Printed circuit board

Abstract

To provide a high quality printed circuit board.SOLUTION: A printed circuit board has a top resin insulating layer, a top conductor layer formed on the top resin insulating layer, a solder resist layer formed on the top resin insulating layer and the top conductor layer, and a dam having a top protruding above an upper surface of the solder resist layer. The dam has a metal protrusion and a resin coating layer that covers the metal protrusion, the coating layer is formed simultaneously with the solder resist layer, and the resin that forms the coating layer is the same as the resin that forms the solder resist layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed by this specification relates to printed circuit boards.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a printed circuit board. The manufacturing method of Patent Document 1 includes forming a first solder resist layer on an intermediate substrate, exposing the first solder resist layer, forming a second solder resist layer on the first solder resist layer, exposing the second solder resist layer, and developing the first solder resist layer and the second solder resist layer simultaneously. And developing includes forming a dam.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] [Problems of Patent Document 1] The first solder resist layer of Patent Document 1 has a first portion that is exposed only once and a second portion that is exposed twice. Since the number of exposures is different, it is considered that the degree of curing of the first portion and the degree of curing of the second portion are different. The printed circuit board of Patent Document 1 is likely to have large warpage and twist.

Means for Solving the Problems

[0005] The printed wiring board of the present invention includes a top resin insulating layer, a top conductor layer formed on the top resin insulating layer, a solder resist layer formed on the top resin insulating layer and the top conductor layer, and a dam having a top protruding upward from the upper surface of the solder resist layer. The dam includes a metal protrusion and a resin coating layer covering the metal protrusion. The coating layer is formed simultaneously with the solder resist layer, and the resin forming the coating layer is common to the resin forming the solder resist layer.

[0006] In the printed wiring board according to an embodiment of the present invention, the coating layer of the dam is formed simultaneously with the solder resist layer, and the resin forming the coating layer is common to the resin forming the solder resist layer. Therefore, there is no difference between the degree of curing of the solder resist layer and the degree of curing of the coating layer of the dam. Alternatively, the printed wiring board according to the embodiment can reduce the difference between the two. The printed wiring board according to the embodiment can suppress warping and twisting. Since the dam of the printed wiring board according to the embodiment has a metal protrusion, the embodiment can increase the strength of the dam. Even if the dam is formed only on one surface of the printed wiring board, the dam is hardly deformed. The printed wiring board according to the embodiment can suppress warping and twisting.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

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Figure 3C

Figure 3D

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Figure 6B

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Figure 6D

BEST MODE FOR CARRYING OUT THE INVENTION

[0008] [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 the line II-II of FIG. 1. As shown in FIGS. 1 and 2, the printed wiring board 2 has a conductor layer 10, an uppermost resin insulating layer 20, an uppermost conductor layer 30, via conductors 42, 44, 46, 48, a solder resist layer 60, and a dam 80. The printed wiring board 2 may have a build-up layer. In that case, the conductor layer 10, the uppermost resin insulating layer 20, and the uppermost conductor layer 30 form a part of the build-up layer.

[0009] As shown in FIG. 1, the uppermost conductor layer 30 has electrodes 32, 34, 36 for mounting electronic components. An electrode group is formed by a plurality of electrodes 34. A first electronic component is mounted on the printed wiring board 2 via the electrode 34. A second electronic component is mounted on the printed wiring board 2 via the electrode 32. A third electronic component is mounted on the printed wiring board 2 via the electrode 36. Each of the electrodes 32, 34, 36 is exposed by openings 62, 64, 66 formed in the solder resist layer 60. The electrode group formed by a plurality of electrodes (electrodes for mounting the first electronic component) 34 is surrounded by a dam 80. The electrodes 32, 36 are arranged outside the dam 80.

