JPH06224529A - Printed wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To simplify the manufacturing process for a printed wiring board by omitting electroless plating and to improve the adhesive strength of a circuit pattern by coating insulating layers on both surfaces of the wiring board on which a first- and second-layer circuits are connected with each other of a conductive material and forming the second-layer circuits on the coating film of the conductive material by electroplating. CONSTITUTION:A copper paste layer 52 is printed as conductive paste on the entire surface of a substrate including a through hole 43 and insulating resin layers 47. Then the binder in the surface section of the layer 52 is removed by performing a swelling and roughening processes so as to expose copper particles 53 and make the surface rough. Since the copper particles 53 are exposed on the surface of the layer 52, electroplating can be performed directly on the layer 52. Then the layers 51 and 52 are simultaneously etched into a prescribed conductor pattern. Finally, a multilayered printed board 60 is obtained by connecting outer-layer circuits 61A and 61B to each other through the hole 43 after circuits 40A-61A and 40B-61B on both surfaces of the substrate are respectively connected to each other on both surfaces through blind via holes 45.

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 first layer circuit and a second layer circuit are connected through a blind via hole formed in an insulating layer and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a multilayer printed (printing) wiring board in which a plurality of double-sided wiring boards having conductive circuits on the front surface side and the back surface side are adhered and laminated by a prepreg (glass fiber reinforced resin), the density of mounted components and wiring is reduced. A so-called blind via hole, which connects only the necessary layers without penetrating the entire wiring board, is being adopted as a method of increasing the height.

In particular, as an application to a thin wiring board, a method has been proposed in which an inner layer through hole is provided in advance in an inner layer process, and this is multilayer-molded to obtain a blind via structure, as in the case of a double-sided wiring board. An example of a double-sided laminated multilayer printed wiring board having such a blind via structure will be described with reference to its manufacturing method shown in FIGS.

First, as shown in FIG. 11, a core material 11A in which copper foils 18 and 19 are bonded to both surfaces of an insulating substrate 17 is prepared.

Next, as shown in FIG. 12, the core material 11A is drilled to form a through hole 15 to be a blind via hole, and further copper plating 22 is applied to the entire surface including the through hole 15. .

Next, as shown in FIG. 13, the copper plating 22 and the copper foil 19 on the back side (lower side in the figure) of the core material 11A are etched into the same pattern by photolithography technique to form the conductive circuit 30A of the inner layer. Further, in the same manner, the other core material 12A is also manufactured, and the conductive circuit 30B of the inner layer is formed on this.

Next, as shown in FIG. 14, the core material 11A and the other core material 12A processed in the same manner are thermocompression-bonded by a prepreg 14 (for example, glass epoxy: glass fiber reinforced epoxy resin) between the surfaces having a circuit pattern. Then, the multilayer board 20A is formed as shown in FIG. By this thermocompression bonding, a part 14a of the prepreg 14 penetrates into the through hole 15 from below and fills up to the upper surface of the plating layer 22 to form a blind via hole.

Then, as shown in FIG. 16, a predetermined portion of the multilayer board 20A is drilled to form a through hole 23 penetrating therethrough, and as shown in FIG. 17, the entire surface including the through hole 23 is plated with copper 21. Give.

Next, as shown in FIG. 18, core materials 11A and 12A
The respective surfaces are etched into a predetermined pattern and processed into the outer conductive circuit patterns 31A and 31B, respectively. by this,
Circuits 31A-31B on the outer layers of the laminated double-sided wiring boards 11 and 12
A multilayer printed wiring board 20 is obtained in which the circuits 30A-31A and 30B-31B on both sides of each double-sided wiring board 11 and 12 are connected to each other through through holes 23 and are connected through blind via holes 15.

