JP2010129575A - Printed circuit board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board, and its manufacturing method which uses a photo-curing solder resist in a black or dark color, makes compatible both productivity and durability as solder resist, and reliability. <P>SOLUTION: The printed circuit board includes a wiring layer 2 where a metal or conductive wiring 2a is formed on the surface of an insulating base material 1, and a photo-curing solder resist layer 5 for protecting the wiring 2a or the like. In the photo-curing solder resist layer 5, two layers of a lower layer solder resist 3 and an upper layer solder resist 4 are stacked on the wiring layer in this order. Here, a colored photo-curing solder resist is the lower layer solder resist 3, while such a photo-curing solder resist as comprising a transparent material or the material wherein the transmissivity of the cured wavelength region of the colored photo-curing solder resist 3 to light is higher than that of the colored photo-curing solder resist is the upper layer solder resist 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printed wiring board in which a colored photo-curing solder resist layer such as a black photo solder resist is formed on a wiring layer in order to ensure clear visibility of, for example, white printing, and its manufacture Regarding the method.

  Conventionally, in this type of printed wiring board and its manufacturing method, desired printing is often performed with white ink, but in order to improve the visibility of the printed characters, its substantial background and As the solder resist, a photocurable solder resist colored in black or other dark color system is used.

FIG. 3 shows an example of the main flow of the black photocurable solder resist layer forming process in such a conventional printed wiring board and the manufacturing method thereof.
First, as shown in FIG. 3A, for example, a conductive foil made of a highly conductive material such as a copper foil is laminated on the surface of an insulating base material 101 made of a polymer resin such as a polyimide resin film, The wiring layer 102 having the wiring 102a, the pad 102b, and the like is formed by patterning it.
Subsequently, as shown in FIG. 3B, a colored photocuring such as a black or dark color system, most typically on the wiring layer 102 and almost the entire surface of the insulating base material 101. A mold solder resist layer 103 is applied.
Then, as shown in FIG. 3C, exposure / development is performed to form an opening 104 at a predetermined position in the photocurable solder resist layer 103. The surface 105 of the pad 102b exposed from the opening 104 serves as a connection terminal portion to, for example, a semiconductor device (not shown) outside the printed wiring board (see Patent Document 1 above).
JP 09-331138 A

  However, a colored photocurable solder resist such as a black or dark color system generally has low light transmittance. Due to this, in the exposure process for performing a predetermined pattern processing on the photocurable solder resist layer 103, the exposure to the deep part of the photocurable solder resist layer 103 becomes insufficient, and as a result, the exposure After the development, there is a high possibility that a so-called undercut pattern formation defect 106, for example, as shown in FIG. When such a pattern formation defect 106 occurs, it becomes impossible to secure the adhesion between the wiring layer 102 and the photocurable solder resist layer 103 at that portion, and the durability and reliability as a printed wiring board is lowered. . In addition, moisture, fine dust, and the like are likely to remain in the portion of the pattern formation defect 106, and abnormal precipitation of various metals constituting the wiring layer 102 is likely to proceed from this portion. Durability and reliability as a wiring board are reduced.

  In order to avoid such a pattern formation defect 106, it can be considered that a technique of sufficiently curing the black photocurable solder resist layer 103 by making the exposure time very long is effective. However, in order to sufficiently cure the black or colored photo-curable solder resist layer 103 that basically has low light transmittance, a long exposure time is required, so it is inevitable that productivity is significantly deteriorated. It is not practical as a method to be adopted in an actual production line.

Or, conversely, by reducing the film thickness of the black or colored photo-curable solder resist layer 103, the light transmittance during exposure is improved and the black photo-curable solder resist layer 103 is sufficiently cured. Although it seems that the technique is effective, since the film thickness of the photo-curing type solder resist layer 103 is reduced by this technique, the original function as a solder resist for protecting the wiring layer 102 is impaired. As a result, durability and reliability as a printed wiring board are lowered, which is not realistic.

As described above, in the conventional printed wiring board using the colored photo-curing solder resist 103 such as black or dark color and the manufacturing method thereof, the deep portion of the photo-curing solder resist layer 103 is sufficient at the time of exposure. There is a problem in that undercut pattern formation defects 106 and the like occur due to the difficulty of reaching such light. Further, when trying to avoid the occurrence of such pattern formation defect 106, there is a problem that an extremely long exposure time is required, and the original function as a solder resist is impaired.
The present invention has been made in view of such problems, and its purpose is to provide a colored light such as a black or dark color system capable of achieving both productivity and durability / reliability as a solder resist. An object of the present invention is to provide a printed wiring board using a curable solder resist and a method for manufacturing the same.

