JP2010258377A - Wiring board, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board capable of securing insulation between respective wiring layers in laminating wiring layers through insulators, and a method of manufacturing the same. <P>SOLUTION: In this wiring board 10 including a first wiring layer 22 formed on a board 20, an insulator 31 for covering at least the first wiring layer 22, and a jumper wire 32 formed on the first wiring layer 22 through the insulator 31 and arranged to straddle the first wiring layer 22, the insulator 31 is formed by laminating a plurality of insulation layers 34, 35. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wiring board and a manufacturing method thereof.

In recent years, as electronic devices have become smaller and lighter and have higher performance, higher patterning of wiring patterns on circuit boards incorporated therein has been demanded. As a countermeasure for such a problem, for example, a configuration using a so-called double-sided printed wiring board in which wiring patterning is formed on both sides of a substrate is known.
However, in order to create the double-sided printed wiring board described above, a double-sided exposure apparatus that performs exposure on both sides of the substrate at once is required, or wirings formed on the front and back surfaces of the substrate are connected to each other. A process of forming a through hole or the like may be necessary. Therefore, there is a problem that the manufacturing cost increases and the manufacturing efficiency decreases.

  In order to cope with the above-described problem, a configuration using a so-called multilayer printed wiring board in which wiring is formed on one surface of a substrate with an insulating layer interposed therebetween is known. As a multilayer printed wiring board, for example, as disclosed in Patent Document 1, a plurality of transfer pattern masters including a conductive layer and an insulating resin layer are produced, and the transfer masters are sequentially transferred to one surface of a substrate. Thus, a technique for laminating a wiring pattern layer on one surface of a substrate is disclosed. Also in this case, the wiring patterns are connected to each other through through holes or the like at the intersections of the wiring patterns.

JP-A-8-116172

Further, in the conventional multilayer printed wiring board, predetermined wiring layers are arranged on both sides along the extending direction of other wiring layers, and the predetermined wiring layers are connected with the other wiring layers interposed therebetween. In some cases, a configuration in which a predetermined wiring layer is bridged via a jumper wiring is also known.
Specifically, as shown in FIG. 6, the wiring board 100 has a first wiring layer 102 formed in the central portion (the central portion in the figure) on the substrate 101, with the first wiring layer 102 interposed therebetween. A pair of second wiring layers 103 are formed on both sides. In this case, in order to connect the second wiring layers 103 to each other, the jumper wiring 106 is disposed on the first wiring layer 102 via the insulator 105, and both ends of the jumper wiring 106 are connected to the second wiring layer 103. To be connected to.

By the way, in order to form the insulator 105, the constituent material of the insulator 105 dissolved in a solvent is applied and then baked. In this case, as described above, the insulator 105 needs to be formed as thin as possible in order to cope with the reduction in size and weight of the electronic device.
However, if the film thickness when the insulator 105 is applied is too thin, the solvent may evaporate during firing and pinholes may be generated. As a result, there is a problem that the jumper wiring 106 and the first wiring layer 102 are short-circuited due to migration.

On the other hand, in order to reliably cover the first wiring layer 102, it is conceivable to apply the insulator 105 relatively thickly.
However, if the film thickness of the insulator 105 is too thick, the difference in the curing rate between the vicinity of the surface of the insulator 105 and the inside becomes large during firing. In this case, when the baking is finished when the vicinity of the surface of the insulator 105 is cured, the solvent of the insulator 105 remains without being cured inside the insulator 105. In the subsequent heating process or the like, when the inside of the insulator 105 is cured, bubbles contained in the solvent are ejected from the inside of the insulator 105 to the surface, and a relatively large pinhole (so-called bleed) is formed on the surface of the insulator 105. May occur.

  Further, when the insulator 105 is formed by a coating method such as a screen printing method, the constituent material of the insulator 105 spreads out during coating, and the film thickness of the insulator 105 is thin at the peripheral edge K and the like of the first wiring layer 102. Become. As a result, the insulator 105 covering the first wiring layer 102 may be broken at the peripheral edge K or the like of the first wiring layer 102.

  Accordingly, the present invention has been made in view of the above-described problems, and provides a wiring board capable of ensuring insulation between each wiring layer and a method for manufacturing the same when laminating wiring layers via an insulator. The purpose is to do.

In order to solve the above-described problems, the present invention provides the following means.
A wiring board according to the present invention is formed on a first wiring layer formed on a substrate, an insulator covering at least the first wiring layer, and formed on the first wiring layer via the insulator, In the wiring board provided with jumper wiring arranged so as to straddle the first wiring layer, the insulator is characterized in that a plurality of insulating layers are laminated.

