JP2013222816A - Connection structure manufacturing method, connection method, and connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To resolve a lack of a pressure when a flexible substrate is thermally pressurized.SOLUTION: In a manufacturing method, a flexible substrate 2 on one face 9a of which plural connection terminals 7 are aligned is arranged on a connection object 1 on which plural electrode terminals 6 connected to the connection terminals 7 are aligned, so that the connection terminals 7 are opposed via an adhesive 3. The substrate 2 is pressed via a cushioning material 20 from the other face 9b opposite to the face 9a on which the connection terminals 7 are formed, and the adhesive 3 is hardened, so as to manufacture a connection structure to which the substrate 2 is connected. A first dummy terminal 10 is formed on the substrate 2 at a position overlapping the connection terminals 7 on the other face 9b.

Description

  The present invention relates to a method for manufacturing a connection structure in which electronic components in which a plurality of connection terminals are arranged are connected via an adhesive, a connection method for connecting electronic components in which a plurality of connection terminals are arranged, and this The present invention relates to a connection structure manufactured using a connection method.

  Conventionally, when connecting a rigid substrate such as a glass substrate or a glass epoxy substrate and a flexible substrate, or connecting flexible substrates, an anisotropic conductive adhesive in which conductive particles are dispersed in a binder resin is used. It has been. The case where the connection terminal of the flexible substrate and the connection terminal of the rigid substrate are connected will be described as an example. An anisotropic conductive adhesive is disposed between the regions where the connection terminals of both the substrates are formed, and heat-pressed. Then, the binder resin exhibits fluidity and flows out from between the connection terminal of the flexible substrate and the connection terminal of the rigid substrate, and the conductive particles in the anisotropic conductive adhesive are sandwiched between the connection terminals. It is crushed.

  As a result, the connection terminal of the flexible substrate and the connection terminal of the rigid substrate are electrically connected via the conductive particles, and the binder resin is cured in this state. The conductive particles that are not between the two connection terminals are dispersed in the binder resin and maintain an electrically insulated state. Thereby, electrical conduction is achieved only between the connection terminal of the flexible substrate and the connection terminal of the rigid substrate.

Japanese Patent Laid-Open No. 11-282002 JP 2000-323523 A

  By the way, when heat-pressing a flexible substrate to a rigid substrate via an anisotropic conductive adhesive, a buffer material is interposed between the heat-pressing surface of the heat-pressing head and the flexible substrate. By interposing the buffer material, it is possible to eliminate the pressure imbalance due to the height variation in each connection terminal region of the flexible substrate and the rigid substrate, and to protect the circuit formed on the flexible substrate from thermal shock.

  However, as shown in FIG. 10, when the flexible substrate 51 is heated and pressed through the buffer material 50, the inter-terminal region 53 where the connection terminal 52 is not provided is bent in the pressing direction, and the pressure of the heating and pressing head is reduced. Escapes to the inter-terminal region 53. As a result, the pressing force from the heating and pressing head is not sufficiently applied to the connection terminal 52, and connection failure due to insufficient pressure may occur.

  Further, when the pressing force is increased to eliminate the pressure shortage, the flexible substrate 51 is further bent, and after the connection to the rigid substrate 54 is finished, the connection terminal 52 is rigidly formed by residual stress as shown in FIG. A reaction (spring back) occurs in a direction away from the electrode terminal 55 of the substrate 54. As a result, the resistance value between the connection terminal 52 and the electrode terminal 55 may increase and conduction failure may occur.

  Therefore, the present invention eliminates the pressure shortage when a flexible substrate is hot-pressed, suppresses the distortion of the substrate, and prevents a conduction failure due to springback. An object of the present invention is to provide a connection method and a connection structure.

  In order to solve the above-described problems, a manufacturing method of a connection structure according to the present invention includes a plurality of connection terminals formed in parallel on one surface, and a flexible substrate connected to the connection terminals. An electrode terminal is placed on a connection object formed in parallel so that the connection terminal is opposed to each other through an adhesive, and the substrate is placed on the other surface side opposite to the one surface on which the connection terminal is formed. In the manufacturing method for manufacturing the connection structure to which the substrate is connected by pressing the cushioning material and curing the adhesive, the substrate overlaps the connection terminal on the other surface. In addition, a first dummy terminal is formed.

  Further, the connection method according to the present invention is a connection object in which a plurality of connection terminals are formed in parallel on one surface and a flexible substrate is formed, and a plurality of electrode terminals connected to the connection terminals are formed in parallel. On the object, the connection terminals are arranged so as to face each other through an adhesive, and the substrate is pressed from the other surface side opposite to the one surface on which the connection terminals are formed via a cushioning material. In the connection method for connecting the substrates by curing the adhesive, the substrate has a first dummy terminal formed at a position overlapping the connection terminals on the other surface.

