Wiring Substrate and Method for Manufacturing the Same

Abstract

To provide a wiring board in which an outer edge of a pad for external connection is located inside an outer edge of an opening of an insulating layer in a plan view.SOLUTION: A wiring board has a pad for external connection and an insulating layer. A part of a lower surface of the pad is coated with the insulating layer. The pad comprises: a main body portion; and an extending portion which is formed integrally with the main body portion and extends toward an outer peripheral side of a lateral face of the main body portion in a plan view, at a lower end side of the lateral face of the main body portion. The insulating layer comprises a groove which is located around the pad in a plan view, exposes a lateral face of the pad and opens toward an upper surface side of the insulating layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wiring board and a method for manufacturing the same.

Background Art

[0002] A wiring board has, for example, pads exposed from an insulating layer disposed on the outermost layer. These pads serve as external connection pads for electrically connecting to, for example, a motherboard or the like. The manufacturing process of this wiring board includes, for example, a step of forming external connection pads on the upper surface of a support, a step of forming an insulating layer covering the external connection pads on the upper surface of the support, and a step of removing the support.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, if the area of the upper surface of the pad is large, the capacitance may increase and the electrical signal may deteriorate. Therefore, in recent years, there has been a demand to reduce the area of the upper surface of the pad in order to reduce the capacitance. On the other hand, from the viewpoint of ensuring compatibility with a conventional wiring board regarding a socket or the like used for connection to the wiring board, even if the pad is miniaturized, there is a demand not to change the size of the opening of the insulating layer around the pad.

[0005] In order to meet these demands, it is necessary to move the outer edge of the pad inside the outer edge of the opening of the insulating layer around the pad without moving the outer edge of the opening of the insulating layer around the pad in a plan view. However, in the above wiring board, it is difficult to move only the outer edge of the pad inside the outer edge of the opening of the insulating layer.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide a wiring board in which the outer edge of a pad for external connection is located inside the outer edge of an opening of an insulating layer in a plan view.

Means for Solving the Problems

[0007] This wiring board has a pad for external connection and an insulating layer. A part of the lower surface of the pad is covered by the insulating layer. The pad includes a main body portion and an extension portion that is formed integrally with the main body portion and extends to the outer peripheral side of the side surface of the main body portion on the lower end side of the side surface of the main body portion in a plan view. The side surface of the pad is exposed in the insulating layer, and a groove that opens on the upper surface side of the insulating layer is provided. is the front 、a groove is provided that exposes the side surface of the pad and opens on the upper surface side of the insulating layer. and 、 the outer edge of the groove is located outside the side surface of the extension portion in a plan view 。

Effects of the Invention

[0008] According to the disclosed technology, it is possible to provide a wiring board in which the outer edge of a pad for external connection is located inside the outer edge of an opening of an insulating layer in a plan view.

Brief Description of the Drawings

[0009] [[Figure 1]] It is a diagram illustrating a wiring board according to the first embodiment. [[Figure 2]] It is a diagram (Part 1) illustrating a manufacturing process of a wiring board according to the first embodiment. [[Figure 3]] It is a diagram (Part 2) illustrating a manufacturing process of a wiring board according to the first embodiment. [[Figure 4]] It is a diagram (Part 3) illustrating a manufacturing process of a wiring board according to the first embodiment. [[Figure 5]] It is a diagram (Part 4) illustrating a manufacturing process of a wiring board according to the first embodiment. [[Figure 6]] It is a diagram illustrating a wiring board according to Modification Example 1 of the first embodiment. [[Figure 7]] It is a diagram illustrating a wiring board according to the second embodiment. [[Figure 8]] It is a diagram (Part 1) illustrating a manufacturing process of a wiring board according to the second embodiment. [[Figure 9]] It is a diagram (part 2) illustrating the manufacturing process of the wiring board according to the second embodiment. [[Figure 10]] It is a diagram (part 3) illustrating the manufacturing process of the wiring board according to the second embodiment. [[Figure 11]] It is a diagram (part 4) illustrating the manufacturing process of the wiring board according to the second embodiment. [[Figure 12]] It is a diagram (part 5) illustrating the manufacturing process of the wiring board according to the second embodiment. [[Figure 13]] It is a diagram illustrating the wiring board according to Modification 1 of the second embodiment.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same constituent parts, and duplicate descriptions may be omitted.

[0011] 〈First Embodiment〉 [Structure of Wiring Board] FIG. 1 is a diagram illustrating the wiring board according to the first embodiment, FIG. 1(a) is a partial plan view, and FIG. 1(b) is a partial cross-sectional view taken along line A-A of FIG. 1(a).

[0012] Referring to FIG. 1, the wiring board 1 has a pad 10, an insulating layer 20, a wiring layer 30, an insulating layer 40, and a wiring layer 50. In the wiring board 1, a larger number of insulating layers and wiring layers may be laminated.

[0013] In this embodiment, for convenience, the side of the wiring board 1 on the insulating layer 20 side in FIG. 1(b) is defined as the upper side or one side, and the side on the insulating layer 40 side is defined as the lower side or the other side. Also, the surface on the insulating layer 20 side of each part is defined as the upper surface or one surface, and the surface on the insulating layer 40 side is defined as the lower surface or the other surface. However, the wiring board 1 can be used in an upside-down state or arranged at an arbitrary angle. Also, the plan view means viewing the object from the normal direction of the upper surface 20a of the insulating layer 20, and the planar shape means the shape of the object viewed from the normal direction of the upper surface 20a of the insulating layer 20.

[0014] The pad 10 is a pad for external connection. The pad 10 can be used, for example, to electrically connect to a mounting board (not shown) such as a motherboard. The pad 10 has a laminated structure and includes a metal layer 11 and a metal layer 12.

