JP2007258410A - Wiring board connecting structure and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board connecting structure which enables sure thermocompression bonding between wiring boards, can suppress the sticking out of a conductive connection layer to the side between interconnection layers, and can also prevent short circuits between the interconnection layers; and also to provide its manufacturing method. <P>SOLUTION: The wiring board connecting structure comprises first and second wiring boards 10 and 11 having first and second interconnection layers 10 and 11, respectively; a first terminal layer J1a having one planar pattern shape which is continuously formed with the first interconnection layer J1 in a partial region of the first wiring board 10; a second terminal layer J2a which is formed continuously with the second interconnection layer J2 in a partial region of the second wiring board 11, and is so arranged as to face the first terminal layer in the thickness direction within a range of the one planar pattern shape; and conductive adhesive layers F1a and F2a for thermocompression bonding which are interposed between the first and second terminal layers. The second terminal layer J2a has such a pattern shape as to have spaces G1 which face the first terminal layer J1a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wiring board connection structure and a manufacturing method thereof, and more particularly, to a wiring board connection structure suitable for inter-board connection by thermocompression bonding of an FPC and an FPC in which the wiring pitch is becoming finer and a manufacturing method thereof.

  In recent years, there has been a demand for miniaturization, thickness reduction, and weight reduction in the field of various electronic devices, and in response to this requirement, a thin and flexible FPC (Flexible Printed Circuit) has been incorporated into electronic devices. In addition, there is an increasing demand and demand for inter-board connection by combining such FPCs with other FPCs.

  Therefore, a general solder thermocompression bonding method between the connection terminal portions of the FPCs will be described with reference to FIGS.

  The first and second wiring boards FPC1 and FPC2 have the same material and structure as each other. Specifically, each of the wiring boards FPC1 (FPC2) is made of a copper foil via a thermosetting PI adhesive layer B1 (B2) on one surface of a polyimide (abbreviated PI) resin board A1 (A2). The wiring layer C1 (C2) is laminated, and a PI film cover layer E1 (E2) is adhered to the surface of the wiring layer C1 (C2) via a thermosetting PI adhesive layer D1 (D2). As shown in FIG. 4B, the wiring layer C1 (C2) has a plurality of parallel patterns.

  One end of each wiring layer C1 (C2) is partially exposed so as not to be covered with the adhesive layer D1 (D2) and the cover layer E1 (E2). Each exposed portion of each wiring layer C1 (C2) is configured as first and second terminal layers 1 and 2 in each end region of each wiring board FPC1 (FPC2), and the first and second terminal layers Solder plating layers F1 and F2 are deposited on the exposed surfaces 1 and 2, respectively.

  In connecting the first and second terminal layers 1 and 2, first, the first and second wiring boards FPC1 and FPC2 are placed on the processing table 3 so that the solder plating layers F1 and F2 face each other. (See FIG. 3). Therefore, the first and second terminal layers 1 and 2 are pressed in the direction of the work table 3 by the pressurizer 4 with a heater disposed above the terminal layer 1 of the first wiring board FPC1, and the solder The plated layers F1 and F2 are thermocompression bonded. At this time, conditions such as heater temperature, pressure (pressing force), and pressure bonding time are appropriately determined.

  By the way, in the mass production process, the pressing amount of the pressurizer 4 is not constant, and the pressing force may be insufficient or excessive. When the pressure is insufficient, although not shown, the solder plating layers F1 and F2 do not come into contact with each other, or even if they come into contact, the mutual fusion becomes uneven, and the first and second terminal layers 1 There is a problem that poor connection between the wiring layers C1 and C2 occurs.

  On the other hand, when the applied pressure is excessive (see FIG. 4A, a sectional view, and FIG. 4B showing the plan view), the overlapping solder plating layers F1, F2 are excessively crushed, and FIG. As shown in b), a large number of solder protrusions 5 may be formed on the side portions of the terminal layers 1 and 2 of the wiring layers C1 and C2. There is a problem that these solder protrusions 5 extend between adjacent wiring layers C1 (C2) to form a solder bridge, causing an electrical short between adjacent wiring layers. This problem becomes more serious as a large number of wiring layers are incorporated into the FPC or the wiring layer pitch is reduced.

