Electric heating unit and preparation method thereof

Abstract

The invention discloses an electric heating unit and a preparation method thereof, the electric heating unit is formed by assembling a glass fiber upper plate, a hot melt adhesive film, conductive glass fiber cloth and a glass fiber lower plate which are arranged layer by layer through a high-temperature and high-pressure process, and the conductive glass fiber cloth is formed by sequentially coating a carbon series conductive coating and a packaging coating on the glass fiber cloth to form a conductive layer and a packaging layer; and copper sheets are inserted among the wire harnesses made of the glass fiber cloth, are completely coated by the conductive layer and the packaging layer, and are tightly combined with the wire harnesses made of the glass fiber cloth. The electric heating unit provided by the invention is stable in resistance, convenient to regulate and control, uniform in heating, stable in temperature and excellent in impact resistance, thermal aging performance and corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of electric heating unit preparation, and in particular relates to an electric heating unit and a preparation method thereof. Background Art

[0002] Glass fiber composite materials are often used as substrate materials for PCBs. For example, the commonly used substrate FR-4 for PCB boards is made of copper foil and glass fiber cloth impregnated with flame-retardant epoxy resin. It has high mechanical properties, good heat resistance and moisture resistance, and good machinability. However, when the PCB board is pressed and connected with the conductive material, there are problems such as loose bonding between the copper foil and the conductive material and hot melt adhesive blocking, which causes quality risks in the electrical connection path. To address this problem, a common solution is to apply a conductive silver paste with the same width as the copper tape on the conductive material, and after drying, use it together with the copper foil as an electrode connected to the external circuit to reduce the defect of loose bonding between the copper foil and the conductive material. In this process, the conductive layer is easily corroded by organic solvents in the silver paste, which has an adverse effect on the uniformity, adhesion and heating uniformity of the conductive material. In addition, due to the poor bending resistance of the conductive silver paste itself, the electric heating unit may fall off or break, generate concentrated heat, and have uneven temperature field, which may reduce or fail in function during use.

[0003] Patent CN 214125554U provides a heating cloth, including a conductive cloth and a plurality of first wires woven on the conductive cloth, and a first electrode and a second electrode provided at both ends of the first wire, which are staggered and connected to each other, can effectively avoid falling off and uneven heating of the heating cloth, and is convenient for stamping or cutting into different specifications. However, the cost of preparing the conductive cloth by the evaporation process is high, and the conductive layer is easily damaged when the wire is woven. During use, the conductive wire is easily broken by external force and causes the problem of wire frying. Patent CN 218735046U provides a new type of heating element, which forms a close conductive contact between the graphene heating layer and the output electrode area by providing an output electrode area on the main body of the PCB board and superimposing a graphene heating layer. However, the heating element prepared by this method has poor weather resistance, and there is a risk of poor bonding strength between the heating layer and the electrode. At the same time, the impact resistance, thermal aging resistance and corrosion resistance of the heating layer are difficult to meet the actual application requirements. Summary of the invention

[0004] In view of the problems existing in the above-mentioned technology, the purpose of the present invention is to provide an electric heating unit, whose electrodes are completely covered by a conductive layer and tightly combined with a glass fiber cloth bundle, so that the coating has high adhesion strength, the electric heating unit heats evenly, and has excellent impact resistance, heat aging resistance and corrosion resistance.

[0005] In order to achieve the purpose, the present invention adopts the following technical scheme:

[0006] An electric heating unit comprises a glass fiber upper plate, a hot melt adhesive film, a conductive glass fiber cloth and a glass fiber lower plate arranged in layers. The conductive glass fiber cloth is formed by coating a carbon-based conductive coating and a packaging coating on the glass fiber cloth in sequence to form a conductive layer and a packaging layer, and copper sheets are interspersed between the wire bundles of the glass fiber cloth, and the copper sheets are completely covered by the conductive layer and the packaging layer and are tightly combined with the wire bundles of the glass fiber cloth.