[0010] As shown in FIG. 2, the conductor layer 10 includes pads 12, 14, 16, 18 and connection wirings 13, 17. The conductor layer 10 is mainly formed of copper. The conductor layer 10 is formed of a seed layer 10a and an electrolytic plating layer 10b on the seed layer 10a. Pad 12 is connected to one end of connection wiring 13. Pad 14 is connected to the other end of connection wiring 13. Pad 16 is connected to one end of connection wiring 17. Pad 18 is connected to the other end of connection wiring 17. Pads 12 and 14 are electrically connected via connection wiring 13. Pads 16 and 18 are electrically connected via connection wiring 17.

[0011] The uppermost resin insulating layer 20 is formed on the conductor layer 10. The uppermost resin insulating layer 20 is formed using a thermosetting resin. The material of the uppermost resin insulating layer 20 may be a photocurable resin. The uppermost resin insulating layer 20 may contain inorganic particles such as silica. The uppermost resin insulating layer 20 may contain a reinforcing material such as glass cloth. The uppermost resin insulating layer 20 has openings (openings for via conductors) 22, 24, 26, 28 that expose the conductor layer 10. Openings 22, 24, 26, 28 extend from the upper surface of the uppermost resin insulating layer 20 to pads 12, 14, 16, 18. Openings 22, 24, 26, 28 expose pads 12, 14, 16, 18.

[0012] The uppermost conductor layer 30 is formed on the upper surface of the uppermost resin insulating layer 20. The uppermost conductor layer 30 has electrodes 32, 34, 36 and a base 39. The base 39 has no electrical function. The base 39 is not connected to any of a power supply, a ground, or a signal wiring. The base 39 functions only as a base for the metal protrusion 50. The uppermost conductor layer 30 is mainly formed of copper. The uppermost conductor layer 30 is formed of a seed layer 30a and an electrolytic plating layer 30b on the seed layer 30a.

[0013] The via conductors 42, 44, 46, 48 are formed in the openings 22, 24, 26, 28. The via conductors 42, 44, 46, 48 connect the conductor layer 10 and the uppermost conductor layer 30. The via conductor 42 connects the pad 12 and the electrode 32. The via conductor 44 connects the pad 14 and the electrode 34. The via conductor 46 connects the pad 16 and the electrode 34. The via conductor 48 connects the pad 18 and the electrode 36. The electrodes (the first electrodes for the second electronic component) 32 and the electrodes (the first electrodes for the first electronic component) 34 are electrically connected via the via conductor 42, the pad 12, the connection wiring 13, the pad 14, and the via conductor 44. The electrodes (the second electrodes for the first electronic component) 34 and the electrodes (the electrodes for the third electronic component) 36 are electrically connected via the via conductor 46, the pad 16, the connection wiring 17, the pad 18, and the via conductor 48. The via conductors 42, 44, 46, 48 are formed of a seed layer 30a and an electrolytic plating layer 30b on the seed layer 30a. The seed layer 30a forming the via conductors 42, 44, 46, 48 and the seed layer 30a forming the uppermost conductor layer 30 are common. The electrolytic plating layer 30b forming the via conductors 42, 44, 46, 48 and the electrolytic plating layer 30b forming the uppermost conductor layer 30 are common.

[0014] Data is sent from one electronic component to another via the connection wirings 13, 17. The connection wiring 13 is a wiring for sending data from the first electronic component to the second electronic component. The connection wiring 17 is a wiring for sending data from the first electronic component to the third electronic component.

[0015] The solder resist layer 60 is formed on the uppermost conductor layer 30 and the uppermost resin insulating layer 20. The solder resist layer 60 is formed using, for example, a photocurable resin. The solder resist layer 60 has openings 62, 64, 66 that expose the respective electrodes 32, 34, 36. The opening 62 exposes the electrode (the electrode for the second electronic component) 32. The opening 64 exposes the electrode (the electrode for the first electronic component) 34. The opening 66 exposes the electrode (the electrode for the third electronic component) 36.

