JP2011029460A - Printed wiring board, connection structure of the same, and method of manufacturing the printed wiring board and the connection structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board, connection structure of the printed wiring board, and the like capable of easily obtaining fully high connection strength by electrically connecting a flying lead of one printed wiring board to conductor wiring (substrate pad) of the other printed wiring board. <P>SOLUTION: The printed wiring board 10 is a printed wiring board including a plurality of conductors 15 positioned on a base material 11, and includes a projection K projecting from the base material 11 among the conductors. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a printed wiring board, a printed wiring board connection structure, and a manufacturing method thereof, more specifically, suitable when one of the wiring boards is connected to a flying lead in an electronic device or the like. The present invention relates to a printed wiring board, a printed wiring board connection structure, and a printed wiring board and a manufacturing method of the printed wiring board connection structure.

  In electronic devices, a structure in which conductor wirings on two printed wiring boards are electrically connected is often used. In some types of electronic equipment, the flexible printed wiring board may be placed along the front, side, and back of mechanical parts in the electronic equipment. Often the front and back are reversed. For this reason, in order to increase the flexibility of parts in production, in the field of use where the front and back surfaces are reversed at both ends as described above, the insulating base material is excluded from the conductor wiring at the connection part of the flexible printed wiring board. Thus, a bare conductor wiring called a flying lead is formed. Since the flying lead is connected facing the other conductor wiring on the front side or the back side, it is not necessary to prepare a flexible printed wiring board for each number of times of folding and for each folding form. Such connection between the flying lead and the conductor of the mating printed wiring board is performed by ultrasonic bonding in particular (Patent Document 1). As a result, a connection structure having a large bonding strength can be easily obtained.

JP 2007-173362 A

However, if the amount of information processed by electronic equipment increases rapidly and the fine pitch of the conductors on the printed wiring board progresses, ultrasonic bonding cannot eliminate the possibility of short-circuiting, and a connection method that supports fine pitch Development is underway. For this reason, a method has been studied in which an anisotropic conductive film (ACF: Anisotropic Conductive Film) is used to connect the flying lead to a substrate pad of a printed wiring board to easily make an electrical connection. This method of electrically connecting the flying leads using the ACF can easily cope with the fine pitch of the conductor, but has a drawback that the connection strength is not sufficiently strong.
The present invention provides a printed wiring board, a printed wiring board, and a printed wiring board that can easily obtain sufficiently high connection strength while electrically connecting a flying lead of one printed wiring board and a conductor wiring (board pad) of the other printed wiring board. It is an object of the present invention to provide a wiring board connection structure and a manufacturing method thereof.

The printed wiring board connection structure of the present invention includes a first printed wiring board having a plurality of conductors positioned on a substrate, a second printed wiring board having a plurality of flying leads, and a first printed wiring board. And an anisotropic conductive adhesive for connecting the second printed wiring board and the flying lead of the second printed wiring board. The first printed wiring board includes protrusions that are located between the plurality of conductors and protrude from the base material, and the anisotropic conductive adhesive is disposed on both sides between the connected (conductor / flying leads). It is characterized in that it accumulates on the base material while covering the side part of (conductor / flying lead) and occupies a part together with the protruding part.
Here, the anisotropic conductive adhesive is referred to as ACF (Anisotropic Conductive Film) unless otherwise specified, even if it does not have a film form because it is solidified after melting or semi-melting.