[0015] The metal layer 11 includes a main body portion 11b and an extending portion 11s. The extending portion 11s is formed integrally with the main body portion 11b and extends to the outer peripheral side of the side surface of the main body portion 11b in a plan view at the lower end side of the side surface of the main body portion 11b. The extending portion 11s is formed, for example, in an annular (ring shape) on the outer peripheral side of the side surface of the main body portion 11b in a plan view.

[0016] The planar shape of the main body portion 11b is, for example, a circle with a diameter of about 600 μm to 800 μm. However, the planar shape of the main body portion 11b may be an ellipse, a rectangle, or any other arbitrary shape. The width of the extending portion 11s is, for example, about 10 to 30 μm. The thickness of the main body portion 11b is, for example, about 10 to 30 μm. The thickness of the extending portion 11s is, for example, about 0.5 to 3.0 μm. The area of the lower surface of the metal layer 11 is larger than the area of the upper surface. The metal layer 11 is, for example, a copper layer (Cu layer).

[0017] The metal layer 12 covers the surface of the metal layer 11 exposed from the insulating layer 20. Specifically, the metal layer 12 continuously covers the upper surface and the side surface of the main body portion 11b and the upper surface of the extending portion 11s. The metal layer 12 is, for example, a gold layer (Au layer). The thickness of the metal layer 12 is, for example, about 5 to 10 μm.

[0018] Note that the metal layer 12 may have a laminated structure with an Au layer as the uppermost layer. The metal layer 12 can be, for example, a Ni / Au layer (a metal layer formed by laminating a Ni layer and an Au layer in this order on the metal layer 11), a Ni / Pd / Au layer (a metal layer formed by laminating a Ni layer, a Pd layer, and an Au layer in this order on the metal layer 11), or the like.

[0019] The pad 10 is exposed on the upper surface 20a side of the insulating layer 20. In the pad 10, a part of the lower surface (the lower surfaces of the main body portion 11b and the extension portion 11s of the metal layer 11) (the portion excluding the portion connected to the via wiring) is covered by the insulating layer 20. Also, the side surface of the extension portion 11s of the metal layer 11 is covered by the insulating layer 20. As the material of the insulating layer 20, for example, an insulating resin mainly composed of an epoxy resin or the like can be used. The insulating layer 20 may contain a filler such as silica (SiO2). The thickness of the insulating layer 20 can be, for example, about 10 to 70 μm.

[0020] The upper surface of the main body portion 11b of the metal layer 11 is at a position lower than the upper surface 20a of the insulating layer 20. The height of the upper surface 20a of the insulating layer 20 with respect to the upper surface of the main body portion 11b of the metal layer 11 is, for example, about 2 to 3 μm. The upper surface 10a (the upper surface of the metal layer 12) of the pad 10 is at a position higher than the upper surface 20a of the insulating layer 20. The height of the upper surface 10a (the upper surface of the metal layer 12) of the pad 10 with respect to the upper surface 20a of the insulating layer 20 is, for example, about 2 to 8 μm.

[0021] The insulating layer 20 is provided with a groove 20g that is located around the pad 10 in a plan view, exposes the side surface of the pad 10, and opens on the upper surface 20a side of the insulating layer 20. When the planar shape of the pad 10 is circular, the groove 20g can be formed in a ring shape such that, for example, in a plan view, the inner edge and the outer edge are circular with different diameters. The width of the groove 20g can be, for example, about 80 μm to 100 μm.

[0022] The metal layer 12 that covers the side surface of the main body portion 11b of the metal layer 11 and the metal layer 12 that covers the upper surface of the extending portion 11s of the metal layer 11 are exposed from the insulating layer 20 within the groove 20g. Here, if the surface at the lowest position among the surfaces formed by the insulating layer 20 exposed within the groove 20g is defined as the bottom surface of the groove 20g, the upper surface of the extending portion 11s is at a position lower than the bottom surface of the groove 20g. The height of the bottom surface of the groove 20g with respect to the upper surface of the extending portion 11s is, for example, about 2 to 3 μm. Also, in the metal layer 12, if the upper surface of the portion laminated on the extending portion 11s is defined as the outer peripheral surface of the metal layer 12, the outer peripheral surface of the metal layer 12 is at a position higher than the bottom surface of the groove 20g. The height of the outer peripheral surface of the metal layer 12 with respect to the bottom surface of the groove 20g is, for example, about 2 to 8 μm.

[0023] The wiring layer 30 is formed on the other side of the insulating layer 20. The wiring layer 30 includes, for example, via wirings filled in via holes 20x that penetrate the insulating layer 20 and expose the lower surface of the pad 10, via receiving pads formed on the lower surface of the insulating layer 20, and wiring patterns. The via wirings penetrate the insulating layer 20 and contact the lower surface of the pad 10. The via hole 20x can be a frustum-shaped recess in which the diameter of the opening on the insulating layer 40 side is larger than the diameter of the bottom surface of the opening formed by the lower surface of the pad 10. As the material of the wiring layer 30, for example, copper or the like can be used. The thicknesses of the via receiving pads and the wiring patterns that constitute the wiring layer 30 can be, for example, about 10 to 30 μm.

[0024] The insulating layer 40 is formed on the lower surface of the insulating layer 20 so as to cover the wiring layer 30. The material and thickness of the insulating layer 40 can be, for example, the same as those of the insulating layer 20. The insulating layer 40 may contain a filler such as silica (SiO2).

