JP7164386B2 - conductive paint - Google Patents

Description

The present invention relates to conductive coatings.

2. Description of the Related Art In recent years, electronic devices such as mobile phones and tablet terminals are equipped with a large number of electronic components for wireless communication for transmitting large amounts of data. Such electronic components for wireless communication not only tend to generate noise, but are also highly susceptible to noise, and are likely to malfunction when exposed to external noise.

On the other hand, it is required to increase the mounting density of electronic components in order to achieve both reduction in size and weight and enhancement of functionality of electronic devices. However, increasing the mounting density not only increases the number of electronic components that generate noise, but also increases the number of electronic components affected by noise.

Conventionally, as a means to solve this problem, by covering the electronic components, which are the sources of noise, with a shield layer together with the package, the generation of noise from the electronic components and the intrusion of noise are prevented. It has been known. For example, Patent Document 1 describes that an electromagnetic shielding member having a high shielding effect can be easily obtained by coating the surface of a package with a conductive or semiconductive material by spraying.

In addition, as a conductive paint that can be applied to electromagnetic wave shielding, for example, Patent Documents 2 to 5 describe a combination of a micron-sized conductive filler and a nano-sized conductive filler. By using micron-sized conductive fillers and nano-sized conductive fillers together, gaps between micron-sized conductive fillers can be filled with nano-sized conductive fillers, resulting in good shielding properties. is obtained.

Japanese Patent Application Laid-Open No. 2003-258137 JP 2014-181316 A JP-A-2005-294254 JP 2010-113912 A Japanese Patent Application Laid-Open No. 2010-118280

However, when the shield layer is formed by spray coating using a solution consisting only of metal particles and a solvent, not only is good shielding property not obtained, but there is also the problem of poor adhesion between the shield layer and the package.

In addition, when the conventional shield package is subjected to severe heating conditions such as a solder reflow process, the color of the shield layer changes, and it is difficult to obtain a desirable appearance.

The present invention has been made in view of the above, and an object of the present invention is to form a shield layer that has good shielding properties, good adhesion to the package, and is resistant to discoloration even under severe heating conditions. To provide an excellent conductive paint.

As a result of intensive studies to achieve the above object, the present inventors have found that at least a part of a According to the conductive paint in which the blending amount of the component is specified, it has good shielding properties, good adhesion to the package, and can form a shield layer that does not easily discolor even under severe heating conditions. I found The present invention has been completed based on these findings.

That is, the present invention comprises (A) a binder component containing (a) an epoxy resin, (b) 40 to 70% by mass of a rubber-modified epoxy resin, and (c) 10 to 40% by mass of an acrylic resin, and (B) metal particles , (C) a curing agent, and (D) a solvent, with respect to 100 parts by mass of the (A) binder component, the content of (B) metal particles is 500 to 2500 parts by mass, and (C) the curing agent A conductive paint is provided in an amount of 1 to 150 parts by weight.

(b) The rubber-modified epoxy resin preferably has a carbon-carbon double bond.

(D) The metal particles are preferably at least one selected from the group consisting of silver particles, silver-coated copper particles, and silver-coated copper alloy particles.

(C) The curing agent is preferably an isocyanate curing agent.

The content of solvent (D) is preferably 20 to 800 parts by weight per 100 parts by weight of binder component (A).

The conductive layer obtained by curing under heating conditions of 190° C. for 30 minutes preferably has a specific resistance value of 1.0×10 ⁻⁵ Ω·cm or less.

According to the conductive paint of the present invention, it is possible to form a shield layer that has good shielding properties, good adhesion to the package, and is resistant to discoloration even under severe heating conditions.

1 is a schematic cross-sectional view showing one embodiment of a shield package having a shield layer formed using the conductive paint of the present invention; FIG. It is a schematic cross section which shows one Embodiment of the manufacturing method of a shield package. FIG. 4 is a top plan view showing an example of a shield package before singulation; It is a schematic diagram which shows the turntable which mounted the spray coating device and sample which were used for the crosscut test. FIG. 3 is a schematic cross-sectional view of a shield package for explaining a method for evaluating uniformity of shield layer thickness;

The conductive paint of the present invention contains at least (A) a binder component, (B) metal particles, (C) a curing agent, and (D) a solvent. The conductive paint of the present invention may contain components other than the above components (A) to (D).

[(A) binder component]
(A) The binder component includes at least (a) epoxy resin, (b) rubber-modified epoxy resin, and (c) acrylic resin. (A) The binder component binds other components in the shield layer formed by curing at least one curable component after applying the conductive paint to the package, and has a role of forming the matrix of the shield layer. .

(a) The epoxy resin imparts heat resistance to the formed shield layer. (a) The epoxy resin preferably has thermosetting properties from the viewpoint of curing by heating and acting as a binder resin for the shield layer. In addition, (b) the epoxy resin preferably has an epoxy group in the molecule. In particular, it preferably has two or more epoxy groups in the molecule, and more preferably has two or more glycidyl groups in the molecule. (a) Epoxy resins may be used alone or in combination of two or more.

In this specification, (a) epoxy resin does not include (b) rubber-modified epoxy resin.

(a) The epoxy resin may be a solid epoxy resin at room temperature or a liquid epoxy resin at room temperature. An epoxy resin that is solid at room temperature is preferable from the viewpoint that it can be applied to the package surface immediately and that the thickness of the shield layer on the side and top surfaces of the package can be made uniform.

