JPH066030A - Manufacturing method of both surface flexible substrate - Google Patents

Abstract

PURPOSE:To realize a manufacturing method of both surface flexible substrate capable of manufacturing said substrate within a relatively short time without deteriorating the reliability upon through holes. CONSTITUTION:This manufacturing method of both surface flexible substrate A' is composed of the four steps enumerated as follows i.e., a first step of coating a copper foil with sensitive polyimide resin solution 2 to be dried up later, a second step of forming through holes 5 in specific positions of the resin 2 using photo process, a third step of heating the resin 2 at specific temperature to form a polyimide film 2', a fourth step of bonding another copper foil 6 conductive to the copper foil 1 onto the surface of the polyimide film 2''. In such a constitution, the both surface flexible substrate A' can be manufactured within a relatively short time without deteriorating the reliability upon the through holes 5.

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 double-sided flexible substrate, and more particularly to a holeless / adhesive-less double-sided flexible substrate.

[0002]

2. Description of the Related Art FIG. 2 is an explanatory view (a) to (g) showing a cross section of a substrate in each manufacturing process in an example of a conventional method for manufacturing a double-sided flexible substrate A. As shown in FIG. 2, in the conventional method for manufacturing a double-sided flexible substrate A, first, a polyimide film 11 is prepared (a), copper foil 12 is deposited on both surfaces of the polyimide film 11 by a sputtering method, and then electrolytic plating is performed. The copper foil 13 is formed to have a predetermined thickness by using the method (b). Next, a photoresist 14 is applied to the surface of the copper foil 13 (c), and a through hole 15 is formed in the polyimide film 11 and the copper foils 12 and 13 by an etching method (d). Next, a copper foil 16 is formed on the side wall of the through hole 15 using electroless plating and electrolytic plating, and electrical continuity is established on both sides (e). Then, after removing the photoresist 14 (f), circuits are formed on both surfaces of the copper foils 12 and 13 (g). In this way, the double-sided flexible substrate A could be manufactured.

[0003]

In the conventional method for manufacturing the double-sided flexible substrate A as described above, the copper foils 1 on both sides are
A through hole 15 is formed by an etching method in order to obtain conduction between 2 and 13. In the case of etching method, first copper foil 1
Polyimide film 11 after etching 2, 13
However, since the polyimide film 11 is a chemically stable substance, there is a problem that the etching takes a relatively long time. Therefore, instead of the etching method, an NC drill method or a die processing for punching with a die may be used. However, in the case of the NC drill method, a hole having a small diameter cannot be formed, and the diameter is at least 0.3 to 0.4 m / m. Further, even in the case of die processing, the limit is about 0.4 m / m diameter. In addition, attention must be paid to the occurrence of burrs in the NC drill method and die processing. That is, if the number of processed pieces increases, burrs are likely to occur, and there is a possibility that the reliability of the so-called through hole, which is the reliability of the conductivity between the two surfaces when plated, may be reduced. Further, in any of the above-described methods, the through hole 15 prevents components from being mounted right above the through hole and in the vicinity thereof, so that high component mounting efficiency cannot be obtained. Moreover, the etching method results in a mortar-shaped hole, which may further lower the pattern density. As a result, the substrate size may increase. The present invention is
In order to solve such problems in the conventional technology,
It is an object of the present invention to improve a method for manufacturing a double-sided flexible board and provide a method for manufacturing a double-sided flexible board that can be manufactured in a relatively short time without lowering the reliability of through holes.

[0004]

In order to achieve the above object, the present invention is to apply a photosensitive resin liquid to a conductive metal plate, dry it, and form a through hole at a predetermined portion of the resin by using a photo process. Then, the resin is heated to a predetermined temperature to form a film, and then a metal foil that conducts to the metal plate is attached to the surface of the resin to form a double-sided flexible substrate.

[0005]