According to this configuration, it is possible to prevent breakage of the insulator at the peripheral edge portion or the like of the first wiring layer by stacking a plurality of insulating layers on the first wiring layer. Thereby, it is possible to prevent a short circuit between the jumper wiring arranged on the first wiring layer and the first wiring layer via the insulator. In this case, unlike the case where the insulator is thickly formed in order to prevent the disconnection, the occurrence of pinholes due to bleed can be prevented, so that the jumper wiring and the first wiring layer can be more reliably connected. Can be prevented from being short-circuited. Even if a pinhole is generated in any of the insulating layers, the pinhole does not penetrate the entire insulator, so that a short circuit due to migration can be prevented.
As a result, when the wiring layers are stacked through the insulator, it is possible to ensure insulation between the lower wiring layer (first wiring layer) and the upper wiring layer (jumper wiring).

Further, on both sides of the substrate along the extending direction of the first wiring layer, a pair of lands of the second wiring layer are formed so as to sandwich the first wiring layer, and the jumper wiring is The land is connected to the lands so as to bridge between the two lands of the second wiring layer, and the insulator includes the first insulating layer covering the first wiring layer and the normal direction of the substrate. The second insulating layer, which is formed wider than the formation region of the first insulating layer, covers the first insulating layer, and covers the land so as to run over a part of the land on the substrate. It is characterized by having.
According to this configuration, since the second insulating layer is formed so as to run on each land, the jumper wiring formed on the second insulating layer is connected between the lands without contacting the substrate. Will be. As a result, the adhesion of the jumper wiring can be ensured, and therefore the continuity between the lands can be ensured by preventing the jumper wiring from being peeled off or disconnected.
In addition, since only the second insulating layer of each insulating layer is formed in the peripheral region (region approaching the land) of the second insulating layer, the second insulating layer and the first insulating layer are formed. The thickness of the insulator is smaller than that of the stacked region with the layer. As a result, the step at the boundary between the land and the insulator can be reduced, so that the jumper wiring is smoothly arranged from the insulator to the land. Thereby, disconnection of the jumper wiring at the end of the insulator can be prevented, and conduction between the lands can be ensured. In addition, when forming the jumper wiring by the screen printing method, it is possible to prevent the jumper wiring from protruding along the boundary line of the insulator.

Further, the second insulating layer is formed so as to surround a periphery of a connection portion with the jumper wiring on the land.
According to this configuration, even if the constituent material of the jumper wiring wets and spreads on the land when the jumper wiring is formed, it can be blocked by the second insulating layer. Thereby, there is no possibility that the jumper wiring flows down on the substrate and bridges another wiring layer to cause a short circuit.

Further, the substrate is a flexible substrate made of polyimide, and the insulator is a resist made of urethane resin or epoxy resin.
According to this configuration, it is possible to ensure the adhesion between the substrate and the insulator and the followability of the insulator with respect to the flexural deformation of the substrate. Can be insulated.

Further, the jumper wiring is characterized in that it is formed using a silver paste in which silver and a resin material are mixed in a diluent.
According to this configuration, it is possible to ensure the adhesion between the insulator and the jumper wiring and the followability of the jumper wiring with respect to the bending deformation of the substrate. Conductivity can be ensured.

In addition, the insulator is characterized in that the total thickness is 20 μm or more and 80 μm or less.
By the way, if the total thickness of the insulator is less than 20 μm, the solvent contained in the insulator may evaporate during the formation of the insulator, which is not preferable. On the other hand, if the total thickness of the insulator is greater than 80 μm, the difference in the curing rate between the vicinity of the insulator surface and the inside during firing of the insulator increases, resulting in the occurrence of the above bleed and the surface of the insulator. This is not preferable because a relatively large pinhole may occur. In such a case, there is a risk of short circuit between the two due to migration that occurs between the jumper wiring and the first wiring layer.
On the other hand, according to the configuration of the present invention, a desired insulator can be formed without generating pinholes by forming the total thickness of the insulator to 20 μm or more and 80 μm or less. And the first wiring layer can be insulated to prevent a short circuit between them.

