JP3185345B2 - Printed circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a printed circuit board for circuit configuration incorporated in various electronic devices, and more particularly to a method of manufacturing a so-called double-sided printed circuit board.

[0002]

2. Description of the Related Art Conventionally, for example, a television receiver,
2. Description of the Related Art In various electronic devices such as a radio receiver, a printed circuit board on which a predetermined wiring circuit is formed is frequently used for mounting electronic components and the like. In recent years, the performance and miniaturization of various electronic devices have been advanced, and it is necessary to accommodate a large number of wirings inside the electronic devices in a compact manner. In the printed circuit board as described above, wiring circuits are formed on both sides of the base material. In order to increase the density of the wiring circuit, this is supported.

A so-called double-sided printed circuit board in which wiring circuits are formed on both sides of a substrate as described above is manufactured, for example, according to the following method.

[0004] First, a copper foil is laminated on both sides of an insulating base material, an etching resist is formed thereon in accordance with a desired wiring pattern, and thereafter, etching is performed to leave a copper foil corresponding to the wiring pattern. . After forming wiring circuits on both sides of the base material as described above, apply a photocurable solder resist on one side, expose and develop through a mask according to a predetermined pattern, develop and cure, and then cure the other A similar process is applied to the surface of the substrate to form a solder resist layer, and the components are mounted by soldering to obtain a printed circuit board.

[0005] The solder resist layer is an insulating film formed to prevent unnecessary portions from being soldered when components are soldered to a printed wiring by an immersion method. This solder resist layer has an effect of protecting the wiring circuit from disconnection and contamination as well as solder resistance, and is indispensable for forming a highly reliable printed circuit board.

[0006]

However, in order to manufacture a double-sided printed circuit board by the above-described manufacturing method,
After forming the wiring circuit on the base material, it is necessary to repeat the process of applying the solder resist → exposure → development twice,
The process is long and takes time. In addition, since the installation place of the device needs to be large, the manufacturing cost is high and the productivity is not good. Therefore, it is advantageous from the viewpoint of mass productivity and manufacturing cost if a soldering resist is applied to both sides after forming a wiring circuit on the base material and development is performed after both sides are exposed at the same time or both sides are continuously exposed. Conceivable. If manufacturing is performed by this manufacturing method, the steps of coating, exposing, and developing a solder resist may be performed only once, and the manufacturing time can be shortened and the installation place of the apparatus can be reduced, so that the manufacturing cost can be reduced. It is possible to improve productivity.

However, after a wiring circuit is formed on the above-mentioned base material, a solder resist is applied to both sides,
When exposure is performed simultaneously on both sides or continuously on both sides, the following problems occur. For example, on a printed circuit board as described above, a component mounting recognition mark for performing alignment when mounting components is formed. This mark is formed by forming an independent copper pattern (for example, a circle) on a base material, and has a portion around which a solder resist layer is not formed. When mounting components on a printed circuit board, the printed circuit board is irradiated with light, the shape of the copper pattern is recognized based on the difference in reflectance and transmittance between the base material and the copper pattern, the position is confirmed, and the component is placed on the printed circuit board. To be mounted at a predetermined position.

As described above, a portion where a solder resist layer is not formed is required around the copper pattern of the component mounting recognition mark on the printed circuit board. It is necessary to form a solder resist layer. However, after forming a wiring circuit on the base material, applying solder resist on both sides and performing exposure simultaneously on both sides or continuously on both sides, the solder resist layer also surrounds the copper pattern of the component mounting recognition mark. As a result, the shape of the copper pattern cannot be recognized and its position cannot be confirmed accurately, and the positional accuracy when mounting the component cannot be maintained.

