JP2021086912A - Electronic component mounting board and electronic device - Google Patents

Abstract

To provide a highly reliable electronic component mounting board and an electronic device with excellent laser printability and ease of evaluation.SOLUTION: An electronic component mounting board includes a substrate, an electronic component, and an electromagnetic wave shield layer, and the electronic component is mounted on the substrate, the electromagnetic wave shield layer is arranged so as to cover at least a part of the substrate and the electronic component, and the electromagnetic wave shield layer includes a conductive filler and a binder resin, and the L* value of the surface of the electromagnetic wave shield layer opposite to the surface in contact with the electronic component and the substrate is 50 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electronic component mounting substrate having an electromagnetic wave shielding layer. The present invention also relates to an electronic device on which the electronic component mounting substrate is mounted.

Electronic components equipped with IC chips and the like are usually provided with an electromagnetic wave shield structure in order to prevent malfunction due to an external magnetic field or radio waves. For example, a method of coating a substrate on which an electronic component is mounted with a shield sheet made of an isotropic conductive adhesive and an anisotropic conductive adhesive is disclosed (Patent Document 1). In such an electronic component mounting board, an electromagnetic wave shield layer is formed directly on the electronic component, and quality inspection such as breakage of the electromagnetic wave shield layer at uneven portions and ground connectivity is a method of confirming conductivity from the upper surface of the electromagnetic wave shield layer. I'm taking it. On the other hand, it is necessary to print on the surface of the electronic component mounting substrate by laser marking or the like for distribution information and product management, and visibility after printing is important. However, it is usually difficult to improve visibility by adding a colorant to the electromagnetic wave shield layer containing a large amount of metal powder, and Patent Document 1 does not mention the laser printability of the electromagnetic wave shield layer. Further, when a colorant is further added to the electromagnetic wave shield layer in addition to the conductive filler, the flexibility of the electromagnetic wave shield sheet deteriorates as it is added, and processing by thermocompression bonding becomes difficult.

International Publication No. 2015/186624

When the conventional electromagnetic wave shield layer is printed with a laser, there is a problem that a difference in printing brightness occurs between the conductive filler and the binder resin contained therein, the outline of the laser printing portion becomes unclear, and the visibility is low (hereinafter, the present invention). "Laser printability"). In addition, simply adding a colorant reduces the conductivity of the electromagnetic wave shield layer, making quality inspection difficult by confirming continuity (hereinafter referred to as "evaluation simplicity"), and is compatible with laser printability. It was difficult.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a highly reliable electronic component mounting substrate and electronic device having excellent laser printability and ease of evaluation.

As a result of diligent studies by the present inventors, they have found that the problems of the present invention can be solved in the following aspects, and have completed the present invention. That is, the present invention includes a substrate, an electronic component, and an electromagnetic wave shield layer, the electronic component is mounted on the substrate, and the electromagnetic wave shield layer covers at least a part of the substrate and the electronic component. The electromagnetic wave shield layer is arranged so as to cover, and contains a conductive filler and a binder resin, and the L ^* value of the surface of the electromagnetic wave shield layer opposite to the surface in contact with the electronic component and the substrate is set. It is a board on which electronic components are mounted, which is 50 or less.

Further, the present invention is the electronic component mounting substrate in which the resistance value of the electronic component of the electromagnetic wave shielding layer and the surface opposite to the surface in contact with the substrate is 200 mΩ or less.

Further, in the present invention, the conductive filler is the electronic component mounting substrate having one or more shapes selected from the group consisting of scale-like, dendrite-like and needle-like.

Further, in the present invention, the electromagnetic wave shielding layer has a conductive layer (a) and a conductive layer (b), and the conductive layer (a) is arranged at a position where it comes into contact with the substrate and the electronic component. The conductive layer (a) contains the conductive filler and the binder resin, and the conductive layer (b) is the electronic component mounting substrate containing the conductive filler, the binder resin and the colorant.

Further, the present invention is an electronic device on which the above-mentioned electronic component mounting substrate is mounted.

According to the present invention having the above configuration, since the laser printability and the evaluation simplicity are excellent, the yield is good in the production process, the quality control is easy, and the electronic component mounting substrate and the electronic device using the same are highly reliable for a long period of time. Can be provided.

The schematic perspective view which shows an example of the electronic component mounting board. FIG. 1 is a cross-sectional view of the II-II cut portion of FIG. Schematic cross-sectional view showing another example of an electronic component mounting substrate. The schematic cross-sectional view which shows an example of the laminated body for electromagnetic wave shielding. The schematic cross-sectional view which shows an example of the manufacturing process of the electronic component mounting substrate. The schematic cross-sectional view which shows an example of the manufacturing process of the electronic component mounting substrate. The schematic cross-sectional view which shows an example of the manufacturing process of the electronic component mounting substrate. The schematic cross-sectional view which shows an example of the manufacturing process of the electronic component mounting substrate. Schematic cross-sectional view showing an example of the test substrate used in the examples.

Hereinafter, an example of an embodiment to which the present invention is applied will be described. The numerical value specified in the present specification is a value obtained by the method disclosed in the embodiment or the embodiment. Further, the numerical values "A to B" specified in the present specification refer to a range satisfying a value larger than the numerical value A and the numerical value A and a value smaller than the numerical value B and the numerical value B. Further, the sheet in the present specification includes not only a sheet defined in JIS but also a film. The following description and drawings have been simplified as appropriate to clarify the description. Unless otherwise specified, the various components mentioned in the present specification may be used independently or in combination of two or more.

<Electromagnetic wave shield layer>
The electromagnetic wave shield layer contains a conductive filler and a binder resin. The electromagnetic wave shield layer 1 can be formed by a method of thermocompression bonding the electromagnetic wave shield sheet 2 or a method of applying or spraying a resin composition, but a method of thermocompression bonding the electromagnetic wave shield sheet is preferable from the viewpoint of improving the yield. The electromagnetic wave shield sheet 2 contains a conductive filler and a thermosetting resin, and preferably further contains a curing agent.

