JPH11274730A - Manufacture of multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high density multilayer printed wiring board which has a via hole on a conduction through hole (hereinafter called IVH) formed in a laminate which will serve as a core. SOLUTION: An IVH 3 of a laminate 1 which is formed with a first plating layer 4 and has the conduction through hole (IVH 3) is filled with resin filler 5. After that, the resin filler 5 is etched by a desired depth to form a recessed resin etched section 6. In this recessed resin etched section 6, a via hole concentrical with the IVH 3 and connected to the IVH 3 is formed on the IVH 3 by forming a conductor layer by filling the recessed section 6 with plating or conductive paste and then building up photosensitive resin and plating on the layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a multilayer printed wiring board, and more particularly to a method of manufacturing a multilayer printed wiring board by a build-up method.

[0002]

2. Description of the Related Art In a method of manufacturing a multilayer printed wiring board using a build-up method, conductive through holes (hereinafter, referred to as IVH) are provided in a laminated board serving as a core in order to obtain front-to-back conduction, and resin is applied to the IVH. It is common to fill.
In order to obtain conduction between the IVH and the circuit in the upper layer, the IVH
Since there is no conductive circuit on the resin, there is adopted a method of extending the corresponding land of the IVH or connecting the IVH and the upper connection land with a conductive circuit.

[0003] In these methods, since there is a limit in increasing the density of the circuit, a method of forming a conductor circuit on an IVH is disclosed in Japanese Patent Application Laid-Open Nos. 5-82945 and 6-275959. Hereinafter, these methods will be described with reference to FIGS. First, as shown in FIG. 4A, a through hole 3a is formed in a laminated plate 1 on which a copper foil 2 is adhered by drilling, punching, or the like. Next, FIG.
As shown in (b), the surface of the laminate 1 and the through holes 3
a is plated. A first plating layer 4 is formed in the laminate 1 and the through holes. The plated through hole that is rendered conductive is referred to as IVH3.

[0004] Next, as shown in FIG. 4 (c), after filling the filling resin 5 into the IVH 3 and filling the IVH 3, FIG.
As shown in (d), the plating process is performed again to form the second plating layer 7 on the surface of the filling resin 5 and the surface of the IVH first plating layer 4.

Next, as shown in FIG. 4 (e), the first plating layers 4 and 7 and the copper foil 2 on the surface of the laminated board are etched by a known dry film method or an electrodeposition resist method or the like to form an inner conductor circuit. 9 and the inner printed wiring board 11 having the conductor land 10 on the IVH 3 are obtained.

Thereafter, as shown in FIG. 5F, a photosensitive insulating resin 12 is applied to the surface of the inner printed wiring board 11 by a known build-up method, and then a via hole 13 is formed by a photo method or a laser method. I do. At this time, since the conductor land 10 is present on the IVH 3, the via hole 13 can be formed coaxially with the IVH 3 (FIG. 5G).

Next, a plating process is performed on the surface of the photosensitive insulating resin 12, a second plating layer 14 is formed, and a circuit is formed to manufacture a multilayer printed wiring board 15 (FIG. 5).
(I)).

[0008]

However, the multilayer printed wiring board 15 thus obtained has the following problems.

First, this multilayer printed wiring board 15
In particular, it is difficult to make the inner layer circuit finer. The reason is that the plating process is performed twice in order to provide the conductor land 10 on the IVH 3.
Thickness (normally 12 to 18 μm), thickness of the first plating layer 4
(Approximately 20 μm) and the thickness of the second plating layer 7 (20 μm), the total thickness is 50 μm or more. As the etching time increases, the amount of side etching on the side surfaces of the inner conductor circuit 9 and the conductor land 10 increases. This is because the resolution of circuit formation deteriorates and it becomes difficult to form a fine circuit.

Considering the formation of a fine circuit, the second
The plating layer 7 is thinly applied.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-107, it is conceivable to perform an etching process after plating to reduce the thickness of the conductor layer. In this case, since the conductor layer on the IVH 3 is similarly thinned, a via hole 13 formed coaxially is used. And the connection reliability of the IVH3 is reduced.

