Protective coating for FPC (flexible printed circuit) ultrathin magnetron sputtering shielding layer as well as preparation method and application of protective coating

Abstract

The invention discloses a protective coating for an ultra-thin magnetron sputtering shielding layer of an FPC (Flexible Printed Circuit) as well as a preparation method and application of the protective coating. The protective coating for the ultra-thin magnetron sputtering shielding layer of the FPC comprises the following components in parts by mass: 100-200 parts of a resin mixture; 20-60 parts of a curing agent; 0 to 10 parts of an initiator; 10 to 100 parts of an acrylate monomer; 0-3 parts of a defoaming agent; 0-3 parts of a leveling agent; wherein the resin mixture is a mixture of thermocuring resin and photocuring resin; the ultraviolet irradiation time is 10-120 seconds when the protective coating is preformed; and the curing temperature is 80-200 DEG C when the protective coating is cured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a protective coating for an FPC ultrathin magnetron sputtering shielding layer, a preparation method and application thereof. BACKGROUND

[0002] With the development of wearable devices towards lightness, thinness and flexibility, the electromagnetic shielding structure of traditional flexible circuit boards faces major technical bottlenecks. At present, the industry generally adopts a three-layer composite structure of "conductive adhesive layer + metal shielding layer + protective film", wherein the conductive adhesive layer is used to bond the metal shielding layer and the substrate, the metal shielding layer is mostly made of copper foil or aluminum foil material, and the surface is covered with polyimide (PI) or polyester (PET) protective film. This scheme has the following defects: (1) the thickness of the conductive adhesive layer is usually 5-10 μm, and after adding the metal foil (about 8-12 μm), the overall thickness is significantly increased; (2) the metal foil material is limited by ductility and processing technology, and it is difficult to realize a reliable shielding layer below 5 μm; (3) the existing protective film is not optimized for the interface characteristics of the ultrathin shielding layer, resulting in a decrease in reliability in the thinning process.

[0003] In recent years, magnetron sputtering technology has provided a new path for shielding layer thinning. A continuous metal shielding layer of 1-3 μm can be directly formed by physical vapor deposition, and the total thickness of the shielding system can be reduced by more than 60% after the conductive adhesive layer is removed. However, this technology puts new requirements on the protective film: on the one hand, the protective layer needs to withstand acid and alkali corrosion in etching and electroplating processes; on the other hand, the interface of the ultrathin metal layer is highly active, and is prone to cracking failure due to peeling of the protective film during dynamic bending (curvature radius < 1 mm). The existing protective material has three major technical shortcomings: 1) it is prone to thermal decomposition at high temperatures, leading to oxidation of the shielding layer; 2) it has insufficient interfacial adhesion with the magnetron sputtered metal layer; 3) it cracks under stress after repeated bending, and cannot meet the life requirements of wearable devices of more than 100,000 bends.

[0004] Therefore, the development of a protective film with high temperature stability, strong interfacial adhesion and excellent mechanical durability has become a key bottleneck for the industrialization of ultrathin FPC shielding technology. There is an urgent need for an innovative protective film solution to match the special working condition requirements of magnetron sputtering shielding layers.

[0005] The above content is only used to assist in understanding the technical solutions of the present application and does not represent an acknowledgement of the above content as prior art. SUMMARY

[0006] The main purpose of the present application is to provide a protective coating for an FPC ultrathin magnetron sputtering shielding layer, a preparation method and application thereof, which aims to solve the above problems.

[0007] In order to achieve the above object, the present application provides a protective coating for FPC ultrathin magnetron sputtering shielding layer, comprising, in terms of mass fraction:

[0008] resin mixture: 100-200 parts;

[0009] curing agent: 20-60 parts;

[0010] initiator: 0-10 parts;

[0011] acrylate monomer: 10-100 parts;

[0012] defoamer: 0-3 parts;

[0013] leveling agent: 0-3 parts;

[0014] wherein the resin mixture is a mixture of thermosetting resin and photocuring resin; the ultraviolet light irradiation time during the preforming of the protective coating is 10-120 seconds; and the curing temperature during the curing of the protective coating is 80-200℃.