《Binder resin》
The binder resin refers to a cured resin of the thermosetting resin described below. Thermosetting resins usually have reactive functional groups. When a thermosetting resin is used, a curing agent can be used in combination. From the viewpoint of simplicity of the manufacturing process, it is preferable to cure during thermocompression bonding. Further, a self-crosslinking resin or a plurality of resins that crosslink each other may be used. Further, a thermoplastic resin may be mixed in addition to these resins. The compounding components such as the resin and the curing agent can be independently used alone or in combination of two or more. At the stage of the electromagnetic wave shield sheet 2, a part of the crosslink may be formed to form a B stage (semi-cured state). For example, a state in which the thermosetting resin reacts with a part of the curing agent to be semi-cured may be included.

Preferable examples of thermosetting resins are polyurethane resins, polycarbonate resins, polystyrene resins, phenoxy resins, polyurethane urea resins, polyamide resins, polyimide resins, polycarbonate imide resins, polyamide imide resins, epoxys. Examples thereof include based resins, epoxy ester based resins, acrylic resins, polyester resins, polyesteramide resins and polyether ester resins.

Among these, the thermosetting resins used under harsh conditions during reflow include polyurethane resins, polyurethane urea resins, polycarbonate resins, polystyrene resins, phenoxy resins, polyamide resins, and polyimide resins. , It is preferable that at least one of an epoxy resin and an epoxy ester resin is contained. Further, by using a resin having a polycarbonate skeleton, the PCT adhesion resistance (adhesion between the electromagnetic wave shield layer and the substrate after the pressure cooker test) is improved. The thermosetting resin can be used alone or in admixture of two or more at any ratio.

Examples of the resin having a polycarbonate skeleton include a polyurethane resin having a polycarbonate skeleton, a polyamide resin, and a polyimide resin, in addition to the polycarbonate resin. For example, according to the polycarbonate imide resin, the heat resistance, the insulating property, and the chemical resistance can be improved by having the polyimide skeleton. On the other hand, having a polycarbonate skeleton can effectively enhance flexibility and adhesion.

As the polyol component used in the polycarbonate urethane resin, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 1,9-nonanediol, or 2-methyl-1,8 -Diols such as octanediol are preferred. The above polyol can be used alone or in combination of two or more.

The thermosetting resin may have a plurality of functional groups that can be used for a cross-linking reaction by heating. Examples of the functional group include a hydroxyl group, a phenolic hydroxyl group, a carboxyl group, an amino group, an epoxy group, an oxetanyl group, an oxazoline group, an oxazine group, an aziridine group, a thiol group, an isocyanate group, a blocked isocyanate group and a silanol group. ..

《Hardener》
The curing agent has a reactive functional group of a thermosetting resin and a crosslinkable functional group. By cross-linking, the adhesion can be further strengthened and the water resistance can be improved. As the curing agent, epoxy compounds, acid anhydride group-containing compounds, isocyanate compounds, polycarbodiimide compounds, aziridine compounds, dicyandiamide compounds, amine compounds such as aromatic diamine compounds, phenol compounds such as phenol novolac resin, organic metal compounds and the like are preferable. ..

The epoxy compound is a compound having two or more epoxy groups in one molecule. The properties of the epoxy compound may be liquid or solid. As the epoxy compound, for example, a glycisyl ether type epoxy compound, a glycisyl amine type epoxy compound, a glycidyl ester type epoxy compound, a cyclic aliphatic (alicyclic) epoxy compound and the like are preferable.

Examples of the glycidyl ether type epoxy compound include bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, bisphenol AD type epoxy compound, cresol novolac type epoxy compound, phenol novolac type epoxy compound, and α-naphthol novolac. Type epoxy compound, bisphenol A type novolac type epoxy compound, dicyclopentadiene type epoxy compound, tetrabrom bisphenol A type epoxy compound, brominated phenol novolac type epoxy compound, tris (glycidyloxyphenyl) methane, tetrakis (glycidyloxyphenyl) ethane And so on.

Examples of the glycidylamine type epoxy compound include tetraglycidyldiaminodiphenylmethane, triglycidylparaaminophenol, triglycidylmethaminophenol, tetraglycidylmethoxylylenediamine and the like.

Examples of the glycidyl ester type epoxy compound include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl tetrahydrophthalate.

Examples of the cyclic aliphatic (alicyclic) epoxy compound include epoxycyclohexylmethyl-epoxycyclohexanecarboxylate and bis (epoxycyclohexyl) adipate. Moreover, a liquid epoxy compound can be preferably used.

Examples of the imidazole compound include imidazole compounds such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-dimethylimidazole, and 2-phenylimidazole, and further, imidazole compounds. A latent curing accelerator having improved storage stability, such as a type in which an epoxy resin is reacted with an epoxy resin and insolubilized in a solvent, or a type in which an imidazole compound is encapsulated in microcapsules, can be used.

The structure and molecular weight of the curing agent can be appropriately designed according to the application. From the viewpoint of adjusting the flexibility of the electromagnetic wave shield sheet 2 to be suitable for thermocompression bonding and improving the ease of evaluation, it is preferable to use two or more kinds of curing agents having different molecular weights. By using two or more kinds of curing agents, a sufficient three-dimensional crosslinked structure is constructed in the electromagnetic wave shield layer, and PCT adhesion resistance can be improved.

The curing agent preferably contains 1 to 75 parts by mass with respect to 100 parts by mass of the binder resin, more preferably 3 to 70 parts by mass, and further preferably 3 to 65 parts by mass. When two or more kinds of curing agents are used in combination, it is preferable to contain 5 to 70 parts by mass, more preferably 10 to 65 parts by mass, and 20 parts by mass of the main curing agent with respect to 100 parts by mass of the thermosetting resin. It is more preferable to contain ~ 65 parts by mass.

