Non-invasive electroencephalography electrode

Abstract

The utility model relates to electroencephalogram signal collection equipment technical field, especially a kind of non-invasive electroencephalogram electrode. The minimum thickness of current product shell is 0.9mm, and the thickness of the best comprehensive performance of conductive silicone is 0.7mm, and the conductive silicone of general electroencephalogram electrode is directly pressed and injected on copper contact, and the conductive silicone cannot completely adhere to head skin, which greatly affects the collection of electroencephalogram signal. The utility model provides a kind of non-invasive electroencephalogram electrode, tin paste layer and a tinned copper sheet are added between conductive silicone and copper contact, under the premise of keeping the elastic property and the best conductive performance of conductive silicone, the height difference of conductive silicone and product shell is eliminated, and the collection quality of electroencephalogram signal is improved.

Description

Technical Field

[0001] This utility model relates to the field of electroencephalogram (EEG) signal acquisition equipment, and in particular to a non-invasive EEG electrode. Background Technology

[0002] Electroencephalogram (EEG) electrodes are widely used in medical diagnosis, neuroscience research, and other fields. Non-invasive EEG electrodes have the following advantages: non-invasiveness, causing no direct invasive damage to the brain, and relatively safe; high temporal resolution, enabling real-time monitoring of brain activity changes, accurate to the millisecond level; reflecting functional information of the brain under different cognitive tasks, emotional states, and physiological conditions; some modern EEG devices are small, lightweight, and portable; and their cost is generally lower compared to other neuroimaging technologies. Existing non-invasive EEG electrodes are mainly made of metal materials and conductive silicone. Conductive silicone has properties such as being skin-friendly, biocompatible, and not easily affected by external temperature changes, making it widely used in non-invasive EEG electrodes. However, the conductivity of conductive silicone is greatly affected by its thickness. This is because the thicker the conductive silicone, the higher its resistance and impedance. Higher resistance and impedance result in poorer signal collection and more noise from the EEG electrode. Therefore, conductive silicone should be as thin as possible. However, when integrating conductive electrodes into products, the minimum thickness of the current product shell is 0.9mm, while the optimal thickness for conductive silicone is 0.7mm. Electrodes that are too thin cannot protrude from the product surface, leading to poor contact with the scalp and affecting signal acquisition quality. Simply increasing the thickness of the conductive silicone, on the other hand, significantly reduces signal collection quality. Therefore, there is an urgent need for a non-invasive EEG electrode that can increase the protrusion height of the conductive silicone without increasing its thickness. Utility Model Content

[0003] Based on this, it is necessary to address the above-mentioned shortcomings by providing a non-invasive EEG electrode, comprising: a flexible printed circuit board, and a plurality of sub-electrodes disposed on the flexible printed circuit board. The sub-electrodes are connected by copper foil wires disposed on the flexible printed circuit board. The ends of the copper foil wires are provided with interface terminals for communication with an external signal collection device. The sub-electrodes, from bottom to top, include: copper contacts connected to the copper foil wires, a solder paste layer, a tin-plated copper sheet, and conductive silicone. The surface of the tin-plated copper sheet facing the solder paste layer is plated with a layer of metallic tin. The tin-plated copper sheet is soldered to the copper contacts using SMT technology through the solder paste layer. The conductive silicone is injected onto the tin-plated copper sheet. The conductive silicone is used to contact the scalp and collect signals.

[0004] Preferably, the solder paste layer has a thickness of 0.1 mm, the tin-plated copper sheet has a thickness of 0.1 mm, and the conductive silicone has a thickness of 0.7 mm.

[0005] Preferably, the copper contact has a positioning hole, the tin-plated copper sheet has a recessed relief groove at the position corresponding to the positioning hole, and the conductive silicone has a protruding positioning post on the surface facing the copper contact that matches the positioning hole. The positioning post passes through the relief groove and is inserted into the positioning hole.

[0006] Preferably, the copper foil conductor extends along the flexible printed circuit board with several fixing plates, and the fixing plates are provided with several fixing holes for fixing the product casing.

[0007] Preferably, the sub-electrodes are arranged in a rectangular or circular lattice at intervals on a two-dimensional plane.

[0008] Preferably, a plurality of the sub-electrodes are arranged in a lattice at intervals along a spherical surface in three-dimensional space.

