JP4574311B2 - Manufacturing method of rigid-flexible substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a rigid-flexible substrate, and more particularly, to manufacture a rigid-flexible substrate in which the main surface of the flexible substrate is connected to the main surface of the rigid substrate so as to be equal to or lower than the main surface of the rigid substrate. Regarding the method.

  In general, when a rigid board is disposed across a bent portion in a housing, the rigid board is divided into a plurality of pieces, and the divided rigid boards are connected with a connector or a flexible board. .

  However, connecting rigid boards with a connector or flexible board increases the height of the connector or flexible board, resulting in an obstacle to thinning the device. After connecting rigid boards, multiple rigid boards are connected. Productivity is reduced because the substrate cannot be processed or processed simultaneously.

  For this reason, a rigid-flexible substrate is used in which a plurality of rigid substrates having the same thickness are connected to each other so that both substrate surfaces are substantially equal or the principal surface of the flexible substrate is lower than the principal surface of the rigid substrate.

  Such a rigid-flexible substrate is formed by a method disclosed in, for example, Japanese Patent Laid-Open No. 7-86749, that is, a conical shape made of a cured conductive composition protruding from a conductive metal plate such as an electrolytic copper foil. If a conductor bump is made to face another conductive metal plate through a heat-melting synthetic resin sheet and integrated by heating and pressing to make a double-sided board, many processes are required: become. In the following drawings, common portions are denoted by common reference numerals, and redundant description is omitted.

  In this method, first, as schematically shown in FIG. 28, a double-sided flexible substrate 2 in which only the edge portion is not covered with the cover film 1 is prepared. The portion of the flexible substrate 2 that is not covered with the cover film 1 is a portion that is laminated within the rigid substrate. In the figure, reference numeral 3 denotes a liquid crystal polymer film, 4 denotes a horizontal wiring portion (conductor pattern), and 5 denotes a vertical wiring portion (conductor bump).

The vertical wiring part 5 is formed by the following method using a conductor bump.
That is, a conical conductor bump is formed on the electrolytic copper foil that becomes the horizontal wiring portion 4 by patterning in a later step, and this conductive bump is connected to another electrolytic copper foil via a liquid crystal polymer film (synthetic resin sheet) 3. And these are integrated by heating and pressing. At this time, the tips of the conductor bumps are pressed against the pair of electrolytic copper foils, and the tips are plastically deformed into a truncated cone shape to form the vertical wiring portion 5 connecting the horizontal wiring portions 4 on both sides. The horizontal wiring part 4 is formed by applying a resist to each electrolytic copper foil surface, exposing through a mask pattern, removing the unexposed part by development, and etching the exposed part of the electrolytic copper foil. .

  The cover film 1 is formed by applying a resist to the substrate surface after the etching process and removing only a portion integrated with the rigid substrate by photolithography.

  Next, this flexible substrate 2 is integrated with a laminated body 6 (symbol 7 is a release film) having conductor bumps 5a separately produced, schematically shown in FIG. (FIG. 30).

The laminate 6 is formed by the following method.
That is, a conical conductor bump is formed on the electrolytic copper foil to be the horizontal wiring portion 4 by etching in a later process, and this conductor bump is passed through another glass-epoxy prepreg (synthetic resin sheet) 3a. It arrange | positions facing the electrolytic copper foil 4a, and is integrated by heating and pressurization. At this time, the front end of the conductor bump is pressed against the electrolytic copper foil 4a, and the front end is plastically deformed into a truncated cone, thereby forming the vertical wiring portion 5 that connects the electrolytic copper foils 4a on both sides. Next, the horizontal wiring portion 4 is formed by patterning the electrolytic copper foil on one side. Further, a conductor bump 5a is formed at a position corresponding to the vertical wiring portion 5 of the horizontal wiring portion 4, laminated with a glass-epoxy prepreg (synthetic resin sheet) 3a with the conductor bump 5a side inside, and heated. While being integrated by pressurization, the tip of the conductor bump 5a is protruded from the synthetic resin sheet 3a.

  The integration of the laminate 6 and the flexible substrate 2 (creation of the laminate 9) is such that the protruding side of the conductor bump 5a is the exposed surface side (the side without the cover film 1) of the horizontal wiring portion 4 of the flexible substrate 2. This is performed by aligning and heating and pressing (FIG. 30). At this time, a slit 8 is formed at the boundary between the laminate 6 and the flexible substrate 2, and a release film 7 that also serves as a spacer is interposed on the surface of the flexible substrate 2 that contacts the cover film 1.

  Further, the flexible substrate 2 side of the laminated body 9 is laminated with a separately produced laminated body 10 schematically shown in FIG. 31 and integrated by heating and pressing to form a laminated body 11 (FIG. 32).

Integration of the laminated body 9 and the laminated body 10 is performed as follows.
That is, the protruding conductor bump 5a of the laminated body 10 is brought into contact with a predetermined horizontal wiring portion 4 of the laminated body 9 (flexible substrate 2), and the surface of the laminated body 9 (flexible substrate 2) that is in contact with the cover film 1 is placed on the surface. The laminate 10 and the laminate 9 are overlapped with a release film 7 also serving as a spacer, and heated and pressed to form a laminate 11 with eight horizontal wiring portions 4 schematically shown in FIG. can get.

