JPH05267840A - Forming method for adhesive layer of additive printed circuit board - Google Patents

Abstract

PURPOSE:To roughen the surface of an adhesive layer formed on an insulating board in a short time and to reduce a deteriorating speed of dissolved solution by decreasing a dissolving amount of the layer necessary for roughing. CONSTITUTION:An adhesive layer 3 made of matrix resin hard soluble in dissolved solution and filler soluble in the solution is formed on a glass epoxy board 1. A surface of the layer 3 is so buffed that its roughness becomes about 5-7mum to form many fine recesses 4 on the surface of the layer 3. Then, the surface part of the layer 3 is dissolved in the solution, the filler near the surface of the layer 3 is dissolved to be removed to form many roughened recesses 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an adhesive layer for an additive method used for manufacturing a printed wiring board.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size, increased in performance, and increased in functionality, and printed wiring boards used for these have been required to have high density and high reliability by fine patterns. There is.

Conventionally, as a method of forming a conductor circuit on a printed wiring board, a subtractive method of forming a conductor circuit by laminating a copper foil on an insulating substrate and then photoetching is widely used. According to this method, it is possible to form a conductor circuit having excellent adhesion to the insulating substrate, but it is difficult to obtain a high-precision fine pattern due to so-called undercut due to the thickness of the copper foil, and it is possible to increase the density. There is a problem that it is difficult to deal with.

Therefore, as an alternative method to the subtractive method, an adhesive is applied to an insulating substrate to form an adhesive layer, the surface of the adhesive layer is roughened, and then electroless plating is applied to form a conductor circuit. The active additive method is attracting attention.

The adhesive for use in the additive method has an average particle size which is soluble in the solution and hardly soluble in the matrix resin solution in the matrix resin solution which is hardly soluble in the solution by the curing treatment. The present applicant has proposed an adhesive in which two different types of fillers are dispersed.
When the adhesive layer is formed on the insulating substrate, the resin mixture is applied to the insulating substrate to a predetermined thickness, and the applied resin mixture is dried to form an adhesive layer. Is cured to form an adhesive layer. Next, when this adhesive layer is immersed in a solution, a large number of roughened recesses are formed due to the difference in solubility between the matrix resin that is hardly soluble in the solution and the filler that is soluble in the solution. At this time, the soluble fillers dispersed in the adhesive layer are different in size 2
Since it is composed of various types of fillers, the roughening recess formed in the adhesive layer has a complicated shape, which makes the adhesion strength between the adhesive layer and the electroless copper plating layer applied to the adhesive layer strong. ..

[0006]

In order to secure the adhesion strength of the electroless copper plating layer to the adhesive layer to a predetermined value or more,
It is necessary that the surface roughness of the adhesive layer after being roughened by the solution be equal to or higher than a predetermined value. However, the adhesive layer has a structure in which a filler soluble in the solution is dispersed in a matrix resin that is hardly soluble in the solution. Then, when the adhesive layer is immersed in the solution, the filler dispersed in the matrix resin which is hardly soluble in the solution is dissolved to form a recess, and the recesses are connected to each other over time to roughen. A recess is formed. Therefore, the process of forming the roughened recesses involves the dissolution of the sparingly soluble matrix resin existing as the matrix of the filler. For this reason, a roughening process involving dissolution of the hardly soluble matrix resin requires a long time.

Further, since the same solution is repeatedly used in the roughening step, the solution gradually deteriorates as the number of times of roughening of the solution increases, and its dissolving power decreases. Therefore, as the number of times of the roughening treatment of the solution increases, the roughening process requires a longer time, which significantly reduces the productivity of the printed wiring board. Then, in order to improve the processing capacity of the roughening step, in order to roughen the adhesive layer for a large number of insulating substrates at once, it is necessary to make the bath of the dissolution liquid large. Further, it is necessary to increase the size of the bath when replacing the deteriorated solution with a new solution or extending the replenishment cycle of the oxidant.

The present invention has been made to solve the above problems, and its purpose is to roughen the surface of an adhesive layer formed on an insulating substrate in a short time and to adjust the amount of dissolution required for roughening. It is an object of the present invention to provide a method for forming an adhesive layer for an additive printed wiring board, which can reduce the deterioration rate of the solution and reduce the size of the bath of the solution.

