Wired circuit board
The wired circuit board design with protruding second wiring layers addresses the need for high-density, low-resistance wiring by increasing cross-sectional area and ensuring adhesion, thus enhancing reliability and reducing thickness.
Patent Information
- Application Number
- JP2019209294
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2019-11-20
- Publication Date
- 2025-09-10
- Estimated Expiration
- 2039-11-20
AI Technical Summary
As semiconductor components on wired circuit boards increase in size and functionality, there is a demand for higher wiring density and lower resistance while maintaining reliability and reducing board size, which existing two-layer wiring technologies struggle to achieve.
A wired circuit board design featuring a first and second wiring layer with a protrusion portion on the second layer that extends into the space between the first layers, increasing cross-sectional area and reducing electrical resistance, and ensuring adhesion through an anchoring effect.
The design achieves high-density wiring with reduced electrical resistance and improved reliability by effectively utilizing space between layers and enhancing adhesion, while avoiding short circuits.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a printed circuit board. [Background technology]
[0002] Some semiconductor components mounted on wired circuit boards are becoming larger as their functionality improves. Furthermore, wired circuit boards are subject to size restrictions and may require further reduction in size in order to reduce the size of the devices into which they are incorporated. As a result, the space available for forming wiring on wired circuit boards tends to decrease.
[0003] In response to this trend, if the width and spacing of wiring routed on the same plane of a substrate are made finer, the reliability and manufacturing yield of the printed circuit board are likely to decrease. Therefore, in order to deal with the reduction in wiring formation space, two-layer wiring routed on a substrate is being considered. Such technology related to two-layer wiring is described, for example, in Patent Document 1 listed below. [Prior art documents] [Patent documents]
[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-252816 Summary of the Invention [Problem to be solved by the invention]
[0005] On the other hand, as wiring density on wiring boards increases, there is also a demand for lower resistance.
[0006] The present invention provides a wired circuit board suitable for achieving high density while reducing the resistance of wiring. [Means for solving the problem]
[0007] The present invention [1] includes a wired circuit board comprising: a first insulating layer; a pair of first wiring layers arranged on the first insulating layer and extending side by side at a distance from each other; a second insulating layer arranged on the first insulating layer so as to cover the pair of first wiring layers; and a second wiring layer arranged on the second insulating layer and extending along the pair of first wiring layers while facing the pair of first wiring layers in the thickness direction of the first wiring layers, wherein the second wiring layer has a protrusion portion that protrudes into the second insulating layer toward a region between the pair of first wiring layers and extends along the region.
[0008] As described above, the wired circuit board of the present invention includes a pair of first wiring layers and a second wiring layer extending along and facing the first wiring layers. This wired circuit board is suitable for achieving high-density wiring. In addition, as described above, the second wiring layer has a protrusion that extends into the second insulating layer toward the region between the first wiring layers and along the region. This configuration is suitable for effectively utilizing the space between the first wiring layers to increase the cross-sectional area of the second wiring layer, thereby reducing electrical resistance (resistance). Additionally, the protrusion of the second wiring layer serves to ensure adhesion of the second wiring layer to the second insulating layer through its anchoring effect, thereby ensuring reliability of the second wiring layer.
[0009] The present invention [2] includes the wired circuit board according to the above [1], wherein the protrusion has a top that is not flat in a cross section in a width direction intersecting with the extension direction of the second wiring layer.
[0010] A configuration in which the protrusion portion has such a top helps to ensure adhesion of the second wiring layer to the second insulating layer due to the anchor effect of the protrusion portion to the second insulating layer, and is therefore suitable for ensuring the reliability of the second wiring layer.
[0011] The present invention [3] includes the wired circuit board described in [2] above, wherein the protrusion portion further has a first curved side surface arranged on one side of the apex in the width direction and recessed toward the inside of the second wiring layer, and a second curved side surface arranged on the other side of the apex in the width direction and recessed toward the inside of the second wiring layer.
