KR102620302B1 - Flexible Printed Circuit Board and Manufacturing Method thereof - Google Patents

Abstract

The present invention is intended to solve the problems of the prior art as described above, and specifically, to provide a flexible printed circuit board and a manufacturing method thereof that can solve the problem of the pattern fuse losing heat by the film layer and increasing the fusing time. The purpose of the present invention is to provide a flexible printed circuit including a pattern fuse, wherein the pattern fuse is formed with a conductive pattern to electrically connect two adjacent circuits, and is a circuit formed with a conductive pattern, and the pattern fuse is included. Metal pattern layer; And a coverlay formed by laminating a film layer and an adhesive layer, and attached to the upper and lower surfaces of the metal pattern layer, respectively, by the adhesive layer. It includes, the upper and lower surfaces of the pattern fuse are closed by the coverlay, and the side forming the thickness of the pattern fuse is spaced apart from the coverlay, so that an air gap is formed on the side of the pattern fuse. Do it as

Description

Flexible printed circuit board and manufacturing method thereof {Flexible Printed Circuit Board and Manufacturing Method thereof}

The present invention relates to a flexible printed circuit board on which a pattern fuse is formed, and more specifically, to a flexible printed circuit board including a pattern fuse in which the fuse is formed with a metal circuit pattern and the pattern is destroyed and blown when an overcurrent is applied, and a method of manufacturing the same. It's about.

A printed circuit board (PCB) or flexible printed circuit board (FPCB, hereinafter referred to as “printed circuit board” or “PCB”) is a device that fixes and connects multiple electronic components in a standardized manner. It is a circuit board with patterned wiring made for this purpose. PCBs can combine multiple circuits mechanically and electrically, and have the advantage of making electrical products smaller and lighter. In addition, the circuit characteristics are stabilized, there is no risk of miswiring, and the production cost is low. Due to these advantages, PCBs and FPCBs are used in various fields, and have recently become essential components in all electronic devices.

Meanwhile, when using a plurality of electrical components by connecting them, if overcurrent occurs due to failure or malfunction of the electrical component or external factors, there is a risk that the multiple connected electrical components may be damaged. Therefore, in order to protect a plurality of electrical components, it is common to install a fuse on the power supply side of the circuit to block the current by destroying the mounted fuse when an overcurrent occurs.

FIG. 1 is a photographic diagram showing a chip fuse mounted as a conventional fuse, and FIG. 2 is a cross-sectional view of the fuse of FIG. 1. Referring to this, conventionally, a surface-mounted component (SMD) is placed on a circuit pattern on an FPCB (1) in which a metal pattern layer (1a), a film layer (1b), and an adhesive (1c) for attaching the metal pattern layer and the film layer are laminated. , Surpace-Mount Devices) were formed on which a pad can be installed, and an SMD type chip fuse (2) was soldered on the pad to prevent damage to the circuit pattern or board due to overcurrent.

However, when mounting the chip fuse (2), costs were incurred for the cost of chip fuse raw materials and soldering and coating work related to mounting, which was a factor in increasing the cost of the product. In addition, in order to apply a chip fuse, the space required for the chip fuse and soldering must be secured, which increases the size of the printed circuit board, which may lead to additional cost increases and limitations in miniaturization.

Therefore, research is being actively conducted on pattern fuses that can function as a fuse while omitting the conventional chip fuse land. The pattern fuse 20 is a circuit pattern that functions as a fuse and refers to a fuse part applied to a printed circuit board. In order to increase space utilization, curved parts 21 and straight parts 22 are alternately formed as shown in FIG. 3. It is becoming.

The pattern fuse has the effect of reducing costs by eliminating the conventional chip fuse and the process for bonding the chip fuse. However, even if the pattern fuse is physically formed with the same resistance value as the chip fuse, the same performance as the conventional chip fuse is realized. This is causing difficulties in development.

In particular, as shown in Figure 4, the FPCB (1) including the pattern fuse (20) is attached and fixed to the injection molded product (4), which is part of the product, when applied to an actual product. In this case, the heat generated from the pattern fuse (20) is transmitted to the film layer. There is a problem in that it conducts quickly through (1b) and the injection molded product (4), and the melting time is long, making it impossible to meet the requirements of the pattern fuse (2).

