JPH11298147A - 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: Insulating resin is applied 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 hardened to form an insulating resin layer 4, and then the substrate is subjected to a laser beam machining to form a non-through hole therein. Next, the substrate is formed therein with an IVH (interstitial via hole) 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, for multilayer printed wiring boards,
An interstitial via hole (hereinafter referred to as IVH), which is an interlayer electrical connection method using a non-penetrating via hole for further improving the wiring accommodation property and the 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.

A conventional multilayer printed wiring board and a method of manufacturing the same will be described below. 2 (a) to 2 (c) show a process of manufacturing a multilayer printed wiring board for forming an IVH using a conventional conductive paste. In FIG.
11 is copper foil, 12 is prepreg, 13 is inner layer material, 13
a is a conductive pattern for the inner layer, 13b is an insulating substrate for the inner layer having holes filled with a conductive paste or the like, 14a is a conductive pattern for the outer layer, 14 is a multilayer printed wiring board having a conductive pattern inside and outside. is there.

[0004] A method of manufacturing a multilayer printed wiring board having the above configuration will be described below. First, as shown in FIG. 2A, an insulating substrate 13b is made of an aromatic polyamide non-woven fabric base epoxy resin laminate or the like in which a hole is formed and a conductive paste or the like is filled in the hole, and copper is provided on both sides thereof. The conductive pattern 1 for the inner layer is formed by using a method such as a screen printing method or a photographic method on the copper foil of the copper-clad laminate obtained by laminating the foil.
3a to obtain an inner layer material 13 for a multilayer printed wiring board.

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 or the like in the hole and a copper foil 11 for forming a conductive pattern of the outermost layer are overlapped, and a stainless steel press is applied to a hot press machine. It is set by sandwiching it between plates, etc., heated and pressed to melt, cool, and solidify the inner layer material 13, the prepreg 12, and the copper foil 11,
The copper foil 11 of the copper-clad laminate obtained by laminating the copper foil 11 is formed on the conductive pattern 14a for the outer layer by using a method such as a screen printing method or a photographic method. The wiring board 14 is obtained.

FIGS. 3 (a) to 3 (c) show a manufacturing process of 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
3 is an inner layer material, 23a is an inner layer conductive pattern, and 24a is a metal plated non-through hole formed in the photosensitive resin film.
VH (hereinafter referred to as a photo via); 24b, a through hole for electrically connecting the inner layers; 24c, a conductive pattern for an outer layer; and 24, a multilayer printed wiring board having conductive patterns inside and outside.

A method for manufacturing a multilayer printed wiring board having the above-described configuration will be described below. First, as shown in FIG. 3A, a copper foil of a copper-clad laminate obtained by laminating a copper foil on both sides of an insulating substrate 23b is applied to a conductive pattern for an inner layer by using a method such as screen printing or photography. 23a to obtain 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. 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, metal plating is performed, and a photo via 24 for electrically connecting the inner and outer layers is formed.
a and a through hole 24b for electrically connecting the inner layer and the inner layer. Thereafter, a conductive pattern 24c for an outer layer is formed on the metal on the surface by using a method such as a screen printing method or a photographic method, thereby obtaining 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.

[0010]

However, in the above-mentioned conventional method, in the through hole filled with the conductive paste of the prepreg 12, the conductive hole is formed by the conductive pattern 14 for the outer layer.
Due to the structure covered by a, the viscosity of the conductive paste cannot be adjusted by the solvent to prevent delamination due to evaporation of the solvent component in the conductive paste due to heating in the post-process and the mounting process, and the viscosity is relatively low. 200 diameter
It is impossible to fill holes of less than μm, and there is a problem that workability is poor.

Furthermore, since the size of the conductive hole is so large that the size of the land placed on the conductive hole must be 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 formed by the photo via 24a, a hole (diameter of 50 to 10) is smaller than a conductive hole formed by the conductive paste because of electrical connection by metal plating.
0 μm) can be formed, but in order to electrically connect both surfaces of the inner layer material 23, it is necessary to provide a through hole 24 b as a through hole after the formation of the photo via 24 a, and the high density wiring is required. There is a problem that it becomes an obstacle. 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. Bad nature.

Further, in order to improve the adhesiveness of the photosensitive resin, it is general to have an OH group in the skeleton of the molecular structure of the resin. However, this OH group has a high ultraviolet absorption rate and a high photosensitivity. There is a problem of deterioration.
There is a limit in improving the adhesion due to the limitation of the ratio of including the group.

