JPH11214848A - Printed wiring board and method of manufacturing printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board, and a production method thereof, which can deal with multilayer structure by filling paste as designed while avoiding damage on the insulating basic material side and flattening the surface surely. SOLUTION: Trough holes 2a, 2b are made through a glass epoxy board 1 and filled with conductive paste 3a, 3b before the surface is flattened. A protective films 4, 5 are provided in the surface regions of the glass epoxy board 1 where the conductive paste 3a, 3b is not present. The protective films 4, 5 are flush with the smooth surface of the conductive paste 3a, 3b and protect the glass epoxy board 1 at the time of polishing the conductive paste 3a, 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open Nos. 5-1297981 and 7-30255 disclose a printed circuit board having wiring on both sides of a substrate and electrically connected through through holes for through holes. In order to increase the wiring density and increase the reliability of the electrical connection, after the first wiring is formed on the substrate, a hole is made, a conductive paste is filled, and the substrate is planarized by polishing.

[0003] This will be described in detail with reference to FIGS. 19, an insulating substrate 51 having a plating layer 50 on both surfaces is prepared as shown in FIG. 19A, a through hole 52 is provided as shown in FIG. 19B, and a through hole 52 is provided as shown in FIG. 52 is filled with a conductive paste 53,
After smoothing by polishing as shown in (d) and forming a plating layer 54 as shown in (e), a wiring pattern 55 is formed by photoetching as shown in (f), (g) and (h). ,
After the insulating film 56 is formed as shown in (i), the conductor 57 is arranged as shown in (j).

In FIG. 20, an insulating substrate 61 having plating layers 60 on both surfaces is prepared as shown in FIG. 20A, and through holes 62a and 62b for through holes are provided as shown in FIG.
A plating layer 63 is formed on the inner walls of the through holes 62a and 62b as shown in FIG. 3C, and the plating layers 60 and 63 are patterned as shown in FIG. The holes 62a and 62b are filled with a conductive paste 64 and covered with a resin film 65 as shown in FIG.
As shown in (g), the surface is smoothed by polishing, and a second wiring pattern 66 is formed as shown in (h) and (i).

[0005]

However, in the method of FIG. 19, unevenness is formed on the surface as shown in FIG. 21, which hinders multilayering. To avoid this, flattening by arranging the insulating film 70 as shown in FIG. 22 increases the number of steps.

In the method shown in FIG. 20, when the conductive paste 64 is filled in the through holes 62a and 62b, as shown in FIG.
The conductive paste 64 at the central portion of 2a, 62b easily has a depression 80, and the copper paste or less is not easily removed.
Therefore, as shown in FIG. 24, even when the insulating film 65 is arranged and flattened later, the dent 80 remains, and the connection by the wiring pattern 81 becomes a defective connection.
The occurrence of bleeding causes a leak between pastes and an increase in design dimensions.

The present invention has been made in view of the above-mentioned circumstances, and performs paste filling according to design dimensions while avoiding damage to the insulating base material side, and furthermore, ensures a flat surface to cope with multilayering. It is an object of the present invention to provide a printed wiring board and a method for manufacturing the printed wiring board that can be performed.

[0008]

According to a first aspect of the present invention, there is provided a printed wiring board in which a conductive paste is filled in through holes for through holes formed in an insulating base material and the surface thereof is smoothed. A protective film is disposed on the surface of the insulating base material in a region where there is no conductive paste, and the protective film is flush with the smooth surface of the conductive paste and protects the insulating base material during polishing of the conductive paste. It is characterized by having.

That is, during polishing of the conductive paste, the insulating base material is protected by the protective film. Therefore, according to the present invention, the insulating base material is not damaged by the presence of the protective film, and can be filled into the through hole for the through hole with high dimensional accuracy. In the method of FIG. 19, the number of steps is increased by arranging the insulating film 70 for planarization as shown in FIG. 22, but according to the present invention, the number of steps is increased without increasing the number of steps. Can be

The surface of the insulating base material thus flattened is multi-layered using the base material as a base material. At this time, in the method shown in FIG. 20, the conductive paste 64 may be easily formed with a dent 80 as shown in FIGS. 23 and 24, which may cause a connection failure. Since the portion is removed, the polishing can be performed deeper than the depression 80 of the conductive paste 64, and the conductive paste can be formed without the depression, so that the electrical connection can be reliably taken.

