JP3251971B2 - Dry film adhesive for additive method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, miniaturization, high performance, and multifunctionality of electronic devices have been promoted, and high density and high reliability by fine patterns have been demanded for printed wiring boards used therein. I have.

Conventionally, as a method of forming a conductive circuit on a printed wiring board, a subtractive method of forming a conductive circuit by laminating a copper foil on an insulating substrate and then performing photoetching has been widely used. According to this method, a conductor circuit having excellent adhesion to an insulating substrate can be formed. However, a so-called undercut occurs due to etching due to the thickness of the copper foil, and it is difficult to obtain a high-precision fine pattern. There is a problem that it is difficult to deal with.

[0004] Therefore, as an alternative 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 electroless plating is performed to form a conductor circuit. Attention is being paid to the additive method.

[0005] As an adhesive for the additive method, an average particle size that is soluble in a dissolving solution and hardly soluble in the matrix resin solution is contained in a matrix resin solution that becomes sparingly soluble in a dissolving solution by curing treatment. An adhesive in which two different types of fillers are dispersed has been proposed by the present applicant.
When the adhesive layer is formed on the insulating substrate, the resin mixed solution is applied on the insulating substrate to a predetermined thickness, and the applied resin mixed solution is dried to form an adhesive layer. Is cured to form an adhesive layer. Next, when this adhesive layer is immersed in the solution, a large number of roughened concave portions 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 filler dispersed in the adhesive layer is large or small having a different particle size.
Since it is composed of different types of fillers, the roughened recess formed in the adhesive layer has a complicated shape, and the adhesion strength between the adhesive layer and the electroless copper plating layer applied to the adhesive layer is strong. .

[0006]

In order to secure the adhesion strength of the electroless copper plating layer to the adhesive layer at a predetermined value or more,
It is necessary that the surface roughness of the adhesive layer after the roughening by the dissolving solution is equal to or more than a predetermined value. However, the adhesive layer has a structure in which a filler that is 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 a plurality of the recesses are connected with time to roughen. A recess is formed. Therefore, the process of forming the roughened concave portion involves dissolving the poorly soluble matrix resin existing as the matrix of the filler. For this reason, the roughening step involving the dissolution of the hardly soluble matrix resin requires a long time.

Further, since the same solution is used repeatedly in the roughening step, the solution gradually deteriorates as the number of times of the roughening treatment of the solution increases, and the dissolving power is reduced. For this reason, as the number of times of the roughening treatment of the solution increases, the roughening step requires a longer time, which significantly reduces the productivity of the printed wiring board. In order to improve the processing capability of the roughening step, in order to roughen the adhesive layer on a large number of insulating substrates at once, it is necessary to increase the size of the bath of the solution. In addition, the bathtub needs to be increased in size when replacing the deteriorated solution with a new solution or extending the replenishment cycle of the oxidizing agent.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to roughen the surface of an adhesive layer formed on an insulating substrate in a short time and to reduce the amount of dissolution required for roughening. It is an object of the present invention to provide a dry film adhesive for an additive method, which can reduce the rate of deterioration of a solution by reducing the amount of the solution and further reduce the size of a bath for the solution.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an uncured or hardened or hardened chromic acid aqueous solution which is hardened on a surface of a heat-resistant base film having a roughened surface. and the matrix resin of the incompletely hardened, dispersed in said matrix resin, was laminated an adhesive layer comprising a hardly soluble fillers for the soluble a and the matrix resin relative to the chromic acid aqueous solution.