[0015] Preferably, in the protective coating for FPC ultrathin magnetron sputtering shielding layer, the resin mixture comprises one or more of epoxy resin, acrylate resin, epoxy acrylate resin, polyurethane resin.

[0016] Preferably, in the protective coating for FPC ultrathin magnetron sputtering shielding layer, the epoxy resin is at least one of bisphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, linear phenolic type epoxy resin, dicyclopentadiene type epoxy resin, aralkyl type phenolic epoxy resin, aralkyl biphenyl type phenolic epoxy resin, or naphthol type phenolic epoxy resin.

[0017] The acrylate resin is any one or more of ethoxylated bisphenol A type acrylate, tricyclodecane type acrylate, neopentyl glycol dimethyl acrylate, alkyl acrylate as a monomer acrylate resin.

[0018] The epoxy acrylate resin is bisphenol A type epoxy acrylate resin or phenolic epoxy acrylate resin.

[0019] Preferably, in the protective coating for FPC ultrathin magnetron sputtering shielding layer, the acrylate monomer is any one or more of pentaerythritol, trimethylolpropane, tripropylene glycol as the backbone of polysubstituted acrylate and methacrylate.

[0020] Preferably, in the protective coating for FPC ultrathin magnetron sputtering shielding layer, the curing agent is one or more of amine curing agent, acid anhydride curing agent, polyamide curing agent.

[0021] Preferably, in the protective coating for the FPC ultrathin magnetron sputtering shielding layer, the defoaming agent is one or more of organic silicon defoaming agent, mineral oil defoaming agent, polyether defoaming agent, alcohol defoaming agent, and composite defoaming agent.

[0022] Preferably, in the protective coating for the FPC ultrathin magnetron sputtering shielding layer, the leveling agent is one or more of polyorganosiloxane, modified polydimethylsiloxane, acrylic copolymer, fluorocarbon modified polyacrylate, and polyether modified silicone leveling agent.

[0023] Preferably, in the protective coating for the FPC ultrathin magnetron sputtering shielding layer, the initiator is one or more of benzoin, acetophenone derivative, acyl phosphine oxide, benzophenone, thioxanthone, and onium salt photoinitiator.

[0024] To achieve the above-mentioned purpose, the present application provides a preparation method of the protective coating for the FPC ultrathin magnetron sputtering shielding layer, which comprises the following steps:

[0025] Mixing the resin mixture, curing agent, initiator, acrylate monomer, defoaming agent, and leveling agent to form a wet film;

[0026] Irradiating the obtained wet film under ultraviolet light to obtain a preformed wet film, wherein the irradiation time is 10-120 seconds;

[0027] Heating and curing the preformed wet film to obtain the protective coating, wherein the curing temperature is 80-200℃.

[0028] To achieve the above-mentioned purpose, the present application provides an application of the protective coating, characterized in that the protective coating for the FPC ultrathin magnetron sputtering shielding layer or the protective coating prepared by the above-mentioned preparation method is applied to the FPC ultrathin magnetron sputtering shielding layer.

[0029] The present application has at least the following beneficial effects:

[0030] The protective coating for the FPC ultrathin magnetron sputtering shielding layer provided by the present application comprises, in terms of mass fraction: resin mixture: 100-200 parts; curing agent: 20-60 parts; initiator: 0-10 parts; acrylate monomer: 10-100 parts; defoaming agent: 0-3 parts; leveling agent: 0-3 parts; wherein the resin mixture is a mixture of thermosetting resin and photocuring resin; the ultraviolet light irradiation time during the preforming of the protective coating is 10-120 seconds; the curing temperature during the curing of the protective coating is 80-200℃, thus the provided protective coating has high temperature stability, strong interfacial bonding force, and excellent mechanical durability.

