JPH11298146A - Multilayered printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayered printed wiring board which can be widely used in various types of electronic devices and which can be mounted with a high density with a small land diameter in an outer layer and without any through-hole. SOLUTION: A light-sensitive insulating resin layer 4 is formed by laminating a film-like insulating resin on an insulating substrate 3 as an inner layer having a conductive pattern 2 for the inner layer and a conductive hole filled with conductive paste, and then the substrate is subjected to light exposing and developing processes to form a non-through hole therein. Next the substrate is formed therein with a photo via 5 for electric connection of conductive patterns 2 and 6 for the inner and outer layers by metal plating or the like. Thereafter the conductive pattern 6 for the outer layer is formed on the metal surface thereof by means such as a screen printing or a photography, thus manufacturing a multilayered printed wiring board 7 for high density mounting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board widely used for various electronic devices such as a personal computer, a mobile communication telephone, and a video camera, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers, word processors, video-integrated cameras, mobile phones, and the like, the demand for multilayer printed wiring boards has been increasing. For reasons such as functionalization, a multi-layer printed wiring board is provided with an interstitial via hole (hereinafter referred to as IVH), which is an interlayer electrical connection method using a non-penetrating via hole in order to further improve wiring accommodation and surface mounting density. ) Has begun to be required. As a means to respond to this, a resin multilayer printed wiring board or a photosensitive resin that can electrically connect all layers by IVH with conductive paste is used as an insulating layer, non-through holes are provided, and metal plating is performed to electrically connect the layers with IVH. A resin multilayer printed wiring board that can be used has been put to practical use.

Hereinafter, a method for manufacturing a conventional multilayer printed wiring board will be described. 2A to 2C show a conventional method for manufacturing a multilayer printed wiring board in which an IVH is formed using a conductive paste. In FIG. 2, 1
1 is a copper foil for forming a conductive pattern for a multilayer.
2 is a prepreg in which a conductive paste 15 is filled in through holes, 13 is an inner layer material, 13a is an inner layer conductive pattern, 1
Reference numeral 3b denotes an insulating substrate for an inner layer having a through hole filled with a conductive paste 16, 14 denotes a multilayer printed wiring board having a conductive pattern inside and outside, and 14a denotes a conductive pattern for an outer layer.

[0004] A method of manufacturing a multilayer printed wiring board configured as described above will be described below.

First, as shown in FIG. 2A, an insulating substrate 13b is made of an aromatic polyamide nonwoven fabric base epoxy resin laminate or the like in which a hole is formed and the hole is filled with a conductive paste 16 and the like. The copper foil of the copper clad laminate obtained by laminating the copper foil is formed on the conductive pattern 13a for the inner layer by using a method such as a screen printing method or a photographic method,
An inner layer material 13 for a multilayer printed wiring board is obtained.

Next, as shown in FIG. 2B, an inner layer material 13 having an inner layer conductive pattern 13a formed on an insulating substrate 13b and an aromatic polyamide non-woven fabric are impregnated with an epoxy resin or the like. Is made into a semi-cured state, and a hole is formed. A prepreg 12 filled with a conductive paste 15 in the hole and a copper foil 11 for forming a conductive pattern of the outermost layer are overlapped. Heating and pressing to melt, cool, and solidify the inner layer material 13, prepreg 12, and copper foil 11, and screen-print the copper foil 11 of the copper clad laminate on which the copper foil 11 is laminated. The multi-layer printed wiring board 14 as shown in FIG. 2C is formed on the conductive pattern 14a for the outer layer using a method such as a method or a photographic method.

FIGS. 3 (a) to 3 (c) show a method of manufacturing a multilayer printed wiring board in which an IVH is formed by metal plating a non-through hole using a conventional photosensitive resin.
In FIG. 3, reference numeral 21 denotes copper foil, 22 denotes a photosensitive resin film, 2
Reference numeral 3 denotes an inner layer material, 23a denotes an inner layer conductive pattern, 24a denotes an IVH (hereinafter referred to as a photo via) in which a non-through hole formed in the photosensitive resin film 22 is metal-plated, and 24b denotes a through that electrically connects the inner layers. The hole 24c is a conductive pattern for an outer layer, and 24 is a multilayer printed wiring board having a conductive pattern inside and outside.

