JP2004266230A - Circuit board and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a circuit board manufacturing method which can make fine conductor patterns when an inexpensive and convenient subtractive method is used for circuit board manufacturing. <P>SOLUTION: Half-etching is performed for a metal layer (2) formed on the surface of an insulating substrate (1) through a first mask made of a resist (4) not sublimable by laser irradiation, and a second mask (20) made of a resist sublimable by laser is applied to cover the upper surface of the first mask and the half-etched surface. The surface covered by the second mask (20) is irradiated with laser for the sublimation of the second mask (20), with the unsublimated part of the second mask (20) in the shadow of the first mask retained as a protective film (22). A conductor pattern is formed on the metal layer (2) by etching through the first mask and through the resist on the protective layer, and then the first mask and the protective layer are peeled off. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit board and a method for manufacturing the same, and more particularly, to a method for manufacturing a circuit board for forming a conductive pattern on an insulating base material by a subtractive method and a circuit board manufactured by the method.
[0002]
[Prior art]
When manufacturing a circuit board, the subtractive method is an inexpensive and simple method and has been most widely used conventionally. On the other hand, there is a disadvantage in that a finer conductor pattern on a circuit board is obtained with the recent increase in density and miniaturization of semiconductor devices and various electronic devices.
[0003]
FIGS. 1A to 1D are cross-sectional views showing steps of manufacturing a circuit board by a conventional subtractive method, and show steps of forming a conductive pattern on a resin base material by etching. First, as shown in FIG. 1A, a substrate material 3 in which a copper foil 2 is adhered to a resin base material 1 is prepared, and then, as shown in FIG. A resist 4 is formed by forming a dry film resist (DFR) or applying a liquid resist on the surface of the resist 4 for masking, and exposing and developing the resist 4 by a known method to form a resist pattern. 4b is formed. Next, as shown in FIG. 1C, an etching solution is sprayed to dissolve portions of the copper foil 2 other than the portions where the resist patterns are formed, leaving the copper pattern portions. Then, as shown in FIG. 1D, by removing the resist pattern 4b, the remaining copper foil portion becomes the conductor pattern 5.
[0004]
However, according to the above-described conventional method for manufacturing a circuit board, as shown in FIG. 1C, the cross-sectional shape of the conductor pattern 5 is changed to the lower side, that is, the side of the interface 6 between the resin substrate 1 and the copper foil 2. With respect to the pattern width (b), the width (a) on the upper side on which the resist is formed tends to be a small trapezoidal shape. This is because the etching solution is applied to the portion immediately below the masking 4 during the progress of the etching. In particular, the interface 6 between the resin substrate 1 and the copper foil 2 generally has minute irregularities as shown in the figure, and it takes time to sufficiently apply the etching solution to the interface 6 of the irregularities. This is because the etchant is applied to the portion immediately below the masking 4 as described above.
[0005]
For this reason, if it is attempted to reduce the width of the pattern 5 itself or the pitch (c) between adjacent patterns, it becomes difficult to secure a sufficient width, particularly on the upper side of the pattern 5 distant from the resin substrate 1. After all, it has been difficult to achieve miniaturization.
[0006]
In order to solve such a problem, in Patent Documents 1 to 4 shown as prior art, when manufacturing a circuit board such as a printed board, first, after a layer to be etched is half-etched, heating and heating of a resist layer are performed. By performing a process such as softening, the side-etched portion of the layer to be etched is covered with the softened resist layer, and then the layer to be etched is etched again, thereby preventing further etching of the side-etched portion, and There has been proposed a method of forming a stable pattern having a small difference in the pattern width between the top and bottom of the pattern.
[0007]
[Patent Document 1]
JP-A-63-153889 [Patent Document 2]
JP-A-5-327179 [Patent Document 3]
JP 2001-94234 A [Patent Document 4]
JP-A-2002-246726
[Problems to be solved by the invention]
According to the method for manufacturing a circuit board disclosed in Patent Documents 1 to 4, a stable pattern having a small difference in pattern width between the top and bottom of a conductor pattern can be formed, but both sides of a resin plate can be formed. It has been extremely difficult to simultaneously and easily form a conductor pattern on the formed metal layer, or to continuously perform each step of manufacturing a circuit board by a simple process.