[0025] The wiring layer 50 is formed on the other side of the insulating layer 40. The wiring layer 50 includes, for example, via wirings filled in via holes 40x that penetrate the insulating layer 40 and expose the lower surface of the via receiving pads of the wiring layer 30, pads formed on the lower surface of the insulating layer 40, and wiring patterns. The via holes 40x can be frustum-shaped recesses in which the diameter of the opening on the lower surface side of the insulating layer 40 is larger than the diameter of the bottom surface of the opening formed by the lower surface of the via receiving pads of the wiring layer 30. The material of the wiring layer 50, the thickness of the via receiving pads and the wiring patterns constituting the wiring layer 50 can be the same as those of the wiring layer 30, for example.

[0026] Thus, in the wiring board 1, the insulating layer 20 is provided with grooves 20g that are located around the pads 10 in plan view and open to the upper surface 20a side of the insulating layer 20. As a result, the outer edge of the pad 10 can be positioned inside the outer edge of the opening of the insulating layer 20 (the outer edge of the groove 20g) in plan view, so that the area of the upper surface 10a of the pad 10 can be reduced. By reducing the area of the upper surface 10a of the pad 10, it becomes possible to reduce the capacitance of the pad 10 and suppress the deterioration of the electrical signal passing through the pad 10.

[0027] Also, if the grooves 20g are not provided, the position of the opening of the insulating layer 20 that exposes the upper surface 10a of the pad 10 will be the same as the outer edge of the pad 10 in plan view. In this case, if the area of the upper surface 10a of the pad 10 is made smaller than before, the size of the opening will also become smaller, and compatibility with the conventional wiring board cannot be ensured.

[0028] That is, when connecting the pad 10 to a mounting substrate such as a motherboard, a socket is used. However, the opening of the insulating layer 20 that exposes the upper surface 10a of the pad 10 is sized such that the socket does not contact the insulating layer 20. Therefore, in order to reduce the capacitance of the pad 10 while ensuring compatibility with a conventional wiring board, it is necessary to reduce the area of the upper surface 10a of the pad 10 without changing the size of the opening of the insulating layer 20. By providing a groove 20g that is located around the pad 10 in a plan view and opens to the upper surface 20a side of the insulating layer 20, it becomes possible to reduce the area of the upper surface 10a of the pad 10 while ensuring compatibility with a conventional wiring board.

[0029] Also, when connecting the pad 10 and a mounting substrate such as a motherboard via solder, since excess solder flows from the upper surface 10a of the pad 10 into the groove 20g, short - circuiting between adjacent pads can be suppressed. Further, since the solder enters the groove 20g, the upper surface 10a and the side surface of the pad 10 are three - dimensionally joined to the solder, so that the joining strength between the pad 10 and the solder can be improved.

[0030] Also, since a step is formed at the boundary between the bottom surface of the groove 20g and the outer peripheral surface of the metal layer 12, the number of corner portions where the solder flowing into the groove 20g contacts increases. As a result, the force applied to the solder is dispersed, so that the durability of the solder can be improved.

[0031] [Manufacturing method of wiring board] Next, a manufacturing method of the wiring board according to the first embodiment will be described. FIGS. 2 to 5 are diagrams illustrating the manufacturing process of the wiring board according to the first embodiment. In this embodiment, a process of forming a single wiring board is shown, but it may also be a process of manufacturing a plurality of parts that will become the wiring board and then separating them into individual wiring boards.

[0032] First, in the process shown in FIG. 2(a), a support 300 whose upper surface is a flat surface is prepared. As the support 300, a metal plate, a metal foil, or the like can be used. In this embodiment, an example in which a copper foil is used as the support 300 is shown. The thickness of the support 300 can be, for example, about 18 to 100 μm.

[0033] Next, sacrificial layers 310 and 320 are formed on the support 300. The sacrificial layer 310 is formed, for example, so as to cover the entire upper surface of the support 300. The sacrificial layer 320 is formed, for example, so as to cover the entire upper surface of the sacrificial layer 310. Also, the sacrificial layer 320 is formed from a material that can be selectively etched with respect to the metal layer 11 in a later process. Here, as an example, the sacrificial layer 310 is a copper layer and the sacrificial layer 320 is a nickel layer. The thickness of the sacrificial layer 310 can be, for example, about 1 to 5 μm, and the thickness of the sacrificial layer 320 can be, for example, about 1 to 5 μm. Note that it is not essential to provide the sacrificial layer 310, which is a copper layer, on the support 300 side. However, by providing the sacrificial layer 310, which is a copper layer, on the support 300 side, an effect of canceling the unevenness on the upper surface of the support 300 and an effect of improving the adhesion to the support 300 can be obtained.

[0034] Next, in the process shown in FIG. 2(b), an annular (ring-shaped) sacrificial layer 330 protruding from the upper surface of the sacrificial layer 320 is formed on the support 300. Specifically, first, a resist layer 400 (for example, a dry film resist or the like) having an opening 400x at a predetermined position on the upper surface of the sacrificial layer 320 in the portion where the sacrificial layer 330 is to be formed is formed. The opening 400x is formed in a ring shape such that, for example, in a plan view, the inner edge and the outer edge are circular with different diameters. Then, by an electrolytic plating method or the like that uses the support 300, the sacrificial layer 310, and the sacrificial layer 320 as a plating power supply layer, the sacrificial layer 330 is formed on the upper surface of the sacrificial layer 320 exposed in the opening 400x of the resist layer 400. The sacrificial layer 330 is formed from a material that can be selectively etched with respect to the metal layer 11 in a later process. Here, as an example, the sacrificial layer 330 is a nickel layer. The width of the sacrificial layer 330 can be, for example, about 5 to 30 μm. The thickness of the sacrificial layer 330 can be, for example, about 5 to 20 μm. After the sacrificial layer 330 is formed, in the process shown in FIG. 2(c), the resist layer 400 is removed. Note that the sacrificial layer 320 is a typical example of the first sacrificial layer according to the present invention. Also, the sacrificial layer 330 is a typical example of the second sacrificial layer according to the present invention.