In this specification, an epoxy resin that is solid at room temperature may be referred to as a "solid epoxy resin". Epoxy resins that are liquid at room temperature may be referred to as "liquid epoxy resins". Further, in the present specification, "solid at room temperature" means a state in which no solvent is present at 25°C and fluidity is not shown. In addition, the phrase "liquid at room temperature" means that the substance exhibits fluidity at 25°C in the absence of a solvent.

Examples of the solid epoxy resin include, but are not limited to, bisphenol-type epoxy resin, spirocyclic-type epoxy resin, naphthalene-type epoxy resin, biphenyl-type epoxy resin, terpene-type epoxy resin, glycidyl ether-type epoxy resin, glycidylamine-type epoxy resin. Resins, novolac type epoxy resins, and the like.

Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetrabromobisphenol A type epoxy resin and the like.

Examples of the glycidyl ether type epoxy resin include tris(glycidyloxyphenyl)methane and tetrakis(glycidyloxyphenyl)ethane.

Examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethane.

Examples of the novolak-type epoxy resins include cresol novolac-type epoxy resins, phenol novolak-type epoxy resins, α-naphthol novolac-type epoxy resins, and brominated phenol novolak-type epoxy resins.

As the solid epoxy resin, bisphenol type epoxy resin is preferred among others, and bisphenol A type epoxy resin is more preferred.

Examples of the liquid epoxy resins include liquid glycidylamine-based epoxy resins and liquid glycidyl ether-based epoxy resins.

(a) The epoxy resin preferably has an epoxy equivalent of 150 to 280 g/eq. When the epoxy equivalent is 150 g/eq or more, defects such as cracks and warpage are less likely to occur in the formed shield layer. When the epoxy equivalent is 280 g/eq or less, the heat resistance of the shield layer is more excellent.

The content of (a) the epoxy resin in the (A) binder component is not particularly limited, but is preferably 3 to 50% by mass, more preferably 5 to 40% with respect to 100% by mass of the total amount of the (A) binder component. % by mass, more preferably 10 to 30% by mass. The heat resistance of a shield layer is more excellent in the said content rate being 3 mass % or more. In addition, blackening progresses during curing, and the L ^* value of the shield layer tends to decrease when formed. Furthermore, the formed shield layer is resistant to discoloration even under severe heating conditions. When the content is 50% by mass or less, (b) the rubber-modified epoxy resin and (c) the acrylic resin can be sufficiently contained, and the effects of these binder components can be sufficiently obtained. The content ratio of the (a) epoxy resin is the total content ratio of all (a) epoxy resins in the conductive paint of the present invention.

(b) The rubber-modified epoxy resin imparts flexibility to the formed shield layer, and (a) maintains the heat resistance of the epoxy resin, improves adhesion to the package, and suppresses the occurrence of cracks. be able to. In addition, the L ^* value of the shield layer at the time of formation can be lowered, and the formed shield layer is less likely to discolor even under severe heating conditions. (b) The rubber-modified epoxy resin preferably has thermosetting properties from the viewpoint of curing by heating and acting as a binder resin for the shield layer. Moreover, it is preferable to have an epoxy group in the molecule (especially at the terminal in the molecule). In this case, blackening progresses during curing, and the L ^* value of the shield layer when formed tends to be lower. (b) The rubber-modified epoxy resin may be used alone or in combination of two or more.

(b) The rubber-modified epoxy resin contains a rubber component in the epoxy resin. Examples of the rubber component include butadiene rubber, acrylic rubber, silicone rubber, butyl rubber, isoprene rubber, styrene rubber, chloroprene rubber, NBR, SBR, IR, and EPR. Only one type of the rubber component may be used, or two or more types may be used. (b) The rubber-modified epoxy resin is preferably an NBR-modified epoxy resin (NBR-modified epoxy resin).

The epoxy resin to be rubber-modified is not particularly limited, but examples thereof include the epoxy resins exemplified as the epoxy resin (a) above. (b) The epoxy resin contained in the rubber-modified epoxy resin may be used alone or in combination of two or more.

(b) The rubber-modified epoxy resin preferably has a carbon-carbon double bond. In this case, the double bonds in the (b) rubber-modified epoxy resin are decomposed during heat curing, and blackening progresses, so that the L ^* value of the formed shield layer becomes lower, and the formed shield layer is more resistant to discoloration even under severe heating conditions. Further, by using the (c) acrylic resin together, the rate of decomposition of the double bond of the (b) rubber-modified epoxy resin is increased, and the blackening of the shield layer during curing is further accelerated.

(b) The rubber-modified epoxy resin preferably has an epoxy equivalent of 200-600 g/eq, more preferably 300-500. When the epoxy equivalent is 200 g/eq or more, the formed shield layer has better adhesion to the package. Further, when the epoxy equivalent is 600 g/eq or less, the heat resistance of the shield layer is more excellent.

The content of the (b) rubber-modified epoxy resin in the (A) binder component is 40 to 70% by mass, preferably 45 to 68% by mass, and more than 100% by mass of the total amount of the (A) binder component. It is preferably 50 to 65% by mass. When the above content is within the above range, the L ^* value of the shield layer during formation can be lowered, and the formed shield layer is less likely to discolor even under severe heating conditions. The content ratio of the (b) rubber-modified epoxy resin is the total content ratio of all (b) rubber-modified epoxy resins in the conductive paint of the present invention.

