JPH1022616A - Both-sided flexible board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount electronic parts in high density on both sides of a board without needing special constitution for getting flatness of the board, in a both- sided flexible board. SOLUTION: Electronic parts mounts 2 and 2' are provided on both sides of the both-sided flexible board B consisting of a base board where circuit patterns are made on both sides, and the vicinity of the electronic part 2 on the topside is coated for insulation with a resist ink layer 16, and the vicinity of the electronic parts mount 2' at the rear is coated for insulation with a cover lay layer 15. Hereby, the width of the resist of the connection land of the electronic parts mount 2 at the topside can be made narrow, so the high- density mounting of electronic parts becomes possible, and also by the thickness of the cover lay layer 15, the flatness of the board can be obtained without needing special constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided flexible substrate, and more particularly, to an insulating coating on a connection land of an electronic component mounting portion.

[0002]

2. Description of the Related Art Conventionally, in a double-sided flexible substrate having electronic component mounting portions on both sides, insulating coating on each surface is performed by a cover film, and connection portions of the electronic components are formed with holes in the cover film by die processing. Had been opened. The insulating coating with the cover film has an excellent effect of protecting the wiring pattern formed on the substrate.

[0003]

However, FIG.
According to the conventional double-sided flexible board as shown in FIGS. 8A and 8B (FIG. 8A is a perspective view showing a conventional double-sided flexible board without an insulating coating,
(B) is a perspective view showing a conventional double-sided flexible board coated with an insulating coating), and a connection area of the flexible board (FIG. 2) connected to an electronic component mounted on the thick cover film 15c in the electronic component mounting section 2 ( Hereinafter, when a hole corresponding to the connection land 20 is formed, if the pitch of the connection land 20 is small, the hole corresponding to each connection land 20 cannot be formed separately. A corresponding large hole 15d was opened. Accordingly, when electronic components are mounted at high density by soldering on the surface provided with the cover film 15c,
Since each connection land 20 is not separated by the cover film 15c, it is necessary to connect with a small amount of solder that does not protrude to the periphery. Therefore, solder failure between the electrode leads of the electronic component and the connection lands 20 is likely to occur, and it is difficult to mount the electronic component at high density on the surface on which the cover film 15c is provided. In addition, in order to achieve high-density mounting of electronic components, a substrate in which both surfaces of the substrate are insulated and coated with a resist ink is conceivable. Is concerned.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems.
An object of the present invention is to provide a double-sided flexible substrate in which protection of a wiring pattern is ensured on the other surface.

[0005]

According to a first aspect of the present invention, there is provided a double-sided flexible substrate comprising a base substrate on which circuit patterns are formed on both sides, and electronic component mounting portions on both sides. A double-sided flexible board provided with an insulating coating with a cover film on one side near the connection lands of the electronic component mounting portion, and an insulating coating with resist ink on the other surface near the connection lands of the electronic component mounting portion. Is what is being done.

In the above configuration, since the insulating coating near the connection land on one surface is made of resist ink, it can be accurately laminated on the pattern by printing or photoetching, and the thickness of the coating can be reduced. As a result, the resist width can be reduced, so that the arrangement of the electric components can be prevented from being restricted, and even fine pitch ICs and surface mount components can be mounted at high density. Since the other surface is insulatively coated near the connection land with the cover film, the wiring pattern can be surely protected.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a double-sided flexible substrate according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a collective substrate in the process of manufacturing according to the present invention. A plurality (two in this example) of electronic component mounting portions 2 on which electronic components are mounted on one collective substrate 1 are arranged. The collective board 1 is a rigid double-sided board having rigidity, and can be transported without a transport carrier in a component mounting process. A notch 3 is formed between the electronic component mounting portions 2 of the collective substrate 1, and a portion 4 serving as a connection terminal with another circuit and a connection wiring portion 5 provided around the electronic component mounting portion 2 are provided. , 5 are single-sided flexible substrates which can be bent. Notch hole 3 above
Is for separating the electronic component mounting portion 2 and the connection wiring portion 5 from the state of the collective substrate, and the collective substrate 1 is cut at the broken line in the drawing to form a double-sided flexible substrate as shown in FIG. B is obtained. Further, a positioning hole 6 for positioning the collective board 1 when the collective board 1 is transported in the component mounting process is provided in the collective board 1. Electronic components 7 such as ICs mounted on the electronic component mounting unit 2 are arranged on both sides of the substrate. The circuit pattern formed by the copper foil layer formed on the collective substrate 1 is not shown.