[0010]

Therefore, according to the present invention, the adhesive layer laminated on the surface of the heat-resistant base film having a roughened surface is laminated on an insulating substrate, and after the adhesive layer is cured, the heat-resistant base film is cured. Is peeled from the insulating substrate, a cured adhesive layer is formed on the insulating substrate. The surface of the adhesive layer has a roughness corresponding to the surface roughness of the heat-resistant base film. Thereafter, when dipping the adhesive layer in an aqueous solution of chromic acid, and Matokkusu resin insoluble in an aqueous chromic acid solution
A roughened concave portion having a complicated shape is formed due to a difference in dissolution rate between the filler and the soluble filler in the chromic acid aqueous solution . At this time, since the surface of the adhesive layer is a rough surface on which fine concave portions are formed in advance, the amount of the matrix resin and filler required to form a roughened concave portion having a predetermined surface roughness is small. Further, the surface of the adhesive layer is a rough surface adhesive layer and the chromic acid
Since the contact area with the aqueous solution increases, the dissolution rate of the adhesive layer increases. Therefore, when the adhesive layer is immersed in the chromic acid aqueous solution , a large number of complex-shaped roughened concave portions are formed on the surface of the adhesive layer in a short time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. First, a dry film adhesive for an additive method according to the present embodiment will be described with reference to FIG. The dry film adhesive DF comprises a heat-resistant base film 1, an adhesive layer 2 laminated on its surface,
And a release paper 3 attached to the surface of the adhesive layer 2. The surface of the base film 1 has a surface roughness of approximately 5 to 7
It is a rough surface roughened to μm, and the adhesive layer 2 is formed on the rough surface side. A release paper 3 is attached to the surface of the adhesive layer 2 to protect the adhesive layer 2. The adhesive layer 2 is an uncured or incompletely cured matrix resin 4 which becomes hardly soluble in a chromic acid aqueous solution as a dissolving liquid by a curing treatment
And a large filler 5a and a small filler 5b which are soluble in a solution dispersed in the matrix resin 4 and have different particle diameters.

Next, a method for forming a dry film adhesive will be described. An adhesive for the adhesive layer 2 was prepared as follows. Bisphenol A type epoxy resin as a matrix resin (manufactured by Yuka Shell, trade name: E-1)
001) 40 parts by weight, 60 parts by weight of a phenol novolak type epoxy resin (manufactured by Yuka Shell, trade name: E-154) as a matrix resin, and 10 parts by weight of an imidazole type curing agent (manufactured by Shikoku Chemicals, trade name: 2PHZ) Part and epoxy resin fine particles as filler (manufactured by Toray, trade name:
10 parts by weight of Trepal EP-B, average particle size 0.5 μm), 25 parts by weight of epoxy resin fine particles (trade name: Trepal EP-B, manufactured by Toray, average particle size 5.5 μm), and 75 parts by weight of butyl cellosolve acetate Was stirred and mixed with three rollers to prepare an adhesive.

As the base film 1, a base film 1 having a thickness of 50 μm made of polymethylpentene (TPX) (trade name: Opulan X-88, softening point 180 ° C., manufactured by Mitsui Petrochemical Industries, Ltd.) was used. The surface of the base film 1 is matted at 200 ° C. at a pressure of 10 kg / cm ² using a stainless steel roller having a surface roughness of about 5 to 7 μm by spraying sand on the surface, and the surface of the base film 1 is finely ground. Many concave portions 1a were formed to have a surface roughness of approximately 5 to 7 μm. The adhesive was applied to the rough surface side of the base film 1 using a roller coater so that the applied thickness was about 30 μm. The applied adhesive was dried to evaporate the solvent of the adhesive, and a dry film adhesive layer 2 was formed on the base film 1. Finally, a release paper 3 was adhered to the surface of the adhesive layer 2 which was formed into a dry film to form a dry film adhesive DF.

Next, a method of using the dry film adhesive will be described. At the time of use, a necessary amount is cut off and the release paper 3 is peeled off before use. The adhesive layer 2 formed into a dry film is laminated on a glass epoxy substrate 6 as an insulating substrate.
The adhesive layer 2 is subjected to a heat treatment at 1 ° C. for one hour, and is thermally cured to form an adhesive layer 7. The adhesive layer 7 is firmly adhered to the glass epoxy substrate 6 by being cured by heat (FIG. 3A).

