JP2826206B2 - Printed wiring board - Google Patents

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 in which a conductive circuit is formed by a metal on an insulating substrate.

[0002]

2. Description of the Related Art As one of the methods for forming this type of printed wiring board, an additive method has been conventionally proposed. According to this forming method, an adhesive layer for electroless plating is applied to an insulating substrate such as a glass epoxy to form an adhesive layer, and after the surface of the adhesive layer is roughened, a plating resist is formed thereon. Further, a metal to be a conductor circuit is attached by electroless plating.

According to this method, since the conductor circuit is basically formed by electroless plating, there is an advantage that a fine pattern can be easily and reliably formed by a small number of manufacturing steps. In addition, since the conductor circuit is adhered to the roughened adhesive layer, excellent bonding between the two is ensured, so that the conductor circuit is less likely to peel off from the adhesive layer. .

[0004]

However, even if the bonding property between the conductor circuit and the adhesive layer is improved as described above, the adhesive layer is formed on an insulating substrate having no rough surface. In such a case, sufficient bonding between the adhesive layer and the insulating substrate is not ensured, and as a result, there is a possibility that separation occurs at the interface between the two. Under these circumstances, in order to further improve the peel strength of the conductor circuit, not only the joint property between the conductor circuit and the adhesive layer but also the joint property between the insulating substrate and the adhesive layer are simultaneously improved. It is hoped that it will.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the bonding between an insulating substrate and an adhesive layer formed on the insulating substrate. It is another object of the present invention to provide a printed wiring board provided with a conductor circuit in which peeling does not easily occur.

[0006]

In order to solve the above-mentioned problems, the present invention relates to a printed wiring board in which a conductive circuit is formed by electroless plating on an adhesive layer applied on an insulating substrate. The surface of the insulating substrate is roughened. According to the configuration of the present invention in which the surface of the insulating substrate is roughened, it is possible to ensure a large contact area between the adhesive layer and the insulating substrate as compared with an insulating substrate having no roughened surface. Can be. Therefore, when the adhesive is applied to the substrate surface, it is possible to provide a sufficient bonding force between the two. Accordingly, there is no occurrence of separation at the interface between the insulating substrate and the adhesive layer unlike the conventional printed wiring board.

Hereinafter, a method for manufacturing a printed wiring board as described above will be described in detail. As the insulating substrate, for example, a glass epoxy resin substrate containing an ultraviolet shielding material is preferably used. By using such a resin material, it is possible to prevent a so-called back fogging phenomenon of a plating resist, in which when a plating resist is exposed to ultraviolet rays at the time of forming the resist, the resist layer is also formed on the back side of the substrate due to the ultraviolet rays transmitted through the substrate. It is planned.

As a material other than the glass epoxy resin substrate containing the ultraviolet shielding material, for example, a glass polyimide resin substrate can of course be applied, as well as a ceramic substrate such as aluminum nitride and alumina, and aluminum, A metal substrate such as iron may be used. Further
In addition, as shown in Embodiment 3, an inner layer circuit is provided on an insulating substrate.
It may be formed. As a method of roughening the surface of the insulating substrate, for example, sandblasting in which polishing is performed by spraying abrasive grains, buff polishing in which polishing is performed by a rotary buff having abrasive grains held on the surface, and the like are preferable. Other conventional polishing methods can be applied sufficiently as long as a desired rough surface can be formed on the insulating substrate.

When the insulating substrate is roughened by using such a polishing method, its surface roughness (Rmax) is determined by JI
It is measured according to SB-0601 (surface roughness measurement test using a stylus type surface roughness measuring instrument). In this case, the surface roughness is preferably in the range of 0.5 μm to 10 μm, and more preferably in the range of 1.0 μm to 5.0 μm.

