entire heating film surface. This may result in the risk of localized overheating (hot spots) that cannot be monitored.
[0039] In this embodiment, the temperature measurement function directly replaces the NTC chip with PTC carbon paste and is integrated onto the substrate through coating. No additional components are required, greatly simplifying the layout and reducing processing steps. The heating film can be manufactured in just three steps, improving production efficiency, reducing costs, and enhancing product reliability and stability. The entire product significantly simplifies the circuitry and reduces space requirements, facilitating the miniaturization and thinning of battery devices.
[0040] Example 2 In this embodiment, a heating film with integrated temperature monitoring function is provided, which is applied to the above-mentioned method for preparing a heating film with integrated temperature monitoring function. (See attached diagram) Figure 2 As shown, the device includes a flexible insulating substrate 1 on which a heating circuit layer 2 is etched. A sensing circuit structure 3 is also provided on the substrate 1. The sensing circuit structure 3 is coated with PTC carbon paste and is directly connected to the internal copper core 5, and is insulated from the heating circuit layer 2. In this embodiment, the sensing circuit structure 3 includes multiple parallel N PTC temperature sensing points 4. Depending on the size of the heating film and the distribution of the internal circuit structure, multiple PTC temperature sensing points 4 can be set in each area, such as 3-5 parallel points arranged in one line, or 4-8 parallel points arranged in one line, etc., without limitation.
[0041] In this embodiment, the heating film is also connected to a controller. The controller is configured to monitor and control temperature based on the resistance signal of a sensing circuit structure formed from PTC slurry. The controller performs differential signal measurement on the parallel sensing network of the main monitoring area and the reference area, and determines local overheating based on the resistance difference. Simultaneously, a current detection device is integrated into the controller, along with a precision reference voltage source. The controller manages both the heating and temperature measurement functions simultaneously.
[0042] In this embodiment, the specific monitoring process is as follows: Heating period: The controller applies power (usually PWM pulses) to the heating circuit.
[0043] Measurement period: During the intervals between heating pulses, i.e., the periods when the heating film is not heating, if pulse width modulation (PWM) control is used for heating, the controller switches to temperature measurement mode during the off-period. At this time, the heating circuit power is disconnected, and a constant small voltage is immediately applied to the PTC sensing network, ensuring that this voltage is small enough not to cause the PTC network to heat up. Then, the current flowing through the PTC network at this time is measured.
[0044] The resistance value is calculated based on the measured current, and then converted into a temperature value using the pre-calibrated resistance-temperature (RT) curve of the PTC sensor network. The temperature value is then quickly obtained using a lookup table. Alternatively, if the RT characteristics of the selected PTC material have a known mathematical model, they can also be calculated using a formula.
[0045] For the overall average temperature, it is directly compared with the set safety threshold. For local overheating, sudden changes or drops in current are monitored. If the membrane is locally overheated, the PTC resistance in that area will increase sharply, causing a sudden decrease in the total current. This abnormal rate of change is a direct signal of local overheating, allowing for rapid monitoring results and timely intervention to ensure safety and reliability.
[0046] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for preparing a heating film with integrated temperature monitoring function, characterized in that, Includes the following steps, Etching: Etching thermal circuitry onto a substrate; Coating: PTC carbon paste is coated onto the substrate according to the set sensing circuit structure and connected to the internal copper core, and the sensing circuit structure is insulated from the heating circuit. Insulation layer hot pressing: The insulating film is attached to the insulating area of the substrate and placed in a hot press. After hot pressing for a predetermined time under set temperature and pressure, it is removed.
2. The method for preparing a heating film with integrated temperature monitoring function according to claim 1, characterized in that: During the coating process, the PTC carbon paste is a PTC paste with a positive temperature coefficient.
3. The method for preparing a heating film with integrated temperature monitoring function according to claim 1, characterized in that: The sensing circuit structure is coated on the surface of the substrate in the form of a distributed network pattern; the distributed network pattern consists of N parallel PTC temperature sensing points, and the multiple temperature sensing points are electrically connected in parallel.
4. The method for preparing a heating film with integrated temperature monitoring function according to claim 3, characterized in that: The sensing circuit structure includes at least one main monitoring area and one reference area; the main monitoring area is the central region of the heating film; and the reference area is the edge region of the heating film.
5. The method for preparing a heating film with integrated temperature monitoring function according to claim 4, characterized in that: The sensing circuit structure includes multiple independent sensing units, which are distributed in different partitions of the heating film and can be selectively addressed to measure the temperature of their respective regions.
6. The method for preparing a heating film with integrated temperature monitoring function according to claim 1, characterized in that: It also includes connecting a current detection device in series with the sensing circuit structure to determine the current temperature.
7. The method for preparing a heating film with integrated temperature monitoring function according to claim 1, characterized in that: During the hot pressing process of the insulation layer, the hot pressing temperature, pressure and time are set according to the characteristics of the selected PTC slurry.
8. A heating film with integrated temperature monitoring function, characterized in that, A method for preparing a heating film with integrated temperature monitoring function according to any one of claims 1-7 includes a flexible insulating substrate, on which a heating circuit layer is etched; a sensing circuit structure is also provided on the substrate, the sensing circuit structure is coated with PTC carbon paste and is insulated from the heating circuit layer; the sensing circuit structure includes multiple parallel N PTC temperature sensing points.
9. A heating film with integrated temperature monitoring function according to claim 8, characterized in that: The heating film is connected to a controller configured to monitor and control the temperature based on the resistance signal of the sensing circuit structure formed by the PTC slurry.
10. A heating film with integrated temperature monitoring function according to claim 9, characterized in that: The controller is used to perform differential signal measurement on the parallel sensor network of the main monitoring area and the reference area, and to determine local overheating based on the resistance difference.