WO2020020195A1

WO2020020195A1 - Fpc electromagnetic shielding film with polyimide film as insulating layer, and preparation method therefor

Info

Publication number: WO2020020195A1
Application number: PCT/CN2019/097407
Authority: WO
Inventors: 刘仁成; 谢文波; 王绍亮; 洪腾; 万彩兵
Original assignee: 深圳市弘海电子材料技术有限公司
Priority date: 2018-07-25
Filing date: 2019-07-24
Publication date: 2020-01-30
Also published as: CN108976457A; CN108976457B

Abstract

Provided is an FPC electromagnetic shielding film with a polyimide film as an insulating layer, the FPC electromagnetic shielding film comprising a PI insulating layer, a reflective shielding coating coating the PI insulating layer, and an absorptive shielding coating coating the reflective shielding coating, wherein a layer of a release protection film layer is arranged on the absorptive electromagnetic shielding coating. Provided are an FPC electromagnetic shielding film with a polyimide film as an insulating layer, and a preparation method therefor, wherein same have improved weather-resistance, flexibility, bending resistance, product smoothness and shielding performance.

Description

FPC electromagnetic shielding film using polyimide film as insulating layer and preparation method thereof

Technical field

The invention relates to the technical field of electromagnetic shielding, in particular to an FPC electromagnetic shielding film using a polyimide film as an insulating layer and a preparation method thereof.

Background technique

Printed circuit boards (FPC for short) are indispensable materials in electronic products, and are currently widely used in computers and their peripheral devices, communication products and consumer electronics. As the demand for consumer electronics continues to grow, printed circuit boards Board requirements are also increasing.

In the prior art, the electromagnetic shielding film has the following problems: (1) Insulating layers of the electromagnetic shielding film for FPC mostly use ink or coating, but the ink or coating is easy to age and has poor weather resistance, especially in the high temperature and high humidity environment in the south The life of electronic products is very affected. Polyimide (PI for short) is the king of materials, but due to technical limitations, the thickness of the film is large and the flexibility is not good, so it cannot be used as an electromagnetic wave shielding film for electronic products. (2) The shielding layer of the electromagnetic shielding film is a metal shielding layer or a conductive layer. The metal shielding layer is prone to chipping and oxidation during the complicated high-temperature and high-pressure operation process of the FPC, which will reduce the shielding performance. , Even lose the shielding performance, and easy to blister and delaminate in the subsequent reflow soldering process. (3) Shielding film made of ordinary conductive adhesive is difficult to meet the needs of the FPC industry because of its low electrical conductivity, poor continuous continuity, and poor shielding performance.

Summary of the Invention

The technical problem to be solved by the present invention is to provide a FPC electromagnetic shielding film using a polyimide film as an insulating layer and a preparation method thereof, which have better weather resistance, flexibility, bending resistance, product flatness and shielding. effect.

In order to solve the above technical problems, the present invention provides a FPC electromagnetic shielding film using a polyimide film as an insulating layer. The FPC electromagnetic shielding film includes a PI insulating layer, a reflective shielding coating coated on the PI insulating layer, and a reflective coating. An absorptive shielding coating on the shielding coating; the absorptive electromagnetic shielding coating is provided with a release protective film layer;

The PI insulating layer is a highly flexible black polyimide film formed by coating a polyimide precursor on a carrier film without direct orientation, directly casting and curing, and the film thickness is 3-9 μm; The flexibility of the PI insulating layer satisfies the glass transition temperature below 350 ° C, the elongation at break greater than 25%, and the tensile strength less than 110MPa; the polyimide precursor is a pigment added in polyimide acid in parts by mass 2 to 15 parts of carbon black, 1 to 10 parts of titanium dioxide, and 1 to 10 parts of silicon oxide;

The thickness of the reflective shielding coating is 5-10 μm. The coating of the reflective shielding coating includes a reflective layer matrix resin and a metal filler, and a weight ratio of the reflective layer matrix resin to the metal filler is 1: 1.5. ～ 1: 5, the base resin of the reflection layer is acrylic type, polyurethane type or rubber type, and the metal filler is sheet-shaped silver-clad glass, sheet-shaped silver-clad copper powder, leaf-shaped silver-clad copper powder, and dendritic silver-clad One or more of copper powders, the thickness of the metal filler in the thickness direction is 1 to 2 μm, the plane size is 3 to 9 μm, and the metal filler has 3 to 5 branches;

The thickness of the absorptive shielding coating is 2 to 5 μm. The absorptive shielding coating includes 10 to 50 parts of the matrix resin of the absorptive layer, and 10 to 30 parts of one or more of polypyrrole, polyaniline, and polythiophene. 20 to 80 parts of one or several kinds of acetylene carbon black, silicon carbide, and ferrite are mixed, and the base layer resin of the absorption layer is acrylic type, polyurethane type, or rubber type.