[0012] The configuration in which the protrusion portion has such first and second curved side surfaces helps to ensure adhesion of the second wiring layer to the second insulating layer due to the anchor effect of the protrusion portion to the second insulating layer, and is therefore suitable for ensuring the reliability of the second wiring layer.
[0013] The present invention [4] includes the wired circuit board according to any one of [1] to [3] above, wherein the distance between the first wiring layer and the second wiring layer in the thickness direction is 2 μm or more and 20 μm or less.
[0014] Such a configuration is suitable for reducing the thickness of the printed circuit board while avoiding short circuits between the first wiring layer and the second wiring layer.
[0015] The present invention [5] includes the wired circuit board according to any one of the above [1] to [4], wherein the distance between the pair of first wiring layers is 5 μm or more and 30 μm or less.
[0016] Such a configuration is suitable for achieving high density wiring while avoiding short circuits between the first wiring layers. [Brief explanation of the drawings]
[0017] [Figure 1] 1 is a schematic plan view of an embodiment of a printed circuit board of the present invention. [Figure 2] 1 is a cross-sectional view in the width direction of a multilayer wiring structure in one embodiment of the wired circuit board of the present invention. [Figure 3] 1 is a partial cross-sectional view of a multilayer wiring structure in an extension direction of an embodiment of the wired circuit board of the present invention. [Figure 4] Some steps in a manufacturing method for one embodiment of the wired circuit board of the present invention are shown as variations of cross sections corresponding to Fig. 2. Fig. 4A shows a preparation step, Fig. 4B shows a first insulating layer forming step, and Fig. 4C shows a first conductor forming step. [Figure 5]These show steps that follow the step shown in Fig. 4. Fig. 5A shows the second insulating layer forming step, Fig. 5B shows the second conductor forming step, and Fig. 5C shows the third insulating layer forming step. [Figure 6] Some steps in a manufacturing method for one embodiment of the wired circuit board of the present invention are shown as variations of cross sections corresponding to Fig. 3. Fig. 6A shows a preparation step, Fig. 6B shows a first insulating layer forming step, and Fig. 6C shows a first conductor portion forming step. [Figure 7] These show steps that follow the step shown in Fig. 6. Fig. 7A shows the second insulating layer forming step, Fig. 7B shows the second conductor forming step, and Fig. 7C shows the third insulating layer forming step. [Figure 8] FIG. 10 is a partial cross-sectional view of a modified example of the printed circuit board in the extension direction of a multilayer wiring structure portion. DETAILED DESCRIPTION OF THE INVENTION
[0018] 1 to 3 show a wired circuit board X according to one embodiment of the present invention. Fig. 1 is a schematic plan view of the wired circuit board X. Fig. 2 is a cross-sectional view in the width direction of a multilayer wiring structure portion of the wired circuit board X. Fig. 3 is a partial cross-sectional view in the extension direction of the multilayer wiring structure portion of the wired circuit board X.
[0019] As shown in FIG. 1, the wired circuit board X has a component mounting region R1 and a surrounding wiring formation region R2. The component mounting region R1 is an area where mounted components such as semiconductor chips are arranged. Pad portions (not shown) for electrical connection with the mounted components are provided in the component mounting region R1. A plurality of wirings (not shown) are routed and formed in the wiring formation region R2. The plurality of wirings includes, for example, power supply wiring, signal wiring, and ground wiring. At least some of the plurality of wirings are electrically connected to terminal portions (not shown) for external connection provided in the wiring formation region R2. Furthermore, the wired circuit board X includes a multilayer wiring structure portion shown in FIGS. 2 and 3 in its wiring formation region R2.
[0020] The multilayer wiring structure is a wiring structure including wires extending side by side and facing each other in the thickness direction, and includes an insulating layer 11 as a first insulating layer, an insulating layer 12 as a second insulating layer, an insulating layer 13 as a third insulating layer, a pair of wiring layers 21 as a pair of first wiring layers, and a wiring layer 22 as a second wiring layer. Figures 2 and 3 show an example of a multilayer wiring structure disposed on a substrate S.
[0021] The substrate S is an element for ensuring the rigidity of the wiring circuit board X, and is provided on the entire or partial region of the wiring circuit board X in the plan view shown in FIG.