However, in the manufacturing of the above-mentioned double-sided laminated type multilayer printed wiring board 20, the number of times of drilling by the drill is 3 times (each core hole forming step shown in FIGS. 12 and 13 and FIG. 16). It is necessary to open the through-holes, and the desmear treatment (resin smear) generated by melting the substrate resin due to the frictional heat caused by the rotation of the drill is removed by chemicals to improve the coverage of the through-hole plating. Then
Processing for preventing breakage of through holes is required each time.

Further, the number of times of plating is required to be 3 times (each copper plating of the two core materials shown in FIGS. 12 and 13 and the copper plating of FIG. 17).

Therefore, the number of man-hours for manufacturing increases and the cost increases.

Therefore, as a multilayer printed wiring board that alleviates these problems, there is a build-up type multilayer structure manufactured by the manufacturing method shown in FIGS.

To manufacture this multilayer printed wiring board,
First, as shown in FIG. 19, a core material in which copper foils 49 are bonded to both surfaces of an insulating substrate 44 (for example, a glass epoxy substrate) is prepared. As such a core material, for example, TL manufactured by Toshiba Chemical Co., Ltd.
C-W-551 (total thickness 0.2 mm, copper foil thickness 35 μm) can be used.

Then, the surface of the copper foil of this core material is subjected to buffing and scrubbing, and then a dry film (for example, Sunfort AQ5044 manufactured by Asahi Kasei Co., Ltd.) is attached to the entire surface of each copper foil. Next, after exposing through a pattern film (for example, using an exposure machine HMW-551D manufactured by Oak Co., Ltd.), it is developed with 3% sodium carbonate at 30 ° C. for 60 seconds to form an etching mask. The foil is etched with ferric chloride solution and the dry film stripped with 3% caustic soda.
As a result, as shown in FIG. 20, the inner-layer conductor circuit 40A made of the copper foil 49 left in a predetermined pattern on both surfaces of the insulating substrate 44,
Form 40B.

Next, as shown in FIGS. 21 and 22, after the surface of the copper foil 49 has been subjected to buffing and scrubbing, insulating layers 47 are formed on both surfaces of the substrate. That is, a liquid photoresist (eg, Ciba Geigy Propimer 52, viscosity 5 to 15 Pa · S) is applied to one surface by a bar coater, and dried by heating in a box oven at 80 ° C. for 30 minutes, and then on the other surface. Similarly, apply liquid photoresist with a bar coater and apply 80% in a box oven.
Heat dry at ℃ for 30 minutes.

Next, in order to form a blind hole having a diameter of 0.1 mm to 0.3 mm at the blind via hole forming position of the insulating layer 47, a photomask film is brought into close contact and exposed one by one (for example, an exposure machine HMW-551D manufactured by Oak Co.).
(An exposure amount of 6400 mJ / cm ² is used), and an organic solvent-based developer (for example, Propima Developer DY-9 manufactured by Ciba-Geigy)
0) to develop and blind hole as shown in Fig. 23.
Forming 45.

Then, as shown in FIG. 24, a through hole 43 is formed. This through hole is a diameter attached to an NC drill machine (for example, H-MARK90J manufactured by Hitachi Seiko).
It is formed by a 0.25 mm drill.

Then, as shown in FIG. 25, the insulating layers 47 on both sides are subjected to a swelling and roughening treatment called a desmearing treatment to finish the insulating layers 47 into a rough surface 47a as shown in a partially enlarged view.

That is, a conditioner cleaner (for example, Electrobright MLB Desmi Initiator DI-46 manufactured by Uemura Kogyo Co., Ltd.) is used to swell the resin insulating layer 47 described above with a solvent such as dimethylformamide, and potassium permanganate / The surface is roughened with NaOH.

Then, as shown in FIG. 26, electroless copper plating (chemical plating) is applied to the entire surface including the through holes 43 to form a copper plating layer 42, and then electrolytic copper plating is applied thereon as shown in FIG. To form the copper plating layer 41. At this time, by the treatment shown in FIG. 25, the adhesion effect between the resin insulation layer 47 and the plating layer is improved by the above-described rough surface anchor effect (anchoring effect).
Can be done with. In order to improve the adhesion between the resin insulating layer 47 and the plated layer, heat treatment may be further performed at 175 ° C. for 15 minutes in a box oven.

