Methods for determining a degree of wetting

Abstract

Method (100) for determining the degree of wetting of a viscous thermal conductivity medium (20) on a connection surface between a battery cell (22) and a heat sink (24) in a battery system, comprising the steps of: - Illuminating (102) the connection surface with a directed optical light source (12) at a shallow illumination angle relative to the connection surface; - Acquiring (104) image data of the illuminated connection surface with a camera unit (14); - Filtering (106) the acquired image data based on the color and / or brightness of the reflected light with an evaluation unit (16); - Determining (108) the actual wetting area based on the illuminated areas with the evaluation unit (16); - Comparing (110) the actual wetting area with a predetermined target wetting area with the evaluation unit (16); - Calculating (112) the degree of wetting with the evaluation unit (16). as the ratio of actual to target area.

Description

The present invention relates to a method for determining a degree of wetting. Premium vehicles are characterized by high charging and discharging capacities, enabling fast charging times and powerful acceleration. Efficient thermal management of the battery cells is crucial for this, as high currents generate a significant amount of heat that must be reliably dissipated. The heat transfer medium between the battery cells and the cooling base is central to this heat dissipation. To ensure consistently high performance and safety, the wetting level of the thermal conductivity medium, i.e., the proportion of the surface area that is actually in thermal contact with the cell, must be checked during production. This check is usually done manually using templates, which is time-consuming and prone to errors. Automated measurement methods using simple cameras reach their limits, as defects such as air inclusions or slowly developing contact losses are difficult to detect reliably. While 3D cameras offer better depth information, they are expensive and often not economical for mass production. Therefore, there is a great need for new, cost-effective measurement methods that can accurately and reproducibly measure the degree of wetting in order to ensure the performance of high-voltage batteries in premium vehicles. DE 10 2024 124 022 A1 and KR 10 2025 0 053 306 A each disclose a device for determining the degree of wettability of a viscous thermal conductivity medium, comprising a directed optical light source with a definable beam angle, a camera for detecting an illuminated surface, and an evaluation unit for image processing and determination of the degree of wettability. CN 1 19 534 453 A relates to a method, a system and a device for the optical detection of adhesive bonds for batteries. It is therefore an object of the invention to provide a reliable and automated measuring method and a corresponding measuring system with which the degree of wettability of the thermal conductivity medium in high-voltage batteries can be accurately determined in order to ensure optimal heat dissipation and thus high charging and system performance. The solution to this problem is achieved according to the teaching of the independent claims. Various embodiments and further developments of the invention are the subject of the dependent claims. According to one aspect, the procedure for determining the degree of wettability of a viscous thermal conductivity medium on a connection surface between a battery cell and a heat sink in a battery system comprises the following steps: illuminating the connection surface using a directed optical light source at a shallow illumination angle relative to the surface, capturing image data of the illuminated area with a camera unit, filtering the image data based on the color and / or brightness of the reflected light, determining the actual wetting area based on the illuminated areas, comparing the actual wetting area with a specified target wetting area, and calculating the degree of wettability as the ratio of actual to target area. The degree of wetting describes the ratio of the actually wetted contact area between the thermal conductivity medium and the battery cell to the ideal, imagined target area. Precise determination of the degree of wetting is essential to ensure optimal heat dissipation. This method enables automated and reproducible analysis, minimizing errors caused by air inclusions and other defects. According to one embodiment, a directed laser light source is used whose light cone is aligned almost parallel to the attachment surface. Such a light source produces a narrow, coherent beam of light with minimal divergence, illuminating the surface at a shallow angle. This arrangement allows for clearer contrasts between wetted and unwetted areas. Particularly under shallow lighting, small air inclusions or defects are more pronounced, increasing the sensitivity of wetting detection and enabling more accurate analysis. According to one embodiment, the color of the laser light is selected so that it differs significantly from the spectral reflection behavior of the thermal interface material. This means that the wavelength of the light used is specifically chosen to enable reliable and simple segmentation of the wetted areas during the image processing process. This spectral delimitation minimizes interference from reflections from adjacent component surfaces and improves the accuracy of automated image evaluation, as the system specifically filters for the characteristic laser light. According to one embodiment, the target wetting area is defined by a marking on the surface or by using a digital reference geometry. The marking can be optically visible or invisible, for example by means of laser marking or a special coating that serves as a reference in the image processing process. Alternatively, a digital reference geometry, defining the idealized shape and extent of the bonding surface, allows for software-assisted overlay with the measured image data. This enables a precise comparison between the target and actual surface area, supporting an objective assessment of the degree of wetting. According to one embodiment, the image data is evaluated either by an internal camera module or by an external processor. The image processing includes filtering, segmenting, and classifying the recorded data to determine and quantify the wetting area. Internal camera analysis enables fast, immediate analysis directly at the measurement point, which is particularly advantageous for inline inspections in production. External analysis allows for more complex algorithms and flexible adjustments to changing requirements, for example, through the use of powerful image processing software. According to one embodiment, the beam angle of the optical light source is varied to detect different tolerance ranges on the bonding surface. A larger beam angle allows for higher surface tolerances and is suitable for detecting coarse wetting defects, while a smaller beam angle enables the detection of minute deviations from an ideal surface. This adaptation offers the advantage that the process can be flexibly adjusted to different quality requirements and manufacturing tolerances. Depending on the testing scenario, a choice can be made between a quick, rough inspection and a precise, error-critical analysis. According to one embodiment, the surface to be inspected is divided into several defined sub-areas, and the wetting is determined individually in each sub-area. This enables zone-specific defect detection, which allows for the precise localization of wetting defects on the bonding surface. Zone classification improves diagnostic quality, as areas with insufficient wetting can be specifically identified and marked for rework or process optimization. This improves the reliability of heat dissipation and reduces the risk of operational failure. According to one aspect, a device for carrying out the method comprises a directed optical light source with a definable beam angle, in particular a laser source, a camera unit for capturing the illuminated surface, an evaluation unit for image processing and wetting degree determination, and a control unit for adjusting the beam angle depending on the desired surface tolerance. This device enables automated and flexible wetting testing in an industrial environment. Controlling the beam angle allows for adaptation to different product variants or quality requirements, while the evaluation unit ensures fast and precise results. According to one embodiment, the camera unit comprises an RGB camera, and the evaluation unit implements a color-selective image analysis for segmenting the reflected laser light areas. The use of an RGB camera enables the acquisition of color information, which, together with the precisely applied laser color, ensures the reliable separation of wetted and unwetted areas. This color-selective analysis increases