Manufacturing method of printed circuit boards

Abstract

To provide a method for manufacturing printed circuit boards that enables uniform correction of the solder resist layer. [Solution] A method for manufacturing a printed circuit board includes forming an outermost resin insulating layer, forming a conductor layer on the outermost resin insulating layer, forming a resin layer made of a first resin for forming a solder resist layer on the outermost resin insulating layer and the conductor layer, exposing the resin layer to light, forming the solder resist layer by developing the resin layer after exposure, and inspecting the solder resist layer. If a pinhole is found in the solder resist layer during the inspection, the solder resist layer is corrected, and the correction includes preparing a second resin made of the same material as the first resin, filling the pinhole with the second resin, and curing the second resin.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a container for a pentatype solder resist correction ink. The solder resist correction ink is placed inside the container, and the appearance of the solder resist layer is corrected by applying the correction ink discharged from the discharge port provided at the tip of the container.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] [Problems of Patent Document 1] Generally, when forming a solder resist layer, a dry film type solder resist layer is used. The solder resist correction ink of Patent Document 1 is expected to contain more solvents than the dry film. Since the solvent evaporates by drying, according to the technology of Patent Document 1, it is considered difficult to match the height of the applied correction ink with the height of the solder resist layer.

Means for Solving the Problems

[0005] The present invention provides a method for manufacturing a printed circuit board, comprising: forming an outermost resin insulating layer; forming a conductor layer on the outermost resin insulating layer; forming a resin layer made of a first resin for forming a solder resist layer on the outermost resin insulating layer and the conductor layer; exposing the resin layer to light; forming the solder resist layer by developing the resin layer after exposure; and inspecting the solder resist layer. If pinholes are found in the solder resist layer during the inspection, the solder resist layer is corrected, and the correction includes preparing a second resin made of the same material as the first resin; filling the pinholes with the second resin; and curing the second resin.

[0006] In the printed circuit board manufacturing method of the embodiment of the present invention, a resin layer made of a first resin is formed. A solder resist layer is formed by developing the resin layer after exposure. The solder resist layer is inspected. Pinholes may occur in the resin layer during development. If pinholes are found during inspection, the solder resist layer is corrected. A second resin made of the same material as the first resin is prepared. The second resin is filled into the pinholes. The second resin is cured after filling, and the solder resist layer is corrected. In this embodiment, a second resin, which is made of the same material as the first resin, is filled into the pinhole and cured. Therefore, it is easy to match the height of the second resin inside the pinhole after curing with the first resin that forms the rest of the solder resist layer. According to this embodiment, the second resin inside the corrected pinhole has almost the same color, thickness, and physical properties as the first resin in the rest of the layer. [Brief explanation of the drawing]

[0007] [Figure 1A] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 1B] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 1C] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 1D]A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 1E] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 2] A schematic plan view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 3A] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Figure 3B] A schematic cross-sectional view illustrating the manufacturing method of a printed circuit board according to this embodiment. [Modes for carrying out the invention]

[0008] <Method for manufacturing a printed circuit board according to an embodiment> Figures 1A to 1C show a manufacturing method for a printed circuit board according to an embodiment. Figures 1A to 1C are cross-sectional views.

[0009] As shown in Figure 1A, an intermediate substrate is prepared having a resin insulating layer (outermost resin insulating layer) 1 and a conductive layer 2 on the resin insulating layer 1.

[0010] As shown in Figure 1B, a resin layer 3 for forming a solder resist layer is formed on the resin insulating layer 1 and the conductor layer 2. The resin layer 3 includes, for example, an epoxy resin (first resin), and may also include additives such as a curing agent and an antifoaming agent. The resin layer 3 consists of a dry film. The dry film has a first surface 15 and a second surface 16 opposite to the first surface 15. The second surface 16 is pressed onto the resin insulating layer 1 and the conductor layer 2.

[0011] Subsequently, a mask (not shown) is placed on the resin layer 3. The mask covers the resin layer 3 on each pad 4. The pads 4 are conductive layers 2 on which bumps for mounting electronic components (not shown) are formed. The mask does not cover the resin layer 3 other than those on each pad 4. As shown in Figure 1C, the resin layer 3 is exposed by light L1 irradiated through the mask. Light L1 is, for example, ultraviolet light. The resin layer 3 on each pad 4 does not harden. The resin layer 3 other than those on each pad 4 hardens.

[0012] The developing process removes the uncured portion of the resin layer 3, forming a solder resist layer 30 as shown in Figure 1D. The solder resist layer 30 has an opening 5. The opening 5 exposes the conductor layer 2. The exposed conductor layer 2 is the pad 4.

[0013] Subsequently, the solder resist layer 30 is inspected. The inspection checks whether or not pinholes have formed in the solder resist layer 30. If air bubbles or foreign matter are present in the solder resist layer 30, exposure will not occur when light L1 is irradiated. Uncured areas will be created in the unexposed areas. When the uncured areas are removed by the development process, pinholes PH are formed in the solder resist layer 30, as shown in Figures 1E and 2. Pinholes PH have a diameter of, for example, 20 μm to 30 μm.

[0014] <Modification of the solder resist layer> If pinhole PH is found during inspection, the solder resist layer 30 is corrected. Figures 3A and 3B show a method for correcting the solder resist layer 30 by filling the pinhole PH with a resin layer. Figures 3A and 3B are cross-sectional views. In Figures 3A and 3B, dry film is abbreviated as "DFR".

