JP2000312061A - Flexible board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible substrate having a connection terminal structure which can reduce the size and pitch of a soldered connection portion when connecting to a printed circuit board or the like, and enables good connection. I will provide a. SOLUTION: Through holes electrically connected to a plate edge surface around a plurality of through holes formed in a flexible substrate through conductive members formed on the inner surfaces of the through holes, respectively. In a flexible substrate having a hole land portion, a through-hole land portion in a predetermined region on at least one plate surface of the substrate is exposed to the outermost side of the plate surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible substrate having a through-hole land formed on a flexible substrate and connecting the through-hole land to a connection terminal such as a printed circuit board. .

[0002]

2. Description of the Related Art In recent years, various types of information equipment have become smaller and smaller.
Weight reduction is being promoted. Along with this, the connection between the flexible substrate and the printed circuit board is being changed from a connection using a connector to a structure that is directly soldered. Hereinafter, a conventional connection terminal structure between a flexible board and a printed board will be described with reference to FIG.

In FIG. 5, a flexible substrate 11 is provided on both sides of an insulating film 12 also called a base film.
A patterned copper foil layer 14 is attached via an adhesive layer 13 made of an epoxy-based or phenol-based adhesive. These copper foil layers 14
8 are electrically connected to each other through a through-hole plating film 16 formed on the inner surface of the substrate 8, and this portion forms a through-hole land portion 15. Furthermore, an insulating film 17 (hereinafter, referred to as a coverlay for distinguishing from the insulating film 12) such as polyimide for protecting the pattern is adhered to the surface of each copper foil layer 14. In order to solder the through-hole land 15 to the printed circuit board 21, the cover lay 17 is circularly opened so as to expose the center of the through-hole land 15.

On the other hand, conductive lands 22 are arranged on the surface of the printed circuit board 21 in accordance with the positions of the through holes 18, and a solder paste 23 is applied on these lands 22. .

To connect the flexible board 11 to the printed board 21, the lands 22 of the printed board 21 and the through-hole lands 15 of the flexible board 11 are aligned with each other. The flexible substrate 11 is printed on the printed circuit board 21 by the heater tool 30 having a flat surface (lower side in the drawing).
The solder paste 23 is melted by the action of heating and pressurizing, and penetrates into the through holes 18 to achieve electrical and mechanical connection.

[0006]

In recent years, there has been an increasing demand for the above connection terminal structure to have a smaller size and a smaller pitch of the soldered connection portion. However, in the configuration in which the cover lay 17 is covered on the through-hole land portion 15, it is difficult to reduce the size and pitch of the through-hole land portion 15 due to limitations in processing the cover lay 17.

When the heater tool 30 is heated and pressurized, the heater tool 30 comes into contact with the cover lay 17 which is the uppermost layer of the flexible substrate 11, and heat conduction in the cover lay 17 and air in the through-hole 18. The heat conduction of the layer heats the copper foil layer 14 and transmits the heat for melting the solder paste 23. For this reason, it is difficult for sufficient heat to be transmitted to the portion to be soldered, which may result in poor connection.

In order to prevent this connection failure, for example, a method of increasing the temperature of the heater tool 30 or extending the heating time can be considered. However, in this case, the adhesive layer 13 between the coverlay 17 and the copper foil layer 14 or between the copper foil layer 14 and the insulating film 12 may be softened, and the reliability of the adhesive material itself may be reduced. was there.

As another method for preventing the connection failure, it is conceivable to make the shape of the pressing surface of the heater tool 30 convex so as to match the shape of the flexible substrate 11, but it is necessary to perform accurate positioning. Was not realistic.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a purpose thereof is to provide a connection terminal structure capable of reducing the size and pitch of a solder connection portion when connecting to a printed circuit board or the like. To provide a flexible substrate having

Another object of the present invention is to provide a flexible substrate having a connection terminal structure that enables good connection.

[0012]

The invention according to claim 1 is
A through-hole land portion electrically connected to each other via a conductive member formed on the inner surface of the through-hole is provided on a plate edge surface around the plurality of through-holes formed in the flexible substrate. In a flexible substrate having the through-hole land portion in a predetermined area on at least one plate surface of the substrate, the land portion is exposed to the outermost surface of the plate surface.

According to a second aspect of the present invention, in the flexible substrate according to the first aspect, only one of the plate surfaces of the substrate is formed so that only a through-hole land protrudes from a flat surface. is there.

According to a third aspect of the present invention, in the flexible substrate according to the first or second aspect, the substrate includes an insulating film, and a through-hole land is formed directly on the surface of the insulating film. is there.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a cross-sectional view showing a configuration of a connection terminal portion of a first embodiment of a flexible substrate according to the present invention. In the drawing, the same elements as those in FIG. The description is omitted.
The flexible substrate 11 </ b> A shown here removes the coverlay 17 on the side to which the heater tool 30 shown in FIG. The height of the through-hole land 15 in the area where the tool 30 contacts is formed to be substantially the same, and the through-hole land 15 is exposed to the outermost surface of the plate surface in this area.

If a cover lay is provided on the side where the heater tool 30 contacts, the through hole land portion 1
5 except for the surface portion, and the through-hole land portion 15
Shall be designed so as to be lower than the surface portion.

