JP3716613B2 - Printed wiring board and manufacturing method thereof - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a printed wiring board and a method for manufacturing the same, and more particularly to a method for removing smear generated when a via hole is drilled.
[0002]
[Prior art]
In recent years, methods for forming via holes in printed wiring boards by laser irradiation have been developed. Specifically, as shown in FIG. 6, first, a metal foil 93 is attached to the surface of the insulating substrate 95, and an opening 933 is formed in advance in the via hole forming portion by etching.
[0003]
Next, a laser is irradiated into the opening hole 933, and the via hole forming portion of the insulating substrate 95 is burned off by the high energy. Then, when the laser reaches the metal foil 93 that forms the bottom, the laser irradiation is stopped and the formation of the via hole 96 is completed. Next, a metal plating film 97 is formed inside the via hole 96 to impart electrical conductivity to the via hole 96.
Thereafter, when the metal foil 93 is etched to form the conductor patterns 931 and 932, a printed wiring board is obtained.
[0004]
[Problems to be solved]
However, in the conventional via hole forming method by laser irradiation, the residue 94 of the insulating substrate 95 remains inside the via hole 96 as shown in FIG. This residue 94 prevents formation of the metal plating film 97 in the via hole 96 as shown in FIG. Further, the adhesion between the metal foil 93 and the metal plating film 97 is lowered. Therefore, the conduction reliability of the via hole 96 is lowered.
[0005]
Therefore, in order to remove the residue 94 in the via hole 96, a desmear process is performed in the via hole 96.
However, when the desmear treatment is insufficient, the residue may not be removed sufficiently. As a result, the via hole conduction reliability is still not sufficient.
[0006]
In view of the conventional problems, the present invention intends to provide a printed wiring board having high via hole conduction reliability and a method for manufacturing the same.
[0007]
[Means for solving problems]
For convenience of explanation, the reference invention will be described first.
The first printed wiring board manufacturing method according to the reference invention includes a step of forming a blackened layer on the metal foil,
Adhering the metal foil to the bottom of the via hole forming portion of the insulating substrate with the blackening layer facing,
Irradiating the via hole forming portion of the insulating substrate with a laser to form a via hole having the metal foil as a bottom;
Applying desmear treatment to the metal foil exposed at the bottom of the via hole;
Performing a soft etching with a dissolution removal thickness of 0.1 to 2 μm on the metal foil exposed at the bottom of the via hole;
Confirming that there is no blackened layer on the metal foil surface at the bottom of the via hole;
Forming a metal plating film inside the via hole without the blackening layer;
A method of manufacturing a printed wiring board, comprising: forming a conductive pattern by etching the metal foil.
[0008]
What should be noted most in the reference invention is that a blackened layer is formed on the surface of the metal foil facing the insulating substrate to place the blackened layer at the bottom of the via hole, and after the desmear treatment is performed inside the via hole. Soft etching is performed to remove the blackened layer on the surface of the metal foil.
[0009]
The desmear treatment removes the insulating substrate remaining inside the via hole. However, if the desmear treatment is insufficient and the residue remains on the metal foil at the bottom of the via hole, the surface of the metal foil is not etched by soft etching. , The blackened layer of the residue adhesion will remain. By inspecting the presence or absence of the remaining blackened layer, it is possible to inspect whether the residue is attached to the bottom of the via hole. By forming a metal plating film, which is a subsequent process, with no residue, the metal plating film adheres firmly to the bottom of the via hole, and a printed wiring board with high conduction reliability of the via hole can be obtained.
[0010]
On the other hand, if the blackened layer remains after the soft etching due to the residue in the via hole, it is regarded as a defective product at the time of inspection, and the via hole is again desmeared or discarded. If a defective product is not subjected to desmear treatment inside the via hole and a subsequent metal plating film is formed, the residue interferes with the adhesion and conductivity between the metal foil and the metal plating film, and the conduction reliability of the via hole decreases. There are things to do.