As a preferred mode, the formula of the polyimide acid is as follows. One or more of 4,4'-diaminodiphenyl ether, diaminobenzophenone, and hexamethylene diamine are added to dimethylformamide or After dissolving in dimethylacetamide or N-methylpyrrolidone solvent, it is cooled to -10 ° C to 5 ° C, and 4,4-biphenyl ether dianhydride, pyromellitic dianhydride, and biphenyl tetracarboxylic acid are added in an equimolar ratio. Formic acid dianhydride, 3,3 '-(m-phenylene) diether dianhydride, 3,3', 4,4 '--- benzophenone tetraacid dianhydride, and stirred to obtain polyimide acid, said The molecular weight of the polyamic acid is more than 200,000, and the solid content is less than 20%.

As a preferred mode, the reflective layer matrix resin of the reflective shielding coating is an acrylic matrix resin, and the formula is as follows:

(1) Take 7 to 15 parts of acrylic acid, 35 to 50 parts of acrylonitrile, 20 to 30 parts of butyl acrylate, and 20 to 30 parts of hydroxyethyl acrylate by weight, and react the above raw materials at 60 to 80 ° C for 10 to 20 hours. Acrylic resin III was obtained through emulsion polymerization; acrylic resin III was obtained with a molecular weight of 50,000 to 70,000;

(2) Take 50 to 70 parts of the above acrylic resin III, 10 to 30 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin by weight, and dicyandiamide 5 to 10 parts, and 5 to 10 parts of diaminodiphenyl sulfone, uniformly stirred to obtain an acrylic reflective layer matrix resin.

As a preferred mode, the reflection-layer matrix resin of the reflection-type shielding coating is a polyurethane-type matrix resin, and the formula is as follows:

(1) Take a polyester polyol with a molecular weight of 4000 to 6000, and one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and the molar ratio of functional groups is 1.3 to 1.5: 1. , Prepolymerization, prepolymerization, adding an organic tin catalyst, and reacting at 50 to 70 ° C. for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer.

(2) Take 60 to 80 parts of the above-mentioned hydroxyl-terminated prepolymer, 1 to 10 parts of hexamethylene diisocyanate trimer or isophorone diisocyanate trimer by weight, bisphenol A epoxy resin, bis 10 to 20 parts of one or more of a phenol F type epoxy resin and a phenolic epoxy resin, and 10 to 20 parts of diaminodiphenyl sulfone, uniformly stirred to obtain a polyurethane-type reflective layer matrix resin.

As a preferred mode, the reflective layer matrix resin of the reflective shielding coating is a rubber-type reflective layer matrix resin, and the formula is as follows:

Take 30 to 60 parts of carboxyl or hydroxybutyronitrile rubber by weight, 30 to 50 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and dicyandiamide 5 ～ 10 parts, diaminodiphenyl sulfone 10-20 parts, stir well to prepare a rubber-type reflective layer matrix resin.

As a preferred mode, the matrix resin of the absorption layer of the absorption-type shielding coating is an acrylic resin, and the formula is as follows:

(1) Take 5 to 10 parts of acrylic acid, 30 to 60 parts of acrylonitrile, 20 to 40 parts of hydroxyethyl acrylate, and 10 to 20 parts of n-butyl methacrylate, and add 0.3% to 1.2% persulfate by weight percentage to initiate Agent at 60 to 80 ° C. for 10 to 20 hours, and the above raw materials are subjected to emulsion polymerization to obtain acrylic resin IV;

(2) Take 60 to 80 parts of the acrylic resin IV, 10 to 30 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin by weight. 5 to 10 parts of phenyl sulfone were stirred uniformly to obtain an acrylic absorbent layer base resin.

As a preferred mode, the matrix resin of the absorption layer of the absorption-type shielding coating layer is a polyurethane-type resin, and the formula is as follows:

(1) Take a polyester polyol with a molecular weight of 4000 to 6000, and one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and the functional group molar ratio of 1.1 to 1.2: 1 , Prepolymerization, adding an organotin catalyst, and reacting at 50 to 70 ° C for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer;

(2) Take 60 to 80 parts of the above-mentioned hydroxyl-terminated prepolymer, 1 to 10 parts of hexamethylene diisocyanate trimer or isophorone diisocyanate trimer by weight, bisphenol A epoxy resin, bis 10 to 20 parts of one or more of phenol F type epoxy resin and phenolic epoxy resin, and 5 to 10 parts of diaminodiphenyl sulfone, and uniformly stirred to obtain a polyurethane-type absorption layer matrix resin.

As a preferred mode, the matrix resin of the absorption layer of the absorption-type shielding coating layer is a rubber-type resin, and the formula is as follows:

Take 30 to 60 parts of carboxyl or hydroxybutyronitrile rubber by weight, 30 to 50 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and dicyandiamide 5 ～ 10 parts, diaminodiphenyl sulfone 10-20 parts, stir well to prepare a rubber-type absorption layer matrix resin.

