Manufacturing method of composite electromagnetic protective cover

Abstract

The invention discloses a method for manufacturing a composite electromagnetic protective cover in the technical field. The method comprises the following steps: 1) paving a lower skin; 2) manufacturing a pre-drawing bag; 3) placing a first layer of adhesive film; 4) placing a lower circuit board according to the positions of components on the circuit board, and placing positioning pins; 5) placing a second layer of adhesive film; (6) PMI foam is placed; 7) placing a third layer of adhesive film; (8) placing the upper circuit board according to the positions of the components on the circuit board, and ensuring that the positioning holes formed in the upper circuit board can coincide with the positioning holes of the lower circuit board through positioning pins; the manufacturing method comprises the following steps of (1) placing a first layer of adhesive film, (2) placing a second layer of adhesive film, (3) placing a third layer of adhesive film, (4) placing a fourth layer of adhesive film, (5) laying an upper skin, (6) manufacturing a vacuum bag, (7) curing, (8) demolding and machining after curing is finished, and (13) carrying out product nondestructive detection.According to the manufacturing method, a co-curing forming method is adopted, co-curing forming of the skin and the circuit board is achieved, and novel material composition equipment is provided for an electromagnetic energy selective surface device with the electromagnetic energy low-pass characteristic.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic pulse technology, and in particular to a method for manufacturing a composite electromagnetic shield. Background Art

[0002] Modern electronic information systems generally include sophisticated and advanced electronic computers, semiconductor integrated circuits, and weak current control software. The higher the degree of electronicization of the system, the more sensitive it is to changes in electromagnetic fields, voltages, and currents in the surrounding environment. Research and experiments have shown that strong electromagnetic pulses can burn out the semiconductor insulation layer or integrated circuit of electronic equipment, causing equipment failure or permanent damage, resulting in huge economic losses. Strong electromagnetic pulses pose a huge threat to the information society that increasingly relies on electronic equipment. How to effectively protect the safe and reliable operation of electronic information systems has become one of the issues that urgently need to be solved.

[0003] The most effective means of protecting against electromagnetic pulses is shielding, and the best shielding means is to cover electronic information equipment with a metal layer. However, metal shielding is a double-edged sword. While effectively shielding strong electromagnetic pulses, it also blocks the signal transmission and reception of the protected equipment. In actual use, electronic information systems must be able to resist strong electromagnetic pulses and effectively receive and send normal electromagnetic signals. Existing protection methods are difficult to meet this demand. From the perspective of protection mechanism, to meet this demand is to achieve the low-pass characteristic of electromagnetic energy, that is, to shield and isolate high-energy electromagnetic pulses that may cause damage to the equipment, while allowing low-energy electromagnetic signals to pass. At present, no structure or material with this function has been retrieved. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for manufacturing a composite electromagnetic shield, which adopts a co-curing molding method to achieve co-curing molding of the skin and the circuit board, and provides a new type of material composition equipment for an electromagnetic energy selective surface device with low-pass characteristics of electromagnetic energy.

[0005] The object of the present invention is achieved by: a method for manufacturing a composite electromagnetic shield, comprising the following steps: 1) Lower skin laying: When laying the lower skin, lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line; 2) Make pre-vacuum bags: Place peelable cloth, medium-temperature non-porous isolation film, medium-temperature breathable felt, and medium-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; 3) Laying the first layer of film: Lay the film evenly on the upper surface of the lower skin. After the film is laid, pre-extraction is performed; 4) Placement of the lower circuit board: Wipe the lower circuit board with a wipe paper moistened with anhydrous ethanol, place it on a non-porous isolation film, and wait for the ethanol to evaporate; place the lower circuit board according to the position of the components, and after placement, vacuum pre-pump the bag; 5) Laying the second layer of adhesive film: Leave the positioning holes of the lower circuit board exposed at the corresponding positions of the adhesive film, place positioning pins at the four positioning holes of the lower circuit board, and evenly lay the adhesive film on the upper surface of the lower circuit board. After the adhesive film is laid, pre-extraction is performed; 6) PMI foam laying: Before laying PMI foam, use anhydrous ethanol to clean it and place it in an oven for dehumidification. Leave the positioning holes of the lower circuit board empty at the corresponding positions of the foam in advance. After the PMI foam is placed, vacuum it. 7) Laying the third layer of adhesive film: Leave the positioning holes of the lower circuit board at the corresponding positions of the adhesive film, and evenly lay the third layer of adhesive film on the upper surface of the lower circuit board. After the adhesive film is laid, pre-extraction is performed; 8) Placement of the upper circuit board: After receiving the upper circuit board, wipe it with a wipe paper moistened with anhydrous ethanol, place it on a non-porous isolation film, and wait for the ethanol to evaporate; place the upper circuit board according to the position of the components so that the upper circuit board overlaps with the positioning pins, and the placement is completed, and the bag is vacuum pre-pumped; 9) Laying the fourth layer of adhesive film: first, leave the positioning holes of the upper circuit board at the corresponding positions of the adhesive film, and evenly lay the adhesive film on the upper surface of the foam. After the adhesive film is laid, pre-extraction is performed; 10) Upper skin laying: When laying the upper skin, leave the positioning holes of the upper circuit board empty at the corresponding position of the prepreg, lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line; 11) Make vacuum bag: Place peelable cloth, high-temperature non-porous isolation film, high-temperature breathable felt, and high-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; turn off the vacuum source and manually check the vacuum degree; 12) Curing in the tank: lift it into the autoclave and run the program according to the prepreg curing parameters.