Next, an etching process similar to the etching process described with reference to FIG. 20 is performed on the copper plating layers 41 and 42, and these are left in the same pattern.
51A and 51B are formed respectively.

Thus, the outer layer circuits 51A-51B on both surfaces are connected to each other through the through holes 43, and the resin insulation layer is formed.
Circuits on both sides of it through 47 blind via holes 45
40A-51A and 40B-51B are connected to each other to obtain a build-up type multilayer printed wiring board 50 having four wiring layers and no prepreg.

As is clear from the manufacturing method described above, this multilayer printed wiring board 50 requires only one drilling (through-hole drilling in FIG. 24) and two platings (FIGS. 26 and 27). Each plating) is sufficient, so that the number of steps can be reduced and the cost can be reduced as compared with those shown in FIGS. 11 to 18.

However, this multilayer printed wiring board 50
In the production of, even if an attempt is made to improve the adhesion of the plated layers 42 and 41 by the roughening treatment of the insulating layer 47 described in FIG. 25, the roughness of the insulating layer 47 does not actually become so large. ~
Only about 3 μm.

Therefore, the peel strength of the circuit pattern (J
The method according to the method of IS-C-6481) is only 600 g / cm, and the pattern may be peeled off by an external impact. Generally, the required adhesion strength (peel strength) is 1,000 g / cm or more, but the conventional peel strength is lower than that, which is not desirable.

[0027]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the number of manufacturing steps and cost, and also to simplify the process and reduce the material cost in that electroless plating can be omitted. It is an object of the present invention to provide a printed wiring board capable of improving the adhesion strength of a circuit pattern and a manufacturing method thereof.

[0028]

That is, the present invention relates to a printed wiring board in which a first layer circuit and a second layer circuit are connected through a blind via hole formed in an insulating layer. A conductive material is deposited by coating on the conductive material coating film, and the second layer is formed by electroplating.
The present invention relates to a printed wiring board having a layer circuit formed therein.

The present invention also provides, as a method for manufacturing the above-mentioned printed wiring board, the first layer circuit and the second layer on the insulating layer via a blind via hole of the insulating layer provided on the first layer circuit. 2. The printed wiring according to claim 1, wherein a conductive material is applied to the insulating layer and then electroplated on the conductive material coating film to form the second layer circuit when connecting to a circuit. It also provides a method of making the plate.

In the printed wiring board and the method for manufacturing the same according to the present invention, the insulating layer is preliminarily swollen and roughened before the second layer circuit is formed, and the conductive material coating film is a conductive paste. Desirably, it is formed by printing or dip coating of a conductive polymer material, and electroplating is electrocopper plating.

[0031]

EXAMPLES Examples of the present invention will be described below. 1 to 4 show a printed wiring board and a method for manufacturing the same according to a first embodiment of the present invention.

The printed wiring board 60 according to the present embodiment has the above-mentioned build-up type multilayer structure,
It can be manufactured through the steps described below.

According to the present embodiment, the above-mentioned steps of FIGS. 19 to 24 are carried out in the same manner, and therefore the description thereof will not be repeated here. What is important is that after the step of FIG. 24, as shown in FIG. 1, a copper paste layer 52, which is a conductive paste, is printed to a thickness of about 5 μm on the entire surface including the through holes 43 and the resin insulating layer 47. .

When printing the entire surface of the copper paste layer 52, 3
A copper paste (for example, NF-2000 manufactured by Tatsuta Electric Wire Co., Ltd.) is extruded to a predetermined thickness with a squeegee using a screen of 00 mesh with a 12 μm thick emulsion layer (mask portion).
As shown in the enlarged view of FIG. 1, the printed copper paste layer 52 is coated with a large number of copper particles 53 dispersed in a binder 54.