As described above, the surface can be reliably flattened while the insulating base material side is prevented from being damaged, and it is possible to cope with a multilayer structure.
Further, heat dissipation through the through holes is also improved. According to the method of manufacturing a printed wiring board according to the second aspect, the first
A protective film is formed on the surface of the insulating base material having no conductor on the surface by the step, a through hole for the through hole is formed in the insulating base by the second step, and a through hole for the through hole of the insulating base material is formed by the third step. The inside is filled with a conductive paste, and in a fourth step, the protective film is polished from the surface side of the insulating base material, and the outermost surface side of the insulating base material including the conductive paste is planarized. At this time, the insulating base material is protected by the protective film. Then, in the fifth step, a wiring pattern to the conductive paste in the through hole for the through hole is formed on the surface of the insulating base material.

Therefore, according to the present invention, the insulating base material is not damaged by the presence of the protective film. Further, in the method of FIG. 19, if the planarization is performed by disposing the insulating film 70 as shown in FIG. 22, the number of steps is increased. However, according to the present invention, the planarization is performed without increasing the number of steps. it can.

Further, in the method of FIG.
Although it is conceivable that the conductive paste 64 is easily formed with the dent 80 as in 3 and 24 and may cause a connection failure, according to the present invention, the dent of the conductive paste 64 is removed because a part of the protective film is removed. It can be polished deeper than 80, it can be made conductive paste without dents, it can ensure electrical connection,
Further, heat dissipation through the through holes is also improved.

Here, as in the invention described in claim 3,
When an interlayer insulating film is used as a protective film, by stacking layers having the same thermal properties, the thermal expansion coefficients are uniform, the effects of stress and the like due to heat are less likely to be adversely affected, the reliability is excellent, and the process design is facilitated. .

Further, when the fifth step is carried out by an additive method, fine wiring can be achieved. That is, in the conventional method shown in FIGS. 19 and 20, since the first wiring is a subtractive method, L (line) / S (space) is small (for example, 7 lines).
Although it is difficult to form a wiring pattern (less than 0 μm), in the present invention, the surface of the base material is flattened by the conductive paste in the through-hole and the protective film, and the first
Wiring can be formed by an additive method, fine wiring can be performed, and the number of layers can be reduced.

According to a fifth aspect of the present invention, the protective film is made of a material that can be peeled off, and after the outermost surface of the insulating base material is flattened in the fourth step, the protective film is removed. Is also good.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a printed wiring board according to the present embodiment. Through holes 2a and 2b for through holes are formed in a glass epoxy substrate 1 as an insulating base material. The diameter of the through holes 2a and 2b is about 0.3 mm. Through hole 2 for through hole
The conductive pastes 3a and 3b are filled in a and 2b, and the upper and lower surfaces of the conductive pastes 3a and 3b are smoothed. The conductive pastes 3a and 3b are not particularly limited as fillers such as Cu, Ag, Sn, or a mixture thereof. The binder is not particularly limited, but for example, an epoxy resin is used.

A protective film 4 is disposed in a region where the conductive pastes 3a and 3b do not exist on the upper surface of the glass / epoxy substrate 1, and the upper surface of the protective film 4 is flush with the smooth surfaces of the conductive pastes 3a and 3b. ing. Similarly, a protective film 5 is disposed in a region of the lower surface of the glass / epoxy substrate 1 where the conductive pastes 3a and 3b are not provided, and the surface of the protective film 5 is flush with the smooth surfaces of the conductive pastes 3a and 3b. ing.

Here, interlayer insulating films are used for the protective films 4 and 5. An interlayer insulating film 6 is formed on the upper surface side of the glass / epoxy substrate 1 (the surfaces of the conductive pastes 3a and 3b and the protective film 4), and photo via holes 7a and 7b are formed in predetermined regions. A conductor pattern (copper plating layer) 8 is formed on the interlayer insulating film 6, and is electrically connected to the conductive pastes 3a and 3b by the conductor pattern 8. The conductor pattern 8 is an interlayer insulating film 9
Are separated by Furthermore, an interlayer insulating film 1 is formed thereon.
0 is formed, and photo via holes 11a and 11b are formed in predetermined regions. A conductor pattern (copper plating layer) 12 is formed on the interlayer insulating film 10, and is electrically connected to the conductor pattern 8 by the conductor pattern 12.

