JP2007266481A - Multilayer board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the connection reliability of a wiring provided on a flexible board and a wiring in a reinforced board. <P>SOLUTION: In a multilayer board in which a flexible wiring board 100 and a metallic body 104 for reinforcement are laminated via an adhering layer 105b, the flexible wiring board 100 comprises an insulation film 101 and a plating land 103a formed of a metallic layer provided to one surface of the insulation film 101. On one surface of the metallic body 104 for reinforcement, a surface plating 103c is provided. From the flexible wiring board 100 extending through to the adhering layer 105b, a via 106 is provided through the flexible wiring board 100 and the adhering layer 105b, and a solder layer 109b, covering the plating land 103a in the state of a layer, is embedded in the via 106 and connected to the plating land 103a and the surface plating 103c. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer substrate, and more particularly to a substrate in which a flexible substrate and a conductor substrate are laminated.

  In recent years, with the downsizing, weight reduction, and multifunctionalization of electronic devices such as mobile phones, flexible wiring boards having a microstrip line structure are widely used as circuit boards constituting these electronic devices. While a flexible wiring board is required to have flexibility, strength and flatness of a component mounting location are also required, and glass epoxy resin or SUS (stainless steel) is generally used as a reinforcing material.

  Conventionally, as a laminated structure of a flexible wiring board and a reinforcing metal body, there are two simple structures in which the flexible wiring board and the reinforcing metal body are not in conductive contact, and a structure in which the laminated structure is provided with conductive contact. There are types.

  Conventionally, as a structure in which a flexible wiring board and a reinforcing metal body are electrically connected, there are those described in Patent Document 1 and Patent Document 2.

  Among these, Patent Document 1 describes that a through hole is provided in a flexible printed circuit board, and the wiring pattern of the flexible printed circuit board and the lead terminal of the metal core wiring board are connected via the through hole.

Further, in Patent Document 2, in a laminate of a reinforcing substrate having a wiring pattern formed on the surface and a flexible substrate having a wiring pattern formed on the surface, the through holes of the flexible substrate are filled with solder, It is described that the wiring pattern is made conductive.
JP-A-62-022497 Japanese Patent Laid-Open No. 7-249872

  However, the techniques described in Patent Document 1 and Patent Document 2 described above still have room for improvement in terms of connection reliability between the wiring pattern provided on the flexible substrate and the conductive material in the reinforcing substrate.

According to the present invention,
A film made of an insulating material;
A first wiring pattern provided on one surface of the film and configured by a metal layer;
A flexible substrate including:
A reinforcing substrate laminated on the flexible substrate;
An insulating adhesive layer that is provided between the flexible substrate and the reinforcing substrate to bond the flexible substrate and the reinforcing substrate;
A solder layer covering the first wiring pattern in layers;
Including
A through hole penetrating the flexible substrate and the adhesive layer is provided from the flexible substrate to the adhesive layer,
Provided is a multilayer board in which the solder layer is embedded in the through hole and connected to the first wiring pattern and a conductive member in the reinforcing board.

  According to the present invention, the solder layer covers the first wiring pattern in layers, and the solder layer is embedded in the through hole that penetrates the flexible substrate and the adhesive layer. For this reason, the connection reliability of the 1st wiring pattern provided in the flexible substrate and the electrically-conductive member in a reinforcement board | substrate can be improved.

  As described above, according to the present invention, the connection reliability between the wiring provided on the flexible substrate and the conductive member on the reinforcing substrate can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, common constituent elements are denoted by the same reference numerals, and description thereof is omitted as appropriate.

FIG. 1 is a perspective view illustrating a configuration of a small electronic device according to the present embodiment.
The small electronic device shown in FIG. 1 includes a main board 12 having a feeding point 11 and a flexible wiring board 100 that functions as a peripheral circuit board. The flexible wiring board 100 is a laminated body with the reinforcing metal body 104.