Then, as shown in FIG. 2, the same swelling and roughening treatment (desmearing treatment) as described above is performed to form a copper paste.
The binder in the surface region of 52 is removed, the copper particles 53 are exposed, and the rough surface 52a is finished.

As described above, this process is originally carried out as a desmear process for removing the resin smear after processing the through hole 43. In this embodiment, the copper paste is applied by applying this process. The surface of layer 52 can be roughened as described above.

In order to carry out this treatment in this example, first, a swelling treatment was carried out with a solvent such as dimethylformamide, dimethylsulfoxide, N-methyl-2-pyrrolidone and pyridine (for example, Desmi Initiator DI-464 described above). , Alkaline permanganate solution (eg KMnO ₄
/ NaOH).

Since the copper particles 53 are exposed in the copper paste layer 52 thus treated, electroplating can be performed thereon. That is, as shown in FIG. 3, a copper plating layer 51 is formed on the entire surface of the copper paste layer 52 by electrolytic copper plating. Therefore, the underlying layer of the electrolytic copper plating layer 51 is not the conventional electroless plating layer but the coated copper paste 52.

At this time, the plated surface of the copper paste layer 52 is a rough surface.
Since it is 52a, its anchor effect (anchor effect)
Thereby, the adhesion of the copper plating layer 51 becomes sufficient. Moreover, since the copper plating layer 51 is adhered to the copper particles 53 of the copper paste 52, a metal-to-metal bond is generated between them and the bonding force (adhesion) is improved.

To increase the adhesion of the copper plating layer 51
It may be heat-treated in a box oven for 15 minutes at ℃.

Then, as shown in FIG. 4, the copper plating layer 51 and the copper paste layer 52 are simultaneously etched by the same photolithography technique as described above to leave a predetermined conductor pattern. Copper chloride (CuCl ₂ ) or iron chloride is used for this etching.
(FeCl ₃ ) solution is used.

Thus, the outer layer circuits 61A-61B on both sides are connected to each other through the through holes 43, and the resin insulation layer is formed.
Circuits on both sides of it through 47 blind via holes 45
40A-61A and 40B-61B are connected to each other, and a build-up type multilayer printed wiring board 60 having four wiring layers and no prepreg is obtained. In this printed wiring board 60, the presence of the copper paste layer 52 can be easily identified.

As is clear from the manufacturing method described above, this multilayer printed wiring board 60 requires only one drilling (through-hole drilling in FIG. 23) and one plating (electroplating in FIG. 3). ) Is sufficient, the number of steps can be reduced and the cost can be reduced as compared with those shown in FIGS.

In this case, further, as compared with those in FIGS. 19 to 28, when forming the electrolytic copper plating layer 51 for forming the outer layer circuit, the base 52 thereof is not applied by electroless (chemical) plating but is simply applied. Since it can be formed, the process can be further simplified, and the cost of auxiliary materials and consumable materials can be reduced.

Further, as to the adhesion strength (peel strength) of the circuit pattern, as shown in the enlarged view of FIG. 4, the copper paste layer 52 has an anchor effect (anchoring effect) due to the rough surface 52a as well as a copper bond due to metal bonding. Since the plating layer 51 is applied with sufficient strength, it has been confirmed that its peel strength is significantly improved from the conventional 600 g / cm to 1,200 g / cm.

5 to 8 show a printed wiring board according to the second embodiment of the present invention and a method for manufacturing the same.

According to the present embodiment, the steps of FIGS. 19 to 25 described above are performed in the same manner, and therefore will not be repeated here. What is important is that after the desmear step of FIG. 25, as shown in FIG. 5, a polypyrrole layer 72, which is a conductive polymer material, is applied to the entire surface including the through hole 43 and the resin insulating layer 47 by a dipping process. .