Similarly, an interlayer insulating film 14 is formed on the lower surface side of the glass / epoxy substrate 1 (the surface of the conductive pastes 3a and 3b and the protective film 5), and photo via holes 15a and 15b are formed in predetermined regions. Is formed. The conductor pattern (copper plating layer) 1 is formed on the surface of the interlayer insulating film 14.
6 are formed, and are electrically connected to the conductive pastes 3a and 3b by the conductor pattern 16. The conductor pattern 16 is separated by an interlayer insulating film 17. Further, an interlayer insulating film 18 is formed on the surface, and photo via holes 19a and 19b are formed in predetermined regions. A conductor pattern (copper plating layer) 20 is formed on the surface of the interlayer insulating film 18.
Is electrically connected to the conductor pattern 16.

As described above, the glass whose surface is flattened by using the conductive pastes 3a and 3b and the protective films 4 and 5 is used.
The first wirings (8, 16) are formed on the epoxy substrate 1 and the second wirings (12, 20) are formed, and the epoxy wiring board 1 is multi-layered.

Next, a description will be given of a method of manufacturing the printed wiring board configured as described above. First, as shown in FIG. 2, a copper-clad laminate is prepared. That is, a substrate is prepared in which copper foils 21 and 22 are provided on the entire upper and lower surfaces of the glass epoxy substrate 1. Then, as shown in FIG. 3, the copper foils 21 and 22 on the surface are removed by etching.

Subsequently, as shown in FIG. 4, protective films 4 and 5 are formed on the upper and lower surfaces of the glass epoxy substrate 1. The use of the above-mentioned copper-clad laminate is for the purpose of using an anchor on an insulating substrate to achieve close contact with a protective film. The thickness of the protective films 4 and 5 is determined in consideration of resin shrinkage and the like this time. Then, the coating was performed with a thickness of about 40 μm.

Further, as shown in FIG. 5, a hole is formed in the glass / epoxy substrate 1 to form a through hole 2a for a through hole.
2b is formed. Then, as shown in FIG.
The conductive pastes 3a and 3b are filled in the through holes 2a and 2b of the epoxy substrate 1 for through holes. After filling, the conductive pastes 3a and 3b become the through holes 2 for the through holes.
Complete filling is performed so as to protrude from the opening surfaces (end surfaces) of a and 2b.

Thereafter, as shown in FIG. 7, polishing is performed from the surface side of the glass / epoxy substrate 1 to a partial area of the protective films 4 and 5, and the glass / epoxy substrate including the conductive pastes 3a and 3b is polished.
The outermost surface side of the epoxy substrate 1 is flattened. By this polishing step, the thickness of the protective films 4 and 5 becomes, for example, about 10 μm. In this surface polishing step, only the protective films 4 and 5 are polished, and the glass epoxy substrate 1 is not damaged. Therefore, glass is used to flatten the substrate surface.
When the polishing is performed to reach the epoxy substrate 1, the glass fiber layer is exposed on the glass-epoxy substrate composed of the laminated body of the glass fiber layer and the resin layer, which causes a decrease in reliability. Such defects can be prevented beforehand by the presence of the films 4 and 5.

Then, as shown in FIG. 1, for example, the insulating layer and the wiring layer are laminated on the upper and lower surfaces of the substrate 1 formed as described above, and a multilayer structure is formed by a build-up method. That is, interlayer insulating films 6 and 14 are formed on the upper and lower sides of the glass / epoxy substrate 1 (the surfaces of the conductive pastes 3a and 3b and the protective films 4 and 5), and the photo via holes 7 are formed in predetermined regions.
a, 7b, 15a, 15b (100 μm or less) are formed. Thereafter, conductor patterns (first wiring) 8, 16 are formed on the surfaces of the interlayer insulating films 6, 14, and the conductor patterns 8, 16 are formed.
Electrically connects to the conductive pastes 3a and 3b.
Further, interlayer insulating films 10 and 18 are formed, and photo via holes 11a, 11b, 19a and 19b are formed in predetermined regions. Thereafter, conductor patterns (second wiring) 12 and 20 are formed on the surfaces of the interlayer insulating films 10 and 18, and are electrically connected to the conductor patterns 8 and 16 by the conductor patterns 12 and 20.

