JP2002338914A - Adhesive sheet for fixing flexible printed circuit board and method for mounting electronic part on flexible printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an adhesive sheet which facilitates the sticking of a flexible printed circuit board(FPC) to a fixing plate and the peeling of the FPC from the plate, and is prevented from a reduction in adhesiveness even when heated in mounting electronic parts on an FPC. SOLUTION: The adhesive sheet is used for fixing a flexible printed circuit board on a fixing plate in mounting electronic parts on the surface of a flexible printed circuit board. It has a pressure-sensitive adhesive layer having multiple projections formed on the surface. The projections may be in the form of lines, which may be formed by stripe coating. It is desirable that the pressure-sensitive adhesive layer is formed at least on one side of a base material in the form of a sheet or film having a melting point of 290 deg.C or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board (hereinafter sometimes abbreviated as "FPC").
More specifically, the present invention relates to an adhesive sheet useful for fixing an FPC to a fixing plate, and more particularly, to easily attach and detach an FPC to and from a fixing plate, and to have an adhesive property even when heated when mounting an electronic component on the FPC. The present invention relates to an adhesive sheet in which the decrease in the adhesiveness is suppressed or prevented. The present invention also relates to a method for mounting an electronic component on an FPC using the adhesive sheet.

[0002]

2. Description of the Related Art Conventionally, mounting of various electronic components (for example, IC and capacitor) at the time of manufacturing an electronic circuit board has
It can be performed automatically using a mounting machine [for example, Panazard (manufactured by Matsushita Electric Industrial Co., Ltd.) or the like] on a rigid substrate (glass plate, epoxy plate, or the like). In the method,
When the electronic components are mounted, the rigid board is required to have a high positional accuracy. Therefore, the rigid board is usually transported in such a manner that the rigid board is sandwiched by transport rails so as not to move.

On the other hand, in recent years, electronic devices have been reduced in size and weight, and therefore, electronic components have been directly mounted on the surface of a flexible printed wiring board (FPC) (surface mounting).
May be done. In case of FPC, FPC itself (substrate)
Because of its lack of rigidity, it is not fixed firmly even if it is sandwiched between transport rails, resulting in low positional accuracy. Therefore, for example, FIG.
The electronic components are mounted by fixing the FPC to a fixing plate by the method shown in FIG. FIG. 6 is a schematic view showing a typical example of a conventional FPC fixing method. In FIG. 6, 4 is an FPC, 6 is a motherboard (fixing plate), 71 is a guide pin for fixing the motherboard, 72 is a guide pin for positioning the FPC, 8 is a fixing base, and 9 is an adhesive tape. FIG.
In the method indicated by, the FPC 4 is placed on the surface of the motherboard 6 (such as an aluminum plate) with the FPC alignment guide pins 72 aligned with the holes provided in the FPC 4, and the adhesive tape 9 (polyimide film or fluororesin-based Affixing the FPC 4 to the motherboard 6 from about 2 to 4 places from above the FPC 4 using a conventional adhesive tape such as an adhesive tape having a film as a base material and having an adhesive layer formed on one surface thereof, and then fixing the FPC 4 , The motherboard 6
Guide pins for fixing the motherboard to the fixing stand 8 for transportation.
The electronic components are mounted by fixing the 71 in accordance with the perforations provided in the motherboard 6 and sandwiching the 71 with a transport rail.

[0004]

However, in the conventional electronic component mounting process as shown in FIG.
When fixing the FPC to the fixing plate, only two or four ends of the FPC are fixed with adhesive tape, so that the fixing strength of the FPC is low and a gap is generated between the FPC and the fixing plate. Therefore, when mounting electronic components on FPC,
Positional accuracy of C, particularly in the vertical direction, is low. Further, since a thin adhesive tape is stuck to one FPC at several places, it takes a lot of time to attach and detach the FPC, and the workability is low.

In the electronic component mounting process, the FPC is exposed to a very high temperature for a short time to melt the solder. For example, heating by infrared (I
In R heating), there are various heating conditions, but a typical example is a heating condition in which the peak temperature at which the maximum temperature is reached is about 260 ° C. and the holding time of the peak temperature is about 20 seconds. In the case of an adhesive sheet such as an adhesive tape that has undergone a heating step at such a very high temperature, the moisture or the like contained in the adhesive rapidly expands (gasifies) during IR heating, and the like. From adhesive sheet to FPC and / or
Alternatively, the fixing plate may be peeled off.

Accordingly, it is an object of the present invention to easily attach and detach a flexible printed wiring board to and from a fixed plate, to firmly fix the flexible printed wiring board, and to mount electronic components on the flexible printed wiring board. An object of the present invention is to provide an adhesive sheet in which a decrease in adhesiveness is suppressed or prevented even when heated, and a method for mounting an electronic component on a flexible printed wiring board using the adhesive sheet. Another object of the present invention is to mount and remove an FPC with respect to a fixing plate with excellent workability when mounting an electronic component on the FPC, and to mount the electronic component on the FPC with high accuracy. It is an object of the present invention to provide a method of mounting an electronic component on a flexible printed wiring board which can perform the method.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, when an adhesive sheet having a pressure-sensitive adhesive layer surface having a specific uneven portion is used, FPC is required. Is easy to fix to the fixing plate,
It can be firmly fixed, and in a heating step at the time of mounting an electronic component, a gas component vaporized in the pressure-sensitive adhesive layer is released to the outside by using a concave portion of the pressure-sensitive adhesive layer, and the FPC
Can be suppressed or prevented from peeling off from the pressure-sensitive adhesive layer, and completed the present invention.

That is, the present invention relates to an adhesive sheet for fixing a flexible printed wiring board to a fixing plate when mounting an electronic component on the surface of the flexible printed wiring board, wherein the convex portion has a surface. An adhesive sheet for fixing a flexible printed wiring board, the adhesive sheet having a plurality of pressure-sensitive adhesive layers formed thereon.