[0009] The aforementioned non-invasive EEG electrodes, by adding a layer of solder paste and a tin-plated copper sheet between the conductive silicone and copper contacts, increase the protrusion height of the conductive silicone. After the non-invasive EEG electrodes are installed in the product casing, the solder paste layer and tin-plated copper sheet eliminate the height difference between the conductive silicone and the casing surface, achieving optimal adhesion between the conductive silicone and the scalp. Simultaneously, this ensures the conductive silicone maintains optimal resistance and impedance, significantly improving the quality and integrity of EEG signal acquisition. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a non-invasive EEG electrode in one embodiment of the present invention;

[0011] Figure 2 for Figure 1 A magnified view of a portion of region A of the non-invasive EEG electrode in the illustrated embodiment;

[0012] Figure 3 This is a cross-sectional view of a sub-electrode of a non-invasive EEG electrode in one embodiment of the present invention.

[0013] Figure 4 This is a top view of a non-invasive EEG electrode in one embodiment of the present invention;

[0014] Figure 5 This is a bottom view of a non-invasive EEG electrode in one embodiment of the present invention.

[0015] Explanation of reference numerals in the attached diagram: 100-sub-electrode, 110-copper contact, 110a-positioning hole, 120-solder paste layer, 130-tinned copper sheet, 130a-relief groove, 140-conductive silicone, 141-positioning post, 200-copper foil wire, 210-interface terminal, 220-fixing piece, 220a-fixing hole, 300-flexible printed circuit board. Detailed Implementation

[0016] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0017] This utility model discloses a non-invasive electroencephalogram (EEG) electrode, such as Figures 1-5 As shown, it includes: a flexible printed circuit board, several sub-electrodes disposed on the flexible printed circuit board, the sub-electrodes being connected by copper foil wires disposed on the flexible printed circuit board, the ends of the copper foil wires being provided with interface terminals for communication with an external signal collection device, and the sub-electrodes including, from bottom to top: copper contacts connected to the copper foil wires, a solder paste layer, a tin-plated copper sheet, and conductive silicone. The surface of the tin-plated copper sheet facing the solder paste layer is plated with a layer of metallic tin, and the tin-plated copper sheet is soldered to the copper contacts using SMT process through the solder paste layer, and conductive silicone is injected onto the tin-plated copper sheet, the conductive silicone being used to contact the scalp and collect signals.

[0018] The non-invasive EEG electrode provided by this invention uses a flexible printed circuit board (FPC) as a substrate. In one embodiment, the FPC is made of polyimide. The FPC serves as the support and circuit carrier for the non-invasive EEG electrode, providing mechanical flexibility to adapt to the curvature of different users' scalps, allowing the sub-electrodes to fit optimally on the skin. Copper foil wires can connect the various sub-electrodes as needed, forming a signal transmission network. The interface terminals at the ends of the copper foil wires can be electrically connected to an external signal collection device via plug-in or soldering, transmitting the electrical signals collected by the sub-electrodes to the external signal collection device for analysis and processing. In the sub-electrodes, copper contacts are integrated into the flexible circuit board through printing or etching processes. The smooth surface is used for soldering solder paste layers. The solder paste layers are used to fix tin-plated copper sheets, forming an electrical connection. The solder paste layers melt at reflow soldering temperature, filling the gaps between the copper contacts and the tin-plated copper sheets. After cooling, a metallic bond is formed, providing both mechanical strength and... In terms of strength and conductivity, the tin-plated copper sheet serves as an intermediate conductive layer, enhancing the interfacial contact with the conductive silicone. The tin-plated copper sheet provides mechanical support and conductivity. The tin plating on the surface (approximately several micrometers thick) prevents copper oxidation (copper easily forms high-resistance CuO / Cu2O). At the same time, tin has lower electrochemical activity than copper, reducing the polarization effect at the electrode-electrolyte interface. It is soldered to copper contacts using surface mount technology (SMT) to achieve high-precision positioning and mass production. The conductive silicone directly contacts the user's scalp, collecting EEG signals and transmitting them to the tin-plated copper sheet. The conductive silicone is a mixture of silicone rubber matrix and conductive fillers (such as silver powder and carbon nanotubes), possessing both elasticity and conductivity. It can closely conform to the skin texture, reducing air gaps (air is an insulating medium and increases contact resistance). EEG signals are essentially ionic currents on the surface of the scalp (formed by the electrical activity of neurons transmitted to the body surface). The conductive fillers in the conductive silicone act as an ion-electron conversion interface, converting ionic currents into electronic currents, which are then transmitted to external electrical signal collection devices through the tin-plated copper sheet and copper foil wires.