The printed wiring board of the present invention is a printed wiring board having a wiring layer formed by forming a metal or conductor wiring on the surface of an insulating substrate, and a photo-curable solder resist layer for protecting the wiring. The photo-curing solder resist layer is a colored photo-curing solder resist as a lower layer solder resist, and the transparent material or the transparency of the colored photo-curing solder resist with respect to light in the curing wavelength region is the colored A photo-curing solder resist made of a material higher than the photo-curing solder resist is used as an upper layer solder resist, and two layers of the lower layer solder resist and the upper layer solder resist are laminated on the wiring layer in this order. It is characterized by being.
The method for producing a printed wiring board according to the present invention includes a step of forming a wiring layer having a wiring of a desired pattern made of a metal or a conductor on the surface of an insulating substrate, and a photocurable solder for protecting the wiring. A method of manufacturing a printed wiring board having a step of forming a resist layer, the step of applying or depositing a colored photo-curable solder resist as a lower layer solder resist after forming the wiring layer, and the lower layer On top of the solder resist, as a top layer solder resist, a photo-curing type made of a transparent material or a material having higher transparency to the light in the curing wavelength range of the colored photo-curable solder resist than the colored photo-curable solder resist Applying or filming a solder resist, patterning by exposure is performed on the upper layer solder resist and the lower layer solder resist. It is characterized by a step of forming a photocurable solder resist layer formed by laminating a the lower solder resist and the upper solder resist.

  According to the present invention, the colored photo-curable solder resist is used as the lower layer solder resist, and the transparency of the colored photo-curable solder resist constituting the transparent material or the lower layer solder resist to light in the curing wavelength region is A photo-curing solder resist layer is formed by laminating a lower-layer solder resist and an upper-layer solder resist on the wiring layer in this order as a photo-curing solder resist made of a material higher than the colored photo-curing solder resist. In the exposure process of the photo-curable solder resist layer, it becomes easier for light to reach the deep part of the lower-layer solder resist under the light-transmitting upper solder resist, and the photo-curable solder resist It becomes possible to cure the layer sufficiently and reliably with a short exposure. As a result, it is possible to achieve both productivity and durability / reliability in a printed wiring board using a colored photo-curable solder resist such as a black or dark color system.

Hereinafter, a printed wiring board and a manufacturing method thereof according to the present embodiment will be described with reference to the drawings.
FIG. 1 is a diagram showing a main configuration of a printed wiring board according to an embodiment of the present invention, and FIG. 2 is a diagram showing a flow of main processes of the method for manufacturing a printed wiring board according to the embodiment of the present invention. It is.

  This printed wiring board is composed mainly of an insulating base material 1, a wiring layer 2, and a photocurable solder resist layer 5 formed by laminating a lower layer solder resist 3 and an upper layer solder resist 4. .

  The insulating substrate 1 is a substrate for a flexible printed wiring board made of a polymer resin made of a material having high electrical insulation, such as a polyimide resin film. In addition to this, the insulating base material 1 can be applied to a substrate material for a rigid printed wiring board such as a glass epoxy substrate.

  The wiring layer 2 is formed by patterning a conductor layer made of a metal such as a copper foil or a conductor, which is bonded to the surface of the insulating substrate 1. The wiring layer 2 mainly includes a wiring 2a and a pad 2b.

The photocurable solder resist layer 5 is for protecting the wiring 2 mechanically and electrically, and two layers of a lower layer solder resist 3 and an upper layer solder resist 4 are laminated on the wiring layer 2 in this order. It will be.
The photo-curing solder resist layer 5 is provided with openings 6 at predetermined positions, and the openings 7 expose the surface 7 of the pad 2b, for example, external semiconductor devices or other printed wirings. It is set to be a connection terminal portion with a plate (both not shown).

  The lower layer solder resist 3 is made of a colored photocurable solder resist such as black or dark color system, and is formed on the surface of the insulating substrate 1 including the wiring layer 2.