When connecting the flying lead of the second printed wiring board and the conductor of the counterpart first printed wiring board by ACF, in order from the bottom (conductor of the first printed wiring board / ACF / second printed wiring) A release film is applied onto the laminate of the board's flying leads), and is thermocompression bonded by pressing with a thermocompression tool from above the release film. The thermocompression bonding is cured by heating to a high temperature, for example, 200 ° C., through a temperature at which the ACF is brought into a molten or semi-molten state. In order to prevent adhesion between the thermocompression bonding tool and the ACF, a thick resin film having a high releasability such as a fluororesin is usually used for the release film. Moreover, since a silicon rubber sheet is also excellent in releasability, it is often used along with a fluororesin. The ACF in a molten or semi-molten state electrically connects the conductor and the flying lead, and accumulates (partially occupies) in the space between the connected (conductor / flying lead), (conductor / flying lead) Stick to reach the top of the side of the.
At the time of thermocompression bonding, the release film tends to soften and be pushed between the flying leads, and the fluidized ACF will be pushed from above. If there is no protrusion, the ACF will be pushed, A large amount is pushed out from between the conductors of the printed wiring board. The space between the conductors opens upward and also laterally, and the ACF is pushed out from the lateral opening. As a result, if there is no projecting portion, the amount of ACF that accumulates between the (conductor / flying lead) and greatly contributes to the connection between the conductor and the flying lead is insufficient, resulting in insufficient connection strength. . As described above, when the protruding portion is provided between the conductors of the first printed wiring board, the release film is reduced to the extent that it is pushed between the conductors by a thermocompression bonding tool, and even if it is pushed to some extent, the protruding object Acts as a flow resistance of the ACF, so that the outflow of the ACF between the conductors is suppressed, and the degree of occupation of the ACF (conductor / flying lead) can be increased. As a result, the connection strength of both of the conductors of the first printed wiring board and the flying leads of the second printed wiring board can be sufficiently increased.
Here, “the ACF partially occupies the connected (conductor / flying lead) together with the protruding portion” means that the ACF in a molten or semi-molten state is between the (conductor / flying lead) during thermocompression bonding. In the space, the protrusion is located so as to wrap around or buried, or when the protrusion is located at the end between the conductors, it is dammed up by the protrusion, collected in the space between them, and cooled and solidified as it is ( A coexistence state of ACF and protrusion). In the usual case, the ACF reaches the upper part of the side surface of the flying lead beyond the height of the conductor.

  The printed wiring board of the present invention includes an insulating base material, a plurality of conductors positioned on the base material, and a protruding portion that protrudes from the base material between the conductors.

  Said printed wiring board respond | corresponds to the 1st printed wiring board of the other party of the printed wiring board (2nd printed wiring board) with a flying lead. Accordingly, the degree of occupation of the ACF in the space between the (conductor / flying lead) is increased while being electrically connected to the flying lead of the printed wiring board having the flying lead by thermocompression bonding using the ACF. be able to. As a result, the connection strength of both printed wiring boards can be increased.

  In the printed wiring board or the printed wiring board connection structure, the protruding portion can be disposed at the end between the conductors so as to dam the anisotropic conductive material. Thus, even if the ACF is about to be pushed out from between the conductors to some extent, the weir-like protrusions prevent the outflow between the conductors. Accordingly, a sufficiently high connection strength can be obtained by increasing the degree of partial occupancy by the ACF.

  The protruding portion can be divided into a plurality of portions between the conductors or can be one continuous long portion. Thereby, the pressing of the release film between the conductors during thermocompression bonding can be suppressed, and the outflow of ACF can be suppressed.

  The width of the protruding portion can be made wider than ½ of the interval between the conductors. As a result, the outflow of fluid ACF can be effectively blocked. Moreover, the pushing of the release film can be more effectively suppressed.

  The height from the base material of a protrusion part can be made higher than 1/2 of the height of a conductor. Thereby, even in the factor of the height (thickness) in the protrusion, it is possible to effectively dam the outflow of the fluid ACF, and to prevent the release film from being pushed in at an early stage.

  The method for manufacturing a printed wiring board connection structure according to the present invention includes a step of preparing a first printed wiring board in which a plurality of conductors are positioned on a base material, and anisotropic conductive adhesion on the first printed wiring board. A step of disposing an agent film, a step of disposing a second printed wiring board having a flying lead on the anisotropic conductive adhesive film, and aligning the flying lead with a conductor of the first printed wiring board; And a step of thermocompression-bonding a release film interposed between the second printed wiring board and the thermocompression-bonding tool and applying pressure with the thermocompression-bonding tool. In the first printed wiring board preparation step, a first printed wiring board having a protruding portion protruding from the base material is prepared between conductors.

