JPS61140194A - Multilayer circuit board and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides a multilayer circuit board, in particular, a multilayer circuit board in which resin and copper wiring have high adhesion, high acid resistance, and are suitable for forming fine copper wiring with high precision. The present invention relates to a multilayer circuit board and a method for manufacturing the same.

[Background of the invention]

Conventionally, a method of increasing the adhesion between the resin and copper foil of a steel clad plate used to manufacture printed wiring boards consisting of resin and copper wiring in contact with it is to roughen the surface of the copper foil and use this surface as the adhesive surface. In particular, methods have been used to increase the adhesive strength between resin and copper foil by utilizing the so-called anchoring effect. However, if the surface of the copper foil is simply roughened mechanically, it cannot be expected to obtain sufficient adhesive strength (unless the irregularities are significantly increased), so usually the surface of the steel foil is roughened by etching. A method has been adopted in which a porous steel oxide film is formed on this roughened surface to increase adhesive strength.

By the way, in the process of manufacturing multilayer printed wiring boards, (1) mechanical through-hole formation using a drill, (2)
) There are steps such as immersion in acidic catalyst liquid for chemical steel plating that are necessary to obtain continuity in the through-hole. For this reason, steel clad plates used in the production of multilayer printed wiring boards are required to have high adhesion of the steel foil to the resin and excellent acid resistance.

However, in the conventional method described above, in which the surface of the steel foil is mechanically or electrochemically roughened and a porous oxide film is formed thereon in order to improve adhesion, the oxide film is not formed on the surface of the steel foil. Therefore, the acid resistance of the oxide film in contact with the through-holes of the obtained multilayer wiring board is extremely poor.Conversely, if the thickness of the oxide film is thinned in an attempt to increase the acid resistance, the adhesion will decrease. There is a problem with doing so.

Furthermore, in order to improve the adhesion between the conventional copper clad plate and the steel foil, the surface of the copper foil is roughened (10 to 20 μm).
)It has become. For this reason, when attempting to form copper wiring on a copper clad plate by etching, the steel foil surface is intricately intertwined with the resin interface, so it is necessary to completely remove the copper in these non-circuit areas. Difficult to remove. Of course, if etching is carried out sufficiently, it is possible to completely remove the steel in non-circuit areas, but this causes a problem in that the quarter-turn accuracy of the copper wiring in the circuit areas is reduced. This problem also occurs in the so-called one-no-turn plating method, in which a resist pattern is formed on a thin steel foil and a thick layer of copper is further deposited only on the circuit area, but after the resist is removed, the copper in the non-circuit area is etched. It becomes a problem when removing it.

If a copper-resin composite board is made by bonding resin directly to the surface of mechanically roughened copper foil, sufficient adhesion strength can be obtained even though there is no problem with acid resistance since there is no intervening oxide film. For this purpose, large unevenness is required, so the above copper wiring /
The problem of mother turn accuracy becomes even more noticeable. Furthermore, increasing the irregularities on the surface of the steel foil also makes it extremely difficult to adhere the thin steel foil onto an insulating substrate.

[Purpose of the invention]

An object of the present invention is to provide a multilayer circuit board that has high adhesion between copper wiring and resin, has good acid resistance even when forming through holes, and has a high precision copper wiring pattern, and a method for manufacturing the same. .

[Summary of the invention]

The multilayer circuit board of the present invention is a laminate of resin and copper wiring in contact with it, and at least the adhesive interface between the resin and copper that intersects with the through hole has a ten-point average roughness specified in JISB0601. It is characterized by being made of an oxidized and reduced copper surface having an unevenness Rz of 0.1 μm or more and 6 μm or less with respect to a standard length L of 100 μm.

The method for manufacturing a multilayer circuit board of the present invention is to oxidize and then reduce one side of a thin steel foil so that R8 is 0 for a standard length L of 100 μm in the ten-point average roughness described in JIS110601.
．． After forming a reduced copper surface with unevenness of 1 μm or more and 6 μm or less, a resin layer is adhered to the liquid surface, and then the other side of the steel foil is oxidized and reduced to form a reduced copper surface with unevenness of the same degree as above. After forming the surface, a steel circuit is thickened on the other surface according to the wiring pattern, and then the surface of the steel circuit is oxidized and reduced to form a reduced surface having the same degree of unevenness as above. After that, the steel foil in the non-circuit part on the seventh register layer is removed by etching, and then the surface perpendicular to the thickness direction of at least the through-hole forming part of the above-mentioned steel circuit is etched. While maintaining the state of the reduced copper, multiple sheets of resin plates that have gone through at least the above process are laminated and bonded via a resin preg, a through hole is formed in a predetermined part of this laminate, and a through hole is formed on the inner surface of the through hole. Characterized by plating copper.