If the value of the surface roughness is less than 0.5 μm, it is not possible to secure a large contact area between the insulating substrate and the adhesive layer, so that a sufficient bonding force is provided between the two. Can not do. Further, the value of the surface roughness is 10 μm.
If it exceeds m, the unevenness on the insulating substrate becomes large, so that even if an adhesive layer is formed, there is a possibility that the smoothness of the layer surface may be adversely affected. Even if a conductor circuit is formed on an adhesive layer that is not smooth in this way, not only will peeling occur,
It is not preferable because mounting failure is likely to occur when electronic components are placed.

Next, the composition of the adhesive applied on the insulating substrate to improve the adhesion between the insulating substrate and the metal conductive circuit will be described in detail. The adhesive for forming the adhesive layer is soluble in an acid or an oxidizing agent and is cured with a heat-resistant resin fine particle (filler resin) in advance. Heat-resistant resin liquid (matrix resin) that becomes hardly soluble
Preferably, the fine particles are dispersed in the resin liquid, and the resin liquid is cured by a curing treatment. Further, the matrix resin may be a photosensitive resin.

The heat-resistant resin fine particles include, for example,
Aggregated particles obtained by condensing heat-resistant resin powder having an average particle diameter of 2 μm or less to have a size of 2 μm to 10 μm, heat-resistant resin powder having an average particle diameter of 2 μm to 10 μm, and having an average particle diameter of 2 μm.
At least one of a heat-resistant resin powder having an average particle diameter of 2 μm or less or an inorganic fine powder is adhered to a particle mixture with a heat-resistant resin powder having a particle diameter of 2 μm or less, or a heat-resistant resin powder having an average particle diameter of 2 μm to 10 μm. Desirably, the particles are selected from pseudo particles formed.

In particular, it is preferable to use the particle mixture as heat-resistant resin fine particles. According to the anchor formed of this resin, a more reliable anchor effect can be secured. Therefore, a sufficient peel strength can be imparted to the conductor circuit and the like formed thereon. The curing of the adhesive is performed by, for example, heat treatment or addition of a catalyst. By this treatment, the adhesive layer becomes a state in which a filler resin soluble in the oxidizing agent or the like is dispersed in a matrix resin hardly soluble in the oxidizing agent or the like. In this state, when an oxidation treatment is performed with, for example, chromate, chromate, permanganate, ozone, or the like, only the filler resin portion is selectively dissolved, and a myriad of micropores serving as anchors are formed on the matrix resin surface. It is formed. As a result, the surface of the adhesive layer is roughened.

If a plating resist or a conductor circuit is formed on the surface of the adhesive layer having the fine holes, a so-called anchor effect is obtained, and this effect makes it difficult for the plating resist and the conductor circuit to peel off from the adhesive layer. . After the above-mentioned roughening treatment, the surface roughness (Rmax) of the adhesive layer surface measured according to JIS-B-0601 is 1 μm to 2 μm.
It is desirable to be within the range of 0 μm.

When the value of the surface roughness is less than 1 μm,
A large contact area cannot be secured between the conductor circuit and the adhesive layer, and in this case, a desired peel strength cannot be secured between the two. The value of the surface roughness is 20
If it exceeds μm, the anchor becomes too large and a sufficient anchor effect cannot be obtained, so that a desired adhesive strength cannot be secured. Surface roughness (Rmax) for the above reasons
Is more preferably in the range of 2 μm to 15 μm.

As the heat-resistant resin fine particles serving as the filler resin, for example, epoxy resin, polyester resin,
It is preferable to use a powder such as a bismaleimide-triazine resin, and the size of such resin fine particles is preferably in the range of 0.1 μm to 10 μm. If the size of the fine particles is less than 0.1 μm, the size of the anchor formed by dissolution and removal is not sufficient, and a desired anchor effect cannot be secured. Therefore, it is difficult to provide a sufficient peel strength to the conductor circuit and the like formed thereon.