[0019] The non-invasive EEG electrode provided by this utility model innovatively adds a layer of solder paste and a tin-plated copper sheet between the conductive silicone and the copper contacts, increasing the protrusion height of the conductive silicone. After the product shell is installed, the presence of the solder paste layer and the tin-plated copper sheet completely eliminates the height difference between the conductive silicone and the shell, allowing the conductive silicone to fully conform to the scalp. At the same time, it maintains the optimal resistance and impedance of the conductive silicone, significantly improving the quality and integrity of EEG signal acquisition.

[0020] In one embodiment, such as Figure 3As shown, the settings are: solder paste layer thickness 0.1mm, tin-plated copper sheet thickness 0.1mm, and conductive silicone thickness 0.7mm. The solder paste layer serves as the connection medium between the copper contacts and the tin-plated copper sheet; excessive thickness will increase resistance (the resistivity of tin is approximately 11 × 10⁻⁶). -8 The solder paste layer is 0.1 mm thick (Ω·m, higher than copper), but too thin a layer may lead to insufficient soldering (cold solder joint). Using a 0.1 mm thick solder paste layer not only ensures that the molten solder paste fully fills the interface gaps to form a continuous conductive path, but also reduces signal transmission loss caused by excessively thick solder layers (especially in high-frequency EEG signals, where the skin effect causes current to concentrate on the conductor surface). A 0.1 mm thick tin-plated copper sheet serves as a support structure for the conductive silicone, possessing high conductivity and adhering well to the conductive silicone for relatively complete signal transmission. The conductive silicone needs to directly contact the scalp, and its thickness affects the physical properties of the electrode-skin interface. If the conductive silicone is too thin, it will lack elasticity and fail to fully fill the gaps in the skin texture, increasing contact resistance; if the conductive silicone is too thick, it will increase resistance and impedance, leading to increased attenuation of high-frequency signals and affecting signal acquisition. A 0.7 mm thick conductive silicone has the best elasticity, resistance, and impedance, providing the best signal acquisition quality. At this thickness, the resistance of the conductive silicone is ≤500 Ω and the impedance is ≤1 kΩ.

[0021] In one embodiment, such as Figures 1-5 As shown, a positioning hole is provided on the copper contact. A recessed groove is provided on the tin-plated copper sheet corresponding to the positioning hole. A positioning post protrudes from the surface of the conductive silicone facing the copper contact, matching the positioning hole. The positioning post passes through the recessed groove and is inserted into the positioning hole to fix the conductive silicone. This structure ensures that the conductive silicone, tin-plated copper sheet, solder paste layer, and copper contact automatically align during the pressing process. The tight fit between the positioning post and the positioning hole (interference of approximately 0.01-0.03 mm) forms a mechanical lock, preventing relative sliding between the tin-plated copper sheet and the copper contact when the electrode is bent or subjected to external force (such as during wearing or removing). This significantly improves structural stability, especially when the flexible circuit board is repeatedly bent (curvature radius < 5 mm). Furthermore, the conductive silicone-metal contact between the positioning post and the positioning hole forms an auxiliary conductive path, diverting approximately 15-20% of the current and reducing the current density of the solder joints in the solder paste layer (from approximately 4 × 10⁻⁶). 4 A / cm² decreased to 8×10 3 (A / cm²), reducing the risk of electrochemical migration and decreasing contact impedance fluctuation from ±20% to ±5%.

[0022] In one embodiment, a plurality of fixing plates extend along the flexible printed circuit board (PCB) with copper foil conductors. Each fixing plate has a plurality of fixing holes. When the copper foil conductors are placed on the PCB, a housing covers the PCB. The housing contains fixing pins that match the fixing holes, which pass through the fixing holes to secure the copper foil conductors. In conventional designs, the copper foil conductors are attached to the PCB solely by a bottom adhesive, resulting in a shear strength of approximately 1-2 N / mm. With the fixing plates embedded in the PCB substrate and secured by the fixing pins, the shear strength is increased to 5-8 N / mm, reducing the risk of peeling of the copper foil conductors during repeated bending by 70%.

