JP2005142254A - Wiring board and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a highly reliable wiring board having a favorable opening shape in patterning of a solder resist on a wiring board having a plurality of conductor circuits in a resin insulating layer. In particular, the present invention is to provide a method of manufacturing a wiring board with improved productivity by a reel-to-reel method and a wiring board using the same.
In a method of manufacturing a wiring board having a solder resist layer on at least one outermost layer of a substrate, when the opening is formed in the solder resist layer, the same portion of the opening is exposed twice. The first exposure process and the second exposure process are a method for manufacturing a wiring board using different photomasks.
[Selection] Figure 1

Description

  The present invention relates to a wiring board and a method for manufacturing the same, and more particularly to a method for forming a solder resist layer of a wiring board.

  A conventional wiring board has an opening such as a terminal hole on the outermost layer on at least one side of the board, and prevents a solder bridge between adjacent circuits of the opening or a circuit on the outermost layer from the environment in which the electronic device is used. It has a solder resist layer for the purpose of protection. That is, the solder resist layer is indispensable for forming a highly reliable wiring board.

  Conventionally, a solder resist layer is obtained by applying a resin solution of a photosensitive solder resist to a substrate on which a wiring circuit is formed, performing exposure through a photomask in accordance with a predetermined pattern, developing, and exposing an exposure light irradiation portion. It was formed by a process of curing. Further, after the solder resist layer is formed, a metal layer such as nickel and gold is provided on the wiring circuit portion exposed from the opening.

  However, the conventional method has a problem of a solder resist resin residue in which the solder resist resin remains at the bottom end of the opening, and a problem that the opening diameter becomes small and the opening cross section does not become a trapezoidal shape.

  4A to 4D are schematic side sectional views of a conventional solder resist layer forming step. As shown in FIG. 4A, the outermost circuit pattern 2 is formed on the substrate 1. The base material is a core substrate on which one or a plurality of wiring layers are laminated, and the circuit pattern of the core substrate and the circuit pattern 2 of the outermost layer are electrically connected. As shown in FIG. 4B, the solder resist layer 3 is applied and formed on the entire surface of the substrate 1 and the circuit pattern. In FIG. 4C, exposure processing is performed using the photomask 4 in order to form openings in the solder resist layer on the circuit pattern 2. The photomask 4 is provided with a light shielding portion 6 in the opening portion of the solder resist layer. When the exposure light is irradiated, the reflected light from the circuit pattern 2 irradiates the exposure light to the portion of the opening where it is not necessary to form the solder resist layer, so that the solder resist hardens and cannot be removed by development. . That is, there is a problem that the cross-sectional shape of the opening of the solder resist layer does not become a normal trapezoid, or a problem that a residue of the solder resist resin is generated on the circuit pattern surface in the vicinity of the cross section. Further, there may be a problem that the shape of the opening is reduced. In FIG. 4D, an opening is formed in the unexposed portion of the solder resist layer by development processing, and the terminal hole 7 is formed. Through the above steps, a terminal hole and a solder resist layer are completed on the outermost layer.

  When patterning the solder resist layer, the unnecessary portion of the solder resist layer can be easily removed by reducing the integrated exposure amount of the solder resist layer forming portion from the specified integrated exposure amount. However, when the integrated exposure amount is small, there is a problem that the reliability of the solder resist layer is lowered. That is, the reliability of protecting the outermost layer circuit is lowered, and the high reliability of the circuit pattern in the environment in which the electronic device is used becomes a problem (see Patent Document 1).

The known literature is described below.
Japanese Patent Laid-Open No. 5-29754

  The present invention eliminates the problems of the conventional wiring board as described above, and has a good opening shape and reliability in the patterning of the solder resist layer of the wiring board having a plurality of conductor circuits in the resin insulating layer. It is in the place of providing a high wiring board. In particular, the present invention is to provide a method of manufacturing a wiring board with improved productivity by a reel-to-reel method.

  In order to solve the above-mentioned problems in the present invention, first, the invention according to claim 1 of the present invention is a method of manufacturing a wiring board in which a wiring layer and an insulating layer are alternately laminated and each wiring is conducted to form a circuit. A wiring board manufacturing method comprising: having a solder resist layer on at least one outermost layer of the substrate; and forming an opening in the solder resist layer, and performing an exposure process twice on the same portion of the opening. Is the method.

  The invention according to claim 2 of the present invention is characterized in that the exposure process uses different photomasks in the first exposure and the second exposure. It is.

  Further, in the invention according to claim 3 of the present invention, the first exposure process is resized and enlarged by a constant dimension width within 1 to 30% from the size of each pattern of the photomask used for the second exposure. 3. The method of manufacturing a wiring board according to claim 1, wherein a photomask on which each pattern is formed is used.

The invention according to claim 4 of the present invention is characterized in that the exposure processing is performed with the integrated exposure amount of the second exposure processing being 30 to 200% of the integrated exposure amount of the first exposure processing. The method for manufacturing a wiring board according to any one of claims 1 to 3.
It is.

  Furthermore, the invention according to claim 5 of the present invention is characterized in that the exposure process is performed by a reel-to-reel method. It is.

