JPH06132629A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To accurately miniaturize a circuit pattern by removing a copper foil layer of a laminated board substantially in a uniform thickness. CONSTITUTION:A laminated board is dipped in an etchant tank to form an outer layer copper foil 10 having a predetermined thickness on a surface. Then, through holes 5 are formed to connect to an inner layer, and then a panel copper plating 4 is conducted on the entire board. Thereafter, a predetermined plating resist pattern 6 is formed on the surface of the board with the plating 4. Further, a pattern copper plating 7 is provided on a part in which the pattern 6 is removed, and a solder plating 8 to become an etching resist is formed on the surface. The pattern 6 is peeled from this state to be removed. Then, with the resist as an etching resist it is etched to form a predetermined circuit pattern. Thus, a thickness of the pattern etched layer can be reduced, and a required time for the etching can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly, to manufacturing a printed wiring board which can improve the accuracy of a pattern formed on the printed wiring board and realize high density pattern formation. Regarding the method.

[0002]

2. Description of the Related Art FIG. 8 shows an example of a cross section of a conventional multilayer copper foil laminated plate in which circuits of inner and outer layers are connected by through holes. This multilayer copper foil laminated plate 50 includes a resin-impregnated prepreg 51 corresponding to an insulating layer and a resin-impregnated prepreg 51.
It is composed of an inner layer pattern 52 formed inside and an outer layer copper foil 53 adhered to the outer surface of the resin-impregnated prepreg 51.

The outer layer copper foil 53 has a matte (roughened) surface 54 having fine irregularities on the adhesive surface in order to enhance the adhesiveness with the resin-impregnated prepreg 51.
On the outer surface of the outer layer copper foil 53, a panel copper plating 55 for protecting the hole wall and a pattern copper plating 56 forming a predetermined circuit pattern are formed.
The portion except the etching resist portion (not shown) by the solder plating applied to the portion except the plating resist pattern (not shown) formed at the same time as the formation of this pattern copper plating reaches the surface of the insulating portion. A final circuit pattern is formed by etching.

By the way, as described above, the through hole 5
In the copper-clad multi-layer laminate that enables interconnection of circuits in the inner and outer layers through 7, the panel copper plating 55 is applied to the entire surface of the hole wall and the outer layer copper foil 53 surface. As a result, in the copper plating of the panel, the hole wall is not eroded by the etching solution when the pattern of the surface layer is etched. Usually, a dry resist film is further laminated on the surface of the panel copper plating 55, and the image is printed by a predetermined ultraviolet exposure device or the like to perform material pattern copper plating, etc., and this pattern copper plating is patterned into a predetermined pattern. Etching is performed to form a predetermined circuit.

[0005]

By the way, the circuit pattern of the laminated plate is formed by stacking the panel copper plating 55 and the pattern copper plating 56 as described above. The etching of the copper foil portion thus formed in multiple layers proceeds only from the surface layer side, and the cross-sectional shape of the formed circuit pattern 60 becomes a substantially trapezoidal shape with the hem widened toward the base portion on the laminated plate side. Such an etching state is called side etching. As is clear from the shape, the side etching proceeds as the copper foil has a larger layer thickness and requires a longer etching time.

For example, in the copper-clad multilayer laminate having the above-mentioned circuit pattern, since the layer thickness of the copper foil is about 35 μm, the spread at the base in this case is 1 / one of the copper foil at one side due to side etching. It reaches about 3. Therefore, in the copper-clad multi-layer laminate as shown in FIG. 8, it is extremely difficult to reduce the pattern spacing and pattern width in order to achieve high density.

It is also possible to use a thin type copper foil (thickness: 9 μm) from the beginning as the outer layer copper foil 53 of the copper-clad multilayer laminate. In this case, the matte (roughened) surface 53 is used.
Since the height of the uneven portion formed in a is small, there is a problem that sufficient adhesion between the reinforcing base resin and the copper foil cannot be obtained. Further, at this time, in the case of a thin type copper foil, aluminum is used as a carrier to form a laminated plate, so aluminum must be removed during the manufacturing process, which complicates the process.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technique, to form a circuit pattern 60 with high precision and high density on a wiring board by a simple method, and to laminate a laminated board. It is an object of the present invention to provide a method for manufacturing a printed wiring board capable of maintaining high adhesion of a copper foil pattern adhered to the.

[0009]

In order to achieve the above object, the present invention is a step of removing a copper foil layer of a laminate having a copper foil layer formed on at least the front and back of the outer surface thereof with a substantially uniform layer thickness. And a step of forming a through hole in the laminated plate and performing panel copper plating on the surface of the copper foil layer from which the hole wall of the through hole and a part of the outer surface are removed, and the panel copper plating surface A step of forming an etching resist on the plating resist and the pattern copper plating, and a step of removing the plating resist and etching the copper plating and the copper foil layer to form a circuit. To do.