FIG. 3 shows a double-sided flexible substrate B according to an embodiment of the present invention, and corresponds to a sectional view taken along line AA of FIG. In the double-sided flexible substrate B, an adhesive layer 11 having a thickness that provides rigidity to the electronic component mounting portion 2
Are the base layer 12 which is the base material of the substrate and the copper foil layer 1 on the front side.
3 are provided in a laminated state. This thick adhesive layer 11 is used for mounting parts on the front and back surfaces of the board,
That is, it is provided only in the portion having the double-sided board configuration, and is not provided in the connection wiring portion 5 having the single-sided board configuration. The thickness of the adhesive layer 11 may be set to 30 μm or more so that the electronic component mounting sections 2 and 2 ′ have appropriate rigidity in consideration of the rigidity of the coverlay layer 15 itself. Note that the coverlay layer contributes to reducing the configuration (the adhesive layer 11) for providing the required flatness to the flexible substrate. On the surface of the copper foil layer 13, a resist ink layer 16 is provided. On the back surface of the base layer 12, a copper foil layer 13 'is provided via an adhesive layer 14,
Further, a coverlay layer 15 is provided via an adhesive layer 14 '. The cover lay layer 15 is formed at a portion other than the connection land portion formed on the copper foil layer 13 'for connecting the terminals 7a of the electronic component 7 by soldering or the like.
The circuit patterns of the copper foil layers 13 and 13 ′ are connected through a through hole 17. The base layer 12
For example, a film made of a polyimide material may be used.

As described above, since the resist ink layer 16 is formed on one surface, the resist ink layer 16 can be accurately laminated in a pattern by printing or photoetching (the deviation is ±
0.05-0.1 mm), and the thickness of the coating can be reduced. As a result, the width of the resist can be reduced (about 0.1 mm between holes), so that the arrangement of electric components can be prevented from being restricted, and the fine pitch IC (pitch: 0.5) and surface mount components can be increased. Can be implemented in density. Therefore, the film bonding accuracy (deviation is about ± 0.3 mm) and the punching dimensions of the mold (0.7 to 0.5 mm between holes) are limited when both surfaces are coated with a cover film. In addition, it is not impossible to mount electronic components at high density. Since the other surface has the cover lay layer 15 formed thereon, the wiring pattern can be reliably protected. In this way, by using a cover film on one side and a resist ink on the other side, a high-density mounting is performed on the resist ink side, and a double-sided flexible substrate that ensures protection of the wiring pattern on the cover film side is provided. be able to. Therefore, in the double-sided flexible substrate of the present invention, it is necessary to protect the wiring pattern on only one side, and
When high-density mounting is required, mounting the cover film on a device so that the surface of the cover film faces the surface where the wiring pattern is likely to be damaged can ensure high-density mounting while ensuring protection of the wiring pattern. (The other side where the wiring pattern is not likely to be damaged is resist ink, so high-density mounting can be performed).

Further, since the thick adhesive layer 11 is provided on the electronic component mounting portions 2 and 2 ', the rigidity of this portion is higher than that of a normal flexible circuit board (hereinafter, referred to as FPC), and it is similar to that of a hard board. Thus, a strength that allows both-side printing of solder cream and mounting of parts can be obtained. In addition, since the connection wiring portion 5 serving as a bent portion is a single-sided substrate and is not provided with a thick adhesive layer, the flexibility characteristic of the FPC is maintained. Therefore, the electronic component mounting portions 2 and 2 'can be mounted on both sides like a hard board, and the connection wiring portion 5 has the same flexibility as a normal FPC, and is equivalent to a board made of two different materials as a whole. Thus, a substrate configuration having the characteristics described above can be obtained.

FIG. 4 shows a double-sided flexible board B according to another embodiment of the present invention. In this figure, the same members as those described above are denoted by the same reference numerals. In this embodiment, two single-sided substrates, ie, base layers 12 and 12 ′ are bonded together with a thick adhesive layer 11 to form an electronic component mounting portion 2. , 2 'are increased in rigidity. In this embodiment, the base layer 1 of the single-sided substrate on the front side is used.
2 is added, the rigidity of the electronic component mounting portions 2 and 2 ′ is further increased as compared with the embodiment of FIG. Furthermore, when the rigidity of the electronic component mounting portions 2 and 2 ′ is more required, by inserting a base material such as a nonwoven fabric into the adhesive layer 11, it is possible to obtain rigidity equivalent to that of a hard substrate. Also in this embodiment, the electronic component mounting sections 2 and 2 ′ can be mounted on both sides of the board like a hard board, and the connection wiring section 5 has the same flexibility as a normal FPC. In addition, this configuration is advantageous in that the number of steps is small in manufacturing.

