JPH04372193A - Printed wiring board - Google Patents

Abstract

PURPOSE:To improve the adhesive properties of an insulating substrate and an adhesive layer for electroless plating getting trouble in a printed wiring board manufactured through an additive method. CONSTITUTION:In a printed wiring board manufactured through the so-called additive method, in which an adhesive layer 3 for electroless plating is formed onto an insulating substrate 1 and a conductor circuit 7 is formed onto the adhesive layer 3, the insulating substrate 1 is roughened. Rmax=0.5-10 may be selected in JIS-B-0601 as the surface roughness of a rougnened surface.

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 conductor circuit is formed of metal on an insulating substrate.

0002

2. Description of the Related Art An additive method has been proposed as one of the methods for forming this type of printed wiring board. According to this formation method, an adhesive layer is formed by applying an adhesive for electroless plating to an insulating substrate such as glass epoxy, and after the surface of the adhesive layer is roughened, a plating resist is formed on it. Furthermore, metal that will become a conductive 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 with a small number of manufacturing steps. Additionally, by adhering the conductor circuit to the roughened adhesive layer, excellent bonding properties are ensured between the two, making it difficult for the conductor circuit to separate from the adhesive layer. .

0004

However, even if the bonding between the conductive circuit and the adhesive layer is improved as described above, it is difficult to form the adhesive layer on an insulating substrate that does not have a rough surface. In such a case, sufficient bonding properties may not be ensured between the adhesive layer and the insulating substrate, and as a result, there is a possibility that separation may occur at the interface between the two. Under these circumstances, in order to further improve the peel strength of the conductor circuit, it is necessary to improve not only the bonding property between the conductive circuit and the adhesive layer, but also the bonding property between the insulating substrate and the adhesive layer. It is hoped that

The present invention has been made in view of the above circumstances, and its purpose is to further improve the bonding properties between an insulating substrate and an adhesive layer coated on the insulating substrate. An object of the present invention is to provide a printed wiring board equipped with a conductor circuit that does not easily peel off.

[0006]

[Means and effects for solving the problems] In order to solve the above problems, the present invention provides a printed wiring board in which a conductor circuit is formed by electroless plating on an adhesive layer applied on an insulating substrate. The insulating substrate is characterized by a roughened surface. According to the configuration of the present invention in which the surface of the insulating substrate is roughened in this way, a larger contact area can be secured between the adhesive layer and the insulating substrate when compared with an insulating substrate that does not have a roughened surface. Can be done. Therefore, when the adhesive is applied to the surface of the substrate, it is possible to provide sufficient bonding force between the two. Therefore, unlike conventional printed wiring boards, peeling does not occur at the interface between the insulating substrate and the adhesive layer.

[0007] Below, a method for manufacturing the above-mentioned printed wiring board will be explained in detail. For example, it is preferable to use a glass epoxy resin substrate containing an ultraviolet shielding material as the insulating substrate. By using such resin materials, it is possible to prevent the so-called back-fogging phenomenon of plating resists, in which when exposed to ultraviolet light during the formation of plating resists, a resist layer is formed on the back side of the substrates due to the ultraviolet rays that have passed through the substrates. It is planned.

[0008] In addition to the above-mentioned glass epoxy resin substrate containing an ultraviolet shielding material, for example, glass polyimide resin substrates can of course be used, as well as substrates made of ceramics such as aluminum nitride and alumina, and substrates made of ceramics such as aluminum, A substrate made of metal such as iron may also be used. Suitable methods for roughening the surface of the insulating substrate include, for example, sandblasting, which performs polishing by jetting abrasive grains, and buff polishing, which performs polishing using a rotating buff with abrasive grains held on the surface. Conventional polishing methods other than these can be sufficiently applied as long as they can form a desired rough surface on an insulating substrate.

When the insulating substrate is roughened using such a polishing method, the surface roughness (Rmax) is JI
Measured according to S-B-0601 (Surface roughness measurement test using stylus type surface roughness measuring device). In this case, the surface roughness is preferably within the range of 0.5 μm to 10 μm, more preferably within the range of 1.0 μm to 5.0 μm.

[0010] If the surface roughness value is less than 0.5 μm, it is not possible to secure a large contact area between the insulating substrate and the adhesive layer, and therefore it is impossible to provide sufficient bonding force between the two. I can't. Also, the value of this surface roughness is 10μ
If m is exceeded, the unevenness on the insulating substrate becomes large, so even if an adhesive layer is formed, there is a possibility that the smoothness of the layer surface will be adversely affected. Forming a conductor circuit on an uneven adhesive layer like this not only causes peeling, but also
This is not preferable because it tends to cause mounting defects when electronic components are placed.