[0016] The dam 80 has a top 82, and the dam 80 is formed such that the top 82 protrudes above the upper surface 61 of the solder resist layer 60. As shown in FIG. 1, the dam 80 surrounds the periphery of the electrode 34. The dam 80 is formed so as to surround all the electrodes (electrodes for the first electronic component) 34. The dam 80 prevents the underfill from flowing out.

[0017] As shown in FIG. 2, the dam 80 is formed of a metal protrusion 50 and a resin coating layer 70 that covers the metal protrusion 50. The metal protrusion 50 is formed on the base 39 and is made of a metal member. The metal protrusion 50 is mainly formed of copper. The metal protrusion 50 is joined to the base 39. The width W2 of the base 39 is larger than the width W1 of the metal protrusion 50.

[0018] The coating layer 70 is formed simultaneously with the solder resist layer 60 and is made of resin. The resin forming the coating layer 70 is common to the resin forming the solder resist layer 60.

[0019] The cross-sectional shape of the dam 80 is formed such that the width decreases toward the top 82. The cross-sectional shape of the dam 80 is substantially trapezoidal. The cross-sectional shape of the dam 80 may also be substantially triangular. The shape of the dam 80 may also be substantially frustoconical. In that case, the dam 80 becomes narrower toward the top. At least one of the surface of the top 82 and the side surface 84 of the dam 80 may be a curved surface. The surface of the top 82 may bulge. Alternatively, the surface of the top 82 may be concave. The side surface 84 may bulge. Alternatively, the side surface 84 may be concave.

[0020] The shape of the metal protrusion 50 is substantially cylindrical. Alternatively, the shape of the metal protrusion 50 is substantially frustoconical. In that case, the metal protrusion 50 becomes narrower toward the top of the dam 80. The cross-section of the dam 80 has a distance D (distance between the coating layer 70 and the metal protrusion 50) between the side surface 84 of the coating layer 70 and the side surface 85 of the metal protrusion 50. As shown in FIG. 2, the distance D between the coating layer 70 and the metal protrusion 50 decreases toward the top 82.

[0021] [Method for manufacturing the printed wiring board 2 of the embodiment] Figs. 3A to 3D show a method for manufacturing the printed wiring board 2 of the embodiment. Figs. 3A to 3D are cross-sectional views. A conductor layer 10 including pads 12, 14, 16, 18 and connection wirings 13, 17 is formed by a semi-additive method. The conductor layer 10 is formed of a seed layer 10a and an electrolytic plating layer 10b on the seed layer 10a. The uppermost resin insulating layer 20 is formed on the conductor layer 10. Openings 22, 24, 26, 28 for via conductors that penetrate the uppermost resin insulating layer 20 and reach the pads 12, 14, 16, 18 are formed in the uppermost resin insulating layer 20. A seed layer 30a is formed on the upper surface of the uppermost resin insulating layer 20. At that time, the seed layer 30a is also formed in the openings 22, 24, 26, 28 for via conductors. A plating resist for forming the uppermost conductor layer 30 is formed on the seed layer 30a. An electrolytic plating layer 30b is formed on the seed layer 30a exposed from the plating resist. At this time, via conductors 42, 44, 46, 48 are simultaneously formed in the openings 22, 24, 26, 28 for via conductors. A part of the electrolytic plating layer 30b also serves as a base 39. The plating resist is removed. By removing the plating resist, an intermediate substrate 3 shown in Fig. 3A is obtained. The intermediate substrate 3 in Fig. 3A has the conductor layer 10, the uppermost resin insulating layer 20, the seed layer 30a, the electrolytic plating layer 30b, and the via conductors 42, 44, 46, 48. The seed layer 30a of the intermediate substrate 3 covers the entire upper surface of the uppermost resin insulating layer 20.

[0022] As shown in Fig. 3B, a plating resist 90 for forming a metal protrusion 50 is formed on the seed layer 30a and the electrolytic plating layer 30b. The plating resist 90 has an opening 92 for forming the metal protrusion 50. The opening 92 exposes the base 39. The opening 92 partially exposes the base 39.

