Method for manufacturing printed wiring board

Abstract

To provide a manufacturing method for manufacturing a printed wiring board having high quality.SOLUTION: The manufacturing method of the embodiment includes forming a resin insulating layer having a first surface and a second surface on a first conductor layer, semi-curing the resin insulating layer, forming an opening for a via conductor that penetrates the resin insulating layer and reaches the first conductor layer, forming a second conductor layer on the first surface of the resin insulating layer after the semi-curing, forming a via conductor in the opening that connects the first conductor layer and the second conductor layer, and curing the resin insulating layer after the forming of the second conductor layer and the forming of the via conductor. The forming of the second conductor layer includes forming a seed layer on the first surface of the resin insulating layer by sputtering, forming a plating resist on the seed layer, forming an electrolytic plating film on the seed layer exposed from the plating resist, removing the plating resist, and removing the seed layer exposed from the electrolytic plating film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a manufacturing method that includes curing a resin insulating layer and forming an alloy layer on the surface of the cured resin insulating layer by sputtering. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-124602 Summary of the Invention

[0004] [Problem of Patent Document 1] In the method for manufacturing a printed wiring board disclosed in Patent Document 1, it is believed that the adhesive strength between the conductor circuit and the resin insulating layer is not sufficient. [Means for solving the problem]

[0005] A method for manufacturing a printed wiring board of the present invention includes forming a resin insulating layer on a first conductor layer, the resin insulating layer having a first surface and a second surface opposite the first surface, semi-curing the resin insulating layer, forming openings for via conductors that penetrate the resin insulating layer and reach the first conductor layer, forming a second conductor layer on the first surface of the resin insulating layer after the semi-curing, forming via conductors in the openings that connect the first conductor layer and the second conductor layer, and curing the resin insulating layer after forming the second conductor layer and the via conductor. Forming the second conductor layer includes forming a seed layer on the first surface of the resin insulating layer by sputtering, forming a plating resist on the seed layer, forming an electrolytic plating film on the seed layer exposed from the plating resist, removing the plating resist, and removing the seed layer exposed from the electrolytic plating film.

[0006] In the manufacturing method of the embodiment of the present invention, a seed layer is formed by sputtering on the first surface of the semi-cured resin insulation layer. Therefore, the embodiment can increase the adhesive strength (peel strength) between the seed layer and the resin insulation layer. The embodiment can increase the adhesive force between the second conductor layer and the resin insulation layer. The embodiment can provide a printed wiring board with stable performance. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a printed wiring board according to an embodiment. [Figure 2A] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. [Figure 2B] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. [Figure 2C] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. [Figure 2D] 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Embodiment] 1 is a cross-sectional view showing a printed wiring board 2 according to an embodiment. As shown in FIG. 1, the printed wiring board 2 has an insulating layer 4, a first conductor layer 10, a resin insulating layer 20, a second conductor layer 30, and via conductors 40.

[0009] The insulating layer 4 is formed using a thermosetting resin. The insulating layer 4 may contain inorganic particles such as silica. The insulating layer 4 may also contain a reinforcing material such as glass cloth. The insulating layer 4 has a third surface 6 and a fourth surface 8 opposite to the third surface 6.

[0010] The first conductor layer 10 is formed on the third surface 6 of the insulating layer 4. The first conductor layer 10 includes signal wiring 12 and pads 14. Although not shown in the figure, the first conductor layer 10 also includes conductor circuits other than the signal wiring 12 and pads 14. The first conductor layer 10 is made of copper. The first conductor layer 10 is formed of a seed layer 10a and an electrolytic plated film 10b on the seed layer 10a.

[0011] The resin insulating layer 20 is formed on the third surface 6 of the insulating layer 4 and the first conductor layer 10. The resin insulating layer 20 has a first surface 22 and a second surface 24 opposite the first surface 22. An opening 26 is formed in the resin insulating layer 20 to expose the pad 14. The resin insulating layer 20 is formed of an epoxy resin and inorganic particles dispersed in the epoxy resin. An example of the resin is a thermosetting resin. The inorganic particles are, for example, silica or alumina.

[0012] The second conductor layer 30 is formed on the first surface 22 of the resin insulating layer 20. The second conductor layer 30 includes a first signal wiring 32, a second signal wiring 34, and a land 36. Although not shown in the figure, the second conductor layer 30 also includes conductor circuits other than the first signal wiring 32, the second signal wiring 34, and the land 36. The second conductor layer 30 also includes signal wiring other than the first signal wiring 32 and the second signal wiring 34. The second signal wiring 34 is formed adjacent to the first signal wiring 32. The first signal wiring 32 and the second signal wiring 34 form a pair wiring. The second conductor layer 30 is formed of copper. The second conductor layer 30 is formed of a seed layer 30a and an electrolytic plating film 30b on the seed layer 30a.