[0006] As a further limitation of the present invention: Step 13) Demolding and machining: After the product is cured, it is demoulded and machined.

[0007] As a further limitation of the present invention: Step 14) Testing: performing non-destructive testing on the product.

[0008] As a further limitation of the present invention: the prepreg in step 1) is cyanate prepreg.

[0009] As a further limitation of the present invention: after the adhesive film laying in step 3), step 5), step 7) and step 9) is completed, pre-evacuation is performed, and the pre-evacuation time is ≥ 15 minutes, and the pre-evacuation timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa.

[0010] As a further limitation of the present invention: the step 11) of turning off the vacuum source and manually detecting the vacuum degree specifically comprises: turning off the vacuum source for 10 minutes, and manually detecting that the vacuum degree decreases by no more than 0.02 MPa, and the vertical edge retaining strips need to be installed in place before making the vacuum bag.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: in the molding process, the method of the present invention first lays the lower skin, places the adhesive film, makes four positioning holes at the same position at the four corner margins of the upper and lower circuit boards, places the lower circuit board according to the position of the components on the circuit board, and places the positioning pins; then places the adhesive film, PMI foam, and adhesive film (all need to reserve the position of the positioning holes), and places the upper circuit board according to the position of the components on the circuit board, ensuring that the positioning holes made in the upper circuit board and the positioning holes of the lower circuit can be overlapped by the positioning pins; lays the upper skin (reserves the position of the positioning pins), and finally makes a vacuum bag for curing. After the product is cured, demoulding, non-destructive testing of the product is carried out, and then the product is machined, and finally final inspection is carried out; the co-curing molding of the skin and the circuit board is realized, which provides a new type of material composition equipment for the electromagnetic energy selective surface device with electromagnetic energy low-pass characteristics, and provides a theoretical basis for its research field. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0013] Figure 1 Flowchart of the present invention.

[0014] Figure 2 Schematic diagram of the structural composition of the composite material electromagnetic shield of the present invention.

[0015] Figure 3 Structural diagram of the composite electromagnetic shield of the present invention.

[0016] Figure 4 The composite material electromagnetic shield performance testing process of the present invention.