The present inventors have discovered that by oxidizing the copper surface and then reducing it to the same degree as the surface roughness of the steel oxide film, the surface can be made into an uneven shape having the surface roughness specified above. Therefore, by using the reduced copper surface with such irregularities as the adhesive interface with the resin, the adhesive force between the copper and the resin becomes high strength comparable to that of conventional adhesives through oxide films. It has been found that reduced copper is extremely difficult to dissolve in acids compared to oxide films. Furthermore, it has been found that the irregularities on the reduced copper surface are minute as described above and do not interfere with the accuracy of forming copper wiring on the resin layer. The present invention has been made based on such findings. Embodiments of the present invention include embodiments in which a steel oxide film is interposed at the adhesive interface between the resin and copper that does not contact the through hole (for example, the embodiment described below). Examples 1 and 2) are also included, but even in that case,
Since the copper-resin interface that intersects with the through-hole exposed to the acidic liquid is reduced copper and has no oxidized film interposed therebetween, acid resistance is not impaired.

In the actual implementation of the present invention, a trace amount of oxide may inevitably be generated on the surface of the reduced copper due to exposure to air or other causes before bonding with the resin; The oxide does not have a negative effect on the adhesion between the resin and the copper, nor does it have a negative effect on the acid resistance. [Embodiments of the Invention] Example 1 In Figure 1, the surface irregularities are as described in JISB0601. For the ten-point average roughness, the standard length L is 100μ
Stainless steel plate 1 whose Rz at m is smaller than 61tn
was used as a substrate for plating, and R@2 was plated on this to a thickness of 4 μm (&). Next, this plating film is etched to roughen the surface of #i2 so that it has irregularities of 1 to 1.5 μm (b). Copper oxidation forms [3] on the roughened copper surface (e). This oxide film is formed when the liquid composition is NILO■4I/! , NasP
O< ・2H201211/7, NaCtOz 30
This is carried out by immersing the specimen in a liquid such as F/A at a temperature of 70° C. for 1 minute. Next, this oxide film is electrically reduced in an alkaline solution (d). This electrolytic reduction is carried out in a NaOH41/lk aqueous solution (pH 12) at 0.2 A/dm2 using a stainless steel plate as a counter electrode. Next, this reduced film 4! Heat toward the reg 5 side,
It adheres to the jig leg 5 by applying pressure, and then peels off the stainless steel plate 1 (・). Next, the outer surface of #t2 is etched)
It is roughened to have an unevenness of 1 to 1.5 μm (f). An oxide film 3 is formed on the roughened outer surface of the steel (g). This formation method is the same as that in (e).

Next, this oxide film 3 is electrically reduced in an alkaline solution (h). This reduction is carried out under the same conditions as in (d).

As described above, the front and back surfaces of each copper 2 become a reduced copper return film 4 after oxidation. Next, a renost/quater 76 is formed on the reduced film 4 (1). Next, plating the part corresponding to the circuit part! Thicken i7 (j).

Next, peel off the lenostro (k). Next, an oxide film 3 is formed on the exposed steel surface (including the side surfaces) (4° This formation method is the same as in (c). Next, this oxide film is electrically heated in an alkaline solution. to form a reduced film 4.This reduction is carried out under the same conditions as in (d).Next,
A resin pattern 8 is formed on a flat surface of the copper wiring perpendicular to the thickness direction of the substrate (11). Next, the steel in the non-circuit portion is removed by etching (0). Next, an oxide film 3 is formed on the exposed steel surface (side surface) (p). This formation method is the same as in (c). After this, it is impossible to form a totobe reduction film because electrical continuity cannot be obtained. However, the oxide film and the reduced film basically have approximately the same adhesion strength, and in this aspect, hydrochloric acid resistance is not required, so there is no problem. Next, the resist 8 is peeled off (q). Next, a plurality of these substrates are laminated and bonded to prepreg 5' (r). However, in this example, the outermost layer is left as a copper foil surface. Next, a through hole H is formed using a drill (8). Next, after applying a catalyst to the side surface of the through hole H, a thin chemical steel plating film 9 is formed on the side surface of the through hole and the outermost layer, and a resist pattern 10 is formed on the outermost layer (1).

