JP2010147151A - Double-sided wiring substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided wiring substrate having an excellent humidity resistance, and to provide a method of manufacturing the same. <P>SOLUTION: A double-sided wiring substrate includes an interlayer insulating substrate 1; first and second wiring layers 2b and 3b respectively buried in both sides of the interlayer insulating substrate so that each outer surface is respectively flush with both sides of the interlayer insulating substrate and each inner surface is separated from each other in a thickness direction; an interlayer conductive via 4 buried in the interlayer insulating substrate to electrically connect the inner surfaces of the first and second wiring layers; first and second solder resist layers 2a and 3a covering both sides of the interlayer insulating substrate 1 and each outer surface of the first and second wiring layers 2b and 3b respectively to be flush with each other; and via holes 2c and 3c formed in each solder resist layer in a way that they lead to each outer surface of the first and second wiring layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a double-sided wiring board and a manufacturing method thereof, and more particularly to a double-sided wiring board suitable for a flexible wiring board excellent in moisture resistance and a manufacturing method thereof.

  In recent years, circuit wiring boards incorporated in various electronic devices such as mobile phones and digital cameras are increasingly required to be smaller, thinner, lighter, and multifunctional. In order to meet such demands in particular with multi-functionalization, development of a laminated wiring board in which a plurality or many circuit wiring boards are laminated has progressed, and on the other hand, it is embedded in a part that receives mechanical operations of various electronic devices. The range of use of a flexible flexible wiring board having a thin thickness suitable for the above has been expanded.

  According to the conventional general technique, such a flexible wiring board has three layers in which copper foil is directly electrodeposited or laminated on both sides of an insulating substrate made of polyimide resin, or is bonded with an adhesive. Using a base material having a structure, a circuit pattern is formed on each of the copper foils on both sides by photolithography.

  The interlayer connection is performed by forming a through hole or a blind hole in the three-layer structure base material by laser or drilling, and subjecting such a hole to electrolysis or electroless plating. Furthermore, in order to protect the surface of the flexible wiring board and form a solder layer, a coating layer such as a coverlay or a solder resist layer is provided on the surface of the wiring board after the interlayer connection by plating.

  However, in such a background, the prior art using a polyimide resin has the following problems (1) to (6).

(1) Since the polyimide resin has a high water absorption rate, the moisture resistance is inferior to a general rigid substrate using a glass epoxy resin substrate or the like.

(2) When the moisture resistance is inferior as described above, moisture easily penetrates into the interlayer conductive via portion and the circuit wiring layer around the laminated boundary, and the portion is easily corroded to cause deterioration of electrical characteristics or poor connection.

(3) When plating the through holes and blind holes for the conductive vias, a plated layer is also formed on the surface of each copper foil patterned to make the circuit pattern layer thicker. This hinders patterning and hinders high density and multi-functionality.

(4) In order to avoid this increase in thickness, a special masking method must be employed, or the dimension for increasing the thickness must be added as a design factor of the wiring board.

(5) In the case of the plating process, a pretreatment process including a seed layer formation in a through hole or a blind hole is necessary, and a number of substrate manufacturing processes including a conductive via formation are required.

(6) When a wiring board on which conductive vias are formed by plating through holes or blind holes is used as a core board and another wiring board is laminated thereon, a non-conductive paste or the like is put in the gaps in the holes. It is necessary to fill and flatten the entire surface of the core substrate, which causes a special increase in man-hours such as the filling step.

In addition, as other prior arts, there are Patent Document 1 in which a solder resist is used for a part of a wiring substrate, Patent Document 2 in which a conductive paste is used for a conductive via, and the like are illustrated for reference.
JP-A-08-51282 JP 2002-344103 A

  An object of the present invention is to solve the problems of the prior art, and particularly to provide a double-sided wiring board excellent in moisture resistance and a method for manufacturing the same.

  The double-sided wiring board of the present invention according to claim 1 is the interlayer insulating substrate, and the interlayer insulating substrate such that each outer surface is flush with both surfaces of the interlayer insulating substrate and the inner surfaces are separated from each other in the thickness direction. First and second wiring layers embedded in both surfaces of the first and second wiring layers, and interlayer conductive vias embedded in the interlayer insulating substrate to electrically connect the inner surfaces of the first and second wiring layers, First and second solder resist layers covering both surfaces of the interlayer insulating substrate and outer surfaces of the first and second wiring layers, respectively, and the first and second wiring layers formed on the respective solder resist layers And a via hole that communicates with each outer surface.