An object of the present invention is to provide a method for manufacturing a high-density multilayer printed wiring board which can solve the above problems and can form a via hole coaxially with an IVH and can also form a fine circuit.

[0012]

According to the present invention, there is provided a method for manufacturing a multilayer printed wiring board, comprising the steps of: forming a through hole in a laminate having copper foil on both sides;
Forming a plating layer, filling the through-hole (hereinafter, referred to as IVH) with the first plating layer with a filling resin, and etching the filling resin in the IVH to a desired depth. A step of forming a recess in the IVH, a step of forming a conductor layer in the recess, and etching the first plating layer to form an inner layer conductor circuit on the surface of the laminate and a conductor land on the surface of the IVH. A step of forming a wiring board, a step of coating the surface of the inner printed wiring board with an insulating resin, and forming a via hole in the insulating resin on the IVH so that the conductor layer in the concave portion of the IVH is exposed. And a step of forming a second plating layer on a surface of the insulating resin including the via hole.

In the present invention, the method of forming the conductive layer in the concave portion of the IVH may include forming a plated film on the surface of the first plating layer so as to fill the concave portion after forming the concave portion. A method of mechanically polishing or chemically etching the plating film so that the first plating layer is exposed, or a method of selectively filling the recess with a conductive paste can be adopted.

In the present invention, the thickness of the copper to be etched when forming the inner conductor circuit of the inner printed wiring board can be reduced, so that the inner conductor circuit of the inner printed wiring board can be made thinner, and the IVH internal circuit can be formed. Since the thickness of the conductor layer on the filling resin can be increased, the effect of maintaining high connection reliability between the IVH and the via hole can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for manufacturing a multilayer printed wiring board according to the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board following FIG. FIG. 3 is an enlarged cross-sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board following FIG.

Referring to FIG. 1, first, a through-hole 3a is formed by drilling, punching, or the like in a laminated plate 1 having copper foils 2 adhered to both sides in FIG. 1 (a). Next, the first plating layer 4 is formed on the through holes 3 a and the surface of the laminate 1.
The through-hole 3a is made conductive and becomes IVH3 (FIG. 1).
(B)).

The first first plating layer 4 is formed by a method of thickening electroless copper plating or a combination of electroless copper plating and electrolytic copper plating. The plating thickness at that time is IVH3
Is required to have a thickness of about 20 μm in order to ensure the reliability of conduction.

Next, as shown in FIG. 1C, the filling resin 5 is filled in the IVH 3 and filling is performed. Examples of the resin include PHP-900 IR manufactured by Yamaei Chemical Co., Ltd.
-1 A thermosetting epoxy resin or the like can be used. After filling the filling resin 5 into the IVH 3 by a screen printing method, baking is performed at a temperature of about 140 ° C. for 30 minutes,
After thermosetting the filling resin 5, the surface of the laminate 1 is polished by mechanical polishing or the like in order to smooth the surface of the IVH3. As a polishing method, a belt sander polishing machine or the like may be used. By using a polishing agent having a high surface smoothness, for example, a resin cross belt RAXB AA # 600 manufactured by Sankyo Rikagaku Co., Ltd., the first plating layer 4 and the IVH3 can be polished. The smoothness of the surface of the filling resin 5 could be realized. As the filling resin 5, an ultraviolet-curing epoxy resin or the like can be used in addition to the thermosetting epoxy resin, and palladium metal may be added to these filling resins 5 in order to improve the adhesion of plating. Good.

Next, as shown in FIG. 1D, the surface layer of the filling resin 5 filled in the IVH 3 is resin-etched to a depth of 10 μm to 20 μm, and a resin-etched portion (hereinafter referred to as a concave portion 6) is formed on the filling resin 5. Form. Recess 6 at this time
If the depth is smaller than 10 μm, there arises a problem that the connection reliability between the conductive layer 7 of the recess 6 and the via hole is reduced. If the depth of the concave portion 6 is larger than 20 μm, the processing time for filling the concave portion with plating increases. Therefore, it is important to control the depth of the resin etching so as to fall within the above range.