Further, the jumper wiring has a thickness of 10 μm or more and 30 μm or less.
By the way, if the film thickness of the jumper wiring is formed to be less than 10 μm, the electric resistance of the jumper wiring is increased and the jumper wiring may be broken, which is not preferable. On the other hand, if the film thickness of the jumper wiring is formed to be larger than 30 μm, it is not preferable because it is difficult to follow the bending deformation of the substrate and disconnection or the like is likely to occur, and the manufacturing cost increases.
On the other hand, according to the configuration of the present invention, by forming the film thickness of the jumper wiring in the range of 10 μm or more and 30 μm or less, the occurrence of disconnection or the like is prevented and each land is connected with a desired resistance value. be able to.

The method for manufacturing a wiring board according to the present invention includes an insulator forming step of forming an insulator so as to cover at least the first wiring layer formed on the substrate, and the first wiring layer on the insulator. A jumper wiring forming step of forming a jumper wiring so as to straddle the substrate, and in the insulator forming step, a plurality of insulating layers are stacked to form the stacked body.
According to this configuration, in the insulator forming step, the insulating layer can be prevented from being cut off at the peripheral edge portion or the like of the first wiring layer by stacking the plurality of insulating layers on the first wiring layer. Therefore, in the subsequent jumper wiring formation step, it is possible to prevent a short circuit between the jumper wiring disposed on the first wiring layer via the insulator and the first wiring layer. In this case, unlike the case where the insulator is thickly formed in order to prevent the disconnection, the occurrence of pinholes due to bleed can be prevented, so that the jumper wiring and the first wiring layer can be more reliably connected. Can be prevented from being short-circuited. Even if a pinhole is generated in any of the insulating layers, the pinhole does not penetrate the entire insulator, so that a short circuit due to migration can be prevented.
As a result, when the wiring layers are stacked via the insulating layer, it is possible to ensure insulation between the lower wiring layer (first wiring layer) and the upper wiring layer (jumper wiring).

A pair of lands of the second wiring layer to which the jumper wiring is connected are formed on both sides of the substrate along the extending direction of the first wiring layer so as to sandwich the first wiring layer. The insulator forming step includes a first insulating layer forming step of forming at least the first insulating layer that covers at least the first wiring layer; a portion of the land that covers the first wiring layer; And a second insulating layer forming step of forming the second insulating layer covering the land so as to run over the land.
According to this configuration, in the second insulating layer forming step, the jumper wiring formed on the second insulating layer is not in contact with the substrate by forming the second insulating layer up to each land. Each land will be connected. As a result, the adhesion of the jumper wiring can be ensured, and therefore the continuity between the lands can be ensured by preventing the jumper wiring from being peeled off or disconnected.
In addition, since only the second insulating layer of each insulating layer is formed in the peripheral region (region approaching the land) of the second insulating layer, the second insulating layer and the first insulating layer are formed. The thickness of the insulator is smaller than that of the stacked region with the layer. As a result, the step at the boundary between the land and the insulator can be reduced, so that the jumper wiring is smoothly arranged from the insulator to the land. Thereby, disconnection of the jumper wiring at the end of the insulator can be prevented, and conduction between the lands can be ensured.

In the insulator forming step, the insulating layer is formed by a screen printing method.
By the way, as a method of forming the insulator, for example, it may be possible to adopt a photolithography technique or the like, but when the insulator is formed by the photolithography technique, a peripheral portion becomes a corner portion, and then a jumper formed on the insulator. There is a possibility that the wiring breaks.
On the other hand, according to the configuration of the present invention, by forming the insulator by screen printing, the peripheral portion of the insulating layer wets and spreads on the surface of the substrate or on the wiring layer when each insulating layer is formed. The part has a smooth curved shape. That is, unlike the case where the insulating layer is formed by a photolithography technique or the like, the step at the boundary between the insulator and the land can be reduced. Thereby, the jumper wiring formed on the insulator is smoothly arranged from the insulator to the land.
As a result, it is possible to prevent the jumper wiring from being cut off at the periphery of the insulator. In addition, when forming the jumper wiring by the screen printing method, it is possible to prevent the jumper wiring from protruding along the boundary line of the insulator.

In the jumper wiring forming step, the jumper wiring is formed by a screen printing method.
According to this configuration, since the jumper wiring can be formed following the shape of the outer surface of the insulator, conduction between the lands can be ensured.