At the time of the above-mentioned thermocompression bonding, in order from the bottom, the laminate of (first printed wiring board conductor / ACF / second printed wiring board flying lead / release film / thermocompression bonding tool (pressing tool)) is pressure. Receive. The thermocompression bonding tool is heated by a built-in heater or the like. When the thermocompression bonding tool presses the release film, the ACF is heated by heat conduction or the like, and is heated to a higher temperature and cured through a molten or semi-molten state. That is, ACF contains a thermosetting resin as a main component and passes through a molten or semi-molten state in a transient temperature range up to the curing temperature. Pressing in the molten or semi-molten state is essential to develop conductivity in the conductor / flying lead. For the release film, in order to prevent adhesion between the thermocompression bonding tool and the ACF, a resin having a high release property such as a fluororesin can be used.
During this thermocompression bonding, the thick release film is heated and softened and tends to be pushed between the flying leads, and the molten or semi-molten ACF is pushed from above. Without the above protrusion, the ACF is pushed into the release film, and is easily pushed out of the side opening along the conductor / flying lead to the outside along the conductor / flying lead. As a result, if there is no protrusion as described above, the amount of ACF that occupies the space between (conductor / flying lead) is insufficient, resulting in insufficient connection strength. With the above-described protrusion, the level of the amount of ACF that reaches the upper part of the side surface of the (conductor / flying lead) and accumulates between the side surfaces can be increased.
As described above, when the protruding portion is provided between the conductors of the first printed wiring board, the release film is reduced to the extent that it is pushed between the conductors by a thermocompression bonding tool, and even if it is pushed to some extent, the protruding object Acts as a flow resistance of ACF, so that outflow between the conductors of ACF is suppressed. As a result, the connection strength can be made sufficiently high while making electrical connection between the conductor of the first printed wiring board and the flying lead of the second printed wiring board.

  The manufacturing method of the printed wiring board of this invention manufactures a printed wiring board provided with the some conductor located on a base material. This manufacturing method includes a step of forming a pattern of a plurality of conductors on a base material, and a step of forming a protruding portion that protrudes from the base material between the plurality of conductors. Is formed by any one of a lithography method, a screen printing method, and a bonding method.

  By the above method, the protrusion can be provided on the printed wiring board easily and inexpensively.

  According to the printed wiring board and the printed wiring board connection structure of the present invention, the flying lead of one printed wiring board and the conductor wiring (board pad) of the other printed wiring board are sufficiently connected while being electrically connected. High connection strength can be easily obtained.

It is a figure which shows the printed wiring board in Embodiment 1 of this invention. It is a figure which shows the state which match | combined the flying lead of the 2nd printed wiring board with the conductor of the printed wiring board of FIG. It is a figure which shows the process of thermocompression bonding. The connection structure of the printed wiring board in Embodiment 1 of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the IVB-IVB line. It is a figure for demonstrating the size requirements which a projection part should satisfy. It is a figure which shows the cross-sectional shape of a projection part. The printed wiring board in the modification of Embodiment 1 of this invention is shown, (a) is a perspective view, (b) is a figure which shows the positional relationship of a projection part and a thermocompression-bonding tool. It is a figure which shows the printed wiring board in Embodiment 2 of this invention. It is a figure which shows the printed wiring board in the modification of Embodiment 2 of this invention.

(Embodiment 1)
FIG. 1 is a diagram illustrating an example of a printed wiring board 10 according to Embodiment 1 of the present invention. The printed wiring board 10 corresponds to a first printed wiring board connected to a second printed wiring board having flying leads, which will be described later. For example, a conductor wiring (hereinafter referred to as a conductor) 15 in which a copper foil is attached and patterned by etching on an insulating base material 11 is arranged in parallel at a predetermined interval. The exposed conductor 15 arranged on the insulating base material 11 in the printed wiring board 10 is a part for connection and may be called a board pad. This embodiment is characterized in that, on the substrate 11 in the space D ₁ of the between the conductors 15, the projecting portion K is provided, moreover the position of the projection K is in a point located at both ends of the board pads. As will be described later, the protrusions K located at both ends of the space between the conductors 15 serve as a weir and can be called a weir-like protrusion. This weir-shaped protrusion K can dam the ACF that is about to flow out under pressure during thermocompression bonding in the ACF connection between the flying lead (not shown) of the second printed wiring board and the conductor 15. Yes (see FIG. 4). For this reason, in thermocompression bonding, a sufficient amount of molten or semi-molten ACF is accumulated in the space between one (conductor / flying lead) and the next (conductor / flying lead) to obtain a connection strength. Improvement can be obtained.

