JP2849191B2 - Manufacturing method of printed wiring board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed circuit board, in which a conductive pattern is embedded in a substrate groove, for example, in a rotary transformer used for a VTR or the like. It relates to a manufacturing method.

2. Description of the Related Art Conventionally, as a printed wiring board, a printed circuit such as a rotary transformer in which a conductor pattern is embedded in a groove on a substrate has been known.

A printed circuit in this rotary transformer is formed by forming a coil (conductor) pattern on a metal plate such as an aluminum plate or a stainless steel plate, and bonding the metal plate and a substrate having a groove with an adhesive. For example, it has been manufactured by a method of dissolving or removing with a chemical such as an aqueous sodium hydroxide solution.

[Problems to be solved by the invention]

When the printed wiring board as described above is manufactured, when the metal plate on which the conductor pattern is formed and the substrate having the groove portion are bonded, the metal plate is not so good in following the groove shape. Due to variations in the depth of the groove between the substrate and the substrate and variations in the amount of adhesive applied, a failure in fixing the conductor as shown in FIG. 8 may occur. In FIG. 8, reference numeral 1 denotes a conductor pattern, and 8 denotes an adhesive.

An object of the present invention is to provide a method for manufacturing a printed wiring board in which such a fixing failure has been eliminated with a good yield.

[Means for solving the problem]

The present invention relates to a method in which a film having a conductor pattern formed on one surface and a substrate having a groove corresponding to the conductor pattern are overlapped with each other so that the conductor pattern is embedded in the groove. A step of integrating the film and the substrate by pressing the conductive pattern from the other surface of the printed wiring board, and a method of manufacturing a printed wiring board including at least a step of selectively removing only the film. The film is extended by the pressing and follows the shape of the groove.

Here, the elongation percentage of the film may satisfy the following expression (1).

In the above formula (1), ε is the elongation percentage of the film, D is the depth of the groove, H is the thickness of the conductor pattern, and d is the gap between the inner wall of the groove and the outside of the conductor pattern. .

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2A is a cross-sectional view of a substrate on which the conductor pattern 1 and the film 2 are integrated. Reference numeral 1 denotes a conductor pattern for forming a circuit, which is formed on the removable film 2 in a planar manner.

The conductor pattern 1 may be obtained by any method, and the material thereof is not particularly limited as long as it is conductive. For example, copper, silver, and the like can be generally used. The thickness of the conductor is not particularly limited, but the present invention is particularly effective when the thickness is smaller than the groove depth of the transfer substrate described later.

On the other hand, the shape of the conductor pattern 1 formed on the film 2 is not particularly limited to a linear shape or a coil shape as long as the shape matches the intended wiring shape of the printed wiring board as shown in FIG. Not done. In FIG. 1, reference numeral 1 denotes a conductor pattern, and 8 denotes an adhesive. Further, the conductor formed on the film may be provided with a circuit pattern other than the conductor pattern, such as a positioning pattern for transfer.

The film 2 is required to have a function of holding the conductor pattern 1 and to be removable after being transferred to another substrate. Therefore, it is necessary to form the film 2 so that a part of the conductor pattern 1 is exposed. For example, in addition to FIG.
(C) and the like. That is, in (a), the conductor pattern 1 is formed so as to be wrapped in a film, whereas in (b), the conductor pattern 1 is formed in a convex shape from the film surface. (C) is intermediate between (a) and (b). Which of the shapes (a) to (c) is to be formed depends on the type of film used, the method of attaching the film, the method of forming the conductor, and the like. For example, if a conductive pattern 1 is formed by plating, and a heat-sealing film or a liquid resin is applied and dried and cured, the shape becomes as shown in (a). (B) when formed by an etching method
The shape is as follows.

In order for the conductor pattern 1 to be transferred to the substrate 4 having the groove 5 corresponding to the conductor pattern 1 as shown in FIG.
In order to push the conductor pattern 1 into the groove 5, sufficient followability is required. For this purpose, the supporting film 2 is preferably soft. Organic films are preferred over metal plates,
If it is hard but extremely thin, it can be used. That is, the elongation rate ε (%) of at least the conductor pattern forming surface side of the film at the time of transfer.
Can be used if it satisfies the expression (1), preferably the expression (2).

Here, D is the depth of the groove 5, H is the thickness of the conductor pattern 1, d is the gap between the groove wall and the outside of the conductor, and is a numerical value determined by the required characteristics of the target printed wiring board (fourth). See figure).