According to the wiring board and the method of manufacturing the same according to the present invention, it is possible to prevent breakage of the insulator at the peripheral edge portion or the like of the first wiring layer by laminating a plurality of insulating layers on the first wiring layer. . Thereby, it is possible to prevent a short circuit between the jumper wiring arranged on the first wiring layer and the first wiring layer via the insulator. In this case, unlike the case where the insulator is thickly formed in order to prevent the disconnection, the occurrence of pinholes due to bleed can be prevented, so that the jumper wiring and the first wiring layer can be more reliably connected. Can be prevented from being short-circuited. Even if a pinhole is generated in any of the insulating layers, the pinhole does not penetrate the entire insulator, so that a short circuit due to migration can be prevented.
As a result, when the wiring layers are stacked through the insulator, it is possible to ensure insulation between the lower wiring layer (first wiring layer) and the upper wiring layer (jumper wiring).

It is a top view of a wiring board. It is sectional drawing which follows the AA line of FIG. It is a flowchart which shows the manufacturing process of a wiring board. It is process drawing which shows the manufacturing process of a wiring board. It is sectional drawing which shows the other structure of a wiring board. It is sectional drawing which shows the conventional wiring board.

1 is a plan view of the wiring board, and FIG. 2 is a cross-sectional view taken along the line AA of FIG.
As shown in FIGS. 1 and 2, the wiring board 10 includes a flexible substrate (hereinafter referred to as a substrate) 20 made of polyimide or the like, and a plurality of wiring patterns 21 formed on the substrate 20.
Each wiring pattern 21 is formed by forming a copper foil or the like on the substrate 20 and is routed to an electronic component such as an IC chip (not shown) mounted on the substrate 20 to electrically connect the electronic components to each other. Yes. The film thickness of the wiring pattern 21 is preferably about 8 μm or more and 25 μm or less. In this embodiment, the film thickness is about 8 μm.
Each wiring pattern 21 is formed in the central portion (the central portion in FIG. 2) of the surface 20a of the substrate 20, and extends along the extending direction of the first wiring layers 22 and a plurality of first wiring layers 22 extending in parallel. On both sides, a pair of second wiring layers 23 are disposed with the first wiring layer 22 interposed therebetween. In the following description, the plurality of first wiring layers 22 are collectively described as the wiring layer group 24.

  The pair of second wiring layers 23 are respectively formed on both sides of the wiring layer group 24 in a direction orthogonal to the extending direction of the wiring layer group 24, and extend in directions opposite to each other. That is, the second wiring layer 23 is blocked by the wiring layer group 24 in the surface direction of the substrate 20. A land 25 having a rectangular shape in plan view is formed at the end of one of the second wiring layers 23 in the second wiring layer 23, and the opposite side of the land 25 with the wiring layer group 24 interposed therebetween. The land 25 of the other second wiring layer 23 is also formed in a rectangular shape in plan view. Although not shown, a plating layer (for example, several μm) made of tin, gold or the like is provided on the wiring pattern 21 in order to improve the wettability of solder when connecting the wiring pattern 21 and each electronic component. Is formed.

Here, an insulator 31 is formed on the substrate 20 so as to cover the wiring layer group 24, and a jumper wiring 32 connecting the lands 25 of the second wiring layers 23 is formed via the insulator 31. Has been.
The insulator 31 covers the first insulating layer 34 and the first insulating layer (first insulating layer) 34 disposed between the lands 25 of the second wiring layer 23 on the surface 20 a of the substrate 20. The second insulating layer (second insulating layer) 35 is disposed.

  The first insulating layer 34 is disposed so as to be sandwiched between the lands 25 and is disposed so as to cover only the wiring layer group 24 at a time, and its peripheral edge portion has a smooth curved shape. That is, the first insulating layer 34 is interposed between the wiring layer group 24 and the jumper wiring 32 mainly at the intersection region, and is formed so that the thickness gradually decreases from the central portion toward the peripheral portion. Yes. The width of the first insulating layer 34 in the longitudinal direction (extending direction of the wiring layer group 24) is longer than the width of the jumper wiring 32 in the short direction (for example, about 0.3 mm). The wiring 32 and the wiring layer group 24 are insulated.

  The second insulating layer 35 is formed in an H shape in plan view (as viewed from the normal direction of the substrate 20) with the connection portion with the jumper wiring 32 exposed on the land 25. The surrounding wiring patterns 21 are collectively covered, and the peripheral edge portion has a smooth curved shape. That is, like the first insulating layer 34, the second insulating layer 35 is formed such that the thickness gradually decreases from the central portion toward the peripheral portion. In this case, the contact angle θ at the peripheral edge of the second insulating layer 35, that is, the angle formed between the second insulating layer 35 and the surface 20 a of the substrate 20 or the land 25 of the second wiring layer 23 is not less than 10 degrees and not more than 70 degrees. Preferably, it is formed at about 40 degrees in this embodiment.

