JPH088541A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance two insulating layers in adhesion between them and in bonding workability by a method wherein the insulating layer is of two or more-layered structure composed of different insulating resins, and one of the insulating layers is formed of photosensitive insulating resin. CONSTITUTION:An SLC multilayer printed wiring board 1A is provided, wherein a circuit is formed on the copper foil of a copper-clad laminate to serve as a first conductor circuit 31. An insulating layer 4a formed of insulating resin excellent in resistance to cracking and migration is provided onto the surface of the copper-clad laminate on which the first conductor circuit 31 is formed. It is preferable that the insulating layer 4a is formed of alkali-soluble non- photosensitive resin. Then, a photosensitive insulating layer 4b is formed on the surface of the insulating film 4a. The insulating layer 4b is formed of alkali- soluble photosensitive insulating resin excellent in adhesion to a second conductor circuit 81 formed by copper plating. As mentioned above, an insulating layer is composed of two or more layers, so that a multilayer printed wiring board of this constitution is enhanced in electrical reliability.

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 by a build-up method and a method for manufacturing the same, and more particularly to an SLC (Su
rFaceLaminer Circuit; Surface layer printed wiring board) The present invention relates to a multilayer printed wiring board and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, in order to reduce the thickness and size of multilayer printed wiring boards as electronic equipment has become smaller and thinner, through-hole holes for electrically connecting the layers of conductor circuits have been formed. The reduction in diameter is remarkable. The through holes that electrically connect the layers of the conductor circuits are roughly classified as through holes (TVH; T).
Hough Via Hole) and perforation called IVH (Intersti)
There are two types, al via holes). A multilayer printed wiring board manufactured by a pin lamination method or a mass lamination method, which is the mainstream of the current method for manufacturing a multilayer printed wiring board, uses many through holes as through holes.

In the multilayer printed wiring board by the pin lamination method or the mass lamination method, if the diameter of the through holes is reduced to improve the wiring density, the number of through holes per area of the multilayer printed wiring board increases, resulting in a product of the multilayer printed wiring board. The price was soaring. The reason is that the through holes must be formed sequentially by a mechanical means such as drilling, so that it takes a very long time to form a large number of through holes. Therefore, recently, the S by the build-up method is generally used, in which many through holes capable of collectively forming a large number of through holes by chemical means are used.
Attention has been paid to a multilayer printed wiring board called an LC multilayer printed wiring board.

The SLC multilayer printed wiring board by the build-up method is a multilayer printed wiring board produced by using a manufacturing method announced to be put into practical use by IBM Japan, Ltd. SLC by this build-up method
The structure of the multilayer printed wiring board will be described with reference to FIG.

The SLC multilayer printed wiring board 1 by the build-up method uses a copper clad laminate as the insulating substrate 2 and forms a circuit on the copper foil of the copper clad laminate to form the first conductor circuit 31. . On the surface of this copper clad laminate, an insulating layer 4 usually made of a photosensitive epoxy insulating resin having a predetermined thickness is formed. Next, the formed insulating layer 4 is collectively formed with a large number of perforations 5 using a photoresist method, that is, chemical means such as ultraviolet exposure and development treatment, and the through holes are formed by mechanical means such as drilling. 6 are sequentially formed. Next, the surface 7 of the insulating layer 4 is roughened with a chemical or the like to facilitate copper plating.

Next, a conductor layer is formed by copper plating on the surface 7 of the insulating layer 4, the holes 5 and the through holes 6. In addition,
The conductor layer formed by copper plating is etched by a photoresist method or the like to form the second conductor circuit 81. The formed second conductor circuit 81 is electrically connected to the first conductor circuit 31 in the hole 5. Further, in the through hole 6, the first conductor circuit 31 formed on the same surface of the copper clad laminate,
The first conductor circuit 31 formed on the other surface of the copper-clad laminate and the second conductor circuit 8 formed on the other surface of the copper-clad laminate
1 is electrically connected. Second conductor circuit 8
If necessary, a solder protective film (not shown in FIG. 4) may be formed on the surface of 1. In the SLC multilayer printed wiring board 1 by the build-up method having such a structure, since the formed insulating layer 4 and the second conductor circuit 81 are thin, the multilayer printed wiring board can be made thin and the second Conductor circuit 8
1 is advantageous for thinning.