In the present invention, it is preferable that the convex portion on the surface of the pressure-sensitive adhesive layer is a linear convex portion. Such linear projections may be formed by stripe coating. Further, the pressure-sensitive adhesive layer may be formed on at least one surface of a sheet-like or film-like base material having a melting point of 290 ° C. or more.

According to the present invention, there is provided a method for fixing an electronic component on a surface of the flexible printed wiring board after fixing the flexible printed wiring board to the fixing plate using the adhesive sheet for fixing the flexible printed wiring board. It also includes the component mounting method.

[0011]

Embodiments of the present invention will be described below with reference to the drawings as necessary. FIG. 1 is a sectional view showing an example of the adhesive sheet of the present invention, and FIG. 2 is a sectional view showing another example of the adhesive sheet of the present invention.

In FIG. 1, reference numeral 1 denotes an adhesive sheet for fixing a flexible printed wiring board (hereinafter sometimes referred to as an “adhesive sheet for fixing an FPC” or simply an “adhesive sheet”);
Reference numeral 2 denotes an adhesive layer, 3 denotes a substrate, 2a denotes a convex portion formed on the surface of the adhesive layer 2, and 2b denotes a concave portion formed on the surface of the adhesive layer 2. In the example of FIG. 1, the FPC fixing adhesive sheet 1 has a structure in which a pressure-sensitive adhesive layer 2 is laminated on one surface (one surface) of a base material 3. 2, reference numeral 11 denotes an FPC fixing adhesive sheet, reference numeral 21 denotes an adhesive layer, reference numeral 31 denotes a base material, reference numeral 21a denotes a convex portion formed on the surface of the adhesive layer 21, and reference numeral 21b denotes a surface of the adhesive layer 21. Are formed in the recess. In the example of FIG. 2, the FPC fixing adhesive sheet 11 is
31 has a structure in which an adhesive layer 21 is laminated on both surfaces.

[Adhesive layer] In FIGS. 1 and 2, FPC
In the fixing adhesive sheet (1, 11), the pressure-sensitive adhesive layer (2, 21) is laminated on one or both surfaces of the substrate, and the surface of the pressure-sensitive adhesive layer (2, 21) has convex portions ( 2a, 21a) are formed in plurality. Therefore, concave portions (2b, 21b) corresponding to the convex portions (2a, 21a) are formed on the surface of the pressure-sensitive adhesive layer (2, 21). As shown in FIG. 3, the convex portions (2a, 21a) are linear convex portions, and a linear concave portion (2b, 21b) is formed between the linear convex portions (2a, 21a). Has become. FIG. 3 is a schematic view of the FPC fixing adhesive sheet according to FIGS. 1 and 2 as viewed from above.

As described above, in the adhesive sheet (1, 11) for fixing an FPC of the present invention, a plurality of convex portions (2a, 21a) are formed on the surface of the pressure-sensitive adhesive layer (2, 21). The surface area of the pressure-sensitive adhesive layer (2, 21) is large, and the distance from the bottom of the protrusion (2a, 21a) or a portion away from the top such as the inside of the center to the surface of the pressure-sensitive adhesive layer ( Shortest distance)
However, it is shorter than the case where the convex portions (2a, 21a) are not formed. Therefore, in a heating step for melting solder or the like (particularly, an IR heating step), even if water or the like contained in the adhesive rapidly expands (vaporizes), an uneven portion is formed on the surface of the adhesive layer. As a result, the surface area of the pressure-sensitive adhesive layer is large, and gaseous components vaporized in the pressure-sensitive adhesive layer can be released to the outside using the concave portions of the pressure-sensitive adhesive layer. Can be suppressed or prevented.

Further, as shown in FIG. 3, the convex portions (2a,
When 21a) has a linear shape, the linear convex portion (2
The linear recesses (2b, 21b) between (a, 21a) are formed from one end to the other end, and the recesses are open ends at the ends. Therefore, even if the upper surface of the concave portion of the pressure-sensitive adhesive layer is covered with the FPC, the gas component vaporized in the pressure-sensitive adhesive layer is removed from the portion that is opened by using the linear shape of the concave portion (the entire surface is covered). In this case, the FPC can be released to the outside (from the open end), so that the FPC can be further suppressed or prevented from peeling off from the pressure-sensitive adhesive layer.

Therefore, when the adhesive sheet for fixing an FPC of the present invention is used, even if it is exposed to a high temperature in a heating step (particularly, an IR heating step), a decrease in adhesiveness is suppressed or prevented, and high adhesiveness is maintained. can do. In other words, even after the heating step at which the temperature becomes extremely high, the state where the FPC and / or the fixing plate is adhered to the FPC fixing adhesive sheet is maintained.

Further, when the FPC fixing adhesive sheet is bonded to the fixing plate or the FPC, it is possible to prevent air bubbles from entering the interface between the pressure-sensitive adhesive layer and the fixing plate or the FPC.

Therefore, in the adhesive sheet for fixing an FPC of the present invention, one of the important points is to increase the surface area of the pressure-sensitive adhesive layer. Further, even if the upper surface of the concave portion of the pressure-sensitive adhesive layer is covered with the FPC, the gaseous component vaporized in the pressure-sensitive adhesive layer is discharged from the portion where the concave portion is opened to the outside using the shape of the concave portion of the pressure-sensitive adhesive layer. It is also important to have a shape that can be released to the air. In other words, as the shape of the surface of the pressure-sensitive adhesive layer, the gas component vaporized in the pressure-sensitive adhesive layer is increased from the surface of the pressure-sensitive adhesive layer to the outside by utilizing the increased surface area, and further utilizing the surface shape. The shape is not particularly limited as long as it can be released.