The elongation required for the film satisfies the above ε and, from the dimensional accuracy, 50 ≦ ε ≦ 500, and further 100 ≦ ε ≦ 40.
0, particularly preferably 150 ≦ ε ≦ 300. When ε is less than 50, it is difficult for the film to follow the groove shape, which causes a fixing failure. If ε is larger than 500, it is difficult to align the conductor pattern with the groove.

Further, the film thickness may be such that Expression (1) can be satisfied.
Considering the ease of pressing, 1 mm or less, further 0.5 mm or less, particularly preferably 0.1 mm or less, but if it is too thin,
There is a danger of breaking when pressing down, and care must be taken.

Further, the film 2 needs to have such a property that after the conductor pattern 1 is transferred to another substrate 4, only the film 2 can be selectively removed while the conductor pattern 1 is left on the substrate 4. The removing method may be any method such as mechanical peeling, chemical peeling, thermal peeling, and dissolving, but mechanical peeling is preferred from the viewpoint of safety and cost. Further, in the case of a peeling type, it is preferable to use a material of a hard-to-bond type for the purpose of improving the releasability from the transfer adhesive 8.

The type and other characteristics of the film are not limited as long as the film satisfies the above conditions. For example, it may be conductive or insulating, or may be a stack of different types of films.

Materials that can be used for the above-mentioned film 2 include polyethylene, polypropylene, fluororesin, silicone resin,
Examples include polyimide, polyester, polyamide resin, and polyvinyl chloride. However, in consideration of the above elongation, polyethylene, polypropylene, fluororesin, silicone resin, polyester, and polyamide resin are preferable, and polyethylene, polypropylene, fluororesin, and silicone resin are more preferable in terms of poor adhesion. From the viewpoint, polyethylene and polypropylene are preferred.

Next, a method of manufacturing the substrate 3 including the conductor pattern 1 and the film 2 will be described. It is necessary that the steps include the formation of a conductor pattern and the formation of a film, but their order is not particularly limited.

The method of forming the conductor pattern 1 is a known plating method, etching method, vapor deposition method, sputtering method, CVD method.
For example, a plating method and an etching method are preferable from the viewpoint of reducing the conductor resistance, and a plating method is particularly preferable from the viewpoint of pattern formation accuracy.

Here, the plating method will be described with reference to FIG. First, a photoresist 7 corresponding to a portion other than the conductor to be formed on the conductive substrate 6 serving as a plating base is formed (FIG. 5A). This is used as a cathode for electrolytic plating to obtain a conductor pattern 1 (FIG. 5 (b)). Next, after a film is formed (FIG. 5 (c)), the plating base 6 is removed (FIG. 5 (d)).

The steps up to the formation of the conductor may be performed by a usual method. For example, when the conductor pattern 1 is copper, aluminum or the like can be used as the conductive substrate 6. The method of forming the film 2 is the conductor pattern 1
Any method may be used as long as the sheet is securely covered, for example, a plate-like film may be attached via an adhesive, or the plate-like film itself may be thermally fused. Further, after the liquid resin is dip-coated by screen printing, the resin may be cured by heat or ultraviolet rays to form the support film 2. At this time,
Whether the photoresist 7 is removed or left as an insulating material can be arbitrarily selected.
The surface of the conductor may be mechanically and chemically roughened in order to improve the adhesion between the conductor and the film. After the support film 2 is formed, the conductive pattern 1 is removed by dissolving or removing the conductive substrate 6 used as a plating base by mechanical peeling.
Can be obtained.

Next, a method of manufacturing a printed wiring board using the above-described substrate 3 will be described with reference to FIG. The steps are as follows.

(A) The transfer adhesive 8 is applied (FIG. 6 (a)).

(B) The substrate 3 and the substrate 4 are bonded together with the adhesive (FIG. 6 (b)).

(C) The film 2 is removed (FIG. 6 (c)).

The adhesive is applied on one or both sides of the groove 5 of the substrate 4 on the conductor pattern 1 to be bonded. (Applied to the substrate 4 in FIG. 6). The adhesive 8 used should be such that the conductor 4 can be applied to the substrate 4 so as not to interfere with the subsequent processes.
As long as it can be fixed to an adhesive, it may be an adhesive, a rubber-based, an epoxy-based, an acrylic-based, or a urethane-based, and is not particularly limited. Further, it may be a one-pack type, a two-pack type, or a sheet. The curing property is not particularly limited, but the initial strength can be obtained at a low temperature and in a short time from the heat resistance and workability of the film 2 to be used. For example, a pressure-sensitive adhesive or an epoxy adhesive is suitable. It is.