(c) The acrylic resin can improve the adhesion of the formed shield layer to the package, and can improve the dispersibility of (B) the metal particles. Furthermore, by using (b) a rubber-modified epoxy resin (in particular, a rubber-modified epoxy resin having a double bond), the L ^* value of the shield layer during formation can be lowered, and the formed shield layer is resistant to discoloration even under severe heating conditions. (c) Acrylic resin may use only 1 type, and may use 2 or more types.

(c) The acrylic resin is a polymer composed of a (meth)acrylate compound as an essential monomer component, that is, a polymer (or copolymer) having at least structural units derived from a (meth)acrylate compound. be. In addition, in this specification, "(meth)acrylate" means an acrylate and/or a methacrylate. And "(meth)acrylate compound" indicates a compound having an acryloyl group and/or a methacryloyl group. The same applies to "(meth)acrylic". Only one kind of the (meth)acrylate compound may be used, or two or more kinds thereof may be used.

(c) acrylic resin, for example, the content of structural units derived from a (meth)acrylate compound in the total amount (100% by mass) of the monomer components constituting the acrylic resin is not particularly limited, but for example 50 mass % or more (50 to 100 mass %), preferably 60 mass % or more (60 to 100 mass %), more preferably 90 mass % or more, still more preferably 95 mass % or more.

Examples of the (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, (meth)acryl isobutyl acid, s-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, etc. (meth)acrylic acid alkyl esters having linear or branched alkyl groups; (meth)acrylic acid; carboxyethyl Carboxyl group-containing (meth)acrylic acid esters such as acrylate; 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 6 - hydroxyl group-containing (meth)acrylic esters such as hydroxyhexyl (meth)acrylate, diethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; Ester; N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide (meth)acrylic acid amide derivatives; dimethylamino Dialkylaminoalkyl (meth)acrylates such as ethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and dipropylaminopropyl (meth)acrylate etc.

The (meth)acrylate compounds include neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth) ) and polyfunctional (meth)acrylates such as acrylates. Furthermore, 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, phenylglycidyl ether (meth)acrylate hexamethylene diisocyanate urethane prepolymer, bisphenol A diglycidyl ether acrylic acid adduct and the like are also included.

(c) The acrylic resin may have structural units derived from monomer components other than the (meth)acrylate compound. Examples of such monomer components include, but are not limited to, crotonic acid, itaconic acid, fumaric acid, maleic acid, and other carboxyl group-containing polymerizable unsaturated compounds or their anhydrides; styrene, vinyltoluene, α- Styrene-based compounds such as methylstyrene; vinyl esters such as vinyl acetate and vinyl propionate; vinyl halides such as vinyl chloride; vinyl ethers such as methyl vinyl ether; cyano group-containing vinyl compounds such as (meth)acrylonitrile; and α-olefins such as

(c) The acrylic resin is a polymer containing no crosslinkable functional group and containing 0% by mass or more and less than 25% by mass of structural units derived from a vinyl-based monomer having an alkyl group having 10 or more carbon atoms. is preferred. Among them, those having a mass average molecular weight in the range of 1000 to 7000 and a glass transition temperature of −30° C. or lower are more preferable. As a result, the flexibility of the shield layer is excellent, cracking of the shield layer is less likely to occur, and heat resistance is superior. Furthermore, the L ^* value of the shield layer when formed can be made lower, and the formed shield layer is less likely to discolor even under severe heating conditions.

The content of the (c) acrylic resin in the (A) binder component is 10 to 40% by mass, preferably 12 to 30% by mass, more preferably 10% by mass to 100% by mass of the total amount of the (A) binder component. It is 15 to 25% by mass. When the above content is within the above range, the L ^* value of the shield layer during formation can be lowered, and the formed shield layer is less likely to discolor even under severe heating conditions. In addition, when the content is 10% by mass or more, the storage stability of the conductive paint is excellent, the adhesion of the formed shield layer to the package is improved, and (B) the dispersibility of the metal particles is improved. In addition, it is possible to suppress dripping during curing. Moreover, when the content is 40% by mass or less, the adhesion between the package and the shield layer tends to be good. The content ratio of the (c) acrylic resin is the total content ratio of all (c) acrylic resins in the conductive paint of the present invention.

(A) The binder component may contain binder components other than the above (a) to (c). Examples of the other binder components include modifiers such as alkyd resins, melamine resins, and xylene resins for the purpose of improving physical properties of the conductive paint. (A) The compounding ratio when the modifier is blended with the binder component is preferably 40% by mass or less with respect to 100% by mass of the total amount of the binder component (A) from the viewpoint of adhesion between the shield layer and the package. , more preferably 10% by mass or less.

In the conductive paint of the present invention, in (A) the binder component, (a) an epoxy resin is blended, and (b) a rubber-modified epoxy resin and (c) an acrylic resin are used in a specific ratio in a well-balanced manner. As a result, it is possible to reduce the L ^* value of the shield layer when formed, while making it difficult to discolor even under severe heating conditions. For example, regardless of whether the content of (b) rubber-modified epoxy resin or (c) acrylic resin is less than or greater than the range specified in the present invention, discoloration of the shield layer may occur under severe heating conditions. likely to occur.

[(B) Metal particles]
(B) The metal particles are conductive and impart conductivity and shielding properties to the formed shield layer. Examples of metals forming the metal particles include gold, silver, copper, nickel, and zinc. Only one kind of the above metals may be used, or two or more kinds thereof may be used.