The present invention solves the above-mentioned conventional problems, and has high adhesion of an insulating resin, does not require through-holes, does not need to bury through-holes, and has a conductive part having a photo-via in a part. It is an object of the present invention to provide a multilayer printed wiring board having a through hole made of a conductive paste and a method for manufacturing the same.

[0015]

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. For an inner layer material with a conductive pattern formed of metal foil bonded to both sides, and an outer layer formed on the outer surface of the insulating resin layer in a non-through hole formed by laser processing on the insulating resin layer formed on both sides of this inner layer material This is a printed wiring board provided with interstitial via holes for connecting the conductive pattern and the conductive pattern of the inner layer material.

According to the above-mentioned structure, a multilayer printed wiring board having a conductive hole therein, a high-density wiring in the outermost layer, and no through-hole can be obtained.

[0017]

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 laminated to the inner layer material, an insulating resin layer formed on both surfaces of the inner layer material, and a non-through hole formed by laser processing in the insulating resin layer, and an outer surface of the insulating resin layer formed in a non-through hole. In this configuration, an interstitial via hole that connects the conductive pattern for the outer layer and the conductive pattern of the inner layer material is provided. By this configuration, a high-density wiring can be formed in the outermost layer, and the through hole can be formed. There can be no multilayer printed wiring board.

According to a second aspect of the present invention, an insulating resin layer having a roughened surface is used.
In addition to the effect described above, a material having excellent adhesion between the insulating resin layer and the conductor pattern for the outer layer can be obtained.

According to a third aspect of the present invention, there is provided a process for 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 applying a metal foil on both sides of the porous base material and heating and pressing to form an inner layer material having a conductive pattern on both sides, and applying an insulating resin on both surfaces of the inner layer material. After curing, a non-through hole is provided by laser processing, and a method of manufacturing a multilayer printed wiring board comprising a step of electrically connecting a conductive pattern for an inner layer and a pattern for an outer layer is provided.
By electrically connecting only the conductive patterns for the inner layer with conductive holes formed of conductive paste, and electrically connecting the conductive patterns for the inner layer and the outer layer with non-through holes by laser, the wiring density of the outermost layer is reduced. And at the same time, has the effect that through holes are unnecessary. further,
Insulating resin does not require photosensitivity, so OH
And the effect of improving the adhesion of the insulating resin can be obtained.

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 the inner layer circuit and the outermost layer are electrically connected by plating the non-through holes with metal. Yes, this method has the effect of reducing the resistance value by metal plating and improving the reliability.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the third 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 sixth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the fifth 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 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 It has the effect that it can be obtained without any difference between locations.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the sixth 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.

According to an eighth aspect of the present invention, there is provided a method of manufacturing a multilayer printed wiring board according to the third aspect, wherein a portion other than the conductor is masked with a metal-resistant plating resin. Since metal plating can be performed on the substrate, the wiring density can be improved.

According to a ninth aspect of the present invention, there is provided a method for manufacturing a multilayer printed wiring board according to the eighth 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 resist forming step later. Has an action.

According to a tenth aspect of the present invention, the non-through hole connecting the conductive pattern for the inner layer and the outermost layer is metal plated, and the through hole provided in advance is also metal plated at the same time. This is a method of manufacturing a printed wiring board. By this method, the inner wall of the through hole is also plated with metal, so when this through hole is used as a component mounting hole, a component insertion pin is inserted into the through hole and soldered. It has the effect that the parts can be fixed by attaching.

According to an eleventh aspect of the present invention, the conductive pattern for the inner layer and the outermost layer is electrically connected by filling the non-through holes with a conductive paste. This is a manufacturing method, and since this method can omit metal plating, it has an effect that it is inexpensive and has excellent workability and productivity as compared with metal plating.

According to a twelfth aspect of the present invention, when the conductive paste is filled into the non-through holes connecting the conductive patterns for the inner layer and the outermost layer, the conductive pattern for the outermost layer is simultaneously formed of the conductive paste. A method of manufacturing a multilayer printed wiring board according to claim 11, which can omit a pattern forming step such as metal plating, a printing method, and a photographic method, and is inexpensive and excellent in workability and productivity. It has the effect of being.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (Embodiment 1) FIGS. 1A to 1C are cross-sectional views showing steps of 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, 2 denotes a conductive pattern for the inner layer, and 3 denotes a compressible porous body made of an aromatic polyamide impregnated with a thermosetting resin in which a through hole is filled with a conductive paste. Insulating substrate for inner layer, 4 for insulating resin layer, 5 for IVH metal-plated non-through hole formed in insulating resin layer 4, 6 for conductive pattern for outer layer, 7 for conductive pattern 2, 6 inside and outside It is a multilayer printed wiring board.