Next, the circuit portion is plated with a thick layer of electrical #i11, and after the resin 10 is peeled off, a circuit is formed by etching (ul).

Multilayer board made by the above process (Fig. 1 (-”)
) has no hydrochloric acid penetration into the interface between the resin and copper that is in contact with the through-hole (I) even when applying a catalyst in the pretreatment process for chemical steel plating in (1) above, and the hydrochloric acid resistance is low. It was good. In addition, the surface roughness of both the oxide film and the reduced film is determined by the standard length L of 100 μm and Rz of 3 in the ten-point average roughness described in JI8B0601.
．． At 5 μm, the adhesive strength between the resin and reduced copper is also 1.2.
KqA-IL was good. Example 2 As shown in FIG. 2, in step (n) of Example 1,
Only the plane part (part P in Fig. 2) corresponding to the pad part of the copper wiring parallel to the substrate (the wide part of the copper wiring for drilling through holes) was masked with resist (n'), and the rest was the same as in Example 1. It was conducted under similar conditions. The multilayer board (Fig. 2 (u2)) created by the above process was prepared by applying hydrochloric acid to the interface between the resin and copper that is in contact with the through hole during the application of catalyst in the pretreatment process for chemical steel plating on the side surface of the through hole. There was no seepage due to water, and the hydrochloric acid resistance was good. Furthermore, the surface roughness of the oxide film and the reduced film was the same as that of the film shown in Example 1. Adhesion between resin and copper is also 1.2
K4/cm was good.

Example 3 As shown in FIG. 3, after completing step (o) of Example 1, the resist 8 was removed, and without going through steps (p) and (q),
After laminating and bonding and forming through holes in the nodal parts,
A catalyst for chemical steel plating is applied and a resist/4 turn is formed on the outermost layer, and then a thick chemical steel plating film is formed on the through holes and the circuit part of the outermost layer, and then the resist is peeled off. Then, a circuit was formed by etching and etching until the copper in the non-circuit area was removed (u3). The surface roughness of the reduced film in the multilayer board (Fig. 3(,')) produced by the above process was the same as that of the film shown in Example 1. In addition, the adhesion between the resin and reduced copper was good (1.2).Also, when applying a catalyst in the pretreatment process for chemical steel plating to the side of the through hole, the adhesiveness of the resin in contact with the through hole was also good. Hydrochloric acid did not seep into the interface between copper and copper, and the hydrochloric acid resistance was good.

In this example, since the side surface of the circuit steel does not have minute irregularities, its adhesion to the resin is weak, but the adhesion between its flat surface and the resin is sufficient. However, in high-density wiring,
In Example 1, fine irregularities were also provided on the side surface because the bonding area between the side surface and the resin could not be ignored compared to the bonding area on the flat surface.

Example 4 As shown in FIG. 4, in step (0) of Example 1,
4 (O' )),
The other conditions were the same as in Example 1. Through the above process, the multilayer board created (Fig. 4 (,')) is also applied to the interface between the resin and copper that is in contact with the through-hole during the application of catalyst in the pre-treatment process for chemical steel plating on the side of the through-hole. There was no penetration by hydrochloric acid, and the hydrochloric acid resistance was good.

Furthermore, the surface roughness of the oxide film and the reduced film was the same as that of the film shown in Example 1. In addition, the adhesion between the resin and reduced copper was 1.2 Kf/an, which was good.Example 5 As shown in Figure 5, after going through the steps up to (e) in Example 1, , (f), (g) + (After forming a resist/4 turn without going through the hJ process, and then using chemical plating to thicken the steel on the circuit part and peeling off the resist, (A multilayer board was formed according to the powder removal process. The multilayer board created by the above process (Fig. 5 (U)
), the surface roughness of the reduced film was the same as that of the film shown in Example 1. Also, the adhesive strength between resin and reduced copper is 1.2
Kf/cm was good. Furthermore, even when a catalyst was applied to the side surface of the through hole in the pretreatment process for chemical steel plating, hydrochloric acid did not seep into the interface between the resin and copper that was in contact with the through hole, and the hydrochloric acid resistance was good.