Specific examples of (B) metal particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, silver-coated alloy particles, and the like. mentioned. Examples of the silver-coated alloy particles include silver-coated copper alloy particles in which alloy particles containing copper (for example, copper alloy particles made of an alloy of copper, nickel and zinc) are coated with silver. (B) As the metal particles, silver particles, silver-coated copper particles, and silver-coated copper alloy particles are preferred. It is presumed that the metal particles whose surface is silver are combined with (b) the rubber-modified epoxy resin to promote the oxidation of silver, and the L ^* value of the shield layer at the time of formation is remarkably lowered, In addition, the formed shield layer is more resistant to discoloration even under severe heating conditions thereafter. Silver-coated copper particles and silver-coated copper alloy particles are particularly preferred from the viewpoints of excellent conductivity, suppression of oxidation and agglomeration of the metal particles, and reduction in the cost of the metal particles. (B) Metal particles may be used alone or in combination of two or more.

(B) The shape of the metal particles includes spherical, flake-like (scale-like), dendritic, fibrous, amorphous (polyhedral), and the like. Among them, the flake shape is preferable from the viewpoint that the coating stability of the conductive paint is higher, the resistance value of the resulting shield layer is lower, and a shield layer with improved shielding properties is obtained.

(B) The average particle size (D50) of the metal particles is preferably 1 to 30 μm, more preferably 1 to 10 μm. When the average particle size is 1 μm or more, the dispersibility of the (B) metal particles is good, aggregation can be suppressed, and oxidation is difficult. When the average particle size is 30 μm or less, the package has good connectivity with the ground circuit.

When the (B) metal particles are flakes, the tap density of the (B) metal particles is preferably 4.0 to 6.5 g/cm ³ . If the tap density is within the above range, the conductivity of the shield layer will be better.

Further, when the (B) metal particles are flaky, the aspect ratio of the (B) metal particles is preferably 2-10. If the aspect ratio is within the above range, the conductivity of the shield layer will be better.

(B) The content of the metal particles is 500 to 2500 parts by mass, preferably 700 to 2300 parts by mass, more preferably 1000 to 2000 parts by mass with respect to 100 parts by mass of the total amount of the binder component (A). . When the content is 500 parts by mass or more, the conductivity of the shield layer is improved. When the content is 2,500 parts by mass or less, the adhesiveness between the shield layer and the package and the physical properties of the conductive paint after curing are good, and the shield layer is less likely to chip when cut with a dicing saw, which will be described later. . Also, when silver-coated particles are used as the (B) metal particles, it is possible to limit the increase in the L ^* value due to silver.

[(C) Curing agent]
(C) The curing agent has a role of curing at least one curable component in the (A) binder component. (C) The curing agent preferably has a functional group reactive with an epoxy group. (C) Curing agents may be used alone or in combination of two or more.

(C) Curing agents include, for example, isocyanate curing agents, phenol curing agents, imidazole curing agents, amine curing agents, cationic curing agents, and radical curing agents. As the (C) curing agent, an isocyanate-based curing agent is particularly preferable.

Examples of the isocyanate-based curing agent include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone. Alicyclic polyisocyanates such as diisocyanate, hydrogenated tolylene diisocyanate and hydrogenated xylene diisocyanate; aromatic polyisocyanates, and the like.

Examples of the phenol-based curing agent include novolac phenol and naphthol-based compounds.

Examples of the imidazole curing agent include imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methyl-imidazole, 1 -Cyanoethyl-2-undecylimidazole, 2-phenylimidazole and the like.

Examples of the amine-based curing agent include aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, diethylaminopropylamine, and polypropylenetriamine; amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)-3,4,8,10-tetraoxaspiro [ 5,5] Alicyclic polyamines such as undecane; Mononuclear polyamines such as diethyltolylene-2,4-diamine and 3,5-diethyltolylene-2,6-diamine, biphenylenediamine, 4,4-diaminodiphenylmethane, 2,5-naphthylenediamine, 2,6 - Aromatic polyamines such as naphthylenediamine.

Examples of the cationic curing agent include amine salts of boron trifluoride, p-methoxybenzenediazonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, triphenylsulfonium, tetra-n-butylphosphonium tetraphenylborate, tetra Onium-based compounds such as n-butylphosphonium-o,o-diethylphosphorodithioate and the like.

Radical curing agents (polymerization initiators) include, for example, dicumyl peroxide, t-butylcumyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide.

The content of the curing agent (C) is 1 to 150 parts by mass, preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass with respect to 100 parts by mass of the total amount of the binder component (A). . When the content is 1 part by mass or more, the curable component in the binder component (A) is sufficiently cured, the adhesion of the shield layer to the package is excellent, and the conductivity of the shield layer is improved. Therefore, it is easy to obtain a shield layer having an excellent shield effect. When the content is 150 parts by mass or less, the conductivity of the shield layer is improved, and a shield layer having an excellent shield effect can be easily obtained.

[(D) Solvent]
(D) The solvent dissolves (A) the binder component and (C) the curing agent, and functions as a dispersion medium for the (B) metal particles in the conductive paint. is an essential component for enabling (D) A solvent may use only 1 type, and may use 2 or more types.