Next, the composition of the adhesive applied to the insulating substrate in order to improve the adhesion between the insulating substrate and the metal conductor circuit will be explained in detail. The adhesive for forming the adhesive layer is made of heat-resistant resin fine particles (filler resin) that are soluble in acids or oxidants and have been cured in advance, and are soluble in acids or oxidants by being cured. Heat-resistant resin liquid that becomes poorly soluble (matrix resin)
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.

[0012] As the heat-resistant resin fine particles, for example,
Agglomerated particles with an average particle size of 2 μm to 10 μm by condensing heat resistant resin powder with an average particle size of 2 μm or less, heat resistant resin powder with an average particle size of 2 μm to 10 μm, and an average particle size of 2 μm
At least one of heat-resistant resin powder with an average particle size of 2 μm or less or inorganic fine powder is attached to the surface of a particle mixture with a heat-resistant resin powder with an average particle size of 2 μm or less or a heat-resistant resin powder with an average particle size of 2 μm to 10 μm. It is desirable that the particles be selected from among pseudoparticles made of

[0013] In particular, it is preferable to use the particle mixture as heat-resistant resin fine particles, and an anchor formed of this resin can ensure a more reliable anchor effect. Therefore, sufficient peel strength can be imparted to conductor circuits and the like formed thereon. The adhesive is cured by, for example, heat treatment or addition of a catalyst. This treatment brings the adhesive layer into a state in which a filler resin that is soluble in oxidizing agents and the like is dispersed in a matrix resin that is sparingly soluble in oxidizing agents and the like. In this state, when oxidation treatment is performed using, for example, chromic acid, chromate, permanganate, ozone, etc., only the filler resin portion is selectively dissolved, and countless micropores as anchors are created on the matrix resin surface. It is formed. As a result, the surface of the adhesive layer is roughened.

[0014] If a plating resist or a conductor circuit is formed on the surface of the adhesive layer having micropores, a so-called anchor effect is obtained, and this effect makes it difficult for the plating resist and conductor circuit to separate from the adhesive layer. . After the 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 that the thickness be within the range of 0 μm.

[0015] If the value of this 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. Also, the value of this surface roughness is 20
If it exceeds μm, the anchor becomes too large and a sufficient anchoring effect cannot be obtained, making it impossible to secure the desired adhesive strength. For the above reasons, surface roughness (Rmax)
is more preferably within the range of 2 μm to 15 μm.

[0016] Examples of the heat-resistant resin fine particles serving as the filler resin include epoxy resin, polyester resin,
It is preferable to use powder such as bismaleimide-triazine resin, and the size of such fine resin particles is preferably within 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 will not be sufficient, making it impossible to ensure the desired anchor effect. Therefore, it becomes difficult to impart sufficient peel strength to conductor circuits and the like formed thereon.

[0017] Furthermore, if the size of the fine particles exceeds 10 μm, the anchors formed when the fine particles are dissolved and removed tend to have low density and non-uniformity, and the anchors become too large to provide sufficient anchoring effect. is not obtained, making it difficult to impart sufficient peel strength to the conductor circuit. As the heat-resistant resin serving as the matrix resin, epoxy resin, epoxy-modified polyimide resin, polyimide resin, phenol resin, etc. can be used. Furthermore, these resins may be imparted with photosensitivity. After adding a predetermined amount of the above resin fine particles to this resin liquid,
By adding a solvent such as butyl cellosolve and stirring, an adhesive varnish in which the resin fine particles are uniformly dispersed can be obtained.

[0018] As a method for applying the adhesive varnish onto 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 properties and apply it to a predetermined thickness. In addition to such coating methods, various methods such as dip coating, spray coating, spinner coating, curtain coating, and screen printing can be used.

When the adhesive varnish is applied by any of these methods, the thickness of the adhesive layer is preferably within the range of 10 μm to 100 μm. If the thickness of the adhesive layer is less than 10 μm, it will be susceptible to the condition of the rough surface of the insulating substrate, and a smooth adhesive layer cannot be formed. In addition, the thickness of the adhesive layer is 100 μm.
If it exceeds 100%, it is not only impossible to increase the density of the wiring board, but also thick coating is required, resulting in a decrease in mass productivity and an increase in cost.