If the size of the fine particles exceeds 10 μm, the anchor formed when the fine particles are dissolved and removed tends to be low-density and non-uniform, and the anchor is too large to provide a sufficient anchor effect. And it becomes difficult to impart sufficient peel strength to the conductor circuit. As the heat-resistant resin serving as the matrix resin,
Epoxy resins, epoxy-modified polyimide resins, polyimide resins, phenol resins, and the like can be used. Also,
Photosensitivity may be imparted to these resins. After blending a predetermined amount of the above resin fine particles with the resin liquid, a solvent such as butyl cellosolve is added and stirred, whereby a varnish of an adhesive in which the resin fine particles are uniformly dispersed can be obtained.

As a method of applying the adhesive varnish on the surface of the insulating base material, it is preferable to apply the adhesive varnish using a roll coater. It is possible to maintain the property and to apply it to a predetermined thickness. In addition to these coating methods, various means such as a dip coating method, a spray coating method, a spinner coating method, a curtain coating method, and a screen printing method can be used.

When the adhesive varnish is applied by any of these methods, it is desirable that the thickness of the adhesive layer be in the range of 10 μm to 100 μm. If the thickness of the adhesive layer is less than 10 μm, it is easily affected by the state of the rough surface of the insulating substrate, and a smooth adhesive layer cannot be formed. The thickness of the adhesive layer is 100 μm.
If it exceeds m, not only the density of the wiring board cannot be increased, but also the thick coating results in a decrease in mass productivity and an increase in cost.

After applying, curing and roughening the adhesive varnish by the above-described method, a catalyst nucleus such as palladium-tin colloid is applied to the rough surface of the adhesive layer. This treatment activates the roughened surface of the adhesive, so that metal can be easily deposited when electroless plating is performed. Then, in order to form a desired conductor circuit pattern on the surface on which the above-described processing has been performed, a plating resist for electroless plating is laminated corresponding to a portion where the conductor circuit is not formed.

As the plating resist, for example,
A photosensitive dry film is suitable. According to such a dry film, a fine conductor circuit can be reliably and accurately formed on the adhesive layer. Therefore,
It is possible to sufficiently respond to demands for higher density and higher integration. Then, after exposing the plating resist laminated on the adhesive layer surface, by performing development,
Only the portion where the conductor circuit is not formed is masked. In this state, electroless copper plating, electroless nickel plating, electroless tin plating, electroless gold plating, electroless silver plating, etc. are performed to deposit metal on the conductor circuit forming portion on the surface of the adhesive layer provided with the catalyst nucleus. . After this electroless plating is done,
A desired conductor circuit pattern can be obtained by removing the plating resist. Note that this method is
It is called the live method. Also, the so-called semi-additive method
May be used. That is, the entire surface of the adhesive
After forming a film, a plating resist is provided and electrolytic plating is performed.
And remove the plating resist to remove the plating resist.
This is for etching the electroless plating film. Any
The method is also a method of forming a conductor circuit by electroless plating
It is.

According to the above-described method, not only can a printed wiring board or the like in which conductor circuits on both sides of a substrate are connected by through holes be manufactured, but also higher integration and higher performance can be achieved by using through holes or via holes. Densified build-up multilayer wiring boards, multilayer printed wiring boards, and the like can also be manufactured. Further, the surface of the printed wiring board obtained by the above method is roughened, so that the bonding property with the adhesive layer is ensured and the peeling of the adhesive does not occur.

[0023]

Examples and Comparative Examples Examples 1, 2 and 3 embodying the present invention and Comparative Examples 1 and 2 for these examples will be described in detail with reference to the drawings. Embodiment 1 In Embodiment 1, a single-layer printed wiring board is manufactured by the additive method. Hereinafter, the manufacturing steps (1) to (5) will be described with reference to FIGS.

Step (1): In Example 1, FR-4 grade insulating substrate LE-67N, W type (manufactured by Hitachi Chemical Co., Ltd.) was used as the insulating substrate 1. High precision jet scrub polisher IJS-60 manufactured by Ishikawa Notation for this substrate 1
The surface of the substrate 1 is polished by using 0, and the surface roughness is 7 μm.
Was obtained. The surface roughness was measured using a needle-type surface roughness meter (Tokyo Seimitsu Surfcom 470A) according to JIS-B-06.
01 (see FIG. 1 (a)). At this time, the discharge pressure of the abrasive was set to 1.8 kg / cm ² , and the line speed (substrate transfer speed) was set to 2 m / min.