[0011]
Further, since the via hole is formed by a laser, it can be formed into a minute hole. Therefore, high-density mounting of the insulating substrate can be realized.
Furthermore, since the blackened layer is formed on the surface of the metal foil facing the insulating substrate, the adhesion between the metal foil and the insulating substrate is high. Therefore, the conductor pattern formed by etching the metal foil has excellent adhesion to the insulating substrate.
[0012]
For example, a copper foil is used as the metal foil.
As the insulating substrate, for example, a glass epoxy substrate, a glass polyimide substrate, a glass bismaleimide triazine substrate or the like is used.
The insulating substrate may have a conductor pattern of one layer or two or more layers formed therein in advance.
The blackening layer is a black layer formed on a metal foil by a blackening treatment using a chemical such as a sodium phosphate solution.
[0013]
Desmear treatment is a chemical treatment that dissolves and removes the residue in the via hole by immersing the insulating substrate in which the via hole is formed in a solution of concentrated sulfuric acid, chromic acid or a mixed acid thereof, or sodium permanganate or potassium permanganate. Say the law.
[0014]
Soft etching means that the metal foil surface exposed at the bottom of the via hole is slightly dissolved and removed by a chemical reaction. The thickness of the metal foil dissolved and removed by soft etching is 0 . Oh Ru in 1~2μ m. If the thickness is less than 0.1 μm, there may be a portion where the blackened layer on the surface of the metal foil cannot be removed even if there is no residue on the surface of the metal foil, and the presence or absence of the residue may not be accurately determined. is there. On the other hand, if it exceeds 2 μm, the process cost of soft etching may be increased.
[0015]
The metal plating film is formed in the via hole by chemical plating. It is preferable to further perform electroplating after chemical plating. Thereby, a metal plating film can be formed in a film thickness, and the electrical conductivity of the via hole is improved. The metal plating film is made of a metal such as copper, nickel, or gold.
[0016]
Before forming the blackening layer, it is preferable to subject the surface of the metal foil facing the insulating substrate to a roughening treatment. The surface of the metal foil becomes a roughened surface by the roughening treatment. When the metal foil and the insulating substrate are bonded, the insulating substrate material bites into the roughened surface, and the adhesion between the metal foil and the insulating substrate is enhanced. Therefore, the conductor pattern is more firmly bonded to the insulating substrate.
[0017]
In addition, the surface of the metal foil exposed at the bottom of the via hole becomes a roughened surface, and the adhesion to the metal plating film is enhanced.
Roughening treatment refers to treatment in which the surface of the metal foil is roughened, and specific examples include physical treatment such as jet scrub and chemical treatment. Although the concept of chemical processing may include blackening processing, in the present invention, chemical processing does not include blackening processing.
[0018]
Next, a method for manufacturing a printed wiring board according to the present invention includes a step of attaching a metal foil to the bottom of a via hole forming portion in an insulating substrate,
Irradiating the via hole forming portion of the insulating substrate with a laser to form a via hole having the metal foil as a bottom;
Applying desmear treatment to the metal foil exposed at the bottom of the via hole;
Forming a nickel plated luster layer on the metal foil exposed at the bottom of the via hole;
A step of confirming that a gloss layer is uniformly formed on the metal foil surface at the bottom of the via hole;
Forming a metal plating film inside the via hole;
A method of manufacturing a printed wiring board, comprising: forming a conductive pattern by etching the metal foil.
[0019]
The manufacturing method of the present invention is different from the manufacturing method of the above reference invention in that a via hole is formed on an insulating substrate and a desmear treatment is performed, and then a nickel plating gloss layer is formed on the metal foil exposed at the bottom. To do.
[0020]
In the manufacturing method of the present invention , when all of the residue of the insulating substrate is removed after the desmear treatment inside the via hole, a gloss layer of nickel plating is uniformly formed on the entire surface of the metal foil exposed at the bottom of the via hole, Uniform gloss. On the other hand, if it remains, a glossy layer is not formed on the remaining adhered portion, and the entire bottom portion emits uneven gloss.