The invention provides a method for preparing an FPC electromagnetic shielding film using a polyimide film as an insulating layer, which includes the following steps: the first step is to prepare a coating; A1, a black polyimide precursor; A2, a reflective electromagnetic shield Coating coating; A3, coating of absorbing electromagnetic shielding coating;

The second step, coating

A4. Apply the prepared black polyimide precursor on the PI coating machine, cast directly without orientation, and dry and cure in the oven to form a highly flexible black polyimide film, that is, the PI insulating layer. Film thickness is 3 ～ 9μm; oven temperature is 60 ～ 120 ℃; linear speed is 5 ～ 30m / min;

A5. Apply the prepared reflective electromagnetic shielding coating on the PI insulation layer and dry and solidify in the oven to form a reflective electromagnetic shielding coating with a thickness of 5-10 μm; the oven temperature is 60-120 ° C; the line speed is 5 ～ 30m / min;

A6. Apply the prepared absorbing electromagnetic shielding coating on the reflective electromagnetic shielding coating and dry it in an oven to form an absorbing electromagnetic shielding coating. The thickness is 2 to 5 μm and the oven temperature is 60 to 120. ℃; linear speed is 5 ～ 30m / min;

A7. Thermally paste a release protective film layer on the absorption electromagnetic shielding coating;

A8. Rewind.

The invention relates to an FPC electromagnetic shielding film using a polyimide film as an insulating layer and a preparation method thereof. Compared with the existing design, the invention has the following advantages: (1) The invention adopts a thickness of 3 to 9 μm and a glass transition temperature. Polyimide (Tg) below 350 ° C, elongation at break greater than 25%, and tensile strength less than 110 MPa as the insulating layer, which meets the requirements of FPC electromagnetic shielding film, improves the weather resistance of the product, and improves the service life.

(2) Apply a reflective shielding coating on the insulating layer to improve the electromagnetic wave shielding effect. Among them, the metal filler in the reflective shielding coating is a sheet-like silver-clad glass or silver-coated copper powder, a leaf-like or dendritic silver-coated copper powder, and mixed with a resin to make a reflective-type shielding coating, sheet-like or leaf-like or branch-like. The conductive fillers are overlapped with each other to achieve long-distance isotropic continuous conductive performance. The thickness of the conductive filler is 1 to 2 μm and the plane size is 3 to 9 μm. Furthermore, each leaf-like silver-clad copper There are 3 to 5 forks on the powder, which is more conducive to the overlap between each other. After the metal filler is activated, the electrical conductivity can be greatly reduced and improved.

(3) Apply an absorbing shielding coating on the reflective shielding coating, and add absorbing materials such as polyaniline, polypyrrole, polythiophene, acetylene black, silicon carbide, iron into the absorption shielding coating. One or more of the oxygen bodies can absorb residual electromagnetic waves.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal sectional view of Embodiment 1 of the present invention.

The reference signs are as follows:

1-PI insulation layer, 2-reflective shielding coating, 3-absorptive shielding coating, 4-release protective film layer.

detailed description

Referring to FIG. 1, the FPC electromagnetic shielding film using a polyimide film as an insulating layer of the present invention includes a PI insulating layer 1, a reflective shielding coating 2 coated on the PI insulating layer 1, and a reflective shielding coating coated on the PI insulating layer 1. An absorption-type shielding coating 3 on 2; the absorption-type electromagnetic shielding coating 3 is provided with a release protective film layer 4.

The PI insulating layer 1 is a highly flexible black polyimide film formed by coating a polyimide precursor on a carrier film without orientation, and directly casting and curing. The glass transition temperature of the polyimide is (Tg) is lower than 350 ° C, the elongation at break is greater than 25%, the tensile strength is less than 110 MPa, and the film thickness is 3 to 9 μm; the polyimide precursor is added with pigment by mass parts in polyimide acid 2 to 15 parts of carbon black, 1 to 10 parts of titanium dioxide, and 1 to 10 parts of silicon oxide;

The formula of the polyimide acid is as follows: one or more of 4,4'-diaminodiphenyl ether (ODA), diaminobenzophenone (ABP), and hexamethylene diamine (HDA) Add dimethylformamide (DMF) or dimethylacetamide (DMAC) or N-methylpyrrolidone (NMP) solvent. After dissolving, cool to -10 ℃ ～ 5 ℃, add equimolar ratio 4,4-biphenyl ether dianhydride (ODPA for short), pyromellitic dianhydride (PMDA), biphenyl tetracarboxylic dianhydride (BPDA), 3,3 '-(m-phenylene) diether dianhydride ( Abbreviated as RsDPA), 3,3 ', 4,4' --- benzophenonetetraacid dianhydride (BTDA), stirred, and through the synthesis reaction of polyamic acid, polyimide acid was obtained. The molecular weight of the polyamic acid is more than 200,000, and the solid content is less than 20%.

The reflective electromagnetic shielding coating 2 is a film layer formed by mixing a reflective matrix resin and a metal filler, and has a thickness of 5 to 10 μm. The reflection type matrix resin is an acrylic type, a polyurethane type, or a rubber type, and the metal filler is a sheet-shaped silver-clad glass or a sheet-shaped silver-coated copper powder or a leaf-shaped silver-coated copper powder or a dendritic silver-coated copper powder. The size of the metal filler in the thickness direction is 1 to 2 μm, the plane length is 3 to 9 μm, and the leaf-like metal filler has 3 to 5 branches; the metal fillers overlap each other to achieve continuous conduction and achieve electromagnetic wave shielding functions.