Thereafter, as schematically shown in FIG. 33, an outer horizontal wiring portion (outer layer pattern) 4 is formed by patterning, and an insulating protective coating 12 is applied with a resist or the like. Finally, as schematically shown in FIG. Then, the cover portions A and B covering the flexible substrate 2 are removed to complete the rigid-flexible substrate.
JP-A-7-86749

  As described above, in the conventional rigid-flexible substrate manufacturing method, in order to laminate the flexible substrate 2 between the layers of the rigid substrate (the main surface of the flexible substrate is equal to or lower than the main surface of the rigid substrate). Therefore, there is a difficulty that requires a large number of steps.

  Further, in this method, a plurality of small unit substrates are usually formed in one large substrate, and the large substrate is laminated and formed, so that a rigid substrate flexible substrate is disposed. The portion where the rigid substrate of the portion or the flexible substrate is to be disposed is punched and becomes waste, and there is a problem that the yield of the material is low.

  In addition, since a plurality of unit rigid-flexible substrates are formed on one large substrate, if a defect occurs in a portion corresponding to one of the unit substrates of the synthetic resin sheet or the laminate in the preparation process, the whole is defective. There was also a problem that the yield rate was low.

  Moreover, since the flexible substrate is a single-sided or double-sided wiring pattern, when the wiring density is high, there is a problem that the width becomes wide to widen the wiring region and the flexibility becomes insufficient. .

  Furthermore, when the flexible substrate is used on both sides, the bending resistance is impaired, so that there is a problem that the resistance to high-speed repeated bending is lowered.

The rigid-flexible substrate manufacturing method of the present invention was made to solve the above-described problems . In the rigid-flexible substrate manufacturing method, the flexible substrate is connected to the corresponding positions of both main surfaces of the rigid substrate. A step of creating a rigid substrate having a vertical wiring portion connected to a horizontal wiring portion at a position where each flexible substrate is connected or on an inner layer side thereof in a region where each flexible substrate is connected; and A step of creating a first flexible substrate and a second flexible substrate having a connection terminal in a region to be connected; and a region to which the first flexible substrate on one main surface of each rigid substrate is connected; Forming a first step portion that is equal to or deeper than the thickness of the first flexible substrate that exposes the vertical wiring portion and serves as a connection terminal Electrically connecting a terminal of the first flexible substrate to the vertical wiring portion of the first step portion of each rigid substrate, and bonding the first flexible substrate integrally to the first step portion; A second step that is equal to or deeper than the thickness of the second flexible substrate that exposes the vertical wiring portion and serves as a connection terminal in a region of the other principal surface of each rigid substrate to which the second flexible substrate is connected. Forming a portion, and electrically connecting a terminal of the second flexible substrate to the vertical wiring portion of the second step portion of each rigid substrate and integrally bonding to the second step portion It is characterized by comprising .

The rigid-flexible board manufacturing method of the present invention is the rigid-flexible board manufacturing method in which the flexible boards corresponding to the corresponding positions of the two principal surfaces of the rigid board are connected to each other. A step of forming an inner-layer rigid substrate having first and second main surfaces in which a horizontal wiring portion is exposed in the region; a plurality of first flexible substrates having a connection terminal in the region connected to the inner-layer rigid substrate; Forming the second flexible substrate, exposing a region where the first flexible substrate is connected to the first main surface of the inner-layer rigid substrate, and attaching the first exterior substrate, A step of forming a first step portion equal to or deeper than a thickness of the first flexible substrate, and a horizontal wiring portion of the first step portion of each rigid substrate Electrically connecting the terminals of the first flexible substrate and integrally bonding to the first stepped portion; and the second flexible substrate being connected to the second main surface of the inner-layer rigid substrate. Forming a second step portion that is equal to or deeper than the thickness of the second flexible substrate by exposing a region to be exposed and adhering a second exterior substrate, and the second step of each rigid substrate And a step of electrically connecting a terminal of the second flexible substrate to a horizontal wiring portion of the portion and integrally bonding to the second step portion .

  When the other end of the flexible substrate is left unconnected without being connected, the other end of the flexible substrate is manufactured longer in the above manufacturing process, and one rigid substrate is held as an insulating substrate without a wiring portion. Connect in a state. Then, in the final process after the connection, unnecessary portions may be cut.

  It is desirable that the rigid substrate has an inspection terminal on its lower surface as necessary, and the connection terminal of the step portion of the rigid substrate is connected by a metal plating layer and / or a solidified conductive paste.

  Moreover, the connection terminal of the step part of a flexible substrate can be formed from the solidified material of a metal wiring, a metal plating layer, or an electrically conductive paste. The flexible substrate may be a double-sided wiring board or a single-sided wiring board.