A method for manufacturing a multilayer printed wiring board having the above-described configuration will be described below. First, as shown in FIG. 1 (a), a through-hole is formed in a prepreg, and an aromatic polyamide nonwoven fabric base epoxy resin laminate or the like in which a conductive paste is filled in the through-hole is used as an insulating substrate 3.
The copper foil of the copper-clad laminate having the copper foil laminated on both sides thereof 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. 1B, the insulating resin is applied to the inner layer material 1 having the inner layer conductive pattern 2 formed on the insulating substrate 3 and then cured by heat. After the layer 4 is formed and a non-through hole is formed by laser processing, an IVH 5 for electrically connecting the conductive patterns 2 and 6 of the inner and outer layers is obtained by metal plating. 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 an outer layer is formed on the metal on the surface by using a method such as a screen printing method or a photographic method, thereby obtaining a multilayer printed wiring board 7 as shown in FIG.

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

In FIG. 1 (b), when a non-through hole is formed in the insulating resin layer 4 formed on the surface of the inner layer material 1 by laser processing, the conductive patterns 2 and 6 of the inner and outer layers are electrically connected by metal plating. By roughening the surface of the insulating resin layer 4 with a solution for dissolving the insulating resin such as a permanganic acid 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 conductive pattern 6 for the outer layer 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. In addition, a permanent resist can be obtained by using an insulating resin as the metal-resistant plating resin.

Further, the surface conductor can be smoothed by filling a low-viscosity conductive paste whose viscosity is adjusted with a solvent or the like without using metal plating to form the IVH5 and then performing metal plating. Further, when the IVH 5 is filled with a low-viscosity conductive paste whose viscosity is adjusted with a solvent or the like, the conductive pattern 6 for the 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. This reduces the number of pattern forming steps, thereby providing an inexpensive multilayer printed wiring board with extremely high productivity.

A comparison between the multilayer printed wiring board according to the present embodiment and the conventional multilayer printed wiring board shows that the land diameter of the outer layer portion is smaller than that in the case where the IVH of all layers is formed by the conductive holes of the conventional conductive paste. It can be halved. Also, compared to the conventional method in which a non-through hole formed in an insulating resin layer is formed on the outside of an inner layer material by metal plating to form an IVH, connection between inner layer conductive patterns by through holes is unnecessary, so that wiring is accommodated. Capability and 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.

[0038]

As described above, according to the present invention, after applying and curing an insulating resin on the surface of an inner layer material in which conductive holes are buried by a conductive paste, non-through holes are formed by laser processing.
By forming H, it is possible to realize a multilayer printed wiring board having a very high wiring capacity and a high mounting density and a high adhesion of an insulating resin.

[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 insulating substrate 4 insulating resin layer 5 IVH 6 outer layer conductive pattern 7 multilayer printed wiring board

Claims (12)

[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. An insulating resin layer formed on both surfaces of the inner layer material, a conductive pattern for the outer layer formed on the outer surface of the insulating resin layer in a non-through hole formed by laser processing in the insulating resin layer, and a conductive pattern of the inner layer material. Multilayer printed wiring board provided with interstitial via holes for connecting 2. The multilayer printed wiring board according to claim 1, wherein the 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.
A step of forming a circuit after heating and pressing a metal foil on both sides of the porous base material to form an inner layer material having a conductive pattern on both sides, and applying and curing an insulating resin on both surfaces of the inner layer material Forming a non-through hole by laser processing and electrically connecting the conductive pattern for the inner layer and the conductive pattern for the outer layer. 4. The method according to claim 3, wherein the inner circuit and the outermost layer are electrically connected by plating the non-through holes with metal. 5. The method according to claim 3, wherein the surface of the insulating resin is roughened. 6. The method for manufacturing a multilayer printed wiring board according to claim 5, wherein the surface of the insulating resin is roughened with a solution for dissolving the insulating resin. 7. The method according to claim 6, wherein the surface of the insulating resin is roughened with a permanganate solution. 8. The method according to claim 3, wherein portions other than the conductor are masked with a metal-resistant plating resin. 9. The method according to claim 8, wherein an insulating resin is used as the metal-resistant plating resin to form a permanent resist. 10. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein when the non-through holes connecting the conductive patterns for the inner layer and the outermost layer are plated with metal, the through holes provided in advance are also plated with metal. 11. The method for manufacturing a multilayer printed wiring board according to claim 3, wherein the conductive patterns for the inner layer and the outermost layer are electrically connected by filling the non-through holes with a conductive paste. 12. The conductive pattern for 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. A method for manufacturing a multilayer printed wiring board.