Examples of (D) solvents include ketones such as methyl ethyl ketone, acetone and acetophenone; ethers such as methyl cellosolve, methyl carbitol, diethylene glycol dimethyl ether and tetrahydrofuran; esters such as methyl cellosolve acetate, butyl acetate and methyl acetate.

The content of the solvent (D) is not particularly limited, but it is preferably 20 to 800 parts by mass, more preferably 50 to 750 parts by mass, and still more preferably 100 parts by mass of the binder component (A). is 100 to 700 parts by mass. When the content is 20 parts by mass or more, the metal particles (B) can be more sufficiently dispersed in the conductive paint, and the viscosity of the conductive paint is more suitable for coating (particularly, spray coating). can be assumed. In addition, when silver-coated ^particles are used, it is presumed that this is due to the leakage of metal components (for example, copper components) from the coated metal particles. , the formed shield layer is more resistant to discoloration even under severe heating conditions thereafter. When the content is 800 parts by mass or less, the adhesion of the shield layer to the package is excellent. Also, the viscosity of the conductive paint can be made more suitable for application (for example, spray application).

The conductive paint of the present invention may contain components other than the components (A) to (D) as long as the effects of the present invention are not impaired. Examples of the above-mentioned other components include components contained in known or commonly used paints. Examples of the other components include antifoaming agents, thickeners, adhesives, fillers, flame retardants, colorants, and the like. Only one kind of the other components may be used, or two or more kinds thereof may be used. When the above other components are included, the total content of components (A) to (C) in the conductive paint of the present invention is 100% by mass of the conductive paint of the present invention, excluding (D) the solvent. On the other hand, for example, it may be 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

The viscosity of the conductive paint of the present invention can be appropriately adjusted according to the application and equipment used for application. The viscosity of the conductive paint of the present invention can be measured with a cone-plate rotary viscometer (so-called cone-plate viscometer) if the conductive paint has a low viscosity, and if it has a high viscosity, a single cylinder type It can be measured with a rotational viscometer (so-called B-type or BH-type viscometer).

Although the viscosity of the conductive paint of the present invention is not particularly limited when measured with a cone-and-plate rotary viscometer, it is preferably 100 mPa·s or more, more preferably 150 mPa·s or more. When the viscosity is 100 mPa·s or more, even when the coating surface is not horizontal, it is easy to suppress dripping during coating and form a uniform conductive layer. In the case of a low viscosity around 100 mPa·s, in order to obtain a uniform coating film with a desired thickness, the operation of forming a thin film by reducing the coating amount at one time and forming another thin film on it is repeated. , a so-called overcoating method is effective. When measuring with a cone-and-plate type rotational viscometer, for example, Brookfield (BROOK FIELD) using cone spindle CP40 (cone angle: 0.8 °, cone radius: 24 mm), measurement at a rotation speed of 0.5 rpm can do.

When measured with a single cylindrical rotational viscometer, the viscosity of the conductive paint of the present invention is not particularly limited, but is preferably 30 dPa·s or less, more preferably 25 dPa·s or less. When the viscosity is 30 dPa·s or less, clogging of the spray nozzle can be prevented, and a uniform coating film can be easily formed. When measuring with a single cylindrical rotational viscometer, for example, rotor No. 5 can be measured at a rotational speed of 10 rpm.

By applying the conductive paint of the present invention to the surface of a package (for example, the surface of a ground circuit formed of copper foil or the like), (A) curing the curable component in the binder component, and (D) volatilizing the solvent, A conductive layer, such as a shield layer, can be formed. In this specification, the shield layer formed using the conductive paint of the present invention may be referred to as "the shield layer of the present invention".

Examples of methods for applying the conductive paint of the present invention include screen printing, flexure printing, gravure printing, spray coating, brush coating, bar coating, transfer molding, potting, vacuum printing, sputtering, and the like. is mentioned. Among them, spray coating is preferable from the viewpoints of easy uniform coating, good shielding properties even by spray coating, and good adhesion to the package.

Conditions for curing the curable component are not particularly limited, and can be appropriately selected from known or commonly used curing conditions for conductive paints.

The L ^* value of the conductive layer obtained by curing the conductive paint of the present invention under heating conditions of 190 ° C. for 30 minutes (sometimes referred to as “L ^* value (190 ° C. 30 minutes)”) is particularly limited However, it is preferably 61.0 or less, more preferably 60.0 or less, and even more preferably 59.5 or less. When the L ^* value is 61.0 or less, the shield layer is blacker than the conventional one, and the L ^* value of the shield layer immediately after formation is low, so the L ^* value is further reduced even under severe heating conditions thereafter. It is hard to wear and is hard to change color. In this specification, the L ^* value is L ^* (lightness) defined by the L ^* a ^* b ^* color system.

The L ^* value of the conductive layer obtained by curing the conductive paint of the present invention under heating conditions of 190 ° C. for 24 hours (sometimes referred to as “L ^* value (190 ° C. 24 hours)”) is particularly limited However, it is preferably 60.0 or less, more preferably 59.0 or less, and even more preferably 58.0 or less. The above L ^* value (190° C. for 24 hours) is a severe test value that serves as an indicator of the L ^* value over time after forming the shield layer.

ΔL, which is the difference between the L ^* value (190°C 30 minutes) and the L ^* value (190°C 24 hours) [L ^* value (190°C 30 minutes) - L ^* value (190°C 24 hours)], is 15 0.0 or less, more preferably 10.0 or less, and even more preferably 6.0 or less. When the ΔL is 15.0 or less, the formed shield layer is more resistant to discoloration even under severe heating conditions, and has a good appearance even after aging.