The shape of the convex portion on the surface of the pressure-sensitive adhesive layer is not particularly limited as long as it is at least protruding, and may be, for example, a mountain shape or a linear shape. Is also good. Examples of the mountain-shaped projection include a cone-like shape, a cylinder-like shape, a polygonal pyramid-like shape (for example, a triangular pyramid-like shape, a quadrangular pyramid-like shape, and the like), and a polygonal column-like shape (for example, a triangular prism-like shape, a square prism-like shape). Similar shapes). On the other hand, examples of the linear convex portion include a convex portion in which the mountain-shaped convex portion linearly extends.

The shape of the projection may be substantially polygonal (for example, substantially square, substantially triangular, etc.) or substantially circular (for example, semi-elliptical, semi-circular, etc.). . The convex portion has a diameter (radius, radius,
Side length) may be smaller or larger,
The same diameter may be maintained. Furthermore, the top is
It may be flat, pointed, or rounded.

The diameter of the convex portion is not particularly limited and can be appropriately selected depending on, for example, the size of the FPC. For example, the average diameter or the average length of the side is 0.01 to 10%.
mm, preferably in the range of about 0.05 to 5 mm.

The height of the convex portion is not particularly limited and can be appropriately selected depending on the size of the FPC, the thickness of the pressure-sensitive adhesive layer, and the like.
Preferably, it can be selected from a range of about 0.03 to 0.1 mm.

Further, the distance between the convex portions (width of the concave portions) is not particularly limited and can be appropriately selected according to the size of the FPC, for example, 0.01 to 10 mm, preferably 0.05 to 10 mm. It can be selected from a range of about 5 mm.

Such a convex portion may be formed over the entire surface of the pressure-sensitive adhesive layer, or may be formed at one or more portions on the surface. In the case where the FPC is partially formed, it is preferable that the part includes at least a predetermined part to which the FPC is attached.

Further, the convex portions may be formed in a regular manner, and may be formed in such a form that the entire convex portion is linear.

Of course, the concave portion has a shape corresponding to the convex portion, and is formed at a portion corresponding to the convex portion. That is, the concave portion has a bottom portion formed by the lower adhesive layer, and a wall portion formed by the convex adhesive layer.

As the pressure-sensitive adhesive (pressure-sensitive adhesive) constituting the pressure-sensitive adhesive layer (2, 21), a commonly used or known pressure-sensitive adhesive in an adhesive sheet such as an adhesive tape can be used. In addition to the system-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive in which an additive such as a tackifying resin is blended with an elastomer is exemplified. As the adhesive, acrylic adhesive,
A silicone-based pressure-sensitive adhesive can be suitably used. An acrylic pressure-sensitive adhesive is preferable from the viewpoint of heat resistance and easy peeling of the FPC after mounting. When particularly high heat resistance is required, a silicone-based pressure-sensitive adhesive is preferred. The adhesives can be used alone or in combination of two or more.

The acrylic pressure-sensitive adhesive contains a (meth) acrylic acid alkyl ester-based copolymer containing a (meth) acrylic acid alkyl ester as a main monomer component as a base polymer. More specifically, (meta)
Acrylic polymer comprising a polymer (including a copolymer) of an alkyl acrylate or a copolymer of the alkyl (meth) acrylate and another monoethylenically unsaturated monomer (copolymerizable monomer) Is used as a base polymer, and additives such as a cross-linking agent (such as a cross-linking agent) and a tackifying resin are added to the base polymer as needed.

As the (meth) acrylic acid alkyl ester, generally, an alkyl (meth) acrylate having an alkyl group having about 4 to 14 carbon atoms can be suitably used. Specifically, as the alkyl (meth) acrylate, butyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, and the like are preferable. Used. The alkyl (meth) acrylates can be used alone or in combination of two or more.

These alkyl (meth) acrylates are used as main monomer components. Specifically, in the acrylic polymer, the proportion of the alkyl (meth) acrylate can be selected, for example, from the range of 50% by weight or more (50 to 100% by weight) based on the total amount of the monomer components. The proportion of the alkyl (meth) acrylate is preferably 80% by weight or more, more preferably 90% by weight or more, and particularly preferably 97% by weight or more.
Most preferably, it is not less than% by weight.

As a monomer component in the acrylic polymer, when a functional group-containing copolymerizable monomer copolymerizable with the alkyl (meth) acrylate is used together with the alkyl (meth) acrylate, FPC
And the like, the adhesiveness to an adherend can be improved. Examples of the functional group-containing copolymerizable monomer include, for example, a carboxyl group-containing copolymerizable monomer, a nitrogen atom-containing copolymerizable monomer, a hydroxyl group-containing copolymerizable monomer, an epoxy group-containing copolymerizable monomer, and a mercapto group-containing copolymerizable monomer. And isocyanate group-containing copolymerizable monomers. More specifically, the functional group-containing copolymerizable monomer includes, for example, a carboxyl group-containing copolymerizable monomer such as acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, and fumaric acid; (Meth) acrylamide, N-vinylpyrrolidone, (meth)
Acryloyl morpholine, (meth) acrylonitrile,
Nitrogen atom-containing copolymerizable monomers such as aminoethyl (meth) acrylate, cyclohexylmaleimide, and isopropylmaleimide; hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate A hydroxyl-containing copolymerizable monomer such as glycerin dimethacrylate;
An epoxy group-containing copolymerizable monomer such as glycidyl (meth) acrylate; an isocyanate group-containing copolymerizable monomer such as 2-methacryloyloxyethyl isocyanate is included, and a mercapto group at the terminal of a chain transfer agent is introduced as a functional group. It is also possible. Among these functional group-containing copolymerizable monomers, a carboxyl group-containing monomer is preferred in terms of reactivity and versatility, and acrylic acid and methacrylic acid are more preferred.