Step (2): 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154), 40 parts by weight of a bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name: E-1001) Parts, 4 parts by weight of an imidazole curing agent (trade name, 2P4MHZ, manufactured by Shikoku Chemicals), 10 parts by weight of an epoxy resin fine powder (manufactured by Toray) having a particle size of 5.5 μm, and 25 parts by weight having a particle size of 0.5 μm. The resulting mixture was kneaded with a three-roll mill, and an appropriate amount of butyl cellosolve acetate was added to prepare an adhesive varnish.

Step (3): After applying the adhesive varnish on the insulating substrate 1 using a roll coater,
It was dried and cured at 0 ° C. for 1 hour and at 150 ° C. for 5 hours to form an adhesive layer 3 having a thickness of 50 μm (see FIG. 1B). Step (4): Next, the epoxy resin fine powder was dissolved and removed by immersion in chromic acid for 10 minutes to make the surface of the adhesive layer 3 rough (see FIG. 1 (c)). Then, after neutralization, chromic acid was removed by washing with water.

Step (5): The rough surface 4 is activated by immersion in a commercially available palladium-tin colloidal catalyst, and the catalyst core layer 5
Was formed. Subsequently, after heat treatment at 120 ° C. for 30 minutes, while laminating a dry film photoresist,
Exposure and development were performed to form a plating resist layer 6 (FIG. 1).
(d)). Then, add 1 to the electroless copper plating solution shown in Table 1.
By immersing for 5 hours, a conductor circuit 7 having a thickness of about 35 μm was formed (see FIG. 1 (e)). After the plating resist layer 6 is removed, the substrate 1 is immersed in a mixed solution of tartaric acid and hydrochloric acid (tartaric acid 5 to 100 g / l, 35% hydrochloric acid 200 to 350 ml / l) to remove the catalyst in the portion where the conductor is to be formed. Thus, a printed wiring board was manufactured (see FIG. 1 (f)). [Embodiment 2] Next, the manufacturing steps (1) to (5) of the multilayer printed wiring board of Embodiment 2 by the build-up method will be described.
This will be described with reference to FIGS.

Step (1): In the second embodiment, the insulating substrate 11 used in the first embodiment is used. The surface of the substrate 11 was polished using an oscillation polishing machine IOP-600 manufactured by Ishikawa Notation, and a rough surface 12 having a surface roughness of 2 μm was obtained. At this time, the number of rotations was set to 2000 rpm, the line speed (substrate transfer speed) was set to 2 m / min, and the number of oscillations was set to 575 times / min.

Then, the additive method is applied to the substrate 11 according to the steps (2) to (5) of the first embodiment, and the insulating substrate 1
1. A wiring board 10 including an adhesive layer 13, rough surfaces 12, 14, a catalyst core layer 15, and an inner layer circuit 16 was formed (FIG. 2A).
reference). Step (2): 60 parts by weight of a 50% acrylate of cresol novolak type epoxy resin (manufactured by Yuka Shell, trade name, Epicoat 180S), bisphenol A type epoxy resin (manufactured by Yuka Shell, trade name, E-1001) 40 Parts by weight, 15 parts by weight of diallyl terephthalate, 2-methyl-
4 parts by weight of 1- [4- (methylthio) phenyl] -2-morpholinopropanone-1 (manufactured by Ciba-Geigy, Irgacure 907), 4 parts by weight of imidazole (manufactured by Shikoku Chemicals, trade name: 2P4MHZ), epoxy resin fine 50 parts by weight of a powder (manufactured by Toray, particle size: 0.5 μm) was blended, and the mixture was stirred with a homodisper stirrer while adding an appropriate amount of butyl cellosolve to prepare an adhesive varnish.

