JPH11214805A - Flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed wiring board capable of sufficiently reducing defective soldering. SOLUTION: Holes 20, 11a are formed in sections where the main body section 17a of an IC 17 with a connecting terminal 17b connected to the land section 16 of a conductor 14 and the main body section 18a of a connector 18 with a connecting terminal 18b joined with the land section 16 of the conductor 14 are placed, in the flexible printed wiring board 10, in which a reinforcing plate 11 is installed to the lower section of a base film 13, in which the patterned conductor 14 is formed in an upper section, through pressure-sensitive adhesives 12, respectively so that the pressure-sensitive adhesives 12 are exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board in which a (flexible) flexible insulating film on which a conductor pattern is formed is reinforced with a reinforcing plate.

[0002]

2. Description of the Related Art Conventionally, flexible printed wiring boards have been used in terms of miniaturization and thinning. This flexible printed wiring board is indicated generally at 9 in FIGS. 4 to 6 and comprises a base film 3 made of a flexible insulating material on which a patterned conductor 4 is formed, for example, an adhesive. The reinforcement plate 1 is reinforced by a reinforcement plate 1. Note that a cover film 5 is further provided above the patterned conductor 4 in FIGS. 4 to 6. The cover film 5 is provided with a plurality of patterned holes 5a, and lands 6 where a part of the conductor 4 is exposed through the holes 5a are formed.

An IC 7 is mounted on a flexible printed circuit board 9.
When mounting an electronic component such as a main body 7a which is molded and a connection terminal 7b protruding from the main body 7a, reflow soldering is performed. That is,
As shown in FIG. 4, the connection terminal 7b of the IC 7 is mounted on the land 6 on which solder (not shown) is provided, and reflow is performed. At this time, since the entire flexible printed wiring board 9 is heated, the moisture contained in the adhesive 2 is rapidly heated and vaporized at a stretch. The vaporized moisture causes a part of the flexible base film 3 to be stretched by the pressure, as shown in FIG. 5, to generate blisters 8 between the base film 3 and the adhesive 2. When the blister 8 occurs, the connection terminal 7b of the IC 7 floats as shown in FIG. 5, or the connection terminal 7b of the IC 7 is fixed to the land 6 not to be connected. That is, a solder defect occurs. Alternatively, as shown in FIG. 6, the main body 7a of the IC 7 is lifted, the connection terminal 7b is completely floated, and the IC 7 flies to somewhere in a subsequent manufacturing process or the like, resulting in a shortage. was there.

Therefore, various techniques for preventing the blister 8 have been developed. As one of the techniques, there is a technique of performing reflow soldering after baking to remove moisture in the adhesive. However, 80 ° C. to 12 ° C. so that the water is not rapidly heated and vaporized.
Long-time baking was necessary to perform the process at a low temperature of 0 ° C. and to evaporate as much as possible the moisture in the central portion of the flexible printed wiring board because moisture evaporates only from the periphery of the flexible printed wiring board 9. . That is, it takes a long time to manufacture the flexible printed circuit board 9 while preventing the blisters 8 by this method. Further, as described above, since water only escapes from the peripheral portion of the flexible printed wiring board 9, it has been difficult to completely prevent blistering at the central portion. That is, poor soldering could not be sufficiently prevented.

In Japanese Utility Model Laid-Open Publication No. 60-18564,
A flexible printed board provided with holes for venting gas in addition to holes for soldering is disclosed.
Japanese Patent Application Laid-Open No. H07-133, discloses a flexible printed board in which a flexible insulating film is provided with a gas vent hole since a gas vent hole is formed in the reinforcing plate to weaken the reinforcing plate.
Further, Japanese Utility Model Application Laid-Open No. 63-55456 discloses that a hole is formed at a desired position on a flexible printed circuit board to thereby allow air to escape. However,
In any of these publications, the position where the hole is provided is not specifically shown (in these publications, Japanese Utility Model Application Laid-open No.
Japanese Patent Application Laid-Open No. 55456/1997 only states that the hole is provided near the component mounting portion). However, the solder failure due to the bulge 8 described above is largely related to the position where the bulge 8 occurs. For example, in a flexible printed wiring board 9 'shown in FIG. 7, a cover film 5' is formed on the uppermost surface, and a patterned conductor 4 'is formed under an adhesive 2' below a base film 3 'formed above. A reinforcing plate 1 'is provided and a hole 1 for venting gas is provided below the land 6' where the conductor 4 'is exposed.
a 'is provided. Usually, before the step of soldering the IC 7 as an electronic component to the flexible printed wiring board 9 ', there is a manufacturing step of pressing the insulating film 3' and the reinforcing plate 1 ', as shown in FIG. The insulating film 3 'and the conductor 4' fall into the hole 1a 'of the reinforcing plate 1', and a space is provided between the connection terminal 7b of the IC 7 and the conductor 4 '.
S will occur. That is, during soldering, the solder enters the space S, so that the solder becomes insufficient and the IC becomes
The connection terminal 7b of the IC 7 comes off the conductor 4 'due to an increase in the contact resistance between the connection terminal 7b of the IC 7 and the conductor 4' or the occurrence of a crack in a portion where solder is insufficient. That is, poor soldering occurs.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flexible printed circuit board which can sufficiently prevent poor soldering with components.