The proportion of the functional group-containing copolymerizable monomer is not more than 10% by weight (for example, 0 to
10% by weight), preferably about 3% by weight or less (0 to 3% by weight).

The acrylic polymer may contain other copolymerizable monomers as monomer components, if necessary, in addition to the main monomer and the functional group-containing copolymerizable monomer. Such a copolymerizable monomer has, for example, an alkyl group such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate having 1 carbon atom. To 3 alkyl (meth) acrylates; alkyl (meth) acrylates having 15 to 20 carbon atoms in the alkyl group such as stearyl (meth) acrylate; vinyl esters such as vinyl acetate; styrenes such as styrene Monomers; α-olefin monomers such as ethylene and propylene are included.

In the acrylic polymer, the monomer component other than the alkyl (meth) acrylate as the main monomer component may be selected from a range of less than 50% by weight based on the total amount of the monomer component, but is preferably used. It is desirable to have less than 20% by weight, more preferably less than 10% by weight, especially less than 3% by weight.

In the present invention, a known crosslinking agent such as an isocyanate-based compound or an epoxy-based compound is added as a cross-linking agent in order to improve the holding characteristics of the pressure-sensitive adhesive, or when a photopolymerization is carried out. It is useful to add a polyfunctional (meth) acrylate. The crosslinking agents can be used alone or in combination of two or more. In the crosslinking agent, as the isocyanate-based compound, for example, a polyfunctional isocyanate compound having two or more isocyanate groups, for example, diphenylmethane diisocyanate, 2,4-tolylene diisocyanate,
Aromatic diisocyanates such as 2,6-tolylene diisocyanate, phenylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate and toluylene diisocyanate; hexamethylene diisocyanate, isophorone diisocyanate, 4,4 '
-In addition to aliphatic or cycloaliphatic diisocyanates such as dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate dimers, reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polyethers Polyisocyanate, polyester polyisocyanate and the like can be mentioned. Further, as the epoxy compound, a polyfunctional epoxy compound having two or more epoxy groups, for example, diglycidyl aniline,
Glycerin diglycidyl ether and the like can be mentioned.

Examples of the polyfunctional (meth) acrylate as a cross-linking agent used in the case of performing photopolymerization include, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ethylene glycol diacrylate. (Meth) acrylate,
Examples include 1,6-hexanediol di (meth) acrylate.

The acrylic polymer can be synthesized from a mixture of the above-mentioned monomer components by a general polymerization method, for example, an emulsion polymerization method or a solution polymerization, by general batch polymerization, continuous drop polymerization, divided drop polymerization, or the like. . In the polymerization, a commonly used or known polymerization initiator may be used. In the emulsion polymerization, a commonly used or known emulsifier may be used. The polymerization temperature is, for example, 3
The range is from 0 to 80 ° C.

When particularly high heat resistance (high heat resistance) is required as the pressure-sensitive adhesive, a polymer obtained by irradiation with ultraviolet rays is preferable. In addition, various known additives such as tackifiers, plasticizers, softeners, fillers, colorants (eg, pigments and dyes), antioxidants, antioxidants, and the like may be added to the adhesive as optional components. Can be added. Examples of the tackifying resin include petroleum resins such as aliphatic petroleum resins, aromatic petroleum resins, and alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins (alicyclic saturated hydrocarbon resins); , Hydrogenated rosin esters, etc.), terpene resins (terpene resins,
Aromatic modified terpene resins, hydrogenated terpene resins, terpene phenol resins, etc.), styrene resins, and cumarone indene resins.

The pressure-sensitive adhesive layer (2, 21) can be formed by applying the pressure-sensitive adhesive to at least one surface of a substrate.

The thickness of the pressure-sensitive adhesive layer (2, 21) (the average thickness or the thickness from the lowermost portion to the upper surface of the convex portion) is not particularly limited, and is selected, for example, from a range of about 10 to 200 μm. And preferably about 20 to 100 μm.

In FIGS. 1 and 2, the pressure-sensitive adhesive layer (2, 2
1) is formed by linear irregularities, and the bottom of the recess is an adhesive layer, but the adhesive layer is not formed at the bottom of the recess, for example, the bottom of the recess is a base material. Even
The same effect as the present invention can be exerted. Specifically, the pressure-sensitive adhesive layer has a shape in which the cross section is mountain-shaped, that is, as shown in FIG. 4, a pressure-sensitive adhesive layer having a mountain-shaped cross section is formed on the base material. The same effect can be exerted even if the cross section is formed as a protrusion by the mountain-shaped pressure-sensitive adhesive layer. FIG. 4 is a sectional view showing still another example of the adhesive sheet of the present invention. In FIG. 4, 12 is an adhesive sheet, 22 is an adhesive layer, 32 is a base material,
The pressure-sensitive adhesive layer 22 is partially formed on both surfaces of the base material 32 so that the cross section thereof has a mountain shape.

[Substrate] In the adhesive sheet (1, 11),
The substrate (3, 31) is not particularly limited, and includes, for example, cellophane, polytetrafluoroethylene, polyethylene,
Plastic film made of plastic such as polyester such as polyethylene terephthalate; natural rubber,
A rubber sheet made of butyl rubber or the like; a foam made of polyurethane, polychloroprene rubber or the like (a sheet-shaped foam or the like); a metal foil such as an aluminum foil or a copper foil may be used; A porous substrate made of a substance can be suitably used.