[0008] A method of manufacturing the multilayer printed wiring board configured as described above will be described below.

First, as shown in FIG. 3 (a), a copper foil of a copper-clad laminate obtained by laminating copper foil on both sides of an insulating substrate 23b is applied to an inner layer using a screen printing method or a photographic method. To form an inner layer material 23 for a multilayer printed wiring board.

Next, as shown in FIG. 3 (b), a photosensitive resin is applied to an inner layer material 23 having an inner layer conductive pattern 23a formed on an insulating substrate 23b to make the resin in a semi-cured state and to expose the photosensitive resin. After forming a non-through hole by forming a conductive resin film 22 and exposing and developing, a through hole is formed by drilling or the like, and metal plating is performed to electrically connect the inner and outer layers.
4a and through holes 24b for electrically connecting the inner layers
Get. Thereafter, the copper foil 21 on the surface is formed on the outer layer conductive pattern 24c by using a method such as a screen printing method or a photographic method.
To obtain a multilayer printed wiring board 24 as shown in FIG.

Thereafter, a solder resist is formed by a known method such as a photographic method to obtain a multilayer printed wiring board.

[0012]

However, among the above-mentioned conventional methods, the through-hole made of conductive paste has a structure in which the conductive hole is buried in the substrate. The viscosity of the conductive paste cannot be adjusted by the solvent to prevent delamination due to evaporation of the solvent component in the solvent, and it is impossible to fill holes having a diameter of 200 μm or less because the viscosity is relatively high. There is a problem that workability is also poor.

Further, since the size of the conductive hole is large and the size of the land to be installed on the conductive hole is relatively large, there is a problem that the improvement of the wiring density is limited.

On the other hand, in the case of a non-through hole by a photo via,
Because of the electrical connection by metal plating, a smaller hole (50-100 μm in diameter) than the conductive hole made by the conductive paste
m) can be formed, but the inner layer material 2
In order to electrically connect both surfaces of the photo via 3, the photo via 24
It is necessary to provide a through hole 24b as a through hole after forming a, which has a problem that high-density wiring is hindered. In addition, when both surfaces of the inner layer material 23 are formed in advance by through holes 24b of through holes, it is very difficult to completely embed the photosensitive resin in the through holes 24b when applying the photosensitive resin, and the workability is high. Is also bad.

Further, since the insulating layer is formed by applying an insulating resin to the inner layer material 23, there is a problem that the thickness of the insulating layer greatly varies and the electrical characteristics are deteriorated.

The present invention has been made to solve the above-mentioned conventional problems, and has a uniform insulating layer thickness and does not require through holes.
It is another object of the present invention to provide a multilayer printed wiring board having a through hole made of a conductive paste having a photo via partially without burying the through hole, and a method of manufacturing the same.

[0017]

In order to achieve this object, the present invention provides a method of filling a conductive paste into a through-hole of a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin. An inner layer material having a conductive pattern formed of metal foil bonded to both sides, a film-like insulating resin layer laminated on both sides of the inner layer material, and a non-through hole provided in the insulating resin layer, and an outer surface of the insulating resin layer formed in a non-through hole. A multi-layer printed wiring board provided with an interstitial via hole for connecting a conductive pattern for an outer layer formed on the substrate and a conductive pattern of an inner layer material.

According to the above configuration, a multilayer printed wiring board having a uniform thickness of the insulating layer, a conductive hole inside, a high-density wiring in the outermost layer, and no through holes can be obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a conductive paste is filled in through holes of a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin. An inner layer material having a conductive pattern formed of a metal foil bonded to the inner layer material, a film-like insulating resin layer laminated on both sides of the inner layer material, and a non-through hole provided in the insulating resin layer formed on the outer surface of the insulating resin layer. This is provided with interstitial via holes for connecting the formed outer layer conductive pattern and the inner layer material conductive pattern, and can have high-density wiring.