《Conductive filler》
Examples of the conductive filler include metal fillers, conductive ceramic particles and mixtures thereof. Examples of the metal filler include core-shell type particles of metal powder such as gold, silver, copper and nickel, alloy powder such as solder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder and gold-coated nickel powder. From the viewpoint of obtaining excellent conductive properties, a conductive filler containing silver is preferable. From the viewpoint of cost, silver-coated copper powder obtained by coating copper powder with silver is particularly preferable.

The silver content in the silver-coated copper is preferably 3 to 30% by mass, more preferably 5 to 25% by mass, still more preferably 8 to 20% by mass, based on 100% by mass of the total of silver and copper. In the case of core-shell type particles, the coverage of the coat layer on the core portion is preferably 60% or more, more preferably 70% or more, still more preferably 80% or more on average. The core portion may be a non-metal, but from the viewpoint of conductivity, a conductive substance is preferable, and metal particles are more preferable.

Examples of the shape of the conductive filler include scaly particles, dendrite (dendritic) particles, needle-like particles, plate-like particles, grape-like particles, fibrous particles, and spherical particles. By containing scaly particles as the conductive filler, it is possible to provide the electromagnetic wave shield layer 1 having excellent coating properties. Here, the scaly shape also includes a flaky shape and a plate shape. The conductive filler may be scaly as a whole particle, and may have an elliptical shape, a circular shape, or a notch or the like around the fine particles. When scaly particles are used, the hardness of the surface of the electromagnetic wave shield layer 1 tends to increase, and spherical and dendritic particles tend to have low conductivity. Further, as the amount of the conductive filler increases, the conductivity tends to increase.

It is preferable to contain a conductive filler of needle-like particles and / and dendrite-like particles. Here, the needle shape means that the major axis is three times or more the minor axis, and includes not only the so-called needle shape but also a spindle shape, a cylindrical shape, and the like. The dendrite shape refers to a shape in which a plurality of branch branches extend two-dimensionally or three-dimensionally from a rod-shaped main axis when observed with an electron microscope (500 to 20,000 times). In the dendrite shape, the branch branch may be bent, or the branch branch may extend further from the branch branch.

The conductive filler is used alone or in combination. For example, a combination of scaly particles and spherical particles, a combination of scaly particles and dendrite-like particles, a combination of scaly particles and needle-like particles, a combination of scaly particles, dendrite-like particles and needle-like particles can be exemplified. Nano-sized spherical particles may be used in combination with these.

Further, by using dendrite-like particles and / and needle-like particles in combination, it is possible to increase the number of contact points between the conductive fillers and improve the shielding characteristics. Further, by using the dendrite-like particles and / and the needle-like particles in combination, the contact area with the binder component can be increased, so that a high-quality electromagnetic wave shield layer 1 can be provided.

The content of the conductive filler is preferably 40 to 85% by mass, more preferably 50 to 80% by mass, based on the solid content (100% by mass) of the electromagnetic wave shield layer. Within the above range, the resistance value of the electromagnetic wave shield layer described later can be set to 200 mΩ or less. Here, the content of the conductive filler is the total of the conductive layer (a) and the conductive layer (b) in the case of laminating the conductive layer (a) and the conductive layer (b), which will be described later. It is the value that was set.

It is preferable that the needle-like particles and / and the dendrite-like particles are contained in an amount of 0.1 to 50% by mass with respect to 100% by mass of the conductive filler in the electromagnetic wave shield layer. It is more preferably 0.5 to 40% by mass, further preferably 1 to 35% by mass, and particularly preferably 1 to 30% by mass. By containing 0.1 to 50% by mass, it is possible to provide an electromagnetic wave shielding layer having better scratch resistance.

The average particle size D ₅₀ of the conductive filler is preferably 2 to 100 μm.
The average particle size D ₅₀ of the scaly particles is preferably 2 to 100 μm, more preferably 2 to 80 μm. It is more preferably 3 to 50 μm, and particularly preferably 5 to 20 μm. The scaly particles may be mixed with a nano-sized conductive filler.

_{The average particle size D 50} of the needle-shaped particles is preferably 2 to 100 μm, more preferably 2 to 80 μm. It is more preferably 3 to 50 μm, and particularly preferably 5 to 20 μm. Similarly, the preferred range of the average particle size D ₅₀ of the dendrite-like particles is preferably 2 to 100 μm, more preferably 2 to 80 μm. It is more preferably 3 to 50 μm, and particularly preferably 5 to 20 μm.

By using the scaly particles and the dendrite-like particles in combination, the surface glossiness can be optimized and the laser printability can be improved.

The average particle size D ₅₀ can be measured by the laser diffraction / scattering method. Specifically, for example, it is a numerical value obtained by measuring each conductive fine particle with a tornado dry powder sample module using a laser diffraction / scattering method particle size distribution measuring device LS 13320 (manufactured by Beckman Coulter). _{, The average particle size D 50} of the particle size diameter in which the integrated value of the particles is 50%. The refractive index is set to 1.6 for measurement. _{The average particle size D 50} of each particle in the electromagnetic wave shield layer 1 can be determined by measuring the particle size of 100 particles using a scanning electron microscope (SEM) and determining the frequency distribution. For needle-like particles and dendrite-like particles, the particle size uses the longest length of each particle. D ₅₀ in the example is a value measured by the laser diffraction / scattering method.

<< L ^* value >>
^{The L *} value of the electromagnetic wave shield layer is 50 or less. By setting the value within the above numerical range, the visibility of the printed portion can be improved in order to prevent the difference in printing brightness caused by the contained conductive filler and the binder resin. ^{The L *} value of the electromagnetic wave shield layer is preferably 40 or less, more preferably 35 or less. In ^{order to keep the L *} value in the above range, it is preferable to use a colorant in the electromagnetic wave shielding layer.