In the electronic component mounting process, the FPC is usually exposed to a very high temperature for a short time to melt the solder. For example, heating by infrared (I
In R heating), there are various heating conditions, but a typical example is a heating condition in which the peak temperature at which the maximum temperature is reached is about 260 ° C. and the holding time of the peak temperature is about 20 seconds. In the case of an adhesive sheet such as an adhesive tape that has undergone a heating step at such a very high temperature, the moisture or the like contained in the adhesive rapidly expands (gasifies) during IR heating, and the like. From adhesive sheet to FPC and / or
Alternatively, the fixing plate may be peeled off. However, when a porous base material is used as the base material of the adhesive sheet for fixing an FPC, even if the porous base material is exposed to a high temperature in a heating step (particularly, an IR heating step), a decrease in adhesion is further suppressed or prevented. Adhesiveness can be maintained. In other words, even after a heating step of a very high temperature, the state in which the FPC and / or the fixing plate is adhered to the adhesive sheet is more stably maintained. More specifically, in a heating step such as melting solder, even when moisture or the like contained in the adhesive rapidly expands (vaporizes), a convex portion having a specific shape is formed on the surface of the adhesive layer. Is formed, and, furthermore, when the substrate is a porous substrate, the gas component vaporized in the pressure-sensitive adhesive layer is passed not only through the concave portions of the pressure-sensitive adhesive layer but also through the porous substrate,
It can be released to the outside, and it is possible to further suppress or prevent the FPC from peeling off from the pressure-sensitive adhesive layer. Therefore, even after the heating step, the FPC is not displaced, and the electronic component can be mounted on the FPC with high positional accuracy. That is, when a porous substrate is used as the substrate, the positional accuracy of mounting the electronic component on the FPC can be further improved.

As such a porous substrate, if it is a porous substrate, in addition to various characteristics such as the shape of the pore, its diameter (average cell diameter) and density, the material of the substrate is particularly Not restricted. As a porous substrate, in the adhesive layer,
In order to discharge the vaporized gas component to the outside, it is preferable to have a form of open cells. That is, when the porous substrate has the form of open cells, gas components (such as water vapor) vaporized in the pressure-sensitive adhesive layer can be released to the outside from the open end of the porous substrate.

In the present invention, examples of the porous substrate, especially a porous substrate made of a fibrous substance, include porous paper materials (for example, kraft paper, crepe paper, Japanese paper, clay-coated paper, woodfree paper, glassine). Paper, clupak paper, etc.),
Porous cloth material (for example, aramid fiber, rayon fiber, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, fluorine fiber, stainless fiber, asbestos, glass cloth, glass fiber, manila hemp, pulp, etc. Nonwoven fabrics and woven fabrics of natural fibers). In the porous substrate made of a fibrous substance, the fibrous substance may be used alone or in combination of two or more. Further, the porous substrates can be used alone or in combination of two or more.

In the present invention, as the porous substrate, Japanese paper or nonwoven fabric is preferable from the viewpoints of anchoring properties of the adhesive, permeability of gas components such as water vapor, heat resistance, and the like. As the porous substrate, aramid fibers can be suitably used from the viewpoint of heat resistance. In addition, Japanese paper and clay-coated paper
Since it is inexpensive and has heat resistance, it is useful as a porous substrate.

In the present invention, it is preferable that the porous substrate (porous substrate) is made of only a fibrous substance (fiber component) without adding a substance such as a binder. In particular, a porous substrate that is neutral or almost neutral and contains rayon fibers as a fiber component is preferable.
As such a porous substrate containing rayon fibers, those having a high content ratio of rayon fibers are preferable,
The content ratio of the rayon fiber can be selected, for example, from a range of 30% by weight or more, preferably 50% by weight or more based on all fiber components.

The thickness of the substrate (particularly, the porous substrate) is not particularly limited and can be appropriately selected depending on the application.
For example, 25 to 200 μm (preferably 50 to 150 μm)
m).

When paper or non-woven fabric is used as the porous substrate, its basis weight is not particularly limited.
It may be about 1 to 300 g / m ² .

[Adhesive Sheet] The adhesive sheet (1, 1) of the present invention
11) is that, for example, an adhesive composition containing an adhesive (pressure-sensitive adhesive) such as an acrylic adhesive is formed on at least one surface (one or both surfaces) of the substrate 3 (or 31), The adhesive layer 2 (or 21) having a convex portion is coated on the base material 3 (or 31) by applying such that a cross-linking treatment is performed by heating or the like, or polymerizing by irradiating ultraviolet rays, if necessary. ) On at least one surface. Furthermore, if necessary, a release liner may be coated on the pressure-sensitive adhesive layer. Therefore, the adhesive sheet (pressure-sensitive adhesive sheet) of the present invention may be a double-sided adhesive sheet having a pressure-sensitive adhesive layer on both sides of a substrate (double-sided adhesive sheet with a substrate), or having a pressure-sensitive adhesive layer on one side of a substrate. Single-sided adhesive sheet (single-sided adhesive sheet with base material)
It may be.

When a linear convex portion is formed on the surface of the pressure-sensitive adhesive layer, a method of applying the pressure-sensitive adhesive composition by stripe coating is preferable. Also, after forming the pressure-sensitive adhesive layer, by performing surface processing so that the surface becomes a convex portion, the pressure-sensitive adhesive layer having a convex portion on the surface can be formed.

The adhesive sheet of the present invention is preferably a double-sided adhesive sheet. In the case of a double-sided adhesive sheet, the adhesives (adhesives) in each of the adhesive layers laminated on both sides of the base material may be different adhesives or may be the same adhesive.