  In addition, the connection structure according to the present invention has the substrate connected by the connection method.

  According to the present invention, since the first dummy terminal is formed at a position overlapping with the connection terminal on the other surface of the substrate, the buffer material is greatly bent by entering the region between the connection terminals, and the heating press head Is prevented from escaping to the inter-terminal region and insufficient pressing force to the connection terminals. Therefore, the connection terminal of the substrate is pressed with an appropriate pressure, and the connection reliability can be improved. In addition, since the substrate does not bend greatly due to pressure concentration in the inter-terminal region, it is possible to suppress the reaction that occurs in the direction in which the connection terminal separates from the electrode terminal due to residual stress. Thereby, the connection structure can prevent a rise in resistance value and a conduction failure between the connection terminal and the electrode terminal.

It is a disassembled perspective view which shows the connection structure of the printed wiring board and flexible substrate to which this invention was applied. It is a disassembled perspective view which shows the connection state in the FOB mounting part of a printed wiring board. It is sectional drawing which shows the connection structure to which this invention was applied. It is sectional drawing which shows the connection structure in which the 1st dummy terminal was formed wider than the connection terminal. It is a top view which shows the flexible substrate in which the 1st dummy terminal and the 2nd dummy terminal were formed. It is a top view for demonstrating the area | region between terminals in a flexible substrate. It is a top view which shows the connection structure of the flexible substrate which formed the 2nd dummy terminal to the board | substrate side edge part, and a printed wiring board. (A) is sectional drawing which shows the connection structure which does not form a 2nd dummy terminal to a board | substrate side edge part, (b) is a cross section which shows the connection structure which formed the 2nd dummy terminal to the board | substrate side edge part FIG. It is sectional drawing which shows an anisotropic conductive film. It is sectional drawing which shows the connection process of the conventional flexible substrate and a rigid board | substrate. It is sectional drawing which shows the state which the springback produced in the connection structure body of the conventional flexible substrate and a rigid board | substrate.

  Hereinafter, a manufacturing method of a connection structure, a connection method, and a connection structure to which the present invention is applied will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention. Further, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[Printed wiring board]
The connection structure to which the present invention is applied is a connection structure in which a flexible substrate and a rigid substrate are connected in an anisotropic conductive manner, or a connection structure in which flexible substrates are connected in an anisotropic conductive manner. It can be used for printed wiring boards incorporated in all electronic devices such as PCs, mobile phones, game machines, audio devices, tablet terminals, and in-vehicle monitors. In such a printed wiring board, a so-called FOB (film on board) in which a flexible substrate on which various circuits are formed is directly mounted on the printed wiring board is adopted from the viewpoints of fine pitch, light weight and thinning. .

  As shown in FIG. 1, the printed wiring board 1 is formed with various wiring patterns and various components such as an IC chip, and a flexible substrate 2 is formed of an anisotropic conductive film (ACF) 3. The connection structure is configured by being connected via the.

  In the printed wiring board 1, a plurality of electrode terminals 6 connected to connection terminals 7 provided on the flexible substrate 2 are formed in the FOB mounting portion 5 to which the flexible substrate 2 is connected. As shown in FIG. 2, the electrode terminals 6 are formed, for example, in a substantially rectangular shape, and are arranged in a plurality over the direction orthogonal to the longitudinal direction.

  The FOB mounting portion 5 is connected to the flexible substrate 2 using an anisotropic conductive film 3 as a conductive adhesive. As will be described later, the anisotropic conductive film 3 contains conductive particles in a binder resin, and the conductive terminals include the connection terminals 7 of the flexible substrate 2 and the electrode terminals 6 formed on the printed wiring board 1. Electrical connection via

[Flexible substrate]
The flexible substrate 2 connected to the FOB mounting portion 5 of the printed wiring board 1 is connected to the electrode terminal 6 on one surface 9a of a flexible substrate 9 such as polyimide as shown in FIG. A plurality of 7 are formed. The connection terminal 7 is formed, for example, by patterning a copper foil or the like and appropriately performing a plating coating process such as nickel gold plating on the surface, and is formed in a substantially rectangular shape, for example, like the electrode terminal 6. A plurality are arranged in a direction orthogonal to the longitudinal direction.