When coating the polypyrrole layer 72,
The substrate in the state of FIG. 25 is dipped in the polypyrrole solution and dried. As shown in FIG. 8, this polypyrrole is synthesized by polymerizing pyrrole, and has the property of exhibiting conductivity due to the movement of π electrons in the molecule. Also, the polypyrrole layer 72
Are sufficiently adhered to the resin insulating layer 47 due to the anchor effect of the rough surface 42a. The conditions of the desmearing treatment for forming the rough surface 42a may be the same as those described in FIG. 25 or FIG.

Since the polypyrrole layer 72 is electrically conductive, it can be electroplated. That is, as shown in FIG. 6, a copper plating layer 71 is formed on the entire surface of the polypyrrole layer 72 by electrolytic copper plating. Therefore, the underlying layer of the electrolytic copper plating layer 71 is not the conventional electroless plating layer but the polypyrrole layer 72 formed by coating.

At this time, since the plated surface of the polypyrrole layer 72 is the rough surface 72a following the rough surface 52a of the resin insulating layer 47, its anchor effect is maintained and the adhesion of the copper plated layer 51 is good. Will be things.

To increase the adhesion of the copper plating layer 71,
It may be heat-treated in a box oven for 15 minutes at ℃.

Then, as shown in FIG. 7, the copper plating layer 71 is etched by the same photolithography technique as described above, and is left in a predetermined conductor pattern. A copper chloride (CuCl ₂ ) or iron chloride (FeCl ₃ ) solution is used for this etching.

By this etching, the polypyrrole layer 72a under the removed copper plating layer is deactivated even if it remains after the etching and loses its conductivity (becomes insulating), as shown in the enlarged view of FIG. Therefore, insulation between the outer layer circuits 71 can be ensured. However, the remaining polypyrrole layer 72, which is the base of the copper plating layer 71, remains conductive.

Thus, the outer layer circuits 81A-81B on both sides are connected to each other through the through holes 43, and the resin insulation layer is formed.
Circuits on both sides of it through 47 blind via holes 45
40A-81A and 40B-81B are connected to each other, and a build-up type multilayer printed wiring board 80 having four wiring layers and no prepreg is obtained.

As is clear from the above-mentioned manufacturing method, this multilayer printed wiring board 80 also requires only one drilling (through-hole drilling in FIG. 23) and one plating (electroplating in FIG. 6). ) Is sufficient, the number of steps can be reduced and the cost can be reduced as compared with those shown in FIGS.

In this case, further, as compared with those of FIGS. 19 to 28, when forming the copper plating layer 71 for forming the outer layer circuit, the base 72 is formed not by electroless (chemical) plating but simply by coating. As a result, the process can be further simplified, and the cost of auxiliary materials and consumable materials can be reduced.

Moreover, as for the adhesion strength (peel strength) of the circuit pattern, as shown in the enlarged view of FIG. 7, copper plating is performed by the anchor effect by the rough surface 47a of the resin insulating layer 47 and the rough surface 72a of the polypyrrole layer 72. Since the layer 71 is applied with sufficient strength, its peel strength is from the conventional 600 g / cm
It has been confirmed to be significantly improved to 1,200 g / cm.

FIG. 9 shows the peel strengths of the circuit patterns of the printed wiring boards according to the first and second embodiments of the present invention in comparison with those of the conventional example. Where the figure
As schematically shown in 10, according to the method of JIS-C-6481, using a JOM2000 type universal tensile compression tester (manufactured by Shinko Communication Industry Co., Ltd.), the resin insulation layer 47 by the method described above.
The peel strength of the copper plating pattern 41, 51 or 71 provided above was measured.

From these results, it is clear that the peel strength is significantly improved by providing the copper plating layer on the underlayer formed according to the present invention.

Although the embodiments of the present invention have been described above, the above-described embodiments can be further modified based on the technical idea of the present invention.

For example, the base of the above-mentioned electroplating layer is
Not limited to the copper paste layer and the polypyrrole layer, other conductive pastes (containing other conductive particles such as nickel powder and carbon black) and conductive polymer materials (polyaniline, polyphenylene sulfide, polyparaphenylene, etc.) And the like.