After the heat curing of the adhesive layer 2, the adhesive layer 7
When the base film 1 is peeled from the base film 1, a large number of fine concave portions 7a corresponding to the convex portions on the rough surface of the base film 1 are formed on the surface of the adhesive layer 7. Since the peeling of the base film 1 is performed after the adhesive layer 2 is completely cured, the convex portion on the surface is not deformed and does not fall off, and the surface roughness of the adhesive layer 7 corresponds to the surface roughness of the base film 1. It is approximately 5 to 7 μm (FIG. 3)
(B)).

Next, the glass epoxy substrate 6 is immersed in a solution ( aqueous solution of chromic acid) and etched until the surface of the adhesive layer 7 has a predetermined surface roughness. As a result, a rough concave portion 8 having a uniformly complicated shape is formed on the surface of the adhesive layer 7 after the roughening (FIG. 3C).

As shown in FIG. 2A, the adhesive layer 7 is composed of a large filler 5a having an average particle size of 5.5 μm and a mean particle size of 5.5 μm, which is soluble in the solution in a matrix resin 4 which is hardly soluble in the solution. It has a structure in which a 5 μm small filler 5b is uniformly dispersed. Prior to the treatment with the solution, fine concave portions 7a corresponding to the convex portions of the rough surface of the base film 1 are formed on the surface of the adhesive layer 7, and the surface roughness is approximately 5 to 7 μm.

Therefore, when the adhesive layer 7 is immersed in the dissolving liquid, the difference in dissolution rate between the poorly soluble matrix resin 4 and the soluble fillers 5a and 5b, which constitute the adhesive layer 7, is shown in FIG. As shown, a roughened concave portion 8 having a complicated shape is formed. At this time, since the concave portion 7a having a surface roughness of approximately 5 to 7 μm is previously formed on the surface of the adhesive layer 7, the roughened concave portion 8 having a predetermined surface roughness (12 ± 2 μm in this embodiment) is formed. The amount of dissolution required for this may be small. In addition, the contact area between the adhesive layer 7 and the solution is relatively increased by the concave portions 7a uniformly formed on the entire surface of the adhesive layer 7, so that the dissolution rate of the adhesive layer 7 is increased.

Therefore, a large number of roughened concave portions 8 having a complicated shape are formed on the surface of the adhesive layer 7 in a short time. In addition, since the amount of dissolution of the adhesive layer 7 necessary for forming the predetermined roughened recess 8 may be small, the deterioration rate of the solution accompanying the dissolution of the adhesive layer 7 is reduced. Is maintained at or above a predetermined level for a long time.

As described above, the adhesive layer 7 of the present embodiment formed with the surface roughness of about 5 to 7 μm having the fine concave portions 7a on the entire surface is made of a new solution of a chromic acid aqueous solution (chromic acid 800 g / l). It was immersed in a solution at 70 ° C., and the relationship between surface roughness and roughening time was measured. For comparison, the same measurement was performed on a flat adhesive layer formed by directly applying the adhesive prepared as described above to the surface of a glass epoxy substrate, drying, and heat-curing the same as before. . FIG. 4 shows the result. The adhesive layer 7 of the present example having a surface roughness of about 5 to 7 μm before roughening is indicated by a hatched portion in the drawing, and an adhesive layer whose surface is not roughened in advance is indicated by a two-dot chain line in the drawing. As shown in FIG. 4, the adhesive layer 7 of this embodiment has a thickness of about 5
The surface roughness is a predetermined value (12 ± 2μm) by immersion for a minute
It became. On the other hand, it took about 15 minutes for the adhesive layer whose surface was not roughened beforehand to have a surface roughness of 12 ± 2 μm.
By setting the surface roughness of the adhesive layer 7 to about 5 to 7 μm in advance, the roughening time was reduced to about one third. Although the roughening time of the adhesive layer 7 largely depends on the oldness and the newness of the solution, the roughening time of the adhesive layer 7 in this embodiment is always constant regardless of the newness of the solution. About one-third of