In the SLC multilayer printed wiring board 1 by the above-mentioned build-up method, the first conductor circuit 31 and the second conductor circuit 81, which are laminated via the insulating layer 4, are electrically connected between the layers. Since the through holes 5 are used as the through holes, the number of the through holes 6 can be reduced and the manufacturing time is short. From the above, it can be seen that the multilayer printed wiring board can be manufactured at low cost by using the build-up method.

Moreover, since the SLC multilayer printed wiring board 1 having the above structure by the build-up method has a smaller number of through holes 6 than the multilayer printed wiring board manufactured by the pin lamination method or the mass lamination method, There is also an advantage that the degree of freedom of wiring of the conductor circuit is improved and the length of the wiring of the conductor circuit can be shortened. Furthermore, in the SLC multilayer printed wiring board 1 by this build-up method, electronic parts can be mounted on the perforations 5 for achieving electrical connection between layers of each conductor circuit, and wiring of further conductor circuits can be performed. It is also possible to improve the density.

[0009]

However, the conventional SLC multilayer printed wiring board 1 produced by the build-up method has a problem that cracks are likely to occur in the insulating layer 4 made of a photosensitive epoxy insulating resin, so that the electrical reliability is improved. It was poor in sex. Furthermore, the insulating layer 4 made of a photosensitive epoxy insulating resin has a weak adhesive force to the conductor layer formed by copper plating, and the conductor layer formed by copper plating is easily peeled off. For this reason, various studies have been conducted on the photosensitive epoxy insulating resin used for the insulating layer 4 so as to have excellent crack resistance and to firmly form a conductor layer by copper plating on the surface.

However, if the insulating layer 4 is formed of a photosensitive epoxy insulating resin having a high hardness when cured, for example, in order to strengthen the adhesive force of the insulating layer 4 to the roughened surface, The flexibility is weakened and cracks are easily generated in the insulating layer 4. On the contrary, when the insulating layer 4 is formed of a photosensitive epoxy insulating resin having excellent flexibility, the crack resistance of the insulating layer 4 is improved. However, since the photosensitive epoxy insulating resin having excellent flexibility is soft, the surface of the insulating layer 4 to be bonded to the second conductor circuit 81 cannot be sufficiently roughened. Therefore, the adhesive force between the second conductor circuit 81 and the insulating layer 4 becomes weak. As described above, in order to simultaneously solve the two problems of improving the adhesiveness between the conductor layer 8 and the insulating layer 4 formed by copper plating or the like and improving the crack resistance of the insulating layer 4, a means for solving the problems. However, they have not been resolved because of conflicts.

Furthermore, in recent years, the epoxy insulating resin used for the insulating layer 4 has also been changed from a solvent-soluble type to an alkali-soluble type as an environmental measure. However, the alkali-soluble photosensitive epoxy insulating resin is more flexible than the solvent-soluble photosensitive epoxy insulating resin and is not suitable for roughening the surface of the insulating layer 4, and is formed by copper plating or the like. The adhesive force with the second conductive circuit 81 is weakened.

[0012]

As a result of various experiments and examinations, the present inventor has prevented the occurrence of cracks in the insulating layer and has excellent electrical reliability in the adhesive force between the insulating layer and the conductor layer. We succeeded in manufacturing SLC multilayer printed wiring board by high build-up method.

SLC by the build-up method according to the present invention
The feature of the multilayer printed wiring board is that preferably the insulating layer existing between the surface of the copper clad laminate and the conductor layer formed by copper plating is made of two or more kinds of insulating resins having different properties. Is sequentially formed, and the insulating layer has a structure of two or more layers.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of one embodiment of the SLC multilayer printed wiring board by the build-up method according to the present invention will be shown and described below with reference to FIG.

SLC by the build-up method according to the present invention
A copper clad laminate is preferably used as the insulating substrate 2 of the multilayer printed wiring board 1A. It is preferable that the insulating substrate 2 of the copper clad laminate according to the present invention uses a glass base material as a reinforcing base material and an epoxy resin as an insulating resin, but any printed wiring board substrate can be used. Is. Specific examples of the insulating resin include BT (bismaleide triazine) resin, phenol resin, polyimide resin, cyanate ester resin, silicone resin, polyester resin,
Examples thereof include fluorine resin, polybutadiene resin, polyetherimide resin, and polyetherimide resin. The reinforcing substrate of the copper-clad laminate according to the present invention includes glass substrates such as glass cloth, glass mat, glass paper or quartz fiber, synthetic resin fiber substrate such as polyester fiber or aramid fiber, linter paper or kraft paper. Paper base materials such as Further, as the insulating substrate 2 according to the present invention, a metal core laminated plate or ceramic substrate having a metal such as aluminum or iron as a base or core may be used.