The absorptive electromagnetic shielding coating 3 is a film layer formed by mixing an absorptive matrix substrate resin and a absorbing filler, and the thickness of the absorptive electromagnetic shielding coating 3 is 2 to 5 μm. Wherein, the base layer resin of the absorption layer is acrylic type, polyurethane type or rubber type, and the wave-absorbing filler is one or more of polypyrrole, polyaniline, polythiophene, acetylene black, silicon carbide, and ferrite. filler.

The release protective film layer 4 is one of a PET release film, a PP release film, a PBT release film, and a release paper. The thickness of the release protective film is 25 to 100 μm, and preferably 50 μm.

The present invention is specifically described below in combination with specific embodiments.

Example 1

The manufacturing process of the FPC electromagnetic shielding film using the polyimide film as the insulating layer of the present invention is as follows.

In the first step, a black polyimide precursor, a reflective electromagnetic shielding coating, and an absorptive electromagnetic shielding coating can be prepared in the following order, but the scope of protection is not limited to the following A1, A2, A3 Order.

A1. Preparing a black polyimide precursor;

(1) 4,4'-diaminodiphenyl ether (ODA for short) is added to dimethylformamide (DMF for short) to reduce the final total solid content to less than 20%. After dissolving, cool to -10 ° C ～ At 5 ° C, add an equivalent molar ratio of 4,4-biphenyl ether dianhydride (ODPA), pyromellitic dianhydride (PMDA), biphenyltetracarboxylic dianhydride (BPDA), 3,3 '-(between Phenyl) diether dianhydride (abbreviated as RsDPA), 3,3 ', 4,4' --- benzophenone tetraacid dianhydride (abbreviated as BTDA), stirred, and synthesized by polyamic acid to obtain polyimide acid. The molecular weight of the polyamic acid is more than 200,000, and the solid content is less than 20%.

Add 8 parts of pigment carbon black, 5 parts of titanium dioxide, and 5 parts of silicon oxide into the polyimide acid by mass to prepare a black polyimide precursor;

A2. Preparation of reflective shielding coating paint;

(1) Take 11 parts of acrylic acid, 43 parts of acrylonitrile, 25 parts of butyl acrylate, 25 parts of hydroxyethyl acrylate, and polymerize the above raw materials through emulsion (or solution polymerization, bulk polymerization) to obtain acrylic resin III. Persulfate is 0.3% to 1.2%, reacted at 60 to 80 ° C for 10 to 20 hours, and the molecular weight of acrylic resin III is 50,000 to 70,000.

(2) Take 60 parts of the above-mentioned acrylic resin III, 20 parts of bisphenol A type epoxy resin, 7 parts of dicyandiamide, 7 parts of diamino diphenyl sulfone, and stir uniformly to obtain an acrylic reflection layer base resin;

(3) Take sheet-shaped silver-clad glass (plate glass, S2015), thickness direction is 1 to 2 microns, plane size is 3 to 9 microns, each piece of conductive powder has 3 to 5 branches, and is activated by ultrasonic activation by an activator for 24 hours to obtain activation. Shielding paste, conductive powder activator is silane coupling agent or titanate coupling agent.

(4) Taking the acrylic reflective layer base resin and the activated shielding paste in a ratio of 1: 1 to obtain a coating of a reflective shielding coating.

A3. Preparation of absorptive shielding coating paint;

(1) Take 7 parts of acrylic acid, 45 parts of acrylonitrile, 30 parts of hydroxyethyl acrylate, 15 parts of n-butyl methacrylate, add 0.3% to 1.2% persulfate by weight percentage, and react at 60 to 80 ° C for 10 -20 hours, the above raw materials are prepared by emulsion polymerization to obtain acrylic resin IV, and the molecular weight of acrylic resin IV is 50,000 to 70,000.

(2) Take 70 parts of the above-mentioned acrylic resin IV, 20 parts of bisphenol A-type epoxy resin, and 10 parts of diaminodiphenylsulfone, and stir uniformly to obtain an acrylic-type absorbent layer matrix resin.

(3) Take 30 parts of the above acrylic-type absorption layer base resin, 20 parts of polypyrrole, and 50 parts of a mixture of acetylene carbon black and ferrite by weight to prepare an acrylic electromagnetic wave absorption layer coating.

The shielding effect of this embodiment is shown in Table 1.

The second step, coating

A4. The prepared black polyimide precursor is coated on a PI coater, directly cast without orientation, and cured and dried (ie, imidized) in an oven to form a highly flexible black polyimide. Film, that is, PI insulation layer, film thickness is 3 ～ 9μm; oven temperature is 60 ～ 120 ℃; linear speed is 5 ～ 30m / min;

A7. Thermally paste a release protective film layer on the absorption electromagnetic shielding coating (4);

A8. Rewind.

The shielding effect of the FPC electromagnetic shielding film using a polyimide film as an insulating layer in this embodiment is shown in Table 1.

Example 2

The manufacturing process of the FPC electromagnetic shielding film using the polyimide film as the insulating layer in this embodiment is basically the same as that in Example 1, except that the components and proportions of the reflective shielding coating coatings in A2 and A3 are:

The proportions of the raw materials for the acrylic resin III obtained in A2 are different. The addition amounts of acrylic acid, acrylonitrile, butyl acrylate, and hydroxyethyl acrylate are 7, 35, 20, and 20 parts, respectively. The ratio of raw materials is different. The bisphenol F-type epoxy resin replaces the bisphenol A-type epoxy resin. The addition amounts of acrylic resin III, bisphenol F-type epoxy resin, dicyandiamide, and diaminodiphenyl sulfone are 50 and 10, respectively. , 5, 5 servings.