[0009]

In order to solve the above problems, the present invention provides an uncured matrix resin which is hardly soluble in a solution by a curing treatment, and an uncured matrix resin which is soluble in the solution. After forming an adhesive layer made of a filler that is hardly soluble in the matrix resin for curing on the insulating substrate, the adhesive layer is cured to form an adhesive layer, and then the surface of the adhesive layer is mechanically treated. After roughening by surface treatment, the surface portion of the adhesive layer was dissolved by the dissolving solution to form a large number of roughened recesses.

[0010]

Therefore, according to the present invention, a concave portion is previously formed by mechanical surface treatment on the surface of the adhesive layer formed by curing the adhesive layer formed on the insulating substrate.
After that, when the adhesive layer is dipped in the solution, a roughened recess having a complicated shape is formed due to the difference in the dissolution rate between the Matox resin that is hardly soluble in the solution and the filler that is soluble in the solution. At this time, since the concave portion is formed in advance on the surface of the adhesive layer, the amount of the matrix resin and the filler required to form the roughened concave portion having a predetermined surface roughness is small. Further, the surface of the adhesive layer is roughened by the mechanical surface treatment to increase the contact area between the adhesive layer and the solution, so that the dissolution rate of the adhesive layer is increased. Therefore, when the adhesive layer is immersed in the solution, a large number of roughened concave portions having a complicated shape are formed on the surface of the adhesive layer in a short time.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. First, 40 parts by weight of a bisphenol A type epoxy resin (made by Yuka Shell, trade name: E-1001) as a matrix resin, and a phenol novolac type epoxy resin (made by Yuka Shell, trade name: E-154) as a matrix resin. ) 60 parts by weight,
Imidazole type curing agent (Shikoku Kasei, trade name: 2PH
Z) 10 parts by weight and 10 parts by weight of epoxy resin fine particles as a filler (manufactured by Toray, trade name: Trepearl EP-B, average particle size 0.5 μm), and epoxy resin fine particles (manufactured by Toray, trade name: Trepearl EP-). B, average particle size 5.5μ
m) 25 parts by weight and 75 parts by weight of butyl cellosolve acetate were mixed by stirring with a three-roller to prepare an adhesive for additive method (hereinafter, simply referred to as an adhesive).

Next, the procedure for forming the adhesive layer will be described with reference to FIG. Glass epoxy substrate 1 as an insulating substrate so that the coating thickness is about 30 μm using a roller coater
The adhesive was applied on top. The applied adhesive is dried to volatilize the solvent in the adhesive, and the glass epoxy substrate 1
An adhesive layer 2 was formed on top (FIG. 1 (a)).

Next, at 120 ° C. for 1 hour, then 150 ° C.
Was heat-treated for 1 hour to thermally cure the adhesive layer 2 to form the adhesive layer 3. The adhesive layer 3 is firmly adhered to the glass epoxy substrate 1 by thermosetting (FIG. 1 (b)).

Next, the surface of the adhesive layer 3 was buffed using a double roll buffing machine under the conditions of buff number # 80, buff rotation speed 1800 rpm, and conveying speed 4 m / min. Many fine recesses 4 were formed on the entire surface. The surface roughness of the adhesive layer 3 after buffing was about 7 μm (FIG. 1 (c)).

Next, the glass epoxy substrate 1 after the buffing treatment was immersed in a solution of a new chromic acid aqueous solution (chromic acid 800 g / l) at 70 ° C. for 5 minutes. A roughened concave portion 5 having a complicated shape is formed on the entire surface of the adhesive layer 3 to obtain an adhesive layer 3 having a surface roughness of 12 ± 2 μm (FIG. 1).
(D)).

Under the normal conditions, the roughened surface of this adhesive layer 3
The electroless copper plating having a thickness of 5 μm was applied, and the adhesion strength between the adhesive layer 3 and the electroless copper plating layer was measured by the method of JIS-C-6481. The adhesive strength was a peel strength of 1.6 kg / cm.

As shown in FIG. 2, the adhesive layer 3 has a large filler 7a having an average particle size of 5.5 .mu.m and an average particle size of 0.
The filler 7b having a small size of 5 μm is uniformly dispersed. Then, prior to the treatment with the solution, the surface of the adhesive layer 3 was buffed to a surface roughness of about 7 μm.
A large number of fine recesses 4 are formed.