SLC by the build-up method according to the present invention
In the multilayer printed wiring board 1A, a circuit is formed on the copper foil of the copper clad laminate described above to form the first conductor circuit 31. The insulating layer 4a is formed on the surface of the copper clad laminate having the first conductor circuit 31 formed of an insulating resin having excellent crack resistance and migration resistance. It is preferable that the insulating resin forming the insulating layer 4a according to the present invention has a relatively high crosslink density in order to prevent copper migration due to the movement of copper ions, and at the same time, be flexible to prevent the occurrence of cracks. Also, it is preferable to select and use an excellent insulating resin.

As a measure against environmental problems, it is more preferable to form the non-photosensitive insulating layer 4a with an alkali-soluble non-photosensitive insulating resin. As the alkali-soluble non-photosensitive insulating resin, an epoxy resin or an epoxy-modified resin containing a hydrophilic group that is soluble in an aqueous alkali solution is preferable, and these alkali-soluble non-photosensitive insulating resins may be used alone or in a mixture. It is preferably used. A crosslinking agent, a curing agent, a flexibility-imparting agent, a refractory agent, or the like may be added to the epoxy resin and the epoxy-modified resin according to the present invention alone or as a mixture as appropriate.

The insulating layer 4a according to the present invention is preferably formed of an alkali-soluble non-photosensitive insulating resin whose viscosity is adjusted with a diluent or the like. In the insulating layer 4a according to the present invention, the perforation 5 by chemical means performed in a later step.
In order to prevent the undercut phenomenon of the insulating layer 4a during the formation of the
That is, the non-alkali solubility of the photosensitive portion may be imparted. However, the range is such that the flexibility of the insulating layer 4a is not hindered.

Next, a photosensitive insulating layer 4b is formed on the surface of the insulating layer 4a. The photosensitive insulating resin forming the photosensitive insulating layer 4b according to the present invention is preferably a photosensitive insulating resin having excellent adhesiveness to the second conductor circuit 81 formed in a later step. Insulating layer 4a and photosensitive insulating layer 4
The adhesiveness with b is stronger than the adhesiveness between the photosensitive insulating layer 4b and the second conductor circuit 81 formed by copper plating or the like. Furthermore, since the insulating layer 4a and the photosensitive insulating layer 4b are completely adhered at the time of thermosetting, there is no problem such as peeling.

In the photosensitive insulating layer 4b according to the present invention, more preferably as an environmental measure, an alkali-soluble photosensitive insulating resin excellent in adhesiveness to the second conductor circuit 81 formed by copper plating or the like. Are formed by using.

The insulating resin of the photosensitive insulating layer 4b according to the present invention has an unexposed portion which is alkali-soluble and is suitable as a constituent material of a printed wiring board, and has suitable electrical characteristics, mechanical characteristics, flame retardancy, and the insulating layer 4a. Any insulating resin can be used as long as it is an insulating resin having adhesiveness with the second conductor circuit 81. For example, an epoxy acrylate having an acryloyl group or a methacryloyl group as a photocrosslinking group, a partial acrylate of epoxy, or a modified product of epoxy acrylate may be mentioned. Further, in view of the characteristics of the insulating layer, a combination of the above-mentioned insulating resin with a heat-curable epoxy insulating resin can be used. The oligomer and the monomer as the raw material of the insulating resin used for the photosensitive insulating layer 4b according to the present invention may be prepared by appropriately selecting and mixing a photopolymerization initiator, a cross-linking agent, a curing agent, a flame retardant, a filler, and the like. If so, adjust the viscosity with a diluent before use.

In the present invention, an adhesive or the like is used between the insulating layer 4a and the photosensitive insulating layer 4b for the purpose of improving the adhesiveness between the two insulating layers, the adhesive workability, and the electrical reliability. The insulating layer may be formed of an insulating resin or the like. Similarly, an insulating layer may be formed between the copper clad laminate 2 and the insulating layer 4 by using another insulating resin such as an adhesive, preferably an alkali-soluble insulating resin.