After the adhesive varnish has been applied, hardened and roughened by the method described above, catalyst nuclei such as palladium-tin colloid are applied to the rough surface of the adhesive layer. This treatment activates the rough surface of the adhesive, allowing metal to be easily deposited during electroless plating. Then, in order to form a desired conductive circuit pattern on the surface subjected to the above-mentioned treatment, a plating resist for electroless plating is laminated corresponding to the portion where the conductive circuit is not formed.

[0021] As the above plating resist, for example,
A photosensitive dry film or the like is suitable. According to such a dry film, it is possible to form fine conductor circuits on the adhesive layer reliably and with high precision. Therefore,
It can fully meet the demands for higher density and higher integration. Then, by exposing the plating resist laminated on the surface of the adhesive layer and then developing it,
Mask only the parts where conductive circuits are not formed. 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 of the adhesive layer surface to which the catalyst nuclei have been applied. . After this electroless plating is performed, a desired conductive circuit pattern is obtained by removing the plating resist.

According to the method described above, it is not only possible to manufacture printed wiring boards, etc. in which conductor circuits on both sides of the board are connected by through holes, but also to achieve higher integration and higher density by using through holes or via holes. Densified build-up multilayer wiring boards, multilayer printed wiring boards, etc. can also be manufactured. Furthermore, since the surface of the printed wiring board obtained by the above method is roughened, bondability with the adhesive layer is ensured, and peeling of the adhesive does not occur.

[0023]

[Examples and Comparative Examples] Hereinafter, Examples 1, 2, and 3 embodying the present invention, and Comparative Examples 1 and 2 relative to these Examples will be described in detail with reference to the drawings. [Example 1] In Example 1, a single-layer printed wiring board was manufactured by an additive method. Manufacturing steps (1) to (5) will be explained below based on FIGS. 1(a) to (f).

Step (1): In Example 1, an FR-4 grade insulating substrate LE-67N, W type (manufactured by Hitachi Chemical) was used as the insulating substrate 1. For this substrate 1, a high-precision jet scrub polishing machine IJS-60 manufactured by Ishikawa Notation Co., Ltd.
The surface of the substrate 1 was polished using 0, and the surface roughness was 7 μm.
A rough surface 2 was obtained. Surface roughness was measured using a contact type surface roughness meter (Tokyo Seimitsu Surfcom 470A) according to JIS-B-06.
01 (see Figure 1(a)). At this time,
The discharge pressure of the abrasive was set to 1.8 kg/cm2, and the line speed (substrate transport speed) was set to 2 m/min.

Step (2): 60 parts by weight of phenol novolak epoxy resin (manufactured by Yuka Shell, trade name, E-154), 40 parts by weight of bisphenol A epoxy resin (manufactured by Yuka Shell, trade name, E-1001) parts, imidazole curing agent (manufactured by Shikoku Kasei Co., Ltd., trade name, 2P4MHZ) 4 parts by weight,
Epoxy resin fine powder (manufactured by Toray) particle size 5.5 μm 1
0 parts by weight, and 25 parts by weight of particles having a particle size of 0.5 μm were blended and kneaded using a triple roll, 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 with a thickness of 50 μm (see Figure 1(b)).
. Step (4): Next, the epoxy resin fine powder was dissolved and removed by immersion in chromic acid for 10 minutes, and the surface of the adhesive layer 3 was made into a rough surface 4 (see FIG. 1(c)). After neutralization, chromic acid was removed by washing with water.

Step (5): Activate the rough surface 4 by immersing it in a commercially available palladium-tin colloidal catalyst to form a catalyst core layer 5.
was formed. Subsequently, after heat treatment at 120°C for 30 minutes, a dry film photoresist was laminated and
A plating resist layer 6 was formed by exposure and development (Figure 1
(d)). Then, it was immersed in the electroless copper plating solution shown in Table 1 for 15 hours to form a conductor circuit 7 with a thickness of about 35 μm (see FIG. 1(e)). After removing the plating resist layer 6, the substrate 1 is coated with a mixed solution of tartaric acid and hydrochloric acid (tartaric acid 5-100 g/l, 35% hydrochloric acid 200-35 g/l).
A printed wiring board was manufactured by immersing it in 0 ml/l) and removing the catalyst in the area where the conductor was formed (see FIG. 1(f)). [Example 2] Next, regarding manufacturing steps (1) to (5) of the multilayer printed wiring board of Example 2 using the build-up method,
This will be explained based on FIGS. 2(a) to 2(f).