The second aspect of the present invention is a structure in which a surface-roughened material is used as the film-like insulating resin layer, and the conductive pattern for the outer layer can have excellent peel strength. .

According to a third aspect of the present invention, there is provided a process of forming a through hole in a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin, and filling the through hole with a conductive paste. And a step of forming a circuit after heating and pressing a metal foil on both surfaces of the porous substrate to form an inner layer material having a conductive pattern on both surfaces, and a film-like insulating resin on both surfaces of the inner layer material. After laminating, a non-through hole is provided, and a method of manufacturing a multilayer printed wiring board having a step of electrically connecting the conductive pattern for the inner layer and the conductive pattern for the outer layer. By electrically connecting only the conductive holes formed by the conductive paste, and electrically connecting the conductive pattern for the inner layer and the conductive pattern for the outer layer with a non-through hole,
This has the effect of increasing the wiring density of the outermost layer and at the same time making through holes unnecessary. Furthermore, since the insulating resin layer is formed from a film, the insulating resin layer has a uniform thickness and excellent electrical characteristics.

According to a fourth aspect of the present invention, there is provided the method for manufacturing a multilayer printed wiring board according to the third aspect, wherein a photosensitive resin is used for the insulating resin layer. It has an effect that a non-through hole for electrically connecting the conductive pattern can be formed by a photographic method utilizing its photosensitivity.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the fourth aspect, wherein the non-through holes are formed by exposure and development. Since the holes can be formed, a non-through hole having a small diameter can be formed with higher productivity than conventional drilling.

According to a sixth aspect of the present invention, there is provided the method for manufacturing a multilayer printed wiring board according to the third aspect, wherein the non-through hole is formed by laser processing. This has the effect that through holes can be formed with high productivity.

According to a seventh aspect of the present invention, there is provided the multilayer printed wiring board according to the third aspect, wherein the conductive pattern for the inner layer and the conductive pattern for the outermost layer are electrically connected by plating the non-through holes with metal. This method has the effect of reducing the resistance value by metal plating and improving the reliability.

According to an eighth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the seventh aspect, wherein the surface of the insulating resin is roughened. It has the effect of increasing the adhesion of metal plating and improving reliability.

According to a ninth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the eighth aspect, wherein the surface of the insulating resin is roughened with a solution for dissolving the insulating resin. Since the solution for dissolving the insulating resin layer makes uniform contact over the surface of the insulating resin and the entire inside of the laser hole, the surface of the insulating resin and the inside of the laser hole can be uniformly roughened, and the adhesion of the metal plating to the substrate There is an effect that it can be obtained without a difference depending on the location.

According to a tenth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the ninth aspect, wherein the surface of the insulating resin is roughened with a permanganic acid solution. Is dissolved by the permanganate solution, which has the effect of uniformly increasing the adhesion of metal plating and improving reliability.

[0029] The invention according to claim 11 is a method for manufacturing a multilayer printed wiring board according to claim 3, wherein portions other than the conductor are masked with a metal-resistant plating resin. Since metal plating can be performed, an effect that the wiring density can be improved is provided.

According to a twelfth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the eleventh aspect, wherein an insulating resin is used as a metal-resistant plating resin to form a permanent resist. Since the insulating resin sometimes used as a plating resist can be used as it is as a permanent resist (solder resist), a peeling step can be omitted, and a permanent resist can be obtained without a separate step of forming a resist later. Has an action.

According to a thirteenth aspect of the present invention, when the non-through hole connecting the conductive pattern for the inner layer and the conductive pattern for the outermost layer is metal-plated, the through hole provided in advance is simultaneously metal-plated. According to this method, the inner wall of the through hole is also subjected to metal plating, so that when this through hole is used as a component mounting hole, a component insertion pin is inserted into the through hole. It has the effect that components can be fixed by insertion and soldering.

According to a fourteenth aspect of the present invention, the conductive pattern for the inner layer and the conductive pattern for the outermost layer are electrically connected by filling the non-through holes with a conductive paste. This is a method for manufacturing a wiring board, and has the effect of being cheaper and more excellent in workability and productivity than metal plating because metal plating can be omitted by this method.