  In the central part of the second insulating layer 35 (the central part in FIG. 1), the first insulating layer 34 is covered in the extending direction of the jumper wiring 32 and is formed from both sides of the wiring layer group 24 to the land 25. A jumper insulating portion 40 is formed. The jumper insulating portion 40 covers each land 25 so as to run on the peripheral edges of each land 25 facing each other.

  The second insulating layer 35 includes a pattern insulating portion 41 that is expanded from the jumper insulating portion 40 in the width direction of the jumper wiring 32. The pattern insulating portion 41 covers the wiring layer group 24 and the second wiring layer 23 around the land 25. Further, the second insulating layer 35 extends from the pattern insulating portion 41 along the extending direction of the jumper wiring 32, and the side insulating portions 42 arranged so as to cover both side edges of each land 25. I have. That is, each of the lands 25 is covered with the second insulating layer 35 at the peripheral edge portions in the three directions (the peripheral edge portions and the peripheral edge portions on both sides), and the second insulating layer 35 is disposed so as to surround the land 25. ing.

As described above, the insulating layers 34 and 35 of this embodiment form a stacked region in which the first insulating layer 34 and the second insulating layer 35 are stacked in the central portion of the jumper insulating portion 40, while In the region (the end portion of the jumper insulating portion 40, the pattern insulating portion 41, and the side insulating portion 42), a single-layer region in which only the second insulating layer 35 is formed is configured.
The constituent material of each of the insulating layers 34 and 35 described above is a urethane resin resist (for example, Ajinomoto Fine Co. Techno AR7100) is preferably used. In addition, as a constituent material of the insulator 31, an epoxy resin resist can be employed.

It is preferable that the thickness of each of the insulating layers 34 and 35 thus configured is in the range of 10 μm to 30 μm. In this case, it is preferable that the total thickness of the stacked region of the first insulating layer 34 and the second insulating layer 35 (jumper insulating portion 40) is 20 μm or more and 80 μm or less. If the total thickness of the insulator 31 is less than 20 μm, the solvent contained in the insulator 31 may evaporate when the insulator 31 is formed, which is not preferable. On the other hand, if the total thickness of the insulator 31 is greater than 80 μm, the difference in the curing rate between the vicinity of the surface of the insulator 31 and the inside thereof is increased in the firing process described later, and as a result, the above-described bleed occurs and the insulator 31 This is not preferable because a relatively large pinhole may be formed on the surface. As a result, there is a risk of short circuit between the jumper wiring 32 and the wiring layer group 24 due to migration.
On the other hand, by forming the total thickness of the insulator 31 to 20 μm or more and 80 μm or less, pinholes are not generated and the desired insulator 31 can be formed. Therefore, the jumper wiring 32 and the wiring layer group 24 can be formed. It is possible to prevent the short circuit between them. Furthermore, by forming the total thickness of the insulator 31 to 30 μm or more and 60 μm or less, a short circuit between the jumper wiring 32 and the wiring layer group 24 can be prevented more reliably.

  Here, the jumper wiring 32 is arranged on the laminated region of the insulator 31 so as to straddle the wiring layer group 24, and both ends thereof are connected to the lands 25 of the second wiring layer 23. Specifically, the center of the jumper wiring 32 is disposed on the laminated region of the insulator 31, while the both ends are disposed on the peripheral edge of the jumper insulating part 40. That is, the jumper wiring 32 is bridged between the lands 25 without contacting the surface 20 a of the substrate 20. Further, the jumper wiring 32 has a smooth curved surface shape along the outer surface shape of the second insulating layer 35, and the periphery thereof is surrounded by the side insulating portion 42 and the jumper insulating portion 40 on the land 25. Surrounded.

  In addition, as a constituent material of the jumper wiring 32, a conductive material (for example, silver) and a resin material (for example, polyester) are considered in consideration of adhesion to the insulator 31 (resist), followability to bending deformation of the substrate 20, and the like. Silver paste (for example, Dotite (registered trademark) FA-353 manufactured by Fujikura Kasei) is preferably used.

The film thickness of the jumper wiring 32 is preferably formed in the range of 10 μm to 30 μm. Setting the film thickness of the jumper wiring 32 to less than 10 μm is not preferable because the electrical resistance of the jumper wiring 32 increases and the jumper wiring 32 may break. On the other hand, if the film thickness of the jumper wiring 32 is set to be larger than 30 μm, it is not preferable because it is difficult to follow the bending deformation of the substrate 20 and disconnection is likely to occur and the manufacturing cost increases.
On the other hand, by forming the film thickness of the jumper wiring 32 in the range of 10 μm or more and 30 μm or less, it is possible to prevent the occurrence of disconnection or the like and connect the lands 25 with a desired resistance value. The film thickness of the jumper wiring 32 is more preferably about 20 μm.

