JP3364933B2 - Multilayer printed wiring board and copper foil for inner layer electric circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board including an inner layer circuit board and an outer layer circuit board laminated with an adhesive insulating layer interposed therebetween and a copper foil for the inner layer electric circuit, and more particularly to an inner layer circuit board. Adhesive failure between the electric circuit made of copper foil and the insulating layer made of adhesive can be prevented, and an appropriate treating agent applied during the manufacturing process is unlikely to remain at the interface between the electric circuit of the inner layer and the adhesive insulating layer. The present invention relates to a method for manufacturing a multilayer printed wiring board.

[0002]

2. Description of the Related Art A multilayer printed wiring board of this type is manufactured through the steps shown in FIGS. 3 to 9, for example.
The outline will be described below. As shown in FIG. 3, a plurality of inner layer circuit boards a having an electric circuit formed of copper foil.
Together with the outer layer copper foil a1 and the adhesive insulating layer (prepreg) b
After the through hole c as shown in FIG. 4 is drilled (drilled) by a suitable drilling means, the inner wall surface of this through hole c is covered with a copper film so that the through hole made of copper is used. A hole electroless plating process is performed to form a plating layer d as shown in FIG. 5 on the surface of the laminate and the inner wall surface of the through hole c.

Next, a photoresist layer e is formed in a pattern on the surface of the plated layer d except for a part around the through hole c and a portion where an outer layer electric circuit is formed (see FIG. 6), and the photoresist layer e is also formed. After forming the copper / solder plating layer f on the exposed portion (see FIG. 7) and removing the photoresist layer e, the copper / solder plating layer f is used as a mask as shown in FIG. The plating layer d and the like are removed by etching to form an outer layer electric circuit, and a solder / resist layer g is further formed on these surfaces to manufacture a multilayer printed wiring board h as shown in FIG. Has been.

By the way, when the plurality of inner layer circuit boards a are laminated via the adhesive insulating layer (prepreg) b, the inner layer electric circuit provided on the inner layer circuit board a is formed of a copper foil having a smooth surface. Therefore, the adhesive strength with the adhesive insulating layer b is insufficient, and there is a drawback that the inner layer electric circuit and the adhesive insulating layer are easily separated with time.

Therefore, in the conventional case, FIG.
To (B), the surface of the inner layer electric circuit i made of copper foil is coated with, for example, sodium hydroxide (NaOH) 15
To 25 g / l dissolved in an alkaline sodium chlorite aqueous solution to form an acicular crystal oxide film j of CuO and Cu ₂ O to roughen the surface of the inner layer electric circuit i. A method of improving the adhesive strength with the adhesive insulating layer b.

[0006]

By adopting such a method, it is possible to improve the adhesive strength between the inner electric circuit i and the adhesive insulating layer b as a whole, but on the other hand, it is composed of CuO and Cu ₂ O. The oxide film j has resistance to an alkaline solution but is relatively easily dissolved in acid. Therefore, as shown in FIG. 11A, the inner wall surface of the through hole c is dissolved during the manufacturing process of the multilayer printed wiring board. When the laminated surface exposed from the substrate comes into contact with an acidic treatment agent (for example, in the case of the above-mentioned electroless plating of through holes, it is necessary to treat with a hydrochloric acid-acidic palladium / tin aqueous solution in order to impart catalytic properties to the electroless plating. 11), the oxide film j at the contact site is shown in FIG.
As shown in (B), it is dissolved by an acid to expose the metal copper of the inner layer electric circuit i, and a pink ring r is formed along the periphery of the through hole c as shown in FIG.
There was a phenomenon called "haloing".

When this phenomenon occurs, a void s is formed at the interface between the inner layer electric circuit i on the inner wall surface of the through hole c and the adhesive insulating layer b as shown in FIG. Of the multi-layer printed wiring board is remarkably reduced because the treatment agent is likely to remain in the voids s. .

Under the above technical background, the inventors of the present invention have conducted extensive studies on a method for imparting acid resistance to the oxide film j, and as a result, the reason why the oxide film does not exhibit acid resistance in the conventional method is easily caused by the acid. CuO dissolved in the oxide film
Since it is present in a large amount in the inside, acid resistance can be imparted to the oxide film j by decreasing the ratio of CuO and increasing the ratio of Cu ₂ O having relatively acid resistance. Miller index (11
1), (110), and (100) three types of single crystal copper having orientations were each formed with an oxide film and measured by X-ray diffractometry. The (111) and (100) planes of single crystal copper were measured. Then C
u ₂ O is not observed, (100) plane (in the X-ray diffraction (200) plane is observed) Cu ₂ O was confirmed by a single crystal, and thus the orientation plane of the Cu crystals and Cu ₂ O in It has been found that the formation is relevant, and therefore the ratio of Cu ₂ O can be increased to impart acid resistance to the oxide film j by making the orientation plane of the Cu crystal a specific orientation plane, and thus the present invention has been completed. is there.