[0035] Next, in the steps shown in FIGS. 3(a) and 3(b), the recesses formed by the sacrificial layer 320 and the sacrificial layer 330 are filled, and a metal layer 11 is formed to cover the inner peripheral side of the upper surface of the sacrificial layer 330 and expose the outer peripheral side. Specifically, first, in the step shown in FIG. 3(a), a resist layer 410 (e.g., dry film resist, etc.) having an opening 410x that covers the outer peripheral side of the upper surface of the ring-shaped sacrificial layer 330 and exposes the inner peripheral side is formed at a predetermined position on the upper surface of the sacrificial layer 320 in plan view. The opening 410x is formed, for example, in a circular shape in plan view. Inside the opening 410x, in plan view, the inner peripheral side of the upper surface of the sacrificial layer 330 and the upper surface of the sacrificial layer 320 surrounded by the sacrificial layer 330 are exposed.

[0036] Next, in the step shown in FIG. 3(b), by an electrolytic plating method or the like that uses the support 300, the sacrificial layer 310, the sacrificial layer 320, and the sacrificial layer 330 as a plating power supply layer, the upper surface of the sacrificial layer 320 exposed inside the opening 410x of the resist layer 410, and the upper surface and the inner side surface of the sacrificial layer 330 are covered to form a metal layer 11. The metal layer 11 includes a main body portion 11b and an extension portion 11s. The portion formed on the upper surface of the sacrificial layer 330 exposed inside the opening 410x is the extension portion 11s, and the rest is the main body portion 11b. The metal layer 11 is formed of a material different from that of the sacrificial layers 320 and 330 so that the sacrificial layers 320 and 330 can be selectively etched in a subsequent process. Here, since the sacrificial layers 310 and 320 are nickel layers, the metal layer 11 is a copper layer.

[0037] Next, in the process shown in FIG. 3(c), an insulating layer 20 that coats the sacrificial layer 320, the sacrificial layer 330, and the metal layer 11 is formed on the support 300. Specifically, first, after removing the resist layer 410, a semi-cured film-like epoxy resin or the like is laminated on the support 300 and cured to form the insulating layer 20. The insulating layer 20 is formed so as to coat the upper surface of the sacrificial layer 320 exposed from the metal layer 11, the upper surface and the outer peripheral side surface of the sacrificial layer 330 exposed from the metal layer 11, and the upper surface and the side surface of the metal layer 11 exposed from the sacrificial layer 330. Alternatively, instead of laminating a film-like epoxy resin or the like, a liquid or paste-like epoxy resin or the like may be applied and then cured to form the insulating layer 20. The thickness and the like of the insulating layer 20 are as described above.

[0038] Next, in the process shown in FIG. 4(a), a via hole 20x that penetrates the insulating layer 20 and exposes the upper surface of the metal layer 11 is formed in the insulating layer 20. The via hole 20x can be formed by a laser processing method using, for example, a CO2 laser or the like. Thereafter, a desmear treatment may be performed to remove the resin residue attached to the upper surface of the metal layer 11 exposed at the bottom of the via hole 20x.

[0039] Next, in the process shown in FIG. 4(b), a wiring layer 30 is formed on the insulating layer 20. The wiring layer 30 includes, for example, via wirings filled in the via holes 20x, via receiving pads formed on the insulating layer 20, and wiring patterns. The wiring layer 30 is electrically connected to the metal layer 11 exposed at the bottom of the via hole 20x. As the material of the wiring layer 30, for example, copper (Cu) or the like can be used. The wiring layer 30 can be formed using various wiring layer formation methods such as a semi-additive method and a subtractive method.

[0040] Next, in the process shown in FIG. 4(c), the same processes as those in FIGS. 3(c) to 4(b) are repeated to form an insulating layer 40 on the wiring layer 30, form a via hole 40x that exposes the upper surface of the via receiving pad of the wiring layer 30 in the insulating layer 40, and further form a wiring layer 50. The material and thickness of the insulating layer 40 can be the same as, for example, those of the insulating layer 20. The material and thickness of the wiring layer 50 can be the same as, for example, those of the wiring layer 30.

[0041] Next, in the processes shown in FIGS. 5(a) to 5(c), the support 300, the sacrificial layer 310, the sacrificial layer 320, and the sacrificial layer 330 are removed by etching to form pads 10 for external connection including the metal layer 11. Specifically, first, in the process shown in FIG. 5(a), the support 300 and the sacrificial layer 310 shown in FIG. 4(c) are removed. The support 300 made of copper foil and the sacrificial layer 310 made of a copper layer can be removed, for example, by wet etching using an aqueous hydrogen peroxide / sulfuric acid solution, an aqueous sodium persulfate solution, an aqueous ammonium persulfate solution, or the like. The sacrificial layer 320 which is a nickel layer serves as an etching stopper layer, and only the support 300 and the sacrificial layer 310 are removed. Note that FIG. 5(a) is drawn in a state where it is inverted vertically with respect to FIG. 4(c) and the like. The same applies to FIGS. 5(b) and 5(c) described later.