2 and 3 are diagrams for explaining a method of connecting the conductor 15 of the first printed wiring board 10 and the flying lead 25 of the second printed wiring board 20. As shown in FIG. 2, the flying lead 25 is disposed so as to match the conductor 15 of the first printed wiring board 10 in plan view. Space D ₂ of the width between the flying lead 25, i.e. the distance of the flying leads, are aligned to the spacing between the conductors 15. At both ends of the space D ₁ of the between the conductors 15 of the first printed wiring board 10, the protruding portion K of the dam-shaped is located.
In the second printed wiring board 20, the flying lead 25, which is a conductor wiring, has one end extending from the insulating base material 21 and the other end entering the insulating base material 21. Between one end and the other end is bare. As shown in FIG. 2, the flying lead 25 may have a configuration in which the other end side is terminated in a bare state even when the wiring is formed by entering the insulating base 21 on both ends. The flying lead regions may be divided into a plurality of locations, and the regions may be arranged side by side or arranged in a staggered manner (in the case of three or more regions).

As shown in FIG. 3, the ACF 33 is arranged between the conductor 15 and the flying lead 25 so as to cross over all the parallel conductors 15. Therefore, the ACF 33 exhibits conductivity only between the flying lead 25 and the conductor 15 to which pressure is applied, and does not develop conductivity in the ACF located between (conductor 15 / flying lead 25). . The thermocompression bonding conditions are preferably a temperature of 100 ° C. to 300 ° C., a holding time of 5 seconds to 45 seconds, a pressure of 1 MPa to 9 MPa, for example, a temperature of 200 ° C., a holding time of 15 seconds, and a pressure of 3 MPa. This temperature is the temperature of ACF33. For this reason, about the above-mentioned thermocompression bonding conditions, the temperature of the thermocompression bonding tool incorporating the heater is set to a higher temperature so that the temperature of the ACF 33 becomes 200 ° C. The holding time is a time for pressing with the pressure by the pressing tool 41.
Further, when the ACF 33 is disposed on the first printed wiring board 10, it can be temporarily attached at 80 ° C. for about 2 seconds for temporary attachment.
As described above, the ACF 33 contains a thermosetting resin as a main component and passes through a molten or semi-molten state in a transient temperature range up to the curing temperature. Pressure is applied to the molten or semi-molten state to thin the conductor 15 / flying lead 25 portion so that the conductive particles are conducted inside the ACF 33.
For the pressure load, it is preferable to use a pressing tool (thermocompression bonding tool) 41 having a width dimension that fits in the length range in which the flying lead 25 is exposed. Between the pressing tool 41 and the flying tool 25, In order to prevent the ACF from sticking to the pressing tool 41, a release film 35 is preferably interposed. The release film 35 is desirably formed of a material that is difficult to stick to the adhesive resin of the ACF 33. At the time of thermocompression bonding, the pressing tool 41, the first and second printed wiring boards 10, 20 and the like of the thermocompression bonding apparatus shown in FIG. 3 are arranged in the air atmosphere. The ACF 33 is softened by heat conduction from the pusher 41 and flows due to pressure caused by the pushing of the release film 35.
The problem here is that the release film 35 is softened due to an increase in temperature. Therefore, the release film 35 is pushed by the pusher 41 and becomes a space D ₂ between the flying leads 25 and further a space D ₁ between the conductors 15. In many cases, it will go in. In FIG. 3, the dotted line indicates the position of pressure application for the thermocompression bonding of the pusher 41. The release film 35 pushed between the flying leads 25 applies pressure to the ACF 33 located immediately below. As a result, if there is nothing between the conductors 15, the ACF 33 flows under pressure and flows out from the side openings between the conductors 15. However, in the embodiment of the present invention, since the weir-shaped protrusions K are provided at both ends of the space between the conductors 15, the ACF 33 that is about to flow out under pressure is blocked. As a result, the ACF accumulates in the space D between the (conductor 15 / flying lead 25) and fills (partially occupies) the upper portion of the side surface of the conductor 15 / flying lead 25, thereby contributing to an improvement in connection strength. . Since the ACF 33 adheres to the side surface of the (conductor 15 / flying lead 25) in the molten or semi-molten state, it does not exhibit a flat surface in the space D (see FIG. 4) between the (conductor 15 / flying lead 25), It exhibits a surface shape peculiar to viscous fluid that hangs down from the side to the middle. If the amount of accumulation of ACF 33 is large, this sag is not steep. If the drooping is steep, the coating thickness on the side surface of (conductor 15 / flying lead 25) becomes thin, and the connection strength becomes low. There is almost no sag from the side surfaces on both sides, and the closer to flatness in the space D, the higher the connection strength. It is preferable that the ACF 33 accumulates in the space D so that the height of the center of drooping from the side surfaces on both sides (that is, the drooping bottom) is equal to or higher than the interface of (conductor 15 / flying lead 25). . It is important that the ACF 33 is slightly higher than the interface on the side surface or does not steeply sag on the side surface even if the ACF 33 exceeds the interface. It goes without saying that the drooping bottom may be somewhat lower than the interface.
For the release film 35 used in the above-described thermocompression bonding, it is preferable to use a fluorine-based resin such as PTFE (Polytetrafluoroethylene) which is difficult to adhere to the adhesive resin. In order to fulfill the function as a release film, the thickness is preferably 10 μm to 300 μm, for example, 50 μm. Moreover, when using a silicon rubber sheet, it is good to make the thickness into the range of 100 micrometers-250 micrometers, for example, it is desirable to set it as 200 micrometers.