According to a fifteenth aspect of the present invention, when the conductive paste is filled in the non-through hole connecting the conductive pattern for the inner layer and the conductive pattern for the outermost layer, the conductive pattern for the outermost layer is simultaneously made conductive. A method for producing a multilayer printed wiring board according to claim 14, wherein the method is a paste.
According to this method, a pattern forming step such as metal plating, a printing method, a photographic method, or the like can be omitted.

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1A to 1C are cross-sectional views illustrating a method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an inner layer material in which a conductive paste 8 is filled in through holes of a compressible porous base material made of an aromatic polyamide impregnated with a thermosetting resin and conductive patterns 2 for inner layers are provided on both sides. 2, a conductive pattern for the inner layer;
Reference numeral 3 denotes an insulating substrate for an inner layer having holes filled with a conductive paste 8, reference numeral 4 denotes a photosensitive insulating resin layer, and reference numeral 5 denotes an IVH in which non-through holes formed in the photosensitive insulating resin layer 4 are metal-plated.
(Photo via), 6 is a conductive pattern for an outer layer, and 7 is a multilayer printed wiring board having a conductive pattern inside and outside.

A method for manufacturing the multilayer printed wiring board configured as described above will be described below.

First, as shown in FIG. 1 (a), a hole is formed in a prepreg, and an aromatic primamide nonwoven fabric-based epoxy resin laminate filled with a conductive paste 8 in the hole is used as an insulating substrate 3. The copper foil of the copper-clad laminate obtained by laminating the copper foil is formed on the conductive pattern 2 for the inner layer by using a method such as a screen printing method or a photographic method to obtain the inner layer material 1 of the multilayer printed wiring board.

Next, as shown in FIG. 1 (b), a film-shaped photosensitive insulating resin is laminated on the inner layer material 1 having the inner layer conductive pattern 2 formed on the insulating substrate 3. After forming a non-through hole by exposure and development, a photo via 5 for electrically connecting the inner and outer layers by metal plating or the like is obtained. At this time, by providing a through hole in advance, it is possible to cope with mounting of a component having a lead wire. Thereafter, a conductive pattern 6 for the outer layer is formed on the metal on the surface formed by laminating or metal plating using a method such as a screen printing method or a photographic method, and a multilayer printed wiring board 7 as shown in FIG.
Have gained.

(Embodiment 2) More detailed contents will be described below with reference to FIGS. 1 (b) and 1 (c).

After the insulating resin layer 4 formed on the surface of the inner layer material 1 in FIG. 1B is laser-processed, when the inner and outer layers are electrically connected by metal plating or the like, the surface of the insulating resin layer 4 becomes permanganic acid. By roughening with a solution that dissolves the insulating resin such as a solution, the adhesive strength between the insulating resin layer 4 and the metal plating can be increased.

Further, when metal plating is performed, portions other than the outer layer conductive pattern 6 are masked with a metal-resistant plating resin, so that only necessary portions are metal-plated as shown in FIG. The pattern 6 can be formed. Further, by using an insulating resin as the metal plating resin, a permanent resist can be obtained.

Further, the surface conductor can be smoothed by filling a low-viscosity conductive paste whose viscosity has been adjusted with a solvent or the like without forming the photovia 5 without using metal plating. Furthermore, when the photo via 5 is filled with a low-viscosity conductive paste whose viscosity has been adjusted with a solvent or the like, a conductive pattern for an outer layer can be simultaneously formed by a known screen printing method or the like, and a printing method, a photographic method, or the like can be formed. This reduces the number of pattern forming steps, thereby providing an inexpensive multilayer printed wiring board with extremely high productivity.

When the multilayer printed wiring board according to the present embodiment is compared with the conventional multilayer printed wiring board, the land diameter of the outer layer portion is smaller than that in the case where the entire layer of the IVH is formed by the conductive holes of the conductive paste according to the conventional method. It can be halved. Also, compared to the case where a non-through hole formed in an insulating resin layer is metal-plated outside the inner layer material of the conventional method to form a photo via, connection between the conductive patterns for the inner layer by the through hole is unnecessary, so the wiring accommodation capacity is reduced. In addition, the mounting density can be improved.