  An upper insulating layer 45 (see FIG. 2) is formed on the jumper wiring 32 so as to cover the jumper wiring 32 and the second insulating layer 35. The upper insulating layer 45 is made of a resist in the same manner as the insulator 31 described above. Thereby, the contact between the jumper wiring 32 and other wiring layers or electronic components can be prevented, and a short circuit between them can be prevented.

(Manufacturing method of wiring board)
Next, a method for manufacturing the above-described wiring board will be described. FIG. 3 is a flowchart for explaining a method for manufacturing a wiring board, and FIG. 4 is a process diagram showing the method for manufacturing a wiring board.
As shown in FIGS. 3 and 4A, first, in step S1, a desired wiring pattern 21 is formed on the surface 20a of the substrate 20 with a copper foil or the like (copper foil patterning process).
Next, in step S2, a plating process for forming a plating layer (not shown) on each wiring pattern 21 is performed.

Next, as shown in FIG. 4B, in step S3, a first insulating layer 34 that covers the wiring layer group 24 disposed between the lands 25 is formed (first insulating layer forming step).
Specifically, first, in step S3A, the constituent material (resist) of the first insulating layer 34 is applied to the formation region of the first insulating layer 34 on the substrate 20 by a screen printing method or the like (resist application). Thereafter, in step S3B, the substrate 20 is baked for about 30 minutes in an atmosphere at a temperature of 150 degrees (curing step). Thereby, the solvent in the first insulating layer 34 can be efficiently evaporated, and the entire first insulating layer 34 can be uniformly cured.

By the way, after the formation of the first insulating layer 34, the first insulating layer 34 has a portion where a pinhole is generated. If the jumper wiring 32 is formed on the first insulating layer 34 in this state, there is a risk of a short circuit between the jumper wiring 32 and the wiring layer group 24.
On the other hand, it is also conceivable to apply the first insulating layer 34 thick enough to completely cover the wiring layer group 24.
However, if the film thickness of the first insulating layer 34 is too thick, the above-described bleed occurs and a relatively large pinhole is generated on the surface of the first insulating layer 34, which also causes the jumper wiring 32, the wiring layer group 24, There is a risk of a short circuit between the two.
Further, when the first insulating layer 34 is formed by a coating method such as a screen printing method, the first insulating layer 34 may be cut off at the peripheral edge K of the wiring layer group 24 to expose the lower wiring layer group 24. There is also.

Therefore, as shown in FIG. 4C, in the present embodiment, in step S4, the second insulating layer 35 is formed on the first insulating layer 34 so as to cover the first insulating layer 34 (second insulation). Layer forming step).
Specifically, as in the first insulating layer forming step described above, first, in step S4A, the constituent material (resist of the second insulating layer 35 is formed in the formation region of the second insulating layer 35 on the substrate 20 by screen printing or the like. ) Is applied (resist application). Thereafter, in step S4B, the substrate 20 is baked for about 30 minutes in an atmosphere at a temperature of 150 degrees (curing step). Thereby, the second insulating layer 35 is formed so as to cover the surrounding wiring pattern 21 including the first insulating layer 34.

In this case, an insulating layer may be formed by, for example, a photolithography technique, but when the insulating layer is formed by a photolithography technique, the peripheral portion becomes a corner portion, and then the jumper wiring 32 formed on the insulating layer is cut off. There is a risk of causing. On the other hand, by forming the insulator 31 by screen printing as in the present embodiment, the peripheral portion of the insulator 31 is applied on the surface 20a of the substrate 20 or the wiring layers 22 and 23 when the insulator 31 is applied. It spreads over the top, and the peripheral edge has a smooth curved shape. That is, unlike the case where the insulating layer is formed by a photolithography technique or the like, the step at the boundary between the insulator 31 and the land 25 can be reduced. Thereby, the jumper wiring 32 is smoothly arranged from the insulator 31 to the land 25. Thereby, disconnection of the jumper wiring 32 at the end portion of the insulator 31 can be prevented, and conduction between the lands 25 can be ensured.
On the land 25, only the second insulating layer 35 of the insulating layers 34 and 35 is formed, and the second insulating layer 35 is formed so that the film thickness gradually decreases toward the periphery. The thickness of the insulator 31 is smaller than that of the stacked region of the second insulating layer 35 and the first insulating layer 34. As a result, the step at the boundary between the land 25 and the second insulating layer 35 can be reduced, so that breakage of the jumper wiring 32 at the peripheral edge of the insulator 31 can be further prevented.