Step (3): Apply the above adhesive varnish to the inner layer circuit 16 using a roll coater,
For 1 hour to form a photosensitive adhesive layer 17 having a thickness of 50 μm (see FIG. 2B). Step (4): Next, a black circle having a diameter of 100 μm and a photomask film having a black cut-out portion printed thereon are brought into close contact with the wiring board 10 which has been subjected to the processing of the above step (3), and 500 mj / m is applied by an ultra-high pressure mercury lamp. Exposure was in cm ² . This is subjected to an ultrasonic development process with a chlorocene solution, so that an opening 18 serving as a via hole having a diameter of 100 μm
Was formed (see FIG. 2 (c)).

Next, the wiring board 10 is exposed to an ultra-high pressure mercury lamp at about 3000 mj / cm ² , and further subjected to heat treatment at 100 ° C. for 1 hour and then at 150 ° C. for 3 hours to obtain a dimensional accuracy equivalent to a photomask film. Excellent opening 1
8 was formed. Then, the surface of the interlayer insulating layer 21 was changed to the rough surface 19 by immersion in chromic acid for 10 minutes, and after neutralization, washed with water to remove chromic acid (see FIG. 2 (d)).

Step (5): A catalyst core layer 22 was formed by dipping in a commercially available palladium-tin colloid catalyst, and heat-treated at 120 ° C. for 30 minutes in a nitrogen atmosphere. Then, exposure and development were performed after laminating the dry film photoresist 20 (see FIG. 2E). Thereafter, the resultant was immersed in an electroless copper plating solution having the composition shown in Table 1 below for 15 hours to form a copper plating layer of about 35 μm as the outer layer circuit 23 (see FIG. 2 (f)). A multilayer printed wiring board having via holes was manufactured.

[0033]

[Table 1]

[Embodiment 3] Embodiment 3 is a build-up type multilayer printed wiring board employing a polishing method different from those of Embodiments 1 and 2, and its manufacturing method is shown in FIGS. Explanation will be made based on d). Step: In Example 3, an FR-4 grade copper-clad laminate MCL-E-67 (manufactured by Hitachi Chemical Co., Ltd.) having a copper layer 32 formed on a substrate 31 was used (see FIG. 3A). And
The copper layer 32 was subjected to an etching process by a conventional method to form an inner layer circuit 33 (see FIG. 3B).

Thereafter, the surface is polished by a high-precision jet scrub polisher in the same manner as in the step (1) of the first embodiment to change the surface of the substrate 31 into a rough surface 34 having a surface roughness of 5 μm. (See FIG. 3 (c)). And the inner layer circuit 3
In order to change the surface of No. 3 into a rough surface 35, a so-called blackening reduction process was performed in which the surface of the inner layer circuit 33 was oxidized and then reduced again (see FIG. 3 (d)). The surface roughness of the inner layer circuit 33 was 3 μm (1 μm to 5 μm is a preferable range).

Thereafter, according to steps (2) to (5) of Example 2, a multilayer printed wiring board having via holes was manufactured by a build-up method. Example 1
As a comparative example with respect to Example 3, a printed wiring board in which the substrate surface was not subjected to the roughening treatment was manufactured. Hereinafter, Comparative Example 1
The manufacturing process of Comparative Example 2 will be described. Comparative Example 1 The surface roughness of the insulating substrate used in Example 1 was 0.4 μm when the surface was not polished. Thereafter, using this substrate, a single-layer printed wiring board was manufactured in the same manner according to the procedure of the steps (2) to (5) of Example 1 described above. Comparative Example 2 As Comparative Example 2, the same copper-clad laminate used in Example 3 was used. Then, an etching process was performed by a conventional method to form an inner layer circuit. Thereafter, the above-mentioned blackening reduction treatment was performed without performing the surface polishing of Example 1, thereby changing the inner layer circuit to a rough surface 35 having a surface roughness of 7 μm. After this,
According to steps (2) to (5) of Example 2, a multilayer printed wiring board having via holes was manufactured by a build-up method.