[0023] By electrolytic plating, a metal protrusion 50 is formed on the base 39 exposed from the plating resist 90. The seed layer for forming the metal protrusion 50 and the seed layer for forming the electrolytic plating layer 30b are the same seed layer 30a. The metal protrusion 50 forming part of the dam 80 and the electrolytic plating layer 30b forming part of the uppermost conductor layer 30 are formed using the same seed layer 30a. The metal protrusion 50 is joined to the upper surface of the base 39. As shown in FIG. 3C, the plating resist 90 is removed. The seed layer 30a exposed from the electrolytic plating layer 30b is removed. The uppermost conductor layer 30 and the metal protrusion 50 are formed. The uppermost conductor layer 30 including the electrodes 32, 34, 36 and the base 39 and the metal protrusion 50 are formed simultaneously. The uppermost conductor layer 30 does not have connection wiring.

[0024] As shown in FIG. 3D, a solder resist layer 60 is formed on the uppermost conductor layer 30, the metal protrusion 50, and the uppermost resin insulating layer 20. A dry film is laminated on the uppermost conductor layer 30, the metal protrusion 50, and the uppermost resin insulating layer 20. The uppermost conductor layer 30, the uppermost resin insulating layer 20, and the metal protrusion 50 are covered by the dry film. The dry film is cured. The solder resist layer 60 is formed. A coating layer 70 is formed simultaneously with the solder resist layer 60. A dam 80 having a top 82 and a side surface 84 is formed. The dry film for forming the solder resist layer 60 and the coating layer 70 may be of a photocuring type or a thermocuring type. The solder resist layer 60 and the coating layer 70 may be formed by applying a resin.

[0025] Openings 62, 64, 66 that penetrate the solder resist layer 60 and reach the electrodes 32, 34, 36 are formed using a laser. The electrodes 32, 34, 36 are exposed by the openings 62, 64, 66. The printed wiring board 2 is obtained.

[0026] In the printed wiring board 2 of the embodiment, the coating layer 70 of the dam 80 is formed simultaneously with the solder resist layer 60. The resin forming the coating layer 70 is common with the resin forming the solder resist layer 60. The coating layer 70 extends from the solder resist layer 60. The solder resist layer 60 and the coating layer 70 are continuous. Therefore, there is no difference between the degree of curing of the solder resist layer 60 and the degree of curing of the coating layer 70. Alternatively, the printed wiring board of the embodiment can reduce the difference between the two. Warping and twisting of the printed wiring board 2 of the embodiment are suppressed. The dam 80 has a metal protrusion 50. Therefore, the strength of the dam 80 is high. Even if the dam 80 is formed only on one surface of the printed wiring board 2, the dam 80 is difficult to deform. Warping and twisting of the printed wiring board 2 are suppressed.

[0027] The metal protrusion 50 is joined to the base 39. Since the base 39 is included in the uppermost conductor layer 30, the base 39 and the metal protrusion 50 are formed using the same seed layer 30a. The metal protrusion 50 and the base 39 are strongly joined. The adhesion strength between the dam 80 and the base 39 is high. The dam 80 is difficult to peel off from the printed wiring board 2. The dam 80 is difficult to deform. The base 39 surrounds an electrode group formed by a plurality of electrodes (electrodes for the first electronic component) 34. The planar shape of the base 39 and the planar shape of the dam 80 are substantially equal. The planar shape of the base 39 and the planar shape of the dam 80 are substantially frame-shaped.

[0028] The coating layer 70 is formed simultaneously with the solder resist layer 60. A dry film is not used only for forming the dam 80. The amount of the dry film removed by development is small. The embodiment can improve the usage efficiency of the material for forming the dam.

[0029] The cross-sectional shape of the dam 80 is formed such that the width becomes smaller toward the top 82. The dam 80 becomes thinner toward the top 82. The center of gravity of the dam 80 is low. The embodiment can suppress warping and twisting of the printed wiring board 2 caused by the formation of the dam 80.