[0022] When the wired circuit board X is configured as a flexible wired circuit board, the substrate S is, for example, a flexible metal support layer. Examples of materials constituting the metal support layer include metal foil. Examples of metal materials for the metal foil include stainless steel, 42 alloy, copper, and copper alloys. Examples of stainless steel include SUS304, which conforms to the standards of the AISI (American Iron and Steel Institute). The thickness of the substrate S as the metal support layer is, for example, 15 μm or more, and, for example, 500 μm or less, preferably 250 μm or less.
[0023] When the wired circuit board X is configured as a rigid wired circuit board, the base material S is a rigid board. Examples of rigid boards include a glass epoxy board and a metal flat plate. The thickness of the base material S as a rigid board is, for example, 0.1 mm or more, for example, 2 mm or less, and preferably 1.6 mm or less.
[0024] The insulating layer 11 is formed on one surface in the thickness direction of the substrate S. Examples of materials constituting the insulating layer 11 include synthetic resins such as polyimide, polyethernitrile, polyethersulfone, polyethylene terephthalate, polyethylene naphthalate, and polyvinyl chloride (similar synthetic resins can also be used as materials constituting the insulating layers 12 and 13 described below). The thickness of the insulating layer 11 is, for example, 1 μm or more, preferably 3 μm or more, and, for example, 35 μm or less, preferably 15 μm or less.
[0025] The pair of wiring layers 21, 21 are disposed on one surface in the thickness direction of the insulating layer 11. The pair of wiring layers 21, 21 extend side by side and spaced apart from each other. In this embodiment, the pair of wiring layers 21, 21 have a predetermined pattern shape on the insulating layer 11.
[0026] The thickness of the wiring layer 21 is, for example, 3 μm or more, preferably 5 μm or more, and for example, 50 μm or less, preferably 30 μm or less. The width of the wiring layer 21 (the dimension in the direction perpendicular to the extension direction of the wiring layer 21) is, for example, 5 μm or more, preferably 8 μm or more, and for example, 100 μm or less, preferably 50 μm or less. The distance L1 between the pair of wiring layers 21, 21 in the separation direction is preferably 5 μm or more, more preferably 8 μm or more, and preferably 30 μm or less, more preferably 20 μm or less.
[0027] Examples of materials constituting the wiring layer 21 include metal materials such as copper, nickel, gold, solder, and alloys thereof, and copper is preferred (the same applies to the materials constituting the wiring layer 22 described below).
[0028] The insulating layer 12 is disposed on one surface in the thickness direction of the insulating layer 11 so as to cover the pair of wiring layers 21, 21. The thickness of the insulating layer 12 (maximum height from the insulating layer 11) is greater than the thickness of the wiring layer 21.
[0029] 2, the wiring layer 22 is disposed on one surface in the thickness direction of the insulating layer 12, and faces the pair of wiring layers 21, 21 in the thickness direction via the insulating layer 12. In addition, the wiring layer 22 extends along each of the pair of wiring layers 21, 21, as shown in Fig. 3. Such a wiring layer 22 is connected to, for example, a conductive pad portion (not shown) provided on the insulating layer 11.
[0030] The width of the wiring layer 22 (the dimension in the direction perpendicular to the extension direction of the wiring layer 22) is, for example, 8 μm or more, preferably 10 μm or more, as long as it faces the pair of wiring layers 21, 21 as described above, and is, for example, 100 μm or less, preferably 80 μm or less.
[0031] The wiring layer 22 has a protruding portion 22A. As shown in Fig. 2, the protruding portion 22A protrudes into the insulating layer 12 toward a region G between the pair of wiring layers 21, 21 and extends along the region G. The protruding portion 22A has an apex 22a. In a cross section (cross section shown in Fig. 2) in a width direction intersecting (orthogonal in this embodiment) the extension direction of the wiring layer 22, the apex 22a is non-flat and has an outwardly bulging curve.