[0009]
Therefore, in the present invention, in the case of manufacturing a circuit board, an inexpensive and simple subtractive method is used, and even in that case, a circuit board manufacturing method capable of achieving finer conductive patterns, It is an object to obtain a circuit board manufactured by such a method.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a first masking made of a resist that does not sublimate by laser light irradiation or has a sublimation rate lower than the second masking is applied to a metal layer formed on the surface of an insulating base material. A step of applying a half-etching through a first masking step, and a step of applying a resist as a second masking that can be sublimated by laser light irradiation on the entire surface including the upper surface of the first masking and the surface of the half-etched portion; The surface coated with the resist as the second mask is irradiated with a laser beam to sublimate the second masking in the laser beam irradiation area, while the unmasked second masking portion in the projection area of the first masking is removed. Leaving a protective film and etching the first masking and the resist of the protective layer through the resist to form a conductive pattern on the metal layer. Forming, said a step of removing the resist of the first masking and protective layer, the manufacturing method of the circuit board, characterized in that it consists of is provided.
[0011]
The resist which is not sublimated by laser beam irradiation or has a sublimation speed lower than the second masking as the first masking is a dry film resist. Further, the resist as the second mask that can be sublimated by irradiation with laser light is a liquid resist or an electrodeposition resist.
[0012]
When a metal layer is formed on both surfaces of the insulating base material, at least one of the above-described steps may be simultaneously performed for each of the metal layers on both surfaces. However, laser light irradiation cannot be performed on both surfaces simultaneously.
[0013]
Further, according to the present invention, the metal layer formed on the surface of the insulating base material is subjected to half etching through a first masking made of a resist that does not sublimate by laser beam irradiation or has a sublimation speed lower than the second masking, A resist as a second maskable sublimable by laser light irradiation is applied to the entire surface including the upper surface of the first mask and the surface of the half-etched portion, and a laser is applied to the surface coated with the resist as the second mask. Irradiating light to sublimate the second masking in the laser light irradiation area, while leaving the unmasked portion of the second masking in the projection area of the first masking as a protective film, and performing the first masking and the protection. Etching is performed through the layer resist to form a conductor pattern on the metal layer, and the first masking and protection layer are patterned. Circuit board formed by peeling off the strike is provided.
[0014]
Still further, according to the present invention, a step of performing half-etching via the first masking on each of the metal layers formed on both surfaces of the insulating base material, and a step of applying a positive-type liquid to the half-etched surface from above the first masking Applying a resist, exposing and developing from the upper part of the first masking to protect the positive liquid resist under the first masking; and forming a resist comprising the first masking and the protected positive liquid resist. 2 etching the metal layer again through masking;
Removing the first masking and the second masking.
[0015]
The exposure of the positive type liquid resist from above the first masking is performed with parallel light in a direction perpendicular to the first masking surface of the circuit board. Further, each of the steps is simultaneously performed on each of the metal layers formed on both surfaces of the insulating base material.
[0016]
Furthermore, according to the present invention, each of the metal layers formed on both surfaces of the insulating base material is subjected to half-etching via the first masking, and a positive liquid resist is applied to the half-etched surface from above the first masking. Coating, exposing from above the first masking and developing to protect the positive liquid resist under the first mask, and through the first mask and the second mask made of the protected positive liquid resist There is provided a circuit board having a metal pattern on a surface of the insulating base material, wherein the metal layer is etched again and the first masking and the second masking are removed. In this case, the insulating base material is flexible and is configured as a TAB tape.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0018]
FIGS. 2A to 2F are sectional views showing the steps of manufacturing the circuit board according to the first embodiment of the present invention using the subtractive method.
[0019]
FIG. 2A shows a state in which a copper foil 2 is formed on a resin base material 1 by a known method to form a substrate material 3. As the resin substrate 1, an epoxy resin or a glass / epoxy resin is generally used.
[0020]
Next, in FIG. 2B, a dry film resist (DFR) is formed as a first masking 4 on the upper surface of the copper foil, and is exposed and developed by a known method to form a resist pattern 4b.