The adhesive sheet of the present invention is, for example, as shown in FIG. 5, FPC (Flexible Printed Wiring Board)
Can be suitably used as an adhesive sheet for fixing to a fixing plate by adhesion. FIG. 5 is a schematic view showing a state in which an FPC is attached to a fixing plate using the adhesive sheet of the present invention, and FIG.
(B) is the figure seen from the side. In FIG. 5, 4 is F
PC, 5 is a double-sided adhesive sheet with a base material, 51 is an adhesive layer of the double-sided adhesive sheet 5, 6 is a fixing plate, 71 is a guide pin for fixing a motherboard, 72 is a guide pin for positioning an FPC, 71a
Is a hole for inserting the guide pin 71 for fixing the motherboard, 72a
Is a perforation for inserting the guide pin 72 for positioning the FPC, and 8 is a fixed base for conveyance. In FIG. 5, the double-sided adhesive sheet 5 is attached to the entire surface or almost the entire surface of one side of the fixing plate 6.
PC4 is pasted. More specifically, the double-sided adhesive sheet 5 is adhered to one surface of the fixing plate 6, and a predetermined portion on the other adhesive layer 51 of the double-sided adhesive sheet 5 is
After the FPC 4 is attached and fixed using the FPC alignment guide pin 72 and the perforation 72a, the motherboard fixing guide pin 71 and the perforation are attached to the fixing plate 6 to which the FPC 4 is attached, on the fixing stand 8 for transportation. It is fixed using 71a. The perforations 71a for passing the guide pins 71 for fixing the motherboard and the perforations 72a for passing the guide pins 72 for aligning the FPC are formed by, for example, punching after the double-sided adhesive sheet 5 is attached to the fixing plate 6. can do.

The fixing plate 6 is a plate that is hard and can maintain flatness, for example, an aluminum plate, a glass plate,
A plate made of epoxy resin can be used,
The material, shape, and the like are not limited at all, and can be appropriately selected according to a mounting device (particularly, an automatic mounting device) of the electronic component on the FPC. Further, the guide pins (71, 72), the fixing stand 8 for conveyance, and the like are not particularly limited, and can be appropriately selected according to a device for mounting electronic components on the FPC (particularly, an automatic mounting device).

In FIG. 5, the double-sided adhesive sheet 5 with a base material as shown in FIG. 2 is provided between the fixing plate 6 and the FPC 4, and the fixing plate 6 and the FPC 4 are adhered. That is, the fixing plate 6 and the FPC 4 are bonded via the double-sided adhesive sheet 5. In particular, in FIG. 5, the double-sided adhesive sheet 5 with the base material as the adhesive sheet for fixing the FPC is the fixing plate 6.
Is fixed to the entire surface of one side of the
May be affixed only to a predetermined portion (for example, a portion where the FPC is installed and its peripheral portion) on one surface.

Further, in the present invention, the adhesive sheet may be a single-sided adhesive sheet (adhesive tape) with a base as shown in FIG. 1, and in this case, the adhesive tape may be applied at several places (from above the FPC). FPC can be fixed to the fixing plate by sticking. Or,
The surface on the base material side of the single-sided adhesive sheet with a base material (adhesive tape) is attached to the entire surface or a predetermined portion of the fixing plate using an adhesive, and a fixing plate having an adhesive layer of the adhesive tape on the surface, An FPC can be attached and fixed to the surface of the pressure-sensitive adhesive layer.

In the present invention, after the electronic component is mounted on the FPC, the FPC on which the electronic component is mounted is peeled from the adhesive sheet or the pressure-sensitive adhesive layer. The force is 7 N / 20 mm or less (for example, 0.5 to 7 N / 20 mm), and more preferably 1 to
It is desirable to be 6 N / 20 mm. When the FPC fixing adhesive sheet of the present invention is a double-sided adhesive sheet,
The adhesive force between the adhesive sheet and the fixing plate is F
It can be selected from the same range as the adhesive strength with the PC. In the present invention, the adhesive strength of the adhesive sheet can be adjusted by appropriately selecting the type of the pressure-sensitive adhesive and the additives and the mixing ratio thereof.

The adhesive sheet of the present invention can be used alone for bonding various articles. In particular, the adhesive sheet is bonded to an FPC (flexible printed wiring board) or its reinforcing plate, and punched into an appropriate shape as required. It can be particularly preferably used as an adhesive sheet (adhesive tape or the like) for the intended use.
In particular, when used as an adhesive sheet for fixing an FPC, it is necessary to go through a heating step as described above. However, the adhesive sheet of the present invention adheres to a gas component such as water vapor generated even after the heating step. Utilizing recesses on the surface of the agent layer (for example,
And when the substrate is a porous substrate, it can be released through the porous substrate and out of the system, so that the adhesion is hardly or not reduced at all, and the FPC is applied to a predetermined portion. Can be kept fixed. Moreover, after mounting the electronic component on the FPC, the FPC can be easily peeled off from the adhesive sheet.

When a double-sided adhesive sheet with a base material (particularly, a double-sided adhesive sheet with a base material made of a porous substrate) is used,
Since the entire surface of the PC can be fixed to the fixing plate by sticking, the PC can be fixed firmly. In addition, as described above, even after a heating step (such as an IR heating step), the adhesiveness (adhesiveness) of the pressure-sensitive adhesive layer by the pressure-sensitive adhesive hardly or not at all decreases. Absent. Therefore, it is possible to mount the electronic component on the FPC with high positional accuracy. That is, F of the electronic component
The positional accuracy of mounting on a PC can be significantly improved.

Further, when the adhesive sheet is a double-sided adhesive sheet with a base material, the adhesive sheet is stuck on a fixing plate, and the FPC is placed on the adhesive layer of the adhesive sheet provided on the fixing plate. It can be fixed by sticking, there is no need to stick adhesive tape as before,
Workability can be greatly improved, processing can be performed quickly, and manufacturing costs can be reduced.

Of course, the FPC can be easily removed from the fixing plate, and the workability of removing the FPC from the fixing plate can be greatly improved.

Therefore, the adhesive sheet of the present invention is extremely useful as an FPC fixing adhesive sheet.