[0031] Further, the present application can provide higher bending resistance by using an acrylate monomer as a diluent. Since the resin mixture provides a strong adhesion when the protective coating is heat cured, the present application can provide a protective coating with higher toughness and bending resistance by using an acrylate monomer as a diluent when heat cured.

[0032] Further, the present application can provide a protective coating with high temperature stability, strong interfacial adhesion and excellent mechanical durability by mixing a heat-cured resin and a light-cured resin.

[0033] Further, the present application can provide a protective coating for an FPC ultra-thin magnetron sputtering shielding layer, which can effectively protect the ultra-thin magnetron sputtering layer and avoid oxidation of the shielding layer, has an ultra-thin protective layer thickness, excellent bending resistance, chemical resistance, boiling resistance, corrosion resistance, high hardness and other advantages. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A schematic diagram of the preparation method of the protective coating for the FPC ultra-thin magnetron sputtering shielding layer provided by the present application;

[0035] Figure 2 A test diagram of the present application for the protective coating when performing the crosshatch test method;

[0036] Figure 3 A test diagram of the present application for the protective coating when performing OSP treatment;

[0037] Figure 4 A test diagram of the present application for the protective coating when performing ethanol immersion test;

[0038] Figure 5 A test diagram of the present application for the protective coating when performing cold and hot impact test;

[0039] Figure 6 A test diagram of the present application for the protective coating when performing reflow soldering test and the reflow soldering number is 5 times;

[0040] Figure 7 A test diagram of the present application for the protective coating when performing reflow soldering test and the reflow soldering number is 15 times;

[0041] Figure 8 A test diagram of the present application for the protective coating when performing tin floating;

[0042] Figure 9 A test diagram of the present application for the protective coating when performing sputtering metal layer bending test;

[0043] Figure 10 The test pattern of the protective coating provided by the present application when tested in a circuit bending test.

[0044] The purposes, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0046] In the embodiments of the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that there are three cases of A alone, A and B together, and B alone. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0047] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence.

[0048] In the embodiments of the present application, the term "a plurality of" means two or more, and other quantifiers are similar.

[0049] In the present application, unless otherwise stated, the orientation words such as "upper", "lower", "top", "bottom" are generally directed to the directions shown in the drawings, or are directed to the vertical, perpendicular or gravity direction of the components themselves; similarly, for the convenience of understanding and description, "inner" and "outer" refer to the inner and outer relative to the contour of each component itself, but the above-mentioned orientation words are not used to limit the present application.

[0050] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, each embodiment of the present application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art can understand that in each embodiment of the present application, many technical details are proposed in order to make the reader better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed by the present application can be realized. The following division of each embodiment is for the convenience of description, and should not constitute any limitation on the specific implementation mode of the present application, and each embodiment can be combined with each other and quoted under the premise of not contradicting.

[0051] The application provides a protective coating for an FPC ultrathin magnetron sputtering shielding layer, which comprises, in terms of mass fraction, 100-200 parts of a resin mixture, 20-60 parts of a curing agent, 0-10 parts of an initiator, 10-100 parts of an acrylate monomer, 0-3 parts of an antifoaming agent, and 0-3 parts of a leveling agent, wherein the resin mixture is a mixture of a thermosetting resin and a photocuring resin, the ultraviolet light irradiation time during the preforming of the protective coating is 10-120 seconds, and the curing temperature during the curing of the protective coating is 80-200 DEG C.

[0052] The thickness of the ultrathin magnetron sputtering shielding layer is usually in the nanometer to micrometer range.

[0053] The resin mixture is a mixture of a thermosetting resin and a photocuring resin, and the protective coating obtained by double curing has high temperature stability, strong interfacial bonding force and excellent mechanical durability.

[0054] The resin mixture comprises one or more of an epoxy resin, an acrylate resin, an epoxy-acrylate resin, and a polyurethane resin.