[0021]
Therefore, by inspecting the glossy state of the bottom of the via hole, it is possible to inspect whether or not the insulating substrate remains on the bottom. That is, when the residue does not remain, the entire bottom portion emits a uniform gloss, and when the residue remains, it generates a non-uniform gloss.
[0022]
Therefore, post-process soft etching and metal plating film formation are performed on an insulating substrate having a via hole with a uniform gloss at the bottom. Thereby, the adhesiveness of the metal foil and metal plating film of a via-hole bottom part improves, and the printed wiring board which has a via hole with high conduction | electrical_connection reliability can be obtained.
[0023]
On the other hand, an insulating substrate having a via hole that emits uneven gloss at the bottom is regarded as a defective product at the time of inspection, as described in the first manufacturing method, and no subsequent process is performed.
[0024]
In addition, since the via hole is formed by laser irradiation, it can be formed minutely. Therefore, high-density mounting of printed wiring boards can be realized.
Next, according to the above reference invention, the manufacturing method of the present invention comprises an insulating substrate, a conductor pattern formed on the surface of the insulating substrate, and a via hole penetrating the insulating substrate and having the conductor pattern at the bottom, and Help printed wiring board glossy layer of nickel plating is formed on the bottom of the via hole are obtained.
[0025]
This printed wiring board has high adhesion to an insulating substrate because a blackened layer is formed on the surface of the conductor pattern. Further, the same effect as described in the above manufacturing method can be exhibited.
[0026]
The blackened layer is preferably formed on the roughened surface of the insulating substrate. This is because the material of the insulating substrate bites into the roughened surface of the conductor pattern, so that it is firmly bonded.
Others are the same as the manufacturing method described above.
In addition, you may laminate | stack the conductor pattern of 1 layer or 2 layers or more on the surface of the printed wiring board of this invention.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 (Reference Example)
For convenience of explanation, first, an embodiment according to the reference invention will be described.
A printed wiring board and a manufacturing method thereof according to an embodiment of the reference invention will be described with reference to FIGS.
As shown in FIG. 3 (j), the printed wiring board of this example has an insulating substrate 5, conductor patterns 31 and 32 formed on the surface of the insulating substrate 5, and the conductive pattern 32 penetrating through the insulating substrate 5. Via hole 6 to be made. The blackened layer 1 is formed on the surface of the conductor patterns 31 and 32 on the side bonded to the insulating substrate 5. The blackened layer 1 is formed on the roughened surface 2 of the insulating substrate 5.
[0028]
Next, a method for manufacturing a printed wiring board will be described.
First, as shown in FIG. 1A, a roughening process is performed on the surface of the metal foil 3 on the side facing the insulating substrate 5 to form a roughened surface 2. As the metal foil 3, a copper foil is used. The size of the metal foil 3 is approximately the same as that of an insulating substrate described later.
[0029]
Next, the blackened layer 1 is formed on the roughened surface 2 of the metal foil 3.
Next, as shown in FIG. 1B, a prepreg made of B-stage epoxy resin and glass cloth is prepared as the insulating substrate 5, and the metal foil 3 is laminated on both surfaces of the insulating substrate 5.
Next, as shown in FIG. 1C, the laminated insulating substrate 5 and metal foil 3 are thermocompression bonded. At this time, the blackened layer 1 faces the portion of the metal foil 3 that becomes the opening of the via hole.
[0030]
Next, as shown in FIG. 1D, etching is performed on the metal foil 3 on the laser irradiation side, that is, on the upper side, and an opening hole 33 is formed in a portion covering the via hole forming portion 63 in the metal foil 3. On the other hand, on the opposite side of the laser irradiation side, that is, the lower metal foil 3, no opening hole is formed in the portion covering the via hole forming portion 63.