[0007]

An object of the present invention is to provide a flexible printed wiring board in which a conductive pattern is provided on one side of a flexible insulating film and a reinforcing plate is bonded on the other side with an adhesive or an adhesive. A hole is formed in a reinforcing plate and / or an insulating film at a portion where a main body of an electronic component having a connection terminal connected to the conductor pattern and a main body is to be disposed, so that an adhesive or an adhesive is exposed. Provide. With such a structure, the moisture contained in the adhesive or the pressure-sensitive adhesive can be released to the outside when heated, so that the occurrence of blisters can be sufficiently prevented. Further, since this hole is provided at a position where the main body of the electronic component to be mounted on the flexible printed wiring board is provided, that is, it is possible to prevent the component from being lifted up by the generated blister. In addition, since the location of the main part of this electronic component is not at the land where the connection terminals of the component to be mounted are connected, it is possible to prevent the conductor from dropping into the gas vent hole and prevent soldering failure due to insufficient solder. can do.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible printed wiring board in which a conductor pattern is provided on one side of a flexible insulating film and a reinforcing plate is bonded on the other side via an adhesive or a pressure-sensitive adhesive. A hole is provided for preventing the occurrence of blistering caused by the water contained in the adhesive or the adhesive being vaporized at a stretch. In the present invention, the hole is provided in the patterned conductor of the flexible printed wiring board with a connection terminal. Where the main body of the electronic component mounted on the flexible printed circuit board is disposed (this is shown in FIG. 1).
Then, the adhesive or the pressure-sensitive adhesive is provided on the reinforcing plate and / or the insulating film having the length L and the length D). For this reason, since the moisture of the adhesive or the pressure-sensitive adhesive is removed from the holes during the heat treatment of the flexible printed wiring board, the flexible printed wiring of the present invention hardly generates blisters. Further, even if slight blistering occurs, the hole of the present invention is provided below the main body of the electronic component, so that no blistering occurs here and the electronic component is not pushed up. Also, the hole of the present invention,
Since it is provided below the main body of the electronic component, that is, the hole is provided in a portion where the land 16 is not formed, it is possible to eliminate defective soldering such as floating of the component, misalignment and missing parts. Further, since the hole is formed below the component, the appearance blister is reduced.

Further, it is preferable that the distance between the end of the hole (the so-called land) where the conductor pattern formed on the insulating film is exposed and the end of the hole is not less than the maximum manufacturing error. With this configuration, even if a manufacturing error occurs during the manufacture of the flexible printed wiring board, no hole is formed in the land. for that reason,
The contact failure as described above with reference to FIG. 7 of the related art does not occur. In addition, below the main body of the electronic component of the present invention, the hole formed in the flexible printed circuit board has a maximum diameter set to a size where the distance from the end of the land to the end of the hole has a maximum manufacturing error. Is good.

[0010] When the insulating film forming the patterned conductor and the reinforcing plate are bonded to each other using an adhesive, the cost is reduced. However, this is because the bonding surface is rougher than the adhesive. , Blisters are easy to occur. However, in the present invention, since this blister can be sufficiently prevented, an adhesive can be applied. Therefore, the cost of the flexible printed wiring board can be reduced.