An example of a conventional technique relating to a method of connecting terminal portions of two wiring boards to each other by a thermocompression bonding method using a solder paste and generation of a solder bridge between wiring layers can be found in Patent Document 1 below.
Japanese Patent Application Laid-Open No. 6-120656

  The present invention has been made to solve the problems as in the prior art described above, and is a reliable connection by thermocompression bonding between wiring boards, a side of a conductive connection layer material (for example, solder) interposed between wiring layers. An object of the present invention is to provide a wiring board connecting structure and a method for manufacturing the same, which can suppress protrusion and prevent a short circuit between wiring layers.

  According to a first aspect of the present invention, there is provided a wiring board connection structure according to the first aspect of the present invention, in which a first wiring board and a second wiring board having a first wiring layer and a second wiring layer, respectively, and in a partial region of the first wiring board. A first terminal layer having a one-plane pattern shape continuously formed on one wiring layer and a second wiring layer formed continuously in a partial region of the second wiring substrate A second terminal layer disposed oppositely in the layer thickness direction within a plane pattern shape; and a conductive adhesive layer for thermocompression bonding interposed between the first and second terminal layers, the second terminal The layer is characterized in that it has a pattern shape having a gap facing the first terminal layer.

  According to a second aspect of the present invention, in the wiring board connection structure according to the first aspect, the second terminal layer has a branch pattern shape, whereby a gap is formed between the branches. Features.

  According to a third aspect of the present invention, in the wiring board connection structure according to the first aspect, the second terminal layer has a strip pattern shape having a smaller layer width than the first terminal layer. An air gap is formed on the side of the second terminal layer.

  According to a fourth aspect of the present invention, the first terminal layer and the second terminal layer formed on the first wiring board and the second terminal layer formed on the second wiring board are opposed to each other in the layer thickness direction. A method of manufacturing a wiring board connection structure in which layers are connected by a conductive adhesive layer, wherein a first terminal layer having a one-plane pattern shape continuous to the first wiring layer is formed in a partial region of the first wiring board. And a second terminal having a pattern shape, which is formed continuously in a part of the second wiring board in a second wiring layer and has a gap for facing the range of the one-plane pattern shape of the first terminal layer. Forming a layer; forming a conductive adhesive layer on at least one surface of the first and second terminal layers; and thermocompression bonding the first and second terminal layers through the conductive adhesive layer. To cause a part of the conductive adhesive layer to flow into the gap portion. Characterized by connecting the terminal layer mutually.

  According to the wiring board connection structure and the method for manufacturing the same according to the present invention, the second terminal layer has a pattern shape having a gap portion facing within the range of the one-plane pattern shape of the first terminal layer. In addition, the conductive connection layer to be thermocompression bonded is prevented from protruding in the direction between the wiring layers arranged in parallel, that is, in the side of the layer, thereby preventing a short circuit between the wiring layers. Further, when forming the pattern of the second terminal layer, the volume of the gap is adjusted according to the environmental conditions such as the applied pressure during thermocompression bonding, the volume of the conductive connection layer, and the temperature characteristics of the conductive connection layer. In such a case, it is possible to obtain the effects of suppressing the protrusion and preventing the short circuit between the wiring layers more reliably.

  Below, Example 1 and Example 2 which are embodiment of the wiring board connection structure by this invention are demonstrated with reference to FIG.1 and FIG.2.

(Example 1):
FIG. 1 is a diagram for explaining a wiring board connection structure according to a first embodiment of the present invention. FIG. 1A is an exploded view showing two wiring boards used in the wiring board connection structure separately. 1B is a cross-sectional view showing a state in which two wiring boards are opposed to each other, and FIG. 1C is a cross-sectional view of the wiring board connection structure after inter-board connection, taken along line AA in FIG. It is sectional drawing shown along the line.

  First, the first wiring board 10 and the second wiring board 11 both of which have a ribbon shape in the planar shape are configured using FPCs that are excellent in miniaturization of wiring pitch and flexibility, and are used in the same manner. Material and structure. Specifically, as can be seen from FIGS. 1B and 1C, the first wiring board 10 is thermosetting on one surface of a first insulating board H1 made of polyimide resin (abbreviated PI). A first wiring layer J1 made of copper foil is laminated via an adhesive layer I1 made of PI, and a first cover layer L1 made of PI film is bonded to the surface thereof via a thermosetting PI adhesive layer K1. Configured.

  Similarly to the first wiring board 10, the second wiring board 11 has a thermosetting PI adhesive layer I 2, a copper foil second wiring layer J 2, and a thermosetting material on the second insulating board H 2 made of PI. The adhesive layer K2 made of PI and the second cover layer L2 made of PI film are laminated in this order.