An etching method using an alkaline aqueous solution of permanganate was used as the method for etching the resin. First, an alkaline aqueous solution (alkaline normality of 0. 1).
The resin is subjected to a swelling treatment at 7 to 0.8 N at a temperature of 70 to 80 ° C., followed by an aqueous alkali permanganate solution (normality: 1.0 to 1.2 N, permanganate concentration: 43 to 55 g /
1, at a bath temperature of 75 ° C. ± 2 ° C.) for about 10 minutes. Thereafter, the mixture is neutralized with sulfuric acid (normality: 0.3 to 0.4 N, temperature: 40 to 50 ° C.), and the etching of the filling resin 5 is completed. As a method for etching the filling resin 3, a plasma etching method using a plasma gas of CF ₄ / O ₂ , O ₂ , Ar, an excimer laser, a YAG laser, a CO ₂ laser, etc., in addition to a chemical treatment method using an alkaline permanganate aqueous solution. Can be used.

Next, as shown in FIG. 1E, the first plating layer 4 is formed by electrolytic copper plating (referred to as IVH surface plating).
The conductor layer 7 is formed on the surface of the substrate and the recess 6. At this time, the thickness of the conductor layer 7 needs to be large enough to bury the concave portion 6 of the filling resin 5, and needs to be at least 20 μm.

Next, as shown in FIG. 2 (f), the surface of the conductor layer 7 which is thickened by plating twice is thinned by mechanical polishing or chemical polishing. Here, the surface conductor layer was polished by about 20 μm by using a mechanical polishing method such as a belt sander, for example, using a resin cross belt RAXB AA # 400 manufactured by Sankyo Rikagaku Co., Ltd. By this polishing, the surface conductor layer can be processed to a thickness of only the copper foil 2 and the first plating layer 4, and the height of the conductor layer in the recess 6 (referred to as the recess conductor layer 8) is equal to the surface of the first plating layer. 4
Is obtained.

The laminate 1 thus obtained is processed into a circuit by a known circuit forming method. The circuit forming method is not particularly limited as long as it includes an etching step. For example, after laminating a dry film photo-etching resist or electrodepositing an electrodeposition type photo-etching resist on the surface conductor layer, exposing and developing the etching resist, cupric chloride or ferric chloride etc. 2 (g), the inner-layer inner-layer conductor circuit 9 and the inner-layer inner-layer printed wiring board 11 having the conductor land 10 on the IVH 3 are formed as shown in FIG. 2 (g).

Thereafter, the surface of the inner layer conductor circuit 9 and the surface of the conductor land 10 were subjected to blackening treatment to form copper oxide.
This is performed for the purpose of roughening the surfaces of the inner layer conductor circuit 9 and the conductor land 10 in order to improve the adhesion between the photosensitive resin to be applied next and the conductor circuit or the like.

Next, as shown in FIG. 2H, a photosensitive insulating resin 12 (for example, epoxy resin) is applied on the inner printed wiring board 11 by a method such as a curtain coater, a roll coater, or screen printing. For example, the photosensitive insulating resin 12 is applied to a thickness of about 60 μm by a curtain coater, and the touch drying is performed at a temperature of 90 ° C. for about 1 hour.
Via holes for connecting the VH 3 and a conductor layer (such as an outer conductor circuit) on the insulating resin 12 are formed by photolithography. That is, after contact exposure using a mask film,
Insulating resin 12 that is not photopolymerized by a developing solution such as a 1% by weight aqueous solution of sodium carbonate (a portion where a via hole is formed).
Is removed by post-baking or ultraviolet curing at a temperature of 130 ° C. for about 90 minutes (for example, an exposure amount of 600 mJ / c).
UV irradiation of m ² , etc.) to form a via hole 13 as shown in FIG.

Next, the surface of the insulating resin 12 is roughened with an alkali permanganate aqueous solution or the like to improve the adhesion of the conductor layer formed on the surface of the insulating resin 12.
Are formed with a depth of 0.1 to 1 [mu] m on the surface.

Thereafter, as shown in FIG. 3J, the second plating layer 14 having a thickness of about 20 μm is formed by dipping in a plating bath and performing plating such as electroless copper plating. Thereafter, an outer layer conductor circuit 15 was formed by a known circuit forming method, and a multilayer printed wiring board 16 having via holes 13 formed on the IVH 3 as shown in FIG. 3K was obtained.