  In the invention according to claim 6 of the present invention, on the circuit pattern exposed from the opening of the outermost solder resist layer by using the method for manufacturing a wiring board according to any one of claims 1 to 5, The wiring board is characterized in that no solder resist resin residue is present.

  By using the wiring substrate of the present invention and the manufacturing method thereof, particularly the method of forming a solder resist layer, it is possible to obtain a wiring substrate having a good opening shape and high reliability in patterning of the solder resist layer.

  Hereinafter, embodiments of the present invention will be described in more detail. FIG. 1 is a side sectional view for explaining the solder resist layer forming step of the present invention, in which (a) is after exposure and (b) is after development. The wiring board of the present invention may be any of the case where the circuit pattern exists only on one side, the case where the circuit pattern exists on both sides, and the case where the circuit pattern is formed in multiple layers. FIG. 1 will be described with reference to the formation of a circuit pattern and a solder resist layer on the outermost layer on one side.

In FIG. 1A, a circuit pattern 9 is formed on the outermost layer of the substrate 8. A solder resist layer 10 is formed on the outermost layer of the substrate and the entire surface of the circuit pattern. The solder resist layer 10 is exposed twice using photomasks 11 and 14. The first exposure process is the first unexposed area 110, and the second exposure process is the second unexposed area 140. As a result, around the uncured portion 22 in the second exposure serving as the opening, a cured portion 21 in the second exposure is formed on the left and right sides, and a cured portion 20 in the first and second exposure is formed on the outer side. FIG. 1B shows the solder resist layer 10 after the development processing, and the uncured portion 22 in the second exposure is an opening, and the terminal hole 17 is formed. The solder resist layer 10 completes a cured portion 21 in the second exposure including the influence of curing by the first exposure, and a cured portion 20 completely cured by the first and second exposures on the outside thereof.

  The solder resist layer 10 of the present invention shown in FIG. 1 (a) can be either a liquid or a dry film. Examples of the application method of the liquid solder resist include, but are not limited to, screen printing, roller coating, dip coating, spray coating, spinner coating, and curtain coating. As a method for forming a solder resist layer using a dry film, various means such as a roll laminating method, a flat plate laminating method, and a flat plate pressing method can be used. In addition, the film thickness of a soldering resist layer is about 10-40 micrometers.

  In the exposure process of the solder resist layer, different photomasks are used for the first exposure and the second exposure. That is, a first photomask having a plurality of patterns (light-shielding portions) having a shape and size substantially equal to the shape and size of the portion (s) to be opened of the solder resist, and the first photomask and pattern Since the shape of each of the pattern parts is similar and the relative arrangement is also equal, when one point on the photomask is the origin, the relative coordinates with respect to the origin of each pattern part are the same, but the pattern (light-shielding part) is 1-30% larger in area ), A photomask is used for the first exposure, and the remaining photomask is used for the second exposure. Note that such a second photomask can be produced by using a resizing technique of enlarging the pattern by giving a constant width to the outer shape of the original pattern.

  Hereinafter, an example in which the second photomask is used for the first exposure and the first photomask is used for the second exposure will be described.

  A part of the appropriate exposure amount of the solder resist layer is irradiated in the first exposure, and the remaining exposure amount is irradiated in the second exposure. The first and second exposure amounts are set so that the sum of the integrated exposure amounts in the first and second exposures becomes the appropriate exposure amount of the solder resist layer. The second exposure amount is 30 to 200% of the first exposure amount, and more preferably 50 to 100%. Thereby, the integrated exposure amount in the vicinity of the opening is relatively reduced, the reflection of light from the circuit pattern is reduced, and it is easily removed by development. As shown in FIG. 1A, the width of the area of the hardened portion 21 in the second exposure depends on the size width of the resize, and the integrated exposure amount of the portion is the integrated exposure amount of the second exposure amount. It depends on. In other words, it is important to optimize the resizing amount and the second exposure condition in consideration of the shape and dimensions of the opening.

  Next, the manufacturing method of the wiring board of one Example of this invention is demonstrated in detail. FIG. 2 is a schematic sectional side view of the solder resist layer forming process of the present invention.

  The substrate 8 on which the conductor circuit is formed on the insulating resin is solid-printed on one side of the base material with a photosensitive solder resist resin solution using a screen, and then the substrate is semi-cured to form a solder resist layer. (See FIGS. 2A and 2B).

Next, exposure is performed through a photomask provided with a light-shielding portion at a location where the solder resist layer is not formed. At this time, the same part is exposed twice. In the exposure process of the solder resist layer, different photomasks are used for the first exposure and the second exposure. In the first exposure, the first photomask 11 having each pattern portion larger than that in the second exposure is used, and in the second exposure, the second photomask 14 is used. Although the relative pattern arrangement is the same for both the first photomask 11 and the second photomask 14, the size of each pattern of the first photomask is 1 to 30% larger than that of the second photomask. A part of the appropriate exposure amount of the solder resist layer is irradiated in the first exposure, and the remaining exposure amount is irradiated in the second exposure. After development of the unused portion, it is cured with heat and, if necessary, with ultraviolet rays to form a solder resist layer having terminal holes 17 (see FIGS. 2C, 2D, and 2E).