  The upper layer solder resist 4 is made of a transparent material or a material having higher transparency to the light in the curing wavelength region of the colored photocurable solder resist constituting the lower layer solder resist 3 than the colored photocurable solder resist. These are made of a photocurable solder resist and are formed on the lower layer solder resist 3.

The film thickness t1 of the lower solder resist 3 is desirably 10 μm or less, and the film thickness t2 of the upper solder resist 4 is desirably 5 μm or more.
This will be described based on specific experimental results in the following examples. In short, if the film thickness t1 of the lower layer solder resist 3 made of a colored photocurable solder resist is more than 10 μm, This is because the exposure to sufficiently and reliably cure the film tends to take a very long time and there is a high risk of pattern formation defects such as undercut. Further, if the film thickness t2 of the upper layer solder resist 4 is less than 5 μm, it becomes difficult to ensure the entire durability and reliability of the photocurable solder resist layer 5 including the upper layer solder resist 4. This is because the fear increases.
Here, the film thickness t 1 of the lower layer solder resist 3 indicates the dimension in the height direction from the upper surface of the wiring layer 2 to the upper surface of the lower layer solder resist 3. Further, the film thickness t of the photocurable solder resist layer 5 refers to the dimension in the height direction from the upper surface of the wiring layer 2 to the upper surface of the photocurable solder resist layer 5.

The lower limit of the film thickness t1 of the lower layer solder resist 3 is practically difficult to define numerically, but qualitatively, the visual concentration (or paint-like) of the lower layer solder resist 3 is considered. From a viewpoint, the thickness is such that the coating property is a predetermined concentration or more. That is, the minimum film thickness that can ensure a density sufficient to improve the visibility of ink such as white ink printed on the surface of the photocurable solder resist layer 5 is minimal. It is necessary.
Further, the upper limit value of the film thickness t2 of the upper layer solder resist 4 changes in consideration of the film thickness t1 of the lower layer solder resist 3, so that it is practically difficult to define it numerically. The film thickness is such that the overall durability and reliability of the photocurable solder resist layer 5 can be ensured. That is, if the entire film thickness t of the photocurable solder resist layer 5 including the film thickness of the upper layer solder resist 4 is reduced, the overall durability and reliability of the photocurable solder resist layer 5 are impaired. Therefore, the minimum film thickness t required to avoid such an inconvenience is secured by the film thickness t2 of the upper solder resist 4. Therefore, it is sufficient that the thickness satisfies such a condition. If the thickness is larger than that, the disadvantages are rather large because it takes too much exposure time or the material cost increases. It means that there is a risk of becoming.

Next, a method for manufacturing a printed wiring board according to an embodiment of the present invention will be described.
First, as shown in FIG. 2 (a), a conductive layer such as a copper foil is patterned on the surface of the insulating substrate 1 to have a desired pattern of wiring 2a, pads 2b, and the like. Form.

After forming the wiring layer 2, as shown in FIG. 2B, a colored photo-curing solder resist 3 such as black or dark color is used as the lower layer solder resist 3, including the wiring layer 2. Application or deposition or lamination (bonding) is performed on the surface of the substrate 1. The film thickness t1 of the lower layer solder resist 3 is desirably 10 μm or less, as described in the description of the above structure.
Here, considering the process consistency with existing equipment and the productivity in the coating process, it is desirable to apply the lower layer solder resist 3 by a screen printing method or a roll coating method.

Subsequently, as shown in FIG. 2C, the upper layer solder resist 4 is formed on the lower layer solder resist 3 so that the transparent material or the light transmittance in the curing wavelength region constitutes the lower layer solder resist 3. A photo-curing solder resist made of a material higher than the colored photo-curing solder resist is applied or deposited or laminated. The film thickness t2 of the upper layer solder resist 4 is desirably 5 μm or more as described in the explanation regarding the structure.
In this process, it is desirable to use a screen printing method or a roll coating method for the same reason as in the case of the lower layer solder resist 3.

Then, as shown in FIG. 2 (d), the upper solder resist 4 and the lower solder resist 3 are simultaneously exposed to light and developed to expose the surface 7 of the pad 2b for each predetermined position. The part 6 is provided, and the photocurable solder resist layer 5 formed by laminating the upper layer solder resist 4 and the lower layer solder resist 3 is completed.
Thus, the main part of the printed wiring board according to the embodiment of the present invention can be manufactured with good productivity.