[0015] <1. Preparation of dry film resist> As shown in Figure 3A, a repair material 100 having a resin layer 101 is prepared. The resin layer 101 has a third surface 103 and a fourth surface 104 opposite to the third surface 103. The repair material 100 consists of three layers: the resin layer 101, a PET layer 102 laminated on the third surface 103, and a PET layer 105 laminated on the fourth surface 104. The resin layer 101 is a different dry film of the same type as the resin layer 3. The resin layer 101 contains a resin (second resin) made of the same material as the resin in the resin layer 3. The resin in the resin layer 101 and the resin in the resin layer 3 are composed of the same components, and the content of each component is the same. For example, the resin in the resin layer 101 has the same type number as the resin in the resin layer 3. Unused portions of the dry film of the resin layer 3 can also be used as the resin in the resin layer 101.

[0016] <2. Removal of Dry Film Resist> After that, in the corrective material 100, the PET layer 102 is peeled off from the third surface 103 of the resin layer 101. A needle 200 having a suction part 201 and a heating part 202 is prepared. The hollow part of the needle 200 has a diameter of, for example, 10 μm or more and 30 μm or less.

[0017] <3. Heating of the Needle> After that, the heating part 202 is turned on, and the needle 200 is heated. The temperature to be heated is, for example, within the range of 60°C or more and 80°C or less. The heated needle 200 is pressed against the third surface 103 of the resin layer 101. The resin 101R constituting the resin layer 101 enters the hollow part of the needle 200.

[0018] <4. Extraction of Dry Film Resist> After that, as shown in FIG. 3B, with the heating part 202 in the ON state, the suction part 201 is turned on. The needle 200 moves away from the resin layer 1C upward. The resin 101R that has entered the hollow part of the needle 200 is sucked to the inner part of the hollow part. The resin 101R is separated from the resin layer 101 and extracted. After the resin 101R is extracted, the heating part 202 is turned off.

[0019] <5. Filling of Dry Film Resist> The heating part 202 is turned on, and the resin 101R held in the hollow part of the needle 200 is heated. The temperature to be heated is, for example, within the range of 60°C or more and 80°C or less. The resin 101R increases its fluidity by being heated. The suction part 201 is turned off, and the heated resin 101R is extruded from the hollow part of the needle 200. The extruded resin 101R is discharged into the pinhole PF of the solder resist layer 30 and filled. The discharge and filling are performed under reduced pressure or in a vacuum.

[0020] <6. Curing of Dry Film Resist > Light L2 is irradiated onto the resin 101R inside the pinhole PH. Light L2 is, for example, ultraviolet light. Heating can also be used instead of irradiation with light L2. The resin 101R hardens, and the repair of the solder resist layer 30 filling the pinhole PH is completed.

[0021] In the printed circuit board manufacturing method of this embodiment, resin 101R, which is the same material as the epoxy resin of the resin layer 3, is filled into the pinhole PH and cured. Therefore, the height of the resin 101R in the pinhole PH after curing can be easily matched with the resin forming the other parts of the solder resist layer 30. According to this embodiment, the resin 101R in the modified pinhole PH has almost the same color, thickness, and physical properties as the resin in the other parts of the solder resist layer 30. Physical properties include strength, thermal expansion coefficient, Young's modulus, etc. [Explanation of symbols]

[0022] 1: Resin insulating layer 2: Conductor layer 3: Resin layer 30: Solder Resist Layer 100: Correction material 101: Resin layer 101R: Resin 200: Needle 201: Suction part 202: Heating section L1: light L2: light PH: Pinhole

Claims

1. Forming the outermost resin insulating layer, Forming a conductive layer on the outermost resin insulating layer, A resin layer made of a first resin for forming a solder resist layer is formed on the outermost resin insulating layer and the conductor layer. Exposing the aforementioned resin layer, The solder resist layer is formed by developing the resin layer after the exposure. A method for manufacturing a printed circuit board, comprising inspecting the solder resist layer, If pinholes are found in the solder resist layer as a result of the inspection, the solder resist layer is corrected, and the correction includes preparing a second resin made of the same material as the first resin, filling the pinholes with the second resin, and curing the second resin.

2. A method for manufacturing a printed circuit board according to claim 1, wherein the first resin is made of a dry film.

3. A method for manufacturing a printed circuit board according to claim 2, wherein preparing the second resin comprises preparing another dry film of the same type as the dry film, the modification further comprises extracting the second resin from the other dry film, and the second resin to be filled into the pinholes is the second resin extracted from the other dry film.

4. A method for manufacturing a printed circuit board according to claim 3, wherein the extraction is performed using a needle.

5. A method for manufacturing a printed circuit board according to claim 4, wherein the extraction is performed under heating.

6. A method for manufacturing a printed circuit board according to claim 5, wherein the heating is performed by heating the needle.

7. A method for manufacturing a printed circuit board according to claim 4, wherein the filling includes discharging the second resin in the needle into the pinhole.

8. A method for manufacturing a printed circuit board according to claim 7, wherein the filling is performed under reduced pressure or vacuum.

9. A method for manufacturing a printed circuit board according to claim 7, wherein the discharge is performed under heating.

10. A method for manufacturing a printed circuit board according to claim 9, wherein the heating is performed by heating the needle.

11. A method for manufacturing a printed circuit board according to claim 1, wherein the diameter of the pinhole is 20 μm or more and 30 μm or less.

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