[0013] The width W1 of the first signal wiring 32 and the second signal wiring 34 is 1.5 μm or more and 4 μm or less. The length of the first signal wiring 32 and the second signal wiring 34 is 10 mm or more and 25 mm or less. The width W2 of the space between the first signal wiring 32 and the second signal wiring 34 is 10 μm or more.

[0014] The via conductor 40 is formed in the opening 26. The via conductor 40 connects the first conductor layer 10 and the second conductor layer 30. In Fig. 1, the via conductor 40 connects the pad 14 and the land 36. The via conductor 40 is formed of a seed layer 30a and an electrolytic plated film 30b on the seed layer 30a.

[0015] [Method for manufacturing a printed wiring board according to an embodiment] 2A to 2D show a method for manufacturing printed wiring board 2 of this embodiment. 2A to 2D are cross-sectional views. 2A shows insulating layer 4 and first conductor layer 10 formed on third surface 6 of insulating layer 4. First conductor layer 10 is formed by a semi-additive method.

[0016] As shown in FIG. 2B, a resin insulating layer 20 is formed on the insulating layer 4 and the first conductor layer 10. The second surface 24 of the resin insulating layer 20 faces the third surface 6 of the insulating layer 4. The resin insulating layer 20 is heat-treated. The resin insulating layer 20 is semi-cured. The degree of cure of the resin insulating layer 20 after semi-curing is 50% or more and 90% or less. The degree of cure of the resin insulating layer 20 after semi-curing is preferably 60% or more and 80% or less. The degree of cure of the resin insulating layer 20 is adjusted by the heating time and heating temperature.

[0017] As shown in FIG. 2C, laser light L is irradiated onto the semi-cured resin insulating layer 20. In this case, an opening 26 is formed in the semi-cured resin insulating layer 20. The resin insulating layer 20 does not have to be semi-cured before being irradiated with laser light L. In that case, the resin insulating layer 20 is semi-cured after being irradiated with laser light L. An opening 26 is formed in the resin insulating layer 20 before being semi-cured, and then the resin insulating layer 20 is semi-cured. The laser light L penetrates the resin insulating layer 20. An opening 26 for a via conductor reaching the pad 14 of the first conductor layer 10 is formed. The laser light L is, for example, UV laser light or CO2 laser light. The pad 14 is exposed by the opening 26. The inside of the opening 26 is cleaned. By cleaning the inside of the opening 26, resin residue generated when the opening 26 was formed is removed.

[0018] As shown in FIG. 2D, a seed layer 30a is formed on the first surface 22 of the semi-cured resin insulating layer 20. The seed layer 30a is formed by sputtering. The seed layer 30a is formed by a dry process. The resin insulating layer 20 has already been semi-cured when the seed layer 30a is formed. The seed layer 30a is also formed on the upper surface of the pad 14 exposed from the opening 26 and on the inner wall surface of the opening 26. The seed layer 30a is made of copper.

[0019] A plating resist is formed on the seed layer 30a. The plating resist has openings for forming the first signal wiring 32, the second signal wiring 34, and the lands 36.

[0020] An electrolytic plated film 30b is formed on the seed layer 30a exposed from the plating resist. The electrolytic plated film 30b fills the opening 26. The seed layer 30a and the electrolytic plated film 30b on the first surface 22 form a first signal wiring 32, a second signal wiring 34, and a land 36. The second conductor layer 30 is formed. The seed layer 30a and the electrolytic plated film 30b in the opening 26 form a via conductor 40. The via conductor 40 connects the pad 14 and the land 36. The first signal wiring 32 and the second signal wiring 34 form a pair of wiring.

[0021] The plating resist is removed. The seed layer 30a exposed from the electrolytic plated film 30b is removed. The second conductor layer 30 and the via conductors 40 are formed simultaneously.

[0022] Heat is applied to the resin insulating layer 20. The resin insulating layer 20 is cured. The resin insulating layer 20 is completely cured. The degree of cure of the cured resin insulating layer 20 is 92% or more. The degree of cure of the cured resin insulating layer 20 is preferably 95% or more. Furthermore, the degree of cure is preferably 97% or more. The printed wiring board 2 of the embodiment is obtained.