In Comparative Example Fig. 6, the standard length L is 100 μm when the surface unevenness is the ten-point average roughness described in JISB0601.
A stainless steel plate 1 whose Rz at m is as small as 6 μm is used as a substrate for plating, and copper 2 is plated on this plate to a thickness of 4 μm (&). Next, the plated film 2 is etched to roughen the copper surface so that it has irregularities of 1 to 1.5 μm (b). An oxide film 3 is formed on the roughened copper surface (c).

Next, the oxide film 3 is attached to the prepreg 5 side (by heating and pressurizing), and the stainless steel plate is peeled off (d). Next, copper 2
The outer surface is roughened by etching so that it has an unevenness of 1 to 1.5 μm (e). Roughened! ! An oxide film 3 is formed on the outer surface of i2 (f). Next, a resist/gutter 76 is formed on this oxide film 3 (SC).Next, a thick layer of copper 7 is applied to a portion corresponding to the circuit portion by chemical plating (h). Next, peel off the resostro (1). Next, copper in non-circuit areas is removed by etching (J).

Next, an oxide film 3 is formed on the exposed steel surface (illustration).Next, a plurality of these substrates are laminated and bonded to the prepreg 5'(<1). Next, use a drill to form a through hole H (e). Next, after applying a catalyst to the side surface of the through hole H, a chemical copper plating film is formed on the side surface of the through hole and the outermost layer, and a resist pattern 10 is formed on the outermost layer (n). Next, the circuit part is plated with #111 thickly, and after peeling off the coating, a circuit is formed (o).

The multilayer board made by the above process has good adhesion between the resin and copper, which is 1.3 degrees, but when applying catalyst in the pretreatment process for chemical plating, the through-hole Hydrochloric acid seeped into the contact between the resin and copper, and the hydrochloric acid resistance was poor.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a multilayer circuit board in which fine copper wiring with high adhesion to insulation substrates is precisely formed on an insulating substrate and has excellent hydrochloric acid resistance.

[Brief explanation of the drawing]

Figure 1 (a) or ul), Figure 2 (n') (,2
), Figure 3 (,) (u3), Figure 4 (o') (u'
) and FIG. 5(e) (u5) are schematic diagrams of the multilayer circuit board forming process according to different embodiments of the multilayer circuit board forming process according to the present invention. Explanation of symbols 1...Stainless steel substrate 2...Copper foil 3...Oxide film 4...Reduced film 5...Shi-kun
6... Resostore... Thick copper film 8... Resist 9... Thin chemical copper plating film 5'... Prepreg. Fig. 1 Fig. 1 Fig. 1 Fig. 2 Section r4ゝ dimension 3 Mi Shibu Fig. 5 Fig. 6 Fig. 6 Fig. 6 Diagram Fig. 6 Procedural amendment (wall) Showa LO year month - date

Claims (1)

[Claims] 1. In a multilayer circuit board made of a laminate of resin and copper wiring in contact with it, at least the bonding interface between the resin and the copper that intersects with the through hole has a ten-point average roughness specified in JISB0601. A multilayer circuit board comprising a surface of oxidized and reduced copper having an unevenness R_z of 0.1 μm or more and 6 μm or less with respect to a standard length L of 100 μm. 2. One side of thin copper foil is oxidized and reduced to JISB060.
After forming a reduced copper surface with unevenness of R_z of 0.1 μm or more and 6 μm or less with respect to the standard length L of 100 μm in the ten-point average roughness described in 1, a resin layer is adhered to the surface, and then After oxidizing and reducing the other side of the copper foil to form a reduced copper surface with the same level of unevenness as above, a copper circuit is thickened on the other side according to the wiring pattern, and then the copper circuit is thickened according to the wiring pattern. After the surface of the circuit is oxidized and reduced to form a reduced copper surface with the same level of unevenness as above, the copper foil in the non-circuit area on the resin layer is removed by etching, and then the copper circuit is removed. At least the surface perpendicular to the thickness direction of the through-hole forming part described later is kept in the above-mentioned reduced copper state, and a plurality of resin plates that have gone through at least the above process are laminated and bonded via a resin prepreg. A method for manufacturing a multilayer circuit board, comprising forming a through hole in a predetermined portion of a laminate, and plating the inner surface of the through hole with copper.