[0055] The epoxy resin is at least one of a bisphenol type epoxy resin, a biphenyl type epoxy resin, a naphthalene type epoxy resin, a naphthol type epoxy resin, a linear phenolic type epoxy resin, a dicyclopentadiene type epoxy resin, an aralkyl type phenolic epoxy resin, an aralkyl biphenyl type phenolic epoxy resin, and a naphthol type phenolic epoxy resin.

[0056] The acrylate resin is an ethoxylated bisphenol A type acrylate, a tricyclodecane type acrylate, a neopentyl glycol dimethyl acrylate, or an alkyl acrylate.

[0057] The epoxy-acrylate resin is a bisphenol A type epoxy-acrylate resin or a phenolic epoxy-acrylate resin.

[0058] The curing agent is a curing agent for an epoxy resin, and in some embodiments, the curing agent is one or more of an amine type curing agent, an acid anhydride type curing agent, and a polyamide type curing agent. In other embodiments, the curing agent can be one or more of any of the amine type curing agents. In other embodiments, the curing agent can also be one or more of any of the aromatic amine type curing agents.

[0059] The initiator is used for the photopolymerization of the acrylate resin. In some embodiments, the initiator is one or more of a benzoin type, a phenylethanone derivative type, an acyl phosphine oxide type, a benzophenone type, a thioxanthone type, and an onium salt type photoinitiator. In other embodiments, the initiator can also be one or more of a phenylethanone derivative type photoinitiator and an acyl phosphine oxide type photoinitiator.

[0060] The acrylate monomer is a low viscosity multifunctional propyl acrylate monomer. In some embodiments, the acrylate monomer is any one or more of pentaerythritol, trimethylolpropane, tripropylene glycol as the backbone of a polysubstituted acrylate and methacrylate.

[0061] The present application can provide higher bending resistance by using acrylate monomer as a diluent. The present application can provide higher toughness and bending resistance of the protective coating during thermal curing by using acrylate monomer as a diluent, because the resin mixture provides a strong adhesion when the protective coating is thermally cured.

[0062] The defoaming agent is one or more of silicone defoaming agent, mineral oil defoaming agent, polyether defoaming agent, alcohol defoaming agent, and composite defoaming agent.

[0063] The leveling agent is one or more of polyorganosiloxane, modified polydimethylsiloxane, acrylic copolymer, fluorocarbon modified polyacrylate, and polyether modified silicone leveling agent.

[0064] The present application also provides a preparation method of the protective coating for the FPC ultrathin magnetron sputtering shielding layer as described above, which comprises steps S210 to S230.

[0065] In step S210, the resin mixture, curing agent, initiator, acrylate monomer, defoaming agent, and leveling agent are mixed to form a wet film. It should be noted that the resin mixture, curing agent, initiator, acrylate monomer, defoaming agent, and leveling agent are mixed in a container according to the above formula, and are preliminarily mixed by stirring, and then are mixed by a three-roll mill. In some embodiments, the temperature of the above mixing process should not exceed 10°C. The mixture formed by the resin mixture, curing agent, initiator, acrylate monomer, defoaming agent, and leveling agent should be stored in a low temperature environment of 2-8°C.

[0066] The wet film can be applied by, but not limited to, screen printing, spraying, and blade coating.

[0067] In some embodiments, the thickness of the wet film is within 15μm.

[0068] In step S220, the obtained wet film is irradiated under ultraviolet light to obtain a preformed wet film, wherein the irradiation time is 10-120 seconds. The preforming is performed by irradiating the wet film under ultraviolet light. The wavelength of the ultraviolet light is between 250nm and 420nm. Preferably, the wavelength of the ultraviolet light is between 360nm and 390nm.

[0069] The wet film is irradiated for a time period that is not too long, otherwise the bending resistance will be poor. If the irradiation time is too short, the curing time will be insufficient and the preform will not be complete. Therefore, in this embodiment, the irradiation time is 10-120 seconds. Preferably, the irradiation time is 30-60 seconds. In some other embodiments, the irradiation time can also be 40 seconds or 50 seconds.