  The main board 12 and the flexible wiring board 100 are usually connected by fitting the connector 14 on the main board 12 and the connector 15 on the flexible wiring board 100. Further, since the power feeding point 11 is provided on the main board 12 side and the flexible wiring board 100 is a board having a different configuration from the power feeding point 11, the ground reinforcement is performed using the pin connector 13 which is a point other than the connector 14. Can also be planned. In this way, even when the flexible wiring board 100 does not have the feeding point 11, it is effective as a countermeasure against being affected by noise or causing noise such as an electrically weak ground. For this countermeasure, it is preferable that the back surface 16 of the flexible wiring board 100, that is, the surface that overlaps the main board 12, be in a conductive contact with the ground of the flexible wiring board 100.

  Next, the configuration of the flexible wiring board 100 in the small electronic device shown in FIG. 1 will be described. FIG. 4 is a cross-sectional view showing a configuration of a multilayer board in which the flexible wiring board 100 and the reinforcing metal are laminated.

  The laminated substrate shown in FIG. 4 includes a film (insulating film 101) made of an insulating material, a first wiring pattern (copper foil 102a) provided on one surface of the insulating film 101, and made of a metal layer. , A flexible substrate (reinforcing metal body 104) having a second wiring pattern (surface plating 103c) formed on one surface, a flexible wiring substrate 100, and a reinforcing metal body 104, an insulating adhesive layer 105b that adheres the flexible wiring board 100 and the reinforcing metal body 104, and a solder layer 109b that covers the copper foil 102a in layers. A copper foil 102a is interposed between the plating land 103a and the solder layer 109b.

  The flexible wiring board 100 is, for example, a single-sided copper foil wiring in which a copper foil wiring layer (copper foil 102a), vias 106, and lands (plating lands 103a) are formed on an insulating base material (insulating film 101) made of an insulating resin film. Have In the flexible wiring substrate 100, a copper foil 102a is provided on one side of an insulating film 101 serving as a base. The copper foil 102a has a predetermined plane pattern and constitutes signal wiring and ground wiring. A plating land 103a that covers the copper foil 102a is formed in layers in contact with the copper foil 102a. Between the adjacent plating lands 103a, an insulating film 108 and an adhesive 107 for bonding the insulating film 108 are laminated, and the plating lands 103a are insulated from each other.

  The reinforcing metal body 104 is a conductive substrate including a metal substrate made of, for example, SUS (stainless steel). The reinforcing metal body 104 may be subjected to a predetermined surface treatment in advance. A surface plating 103 c is formed in a layered manner at a predetermined position on one surface of the reinforcing metal body 104. The surface plating 103c functions as a wiring layer and has a predetermined plane pattern. The adhesive layer 105b can be made of, for example, a thermosetting resin.

  Further, as shown in FIG. 4, through holes (vias 106) penetrating the flexible wiring substrate 100 and the adhesive layer 105b are provided from the flexible wiring substrate 100 to the adhesive layer 105b. The via 106 has an enlarged diameter in the adhesive layer 105b, and has an overhanging portion that protrudes in the surface direction of the surface plating 103c in the adhesive layer 105b. Further, in the flexible wiring substrate 100, the via 106 has a tapered shape with a narrow diameter from the plating land 103a toward the adhesive layer 105b. That is, the via 106 has a diameter reduced in a taper shape from the plating land 103a toward the adhesive layer 105b, and then expanded in the adhesive layer 105b. The inner wall of the via 106 is covered with through-hole plating 103b. The through-hole plating 103b may be formed in the same process as the plating land 103a, or may be formed in a separate process. In the case of another process, for example, the through-hole plating 103b may be formed by a copper foil process.

  The solder layer 109b is embedded in the via 106 and connected to the conductive member (surface plating 103c) in the copper foil 102a and the reinforcing metal body 104. Further, since the reinforcing metal body 104 has conductivity, the solder layer 109b electrically connects the copper foil 102a and the reinforcing metal body 104.

  The solder layer 109b has a wiring region that covers the through-hole plating 103b and a plug region embedded in the via 106, and these are formed continuously and integrally. Here, continuous integration means that it is integrally formed as a continuous member, and preferably does not have a joint portion. Since the solder layer 109b extends from the plug region to the wiring region, the bonding area between the plating land 103a and the solder layer 109b is large, and the connection reliability is excellent.