robustness against stray light and reflections and supports precise and automated determination of the degree of wetting. A system and / or means according to the present invention can be configured as hardware and / or software, in particular comprising at least one processing unit, preferably a microprocessor unit (CPU), graphics processing unit (GPU), or the like, preferably connected to a storage and / or bus system via data or signals, and / or comprising one or more programs or program modules. The processing unit can be configured to execute instructions implemented as a program stored in a storage system, to acquire input signals from a data bus, and / or to output signals to a data bus. A storage system can comprise one or more, in particular different, storage media, in particular optical, magnetic, solid-state, and / or other non-volatile media. The program can be configured to embody the methods described herein.is capable of performing such processes, so that the processing unit can execute the steps of such procedures and thus, in particular, operate or monitor the machine. A computer program product may, in one embodiment, include a storage medium, in particular a computer-readable and / or non-volatile medium, for storing a program or instructions, or with a program or instructions stored thereon. In one embodiment, the execution of this program or these instructions by a system or a controller, in particular a computer or an arrangement of several computers, causes the system or the controller, in particular the computer(s), to execute a procedure described herein or one or more of its steps, or the program or instructions are configured for this purpose. In one implementation, one or more, in particular all, steps of the process are carried out fully or partially automatically, in particular by the control system or its means. Any terms used herein, such as "comprises," "includes," "includes," "features," "has," "with," or any other variant thereof, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or features a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent in such method or apparatus. Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive or and not an exclusive "or". For example, a condition A or B is satisfied by one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). The terms "ein" or "eine," as used here, are defined as "one or more." The terms "ein anderer" and "ein Weitere," as well as any other variant thereof, are to be understood as "at least one more." The term "plural", as it may be used here, is to be understood in the sense of "two or more". The terms "configured" or "set up" to perform a specific function (and their respective variations), as used here, mean that a device or component thereof already exists in a configuration or setting capable of performing the function, or at least is adjustable—i.e., configurable—so that it can perform the function after appropriate adjustment. Configuration can be achieved, for example, by adjusting process parameters or by using switches or similar devices to activate or deactivate functionalities or settings. In particular, the device may have several predefined configurations or operating modes, allowing configuration by selecting one of these. Further advantages, features, and applications of the present invention will become apparent from the following detailed description in conjunction with the figures. Figure 1 schematically shows a flowchart of a method for determining the degree of wetting of a viscous thermal conductivity medium. Figure 2 shows a device for carrying out the method illustrated in Figure 1. Fig. 1 shows a flowchart of a method 100 for determining the degree of wetting of a viscous thermal conductivity medium 20 applied to a connection surface between a battery cell 22 and a heat sink 24 in a battery system. The aim of the method is to make a quantitative statement about the extent to which the intended connection surface is actually wetted by the thermal conductivity medium 20. The process begins with a first step in which the bonding surface is illuminated by a directed optical light source 12 102. The illumination takes place at a shallow angle relative to the surface, so that differences in light reflection - especially from wetted and unwetted areas - become more visible. In a subsequent step, 104 one or more camera units 14 capture the reflected light signals and generate image data that provide a visual representation of the illuminated area. This raw data contains image information about fully wetted, partially wetted, and unwetted areas. Subsequently, this image data is filtered by an evaluation unit. The filtering is preferably based on characteristic features such as color and / or brightness in order to clearly distinguish wetted areas from unwetted areas. The filtering prepares the data for precise analysis and reduces interference or image artifacts. Based on the filtered image data, an actual wetting area is determined in the next step 108. This is the actual proportion of the connection surface that is completely wetted by the thermal conductivity medium 20. This area is calculated by the evaluation unit 16. In the following step, this actual wetting area is compared with a previously defined target wetting area 110. This target area represents the ideal, fully wetted state and serves as a reference value for the subsequent evaluation. Finally, evaluation unit 16 calculates a wetting degree. This is the ratio of the determined actual wetting area to the target wetting area and allows a quantitative assessment of the application quality of the thermal conductivity medium 20. The method enables an automated, repeatable and objective evaluation of the wetting quality in battery systems and is particularly suitable for quality assurance in the production of thermally highly stressed cell modules. Fig. 2 schematically shows a prior art device 10 for carrying out the method 100 shown in Fig. 1 for determining the degree of wetting of a viscous heat transfer medium on a connection surface between a battery cell and a heat sink. The device has a modular design and comprises several functionally coordinated components. A central component is a directed optical light source 12, preferably a laser source, whose beam angle is definable. The light source is oriented such that it illuminates the bonding surface at a shallow angle. This creates reflection patterns on the surface that allow differentiation between wetted and unwetted areas. A camera unit 14 is positioned to capture the illuminated area and generate high-resolution image data. This image data is forwarded to an evaluation unit 16, which filters the reflected light components according to brightness and / or color in order to identify the wetted zones. Subsequently, the actual wetted area and the degree of wetting are determined. In the embodiment shown, an additional control unit 18 is provided, which controls the light source 12 and adjusts the beam angle depending on the desired surface tolerance. The diagram clearly shows an area of ​​reduced wetting on the right side of the thermal interface material layer. This area exhibits lower light reflection, indicating an incomplete or uneven distribution of the thermal interface material. This area can be clearly detected and quantified by the evaluation unit 16 to assess the wetting quality. The device 10 thus enables a precise, visual analysis of the wetting distribution and is particularly suitable for automated quality checks in the production environment of battery systems. In the figures, identical reference symbols denote identical, similar, or corresponding elements. Elements depicted in the figures are not necessarily shown to scale. Rather, the various elements depicted in the figures are represented in such a way that their function and general purpose are understandable to a person skilled in the art. Connections and couplings between functional units and elements shown in the figures can, unless expressly stated otherwise, also be implemented as indirect connections or couplings. Functional units can, in particular, be implemented as hardware, software, or a combination of hardware and software. While at least one exemplary embodiment has been described above, it should be noted that a large number of variations exist. It should also be noted that the described exemplary embodiments are merely non-limiting examples, and it is not intended to restrict the scope, applicability, or configuration of the devices and methods described herein. Rather, the preceding description will provide the person skilled in the art with guidance for implementing at least one exemplary embodiment. It is understood that various modifications to the function and arrangement of the elements described in an exemplary embodiment can be made without derogating from the subject matter defined in the appended claims and their legal equivalents.