Next, an electroless copper plating layer having a thickness of 35 μm was formed on the roughened surface of the adhesive layer having a surface roughness of 12 ± 2 μm, and the adhesion strength of the electroless copper plating layer to the adhesive layer was measured according to JIS. It measured by the method of -C-6481. As a result, the adhesion strength was equal between the case where the surface roughness was approximately 5 to 7 μm and the case where the surface was roughened beforehand, and the peel strength was 1.6 kg / cm in both cases. That is, if the surface roughness after roughening was the same, the same level of adhesion strength to the electroless copper plating layer was obtained regardless of the surface roughness before roughening. Therefore, according to the present embodiment, it is possible to form the roughened concave portion 8 having a predetermined surface roughness on the surface of the adhesive layer 7 with the roughening time of the adhesive layer 7 being about one third of the conventional one. Layer 7
And the adhesion strength between the electrode and the electroless copper plating are almost the same as those of the prior art.

It should be noted that the present invention is not limited to the above embodiment, but may be configured as follows without departing from the spirit of the invention. (1) In the above example, the surface roughness of the base film 1 was set to approximately 5 to 7 μm. However, the surface roughness of the base film 1 is not limited to approximately 5 to 7 μm and is within a range in which the roughening time can be reduced. May be set as appropriate.

(2) Matrix resin 4 as adhesive
A filler having a uniform size of filler dispersed therein, a filler having a wide distribution of filler sizes, or a combination other than epoxy resin-epoxy resin may be used.

(3) In the above embodiment, the base film 1 is made of polymethylpentene (TPX). However, for example, a fluorine-based resin which is a heat-resistant resin having a softening point higher than the thermosetting temperature of the adhesive layer 2 Or a metal such as aluminum which is dissolved in a solution.
When the base film is made of metal, even if the metal from the base film remains on the surface of the adhesive layer 7 when the base film is peeled off from the adhesive layer 7 formed on the glass epoxy substrate 6, the remaining metal is It is dissolved and removed by the dissolving solution at the time of roughening.

(4) In the above embodiment, the surface roughness of the base film 1 is set to approximately 5 to 7 μm by performing the map processing on the base film 1. However, for example, the film is formed so that the surface of the base film 1 is roughened. As long as the surface of the base film 1 can be roughened, for example, by sandblasting the surface of the base film 1 or roughening the surface of the base film 1 by chemical treatment, the method can be appropriately selected.

(5) In the above embodiment, the surface roughness of the adhesive layer 7 was 12 ± 2 μm, but the surface roughness was 12 ± 2 μm.
However, the present invention is not limited to this, and may be appropriately set as long as the adhesion strength is obtained.

[0027]

According to the present invention as described in detail above, according to the present invention, as well as roughening in a short time the surface of the adhesive layer formed on the insulating substrate, solution to reduce the dissolved amount required for roughening ( chromium
Acid solution) can be reduced. In addition, since the surface of the adhesive layer can be roughened in a short time, an excellent effect that the bath for the solution can be downsized can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic partial sectional view of a dry film adhesive for an additive method of the present embodiment.

FIG. 2A is a schematic partial cross-sectional view of an adhesive layer before roughening,
(B) is a schematic partial cross-sectional view of the adhesive layer after roughening.

FIG. 3 is a partial cross-sectional view schematically showing a procedure for forming an adhesive layer.

FIG. 4 is a graph showing the relationship between the surface roughness of the adhesive layer and the roughening time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base film, 1a ... Depression, 2 ... Adhesive layer, 4 ...
Matrix resin, 5a, 5b ... filler.

Claims (1)

(57) [Claims] An uncured or incompletely cured matrix resin which becomes hardly soluble in a chromic acid aqueous solution by a curing treatment on a surface of a heat-resistant base film having a roughened surface,
Said dispersed in a matrix resin, dry for additive method, characterized in that a laminate of the adhesive layer made of a hardly soluble fillers for the soluble a and the matrix resin relative to the chromic acid aqueous solution <br/> Film adhesive.