Printed circuit board and method for manufacturing the same

Abstract

The present invention provides a printed circuit board and a method for manufacturing the same that can prevent a decrease in the reliability of solder bumps. [Solution] The printed circuit board according to the present invention comprises an insulating layer, pads disposed on the insulating layer, a solder resist layer disposed on the insulating layer and having openings that expose at least a portion of the pads, and solder bumps, at least a portion of which are disposed within the openings of the solder resist layer, wherein the cross-section of the solder bump, cut in a direction parallel to the height direction perpendicular to the surface of the solder resist layer, has a rectangular shape.

Description

Technical Field

[0001] The present invention relates to a printed circuit board and a method for manufacturing the same, and more particularly to a printed circuit board and a method for manufacturing the same that can prevent a decrease in the reliability of solder bumps.

Background Art

[0002] As electronic devices in the IT field such as mobile phones are miniaturized, the size of metal posts formed on printed circuit boards on which electronic components are mounted is also decreasing.

[0003] During the manufacturing process of forming solder bumps on a pad layer, a thickness difference may occur in the solder resist layer due to anisotropic etching of the solder resist layer, and the reliability of the solder bumps located within the openings of the solder resist layer may be reduced.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made in view of the problems in the above conventional printed circuit board, and an object of the present invention is to provide a printed circuit board and a method for manufacturing the same that can prevent a decrease in the reliability of solder bumps.

Means for Solving the Problems

[0005] The printed circuit board according to the present invention made to achieve the above object includes an insulating layer, pads disposed on the insulating layer, a solder resist layer disposed on the insulating layer and having openings exposing at least a part of the pads, and solder bumps at least a part of which are disposed within the openings of the solder resist layer, and a cross section of the solder bump cut in a direction parallel to the height direction perpendicular to the surface of the solder resist layer has a rectangular shape.

[0006] Preferably, the solder bump includes a first portion located within the opening and a second portion extending from the first portion and protruding from the solder resist layer along the height direction. In the cross-section, it is preferable that the first width of the first portion and the second width of the second portion are the same as each other. In the cross-section, it is preferable that the third width of the opening is the same as the first width of the first portion. Preferably, the second portion is not extended onto the solder resist layer along a planar direction parallel to the surface of the solder resist layer. In a plan view parallel to the surface of the solder resist layer, it is preferable that the planar shape of the solder bump is the same as the planar shape of the opening.

[0007] A method for manufacturing a printed circuit board according to the present invention, made to achieve the above objective, is characterized by comprising the steps of: forming pads to be placed on an insulating layer; forming a solder resist layer on the insulating layer having openings for at least a portion of the pads; forming solder bumps within the openings of the solder resist layer; and removing a portion of the solder resist layer by plasma treatment.

[0008] The step of forming the solder bump preferably includes the steps of filling the openings in the solder resist layer and applying a solder material layer located on the solder resist layer, and removing the solder material layer located on the solder resist layer. The solder bump includes a first portion located within the opening and a second portion extending from the first portion and protruding from the solder resist layer along a height direction perpendicular to the surface of the solder resist layer, wherein in the step of removing a portion of the solder resist layer by plasma treatment, the second portion of the solder bump preferably protrudes from the solder resist layer along the height direction. In a cross-section cut in a direction parallel to the height direction, it is preferable that the first width of the first portion and the second width of the second portion are the same. In the cross-section, it is preferable that the third width of the opening is the same as the first width of the first portion. Preferably, the cross-section of the solder bump, cut in a direction parallel to the height direction, has a rectangular shape. The step of forming the solder bump preferably includes the steps of: forming a mask layer on the solder resist layer that exposes the opening; applying a solder material layer located on the solder resist layer that fills the opening in the solder resist layer and is not covered by the mask layer; and removing the solder material layer located on the solder resist layer. The mask layer is preferably a metal mask. The mask layer preferably includes a dry film. The solder bump includes a first portion located within the opening and a second portion extending from the first portion and protruding from the solder resist layer along a height direction perpendicular to the surface of the solder resist layer, wherein in the step of removing a portion of the solder resist layer by plasma treatment, the second portion of the solder bump preferably protrudes from the solder resist layer along the height direction. Preferably, the process further includes the step of removing the mask layer. The step of removing the mask layer is preferably performed simultaneously with the step of removing the solder material layer. [Effects of the Invention]

