Printed wiring board and printed wiring board manufacturing method

Abstract

To provide a high-quality printed wiring board.SOLUTION: A printed wiring board comprises: a resin insulating layer; a conductor layer formed on the resin insulating layer; a solder resist layer formed on the resin insulating layer and the conductor layer; a groove penetrating the solder resist layer to expose the resin insulating layer and the conductor layer; and a dam comprising a first portion within the groove and a second portion formed on the first portion and protruding above an upper surface of the solder resist layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a printed wiring board and a manufacturing method thereof. [Background technology]

[0002] Patent Document 1 discloses a printed wiring board having a base substrate and a dam formed on the base substrate. The dam is formed by applying a dam ink onto the base substrate by an inkjet method and curing the dam ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-96558 A Summary of the Invention

[0004] [Problem of Patent Document 1] It is believed that the dam ink applied by the inkjet method spreads on the base substrate. It is believed that with the technology of Patent Document 1, the width of the dam will be wider than desired. It is believed that it is necessary to secure an excessive area to form the dam on the base substrate. It is also believed that it is difficult to secure the height of the dam. It is believed that it is impossible to obtain a small printed wiring board. It is believed that it is difficult to provide a high-quality printed wiring board. [Means for solving the problem]

[0005] The printed wiring board of the present invention comprises a resin insulation layer, a conductor layer formed on the resin insulation layer, a solder resist layer formed on the resin insulation layer and the conductor layer, a groove penetrating the solder resist layer to expose the resin insulation layer and the conductor layer, and a dam formed of a first portion formed in the groove and a second portion formed on the first portion and protruding above an upper surface of the solder resist layer.

[0006] In the printed wiring board of the embodiment of the present invention, the dam has a first portion formed in the groove and a second portion formed on the first portion and protruding above the upper surface of the solder resist layer. Therefore, the width of the dam is controlled by the width of the groove. By forming the width of the groove to a desired size, the width of the dam is defined to a desired size. The height of the dam is ensured. A small printed wiring board is obtained. A high-quality printed wiring board is obtained.

[0007] The method for manufacturing a printed wiring board of the present invention includes forming a conductor layer on a resin insulating layer, forming a solder resist layer on the resin insulating layer and the conductor layer, forming a groove in the solder resist layer to expose the resin insulating layer and the conductor layer, forming a dam ink in the groove, forming the dam ink on the dam ink in the groove, and hardening the dam ink to form a dam having a first portion formed in the groove and a second portion formed on the first portion, the second portion protruding above an upper surface of the solder resist layer.

[0008] The manufacturing method of the present embodiment includes forming the dam ink in the groove, so that the embodiment can control the width of the dam ink by the groove. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view illustrating a printed wiring board according to an embodiment. [Diagram 2] Cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is a cross-sectional view taken along line III-III of FIG. 1. [Figure 4A] 1A to 1C are cross-sectional views each showing a schematic diagram of a method for manufacturing a printed wiring board according to an embodiment. [Figure 4B] 1A to 1C are cross-sectional views each showing a schematic diagram of a method for manufacturing a printed wiring board according to an embodiment. [Figure 4C] 1A to 1C are cross-sectional views each showing a schematic diagram of a method for manufacturing a printed wiring board according to an embodiment. [Figure 4D]1A to 1C are cross-sectional views each showing a schematic diagram of a method for manufacturing a printed wiring board according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment] FIG. 1 is a plan view showing a printed wiring board 2 of an embodiment. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. As shown in FIGS. 1 to 3, the printed wiring board 2 has a resin insulating layer 10, a conductor layer 20, a solder resist layer 30, a groove 40 penetrating the solder resist layer 30, and a dam 50. The resin insulating layer 10 has a first surface 10a and a second surface 10b opposite to the first surface 10a. The conductor layer 20 is formed on the first surface 10a of the resin insulating layer 10. The solder resist layer 30 is formed on the first surface 10a of the resin insulating layer 10 and on the conductor layer 20. The printed wiring board 2 may have a core substrate below the resin insulating layer 10 and the conductor layer 20.

[0011] The resin insulating layer 10 is formed using a thermosetting resin. The material of the resin insulating layer 10 may be a photocurable resin. The resin insulating layer 10 may contain inorganic particles such as silica. The resin insulating layer 10 may contain a reinforcing material such as glass cloth.

[0012] The conductor layer 20 is formed on the resin insulating layer 10. The conductor layer 20 includes a plurality of conductor circuits 22. Examples of the conductor circuits 22 are signal wiring, a power supply circuit, a ground circuit, and pads 24. In FIG. 1, the conductor circuits 22 are depicted by dotted lines. Electronic components are mounted on the printed wiring board 2 via pads 24. The pads 24 are formed in a mounting area directly below the electronic components mounted on the printed wiring board 2. The conductor circuits 22 are mainly made of copper. The pads 24 are connected to the ends of the signal wiring. The pads 24 may be part of the conductor circuits 22. The pads 24 are integrated with the power supply circuit. The pads 24 are integrated with the ground circuit.