[0007] Preferably, the fiberglass upper plate and the fiberglass lower plate are one of polypropylene fiberglass plates, polyurethane fiberglass plates and epoxy fiberglass plates; at least two holes for connecting positive and negative electrodes and copper sheets are provided on the fiberglass upper plate.

[0008] Preferably, the hot melt adhesive film is a PA hot melt adhesive film, a TPU hot melt adhesive film or a PES hot melt adhesive film, and the softening point of the hot melt adhesive film is 120-140°C.

[0009] Preferably, in the conductive glass fiber cloth: the weight per unit area of ​​the glass fiber cloth is 100 to 600 g / m 2 The conductive layer has a dry weight of 2-50 g / m 2 , square resistance is 10-5000Ω / sq; the encapsulation layer is a modified polyurethane coating composed of polyurethane and nano-silicon dioxide, and the dry weight of the coating is 0.5-2g / m 2 ; The thickness of the copper sheet is 0.05-0.5 mm and the width is 0.2-2 mm.

[0010] As a preference, Figure 2 and Figure 3 As shown, the multiple copper sheets interspersed in the glass fiber cloth are divided into two groups, and the copper sheets in each group are arranged at intervals and connected to form a group of electrodes, and the two groups of electrodes serve as positive and negative electrodes respectively.

[0011] Preferably, a heat insulation board can be provided on the side of the glass fiber lower plate away from the conductive glass fiber cloth, so that the electric heating unit can heat only one side of the glass fiber upper plate; when the heat insulation board is not provided, the electric heating unit can achieve double-sided heating.

[0012] The present invention also provides a method for preparing the electric heating unit, comprising the following steps:

[0013] S1: implanting the copper sheet into the mesh of the glass fiber wiring bundle by weaving or interlacing to obtain a glass fiber cloth containing the copper sheet; pasting barrier glue points on the copper sheet corresponding to the hole positions of the glass fiber upper plate;

[0014] S2: Immerse the glass fiber cloth containing the copper sheet into the carbon-based conductive coating, and obtain the glass fiber cloth coated with the conductive layer after pressing, drying and cooling. Adjust the coating dry weight and coating times (1 to 4 times) according to the square resistance target;

[0015] S3: immersing the glass fiber cloth coated with the conductive layer into the encapsulation coating, and forming an encapsulation layer after pressing, drying and cooling to obtain the conductive glass fiber cloth;

[0016] S4: Remove the blocking glue points on the conductive glass fiber cloth, and stack the glass fiber upper plate, conductive glass fiber cloth, hot melt adhesive film, and glass fiber lower plate in sequence, transfer them to the pressing equipment for pressing and forming, and set the pressing temperature to 160-200℃ and the pressing pressure to 50-300kg / cm 2 , the pressing time is 0.5 to 10 minutes, and the electric heating unit is obtained after cooling.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention uses a glass fiber cloth with good flexibility as a carrier, implants a copper sheet into the carrier according to certain design specifications, and then applies a carbon-based conductive coating on the glass fiber cloth containing the copper sheet, and further applies a high-temperature resistant encapsulation coating, so that the copper sheet is completely covered by the conductive layer and the encapsulation layer and is tightly combined with the glass fiber cloth strands. The carbon-based conductive coating can completely cover the tiny uneven structures on the surface of the copper sheet, which prevents the hot melt adhesive film from penetrating between the copper sheet and the conductive layer when it melts at high temperature, thereby avoiding reducing the contact resistance between the copper sheet and the conductive layer.

[0019] (2) The carbon-based conductive coating of the present invention uses graphene, carbon nanotubes, conductive carbon black and spherical graphite as electric heating materials, and water-based polyurethane as a connecting resin. The formed conductive layer has a high bonding strength with the glass fiber cloth and the copper sheet, and the coating is dense, with a stable electronic transmission network and good impact resistance. At the same time, the present invention does not need to use conductive silver paste, has good environmental protection, and reduces the adverse phenomena such as cracking of the electrode layer that may occur.