FIG. 5 shows a double-sided flexible substrate B according to still another embodiment of the present invention. In this embodiment, in order to further increase the rigidity of the substrate, a thick adhesive layer 11 'is further provided between the base layer 12 and the copper foil layer 13' on the back side. In addition, the adhesive layer 11 is also provided in the connection wiring portion 5 serving as a bent portion, which slightly reduces the flexibility of the FPC. For this reason, in the configuration of the present embodiment, by appropriately selecting the thickness of the adhesive layer and the adhesive, the electronic component mounting sections 2 and 2 ′ can secure the rigidity necessary for mounting components on both sides, The connection wiring portion 5 needs to be formed with a well-balanced substrate so that the bending and flexibility required for the FPC can be secured.

The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, as shown in FIG. 6, the double-sided flexible board B may be a multilayer board. FIG. 6 is a sectional view showing the multilayer (three-layer) FPC. In addition, as shown in FIG.
To the wiring pattern portion (not shown).
May be provided. FIG. 7 is a sectional view showing the double-sided flexible substrate B in which a cover film is provided on a wiring pattern portion. According to the double-sided flexible substrate B shown in FIG.
Since the wiring pattern can be protected by providing the wiring portion 5c, the wiring portion 5 can be arranged on either side of the substrate. At this time, if the resist ink layer 16 is provided in the vicinity of the connection land of the electronic component mounting portion 2 and the cover film 15c is provided in a portion deviated from the vicinity of the connection land,
The resist ink layer 16 can be laminated, and even the electronic components 7 such as fine terminal components can be selectively arranged on both surfaces. In addition, since the vicinity of the connection land on one surface of the substrate is the resist ink layer 16 and the vicinity of the connection land on the other surface is the coverlay layer 15c, the rigidity required for obtaining the flatness of the substrate can be provided. .

[0014]

As described above, according to the double-sided flexible substrate according to the first aspect of the present invention, since the vicinity of the connection land on one side is insulated and coated with the resist ink, it is accurately printed or photo-etched. It can be laminated on a pattern and the thickness of the coating can be reduced. As a result, the resist width can be reduced, so that the arrangement of the electric components can be prevented from being restricted, and even fine pitch ICs and surface mount components can be mounted at high density. Therefore, it is said that it is impossible to mount electronic components at a high density due to the limitation of the bonding accuracy of the cover film and the punching dimensions of the mold, which were observed in the conventional double-sided flexible substrate in which both sides were insulated by the cover film. The problem can be solved. Since the other surface is insulatively coated near the connection land with the cover film, the wiring pattern can be surely protected. Further, since the cover film itself has rigidity, it can contribute to reducing the configuration for obtaining the flatness required for the flexible substrate.

[Brief description of the drawings]

FIG. 1 is a plan view of a collective substrate in the process of manufacturing according to the present invention.

FIG. 2 is a plan view of a flexible substrate obtained from the collective substrate.

FIG. 3 is a cross-sectional view of the flexible substrate according to the embodiment of the present invention, taken along line AA of FIG. 1;

FIG. 4 is a sectional view of a flexible substrate according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a flexible circuit board according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view of a multilayer flexible substrate according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of a double-sided flexible substrate in which a cover film is provided in a wiring pattern portion according to still another embodiment of the present invention.

FIG. 8A is a perspective view showing a double-sided flexible substrate without an insulation coating, which is a conventional example of the present invention, and FIG. 8B is a perspective view showing the same double-sided flexible substrate with an insulation coating. is there.

[Explanation of symbols]

 B Flexible substrate 2 Electronic component mounting part 12 Base layer (base substrate) 15, 15c Cover film 16 Resist ink layer (resist ink)

Claims (1)

[Claims] 1. A double-sided flexible substrate comprising a base substrate having a circuit pattern formed on both sides thereof and having electronic component mounting portions on both surfaces, wherein one surface of the vicinity of a connection land of the electronic component mounting portion is insulated by a cover film. A double-sided flexible substrate, wherein coating is performed, and insulating coating is performed on the other surface near the connection land of the electronic component mounting portion with resist ink.