[0070] In step S230, the preformed wet film is heated and cured to obtain the protective coating, wherein the curing temperature is 80-200℃. If the curing temperature is too low, the adhesion will be poor. If the curing temperature is too high, the protective coating obtained will be brittle and the color will be dark. Therefore, in this embodiment, the curing temperature is 80-200℃. Preferably, the curing temperature is 100-180℃. In some other embodiments, the curing temperature can also be 120℃ or 150℃.

[0071] The application also provides a protective coating for FPC ultra-thin magnetron sputtering shielding layer. The protective coating for FPC ultra-thin magnetron sputtering shielding layer is prepared by the method described above. It should be noted that the embodiments of the application for FPC ultra-thin magnetron sputtering shielding layer include the embodiments of the protective coating for FPC ultra-thin magnetron sputtering shielding layer and the embodiments of the method described above. The advantages of the protective coating for FPC ultra-thin magnetron sputtering shielding layer and the advantages of the method described above can also be applied to the application of the protective coating.

[0072] It is worth noting that the magnetron sputtering layer is usually very thin. If the protective film is a little thick, it will stretch or even crack the magnetron sputtering layer. This not only makes the protective layer have poor bending resistance, but also makes the magnetron sputtering layer crack, which greatly reduces the shielding performance. The application of the protective coating described above to the FPC ultra-thin magnetron sputtering shielding layer can ensure the bending resistance and chemical resistance of the FPC ultra-thin magnetron sputtering shielding layer.

[0073] In order to verify the effect of the protective coating provided by the application, the following examples and comparative examples are used for comparison.

[0074] Example 1

[0075] The formula of the protective coating is as follows: bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, phenylethanone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 70 parts, tripropylene glycol methyl acrylate 30 parts, silicone defoaming agent 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0076] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0077] Example 2

[0078] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 35 parts, tripropylene glycol methyl acrylate 35 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0079] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0080] Example 3

[0081] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 35 parts, tripropylene glycol methyl acrylate 35 parts.

[0082] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0083] Comparative Example 1

[0084] The protective coating formula: by weight, bisphenol type epoxy resin 100 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 70 parts, tripropylene glycol methyl acrylate 35 parts, silicone defoaming agent 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0085] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0086] Comparative Example 2

[0087] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 50 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 70 parts, tripropylene glycol methyl acrylate 35 parts, silicone defoaming agent 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0088] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160°C high temperature molding for 2.5 h

[0089] Comparative Example 3

[0090] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 15 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 70 parts, tripropylene glycol methyl acrylate 35 parts, silicone defoamer 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0091] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160°C high temperature molding for 2.5 h

[0092] Comparative Example 4

[0093] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 70 parts, tripropylene glycol methyl acrylate 35 parts, silicone defoamer 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0094] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160°C high temperature molding for 2.5 h

[0095] Comparative Example 5

[0096] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 5 parts, silicone defoamer 0.5 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0097] Application method: 350 mesh screen printing, 60 seconds of 360 nm UV light pre-curing, 160°C high temperature molding for 2.5 h.

[0098] Comparative Example 6

[0099] The protective coating formula: by weight, bisphenol type epoxy resin 150 parts, ethoxylated bisphenol A type acrylate 10 parts, amine curing agent 45 parts, acetophenone derivative initiator 2 parts, acyl phosphine oxide photoinitiator 3 parts, trimethylolpropane methyl acrylate 35 parts, tripropylene glycol methyl acrylate 35 parts, modified polydimethylsiloxane leveling agent 0.5 parts.

[0100] Application method: 350 mesh screen printing, 5 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0101] The protective coating of Comparative Example 6 has the same formulation as that of Example 2, but different application method.

[0102] Comparative Example 7

[0103] The protective coating has the following formulation: 150 parts by weight of bisphenol type epoxy resin, 10 parts by weight of ethoxylated bisphenol A type acrylate, 45 parts by weight of amine curing agent, 2 parts by weight of acetophenone derivative initiator, 3 parts by weight of acyl phosphine oxide photoinitiator, 35 parts by weight of trimethylolpropane methyl acrylate, 35 parts by weight of tripropylene glycol methyl acrylate, and 0.5 parts by weight of modified polydimethylsiloxane leveling agent.