[0020] (3) Since the resistance of the conductive glass fiber cloth used is less affected by the pressing process, the present invention adopts a multi-layer pressing molding process to prepare the electric heating unit, so that the resistance of the electric heating unit is highly controllable, the storage is stable, the regulation is convenient, the heat is uniform and the temperature is stable. At the same time, the glass fiber board is used as the upper and lower layer structures, giving the electric heating unit excellent impact resistance, thermal aging performance, corrosion resistance and insulation properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the preparation process and cross-sectional structure of the electric heating unit in the present invention.

[0022] Figure 2 It is a schematic diagram of a structure in which a copper sheet is inserted into a glass fiber cloth in the present invention.

[0023] Figure 3 This is another schematic diagram of the structure of inserting copper sheets into glass fiber cloth in the present invention.

[0024] Among them, 1-glass fiber cloth; 2-copper sheet; 3-conductive layer; 4-packaging layer; 5-glass fiber upper plate, 6-hot melt adhesive film, 7-glass fiber lower plate, 8-electric heating unit, 9-barrier glue point. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with embodiments. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0026] The components of the carbon-based conductive coating used in the following examples are composed by weight: 5 parts of graphene, 5 parts of carbon nanotubes, 2 parts of conductive carbon black, 4 parts of spherical graphite, 20 parts of polyurethane resin emulsion (PU-6155), 1.6 parts of dispersant (polyvinyl pyrrolidone), wetting agent (9300), 0.1 parts of defoaming agent (AFCONA-2508), and 60 parts of deionized water.

[0027] The components of the encapsulation coating used in the following examples are composed of 30 parts by weight of polyurethane resin emulsion (model PU-6155), 5 parts of nano-silicon dioxide solution (VK-S01N), 20 parts of ethanol, and 60 parts of deionized water.

[0028] Example 1

[0029] This embodiment provides an electric heating unit, such as Figure 1 and Figure 2 As shown, it is prepared by the following steps:

[0030] S1: Multiple copper sheets 2 (thickness 0.05 mm, width 0.4 mm) are inserted into the glass fiber cloth 1 (weight per unit area 100 g / m 2 ) A rectangular glass fiber cloth containing a group of positive and negative copper sheet electrodes is obtained inside the grid of the wiring harness; and barrier glue dots 9 are pasted on the copper sheet corresponding to the hole positions on the glass fiber upper plate.

[0031] S2: Dip the glass fiber cloth containing copper sheets into the carbon conductive coating, and adjust the amount of carbon conductive coating applied in a single time by the coating solid content, pressing spacing and other processes. Apply twice, press, dry and cool to form a conductive layer 3 (coating dry weight 3.2g / m 2 ) to obtain a glass fiber cloth coated with a conductive layer.

[0032] S3: Dip the glass fiber cloth coated with the conductive layer into the encapsulation coating, adjust the ink amount of the encapsulation coating by the coating solid content, pressing spacing and other processes, apply once, press, dry and cool to form an encapsulation layer 4 (coating dry weight 0.5g / m 2 ), that is, a conductive glass fiber cloth containing a copper sheet 2, a conductive layer 3 and a packaging layer 4 is obtained.

[0033] S4: Remove the blocking glue dots 9 on the copper sheet 2, and stack the glass fiber upper plate 5 (using epoxy glass fiber board), the conductive glass fiber cloth of step S3, the hot melt adhesive film 6 (using PA hot melt adhesive film), and the glass fiber lower plate 7 (using epoxy glass fiber board) in sequence, and transfer them to the pressing equipment for pressing and molding. Set the pressing temperature to 180°C and the pressing pressure to 100kg / cm 2 The pressing time is 2 minutes. After the pressing is completed, the electric heating unit 8 is taken out and cooled.