《Colorant》
Colorants can be exemplified from inorganic pigments, organic pigments and mixtures thereof, and dyes. Examples of organic pigments include perylene black, carbon black, ketjen black, carbon nanotubes and single or pigment mixtures such as red, green, blue, purple and yellow. Examples of the inorganic pigment include iron black, titanium black, ultramarine blue, petal handle, zinc oxide, and titanium oxide.
Organic pigments are preferable from the viewpoint of quality stability. Carbon black is particularly preferable from the viewpoint of coloring power and dispersion stability. By using carbon black, the binder resin is reinforced and the hardness is increased, so that an electromagnetic wave shield layer having more excellent PCT adhesion can be provided.

The arithmetic mean particle size of the colorant is preferably 10 to 200 nm, more preferably 10 to 80 nm. The arithmetic mean particle size is a value obtained by observing with an electron microscope.

The amount of the colorant added is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, based on the solid content (100% by mass) of the entire electromagnetic wave shield layer. By setting the value within the above numerical range, the L ^* value can be lowered to a value suitable for laser printing, so that an electromagnetic wave shielding layer having more excellent laser printability can be obtained.

<< Resistance value of electromagnetic wave shield layer >>
The conductive filler in the electromagnetic wave shield layer 1 is continuously in contact with each other and exhibits conductivity. From the viewpoint of enhancing the electromagnetic wave shielding property, the sheet resistance value of the electromagnetic wave shielding layer 1 is preferably 1000 mΩ / □ or less.

The resistance value of the electromagnetic wave shield layer is preferably 200 mΩ or less, more preferably 100 mΩ or less, and even more preferably 50 mΩ or less. By setting the above numerical range, the breakage of the electromagnetic wave shield layer and the ground connectivity can be easily evaluated by measuring the resistance value of the surface layer of the electromagnetic wave shield layer, so that the simple evaluation property is improved. The method for measuring the resistance value will be described in Examples.

The electromagnetic wave shield layer preferably has a two-layer laminated structure. Specifically, it has a conductive layer (a) and a conductive layer (b), the conductive layer (a) is arranged at a position where it comes into contact with a substrate and an electronic component, and the conductive layer (a) is a conductive filler and It contains a binder resin, and the conductive layer (b) contains a conductive filler, a binder resin and a colorant. By separating the functions in this way, it is possible to provide an electromagnetic wave shield layer having high shielding property and laser printing property.

The content of the conductive filler in the conductive layer (a) is preferably 40 to 85% by mass, more preferably 50 to 80% by mass, based on the solid content (100% by mass) of the electromagnetic wave shield layer 1.

The content of the conductive filler in the conductive layer (b) is preferably 10 to 60% by mass, more preferably 15 to 40% by mass, based on the solid content (100% by mass) of the electromagnetic wave shield layer 1. The content of the colorant is preferably 3 to 40% by mass, more preferably 10 to 30% by mass. By containing 15% or more of the conductive filler and 5% by mass or more of the colorant, the resistance value can be kept at 200 mΩ or less and the L value can be lowered, so that the electromagnetic wave shield layer 1 having excellent laser printability is provided. it can.

The composition constituting the electromagnetic wave shield layer 1 may further contain a flame retardant, an indefinite additive, a lubricant, an antiblocking agent, an electromagnetic wave absorbing filler, and the like. Examples of the flame retardant include a halogen-containing flame retardant, a phosphorus-containing flame retardant, a nitrogen-containing flame retardant, and an inorganic flame retardant. Examples of the inorganic additive include glass fiber, silica, talc, ceramic, ion catcher and the like. Examples of the lubricant include fatty acid esters, hydrocarbon resins, paraffins, higher fatty acids, fatty acid amides, fatty alcohols, metal soaps, modified silicones and the like. Examples of the blocking inhibitor include calcium carbonate, silica, polymethylsilsesquiosan, aluminum silicate and the like.

From the viewpoint of obtaining the shielding effect by absorbing electromagnetic waves, it is preferable to add an electromagnetic wave absorbing filler. Examples of the electromagnetic wave absorbing filler include iron, Fe-Ni alloy, Fe-Co alloy, Fe-Cr alloy, Fe-Si alloy, Fe-Al alloy, Fe-Cr-Si alloy, Fe-Cr-Al alloy, and Fe. Iron alloys such as −Si—Al alloys, ferrite materials such as Mg—Zn ferrite, Mn—Zn ferrite, Mn—Mg ferrite, Cu—Zn ferrite, Mg—Mn—Sr ferrite, Ni—Zn ferrite, and carbon fillers. And so on. Examples of the carbon filler include acetylene black, ketjen black, furnace black, carbon black, carbon fiber, particles composed of carbon nanotubes, graphene particles, graphite particles and carbon nanowalls.

The electromagnetic wave shield sheet 2 can be obtained by applying and drying a resin composition containing a conductive filler and a thermosetting resin.

<Electronic component mounting board>
FIG. 1 shows a schematic perspective view showing an example of an electronic component mounting substrate, and FIG. 2 shows a cross-sectional view of the II-II cut portion of FIG. The electronic component mounting substrate 51 includes a substrate 20, an electronic component 30, an electromagnetic wave shield layer 1, and the like.

The substrate 20 may be any substrate as long as it can mount the electronic component 30 and can withstand the thermocompression bonding step described later. For example, a work board in which a conductive pattern made of copper foil or the like is formed on the surface or inside, a mounting module board, a printed wiring board, or a build-up board formed by a build-up method or the like can be mentioned. Further, a film or sheet-shaped flexible substrate may be used. The conductive pattern is, for example, an electrode / wiring pattern (not shown) for electrically connecting to the electronic component 30, and a ground pattern 22 for electrically connecting to the electromagnetic wave shield layer 1. Electrodes / wiring patterns, vias (not shown) and the like can be arbitrarily provided inside the substrate 20. The substrate 20 may be a flexible substrate as well as a rigid substrate.