Take flake silver-coated copper powder (Mitsui metal 1100YP, ball mill, use after 400 mesh sieving; or Fukuda Metal, 10% Agcoto Cu-HWQ 5μm, use directly), activate the ultrasonic shielding agent for 24 hours to obtain an activated shielding slurry .

The acrylic reflective layer base resin and the activated shielding paste are mixed in a ratio of 1: 5 to obtain a coating of a reflective shielding coating.

The proportions of the raw materials for obtaining the acrylic resin IV in A3 are different. The addition amounts of acrylic acid, acrylonitrile, hydroxyethyl acrylate, and n-butyl methacrylate are 5, 30, 20, and 10 parts, respectively. Acrylic electromagnetic wave absorption is obtained. The raw material ratio of the layer resin is different. The bisphenol F-type epoxy resin replaces the bisphenol A-type epoxy resin. The addition amounts of acrylic resin IV, bisphenol F-type epoxy resin, and diaminodiphenylsulfone are 60, 10, 5 servings.

Example 3

The manufacturing process of the novel composite electromagnetic shielding film for FPC in this embodiment is basically the same as that in Embodiment 1, except that the group distribution ratio of the coating materials in A2 and A3 is:

The proportions of the raw materials for the acrylic resin III obtained in A2 are different. The addition amounts of acrylic acid, acrylonitrile, butyl acrylate, and hydroxyethyl acrylate are 15, 50, 30, and 30 parts, respectively. The proportion of raw materials is different. The phenolic epoxy resin replaces the bisphenol A type epoxy resin. The addition amounts of acrylic resin III, phenolic epoxy resin, dicyandiamide, and diaminodiphenyl sulfone are 70, 30, 10, and 10 parts, respectively.

Take a sheet-shaped silver-clad copper powder with a thickness of 1 to 2 μm and a plane size of 3 to 9 μm (Mitsui Metal 1100YP, ball mill, used after sieving at 400 mesh; or Fukuda Metal, 10% Agcoto Cu-HWQ 5 μm, used directly), after The activator was ultrasonically activated for 24 hours to obtain an activated shielding slurry.

Take the acrylic reflective layer base resin and the activated shielding paste in a ratio of 1.5: 1 to mix uniformly to obtain a coating of a reflective electromagnetic shielding coating.

The proportions of the raw materials for obtaining the acrylic resin IV in A3 are different. The addition amounts of acrylic acid, acrylonitrile, hydroxyethyl acrylate, and n-butyl methacrylate are 10, 60, 40, and 20 parts; acrylic electromagnetic wave absorption is obtained. The raw material ratio of the layer resin is different. The phenolic epoxy resin replaces the bisphenol A type epoxy resin. The addition amounts of acrylic resin IV, phenolic epoxy resin, and diaminodiphenyl sulfone are 80, 30, and 15 parts, respectively.

Example 4

The manufacturing process of the novel composite electromagnetic shielding film for FPC of the present invention is as follows.

A1. Preparing a black polyimide precursor;

(1) Diaminobenzophenone (ABP for short) is added to dimethylacetamide (DMAC) solvent. After dissolving, it is cooled to -10 ° C to 5 ° C, and 4,4-diphenyl ether dianhydride is added in an equimolar ratio. (Abbreviated as ODPA), pyromellitic dianhydride (abbreviated as PMDA), biphenyltetracarboxylic dianhydride (abbreviated as BPDA), 3,3 '-(m-phenylene) diether dianhydride (abbreviated as RsDPA), 3,3', 4,4'-benzophenonetetraacid dianhydride (BTDA for short), stirred, and through the synthesis reaction of polyamic acid, polyimide acid is obtained. The molecular weight of the polyamic acid is more than 200,000, and the solid content is less than 20%.

Adding 2 parts of pigment carbon black, 1 part of titanium dioxide, and 1 part of silicon oxide into the above polyimide acid by mass to prepare a black polyimide precursor;

A2. Preparation of reflective shielding coating paint;

(1) Take a polyester polyol (PEPA) and toluene diisocyanate (TDI) with a molecular weight of 4000 to 6000 and prepolymerize it with a functional group molar ratio of 1.4: 1, and add an organotin catalyst with a resin solid weight ratio of 0.5 to 1%, 50 to The reaction was performed at 70 ° C. for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer.

(2) Take 60 parts of the above-mentioned hydroxyl-terminated prepolymer, 5 parts of hexamethylene diisocyanate (HDI) trimer, 15 parts of bisphenol A type epoxy resin, and 15 parts of diaminodiphenyl sulfone, stir uniformly to prepare Obtain a polyurethane-type reflective layer matrix resin;

(3) Take flake silver-coated copper powder (Mitsui Metal 1100YP, ball mill, use after sieving at 400 mesh; or Fukuda Metal, 10% Agcoto Cu-HWQ 5μm, use directly), thickness direction 1 ~ 2 microns, plane size 3 to 9 microns, each leaf-like silver-clad copper powder has 3 to 5 branches, and an ultrasonic shielding paste is obtained after 24 hours of ultrasonic activation.