[0034] Example 2

[0035] This embodiment provides an electric heating unit, such as Figure 1 and Figure 2 As shown, it is prepared by the following steps:

[0036] S1: Multiple copper sheets 2 (thickness 0.1 mm, width 0.4 mm) are inserted into the glass fiber cloth 1 (weight per unit area 200 g / m 2 ) Inside the grid of the wiring harness, a rectangular glass fiber cloth containing two continuous copper sheets is obtained; and barrier glue dots 9 are pasted on the copper sheets corresponding to the positions of the holes on the glass fiber upper plate.

[0037] S2: Dip the glass fiber cloth containing copper sheets into the carbon conductive coating, and adjust the amount of carbon conductive coating applied in a single time by the coating solid content, pressing spacing and other processes. Apply twice, press, dry and cool to form a conductive layer 3 (coating dry weight 5.6g / m 2 ) to obtain a glass fiber cloth coated with a conductive layer.

[0038] S3: Dip the glass fiber cloth coated with the conductive layer into the encapsulation coating, and adjust the ink amount of the single encapsulation coating by the coating solid content, pressing spacing and other processes. Apply once, press, dry and cool to form an encapsulation layer 4 (coating dry weight 1.8g / m 2 ), that is, a conductive glass fiber cloth containing a copper sheet 2, a conductive layer 3 and a packaging layer 4 is obtained.

[0039] S4: Remove the blocking glue dots 9 on the copper sheet 2, and stack the glass fiber upper plate 5 (using epoxy glass fiber board), the conductive glass fiber cloth of step S3, the hot melt adhesive film 6 (using PA hot melt adhesive film), and the glass fiber lower plate 7 (using epoxy glass fiber board) in sequence, and transfer them to the pressing equipment for pressing and molding. Set the pressing temperature to 180°C and the pressing pressure to 100kg / cm 2 The pressing time is 2 minutes. After pressing is completed, take it out and get the electric heating unit after cooling.

[0040] Example 3

[0041] The present invention provides an electric heating unit, such as Figure 1 and Figure 2 As shown, it is prepared by the following steps:

[0042] S1: Multiple copper sheets 2 (thickness 0.2 mm, width 0.5 mm) are inserted into the glass fiber cloth 1 (weight per unit area 400 g / m 2 ) Inside the grid of the wiring harness, a rectangular glass fiber cloth containing two continuous copper sheets is obtained; and barrier glue dots 9 are pasted on the copper sheets corresponding to the positions of the holes on the glass fiber upper plate.

[0043] S2: Dip the glass fiber cloth containing copper sheets into the carbon conductive coating, and adjust the amount of carbon conductive coating applied in a single time by the coating solid content, pressing interval and other processes. Apply 4 times, press, dry and cool to form a conductive layer 3 (coating dry weight 17.3g / m 2 ) to obtain a glass fiber cloth coated with a conductive layer.

[0044] S3: Dip the glass fiber cloth coated with the conductive layer 3 into the encapsulation coating, and adjust the ink amount of the single encapsulation coating by the coating solid content, pressing spacing and other processes. Apply twice, press, dry and cool to obtain the encapsulation layer 4 (coating dry weight 3.6g / m 2 ), that is, a conductive glass fiber cloth containing a copper sheet 2, a conductive layer 3 and a packaging layer 4 is obtained.

[0045] S4: Remove the blocking glue dots 9 on the copper sheet 2, and stack the glass fiber upper plate 5 (using epoxy glass fiber board), the conductive glass fiber cloth of step S3, the hot melt adhesive film 6 (using PES hot melt adhesive film), and the glass fiber lower plate 7 (using epoxy glass fiber board) in sequence, and transfer them to the pressing equipment for pressing and molding. Set the pressing temperature to 200°C and the pressing pressure to 80KG / cm 2 The pressing time is 4 minutes. After the pressing is completed, it is taken out and the electric heating unit is obtained after cooling.

