Method for manufacturing a composite electromagnetic shield

Abstract

The application discloses a kind of composite electromagnetic shield manufacturing method in technical field, 1) lay down skin, 2) make pre-extraction bag;3) place first layer of adhesive film;4) according to the position of component on circuit board, place lower circuit board, place positioning pin;5) place second layer of adhesive film;6) place PMI foam;7) place third layer of adhesive film;8) according to the position of component on circuit board, place upper circuit board, ensure that the positioning hole made of upper circuit board and the positioning hole of lower circuit can be coincided by positioning pin;9) place fourth layer of adhesive film;10) lay up skin;11) make vacuum bag;12) solidification;13) after solidification, demoulding, machining;13) carry out product nondestructive testing.The application uses co-curing forming method, realizes skin and circuit board co-curing forming, and provides a new type of material composition equipment for electromagnetic energy low-pass characteristic electromagnetic energy selective surface device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic pulse, in particular to a manufacturing method of composite electromagnetic shield. BACKGROUND

[0002] Modern electronic information system generally includes precise advanced electronic computer, semiconductor integrated circuit and weak current control software. The higher the degree of electronic system, the more sensitive to the change of electromagnetic field, voltage and current in the surrounding environment. Research and experiments show that strong electromagnetic pulse can make the semiconductor insulating layer or integrated circuit of electronic equipment burn out, resulting in equipment failure or permanent damage, thus causing huge economic losses. Strong electromagnetic pulse poses a great threat to the information society which relies more and more on electronic equipment. How to effectively protect the safe and reliable operation of electronic information system has become one of the urgent problems to be solved.

[0003] The most effective means of protecting electromagnetic pulse is shielding, and the best shielding means is to cover electronic information equipment with metal layer. However, metal shielding is a double-edged sword, which effectively shields strong electromagnetic pulse while blocking the signal receiving and sending of the protected equipment. In actual use, electronic information system should be able to resist strong electromagnetic pulse and effectively receive and send normal electromagnetic signals. The existing protection means is difficult to meet this demand. From the protection mechanism, to meet this demand is to realize the low-pass characteristic of electromagnetic energy, that is, to shield and isolate high-energy electromagnetic pulse which may cause equipment damage, and to allow low-energy electromagnetic signal to pass. At present, no structure or material with such function has been searched. SUMMARY

[0004] In view of the deficiencies in the prior art, the present application provides a manufacturing method of composite electromagnetic shield, which adopts co-curing forming method to realize co-curing forming of skin and circuit board, and provides a new material composition device for electromagnetic energy low-pass characteristic electromagnetic energy selective surface device.

[0005] The purpose of the present application is achieved by a manufacturing method of composite electromagnetic shield, comprising the following steps:

[0006] 1) Lower skin laying: when laying the lower skin, the cut pre-impregnated material is laid on the mold, and the pre-impregnated material edge is laid 20mm outside the product line of the mold;

[0007] 2) Making pre-extraction bag: placing peelable cloth, medium-temperature non-porous isolation film, medium-temperature air-permeable felt and medium-temperature vacuum bag film in sequence on the upper surface of the part blank, placing vacuum nozzle at the marked position on the mold, and sealing the vacuum bag;

[0008] 3) First layer of adhesive film laying: evenly laying the adhesive film on the upper surface of the lower skin, and pre-extracting after the adhesive film laying is completed;

[0009] 4) Lower circuit board placement: The lower circuit board is wiped with a wetted alcohol-free ethanol wipe and placed on a non-porous isolation film, and left to stand for ethanol evaporation; the lower circuit board is placed according to the component positions, and the bag-making vacuum pre-extraction is performed after the placement is completed;

[0010] 5) Second layer of adhesive film laying: The positioning holes of the lower circuit board are exposed at the corresponding positions of the adhesive film, positioning pins are placed at the four positioning holes of the lower circuit board, and the adhesive film is uniformly laid on the upper surface of the lower circuit board. After the adhesive film laying is completed, pre-extraction is performed.

[0011] 6) PMI foam laying: Before laying the PMI foam, the PMI foam is cleaned with alcohol-free ethanol and placed in an oven for drying. The positioning holes of the lower circuit board are exposed at the corresponding positions of the foam, and the PMI foam is placed and vacuum extracted after the placement is completed.

[0012] 7) Third layer of adhesive film laying: The positioning holes of the lower circuit board are exposed at the corresponding positions of the adhesive film, and the third layer of adhesive film is uniformly laid on the upper surface of the lower circuit board. After the adhesive film laying is completed, pre-extraction is performed.