If the hole formed in the flexible printed wiring board is a round hole having a diameter of 0.5 mm or more, a tool for punching a round hole having a diameter of 0.5 mm or more, such as a punch or a drill, is a general one. Because there is, it can be easily processed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of a flexible printed wiring board 10 according to this embodiment. The flexible printed wiring board 10 of the present invention includes a base film 13 which is an insulating film made of, for example, polyimide or polyester.
The reinforcing plate 11 is adhered below the adhesive plate 12 via an adhesive 12. A conductor 14 having a pattern is formed above the base film 13 by, for example, plating, and further above the base film 13, a plurality of patterned holes 15 a, 15
A cover film 15 having b (which is made of, for example, polyimide or polyester) is provided. The hole 15 a is provided on the conductor 14 and the land 16
Is formed. The hole 15b has a
The holes for exposing the adhesive 14 are provided so as to match the holes 13 a formed in the base film 13.

The flexible printed circuit board 10 includes
IC1 having a main body portion 17a molded with a resin having a length L and connection terminals 17b protruding from the main body portion 17a
7 and a main body 1 formed of a rigid resin having a length D or the like.
The receptacle 18 of the connector C, which has a connection terminal 8a and a connection terminal 18b protruding therefrom, is mounted. That is, the connection terminals 17b and 18b are fixed to the lands 16 by solder (not shown). The front end of an FFC (flexible flat cable) 19 is inserted into the receptacle 18 as shown by a dotted line.

Next, the hole 11a and the hole 20 according to the present invention will be described.

The hole 11a is a round hole having a diameter b 'of about 0.5 to 3.0 mm formed in the reinforcing plate 11 so that a part of the adhesive 12 is exposed. This is receptacle 1
8 and is provided at a distance a ′ from the end of the land 16. This distance a '
Is provided so as to be larger than the maximum manufacturing error of the flexible printed wiring board 10 (about 0.2 mm in this embodiment). The hole 20 is provided in the main body 17 of the IC 17.
a, the hole 13a formed in the base film 13 and the hole 15b of the cover film 15 disposed above the hole 13a are aligned with each other. The upper surface of the adhesive 12 is exposed. This hole 20 has a size of about 0.5 to
It is a round hole having a diameter b of 3.0 mm and is provided at a distance a, a ″ from the end of the land 16. The distances a, a ′, a ″ are the same as those of the flexible printed wiring board 1.
The value is larger than the maximum manufacturing error of 0 (about 0.2 mm in this embodiment). In this embodiment, the distance a,
When a ″ is 0.2 mm, the diameter b of the hole 20 is
Has a size of about 3.0 mm, that is, I
The distance R between the ends of the lands 16 to which the connection terminals 17b of C17 are connected is about 3.4 mm in this embodiment.

Next, an IC 17 as an electronic component and a receptacle 18 are provided on the flexible printed circuit board 10.
The manufacturing method up to mounting the device will be described.

First, a base film 1 having a reinforcing plate 11, an adhesive 12, and a conductor 14 formed in a predetermined pattern
3 and the cover film 15 in which the holes 16a are formed in a predetermined pattern are overlapped and pressed by a press. Then, the hole 11a and the hole 20 are formed by a drill or a punch. Then, solder (not shown) is applied to the land 16, and the IC 17 and the receptacle 18 as electronic components are mounted.
Solder by reflow.

That is, in this embodiment, since the holes 11a and the holes 20 are formed before the soldering step to which heat is applied, the heat is applied and the moisture contained in the adhesive 12 is blown at once. Even if it is vaporized, it is released from the holes 11a and 20 and almost no blistering occurs. Further, in this embodiment, the holes 11 and 20 are
Is provided below the main body portion 17a of the main body 17a and the main body portion 18a of the receptacle 18, that is, when the swelling occurs, the component is pushed up and provided in a portion where poor contact of soldering is likely to occur. Can be prevented. In the present embodiment, the distance from the end of the land 16 to the hole 11a or the hole 20 is set to a maximum manufacturing error of 0.2 mm or more, so that the adhesive 12 is exposed even if there is a manufacturing error. Hole, ie hole 1
1a, the hole 20 does not open in the land 16. Therefore, the problem described with reference to FIG. 7 that the holes 11a and 20 are opened in the land 16 to cause a contact failure does not occur. In this embodiment, since the holes 11a and 20 are round holes of 0.5 mm or more, the holes can be easily formed.

Although the embodiment of the present invention has been described above, the present invention is, of course, not limited to this, and various modifications can be made based on the technical concept of the present invention.