[First dummy terminal]
The flexible substrate 2 has a first dummy terminal 10 formed at a position overlapping the connection terminal 7 on the other surface 9 b of the substrate 9. The first dummy terminal 10 is formed on the back side of the connection terminal 7, thereby suppressing the buffer material 20 from entering the region 8 between the adjacent connection terminals 7. As a result, as shown in FIG. 3, the first dummy terminal 10 has the flexible substrate 2 greatly bent by the buffer material 20 entering the region 8 between the connection terminals 7, and the pressure from the heating and pressing head is affected by the terminal. This prevents escape to the intermediate region 8 and insufficient pressure on the connection terminal 7. Therefore, in the flexible substrate 2, the connection terminal 7 is pressed with an appropriate pressure, and the connection reliability can be improved.

  Further, since the flexible substrate 2 does not bend greatly due to the concentration of pressure in the inter-terminal region 8, it suppresses a reaction (springback) that occurs in a direction in which the connection terminal 7 is separated from the electrode terminal 6 due to residual stress. be able to. As a result, the printed wiring board 1 can prevent an increase in the resistance value between the connection terminal 7 and the electrode terminal 6 and poor conduction.

  The first dummy terminal 10 can be formed by a known pattern forming method such as etching of a copper foil or the like, or printing of a conductive paste or an insulating paste. Further, like the connection terminal 7, the first dummy terminals 10 are formed, for example, in a substantially rectangular shape, and are arranged in a plurality over the direction orthogonal to the longitudinal direction.

  It is preferable that the first dummy terminals 10 are provided in parallel at positions overlapping with the connection terminals 7 provided in parallel. Thereby, the flexible substrate 2 can suppress the entry of the buffer material in all the inter-terminal regions 8, and reliably prevent insufficient connection to the connection terminals 7 and poor conduction with the electrode terminals 6 due to springback. Can do.

  The first dummy terminal 10 is preferably formed with a width equal to or smaller than the width of the connection terminal 7. When the first dummy terminal 10 is formed with a width wider than the width of the connection terminal 7, the first dummy terminal 10 is connected to the connection terminal 7 by pressing the flexible substrate 2 as shown in FIG. 4. The so-called doming occurs in which the outer edge portion that protrudes from both sides to the inter-terminal region 8 is curved.

  Since the first dummy terminal 10 is formed by patterning a copper foil or the like, the repulsive force against bending is large. For this reason, the first dummy terminal 10 may spring back in the direction in which the connection terminal 7 is separated from the electrode terminal 6 due to the residual stress of the first dummy terminal 10 after the flexible substrate 2 is connected. Therefore, the first dummy terminal 10 is preferably formed with a width equal to or smaller than the width of the connection terminal 7.

Further, the width W ₁ of the first dummy terminal 10 is preferably formed to be 45% or more of the width W ₂ of the connection terminal 7. If the width W _{1 of} the first dummy terminal 10 is less than 45% of the width W ₂ of the connection terminal 7, the entry of the cushioning material 20 into the inter-terminal region 8 cannot be suppressed, and the inter-terminal region 8. Is bent in the pressing direction, and the pressure of the heating and pressing head escapes to the inter-terminal region 8. As a result, the pressing force from the heating and pressing head is not sufficiently applied to the connection terminal 7 and the electrode terminal 6, and connection failure due to insufficient pressure may occur.

[Second dummy terminal]
In addition, as shown in FIG. 5, the flexible substrate 2 may be formed with the second dummy terminal 11 that is substantially orthogonal to the first dummy terminal 10 at the position overlapping the inter-terminal region 8 on the other surface 9 b. Good. The second dummy terminal 11 is formed at a position overlapping the inter-terminal region 8, thereby suppressing the buffer material 20 from entering the inter-terminal region 8 together with the first dummy terminal 10. By providing the second dummy terminal 11, the flexible substrate 2 has increased rigidity in the inter-terminal region 8, and can further prevent the buffer material 20 from entering the region 8 between the connection terminals 7.

  Similar to the first dummy terminal 10, the second dummy terminal 11 can be formed by a known pattern forming method such as etching of a copper foil or the like, printing of a conductive paste or an insulating paste, for example. In addition, the second dummy terminals 11 are formed, for example, in a line shape, and are arranged in a plurality at regular intervals in a direction orthogonal to the longitudinal direction, thereby forming a lattice pattern together with the first dummy terminals 10. To do.

  The second dummy terminals 11 have an area of 10% to 50% of the area of the inter-terminal region 8 by adjusting the number and width provided between the adjacent first dummy terminals 10 and 10. It is preferable to be formed as follows. Here, the inter-terminal region 8 is a region between adjacent connection terminals 7 and 7 in the flexible substrate 2 as shown in FIG. If the occupied area in the inter-terminal region 8 of the second dummy terminals 11 is less than 10%, the rigidity in the inter-terminal region 8 is not sufficiently improved. Further, when the occupied area of the second dummy terminal 11 in the inter-terminal region 8 is larger than 50%, the effect of providing the first dummy terminal 10 at a position overlapping the connection terminal 7 is reduced.