As described above, on the surface of the glass / epoxy substrate 1, the wiring patterns 8, 12, 16, 2 to the conductive pastes 3a, 3b in the through holes 2a, 2b for through holes are provided.
0 is formed.

The via holes 7a and 7b are shown in FIG.
As shown in FIG. 9, a paste connection or a plating column shown in FIG. 9 is also possible. Here, the surface of the substrate is flat, and the first wiring pattern 8 and thereafter can be formed by the additive method, so that fine wiring can be formed. For example, L (line) / S (pace) can be reduced to 70 μm or less, and high-density wiring can be realized.

As described above, this embodiment has the following features. (A) As a structure of the printed wiring board, as shown in FIG. 7, conductive pastes 3a and 3b are filled in through holes 2a and 2b for through holes formed in the glass / epoxy substrate 1, and the surface thereof is smooth. Protective films 4 and 5 are arranged in a region of the surface of the glass / epoxy substrate 1 where the conductive pastes 3a and 3b are not provided,
The protective films 4 and 5 are flush with the smooth surfaces of the conductive pastes 3a and 3b, and protect the glass / epoxy substrate 1 when polishing the conductive pastes 3a and 3b. Therefore, the surface of the insulating base material thus flattened can be multilayered as a base material. (B) As a manufacturing process, as shown in FIG. 4, protective films 4 and 5 are formed on the surface of the glass / epoxy substrate 1 having no conductor on the surface.
(First step), through holes 2a and 2b for through holes are formed in the glass / epoxy substrate 1 as shown in FIG. 5 (second step), and the glass / epoxy substrate 1 is formed as shown in FIG.
The conductive pastes 3a, 3b are filled in the through holes 2a, 2b for the through holes (third step), and a part of the protective films 4, 5 from the surface side of the glass / epoxy substrate 1 as shown in FIG. The outermost surface side of the glass / epoxy substrate 1 including the conductive pastes 3a and 3b was planarized by polishing to the region (fourth step). At this time, the glass / epoxy substrate 1 is protected by the protective films 4 and 5. Then, as shown in FIG. 1, on the surface of the glass / epoxy substrate 1, wiring patterns 8, 12, 16, 20 to the conductive pastes 3a, 3b in the through holes 2a, 2b for through holes were formed ( Fifth step).

Therefore, in this embodiment, the protective films 4 and 5 do not damage the glass / epoxy substrate 1. Further, in the method of FIG. 19, surface irregularities occur and it is difficult to form a multilayer structure. To solve this, flattening by arranging the insulating film 70 as shown in FIG. 22 increases the number of steps. However, in the present embodiment, flattening can be performed without increasing the number of steps.

Further, in the method of FIG.
As shown in 3, 24, the conductive paste 64 easily forms the dent 80, and the copper pattern on the surface makes it difficult to remove the dent below the copper pattern, and it has been considered that this dent may cause poor connection. In the present embodiment, since the protective films 4 and 5 are partially removed, the polishing can be polished deeper than the recesses 80 of the conductive paste 64, and the conductive pastes 3a and 3b having no recesses can be reliably connected. Can be taken.

As described above, it is possible to reliably flatten the surface and to cope with multilayering while avoiding damage to the glass / epoxy substrate 1 or lowering the reliability. (C) Since the interlayer insulating films are used as the protective films 4 and 5, the layers having the same thermal properties are laminated, so that the thermal expansion coefficients are uniform and the layers are less susceptible to adverse effects such as stress due to heat and have excellent reliability. Become. (D) Since the glass / epoxy substrate 1 is used as the substrate and the conductive pastes 3a and 3b are those containing an epoxy resin as a binder, the coefficient of thermal expansion can be made close to the substrate and cracks or the like can be caused. Failures can be prevented beforehand. That is, the conductive paste using an epoxy-based resin as a binder has a smaller shrinkage due to heat and is more preferable than the case where a conductive paste using a phenol-based resin as a binder is used. (E) By filling the conductive pastes 3a and 3b, heat can be radiated through the through holes.