According to the present invention, the photosensitive resin liquid is first applied and dried on the conductive metal plate. Next, a through hole is formed in a predetermined portion of the resin by using a photo process. Then, after heating the resin to a predetermined temperature to form a film, a metal foil that conducts to the metal plate is attached to the surface of the resin. As a result, the double-sided flexible substrate can be manufactured in a relatively short time without lowering the reliability of the through hole.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not intended to limit the technical scope of the present invention. Here, FIG. 1 is explanatory views (a) to (e) showing substrate cross sections in each manufacturing step in the method for manufacturing a double-sided flexible substrate A ′ according to an embodiment of the present invention. As shown in FIG. 1, in the method for manufacturing the double-sided flexible substrate A ′ according to this embodiment,
First, copper foil 1 (either electrolytic copper foil or rolled copper foil is acceptable)
A photosensitive polyimide resin liquid 2 (corresponding to a photosensitive resin liquid) dissolved in a solvent is applied onto (corresponding to a conductive metal plate) (a). The resin liquid 2 is pre-baked (dried) to form a resin 2'in a dried state and then passed through a photo process. That is, the resin 2'is exposed by the ultraviolet ray 4 through the mask 3 (b). When the exposed resin 2'is developed with a developer,
A hole 5 that does not penetrate is opened and a part of the back side of the copper foil 1 is exposed (c). In order to remove the photosensitive group from the resin 2 ′, the resin 2 ′ is heated and cured at 300 to 400 ° C. to form a chemically stable polyimide film 2 ″. Next, the polyimide film 2 ″ is sputtered. A copper foil 6 (corresponding to a metal foil) is attached to the surface so as to be electrically connected to the copper foil 1, and is grown using an electroless or electrolytic plating method (d). Thereafter, similarly to the conventional example, upper and lower circuit patterns are formed on the surfaces of the copper foils 1 and 6 through the steps of photoresist coating, prebaking, exposure, development, etching, and peeling (e). The upper and lower circuit patterns are electrically connected to each other, and the double-sided flexible substrate A'is completed by the above series of steps. As described above, according to the manufacturing method of this embodiment, when the photosensitive polyimide resin 2'is passed through the photo process, the through hole pattern is used as the mask 3 to expose, develop and cure, so that the resin 2'can be punched and formed into a film at the same time. Therefore, the double-sided flexible substrate A'can be manufactured in a comparatively short time as compared with the case where the through holes are provided by the conventional etching method. Also, since there is no possibility of burrs occurring in the conventional NC drill method or die machining, the reliability of the through hole can be improved. Further, in the manufacturing method of the above-described embodiment, the holes 15 which do not penetrate the copper foils 1 and 6 are formed. This hole 15 is made straight and does not have a mortar shape as in the etching method. As a result, components can be mounted directly above or in the vicinity of the through holes, and the mounting efficiency can be improved and the board size can be reduced. Furthermore, the thickness of the polyimide film 2 ″ can be controlled by adjusting the coating amount of the photosensitive polyimide resin liquid 2, and since it is a photo process, it can also handle irregular holes, so that various double-sided flexible substrates can be manufactured. Also, even if the number of holes is large, the batch processing is performed at the same time, so there is almost no effect on the cost.

[0007]

Since the method of manufacturing a double-sided flexible substrate according to the present invention is configured as described above, when the photosensitive polyimide resin is exposed to the photo process, the through-hole pattern is used as a mask for exposure, development, and curing, Holes in resin and film can be formed at the same time. Therefore, the double-sided flexible substrate can be manufactured in a relatively short time compared to the case where the through hole is provided by the conventional etching method. Also, since there is no possibility of burrs occurring in the conventional NC drill method or die machining, the reliability of the through hole can be improved. In addition, this method creates holes that do not penetrate the copper foil. This hole is made straight and does not have a mortar-like shape as in the etching method. As a result, components can be mounted directly above or in the vicinity of the through holes, and the mounting efficiency can be improved and the board size can be reduced. Furthermore, the thickness of the polyimide film can be controlled by adjusting the coating amount of the photosensitive polyimide resin liquid, and since it is a photo process, it can also handle irregular holes, so that various double-sided flexible substrates can be manufactured. Further, even if the number of holes is large, the cost is hardly affected because the simultaneous processing is performed at once.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a substrate cross section in each manufacturing process in a method for manufacturing a double-sided flexible substrate A ′ according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a substrate cross section in each manufacturing process in an example of a conventional method for manufacturing a double-sided flexible substrate A.

[Explanation of symbols]

 A '... Double-sided flexible substrate 1, 6 ... Copper foil (corresponding to metal plate and metal foil) 2 ... Photosensitive polyimide resin liquid (corresponding to photosensitive resin liquid) 2' ... Resin 2 "... Polyimide film 3 ... Mask 4 ... Ultraviolet ray 5 ... through hole

Claims (1)

[Claims] 1. After a photosensitive resin liquid is applied to a conductive metal plate and dried, a through hole is formed at a predetermined portion of the resin by using a photo process, and the resin is heated to a predetermined temperature to form a film. A method for manufacturing a double-sided flexible substrate, which comprises attaching a metal foil that conducts to the metal plate to the surface of the resin.