  The vertical wiring portion to which the connection terminal of the flexible substrate of the rigid substrate is connected can be formed by connecting conductor bumps in the thickness direction of the substrate, but can also be formed by via holes or through holes. Further, the connection terminals connected to the vertical wiring portion of the rigid substrate of the flexible substrate can also be formed with conductor bumps, but can also be configured with other terminals such as high-temperature solder or electrolytic copper foil.

  In the present invention, the conductor bumps used for the rigid wiring board, the vertical wiring portion of the flexible board, and the connection terminal of the flexible board are usually formed on the conductive metal layer. Examples of such a conductive metal layer include a conductive sheet (foil) such as an electrolytic copper foil. The conductive metal layer may be a single sheet or a patterned sheet. The shape is not particularly limited, and the conductor bumps may be formed not only on one main surface but also on both main surfaces.

  Conductive bumps are, for example, conductive powders such as silver, gold, copper, solder powder, alloy powders or composite (mixed) metal powders, and polycarbonate resins, polysulfone resins, polyester resins, phenoxy resins, phenol resins, polyimide resins, etc. It is comprised with the electroconductive composition prepared by mixing binder components, such as these, or an electroconductive metal. When the conductive bump is formed of a conductive composition, the bump having a high aspect ratio can be formed by, for example, a printing method using a relatively thick metal mask. In general, the height of the conductor bump is desirably about 100 to 400 μm, and the height of the conductor bump is high enough to penetrate a single synthetic resin sheet and high enough to penetrate a plurality of synthetic resin sheets. May be mixed as appropriate. As means for forming a conductive bump with a conductive metal, (a) a fine metal soul having a certain shape or size is spread on a conductive metal layer surface on which an adhesive layer has been provided in advance, and is selectively fixed. (This may be done by placing a mask), (b) A plating resist is printed and patterned on the surface of the electrolytic copper foil, and copper, tin, gold, silver, solder, etc. are plated to selectively make a minute metal Forming columns (bumps); (c) applying and patterning a solder resist on the surface of the conductive metal layer; and dipping in a solder bath to selectively form minute metal columns (bumps); (d) metal plate A part of the film is covered with a resist and etched to form a fine metal bump. Here, the fine metal soul or the fine metal pillar corresponding to the conductor bump may have a multilayer structure or a multilayer shell structure in which different metals are combined. For example, copper may be cored and the surface may be coated with a gold or silver layer to provide oxidation resistance, or copper may be cored and the surface may be coated with a solder layer to provide solder jointability. In the present invention, when the conductive bump is formed of a conductive composition, the process can be further simplified as compared with the case where the conductive bump is formed by means such as plating, which is effective in terms of cost reduction.

  In the present invention, as the synthetic resin-based sheet constituting the insulating layer of the rigid substrate or flexible substrate into which the conductor bumps are inserted, for example, a thermoplastic resin film (sheet) or a thermosetting resin sheet held in a state before curing is used. The thickness is preferably about 50 to 300 μm. Here, examples of the thermoplastic resin sheet include sheets such as polycarbonate resin, polysulfone resin, thermoplastic polyimide resin, tetrafluoropolyethylene resin, hexafluoropolypropylene resin, and polyetheretherketone resin. In addition, the thermosetting resin sheet held in the pre-curing state includes epoxy resin, bismaleimide triazine resin, polyimide resin, phenol resin, polyester resin, melamine resin, or butadiene rubber, butyl rubber, natural rubber, neoprene rubber, silicone. Examples thereof include raw rubber sheets such as rubber. These synthetic resins may be used alone or may contain insulating inorganic or organic fillers, and sheets made of glass cloth or mat, organic synthetic fiber cloth or mat, or a sheet combined with a reinforcing material such as paper. There may be.

  Furthermore, in the present invention, a plurality of layers having a structure in which the main surface of the synthetic resin sheet is in contact with the main surface of the conductive metal layer in which the conductor bumps are formed in order to form a rigid substrate or a flexible substrate are laminated. When heating and pressurizing the laminated body, the base (pad) on which the synthetic resin sheet is placed is used as a metal plate or heat-resistant resin plate, such as stainless steel plate, brass plate, polyimide resin, with little size and deformation. A plate (sheet), a polytetrafluoroethylene resin plate (sheet), or the like is used.

  According to the method for manufacturing a printed wiring board according to the present invention, a rigid-flexible substrate can be created by a simple method in which a flexible substrate and a rigid substrate are separately manufactured and connected to each other, greatly increasing the production process. Can be simplified. In addition, there is no flexible substrate in the rigid substrate, and there is no process for removing the rigid substrate only in the portion of the flexible substrate, so that the material utilization efficiency can be improved. In addition, since each of the rigid substrate and the flexible substrate can be judged as good or bad in the almost completed unit substrate state before connection, loss can be minimized even if a defect occurs in the production process.