[0009] According to the printed circuit board and its manufacturing method of the present invention, the planar area of ​​the opening in the solder resist layer where the solder bumps connected to the pads are located is not larger than the planar area of ​​each solder bump, the pads are not unnecessarily exposed through the opening in the solder resist layer, not only the first portion of the solder bump but also the second portion of the solder bump can be aligned with the opening in the solder resist layer along the height direction, misalignment between the solder bump and the pad does not occur, and the second portion of each solder bump that protrudes upward from the solder resist layer has a uniform thickness, thereby reducing variations in the thickness of the solder bumps and preventing a decrease in the reliability of the solder bumps. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view showing a schematic configuration of a printed circuit board according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along the line I-I' in Figure 1. [Figure 3] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 4] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 5] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 6] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 7] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 8] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Figure 9] This is a cross-sectional view illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] Next, specific examples of embodiments for implementing the printed circuit board and its manufacturing method according to the present invention will be described while referring to the drawings.

[0012] Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be realized in various different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention, parts that are unnecessary for the explanation are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification. Also, the attached drawings are merely for facilitating the understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the attached drawings. It should be understood that all modifications, equivalents, or alternatives included in the idea and technical scope of the present invention are included. Moreover, the sizes and thicknesses of each configuration shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to the illustration. In the drawings, the thicknesses are shown enlarged to clearly represent various layers and regions. And in the drawings, for convenience of explanation, the thicknesses of some layers and regions are exaggeratedly shown.

[0013] Also, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where it is "directly above" the other part but also the case where there are other parts in between. Conversely, when a part is said to be "directly above" another part, it means that there are no other parts in between. Also, being "on" a reference part means being located above or below the reference part, and does not necessarily mean being "above" in the opposite direction of gravity. Furthermore, throughout the specification, when a part "includes" a certain component, this means that other components can be further included, rather than excluding other components, unless otherwise stated. Also, throughout the specification, when it is stated as "on a plane", this means when the target part is viewed from above, and when it is stated as "in a cross-section", this means when the cross-section obtained by vertically cutting the target part is viewed from the side. In addition, throughout the specification, when it is stated as "connected", this does not only mean that two or more components are directly connected, but also means that two or more components are indirectly connected via other components, physically connected, electrically connected, or can mean any of those named differently depending on their position or function.

[0014] Hereinafter, various embodiments and variations of the present invention will be described in detail with reference to the drawings. Referring to FIGS. 1 and 2, a printed circuit board according to an embodiment of the present invention will be described. FIG. 1 is a plan view showing a schematic configuration of a printed circuit board according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line I-I' of FIG. 1.

[0015] Referring to FIGS. 1 and 2, a printed circuit board according to an embodiment of the present invention includes an insulating layer 110, a wiring layer 120 at least partially embedded in the insulating layer 110, a solder resist layer 130 disposed on the insulating layer 110 and having a plurality of openings 131 exposing pads 122, and a plurality of solder bumps 141 located within the plurality of openings 131 of the solder resist layer 130. The insulating layer 110 may include a thermosetting resin such as an epoxy resin, a thermoplastic resin such as a polyimide, or a resin impregnated with a reinforcing material such as glass fiber or an inorganic filler, for example, a prepreg, but the embodiment is not limited thereto. The insulating layer 110 may be a plurality of layers.