Therefore, when the adhesive layer 3 is immersed in the solution, as shown in FIG. 3, due to the difference in the dissolution rate between the hardly soluble matrix resin 6 and the soluble fillers 7a and 7b which form the adhesive layer 3. The roughened concave portion 5 having a complicated shape is formed. At this time, the surface of the adhesive layer 3 has a surface roughness of about 7 μm in advance.
Since the concave portions 4 of m are formed, the amount of dissolution required to form the roughened concave portions 5 having a predetermined surface roughness (12 ± 2 μm in this embodiment) may be small. Moreover, since the contact area between the adhesive layer 3 and the solution is relatively increased, the dissolution rate of the adhesive layer 3 is relatively increased.

Therefore, a large number of roughened concave portions 5 having a complicated shape are formed on the surface of the adhesive layer 3 in a short time. Further, since the dissolution amount of the adhesive layer 3 necessary for forming the predetermined roughened recess 5 is small, the deterioration rate of the dissolution liquid accompanying the dissolution of the adhesive layer 3 is reduced, and therefore the dissolution liquid roughening treatment is performed. Ability is maintained above a predetermined level for a long time. Furthermore, since the processing capacity of the roughening process is improved by shortening the roughening time of the adhesive layer 3, the bath of the solution can be downsized. (Comparative Example) The adhesive layer 3 without buffing was immersed in a solution of a new chromic acid aqueous solution (chromic acid 800 g / l) at 70 ° C to roughen the surface.
It took 15 minutes to obtain a roughened surface of ± 2 μm. Then, the roughened surface of the adhesive layer 3 was subjected to electroless copper plating with a plating thickness of 35 μm, and the adhesion strength was measured as described above.
The adhesive strength was a peel strength of 1.6 kg / cm. That is, if the surface roughness after roughening is the same, the adhesion strength with the electroless copper-plated layer is similar when buffed before roughening and without buffed before roughening. ..

Prior to roughening, buffing was performed so that the surface roughness became approximately 7 μm, so that the roughening time for forming the predetermined roughening concave portion 5 on the surface of the adhesive layer 3 was reduced to 1/3. ..
Further, the roughening time of the adhesive layer 3 largely depends on the old and new of the dissolving liquid, but the roughening time of the buff-polished adhesive layer 3 is the roughening of the adhesive layer 3 without buffing regardless of the old and new of the dissolving liquid. It was always about one-third of the time. (Another Example) Next, a case where the polishing conditions for the adhesive layer 3 are changed will be described. The buffing number was variously changed to keep the buffing speed constant, and the conveying speed was changed to buff the surface of the adhesive layer 3 using a double roll buffing machine. These adhesive layers 3 having different surface roughness are immersed in a solution of a new chromic acid aqueous solution (chromic acid 800 g / l) at 70 ° C. until the surface roughness of the adhesive layer 3 becomes 12 ± 2 μm. Roughened. Then, a plating thickness of 35 is formed on the roughened surface of the adhesive layer 3.
Adhesion strength was measured by applying electroless copper plating of μm.

FIG. 4 shows the relationship between the surface roughness after buffing and the etching time required to obtain a predetermined surface roughness (12 ± 2 μm). In the figure, the two-dot chain line shows the range of variation. The etching time of the adhesive layer 3 without buffing was 15 minutes. The higher the surface roughness after buffing, the shorter the etching time until the surface roughness reaches a predetermined value. When the surface roughness after buffing was about 5 μm, the etching time was 10 minutes, which was two-thirds of that without buffing. Also, the surface roughness after buffing is about 6μ.
At m, the etching time was 8 minutes, which was about one half of that without buffing. Furthermore, when the surface roughness after buffing was approximately 7 μm, the etching time was 5 minutes, which was one-third of that without buffing. The effect of shortening the etching time was always recognized at the same rate regardless of whether the solution was old or new. In this way, by setting the surface roughness of the adhesive layer 3 to 5 to 7 μm by buffing, the etching time could be shortened to ⅔ or less of that without buffing.