(4) Take the above-mentioned polyurethane-type reflective layer base resin and the above-mentioned activated shielding paste and mix them in a 1: 1 ratio to obtain a coating of a reflective electromagnetic shielding coating.

A3. Preparation of absorbing electromagnetic shielding coatings;

(1) Take a polyester polyol with a molecular weight of 4000 to 6000, prepolymerize with toluene diisocyanate at a functional group molar ratio of 1.15: 1, add an organic tin catalyst, and react at 50 to 70 ° C for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer. ;

(2) Take 70 parts of the above hydroxyl-terminated prepolymer, 5 parts of hexamethylene diisocyanate trimer, 15 parts of bisphenol A epoxy resin, 7 parts of diaminodiphenyl sulfone by weight, and stir to obtain Polyurethane-type absorbent base resin.

(3) Take 10 parts of the above-mentioned polyurethane-type absorption layer base resin, 10 parts of polyaniline, and 20 parts of silicon carbide by weight, and mix them to make an acrylic electromagnetic wave absorption layer coating.

The second step, coating

A8. Rewind.

Example 5

The manufacturing process of the novel composite electromagnetic shielding film for FPC in this embodiment is basically the same as that in Embodiment 4, except that the group allocation ratio of the coating materials in A2 and A3 is:

In A2, diphenylmethane diisocyanate (MDI) replaces toluene diisocyanate (TDI), and the molar ratio of polyester polyol (PEPA) to its functional groups is 1.3: 1 to prepare a hydroxyl-terminated prepolymer; bisphenol F-type epoxy The resin replaces the bisphenol A type epoxy resin, and the added amounts of the hydroxyl-terminated prepolymer, hexamethylene diisocyanate (HDI) trimer, bisphenol F type epoxy resin, and diaminodiphenyl sulfone obtained above are 60, respectively. , 1, 10, 10 to obtain a polyurethane-type reflective layer matrix resin.

A leaf-shaped silver-clad copper powder having a thickness of 1 to 2 μm and a plane size of 3 to 9 μm was taken, and the activated shielding slurry was obtained after ultrasonic activation for 24 hours.

Take the above-mentioned polyurethane-type reflective layer base resin and the above-mentioned activated shielding paste in a ratio of 1: 5 and mix uniformly to obtain a coating of a reflective electromagnetic shielding coating.

Diphenylmethane diisocyanate (MDI) in A3 replaces toluene diisocyanate (TDI), and the molar ratio of polyester polyol (PEPA) to its functional groups is 1.1: 1, and a hydroxyl-terminated prepolymer is prepared; bisphenol F-type epoxy The resin replaces the bisphenol A type epoxy resin, and the added amounts of the hydroxyl-terminated prepolymer, hexamethylene diisocyanate (HDI) trimer, bisphenol F type epoxy resin, and diaminodiphenyl sulfone obtained above are 60, respectively. , 1, 10, 5 to obtain a polyurethane-type reflective layer matrix resin. Polyaniline replaces polypyrrole, the above-mentioned polyurethane-type reflective matrix resin

Example 6

In A2, xylylene diisocyanate (XDI) replaces toluene diisocyanate (TDI), and the molar ratio of polyester polyol (PEPA) to its functional groups is 1.5: 1 to prepare a hydroxyl-terminated prepolymer; phenolic epoxy resin replaces Bisphenol A epoxy resin, isophorone diisocyanate (IPDI) trimer instead of hexamethylene diisocyanate (HDI) trimer, hydroxyl-terminated prepolymer obtained above, phenolic epoxy resin, isophor Ketone diisocyanate (IPDI) and diaminodiphenyl sulfone were added in amounts of 80, 10, 20, and 20, respectively, to obtain a polyurethane-type reflective layer matrix resin.

A leaf-shaped silver-clad copper powder having a thickness of 1 to 2 μm and a plane size of 3 to 9 μm was taken, and activated with ultrasonic waves for 24 hours to obtain an activated shielding paste.

Take the above-mentioned polyurethane-type reflective layer base resin and the above-mentioned activated shielding paste in a 1.5: 5 ratio and mix uniformly to obtain a coating of a reflective electromagnetic shielding coating.

In A3, xylylene diisocyanate (XDI) replaces toluene diisocyanate (TDI), and the molar ratio of polyester polyol (PEPA) to its functional groups is 1.3: 1, and a hydroxyl-terminated prepolymer is prepared; phenolic epoxy resin replaces Bisphenol A epoxy resin, isophorone diisocyanate (IPDI) trimer instead of hexamethylene diisocyanate (HDI) trimer, the hydroxyl-terminated prepolymer obtained above, isophorone diisocyanate (IPDI) ), Phenolic epoxy resin, and diaminodiphenylsulfone were added in amounts of 80, 10, 20, and 10, respectively, to obtain a polyurethane-type reflective layer matrix resin.