[0013] 8) Upper circuit board placement: After the upper circuit board is taken, it is wiped with a wetted alcohol-free ethanol wipe and placed on a non-porous isolation film, and left to stand for ethanol evaporation. The upper circuit board is placed according to the component positions, and the bag-making vacuum pre-extraction is performed after the placement is completed.

[0014] 9) Fourth layer of adhesive film laying: The positioning holes of the upper circuit board are exposed at the corresponding positions of the adhesive film, and the adhesive film is uniformly laid on the upper surface of the foam. After the adhesive film laying is completed, pre-extraction is performed.

[0015] 10) Upper skin laying: When laying the upper skin, the positioning holes of the upper circuit board are exposed at the corresponding positions of the prepreg, and the cut prepreg is laid on the mold. The prepreg is laid 20mm outside the product line of the mold.

[0016] 11) Vacuum bag making: The peelable cloth, high-temperature non-porous isolation film, high-temperature air-permeable felt, and high-temperature vacuum bag film are placed in sequence on the upper surface of the part blank, the vacuum nozzle is placed at the marked position on the mold, and the vacuum bag is sealed. The vacuum source is closed, and the vacuum degree is manually detected.

[0017] 12) Tank curing: The product is hoisted into the hot press tank and subjected to program operation according to the prepreg curing parameters.

[0018] As a further limitation of the present application: Step 13) demolding and machining: After the product is cured, it is demolded and machined.

[0019] As a further limitation of the present application: Step 14) detection: The product is subjected to non-destructive testing.

[0020] As a further limitation of the present application: the prepreg in step 1) adopts cyanate ester prepreg.

[0021] As a further limitation of the present application: the film laying in steps 3), 5), 7) and 9) is ended, and pre-extraction is carried out, and the pre-extraction time is greater than or equal to 15 min, and the pre-extraction time is counted from when the vacuum degree in the vacuum bag is less than -0.085 MPa.

[0022] As a further limitation of the present application: the closing of the vacuum source in step 11) specifically includes: closing the vacuum source for 10 min, and manually detecting that the vacuum degree is reduced by not more than 0.02 MPa, and meanwhile, the vertical edge baffle needs to be installed in place before the vacuum bag is made.

[0023] Compared with the prior art, the present application has the beneficial effects that: in the molding process of the present application, the lower skin is laid first, the film is placed, four positioning holes are made at the same position on the four corner edges 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 pin is placed; then the film, PMI foam and film (all of which need to reserve the position of the positioning hole) are placed, the upper circuit board is placed according to the position of the components on the circuit board, and it is ensured that the positioning holes made on the upper circuit board can coincide with the positioning holes of the lower circuit through the positioning pin; the upper skin (reserving the position of the positioning pin) is laid, and finally the vacuum bag is made for curing. After the product curing is completed, demolding is carried out, non-destructive testing of the product is carried out, machining of the product is carried out, and finally final inspection is carried out; the skin and the circuit board are co-cured to form, a new type of material composition equipment is provided for the electromagnetic energy low-pass characteristic electromagnetic energy selection surface device, and a theoretical basis is provided for the research field. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can also obtain other drawings according to the provided drawings without creative labor.

[0025] Figure 1 Flowchart of the present application.

[0026] Figure 2 Structure composition schematic diagram of the composite material electromagnetic shield of the present application.

[0027] Figure 3 Structure diagram of the composite material electromagnetic shield of the present application.

[0028] Figure 4 Performance detection flowchart of the composite material electromagnetic shield of the present application.

[0029] Figure 5 Energy mechanism of the composite electromagnetic shield. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort fall within the protection scope of the present application.

[0031] As shown in a kind of composite electromagnetic shield manufacturing method, comprising the following steps: Figure 1

[0032] 1) Lower skin laying: XYQ100 / C1801 brand prepreg is used, when laying the lower skin, the cut prepreg is laid on the mold, and the prepreg edge is laid 20mm outside the product line of the mold;

[0033] 2) Pre-evacuation bag making: peelable cloth, medium-temperature non-porous release film, medium-temperature air-permeable felt and medium-temperature vacuum bag film are placed in sequence on the upper surface of the part blank, the vacuum nozzle is placed at the marked position on the mold, and the vacuum bag is packaged;

[0034] 3) First layer of adhesive film laying: H-3C brand adhesive film is evenly laid on the upper surface of the lower skin, the adhesive film can be overlapped, and the overlap joint is ≤5mm; after the adhesive 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;