Incidentally, Cu ₂ in the oxide film in the conventional method is
The ratio of O to CuO (Cu ₂ O / CuO × 100) is about 30 to 40%, and the amount of haloing generated (through hole c having a diameter of 0.35 mm in FIG. 12).
(Indicated by the width of the ring indicated by the distance L from the edge) was 130 to 150 μm on average and could be several hundred μm.

Therefore, an object of the present invention is to reduce the amount of haloing generated as much as possible so that the inner layer electric circuit made of copper foil provided on the inner layer circuit board and the adhesive insulating layer are provided. The multilayer printed wiring board which can prevent the adhesion failure of the above, and the appropriate treatment agent applied during the manufacturing process does not easily remain at the interface between the wiring layer and the adhesive insulating layer, and the inner layer electric wiring used for this multilayer printed wiring board. It is to provide a copper foil for a circuit.

[0011]

That is, according to the invention of claim 1, at least the surface of the inner layer electric circuit of the inner layer circuit board having the inner layer electric circuit formed of a copper foil is acidified.
Process to form oxide film of CuO and Cu ₂ O
And an adhesive insulating resin layer on the oxidation treated surface of the inner layer electric circuit.
The step of laminating the outer layer copper foil via the
The step of forming a through hole and the inner wall surface of the through hole
The inside of the through hole with a step of treating the
The process of forming a plating layer on the wall surface and outer layer copper foil, and
Form a layered copper foil and plated layer laminate into a predetermined pattern
Process for forming outer layer electric circuit and solder resist layer
In the multilayer printed wiring board obtained by performing the step of forming the peak intensity of the light diffracted by the mirror index (200) face X-ray diffraction method is 41% of the peak intensity of the diffracted light (111) plane The inner layer electric circuit is constructed with the above copper foil.
By the formation of Cu ₂ O formed during the above-mentioned oxidation treatment.
The ratio of CuO is higher than that of CuO and oxidation by the acidic pretreatment agent
It is characterized by preventing dissolution of the film .

The invention according to claim 2 is based on the invention according to claim 1, and is based on the inner wall surface and the outside of the through hole.
The plating layer formed on the layer copper foil is an electroless plating layer .

Further, the invention according to claim 3 is the copper foil constituting the inner layer electric circuit of the multilayer printed wiring board according to claim 1 or 2, wherein the diffracted light of the mirror index (200) plane by the X-ray diffraction method. Is 41% or more of the peak intensity of the diffracted light on the (111) plane.

In such technical means, Cu X
The peak intensity by the line diffraction method is the intensity of the highest intensity of the diffracted light. Specifically, 2θ defined by the angle between the incident ray and the diffracted ray is on the horizontal axis and the intensity of the diffracted light is on the vertical axis. Just draw a graph, and measure the strength at which the maximum height is reached on this graph. Then, the X of the (200) plane of Cu
The copper foil having a peak intensity of the diffracted light by the line diffraction method of 41% or more of the peak intensity of the diffracted light of the (111) plane has more Cu ₂ O than the conventional copper foil when oxidized. Even when the formed and thus oxidized copper foil comes into contact with an acidic treatment agent such as a pretreatment agent for electroless plating, the occurrence of the haloing phenomenon is suppressed, and the acid treatment agent is unlikely to remain.

A second aspect of the present invention is based on such a technical background. A through hole which penetrates an inner layer electric circuit and whose inner wall surface is treated with an acidic pretreatment agent is laminated on the pretreatment surface. It is characterized by having an electroless copper plating layer, and the generation of pink rings around the through holes and the residual pretreatment agent are suppressed. Here, as the acidic pretreatment agent, conventionally used palladium chloride or the like can be used as it is.

Further, in such a technical means, as the treatment liquid for oxidizing the copper foil, an alkaline sodium chlorite aqueous solution, an alkaline potassium persulfate aqueous solution or the like can be applied as it is, as before. Similarly to the conventional method, the treatment method is also performed by immersing the inner layer circuit board that has been degreased in advance in this treatment solution.

Incidentally, the manufacturing process of the multilayer printed wiring board after laminating the inner layer circuit boards subjected to the above-mentioned oxidation treatment is arbitrary, and for example, it may be manufactured through the same steps as the above-mentioned conventional method. However, other steps may be performed. Further, the inner layer circuit board to be applied may be one having a copper foil only on one surface side thereof or one having wiring layers on both surface sides respectively.