  That is, the flexible substrate 2 prevents the buffer material 20 from entering the inter-terminal region 8 by providing the first dummy terminal 10 at a position overlapping the connection terminal 7. When the second dummy terminal 11 is provided and the area occupied by the second dummy terminal 11 increases, the area where the height difference between the position overlapping the connection terminal 7 and the inter-terminal region 8 decreases, and the pressure of the heating and pressing head is reduced to the first dummy terminal. Therefore, the effect of preventing the occurrence of insufficient pressing force on the connection terminal 7 is diminished. For this reason, it is preferable that the occupied area in the inter-terminal region 8 of the second dummy terminal 11 is 50% or less of the area of the inter-terminal region 8.

  Further, as shown in FIG. 7, the second dummy terminal 11 may be formed up to the substrate side edge portion of the flexible substrate 2 where the first dummy terminal 10 is not provided. As shown in FIG. 8A, in the flexible substrate 2, when the second dummy terminal 11 is not formed up to the substrate side edge 2 a, the flexible substrate 2 has a boundary between the second dummy terminal 11 and the substrate side edge 2 a. Stiffness decreases. Therefore, when the flexible substrate 2 is pressed by the heating and pressing head through the buffer material 20, the substrate side edge 2a is deformed to the printed wiring board 1 side, and the connection terminal 7 is provided as a fulcrum on the inside of the substrate. There is a possibility that the connection reliability may be impaired when the connecting terminal 7 is lifted away from the printed wiring board 1.

  On the other hand, as shown in FIG. 8B, the rigidity can be maintained up to the board side edge 2a by forming the second dummy terminals 11 up to the board side edge 2a. Therefore, even if the flexible substrate 2 is pressed by the heating and pressing head via the cushioning material 20, the substrate side edge portion 2a does not bend toward the printed wiring board 1 side, and the connection terminal 7 is prevented from floating. Can be improved.

[Method of manufacturing first dummy terminal / second dummy terminal]
As described above, the first dummy terminal 10 and the second dummy terminal 11 can be formed by a known pattern forming method such as etching of a copper foil or the like, printing of a conductive paste or an insulating paste. At this time, the 1st dummy terminal 10 and the 2nd dummy terminal 11 can be efficiently formed by forming by the same formation method and the same process.

  The first dummy terminal 10 and the second dummy terminal 11 are simultaneously formed in the other wiring pattern forming step when another wiring pattern is provided on the other surface 9 b of the substrate 9 of the flexible substrate 2. Therefore, it can form efficiently.

[Anisotropic conductive film]
The anisotropic conductive film 3 is a thermosetting or ultraviolet curable adhesive, which is fluidized by heat and pressure applied by a heating and pressing head (not shown), so that the conductive particles become electrode terminals 6 and a flexible substrate. It is crushed between the two connection terminals 7 and cured in a state where the conductive particles are crushed by heating or ultraviolet irradiation. Thereby, the anisotropic conductive film 3 electrically and mechanically connects the printed wiring board 1 and the flexible substrate 2.

  For example, as shown in FIG. 9, the anisotropic conductive film 3 is conductive to a normal binder resin 15 (adhesive) containing a film-forming resin, a thermosetting resin, a latent curing agent, a silane coupling agent, and the like. The particles 16 are dispersed, and this thermosetting adhesive composition is applied onto the base film 17 to be formed into a film shape.

  The base film 17 is formed, for example, by applying a release agent such as silicone to PET (Poly Ethylene Terephthalate), OPP (Oriented Polypropylene), PMP (Poly-4-methlpentene-1), PTFE (Polytetrafluoroethylene) or the like.

  The film forming resin contained in the binder resin 15 is preferably a resin having an average molecular weight of about 10,000 to 80,000. Examples of the film forming resin include various resins such as an epoxy resin, a modified epoxy resin, a urethane resin, and a phenoxy resin. Among these, phenoxy resin is particularly preferable from the viewpoint of film formation state, connection reliability, and the like.

  It does not specifically limit as a thermosetting resin, For example, a commercially available epoxy resin, an acrylic resin, etc. are mentioned.