[0035] 4) Lower circuit board placement: the lower circuit board is wiped with a wetted anhydrous ethanol wiping paper, placed on the non-porous release film, and left to stand for 15min to wait for the ethanol to evaporate; the lower circuit board is placed according to the position of the components, and the bag-making vacuum pre-evacuation is carried out; nylon woven gloves or other non-sweating gloves are needed when taking and placing the circuit board, because the skin grease is usually weakly acidic and can easily corrode the copper surface;

[0036] 5) Second layer of adhesive film laying: the positioning holes of the lower circuit board are exposed at the corresponding positions of the adhesive film, positioning pins are placed at the four positioning holes of the lower circuit board, and H-3C brand adhesive film is evenly laid on the upper surface of the lower circuit board; the adhesive film can be overlapped, and the overlap joint is ≤5mm; after the adhesive 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;

[0037] ​6) PMI foam laying: Before PMI foam laying, clean with anhydrous ethanol, place in the oven (use non-porous isolation film to block debris) for dehumidification, 120°C for 1 hour, expose the positioning holes of the lower circuit board to the corresponding position of the foam in advance, and vacuumize after the PMI foam is placed;

[0038] 7) Third layer of adhesive film laying: Expose the positioning holes of the lower circuit board to the corresponding position of the adhesive film, evenly lay the H-3C brand adhesive film on the upper surface of the lower circuit board, the adhesive film can be overlapped, the overlap joint is ≤5mm, and the adhesive film laying is completed, and pre-evacuation is performed; 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;

[0039] 8) Upper circuit board placement: After the upper circuit board is taken, wipe it with a wetted anhydrous ethanol wipe, place it on a non-porous isolation film, and wait for 15min or more for ethanol evaporation; place the upper circuit board according to the component position, so that the upper circuit board coincides with the positioning pin, and the bag is made and vacuumized; nylon woven gloves or other non-sweaty gloves are needed when taking and placing the circuit board, because skin grease is usually weakly acidic and can easily corrode the copper surface;

[0040] 9) Fourth layer of adhesive film laying: Expose the positioning holes of the upper circuit board to the corresponding position of the adhesive film, evenly lay the H-3C brand adhesive film on the upper surface of the foam, the adhesive film can be overlapped, the overlap joint is ≤5mm, the adhesive film laying is completed, and pre-evacuation is performed; 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;

[0041] 10) Upper skin laying: Lay the XYQ100 / C1801 brand prepreg, when laying the upper skin, expose the positioning holes of the upper circuit board to the corresponding position of the prepreg, lay the cut prepreg on the mold, and the prepreg edge is laid 20mm outside the product line of the mold;

[0042] 11) Vacuum bag making: Place the peelable cloth, high-temperature non-porous isolation film, high-temperature air-permeable felt, and high-temperature vacuum bag film on the upper surface of the part blank in sequence, place the vacuum nozzle at the marked position on the mold, and seal the vacuum bag; close the vacuum source and manually detect the vacuum degree; close the vacuum source for 10min, and manually detect that the vacuum degree decreases by no more than 0.02MPa. The vertical edge barrier needs to be installed in place before making the vacuum bag;

[0043] 12) Autoclave curing: Hoist into the autoclave, and perform program operation according to the prepreg curing parameters;

[0044] 13) Demolding and machining: After the product is cured, demold and machine;

[0045] 14) Detection: Perform non-destructive testing on the product.

[0046] As shown in Figures 2-3 The structural sequence of the electromagnetic shield design is prepreg-film-circuit board-film-PMI foam-film-circuit board-film-prepreg. The prepreg is selected as cyanate ester prepreg (the cyanate ester prepreg has superior dielectric properties), the circuit board is selected as a copper-clad circuit board of Rogers PCB material (the circuit board of the Rogers series has superior dielectric properties), a certain number of protective diodes are welded on the circuit board, and appropriate diode junction capacitances are selected according to the working principle of the electromagnetic shield.

[0047] The electromagnetic shield manufactured by the above method is tested for its shielding performance and insertion loss according to the method of GJB 7954-2012 Radar Wave Transparent Material Wave Transparency Test. The method is as follows: the sample is placed in a microwave darkroom for near-field testing, and the microwave darkroom is equipped with a professional testing system, and the principle is as shown in 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 the electromagnetic waves is reflected by the sample, and part of the electromagnetic waves is transmitted by the sample, and the transmitted electromagnetic waves are received by the receiving antenna.

[0048] As shown in Figure 5 The working principle of the electromagnetic shield is as follows: the electromagnetic shield includes shielding materials and filtering structures, energy selection structures, PMI foam, frequency selection surfaces (prepreg skin), energy selection surfaces (circuit board and protective components on the circuit board), etc. These measures can weaken the energy entering the system interior, achieving the purpose of protection.