On the other hand, in the OPEN type pattern fuse, a film layer is formed on both sides of the metal pattern layer, but the film of the pattern fuse portion is open on the side exposed to the outside, and the open portion is secured by a separately attached tape (Tape, 5). protected. In this case, a gap may occur between the tape and the upper surface of the metal pattern layer, and as a result, there is a problem in that the airtightness of the pattern fuse cannot be guaranteed.

The present invention is intended to solve the problems of the prior art as described above, and specifically, to provide a flexible printed circuit board and a manufacturing method thereof that can solve the problem of the pattern fuse losing heat by the film layer and increasing the fusing time. The purpose is to

Another object of the present invention is to provide a flexible printed circuit board and a manufacturing method thereof that can prevent the problem of lack of airtightness due to a gap formed between the tape and the metal pattern layer in the case of an OPEN type pattern fuse.

In order to solve the above problems, embodiments of the present invention provide the following flexible printed circuit board and its manufacturing method.

The present invention is a flexible printed circuit including a pattern fuse, wherein the pattern fuse is formed of a conductive pattern to electrically connect two adjacent circuits, and is a circuit formed of a conductive pattern, the pattern fuse comprising: a metal pattern layer including the pattern fuse; And a coverlay formed by laminating a film layer and an adhesive layer, and attached to the upper and lower surfaces of the metal pattern layer, respectively, by the adhesive layer. It includes, the upper and lower surfaces of the pattern fuse are closed by the coverlay, and the side forming the thickness of the pattern fuse is spaced apart from the coverlay, so that an air gap is formed on the side of the pattern fuse. Do it as

In addition, the conductive pattern of the pattern fuse is formed in a serpentine shape, and the intersection angle between the virtual line connecting both ends of the conductive pattern and the virtual line connecting the two most protruding parts of the conductive pattern is 30° or less. It is characterized by

In addition, as a CLOSE type, the coverlay attached to the upper or lower surface of the pattern fuse is removed in an area of the adhesive layer corresponding to the position where the pattern fuse is formed, and the width of the area from which the adhesive layer is removed is that of the pattern fuse. It is formed larger than the width, and the air gap is formed by the thickness and width of the area from which the adhesive layer is removed.

In addition, as an OPEN type, the coverlay attached to the upper or lower surface of the pattern fuse is removed in an area corresponding to the position where the pattern fuse is formed, and the width of the area from which the coverlay is removed is larger than the width of the pattern fuse. A tape of a flexible material is formed and disposed between the area from which the coverlay is to be removed and the pattern fuse; It further includes, wherein the edge of the tape is fixed by the coverlay attached to the upper and lower surfaces of the metal pattern layer, and the air gap is formed between the tape and the side surface of the pattern fuse.

In addition, the present invention relates to a method of manufacturing a CLOSE type flexible printed circuit board in which both the upper and lower surfaces of a pattern fuse are covered by a coverlay, wherein a metal pattern layer is placed on the upper surface of the coverlay disposed on the lower surface of the pattern fuse and hot pressed. steps; forming a pattern fuse by etching the metal pattern layer; Tack welding by placing a coverlay on the upper surface of the pattern fuse; and hot pressing the coverlay and pattern fuse; It includes, wherein the coverlay disposed on the upper surface of the pattern fuse is manufactured by punching an adhesive layer and then laminating it to a film layer, and the adhesive layer is punched at a portion corresponding to the position of the pattern fuse.

Furthermore, the width of the area where the adhesive layer is punched is characterized in that it is formed larger than the width of the pattern fuse.

In addition, the present invention provides a method of manufacturing an OPEN type flexible printed circuit board in which one surface of a pattern fuse is covered by a coverlay, comprising the steps of placing a metal pattern layer on the upper surface of the coverlay disposed on the lower surface of the pattern fuse and hot pressing; forming a pattern fuse by etching the metal pattern layer; Attaching a tape to the upper surface of the pattern fuse; Placing a coverlay on the upper surface of the tape and tack welding it; Hot pressing the coverlay, pattern fuse and tape; It includes, and the coverlay disposed on the upper surface of the tape is characterized in that a portion corresponding to the position of the pattern fuse is punched.

Furthermore, a method of manufacturing a flexible printed circuit board, characterized in that the width of the area where the coverlay is punched is formed to be larger than the width of the pattern fuse.