As described above, in the printed wiring board and the manufacturing method thereof according to the present invention, the lower layer solder resist 3 is formed using a colored photo-curing solder resist such as a black or dark color system, and a transparent solder resist is formed thereon. A photo-curing solder resist made of a material having a higher transparency to light in the curing wavelength region of the colored photo-curing solder resist constituting the lower layer solder resist 3 The upper layer solder resist 4 is formed by using the two layers, and the lower layer solder resist 3 and the upper layer solder resist 4 are laminated in this order to form the photocurable solder resist layer 5. By doing in this way, in the exposure / development process of the photocurable solder resist layer 5, reliable exposure to the upper solder resist 4 having higher light transmittance than the lower solder resist 3 made of a colored photocurable solder resist. Of course, the lower layer solder resist 3 having a low light transmission can be irradiated with sufficient light through the upper layer solder resist 4 so that the lower layer solder resist 3 can be exposed to light in a short time. It is possible to cure sufficiently and reliably. At the same time, the overall film thickness t of the photocurable solder resist layer 5 can be ensured by setting the film thickness t2 of the upper solder resist 4 to a thickness of 5 μm or more. Even if the film thickness t1 of the resist 3 is reduced to such a thickness that pattern formation defects such as undercuts do not occur, the overall durability and reliability of the photocurable solder resist layer 5 are ensured. It becomes possible.
That is, according to the printed wiring board and the manufacturing method thereof according to the embodiment of the present invention, productivity, durability, and reliability in a printed wiring board using a colored photo-curable solder resist such as black or dark color system. It is possible to achieve both compatibility.

  A printed wiring board as described in the above embodiment was manufactured, and its durability and reliability were experimentally confirmed. In addition, for comparison with that, a printed wiring board is manufactured with settings that are different from the settings described in the above embodiment, and the durability and reliability of the same experiment as in the case of the example is performed. The experimental results of the comparative example and the example were compared and examined. Table 1 summarizes the settings and types of these printed wiring boards.

(Example)
As the insulating base material 1, Upicel (registered trademark) made by Ube Industries with a thickness of 25 μm was used. As a copper foil (conductor layer) for forming the wiring 2, an electrolytic copper foil SQ-VLP made of Mitsui Metals having a thickness of 18 μm was used. Also, a black lower layer solder resist 3 and a transparent upper layer solder resist 4 are prepared using a photo-curing solder resist manufactured by Asahi Chemical Co., Ltd., and the lower layer solder resist 3 is applied to the surface of the insulating substrate 1 by a printing method. The upper solder resist 4 was applied in this order. The film thickness t1 of the lower solder resist 3 was 5 μm (≦ 10 μm; desirable numerical mode). Further, the film thickness t2 of the upper solder resist 4 was set to 10 μm (≧ 5 μm; desirable numerical mode).
The printed wiring board according to the present example manufactured in such a setting is ² at 500 mJ / cm ² .
Even with a small amount of light and a short exposure of 0 second, pattern formation defects such as undercuts do not occur around the opening 6 of the photocurable solder resist layer 5, and the pads 2b and the wiring 2a and the photocurable solder It was confirmed that the adhesion with the resist layer 5 was also good. Furthermore, when a THB test was carried out, it was proved that it had durability and reliability of 1000 hours or more.

(Comparative example)
For comparison with the printed wiring board according to the embodiment of the present invention as described above and the manufacturing method thereof, the case where the film thickness t1 of the black lower layer solder resist 3 is thicker than 10 μm and the transparent upper layer solder resist 4 Also in the case where the film thickness t2 of the film was made thinner than 5 μm, a printed wiring board was produced for each of them and the same experiment as described above was performed.
As a result, when the film thickness t1 of the black lower layer solder resist 3 is thicker than 10 μm, the exposure around the opening 6 after development is performed with a small amount of light and short exposure similar to the case of the printed wiring board according to the above embodiment. Undercut pattern formation defects and the like frequently occur, and it becomes impossible to ensure the adhesion between the wiring layer 2 and the photocurable solder resist layer 5. In addition, as shown in Table 1, when the photocurable solder resist layer 5 is made of a black photocurable solder resist and has a film thickness of t = 15 μm, the amount of light is twice that of the example. Even if the exposure time is set to 1000 mJ / cm ² and the exposure time is 40 seconds which is twice that of the embodiment, undercut pattern formation defects frequently occur around the opening 6 after the exposure / development. It becomes impossible to secure the adhesion between the photocurable solder resist layer 5 and the photocurable solder resist layer 5.
If the film thickness t2 of the transparent upper layer solder resist 4 is made thinner than 5 μm, the total of the upper layer solder resist 4 and the lower layer solder resist 3 having a thickness of 5 μm (that is, the entire photocurable solder resist layer 5). It was confirmed that the film thickness t becomes too thin, and the durability / reliability of 1000 hours cannot be secured in the THB test.