  The method for manufacturing a double-sided wiring board of the present invention according to claim 2 includes: (A) a step of laminating first and second solder resist layers on one side of each of the first and second wiring base layers; (B) forming a via hole in each of the first and second solder resist layers to partially expose the one surface of the first and second wiring substrate layers; and (C) the first and second layers. First and second wiring board materials in which the first and second wiring layers are respectively provided on the solder resist layers by patterning two wiring base layers to form first and second wiring layers (D) forming a via hole for an interlayer conductive via for the first and second wiring layers in a plastic interlayer insulating substrate material, and filling the via hole with a conductive paste; ) The first and second wiring layers are formed on both surfaces of the interlayer insulating substrate material. And a step of superposing the first and second wiring board materials to face each other and crimping the interlayer insulating board material and the first and second wiring board materials to each other. Features.

  According to the double-sided wiring board and the manufacturing method thereof of the present invention, the solder resist layer covering the outer surfaces of the first and second wiring layers on both sides of the interlayer insulating board has a moisture resistance (low water absorption) of polyimide resin or the like. Since it has remarkably superior properties, it is possible to prevent water or moisture from entering the first and second wiring layers and the interlayer conductive vias over a long period of time. Therefore, corrosion of the electric circuit members such as the first and second wiring layers in the interlayer conductive via portion and the surrounding lamination boundary can be avoided, and the required design electrical characteristics and connection state can be maintained over a long period. Maintained well.

  In addition, the interlayer conductive via is formed by filling a via hole provided in the interlayer insulating substrate material with a conductive paste, and both ends thereof are crimped and connected to the first and second wiring layers, so that a plating process is unnecessary. It is possible to avoid an increase in thickness that hinders the fine patterning of the first and second wiring layers, the addition of special masking, the addition of extra design factors and the complexity of the pre-plating process.

  And, since the gap as described in the problem (6) of the prior art does not exist in the double-sided wiring board, when other wiring boards are laminated, the gap is filled with a non-conductive paste. No special process is required, the manufacturing is easy, and the manufacturing cost can be reduced.

  In addition, the solder resist layer is formed so as to cover both surfaces of the interlayer insulating substrate and the outer surfaces of the first and second wiring layers embedded on both sides of the insulating substrate, so that flatness is obtained. Even when another wiring board is laminated thereon to form a laminated wiring board, flatness is maintained.

  Furthermore, although the first and second wiring base layers and the first and second wiring layers are generally thin and easily deformed, the solder resist layer is formed through the manufacturing process of the double-sided wiring board. It can be used as a support layer or supporter layer. Therefore, the shape can be maintained and the improvement of workability during the process can be ensured.

  Hereinafter, an embodiment of a double-sided wiring board and a manufacturing method thereof according to the present invention will be described with reference to FIGS. FIG. 1A to FIG. 1H are cross-sectional views showing a manufacturing process of a double-sided wiring board according to an embodiment, and FIG. 2 is an interlayer insulation incorporated in the process shown in FIG. It is sectional drawing according to process which shows the manufacturing process of a board | substrate material.

  First, the structure of the double-sided wiring board according to the present embodiment will be described with reference to FIG. 1H. The interlayer insulating substrate 1 is appropriately selected from a thermosetting resin, a thermoplastic resin, a photocurable resin, and the like. It is formed using an insulating flexible film. In addition, any of these resins for the interlayer insulating substrate may be formed including glass cloth.

  First and second wiring board materials 2 and 3 are respectively disposed on both surfaces of the interlayer insulating substrate 1, and the first wiring board material 2 is a first moisture-resistant insulating layer having a low water absorption rate. The solder resist layer 2a, the first wiring layer 2b formed by patterning, for example, copper foil on one surface thereof, and the first solder resist layer 2a so as to penetrate a part of the outer surface of the first wiring layer 2b The via hole 2c is formed.

  Similar to the first wiring board material 2, the second wiring board material 3 penetrates the second solder resist layer 3a, the second wiring layer 3b formed on one surface thereof, and the solder resist layer 3a. There is a via hole 3c that communicates with part of the outer surface of the second wiring layer 3b.

  The solder resist layers 2a and 3a and the wiring layers 2b and 3b are made of the same material. However, each circuit pattern shape of the first and second wiring layers 2b and 3b is in an appropriate form according to the circuit or system incorporated in the double-sided wiring board. The via holes 2c and 3c are blind holes because the opening surfaces of the one ends are closed by the first and second wiring layers 2b and 3b.