According to the problem solving means of the present invention as discussed above, various effects including the following can be expected. However, the present invention does not require all of the following effects to be achieved.

According to the present invention, an air gap is formed along the side of the pattern fuse, so the amount of heat emitted through the film layer is reduced, and thus the temperature at which the metal pattern melts is quickly reached, thereby reducing disconnection time.

In addition, in the case of the OPEN type, there was a concern about air tightness due to the conventional method of automatically punching and attaching the tape, but in the case of the present invention, the air gap is formed only on the side of the pattern fuse and the hot press work is performed after attaching the tape. Confidentiality was secured by this.

Furthermore, the present invention forms the pattern of the pattern fuse in a gently curved shape, thereby preventing the problem of the pattern scattering within the air gap and causing a short circuit again after disconnection.

In the present invention, an air gap is formed on both sides of the pattern of the pattern fuse, and the experiment described in [Table 1] below was conducted by forming an air gap outside the lower film of the pattern fuse. That is, the following experiment does not apply the structure of the present invention as is, but as in the present invention, an air gap (air layer) is formed adjacent to the pattern fuse, so the disconnection effect due to the air gap can be indirectly confirmed. The detailed experimental results are as follows.

division Pattern Fuse CLOSE TYPE Pattern Fuse OPEN TYPE sample 1 sample 2 Sample 3 Sample 4 Sample 5 sample 1 sample 2 Sample 3 Sample 4 Sample 5
stick 9.41 8.93 10 seconds
more 10 seconds
more 10 seconds
more 10 seconds
more 6.16 6.7 10 seconds
more 10 seconds
more air gap 3.14 2.84 2.75 3.56 3.67 1.72 2.7 4.21 4.36 3.29

- Specimen conditions: pattern length (45mm), current capacity (1.5~2A)

- Unit: seconds

This experiment measured the melting time of the pattern fuse in a model without an air gap outside the lower film of the pattern fuse (classified as "close") and a model with an air gap formed (classified as "air gap"). The specimens were composed of the same pattern, width, thickness, and length to ensure the same current capacity. As a result of the experiment, it was confirmed that the disconnection time of the pattern fuse was reduced by more than 50% when an air gap was formed.

Therefore, the present invention can also be expected to have the effect of preventing heat generated from the pattern fuse from easily dissipating due to the air gap and shortening the blowing time of the pattern fuse, thereby improving fuse performance.

1 is a photographic view showing a chip fuse mounted as a conventional fuse;
Figure 2 is a cross-sectional view of the fuse of Figure 1;
3 is a plan view schematically showing a pattern fuse;
Figure 4 is a cross-sectional view of the pattern fuse of Figure 3;
5 is a diagram showing a manufacturing method of a conventional CLOSE type pattern fuse;
6 is a diagram showing a method of manufacturing the CLOSE type pattern fuse of the present invention;
Figure 7 is a cross-sectional view of the pattern fuse manufactured by Figure 6;
8 is a plan view showing the pattern shape of the pattern fuse of the present invention;
9 is a diagram showing a manufacturing method of a conventional OPEN type pattern fuse;
10 is a diagram showing a method of manufacturing the OPEN type pattern fuse of the present invention;
Figure 11 is a cross-sectional view of the pattern fuse manufactured by Figure 10;
Figure 12 is a graph showing the melting time according to the air space separation distance.

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

FIG. 5 is a diagram showing a method of manufacturing a conventional CLOSE type pattern fuse, FIG. 6 is a diagram showing a method of manufacturing a CLOSE type pattern fuse of the present invention, FIG. 7 is a cross-sectional view of the pattern fuse manufactured by FIG. 6, and FIG. 8 is a diagram of the present invention. A plan view showing the pattern shape of the pattern fuse, FIG. 9 is a diagram showing a manufacturing method of a conventional OPEN type pattern fuse, FIG. 10 is a diagram showing a manufacturing method of the OPEN type pattern fuse of the present invention, and FIG. 11 is a diagram showing the manufacturing method of the OPEN type pattern fuse of the present invention. This is a cross-sectional view of a pattern fuse.