The electronic components mounted on the FPC are not particularly limited. For example, an IC, a capacitor, a connector, a resistor, an LED (Light Emitting Diode; Light Em)
Itting Diode).

[0064]

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In the following, “parts” means “parts by weight”.

Example 1 An acrylic rubber (trade name “Leocoat R5000” manufactured by Toray Cotex) was dissolved in toluene to prepare a solution having a base polymer content of 15% by weight. To 100 parts of this solution, 5 parts of an isocyanate-based crosslinking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.) was added and mixed to prepare a pressure-sensitive adhesive composition. After applying the pressure-sensitive adhesive composition to both surfaces of a porous substrate (trade name “Nomex” manufactured by DuPont) using an aramid fiber as a porous substrate using an applicator to which a 2 mm pitch spacer is attached, After drying in a hot air dryer at 130 ° C. for 5 minutes to form a 50 μm thick pressure-sensitive adhesive layer (pressure-sensitive adhesive layer), a double-sided adhesive sheet with a porous substrate (tape thickness: 150 μm) ) Was prepared. In the double-sided adhesive sheet with a base material, an adhesive is stripe-coated, and an adhesive layer having a linear convex portion on the surface is formed.

Then, one side of the double-sided adhesive sheet was bonded to an aluminum plate to prepare a fixing plate having an adhesive layer having a linear convex portion on the surface.

Example 2 A pressure-sensitive adhesive composition was prepared by mixing and stirring 2.0 parts of benzoyl peroxide and toluene with 100 parts of a silicone polymer (“SH4280” manufactured by Dow Corning Toray Silicone Co., Ltd.). Was prepared. The adhesive composition was applied to both sides of a polyimide film substrate (non-porous substrate) using an applicator to which a 2 mm pitch spacer was attached, and then heated in a hot air drier at 170 ° C.
For 5 minutes to form a pressure-sensitive adhesive layer (pressure-sensitive adhesive layer) having a thickness of 50 μm, thereby producing a double-sided adhesive sheet with a substrate (tape thickness: 150 μm). In the double-sided adhesive sheet with a base material, an adhesive is stripe-coated, and an adhesive layer having a linear convex portion on the surface is formed.

Then, one surface of the double-sided adhesive sheet was bonded to an aluminum plate to prepare a fixing plate having a pressure-sensitive adhesive layer having linear convex portions on the surface.

Example 3 100 parts of 2-ethylhexyl acrylate, 2 parts of acrylic acid in 210 parts of toluene, 0.2 part of benzoyl peroxide and 0.01 part of trimethylolpropane triacrylate (crosslinking agent) Under a nitrogen atmosphere and a solution polymerization treatment with stirring at 60 to 80 ° C. to give a viscosity of about 120 poise and a conversion of 99.
A pressure-sensitive adhesive solution (pressure-sensitive adhesive solution) having a concentration of 2% and a solid content of 30.0% by weight was prepared, and 100 parts of this solution was mixed with 5 parts of an isocyanate-based cross-linking agent (trade name "Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.). The mixture was added and mixed to prepare a pressure-sensitive adhesive composition. The adhesive composition was applied to both sides of a polyimide film substrate (non-porous substrate) using an applicator to which a 2 mm pitch spacer was attached, and then dried at 130 ° C. for 5 minutes in a hot air drier. Then, an adhesive layer (pressure-sensitive adhesive layer) having a thickness of 50 μm was formed, and a double-sided adhesive sheet with a base material (tape thickness: 150 μm) was produced. In the double-sided adhesive sheet with a base material, an adhesive is stripe-coated, and an adhesive layer having a linear convex portion on the surface is formed.

Then, one side of the double-sided adhesive sheet was bonded to an aluminum plate to prepare a fixed plate having an adhesive layer having linear convex portions on the surface.

Comparative Example 1 An aluminum plate was used as a fixing plate. That is, the fixing plate according to Comparative Example 1 is made of only an aluminum plate, and has no pressure-sensitive adhesive layer on the surface as in Examples 1 to 3.

Comparative Example 2 2.0 parts of benzoyl peroxide and toluene were mixed with 100 parts of a silicone polymer (trade name “SH4280” manufactured by Dow Corning Toray Silicone Co., Ltd.) and stirred to form an adhesive composition. Was prepared. The pressure-sensitive adhesive composition is applied to both sides of a polyimide film substrate (non-porous substrate) and then dried in a hot air drier at 170 ° C. for 5 minutes to form a 50 μm-thick pressure-sensitive adhesive layer (pressure-sensitive layer). An adhesive layer was formed to prepare a double-sided adhesive sheet with a substrate (tape thickness: 150 μm). In the double-sided adhesive sheet with the base material, the pressure-sensitive adhesive is not stripe-coated, and a pressure-sensitive adhesive layer having a flat surface is formed.

Then, one side of the double-sided adhesive sheet was bonded to an aluminum plate to prepare a fixed plate having a flat pressure-sensitive adhesive layer on the surface.

(Evaluation) Examples 1 to 3 and Comparative Example 1
2, the time required for fixing the FPC, the gap between the FPC and the fixed plate when the FPC was bonded to the fixed plate, the time required for removing the FPC, IR
The presence or absence of swelling / peeling upon heating was measured by the following method to evaluate the workability and the fixed state of the FPC.

(Time Required for Fixing FPC)
As for the fixing plates according to Comparative Example 3 and Comparative Example 2, as shown in FIG. 5, after six FPCs were respectively aligned with respect to one fixing plate having an adhesive layer on the surface, the fixing was performed. The FPC was fixed to a fixing plate by placing it on the pressure-sensitive adhesive layer formed on the surface of the plate and pressing it by hand to adhere. On the other hand, as for the fixing plate according to Comparative Example 1, as shown in FIG.
After alignment, place on the fixing plate and set one FP
An adhesive tape (an adhesive tape in which a silicone-based adhesive was applied to one surface of a substrate made of polyimide) was attached to four corners of C, and the FPC was fixed to a fixing plate. The time (second) required for fixing the FPC to the fixing plate was measured. The evaluation results are shown in the column of "Time required for FPC fixing" in Table 1.