[0032] 2, the protrusion 22A has a curved side surface 22b (first curved side surface) and a curved side surface 22c (second curved side surface). The curved side surface 22b is disposed on one side of the apex 22a in the width direction and is recessed toward the inside of the wiring layer 22. The curved side surface 22c is disposed on the other side of the apex 22a in the width direction and is recessed toward the inside of the wiring layer 22.
[0033] Furthermore, the wiring layer 22 has a portion 22F that is thicker than a portion 22E facing the wiring layer 21 at a position between the pair of wiring layers 21 in the separation direction (specifically, at the position where the protrusion 22A is formed). The thickness of the portion 22E is preferably 3 μm or more, more preferably 5 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less. The thickness of the portion 22F, as long as it is thicker than the portion 22E, is preferably 3 μm or more, more preferably 5 μm or more, and is preferably 60 μm or less, more preferably 40 μm or less.
[0034] The distance L2 between the wiring layer 21 and the wiring layer 22 or its portion 22E in the thickness direction is preferably 2 μm or more, more preferably 5 μm or more, and is preferably 20 μm or less, more preferably 15 μm or less.
[0035] Insulating layer 13 is disposed on one thickness-wise surface of insulating layer 12 so as to cover wiring layer 22. The thickness of insulating layer 13 (height from insulating layer 12) is greater than the thickness of wiring layer 22. As long as the thickness of insulating layer 13 is thicker than wiring layer 22, it is, for example, 4 μm or more, preferably 6 μm or more, and for example, 60 μm or less, preferably 40 μm or less.
[0036] The wiring layer 21 and the wiring layer 22 in the multilayer wiring structure of the wiring circuit board X are signal wiring or power supply wiring (i.e., wiring for power supply). There is often a strong demand for low resistance in the power supply wiring, and the wiring circuit board X is suitable for achieving high density while achieving low resistance in such power supply wiring.
[0037] 4 to 7 show an example of a method for manufacturing a wired circuit board X. Fig. 4 and Fig. 5 show this manufacturing method as a change in a cross section corresponding to Fig. 2, and Fig. 6 and Fig. 7 show this manufacturing method as a change in a cross section corresponding to Fig. 3.
[0038] In this manufacturing method, first, as shown in FIGS. 4A and 6A, a substrate S is prepared (preparation step).
[0039] Next, as shown in FIGS. 4B and 6B, an insulating layer 11 is formed on the substrate S (first insulating layer forming step). In this step, for example, the insulating layer 11 is formed by applying a resin solution (varnish) for forming the insulating layer 11 onto the substrate S and drying it. When the insulating layer 11 has a predetermined pattern shape in a plan view, for example, a photosensitive resin solution (varnish) for forming the insulating layer 11 is applied onto the substrate S and dried, and then the coating film formed thereby is subjected to an exposure process through a predetermined mask, a subsequent development process, and then a baking process as necessary. In this way, an insulating layer 11 of a predetermined pattern is formed on the substrate S.
[0040] Next, as shown in Figures 4C and 6C, the wiring layer 21 is patterned on the insulating layer 11 (first conductor forming step). Examples of methods for forming the wiring layer 21 include an additive method and a subtractive method. When the additive method is used in this step, the wiring layer 21 is formed, for example, as follows.
[0041] First, a thin seed layer (not shown), which is a conductive layer for forming an electroplated film, is formed on the exposed surface of the insulating layer 11, for example, by sputtering. Examples of materials for the seed layer include copper, chromium, nickel, and alloys thereof. Next, a resist pattern is formed on the seed layer. The resist pattern has openings with a pattern shape corresponding to the pattern shape of the wiring layer 21. To form the resist pattern, for example, a photosensitive resist film is attached to the seed layer to form a resist film, and then the resist film is exposed through a predetermined mask, developed, and then baked as needed. To form the wiring layer 21, a metal material is then grown on the seed layer in the regions within the openings of the resist pattern by electroplating. Copper is preferably used as the metal material. Next, the resist pattern is removed by etching. Next, the portions of the seed layer exposed by removing the resist pattern are removed by etching. For example, in the manner described above, a predetermined pattern of the wiring layer 21 can be formed on the insulating layer 11.