[0042] Next, in the process shown in FIG. 5(b), the sacrificial layers 320 and 330 shown in FIG. 5(a) are removed. The sacrificial layers 320 and 330 which are nickel layers can be removed, for example, by wet etching using an aqueous hydrogen peroxide / nitric acid solution or the like. Since copper is not removed in the etching solution for the nickel layer, the metal layer 11 is not etched. As a result, a groove 20g is formed in the insulating layer 20, which is located around the metal layer 11 in plan view and opens to the upper surface 20a side of the insulating layer 20. The groove 20g is formed in a ring shape such that, for example, in plan view, the inner edge and the outer edge are circular with different diameters. Also, in the metal layer 11, the side surface of the main body portion 11b and the upper surface of the extending portion 11s are exposed in the groove 20g. At this point, the upper surface of the main body portion 11b is substantially flush with the upper surface 20a of the insulating layer 20. Also, the upper surface of the extending portion 11s is substantially flush with the bottom surface of the groove 20g of the insulating layer 20.

[0043] Next, as necessary, in order to remove the oxide films formed on the upper surface and side surfaces of the main body portion 11b and the upper surface of the extending portion 11s, the upper surface and side surfaces of the main body portion 11b and the upper surface of the extending portion 11s are etched by about 2 to 3 μm. As a result, as shown in FIG. 5(b), the upper surface of the main body portion 11b is exposed at a position recessed by about 2 to 3 μm from the upper surface 20a of the insulating layer 20. Further, the upper surface of the extending portion 11s is exposed at a position recessed by about 2 to 3 μm from the bottom surface of the groove 20g of the insulating layer 20.

[0044] Next, in the process shown in FIG. 5(c), for example, by electroless plating, a metal layer 12 is formed on the surface of the metal layer 11 exposed from the insulating layer 20. Thereby, the wiring substrate 1 is completed. The metal layer 12 can be, for example, an Au layer, a Ni / Au layer (a metal layer in which a Ni layer and an Au layer are laminated in this order on the pad 10), a Ni / Pd / Au layer (a metal layer in which a Ni layer, a Pd layer, and an Au layer are laminated in this order on the pad 10), or the like.

[0045] In this process, the metal layer 12 covering the side surface of the main body portion 11b of the metal layer 11 and the metal layer 12 covering the upper surface of the extending portion 11s of the metal layer 11 are exposed from the insulating layer 20 within the groove 20g. Further, the upper surface of the metal layer 12 is at a position about 2 to 8 μm higher than the upper surface 20a of the insulating layer 20. Also, the outer peripheral surface of the metal layer 12 is at a position about 2 to 8 μm higher than the bottom surface of the groove 20g.

[0046] <Modification Example 1 of the First Embodiment> In Modification Example 1 of the first embodiment, an example of a wiring substrate having a different layer structure of pads is shown. In Modification Example 1 of the first embodiment, the description of the same components as those in the embodiment already described may be omitted.

[0047] FIG. 6 is a diagram illustrating a wiring substrate according to Modification Example 1 of the first embodiment, FIG. 6(a) is a partial plan view, and FIG. 6(b) is a partial cross-sectional view taken along line B-B of FIG. 6(a).

[0048] Referring to FIG. 6, the wiring board 1A is different from the wiring board 1 (see FIG. 1 etc.) in that the pad 10 has a single-layer structure. The pad 10 is, for example, a copper layer. The pad 10 has a main body portion 11b and an extension portion 11s, but does not have a metal layer 12.

[0049] The upper surface 10a of the pad 10 (the upper surface of the main body portion 11b) is at a position lower than the upper surface 20a of the insulating layer 20. The height of the upper surface 20a of the insulating layer 20 with respect to the upper surface of the main body portion 11b of the pad 10 is, for example, about 2 to 3 μm. The upper surface of the extension portion 11s is at a position lower than the bottom surface of the groove 20g. The height of the bottom surface of the groove 20g with respect to the upper surface of the extension portion 11s is, for example, about 2 to 3 μm.

[0050] An organic film may be provided to cover the upper surface and side surface of the main body portion 11b of the pad 10 and the upper surface of the extension portion 11s. The organic film contains, for example, an azole compound, an imidazole compound, or the like. The thickness of the organic film can be, for example, about 1 μm or less.

[0051] The wiring board 1A shown in FIG. 6 can be manufactured, for example, by the same processes as those shown in FIGS. 2(a) to 5(b) of the first embodiment. After the process shown in FIG. 5(b), if necessary, an OSP (Organic Solderability Preservative) treatment can be performed on the main body portion 11b and the extension portion 11s to form an organic film.

[0052] Note that when the pad 10 has a single-layer structure and no organic film is formed, an etching process for removing the oxide film is unnecessary.

[0053] <Second Embodiment> In the second embodiment, an example of a wiring board in which the shape of the groove formed in the insulating layer is different is shown. In the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0054] FIG. 7 is a diagram illustrating a wiring board according to the second embodiment, FIG. 7(a) is a partial plan view, and FIG. 7(b) is a partial cross-sectional view taken along line C-C of FIG. 7(a).

[0055] Referring to FIG. 7, the wiring board 2 is different from the wiring board 1 (see FIG. 1 etc.) in that a stepped surface 20s is formed on the side surface of the insulating layer 20 on the groove 20g side, and the upper surface 10a of the pad 10 is recessed with respect to the upper surface 20a of the insulating layer 20. The height of the upper surface 20a of the insulating layer 20 with respect to the upper surface 10a of the pad 10 is, for example, about 5 to 20 μm.

[0056] In the insulating layer 20, the stepped surface 20s is located between the upper surface 20a of the insulating layer 20 and the bottom surface of the groove 20g in the thickness direction of the wiring board 2. The stepped surface 20s is substantially parallel to the upper surface 20a of the insulating layer 20 and the bottom surface of the groove 20g. The upper surface of the main body portion 11b is at a position lower than the stepped surface 20s. The height of the stepped surface 20s with respect to the upper surface of the main body portion 11b is, for example, about 2 to 3 μm. Also, the upper surface 10a (upper surface of the metal layer 12) of the pad 10 is at a position higher than the stepped surface 20s. The height of the upper surface 10a (upper surface of the metal layer 12) of the pad 10 with respect to the stepped surface 20s is, for example, about 2 to 8 μm.

