JP7728155B2 - Printed wiring board manufacturing method - Google Patents

Description

The technology disclosed in this specification relates to a method for manufacturing printed wiring boards.

Patent Document 1 discloses a method for manufacturing a wiring board that includes the steps of preparing an insulating layer-forming member having a semi-cured insulating layer provided on one side of a support film, attaching the insulating layer-forming member so that the semi-cured insulating layer contacts the pad, and curing the insulating layer after the insulating layer-forming member has been attached.

JP 2009-99649 A

[Problems of Patent Document 1]
In the technology of Patent Document 1, it is believed that pressure is applied to the support film and the semi-cured insulating layer when the insulating layer-forming member is attached. It is believed that the pressure causes a portion of the semi-cured insulating layer to protrude outward from the outer periphery of the support film. The protruding portion of the insulating layer is called bleed. It is believed that a portion of the bleed protrudes upward from the support film. If the bleed protrudes upward, it is believed that the flatness of the wiring board will be impaired. As a result, it is believed that the quality of the wiring board will be reduced.

The method for manufacturing a printed wiring board of the present invention includes forming a conductor layer having a conductor circuit on an insulating layer; preparing a forming member having a resin insulating layer having a first surface and a second surface opposite the first surface, and a first protective film formed on the first surface of the resin insulating layer, wherein each side of the outer periphery of the first protective film overlaps each side of the resin insulating layer when the resin insulating layer and the first protective film are projected with light perpendicular to the first surface; attaching the forming member to the conductor layer so that the conductor circuit and the second surface are in contact; and pressing from above a portion of the resin insulating layer that protrudes outward and above the outer periphery of the first protective film due to the attachment, thereby flattening the first surface.

In the manufacturing method of an embodiment of the present invention, when a forming member is attached to the conductor layer, a portion of the resin insulating layer may protrude outward from the outer edge of the first protective film and protrude above the first protective film. However, in the manufacturing method of an embodiment of the present invention, the attachment of the forming member presses the portion of the resin insulating layer that protrudes outward and above the outer edge of the first protective film from above, flattening the first surface. Therefore, after flattening, there are no upwardly protruding portions on the first surface. As a result, the flatness of the printed wiring board manufactured by the manufacturing method of the present invention is prevented from being impaired. A high-quality printed wiring board is provided.

FIG. 1 is a cross-sectional view schematically showing a printed wiring board according to an embodiment. 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. 1A to 1C are plan views schematically showing a method for manufacturing a printed wiring board according to an embodiment. 1A to 1C are plan views schematically showing a method for manufacturing a printed wiring board according to an embodiment. FIG. 2F is a plan view schematically showing the step of FIG. 2E. 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment. 1A to 1C are cross-sectional views schematically illustrating a method for manufacturing a printed wiring board according to an embodiment.

[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 60, and via conductors 70.

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

The resin insulating layer 20 is formed on the insulating layer 4 and the first conductor layer 10. The resin insulating layer 20 has a first surface 20F (the upper surface in the figure) and a second surface 20B (the lower surface in the figure) opposite the first surface 20F. An opening 22 is formed in the resin insulating layer 20 to expose the pad 12. The resin insulating layer 20 is made of a thermosetting resin. The thermosetting resin contains an epoxy-based resin, a polymer-based resin, and an inorganic filler.

The second conductor layer 60 is formed on the first surface 20F of the resin insulating layer 20. The second conductor layer 60 includes lands 62 and signal wiring 64. Although not shown in the figure, the second conductor layer 60 also includes conductor circuits other than the lands 62 and signal wiring 64. The second conductor layer 60 is formed of copper. The second conductor layer 60 is formed of a seed layer 60a and an electrolytic plating film 60b on the seed layer 60a.

The via conductor 70 is formed in the opening 22. The via conductor 70 connects the first conductor layer 10 and the second conductor layer 60. In FIG. 1, the via conductor 70 connects the pad 12 and the land 62. The via conductor 70 is formed by the seed layer 60a and the electrolytic plating film 60b on the seed layer 60a.

[Method for manufacturing printed wiring board 2 according to the embodiment]
2A to 2H show a method for manufacturing the printed wiring board 2 of the embodiment. 2A to 2H are cross-sectional views.

Figure 2A shows an insulating layer 4 and a first conductor layer 10 formed on the insulating layer 4. The first conductor layer 10 is formed by a semi-additive method.

As shown in FIG. 2B, a forming member 30 is prepared, including a resin insulating layer 20 and a first protective film 32 formed on the first surface 20F of the resin insulating layer 20. At this point, the resin insulating layer 20 is in a semi-cured state. The first protective film 32 completely covers the first surface 20F of the resin insulating layer 20. When the forming member 30 is viewed in a planar view, each side of the outer periphery of the first protective film 32 overlaps with each side of the outer periphery of the resin insulating layer 20. In other words, when the resin insulating layer 20 and the first protective film 32 are projected using light perpendicular to the first surface 20F of the resin insulating layer 20, each side of the outer periphery of the first protective film 32 overlaps with each side of the outer periphery of the resin insulating layer 20. An example of the first protective film 32 is a film made of polyethylene terephthalate (PET). A release agent is formed between the first protective film 32 and the resin insulating layer 20.