In the example of FIG. 1, the electronic components 30 are arranged in an array of 5 × 4 on the substrate 20. An electromagnetic wave shield layer 1 is provided so as to cover the exposed surfaces of the substrate 20 and the electronic component 30. That is, the electromagnetic wave shield layer 1 is covered so as to follow the unevenness formed by the electronic component 30. The electromagnetic wave shield layer 1 can shield unnecessary radiation generated from signal wiring or the like built in the electronic component 30 and / or the substrate 20, and can prevent malfunction due to an external magnetic field or radio waves.

The number, arrangement, shape and type of the electronic components 30 are arbitrary. Instead of arranging the electronic components 30 in an array, the electronic components 30 may be arranged at arbitrary positions. When the electronic component mounting substrate 51 is individualized into unit modules, as shown in FIG. 2, a half dicing groove 25 may be provided so as to partition the unit modules in the thickness direction of the substrate from the upper surface of the substrate. The electronic component mounting substrate includes both a substrate before being fragmented into a unit module and a substrate after being fragmented into a unit module. That is, in addition to the electronic component mounting board 51 on which a plurality of unit modules (electronic components 30) as shown in FIGS. 1 and 2 are mounted, the electronic component mounting board 52 after being individualized into the unit modules as shown in FIG. Also includes. An electronic component mounting substrate in which one electronic component 30 is mounted on the substrate 20 and coated with an electromagnetic wave shield layer without going through an individualization step is also included. That is, the electronic component mounting substrate includes a structure in which at least one electronic component is mounted on the substrate and at least a part of the step portion formed by mounting the electronic component is covered with the electromagnetic wave shield sheet 2.

The electronic component 30 includes all components in which an electronic element such as a semiconductor integrated circuit is integrally covered with an insulator. For example, there is an embodiment in which a semiconductor chip 31 (see FIG. 3) on which an integrated circuit (not shown) is formed is molded by a sealing material (mold resin 32). The substrate 20 and the semiconductor chip 31 are electrically connected to the wiring or the electrode 21 formed on the substrate 20 via these abutting regions or via a bonding wire 33, a solder ball (not shown), or the like. Examples of electronic components include inductors, thermistors, capacitors, resistors, and the like, in addition to semiconductor chips.

The electronic component 30 and the substrate 20 are widely applicable to known embodiments. In the example of FIG. 3, in the semiconductor chip 31, the solder balls 24 are connected to the back surface of the substrate 20 via the inner via 23. Further, a ground pattern 22 for electrically connecting to the electromagnetic wave shield layer 1 is formed in the substrate 20. Further, a single or a plurality of electronic elements or the like can be mounted in the electronic component 30.

<Manufacturing method of electronic component mounting board>
Hereinafter, an example of a method for manufacturing an electronic component mounting substrate will be described with reference to FIGS. 5 to 8. However, the method for manufacturing the electronic component mounting substrate of the present invention is not limited to the following manufacturing method.

The method of manufacturing the electronic component mounting substrate includes [a] a step of mounting the electronic component 30 on the substrate 20, [b] a step of mounting the electromagnetic wave shield sheet 2 on the substrate 20 on which the electronic component 30 is mounted, and [ c] A step of joining the electromagnetic wave shield sheet 2 by thermal pressure bonding so as to follow at least a part of the side surface of the stepped portion formed by mounting the electronic component 30 and the exposed surface of the substrate 20, and [d] the releasable cushion. A step of peeling off the member 3 and a step of separating the [e] electric plate 51 into individual pieces are provided. Hereinafter, each step will be described.

[A] Step of mounting electronic components on a substrate:
First, the electronic component 30 is mounted on the substrate 20. For example, a semiconductor chip (not shown) is mounted on the substrate 20, and the substrate 20 on which the semiconductor chip is formed is molded with a sealing resin so as to reach the inside of the substrate 20 from above between the electronic components 30. , The mold resin and the substrate 20 are half-cut by dicing or the like. A method of arranging the electronic components 30 in an array on the substrate 20 which has been half-cut in advance may also be used. Through these steps, for example, a substrate 20 on which the electronic component 30 as shown in FIG. 5 is mounted is obtained. In the example of FIG. 5, the electronic component 30 refers to an integral body obtained by molding a semiconductor chip, and refers to all electronic elements protected by an insulator. The half cut includes a mode of reaching the inside of the substrate 20 and a mode of cutting to the surface of the substrate 20. Further, the entire substrate 20 may be cut at this stage. In this case, it is preferable to place the substrate 20 on the substrate with the adhesive tape so that the position shift does not occur. The material of the sealing resin for molding is not particularly limited, but a thermosetting resin is usually used. The method for forming the sealing resin is not particularly limited, and examples thereof include printing, laminating, transfer molding, compression, and casting. Molding is optional, and the mounting method of the electronic component 30 can be arbitrarily changed.

[B] Step of placing the electromagnetic wave shielding laminate on the substrate:
Next, an electromagnetic wave shielding laminate 4 is prepared, which melts and covers the substrate 20 on which the electronic component 30 is mounted by thermocompression bonding (see FIG. 4). The electromagnetic wave shield laminate 4 is a laminate of a releasable cushion member 3 and an electromagnetic wave shield sheet 2. The releasable cushion member 4 is a sheet that functions as a cushion material that promotes the followability of the electromagnetic wave shield layer 1 to the electronic component 30.

As the releasable cushion member 3, polyethylene, polypropylene, polyether sulfone, polyphenylene sulfide, polystyrene, polymethylpentene, polybutylene terephthalate, cyclic olefin polymer, and silicone are preferable. Among these, polypropylene, polymethylpentene, polybutylene terephthalate, and silicone are more preferable from the viewpoint of achieving both embedding property and peelability. The releasable cushion member may be used in a single layer or in multiple layers. In the case of multiple layers, the same or different types of sheets can be laminated.