  The epoxy resin is not particularly limited. For example, naphthalene type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, bisphenol type epoxy resin, stilbene type epoxy resin, triphenolmethane type epoxy resin, phenol aralkyl type epoxy resin. Naphthol type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin and the like. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as an acrylic resin, According to the objective, an acrylic compound, liquid acrylate, etc. can be selected suitably. For example, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, epoxy acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, dimethylol tricyclodecane diacrylate, tetramethylene glycol tetraacrylate, 2-hydroxy- 1,3-diacryloxypropane, 2,2-bis [4- (acryloxymethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, dicyclopentenyl acrylate, tricyclo Examples include decanyl acrylate, tris (acryloxyethyl) isocyanurate, urethane acrylate, and epoxy acrylate. In addition, what made acrylate the methacrylate can also be used. These may be used individually by 1 type and may use 2 or more types together.

  The latent curing agent is not particularly limited, and examples thereof include various curing agents such as a heat curing type and a UV curing type. The latent curing agent does not normally react, but is activated by various triggers selected according to applications such as heat, light, and pressure, and starts the reaction. The activation method of the thermal activation type latent curing agent includes a method of generating active species (cation, anion, radical) by a dissociation reaction by heating, etc., and it is stably dispersed in the epoxy resin near room temperature, and epoxy at high temperature There are a method of initiating a curing reaction by dissolving and dissolving with a resin, a method of initiating a curing reaction by eluting a molecular sieve encapsulated type curing agent at a high temperature, and an elution / curing method using microcapsules. Thermally active latent curing agents include imidazole, hydrazide, boron trifluoride-amine complexes, sulfonium salts, amine imides, polyamine salts, dicyandiamide, etc., and modified products thereof. The above mixture may be sufficient. Among these, a microcapsule type imidazole-based latent curing agent is preferable.

  Although it does not specifically limit as a silane coupling agent, For example, an epoxy type, an amino type, a mercapto sulfide type, a ureido type etc. can be mentioned. By adding the silane coupling agent, the adhesion at the interface between the organic material and the inorganic material is improved.

  Examples of the conductive particles 16 include any known conductive particles used in the anisotropic conductive film 3. Examples of the conductive particles 16 include particles of various metals and metal alloys such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, metal oxide, carbon, graphite, glass, ceramic, Examples thereof include those in which the surface of particles such as plastic is coated with metal, or those in which the surface of these particles is further coated with an insulating thin film. In the case where the surface of the resin particle is coated with metal, examples of the resin particle include an epoxy resin, a phenol resin, an acrylic resin, an acrylonitrile / styrene (AS) resin, a benzoguanamine resin, a divinylbenzene resin, a styrene resin, and the like. Can be mentioned.

  In addition, the anisotropic conductive film 3 is good also as a structure which provides a cover film in the surface opposite to the surface where the base film 17 was laminated | stacked from viewpoints of the ease of handling, storage stability, etc. The shape of the anisotropic conductive film 3 is not particularly limited. For example, as shown in FIG. 9, the shape of the anisotropic conductive film 3 is a long tape shape that can be wound around the take-up reel 18, and is used by cutting a predetermined length. can do.

  Moreover, although the above-mentioned embodiment demonstrated as an example the adhesive film which shape | molded the thermosetting resin composition which contained the electroconductive particle 16 in the binder resin 15 suitably as an adhesive agent, it concerns on this invention. The adhesive is not limited to this, and for example, an insulating adhesive layer made of only the binder resin 15 and a conductive particle-containing layer made of the binder resin 15 containing the conductive particles 16 can be laminated. . Further, the adhesive is not limited to the conductive adhesive film formed by such a film, and may be a conductive adhesive paste in which the conductive particles 16 are dispersed in the binder resin composition. Further, the adhesive may be an insulating adhesive film in which the conductive particles 16 are not contained in the binder resin 15 or an insulating adhesive paste. The adhesive according to the present invention includes any of the forms described above.

[Manufacturing method / connecting method of connection structure]
Next, the process of connecting the flexible substrate 2 to the printed wiring board 1 will be described. The flexible substrate 2 has a connection terminal 7 formed on one surface 9a of the substrate 9, and a first dummy terminal 10 or first and second dummy terminals 10 and 11 formed on the other surface 9b. In addition, the anisotropic conductive film 3 is temporarily attached to the FOG mounting portion 5 on the printed wiring board 1. The temporary attachment of the anisotropic conductive film 3 is performed by placing the surface on which the binder resin 15 is formed on the FOG mounting portion 5 and pressing the surface of the base film 17 with a heat pressing head, or the binder resin 15 is fluid. However, it is performed by applying heat and pressure at a low pressure for a short time at a temperature at which thermosetting does not start.

  Next, the flexible substrate 2 is placed on the FOB mounting portion 5 on which the anisotropic conductive film 3 is temporarily attached. At this time, the flexible substrate 2 is aligned so that the connection terminal 7 is placed on the predetermined electrode terminal 6. And it heat-presses only for the predetermined | prescribed pressure and predetermined | prescribed time from the other surface 9b of the flexible substrate 2 with the heating press head heated to the curing temperature of the binder resin 15. FIG.