The shield layer of the present invention has good shielding properties. Therefore, the conductive layer obtained by curing the conductive paint of the present invention under heating conditions of 190° C. for 30 minutes preferably has a specific resistance value of 1.2×10 ⁻⁵ Ω·cm or less. More preferably, it is 1.0×10 ⁻⁵ Ω·cm or less.

Using the conductive paint of the present invention, a shield having a package containing a substrate, an electronic component mounted on the substrate, and a sealing material for sealing the electronic component, and a shield layer covering the surface of the package Packages can be manufactured. In the shield package, the shield layer is the shield layer of the present invention.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a shield package in which a shield layer formed using the conductive paint of the present invention is formed on the package surface. The shield package 1 shown in FIG. 1 includes a substrate 11, an electronic component 12 mounted on the substrate 11, a sealing material 14 for sealing the electronic component 12, and a shield layer 15 covering the surface of the package. and In the shield package 1, the shield layer 15 is a shield layer formed from the conductive paint of the present invention. A ground circuit pattern 13 made of copper foil or the like is provided on the substrate 11 .

The package (package before shield layer formation) mounts a plurality of electronic components on a substrate, and seals the electronic components by filling and curing a sealing agent that forms a sealing material on the substrate. It can be obtained by sealing with a material. After that, for example, the sealing material is cut between the plurality of electronic components to form grooves, and these grooves separate the packages of the electronic components on the substrate into individual pieces.

Then, the conductive paint of the present invention is applied to the surface of the package by, for example, spray coating, and the package coated with the conductive paint is heated to cure the conductive paint to form a shield layer. After that, the substrate is cut along the grooves to obtain individualized shield packages.

An embodiment of a method for manufacturing the shield package will be described with reference to the drawings.

First, as shown in FIG. 2A, a substrate 11 is provided with a plurality of electronic components (IC, etc.) 12, and a ground circuit pattern (copper foil) 13 is provided between the plurality of electronic components 12. prepare.

Next, as shown in FIG. 1B, a sealant is filled on the electronic component 12 and the ground circuit pattern 13 and hardened to form a sealant 14, and the electronic component 12 and the ground circuit pattern 13 are sealed. is sealed.

Next, as shown by the arrows in FIG. 1C, the sealing material 14 is cut between the plurality of electronic components 12 to form grooves, and the individual electronic component packages on the substrate 11 are separated by these grooves. make it Symbol A indicates individualized packages. At least a part of the ground circuit is exposed from the wall surfaces forming the groove, and the bottom of the groove does not completely penetrate the substrate.

On the other hand, (A) a binder component, (B) metal particles, (C) a curing agent, (D) a solvent, and optionally other components are mixed to prepare a conductive paint.

Next, the conductive paint is sprayed in the form of a mist by a known spray gun or the like, and is evenly applied so that the ground circuit exposed from the package surface and the wall surface is covered with the conductive paint. The injection pressure, the injection flow rate, and the distance between the injection port of the spray gun and the surface of the package at this time are appropriately set as necessary.

Next, the package coated with the conductive paint is heated to sufficiently remove the solvent, and then heated to further heat the curable component (e.g., (a) epoxy resin) in the (A) binder component contained in the conductive paint. etc.) is sufficiently cured to form a shield layer (conductive layer) 15 on the surface of the package as shown in FIG. The heating conditions at this time can be appropriately set. FIG. 3 is a plan view showing the substrate in this state. Reference numerals B1 to B9 denote shield packages before singulation, and reference numerals a1 to a4 and b1 to b9 respectively denote grooves between these shield packages.

Next, as indicated by the arrows in FIG. 2(e), the substrate is cut with a dicing saw or the like along the bottom of the groove between the shield packages before singulation to obtain the shield packages B singulated. be done.

The individualized shield package B obtained in this manner has a uniform shield layer formed on the package surface (all of the upper surface, the side surface, and the corners of the boundary between the upper surface and the side surface). Therefore, good shielding characteristics can be obtained. In addition, since the adhesion between the shield layer and the package surface and the ground circuit is excellent, it is possible to prevent the shield layer from peeling off from the package surface and the ground circuit due to the impact when the package is singulated with a dicing saw or the like. . The surface of the shield package provided with the shield layer is less likely to discolor even under severe heating conditions.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited only to these examples. The amounts shown in the table are relative amounts of each component, and are expressed in "parts by mass" unless otherwise specified. Also, "-" indicates that the component is not blended.

Examples 1-8, Comparative Examples 1-6
Each component described in the table was blended and mixed to prepare each conductive paint of Examples and Comparative Examples. Details of each component used are as follows.

<(a) epoxy resin>
Solid epoxy resin: manufactured by Mitsubishi Chemical Corporation, trade name "JER157S70"
<(b) Rubber-modified epoxy resin>
Rubber-modified epoxy resin: manufactured by ADEKA Co., Ltd., trade name "EPR-1415-1" (NBR-modified epoxy resin)
<(c) acrylic resin>
Acrylic resin: manufactured by Toagosei Co., Ltd., trade name "ARUFON UP-1000"
<(B) Metal particles>
Silver-coated copper particles: Flake-like silver-coated copper particles (average particle diameter 5 μm, aspect ratio 5)
Silver particles: flaky silver particles (average particle diameter 5 μm, aspect ratio 5)
Silver-coated copper alloy particles: Flake-like silver-coated copper alloy particles (average particle diameter 5 μm, aspect ratio 5)
<(C) Curing agent>
Curing agent: Polyisocyanate compound (manufactured by DIC Corporation, trade name “DN-992”)
<(D) Solvent>
Solvent: 1-methoxy-2-propanol (manufactured by Kishida Chemical Co., Ltd.)