Subsequently, as shown in FIG. 4D, in step S5, a jumper wiring 32 for connecting the lands 25 of the second wiring layer 23 is formed (jumper wiring forming step). Specifically, first, in step S5A, silver paste, which is a constituent material of the jumper wiring 32, is applied to the formation region of the jumper wiring 32 by screen printing.
Thus, by applying the silver paste to be the jumper wiring 32 by the screen printing method, the jumper wiring 32 can be formed following the outer surface shape of the second insulating layer 35. Can be secured. In this case, since the periphery of the land 25 is surrounded by the second insulating layer 35 (the jumper insulating portion 40 and the side insulating portion 42), the silver paste wets and spreads on the land 25 when the silver paste is applied. However, it can be blocked by the second insulating layer 35. Thereby, there is no possibility that the jumper wiring 32 flows down on the substrate 20 and bridges another wiring layer to cause a short circuit. When the jumper wiring 32 is formed by the screen printing method, the jumper wiring 32 can be prevented from protruding along the boundary line of the insulator 31.

  In step S5B, the substrate 20 is baked for about 30 minutes in an atmosphere at a temperature of 150 degrees (curing step). As a result, the jumper wiring 32 that bridges the lands 25 is formed on the second insulating layer 35.

Finally, in step S6, the upper insulating layer 45 that covers the jumper wiring 32 is formed (upper insulating layer forming step). Specifically, in the same manner as each of the insulating layer forming steps described above, first, in step S6A, the constituent material (resist) of the upper insulating layer 45 is applied to the formation region of the upper insulating layer 45 on the substrate 20 by screen printing or the like. (Resist application). Thereafter, in step S6B, the substrate 20 is baked for about 30 minutes in an atmosphere at a temperature of 150 degrees (curing step). Thereby, the upper insulating layer 45 is formed so as to cover the jumper wiring 32 and the insulator 31.
The wiring board 10 mentioned above is completed by the above.

As described above, in the present embodiment, by forming the insulator 31 in which the first insulating layer 34 and the second insulating layer 35 are laminated on the wiring layer group 24, in the peripheral portion K of the wiring layer group 24 and the like. Since disconnection of the insulator 31 can be prevented, a short circuit between the jumper wiring 32 and the wiring layer group 24 disposed on the wiring layer group 24 via the insulator 31 can be prevented. In this case, unlike the case where the insulator 31 is thickly formed with a single layer in order to prevent the disconnection, the occurrence of pinholes due to bleed can be prevented, so that the jumper wiring 32 and the wiring layer group can be more reliably formed. A short circuit with 24 can be prevented. Even if a pinhole is generated in any one of the insulating layers 34 and 35, the pinhole does not penetrate the entire insulator 31, so that a short circuit due to migration can be prevented.
As a result, when the wiring (first wiring layer 22 and jumper wiring 32) is stacked via the insulator 31, the lower wiring layer (first wiring layer 23) and the upper wiring layer (jumper wiring 32) are separated. Insulation between them can be ensured.

  Further, since the second insulating layer 35 is formed so as to run on each land 25, the jumper wiring 32 formed on the second insulating layer 35 is connected between the lands 25 without contacting the substrate 20. Will be. Therefore, it is possible to prevent the jumper wiring 32 from being peeled off or to be disconnected, and to ensure conduction between the lands 25.

In addition, the substrate 20 is made of polyimide, and a resist made of urethane resin is used for the insulator 31, so that the adhesion between the substrate 20 and the insulator 31 and the follow-up of the insulator 31 to the bending deformation of the substrate 20. Therefore, it is possible to reliably insulate between the jumper wiring 32 and the wiring layer group 24 by preventing the insulator 31 from peeling or cracking. Note that even if an epoxy resin resist is used as the constituent material of the insulator 31, the same effect as described above can be obtained.
Further, by adopting a silver paste in which silver and a resin material are mixed in a diluent as the jumper wiring 32, the adhesion between the insulator 31 and the jumper wiring 32 and the follow-up of the jumper wiring 32 to the bending deformation of the substrate 20 are achieved. Therefore, the continuity between the lands 25 can be ensured by preventing the jumper wiring 32 from being peeled off or disconnected.