  The inner surfaces of the first and second wiring layers 2b and 3b are separated from each other in the thickness direction across the interlayer insulating substrate 1, and the outer surfaces of the wiring layers 2b and 3b are The interlayer insulating substrate 1 is embedded in both surfaces so as to be flush with both surfaces of the interlayer insulating substrate 1.

  Between the inner surfaces of the first and second wiring layers 2b and 3b, an interlayer conductive via 4 made of a conductive paste is embedded in the interlayer insulating substrate 1 so as to penetrate the wiring layers 2b and 3b. Electrically connected. The first and second solder resist layers 2a and 3a are coated on both surfaces of the interlayer insulating substrate 1 and the outer surfaces of the first and second wiring layers 2b and 3b, respectively, so as to maintain flatness. Yes.

  As described above, the solder resist layers 2a and 3a covering the outer surfaces of the first and second wiring layers 2b and 3b on both surfaces of the interlayer insulating substrate 1 have a moisture resistance (low water absorption) and are generally rigid boards. Therefore, the first and second wiring layers 2b and 3b and the interlayer conductivity between them can be reduced. Intrusion of moisture or moisture from the outside into the via 4 can be prevented over a long period of time. Therefore, corrosion of the electric circuit members such as the interlayer conductive via 4 and the first and second wiring layers 2b and 3b at the peripheral boundary of the interlayer conductive via 4 can be avoided, and the required design electrical characteristics and connection state can be maintained for a long period. The problems (1) and (2) of the prior art can be solved.

  In addition, the solder resist layers 2a and 3a are formed so as to cover both surfaces of the interlayer insulating substrate and the outer surfaces of the first and second wiring layers 2b and 3b embedded on both sides of the insulating substrate. Therefore, even when another wiring board is laminated on this to form a laminated wiring board, the flatness of the laminated wiring board can be obtained.

  Next, a method for manufacturing the double-sided wiring board will be described. FIG. 1A to FIG. 1F are diagrams for explaining the manufacturing process of the first and second wiring board materials 2 and 3, and the portions related to the second wiring board material 3 are shown in FIG. The description will be given with a quotation mark in parentheses ().

  In the process of FIG. 1A, the first and second solder resist layers 2a and 3a are respectively laminated on one surface of each of the first and second wiring base layers 2B and 3B using, for example, copper foil as a conductive material. A prepared substrate is prepared. As the solder resist material, a liquid or dry film can be used, and any one of a thermosetting type, a UV ink type, a photographic development type solder resist and the like can be selected and used. As a specific example of the solder resist material, a dry film solder resist for a flexible printed board; Model No. DM-140 manufactured by Nichigo Morton can be used.

  Accordingly, each of the laminated forms of the first and second wiring base layers 2B and 3B and the first and second solder resist layers 2a and 3a is a method of applying a liquid solder resist material or a solder resist film. It can be obtained by appropriately selecting and adopting a method of superposition adhesion.

  In particular, when the solder resist film is adopted, both of the strip-shaped copper foil roll and the solder resist film roll having the same width are put on each other on the RR automatic production line and cut to a predetermined length. Thus, a laminated substrate composed of individual wiring layer substrate layers and solder resist layers can be produced with high productivity.

  In the step of FIG. 1B, via holes 2c and 3c are formed, for example, by applying pattern formation by photolithography to each of the first and second solder resist layers 2a and 3a.

  Each of the via holes 2c and 3c is formed so as to penetrate the solder resist layers 2a and 3a, respectively, and to partially expose the outer surface that is one surface of each of the wiring base material layers 2B and 3B. For example, a conductive via can be formed by filling the inside with a conductive paste, for example.

  In this step, if a photo-developing solder resist is used as the first and second solder resist layers 2a and 3a, a step of coating an individual photoresist on the surface of the solder resist layer is not required, and a predetermined pattern shape is obtained. Since the solder resist layers 2a and 3a themselves can be directly patterned only by using a mask, there is an advantage that the process can be shortened and the cost can be reduced.

  In the step of FIG. 1C, a photoresist film P is coated on the other surfaces (inner surfaces) of the first and second wiring substrate layers 2B and 3B. This photoresist film P may be performed simultaneously with or immediately after the formation of the solder resist layers 2a and 3a. Accordingly, as shown in FIG. 1D, an etching resist pattern Pa corresponding to a predetermined circuit pattern is formed by applying a photolithography technique to the photoresist film P.