[0016] The wiring layer 120 includes a buried wiring layer 121 embedded in the insulating layer 110, pads 122 disposed on the insulating layer 110, and vias 123 connecting the wiring layer 121 and the pads 122. Pad 122 electrically connects an external element, such as a semiconductor chip, to the printed circuit board. The wiring layer 120 includes a conductive metal, such as copper, but the embodiment is not limited thereto. The solder resist layer 130 covers the insulating layer 110 and the wiring layer 120, and the openings 131 in the solder resist layer 130 expose at least one portion of each of the pads 122. The solder resist layer 130 is a photoresist layer, but the embodiment is not limited thereto. At least a portion of each solder bump 141 is placed inside one of the openings 131 of the solder resist layer 130.

[0017] In a cross-section cut along a third direction DR3, which is the height direction perpendicular to the first direction DR1 and second direction DR2 parallel to the surface of the solder resist layer 130, each cross-section of the solder bump 141 has a substantially rectangular shape. Each solder bump 141 includes a first portion 141A located within an opening 131 in the solder resist layer 130, and a second portion 141B extending from the first portion 141A and projecting above the solder resist layer 130 along a third direction DR3 which is the height direction. On the cross-section of each solder bump 141, the first portion 141A of each solder bump 141 has a first width W1, and the second portion 141B has a second width W2. The first width W1 and the second width W2 are identical to each other. Each second portion 141B of the solder bump 141 has a substantially constant second width W2 up to the end.

[0018] In one embodiment, in a cross-section cut along a direction parallel to the third direction DR3, each cross-section of the solder bump 141 has a substantially trapezoidal shape. For example, the first width W1 of the first part 141A and the second width W2 of the second part 141B of each solder bump 141 gradually increase along the third direction DR3. However, the embodiments are not limited thereto. Each solder bump 141 has the same width as the third width W3 of each opening 131 of the solder resist layer 130, and the first portion 141A of each solder bump 141 has a shape that fills each opening 131. The second portion 141B of each solder bump 141 is not extended onto the solder resist layer 130 along a planar direction parallel to the surface of the insulating layer 110. On a single plane viewed from above, the planar shape of each solder bump 141 is substantially identical to the planar shape of each opening 131 in the solder resist layer 130. Figure 1 shows that the planar shapes of each opening 131 in the solder resist layer 130 and each solder bump 141 are substantially circular. However, the embodiments are not limited to this, and the planar shapes of each solder bump 141 and each opening 131 in the solder resist layer 130 can be varied in various ways under the condition that they have the same planar shape as each other.

[0019] According to a printed circuit board according to an embodiment of the present invention, each solder bump 141 includes a first portion 141A located within an opening 131 of the solder resist layer 130, and a second portion 141B extending from the first portion 141A and projecting above the solder resist layer 130 along a third direction DR3 which is the height direction, wherein the first portion 141A and the second portion 141B have the same width as each other. Furthermore, in cross-sections cut in directions perpendicular to the first direction DR1 and the second direction DR2, which are parallel to the surface of the insulating layer 110, each solder bump 141 has a substantially rectangular shape. Furthermore, each first portion 141A of the solder bump 141 has a shape that fills each of the openings 131 in the solder resist layer 130, and each second portion 141B of the solder bump 141 does not extend onto the solder resist layer 130 along a planar direction parallel to the surface of the insulating layer 110, and the thickness of each second portion 141B of the solder bump 141 that protrudes from the solder resist layer 130 along a third direction DR3 which is the height direction is substantially the same as that of the solder bump 141.

[0020] Therefore, the planar area of ​​the opening 131 in the solder resist layer 130 where the solder bumps 141 connected to the pads 122 are placed is not larger than the planar area of ​​each solder bump 141, the pads 122 are not unnecessarily exposed through the openings 131 in the solder resist layer 130, not only the first portion 141A of the solder bump 141 but also the second portion 141B of the solder bump 141 can be aligned with the opening 131 in the solder resist layer 130 along the height direction, no misalignment occurs between the solder bumps 141 and the pads 122, the second portion 141B of each solder bump 141 that protrudes above the solder resist layer 130 can have a uniform thickness, thickness variations of the solder bumps can be reduced, and a decrease in the reliability of the solder bumps can be prevented.