  In addition, the solder layer 109b has a flange in contact with the back surface of the insulating film 101 and extending outward from the insulating film 101 and projecting in the in-plane direction of the adhesive layer 105b in the plug region. Since it has a collar part, a joining area with surface plating 103c increases, and it has composition excellent in joining reliability.

  In FIG. 4, an alloy is formed between the metal in the plating land 103a and the metal in the solder layer 109b, and the alloy layer 110 is included between the copper foil 102a and the solder layer 109b. The alloy layer 110 includes a metal element constituting the solder layer b109. Further, by using, for example, gold plating as the plating land 103a and the through-hole plating 103b, it is possible to reliably form an alloy containing the metal element constituting the through-hole plating 103b and the metal element constituting the solder layer 109b. Note that the alloy existing between the copper foil 102a and the solder layer 109b does not necessarily have to be layered. By providing the alloy layer 110 on the copper foil 102a, the connection reliability between the solder layer 109b and the copper foil 102a can be further improved.

  Next, a method for manufacturing the multilayer substrate shown in FIG. 4 will be described. In this laminated substrate, vias 106 are provided in the insulating base material (insulating film 101) and the copper foil wiring layer (plating land 103a) of the flexible wiring substrate 100, and components are mounted on the plating land 103a formed in the flexible wiring substrate 100. It is obtained by burying the solder at that time in the via 106 and conducting contact with the reinforcing metal body 104 laminated on the flexible wiring board 100.

  2 and 3 are cross-sectional views showing a manufacturing process of the laminated substrate shown in FIG. Hereinafter, a more detailed description will be given with reference to FIGS.

First, the flexible wiring board 100, the reinforcing metal body 104, and the adhesive layer 105b are prepared.
For the flexible wiring board 100, as shown in FIG. 2, when a component is mounted, a portion of the insulating film 108 that should not be soldered in a process described later with reference to FIG. Mask by. The insulating film 108 is bonded onto the copper foil 102a via an adhesive 107 embedded in the copper foil 102a.

  And copper foil 102a is laminated | stacked only on the single side | surface of the insulating film 101 used as the base of the flexible wiring board 100 in area | regions other than the area | region in which the insulating film 108 was provided. Further, vias are formed at predetermined positions on the flexible wiring substrate 100 by, for example, drilling, and through-hole plating 103b is applied to the surface of the vias by surface treatment. However, the through-hole plating 103b may be performed as a copper foil treatment in the same manner as the copper foil 102a instead of the surface treatment.

  Further, the surface plating 103c is formed by surface plating treatment at a predetermined position on the surface of the metal substrate to be the reinforcing metal body 104.

  The material of the adhesive that forms the adhesive layer 105b that bonds the flexible wiring substrate 100 and the reinforcing metal body 104 is, for example, a thermosetting resin. In addition, vias are formed in the adhesive layer 105b at positions corresponding to the positions of the vias formed in the flexible wiring board 100. At this time, the diameter of the via formed in the adhesive layer 105 b is set to be equal to or larger than the via diameter of the flexible wiring board 100.

  The flexible wiring board 100 and the reinforcing metal body 104 thus obtained are laminated via the adhesive layer 105b. At this time, the vias formed in the flexible wiring board 100 and the vias formed in the reinforcing metal body 104 are made to correspond to each other, and the positions of these vias are made to correspond to the positions of the surface plating 103c. In this state, the flexible wiring board 100 and the reinforcing metal body 104 are not electrically connected.

  Next, as shown in FIG. 3, cream solder 109 a is applied onto the plating land 103 a of the flexible wiring substrate 100 by a method such as a printing method. A solder mask (not shown) is provided at a predetermined position on the plating land 103a. At this time, a layer of cream solder 109a having a uniform thickness is formed on the entire surface of the plating land 103a. By forming an area corresponding to the via 106 of the solder mask as an opening, a layer of cream solder 109a can be formed on the plating land 103a, and the cream solder 109a can be embedded in the via 106.

  In addition, there is no restriction | limiting in particular in the kind of cream solder 109a, According to the kind of components (not shown) mounted in the flexible wiring board 100, it can select suitably. The cream solder 109a may include, for example, predetermined solder particles and flux.