FIG. 10 shows an application example of the present embodiment.
This is because conductive patterns 25a, 25b and resist 26 are arranged on the upper surface of substrate 1 processed to FIG. 7, conductive pattern 25a is electrically connected to conductive paste 3a, and conductive pattern 25b is electrically connected to conductive paste 3b. ing. Furthermore, conductive pastes 29a, 29
b, 36a, 36b are formed, the insulating film 27 is formed, and the surface is polished and flattened. The conductive paste 29a is conductive with the conductive pattern 25a, and the conductive paste 29b is conductive with the conductive pattern 25b. Conductive patterns 30a, 30b and resist 31 are arranged on the upper surface, and conductive pattern 30a is electrically connected to conductive paste 29a, and conductive pattern 30b is electrically connected to conductive paste 29b.
The conductive pastes 29a, 29b, 36a, 3
6b may be a plating column. Similarly, conductor patterns 32a and 32b and a resist 33 are disposed on the lower surface of the substrate 1, and an insulating film 34 is formed on the surface thereof.
In the holes 35a, 35b, conductive pastes 36a, 3
6b is filled. The conductor pattern 37 on the surface
a, 37b and a resist 38 are arranged.

This has the following effects. Protective films 4 and 5 are formed → drilling → paste filling → polishing → first wiring → insulating layer formation → second wiring →... It can be carried out. That is, in the conventional method shown in FIGS. 19 and 20, since the first wiring is a subtractive method, it is necessary to form a through-hole plating or a wiring pattern having a small L (line) / S (space) (for example, 70 μm or less). However, in this example, the conductive pastes 3a and 3b in the through holes 2a and 2b and the protective film 4,
5, the surface of the substrate is flattened, and the first wirings 25a, 25b, 32a, 32b formed thereon can be formed by the additive method, and fine wiring can be performed. (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

FIG. 11 is a sectional view of a printed wiring board according to the present embodiment. Glass as an insulating substrate
In the epoxy substrate 1, through holes 2a and 2b for through holes are formed. The conductive pastes 3a, 3b are filled in the through holes 2a, 2b for through holes, and the upper and lower surfaces of the conductive pastes 3a, 3b are smoothed. This smooth surface slightly protrudes from the surface of the glass / epoxy substrate 1. An interlayer insulating film 6 is formed on the upper surface side of the glass / epoxy substrate 1, and photo via holes 7a and 7b are formed in predetermined regions. A conductor pattern 8 is formed on interlayer insulating film 6, and is electrically connected to conductive pastes 3a and 3b by conductor pattern 8. The conductor pattern 8 is separated by an interlayer insulating film 9. Further, an interlayer insulating film 10 is formed thereon, and photo via holes 11a and 11a are formed in predetermined regions.
1b is formed. A conductor pattern 12 is formed on the interlayer insulating film 10, and is electrically connected to the conductor pattern 8 by the conductor pattern 12.

Similarly, an interlayer insulating film 14 is formed on the lower surface side of the glass / epoxy substrate 1, and photo via holes 15a and 15b are formed in predetermined regions.
A conductive pattern 16 is formed on the surface of the interlayer insulating film 14, and the conductive pattern 16 allows the conductive paste 3a,
3b. Also, conductor pattern 1
6 are separated by an interlayer insulating film 17. An interlayer insulating film 18 is formed on the surface, and photo via holes 19a and 19b are formed in predetermined regions. A conductor pattern 20 is formed on the surface of the interlayer insulating film 18, and is electrically connected to the conductor pattern 16 by the conductor pattern 20.

Next, a method of manufacturing the printed wiring board thus configured will be described. First, as shown in FIG. 12, a copper-clad laminate is prepared. That is, a substrate is prepared in which copper foils 21 and 22 are provided on the entire upper and lower surfaces of the glass epoxy substrate 1. Then, as shown in FIG. 13, the copper foils 21 and 22 on the surface are removed by etching.

Subsequently, as shown in FIG.
The peelable protective films 40 and 41 are formed (applied) on the upper and lower surfaces of the epoxy substrate 1. Further, as shown in FIG. 15, through holes are made in the glass epoxy substrate 1 to form through holes 2a and 2b for through holes. Then, as shown in FIG. 16, the conductive pastes 3a, 3b are inserted into the through holes 2a, 2b of the glass epoxy substrate 1.
Fill b.

Thereafter, as shown in FIG. 17, polishing from the surface side of the glass-epoxy substrate 1 to a partial area of the protective films 40, 41 is performed so that the glass-epoxy substrate 1 including the conductive pastes 3a, 3b is polished. Flatten the outermost surface. In this polishing step, the polishing amount is adjusted so that the protective films 40 and 41 are as thin as possible.