[0013] The solder resist layer 30 is formed on the resin insulating layer 10 and the conductor layer 20. The solder resist layer 30 has openings 34 that expose each pad 24.

[0014] The groove 40 exposes the first surface 10a of the resin insulating layer 10 and the upper surface of the conductor layer 20. The first surface 10a exposed by the groove 40 is simultaneously exposed by the conductor layer 20. When the groove 40 exposes the upper surface of the conductor circuit 22, the upper surface of the conductor circuit 22 exposed by the groove 40 is a conductor portion. When the groove 40 exposes the first surface 10a of the resin insulating layer 10, the first surface 10a of the resin insulating layer 10 exposed by the groove 40 is a resin portion. The number of conductor portions and the number of resin portions are plural. The conductor portions and the resin portions are connected. The conductor portions and the resin portions are alternately connected. When the conductor portions and the resin portions are connected, the conductor portions and the resin portions form a substantially frame-like planar shape. As shown in FIG. 1, the groove 40 surrounds the periphery of the pad 24. The groove 40 surrounds the mounting area.

[0015] The dam 50 prevents the underfill from flowing out. As shown in FIG. 2 and FIG. 3, the dam 50 has a first portion 51 formed in the groove 40 and a second portion 52 formed on the first portion 51 and protruding upward from the upper surface 32 of the solder resist layer 30. The second portion 52 protrudes upward from the upper surface 32 of the solder resist layer 30. The first portion 51 and the second portion 52 are formed of the same material. The dam 50 is formed of an organic insulating material. The dam 50 is formed of a photocurable resin or a thermosetting resin. The solder resist layer 30 and the dam 50 are formed of the same organic insulating material. In another example, the dam 50 and the solder resist layer 30 may be formed of different organic insulating materials.

[0016] As shown in Fig. 2, dam 50 in groove 40 which forms the conductor portion is formed on conductor circuit 22. A first portion 51 in groove 40 which forms the conductor portion is formed on conductor circuit 22. As shown in Fig. 3, dam 50 in groove 40 which forms the resin portion is formed on first surface 10a of resin insulation layer 10. A first portion 51 in groove 40 which forms the resin portion is formed on first surface 10a of resin insulation layer 10.

[0017] As shown in FIG. 2 and FIG. 3, the width W1 of the first portion 51 is larger than the width W2 of the second portion 52. The width W1 of the first portion 51 is the same as the width Wg of the groove 40. The height of the first portion 51 near the boundary between the first portion 51 and the second portion 52 is higher than the height of the side wall of the first portion 51. The side wall of the first portion 51 faces the side wall of the groove 40. The upper surface 51a of the first portion 51 is formed so that the height of the upper surface 51a increases from the vicinity of the side wall of the groove 40 toward the vicinity of the boundary between the first portion 51 and the second portion 52. The upper surface 51a of the first portion 51 is not parallel to the first surface 10a of the resin insulating layer 10. The upper surface 51a between the vicinity of the side wall of the groove 40 and the vicinity of the boundary between the first portion 51 and the second portion 52 is curved. The upper surface 51a is formed so that it curves from the vicinity of the side wall toward the vicinity of the boundary between the first portion 51 and the second portion 52.

[0018] The upper surface 52a of the second portion 52 is formed such that the central portion protrudes upward. The central portion is the center in the width direction. The upper surface 52a of the second portion 52 is a curved surface.

[0019] In the printed wiring board 2 of the embodiment, the dam 50 has a first portion 51 formed in the groove 40 and a second portion 52 formed on the first portion 51 and protruding above the upper surface 32 of the solder resist 30 layer. This prevents the width (W1, W2) of the dam 50 from becoming larger than the width Wg of the groove 40. By forming the width Wg of the groove 40 to a desired size, the width of the dam 50 is defined to a desired size. The height of the dam 50 is ensured. The embodiment can form a small printed wiring board 2. A high-quality printed wiring board 2 can be obtained.

[0020] The grooves 40 simultaneously expose the conductive circuits 22 having different functions. They are covered with an insulating dam 50. Therefore, even if the embodiment has grooves 40 that expose the conductive circuits 22 having different functions, for example, the conductive circuit 22 for power supply and the conductive circuit 22 for ground are not short-circuited. The conductive circuits 22 having different functions are the conductive circuit 22 for power supply, the conductive circuit 22 for ground, and the conductive circuit 22 for signals.

[0021] [Method of manufacturing printed wiring board 2 according to embodiment] 4A to 4D are cross-sectional views showing a method for manufacturing a printed wiring board 2 according to an embodiment of the present invention. Fig. 4A shows a resin insulating layer 10 and a conductor layer 20 formed on the resin insulating layer 10.

[0022] As shown in FIG. 4B, a solder resist layer 30a is formed on the resin insulating layer 10 and the conductor layer 20.