[0031]
Next, as shown in FIG. 2 (e), the opening hole 33 of the upper metal foil 3 is irradiated with the laser 8 to make a hole in the via hole forming portion 63 of the insulating substrate 5. The drilling by the laser stops at the surface of the metal foil 3 covering the bottom of the via hole forming portion. As a result, a via hole 6 having the bottom metal foil 3 as a bottom is formed.
[0032]
Next, as shown in FIG. 2 (f), desmear treatment is performed on the metal foil 3 exposed at the bottom of the via hole 6. The desmear process is performed by immersing the insulating substrate 5 in a permanganate solution. As a result, as shown in FIG. 2F1, the residue 4 of the insulating substrate 5 adhered in the via hole 6 is removed. On the other hand, when the desmear process is insufficient, the residue 4 remains in the via hole 6 as shown in FIG.
[0033]
Next, as shown in FIG. 2G, the metal foil 3 exposed at the bottom of the via hole 6 is soft etched. As a result, as shown in FIG. 2 (g1), the blackened layer is removed from the surface of the metal foil 3 exposed at the bottom of the via hole 6. On the other hand, as shown in FIG. 2 (g2), when the residue of the insulating substrate remains, the blackened layer 1 in the portion where the residue 4 is adhered is not removed.
[0034]
Next, as shown in FIG. 2H, it is confirmed that there is no blackened layer on the surface of the metal foil 3 at the bottom of the via hole 6. Specifically, it is inspected by an optical means such as a microscope whether a blackened layer remains at the bottom of the via hole.
[0035]
Next, as shown in FIG. 3I, a metal plating process is performed on the insulating substrate 5 (FIG. 2G1) in which the blackened layer does not remain at the bottom of the via hole. Specifically, chemical copper plating and electrolytic copper plating are performed on the entire surface of the metal foil 3 including the inside of the via hole 6 to form the metal plating film 7.
[0036]
Next, as shown in FIG. 3 (j), the metal foil 3 on the surface of the insulating substrate 5 is etched to form conductor patterns 31 and 32.
Thus, a printed wiring board is obtained.
[0037]
On the other hand, as shown in FIG. 2 (g2), the blackened layer 1 remaining after the soft etching due to the residue 4 in the via hole is regarded as a defective product at the time of inspection, and desmear treatment is again performed in the via hole or discarded. . If a defective product is not subjected to desmear treatment inside the via hole and a subsequent metal plating film is formed, the residue interferes with the adhesion and conductivity between the metal foil and the metal plating film, reducing the conduction reliability of the via hole. There are things to do.
[0038]
Next, the operation and effect of this example will be described.
In this example, the blackened layer 1 is formed on the bottom of the via hole 6 by forming the blackened layer 1 on the surface of the metal foil 3 facing the insulating substrate 5 (FIG. 2E), and the inside of the via hole 6 After being subjected to desmear treatment (FIG. 2 (f)), soft etching is performed to remove the blackened layer on the surface of the metal foil (FIG. 2 (g)).
[0039]
By the desmear process, the insulating substrate remaining in the via hole is removed, and by performing soft etching, the blackened layer 1 on the surface of the metal foil 3 at the bottom of the via hole 5 is removed by performing soft etching as shown in FIG. .
However, when the desmear treatment is insufficient and the residue remains on the metal foil at the bottom of the via hole, the blackened layer 1 on the surface of the metal foil 3 is not etched by the soft etching as shown in FIG. The blackened layer 1 of the part to which 4 adheres remains.
[0040]
Therefore, as shown in FIG. 2 (h), it is possible to inspect whether or not the residue is attached to the bottom of the via hole by inspecting the presence or absence of the remaining blackened layer.
Then, as shown in FIG. 3 (i), by forming a metal plating film 7 as a subsequent process on the insulating substrate having no residue at the bottom of the via hole, the metal plating film 7 is firmly adhered to the bottom of the via hole 6 and the via hole 6 A printed wiring board having high conduction reliability can be obtained.