The total thickness of the insulating layers existing between the first conductor circuit 31 and the second conductor circuit 81 according to the present invention is 30 after the formation and curing of all the insulating layers.
It preferably has a thickness in the range of μm to 100 μm. The thickness of the insulating layer 4a according to the present invention is preferably equal to or more than the thickness of the photosensitive insulating layer 4b in order to prevent cracks, pinholes, migration and the like of the insulating layer. . Furthermore, since the thickness of the photosensitive insulating layer 4b is not related to the adhesiveness to the conductor layer formed by copper plating or the like, it is preferable to make it as thin as possible in order to prevent cracking of the insulating layer. Therefore,
The thickness of the insulating layer 4a is preferably in the range of 20 μm to 80 μm, and the thickness of the photosensitive insulating layer 4b is 10 μm to 40 μm.
It is preferably in the range of μm.

Next, the insulating layer 4a is formed by utilizing a photoresist method, that is, chemical means such as ultraviolet exposure and developing treatment.
And a large number of perforations 5 are formed in the photosensitive insulating layer 4b.
Further, the through holes 6 are formed by a mechanical means such as drilling or pressing if necessary. Next, the surface 7 of the photosensitive insulating layer 4b is roughened with a chemical or the like so that the copper plating can be easily attached. A second conductor circuit 81 is preferably formed by copper plating on the surface 7 of the alkali-soluble photosensitive insulating layer 4b. The formed second conductor circuit 81 has the first conductor circuit 31 in the perforation 5.
Is electrically connected to. Further, in the through hole 6, the first conductor circuit 31 formed on the same surface of the copper-clad laminate, the first conductor circuit 31 formed on the other surface of the copper-clad laminate and the copper-clad laminate other than Is electrically connected to the second conductor circuit 81 formed on the surface. The second conductor circuit 81 according to the present invention is preferably formed by forming a conductor layer by copper plating and then etching this conductor layer to form a circuit. Alternatively, a known conductive paste such as a copper paste, a gold paste, a carbon paste, and a silver paste, or gold plating may be used.

The SLC multilayer printed wiring board 1A produced by the above-mentioned build-up method according to the present invention may be further multilayered. When the SLC multilayer printed wiring board is manufactured by the build-up method according to the present invention using the single-sided copper clad laminate, the through holes may not be used. Further, although not shown, a solder protective film and a symbol mark may be formed on the surface if necessary.

Next, FIGS. 2A to 2D and FIG.
(A)-(c) S by the build-up method according to the present invention
An example of the manufacturing process of the LC multilayer printed wiring board will be described below. The insulating substrate 2 of the SLC multilayer printed wiring board 1A produced by the build-up method according to the present invention is preferably the one shown in FIG.
The copper clad laminate shown in (a) is used. As shown in FIG. 2B, the copper foil 32 of this copper-clad laminate is made into a first conductor circuit 31 by etching or the like. On the surface of this copper-clad laminate, preferably an alkali-soluble epoxy insulating resin is uniformly applied to a predetermined thickness by screen printing or the like, and then the applied insulating resin is dried and cured to obtain a resin composition shown in FIG.
The insulating layer 4a shown in (c) is formed.

Next, a photosensitive epoxy insulating resin, which is preferably alkali-soluble, is uniformly applied to the surface of the dried and hardened insulating layer 4a by screen printing or the like, and then dried and hardened, as shown in FIG. A photosensitive insulating layer 4b shown in is formed.

The method for forming an insulating layer according to the present invention, which includes the insulating layer 4a and the photosensitive insulating layer 4b, is performed by forming an insulating layer using a liquid insulating resin which is currently used for forming an insulating layer of a printed wiring board. Most of the methods can be adopted. That is, the insulating layer 4a and the insulating layer 4b according to the present invention can be formed by a curtain coating method, a spray coating method, a screen printing method, a roll coating method, or the like. Furthermore, the curtain coating method and the spray coating method are advantageous in uniformly forming the insulating layer among the above-mentioned insulating layer forming methods, and the screen printing method can industrially easily form the insulating layer.