The method of laminating the releasable cushion member 3 and the electromagnetic wave shield sheet 2 is not particularly limited, and examples thereof include a method of laminating these sheets. Since the releasable cushion member 3 is finally peeled off, a material having excellent releasability is preferable. The thickness of the releasable cushion member is, for example, about 50 μm to 3 mm, more preferably about 100 μm to 1 mm.

In the electromagnetic wave shielding laminate 4, the electromagnetic wave shielding laminate 4 is placed on the top surface of the electronic component 30 so that the electromagnetic wave shielding sheet 2 is on the electronic component 30 side. Depending on the manufacturing equipment, the size of the substrate 20, and the like, a plurality of electromagnetic wave shielding laminates 4 may be used for each region of the substrate 20. Further, the electromagnetic wave shielding laminate 4 may be used for each of the electronic components 30. From the viewpoint of simplifying the manufacturing process, it is preferable to use one electromagnetic wave shielding laminate 4 for the entire plurality of electronic components 30 mounted on the substrate 20.

[C] Step of forming an electromagnetic wave shield layer:
Subsequently, the electromagnetic wave shielding laminate 4 is sandwiched between the pair of press substrates 40 on the substrate 20 on which the electronic component 30 is mounted, and thermocompression bonded (see FIG. 6). In the electromagnetic wave shielding laminate 4, the electromagnetic wave shielding sheet 2 and the releasable cushion member 3 are melted by heat and stretched along a half-cut groove provided on the manufacturing substrate by pressing, and are formed on the electronic component 30 and the substrate 20. Followed and covered. The electromagnetic wave shield sheet 2 is bonded to the electronic component 30 and the substrate 20 and functions as the electromagnetic wave shield layer 1 by thermocompression bonding. After thermocompression bonding, a separate heat treatment can be performed for the purpose of promoting thermosetting.

When the electromagnetic wave shielding laminate 4 is thermocompression-bonded, a heat-softening member, cushion paper, or the like may be used between the electromagnetic wave shielding laminate 4 and the press substrate 40, if necessary.

The temperature and pressure of the thermocompression bonding step can be arbitrarily set independently within a range in which the coverage of the electromagnetic wave shielding sheet 2 can be ensured, depending on the heat resistance and durability of the electronic component 30, the manufacturing equipment, or the needs. The pressure range is not limited, but is preferably about 0.1 to 15 MPa, more preferably 0.5 to 10 MPa. By releasing the press substrate 40, a manufacturing substrate as shown in FIG. 7 can be obtained. In this way, the electromagnetic wave shield layer 1 covers the top surface and side surface of the electronic component and the exposed surface of the substrate.

The heating temperature in the thermocompression bonding step is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and even more preferably 100 ° C. or higher. The upper limit value depends on the heat resistance of the electronic component 30, but is preferably 220 ° C., more preferably 200 ° C., and even more preferably 180 ° C.

The thermocompression bonding time can be set according to the heat resistance of the electronic component 30, the binder resin used for the electromagnetic wave shield layer 1, the production process, and the like. When a thermosetting resin is used as the binder resin precursor, the range of about 1 minute to 2 hours is preferable. The thermocompression bonding time is more preferably about 1 minute to 1 hour. The thermosetting resin is cured by this thermocompression bonding. However, the thermosetting resin may be partially cured or substantially cured before thermocompression bonding as long as it can flow.

The thickness of the electromagnetic wave shield sheet 2 is such that the top surface and side surfaces of the electronic component 30 and the exposed surface of the substrate 20 can be covered to form the electromagnetic wave shield layer 1. Although it may vary depending on the fluidity of the thermosetting resin precursor used and the distance and size between the electronic components 30, it is usually preferably about 10 to 200 μm, more preferably about 15 to 100 μm, still more preferably about 20 to 70 μm. .. As a result, the electromagnetic wave shielding property can be effectively exhibited while improving the covering property on the sealing resin.

The releasable cushion member 3 has a function of softening to promote coating of the electromagnetic wave shield sheet 2 and covering the top surface and side surface of the electronic component 30 and the exposed surface of the substrate 20, and is excellent in releasability in the peeling process. Materials can be used. A heat-softening member that functions as a cushioning material may be used as an upper layer of the releasable cushion member 3, if necessary. By covering the electromagnetic wave shield layer 1, the ground pattern 22 formed in the substrate 20 and the electromagnetic wave shield layer 1 are electrically connected (see FIG. 7).

[D] Step of peeling off the releasable cushion member:
The releasable cushion member 3 coated on the upper layer of the electromagnetic wave shield layer 1 is peeled off. As a result, an electronic component mounting substrate 51 having an electromagnetic wave shield layer 1 that covers the electronic component 30 is obtained (see FIGS. 1 and 2). For example, the releasable cushion member 3 may be peeled off manually from the end portion, or the outer surface of the releasable cushion member 3 may be sucked and peeled off from the electromagnetic wave shield layer 1. Peeling by suction is preferable from the viewpoint of improving the yield by automation.

[E] Step of individualizing:
Using a cutting tool such as a dicing blade, dicing is performed in the X and Y directions at positions corresponding to the individual product areas of the electronic component mounting substrate 51 (see FIG. 2). Through these steps, the electronic component 30 is covered with the electromagnetic wave shield layer 1, and the ground pattern 22 formed on the substrate 20 and the electromagnetic wave shield layer 1 are electrically connected to each other. 51 is obtained. The dicing method is not particularly limited as long as it can be separated into individual pieces. Dicing is performed from the substrate 20 side or the electromagnetic wave shielding laminate 4 side. During dicing, high-pressure water washing may be performed to cool the frictional heat and wash away the dicing debris generated by the dicing. However, in the electronic component mounting substrate 51, the electromagnetic wave shield layer 1 has sufficient hardness before PCT. Because it has, it is difficult to peel off.