That is, as shown in FIG. 16, solder resists 3a and 4a are applied to both surfaces of a substrate 1 of a printed circuit board, and a copper pattern 2 is formed on a surface on which a copper pattern 2 is to be formed.
The portion corresponding to the portion where the solder resist layer does not need to be formed around the mask 5 is a light shielding portion 6, and the other surface is provided only on the portion of the wiring pattern (not shown) which does not need to be soldered. Exposure is performed with the mask 11 having the following. At this time, as shown in FIG. 16, the light irradiated on the surface on which the copper pattern 2 is formed as indicated by an arrow A in the figure is transmitted through the transmission part 5 a of the mask 5,
The solder resist 3a is hardened, transmits through the substrate 1 as shown by the dotted line, and is reflected at the light shielding portion 6. On the other hand, the light irradiated on the other surface indicated by the arrow B in the figure does not have a light-shielding portion at a position corresponding to the periphery of the copper pattern 2 forming portion of the mask 11, so that the light is entirely transmitted to cure the solder resist 4a. Let it. However, the light irradiated on the other surface indicated by arrow B in the figure is
After curing, the substrate 1 is also transmitted and reaches the solder resist 3a on the surface on which the copper pattern 2 is to be formed, as shown by the dotted line, and the mask 5 of the solder resist 3a is formed.
The unshielded portion which is shielded by the arrangement of the light shielding portion 6 is hardened from the back surface. Therefore, as shown in FIG. 17, the solder resist layer 3b is also formed around the copper pattern 2 of the component mounting recognition mark. As a result, the shape of the copper pattern 2 cannot be recognized and its position cannot be confirmed accurately, and a problem has arisen that the positional accuracy when mounting the component cannot be maintained.

A portion of the printed circuit board on which the copper pattern of the component mounting recognition mark on which the copper pattern is formed, which does not require the formation of a solder resist layer, is prevented from being cured from the back surface by the light irradiated on the other surface. In order to reduce the amount of light applied to the other surface, it is conceivable to prevent the light applied to the other surface from reaching the surface on which the copper pattern is formed. This is inappropriate because the formed solder resist layer cannot be sufficiently cured.

Accordingly, the present invention has been proposed in view of such circumstances, and it is possible to reliably recognize the shape of a copper pattern of a component mounting recognition mark and confirm its position, and to provide a component on a printed circuit board. It is possible to manufacture a printed circuit board that can improve the positional accuracy when mounting a semiconductor device, and reduce the time required for manufacturing and the place for installing the manufacturing apparatus by shortening the process, thereby reducing the manufacturing cost. It is an object of the present invention to provide a method for manufacturing a printed circuit board that can improve productivity.

[0012]

In order to achieve the above object, a method of manufacturing a printed circuit board according to the present invention comprises applying a photocurable solder resist to both surfaces of a substrate on which a wiring circuit made of a copper pattern is formed. When exposing the resist layers formed on both sides of these base materials through respective masks and performing photo-curing, it is not necessary to form a solder resist layer around the copper pattern on one side of the base material. The mask used for exposing the other surface of the substrate corresponding to the portion is provided with a portion having a relatively lower transmitted light amount than the other portion.

Further, in the above-described method of manufacturing a printed circuit board, a portion where the transmitted light amount is relatively low has a transmitted light amount of 5 to 80% of another portion.

[0014]

In the present invention, after a wiring circuit composed of a copper pattern is formed, a photocurable solder resist is applied to both sides of the base material, and both sides are exposed simultaneously or sequentially through a mask. When performing photo-curing, one side of the base material corresponds to a part where the solder resist layer around the copper pattern of the component mounting recognition mark does not need to be formed, and the other mask is interposed on the other side. Is provided, the light irradiated on the other surface does not reach the surface on which the copper pattern of the component mounting recognition mark is formed. The part of the solder resist that does not need to form a solder resist layer around the copper pattern is not photo-cured.

[0015]

EXAMPLES Specific examples to which the present invention is applied will be specifically described below based on experimental results.