At this time, the laminated plate is made of a sulfuric acid / hydrogen peroxide system, a ferric chloride system, a cupric chloride system, an alkali etchant, or a hard etching solution or ammonium persulfate or a sulfuric acid / hydrogen peroxide system. It is preferable to immerse the copper foil layer in a bath filled with any one of the soft etching solutions for a predetermined time so that the copper foil layer is removed by a predetermined thickness by etching.

Further, the laminated plate is made of a sulfuric acid / hydrogen peroxide system, a ferric chloride system, a cupric chloride system, an alkaline etchant, or a hard etching solution or ammonium persulfate or a sulfuric acid / hydrogen peroxide system. It is preferable that a soft etching liquid containing any one of them is sprayed onto the surface of the copper foil layer by a spray nozzle so that the copper foil layer is removed by a predetermined layer thickness by etching.

[0012]

According to the present invention, at least the copper foil layer of a laminate having a copper foil layer formed on the front and back of the outer surface is removed with a substantially uniform layer thickness, and a through hole is formed in the laminate,
Panel copper plating is performed on the surface of the copper foil layer from which the hole wall of the through hole and a part of the outer surface are removed, and a plating resist and a pattern copper plating are applied to the panel copper plating surface, and then an etching resist is formed. However, since the plating resist is removed and the copper plating and copper foil layers are etched to form a circuit, it is possible to reduce the thickness of the pattern-etched layer and reduce the time required for etching. The side etching can be reduced. This allows adjacent circuit patterns to be formed with high accuracy.

At this time, the laminated plate is made of either a sulfuric acid / hydrogen peroxide system, a ferric chloride system, a cupric chloride system, an alkali etchant, a hard etching solution, or ammonium persulfate or a sulfuric acid / hydrogen peroxide system. It was soaked in a bath filled with a soft etching solution consisting of the above for a predetermined time, and the copper foil layer was removed by a predetermined layer thickness by etching, so an appropriate etching solution was used efficiently and the manufacturing process was simplified. Can be achieved.

Further, a hard etching solution containing any one of sulfuric acid / hydrogen peroxide system, ferric chloride system, cupric chloride system and alkali etchant, or a soft etching solution containing ammonium persulfate or sulfuric acid / hydrogen peroxide system. Since the etching liquid is sprayed onto the surface of the copper foil layer by a spray nozzle to remove the copper foil layer by a predetermined thickness by etching, the outer copper foil can be accurately etched to a predetermined thickness. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a printed wiring board according to the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 1 indicates an outer layer copper foil 1 of a printed wiring board before forming a circuit. This outer layer copper foil 1 is a conductor having a thickness of 18 μm, in which a mat (roughened) surface 1a having fine irregularities on the adhesive surface is formed in order to enhance the adhesiveness with the resin-impregnated prepreg 2 that constitutes the laminated plate. Further, inner layer patterns 3 and 3 are formed inside the laminated plate. Like the outer layer copper foil 1, the inner layer pattern 3 is formed by etching a predetermined pattern of copper foil, adhering the prepreg 2 and the patterns of a plurality of layers, and pressurizing and molding.

FIG. 2 shows a state in which the laminated plate of FIG. 1 is immersed in an etching solution tank and etched so that the outer copper foil 1 has a predetermined thickness of approximately 4 to 12 μm. At this time, the etching liquid is a hard etching liquid containing sulfuric acid / hydrogen peroxide, ferric chloride, cupric chloride, or an alkali etchant, or ammonium persulfate or sulfuric acid / hydrogen peroxide. A soft etchant can be used.

The sulfuric acid / hydrogen peroxide type etching solution has an advantage that it can be used in both hard etching and soft etching. Ferric chloride-based etching solutions are difficult to regenerate, but cupric chloride-based etching solutions should be applied with various regeneration methods so that the concentration of cuprous chloride in the solution is suppressed and the etching rate is not reduced. You can The alkaline etchant is an alkaline aqueous solution containing copper ammonium complex ions as a main component.
As a result, the etched outer layer copper foil 10 is formed on the surface of the laminate.

Next, as shown in FIG. 3, a through hole 5 is drilled for connection with an inner layer by a drill, and then a copper plate 4 is plated on the entire laminated plate. It is necessary to ensure accurate positional accuracy during drilling, and to pay close attention to the rotational speed of the drill to prevent smearing and nail heads on the hole wall surface. The panel copper plating 4 is formed so as to integrally cover the hole wall of the through hole 5 and the etched outer layer copper foil 1 as in the conventional case.