[0104] Application method: 350 mesh screen printing, 5 seconds of 360 nm UV light pre-curing, 160 °C high temperature molding for 2.5 h.

[0105] The protective coating of Comparative Example 7 has the same formulation as that of Example 2, but different application method.

[0106] The examples and comparative examples are tested respectively, and the test methods include crosshatch test, pencil hardness test, chemical resistance test, high temperature resistance test, cold and hot impact test, constant temperature and humidity test, reflow soldering test, and bending performance test.

[0107] Crosshatch test method: After the sputtering layer is coated with an organic polymer film, 10 equally spaced straight lines are drawn on a 1 cm 2 area with a knife, and then 10*10 squares are formed by drawing lines at the perpendicular positions of the straight lines. When drawing the crosshatch, the sputtering layer should not be broken. 3M tape is applied to the crosshatch position, and the tape is tightly attached with a finger. Then, the tape is torn off with an instant force, and it is observed whether the organic film on the sputtering layer is detached or not, and whether the organic film is left on the tape or not.

[0108] Pencil hardness test method: 5 pcs of FPC prepared with the new shielding material are prepared, and pencils with hardness of 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B and 4B are prepared, and a trolley is used for testing. The pencil is inserted into the trolley at 45°, and the screw is tightened to fix the pencil. The trolley is pushed at a constant speed to make the pencil draw across the surface of the FPC, and the scratch is observed. The hardest pencil 6H is used for testing, and the softer pencils are tested in turn until the surface of the EMI is not scratched, and then the pencil hardness of the sample is determined.

[0109] Resistance to chemical test: Two pieces of FPC with new shielding material were prepared, one piece of FPC was treated with OSP for three times, and the appearance was checked and the grid test was performed; the other piece of FPC was immersed in ethanol solution for 10 min, the appearance was checked and the grid test was performed.

[0110] OSP test: chemical cleaning (28°C, sulfuric acid-hydrogen peroxide system (26Ml / L, 30s)), organic solvent pre- immersion (20-40°C, pH 8-11, 30-60s), OSP (35-40°C, pH 2.7-3.4, 30-60s)

[0111] High temperature resistance test: 288°C, 10s, three times of tin floating, no adverse hot dipping such as blistering, and grid test was performed.

[0112] Cold and hot impact test: the FPC with new shielding material was placed in a temperature chamber (high temperature 125°C / 15min), and was treated for 200 cycles, whether the sample had delamination, blistering or damage was observed, and the grid test was performed on the FPC.

[0113] Constant temperature and humidity test: the FPC with new shielding material was placed in a constant temperature and humidity chamber at 85°C / 85% RH for 168h, after the test was completed, the sample was taken out, whether the surface was contaminated, delaminated and blistered was observed, and the grid test was performed on the sample.

[0114] Reflow soldering test: the FPC with new shielding material was placed in an oven at 105°C for 24h, then the sample was placed in a constant temperature and humidity chamber at 60°C / 60% RH for 15h. The treated FPC was placed on a high temperature magnetic plate, a reflow furnace with a reflow temperature peak of 260°C was selected, and the FPC was reflowed for 5 times and 15 times respectively, whether the surface was contaminated, delaminated and blistered was observed, and the grid test was performed on the FPC.

[0115] Bending performance test: the sample was bent 180°, the bending radius was 0.6mm, and the resistance change rate was measured after the bending target.

[0116] Table 1 performance test comparison of examples and comparative examples

[0117]

[0118]

[0119] In Table 1, resistance to chemical test 1 was tested by OSP, and resistance to chemical test 1 was tested by ethanol. In Table 1, reflow soldering test 1 was reflowed for 5 times, and reflow soldering test 2 was reflowed for 15 times. In Table 1, the high temperature resistance test was the grid test after tin floating. In Table 1, the line bending test was the bending performance test when the bending was 100000 times.