  In the step shown in FIG. 1E, the etching resist pattern Pa is used as a mask, and the portions of the first and second wiring base layers 2B and 3B exposed from the mask are removed by chemical etching and patterned. Thus, the first and second wiring layers 2b and 3b formed in a predetermined circuit pattern shape are respectively provided on the solder resist layers 2a and 3a (lower surfaces in the drawing).

  In the step of FIG. 1F, the etching resist pattern Pa is removed, and the first and second solder resist layers 2a and 3a are formed on one surface (outer surface) of each of the first and second wiring layers 2b and 3b. The first and second wiring board materials 2 and 3 formed in a two-layered stacked structure overlapping each other are taken out.

  In the step of FIG. 1G, the first and second wiring board materials 2 and 3 are arranged such that the first and second wiring layers 2b and 3b face the upper and lower surfaces of the interlayer insulating substrate material 1a. Place. Here, the manufacturing process of the said interlayer insulation board | substrate material 1a is demonstrated with reference to FIG.

  First, as shown in FIG. 2A, a base material 1A is prepared as a base material of the interlayer insulating substrate material 1a. The base material 1A is formed using an insulating flexible film appropriately selected from a thermosetting resin, a thermoplastic resin, a photocurable resin, and the like. Moreover, you may include glass cloth in these resins.

  Next, as shown in FIG. 2B, an interlayer insulating substrate material 1a is formed by providing a plurality of via holes H in the base material 1A. Each of the via holes H is formed in accordance with a predetermined interlayer connection pattern arrangement. The via hole H can be formed by drilling or laser processing or by photolithography when the substrate 1A is, for example, a thermosetting resin or a thermoplastic resin. In addition, a positive or negative photographic developing resin can be used as the substrate 1A. In this case, a photo-via type via hole H can be optically directly formed on the substrate 1A.

  Then, as shown in FIG. 2 (c), in the plurality of via holes H of the interlayer insulating substrate material 1a, for example, highly conductive metal particles such as silver or metal particles that promote intermetallic alloys are mixed in the thermosetting resin. The conductive paste 4a is filled. The conductive paste 4a is formed by filling the entire inside of the via hole H with such a thickness that both end surfaces thereof are flush with both surfaces of the interlayer insulating substrate material 1a. However, although not shown, the conductive paste 4a may be formed so that both ends thereof protrude somewhat from both surfaces of the interlayer insulating substrate material 1a.

  As described above, the interlayer insulating substrate material 1a formed in this way is brought into the process of FIG. 1G, and at this stage, it is in an uncured or semi-cured state together with the conductive paste 4a. , Has plasticity.

  Next, in the step of FIG. 1 (h), the first and second wiring board materials 2 and 3 superposed on both surfaces of the interlayer insulating substrate material 1a are added together from the upper and lower surfaces under heating conditions. By pressing, the interlayer insulating substrate material 1a and the first and second wiring substrate materials 2 and 3 are thermocompression bonded to each other.

  In the batch thermocompression bonding process as described above, after the interlayer insulating substrate material 1a plastically flows and plastically deforms so as to entirely fill the gap between the first and second wiring substrate materials 2 and 3, By curing, an interlayer insulating substrate 1 in which these members are bonded to each other is formed. In addition, the conductive paste 4a is compressed from the upper and lower ends by the thermocompression bonding, and both end surfaces are pressed and bonded to the inner surfaces of the first and second wiring layers 2b and 3b, respectively. It is formed.

By the way, the first and second solder resist layers 2a and 3a are formed through the first and second wiring base layers 2B and 3B and the first through the steps shown in FIGS. , Acting as a support layer or supporter for the second wiring layers 2b, 3b to prevent deformation of these wiring members,
It is possible to improve the workability of component operation in the manufacturing process of the double-sided wiring board.

  When the double-sided wiring board formed as described above is used as a core board and another wiring board is further laminated thereon to produce a laminated wiring board, the first wiring shown in FIG. Similar to the first and second wiring board materials 2 and 3, other necessary wiring board materials each having a wiring layer having a desired circuit pattern shape on the solder resist layer are prepared individually.

  Then, a conductive paste is filled in the via holes 2c and 3c provided in the solder resist layers 2a and 3a which are the outermost layers of the double-sided wiring board as the core substrate, and wiring layers of other wiring board materials laminated thereon The one end face of the conductive paste is brought into contact with and brought into contact with the surface, and the adjacent wiring board materials are bonded together with an adhesive.