[0042] Next, in this manufacturing method, as shown in FIGS. 5A and 7A, an insulating layer 12 is formed on the insulating layer 11 so as to cover the wiring layers 21, 21 (second insulating layer formation process). In this process, for example, a photosensitive resin solution (varnish) for forming the insulating layer 12 is applied to the insulating layer 11 and the wiring layers 21, 21 and dried, and the resulting coating is then subjected to an exposure process through a predetermined mask, a subsequent development process, and a baking process as necessary. In this way, the insulating layer 12 of a predetermined pattern that covers the wiring layers 21, 21 of the predetermined pattern is formed on the insulating layer 11. The insulating layer 12 is formed so as to form a recess 12a (i.e., to a thickness that creates the recess 12a) at a position between the pair of wiring layers 21, 21 in the separation direction of the pair of wiring layers 21, 21, as shown in FIG. 5A.
[0043] 5B and 7B, a wiring layer 22 is patterned on the insulating layer 12 (second conductor forming step). Examples of methods for forming the wiring layer 22 include an additive method and a subtractive method. When the additive method is used in this step, the wiring layer 22 is formed, for example, as follows.
[0044] First, a thin seed layer (not shown) serving as a conductive layer for forming an electrolytic plating film is formed on the exposed surface of the insulating layer 12, for example, by sputtering. Examples of materials for the seed layer include copper, chromium, nickel, and alloys thereof. Next, a resist pattern is formed on the seed layer. The resist pattern has openings with a pattern shape corresponding to the pattern shape of the wiring layer 22. To form the resist pattern, for example, a photosensitive resist film is attached to the seed layer to form a resist film, and then the resist film is exposed through a predetermined mask, developed, and then baked as needed. To form the wiring layer 22, a metal material is then grown on the seed layer in the regions within the openings of the resist pattern by electroplating. Copper is preferably used as the metal material. Next, the resist pattern is removed by etching. Next, the portions of the seed layer exposed by removing the resist pattern are removed by etching. For example, a wiring layer 22 having a predetermined pattern can be formed in the manner described above.
[0045] 5C and 7C, in this manufacturing method, an insulating layer 13 is next formed on the insulating layer 12 so as to cover the wiring layer 22 (third insulating layer formation step). In this step, for example, a photosensitive resin solution (varnish) for forming the insulating layer 13 is applied to the insulating layer 12 and the wiring layer 22 and dried, and then the coating film formed thereby is subjected to an exposure process through a predetermined mask, a subsequent development process, and then a baking process as necessary. In this way, the insulating layer 13 of a predetermined pattern that covers the wiring layer 22 of the predetermined pattern is formed on the insulating layer 12.
[0046] For example, by going through the steps described above, it is possible to manufacture a wired circuit board X having a multilayer wiring structure.
[0047] As described above, the wired circuit board X has wiring that is routed in a multilayer wiring structure including a pair of wiring layers 21, 21 and a wiring layer 22 that faces and extends along the pair of wiring layers 21, 21. Such a wired circuit board X is suitable for achieving high-density wiring.
[0048] As described above, the wiring layer 22 has the protrusions 22A that protrude into the insulating layer 12 toward the region G between the wiring layers 21, 21 and extend along the region G. Such a configuration effectively utilizes the space between the wiring layers 21, 21 to increase the cross-sectional area (for example, the cross-sectional area perpendicular to the wiring extension direction) of the wiring layer 22, and is therefore suitable for reducing (lowering) electrical resistance such as DC resistance.
[0049] As described above, the wired circuit board X is suitable for achieving high density while reducing the resistance of the wiring.
[0050] Furthermore, the protrusions 22A of the wiring layer 22 serve to ensure adhesion of the wiring layer 22 to the insulating layer 12 due to their anchoring effect on the insulating layer 12, and are therefore suitable for ensuring the reliability of the wiring layer 22.