[0046] Comparative Example 1

[0047] In this comparative example, an electric heating unit is prepared in the same manner as in Example 1, except that: Step S1 is omitted, and a conductive glass fiber cloth containing a conductive layer 3 and a packaging layer 4 is obtained by dipping a carbon-based conductive coating and an encapsulation coating directly on the glass fiber cloth 1 in sequence in accordance with Steps S2 and S3. Then, a glass fiber upper plate 5 (using an epoxy glass fiber board), a copper sheet 2, a conductive glass fiber cloth, a hot melt adhesive film 6 (using a PA hot melt adhesive film), and a glass fiber lower plate 7 (using an epoxy glass fiber board) are stacked in sequence, wherein the position of the copper sheet is the same as that of the corresponding copper sheet in Example 1. The mixture is transferred to a pressing device for pressing and molding to obtain an electric heating unit.

[0048] Comparative Example 2

[0049] In this comparative example, an electric heating unit is prepared in the same manner as in Example 1, with the only difference being that: there is no step S1, and a conductive glass fiber cloth containing a conductive layer 3 and a packaging layer 4 is obtained by dipping a carbon-based conductive coating and an encapsulation coating directly on the glass fiber cloth 1 in sequence according to steps S2 and S3. Then, a conductive silver paste is applied to the position of the copper sheet corresponding to that in Example 1, and the mixture is transferred to a 150°C oven for curing for 30 minutes to obtain a conductive glass fiber cloth containing a conductive layer 3, an encapsulation layer 4 and a silver paste electrode. Then, a glass fiber upper plate 5 (using an epoxy glass fiber board), a copper sheet 2, a conductive glass fiber cloth, a hot melt adhesive film 6 (using a PA hot melt adhesive film), and a glass fiber lower plate 7 (using an epoxy glass fiber board) are stacked in sequence, wherein the position of the copper sheet is the same as that of the corresponding copper sheet in Example 1. Transfer to a pressing device for pressing and molding to obtain an electric heating unit.

[0050] Comparative Example 3

[0051] In this comparative example, the electric heating unit is prepared in the same manner as in Example 1, except that there is no S3 step.

[0052] The performance of the electric heating units obtained in the above-mentioned embodiments and comparative examples was tested as follows according to the following testing methods.

[0053] (1) Resistance: Connect the positive and negative electrodes of the multimeter to the copper sheet at the location of the hole on the fiberglass upper plate to measure the resistance.

[0054] (2) Lamination stability: The electric heating unit was placed in an environment of 23°C and 50% RH before and after lamination. After equilibration for 2 hours, the resistance was detected and the resistance change rate before and after lamination was calculated.

[0055] (3) Storage stability: The pressed electric heating unit was placed in an environment of 30°C and 70% RH. After balancing for 600 hours, the resistance was detected and the resistance change rate before and after storage was calculated.

[0056] (4) Heating temperature: Connect the electric heating unit to an AC voltage-regulated power supply and use an infrared imager to detect the heating temperature. After power is turned on, slowly increase the output operating voltage and adjust it to a heating target temperature of 120°C.

[0057] (5) Repeated heating stability: Apply rated working voltage to the electric heating unit, heat to 120°C, power on continuously for 16 hours and then turn off the power to cool for 8 hours. After repeatedly powering on and off 25 times, measure the resistance after complete cooling and calculate the resistance change rate.

[0058] The above test results are shown in Table 1.

[0059] Table 1

[0060]

[0061] It can be seen from the above table:

[0062] (1) The electric heating units prepared in Example 1, Example 2, and Example 3 showed relatively excellent lamination stability, storage stability, and repeated heating stability. The resistance after lamination showed a certain degree of decreasing trend, which was caused by the reduction of the spacing between the glass fiber bundles and the thickness of the glass fiber cloth during the lamination process.