[0023] In one embodiment, several of the sub-electrodes are arranged in a rectangular dot matrix at intervals on a two-dimensional plane. The rectangular dot matrix (such as an 8×8 or 16×16 array) achieves regular sampling through an equally spaced grid (the spacing is usually 5-10 mm), which conforms to the Nyquist sampling theorem. The spatial frequency components of the EEG signal are mainly concentrated in the range of 0.1-20 cm. -1 When the sampling interval is ≤10mm, it can effectively capture ≥95% of the effective signal components. The rectangular grid facilitates two-dimensional Fourier transform and spatial filtering in subsequent signal processing, reducing computational complexity by 30% (compared to irregular arrangement).

[0024] In one embodiment, several of the sub-electrodes are arranged in a circular lattice at intervals on a two-dimensional plane. The circular lattice (such as concentric circles with high density at the center and sparse density at the periphery) better conforms to the curvature of the scalp and the distribution of functional areas of the cerebral cortex. The sampling point density in key areas such as the prefrontal cortex and motor cortex is increased by 50%, enhancing the ability to capture cognitive activities and motor intentions. The density in the edge areas is appropriately reduced to reduce the number of electrodes (such as reducing the total number of electrodes by 20%) while maintaining coverage and optimizing the signal-to-noise ratio.

[0025] In one embodiment, several sub-electrodes are arranged in a lattice at intervals along a spherical surface in three-dimensional space. The spherical lattice (with a radius of curvature of 8-12 cm, matching the average radius of the adult skull) ensures that all sub-electrodes are equidistantly attached to the scalp. Compared with the oversampling of the parietal lobe signal (sampling density >20 electrodes / in²) and the undersampling of the temporal lobe (<5 electrodes / in²) by the two-dimensional array, the spherical array controls the sampling deviation of each brain region within ±10%. The spherical lattice also enables the flexible circuit board to have uniform stress distribution when subjected to force, which greatly improves the service life of the EEG electrodes.

[0026] The aforementioned non-invasive EEG electrodes, by adding a layer of solder paste and a tin-plated copper sheet between the conductive silicone and copper contacts, increase the protrusion height of the conductive silicone. After the non-invasive EEG electrodes are fitted with a shell, the solder paste layer and tin-plated copper sheet eliminate the height difference between the conductive silicone and the shell surface, achieving optimal adhesion between the conductive silicone and the scalp. Simultaneously, this ensures the conductive silicone maintains optimal resistance and impedance, significantly improving the quality and integrity of EEG signal acquisition.

[0027] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0028] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A non-invasive electroencephalogram (EEG) electrode, characterized in that, include: A flexible printed circuit board (PCB) and several sub-electrodes disposed on the PCB. The sub-electrodes are connected by copper foil conductors disposed on the PCB. The ends of the copper foil conductors are provided with interface terminals that communicate with an external signal collection device. The sub-electrodes, from bottom to top, include: copper contacts connected to the copper foil conductors, a solder paste layer, a tin-plated copper sheet, and conductive silicone. The surface of the tin-plated copper sheet facing the solder paste layer is plated with a layer of metallic tin. The tin-plated copper sheet is soldered to the copper contacts using SMT technology through the solder paste layer. The conductive silicone is injected onto the tin-plated copper sheet. The conductive silicone is used to contact the scalp and collect signals.

2. The non-invasive EEG electrode according to claim 1, characterized in that, The solder paste layer has a thickness of 0.1 mm, the tin-plated copper sheet has a thickness of 0.1 mm, and the conductive silicone has a thickness of 0.7 mm.

3. The non-invasive EEG electrode according to claim 1, characterized in that, The copper contact has a positioning hole, and the tin-plated copper sheet has a recessed relief groove at the position corresponding to the positioning hole. The conductive silicone has a protruding positioning post on the surface facing the copper contact that matches the positioning hole. The positioning post passes through the relief groove and is inserted into the positioning hole.

4. The non-invasive EEG electrode according to claim 1, characterized in that, The copper foil conductor extends along the flexible printed circuit board with several fixing plates, and the fixing plates are provided with several fixing holes for fixing the product shell.

5. The non-invasive EEG electrode according to claim 1, characterized in that, The sub-electrodes are arranged in a rectangular or circular lattice at intervals on a two-dimensional plane.

6. The non-invasive EEG electrode according to claim 1, characterized in that, Several of the sub-electrodes are arranged in a lattice at intervals along a spherical surface in three-dimensional space.

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