  The wiring board 10 of the present embodiment is not limited to portable electronic devices such as watches and mobile phones, but can be employed in wiring structures of various electronic devices such as printers. As a result, it is possible to increase the density of wiring patterning while reducing the manufacturing cost and improving the manufacturing efficiency. Therefore, it is possible to provide an electronic device that is reduced in size, weight, and performance.

The technical scope of the present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention. That is, the specific structure and shape described in the embodiment are merely examples, and can be changed as appropriate.
In the above-described embodiment, the case where a flexible substrate is adopted as the substrate 20 has been described.
In the above-described embodiment, the upper insulating layer (second insulating layer 35) is formed wider than the lower insulating layer (first insulating layer 34), and the lower insulating layer and the like are collectively formed by the upper insulating layer. Although the case of covering is described, the lower insulating layer may be formed wider than the upper insulating layer. In this case, the upper insulating layer needs to be disposed so as to cover at least the wiring layer group 24.
Further, the insulator 31 is not limited to two layers, and it is sufficient that a plurality of layers of two or more layers are formed.
Furthermore, as long as the wiring layer group 24 is covered, there is no problem even if the second insulating layer 35 is cut off at the peripheral edge of the second insulating layer 35.

FIG. 6 is an explanatory diagram showing another configuration of the wiring board.
As shown in FIG. 6, in the wiring board 200, the area of the first insulating layer 134 is formed substantially equal to the area of the second insulating layer 35, and both overlap between the wiring pattern 21 and the jumper wiring 32. Are arranged as follows. Also with this configuration, the wiring layer group 24 and the substrate 20 can be reliably covered, so that the adhesion and insulation of the jumper wiring 32 can be ensured.

DESCRIPTION OF SYMBOLS 10,200 ... Wiring board 20 ... Board | substrate 22 ... 1st wiring layer 23 ... 2nd wiring layer 25 ... Land 31 ... Insulator 32 ... Jumper wiring 34 ... 1st insulating layer (1st insulating layer) 35 ... 2nd insulation Layer (second insulating layer)

Claims (11)

A first wiring layer formed on the substrate;
An insulator covering at least the first wiring layer;
In a wiring board comprising jumper wiring formed on the first wiring layer via the insulator and disposed so as to straddle the first wiring layer,
A wiring board, wherein the insulator is formed by laminating a plurality of insulating layers. On both sides along the extending direction of the first wiring layer on the substrate, a pair of lands of the second wiring layer are formed so as to sandwich the first wiring layer therebetween,
The jumper wiring is connected to the land so as to bridge between both lands of the second wiring layer,
The insulator includes a first insulating layer covering the first wiring layer;
The land is formed wider than the formation region of the first insulating layer when viewed from the normal direction of the substrate, covers the first insulating layer, and rides on a part of the land on the substrate. The wiring board according to claim 1, further comprising: the second insulating layer covering the substrate.   3. The wiring board according to claim 2, wherein the second insulating layer is formed so as to surround a periphery of a connection portion with the jumper wiring on the land. The substrate is a flexible substrate made of polyimide,
The wiring board according to any one of claims 1 to 3, wherein the insulator is a resist made of urethane resin or epoxy resin.   The wiring board according to claim 4, wherein the jumper wiring is formed using a silver paste in which silver and a resin material are mixed in a diluent.   The wiring board according to claim 1, wherein the insulator has a total thickness of 20 μm to 80 μm.   7. The wiring board according to claim 1, wherein a film thickness of the jumper wiring is 10 μm or more and 30 μm or less. An insulator forming step of forming an insulator so as to cover at least the first wiring layer formed on the substrate;
A jumper wiring forming step of forming a jumper wiring on the insulator so as to straddle the first wiring layer;
In the insulator forming step, a method of manufacturing a wiring board, wherein a plurality of insulating layers are stacked to form the stacked body. On both sides along the extending direction of the first wiring layer on the substrate, a pair of lands of the second wiring layer to which the jumper wiring is connected are formed so as to sandwich the first wiring layer,
The insulator forming step includes a first insulating layer forming step of forming the first insulating layer covering at least the first wiring layer;
And a second insulating layer forming step of forming the second insulating layer for covering the land so as to run over a part of the land while covering the first wiring layer. The manufacturing method of the wiring board of Claim 8.   The method for manufacturing a wiring board according to claim 8 or 9, wherein, in the insulator forming step, the insulating layer is formed by a screen printing method.   The method for manufacturing a wiring board according to claim 8, wherein the jumper wiring forming step forms the jumper wiring by a screen printing method.

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