As shown in FIG. 2C , a forming member 30 is attached to the insulating layer 4 and the first conductor layer 10 so that the second surface 20B contacts the pads 12 and signal wiring 14 of the first conductor layer 10. At this time, heat and pressure are applied to the first protective film 32 and the semi-cured resin insulating layer 20. The first protective film 32 and the resin insulating layer 20 are pressed toward the insulating layer 4 by a pressure plate 50 placed on the first protective film 32. The pressure plate 50 is, for example, a stainless steel (SUS) plate. In this embodiment, the semi-cured resin insulating layer 20 is deformed by the attachment of the forming member 30. A portion of the resin insulating layer 20 protrudes outward from the outer periphery of the first protective film 32. The protruding portion of the resin insulating layer 20 protrudes above the first protective film 32. The protruding portion of the resin insulating layer 20 (i.e., the portion of the resin insulating layer 20 protruding outward and above the outer periphery of the first protective film 32) is called a bleed 23. The bleed 23 has a protrusion 21 that protrudes above the first protective film 32. The resin insulation layer 20 is heated by a heating mechanism (not shown). Heating promotes hardening of the resin insulation layer 20.

As shown in FIG. 2D, the bleed 23 (a portion of the resin insulation layer 20 that protrudes outward and upward from the outer periphery of the first protective film 32) is pressed from above. The bleed 23 is pressed by a pressing member 55 that is pressed against the bleed 23. The pressing member 55 also abuts against a portion of the outer periphery of the first protective film 32, but is not pressed against the entire surface of the first protective film 32. The pressing member 55 is, for example, a rubber member. In another example, the pressing member 55 may be a stainless steel member. Pressing the bleed 23 from above flattens the first surface 20F of the resin insulation layer 20. The protruding portion 21 (FIG. 2C) of the bleed 23 disappears. After flattening, there is no upwardly protruding portion on the first surface 20F.

As shown in Figure 2E, laser light L is irradiated from above the first protective film 32. The laser light L simultaneously penetrates the first protective film 32 and the resin insulating layer 20. An opening 22 for a via conductor is formed, leading to the pad 12 on the first conductor layer 10. The laser light L is, for example, UV laser light or CO2 laser light. The pad 12 is exposed through the opening 22.

As shown in Figure 2F, the first protective film 32 is removed from the first surface 20F of the resin insulation layer 20.

As shown in FIG. 2G, a seed layer 60a is formed on the first surface 20F of the resin insulating layer 20. The seed layer 60a is formed by electroless plating. A plating resist 100 is formed on the seed layer 60a. The plating resist 100 has openings for forming the lands 62 and signal wiring 64 (FIG. 1).

As shown in FIG. 2H, an electrolytic plated film 60b is formed on the seed layer 60a exposed from the plating resist 100. The electrolytic plated film 60b fills the opening 22. The seed layer 60a and electrolytic plated film 60b on the first surface 20F form a land 62 and a signal wiring 64. The second conductor layer 60 is formed. The seed layer 60a and electrolytic plated film 60b in the opening 22 form a via conductor 70. The via conductor 70 connects the pad 12 and the land 62.

Then, the plating resist 100 is removed. The seed layer 60a exposed from the electrolytic plating film 60b is removed. The second conductor layer 60 and via conductors 70 are formed simultaneously. A heat treatment is performed, and the resin insulating layer 20 is completely cured. The printed wiring board 2 (Figure 1) of the embodiment is obtained.

According to the manufacturing method of the embodiment, when the forming member 30 is attached to the first conductor layer 10, a portion of the resin insulating layer 20 protrudes outward from the outer periphery of the first protective film 32 and protrudes above the first protective film 32 ( FIG. 2C ). In other words, a bleed 23 is formed. However, in the manufacturing method of the embodiment, after the forming member 30 is attached, the bleed 23 is pressed from above by a pressing member 55 ( FIG. 2D ). Pressing the bleed 23 from above flattens the first surface 20F of the resin insulating layer 20. The protruding portion 21 of the bleed 23 disappears. After flattening, there is no upwardly protruding portion on the first surface 20F. As a result, the flatness of the printed wiring board 2 manufactured by the manufacturing method of the embodiment is prevented from being impaired. A high-quality printed wiring board 2 is provided.

2: Printed wiring board 4: Insulating layer 10: First conductor layer 12: Pad 14: Signal wiring 20: Resin insulating layer 20F: First surface 20B: Second surface 21: Protrusion 23: Bleed 30: Forming member 32: First protective film 50: Pressing plate 55: Pressing member

Claims (2)

forming a conductor layer having a conductor circuit on an insulating layer;
preparing a forming member having a resin insulating layer having a first surface and a second surface opposite to the first surface, and a first protective film formed on the first surface of the resin insulating layer, wherein when the resin insulating layer and the first protective film are projected by light perpendicular to the first surface, each side of the outer periphery of the first protective film overlaps each side of the resin insulating layer;
attaching the forming member onto the conductor layer so that the conductor circuit and the second surface are in contact;
and pressing from above a portion of the resin insulating layer that protrudes outward and upward from the outer peripheral edge of the first protective film due to the attachment, thereby flattening the first surface. In the method for manufacturing a printed wiring board of claim 1, the attaching step includes applying heat and pressure to the first protective film and the resin insulating layer.