[0017] Figure 5 The energy mechanism of the composite electromagnetic shield of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 The method for manufacturing a composite electromagnetic shield shown in the figure comprises the following steps: 1) Lower skin laying: Use XYQ100 / C1801 brand prepreg. When laying the lower skin, lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line; 2) Make pre-vacuum bags: Place peelable cloth, medium-temperature non-porous isolation film, medium-temperature breathable felt, and medium-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; 3) Laying the first layer of film: Lay H-3C film evenly on the upper surface of the lower skin. The film can be overlapped, and the overlap seam is ≤5mm. After the film is laid, pre-evacuation is carried out. The pre-evacuation time is ≥15min, and the pre-evacuation timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa. 4) Placement of lower circuit board: Wipe the lower circuit board with a wipe paper soaked in anhydrous ethanol, place it on a non-porous isolation film, and let it stand for 15 minutes to wait for the ethanol to evaporate; place the lower circuit board according to the position of the components, and after the placement is completed, vacuum pre-pump the bag; Nylon knitted gloves or other non-sweat-absorbing gloves need to be worn when taking and placing the circuit board, because skin oil is usually weakly acidic and easily corrodes the copper surface; 5) Second layer of film laying: expose the positioning holes of the lower circuit board at the corresponding positions of the film, place positioning pins at the four positioning holes of the lower circuit board, and evenly lay the H-3C brand film on the upper surface of the lower circuit board. The film can be overlapped, and the overlap seam is ≤5mm. After the film laying is completed, pre-evacuation is carried out; the pre-evacuation time is ≥15min, and the pre-evacuation timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa; 6) PMI foam laying: Before laying PMI foam, use anhydrous ethanol to clean it, place it in an oven (use a non-porous isolation film to block debris) for dehumidification, keep it warm at 120℃ for 1 hour, and leave the positioning holes of the lower circuit board at the corresponding position of the foam in advance. After the PMI foam is placed, vacuum it; 7) Third layer of film laying: expose the positioning holes of the lower circuit board at the corresponding positions of the film, and evenly lay the H-3C brand film on the upper surface of the lower circuit board. The film can be overlapped, and the overlap seam is ≤5mm. After the film laying is completed, pre-evacuation is carried out; the pre-evacuation time is ≥15min, and the pre-evacuation timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa; 8) Placement of the upper circuit board: After receiving the upper circuit board, wipe it with a wipe paper moistened with anhydrous ethanol, place it on a non-porous isolation film, and let it stand for more than 15 minutes to wait for the ethanol to evaporate; place the upper circuit board according to the position of the components so that the upper circuit board overlaps with the positioning pins, and the placement is completed, and the bag is vacuum pre-pumped; Nylon knitted gloves or other non-sweat-absorbing gloves need to be worn when taking and placing circuit boards, because skin oil is usually weakly acidic and easily corrodes the copper surface; 9) Laying the fourth layer of adhesive film: first, expose the positioning holes of the upper circuit board at the corresponding positions of the adhesive film, and evenly lay the H-3C brand adhesive film on the upper surface of the foam. The adhesive film can be overlapped, and the overlap seam is ≤5mm. After the adhesive film is laid, pre-evacuation is carried out; the pre-evacuation time is ≥15min, and the pre-evacuation timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa; 10) Upper skin laying: Lay XYQ100 / C1801 brand prepreg. When laying the upper skin, leave the positioning holes of the upper circuit board at the corresponding position of the prepreg. Lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line. 11) Make vacuum bags: Place peelable cloth, high-temperature non-porous isolation film, high-temperature breathable felt, and high-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; turn off the vacuum source and manually check the vacuum degree; turn off the vacuum source for 10 minutes, and manually check that the vacuum degree does not drop by more than 0.02MPa. Before making the vacuum bag, the vertical edge guard must be installed in place; 12) Entering the tank for curing: hoisting into the autoclave and running the program according to the prepreg curing parameters; 13) Demolding and machining: After the product is cured, demoulding and machining are performed; 14) Testing: Conduct non-destructive testing on products.

[0020] like Figure 2-3 As shown, the structural order of the electromagnetic shield design is prepreg-adhesive film-circuit board-adhesive film-PMI foam-adhesive film-circuit board-adhesive film-prepreg. The prepreg is cyanate prepreg (cyanate prepreg has excellent dielectric properties), the circuit board is Rogers PCB material copper clad circuit board (Rogers series circuit boards have excellent dielectric properties), a certain number of protection diodes are welded on the circuit board, and the appropriate diode junction capacitor is selected according to the working principle of the electromagnetic shield.

[0021] The electromagnetic shield manufactured by the above method is tested for its protection performance and insertion loss in accordance with GJB 7954-2012 Radar Wave Transmittance Test Method of Materials. The method is as follows: Place the sample in a microwave darkroom for near-field testing. The microwave darkroom is equipped with a professional testing system. The principle is as follows: Figure 4 First, the sample is placed on the sample table between the two antennas, and the electromagnetic waves emitted by the transmitting antenna are incident on the sample, part of which is reflected by the sample, and the other part is transmitted by the sample, and the transmitted electromagnetic waves are received by the receiving antenna.

[0022] like Figure 5 As shown in the figure, the working principle of the electromagnetic shield: the electromagnetic shield includes shielding materials and filtering structures, energy selection structures, PMI foam, frequency selective surfaces (prepreg skins), energy selective surfaces (circuit boards and protective components on circuit boards), etc. These measures can be used to reduce the energy entering the system and achieve the purpose of protection.