  At this time, the buffer material 20 is interposed between the heating and pressing head and the flexible substrate 2. The buffer material 20 is made of a sheet-like elastic material, and for example, silicon rubber is used. And since the 1st dummy terminal 10 is formed in the flexible substrate 2, even when it heat-presses through the buffer material 20, it is to the area | region 8 between the connection terminals 7 which the buffer material 20 adjoins. Intrusion can be suppressed. Thereby, as shown in FIG. 3, the flexible substrate 2 has the shock absorbing material 20 entering the region 8 between the connection terminals 7, so that the inter-terminal region 8 is greatly bent downward, and the pressure from the heating and pressing head is applied to the terminal. This prevents escape to the intermediate region 8 and insufficient pressure on the connection terminal 7. Therefore, in the flexible substrate 2, the connection terminal 7 is pressed with an appropriate pressure, and the connection reliability can be improved.

  In the anisotropic conductive film 3, the binder resin 15 is fluidized and flows out between the electrode terminal 6 and the connection terminal 7, and the conductive particles 16 are sandwiched between the electrode terminal 6 and the connection terminal 7. Cured with. Thereby, a connection structure in which the printed wiring board 1 and the flexible substrate 2 are electrically and mechanically connected is manufactured.

  Further, in the connection structure of the printed wiring board 1 and the flexible substrate 2, the flexible substrate 2 is not greatly bent due to the pressure concentration on the inter-terminal region 8, so that the connection terminal 7 is separated from the electrode terminal 6 by the residual stress. The reaction (spring back) that occurs in the separating direction can be suppressed. Therefore, this connection structure can prevent an increase in resistance value and conduction failure between the connection terminal 7 and the electrode terminal 6.

  When the first and second dummy terminals 10 and 11 are formed on the other surface 9 b of the flexible substrate 2, the connection structure has increased rigidity in the inter-terminal region 8, and the connection material 7 between the buffer materials 20 is connected. Intrusion into the region 8 can be further suppressed, and insufficient pressure and springback to the connection terminal 7 can be more reliably prevented.

  In the above description, the case where the flexible substrate 2 is connected to the printed wiring board 1 as an example of the connection structure has been described. However, the present invention is not limited to FOB mounting. For example, the connection structure includes a pair of flexible substrates connected to each other. Can be applied to. At this time, the pair of flexible boards forms the first dummy terminals 10 and the second dummy terminals 11 on the other surface of at least one of the boards, but the first dummy terminals 10 and the second dummy terminals are formed on both boards. 11 is preferably formed.

  The first dummy terminals 10 and the second dummy terminals 11 are preferably formed uniformly on the other surface 9 b of the substrate 9. That is, the first dummy terminals 10 are formed at equal intervals according to the connection terminals 7 formed at equal intervals, and the plurality of second dummy terminals 11 substantially orthogonal to the first dummy terminals 10 are also equal. It is preferable to form at intervals. Thereby, a pressure is equally applied over all the connection terminals 7, and predetermined pressure can be applied without excess and deficiency.

  Next, examples of the present invention will be described. In the present embodiment, the flexible substrate having the first dummy terminal 10 formed on the other surface of the substrate, the flexible substrate having the first and second dummy terminals 10 and 11 formed on the other surface of the substrate, and the first substrate on the other surface of the substrate. A conventional flexible board in which the dummy terminal 10 and the second dummy terminal 11 are not formed is prepared, and each flexible board is disposed on the electrode terminal of the printed wiring board via an anisotropic conductive film, and a cushioning material is interposed therebetween. Then, a connection structure sample was formed by heating and pressing the flexible substrate.

  And about each connection structure sample, the conduction resistance of the connection terminal formed in one surface of the flexible substrate and the electrode terminal formed in the printed wiring board was measured, and reliability was evaluated. Further, for each connection structure sample, it was observed whether or not the flexible substrate springback occurred.

  The anisotropic conductive film used to connect the flexible substrate is ACF (CP801AM-35AC) manufactured by Sony Chemical & Information Device Corporation. This ACF contains gold / nickel plating resin particles having a particle diameter of 10 μm in a binder resin.

  In the flexible substrate used in the examples and comparative examples, a Cu wiring with a thickness of 18 μm on which Ni / Au plating is applied as a connection terminal on one surface of a polyimide substrate with a thickness of 50 μm has a pitch of 600 μm (L / S = 1). / 1).

  The printed wiring board used in the examples and comparative examples is a FR-4 grade glass epoxy substrate with a thickness of 1 mm, and a 35 μm thick Cu wiring with Ni / Au plating as the electrode terminal is 600 μm. It is formed with a pitch (L / S = 1/1).