[0041]
Further, since the via hole is formed by a laser, it can be formed into a minute hole. Therefore, high-density mounting of the insulating substrate can be realized.
Further, as shown in FIG. 3 (j), since the blackening layer 1 is formed on the surface of the metal foil 3 on the side facing the insulating substrate 5, the adhesion between the metal foil 3 and the insulating substrate 5 is high. Therefore, the conductor patterns 31 and 32 formed by etching the metal foil 3 have excellent adhesion to the insulating substrate 5.
[0042]
Further, as shown in FIG. 1A, the surface of the metal foil 3 on the side facing the insulating substrate 5 is roughened. For this reason, when the metal foil 3 and the insulating substrate 5 are bonded, the material of the insulating substrate 5 bites into the roughened surface 2 and the adhesiveness between the metal foil 3 and the insulating substrate 5 is increased. Therefore, as shown in FIG. 3 (j), the conductor patterns 31 and 32 are more firmly bonded to the insulating substrate 5.
[0043]
Embodiment 2 ( Embodiment of the present invention)
The method for manufacturing a printed wiring board of the present invention is shown in FIGS. 4 (e) and 4 (f) instead of forming a blackened layer on the metal foil in advance before sticking as in Embodiment 1 (reference invention) . After forming the via hole 6 and performing the desmear treatment, as shown in FIG. 4G, a nickel-plated gloss layer 10 (hereinafter abbreviated as the gloss layer 10) is formed on the metal foil 3 exposed at the bottom. Yes.
[0044]
That is, first, a roughened surface is formed on the surface of the metal foil opposite to the side facing the insulating substrate. Next, without forming a blackened layer on the roughened surface, a metal foil is laminated on the upper and lower surfaces of the insulating substrate and thermocompression bonded to form an opening in a portion covering the via hole forming portion (FIG. 1A ) To FIG. 1 (d)).
[0045]
Next, as shown in FIG. 4E, the insulating substrate 5 exposed in the opening 33 of the metal foil 3 is irradiated with a laser 8 to form a via hole 6 having the metal foil 3 as a bottom.
Next, desmear processing is performed as shown in FIG. As a result, as shown in FIG. 4F1, the residue of the insulating substrate attached to the bottom of the via hole 6 is removed. On the other hand, if the desmear process is insufficient, a residue 4 remains at the bottom of the via hole 6 as shown in FIG.
[0046]
Next, as shown in FIG. 4G, the gloss layer 10 is formed at the bottom of the via hole 6. At this time, the gloss layer 10 is uniformly formed in the via hole 6 from which the residue is removed, as shown in FIG. 4 (G1). On the other hand, when the residue 4 remains, the gloss layer 10 is formed unevenly as shown in FIG. 4 (G2).
[0047]
Next, as shown in FIG. 5H, the formation state of the gloss layer in the via hole is inspected by an optical means such as a microscope. As shown in FIG. 4G1, when the gloss layer is uniformly formed, uniform gloss is emitted. On the other hand, as shown in FIG. 4 (G2), when the gloss layer is formed non-uniformly, non-uniform gloss is emitted.
[0048]
Next, as shown in FIG. 5I, the insulating substrate is subjected to chemical copper plating and electrolytic copper plating to form a metal plating film 7 inside the via hole. Thereafter, as shown in FIG. 5 (j), the metal foil 3 is etched to form a conductor pattern (see FIG. 3 (j)). A printed wiring board is obtained as described above.
[0049]
In this example, when all of the residue of the insulating substrate is removed after the desmear process inside the via hole as shown in FIG. 4 (f1), the metal foil exposed at the bottom of the via hole 6 as shown in FIG. 4 (G1). The gloss layer 10 is uniformly formed on the entire surface. On the other hand, when the residue 4 remains as shown in FIG. 4 (f2), the gloss layer 10 is not formed on the adhesion portion of the residue 4 remaining at the bottom of the via hole 6 as shown in FIG. 4 (G2).