[0120] From Figures 2 to 10 , and Table 1, it can be seen that the protective coating provided by the present application has high temperature stability, strong interfacial bonding force and excellent mechanical durability. Further, the formulations of Comparative Examples 6 and 7 are the same as that of Example 2, but the application methods are different. From Example 2, Comparative Example 6 and Comparative Example 7, it can be seen that the formulation and the curing conditions (ultraviolet light irradiation time, curing temperature) in the present application work together to achieve high temperature stability, strong interfacial bonding force and excellent mechanical durability. When the curing temperature is reduced and is not within the preset range of the present application, the performance of the formed film will be poor. Similarly, when the ultraviolet light irradiation time is reduced, the effect will also be poor.

[0121] Obviously, the above-described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, other different forms of changes or modifications can be made by those of ordinary skill in the art without creative labor, and all should fall within the scope of protection of the present application.

Claims

1. A protective coating for FPC ultrathin magnetron sputtering shield layer, characterized in that, According to the mass parts, comprising: Resin mixture: 100-200 parts; Curing agent: 20-60 parts; Initiator: 0-10 parts; Acrylate monomer: 10-100 parts; Defoaming agent: 0-3 parts; Leveling agent: 0-3 parts; The resin mixture is a mixture of thermosetting resin and photocuring resin; the ultraviolet light irradiation time is 10-120 seconds when the protective coating is preformed; the curing temperature is 80-200°C when the protective coating is cured.

2. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The resin mixture comprises one or more of epoxy resin, acrylate resin, epoxy acrylate resin, polyurethane resin.

3. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 2, characterized in that, The epoxy resin is at least one of bisphenol type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, naphthol type epoxy resin, linear phenolic type epoxy resin, dicyclopentadiene type epoxy resin, aralkyl type phenolic epoxy resin, aralkyl biphenyl type phenolic epoxy resin, or naphthol type phenolic epoxy resin; The acrylate resin is any one or more of ethoxylated bisphenol A type acrylate, tricyclodecane type acrylate, neopentyl glycol dimethyl acrylate, alkyl acrylate as a monomer; The epoxy acrylate resin is bisphenol A type epoxy acrylate resin or phenolic epoxy acrylate resin.

4. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The acrylate monomer is any one or more of pentaerythritol, trimethylolpropane, tripropylene glycol as the backbone of polysubstituted acrylate and methacrylate.

5. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The curing agent is one or more of amine curing agent, acid anhydride curing agent, polyamide curing agent.

6. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The defoaming agent is one or more of silicone defoaming agent, mineral oil defoaming agent, polyether defoaming agent, alcohol defoaming agent, and composite defoaming agent.

7. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The leveling agent is one or more of polyorganosiloxane, modified polydimethylsiloxane, acrylic copolymer, fluorocarbon modified polyacrylate, and polyether modified silicone leveling agent.

8. The protective coating for FPC ultrathin magnetron sputtering shield layer according to claim 1, characterized in that, The initiator is one or two of benzoin, phenylacetone derivative, acyl phosphine oxide, benzophenone, thioxanthone, and onium salt photoinitiator.

9. A method for producing a protective coating for an ultra-thin magnetron sputtering shield layer of an FPC according to any one of claims 1 to 8, characterized in that Comprising the following steps: Mixing the resin mixture, curing agent, initiator, acrylate monomer, defoaming agent, and leveling agent to form a wet film; Irradiating the obtained wet film under ultraviolet light to obtain a preformed wet film, wherein the irradiation time is 10-120 seconds; Heating and curing the preformed wet film to obtain the protective coating, wherein the curing temperature is 80-200°C.

10. Use of a protective coating, characterized in that The protective coating for FPC ultrathin magnetron sputtering shielding layer according to any one of claims 1 to 8, or the protective coating prepared by the preparation method of claim 9, is applied to the FPC ultrathin magnetron sputtering shielding layer.

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