First, a method of manufacturing a printed circuit board according to this embodiment will be described. First, a wiring pattern and a copper pattern of a component mounting recognition mark are formed. Laminate copper foil on both sides of the base material, form an etching resist on this in accordance with the desired wiring pattern, perform an etching treatment on this, remove the etching resist, and paste the copper foil with a predetermined wiring pattern. The copper pattern 2 of the component mounting recognition mark is formed on the substrate 1 as shown in FIG.

The material of the substrate 1 is not particularly limited as long as it is used for a normal printed circuit board. For example, the substrate 1 is produced by impregnating or coating a paper with a phenol resin or the like. Further, the etching resist may be patterned by a normal photolithography technique, and the copper foil may be etched by a normal method such as wet etching or dry etching.

Next, scrub polishing was performed, and a solid photo-curable solder resist was printed on one surface of the substrate 1 as a solder resist 3a as shown in FIG. 2 using a screen, and the surface was semi-cured. Thereafter, the solder resist 4a is similarly solid-printed on the opposite surface, and the surface is semi-cured. As the solder resists 3a and 4a, any ones may be used as long as they are photo-curable and used for manufacturing a normal printed circuit board, and include ink-like and dry film-like ones.

Thereafter, as shown in FIG. 3, a mask 5 having a light-shielding portion 6 is applied to the surface on which the copper pattern 2 is to be formed at a position corresponding to the periphery of the copper pattern 2 forming portion, and the other surface is provided with a copper A mask 7 having a transmission light amount reducing portion 8 which is a portion having a transmission light amount relatively lower than other portions is applied to a position corresponding to the periphery of the pattern 2 forming portion, exposed, and then developed. Each of the masks 5 and 7 has a light-shielding portion (not shown) in a portion of each of the corresponding surfaces which does not require soldering in a predetermined wiring circuit.

At this time, the amount of transmitted light, which is a portion where the amount of transmitted light is relatively low as compared with other portions formed at positions corresponding to the periphery of the copper pattern 2 forming portion of the mask 7 applied to the other surface, is reduced. The transmitted light amount of the part 8 is 5 to 8 of the other parts.
It is preferably 0%. If the transmitted light amount of the transmitted light amount reducing portion 8 is lower than 5% of the other portions, the light amount is too small and the solder resist 4a on the surface cannot be cured. Further, if the transmitted light amount of the transmitted light amount reducing portion 8 is higher than 80% of the other portions, the light amount is too large, and the solder resist 3a on the surface on which the copper pattern 2 is formed is also cured.

The mask 7 applied to the other surface as described above
FIG. 4 shows that the transmitted light amount of the transmitted light amount reducing portion 8 formed at a position corresponding to the periphery of the copper pattern 2 forming portion is within the above-described range.
As shown in FIG. 3, light emitted from the other surface indicated by the arrow B in the figure is transmitted through the transmitting portion 7a of the mask 7, and after the solder resist 4a is cured, the light is applied to the base as indicated by the dotted line. The light transmitted through the material 1 but transmitted through the transmitted light reduction portion 8 does not reach the surface on which the copper pattern 2 is formed as indicated by the dotted line. Further, the light irradiated on the surface on which the copper pattern 2 is formed, which is indicated by an arrow A in the figure, is transmitted through the transmitting portion 5a of the mask 5, and after the solder resist 3a is cured, as shown by a dotted line. The light is transmitted through the base material 1, but is reflected at the light shielding portion 6.