[0021] A method for manufacturing a printed circuit board according to an embodiment of the present invention will be described with reference to Figures 1 and 2, as well as Figures 3 to 7. Figures 3 to 7 are cross-sectional views illustrating a method for manufacturing a printed circuit board according to an embodiment of the present invention.

[0022] Referring to Figure 3, an embedded wiring layer 121 is formed, an insulating layer 110 is formed to embed the embedded wiring layer 121, via holes are formed within the insulating layer 110, vias 123 located within the via holes and pads 122 connected to the vias 123 are formed together, and then a solder resist layer 130 is laminated on the insulating layer 110 and the pads 122. The thickness of the stacked solder resist layer 130 may be equal to or greater than the sum of the thickness of the pad 122 and the thickness of the solder bump 141.

[0023] Referring to Figure 4, the stacked solder resist layers 130 are exposed and developed to form openings 131 that expose at least a portion of each pad 122. In a cross-section cut in the third direction DR3, which is the height direction, each of the openings 131 has a third width W3, and as explained with reference to Figures 1 and 2, the third width W3 of each opening 131 is substantially the same as the widths (W1, W2) of each solder bump 141.

[0024] Referring to Figure 5, the solder material layer 140 is applied so as to fill the openings 131 of the solder resist layer 130 and extend onto the solder resist layer 130. The solder material layer 140 is liquid. The solder material layer 140 can be substantially planar on its upper surface by being applied so as to overflow onto the solder resist layer 130 after completely filling the openings 131.

[0025] Referring to Figure 6, the solder material layer 140 located on the solder resist layer 130 is removed by methods such as wet etching to form a solder bump 141 located within the opening 131 of the solder resist layer 130. The first thickness T1 of the solder resist layer 130 located on the pad 122 and the second thickness T2 of the solder bump 141 are substantially the same.

[0026] Referring to Figure 7, a portion of the solder resist layer 130 is etched by the plasma treatment 200. By removing a portion of the solder resist layer 130, the thickness of the solder resist layer 130 is reduced, exposing the second portion 141B of each solder bump 141. This forms a solder bump 141, as shown in Figure 2, which includes a first portion 141A located within the opening 131 of the solder resist layer 130, and a second portion 141B extending from the first portion 141A and protruding above the solder resist layer 130 along the third direction DR3, which is the height direction.

[0027] According to the method for manufacturing a printed circuit board according to an embodiment of the present invention, an opening 131 is formed in the solder resist layer 130, a solder material layer 140 is applied to fill the opening 131 in the solder resist layer 130 and to extend onto the solder resist layer 130, the solder material layer 140 located on the solder resist layer 130 is removed by a method such as wet etching, and then a portion of the solder resist layer 130 is etched by plasma treatment 200 to form a solder bump 141. When wet etching is used to remove a portion of the solder resist layer during the manufacturing process, the etching solution may be sprayed unevenly depending on the location, which may result in an uneven etching of the solder resist layer. However, according to the embodiment of the present invention, after exposure and development of the solder resist layer, a portion of the solder resist layer 130 can be etched and removed by plasma treatment 200, thereby uniformly removing the solder resist layer, and the thickness of the second portion 141B of the solder bump 141 protruding from the solder resist layer 130 is uniform. This reduces the thickness variation of the second portion 141B of the solder bump 141, which may occur due to thickness variations of the solder resist layer 130 depending on the position, and prevents a decrease in the reliability of the solder bump. Many of the features of the printed circuit board according to the embodiments described above are all applicable to the method for manufacturing the printed circuit board according to the embodiments of the present invention.