The flexible circuit board 1 is formed of a metal pattern layer 1a that serves as a circuit and a coverlay that is attached to both sides of the metal pattern layer 1a to protect the metal pattern layer 1a. The metal pattern layer 1a is formed of a conductive material such as copper, and when etched, an electrically conductive circuit can be formed. Here, when the circuit functions as a fuse, it can be defined as a pattern fuse 20. Accordingly, the pattern fuse 20 is formed as a conductive pattern, and both ends are connected to two circuits, so that it can serve to block overcurrent flowing between the two circuits.

Meanwhile, the coverlay consists of a film layer (1b) made of PI or the like and an adhesive layer (1c) formed of an adhesive component, and can be formed by laminating the film layer (1b) and the adhesive layer (1c). A lamination method includes forming the film layer 1b and the adhesive layer 1c into a film shape and laminating them. And the adhesive layer (1c) of the coverlay is formed of a curable material, and when the metal pattern layer (1a) is placed on the adhesive layer (1c) and heat and pressure are applied by hot pressing, the metal pattern layer (1a) is formed. It can be fixed in close contact with the adhesive layer (1c).

Below, the manufacturing method of the flexible printed circuit board 1 will first be described, and then the structure of the flexible printed circuit board 1 formed by the manufacturing method will be described later. Additionally, the pattern fuse 20 exists in a CLOSE type and an OPEN type, and each will be described.

First, the CLOSE type will be described using FIGS. 5 to 8. Figure 5 is a diagram showing a manufacturing method of a conventional CLOSE type pattern fuse 100, which involves hot pressing and fixing a coverlay in which a film layer (1b) and an adhesive layer (1c) are laminated to both sides of a metal pattern layer (1a). It is showing. In more detail, the metal pattern layer 1a is placed on the adhesive layer 1c of the coverlay, hot pressed, and then etched to form a circuit (pattern fuse 20). It can then be manufactured by tack welding the punched coverlay on the top and hot pressing. Here, punching the coverlay is for another purpose unrelated to the pattern fuse 20.

In contrast, the manufacturing method of the CLOSE type pattern fuse 100 of the present invention will be described using FIG. 6. In the present invention, the coverlay disposed below the pattern fuse 20 is the same as the conventional one, but is provided above the pattern fuse 20. The disposed coverlay is characterized in that the film layer 1b and the adhesive layer 1c are cut separately and laminated. That is, the film layer 1b and the adhesive layer 1c are cut separately, and in particular, the adhesive layer 1c is It is further processed through primary punching and then laminated with the film layer 1b. Here, the primary punching is processed at a position corresponding to the pattern fuse 20, and the width (W') of the punched area is determined by the pattern fuse ( It can be formed larger than the width W of 20). Furthermore, secondary punching can be performed after lamination of the adhesive and the film layer 1b. The secondary punching is for additionally forming a circuit. Examples of circuits formed on the secondary punched portion include terminals, pattern fuses, chips, or other general circuit patterns.

Therefore, in the present invention, when the coverlay with the adhesive layer (1c) cut is placed on top of the pattern fuse (20), the pattern fuse (20) is located in the area where the adhesive layer (1c) was punched out and removed, and the lower coverlay and the upper side The coverlay of is tack welded. Additionally, since the width W' of the area to be punched is formed to be larger than the width W of the pattern fuse 20, an air gap A (AIR GAP) may be formed on the side of the pattern fuse 20. Afterwards, through the hot press process, the coverlay and the pattern fuse 20 are brought into close contact up and down, and the adhesive layer 1c can be hardened and fixed.

The longitudinal cross-sectional view of the CLOSE type pattern fuse 100 described above is as shown in FIG. 7. The upper and lower surfaces of the pattern fuse 20 are in contact with the coverlay, and the side forming the thickness of the pattern fuse 20 is an adhesive layer ( 1c) is separated from the coverlay by the area removed by the first punching. Accordingly, an air gap A may be formed on the side of the pattern fuse 20. The air gap (A) minimizes heat dissipation outside the fuse when overcurrent flows, allowing the conductive pattern to quickly reach the melting temperature (1085°C for Cu).