(evaluation)
Each conductive paint obtained in Examples and Comparative Examples was evaluated as follows. The evaluation results are shown in the table.

(1) Specific resistance value A polyimide film having a thickness of 55 μm with a slit of 5 mm width was pasted on a glass epoxy substrate to prepare a printing plate. Line printing (length 60 mm, width 5 mm, thickness about 100 μm) was performed using a printing plate, and cured by heating at 190° C. for 30 minutes. After that, the polyimide film was peeled off. As described above, a conductive layer was produced on the glass epoxy substrate. The electrical resistance value R at ^both ends of the conductive layer is measured using a tester, and the specific resistance value ( Ω·cm) was calculated.
Specific resistance value = S/L x R (1)

(2) Acetone Rubbing Test A cured product sample using a conductive paint was prepared in the same manner as the conductive layer prepared in the above (1) resistivity test. A paper towel soaked with acetone was reciprocated 10 times over the cured sample. Then, in the cured product sample, the rate (%) of the cured product of the conductive paint being peeled off was measured according to the following formula (2). In this evaluation, the lower the rate of peeling of the cured sample of the conductive paint, the better the conductive paint is cured.
Peeling rate of conductive paint =
{1−[Area of cured product sample remaining after treatment with paper towel]/[Area of cured product sample before treatment with paper towel]}×100 (2)

(3) Cross-cut test Adhesion between the shield layer and the package surface or ground circuit was evaluated based on JIS K 5600-5-6:1999 (cross-cut method). Specifically, a copper-clad laminate for evaluation of adhesion to the ground circuit and a mold resin for evaluation of adhesion to the surface of the package were prepared. A test sample was prepared by masking with a polyimide tape so that an opening having a width of 5 cm and a length of 10 cm was formed in each of the copper-clad laminate and the mold resin. The conductive paint according to each example and comparative example was applied using a coating device (manufactured by Spraying Systems Japan LLC, Spray Cart III, spray nozzle: YB1/8MVAU-SS + SUMV91-SS) schematically shown in FIG. The area containing the opening of the test sample was sprayed. After that, the conductive paint was cured by heating at 190° C. for 30 minutes, the polyimide tape was peeled off, and a coating film having a thickness of about 20 μm was formed on each of the copper-clad laminate and the mold resin. A cross-cut test was performed on the copper-clad laminate with the coating film formed thereon and the mold resin. Then, evaluation of adhesion was performed according to the following criteria.
◯: In both the copper-clad laminate and the mold resin, the edges of the cut were completely smooth, and there was no peeling at any lattice mesh.
x: In at least one of the copper-clad laminate and the mold resin, small peeling of the coating film occurred at the intersection of the cuts, or peeling occurred at the edges of the cut, at the intersections, and over the entire surface.

In FIG. 4, reference numeral 21 indicates a tank (paint container), reference numeral 22 indicates a tube, reference numeral 23 indicates a nozzle, reference numeral 24 indicates a turntable, reference numeral 25 indicates a stirring device, and reference numeral 26 indicates a A gas introduction pipe is indicated, and reference numeral 27 indicates a test sample. The tank 21 is a substantially cylindrical vessel with a capacity of 3 liters, is equipped with a stirring device 25 having stirring blades, and is pressurized by introducing a gas such as nitrogen through a gas introduction pipe 26 . The tube 22 has a length of 3 m and an inner diameter of 4 mm, and connects the tank 21 and the nozzle 23 to each other. The tube 22 has a slack (22a) in one part, and the height difference (t in FIG. 4) of the slack part is 3 cm. The nozzle 23 has a length of 78 mm and a jet diameter of 0.5 mm. The distance from the upper surface of the rotating plate 24 to the tip of the nozzle 23 is 8 cm.

(4) Discoloration test The L ^* value of the conductive layer produced in the above (1) resistivity test was measured using a color difference meter, and this value was taken as the L ^* value (190°C, 30 minutes). In addition, except that the heating condition was 190 ° C. for 24 hours, a conductive layer was prepared in the same manner as the conductive layer prepared in the above (1) Specific resistance test, and the L ^* value of the conductive layer was measured using a color difference meter. This value was taken as the L ^* value (190°C for 24 hours). As the color difference meter, a portable integrating sphere spectrophotometer (trade name “Ci6x”, manufactured by X-Rite Co., Ltd.) was used. The difference between the L ^* value (190°C for 30 minutes) and the L ^* value (190°C for 24 hours) was calculated as ΔL. Regarding the discoloration evaluation, if ΔL was 10 or less, discoloration was suppressed, so it was marked as “○”. and the case of exceeding 10 was evaluated as "x".