  When two single-sided flexible boards are used and the other end of each flexible board is connected to another rigid board, the amount of wiring in the flexible board portion is smaller than when one double-sided flexible board is connected. Flexibility and flexibility can be improved without decreasing. In addition, if the other end of the two flexible boards connected to one rigid board is made a free end without being connected, it is possible to connect to separate boards and devices later. Also, the degree of freedom of design increases.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 23, the same reference numerals are given to the portions common to FIGS. 24 to 30, and the overlapping description will be omitted.

  First, Example 1 in which a rigid-flexible substrate in which two equal-thickness rigid substrates are connected via two equal-length equal-thickness flexible substrates arranged with their main surfaces substantially parallel to each other was produced. explain.

(Create flexible substrate)
First, an electrolytic copper foil (4a) having a thickness of 18 μm was adhered to both sides of a polyimide film 3 (PI) having a thickness of 25 μm to form a through hole TH at a predetermined position of the substrate to obtain a double-sided copper-clad flexible substrate.

  A normal etching resist ink (trade name, PSR-4000 H, Taiyo Ink KK) is screen-printed on the electrolytic copper foil 4a on both sides of this double-sided copper-clad laminate, masking the conductor pattern, and then cupric chloride. After performing an etching treatment using as a etchant, the resist mask was peeled off to obtain a double-sided flexible substrate 20 shown in FIG. Reference numeral 4 denotes a horizontal wiring portion obtained by patterning the electrolytic copper foil 4a by etching. Further, the cover film 1 was formed by photolithography on the horizontal wiring portion 4 except for the vicinity of the through hole TH of the double-sided flexible substrate 20.

  Next, as shown in FIG. 2, a conductor bump 5a is formed on the portion of the horizontal wiring portion 4 connected to the through hole TH, and a glass-epoxy prepreg (synthetic resin sheet) 3a having a thickness of 60 μm is formed thereon. Abutting and placing between an aluminum foil and a rubber sheet, for example, between hot plates kept at 100 ° C., heating and pressurizing at 1 MPa for about 1 minute, the tip of the conductor bump 5a is a glass-epoxy prepreg (synthetic resin) A flexible substrate 21 protruding from the system sheet 3a was prepared.

  The flexible substrate 21 shown in FIG. 2 is for connecting the two rigid substrates shown in FIG. 4 and is connected to the front side (first main surface side) of the edge of the rigid substrate. Both the first flexible substrate to be connected and the second flexible substrate to be connected to the back side (second main surface side) of the edge of the rigid substrate were made to be the same length. The flexible substrate 21 is formed by making a large number of substrates in a large substrate and is completed up to the state shown in FIG. 2, and then divided into individual flexible substrates and connected to the rigid substrate.

(Rigid board creation)
As a B2it (B Square It: registered trademark) except that the glass-epoxy prepreg (synthetic resin sheet) 3a before curing having a thickness of 60 μm is used instead of the polyimide film 3 (PI) described above. 3 using the double-sided rigid substrate having the same structure as that of the flexible substrate shown in FIGS. 1 and 2 by a known method described in, for example, Japanese Patent Laid-Open No. 8-204332. A rigid substrate 22 having the horizontal wiring portion 4 was prepared.

  This rigid substrate 22 has the same structure as the rigid substrate portion of the laminate 11 shown in FIG. 29, except that each insulating layer is made of glass-epoxy prepreg (synthetic resin sheet) 3a. .

  The rigid substrate 22 shown in FIG. 3 is also made by making a large number of substrates in a large single substrate and formed up to the state of FIG. 3 or after the countersink processing described later is completed. Divided into individual rigid substrates.

(Production of a rigid substrate having a first step)
In the state of a large substrate before being divided into individual rigid substrates, countersink processing is performed in the vicinity of the vertical wiring portion 5 connected to the flexible substrate of each rigid substrate 21, and is equal to the thickness of the flexible substrate 20 to be connected? The rigid substrate 23 having the stepped portion S, which is deeper and is exposed to expose the vertical wiring portion 5 and serve as a connection terminal, was created (FIG. 4).

(Connection between rigid board and first flexible board)
Next, the unit rigid board | substrate 23 and the 1st unit flexible board | substrate 21 which were divided | segmented separately are arrange | positioned so that it may become the positional relationship which can be connected in a frame. Usually, the frame is of such a size that a plurality of rigid-flexible substrates can be assembled.

  In FIG. 5, the rigid substrate 23 in which the stepped portion S is formed in the frame body 24 is disposed so that the stepped portion S faces each other, and the first substrate straddles the stepped portion S of each rigid substrate 23. In this example, the flexible substrate 21 is disposed and temporarily fixed. In this embodiment, small projections 25 whose overall width is substantially the same as the width of the holding portion of the frame body 24 are formed on the outer periphery of each rigid substrate 23, and the rigid substrate disposed in the frame body 24. 23 is held and fixed in the frame 24 by the small protrusion 25.

  In this way, a plurality of frames 24 holding a plurality of rigid substrates 23 and flexible substrates 21 in a connectable positional relationship are stacked and integrated by heating and pressing, and the cross section is schematically shown in FIG. As shown, a rigid-flexible substrate in which both ends of the first flexible substrate are respectively connected to the first step portions of the two rigid substrates is obtained.