[0023] The present invention provides a method for manufacturing a composite electromagnetic shield. By adopting a co-curing molding method, the circuit board and components can withstand a temperature of more than 200°C, the maximum curing temperature of the prepreg molding is 190°C, and the co-curing molding of the skin and the circuit board can be realized. During the molding process, the lower skin is first laid, the adhesive film is placed, and four positioning holes at the same position are made at the four corner margins of the upper and lower circuit boards. The lower circuit board is placed according to the position of the components on the circuit board, and the positioning pins are placed; then the adhesive film, PMI foam, and adhesive film are placed (the positions of the positioning holes need to be reserved), and the upper circuit board is placed according to the positions of the components on the circuit board to ensure that the positioning holes made in the upper circuit board and the positioning holes of the lower circuit board can be overlapped by the positioning pins; the upper skin is laid (the positions of the positioning pins are reserved), and finally the vacuum bag is made for curing. After the product is cured, demoulding is performed, non-destructive testing of the product is performed, and then the product is machined, and finally a final inspection is performed; a new type of material composition equipment is provided for an electromagnetic energy selective surface device with low-pass characteristics of electromagnetic energy.

[0024] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a composite electromagnetic shield, characterized in that: The following steps are involved: 1) Lower skin laying: When laying the lower skin, lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line; 2) Make pre-vacuum bags: Place peelable cloth, medium-temperature non-porous isolation film, medium-temperature breathable felt, and medium-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; 3) Laying the first layer of film: Lay the film evenly on the upper surface of the lower skin. After the film is laid, pre-extraction is performed; 4) Placement of the lower circuit board: Wipe the lower circuit board with a wipe paper moistened with anhydrous ethanol, place it on a non-porous isolation film, and wait for the ethanol to evaporate; place the lower circuit board according to the position of the components, and after placement, vacuum pre-pump the bag; 5) Laying the second layer of adhesive film: Leave the positioning holes of the lower circuit board exposed at the corresponding positions of the adhesive film, place positioning pins at the four positioning holes of the lower circuit board, and evenly lay the adhesive film on the upper surface of the lower circuit board. After the adhesive film is laid, pre-extraction is performed; 6) PMI foam laying: Before laying PMI foam, use anhydrous ethanol to clean it and place it in an oven for dehumidification. Leave the positioning holes of the lower circuit board empty at the corresponding positions of the foam in advance. After the PMI foam is placed, vacuum it. 7) Laying the third layer of adhesive film: Leave the positioning holes of the lower circuit board at the corresponding positions of the adhesive film, and evenly lay the third layer of adhesive film on the upper surface of the lower circuit board. After the adhesive film is laid, pre-extraction is performed; 8) Placement of the upper circuit board: After receiving the upper circuit board, wipe it with a wipe paper moistened with anhydrous ethanol, place it on a non-porous isolation film, and wait for the ethanol to evaporate; place the upper circuit board according to the position of the components so that the upper circuit board overlaps with the positioning pins, and the placement is completed, and the bag is vacuum pre-pumped; 9) Laying the fourth layer of adhesive film: first, leave the positioning holes of the upper circuit board at the corresponding positions of the adhesive film, and evenly lay the adhesive film on the upper surface of the foam. After the adhesive film is laid, pre-extraction is performed; 10) Upper skin laying: When laying the upper skin, leave the positioning holes of the upper circuit board empty at the corresponding position of the prepreg, lay the cut prepreg on the mold, and lay the edge of the prepreg 20mm outside the mold product line; 11) Make vacuum bag: Place peelable cloth, high-temperature non-porous isolation film, high-temperature breathable felt, and high-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the position marked on the mold, and seal the vacuum bag; turn off the vacuum source and manually check the vacuum degree; 12) Curing in the tank: lift it into the autoclave and run the program according to the prepreg curing parameters.

2. The method for manufacturing a composite electromagnetic shield according to claim 1, characterized in that: Also includes: Step 13) Demolding and machining: After the product is cured, demoulding and machining are performed.

3. The method for manufacturing a composite electromagnetic shield according to claim 1, characterized in that: Also includes: Step 14) Testing: Perform non-destructive testing on the product.

4. The method for manufacturing a composite electromagnetic shield according to claim 1, characterized in that: The prepreg in step 1) is cyanate prepreg.

5. The method for manufacturing a composite electromagnetic shield according to claim 1, characterized in that: After the film laying in step 3), step 5), step 7) and step 9) is completed, pre-pumping is performed, and the pre-pumping time is ≥ 15 minutes. The pre-pumping timing starts when the vacuum degree in the vacuum bag is lower than -0.085MPa.

6. The method for manufacturing a composite electromagnetic shield according to claim 1, characterized in that: The step 11) of turning off the vacuum source and manually detecting the vacuum degree specifically includes: turning off the vacuum source for 10 minutes, and manually detecting that the vacuum degree decreases by no more than 0.02 MPa. Meanwhile, the vertical edge retaining strips need to be installed in place before making the vacuum bag.

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