  Subsequently, a predetermined component (not shown) is mounted on the cream solder 109a. Then, the flexible wiring substrate 100 on which the reinforcing metal body 104 that is a metal substrate for reinforcing the flexible wiring substrate 100 is laminated is reflowed. Thereafter, as shown in FIG. 4, the cream solder 109a is cured to become a solder layer 109b. Further, the metal contained in each plating layer of the plating 103a on the component land, the through-hole plating 103b, and the plating 103c on the laminated metal body forms an alloy (alloy layer 110) with the metal contained in the solder layer 109b. . In this way, the solder layer 109b and the copper foil 102a can be brought into conductive contact, and the laminated conductive contact between the flexible wiring board 100 and the reinforcing metal body 104 is realized.

  As described above, the wiring of the flexible wiring board 100 of the single-sided copper foil wiring, that is, the copper foil 102a and the reinforcing metal body 104 can be brought into conductive contact with the solder.

  In the present embodiment, the planar shape of the multilayer substrate can be appropriately designed according to the configuration of the electronic device to which the multilayer substrate is applied. FIG. 5 is a perspective view showing an example of a planar shape of the laminated substrate. In FIG. 5, an insulating film 108 is provided at the center of a rectangular flexible wiring board 100, and a plurality of connectors 14 are provided on the insulating film 108.

  According to the present embodiment, the single-sided wiring flexible wiring substrate 100 is used, and the via 106 penetrating the insulating film 108 and the copper foil 102 a is provided, and when the component is mounted on the plating land 103 a formed on the flexible wiring substrate 100. The structure is such that layered solder is embedded in the via 106. For this reason, even when the flexible wiring board 100 provided with the copper foil wiring only on one side is used, a good conductive contact between the reinforcing metal body 104 and the copper foil 102a is ensured, and the reliability of the electrical connection is improved. Can be improved. In addition, the laminated substrate can be thinned.

Here, as a reference for the configuration of the present embodiment, a configuration in which a reinforcing metal body is laminated on a flexible wiring board of double-sided copper foil wiring will be described.
FIG. 6 is a cross-sectional view for explaining a laminated conductive contact method between a flexible wiring board having wiring on both sides and a reinforcing metal body.
In FIG. 6, a copper foil 202 a is formed on one surface of an insulating film 201 that serves as a base of the flexible wiring board 200, and a copper foil 202 b is formed on the opposite surface. These copper foils constitute signal wiring and ground wiring.

  In addition, plating 203a is applied on the copper foil 202a by surface treatment. Further, the flexible wiring board 200 has a via 206 provided by drilling so as to connect the copper foil 202a and the copper foil 202b. Through-hole plating 203b is applied to the surface of the via 206 by surface treatment.

  An insulating film 208 and an adhesive 207 for bonding the insulating film 208 are laminated between the adjacent platings 203a. The reinforcing metal body 204 laminated on the flexible wiring board 200 is subjected to surface treatment in advance, and plating 203c is laminated on the surface. Such a flexible wiring board 200 and the reinforcing metal body 204 are bonded with a conductive adhesive 205a to provide a conductive contact.

  As shown in FIG. 6, when a reinforcing metal body is laminated on a flexible wiring board in which copper foil wiring is formed on both sides and a conductive adhesive is used as an adhesive material, the flexible wiring board is placed on both sides. Copper foil wiring increases the thickness of the board, increases the board cost, and makes it difficult to use a conductive adhesive that can withstand reflow. However, these can be avoided by adopting the configuration described above with reference to FIGS.

  The use of the multilayer substrate of the present embodiment is not particularly limited. For example, a flexible wiring substrate can be used by using the multilayer substrate of the present embodiment that can be used as a circuit substrate constituting an electronic device such as a mobile phone. It is possible to improve the electrical connection reliability between the reinforcing metal body and the reinforcing metal body, and to improve the strength and flatness of the component mounting location. In particular, in the present embodiment, the entire surface of the plating land 103a is coated in layers with a substantially constant thickness, so that the surface of the flexible wiring board 100 has a high flatness.