Step (1): In Example 2, the insulating substrate 11 used in Example 1 was used. The surface of this substrate 11 was polished using an oscillation polisher IOP-600 manufactured by Ishikawa Jyoki Co., Ltd. to obtain a rough surface 12 having a surface roughness of 2 μm. At this time, the rotation speed was set to 2000r. p. m. Then, the line speed (substrate transport speed) was set to 2 m/min. Then, the number of oscillations was set to 575 times/min. were set respectively.

Then, the additive method is applied to the substrate 11 according to steps (2) to (5) of Example 1, and the insulating substrate 1
1. A wiring board 10 including an adhesive layer 13, rough surfaces 12 and 14, a catalyst core layer 15, and an inner circuit 16 was formed (see FIG. 2(a)
) reference). Step (2): 60 parts by weight of 50% acrylate of cresol novolak epoxy resin (manufactured by Yuka Shell, trade name, Epicoat 180S), 40 parts by weight of bisphenol A epoxy resin (manufactured by Yuka Shell, trade name, E-1001) Parts by weight, 15 parts by weight of diallyl terephthalate, 2-methyl-1
-[4-(Methylthio)phenyl]-2-morpholinopropanone-1 (manufactured by Ciba Geigy, Irgacure 9
07) 4 parts by weight, imidazole (manufactured by Shikoku Kasei, trade name,
2P4MHZ) and 50 parts by weight of epoxy resin fine powder (manufactured by Toray Industries, particle size: 0.5 μm) were blended and 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, and heat at 100°C.
The adhesive was dried and cured for 1 hour to form a photosensitive adhesive layer 17 with a thickness of 50 μm (see FIG. 2(b)). Step (4): Next, a photomask film on which a black circle with a diameter of 100 μm and a punched cut portion are printed in black is brought into close contact with the wiring board 10 treated in step (3), and heated at 500 mJ/cm using an ultra-high pressure mercury lamp. Exposure was made at cm2. By ultrasonic development treatment with chlorocene solution,
An opening 18 serving as a via hole with a diameter of 100 μm was formed on the wiring board 10 (see FIG. 2(c)).

Next, the wiring board 10 is exposed to light at about 3000 mj/cm2 using an ultra-high pressure mercury lamp, and further heated to 100°C.
By heat treating at 150° C. for 1 hour and then 3 hours at 150° C., an interlayer insulating layer 21 having openings 18 with excellent dimensional accuracy corresponding to a photomask film was formed. and,
The interlayer insulating layer 21 is immersed in chromic acid for 10 minutes.
The surface was changed to a rough surface 19, and after neutralization, the chromic acid was removed by washing with water (see FIG. 2(d)).

Step (5): A catalyst core layer 22 was formed by immersing it in a commercially available palladium-tin colloidal catalyst, and heat treatment was performed at 120° C. for 30 minutes in a nitrogen atmosphere. Then, after laminating the dry film photoresist 20, exposure and development was performed (see FIG. 2(e)). Thereafter, it was immersed in an electroless copper plating solution having the composition shown in Table 1 below for 15 hours,
After forming a copper plating layer of approximately 35 μm as the outer layer circuit 23 (see FIG. 2(f)), the plating resist was removed to produce a multilayer printed wiring board with via holes.

[0033]

[Table 1]

[Example 3] Example 3 is a build-up type multilayer printed wiring board in which a polishing method different from that of Example 1 and Example 2 is adopted, and the manufacturing method thereof is shown in FIGS. The explanation will be based on d). Process: In Example 3, an FR-4 grade copper clad laminate MCL-E-67 (manufactured by Hitachi Chemical) in which a copper layer 32 was formed on a substrate 31 was used (see FIG. 3(a)). Then, the copper layer 32 was etched by a conventional method to form an inner layer circuit 33 (see FIG. 3(b)).

Thereafter, the surface of the substrate 31 was polished using a high-precision jet scrubbing machine in the same manner as in step (1) of Example 1 to change the surface of the substrate 31 to a rough surface 34 with a surface roughness of 5 μm. (See Figure 3(c)). Then, in order to change the surface of the inner layer circuit 33 to a rough surface 35, the inner layer circuit 33 is
A so-called blackening reduction treatment was performed in which the surface was oxidized and then reduced again (see Figure 3(d)). The surface roughness of the inner layer circuit 33 is 3 μm (1 μm to 5 μm is the preferred range)
Met.