(Formation of second step)
Next, each rigid-flexible substrate connected in the state of FIG. 6 is fixed to the frame body 24 at a position (in the vicinity of the vertical wiring portion 5) where the second flexible substrate is connected. Processing was performed to form a second step S (FIG. 7). FIG. 8 is a perspective view schematically showing the first step portion S and the second step portion S of the rigid substrate 23. As shown in the drawing, the second step portion S is formed at substantially the same position and the same size as the first step portion S when viewed from directly above. However, the widths of the first flexible substrate and the second flexible substrate can be designed to be increased or decreased depending on the number of necessary wirings.
(Connection between rigid substrate and second flexible substrate)
Next, as shown in FIG. 9, the second flexible substrate is placed across the second stepped portion S of each rigid substrate 23 with the spacer 31 interposed therebetween, while being fixed to the frame body 24. 21 was disposed and integrated by heat and pressure to connect the rigid substrate and the second flexible substrate. The reason why the spacer 31 is interposed between each first flexible substrate and the second flexible substrate is to prevent deformation of the flexible substrate.

  6 to 10, the second step portion is shown below. However, when actually processing and connecting, the second step portion is turned upside down while being fixed to the frame body 24 so as to be easily processed and connected.

(Completion of rigid-flexible substrate)
After the connection, the spacers 31 between the flexible substrates 21 are removed, and the rigid-flexible substrates are punched out to complete the rigid-flexible substrate schematically shown in FIG.

  In addition, in the figure, since it shows schematically, the flexible substrate 21 is short, and the cross section of the spacer 31 looks like a square, but actually, the cross section of the spacer 31 is like a line. is there. Specifically, the thickness of the flexible substrate 21 is about 60 μm (as described above, the thickness of the polyimide film 3 is 25 μm, and the thickness of the copper foil serving as the horizontal wiring portion is 18 μm). The distance between the second flexible substrate 21 and the second flexible substrate 21 is about 60 to 300 μm although it depends on the thickness of the rigid substrate. The length of the flexible substrate 21 is about several centimeters. The width of the step portion is, for example, about 1 cm, and the length of the step portion is, for example, about 3 mm.

  As described above, one end of one flexible substrate is connected to the corresponding position of both main surfaces of one rigid substrate, and the other end of each flexible substrate is connected to both main surfaces of the other rigid substrate. A rigid-flexible substrate connected to the corresponding position is completed.

  Next, Example 2 in which a rigid-flexible substrate in which one end of each of the two flexible substrates is connected to the same rigid substrate and the other end is not connected and is a free end (free) will be described. .

  Even if one end is free, it is necessary to hold both ends of the flexible board in the manufacturing process, so make one end of the flexible board free to be longer, and use it as an outer frame board without wiring. Connecting. Then, after mounting, unnecessary portions are cut to make them free. Other points are basically the same as in the first embodiment. Example 2 will be specifically described below.

(Create flexible substrate)
In the manufacturing process, the polyimide film 3 at one end is made longer than the length of the product (for example, about 5 mm longer) so that both ends of the flexible substrate can be held. A flexible substrate 21 was created (FIG. 11).

(Rigid board creation)
A rigid substrate 23 having a horizontal wiring portion 4 and a vertical wiring portion 5 was produced in the same manner as in Example 1. On the other hand, in order to hold one side of the flexible substrate, an outer frame substrate 30 without a wiring portion was also created. The outer frame substrate 30 was formed using the same glass-epoxy prepreg (synthetic resin sheet) 3 a as the insulating material of the rigid substrate 23 so as to have the same thickness as the rigid substrate 23.

(Production of a rigid substrate having a first step)
Countersinking was performed in the same manner as in Example 1 to produce a rigid substrate 23 having a stepped portion S where the vertical wiring portion 5 was exposed and an outer frame substrate 30 having a stepped portion S having no wiring portion (see FIG. 12).

(Connection between rigid board and first flexible board)
Next, as shown in FIG. 5, the unit rigid board 23, the unit flexible board 21, and the non-unit frame board 30 that are individually divided in the frame body 24, and the rigid board 23 and the outer frame board 30. With the first step S facing each other, the flexible substrate 21 has the longer end of the polyimide film 3 on the step S of the outer frame substrate 30 and the other end of the unit rigid substrate 23. Each was placed on the step S.

A plurality of the frame bodies 24 were stacked and integrated by heating and pressing, and the rigid substrate 23, the outer frame substrate 30, and the first flexible substrate 21 were connected (FIG. 13).
(Formation of second step)
Next, in the same manner as in Example 1, the countersinking process was performed while being fixed to the frame body 24 to create the second step S on the rigid board 23 and the outer frame board 30 (FIG. 14).
(Connection between rigid substrate and second flexible substrate)
Next, in the same manner as when the first flexible substrate is connected, the flexible substrate 21 is fixed to the outer frame through the spacer 31 through the spacer 31 while being fixed to the frame body 24. On the step S of the substrate 30, the other end was disposed on the step S of the unit rigid substrate 23.