As a supply method, a sheet-shaped material is supplied by punching, and a liquid material is screen-printed, dispenser-coated, stamp-coated, spray-coated, etc., but is not particularly limited. However, screen printing is preferred from the viewpoint of the stability of the application amount and workability.

Next, after positioning the substrate 3 and the substrate 4 having the groove, the substrates 3 and 4 are integrated so that the conductor pattern 1 is embedded in the groove 5. At this time, by using a positioning pattern formed simultaneously with the conductor pattern 1 for positioning, integration can be performed with high positional accuracy. The pressing conditions need to be set such that the film 2 is sufficiently deformed so that the conductive pattern 1 and the bottom of the groove 5 of the substrate 4 can contact each other via the adhesive 8. In order to deform the film 2 more efficiently, it is preferable to press only the groove with a jig as shown in FIG.

The transfer conditions are determined by the combination of the film 2, the adhesive, and the substrate 4 used. Above all, the curing conditions of the adhesive have a particular influence, which determines the temperature. The range is from room temperature to about 200 ° C. in consideration of the heat resistance of the film 2, preferably 80 ° C. or lower, more preferably room temperature. The pressing force is optional as long as the substrate 4 is not broken or deformed.

For removing the film 2, a method of mechanically peeling off the film 2,
There is a method of dissolving and removing the acid with a chemical solution such as an alkali and an organic solvent. The method is not particularly limited, but mechanical peeling is preferable from the viewpoint of safety and cost. According to the above method, a printed wiring board in which the conductor pattern 5 is securely embedded in the groove can be obtained.

Here, the material and dimensions of the substrate 4 having the groove 5 are not particularly limited. For example, a plastic plate or a ceramic plate having a thickness of 5 mm or less, a groove depth of 2 mm or less, and a groove width of 5 mm or less is preferably used. It is possible.

Experimental Example 1 The present invention was applied to the production of a rotary transformer. The conductor pattern was formed by plating, a polyethylene film was used as a support, and a ferrite core was used as a substrate having a groove.

First, a photoresist (using Nagase microresist 747) corresponding to a conductor other than the conductor formed on an 80 μm-thick plated substrate made of Al was formed. By using this as a cathode and performing electrolytic copper plating, a coil pattern and a positioning pattern are simultaneously formed, and then the photoresist is removed with a resist stripper (Nagase resist strip N).
= 530). Conductor thickness 4 produced in this way
A polyethylene film (thickness: 75 μm, elongation: 200%) is formed at 140 ° C using a laminator on a plurality of coils with different diameters and representative patterns of 0 μm, line width of 130 μm, pitch of 170 μm, and winding width of 820 μm. Heat fusion was performed.

Next, the substrate in which the coil pattern and the positioning pattern were integrated on the polyethylene film was obtained by dissolving and removing the Al plate as the plating substrate with a 10% HCl solution. In the cross-sectional structure of this substrate, the conductor pattern was embedded in the film as shown in FIG. Next, a ferrite substrate (groove depth 150 μm, groove width 1.23 mm) having a groove portion corresponding to the coil pattern, an epoxy resin adhesive (Cemedine EP001) diluted with a toluene solvent was applied to the groove portion by a dispenser, and then applied. After the solvent was removed by volatilization, the coil pattern was aligned with the groove of the ferrite core. Then, as shown in FIG. 6 (b), a convex jig (projection width 0.92) was used so that the coil pattern surface faced the core groove surface. mm, height
Using a pressure of 0.9 kg / cm ² at 25 ° C. for 90 minutes, the adhesive was cured and bonded to embed and integrate the coil pattern in the groove. After the adhesive was cured, the polyethylene film was mechanically peeled off to obtain a printed wiring board as shown in FIG. 6 (c). In each of the 100 printed wiring boards produced by the above method, the coil pattern was securely fixed to the groove surface without the coil pattern sticking out from the ferrite groove portion.

[Experimental Example 2] A conductive pattern was formed by plating, an adhesive film based on polyethylene was used as a support, and a ferrite core was used as a substrate having a groove.

The formation of the conductor pattern by the plating method, the method of removing the resist, the conductor pattern, and the dimensions of the ferrite core were the same as those in Experimental Example 1. Surface protective adhesive film (Nitto Denko SPV-363, film thickness 65) on the conductor pattern formed on the plating substrate
μm, elongation 20%) was attached with a laminator. Next, a substrate in which a conductor pattern was integrated on a film was obtained by dissolving and removing Al as a plating substrate with a 10% HCl solution. At this time, the conductor pattern was held in a convex shape on the film as shown in FIG. 2 (b).
Next, using a ferrite core, a printed wiring board having a conductor pattern embedded in a groove was formed in exactly the same manner as in Experimental Example 1.
100 were produced. In each case, the coil pattern was securely fixed to the bottom of the groove without sticking out from the ferrite groove.