[0030] In the embodiment, the base 39 and the metal protrusion 50 are formed in separate processes. Therefore, the embodiment can reduce the variations in the thickness of the base 39 and the variations in the height of the metal protrusion 50. The height of the top of the metal protrusion 50 does not vary significantly from place to place. The height of the dam 80 does not vary significantly from place to place.

[0031] [Modified Example] FIG. 4 is a plan view showing a printed wiring board 102 of a modified example. FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 4. As shown in FIGS. 4 and 5, the printed wiring board 102 of the modified example has a top resin insulating layer 20, a top conductor layer 30, a solder resist layer 60, and a dam 80. The dam 80 has a top 82 and a side surface 84. The top 82 protrudes upward from the upper surface 61 of the solder resist layer 60.

[0032] The top conductor layer 30 of the modified example has electrodes 32, 34, 36 and connection wirings 33, 37. The top conductor layer 30 is formed of a seed layer 30a and an electrolytic plating layer 30b on the seed layer 30a. The top conductor layer 30 does not have a base. The electrode 32 is connected to one end of the connection wiring 33. The electrode (first electrode for the first electronic component) 34 is connected to the other end of the connection wiring 33. The electrode (second electrode for the first electronic component) 34 is connected to one end of the connection wiring 37. The electrode 36 is connected to the other end of the connection wiring 37. The electrodes 32, 34 are electrically connected via the connection wiring 33. The electrodes 34, 36 are electrically connected via the connection wiring 37.

[0033] The solder resist layer 60 of the modified example has a first layer 60a on the top resin insulating layer 20 and the top conductor layer 30 and a second layer 60b on the first layer 60a. The solder resist layer 60 has openings 62, 64, 66 that expose the respective electrodes 32, 34, 36. The metal protrusion 50 is formed on the first layer 60a. The metal protrusion 50 is formed of a seed layer 50a and an electrolytic plating layer 50b on the seed layer 50a. The coating layer 70 is formed simultaneously with the second layer 60b. The resin forming the coating layer 70 is common with the resin forming the second layer 60b.

[0034] [Manufacturing Method of Printed Wiring Board 102 of Modified Example] Figs. 6A to 6D show a method of manufacturing a modified printed wiring board 102. Figs. 6A to 6D are cross-sectional views. A seed layer 30a is formed on the upper surface of the uppermost resin insulating layer 20. A plating resist for forming the uppermost conductor layer 30 is formed on the seed layer 30a. An electrolytic plating layer 30b is formed on the seed layer 30a exposed from the plating resist. The plating resist is removed. The seed layer 30a exposed from the electrolytic plating layer 30b is removed. The uppermost conductor layer 30 is formed. The uppermost conductor layer 30 has electrodes 32, 34, 36 and connection wirings 33, 37. A dry film is laminated on the uppermost resin insulating layer 20 and the uppermost conductor layer 30. The dry film is cured. A first layer 60a is formed. An intermediate substrate 4 shown in Fig. 6A is obtained. The dry film for forming the first layer 60a may be of a photo-curing type or a thermo-curing type. The first layer 60a may be formed by applying a resin.

[0035] As shown in Fig. 6B, a seed layer 50a is formed on the first layer 60a. A plating resist 110 is formed on the seed layer 50a. The plating resist 110 has an opening 112 for forming a metal protrusion 50. The opening 112 exposes the seed layer 50a.

[0036] By electrolytic plating, an electrolytic plating layer 50b is formed on the seed layer 50a exposed from the plating resist 110. The plating resist 110 is removed. The seed layer 50a exposed from the electrolytic plating layer 50b is removed. As shown in Fig. 6C, a metal protrusion 50 is formed.

[0037] As shown in FIG. 6D, a second layer 60b is formed on the first layer 60a and the metal protrusion 50. A dry film is laminated on the first layer 60a and the metal protrusion 50. The first layer 60a is covered by the dry film. The metal protrusion 50 is covered by the dry film. The dry film is cured. The second layer 60b is formed. A solder resist layer 60 is formed. A coating layer 70 is formed simultaneously with the second layer 60b. A dam 80 is formed. The dry film for forming the second layer 60b and the coating layer 70 may be of a photo-curing type or a thermo-curing type. The second layer 60b and the coating layer 70 may be formed by applying a resin.