  As shown in FIG. 3A, firstly, the first exposure is performed to generate a cured portion 18 in the first exposure and an uncured portion 19 in the first exposure. Next, as shown in FIG. 3B, by performing the second exposure, the curing unit 20 by the first and second exposures in which the curing proceeds by the first and second exposures, in the first exposure Is not cured without being irradiated with light, but the light is irradiated and cured by the second exposure, the cured portion 21 in the second exposure, and the light is not irradiated by any of the first and second exposures. An uncured portion 22 in the second exposure occurs.

  The uncured portion 22 in the second exposure is removed by development. At this time, since the uncured portion 22 in the second exposure is surrounded by the cured portion 21 in the second exposure with a small integrated exposure amount, the reflected light from the circuit pattern is small and is easily removed by development.

  Furthermore, since the light which becomes the appropriate exposure amount of the solder resist layer is irradiated with the integrated exposure amount in the first exposure and the second exposure, the reliability of the solder resist layer is also ensured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  This will be described with reference to FIG. A photo solder resist PSR-4000 (manufactured by Taiyo Ink Co., Ltd., trade name) was solid-printed on the wiring board prepared by the above method using a screen, and then semi-cured at 80 ° C. for 30 minutes.

The first exposure was performed using a photomask provided with a light-shielding portion at a location where the solder resist layer was not formed. The integrated exposure amount at this time is 400 mJ / cm ² .

Next, a second exposure was performed. The integrated exposure amount at this time is 200 mJ / cm ² . In the first exposure and the second exposure, the total integrated exposure amount of the transmission part is 600 mJ / cm ² which is an appropriate exposure amount.

  The substrate was developed and post-cure and post-exposure were performed to form a photo solder resist layer.

  When the light shielding part diameter of the photomask in the first exposure is 180 μm and the light shielding part diameter of the photomask in the second exposure is 150 μm according to the evaluation of the substrate of Example 1, the top diameter of the upper part of the photo solder resist layer in the opening part Was 141 μm, and the bottom diameter of the lower part of the photo solder resist layer was 127 μm.

  Below, the comparative example of this invention is demonstrated.

Please refer to FIG. In the exposure step, a photo solder resist layer was formed in the same manner as in the example except that the second photo mask of the example was used as the photo mask 4 and the integrated exposure amount was 600 mJ / cm ² .

  According to the evaluation of the substrate of Example 2, when the light shielding part diameter of the photomask was 150 μm, the top diameter of the upper part of the photo solder resist layer in the opening part was 123 μm, and the bottom diameter of the lower part of the photo solder resist layer was 99 μm.

  As a result, in the manufacturing method of the present invention, a solder resist layer having an opening having a shape near the design value could be formed.

It is a sectional side view explaining the soldering resist layer formation process of this invention, (a) is after exposure, (b) is after image development. It is a schematic sectional side view of the soldering resist layer formation process of this invention. It is the model side sectional view which showed the hardening process of the soldering resist layer in the exposure process of this invention. It is a typical sectional side view of the formation process of the conventional soldering resist layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Circuit pattern 3 ... Solder resist layer 4 ... Photomask 5 ... Transmission part 6 ... Light-shielding part 7 ... Terminal hole 8 ... Base material 9 ... Circuit pattern 10 ... Solder resist layer 11 ... 1st photomask 12 ... transmission part 13 ... light-shielding part 14 ... second photomask 15 ... transmission part 16 ... light-shielding part 17 ... terminal hole 18 ... cured part 19 in the first exposure ... uncured part 20 in the first exposure ... first, Cured portion 21 in second exposure ... Cured portion 22 in second exposure ... Uncured portion 110 in second exposure ... Unexposed area 140 of first photomask ... Unexposed area of second photomask

Claims (6)

  In a method of manufacturing a wiring board in which wiring layers and insulating layers are alternately laminated and each wiring is made conductive to form a circuit, a solder resist layer is provided on at least one outermost layer of the board, and an opening is formed in the solder resist layer. In this case, the wiring substrate manufacturing method is characterized in that the same portion of the opening is subjected to exposure processing twice.   2. The method of manufacturing a wiring board according to claim 1, wherein the exposure process uses different photomasks in the first exposure and the second exposure.   The first exposure process uses a photomask in which a certain dimension width within 1 to 30% is resized from the size of each pattern of the photomask used for the second exposure and each enlarged pattern is formed. The method for manufacturing a wiring board according to claim 1 or 2, wherein   4. The wiring board manufacturing method according to claim 1, wherein the exposure process is performed so that the integrated exposure amount of the second exposure process is 30 to 200% of the integrated exposure amount of the first exposure process. Method.   The method for manufacturing a wiring board according to claim 1, wherein the exposure process is performed by a reel-to-reel method.   By using the method for manufacturing a wiring board according to claim 1, no solder resist resin residue is present on the circuit pattern exposed from the opening of the outermost solder resist layer. Wiring board.

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