[0023] As shown in Fig. 4C, a solder resist layer 30 is formed having openings 34 exposing pads 24 and grooves 40. The grooves 40 penetrate the solder resist layer 30. The grooves 40 reach the first surface 10a of the resin insulation layer 10 and the upper surface of the conductor circuit 22. The grooves 40 are formed by a laser. The grooves 40 are formed by exposure and development. The planar shape of the grooves 40 is approximately frame-shaped.

[0024] As shown in FIG. 4D, the ink for dam 80 is formed in the groove 40. For example, the ink for dam 80 is applied to the groove 40 to form an ink for dam 81 in the groove 40. An example of application is an inkjet method or a dispense method. Drop-shaped ink for dam 80a is continuously dropped from a nozzle 90 into the groove 40. The maximum diameter R1 of the ink droplets 80a is smaller than the width Wg of the groove 40. Alternatively, the ink for dam 80 is continuously ejected from the nozzle 90 into the groove 40. The width of the ejected ink for dam 80 is smaller than the width Wg of the groove 40. The ink for dam 80 is applied so that the top of the ink for dam 80 protrudes from the upper surface 32 of the solder resist layer 30. The ink for dam 82 is formed on the ink for dam 81 that almost fills the groove 40. The ink for dam 82 protrudes above the upper surface 32 of the solder resist layer 30. The ink for dam 80 and the ink droplets 80a are formed of an organic insulating material. The dam ink 80 and the ink droplets 80a are formed from the same material as the solder resist layer 30, or from a different material. The dam 50 is formed by curing the dam ink 80, which is formed from the dam ink 81 formed in the groove 40 and the dam ink 82 on the dam ink 81. The printed wiring board 2 of the embodiment is obtained. Most of the groove 40 is filled with the dam ink 80. Then, in the embodiment, the dam ink 80 in the groove 40 can be cured (first curing). After the first curing, the dam ink 80 is further applied on the dam ink 80 in the groove 40. Then, the dam ink 80 is cured (second curing).

[0025] In the manufacturing method of the embodiment, the dam ink 80 is applied inside the groove 40. Therefore, the spread of the dam ink 80 is suppressed. The width of the applied dam ink 80 is restricted to be equal to or less than the width Wg of the groove 40. As a result, the width (W1, W2) of the completed dam 50 is suppressed from becoming larger than the width Wg of the groove 40. By forming the width Wg of the groove 40 to a desired size, the width of the dam 50 is regulated to a desired size. Since the spread of the dam 50 is suppressed, the height of the dam 50 is ensured. A small printed wiring board 2 is obtained. A high-quality printed wiring board 2 is obtained.

[0026] [Another embodiment] In another embodiment, the first portion 51 and the second portion 52 of the dam 50 are formed of different materials. The first portion 51 and the second portion 52 are formed of different organic insulating materials. [Explanation of symbols]

[0027] 2: Printed wiring board 10: Resin insulation layer 20: Conductive layer 30: Solder resist layer 32:Top surface 40: Groove 50: Dam 51: Part 1 52:Second part 80: Dam ink 80a: ink drop

Claims

1. A resin insulating layer; a conductor layer formed on the resin insulating layer; a solder resist layer formed on the resin insulating layer and the conductor layer; a groove penetrating the solder resist layer and exposing the resin insulating layer and the conductor layer; a dam having a first portion formed in the groove and a second portion formed on the first portion and protruding above an upper surface of the solder resist layer.

2. 2. The printed wiring board of claim 1, wherein the width of the first portion is greater than the width of the second portion.

3. 2. The printed wiring board of claim 1, wherein the first portion and the second portion are formed of the same material.

4. 2. The printed wiring board according to claim 1, wherein the upper surface of the second portion is formed so that a central portion thereof protrudes upward.

5. 5. The printed wiring board according to claim 4, wherein the upper surface is a curved surface.

6. 2. The printed wiring board according to claim 1, wherein an upper surface of the first portion is formed so that the height of the upper surface increases from a vicinity of a side wall of the groove toward a vicinity of a boundary between the first portion and the second portion.

7. 2. The printed wiring board of claim 1, wherein said dam is formed of an organic insulating material.

8. forming a conductor layer on the resin insulating layer; forming a solder resist layer on the resin insulating layer and the conductor layer; forming a groove in the solder resist layer to expose the resin insulating layer and the conductor layer; forming a dam ink in the groove; forming a further dam ink on the dam ink in the groove; and forming a dam having a first portion formed in the groove and a second portion formed on the first portion by curing the dam ink, The second portion protrudes above an upper surface of the solder resist layer.

9. 9. The method for manufacturing a printed wiring board according to claim 8, wherein forming the ink for the dam includes applying the ink for the dam in droplets by an inkjet method, and a maximum diameter of the applied ink droplets is smaller than a width of the groove.

10. 9. The method for manufacturing a printed wiring board according to claim 8, wherein the dam ink is made of an organic insulating material.

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