[Modification example]
The electronic component mounting substrate according to the modified example is different from the above-described embodiment in which the electromagnetic wave shield layer is composed of a laminated body of the electromagnetic wave shield layer and the insulating coating layer, but is different from the above-described embodiment in which the electromagnetic wave shield layer is a single layer. The configuration and manufacturing method are the same as those in the first embodiment. The insulating coating layer is located between the electronic component mounting substrate and the electromagnetic wave shielding layer, and has a role of protecting the electronic components.

The substrate in the modified example is a substrate on which a plurality of electronic components (for example, a semiconductor package) are formed, which has not been individualized or has been individualized. In this case, the electronic component mounting substrate can take GND from the upper surface of the electromagnetic wave shield layer. Instead of this method, a ground pattern is provided on the substrate, and in order to make the ground pattern and the electromagnetic wave shield layer conductive, an insulating coating layer is removed on the ground pattern, and a conductive connector portion that conducts with the electromagnetic wave shield layer. May be provided.

The insulating coating layer is a layer formed from a resin composition containing a thermosetting resin. Examples and preferred examples of the thermosetting resin include the thermosetting resin of the electromagnetic wave shield sheet.

The insulating coating layer should contain a colorant, a silane coupling agent, an ion collector, an antioxidant, a tackifier resin, a plasticizer, an ultraviolet absorber, a leveling adjuster, a flame retardant, an inorganic filler, etc., if necessary. Can be done.

According to the electronic component mounting substrate according to the modified example, by laminating the electromagnetic wave shield layer on the insulating coating layer 9c, it is possible to prevent a short circuit between the conductor portion such as a circuit or electrode pattern other than the ground pattern and the electromagnetic wave shield layer, and to obtain electrons. The joint reliability between the component and the electromagnetic wave shield layer can be improved. In addition, the insulation reliability of electronic components can be improved. Therefore, it is possible to provide an electronic component mounting substrate having excellent durability. Further, since the shield layer can be formed on the entire substrate at once, the manufacturing process is simple, and there is an advantage that the thickness can be remarkably reduced as compared with a shield can or the like.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The following "parts" and "%" are values based on "parts by mass" and "% by mass", respectively.

(Preparation of test board)
A substrate was prepared in which 5 × 5 electronic components (1 cm × 1 cm) molded and sealed were mounted in an array on a substrate made of glass epoxy. As shown in FIG. 9, the thickness of the substrate is 0.3 mm, and the mold encapsulation thickness, that is, the height from the upper surface of the substrate to the top surface of the mold encapsulant (part height) is 0.7 mm. Then, half dicing was performed along the groove, which is a gap between the parts, to obtain a test substrate. The half-cut groove depth was 0.8 mm (the cut groove depth of the substrate 20 was 0.1 mm), and the half-cut groove width was 200 μm.

The materials used in the examples are shown below.
-Thermosetting resin Thermosetting resin 1 (polyurethane resin): manufactured by Toyochem Co., Ltd., acid value = 10 mgK OH / g, amine value = 0.1 mgK OH / g
Thermosetting resin 2 (polycarbonate resin): manufactured by Toyochem Co., Ltd., acid value = 10 mgKOH / g, amine value = 0.1 mgKOH / g
-Curing agent Hardener 1 (epoxy resin): Bisphenol A type epoxy resin "j ER828" manufactured by Mitsubishi Chemical Co., Ltd. (epoxy equivalent = 189 g / eq)
Hardener 2 (epoxy resin): Mitsubishi Chemical Corporation's bisphenol F type epoxy resin "j ER806H" (epoxy equivalent = 175 g / eq)
Hardener 3: Nippon Shokubai "Chemitite PZ-33" (epoxy equivalent = 144 g / eq)
-Conductive filler Conductive filler 1: (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., scaly silver powder, average particle size D ₅₀ = 11.0 μm),
Conductive filler 2: (manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd., dendrite-like silver-coated copper powder, average grain diameter D ₅₀ = 4.2 μm)
Conductive filler 3: (manufactured by Fukuda Metal Mining Co., Ltd., acanthite-coated copper powder, average particle size D ₅₀ , 7.5 μm)
-Colorant Black pigment 1: Carbon black "MA100R" manufactured by Mitsubishi Chemical Corporation (arithmetic mean particle size = 24 nm)
Black pigment 2: Carbon black "RCF / SB270" manufactured by Asahi Carbon Co., Ltd. (arithmetic mean particle size = 40 nm)
White pigment 1: Titanium oxide manufactured by Ishihara Sangyo Co., Ltd. (rutile type crystal structure silica and alumina surface treatment, arithmetic mean particle size = 0.25 μm, oil absorption 30 (ml / 100 g))

[Example 1]
(Making an electromagnetic wave shield sheet)
100 parts of binder resin 2 as a thermosetting resin, 303 parts of conductive filler 1, 60.6 parts of conductive filler 2 are charged in a container, 55 parts of curing agent 1 and 0.5 parts of curing agent 3 are charged as a curing agent. In addition, toluene was added so that the non-volatile content concentration became 32%. After stirring with a disper for 10 minutes, the peelable sheet is coated with a doctor blade so that the drying thickness becomes 30 μm, and dried in an electric oven at 120 ° C. for 2 minutes to obtain a conductive layer (a). It was.

100 parts of the thermosetting resin 2, 55 parts of the conductive filler 1 and 55 parts of the black pigment 1 were placed in a container, and toluene was added so that the non-volatile content concentration became 27%. After adding 60 parts of the curing agent 1 and 0.5 part of the curing agent 3 as the curing agent and stirring with a disper for 10 minutes, the peelable sheet is coated with a doctor blade so that the dry thickness becomes 8 μm. , The conductive layer (b) was obtained by drying in an electric oven at 120 ° C. for 2 minutes. Then, an electromagnetic wave shield layer sheet was obtained by laminating the surfaces of the conductive layer (a) and the conductive layer (b) to which the peelable sheet was not attached.