[0038] Openings 62, 64, 66 that penetrate the solder resist layer 60 and reach the electrodes 32, 34, 36 are formed using a laser. Due to the openings 62, 64, 66, the electrodes 32, 34, 36 are exposed. A printed wiring board 102 is obtained.

[0039] In the modified example of the printed wiring board 102, the first layer 60a and the second layer 60b cover substantially equal areas. The amount of shrinkage due to the curing of the first layer 60a and the amount of shrinkage due to the curing of the second layer 60b are substantially equal. Since the dam 80 has the metal protrusion 50, the strength of the dam 80 is high. Warping and twisting of the printed wiring board 102 are suppressed.

[0040] In the modified example, the electrodes 32, 34 are electrically connected via a connection wiring 33. The electrodes 34, 36 are electrically connected via a connection wiring 37. The path connecting the two electrodes does not have a via conductor and a wiring under the uppermost resin insulation layer 20. The two electrodes can be connected by a short path. The modified example can reduce transmission loss.

[0041] In the modified example, the metal protrusion 50 is formed on the first layer 60a. Therefore, even if the thickness of the electrolytic plating layer 50b for forming the metal protrusion 50 is small, the modified example can ensure the height of the metal protrusion 50. The modified example can reduce the variation in the height of the metal protrusion 50. The height of the top of the metal protrusion 50 does not vary greatly from place to place. The height of the dam 80 does not vary greatly from place to place.

[0042] The modified example may have a base between the first layer 60a and the seed layer 50a that forms the metal protrusion 50. In this case, the metal protrusion 50 is formed on the base on the first layer 60a.

[0043] The shape of the coating layer 70 in the embodiment is the same as that of the coating layer 70 in the modified example. The shape of the metal protrusion 50 in the embodiment is the same as that of the metal protrusion 50 in the modified example. The shape of the dam 80 in the embodiment is the same as that of the dam 80 in the modified example.

Explanation of Reference Numerals

[0044] 2, 102: Printed Wiring Board 10: Conductor Layer 20: Resin Insulation Layer 30: Top Conductor Layer 39: Base 50: Metal Protrusion 60: Solder Resist Layer 60a: First Layer 60b: Second Layer 61: Upper Surface 70: Coating Layer 80: Dam 82: Top 84: Side Surface

Claims

1. The uppermost resin insulating layer, The uppermost conductor layer formed on the uppermost resin insulating layer, The solder resist layer formed on the uppermost resin insulating layer and the uppermost conductor layer, A printed wiring board having a dam having a top protruding upward from the upper surface of the solder resist layer, The dam has a metal protrusion and a resin coating layer covering the metal protrusion, The coating layer is formed simultaneously with the solder resist layer, and the resin forming the coating layer is common to the resin forming the solder resist layer.

2. The printed wiring board according to Claim 1, wherein the cross-sectional shape of the dam is formed such that the width decreases toward the top.

3. The printed wiring board according to Claim 2, wherein the cross-sectional shape of the dam is substantially trapezoidal or substantially triangular.

4. The printed wiring board according to Claim 1, wherein at least one of the top and the side surface of the dam is a curved surface.

5. The printed wiring board according to Claim 1, wherein the uppermost conductor layer has a base, and the metal protrusion is joined to the base.

6. The printed wiring board according to Claim 5, wherein the width of the base is larger than the width of the metal protrusion.

7. The printed wiring board according to Claim 1, wherein the solder resist layer has a first layer on the uppermost resin insulating layer and the uppermost conductor layer and a second layer on the first layer, the metal protrusion is formed on the first layer, the coating layer is formed simultaneously with the second layer, and the resin forming the coating layer is common to the resin forming the second layer.

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