  A plurality of the frame bodies 24 were stacked and integrated by heating and pressing, and the rigid substrate 23, the outer frame substrate 30, and the second flexible substrate 21 were connected (FIG. 15).

(Completion of rigid-flexible substrate)
After the connection, the spacers 31 between the flexible substrates 21 are removed, and each rigid-flexible substrate is punched out. As shown schematically in FIG. 16, one end of each of the two flexible substrates 21 is the same rigid substrate. The rigid-flexible substrate with the other end connected to the outer frame substrate 30 is completed.

  Thereafter, each component is mounted and cut at the position indicated by the cut line 32 in FIG. 16, and the non-product portion of the flexible substrate 21 and the outer frame substrate 30 are removed.

  As described above, one end of each of the two flexible boards 21 is connected to the corresponding positions of the two main surfaces of one rigid board, and the other end is not connected, and the rigid-flexible flexible. The substrate is completed (FIG. 17).

  In Examples 1 and 2 above, in the process of creating a rigid substrate having a stepped portion, a stepped shape was obtained by performing countersink processing, but the outer layer rigid substrate in which the stepped portion was previously removed by router processing or the like It is also possible to separately form an inner-layer rigid substrate having a connection portion with a flexible substrate and stack them.

  18 to 24 illustrate Example 3 of another method for manufacturing a rigid substrate having such a stepped portion and a method for manufacturing a rigid-flexible substrate connected using the same.

  Hereinafter, the description of the same parts as those of the first embodiment such as the production of the flexible substrate 21 will be omitted, and description will be made focusing on other manufacturing methods of the rigid substrate having such stepped portions.

  First, a two-layer rigid double-sided wiring board was prepared by the above-described B2it manufacturing method, and a portion to be the stepped portion S was previously removed by router processing or the like. Thus, a first outer layer rigid substrate 50a was obtained (FIG. 18A). Similarly, a second outer layer rigid substrate 50c was obtained (FIG. 18C). On the other hand, a four-layer rigid double-sided wiring board was prepared by the above-described B2it manufacturing method to obtain an inner-layer rigid board 50b in which the horizontal wiring portion 4 was exposed at a position where it was connected to the flexible board (FIG. 18B).

  These rigid substrates 50a, 50b, and 50c are also made by making a large number of substrates into one large substrate and forming them up to the state shown in FIG. 3, and are divided into individual rigid substrates.

  Next, conductor bumps 5 are formed on the horizontal wiring portion 4 on the main surface side of the first outer layer rigid substrate 50a that is connected to the inner layer rigid substrate 50b, and the flexible substrate on the first main surface of the inner layer rigid substrate 50b is connected. The six-layer rigid substrate 50 having the first step S was created by exposing the region to be exposed, and positioning and heating and pressing through the uncured prepreg 3a (FIG. 19). . In the case of the first embodiment, the vertical wiring portion 5 is exposed at the step portion of the rigid substrate. However, in this third embodiment, the step is formed by attaching the double-sided wiring board without performing the countersinking process. Therefore, the difference is that the horizontal wiring part 4 is exposed on the surface of the step part and serves as a connection terminal.

  Next, in the same manner as in Example 1, the six-layer rigid board 50 having the first step S and the first unit flexible board 21 are in a positional relationship in which the frame body 24 can be connected. A plurality of the frame bodies 24 are stacked and integrated by heating and pressurization, and as shown schematically in cross section in FIG. 20, both ends of the first flexible substrate are the first of the two rigid substrates. A rigid-flexible substrate in a state of being connected to each step is obtained (FIG. 20).

  Next, with each rigid-flexible substrate connected in the state of FIG. 20 fixed to the frame 24, the second outer layer rigid substrate 50c previously created is replaced with the second rigid substrate 50b of the inner layer rigid substrate 50b. An 8-layer rigid substrate having a second stepped portion S is exposed by exposing a region to which a flexible substrate on one main surface is connected, positioning through uncured prepreg 3a, and heating and pressing. 50 was created (FIGS. 21 and 22).

  Next, the rigid board | substrate and the 2nd flexible substrate were connected like Example 1 with the state fixed to the frame 24 (FIG. 23).

  After the connection, the spacers 31 between the flexible substrates 21 are removed, and the rigid-flexible substrates are punched out to complete the rigid-flexible substrate schematically shown in FIG.

(Other examples)
In addition, this invention is not limited to the above Example, You may make it as follows.
For example, in the production of a rigid substrate having a stepped portion, the conductor bump of the countersink portion may be sandwiched between copper wirings, but in order to expose the conductor bump portion on the surface in consideration of the countersink accuracy in the depth direction The countersunk portion may be free of copper wiring. Moreover, although it may be divided into individual rigid substrates after being countersunk in the state of a large substrate as in the first embodiment, the countersinking may be performed after being divided into individual rigid substrates.