Further, the adhesion strength between each adhesive layer 3 and the electroless copper plating layer applied to the roughened surface thereof is not affected by the surface roughness after buffing, and the peel strength is 1.6 k.
A value equivalent to g / cm was obtained. That is, if the surface roughness after roughening was the same, the same degree of adhesion strength with the electroless copper plating layer was obtained regardless of the difference in the buffing treatment before roughening.

Next, the transfer speed (m / min) of the substrate and the surface roughness (μm) of the adhesive layer after polishing in the buff numbers # 80, # 120, and # 180 when the buff rotation speed is 1800 rpm. The relationship will be explained. As shown in FIG.
The smaller the buff number, the higher the surface roughness of the adhesive layer 3,
In all the buff numbers, the surface roughness after polishing tended to increase as the conveying speed increased. When the transportation speed is 4 m / min or more, the surface roughness of the adhesive layer 3 increases, but the recesses 4 are not uniformly formed on the entire surface of the adhesive layer 3. On the other hand, when the conveying speed is 2 m / min or less, the concave portions 4 are uniformly formed on the entire surface of the adhesive layer 3, but excessive polishing causes the convex portions to be rounded to reduce the surface roughness and easily cause scratches. Become. Therefore, in order to uniformly form the recesses 4 on the entire surface of the adhesive layer 3 without any trouble, it is preferable to set the transport speed to 3 to 4 m / min. It is desirable that a large number of fine recesses 4 having a surface roughness be uniformly formed. 5 if the buff rating is less than # 80
Although the surface roughness of μm or more can be obtained, it is difficult to obtain the fine recesses 4. When the buff number is larger than # 180, the fine recesses 4 can be obtained, but the surface roughness of 5 μm or more is difficult to obtain. Therefore, it has an appropriate surface roughness of 5 μm to 7 μm,
Buffing # 80 to get the finest possible recess 4
It is appropriate to use ~ # 180.

The present invention is not limited to the above embodiment, and for example, fillers dispersed in the matrix resin 6 as an adhesive may have a uniform size, or fillers may have a wide distribution. It is possible to use the ones that have, or the ones that are combinations other than the epoxy resin-epoxy resin. Also, a dry film adhesive may be used instead of the liquid adhesive. Further, the surface of the adhesive layer 3 may be roughened by a mechanical treatment other than buffing.

Further, although the surface roughness of the adhesive layer 3 is set to 12 ± 2 μm in the above-mentioned embodiment, the surface roughness is not limited to 12 ± 2 μm, and may be appropriately set within the range where the adhesion strength can be obtained. Good.

[0026]

As described in detail above, according to the present invention, the surface of the adhesive layer formed on the insulating substrate can be roughened to a predetermined surface roughness in a short time, and the amount of dissolution required for roughening can be reduced. It is possible to reduce the deterioration rate of the solution by reducing the deterioration rate. In addition, since the surface of the adhesive layer can be roughened in a short time, there is an excellent effect that the bath of the solution can be downsized.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view schematically showing a procedure for forming an adhesive layer.

FIG. 2 is a schematic partial cross-sectional view of an adhesive layer after buffing in this example.

FIG. 3 is a schematic partial cross-sectional view of an adhesive layer after being immersed in a solution to roughen the surface.

FIG. 4 is a graph showing the relationship between the transport speed and the surface roughness after polishing.

FIG. 5 is a graph showing the relationship between the surface roughness after polishing and the etching time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass epoxy substrate as an insulating substrate, 2 ... Adhesive layer, 3 ... Adhesive layer, 4 ... Recess, 5 ... Roughening recess, 6 ... Matrix resin, 7a, 7b ... Filler.

[Procedure amendment]

[Submission date] October 30, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

FIG. 4 is a graph showing the relationship between the surface roughness after polishing and the etching time.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

FIG. 5 is a graph showing the relationship between the transport speed and the surface roughness after polishing.

Claims (1)

[Claims] 1. An adhesive comprising an uncured matrix resin which is hardly soluble in a solution by a curing treatment, and a filler which is soluble in the solution and hardly soluble in the uncured matrix resin. After forming the layer on the insulating substrate, the adhesive layer is cured to form an adhesive layer, and then the surface of the adhesive layer is roughened by a mechanical surface treatment, and then the adhesive layer is formed by the dissolving solution. A method for forming an adhesive layer for an additive printed wiring board, which comprises dissolving a surface portion to form a large number of roughened recesses.