(5) Uniformity of thickness As a model of the package before singulation, counterbore processing with a groove width of 1 mm and a depth of 2 mm was performed in 10 rows each in the vertical and horizontal directions, and island parts were formed in 9 rows and 9 rows to resemble a 1 cm square package. A glass epoxy substrate was used. Each conductive paint obtained in Examples and Comparative Examples is applied to the surface of the package using a commercially available spray gun (manufactured by Anest Iwata Co., Ltd., trade name "LPH-101A-144LVG") under the conditions shown below. It was sprayed and allowed to stand at 25° C. for 30 minutes to volatilize the solvent. Then, it was heated at 100° C. for 10 minutes and further heated at 190° C. for 30 minutes to cure the conductive paint and form a shield layer.
<Spray conditions>
Application amount: Apply for 9 seconds at a flow rate of 200 L / min Supply pressure: 0.5 MPa
Package surface temperature: 25°C
Distance from package surface to nozzle: about 20cm

The thickness of the shield layer formed on the surface of the package was calculated from the difference in the thickness of the shield layer between the corners and wall portions in the cross section of the package on which the shield layer was formed. Specifically, as shown in FIG. 5, the thickness of the shield layer formed on the side surface of the package is D1 (where D1 is measured at the center in the height direction of the side surface, and the distance L1 from the top surface to the measurement position and the bottom surface to the measurement position), and the thickness of the shield layer formed at the corner of the package (measured at an angle of 45° upward from the horizontal plane) is D2, calculated by the following formula (3) The ratio (%) obtained was used as an index of uniformity. If this ratio is 60% or less, it can be appropriately used as a shield layer, so it was evaluated as "good", and if it exceeded 60%, it was evaluated as "poor".
Ratio (%) = ((D1-D2)/D1) x 100 (3)

The closer the difference in the thickness of the shield layer to zero, the more uniform the thickness of the shield layer. Nonuniformity occurs in the resistance value. On the other hand, if the thickness of the wall surface is reduced, the shield layer will not be formed on the corners, and the shield effect will not be obtained. In each example, the ratio of the difference in the thickness of the shield layer between the corner portion and the wall portion was 60% or less, and it was confirmed that the shield layer can be appropriately used.

(6) Electrical Conductivity of Shield Layer The electrical conductivity of the shield layer produced in the above (5) Evaluation of thickness uniformity was measured as a resistance value. Specifically, an arbitrary row is selected from among the rows constituted by the cubic islands formed by counterbore processing, and between the islands at both ends of the row (between B1 and B9 in FIG. 3) ) was measured. If the resistance value was 100 mΩ or less, it could be used appropriately as a shield layer, so it was evaluated as “◯”, and if it exceeded 100 mΩ, it was evaluated as “×”.

The conductive paint (Example) of the present invention had good shielding properties, good adhesion to the package, and was able to form a conductive layer that was resistant to discoloration even under severe heating conditions. On the other hand, when the content of (b) rubber-modified epoxy resin and (c) acrylic resin was high or low (Comparative Examples 1 and 2), the degree of discoloration was large under severe heating conditions. (C) When the content of the curing agent is small (Comparative Example 3), the conductive layer has a large specific resistance value and poor shielding properties, and the results of the acetone rubbing test and the cross-cut test are unsatisfactory. Adhesion was poor. In addition, since the content of the curing agent (C) is small and the viscosity of the conductive paint is low, the uniformity of the thickness of the shield layer is poor. (C) When the content of the curing agent was large (Comparative Example 4), the specific resistance of the shield layer was large and the shielding properties were poor. (B) When the content of metal particles was small (Comparative Example 5), the resistivity of the conductive layer was large, the shielding property was poor, and the degree of discoloration was large under severe heating conditions. (B) When the content of metal particles was large (Comparative Example 6), the results of the acetone rubbing test and the crosscut test were poor, indicating poor adhesion to the package. Further, in Comparative Example 5, the uniformity of the thickness of the shield layer was poor because the (D) solvent was large and the conductive paint had a low viscosity.

1 shield package 11 substrate 12 electronic component 13 ground circuit (ground circuit pattern)
14 sealing material 15 shield layer (conductive layer)
a1-a4 Grooves b1-b10 Grooves A Packages singulated on substrate B Shield packages singulated B1-B9 Shield packages before singulation 21 Tank (paint container)
22 tube 23 nozzle 24 turntable 25 stirring device 26 gas introduction pipe 27 test sample

Claims (6)

(A) a binder component containing (a) an epoxy resin, (b) 40 to 70% by mass of a rubber-modified epoxy resin, and (c) 10 to 40% by mass of an acrylic resin, (B) metal particles, and (C) curing and (D) a solvent,
(A) A conductive paint containing 500 to 2,500 parts by mass of metal particles and 1 to 150 parts by mass of (C) a curing agent relative to 100 parts by mass of a binder component. (b) The conductive paint according to claim 1, wherein the rubber-modified epoxy resin has a carbon-carbon double bond. 3. The conductive paint according to claim 1 or 2, wherein (D) the metal particles are at least one selected from the group consisting of silver particles, silver-coated copper particles, and silver-coated copper alloy particles. (C) The conductive paint according to any one of claims 1 to 3, wherein the curing agent is an isocyanate curing agent. 5. The conductive paint according to any one of claims 1 to 4, wherein the content of (D) the solvent is 20 to 800 parts by mass per 100 parts by mass of the binder component (A). The conductive paint according to any one of claims 1 to 5, wherein the conductive layer obtained by curing under heating conditions of 190°C for 30 minutes has a specific resistance of 1.0 × 10 ^-5 Ω·cm or less. .

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