[0057] When the planar shape of the pad 10 is circular, the groove 20g can be formed in a ring shape such that, for example, in a plan view, the inner edge and the outer edge are circular with different diameters. In the groove 20g, the width of the portion below the stepped surface 20s can be, for example, about 80 μm to 100 μm. Also, the width of the stepped surface 20s can be, for example, about 10 to 30 μm.

[0058] The wiring board 2 shown in FIG. 7 can be formed, for example, as follows. First, in the steps shown in FIGS. 8(a) to 9(b), the sacrificial layers 340 and 350 are sequentially formed in a predetermined region on the support 300, and further an annular sacrificial layer 360 protruding from the upper surface of the sacrificial layer 350 is formed. Note that the sacrificial layer 350 is a typical example of the first sacrificial layer according to the present invention. Also, the sacrificial layer 360 is a typical example of the second sacrificial layer according to the present invention.

[0059] Specifically, first, in the process shown in FIG. 8(a), a resist layer 420 (e.g., dry film resist, etc.) having an opening 420x is formed in a predetermined region on the upper surface of the support 300. Then, by an electrolytic plating method or the like using the support 300 as a plating power supply layer, a sacrificial layer 340 and a sacrificial layer 350 are sequentially laminated on the upper surface of the support 300 exposed in the opening 420x of the resist layer 420. Thereafter, the resist layer 420 is removed. Here, as an example, the sacrificial layer 340 is a copper layer, and the sacrificial layer 350 is a nickel layer. Note that the sacrificial layers 340 and 350 are metal layers that are finally removed by etching. The thickness of the sacrificial layer 340 can be, for example, about 5 to 20 μm, and the thickness of the sacrificial layer 350 can be, for example, about 1 to 10 μm. Note that it is not essential to provide the sacrificial layer 340 which is a copper layer on the support 300 side, but by providing the sacrificial layer 340 which is a copper layer on the support 300 side, an effect of canceling the unevenness on the upper surface of the support 300 and an effect of improving the adhesion to the support 300 can be obtained.

[0060] Next, in the process shown in FIG. 8(b), a resist layer 430 (e.g., dry film resist, etc.) having an opening 430x that opens in a ring shape on the outer peripheral side of the upper surface of the sacrificial layer 350 is formed on the upper surface of the support 300. In order to prevent misalignment with the upper surface of the sacrificial layer 350, it is preferable not to provide the opening 430x at the outermost peripheral portion of the upper surface of the sacrificial layer 350. In other words, it is preferable that the outermost peripheral portion of the upper surface of the sacrificial layer 350 is covered with the resist layer 430.

[0061] Next, in the process shown in FIG. 9(a), an annular (ring-shaped) sacrificial layer 360 protruding from the upper surface of the sacrificial layer 350 is formed on the support 300. Specifically, the sacrificial layer 360 is formed on the upper surface of the sacrificial layer 350 exposed within the opening 430x of the resist layer 430 by an electrolytic plating method or the like that uses the support 300, the sacrificial layer 340, and the sacrificial layer 350 as plating power supply layers. The sacrificial layer 360 is formed of a material that can be selectively etched with respect to the metal layer 11 in a later process. Here, as an example, the sacrificial layer 360 is a nickel layer. The width of the sacrificial layer 360 can be, for example, about 5 to 30 μm. The thickness of the sacrificial layer 360 can be, for example, about 10 to 30 μm. After forming the sacrificial layer 360, in the process shown in FIG. 9(b), the resist layer 430 is removed. The sacrificial layer 340 and the sacrificial layer 350 are formed at overlapping positions in plan view, and the outer edge of the sacrificial layer 360 is formed inside the outer edges of the sacrificial layers 340 and 350 in plan view.

[0062] Next, in the processes shown in FIGS. 9(c) and 10(a), the recess formed by the sacrificial layer 350 and the sacrificial layer 360 is filled, and a metal layer 11 that covers the inner peripheral side of the upper surface of the sacrificial layer 360 and exposes the outer peripheral side is formed. Specifically, first, in the process shown in FIG. 9(c), a resist layer 440 (for example, a dry film resist or the like) having an opening 440x that covers the outer peripheral side of the upper surface of the ring-shaped sacrificial layer 360 and exposes the inner peripheral side in plan view is formed at a predetermined position on the upper surface of the support 300. The opening 440x is formed, for example, in a circular shape in plan view. Inside the opening 440x, the inner peripheral side of the upper surface of the sacrificial layer 360 and the upper surface of the sacrificial layer 350 surrounded by the sacrificial layer 360 are exposed in plan view.

[0063] Next, in the process shown in Fig. 10(a), by an electrolytic plating method or the like that uses the support 300, the sacrificial layer 340, the sacrificial layer 350, and the sacrificial layer 360 as the plating power supply layer, a metal layer 11 is formed to cover the upper surface of the sacrificial layer 350 exposed in the opening 440x of the resist layer 440, as well as the upper surface and the inner surface of the sacrificial layer 360. The metal layer 11 includes a main body portion 11b and an extension portion 11s. The portion formed on the upper surface of the sacrificial layer 360 exposed in the opening 440x is the extension portion 11s, and the rest is the main body portion 11b. The metal layer 11 is formed of a material different from that of the sacrificial layers 350 and 360 so that the sacrificial layers 350 and 360 can be selectively etched in a subsequent process. Here, since the sacrificial layers 350 and 360 are nickel layers, the metal layer 11 is a copper layer.