Next, the perforations 5 shown in FIG. 3 (a) are formed. The perforations 5 are preferably formed using chemical means. More specifically, when the photosensitive insulating layer 4b is subjected to the photoresist method, that is, the ultraviolet exposure and the developing treatment with the alkaline aqueous solution, it is preferable that the insulating layer 4a is simultaneously dissolved in the alkaline aqueous solution to be formed. Subsequently, the thermosetting resin components of the insulating layer 4a and the photosensitive insulating layer 4b are heat-cured to obtain heat resistance, chemical resistance, electrical characteristics, and other properties required for a printed wiring board constituent material. Further, if necessary, the through holes 6 are formed before or after the thermosetting resin components of the insulating layer 4a and the photosensitive insulating layer 4b are cured by heating. Through hole 6
Are formed by mechanical means such as drilling or pressing.

Next, as shown in FIG. 3B, the conductor layer 8 is formed.
Form 2 That is, the surface 7 of the insulating layer 4b is roughened by a chemical agent or mechanical means so that the conductor layer 82 such as copper plating can be easily adhered, and the roughened surface 7 of the insulating layer 4b is preferably known. The conductor layer is formed by the copper plating method, and is also formed in the holes 5 and the through holes 6. Next, as shown in FIG. 3C, a circuit is formed on the conductor layer 82 by a known method such as a photoresist method to form a second conductor circuit 81. After the step of FIG. 3C, a solder protective film, a symbol mark and the like (not shown) may be formed if necessary. By performing these manufacturing steps, S by the build-up method according to the present invention can be obtained.
An LC multilayer printed wiring board is produced.

[0031]

According to the present invention, since the insulating resin used for the insulating layer 4a formed on the surface of the copper clad laminate does not have to be a photosensitive insulating resin, the flexibility of the insulating layer is improved. It is easy to do.

As described above, the present invention has two or more insulating layers, so that it has excellent electrical reliability and adhesiveness to copper plating as compared with the conventional one-layer insulating layer. You can see that Furthermore, since the photosensitive insulating layer is thinned, the range of the proper exposure amount at the time of ultraviolet exposure is widened, and there is also an effect of improving the yield when manufacturing the SLC multilayer printed wiring board by the build-up method.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main structure of an SLC multilayer printed wiring board by a build-up method according to the present invention.

FIG. 2 is a sectional view showing a main manufacturing process of an SLC multilayer printed wiring board by a build-up method according to the present invention.

FIG. 3 is a cross-sectional view showing a main manufacturing process of an SLC multilayer printed wiring board by a build-up method according to the present invention.

FIG. 4 is a cross-sectional view showing the main structure of an SLC multilayer printed wiring board according to a conventional build-up method.

[Description of sign]

 1 SLC multilayer printed wiring board by build-up method 1A SLC multilayer printed wiring board by build-up method 2 Insulating substrate 31 First conductor circuit 32 Copper foil 4 Insulating layer 4a Insulating layer 4b Photosensitive insulating layer 5 Perforation 6 Through hole 7 Surface of Insulating Layer 81 Second Conductor Circuit 82 Conductor Layer

Claims (3)

[Claims] 1. An insulating substrate having a surface on which a first conductor circuit is formed, an insulating layer formed on the surface of the insulating substrate, and a second conductor circuit formed on the surface of the insulating layer. In the printed wiring board in which the conductor circuit and the second conductor circuit are connected via the second conductor circuit formed in the hole of the hole formed in the insulating layer, the insulating layers are made of different insulating resins. A multilayer printed wiring board having a structure of two or more layers, at least one layer of which is formed of a photosensitive insulating resin. 2. An insulating substrate having a surface on which a first conductor circuit is formed, an insulating layer formed on the surface of the insulating substrate, and a second conductor circuit formed on the surface of the insulating layer. In the printed wiring board in which the conductor circuit and the second conductor circuit are connected via the second conductor circuit formed in the hole of the hole formed in the insulating layer, the insulating layer has an alkali-soluble photosensitive layer. A multilayer printed wiring board having a two-layer structure of a conductive insulating resin and an alkali-soluble non-photosensitive insulating resin. 3. A step of forming a first conductor circuit on at least an insulating substrate, a step of forming an insulating layer on the surfaces of the insulating substrate and the first conductor circuit, and a photosensitive insulating layer on the surface of the insulating layer. Forming a layer, forming a perforation in the insulating layer and the photosensitive insulating layer, forming a conductor layer on the surface of the photosensitive insulating layer, and forming a conductor layer in the perforation. A multilayer comprising a step of connecting the first conductor circuit and a conductor layer formed on the surface of the photosensitive insulating layer, and a step of forming a circuit on the conductor layer to form a second conductor circuit. Manufacturing method of printed wiring board.