[0018]

According to the present invention, the peak intensity of the light diffracted by the X-ray diffraction method of the mirror index (200) plane of the copper foil forming the inner layer electric circuit is (111) plane. Since the peak strength is 41% or more, the copper foil for the inner layer electric circuit is subjected to an oxidation treatment to form an oxide film having a high Cu ₂ O ratio on this crystal face, and the haloing phenomenon occurs even when subjected to an acid treatment or the like. Hard to happen.

[0019]

EXAMPLE (Example 1) First, R = (Miller index (20
(0) peak X-ray diffracted light intensity / (111) -face X-ray diffracted light peak intensity) x 100% glass foil / epoxy copper laminated plate (340 m) with a copper foil adhered to both sides
(m × 510 mm × 1.6 mm), the inner layer circuit board was manufactured by patterning the copper foil into the inner layer electric circuit shape by photoetching treatment as in the conventional case.

Next, using a 25% solution of Neutral Clean 68 (trademark, manufactured by Shipley Co., Ltd.), the inner layer electric circuits formed on both sides of the inner layer circuit board were degreased at 60 ° C., and , After washing with water, Etch (Etc
h) 15% 746 (trademark, manufactured by Shipley) and H ₂
A treatment solution containing 10% of O ₂ was used for soft etching treatment for 60 seconds, followed by washing with water, further with a solid acid containing sulfuric acid as a main component (44 g / l), and then washing with water.

The inner layer electric circuit of the inner layer circuit board thus pretreated is oxidized under the following conditions and washed with water to form an oxide film of Cu ₂ O and CuO having a thickness of 1 μm on the surface of the inner layer electric circuit. Formed. Composition of oxidation treatment solution: Na ₃ PO ₄ · 12H ₂ O 17 g / l NaOH 31 g / l NaClO ₂ 43 g / l Treatment solution temperature: 80 ° C. Treatment time: 4 minutes 30 seconds

The thickness of the oxide film 2 is 0.6 μm according to Auger spectroscopic analysis, which means that Cu ₂ O / CuO ×
The ratio of 100 was found to be 177% by X-ray diffractometer.

Next, after drying the inner layer circuit board having the oxide film 2 formed thereon, a plurality of inner layer circuit boards are polymerized together with the outer layer copper foil through the adhesive insulating layer, and heated and pressed to form a multilayer. A printed wiring board was manufactured.

Then, as shown in FIG. 2, this multilayer printed wiring board is drilled in the same manner as in the prior art to form a through hole having a diameter of 0.35 mm, and a palladium chloride treatment liquid having the following composition is used. 20μ on the inner wall surface of the through hole and the surface of the multilayer printed wiring board
m copper plating layer is formed, and further, a treatment such as water washing, pickling, etc. is performed, and a photoresist layer forming treatment similar to the conventional one, 20 μm
m electrolytic copper plating treatment, etching treatment, solder / resist layer formation treatment and the like to produce a multilayer printed wiring board.

[0025]   Palladium chloride treatment liquid composition:     NKM-552A (manufactured by Nikko Metal Plating Co., Ltd.) 3.5% by volume     NKM-552B (manufactured by Nikko Metal Plating Co., Ltd.) 1.5% by volume     NKM-552C (manufactured by Nikko Metal Plating Co., Ltd.) 2.7% by volume     Formalin 0.3% by volume         Treatment liquid temperature: 30 ° C           Processing time: about 12 minutes

When the amount of haloing generated in the thus obtained multilayer printed wiring board was measured, the average value of the pink ring width L was 40 μm.

(Comparative Example 1) An oxide film 2 was formed on the surface of the inner layer electric circuit in substantially the same manner as in Example 1 except that a copper foil of R = 39% was used as the inner layer copper foil. Cu ₂ O of oxide film 2
/ CuO × 100 ratio is 147% by X-ray diffractometer
It turned out that

In addition, the inner layer circuit board is used in the first embodiment.
A multilayer printed circuit board was manufactured in substantially the same manner as. The average width L of the pink ring was 59 μm.

(Comparative Example 2) An oxide film 2 was formed on the surface of the inner layer electric circuit in substantially the same manner as in Example 1 except that a copper foil with R = 32% was used as the copper foil for the inner layer circuit. Cu ₂ O of oxide film 2
/ CuO x 100 ratio is 117% by X-ray diffractometer
It turned out that

In addition, this inner layer circuit board is used in the first embodiment.
A multilayer printed circuit board was manufactured in substantially the same manner as. The average width L of the pink ring was 76 μm.

(Comparative Example 3) An oxide film 2 was formed on the surface of the inner layer electric circuit in substantially the same manner as in Example 1 except that a copper foil with R = 24% was used as the copper foil for the inner layer circuit. Cu ₂ O of oxide film 2
The ratio of / CuO × 100 was found to be 89% by X-ray diffractometer.