  The pressure bonding conditions of the flexible substrate are 190 ° C., 5 MPa, and 20 seconds. In addition, a silicon rubber having a thickness of 350 μm was used as a buffer material provided between the heating and pressing head and the flexible substrate.

  In Example 1, only the first dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the first embodiment has a width of 135 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 45%.

  In Example 2, only the first dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the second embodiment has a width of 165 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 55%.

  In Example 3, only the first dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the third embodiment has a width of 270 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 90%.

  In Example 4, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the fourth embodiment is the same as that of the first embodiment, and the second dummy terminal is formed with ten lines having a width of 90 μm, and the second dummy terminal occupies the area of the inter-terminal region. The area ratio is 30%. In Example 4, the second dummy terminals were formed up to the substrate side edge.

  In Example 5, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the fifth embodiment is the same as that of the second embodiment, and the second dummy terminal is formed with 10 lines having a width of 30 μm, and the second dummy terminal occupies the area of the inter-terminal region. The area ratio is 10%. In Example 5, the second dummy terminal was formed up to the substrate side edge.

  In Example 6, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the sixth embodiment is the same as that of the second embodiment. As the second dummy terminal, ten lines having a width of 90 μm are formed, and the second dummy terminal occupies the area of the inter-terminal region. The area ratio is 30%. In Example 6, the second dummy terminal was formed up to the substrate side edge.

  In Example 7, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the seventh embodiment is the same as that of the second embodiment. As the second dummy terminal, ten lines having a width of 150 μm are formed, and the second dummy terminal occupies the area of the inter-terminal region. The area ratio is 50%. Further, in Example 7, the second dummy terminal was formed up to the substrate side edge.

  In Example 8, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to Example 8 has a width of 195 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 65%. In addition, the second dummy terminal has the same conditions as in Example 4.

  In Example 9, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. In Example 9, the first and second dummy terminals were set to the same conditions as in Example 6 except that the second dummy terminal was not formed up to the substrate side edge of the flexible substrate.

  In Comparative Example 1, a conventional flexible substrate in which the first and second dummy terminals are not provided on the other surface of the flexible substrate was used.

  In Comparative Example 2, a copper foil was provided over the entire other surface of the substrate. That is, the first dummy terminal according to Comparative Example 2 has a width of 300 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 100%. In the second dummy terminal according to Comparative Example 2, the area ratio occupied by the second dummy terminal with respect to the area of the inter-terminal region is 100%. Moreover, in Example 4, the copper foil is not formed up to the substrate side edge.

  In Comparative Example 3, only the second dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The second dummy terminal has 10 lines with a width of 90 μm, and the area ratio occupied by the second dummy terminal with respect to the area of the inter-terminal region is 30%. In Comparative Example 3, the second dummy terminal is not formed up to the substrate side edge.

  In Comparative Example 4, only the first dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to Comparative Example 4 has a width of 120 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 40%.

  In Comparative Example 5, only the first dummy terminal was formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to Comparative Example 5 has a width of 360 μm, and the ratio of the first dummy terminal width to the connection terminal width (300 μm) is 120%.

  In Comparative Example 6, the first dummy terminal and the second dummy terminal were formed by etching the copper foil provided on the other surface of the substrate. The first dummy terminal according to the comparative example 6 is the same as that of the second embodiment, and the second dummy terminal is formed with 10 lines having a width of 210 μm, and the second dummy terminal occupies the area of the inter-terminal region. The area ratio is 70%. In Comparative Example 6, the second dummy terminal was formed up to the substrate side edge.

  For the connection structure samples according to each of the examples and comparative examples, the conduction resistance between the electrode terminal and the connection terminal was measured at the initial stage of connection and after TCT, and the resistance increase value was less than 0.7Ω. A value less than 1.0Ω was indicated as ◯, and a value equal to or greater than 1.0Ω was indicated as ×. The TCT conditions are −40 ° C. for 30 minutes to 100 ° C. for 30 minutes and 100 cycles. Moreover, about the connection structure sample which concerns on each Example and a comparative example, the presence or absence of the springback was confirmed with the optical microscope. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 3 in which the first dummy terminals were formed, although the springback was confirmed, the increase in conduction resistance was 0.7Ω or more and less than 1.0Ω. On the other hand, in Comparative Example 1 in which the first and second dummy terminals are not provided, and in Comparative Example 4 in which the width W ₁ of the first dummy terminal is less than 45% of the connection terminal width W ₂ , spring back is confirmed. In addition, the conduction resistance increased by 1.0Ω or more after TCT. Further, in Comparative Example 3 in which only the second dummy terminal is provided without providing the first dummy terminal, and in Comparative Example 5 in which the width W ₁ of the first dummy terminal is 120% of the connection terminal width W ₂ , the spring is used. Although no back was confirmed, the conduction resistance increased by 1.0Ω or more after TCT.