(Manufacturing of laminated body for electromagnetic wave shield)
After that, the releasable cushion member 3 is prepared, the releasable sheet on the conductive layer (b) side is peeled off, and the surface thereof and the releasable cushion member 3 are laminated to laminate the electromagnetic wave shield according to the first embodiment. Obtained body 4. As the releasable cushion member 3, a layer structure (thickness 150 μm, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) in which both sides of a CR1040 soft resin layer were sandwiched between polymethylpentene was used.

(Manufacturing of electronic component mounting board)
Next, the electromagnetic wave shielding laminate 4 is cut into a size of 10 × 10 cm, the releasable sheet on the conductive layer (a) side is peeled off, and then the electromagnetic wave shielding laminate 4 is laminated on the test substrate (see FIG. 9). The body 4 was placed so as to be in contact with the conductive layer (a) side, and temporarily attached. Then, thermocompression bonding was performed from above the electromagnetic wave shielding laminate against the substrate surface under the conditions of 10 MPa and 180 ° C. for 5 minutes. After thermocompression bonding, the releasable cushion member 3 was peeled off and heat-cured at 180 ° C. for 2 hours to prepare an electronic component mounting substrate according to Example 1 in which the electromagnetic wave shield layer 1 was covered.

[Examples 2 to 11 and Comparative Examples 1 to 3]
The same conductive layer (a) as in Example 1 was used. For the conductive layer (b), an electromagnetic wave shield sheet was prepared by performing the same as in Example 1 except that the raw materials for forming the conductive layer were changed to the types and blending amounts shown in Table 1, and each electromagnetic wave was further prepared. An electronic component mounting substrate coated with a shield layer was produced.

<L ^* value>
^{The L *} value on the electromagnetic wave shield layer side of the electronic component mounting board was measured by the following method. That is, the measurement was carried out in a constant temperature room at 25 ° C. using a color difference meter CR-400 (manufactured by Konica Minolta). Was L ^* value on average a surface in contact with the substrate of the electromagnetic wave shielding layer 1 opposite L ^* value of the surface obtained by measuring three randomly.

<Laser printability>
The visibility was confirmed by laser printing the electronic component mounting board by the following method. That is, using the UV laser marker MD-U series (manufactured by KEYENCE), the surface of the electromagnetic wave shield layer was irradiated with a laser beam having a wavelength of 355 nm to perform printing. This was judged to be easy to see visually and evaluated according to the following criteria including ^{the L * value.}
⊚: 1 <(L ^* value) ≤ 30, the printed characters can be confirmed more clearly (extremely good)
◯: 30 <(L ^* value) ≤ 40, printed characters can be clearly confirmed (good)
Δ: 40 <(L ^* value) ≤ 50, printed characters can be confirmed (within practical range)
×: 50 <(L ^* value), printed characters are difficult to see depending on the angle (defective)

<Evaluation simplicity>
The resistance value of the obtained electronic component mounting substrate was measured by the following method. That is, based on JIS K 7194, a pin type lead L2103 (manufactured by Hioki Electric Co., Ltd.) was connected to the resistance meter RM3544 (manufactured by Hioki Electric Co., Ltd.), and measurements were taken on the electromagnetic wave shield layer 1 at intervals of 5 mm width. The resistance value of the electromagnetic wave shield layer 1 was measured, and the ease of evaluation was judged based on the following criteria.
⊚: 1 mΩ <(resistance value) ≤ 50 mΩ (extremely good)
◯: 50 mΩ <(resistance value) ≤ 100 mΩ (good)
Δ: 100 mΩ <(resistance value) ≤ 200 mΩ (within practical range)
×: 200 mΩ <(resistance value) (defective)

Table 1 shows the evaluation results of Examples 1 to 11 and Comparative Example 1. In Table 1, unless otherwise specified, the numerical values represent "parts" and the blanks indicate that they are not mixed.

1 Electromagnetic wave shield layer 2 Electromagnetic wave shield sheet 3 Releasable cushion member 4 Electromagnetic wave shield laminate 20 Substrate 21 Electrode 22 Ground pattern 23 Inner via 24 Solder ball 25 Half dicing groove 30 Electronic component 31 Semiconductor chip 32 Mold resin 33 Bonding wire 40 Press board 51, 52 Electronic component mounting board

Claims (5)

It is equipped with a substrate, electronic components, and an electromagnetic wave shield layer.
The electronic component is mounted on the substrate and
The electromagnetic wave shield layer is arranged so as to cover at least a part of the substrate and the electronic component.
The electromagnetic wave shield layer contains a conductive filler and a binder resin, and contains
^{An electronic component mounting substrate having an L *} value of 50 or less on the surface of the electromagnetic wave shield layer opposite to the surface in contact with the electronic component and the substrate. The electronic component mounting substrate according to claim 1, wherein the resistance value of the electronic component of the electromagnetic wave shield layer and the surface opposite to the surface in contact with the substrate is 200 mΩ or less. The electronic component mounting substrate according to claim 1 or 2, wherein the conductive filler has one or more shapes selected from the group consisting of scales, dendrites, and needles. The electromagnetic wave shield layer has a conductive layer (a) and a conductive layer (b).
The conductive layer (a) is arranged at a position where it comes into contact with the substrate and the electronic component.
The conductive layer (a) contains a conductive filler and a binder resin.
The conductive layer (b) contains a conductive filler, a binder resin and a colorant.
The electronic component mounting substrate according to any one of claims 1 to 3. An electronic device on which the electronic component mounting substrate according to any one of claims 1 to 4 is mounted.

Images