[0051] As described above, in the wired circuit board X, the protrusions 22A have tops 22a that are non-flat in a cross section (for example, the cross section shown in FIG. 2 ) in the width direction intersecting the extension direction of the wiring layer 22. The configuration in which the protrusions 22A have such tops 22a helps to ensure adhesion of the wiring layer 22 to the insulating layer 12 due to the anchor effect of the protrusions 22A to the insulating layer 12, and is therefore suitable for ensuring the reliability of the wiring layer 22.
[0052] As described above, the protrusion 22A further has a curved side surface 22b that is disposed on one widthwise side of the top 22a and recessed toward the inside of the wiring layer 22, and a curved side surface 22c that is disposed on the other widthwise side of the top 22a and recessed toward the inside of the wiring layer 22. The configuration in which the protrusion 22A has such curved side surfaces 22b, 22c in addition to the top 22a helps to ensure adhesion of the wiring layer 22 to the insulating layer 12 due to the anchor effect of the protrusion 22A on the insulating layer 12, and is therefore suitable for ensuring the reliability of the wiring layer 22.
[0053] As described above, the distance L1 between the pair of wiring layers 21 is preferably 5 μm or more, more preferably 8 μm or more, and is preferably 30 μm or less, more preferably 20 μm or less. Such a configuration is suitable for achieving high density wiring while avoiding short circuits between the wiring layers 21.
[0054] As described above, the distance L2 between the wiring layer 21 and the wiring layer 22 in the thickness direction is preferably 2 μm or more, more preferably 5 μm or more, and is preferably 20 μm or less, more preferably 15 μm or less. Such a configuration is suitable for reducing the thickness of the wired circuit board X while avoiding short circuits between the wiring layer 21 and the wiring layer 22.
[0055] 8, the wired circuit board X may have a configuration in which the wiring layer 21 and the wiring layer 22 are electrically connected to each other through vias 23. Specifically, in this configuration, each of the pair of wiring layers 21 and the wiring layer 22 is electrically connected to each other through vias 23 (for example, a plurality of vias 23 between each of the wiring layers 21 and the wiring layer 22) that penetrate the insulating layer 12. [Explanation of symbols]
[0056] X Wiring Circuit Board R1 Component mounting area R2 wiring formation area S base material 11 Insulating layer (first insulating layer) 12 Insulation layer (second insulation layer) 13 Insulation layer (third insulation layer) 21 Wiring layer (1st wiring layer) 22 Wiring layer (2nd wiring layer) 22A Projection part 22a Top 22b Curved side (first curved side) 22c curved side (second curved side) 23 Beer G area (area between the first wiring layers)
Claims
1. a first insulating layer; a pair of first wiring layers disposed on the first insulating layer and extending side by side and spaced apart from each other; a second insulating layer disposed on the first insulating layer so as to cover the pair of first wiring layers; a second wiring layer disposed on the second insulating layer and extending along the pair of first wiring layers while facing the pair of first wiring layers in a thickness direction of the first wiring layers; the second wiring layer has a protrusion portion that protrudes into the second insulating layer toward a region between the pair of first wiring layers and extends along the region; the thickness of the pair of first wiring layers is 3 μm or more and 30 μm or less; a distance between the first wiring layer and the second wiring layer in the thickness direction is 2 μm or more and 20 μm or less; the distance between the pair of first wiring layers is 5 μm or more and 30 μm or less; the thickness of the second wiring layer is greater at the position where the protrusion is formed than at a position other than the position where the protrusion is formed; the thickness of the second wiring layer at the position where the protrusion is formed is 5 μm or more and 60 μm or less; The printed circuit board, wherein the thickness of the second wiring layer at a position excluding the position where the protrusion is formed is 3 μm or more and 50 μm or less.
2. 2. The printed circuit board according to claim 1, wherein the protrusion has a top that is not flat in a cross section in a width direction intersecting with the extension direction of the second wiring layer.
3. 3. The wired circuit board according to claim 2, wherein the protrusion portion further has a first curved side surface disposed on one side of the top in the width direction and recessed toward the inside of the second wiring layer, and a second curved side surface disposed on the other side of the top in the width direction and recessed toward the inside of the second wiring layer.
Citation Information
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