(Gap Between FPC and Fixed Plate) With respect to the fixed plate to which the FPC was fixed in the measurement of the time required for fixing the FPC, the gap (m
m) is measured, and the FPC when the FPC is bonded to the fixing plate is measured.
The gap (mm) between the PC and the fixing plate was examined. The evaluation results are shown in the column of "gap between FPC and fixed plate" in Table 1.

(Time Required for Removing FPC)
After measuring the gap between the PC and the fixing plate, the electronic component is mounted on the FPC, and after the mounting is completed, the FPC on which the electronic component is mounted.
Was removed with tweezers. In the fixing plate according to Comparative Example 1, the adhesive tape attached to the four corners of the FPC was peeled off, and then the FPC on which the electronic components were mounted was removed with tweezers. The time (second) required for removing the FPC from the fixing plate was measured. Table 1 shows the evaluation results.
In the column "Time required for FPC removal".

(Existence of swelling / peeling upon IR heating)
Further, after measuring the gap between the FPC and the fixing plate, IR heating is performed, and after IR heating, the presence or absence of swelling / peeling between the aluminum plate and the adhesive layer is visually observed. The swelling / peeling-prevention property of each was evaluated. The results of the evaluation are shown in Table 1 in the column "Presence of swelling / peeling during IR heating".

[0079]

[Table 1]

As can be seen from Table 1, in the fixing plates of Examples 1 to 3 in which the pressure-sensitive adhesive layer having a linear convex portion on the surface is formed, the time required for attachment and the time required for removal are extremely short. Excellent workability. Further, there is almost no gap between the FPC and the fixing plate, and the FPC is firmly adhered to the fixing plate, so that the FPC does not shift. In addition, even when IR heating is performed, no swelling or peeling occurs between the aluminum plate and the adhesive layer, and the aluminum plate and the pressure-sensitive adhesive layer remain firmly fixed, preventing swelling and peeling during IR heating. Have. Therefore, the electronic component can be mounted on the flexible printed wiring board with high accuracy.

[0081]

According to the adhesive sheet of the present invention, since the surface of the pressure-sensitive adhesive layer has a convex portion, the FP can be easily formed.
C can be attached, and at the time of IR heating, FPC
Alternatively, the electronic component can be mounted with high precision without peeling off from the fixed plate.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of an adhesive sheet of the present invention.

FIG. 2 is a sectional view showing another example of the adhesive sheet of the present invention.

FIG. 3 is a schematic view of the FPC fixing adhesive sheet according to FIGS. 1 and 2 as viewed from above.

FIG. 4 is a sectional view showing still another example of the adhesive sheet of the present invention.

FIG. 5 is a schematic view showing a state in which an FPC is stuck to a fixing plate using the adhesive sheet of the present invention, wherein FIG. 5 (a) is a view from above, and FIG. 5 (b) is a view from the side. FIG.

FIG. 6 is a schematic view showing a typical example of a conventional fixing method of an FPC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adhesive sheet for fixing a flexible printed wiring board 2 Adhesive layer 2a Convex part 2b Concave part 3 Porous base material 11 Adhesive sheet for fixing a flexible printed wiring board 21 Adhesive layer 21a Convex part 21b Concave part 31 Porous base material 4 Flexible printed wiring Board 5 Double-sided adhesive sheet 51 Adhesive layer of double-sided adhesive sheet 5 6 Fixing plate (motherboard) 71 Guide pin for fixing motherboard 72 Guide pin for positioning FPC 71a Perforation for inserting guide pin 71 for fixing motherboard 72a Guide for positioning FPC Hole 72 for insertion of pin 72 8 Fixing table for conveyance 9 Adhesive tape 12 Adhesive sheet 22 Adhesive layer 32 Substrate

Continued on the front page (72) Inventor Kazumasa Tanaka 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Takeshi Sano 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko (72) Inventor Hiroshi Yamamoto 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4J004 AA05 AA10 AA11 AA13 AA14 AB01 AB05 AB06 AB07 CA02 CA04 CA05 CA06 CA08 CB01 CB04 CC05 CE01 EA05 EA06 FA05 FA08 4J040 DF041 DF051 EF281 EK031 GA05 GA07 GA11 GA19 GA20 GA22 GA24 HC16 JB02 KA16 LA06 LA08 MA02 MA09 MA10 MA11 MA12 MB03 MB11 NA20 PA23 PA30 5E313 AA02 AA12 CC05 DD12 DD13 FF14

Claims (5)

[Claims] 1. An adhesive sheet for fixing a flexible printed wiring board to a fixing plate when mounting an electronic component on the surface of the flexible printed wiring board, wherein a plurality of convex portions are formed on the surface. An adhesive sheet for fixing a flexible printed wiring board, comprising an adhesive layer. 2. The adhesive sheet for fixing a flexible printed wiring board according to claim 1, wherein the projections on the surface of the pressure-sensitive adhesive layer are linear projections. 3. The adhesive sheet for fixing a flexible printed wiring board according to claim 2, wherein the linear projections are formed by stripe coating. 4. The flexible printed wiring board fixing device according to claim 1, wherein the pressure-sensitive adhesive layer is formed on at least one surface of a sheet-like or film-like base material having a melting point of 290 ° C. or higher. Adhesive sheet. 5. After fixing the flexible printed wiring board to the fixing board by the flexible printed wiring board fixing adhesive sheet according to claim 1, an electronic component is provided on the surface of the flexible printed wiring board. How to mount electronic components on a flexible printed wiring board that mounts.