  As can be seen from FIG. 1 (a), the first and second wiring layers J1 and J2 are each a plurality of (for example, a plurality of) arranged in parallel at a predetermined pitch so as to be parallel to the longitudinal direction of the wiring boards. (4 each) are patterned into strip lines. A plurality of first terminal layers J1a that are respectively continuous with the plurality of first wiring layers J1 are formed at one end, which is a partial region of the ribbon-shaped first wiring substrate 10.

  Each first terminal layer J1a is subjected to patterning so as to constitute one end of the first wiring layer J1 on a copper foil as a material, and is integrally included in the strip line of the first wiring layer J1. It is formed as follows. Further, the first cover layer L1 and the adhesive layer K1 below the first cover layer L1 are processed so as to expose the first terminal layers J1a. Accordingly, the first terminal layer J1a is a rectangular pattern having a line width equivalent to that of the first wiring layer J1 and an exposed length in the longitudinal direction from the layer L1 and the adhesive layer K1 as a one-plane pattern shape. ing. Of course, the width and length of the first terminal layer J1a may be appropriately set as necessary.

  A plurality of second terminal layers J2a that are respectively continuous with the plurality of second wiring layers J2 are formed at one end, which is a partial region of the ribbon-shaped second wiring substrate 11. Each of the second terminal layers J2a is patterned so as to be integrally included in the strip line of the second wiring layer J2, as in the case of the first terminal layer J1a, and the second cover layer L2 and the adhesive layer K2 is processed so as to expose the second terminal layers J2a.

  Each of the second terminal layers J2a is formed into, for example, a bifurcated pattern shape at the time of the patterning, and the overall outline is a line width and exposure of a rectangular pattern as a one-plane pattern shape of the first terminal layer J1a. It is formed to be a rectangular pattern having the same dimensions as the length. Between the central portion of the first terminal layer J1a, that is, between the two branches, a strip-shaped void portion or gap G1 parallel to the longitudinal direction is formed on the side of the terminal layer.

  A first conductive connection layer F1a and a second conductive connection layer F2a are respectively deposited on the surfaces of the first terminal layer J1a and the second terminal layer J2a, and both of these connection layers F1a and F2a are attached. For example, a solder plating layer is used.

  Therefore, as described above, the step of forming the first terminal layer J1a continuous with the first wiring layer J1 at one end of the first wiring substrate 10, the second wiring layer at the one end of the second wiring substrate 11 is formed. After the step of continuously forming the second terminal layer having the gap G1 and the step of forming the conductive connection layers F1a and F2a, the first wiring substrate 10 and the second wiring substrate 11 are connected to each other.

  When connecting the substrates, as shown in FIG. 1B, the first wiring substrate 10 is turned over from the state of FIG. At this time, each of the first terminal layers J1a and each of the second terminal layers J2a is exactly the same as the rectangular pattern of each of the terminal layers J1a and J2a in the range of the one-plane pattern shape of the first terminal layer J1a. It is opposed in the layer thickness direction so as to overlap.

  That is, the rectangular pattern outline (outer shape) of the second terminal layer J2a substantially coincides with the projected image of the rectangular pattern which is a one-plane pattern shape of the first terminal layer J1a. Further, since the gap G1 in the second terminal layer J2a is opposed to the range of the one-plane pattern shape of the first terminal layer J1a, the second terminal layer J2a is the first terminal layer. The area is smaller by the area of the gap G1 than J1a.

  Therefore, the first and second wiring boards 10 and 11 facing each other as shown in FIG. 1B are arranged on the processing table 3 of the thermocompression bonding apparatus as shown in FIG. Then, the first and second terminal layers J1a and J2a are heated and pressed in the direction of the work table 3 by the pressurizer 4 with a heater disposed above the first terminal layer J1a of the first wiring board 10, and The first and second terminal layers are thermocompression bonded via the conductive connection layers F1a and F2a (see FIG. 1C). At this time, conditions such as heater temperature, pressure (pressing force), and pressure bonding time are appropriately adjusted and managed.

  In this thermocompression bonding step, as shown in FIG. 1C, the solder plating layers F1a and F2a are also provided between the surfaces of the first and second terminal layers J1a and J2a and inside the gap G1. Inflow and fill. Therefore, even if a slightly higher pressing force (pressing force) than before is applied, the solder plating layers F1a and F2a have a flow (outflow) amount of the terminal layers J1a and J2a to the outside of the gap G1. And the protrusion of the terminal layer to the outside is reduced or suppressed.