Then, as shown in FIG. 18, the protective films 40 and 41 are removed with a stripping solution or the like. At this time, the protective film 4
Nos. 0 and 41 are extremely thin, and almost no steps are formed between the through holes 2a and 2b for through holes and other portions as the surface shape of the substrate.

As an example of the peelable protective films 40 and 41, for example, an alkali peeling type dry film can be used. Further, as shown in FIG. 11, the interlayer insulating films 6 and 1 are formed on the upper and lower surfaces of the glass / epoxy substrate 1.
4 is formed, and photo via holes 7a, 7
b, 15a and 15b are formed. Thereafter, conductor patterns 8 and 16 are formed on the surfaces of the interlayer insulating films 6 and 14, and are separated by the interlayer insulating films 9 and 17. Further, interlayer insulating films 10 and 18 are formed, and photo via holes 11a, 11b, 19a and 19b are formed in predetermined regions. After that, the conductor patterns 12,
20 is formed.

As described above, this embodiment has the following features. (A) The protective films 40 and 41 shown in FIG. 14 are peelable. After the outermost surface of the glass epoxy substrate 1 is flattened as shown in FIG. 17, the protective films 40 and 41 are formed as shown in FIG. Remove. Then, as shown in FIG. 1, using this as a base material, even if it is multilayered, the surface can be reliably flattened while avoiding damage to the insulating base material side, and it is possible to cope with multilayering.

[Brief description of the drawings]

FIG. 1 is a sectional view of a printed wiring board according to a first embodiment.

FIG. 2 is a cross-sectional view for explaining a manufacturing process of the printed wiring board according to the first embodiment.

FIG. 3 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 4 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 5 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 6 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 7 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 8 is a sectional view of a printed wiring board.

FIG. 9 is a sectional view of a printed wiring board.

FIG. 10 is a sectional view of a printed wiring board according to an application example of the first embodiment.

FIG. 11 is a sectional view of a printed wiring board according to the second embodiment.

FIG. 12 is a sectional view for explaining a manufacturing step of the printed wiring board in the second embodiment.

FIG. 13 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 14 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 15 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 16 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 17 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 18 is a cross-sectional view for explaining a manufacturing process of the printed wiring board.

FIG. 19 is a cross-sectional view for explaining a conventional manufacturing process of a printed wiring board.

FIG. 20 is a cross-sectional view for explaining a conventional process for manufacturing a printed wiring board.

FIG. 21 is a cross-sectional view illustrating a conventional printed wiring board.

FIG. 22 is a cross-sectional view illustrating a conventional printed wiring board.

FIG. 23 is a sectional view for explaining a conventional printed wiring board.

FIG. 24 is a cross-sectional view illustrating a conventional printed wiring board.

[Explanation of symbols]

1: glass epoxy substrate as insulating substrate, 2a, 2
b: through hole for through hole, 3a, 3b: conductive paste, 4: protective film, 5: protective film, 40: protective film, 41: protective film

Claims (5)

[Claims] An insulating base; a through-hole formed in the insulating base; a conductive paste filled in the through-hole and having a smooth surface; A protective film that is disposed in a region where the conductive paste is absent on the surface of the material, is flush with the smooth surface of the conductive paste, and protects an insulating base material during polishing of the conductive paste. A printed wiring board characterized by the above-mentioned. 2. A first step of forming a protective film on the surface of the insulating base material having no conductor on the surface, a second step of forming a through hole for a through hole in the insulating base material, A third step of filling the conductive paste into the through holes for holes, and polishing the protective film from the surface side of the insulating base material to flatten the outermost surface side of the insulating base material including the conductive paste. A fourth step of forming a wiring pattern to the conductive paste in the through hole for the through hole on the surface of the insulating base material;
And a method for manufacturing a printed wiring board. 3. The method according to claim 2, wherein the protective film uses an interlayer insulating film. 4. The method according to claim 2, wherein the wiring is performed by an additive method in the fifth step. 5. The method according to claim 1, wherein the protective film is peelable, and the protective film is removed after the outermost surface of the insulating base material is flattened in the fourth step. 3. The method for manufacturing a printed wiring board according to item 2.