  This is because the first dummy terminal is not provided or the pressure is not enough due to the entry of the buffer material in the inter-terminal region 8 where the narrow first dummy terminal is provided, or the first curved terminal protrudes from both sides of the connection terminal. This is considered to be caused by the springback by the dummy terminal 1.

  As a result, by providing the first dummy terminal, the entry of the cushioning material into the inter-terminal region can be suppressed, sufficient pressure can be applied to the connection terminal, and the spring back of the flexible substrate can be suppressed to ensure reliable connection. It can be seen that the performance can be improved. Further, it can be seen that the width of the first dummy terminal is preferably 45% or more of the width of the connection terminal and not more than the connection terminal width.

In Examples 4 to 9 in which the second dummy terminal was provided in addition to the first dummy terminal, no springback was confirmed. Of these, the first dummy terminal width W ₁ is 55% of the connection terminal width W ₂ , and the second dummy terminal occupies 30% of the inter-terminal region 8 area and is formed to the edge on the substrate side. Then, the increase in conduction resistance after TCT was as good as less than 0.7Ω.

  On the other hand, in Comparative Example 2 in which the copper foil is provided over the entire other surface of the substrate and Comparative Example 6 in which the occupation ratio of the area of the second dummy terminal to the inter-terminal region area is 70%, the conduction resistance is increased after TCT. Increased by more than 1.0Ω. This is because the area ratio of the second dummy terminal becomes too high, and it is not possible to prevent pressure concentration in the inter-terminal region by providing the first dummy terminal, and also due to the repulsive force of the curved copper foil This is because the springback has worked greatly.

  Thereby, it can be seen that the occupation ratio of the area of the second dummy terminal to the area between the terminals is preferably 10 to 50%.

DESCRIPTION OF SYMBOLS 1 Printed wiring board, 2 Flexible board, 2a Board | substrate side edge part, 3 Anisotropic conductive film, 5 FOB mounting part, 6 Electrode terminal, 7 Connection terminal, 8 Area | region between terminals, 9 Board | substrate, 9a One side, 9b Other side, 10 first dummy terminal, 11 second dummy terminal, 15 binder resin, 16 conductive particles, 20 cushioning material

Claims (10)

A flexible substrate in which a plurality of connection terminals are formed in parallel on one surface is connected to the connection object formed in parallel with a plurality of electrode terminals connected to the connection terminals via an adhesive. Arrange so that the connection terminals face each other,
A connection structure to which the substrate is connected is manufactured by pressing the substrate from the other surface side opposite to the surface on which the connection terminal is formed via a cushioning material and curing the adhesive. In the manufacturing method,
The method for manufacturing a connection structure in which the substrate has a first dummy terminal formed at a position overlapping the connection terminal on the other surface.   2. The method for manufacturing a connection structure according to claim 1, wherein a second dummy terminal orthogonal to the first dummy terminal is formed on the other surface at a position overlapping the region between the electrode terminals. .   The method for manufacturing a connection structure according to claim 1, wherein the first dummy terminal is formed with a width equal to or less than a width of the connection terminal.   4. The method for manufacturing a connection structure according to claim 3, wherein the first dummy terminal is formed with a width of 45% or more of the width of the connection terminal.   The method for manufacturing a connection structure according to claim 2, wherein the second dummy terminal is formed with an area of 10 to 50% of an area of the inter-electrode terminal region.   The method for manufacturing a connection structure according to claim 2, wherein the second dummy terminal is formed up to a side edge portion of the substrate on which the first dummy terminal is not provided.   The method for manufacturing a connection structure according to claim 1, wherein the first dummy terminal and the second dummy terminal are formed of a conductive material.   The method for manufacturing a connection structure according to claim 1 or 2, wherein the first dummy terminal and the second dummy terminal are uniformly formed on the other surface of the substrate. A flexible substrate in which a plurality of connection terminals are formed in parallel on one surface is connected to the connection object formed in parallel with a plurality of electrode terminals connected to the connection terminals via an adhesive. Arrange so that the connection terminals face each other,
In the connection method of connecting the substrate by pressing the substrate from the other surface side opposite to the one surface on which the connection terminal is formed through a cushioning material and curing the adhesive.
A connection method in which a first dummy terminal is formed at a position where the substrate overlaps the connection terminal on the other surface.   A connection structure in which substrates are connected by the connection method according to claim 9.

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