The masks 5 and 7 as described above may be used as long as they are commonly used. For example, a photosensitive sheet is used, and a solder resist layer to be formed on the sheet by exposure and development is used. An opening corresponding to the pattern may be formed. At this time, the transmitted light amount reducing unit 8, which is a portion where the transmitted light amount is relatively low as compared with the other portions formed on the mask 7, adds or subtracts light and shade to the portion corresponding to the transmitted light amount reducing unit 8 of the mask 7. It may be formed by arranging fine dots smaller than the resolution of the photosensitive sheet.
As shown in FIG. 5, the light irradiated on the other surface indicated by the arrow B in the figure passes through the transmitted light amount reducing portion 8 and then scatters in the solder resist 4a. Even in the case where fine dots are formed on the substrate 8, the same effect as when the amount of transmitted light is uniformly reduced can be obtained. In addition, as fine dots, 100 μm
It is preferable that a light-shielding portion of m or more cannot be formed. If a light-shielding portion of 100 μm or more is present in the transmitted light amount reducing portion 8, a portion that is shielded from light is formed in the solder resist 4 a at a position corresponding to the transmitted light amount reducing portion 8, and a portion that is not sufficiently cured is formed.

In the printed circuit board manufactured by such a manufacturing method, as shown in FIG. 6, the solder resist layer 3b is not formed around the copper pattern 2 of the component mounting recognition mark. 7, the periphery of the copper pattern 2 is formed by the base material 1 as shown in FIG.

Therefore, a printed circuit board was manufactured using the above-described manufacturing method. First, as a solder resist, a photo-cured solder resist SR-
Manufacture was performed using 4000. After the wiring pattern and the copper pattern of the component mounting recognition mark were formed on the base material by the above-described manufacturing method, the solder resist was solid-printed and semi-cured to prepare four sheets.

With respect to one of these, the surface on which the copper pattern is to be formed is placed on the other surface through a portion of the wiring circuit which does not need to be soldered and a mask having a light shielding portion around the copper pattern forming portion. After exposing a portion of the wiring circuit that does not need to be soldered through a mask that has a light-shielding portion and a portion that reduces the amount of transmitted light at a position corresponding to the periphery of the copper pattern forming portion, develop and form a solder resist layer Example 1
And At this time, dots having a diameter of 25 μm were arranged in the transmission light amount reduction portion, and the average transmission light amount was set to 20% of the other portions. In the first embodiment, no solder resist layer is formed around the copper pattern of the component mounting recognition mark.
Problems such as poor appearance and poor adhesion did not occur in the solder resist layer at the position corresponding to the transmitted light amount reduced portion on the other surface.

Next, on two of these, the same pattern as that of the first embodiment is applied to the surface on which the copper pattern is formed, and to the other surface, the portion of the wiring circuit that does not require soldering. After exposure with a normal light amount and a light amount of 50% of the normal light amount through a mask having a light-shielding portion, development was performed, and the former was referred to as Comparative Example 1 and the latter as Comparative Example 2. In Comparative Example 1,
Since the solder resist layer is also formed around the copper pattern of the component mounting recognition mark, it is difficult to recognize the shape and position of the copper pattern. In Comparative Example 2, the solder at the position corresponding to the transmitted light amount reduction portion was used. The adhesion of the resist layer was not good, and it could not be used as a product.

Next, on the other one of the sheets, the same mask as in the first embodiment is applied to the surface on which the copper pattern is formed, and to the surface where the copper pattern is not formed, soldering in the wiring circuit is required. The exposed portion was exposed to light through a mask having a portion for reducing the amount of transmitted light at a position corresponding to the periphery of the light-shielding portion and the copper pattern forming portion, and then developed to form a solder resist layer. At this time, a dot having a diameter of 200 μm was arranged in the transmitted light amount decreasing portion, and the average transmitted light amount was set to 50% of the other portions. In Comparative Example 3, a solder resist layer was not formed around the copper pattern of the component mounting recognition mark, but a crater-like depression was generated in the solder resist layer at a position corresponding to the transmitted light amount reduction portion on the other surface. Then, poor appearance occurred.

Next, after the wiring pattern of the printed circuit board and the copper pattern of the component mounting recognition mark are formed, the solder resist to be applied is coated with DRD-220 manufactured by Tamura Kaken.
The printed circuit board was manufactured by changing to 0. After forming a wiring pattern and a copper pattern of a component mounting recognition mark on a base material, two pieces of the above solder resist were solid-printed and semi-cured.