Example 7

The manufacturing process of the novel composite electromagnetic shielding film for FPC in this embodiment is basically the same as that in Example 1, except that the hexamethylene diamine (abbreviated as HDA) in the polyimide prepared by A1 replaces 4,4'-diamino Diphenyl ether (abbreviated as ODA), N-methylpyrrolidone (abbreviated as NMP) solvent instead of dimethylformamide (abbreviated as DMF), 15 parts of pigment carbon black and 10 parts of titanium dioxide were added to the above polyimide acid by mass. 10 parts of silicon oxide were mixed to obtain a black polyimide precursor; the acrylic-type reflective layer base resin in the reflective electromagnetic shielding coating 4 was replaced with a rubber-type reflective layer base resin, and carboxyl or hydroxybutyronitrile rubber 30 to 60 30-50 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy multifunctional epoxy resin, 5-10 parts of dicyandiamide, and diaminodiamine 10 to 20 parts of phenylsulfone were stirred uniformly to obtain a rubber-type reflective layer base resin. Preferably, 45 parts of carboxyl or hydroxybutyronitrile rubber, 40 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy polyfunctional epoxy resin, dicyandiamide 7 parts and 15 parts of diaminodiphenyl sulfone. The base resin of the absorptive electromagnetic shielding coating is a rubber type. Take 30 to 60 parts of carboxyl or hydroxybutyronitrile rubber by weight, bisphenol A epoxy resin, bisphenol F epoxy resin, phenolic epoxy polyfunctional ring. One or several of oxygen resins, 30 to 50 parts, dicyandiamide 5 to 10 parts, and diamino diphenyl sulfone 10 to 20 parts, stir well to prepare a rubber-type absorption layer base resin. Preferably, 45 parts of carboxyl or hydroxybutyronitrile rubber, 40 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy polyfunctional epoxy resin are taken by weight, 7 parts of dicyandiamide and 15 parts of diaminodiphenyl sulfone were made into a rubber-type absorption layer base resin; 50 parts of the above rubber-type absorption layer base resin, 30 parts of polythiophene, and 80 parts of ferrite were mixed by weight to make a rubber Type electromagnetic wave absorbing layer coating.

The performance of each layer of the FPC electromagnetic shielding film using a polyimide film as an insulating layer in each embodiment of the present invention is shown in Table 1.

Table 1 Performance test results of each film layer

Claims

A FPC electromagnetic shielding film using a polyimide film as an insulating layer, comprising: a PI insulating layer (1); a reflective shielding coating (2) coated on the PI insulating layer (1); An absorptive shielding coating (3) disposed on a reflective shielding coating (2); the absorptive electromagnetic shielding coating (3) is provided with a release protective film layer (4);

The PI insulating layer (1) is a highly flexible black polyimide film formed by applying a polyimide precursor on a carrier film without direct orientation, directly casting and curing, and the film thickness is 3-9 μm. The flexibility of the PI insulating layer (1) satisfies a glass transition temperature below 350 ° C, an elongation at break of more than 25%, and a tensile strength of less than 110 MPa; the polyimide precursor is made of polyimide acid 2 to 15 parts of pigment carbon black, 1 to 10 parts of titanium dioxide, and 1 to 10 parts of silicon oxide are added by mass parts;

The thickness of the reflective shielding coating (2) is 5-10 μm. The coating of the reflective shielding coating (2) includes a reflective layer base resin and a metal filler. The weight ratio is 1: 1.5 to 1: 5, the base resin of the reflection layer is acrylic type, polyurethane type, or rubber type, and the metal filler is sheet-shaped silver-clad glass, sheet-shaped silver-clad copper powder, and leaf-shaped silver-clad copper. One or more of powder, dendritic silver-clad copper powder, the thickness of the metal filler in the thickness direction is 1 to 2 μm, the plane size is 3 to 9 μm, and the metal filler has 3 to 5 branches;

The thickness of the absorptive shielding coating (3) is 2 to 5 μm, and the absorptive shielding coating (3) includes 10 to 50 parts of the base resin of the absorptive layer, one of polypyrrole, polyaniline, and polythiophene, or Several 10 to 30 parts, one or several 20 to 80 parts of acetylene carbon black, silicon carbide, and ferrite are mixed, and the absorption layer matrix resin is acrylic type, polyurethane type, or rubber type.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 1, wherein the formula of the polyimide acid is as follows: 4,4'-diaminodiphenyl ether One or more of diaminobenzophenone and hexamethylene diamine are added to a dimethylformamide or dimethylacetamide or N-methylpyrrolidone solvent. After dissolving, cool to -10 ° C to 5 ° C. Add 4,4-biphenyl ether dianhydride, pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, 3,3 '-(m-phenylene) diether dianhydride, 3,3' in equal molar ratios. 4,4'-benzophenonetetraacid dianhydride, and stirred to obtain polyimide acid, the molecular weight of the polyamic acid is more than 200,000, and the solid content is less than 20%.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the reflective layer base resin of the reflective shielding coating (2) is an acrylic base resin, and the formula as follows:

(1) Take 7 to 15 parts of acrylic acid, 35 to 50 parts of acrylonitrile, 20 to 30 parts of butyl acrylate, and 20 to 30 parts of hydroxyethyl acrylate by weight, and react the above raw materials at 60 to 80 ° C for 10 to 20 hours. Acrylic resin III was obtained through emulsion polymerization; acrylic resin III was obtained with a molecular weight of 50,000 to 70,000;

(2) Take 50 to 70 parts of the above acrylic resin III, 10 to 30 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin by weight, and dicyandiamide 5 to 10 parts, and 5 to 10 parts of diaminodiphenyl sulfone, uniformly stirred to obtain an acrylic reflective layer matrix resin.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the reflective layer matrix resin of the reflective shielding coating (2) is a polyurethane-type matrix resin, and has a formula as follows:

(1) Take a polyester polyol with a molecular weight of 4000 to 6000, and one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and the molar ratio of functional groups is 1.3 to 1.5: 1. , Prepolymerization, adding an organotin catalyst, and reacting at 50 to 70 ° C. for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer.

(2) Take 60 to 80 parts of the above-mentioned hydroxyl-terminated prepolymer, 1 to 10 parts of hexamethylene diisocyanate trimer or isophorone diisocyanate trimer by weight, bisphenol A epoxy resin, bis 10 to 20 parts of one or more of a phenol F type epoxy resin and a phenolic epoxy resin, and 10 to 20 parts of diaminodiphenyl sulfone, uniformly stirred to obtain a polyurethane-type reflective layer matrix resin.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the reflective layer base resin of the reflective shielding coating (2) is a rubber-type reflective layer base resin The formula is as follows:

Take 30 to 60 parts of carboxyl or hydroxybutyronitrile rubber by weight, 30 to 50 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and dicyandiamide 5 ～ 10 parts, diaminodiphenyl sulfone 10-20 parts, stir well to prepare a rubber-type reflective layer matrix resin.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the absorption layer base resin of the absorption-type shielding coating (3) is an acrylic resin, and the formula is as follows :

(1) Take 5 to 10 parts of acrylic acid, 30 to 60 parts of acrylonitrile, 20 to 40 parts of hydroxyethyl acrylate, and 10 to 20 parts of n-butyl methacrylate, and add 0.3% to 1.2% persulfate by weight percentage to initiate Agent at 60 to 80 ° C. for 10 to 20 hours, and the above raw materials are subjected to emulsion polymerization to obtain acrylic resin IV;

(2) Take 60 to 80 parts of the acrylic resin IV, 10 to 30 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin by weight. 5 to 10 parts of phenyl sulfone were stirred uniformly to obtain an acrylic absorbent layer base resin.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the absorption layer base resin of the absorption-type shielding coating (3) is a polyurethane-type resin, and the formula is as follows :

(1) Take a polyester polyol with a molecular weight of 4000 to 6000, and one or more of toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and the functional group molar ratio of 1.1 to 1.2: 1 , Prepolymerization, adding an organotin catalyst, and reacting at 50 to 70 ° C for 8 to 12 hours to obtain a hydroxyl-terminated prepolymer;

(2) Take 60 to 80 parts of the above-mentioned hydroxyl-terminated prepolymer, 1 to 10 parts of hexamethylene diisocyanate trimer or isophorone diisocyanate trimer by weight, bisphenol A epoxy resin, bis 10 to 20 parts of one or more of phenol F type epoxy resin and phenolic epoxy resin, and 5 to 10 parts of diaminodiphenyl sulfone, and uniformly stirred to obtain a polyurethane-type absorption layer matrix resin.
The FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 2, characterized in that the base resin of the absorption layer of the absorption-type shielding coating (3) is a rubber-type resin, and the formula is as follows :

Take 30 to 60 parts of carboxyl or hydroxybutyronitrile rubber by weight, 30 to 50 parts of one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and dicyandiamide 5 ～ 10 parts, diaminodiphenyl sulfone 10-20 parts, stir well to prepare a rubber-type absorption layer matrix resin.
The method for preparing an FPC electromagnetic shielding film using a polyimide film as an insulating layer according to claim 1, comprising the following steps: first step, preparing a coating; A1, before black polyimide Body; A2, coating of reflective electromagnetic shielding coating; A3, coating of absorptive electromagnetic shielding coating;

The second step, coating

A4. Apply the prepared black polyimide precursor on the PI coating machine, cast directly without orientation, and dry and cure in the oven to form a highly flexible black polyimide film, that is, the PI insulating layer. Film thickness is 3 ～ 9μm; oven temperature is 60 ～ 120 ℃; linear speed is 5 ～ 30m / min;

A5. Apply the prepared reflective electromagnetic shielding coating on the PI insulation layer and dry and solidify in the oven to form a reflective electromagnetic shielding coating with a thickness of 5-10 μm; the oven temperature is 60-120 ° C; the line speed is 5 ～ 30m / min;

A6. Apply the prepared absorbing electromagnetic shielding coating on the reflective electromagnetic shielding coating and dry it in an oven to form an absorbing electromagnetic shielding coating. The thickness is 2 to 5 μm and the oven temperature is 60 to 120. ℃; linear speed is 5 ～ 30m / min;

A7. Thermally paste a release protective film layer on the absorption electromagnetic shielding coating (4);

A8. Rewind.