  Further, when each unit substrate is held on the frame body 24 in steps such as counterboring and bonding (see FIG. 5), the small protrusions 25 are temporarily fixed to the inner surface of the frame body 24 with an adhesive as necessary. You may make it do. Further, as shown in FIG. 25, a T-shaped projection 26 is provided on the edge of the rigid substrate 23, and a recess 27 is provided at the corresponding position on the inner surface of the frame 24 to fit the projection. The rigid substrate 23 may be held on the frame body by a mating structure.

  In the above embodiment, the example in which the vertical wiring portion to which the flexible substrate is connected is formed by the conductor bump has been described. However, it is also possible to fill the via hole 28a shown in FIG. 26 with the conductive paste 28b. It is. Further, as shown in FIG. 27, the conductor bumps 29 are formed by high-temperature solder (for example, solder having a melting point of about 200 ° C. to 240 ° C.), and the terminals 27 (substantially the same as the horizontal wiring portion 4) formed on the stepped portion of the rigid substrate 23. May be soldered to the same). In this case, remelting of the connecting solder between the flexible substrate and the rigid substrate can be avoided by using a solder having a melting point lower than that of the high temperature solder described above when mounting the electronic component. Alternatively, the insulating layer can be made conductive by drilling holes with a laser or the like, embedding a conductive paste in the insulating layer, and then laminating.

  Furthermore, as a connection between the flexible substrate and the rigid substrate, (a) a method of connecting by sandwiching an anisotropic conductive film, (b) gold plating is applied to each terminal of the flexible substrate and the rigid substrate, Connection is also possible by a method of crimping connection, (c) a method of connecting by insulating hot layers filled with a conductive paste and vacuum hot pressing.

  Moreover, although the above Example demonstrated the example which used the flexible substrate as the double-sided wiring board, the single-sided wiring board may be sufficient as a flexible substrate. If the horizontal wiring part 4 and the vertical wiring part 5 of the flexible substrate are formed at a position where the vertical wiring part 5 of the step portion of the rigid board can be connected, even single-sided wiring can be connected.

  When manufacturing rigid-flexible substrates, the rigid substrate and flexible substrate can be manufactured in separate processes, and after both are divided into unit substrates, the rigid substrate and flexible substrate can be manufactured, which greatly simplifies the production process. And there are few parts which become waste, and a yield can be improved by using a material effectively. In addition, since it is possible to determine pass / fail for each unit substrate and perform the final connection process using only non-defective products, it is possible to minimize waste even if a defect occurs in the substrate manufacturing process. In addition, when two single-sided flexible boards are used, one end of each flexible board is connected to the same rigid board, and the other end is connected to another same rigid board, one double-sided flexible board is attached. As compared with the case where the two rigid boards are connected via each other, flexibility and flexibility can be improved without reducing the wiring amount of the flexible board portion. In addition, if the other ends of the two flexible boards connected to the same rigid board are made free ends without being connected, they can be connected to separate boards and devices later. Also, the degree of freedom of design increases.