[0049] The present application provides a composite material electromagnetic shield manufacturing method, which adopts co-curing forming method, the circuit board and components can withstand temperature above 200℃, the prepreg forming and curing temperature is up to 190℃, and the skin and circuit board can be co-cured and formed. In the forming process, the lower skin is first laid and pasted, the film is placed, four positioning holes are made at the same position on the four corner edges 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 pin is placed; then the film, PMI foam and film (all need to reserve the positioning hole position) are placed, the upper circuit board is placed according to the position of the components on the circuit board, and the positioning holes made on the upper circuit board and the positioning holes of the lower circuit board can be overlapped by the positioning pin; the upper skin is laid (the positioning pin position is reserved), and finally the vacuum bag curing is made. After the product curing is completed, the product is demolded, nondestructive testing is performed, the product is machined, and finally the final inspection is performed; a new type of material composition equipment is provided for the electromagnetic energy selection surface device with low-pass characteristic of electromagnetic energy.

[0050] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for manufacturing a composite material electromagnetic shield, characterized in that, Includes the following steps: 1) Lower skin installation: When installing the lower skin, lay the cut prepreg on the mold, with the edge of the prepreg 20mm outside the product line of the mold. 2) Making pre-sealed 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 marked position on the mold, and seal the vacuum bag; 3) First layer of adhesive film: Evenly apply the adhesive film to the upper surface of the lower skin. After the adhesive film is applied, perform pre-extraction. 4) Placement of the lower circuit board: Wipe the lower circuit board with a wiping paper moistened with anhydrous ethanol, place it on the non-porous isolation film, and let it stand for the ethanol to evaporate; place the lower circuit board according to the position of the components, and after placement, vacuum pre-tighten the bag; 5) Second layer of adhesive film: Expose the positioning holes of the lower circuit board in the corresponding positions of the adhesive film, place positioning pins at the four positioning holes of the lower circuit board, and evenly apply the adhesive film to the upper surface of the lower circuit board. After the adhesive film is applied, perform pre-extraction. 6) PMI foam placement: Before placing the PMI foam, clean it with anhydrous ethanol and place it in an oven for dehumidification. Make sure the positioning holes of the lower circuit board are exposed at the corresponding positions of the foam beforehand. After the PMI foam is placed, vacuum compact it. 7) Applying the third layer of adhesive film: Expose the positioning holes of the lower circuit board in the corresponding positions of the adhesive film, and evenly apply the third layer of adhesive film to the upper surface of the lower circuit board. After the adhesive film is applied, perform pre-extraction. 8) Placing the upper circuit board: After receiving the upper circuit board, wipe it with a wiping paper moistened with anhydrous ethanol, place it on the non-porous isolation film, and let it stand for the ethanol to evaporate; place the upper circuit board according to the position of the components, so that the upper circuit board coincides with the positioning pin, and the placement is completed. Vacuum pre-tighten the bag. 9) Fourth layer of adhesive film: First, expose the positioning holes of the upper circuit board in the corresponding positions of the adhesive film, then evenly apply the adhesive film to the upper surface of the foam. After the adhesive film is applied, perform pre-extraction. 10) Upper skin installation: When installing the upper skin, expose the positioning holes of the upper circuit board at the corresponding positions of the prepreg, and install the cut prepreg on the mold, with the edge of the prepreg installed 20mm outside the product line of the mold. 11) Making 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 marked position on the mold and seal the vacuum bag; turn off the vacuum source and manually check the vacuum degree. 12) In-tank curing: Hoist the material into the autoclave and run the program according to the prepreg curing parameters.

2. The method for manufacturing a composite material electromagnetic shield according to claim 1, characterized in that, Also includes: Step 13) Demolding and machining: After the product has cured, demold it and perform machining.

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

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

5. The method for manufacturing a composite material electromagnetic shield according to claim 1, characterized in that, After the adhesive film is laid in steps 3), 5), 7), and 9), pre-extraction is performed for ≥15 minutes. Pre-extraction timing starts when the vacuum level inside the vacuum bag is below -0.085 MPa.

6. The method for manufacturing a composite material electromagnetic shield according to claim 1, characterized in that, Step 11) involves shutting off the vacuum source and manually checking the vacuum level. Specifically, this includes shutting off the vacuum source for 10 minutes and manually checking that the vacuum level decreases by no more than 0.02 MPa. Additionally, the side guard strips must be installed in place before making the vacuum bag.

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