4 shows a printed wiring board connection structure 50 formed through the thermocompression bonding process of FIGS. 2 and 3, FIG. 4 (a) is a plan view, and FIG. 4 (b) is an IVB-IVB line. FIG. In FIG. 4A, a weft-like protrusion K provided on the substrate 11 of the first printed wiring board 10 causes the ACF 33 to flow out through the space between (conductor 15 / flying lead 25). Is damming up. For this reason, the ACF 33 can fill up to a predetermined level in the space D (= D ₁ + D ₂ ) between the conductor 15 and the flying lead 25), and can occupy the space together with the protrusions K to a high level. That is, the sagging does not become steep, and the thickness of the coating on the side surface can be increased. As a result, the ACF 33 is located between the first printed wiring board 10 and the second printed wiring board 20, and conductively connects the conductor 15 and the flying lead 25, and the first printed wiring board. The connection strength between 10 and the second printed wiring board 20 is sufficiently high.
As shown in FIG. 4B, the ACF 33 partially occupies the space D between the (conductor 15 / flying lead 25) (along with the protrusion K as shown in FIG. 4A). The ACF 33 reaches the upper part of the side surface of the conductive connection (conductor 15 / flying lead 25), and exhibits a surface shape that accumulates along the side surface (hangs down) between the side surfaces (space D). The more ACFs that partially occupy between the side surfaces, the stronger the connection between the conductor 15 and the flying lead 25. In FIG. 4 (b), the ACF 33 that is interposed between the conductor 15 and the flying lead 25 and conductively connects the two is not shown. However, since it is as thin as about 1 μm, it is naturally omitted because it is omitted. The ACF 33 that is conductively connected by bonding is disposed. The ACF 33 that partially occupies the space D should not exhibit electrical conductivity.

The first and second printed wiring boards 10 and 20 are preferably flexible printed wiring boards (FPC), but may be other types of printed wiring boards. In the case of a flexible printed wiring board, the insulating base materials 11 and 21 can use, for example, a resin having versatility for a printed wiring board, such as polyimide and polyester. In addition, it is particularly preferable to have high heat resistance in addition to flexibility, and as such a resin, for example, a polyamide-based resin or a polyimide-based resin such as polyimide or polyamideimide is preferable. used.
As a material for forming the protruding portion K of the first printed wiring board 10, it is preferable to use an insulating resin such as a polyimide resin, an epoxy resin, or an acrylic resin. The protrusion K can be provided by using a lithography method, a screen printing method, a bonding method, or the like. The first printed wiring board 10 does not have to be reinforced, but when reinforced, it is preferable to reinforce from the back surface. When reinforcing from the back side, a glass epoxy plate, a polyimide plate, a polyethylene terephthalate (PET) plate, a stainless plate, or the like having an appropriate thickness is preferably bonded.