  At this time, by applying thermocompression to these laminates, the conductive paste is cured in a state in which both end surfaces are pressure-bonded to the surfaces of the adjacent wiring layers, and other interlayer conductive layers for the laminated substrate. A via is formed. At this time, the adjacent wiring board materials are firmly bonded by the adhesive. The adhesive material may be a liquid material that is applied to the wiring board material, or may be a thermosetting adhesive film material that is thermocompression-bonded between the wiring board materials. .

  According to such a double-sided wiring board according to an embodiment of the present invention and a method of manufacturing a multilayer wiring board using the same as a core board, the outermost layer of these wiring boards is covered with a solder resist layer, and therefore, a low water absorption Accordingly, the wiring board having excellent moisture resistance can be obtained with certainty, and the problems (1) and (2) of the prior art can be solved.

  In addition, since the interlayer conductive via can be formed by filling the via hole provided in the interlayer insulating substrate material or the solder resist layer with the filling conductive paste without requiring a plating process, the problems (3) to (3) of the prior art described above. (5) can be solved easily and reliably. In addition, since the interlayer conductive via itself completely fills the via hole provided in the interlayer insulating substrate and the solder resist layer, the problem (6) in the prior art is achieved through the manufacturing process of the multilayer wiring substrate. Since there is no air gap, there is no flattening step with a special via hole filling step, and this problem can be solved.

  Further, the solder resist layers 2a and 3a are wiring base material layers (2B and 3B) which are constituent members of the first and second wiring board materials 2 and 3 through the entire manufacturing process of the double-sided wiring board and the laminated wiring board. ) And the wiring layers (2b, 3B) and the role of improving the moisture resistance of the outermost layer in the final structure of each wiring substrate. Therefore, in terms of the manufacturing process, the shape of the wiring board material and the wiring layer that are easily deformed by the material is supported by the solder resist layer, so that the workability is improved and the double-sided wiring board and the laminated wiring having excellent moisture resistance are improved. The final structure of the substrate is obtained.

  In the above embodiment, the interlayer insulating substrate 1 is made of a flexible material, so that the double-sided wiring substrate and the multilayer wiring substrate constitute a flexible wiring substrate. However, the interlayer insulating substrate 1 is a glass epoxy resin substrate. In addition, a rigid wiring board can be formed by using a material having high rigidity.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the double-sided wiring board which concerns on one Embodiment of this invention, and its manufacturing method, (a)-(h) is a cross section according to a process, Among them, (h) is a cross section which shows the structure of the double-sided wiring board. FIG. It is a figure for demonstrating the manufacturing method of the interlayer insulation board | substrate material taken in to the process of FIG.1 (g), (a)-(c) is sectional drawing according to process.

Explanation of symbols

1 Interlayer Insulating Substrate 1a Interlayer Insulating Substrate Material 1A Base Material 2 First Wiring Substrate Material 2a First Solder Resist Layer 2b First Wiring Layer 2B First Wiring Substrate Layer 2c, 3c, H Via Hole 3 Second Wiring Substrate Material 3a First 2 solder resist layer 3b second wiring layer 3B second wiring substrate layer 4 interlayer conductive via 4a conductive paste P photoresist film Pa etching resist pattern

Claims (2)

  An interlayer insulating substrate, and first and second wirings embedded in both surfaces of the interlayer insulating substrate such that each outer surface is flush with both surfaces of the interlayer insulating substrate and each inner surface is separated from each other in the thickness direction An interlayer conductive via embedded in the interlayer insulating substrate to electrically connect the inner surface of each of the first and second wiring layers, both surfaces of the interlayer insulating substrate, and the first and second wirings The first and second solder resist layers covering each outer surface of the layer flush with each other, and via holes formed in the respective solder resist layers and leading to the respective outer surfaces of the first and second wiring layers. Double-sided wiring board. (A) a step of laminating first and second solder resist layers on one surface of each of the first and second wiring substrate layers;
(B) forming a via hole in each of the first and second solder resist layers and partially exposing the one surface of the first and second wiring base layers;
(C) The first and second wiring layers are provided on the solder resist layers by patterning the first and second wiring base layers to form the first and second wiring layers, respectively. Forming first and second wiring board materials;
(D) forming a via hole for an interlayer conductive via for the first and second wiring layers in a plastic interlayer insulating substrate material, and filling the via hole with a conductive paste;
(E) The first and second wiring board materials are overlapped with the first and second wiring layers facing each other on both surfaces of the interlayer insulating substrate material, and the interlayer insulating substrate material and the first and second wiring layers are overlapped. A step of crimping the wiring board material to each other;
A method for manufacturing a double-sided wiring board, comprising:

Images