After this, steps (2) to (5) of Example 2 are carried out.
), a multilayer printed wiring board with via holes was manufactured by the build-up method. As a comparative example for Examples 1 to 3, a printed wiring board was manufactured in which the surface of the substrate was not roughened. The manufacturing process of Comparative Example 1 and Comparative Example 2 will be explained below. [Comparative Example 1] When the surface roughness of the insulating substrate used in Example 1 was measured without surface polishing, it was found to be 0.
It was 4 μm. Thereafter, using this substrate, a single-layer printed wiring board was manufactured in the same manner as in the steps (2) to (5) of Example 1 above. [Comparative Example 2] As Comparative Example 2, the same copper-clad laminate as that used in Example 3 was used. Then, an etching process was performed using a conventional method to form an inner layer circuit. Thereafter, the blackening reduction treatment described above was performed without performing the surface polishing of Example 1, thereby changing the inner layer circuit to a rough surface 35 with a surface roughness of 7 μm. Thereafter, a multilayer printed wiring board with via holes was manufactured by the build-up method according to steps (2) to (5) of Example 2.

Example 1 manufactured by the above method,
In order to comparatively evaluate the bonding state between the insulating substrate and the adhesive layer in each printed wiring board of Examples 2 and 3 and Comparative Examples 1 and 2, a solder heat resistance test and a vapor phase heat cycle test were conducted. In the solder heat resistance test, each printed wiring board was
The bonding state between the insulating substrate and the adhesive layer was investigated by immersing it in solder at 0° C. for 15 seconds. As shown in Table 2, in each of 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, partial peeling was observed between the insulating substrate and the adhesive layer, and in Comparative Example 2, overall peeling was observed between the two.

In addition, in the gas phase heat cycle test, heating/cooling cycles in the gas phase (from -65°C to 125°C
After repeating the above steps 1000 times, the bonding state between the insulating substrate and the adhesive layer was investigated. The results are also the same as the solder heat resistance test, and Table 2
As shown, no peeling was observed between the insulating substrate and the adhesive layer. On the other hand, Comparative Example 1 and Comparative Example 2
Partial and total peeling was observed between the two.

[0039]

[Table 2]

[0040] In the table, the ○ mark indicates that no peeling is observed between the insulating substrate and the adhesive layer, and the △ mark indicates that partial peeling is observed between the insulating substrate and the adhesive layer. condition,
The x mark indicates a state in which peeling is observed throughout between the insulating substrate and the adhesive layer. According to the above results,
By roughening the substrate surface as in Examples 1, 2, and 3, a larger contact area between the adhesive layer and the insulating substrate can be secured than when no roughening treatment is performed. Can be done. Therefore, the bondability between the two is improved, and peeling at the interface between the two is effectively prevented.

[0041]

Effects of the Invention As detailed above, according to the printed wiring board of the present invention, the bondability between the insulating substrate and the adhesive layer coated thereon is improved, so that conductor circuits can be easily formed. It has the excellent effect of making peeling less likely to occur.

[Brief explanation of the drawing]

FIG. 1 (a) to (f) are schematic diagrams showing the manufacturing process of a printed wiring board of Example 1.

2(a) to (f) are schematic diagrams showing the manufacturing process of a printed wiring board of Example 2. FIG.

3(a) to (d) are schematic diagrams showing the manufacturing process of a printed wiring board of Example 3. FIG.

[Explanation of symbols]

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

Claims (6)

[Claims] 1. A printed wiring board in which a conductive circuit (7) is 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 by: 2. The printed wiring board according to claim 1, wherein the surface of the adhesive layer (3) is roughened by acid or oxidizing agent treatment. 3. The adhesive for forming the adhesive layer (3) is made of heat-resistant resin fine particles that have been cured in advance and are soluble in acids or oxidants, and are made of heat-resistant resin particles that are soluble in acids or oxidizers and that are soluble in acids or oxidizers by curing. The adhesive comprises a heat-resistant resin liquid that is hardly soluble in an adhesive, the fine particles are dispersed in the resin liquid, and the resin liquid is cured by a curing treatment. The printed wiring board according to item 1 or 2. 4. Surface roughness (Rm
The printed wiring board according to any one of claims 1 to 3, characterized in that ax) is 0.5 μm to 10 μm. 5. The thickness of the adhesive layer (3) is 10 μm.
The printed wiring board according to any one of claims 1 to 4, wherein the printed wiring board has a thickness of 100 μm to 100 μm. [Claim 6] The size of the heat-resistant fine particles is 0.1μ.
The printed wiring board according to any one of claims 1 to 5, wherein the printed wiring board has a thickness of m to 10 μm.