[0021]
Next, in FIG. 2C, half etching is performed by spraying an etching solution toward the first masking 4 of the resist pattern. By this half-etching, the peripheral region of the copper foil 2 below the etching solution passage portion 4a of the first masking 4 of the copper foil 2 is dissolved. Then, the half-etching conditions (etching time, injection pressure, injection amount, etc.) are adjusted so that the dissolving portion 11 of the copper foil 2 leaves a desired width above the pattern 17.
[0022]
As a result, as shown in the figure, in the upper portion of the copper foil 2 close to the first resist pattern 4b, the dissolved portion 11 of the copper foil 2 is larger than the width (d) of the etching solution passage portion 4a of the resist pattern. And the width (e) of the melted portion 11 is larger than the resist pattern interval (d), and is halfway between the upper portion of the copper foil 2 and the interface 6 in contact with the resin substrate 1. In the region, a groove 11 which is rounded and has a substantially U-shaped cross section as a whole is formed.
[0023]
Next, in FIG. 2D, a positive-type liquid resist 12 is applied to the entire surface of the portion subjected to the half-etching in the previous step. In this state, the entire surface of the portion to which the positive type liquid resist 12 is applied is exposed with the parallel light 13. As described above, the light 13 used for exposure is desirably a parallel light irradiated toward the first resist pattern 4b in a direction orthogonal to the surface of the first masking 4 of the circuit board. When the light beam reaches the inside of the resist 12 in a deep range, the light beam does not necessarily need to be parallel light.
[0024]
By this exposure step, the portion of the positive type liquid resist 12 exposed to the light, that is, the region portion 12a above the first resist pattern 4b of the positive type liquid resist 12 and the etching liquid passage portion 4a of the first masking 4b The area portion 12b immediately below is exposed. In other words, the lower region of the first resist pattern 4b, which is a region 12c that is slightly bitten into the inside of the copper foil 2 from the distance (d) between the resist patterns during the half-etching in the previous process, is dissolved. Will remain unexposed. In addition, as a method of forming the resist of the second masking 12, positive electrodeposition (Electro-Deposition) in which a resist is adhered only to a portion where a metal exists may be used.
[0025]
In this embodiment, two photosensitive resists constituting the first masking and the second masking, that is, the dry film resist 4 and the positive type liquid resist or the positive type electrodeposition resist 12 are used. It is necessary to appropriately combine the photosensitive wavelength of the photosensitive resist with the exposure wavelength to be used. For this reason, for example, the wavelength of the parallel light 13 for exposing the positive-type liquid resist or the positive-type electrodeposition resist 12 is absorbed by the positive-type liquid resist or the positive-type electrodeposition resist 12. A resist having a wavelength that does not pass through or hardly passes through the resist 4 is selected.
[0026]
Next, in FIG. 2E, by developing the exposed portions 12a and 12b of the positive type liquid resist 12, only the exposed portions 12a and 12b of the positive type liquid resist are dissolved. Therefore, the dissolved portions 12a and 12b of the positive type liquid resist 12 can be removed. The undissolved portion 12c of the positive type liquid resist 12 remains as it is, and the above-mentioned substantially U-shaped groove 11 becomes a groove 14 having inner walls on both sides parallel to each other. Can be used as a mask pattern (second masking) in the next step.
[0027]
Next, secondary etching is performed using the dry film resist (first masking) 4 on the surface of the copper foil 2 and the remaining portion 12c (second masking) of the positive type liquid resist as a mask pattern. As a result, the copper foil portion 15 below the parallel groove 14 is melted, and the melted portion reaches the interface 6 where the copper foil 2 and the resin substrate 1 are in contact.
[0028]
Next, the dry film resist 4 and the remaining positive liquid resist 12c are removed.
[0029]
As a result, as shown in FIG. 2 (f), a dharma-shaped groove 16 having a narrow width at the center in the depth direction and a circular cross section bulging at the upper and lower portions is formed. That is, as for the conductor pattern 17, the difference between the width (g) of the portion having the smallest width and the width (h) of the largest portion in the sectional shape is different from the sectional shape of the conductor pattern as in the conventional example shown in FIG. Is much smaller than the width difference (ba) in the case where is a trapezoid, so that the pitch (c) between adjacent patterns can be narrowed, and miniaturization of a circuit board can be achieved. Can be. Further, the width (g) of the pattern can be made much wider than the width (a) when formed by a conventional method.