  Further, in the present embodiment, the via 106 can be filled with solder simultaneously with the solder application at the time of mounting the component, thereby enabling conductive contact. Therefore, the flexible wiring board 100 and the reinforcing metal body 104 are laminated and conductive contact is made. It is possible to prevent the production / manufacturing process from increasing.

  In the present embodiment, the solder provided in a layer on the plating land 103a and the solder embedded in the via 106 are integrated, and the solder in the via 106 is in-plane on the reinforcing metal body 104 side. It has a configuration that protrudes in the direction. For this reason, on both sides of the flexible wiring board 100 side and the reinforcing metal body 104 side, the bonding area between the solder and the plating (plating land 103a or surface plating 103c) is large, and the connection reliability is excellent.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable.

  For example, in the above description, SUS (stainless steel) is used as the reinforcing metal body 104, but metals such as copper, aluminum, and iron, and other conductive materials may be applied. In the above description, the configuration in which the surface plating 103c is provided on the reinforcing metal body 104 has been described as an example. However, the surface plating 103c is not provided, and the solder layer 109b directly contacts the reinforcing metal body 104. It is good also as a structure.

  In the above description, gold plating in which solder and an alloy are formed is used as the plating material for the plating land 103a and the through-hole plating 103b. However, solder plating is also applicable.

  In the above description, drilling is used as a processing method for forming the via 106. However, other processing methods such as laser processing can be applied.

  Furthermore, in the above, the laminated structure of the insulating film 108 and the adhesive 107 that adheres the insulating film 108 is exemplified as the material formed between the adjacent plating lands 103a, but instead, a resist is formed into a predetermined shape. It may be patterned.

It is a perspective view which shows the structure of the small electronic device in this embodiment. It is sectional drawing explaining the structure of the laminated substrate in this embodiment. It is sectional drawing explaining the lamination | stacking conduction contact method of the lamination substrate in this embodiment. It is sectional drawing which shows the structure of the laminated substrate in this embodiment. It is a perspective view which shows the structure of the laminated substrate in this embodiment. It is sectional drawing which shows the structure of the laminated substrate in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Feeding point 12 Main board 13 Pin connector 14 Connector 15 Connector 16 Back surface 100 Flexible wiring board 101 Insulating film 102a Copper foil 103a Plating land 103b Through-hole plating 103c Surface plating 104 Reinforcing metal body 105b Adhesive layer 106 Via 107 Adhesive 108 Insulation Film 109a Cream solder 109b Solder layer 110 Alloy layer 200 Flexible wiring board 201 Insulating film 202a Copper foil 202b Copper foil 203a Plating 203b Through-hole plating 203c Plating 204 Reinforcing metal body 205a Conductive adhesive 206 Via 207 Adhesive 208 Insulating film

Claims (6)

A film made of an insulating material;
A first wiring pattern provided on one surface of the film and configured by a metal layer;
A flexible substrate including:
A reinforcing substrate laminated on the flexible substrate;
An insulating adhesive layer that is provided between the flexible substrate and the reinforcing substrate to bond the flexible substrate and the reinforcing substrate;
A solder layer covering the first wiring pattern in layers;
Including
A through hole penetrating the flexible substrate and the adhesive layer is provided from the flexible substrate to the adhesive layer,
A multilayer board in which the solder layer is embedded in the through-hole and connected to a conductive member in the first wiring pattern and the reinforcing board. The multilayer substrate according to claim 1,
A multilayer substrate in which the reinforcing substrate is a conductor substrate. The multilayer substrate according to claim 1 or 2,
A multilayer substrate in which a second wiring pattern is provided on a surface of the reinforcing substrate facing the flexible substrate, and the solder layer is connected to the first and second wiring patterns. The multilayer substrate according to any one of claims 1 to 3,
A multilayer board including an alloy containing a metal element constituting the solder layer between the first wiring pattern and the solder layer. The multilayer substrate according to any one of claims 1 to 4,
A multilayer substrate in which the through hole has a diameter increased in the adhesive layer. The multilayer substrate according to any one of claims 1 to 5,
The multilayer substrate, wherein the through-hole has a tapered shape with a diameter narrowed from the first wiring pattern toward the adhesive layer.

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