[0050]
Therefore, as shown in FIG. 5H, it is possible to inspect whether or not the insulating substrate remains on the bottom by inspecting the glossy state of the bottom of the via hole 6. That is, when the residue does not remain, the entire bottom portion emits a uniform gloss, and when the residue remains, it generates a non-uniform gloss.
[0051]
Then, a post-process metal plating film formation (FIG. 5I) is performed on the insulating substrate 5 having the via hole 6 that emits a uniform gloss at the bottom. Thereby, the adhesiveness of the metal foil 3 and the metal plating film 7 of the bottom part of the via hole 6 improves, and the printed wiring board which has the via hole 6 with high conduction | electrical_connection reliability can be obtained.
[0052]
On the other hand, an insulating substrate having a via hole that emits uneven gloss at the bottom is regarded as a defective product at the time of inspection, as described in the first manufacturing method, and no subsequent process is performed.
[0053]
In addition, since the via hole is formed by laser irradiation, it can be formed minutely. Therefore, high-density mounting of printed wiring boards can be realized.
[0054]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the printed wiring board with high conduction | electrical_connection reliability of a via hole, and its manufacturing method can be provided.
[Brief description of the drawings]
FIG. 1 shows a roughening treatment and blackening layer formation (a), lamination (b), thermocompression bonding (c), and opening hole formation (d) on a metal foil in the manufacturing method of Embodiment 1 according to the reference invention . Explanatory drawing which shows the method of performing.
FIG. 2 is an explanatory diagram showing a method for performing via hole formation (e), desmear treatment (f), soft etching (g), and inspection for presence / absence of a glossy layer (h) following FIG. 1; Description of the insulating substrate (f1) from which the residue is removed, the insulating substrate (f2) from which the residue is left, the insulating substrate (g1) from which the blackened layer is removed by soft etching, and the insulating substrate (g2) from which the blackened layer remains Figure.
FIG. 3 is an explanatory diagram showing a method for performing plating treatment (i) and pattern formation (j) following FIG. 2;
FIG. 4 shows insulation in which the residue of the insulating substrate is removed by via hole formation (e), desmear treatment (f), gloss layer formation (G), and desmear treatment in the manufacturing method according to the second embodiment of the present invention . Explanatory drawing of the board | substrate (f1), the insulation board | substrate (f2) with which the residue remained, the insulation board | substrate (G1) in which the glossy layer was formed uniformly, and the insulation board | substrate (G2) in which it formed unevenly.
FIG. 5 is an explanatory diagram showing a method for performing a glossy layer inspection (h), plating treatment (i), and pattern formation (j) following FIG. 4;
FIG. 6 is a cross-sectional view of a printed wiring board in a conventional example.
FIG. 7 is an explanatory diagram for illustrating a problem in a conventional example.
[Explanation of symbols]
1. . . Blackening layer,
10. . . Glossy layer,
2. . . Roughened surface,
3. . . Metal foil,
31, 32. . . Conductor pattern,
33. . . Aperture,
4). . . The rest,
5. . . Insulating substrate,
6). . . Beer hall,
63. . . Via hole formation part,
7. . . Metal plating film,
8). . . laser,

Claims (2)

Attaching a metal foil to the bottom of the via hole forming part of the insulating substrate;
Irradiating the via hole forming portion of the insulating substrate with a laser to form a via hole having the metal foil as a bottom;
Applying desmear treatment to the metal foil exposed at the bottom of the via hole;
Forming a nickel plated luster layer on the metal foil exposed at the bottom of the via hole;
A step of confirming that a gloss layer is uniformly formed on the metal foil surface at the bottom of the via hole;
Forming a metal plating film inside the via hole;
A method of manufacturing a printed wiring board, comprising: forming a conductor pattern by etching the metal foil. The method for manufacturing a printed wiring board according to claim 1, wherein the metal foil has a roughened surface on a surface of the metal foil facing the insulating substrate.

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