[0064] Next, in the process shown in Fig. 10(b), an insulating layer 20 is formed on the support 300 to cover the sacrificial layer 340, the sacrificial layer 350, the sacrificial layer 360, and the metal layer 11. Specifically, first, after removing the resist layer 440, a semi-cured film-like epoxy resin or the like is laminated on the support 300 and cured to form the insulating layer 20. The insulating layer 20 is formed so as to cover the upper surface and the outer surface of the sacrificial layer 360 exposed from the metal layer 11, the upper surface and the side surface of the metal layer 11 exposed from the sacrificial layer 360, the outer peripheral portion and the side surface of the upper surface of the sacrificial layer 350, and the side surface of the sacrificial layer 340. Alternatively, instead of laminating a film-like epoxy resin or the like, a liquid or paste-like epoxy resin or the like may be applied and then cured to form the insulating layer 20. The thickness and the like of the insulating layer 20 are as described above.

[0065] Next, in the process shown in Fig. 11(a), in the same manner as in Figs. 4(a) to 4(c), via holes 20x that expose the upper surface of the metal layer 11 are formed in the insulating layer 20, and then a wiring layer 30 is formed. Then, an insulating layer 40 is formed on the wiring layer 30, via holes 40x that expose the upper surface of the via receiving pads of the wiring layer 30 are formed in the insulating layer 40, and then a wiring layer 50 is formed.

[0066] Next, in the steps shown in FIGS. 11(b) to 12(b), the support 300, the sacrificial layer 340, the sacrificial layer 350, and the sacrificial layer 360 are removed by etching to form the pad 10 for external connection including the metal layer 11. Specifically, first, in the step shown in FIG. 11(b), the support 300 shown in FIG. 11(a) is removed. The support 300 can be removed, for example, by mechanical peeling. In this case, the sacrificial layer 340 is not removed. The support 300 made of copper foil may be removed by wet etching using, for example, a hydrogen peroxide / sulfuric acid-based aqueous solution, a sodium persulfate aqueous solution, an ammonium persulfate aqueous solution, or the like. In this case, the sacrificial layer 340 which is a copper layer is also removed. Note that FIG. 11(b) is drawn in a state where it is inverted vertically with respect to FIG. 10(b) and the like. The same applies to FIGS. 12(a) and 12(b) described later.

[0067] Next, in the step shown in FIG. 12(a), the sacrificial layers 340, 350, and 360 shown in FIG. 11(b) are removed. The sacrificial layer 340 which is a copper layer can be removed by wet etching using, for example, an etching solution such as a hydrogen peroxide / sulfuric acid-based aqueous solution, a sodium persulfate aqueous solution, or an ammonium persulfate aqueous solution. The sacrificial layer 350 and the sacrificial layer 360 which are nickel layers can be removed by wet etching using, for example, a hydrogen peroxide / nitric acid-based aqueous solution. Note that when the sacrificial layer 340 is removed in the step shown in FIG. 11(b), the etching of the sacrificial layer 340 is not necessary. Since copper is not removed by the etching solution for the nickel layer, the metal layer 11 is not etched. As a result, a groove 20g is formed in the insulating layer 20 so as to be located around the metal layer 11 in plan view and open to the upper surface 20a side of the insulating layer 20. The groove 20g is formed in a ring shape such that, for example, in plan view, the inner edge and the outer edge are circular with different diameters. In addition, a stepped surface 20s is formed on the side surface of the groove 20g on the insulating layer 20 side. Further, in the metal layer 11, the upper surface of the main body portion 11b is exposed at a position recessed with respect to the upper surface 20a of the insulating layer 20, and the side surface of the main body portion 11b and the upper surface of the extending portion 11s are exposed in the groove 20g. At this point, the upper surface of the main body portion 11b is substantially flush with the stepped surface 20s. Also, the upper surface of the extending portion 11s is substantially flush with the bottom surface of the groove 20g of the insulating layer 20.

[0068] Next, if necessary, in order to remove the oxide films formed on the upper surface and side surfaces of the main body portion 11b and the upper surface of the extending portion 11s, the upper surface and side surfaces of the main body portion 11b and the upper surface of the extending portion 11s are etched by about 2 to 3 μm. As a result, as shown in FIG. 12(a), the upper surface of the main body portion 11b is exposed at a position recessed by about 2 to 3 μm from the stepped surface 20s. Also, the upper surface of the extending portion 11s is exposed at a position recessed by about 2 to 3 μm from the bottom surface of the groove 20g of the insulating layer 20.

[0069] Next, in the process shown in FIG. 12(b), for example, a metal layer 12 is formed on the surface of the metal layer 11 exposed from the insulating layer 20 by electroless plating. The metal layer 12 is as described above. Thereby, the wiring substrate 2 is completed.

[0070] In this process, the metal layer 12 covering the side surface of the main body portion 11b of the metal layer 11 and the metal layer 12 covering the upper surface of the extending portion 11s of the metal layer 11 are exposed from the insulating layer 20 in the groove 20g. Also, the upper surface of the metal layer 12 is at a position about 2 to 8 μm higher than the stepped surface 20s. Further, the outer peripheral surface of the metal layer 12 is at a position about 2 to 8 μm higher than the bottom surface of the groove 20g.

[0071] The wiring substrate 2 exhibits the following further effects in addition to the effects exhibited by the wiring substrate 1. That is, in the wiring substrate 2, since the upper surface 10a of the pad 10 is at a position further lower than the upper surface 20a of the insulating layer 20 compared to the wiring substrate 1, the center of gravity of the entire solder is positioned closer to the center of the wiring substrate 2. Therefore, the connection stability between the pad 10 and the solder can be improved. In particular, the durability of the solder against the force applied in the horizontal direction (the direction parallel to the upper surface 10a) of the wiring substrate 2 can be significantly improved.