As described above, according to the present embodiment, it is possible to provide a multilayer printed wiring board capable of dramatically improving the mounting density.

[0044]

As described above, according to the present invention, a metal-plated photovia is formed by laminating a film-shaped insulating resin on the surface of an inner layer material in which conductive holes are buried by a conductive paste, and then exposing and developing the film. Thus, a multilayer printed wiring board having a very high wiring capacity and a high mounting density can be realized. Further, the thickness of the insulating layer can be made uniform, and a printed wiring board having excellent electric characteristics can be realized.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views showing a process of manufacturing a multilayer printed wiring board according to an embodiment of the present invention.

2 (a) to 2 (c) are cross-sectional views of a process for manufacturing a conventional multilayer printed wiring board.

3 (a) to 3 (c) are cross-sectional views of a process for manufacturing a conventional multilayer printed wiring board.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner layer material 2 inner layer conductive pattern 3 inner layer insulating substrate 4 photosensitive insulating resin layer 5 IVH (photo via) 6 outer layer conductive pattern 7 multilayer printed wiring board

Claims (15)

[Claims] 1. An inner layer material in which a conductive pattern is formed by filling a through hole of a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin with a conductive paste and bonding both surfaces to a metal foil. A film-shaped insulating resin layer laminated on both sides of the inner layer material, and a conductive pattern for the outer layer formed on the outer surface of the insulating resin layer and a conductive pattern of the inner layer material formed in the non-through hole provided in the insulating resin layer. Multilayer printed wiring board with interstitial via holes to connect. 2. The multilayer printed wiring board according to claim 1, wherein the film-shaped insulating resin layer has a roughened surface. 3. A step of forming a through-hole in a compressible porous substrate made of an aromatic polyamide impregnated with a thermosetting resin, and a step of filling the through-hole with a conductive paste.
After laminating a metal foil on both sides of the porous base material, heating and pressing, forming a circuit and forming an inner layer material having a conductive pattern on both sides, and laminating a film-like insulating resin on both surfaces of the inner layer material A method for manufacturing a multilayer printed wiring board, comprising the steps of: providing a non-through hole; and electrically connecting the conductive pattern for the inner layer and the conductive pattern for the outer layer. 4. A photosensitive resin is used as the insulating resin.
3. The method for producing a multilayer printed wiring board according to item 1. 5. The method for manufacturing a multilayer printed wiring board according to claim 4, wherein the non-through holes are formed by exposure and development. 6. The method according to claim 3, wherein the non-through holes are formed by laser processing. 7. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein the conductive pattern for the inner layer and the conductive pattern for the outermost layer are electrically connected by metal plating the non-through holes. 8. The method according to claim 7, wherein the surface of the insulating resin is roughened. 9. The method according to claim 8, wherein the surface of the insulating resin is roughened with a solution for dissolving the insulating resin. 10. The method for producing a multilayer printed wiring board according to claim 9, wherein the surface of the insulating resin is roughened with a permanganate solution. 11. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein a portion other than the conductor is masked with a metal-resistant plating resin. 12. The method for manufacturing a multilayer printed wiring board according to claim 11, wherein an insulating resin is used as the metal-resistant plating resin to form a permanent resist. 13. The multi-layer printed wiring board according to claim 7, wherein when the non-through hole connecting the conductive pattern for the inner layer and the conductive pattern for the outermost layer is metal-plated, the through hole provided in advance is also metal-plated. Production method. 14. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein the inner layer circuit and the outermost layer are electrically connected by filling the non-through hole with a conductive paste. 15. The circuit of the outermost layer is formed simultaneously with the conductive paste when filling the non-through hole connecting the conductive pattern for the inner layer and the conductive pattern for the outermost layer with the conductive paste. Of manufacturing a multilayer printed wiring board.