[0030]
The circuit board described and illustrated in FIGS. 2A to 2F has the copper foil 2 formed on one surface of the resin substrate 1, but the copper foil 2 is formed on both surfaces of the resin substrate 1. The same applies to the formed substrate. Further, in this case, the above-described processing steps can be simultaneously performed on the copper foils formed on both sides, and a circuit pattern can be formed at the same time, and both of the circuit patterns formed on both sides have upper and lower cross-sectional shapes. The difference in width can be reduced.
[0031]
FIGS. 3A to 3G are sectional views showing the steps of manufacturing a circuit board according to the second embodiment of the present invention using a subtractive method.
[0032]
The steps of FIGS. 3A to 3C are the same as the steps of the first embodiment shown in FIGS. 2A to 2C, and half etching is performed in the same manner. Note that the dry film resist (DFR) as the first masking 4 needs to be a resist that does not sublime by laser light irradiation in any of the first and second embodiments.
[0033]
In FIG. 3D, covering the entire surface of the portion subjected to the half-etching in the previous process, that is, the entire surface including the upper surface of the resist pattern portion 4b of the first masking 4 and the surface of the groove 11 formed by the half-etching. A second resist 20 having characteristics, that is, sublimable by irradiating a laser beam, is applied. Therefore, the second resist 20 is also applied to the side of the groove formed by the half-etching, that is, the side-etched portion in the projection area below the first masking 4. The second resist 20 is a liquid resist or an electrodeposition resist, but need not be a photosensitive resist. As described above, since the second resist 20 does not need to be photosensitive, selection of a material for the resist is wide and easy. Needless to say, the adhesiveness and peelability of the resist are necessary.
Next, in this state, as shown in FIG. 3E, the entire surface of the region where the second resist 20 is applied is irradiated with the laser beam 21. The second resist 20 excluding the region below the first resist pattern 4b is ablated (sublimated) by the irradiation of the laser beam 21. For this reason, the second resist 20 in the region below the first resist pattern 4b is left as the protective layer 22 in the depressed portion as the side etching region in the half etching.
[0034]
Next, in FIG. 3 (f), the dry film resist (first masking pattern) 4b on the surface of the copper foil 2 and the non-sublimated protective layer 22 (second masking) of the second resist are used as mask patterns, A second etching is performed. As a result, the copper foil portion 15 below the groove 14 is melted, and the melted portion reaches the interface 6 where the copper foil 2 and the resin substrate 1 come into contact.
[0035]
Next, the dry film resist (first masking) 4b and the unsublimated protective layer 22 of the second resist are peeled off.
[0036]
As a result, as shown in FIG. 3 (g), a Dharma-shaped groove 16 having a narrow width at the center in the depth direction and a circular cross-section at the upper and lower parts is formed. That is, as for the conductor pattern 17, the difference between the width (g) of the portion having the smallest width and the width (h) of the largest portion in the sectional shape is different from the sectional shape of the conductor pattern as in the conventional example shown in FIG. Is much smaller than the width difference (ba) in the case where is a trapezoid, so that the pitch (c) between adjacent patterns can be narrowed, and miniaturization of a circuit board can be achieved. Can be.
[0037]
In the second embodiment shown in FIGS. 3 (a) to 3 (g), in the case where the copper foil is formed on the upper and lower surfaces of the insulating base material 1, the respective processes are simultaneously performed on both surfaces, and the circuit is simultaneously performed. Patterns can also be formed.
[0038]
Although the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments, and various forms, modifications, modifications, and the like are included within the spirit and scope of the present invention. Is possible.
[0039]
For example, in the above embodiment, the case where the conductor pattern is formed on the surface of the resin base material 1 has been described. However, the present invention uses the resin base material as shown in FIG. A tab tape (TAB-TAPE) can be manufactured by manufacturing a lead frame from the metal plate 2 without using it, or by using a flexible resin base material. As described above, the present invention is applicable to any circuit board product manufactured by the subtractive method.