Thereafter, the surface on which the copper pattern is to be formed is provided with the same mask as in the first embodiment, and the surface on which the copper pattern is not to be provided is a light-shielding portion in a portion of the wiring circuit which does not require soldering. After exposing through a mask having a transmission light amount reducing portion at a position corresponding to the periphery of the copper pattern forming portion, development was performed to form a solder resist layer. At this time, the average transmitted light amount of the transmitted light amount decreasing portion is 70% of that of the other portions.
The former was used as Example 2 and the latter as Comparative Example 3. In Example 2, the solder resist layer was not formed around the copper pattern forming portion of the component mounting recognition mark, so that the shape of the copper pattern could be recognized and the position could be confirmed without fail. In addition, there were no problems such as poor appearance or poor adhesion of the solder resist layer at a position corresponding to the transmitted light amount reduced portion on the other surface. In Comparative Example 3, the solder resist layer on the back surface of the component mounting recognition mark was not sufficiently cured by light, and was partially damaged in the developing step, and was not usable.

Further, after the wiring pattern of the printed circuit board and the copper pattern of the component mounting recognition mark were formed, the solder resist to be applied was changed to a dry film type manufactured by Dynachem to manufacture the printed circuit board. After forming the wiring pattern and the copper pattern of the component mounting recognition mark on the base material, the above solder resist is solid printed,
A semi-cured one was prepared.

Thereafter, after exposing through the same mask as in Example 1, development was performed to obtain a printed circuit board. In Example 3, no solder resist layer was formed around the copper pattern forming portion of the component mounting recognition mark, so that the shape of the copper pattern could be recognized and the position could be reliably confirmed. In addition, there were no problems such as poor appearance or poor adhesion of the solder resist layer at a position corresponding to the transmitted light amount reduced portion on the other surface.

Further, when the solder resist is photo-cured, the amount of transmitted light is smaller than that of a transmission portion disposed on a position corresponding to the periphery of the copper pattern forming portion of the mask on the surface where the copper pattern of the component mounting recognition mark is not formed. The printed circuit board was manufactured by changing the shape of the light shielding portion of the transmitted light amount decreasing portion, which is a relatively low portion.

After forming the wiring pattern of the printed circuit board and the copper pattern of the component mounting recognition mark in the same manner as in the first embodiment, scrub polishing is performed, and a solid solder resist is printed in the same manner as in the first embodiment. 8
I prepared it.

On the surface on which the copper pattern is to be formed, a mask similar to that in the first embodiment is used. On the surface on which the copper pattern is not to be formed, a light-shielding portion is provided on a portion of the wiring circuit which does not require soldering. After exposing through a mask having a transmitted light amount decreasing portion at a position corresponding to the periphery of the copper pattern forming portion, development was performed to form a solder resist layer. At this time, the transmitted light amount decreasing portion has a circular shape as shown in FIG. 8, a square as shown in FIG. 9, a stripe as shown in FIG. 10, a lattice as shown in FIG. , A shape obtained by combining a circle and a rectangle as shown in FIG. 13, a shape in which the center of the square is hollowed out as shown in FIG. 13, a broken stripe as shown in FIG. 14, and a concentric shape as shown in FIG. 15 , And the average amount of transmitted light in the reduced portion of transmitted light was set to 20% of the other portions, and the obtained printed circuit boards were used as Examples 4 to 11.

In the printed circuit boards of Examples 4 to 11 thus obtained, no solder resist layer is formed around the copper pattern forming portion of the component mounting recognition mark, and the shape of the copper pattern is recognized. And the position could be confirmed without fail. In addition, there were no problems such as poor appearance or poor adhesion of the solder resist layer at a position corresponding to the transmitted light amount reduced portion on the other surface.