[0028] A method for manufacturing a printed circuit board according to an embodiment of the present invention will be described with reference to Figures 1 to 4, as well as Figures 8 and 9. As described with reference to Figures 3 and 4, a wiring layer 120 is formed with at least a portion embedded in the insulating layer 110, a solder resist layer 130 is laminated on the insulating layer 110 and the pad 122, and the laminated solder resist layer 130 is exposed and developed to form openings 131 that expose at least a portion of each of the pads 122.

[0029] As shown in Figure 8, a mask layer 300 having a large-diameter opening 31 is formed on the solder resist layer 130 so as to fully expose the opening 131. The mask layer 300 may be a metal mask layer, and the mask layer 300 may include a dry film. However, the embodiments are not limited to this, and a variety of mask layers can be used.

[0030] Referring to Figure 9, the solder material layer 140 is applied to the opening 31 of the mask layer 300. The solder material layer 140 fills the opening 31 of the mask layer 300. Therefore, the solder material layer 140 is located on the solder resist layer 130, filling the openings 131 of the solder resist layer 130 and not covered by the mask layer 300. According to this embodiment, since the solder material layer 140 is not applied to the portion covered by the mask layer 300, the amount of solder material layer 140 to be applied can be reduced, thereby reducing manufacturing costs.

[0031] Next, the mask layer 300 is removed, and the solder material layer 140 located on the solder resist layer 130 is removed by methods such as wet etching to form solder bumps 141 located within the openings 131 of the solder resist layer 130. The mask layer 300 can be removed together with the solder material layer 140. Next, a portion of the solder resist layer 130 is etched by plasma treatment 200, thereby reducing the thickness of the solder resist layer 130 and exposing the second portion 141B of each solder bump 141. This forms a solder bump 141, as shown in Figure 2, which includes a first portion 141A located within the opening 131 of the solder resist layer 130, and a second portion 141B extending from the first portion 141A and protruding above the solder resist layer 130 along the third direction DR3, which is the height direction.

[0032] According to the method for manufacturing a printed circuit board of this embodiment, an opening 131 is formed in the solder resist layer 130, a mask layer 300 having a large diameter opening 31 is formed on the solder resist layer 130 so as to sufficiently expose the opening 131, a solder material layer 140 is applied so as to fill the opening 131 of the solder resist layer 130 and extend to the part of the solder resist layer 130 that is not covered by the mask layer 300, the solder material layer 140 located on the solder resist layer 130 is removed by a method such as wet etching, and then a part of the solder resist layer 130 is etched by plasma treatment 200 to form a solder bump 141. According to this embodiment, after exposure and development of the solder resist layer, a portion of the solder resist layer 130 can be etched and removed by plasma treatment 200, thereby uniformly removing the solder resist layer, and the second portion 141B of the solder bump 141 can protrude uniformly from the solder resist layer 130. This reduces the thickness variation of the second portion 141B of the solder bump 141 caused by the thickness variation of the solder resist layer 130, thereby preventing a decrease in the reliability of the solder bump. Many of the features of the printed circuit board and the method for manufacturing the printed circuit board according to the above-described embodiment are all applicable to the method for manufacturing the printed circuit board according to this embodiment.

[0033] Furthermore, the present invention is not limited to the embodiments described above. It can be modified and implemented in various ways without departing from the technical scope of the present invention. [Explanation of Symbols]

[0034] 110 Insulating layer 120 wiring layer 121 Embedded wiring layer 122 pads 123 Beer 130 Solder Resist Layers 131 Opening 141 Solda Bump 200 Plasma Treatment

Claims

1. Insulating layer and, A pad placed on the insulating layer, A solder resist layer disposed on the insulating layer and having an opening that exposes at least a portion of the pad, The solder bump comprises at least a portion of which is disposed within the opening in the solder resist layer, A printed circuit board characterized in that the cross-section of the solder bump, cut in a direction parallel to the height direction perpendicular to the surface of the solder resist layer, has a rectangular shape.