In the first embodiment, the via hole 13 is formed by photolithography. However, the via hole can be formed by irradiating a laser beam such as an excimer laser, a YAG laser, or a CO ₂ laser.
In this case, a thermosetting insulating resin may be used as the insulating resin 12.

Next, a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention will be described. In the method for manufacturing a multilayer printed wiring board according to the embodiment of the present invention, after the filling resin 5 of the IVH 3 in the first embodiment is etched, the concave portion of the IVH 3 is filled with a conductive paste, and then the inner layer conductor circuit is etched. With the method of forming the conductive lands, the IVH surface plating and the surface polishing treatment in the first embodiment can be omitted. Since the conductive paste may be formed in a recess having a depth of about 20 μm of the IVH, the conductive paste can be easily filled and an IVH having a smooth surface can be obtained. As the conductive paste, a silver or copper paste can be used. However, the addition of palladium metal to the conductive paste increases the adhesion between the conductive paste filled in the recesses and the copper plating (electroless copper plating) to increase the IVH and via hole. The effect of improving connection reliability is obtained.

[0031]

A first effect of the method for manufacturing a multilayer printed wiring according to the present invention is that a via on the IVH coaxial can be formed, and the degree of freedom of wiring is improved. The reason is IVH
This is because the conductor layer is formed on the filling resin filled into the substrate. A second effect of the present invention is that the circuit formation accuracy when forming a fine circuit is improved and the line is thinned. The reason for this is that after etching the filled filling resin to a certain depth, the recess can be filled with a conductive layer with copper plating or a conductive paste to smoothen the thickness of the etched copper.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a substrate for describing steps of a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of a substrate, for illustrating steps of a method of manufacturing the multilayer printed wiring board following FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a main part of the substrate, for illustrating steps of a method of manufacturing the multilayer printed wiring board following FIG. 2;

FIG. 4 is an enlarged cross-sectional view of a main part of a substrate for describing steps of a conventional method for manufacturing a multilayer printed wiring board.

FIG. 5 is an enlarged cross-sectional view of a main part of the substrate, for explaining steps of a conventional method for manufacturing a multilayer printed wiring board following FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laminated board 2 copper foil 3 IVH 3a through hole 4 first plating layer 5 filling resin 6 recess 7 conductive layer 8 concave conductive layer 9 inner conductor circuit 10 conductor land 11 inner printed wiring board 12 insulating resin 13 via hole 14th 2 plating layer 15 outer layer conductor circuit 16 multilayer printed wiring board

Claims (7)

[Claims] 1. A step of forming a through hole in a laminate having copper foils on both sides, and a first step in a surface of the laminate including the through hole.
Forming a plating layer, filling the through hole with the first plating layer with a filling resin, and etching the filling resin in the through hole to a desired depth to form a recess in the through hole. Forming a conductor layer in the recess, etching the first plating layer to form an inner printed circuit board having an inner conductor circuit on the surface of the laminate and a conductor land on the surface of the through hole. Forming, coating the surface of the inner printed wiring board with an insulating resin, and exposing the conductive layer in the recess of the through hole to the insulating resin on the through hole of the inner printed wiring board. Forming a second plated layer on the surface of the insulating resin including the via hole. 2. The multilayer printed wiring board according to claim 1, wherein the method of etching the filling resin in the through-holes is a chemical treatment method using alkaline permanganate, a plasma etching method or a laser etching method. Production method. 3. A plating film is formed on the surface of the laminated plate so as to fill the conductive layer in the concave portion of the through hole with the concave portion, and then the laminated plate is exposed until the first plated layer is exposed. 3. The method according to claim 1, wherein the surface is formed by mechanical polishing or chemical polishing. 4. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the conductive layer in the concave portion of the through hole is formed by filling the concave portion with a conductive paste. 5. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein a conductive paste containing silver and palladium metal or copper and palladium metal is used as said conductive paste. 6. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein a photosensitive or thermosetting insulating resin is used as the insulating resin formed on the surface of the inner printed wiring board. 7. The method for producing a multilayer printed wiring board according to claim 1, wherein a thermosetting or ultraviolet curing epoxy resin to which palladium metal is added is used as the filling resin.