  The conductor 15 or the flying lead 25 can be formed by etching and processing a metal foil such as a copper foil by a conventional method. The conductor 15 can also be formed by plating by a semi-additive method. The thickness of the conductor 15 is preferably in the range of 10 μm to 30 μm, for example, 18 μm. The thickness of the flying lead 25 is preferably in the range of 10 μm to 25 μm, for example 20 μm.

  ACF33 is an anisotropic conductive adhesive having anisotropic conductivity containing conductive particles (not shown), and includes an epoxy resin, a high molecular weight epoxy resin phenoxy resin, a curing agent, and conductive particles as essential components. It is a thermosetting adhesive. As the ACF 33, for example, an epoxy resin and a phenoxy resin that are insulating thermosetting resins as main components and conductive particles such as nickel, copper, silver, and gold dispersed therein can be used. By using an epoxy resin, it becomes possible to improve the film formability, heat resistance, and adhesive strength of ACF33. The thickness of the ACF 33 is preferably in the range of 30 μm to 45 μm, for example 35 μm.

  Examples of the epoxy resin contained in the ACF 33 include bisphenol A type, F type, S type, AD type, or a copolymer type epoxy resin of bisphenol A type and bisphenol F type, naphthalene type epoxy resin, and novolak type. An epoxy resin, a biphenyl type epoxy resin, a dicyclopentadiene type epoxy resin, or the like can be used. Moreover, ACF33 should just contain at least 1 sort (s) among the above-mentioned epoxy resins.

  The molecular weight of the epoxy resin and the phenoxy resin can be appropriately selected in consideration of the performance required for the ACF 33. For example, when a high molecular weight epoxy resin is used, the film forming property is high, the melt viscosity of the resin at the connection temperature can be increased, and there is an effect that the connection can be made without disturbing the orientation of the conductive particles described later. On the other hand, when a low molecular weight epoxy resin is used, the effect of increasing the crosslink density and improving the heat resistance is obtained. Moreover, the effect of reacting with the above-mentioned hardening | curing agent rapidly at the time of a heating, and improving adhesive performance is acquired. Therefore, it is preferable to use a combination of a high molecular weight epoxy resin having a molecular weight of 15000 or more and a low molecular weight epoxy resin having a molecular weight of 2000 or less in order to balance the performance. In addition, the compounding quantity of a high molecular weight epoxy resin and a low molecular weight epoxy resin can be selected suitably. In addition, the “average molecular weight” herein means a weight molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) developed with THF.

  Moreover, ACF33 contains a latent curing agent as a curing agent, and a high adhesive force can be obtained by containing a curing agent for promoting the curing of the epoxy resin. A latent curing agent is a curing agent that is excellent in storage stability at low temperatures and hardly undergoes a curing reaction at room temperature, but rapidly undergoes a curing reaction by heat, light, or the like. Examples of such latent curing agents include imidazole, hydrazide, boron trifluoride-amine complexes, amine imides, polyamines, tertiary amines, alkyl ureas and other amines, dicyandiamides, acid anhydrides, Phenol-based compounds and modified products thereof are exemplified, and these can be used alone or as a mixture of two or more.

  Among these latent curing agents, an imidazole-based latent curing agent is preferably used from the viewpoint of excellent storage stability at a low temperature and rapid effect. As the imidazole-based latent curing agent, a known imidazole-based latent curing agent can be used. More specifically, an adduct of an imidazole compound with an epoxy resin is exemplified. Examples of the imidazole compound include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-dodecylimidazole, 2-finylimidazole, 2-finyl-4-methylimidazole, and 4-methylimidazole.

  In particular, these latent curing agents coated with a polymer material such as polyurethane and polyester, a metal thin film such as nickel and copper, and an inorganic material such as calcium silicate, This is preferable because it is possible to achieve both contradictory properties of storage stability and fast curability. Therefore, a microcapsule type imidazole-based latent curing agent is particularly preferable.