[0040]
【The invention's effect】
As described above, according to the present invention, the pitch of the conductor pattern on the circuit board can be reduced. Further, the upper width of the conductor pattern can be secured, and the difference between the pattern width near the upper portion and the pattern width near the lower portion can be reduced. Furthermore, the subtractive method can be applied to a circuit board having a thick conductor pattern. Further, in the present invention, a material that does not require photosensitivity can be used as the second resist, so that the material of the resist can be easily selected.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a circuit board manufactured by a conventional subtractive method.
FIG. 2 is a cross-sectional view showing a manufacturing process of the circuit board according to the first embodiment of the present invention by a subtractive method.
FIG. 3 is a cross-sectional view illustrating a process of manufacturing a circuit board according to a second embodiment of the present invention by a subtractive method.
FIG. 4 is a cross-sectional view illustrating a step of manufacturing a circuit board according to a third embodiment of the present invention by a subtractive method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Resin base material 2 ... Copper foil 3 ... Substrate material 4 ... Resist pattern 4b ... First masking pattern 11 ... U-shaped groove 12 ... Second masking (positive liquid resist)
12c second masking 13 parallel light 14 parallel groove 15 secondary etching 16 copper pattern 20 resist 21 serving as second masking laser light 22 protection layer

Claims (11)

A step of subjecting the metal layer formed on the surface of the insulating base material to half-etching via first masking made of a resist that does not sublimate by laser beam irradiation or has a sublimation rate lower than the second masking,
Applying a second masking made of a resist that can be sublimated by irradiation of a laser beam on the entire surface including the upper surface of the first masking and the surface of the half-etched portion;
The surface coated with the resist as the second masking is irradiated with laser light to sublimate the second masking in the laser light irradiation area, while the non-sublimated portion of the second masking in the projection area of the first masking Leaving as a protective film,
Performing etching through the first masking and the resist of the protective layer to form a conductor pattern on the metal layer;
Removing the first masking and the resist of the protective layer. 2. The method according to claim 1, wherein the first masking is made of a resist that does not sublimate by irradiation with a laser beam. 3. The method according to claim 1, wherein the resist as the first masking is a dry film resist. 4. The method according to claim 1, wherein the resist as the second mask that can be sublimated by irradiation with a laser beam is a liquid resist or an electrodeposition resist. 5. The circuit board according to any one of claims 1 to 4, wherein at least one of the steps is simultaneously performed for each of metal layers formed on both surfaces of the insulating base material. Production method. The metal layer formed on the surface of the insulating base material is subjected to half-etching via a first mask made of a resist that does not sublimate by laser beam irradiation or has a sublimation speed lower than that of the second mask, and an upper surface and a half of the first mask are formed. A second masking made of a resist that can be sublimated by irradiation with laser light is applied to the entire surface including the surface of the etched portion, and the surface to which the second masking has been applied is irradiated with laser light to form a laser light irradiation area. Sublimating the second masking, while leaving the portion of the second masking that is not sublimated in the projection area of the first masking as a protective film, performing etching through the resist of the first masking and the protective layer, A circuit board formed by forming a conductor pattern on the metal layer and removing the resist of the first masking and protection layer. A step of subjecting each of the metal layers formed on both surfaces of the insulating base material to half etching via the first masking;
Applying a positive liquid resist to the half-etched surface from above the first mask, exposing and developing from above the first mask to protect the positive liquid resist below the first mask; ,
Etching the metal layer again via the first masking and a second masking made of the protected positive liquid resist;
Removing the first masking and the second masking. 8. The circuit board according to claim 7, wherein the exposure of the positive liquid resist from above the first masking is performed by parallel light in a direction perpendicular to the first masking surface of the circuit board. Manufacturing method. 9. The method according to claim 7, wherein each of the steps is simultaneously performed on each of the metal layers formed on both surfaces of the insulating base material. Each of the metal layers formed on both surfaces of the insulating base material is subjected to half-etching via a first masking, a positive type liquid resist is applied to the half-etched surface from above the first masking, and the first masking is performed. By exposing and developing from above, the positive type liquid resist under the first masking is protected, and the metal layer is etched again through the first masking and the second masking made of the protected positive type liquid resist. And a circuit board having a metal pattern on a surface of the insulating base material, wherein the first masking and the second masking are removed. The circuit board according to claim 6, wherein the insulating base is flexible and configured as a TAB tape.

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