  Considering the experimental results of the comparative example and the experimental results of the example of the present invention, the adhesion between the wiring layer 2 and the photocurable solder resist layer 5 is ensured in a short exposure time, and the productivity is improved. In order to achieve both durability and reliability, it has been found that it is desirable that the black lower layer solder resist 3 be 10 μm or less and that the film thickness of the transparent upper layer solder resist 4 be 5 μm or more.

  In the above-described embodiment, the case where a black photocurable solder resist is used as the lower layer solder resist 3 has been described. However, the so-called color is not limited to black. In addition, as a background of white printing, such as dark brown or dark gray, for example, a photocurable solder resist having a color tone that can improve the visibility of the printing is used. The present invention can also be applied to the case where it is used.

It is a figure which shows the main structures of the printed wiring board which concerns on embodiment of this invention. It is a figure which shows the flow of the main processes of the manufacturing method of the printed wiring board which concerns on embodiment of this invention. It is a figure which shows an example of the main flows of the formation process of the black photocurable soldering resist layer in the conventional printed wiring board and its manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating base material 2 Wiring layer 3 Lower layer solder resist 4 Upper layer solder resist 5 Photocurable solder resist layer 6 Opening part

Claims (8)

A printed wiring board having a wiring layer formed by forming a metal or conductor wiring on the surface of an insulating substrate, and a photo-curable solder resist layer for protecting the wiring,
The photo-curing solder resist layer has a colored photo-curing solder resist as a lower layer solder resist, and the transparent material or the light-curing wavelength region of the colored photo-curing solder resist is transparent to the light. A photo-curing type solder resist made of a material higher than the type solder resist is used as an upper layer solder resist, and the lower layer solder resist and the upper layer solder resist are laminated on the wiring layer in this order. Printed wiring board. The printed wiring board according to claim 1,
The printed wiring board, wherein the lower layer solder resist is made of a black photocurable solder resist. In the printed wiring board according to claim 1 or 2,
The film thickness of the lower layer solder resist is 10 μm or less,
And the film thickness of the said upper layer solder resist is 5 micrometers or more, The printed wiring board characterized by the above-mentioned. Printed wiring having a step of forming a wiring layer having a wiring of a desired pattern made of a metal or a conductor on the surface of an insulating substrate, and a step of forming a photocurable solder resist layer for protecting the wiring A method of manufacturing a board,
After forming the wiring layer, as a lower layer solder resist, a step of applying or depositing a colored photocurable solder resist;
On the lower layer solder resist, as an upper layer solder resist, a light made of a transparent material or a material having higher transparency to light in the curing wavelength region of the colored photocurable solder resist than the colored photocurable solder resist. Applying or depositing a curable solder resist; and
Forming a photocurable solder resist layer formed by laminating the upper layer solder resist and the lower layer solder resist by performing pattern processing by exposure on the upper layer solder resist and the lower layer solder resist. A method for producing a printed wiring board. In the manufacturing method of the printed wiring board of Claim 4,
A method for producing a printed wiring board, wherein a black photocurable solder resist is used as the lower layer solder resist. In the manufacturing method of the printed wiring board of Claim 4 or 5,
The film thickness of the lower layer solder resist is 10 μm or less,
And the film thickness of the said upper layer solder resist shall be 5 micrometers or more, The manufacturing method of the printed wiring board characterized by the above-mentioned. In the manufacturing method of the printed wiring board as described in any one of Claims 4 thru | or 6,
After forming the upper layer solder resist on the lower layer solder resist, the lower layer solder resist and the upper layer solder resist are simultaneously subjected to collective exposure to form a photocurable solder resist layer having a desired pattern. A printed wiring board manufacturing method characterized by the above. In the manufacturing method of the printed wiring board as described in any one of Claims 4 thru | or 7,
A method for producing a printed wiring board, wherein the upper layer solder resist and the lower layer solder resist are applied by a screen printing method or a roll coating method.

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