  Conductive particles are dispersed in the ACF, and the conductive particles include a large number of fine metal particles (for example, metal particles made of spherical metal particles or spherical resin particles plated with metal) in a linear form. It is formed of a metal powder having a connected shape or a needle shape, a shape having a large so-called aspect ratio. In the present embodiment, the proportion of conductive particles in ACF 33 is preferably 0.0001% by volume or more and 0.2% by volume or less.

FIG. 5 is a diagram for explaining the size and the like of the protrusion K. In the printed wiring board 10, the protrusion K is located on the base material 11 between the conductors 15. The height K _h of the protrusion K is preferably higher than ½ of the thickness t ₁ of the conductor 15, and is preferably smaller than the sum of the thickness t _{1 of} the conductor and the thickness t _{2 of the} flying lead. _{That, (t} 1/2) <height _K h of the protrusion _{<(t 1 + t 2)} , it is preferable to. Further, the width Kw of the protrusion K is preferably larger than ½ of the interval g between the conductors 15 and, naturally, is smaller than the interval g. That is, it is preferable that (g / 2) <projection width K _w <g.
Depending on the size, the dam-like protrusion K can dam the ACF about to flow out and can remain in the space D in a sufficient amount. As a result, the ACF 33 reaches the upper part of the side surface of the (conductor 15 / flying lead 25), and the connection strength between the two printed wiring boards can be ensured. At this time, the conductivity is developed only between the conductor 15 and the flying lead 25, and the conductivity is not developed in other places.
FIG. 6 is a diagram showing a cross-sectional shape of the protrusion K in the first printed wiring board 10. As shown in FIG. 6, the cross section of the protrusion K may be rectangular, kamaboko, semicircular, or anything.
The size and shape of the protrusions K in FIGS. 5 and 6 are not limited to the present embodiment (weir-like protrusions), and the protrusions for suppressing the pressing by the release film 35 pusher, which will be described later. The same applies to the case of K (Embodiment 2).

(Modification of Embodiment 1)
FIG. 7 is a diagram showing a printed wiring board 10 which is a modification of the first embodiment of the present invention and is one embodiment of the present invention. FIG. 7A shows the first printed wiring board 10 having the protrusions K. FIG. 7B is a cross-sectional view taken along the line VIIB-VIIB in FIG. 7A, showing the positional relationship between the protrusion K and the pressing tool 41 (ACF and the second printed wiring board are omitted). ). Naturally, the pressing tool 41 extends along the longitudinal direction so as to be orthogonal to the parallel direction across the plurality of parallel conductors 15 and the flying leads (not shown). 7A and 7B, the protrusions K are arranged directly below both ends of the width Pw of the pusher 41, and exert a force against the pusher 41 indirectly from below. That is, when the pressing tool 41 pushes the release film 35 into the space D ₁ between the conductors 15, a reaction force can be exerted on the pressing tool 41 through the release film 35. As a result, the drag (pressure) change at the time of pressing can be detected together with the stroke of the pressing tool 41, and further unnecessary strokes of the pressing tool can be stopped.

In the printed wiring board 10 shown in FIG. 1, for providing a projection K at both ends of the space D _1, the width Pw of the pusher 41, had taken a positional relationship sandwiched with a margin into two projections K. For this reason, the reaction force as described above could not be detected. The distance between the two protrusions K in space D _1, by within the width Pw of the pusher 41, it is possible to stop the pushing of the release film 35 at an appropriate stage.

(Embodiment 2)
FIG. 8 is a diagram showing the printed wiring board 10 according to the second embodiment of the present invention. In the present embodiment, the protrusion K is provided on the base material 11 in the space between the conductors 15, but is not limited to both ends of the space between the conductors 15 as in the first embodiment, and is provided at the center of the space. Is also provided. The protrusion K having such a configuration can block the release film 35 pushed into the space between the adjacent conductors 15 by the pressing tool 41 during thermocompression bonding (see FIG. 3). The reason why the ACF 33 flows out often is that the release film 35 is pushed between the adjacent conductors 15, and the release film 35 often causes the ACF 33 located in the space between the conductors 15 to flow out. By providing the protrusions K at both ends and the middle position in the space D ₁ between the conductors 15, it is possible to prevent the release film 35 from being pushed into the space D ₁ .