Further, the processing method and the processing method of the above-mentioned base layer may be variously changed. For example, not only the above-mentioned etching (simultaneous etching with the electrolytic copper plating layer) but also etching or alteration treatment separately, It is considered that if the desmear process is also performed on the resin insulating layer in advance, the coverage of the underlying layer with respect to the through hole is improved.

In addition, the layer structure of the above-mentioned multilayer printed wiring board, the material of each part (including the electroplating layer), the forming method and the like may be changed.

[0064]

As described above, according to the present invention, through the blind via hole of the insulating layer provided on the first layer circuit,
When connecting the first layer circuit and the second layer circuit on the insulating layer, a conductive material is applied on the insulating layer, and the conductive material coating film is electroplated to form the second layer. Since the circuit is formed, when forming the electroplating layer for forming the second layer circuit, the underlying conductive layer can be formed by simple coating rather than electroless (chemical) plating, thus simplifying the process. Therefore, the cost can be reduced.

Moreover, since the above conductive layer is formed by coating,
By controlling the surface property, the adhesion strength of the electroplating layer to the insulating layer can be improved.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view showing one stage of a manufacturing process of a multilayer printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 3 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 4 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 5 is a partially enlarged cross-sectional view showing a step in the manufacturing process of the multilayer printed wiring board according to the second embodiment of the present invention.

FIG. 6 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 7 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 8 is an explanatory diagram of a conductive polymer used in the manufacturing process.

FIG. 9 is a graph showing a comparison of peel strengths of circuit patterns.

FIG. 10 is a schematic diagram showing a method for measuring the peel strength.

FIG. 11 is a cross-sectional view showing a step in the manufacturing process for the multilayer printed wiring board according to the conventional example.

FIG. 12 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 13 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 14 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 15 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 16 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 17 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 18 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 19 is a cross-sectional view showing a step in the manufacturing process of a multilayer printed wiring board according to another conventional example.

FIG. 20 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 21 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 22 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 23 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 24 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 25 is a partially enlarged cross-sectional view showing another stage of the manufacturing process.

FIG. 26 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 27 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

FIG. 28 is a partially enlarged cross-sectional view showing another step of the manufacturing process.

[Explanation of symbols]

 40A, 40B ... Inner layer conductor circuits 41, 51, 71 ... Electrolytic copper plating 42 ... Electroless (chemical) plating layer 43 ... Through hole 44 ... Insulating substrate 45 ... Blind via hole 47 ... Resin insulation layers 47a, 52a, 72a ... Rough surface 49 ... Copper foil 52 ... Copper paste layer 53 ... Copper particles 54 ... Binder 60, 80 ... Multilayer printed wiring Plates 61A, 61B, 81A, 81B ... Outer layer conductor circuit 72 ... Polypyrrole layer

Claims (6)

[Claims] 1. In a printed wiring board in which a first layer circuit and a second layer circuit are connected through a blind via hole formed in an insulating layer, a conductive material is applied onto the insulating layer by coating. And a second wiring circuit formed by electroplating on the conductive material coating film. 2. When connecting the first layer circuit and the second layer circuit on the insulating layer through a blind via hole in the insulating layer provided on the first layer circuit, the conductive layer is formed on the insulating layer. The method for manufacturing a printed wiring board according to claim 1, wherein after applying the conductive material, electroplating is performed on the conductive material coating film to form the second layer circuit. 3. The printed wiring board according to claim 1 or 2, wherein the insulating layer is preliminarily swollen and roughened before forming the second layer circuit. 4. The printed wiring board according to claim 1, wherein the conductive material coating film is formed by printing a conductive paste. 5. The printed wiring board according to any one of claims 1 to 3, or the method for producing the same, wherein the conductive material coating film is formed by immersion coating of a conductive polymer material. 6. The printed wiring board according to claim 1, wherein the electroplating is electrocopper plating, or a method for producing the same.