[0072] Also, since the stepped surface 20s is formed on the side surface of the insulating layer 20 side of the groove 20g, the number of corner portions where the solder flowing into the groove 20g comes into contact increases. As a result, the force applied to the solder is dispersed, so that the durability of the solder can be improved.

[0073] <Second Embodiment, Modification 1> In Modification 1 of the second embodiment, an example of a wiring board with a different layer structure of pads is shown. In Modification 1 of the second embodiment, the description of the same components as those in the embodiments already described may be omitted.

[0074] FIG. 13 is a diagram illustrating a wiring board according to Modification 1 of the second embodiment. FIG. 13(a) is a partial plan view, and FIG. 13(b) is a partial cross-sectional view taken along line D-D of FIG. 13(a).

[0075] Referring to FIG. 13, the wiring board 2A is different from the wiring board 2 (see FIGS. 7 etc.) in that the pad 10 has a single-layer structure. The pad 10 is, for example, a copper layer. The pad 10 has a main body portion 11b and an extension portion 11s, but does not have a metal layer 12.

[0076] The upper surface 10a (the upper surface of the main body portion 11b) of the pad 10 is at a position lower than the upper surface 20a of the insulating layer 20. The height of the upper surface 20a of the insulating layer 20 with respect to the upper surface of the main body portion 11b of the pad 10 is, for example, about 10 to 70 μm. Also, the upper surface 10a (the upper surface of the main body portion 11b) of the pad 10 is at a position lower than the stepped surface 20s. The height of the stepped surface 20s with respect to the upper surface of the main body portion 11b of the pad 10 is, for example, about 2 to 3 μm. The upper surface of the extension portion 11s is at a position lower than the bottom surface of the groove 20g. The height of the bottom surface of the groove 20g with respect to the upper surface of the extension portion 11s is, for example, about 2 to 3 μm.

[0077] An organic film may be provided to cover the upper surface and side surface of the main body portion 11b of the pad 10 and the upper surface of the extension portion 11s. The organic film contains, for example, an azole compound, an imidazole compound, or the like. The thickness of the organic film can be, for example, about 1 μm or less.

[0078] The wiring board 2A shown in FIG. 13 can be manufactured, for example, by the same processes as those shown in FIGS. 8(a) to 12(a) of the second embodiment. After the process shown in FIG. 12(a), an OSP treatment can be performed on the main body portion 11b and the extension portion 11s as necessary to form an organic film.

[0079] In addition, when the pad 10 has a single-layer structure and does not form an organic film, the etching process for removing the oxide film is unnecessary.

[0080] As described above in detail for the preferred embodiments and the like, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments and the like without departing from the scope described in the claims.

Explanation of Reference Numerals

[0081] 1, 1A, 2, 2A Wiring Substrate 10 Pad 10a, 20a Upper Surface 11 Metal Layer 11b Main Body Portion 11s Extension Portion 20, 40 Insulating Layer 20g Groove 20s Step Surface 20x, 40x Via Hole 30, 50 Wiring Layer 300 Support 310, 320, 330, 340, 350, 360 Sacrificial Layer 400, 410, 420, 430, 440 Resist Layer 400x, 410x, 420x, 430x, 440x Opening

Claims

1. having an external connection pad and an insulating layer, a part of the lower surface of the pad is covered by the insulating layer, the pad includes a main body portion, and an extension portion that is formed integrally with the main body portion and extends to the outer peripheral side of the side surface of the main body portion in a plan view at the lower end side of the side surface of the main body portion, the insulating layer is provided with a groove that exposes the side surface of the pad and opens to the upper surface side of the insulating layer, a wiring board, wherein an outer edge of the groove is located outside a side surface of the extension portion in a plan view.

2. The wiring board according to claim 1, wherein an upper surface of the main body portion is at a position lower than an upper surface of the insulating layer.

3. a stepped surface is formed on a side surface of the groove on the insulating layer side, The wiring board according to claim 2, wherein an upper surface of the main body portion is at a position lower than the stepped surface.

4. The wiring board according to any one of claims 1 to 3, wherein an upper surface of the extension portion is at a position lower than a bottom surface of the groove.

5. The wiring board according to any one of claims 1 to 4, wherein a metal layer is provided to cover an upper surface and a side surface of the main body portion and an upper surface of the extension portion.

6. The wiring board according to claim 5, wherein an upper surface of the metal layer is at a position higher than an upper surface of the insulating layer.

7. The wiring board according to claim 5 or 6, wherein an upper surface of a portion of the metal layer laminated on the extension portion is at a position higher than a bottom surface of the groove.

8. The wiring board according to any one of claims 1 to 4, wherein an organic film is provided to cover an upper surface and a side surface of the main body portion and an upper surface of the extension portion.

9. forming a first sacrificial layer on a support, and further forming an annular second sacrificial layer protruding from an upper surface of the first sacrificial layer; filling a recess formed by the first sacrificial layer and the second sacrificial layer, and further forming a metal layer that covers an inner peripheral side of an upper surface of the second sacrificial layer and exposes an outer peripheral side; forming an insulating layer on the support to cover the first sacrificial layer, the second sacrificial layer, and the metal layer; removing the support, the first sacrificial layer, and the second sacrificial layer by etching to form an external connection pad including the metal layer, A method of manufacturing a wiring board, wherein the first sacrificial layer and the second sacrificial layer are formed of a material that can be selectively etched with respect to the metal layer.

10. The first sacrificial layer is formed in a predetermined region on the support, The manufacturing method of a wiring substrate according to claim 9, wherein an outer edge of the second sacrificial layer is formed inside an outer edge of the first sacrificial layer in a plan view.

Images