(Modification of Embodiment 2)
FIG. 9 shows a printed wiring board 10 according to a modification of the second embodiment of the present invention, which is one embodiment of the present invention. In the printed wiring board 10 of FIG. 9, a long continuous projection K is provided in the space D ₁ between the conductors 15. Such, by a long protrusion K in succession, the push to release film 33 in the space D _1, it is possible to prevent. Longer continuous protrusions K can more reliably prevent the release film from being pushed in.

  Although the embodiments of the present invention have been described above, the embodiments of the present invention disclosed above are merely examples, and the scope of the present invention is not limited to these embodiments. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the printed wiring board and the printed wiring board connection structure of the present invention, the flying lead of one printed wiring board and the conductor wiring (board pad) of the other printed wiring board are sufficiently connected while being electrically connected. High connection strength can be easily obtained, and it is possible to cope with high density of the substrate pads.

10 (first) printed wiring board, 11 substrate, 15 conductor (wiring), 20 (second) printed wiring board, 21 substrate, 25 flying lead, 33 ACF, 35 release film, 41 pressing tool, 50 Printed wiring board connection structure, space between D (conductor / flying lead), space between D ₁ conductor, space between D ₂ flying leads, g spacing between conductors, height of K protrusion, K _h protrusion is, _{K w} protrusion width, _{P w} pusher width, _{t 1} conductors of thickness, _{t 2} flying leads thickness.

Claims (12)

A first printed wiring board having a plurality of conductors located on the substrate;
A second printed wiring board having a plurality of flying leads;
An anisotropic conductive adhesive for connecting the conductor of the first printed wiring board and the flying lead of the second printed wiring board;
The first printed wiring board includes a protruding portion that is positioned between the plurality of conductors and protrudes from the base material,
The anisotropic conductive adhesive accumulates on the base material while covering the sides of the (conductor / flying lead) on both sides between the connected (conductor / flying lead), A printed wiring board connection structure characterized in that the printed wiring board is partially occupied together with a protruding portion.   2. The printed wiring board connection structure according to claim 1, wherein the protruding portion is located at an end between the conductors so as to dam the anisotropic conductive adhesive. 3.   2. The printed wiring board connection structure according to claim 1, wherein the protruding portion includes a plurality of divided portions or a continuous long portion between the conductors.   The printed wiring board connection structure according to any one of claims 1 to 3, wherein a width of the protruding portion is wider than a half of an interval between conductors.   5. The printed wiring board connection structure according to claim 1, wherein a height of the protruding portion from the base material is higher than ½ of a height of the conductor. An insulating substrate;
A plurality of conductors located on the substrate;
A printed wiring board comprising a protruding portion protruding from the base material between the conductors.   The printed wiring board according to claim 6, wherein the protrusion is located at an end between the conductors so as to dam the anisotropic conductive material.   The printed wiring board according to claim 6, wherein the protruding portion is composed of a plurality of divided portions or a continuous long portion between the conductors.   9. The printed wiring board according to claim 6, wherein a width of the dam-like protruding portion is wider than ½ of an interval between conductors.   The printed wiring board according to claim 6, wherein a height of the protruding portion from the base material is higher than ½ of a height of the conductor. A step of preparing a first printed wiring board in which a plurality of conductors are positioned on a substrate;
Arranging an anisotropic conductive adhesive film on the first printed wiring board;
Placing the second printed wiring board having a flying lead on the anisotropic conductive adhesive film in accordance with the conductor of the first printed wiring board;
A step of interposing a release film between the second printed wiring board and the thermocompression bonding tool, and applying thermocompression with a thermocompression bonding tool,
In the first printed wiring board preparation step, a first printed wiring board having a protruding portion protruding from the base material is prepared between the conductors. Method. A method for producing a printed wiring board comprising a plurality of conductors located on a substrate,
Forming a pattern of the plurality of conductors on the substrate;
Forming a projecting portion projecting from the base material between the plurality of conductors,
The method for producing a printed wiring board, wherein in the step of forming the protruding portion, the protruding portion is formed by any one of a lithography method, a screen printing method, and a bonding method.

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