Example 1 manufactured by the above method
A solder heat resistance test and a gas phase heat cycle test were performed to comparatively evaluate the bonding state between the insulating substrate and the adhesive layer in each of the printed wiring boards of Comparative Examples 2 and 3 and Comparative Examples 1 and 2. In the solder heat resistance test, each printed wiring board was
The state of bonding between the insulating substrate and the adhesive layer was investigated by immersing the substrate in the solder at 0 ° C. for 15 seconds. As shown in Table 2, in Examples 1, 2, and 3, no peeling was observed between the insulating substrate and the adhesive layer, and the bonding state of the adhesive layer was good. On the other hand, in Comparative Example 1, peeling was partially observed between the insulating substrate and the adhesive layer, and in Comparative Example 2, peeling was entirely observed therebetween.

In the gas phase heat cycle test, a cycle of heating and cooling in the gas phase (from −65 ° C. to 125 ° C.)
Was repeated 1000 times, and then the bonding state between the insulating substrate and the adhesive layer was examined. The results are the same as those in the solder heat resistance test.
As shown in FIG. 7, no peeling was observed between the insulating substrate and the adhesive layer. In contrast, Comparative Examples 1 and 2
In this case, peeling was partially and entirely observed between the two.

[0039]

[Table 2]

In the table, the mark ○ indicates that no peeling was observed between the insulating substrate and the adhesive layer, and the mark △ indicates that partial peeling was observed between the insulating substrate and the adhesive layer. State
The crosses indicate the state where peeling is generally observed between the insulating substrate and the adhesive layer. According to the above results,
By performing the roughening process on the substrate surface as in the first, second, and third embodiments, a larger contact area can be secured between the adhesive layer and the insulating substrate than when the roughening process is not performed. Can be. Therefore, the bondability between the two is improved, and peeling off at the interface between the two is effectively prevented.

[0041]

As described above in detail, according to the printed wiring board of the present invention, the bonding property between the insulating substrate and the adhesive layer formed thereon is improved, so that the printed circuit board can be used for the conductor circuit. It has an excellent effect that peeling is less likely to occur.

[Brief description of the drawings]

1 (a) to 1 (f) are schematic views showing steps of manufacturing a printed wiring board of Example 1. FIG.

2 (a) to 2 (f) are schematic views showing steps of manufacturing a printed wiring board of Example 2. FIG.

3 (a) to 3 (d) are schematic views showing steps of manufacturing a printed wiring board of Example 3. FIG.

[Explanation of symbols]

 1. Insulating substrate, 3. Adhesive layer, 7. Conductor circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3/38 H05K 3/18 H05K 3/46

Claims (7)

(57) [Claims] 1. A printed wiring board having a conductive circuit (7) formed by electroless plating on an adhesive layer (3) applied on an insulating substrate (1), wherein the surface of the insulating substrate (1) is rough. A printed wiring board characterized in that it is formed. 2. The printed wiring board according to claim 1, wherein the surface of the adhesive layer is roughened by an acid or oxidizing agent treatment. 3. An adhesive for forming the adhesive layer (3) is prepared by preliminarily curing heat-resistant resin fine particles which are soluble in an acid or an oxidizing agent, and an acid or an oxidizing agent by a curing treatment. An adhesive comprising a heat-resistant resin liquid that becomes hardly soluble in an agent, wherein the fine particles are dispersed in the resin liquid, and the resin liquid is cured by a curing treatment. Item 3. The printed wiring board according to item 1 or 2. 4. The surface roughness (Rma) of the insulating substrate (1).
4. The printed wiring board according to claim 1, wherein x) is 0.5 μm to 10 μm. 5. The adhesive layer (3) has a thickness of 10 μm or less.
The printed wiring board according to claim 1, wherein the thickness is 100 μm. 6. The size of the heat-resistant fine particles is 0.1 μm.
The printed wiring board according to claim 1, wherein the thickness is from 10 μm to 10 μm. 7. An internal circuit is formed on the insulating substrate.
The print according to any one of claims 1 to 6, wherein the print is
Wiring board.