[0063] (2) The electric heating units in Comparative Examples 1 and 2 also have good storage stability, but their resistance increases significantly before and after lamination. This is because the contact resistance between the copper sheet and the conductive glass fiber cloth is relatively large. At the same time, when the laminated structure of the copper sheet and the conductive glass fiber cloth is pressed, the hot melt adhesive easily melts and penetrates between the conductive glass fiber cloth and the copper sheet, and the conductive layer structure of the conductive glass fiber cloth at the edge of the copper sheet is prone to local damage and short circuit. During repeated heating, the copper sheet or silver paste electrode is easily oxidized in a high temperature environment, and a fine oxide layer will be formed on the surface, resulting in an increase in the contact resistance between the conductive glass fiber cloth and the hot melt adhesive will further melt and penetrate between the conductive glass fiber cloth and the copper sheet, causing the resistance of the electric heating unit to increase.

[0064] (3) The pressing stability, storage stability and pressing stability of the electric heating unit in Comparative Example 3 are not good, indicating that the encapsulation layer can effectively isolate and protect the conductive layer of the glass fiber cloth. Combined with the encapsulation of the hot melt adhesive film and the glass fiber board, its water-proof and oxygen-proof properties are further increased, and it has good temperature resistance.

[0065] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An electric heating unit, characterized in that: It comprises a glass fiber upper plate, a hot melt adhesive film, a conductive glass fiber cloth and a glass fiber lower plate arranged in layers; the conductive glass fiber cloth is formed by coating a carbon-based conductive coating and a packaging coating in sequence on the glass fiber cloth to form a conductive layer and a packaging layer, copper sheets are interspersed between the wire bundles of the glass fiber cloth, and the copper sheets are completely covered by the conductive layer and the packaging layer and are tightly combined with the wire bundles of the glass fiber cloth.

2. An electric heating unit according to claim 1, characterized in that: The fiberglass upper plate and the fiberglass lower plate are one of polypropylene fiberglass plates, polyurethane fiberglass plates and epoxy fiberglass plates; at least two holes for connecting positive and negative electrodes and copper sheets are arranged on the fiberglass upper plate.

3. An electric heating unit according to claim 1, characterized in that: The hot melt adhesive film is a PA hot melt adhesive film, a TPU hot melt adhesive film or a PES hot melt adhesive film, and the softening point of the hot melt adhesive film is 120-140°C.

4. The electric heating unit according to claim 1, characterized in that: In the conductive glass fiber cloth: the weight per unit area of ​​the glass fiber cloth is 100 to 600 g / m 2 The conductive layer has a dry weight of 2-50 g / m 2 , the square resistance is 10-5000Ω / sq; the coating dry weight of the encapsulation layer is 0.5-2g / m 2 ; The thickness of the copper sheet is 0.05-0.5 mm and the width is 0.2-2 mm.

5. The electric heating unit according to claim 1, characterized in that: A heat insulation board can be provided on the side of the glass fiber lower plate away from the conductive glass fiber cloth, so that the electric heating unit only generates heat on one side of the glass fiber upper plate; when the heat insulation board is not provided, the electric heating unit can generate heat on both sides.

6. A method for preparing the electric heating unit according to any one of claims 1 to 5, characterized in that: The steps include: S1: implanting the copper sheet into the mesh of the glass fiber wiring bundle by weaving or interlacing to obtain a glass fiber cloth containing the copper sheet; pasting barrier glue points on the copper sheet corresponding to the hole positions of the glass fiber upper plate; S2: immersing the glass fiber cloth containing the copper sheet into the carbon-based conductive coating, and obtaining the glass fiber cloth coated with the conductive layer after pressing, drying and cooling; S3: immersing the glass fiber cloth coated with the conductive layer into the encapsulation coating, and forming an encapsulation layer after pressing, drying and cooling to obtain the conductive glass fiber cloth; S4: Remove the blocking glue points on the conductive glass fiber cloth, and stack the glass fiber upper plate, conductive glass fiber cloth, hot melt adhesive film, and glass fiber lower plate in sequence, transfer them to the pressing equipment for pressing and forming, and set the pressing temperature to 160-200℃ and the pressing pressure to 50-300kg / cm 2 , the pressing time is 0.5 to 10 minutes, and the electric heating unit is obtained after cooling.

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