In the embodiments described so far, when the solder resist is light-cured, a light-shielding portion such as a dot is provided as a portion for reducing the amount of transmitted light of the mask to be applied to the surface of the component mounting recognition mark where the copper pattern is not formed. However, it can also be formed by other methods.

For example, the thickness of the mask is partially increased, another type of mask is overlapped, only that portion is replaced with another type of mask, the material of the portion is exposed, heated,
The same effects as those of the masks of the first to fourth embodiments can be obtained by a technique such as altering the quality by chemical treatment or shading, or physically roughening the portion.

[0038]

As is clear from the above description, in the present invention, a photocurable solder resist is applied to both sides of a substrate on which a wiring circuit composed of a copper pattern is formed, and one side of the substrate is coated. When the resist layer formed on the substrate is exposed to light through a mask and photo-cured, it corresponds to a portion of the other surface of the substrate where a copper pattern is not formed and a solder resist layer does not need to be formed. The mask has a portion where the transmitted light amount is relatively lower than other portions,
Further, since the transmitted light amount of the portion where the transmitted light amount is relatively low is 5 to 80% of that of the other portion, the solder resist layer is formed around the copper pattern of the component mounting recognition mark on the printed circuit board. Therefore, since the shape of the copper pattern can be recognized and the position can be reliably confirmed, the positional accuracy when mounting the component on the printed circuit board is improved. Further, since the steps are shortened, the time required for manufacturing can be shortened, and the place where the manufacturing apparatus is installed can be reduced, so that manufacturing costs can be reduced and productivity can be improved. it can.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a principal part showing an example of a method of manufacturing a printed circuit board to which the present invention is applied in the order of steps, and showing a step of forming a component mounting copper pattern.

FIG. 2 is a schematic cross-sectional view of a main part showing a step of forming a solder resist.

FIG. 3 is a schematic cross-sectional view of a main part showing a step of exposing a solder resist.

FIG. 4 is a schematic view showing a light transmission state in a solder resist exposure step.

FIG. 5 is an enlarged schematic diagram showing a light transmission state in a solder resist exposing step.

FIG. 6 is a cross-sectional view of a printed circuit board manufactured by a method for manufacturing a printed circuit board to which the present invention is applied.

FIG. 7 is a plan view of a printed circuit board manufactured by a method of manufacturing a printed circuit board to which the present invention is applied.

FIG. 8 is a diagram illustrating an example of a transmitted light amount reducing section of a mask.

FIG. 9 is a diagram showing another example of the transmitted light amount reducing portion of the mask.

FIG. 10 is a diagram showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 11 is a diagram showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 12 is a diagram showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 13 is a view showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 14 is a diagram showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 15 is a diagram showing still another example of the transmitted light amount reducing portion of the mask.

FIG. 16 is a schematic diagram showing a light transmitting state in a conventional printed circuit board manufacturing method.

FIG. 17 is a cross-sectional view illustrating an example of a printed circuit board manufactured by a conventional method for manufacturing a printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Copper pattern 3a, 4a ... Solder resist 3b, 4b ... Solder resist layer 5, 7, 11 ... Mask 5a, 7a... Transmissive part 6... Light-shielding part 8.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Taisuke Watanabe 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 3 / 28

Claims (3)

(57) [Claims] 1. A photocurable solder resist was applied to both sides of the copper wiring circuit consisting pattern formed substrate, this
Mask the resist layers formed on both sides of
When exposing through a solder and photo-curing, the solder resist around the copper pattern on one side of the substrate
For areas where it is not necessary to form a strike layer,
The mask used when exposing one side is better than the other
A method for manufacturing a printed circuit board, comprising providing a portion having a relatively low transmitted light amount . 2. The method for manufacturing a printed circuit board according to claim 1, wherein the transmitted light amount in a portion where the transmitted light amount is relatively low is 5 to 80% of the other portions. 3. The method according to claim 1, wherein the copper pattern is a pattern of a component mounting recognition mark.