In addition, this inner layer circuit board is used in the first embodiment.
A multilayer printed circuit board was manufactured in substantially the same manner as. The average width L of the pink ring was 94 μm.

[0033]

According to the first aspect of the present invention, the copper foil for the inner layer electric circuit is subjected to an oxidation treatment to form an oxide film having a high Cu ₂ O ratio on the crystal plane, and the oxidation treatment is performed. Since the haloing phenomenon is also suppressed, the adhesion failure between the inner layer electric circuit and the adhesive insulating layer can be prevented, and at the same time, the acid treatment agent and the like hardly remain at the interface between the inner layer electric circuit and the adhesive insulating layer. This has the effect of significantly improving the reliability of the multilayer printed wiring board.

According to the second aspect of the invention, Cu ₂ O is formed on the copper foil for the inner layer electric circuit exposed on the inner wall of the through hole.
The oxide film with a high ratio is formed, and the haloing phenomenon is suppressed even when subjected to acid treatment, etc., so that the adhesion failure between the inner layer electric circuit and the adhesive insulating layer is prevented and the adhesive strength around the through hole is improved. At the same time, the acid treatment agent and the like are less likely to remain at the interface between the inner layer electric circuit and the adhesive insulating layer, so that the reliability of the multilayer printed wiring board can be significantly improved.

Further, according to the invention described in claim 3, there is an effect that a copper foil which can be used for such a multilayer printed wiring board having improved reliability is provided.

[0036]

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an inner layer circuit board according to an embodiment.

FIG. 2 is a partially enlarged perspective view of a multilayer printed wiring board according to an embodiment.

FIG. 3 is a perspective view of a conventional multilayer printed wiring board during a manufacturing process.

FIG. 4 is a perspective view in the process of manufacturing a conventional multilayer printed wiring board.

FIG. 5 is a perspective view of a conventional multilayer printed wiring board during a manufacturing process.

FIG. 6 is a perspective view of a conventional multilayer printed wiring board during a manufacturing process.

FIG. 7 is a perspective view of a conventional multilayer printed wiring board during a manufacturing process.

FIG. 8 is a perspective view of a conventional multilayer printed wiring board during a manufacturing process.

FIG. 9 is a schematic perspective view of a conventional multilayer printed wiring board.

FIG. 10A to FIG. 10B are explanatory views of a process of oxidizing the surface of a conventional inner layer electric circuit.

11 (A) and 11 (B) are partially enlarged cross-sectional views of a conventional multilayer printed wiring board after formation of through holes.

FIG. 12 is a partially enlarged perspective view of a conventional multilayer printed wiring board after forming through holes.

13 is a partial cross-sectional view taken along the line WW of FIG.

[Explanation of symbols]

1 Inner layer electric circuit 2 oxide film

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-3-80595 (JP, A) JP-A-63-119594 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/10-3/46

Claims (3)

(57) [Claims] 1. At least the surface of an inner layer electric circuit of an inner layer circuit board having an inner layer electric circuit formed of a copper foil.
Oxidation process to form an oxide film consisting of CuO and Cu ₂ O
And an adhesive insulating resin on the oxidation treated surface of the inner layer electric circuit.
A step of laminating the outer layer copper foil through the layer, and the laminated body
The step of forming a through hole, and the inner wall of the through hole
The step of treating the surface with an acidic pretreatment agent, and the through hole
A step of forming a plating layer on the inner wall surface and the copper foil for the outer layer,
Laminate the outer layer copper foil and plating layer into a predetermined pattern
Process to form outer layer electric circuit and solder resist
In the multilayer printed wiring board obtained by performing a step of forming a layer, the peak intensity of the light diffracted by the mirror index (200) face X-ray diffraction method is the peak intensity of the diffracted light (111) plane 41
Constituting the above inner layer electric circuit with copper foil whose content is at least%.
The ratio of Cu ₂ O formed during the above-mentioned oxidation treatment is C
higher than uO to dissolve the oxide film by the acidic pretreatment agent
A multilayer printed wiring board characterized by being prevented . 2. A copper foil for the inner wall surface of the through hole and the outer layer
The multilayer printed wiring board according to claim 1, wherein the plating layer formed on the substrate is an electroless plating layer . 3. The copper foil constituting the inner layer electric circuit of the multilayer printed wiring board according to claim 1 or 2, wherein the peak intensity of the diffracted light by the X-ray diffraction method on the Miller index (200) plane is (111). ) Surface of the peak intensity of the diffracted light 41
% Or more, a copper foil for an inner layer electric circuit of a multilayer printed wiring board.