For example, in the above embodiment, the case where the hole 20 is not formed on the patterned conductor 14 has been described. However, as shown in FIG.
The present invention can also be applied to a case where a part p of the patterned conductor 14 ′ is disposed below 7. In this case, like the flexible printed wiring board 10 ′ shown in FIG. 2, the holes are aligned with the holes 15 b ′ of the cover film 15 and the holes 13 a ′ of the base film 13 below the main body 17 a of the IC 17 as an electronic component. Hole 14
a ′ is provided on the patterned conductor 14 ′, and the adhesive 12 bonding the base film 13 and the reinforcing plate 11
May be formed as a hole 20 ′ exposing.

In the above embodiment, the base film 13, which is an insulating film, and the reinforcing plate 11 are integrated with the adhesive 12, but the present invention is also applicable to the case where the base film 13 is integrated with the adhesive. Can be. Although the type of the pressure-sensitive adhesive 12 in the above embodiment is not described, any type such as a rubber type, an acrylic type, and a silicone type may be used.

In the above embodiment, the electronic component IC 17
And holes 20, 1, respectively below the receptacle 18.
1a are provided one by one. For example, as shown in FIG.
The flexible printed wiring board 10 ″ may be provided with a plurality of holes 21 and 22 below the IC 17. However, in this case, the distance A between the ends of the holes 21 and 22 and the end of the land 16 closest to each of them. , A ′ are preferably equal to or greater than the maximum manufacturing error as described above, and the holes for evaporating the vaporized water are provided below the electronic components other than the IC and the receptacle shown as the electronic components in the above embodiment. May be provided.

[0024]

As described above, according to the flexible printed wiring board of the present invention, moisture contained in the adhesive or the pressure-sensitive adhesive can be released during heating, and the occurrence of blisters can be prevented. In addition, since a hole for releasing vaporized moisture is provided below the main body of the electronic component, the component is not pushed up even if the blister cannot be completely prevented. Further, since holes for releasing moisture are not formed in the lands, there is no space between the electronic component and the lands, and thus, it is possible to further prevent poor soldering as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a flexible printed wiring board according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a flexible printed wiring board according to a first modification of the present invention.

FIG. 3 is a sectional view of a main part of a flexible printed wiring board according to a second modification of the present invention.

FIG. 4 is a cross-sectional view of a main part of a flexible printed circuit board in a conventional example, showing a state where an IC, which is an electronic component before soldering, is mounted.

FIG. 5 is a cross-sectional view of a main part of a flexible printed circuit board in a conventional example, showing a state in which the other connection terminal of an IC as an electronic component after soldering is floating.

FIG. 6 is a cross-sectional view of a main part of a flexible printed wiring board in a conventional example, and shows a state where both connection terminals of an IC as an electronic component after soldering are floating.

FIG. 7 is a cross-sectional view of a main part of a flexible printed wiring board in which a land is provided with a hole for releasing moisture of an adhesive in another conventional example.

[Explanation of symbols]

10, 10 '... flexible printed wiring board, 11
...... Reinforcing material, 11a ... Hole, 12 ... Adhesive, 13 ...
Base film, 13a hole, 14, 14 'conductor, 15 cover film, 15b hole, 16 land, 17 IC, 17a body portion, 17b connection terminal, 18 Receptacle, 18a Body part, 18
b connection terminal, 20, 20 ', 21, 22 ... hole,
A, A ', a, a', a "... distance between the end of the land and the end of the hole, b, b '... diameter of the hole.

Claims (6)

[Claims] 1. A conductive pattern is formed on one side of a flexible insulating film, and a reinforcing plate is bonded on the other side via an adhesive or a pressure-sensitive adhesive. Wherein the adhesive or the pressure-sensitive adhesive is exposed on the reinforcing plate and / or the insulating film in a portion where the main body of the electronic component is to be disposed. Flexible printed wiring board characterized by having a plurality of holes. 2. A cover film having a pattern is provided on a side of the conductive pattern opposite to the insulating film, and the cover film is not covered by the cover film, and the end of the conductive pattern is exposed. The flexible printed wiring board according to claim 1, wherein a distance to an end of the hole is larger than a maximum manufacturing error. 3. The flexible printed circuit board according to claim 2, wherein the maximum manufacturing error is about 0.2 mm. 4. The flexible printed wiring board according to claim 1, wherein the hole is a round hole. 5. The method of claim 5, wherein the diameter of the holes is from about 0.5 to about 3.0.
The flexible printed wiring board according to claim 4, wherein 6. The flexible printed wiring board according to claim 5, wherein the hole is formed by a punch or a drill.