Experimental Example 3 A conductive pattern was formed by plating, a silicone resin was used as a support, and a ferrite core was used for a substrate having a groove.

The formation of the conductor pattern, the resist peeling method, the conductor pattern, and the core dimensions were the same as those in Experimental Example 1. Liquid silicone resin (Hayakawa Rubber Hayatone-GHS elongation 280%) is applied on the coil and positioning pattern surface of the prepared substrate to a thickness of 0.1%.
After coating by screen printing to a thickness of 1 mm, it was cured by ultraviolet rays to form a film. Next, the plating substrate Al
The substrate was immersed in a 10% HCl solution and dissolved and removed to obtain a substrate having a conductive pattern held on a silicone film. The cross section of this substrate had a shape in which the conductor pattern was partially embedded in the film as shown in FIG. 2 (a).

Next, using a ferrite core, a printed wiring board having a conductor pattern buried in a groove was formed in exactly the same manner as in Experimental Example 1.
0 were produced. In each case, the coil was securely fixed to the groove bottom without sticking out from the ferrite core groove.

(Comparative example)

A conductive pattern was formed by plating, an Al plate (80 μm thick, 13% elongation), which was a plated substrate, was used for a support, and a ferrite core was used for a substrate having a groove.

The method for forming the conductor pattern, the method for removing the resist, the conductor pattern, and the core dimensions were the same as those in Experimental Example 1. It can be seen that the cross section at this time has a shape in which the conductor pattern is held in a convex shape on the support as shown in FIG. 2 (b).

Next, a conductor pattern was bonded to the ferrite core in exactly the same manner as in Experimental Example 1. However, unlike the example 1, the support was removed by dissolving and removing the 80 μm Al substrate with a 10% HCl solution. When 100 printed wiring boards in which the conductor pattern was embedded in the groove were produced by this method, only 30 pieces in which the coil pattern was securely fixed to the bottom of the ferrite groove were obtained.

〔The invention's effect〕

As described above, according to the present invention, a film having a conductor pattern formed on one surface and a substrate having a groove corresponding to the conductor pattern are formed such that the conductor pattern is embedded in the groove. After superimposing, the step of integrating the film and the substrate by pressing the conductor pattern from the other surface of the film, and at least a step of selectively removing only the film, the film Since the one that is extended by the pressing and follows the shape of the groove is used, the conductor pattern can be more securely fixed to the groove bottom without any inconvenience such as poor fixation, and the printed wiring board can be efficiently produced with good yield. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a structure of a printed wiring board manufactured according to the present invention, FIGS. 2 (a) to 2 (c) are schematic cross-sectional views showing various states of a conductor pattern on a printed circuit board, FIG. 3 (a) is a schematic sectional view showing the product, FIG. 3 (b) is a schematic sectional view showing a state where two substrates are bonded, and FIG. 4 is a schematic sectional view showing the relationship between a conductor and a groove. FIGS. 5 (a) to 5 (d) are schematic cross-sectional views for explaining a manufacturing process of a printed circuit board. FIG. 6 shows a manufacturing process of a printed wiring board using the printed circuit board shown in FIG. FIG. 7 (a) is a schematic plan view showing a substrate having a groove,
FIG. 7 (b) is a schematic perspective view showing a convex jig corresponding to the substrate, and FIG. 8 is a schematic cross-sectional view showing the structure of a defective printed wiring board manufactured by a conventional technique. DESCRIPTION OF SYMBOLS 1 ... Conductor pattern, 2 ... Support board, 3 ... Printed board, 4 ... Substrate with groove, 5 ... Groove, 6 ... Plating base, 7 ... Photoresist, 8 ... Adhesive, 9 …… a convex jig.

Claims (2)

(57) [Claims] 1. A method in which a film having a conductor pattern formed on one surface thereof and a substrate having a groove corresponding to the conductor pattern are overlapped so that the conductor pattern is buried in the groove. A method for manufacturing a printed wiring board, comprising: a step of integrating the film and the substrate by pressing the conductor pattern from the other surface of the film; and a step of selectively removing only the film. The method for manufacturing a printed wiring board, wherein the film is extended by the pressing and follows the shape of the groove. 2. The elongation percentage of the film is expressed by the following equation (1). (Where ε is the elongation percentage of the film, D is the depth of the groove,
2. The method according to claim 1, wherein H is a thickness of the conductor pattern, and d is a gap between an inner wall of the groove and an outer side of the conductor pattern.