Further, a dry film resist (not shown) is thermocompression-bonded to the surface of the panel copper-plated laminate 4 by a thermocompression-bonding roller of a laminator. Then, the film is exposed to ultraviolet light through a positive or negative film on which a predetermined pattern is printed, a pattern image is printed, and then developed to form a predetermined plating resist pattern 6. Further, a pattern copper plating 7 is applied to a portion excluding the plating resist pattern 6 and a solder plating 8 serving as an etching resist is formed on the surface thereof (see FIG. 4). From this state, as shown in FIG. 5, the plating resist pattern 6 is formed.
Peel off and remove.

Then, as shown in FIG. 6, the above-mentioned solder resist is etched as an etching resist to form a predetermined circuit pattern. At this time, the portion removed by etching reaches the insulating portion of the laminated plate, and the side wall surface of the patterned copper plating 7 is also side-etched.
At this time, the layer thickness of the copper foil pattern-etched is 20μ.
m, the time required for etching can be reduced as compared with the conventional case. Therefore, the side etching amount L1 is greatly reduced compared to the side etching amount L0 after the conventional pattern etching shown in FIG. As a result, adjacent circuit patterns can be arranged closer to each other, and a finer pattern can be formed.

If desired, a solder resist and an outer shape process are applied to complete a desired printed wiring board.

In this embodiment, the laminated plate was immersed in the etching solution bath to etch the outer layer copper foil 1.
It is also possible to spray and remove the etching liquid E on the surface of the laminated plate by the spray device 20 provided in the in-line etching apparatus as shown in FIG.
According to the spray device 20 of this etching device, it is possible to dissolve and remove the copper foil on the surface without deteriorating the base material and resin of the laminated plate and maintaining a uniform etching rate without destroying the etching resist on the surface. You can At this time, as a spray device, the nozzle 21 is provided with a swinging mechanism,
The spray pressure and spray amount can be controlled and adjusted.

[0023]

As is clear from the above description, according to the present invention, the pattern copper plating 7 layer is thinned to reduce the side etching at the time of pattern etching. And the adhesion between the laminated board and the pattern copper plating 7 layer is maintained, and a high quality printed wiring board can be manufactured by a simple method.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a wiring board showing steps of an embodiment of a method for manufacturing a printed wiring board according to the present invention.

FIG. 2 is a partial cross-sectional view of a wiring board showing a step subsequent to the step shown in FIG.

FIG. 3 is a partial cross-sectional view of a wiring board showing a step subsequent to the step shown in FIG.

FIG. 4 is a partial cross-sectional view of a wiring board showing a step subsequent to the step shown in FIG.

5 is a partial cross-sectional view of a wiring board showing a step subsequent to the step shown in FIG.

FIG. 6 is a partial cross-sectional view of a wiring board showing a step subsequent to the step shown in FIG.

FIG. 7 is a perspective view showing an etching process using a spray device.

FIG. 8 is a through hole 5 as an example of a conventional printed wiring board.
FIG. 3 is a partial cross-sectional view of a wiring board showing a partial cross-sectional structure.

[Explanation of symbols]

 1 outer layer copper foil 1a matte surface 2 resin impregnated prepreg 3 inner layer pattern 4 panel copper plating 5 through holes 6 plating resist pattern 7 pattern copper plating 8 solder plating 10 etched outer layer copper foil 20 sprayer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H05K 3/46 B 6921-4E

Claims (3)

[Claims] 1. A step of removing a copper foil layer of a laminate having a copper foil layer formed on at least the front and back surfaces of the outer surface thereof with a substantially uniform layer thickness, and forming a through hole in the laminate and forming the through hole. A step of performing panel copper plating on the surface of the copper foil layer from which a part of the hole wall and the outer surface of the hole is removed, and a plating resist and a pattern copper plating are applied to the panel copper plating surface to form an etching resist And a step of removing the plating resist and etching the copper plating and copper foil layers to form a circuit. 2. The laminated plate is made of a hard etching solution containing any one of sulfuric acid / hydrogen peroxide, ferric chloride, cupric chloride, and alkali etchant, or ammonium persulfate, sulfuric acid / hydrogen peroxide. 2. A printed wiring board according to claim 1, wherein the copper foil layer is removed by etching to a predetermined layer thickness by immersing the copper foil layer in a bath filled with any one of the soft etching solutions for a predetermined time. Method. 3. The hard disk of any one of sulfuric acid / hydrogen peroxide type, ferric chloride type, cupric chloride type and alkali etchant, or ammonium persulfate, sulfuric acid / hydrogen peroxide type. 2. The print according to claim 1, wherein a soft etching liquid containing any one of them is sprayed onto the surface of the copper foil layer by a spray nozzle so that the copper foil layer is removed by a predetermined thickness by etching. Wiring board manufacturing method.