Sectional drawing which shows typically the double-sided type flexible substrate used for manufacture of a rigid-flexible substrate. Sectional drawing which shows typically the state which provided the conductor bump in the flexible substrate of FIG. Sectional drawing which shows typically the rigid board | substrate used for manufacture of a rigid-flexible board | substrate. Sectional drawing which shows typically the state which gave the countersink process to the flexible substrate connection part of the rigid board | substrate of FIG. The top view which shows the state which incorporated the unit rigid board | substrate and the unit flexible board | substrate in the frame. Sectional drawing which shows typically the state which connected the rigid board | substrate and the 1st flexible substrate in Example 1. FIG. FIG. 7 is a cross-sectional view schematically illustrating a state in which a stepped portion is formed by performing countersink processing on a second flexible substrate connecting portion of the rigid substrate of FIG. 6. The perspective view which shows typically two step parts provided in the rigid board | substrate. Sectional drawing which shows typically the state which connected the 2nd flexible substrate via the spacer to the rigid board | substrate of FIG. Sectional drawing which shows typically the rigid-flexible board | substrate of Example 1 completed by removing the spacer of FIG. In Example 2, sectional drawing which shows typically the state which provided the conductor bump in the flexible substrate. Sectional drawing which shows typically the state which formed the step part S in the outer frame board | substrate in Example 2. FIG. Sectional drawing which shows typically the state which connected the rigid board | substrate and the outer frame board | substrate, and the 1st flexible substrate in Example 2. FIG. FIG. 14 is a cross-sectional view schematically illustrating a state in which a stepped portion S is formed by performing countersink processing on the second flexible substrate connecting portion of the rigid substrate and the outer frame substrate of FIG. 13. FIG. 15 is a cross-sectional view schematically showing a state in which a second flexible substrate is connected to the substrate of FIG. 14 via a spacer. Sectional drawing which shows typically the rigid-flexible board | substrate of the state which removed the spacer of FIG. Sectional drawing which shows typically the rigid-flexible board | substrate of Example 2 of the state completed by cut | disconnecting an unnecessary part. Schematic sectional view for explaining another method for manufacturing a rigid substrate having a stepped portion. Schematic sectional view for explaining another method for manufacturing a rigid substrate having a stepped portion. Sectional drawing which shows typically the state which connected the rigid board | substrate and the 1st flexible substrate in Example 3. FIG. Schematic sectional view for explaining another method for manufacturing a rigid substrate having a stepped portion. Sectional drawing which shows typically the state which stuck the rigid board | substrate of FIG. 21 and was set as the board | substrate with a 2nd step part. FIG. 23 is a cross-sectional view schematically showing a state in which a second flexible substrate is connected to the substrate of FIG. 22 via a spacer. FIG. 24 is a cross-sectional view schematically showing a rigid-flexible substrate in a state where the spacer of FIG. 23 is removed. The top view which shows a part of engaging part of a frame and a unit rigid board | substrate. Sectional drawing which shows typically the state of the connection part of the rigid board | substrate and flexible substrate by another connection method. Sectional drawing which shows typically the state of the connection part of the rigid board | substrate and flexible substrate by another connection method. Sectional drawing which shows typically the flexible substrate used for manufacture of the conventional rigid-flexible substrate. Sectional drawing which shows typically the laminated body laminated | stacked with the flexible substrate of FIG. FIG. 29 is a cross-sectional view schematically showing a laminate in which the flexible substrate of FIG. 28 and the laminate of FIG. 25 are laminated. Sectional drawing which shows typically the laminated body laminated | stacked with the laminated body of FIG. Sectional drawing which shows typically the laminated body which laminated | stacked the laminated body of FIG. 30 and the laminated body of FIG. Sectional drawing which shows typically the laminated body which patterned the outer layer of the laminated body of FIG. Sectional drawing which shows a rigid-flexible board | substrate typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cover film, 2 ... Double-sided type flexible substrate which is not coat | covered 3 ... Polyimide film, 3a ... Glass-epoxy type prepreg (synthetic resin type sheet), 4 ... Horizontal wiring part (conductor pattern), 4a ... electrolytic copper foil, 5 ... vertical wiring part (conductor bump), 5a ... conductor bump, 6, 9, 10, 11 ... laminated body, 8 ... slit, 12 ... insulating protective coating, 20, 21 ... flexible substrate, 22, DESCRIPTION OF SYMBOLS 23 ... Rigid board | substrate, 24 ... Frame body, 25 ... Small protrusion, 26 ... Protrusion part, 27 ... Recessed part, 28 ... Via hole, 29 ... Conductor bump by high temperature solder, 30 ... Outer frame board | substrate, 31 ... Spacer, 32 ... Cut-off line , TH ... Through hole.

Claims (2)

In the rigid-flexible board manufacturing method in which the flexible board is connected to the corresponding positions on both main surfaces of the rigid board, respectively.
A step of creating a rigid substrate having a vertical wiring portion connected to a horizontal wiring portion at a position where each flexible substrate is connected or an inner layer side thereof in a region where each flexible substrate is connected;
Creating a first flexible substrate and a second flexible substrate having connection terminals in a region connected to the rigid substrate;
The first flexible substrate is exposed to the first flexible substrate on one main surface of each rigid substrate, and the vertical wiring portion is exposed to form a connection terminal, which is equal to or deeper than the thickness of the first flexible substrate. Forming a step, and
Electrically connecting the terminals of the first flexible substrate to the vertical wiring portion of the first step portion of each rigid substrate and bonding the first flexible substrate integrally to the first step portion;
A second layer that is equal to or deeper than the thickness of the second flexible substrate that is used as a connection terminal by exposing the vertical wiring portion to a region of the other main surface of each rigid substrate to which the second flexible substrate is connected. Forming a step, and
Electrically connecting a terminal of the second flexible substrate to a vertical wiring portion of the second step portion of each rigid substrate and integrally bonding to the second step portion;
A method of manufacturing a rigid-flexible substrate, comprising: In the rigid-flexible board manufacturing method in which the flexible boards corresponding to the corresponding positions of both main surfaces of the rigid board are connected,
Creating an inner-layer rigid substrate having first and second main surfaces in which a horizontal wiring portion is exposed in a region to which each flexible substrate is connected;
Creating a plurality of first flexible substrates and a plurality of second flexible substrates having connection terminals in a region connected to the inner layer rigid substrate;
A region to which the first flexible substrate is connected is exposed on the first main surface of the inner layer rigid substrate, and the first exterior substrate is attached to be equal to or deeper than the thickness of the first flexible substrate. Forming a first step;
Electrically connecting the terminals of the first flexible substrate to the horizontal wiring portion of the first step portion of each rigid substrate, and bonding them integrally to the first step portion;
An area to which the second flexible substrate is connected is exposed on the second main surface of the inner layer rigid substrate, and a second exterior substrate is adhered to the second flexible substrate so as to be equal to or deeper than the thickness of the second flexible substrate. Forming a second step,
Electrically connecting a terminal of the second flexible substrate to a horizontal wiring portion of the second step portion of each rigid substrate, and bonding the second flexible substrate integrally to the second step portion;
A method of manufacturing a rigid-flexible substrate, comprising:

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