In this case, the land portions of the flexible substrate 11A, that is, the copper foil layers 14 forming the front and rear patterns are connected by through-hole land portions 15 connected by through-hole plating films 16 as conductive members. ing.

With such a terminal structure, even when a heater tool 30 having a flat pressing surface is used at the time of soldering, the heater tool 30 can be brought into direct contact with the through-hole land 15 of the copper foil layer 14. .

Thus, according to the first embodiment shown in FIG. 1, it is possible to obtain a flexible board which can reduce the size and pitch of the soldered connection portion when connecting to a printed board.

Although the first embodiment shown in FIG. 1 shows a two-layer pattern in which a copper foil layer 14 is formed on each of the front and back surfaces, the present invention is not limited to this. However, the present invention is also applicable to those having a pattern of three or more layers in which a copper foil layer is formed between the front surface and the back surface.

FIG. 2 is a plan view showing a configuration of a connection terminal portion of a flexible board according to a second embodiment of the present invention.
Particularly, it is a plan view seen from the heater tool 30 side. In this embodiment, the pattern in the contact area 31 of the heater tool is only the through-hole land 15. That is, even if the copper foil layer 14 and the cover lay 17 are present, they are housed in a uniform flat surface, and only the through-hole lands 15 protrude from this flat surface. Here, the plurality of through-hole lands 15 are arranged in a matrix at substantially equal intervals. This makes it possible to further reduce the size and pitch of the soldered connection portion, and at the same time, to make a better connection than in the first embodiment.

Note that the arrangement of the plurality of through-hole lands 15 is not limited to a matrix. For example, as shown in FIG. 3, the same effects as described above can be obtained even if they are arranged in a staggered manner.

FIG. 4 is a sectional view showing the structure of the connection terminal portion of the third embodiment of the flexible substrate according to the present invention.
In the figure, the same elements as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The first shown in FIG.
In the embodiment, the adhesive layer 13 is interposed between the insulating film 12 and the copper foil layer 14, but the flexible substrate 11B shown in FIG. 4 is of a type not having the adhesive layer 13 shown in FIG. The copper foil layer 14 is directly formed on each of the front and back surfaces of the insulating film 12, and the through-hole land portion 15 in a region where the heater tool 30 contacts is exposed to the outermost surface of the plate surface. Thereby, the heater tool 30 is moved to the copper foil layer 1.
4 can be in direct contact with the through-hole land portion 15 of FIG.
This makes it less susceptible to the effects of the heat of soldering, enables good connection, and improves reliability.

Incidentally, even in the type having no adhesive layer 13 shown in FIG. 4, as shown in FIG. 2 or FIG.
By making only the through-hole land portion 15 protrude from the flat surface, the connection state can be further improved.

Although the above embodiments have been described with reference to a printed circuit board as an object to be connected, the present invention is not limited to this, and may be applied to other substrates having a large number of pads arranged in parallel. Needless to say, it's good.

[0026]

As is apparent from the above description, according to the first aspect of the present invention, a plurality of through-hole lands in a predetermined region on one plate surface are exposed to the outermost surface of the plate surface. When connecting to a printed circuit board or the like, the size and pitch of the soldered connection portion can be made smaller than in the conventional case.

According to the second aspect of the present invention, since only one of the through-hole lands protrudes from the flat surface on the one plate surface of the substrate, the effect that good soldering connection is possible is achieved. can get.

According to the third aspect of the present invention, since the through-hole lands are directly mounted on the insulating film surface, good soldering connection becomes possible and reliability can be improved. There is also an effect.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a connection terminal portion of a first embodiment of a flexible board according to the present invention.

FIG. 2 is a plan view showing a configuration of a connection terminal portion of a flexible board according to a second embodiment of the present invention.

FIG. 3 is an exemplary plan view showing a modification of the connection terminal unit according to the second embodiment shown in FIG. 2;

FIG. 4 is a sectional view showing a configuration of a connection terminal portion of a flexible board according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a configuration of a connection terminal portion of a conventional flexible substrate.

[Explanation of symbols]

 11, 11A, 11B Flexible board 12 Insulating film (base film) 13 Adhesive layer 14 Copper foil layer 15 Through-hole land 16 Through-hole plating film (conductive member) 17 Insulating film (cover lay) 18 Through-hole 21 Printed circuit board 22 Land 23 Solder paste 30 Heater tool 31 Heater tool contact area

Continued on front page F term (reference) 5E317 AA04 AA06 AA07 AA24 BB03 BB11 CC15 CC31 CD23 GG07 GG14 GG16 5E344 AA02 AA22 BB02 BB04 BB05 BB10 BB13 CC09 CC14 CC23 CD12 DD03 EE01 EE13 EE21 EE26

Claims (3)

[Claims] An electronic device comprising: a plurality of through holes formed in a flexible substrate, the plurality of through holes being electrically connected to each other via conductive members formed on inner surfaces of the through holes; A flexible substrate having a through hole land portion, wherein the through hole land portion in a predetermined region on at least one plate surface of the substrate is exposed to the outermost surface of the plate surface. 2. The flexible substrate according to claim 1, wherein only one of the plate surfaces of the substrate is formed so that only the through hole land portion protrudes from a flat surface. 3. The flexible substrate according to claim 1, wherein the substrate includes an insulating film, and the through-hole lands are formed directly on the surface of the insulating film.