  Therefore, it is possible to prevent the occurrence of a solder bridge between adjacent wiring layers and an electrical short between wiring layers as shown in FIG. Further, since the pressure (pressing force) can be applied more strongly than in the past, the thermocompression bonding between the first and second terminal layers J1a and J2a and the connection between the terminals can be performed more reliably than in the past.

  Further, in the patterning of the second terminal layer J2a, by adjusting the volume of the gap G1, for example, it is possible to suppress the protrusion of the solder bridge according to various connections between wiring boards having different wiring layer pitches. Is possible. The strictness of condition adjustment and management such as heater temperature, pressure (pressing force) and pressure bonding time is alleviated, and it is possible to reduce process costs and product costs.

  The gap G1 is not limited to the shape penetrating the second terminal layer J2a, but may be a bottomed concave shape recessed within the thickness of the second terminal layer J2a. In that case, the solder plating layer The contact area between the surface of the second terminal layer and the surface of the second terminal layer can be increased as compared with the case of the through gap, thereby reducing the contact resistance.

  Furthermore, before the thermocompression bonding step, only one of the first and second conductive connection layers F1a and F2a is used and is attached to only one of the first and second terminal layers J1a and J2a. The conductive connection layer may be deposited on at least one surface of the first and second terminal layers J1a and J2a by adjusting the thickness and filling amount.

(Example 2):
FIG. 2 is a diagram for explaining a wiring board connection structure according to a second embodiment of the present invention. FIG. 2A is an exploded view showing two wiring boards used in the wiring board connection structure. FIG. 2B is a plan view showing a cross section of the wiring board connection structure after inter-board connection as a cut surface in the same direction as FIG. 1C according to the first embodiment. The same parts as those in the wiring board connection structure of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment, the same wiring board as the first wiring board 10 in the first embodiment is used as one wiring board, and the second wiring board is replaced with the second wiring layer 11 in the first embodiment. A two-wiring board 11a is used. The ribbon-like second wiring board 11a has a plurality of strip-line-like second wiring layers J2 arranged in parallel as in the first embodiment.

  A plurality of second terminal layers J2b that are respectively continuous with the plurality of second wiring layers J2 are formed at one end, which is a partial region of the ribbon-shaped second wiring substrate 11a. The second terminal layers J2b are patterned so as to be integrally included in the strip lines of the second wiring layer J2, and the second cover layer L2 and the adhesive layer K2 expose the second terminal layers J2b. It is processed as follows.

  Each of the second terminal layers J2b has a strip pattern shape having a smaller layer width than the second wiring layer J2, and is linearly formed so as to be continuous in the longitudinal direction at the center of one end of the second wiring layer J2. Patterned. Further, when each of the second terminal layers J2b is opposed to the first terminal layer J1a of the first wiring substrate 10, a projected image range S of a rectangular pattern which is a one-plane pattern shape of the first terminal layer J1a. It is located in the center of (refer to the second wiring board 11a in FIG. 2A). Then, on both sides of the second terminal layer J2b, narrow gaps G2 and G3 parallel to the longitudinal direction are formed between both side edges of the projected image range S of the planar image of the first terminal layer J1a. Has been.

  A first conductive connection layer F1a and a second conductive connection layer F2a are respectively deposited on the surfaces of the first terminal layer J1a and the second terminal layer J2b, and both of these connection layers F1a and F2a are attached. For example, a solder plating layer is used.

  Therefore, as in Example 1, the formation process of the first terminal layer J1a, the formation process of the second terminal layer J2b having the gaps G2 and G3 of the second wiring board 11a, and the formation of the conductive connection layers F1a and F2a. After the process, inter-substrate connection of the first wiring substrate 10 and the second wiring substrate 11a is performed.

  In connection between the substrates, as shown in FIG. 2A, the first wiring substrate 10 is disposed opposite to the second wiring substrate 11a in the plate thickness or layer thickness direction, and at this time, the first terminal layer J1a is arranged. The rectangular pattern is opposed to the projection image range S of the first terminal layer J1a surrounding the second terminal layer J2b so as to be exactly overlapped.

  In such an opposed arrangement, the first and second wiring boards 10 and 11a are arranged on a processing table 3 of a thermocompression bonding apparatus as shown in FIG. 3 and heated / pressurized by a presser 4 with a heater, The first and second terminal layers are thermocompression bonded via the conductive connection layers F1a and F2a (see FIG. 2B).