Claims

Method (100) for determining the degree of wettability of a viscous thermal conductivity medium (20) on a connection surface between a battery cell (22) and a heat sink (24) in a battery system, comprising the steps of: - Illuminating (102) the connection surface with a directed optical light source (12) at a shallow illumination angle relative to the connection surface; - Acquiring (104) image data of the illuminated connection surface with a camera unit (14); - Filtering (106) the acquired image data with an evaluation unit (16) based on the color and / or brightness of the reflected light; - Determining (108) the actual wettability area based on the illuminated areas with the evaluation unit (16); - Comparing (110) the actual wettability area with a predetermined target wettability area with the evaluation unit (16); - Calculating (112) the degree of wettability with the evaluation unit (16). as the ratio of actual to target area. Method (100) according to claim 1, wherein the optical light source (12) comprises a directed laser light source whose light cone is aligned almost parallel to the attachment surface. Method (100) according to one of the preceding claims, wherein the color of the laser light is specifically chosen to be spectrally distinct from the thermal conductivity medium and to enable reliable segmentation in the image processing algorithm. Method (100) according to one of the preceding claims, wherein a marking on the surface or a digital reference geometry is used to delimit the desired wetting area. Method (100) according to one of the preceding claims, wherein the evaluation of the image data is carried out by a camera-internal module or by an external processor. Method (100) according to one of the preceding claims, wherein different tolerance ranges of the attachment surface are detected by varying the illumination angle or the beam angle of the optical aid, wherein a larger beam angle allows a higher surface tolerance and a smaller beam angle serves to detect fine deviations. Method (100) according to one of the preceding claims wherein the surface to be inspected is divided into several defined sub-areas and the wetting in each sub-area is determined individually, so that zone-specific defect detection is enabled. Computer program product with program code which, when executed on a computing unit, performs the method (100) according to one of claims 1 to 7, in particular for automated detection of the actual wetting area, comparison with a target area and calculation of the degree of wetting based on color or geometric features.

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