2. The aforementioned solder bump is The first portion located within the opening, The printed circuit board according to claim 1, further comprising: a second portion extending from the first portion and protruding from the solder resist layer along the height direction.

3. The printed circuit board according to claim 2, characterized in that, in the cross-section, the first width of the first portion and the second width of the second portion are the same as each other.

4. The printed circuit board according to claim 3, characterized in that, in the cross-section, the third width of the opening is the same as the first width of the first portion.

5. The printed circuit board according to claim 4, characterized in that the second portion is not extended onto the solder resist layer along a planar direction parallel to the surface of the solder resist layer.

6. The printed circuit board according to claim 5, characterized in that, in a plan view parallel to the surface of the solder resist layer, the planar shape of the solder bump is the same as the planar shape of the opening.

7. The printed circuit board according to claim 1, characterized in that, in a plan view parallel to the surface of the solder resist layer, the planar shape of the solder bump is the same as the planar shape of the opening.

8. The printed circuit board according to claim 7, characterized in that the solder bumps are not extended onto the solder resist layer along a planar direction parallel to the surface of the solder resist layer.

9. The steps include forming a pad to be placed on the insulating layer, The steps include forming a solder resist layer on the insulating layer, having an opening that exposes at least a portion of the pad, The steps include forming solder bumps within the openings of the solder resist layer, A method for manufacturing a printed circuit board, characterized by comprising the step of removing a portion of the solder resist layer by plasma treatment.

10. The step of forming the solder bump is as follows: The steps include: filling the openings in the solder resist layer and applying a solder material layer located on the solder resist layer; The method for manufacturing a printed circuit board according to claim 9, comprising the step of removing a solder material layer located on the solder resist layer.

11. The aforementioned solder bump is The first portion located within the opening, It includes a second portion that extends from the first portion and protrudes from the solder resist layer along a height direction perpendicular to the surface of the solder resist layer, The method for manufacturing a printed circuit board according to claim 10, characterized in that, in the step of removing a portion of the solder resist layer by plasma treatment, the second portion of the solder bump protrudes from the solder resist layer along the height direction.

12. The method for manufacturing a printed circuit board according to claim 11, characterized in that, in a cross-section cut in a direction parallel to the height direction, the first width of the first portion and the second width of the second portion are the same as each other.

13. The method for manufacturing a printed circuit board according to claim 12, characterized in that, in the cross-section, the third width of the opening is the same as the first width of the first portion.

14. The method for manufacturing a printed circuit board according to claim 11, characterized in that the cross-section of the solder bump, cut in a direction parallel to the height direction, has a rectangular shape.

15. The step of forming the solder bump is as follows: The steps include forming a mask layer on the solder resist layer that exposes the opening, The steps include: applying a solder material layer located on the solder resist layer that fills the openings in the solder resist layer and is not covered by the mask layer; The method for manufacturing a printed circuit board according to claim 9, comprising the step of removing a solder material layer located on the solder resist layer.

16. The method for manufacturing a printed circuit board according to claim 15, characterized in that the mask layer is a metal mask.

17. The method for manufacturing a printed circuit board according to claim 15, characterized in that the mask layer includes a dry film.

18. The aforementioned solder bump is The first portion located within the opening, It includes a second portion that extends from the first portion and protrudes from the solder resist layer along a height direction perpendicular to the surface of the solder resist layer, The method for manufacturing a printed circuit board according to claim 15, characterized in that, in the step of removing a portion of the solder resist layer by plasma treatment, the second portion of the solder bump protrudes from the solder resist layer along the height direction.

19. The method for manufacturing a printed circuit board according to claim 15, further comprising the step of removing the mask layer.

20. The method for manufacturing a printed circuit board according to claim 19, characterized in that the step of removing the mask layer is performed simultaneously with the step of removing the solder material layer.

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