  In this thermocompression bonding process, as shown in FIG. 2B, the solder plating layers F1a and F2a also flow into the gaps G2 and G3 between the surfaces of the first and second terminal layers J1a and J2b. Filled. Therefore, even if a slightly higher pressing force (pressing force) than before is applied, the solder plating layer has a flow (outflow) amount to the outside of the first terminal layer J1a to the gaps G2 and G3. It is reduced by the inflow, and the protrusion of the terminal layer to the outside is reduced or suppressed. In this way, the same effects as those of the first embodiment can be obtained, such as generation of solder bridges between wiring layers and electrical short-circuiting.

  By the way, in any of the first and second embodiments, the one-plane pattern shape of the first terminal layer J1a of the first wiring board 10 is not limited to the rectangular pattern, but is an elliptical or oval pattern. Is also free.

  Further, the gap portion G1 of the first embodiment and the second terminal portion J2b of the second embodiment shown by the strip pattern are not limited to a linear shape, but meander patterns such as a zigzag shape, a linear wave shape, or a rectangular pulse wave shape. It may be a shape. The gap portion G1 as shown in the first embodiment is not limited to the second terminal portion, and may be appropriately formed in the first terminal layer J1a while maintaining appropriate design values of the bulk resistance and contact resistance. If it does so, the total volume of a space | gap part can be increased and the solder protrusion to the outer side of the said terminal layer can be further reduced or suppressed.

  The conductive connection layers F1a and F2a are not limited to solder plating layers, and conductive adhesive materials such as solder paste layers may be used, and these materials are applied by plating, printing, coating methods, or the like. Further, the first and second wiring boards can be configured by a combination of FPC and RPC (Rigid Printed Circuit).

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the wiring board connection structure which concerns on Example 1 of this invention, FIG.1 (a) is an exploded top view which decomposes | disassembles and shows the components of a wiring board connection structure, FIG.1 (b) is FIG. FIG. 1C is a cross-sectional view showing a cross-sectional view of the wiring board connection structure after inter-board connection along the line AA in FIG. 1B. is there. It is a figure for demonstrating the wiring board connection structure which concerns on Example 2 of this invention, FIG.2 (a) is a disassembled top view which decomposes | disassembles and shows the components of a wiring board connection structure, FIG.2 (b) is FIG. It is sectional drawing of the wiring board connection structure after board-to-board connection. It is sectional drawing for demonstrating the connection method between wiring boards. It is a figure for demonstrating the wiring board connection structure based on a prior art, Fig.4 (a) is sectional drawing of a wiring board connection structure, FIG.4 (b) is the top view.

Explanation of symbols

10 1st wiring board 11, 11a 2nd wiring board J1 1st wiring layer J2 2nd wiring layer J1a 1st terminal layer J2a, J2b 2nd terminal layer F1, F2 Conductive connection layer G1, G2, G3 Gap

Claims (4)

  A first wiring board and a second wiring board each having a first wiring layer and a second wiring layer, and a one-plane pattern-shaped first formed continuously in the first wiring layer in a partial region of the first wiring board. A first terminal layer and a second wiring layer formed in a partial region of the second wiring board and continuously disposed in a layer thickness direction within the range of the one-plane pattern shape with respect to the first terminal layer; A pattern shape comprising a two-terminal layer and a thermocompression-bonding conductive adhesive layer interposed between the first and second terminal layers, the second terminal layer having a gap facing the first terminal layer A wiring board connection structure characterized by the above.   2. The wiring board connection structure according to claim 1, wherein the second terminal layer has a branch pattern shape so that a gap is formed between the branches.   The void portion is formed on the side of the second terminal layer by forming the second terminal layer into a strip pattern shape having a layer width smaller than that of the first terminal layer. Wiring board connection structure described in 1.   A wiring board in which a first terminal layer formed on a first wiring board and a second terminal layer formed on a second wiring board are opposed to each other in a layer thickness direction, and the first and second terminal layers are connected by a conductive adhesive layer. A method for manufacturing a connection structure, comprising: forming a first terminal layer having a one-plane pattern continuous to a first wiring layer in a partial region of the first wiring board; and part of the second wiring board Forming a pattern-shaped second terminal layer formed in a region continuously with the second wiring layer and having a gap for facing the range of the one-plane pattern shape of the first terminal layer; And forming a conductive adhesive layer on at least one surface of the second terminal layer, and thermocompression bonding the first and second terminal layers through the conductive adhesive layer, and a part of the conductive adhesive layer is The first and second terminal layers are connected to each other by flowing into the gap. A method for manufacturing a wiring board connecting structure according to claim.

Images