[0023] According to the manufacturing method of the embodiment, the seed layer 30a is formed by sputtering on the first surface 22 of the semi-cured resin insulating layer 20. Therefore, the embodiment can increase the adhesive strength (peel strength) between the seed layer 30a and the resin insulating layer 20. The embodiment can increase the adhesion force between the second conductor layer 30 and the resin insulating layer 20. The embodiment can provide a printed wiring board 2 with stable performance.

[0024] The width W1 of the first signal wiring 32 and the second signal wiring 34 is 1.5 μm or more and 4 μm or less. The length of the first signal wiring 32 and the second signal wiring 34 is 10 mm or more and 25 mm or less. Such thin and long signal wiring is likely to peel off from the resin insulating layer 20. However, the manufacturing method of the embodiment can increase the adhesion strength between the first signal wiring 32 and the resin insulating layer 20. The same is true for the adhesion strength between the second signal wiring 34 and the resin insulating layer 20. Therefore, even when thin and long first signal wiring 32 and second signal wiring 34 are formed, they are unlikely to peel off from the resin insulating layer 20. The manufacturing method of the embodiment can provide a printed wiring board 2 with high quality.

[0025] The width W2 of the space between the first signal wiring 32 and the second signal wiring 34 is 10 μm or more. If the width W2 of the space is large, etching liquid is likely to enter the space when the seed layer 30a exposed from the electrolytic plating film 30b is removed. Therefore, if the width W2 of the space is large, the signal wiring is likely to peel off from the resin insulating layer 20. However, the manufacturing method of the embodiment can increase the adhesion strength between the first signal wiring 32 and the resin insulating layer 20. The same is true for the adhesion strength between the second signal wiring 34 and the resin insulating layer 20. Therefore, even if the width W2 of the space between the first signal wiring 32 and the second signal wiring 34 is large, they are unlikely to peel off from the resin insulating layer 20. The manufacturing method of the embodiment can provide a high-quality printed wiring board 2.

[0026] [Method for manufacturing a printed wiring board according to a modified embodiment] In the modified example, the resin insulating layer 20 is completely cured after the seed layer 30a is formed. When the resin insulating layer 20 is completely cured after the seed layer 30a is formed, the resin insulating layer 20 is completely cured before the plating resist is formed. In the manufacturing method of the modified example, the resin insulating layer 20 may further be cured after the plating resist is removed. The manufacturing method of the modified example and the manufacturing method of the embodiment are substantially equivalent. [Explanation of symbols]

[0027] 2: Printed wiring board 4: Insulating layer 10: First conductor layer 12: Signal wiring 14: Pad 20: Resin insulating layer 22: 1st page 24:Second side 26 :Aperture 30: Second conductor layer 30a: seed layer 30b: Electroplated film 32: First signal wiring 34: Second signal wiring 36: Land 40: Via conductor L: Laser light

Claims

1. forming a resin insulating layer on a first conductor layer, the resin insulating layer having a first surface and a second surface opposite to the first surface; semi-curing the resin insulating layer; forming an opening for a via conductor that penetrates the resin insulating layer and reaches the first conductor layer; forming a second conductor layer on the first surface of the resin insulating layer after the semi-curing; forming a via conductor in the opening to connect the first conductor layer and the second conductor layer; A method for manufacturing a printed wiring board, comprising: forming the second conductor layer and the via conductor, and then curing the resin insulating layer; Forming the second conductor layer includes forming a seed layer by sputtering on the first surface of the resin insulating layer, forming a plating resist on the seed layer, forming an electrolytic plating film on the seed layer exposed from the plating resist, removing the plating resist, and removing the seed layer exposed from the electrolytic plating film.

2. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the resin insulating layer is formed of a thermosetting resin, and the semi-curing and curing include heating the resin insulating layer.

3. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the degree of cure of the resin insulating layer after the semi-curing is 50% or more and 90% or less.

4. 4. The method for manufacturing a printed wiring board according to claim 3, wherein the degree of cure of the resin insulating layer after semi-curing is 60% or more and 80% or less.

5. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the second conductor layer includes a signal wiring.

6. 6. A method for manufacturing a printed wiring board according to claim 5, wherein the width of the signal wiring is 1.5 μm or more and 4 μm or less.

7. 6. The method for manufacturing a printed wiring board according to claim 5, wherein the length of the signal wiring is 10 mm or more and 25 mm or less.

8. 6. The method for manufacturing a printed wiring board according to claim 5, wherein the signal wiring includes a first signal wiring and a second signal wiring formed adjacent to the first signal wiring, and the width of the space between the first signal wiring and the second signal wiring is 10 μm or more.

9. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the semi-curing is performed before the forming of the opening.

10. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the semi-curing is performed after the opening is formed.

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