Figure 8 shows the pattern shape of the pattern fuse 20. As shown in FIG. 3, the general pattern shape has curved portions 21 and straight portions 22 alternately formed, and the straight portions 22 are arranged in parallel. However, when an air gap A is formed on the side of the pattern fuse 20 as in the present invention, there is a risk that the fuse may blow and scatter, causing interference between metal patterns and reconnecting the circuit. Therefore, as shown in FIG. 8, it is preferable that the curves of the patterns are formed at an angle of 30° or less so that even if the patterns are scattered, they do not interfere with each other. More specifically, the intersection angle (acute angle) of the virtual line (a-a') connecting both ends of the pattern fuse 20 in the metal pattern layer 1a and the virtual line connecting the two most protruding parts of the pattern is It is desirable to have an angle of 30° or less. The two most protruding parts of the pattern in the drawing are the two adjacent curved parts 21, and the acute angle (x) between the straight part 22 disposed between the two curved parts 21 and the above-described imaginary line (a-a') ) can be explained as being less than 30°. The pattern shape shown in FIG. 8 can be equally applied to the OPEN type pattern fuse 200 described below.

Next, the CLOSE type will be described using FIGS. 9 to 11. Figure 9 is a diagram showing a manufacturing method of a conventional OPEN type pattern fuse 200. After placing a metal pattern layer (1a) on the adhesive layer (1c) of the coverlay and hot pressing, the circuit (pattern fuse 20) is formed by etching. ) is formed, and a coverlay in which the position corresponding to the pattern fuse 20 is punched is placed on the upper surface of the metal pattern layer 1a, tack-welded and hot pressed, and then the tape 5 is automatically punched and attached. The open portion of the pattern fuse 20 is sealed. However, this method has the problem of forming a gap (G) between the tape 5 and the upper surface of the pattern fuse 20, resulting in a high rate of defective airtightness performance.

In contrast, the present invention changes the arrangement order of the tape 5 and the coverlay, as shown in FIG. 10. Therefore, the metal pattern layer 1a is placed on the adhesive layer 1c of the coverlay, hot pressed, and then etched to form a circuit (pattern fuse 20), and the tape 5 is applied to the upper surface of the formed pattern fuse 20. After attachment, the punched coverlay is tack-welded and hot pressed. Here, the upper coverlay is removed by punching the position corresponding to the pattern fuse 20, and the width W' of the area to be removed may be larger than the width W of the pattern fuse 20. Therefore, when the coverlay is placed on the upper part of the tape 5 and hot pressed, the edge of the tape 5 can be fixed while being in close contact with the lower coverlay.

The longitudinal cross-sectional view of the above-described OPEN type pattern fuse 200 is as shown in FIG. 11, and the upper and lower surfaces of the pattern fuse 20 are in contact with the coverlay, and only the edge of the tape 5 is in close contact with the lower coverlay. As a result, the side forming the thickness of the pattern fuse 20 and the tape 5 and the coverlay are spaced apart. Accordingly, an air gap A may be formed on the side of the pattern fuse 20. The air gap (A) minimizes heat dissipation outside the fuse when overcurrent flows, allowing the conductive pattern to quickly reach the melting temperature (1085°C for Cu). Furthermore, when the tape 5 is placed inside the curable adhesive layer 1c and hot pressed, the tape 5 is fixed as the adhesive layer 1c hardens, which has the effect of preventing airtightness defects as in the past.

In this specification, each embodiment has been described separately, but embodiments that can be derived by combining each embodiment also fall within the scope of the present invention.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations can be made by those skilled in the art in the technical field to which the present invention pertains without departing from the essential characteristics of the present invention. The scope of protection shall be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope shall be construed as being included in the scope of rights of the present invention.

1 Flexible printed circuit board 1a metal pattern layer
1b film layer 1c adhesive layer
2 Chip fuse 3 Solder part
4 Injection 5 Tape
20 pattern fuse 21 bend
22 Straight section A air gap
100 CLOSE type pattern fuse 200 OPEN type pattern fuse

Claims (5)

1. A flexible printed circuit comprising a patterned fuse, comprising:
The pattern fuse is formed as a conductive pattern to electrically connect two adjacent circuits,
A circuit formed with a conductive pattern, comprising: a metal pattern layer including the pattern fuse; and
A coverlay formed by stacking a film layer and an adhesive layer and attached to the upper and lower surfaces of the metal pattern layer, respectively, by the adhesive layer;
Includes,
The upper and lower surfaces of the pattern fuse are closed by the coverlay, and the side forming the thickness of the pattern fuse is spaced apart from the coverlay, so that an air gap is formed on the side of the pattern fuse,
A flexible printed circuit board, wherein the pattern fuse is formed of a film made of the same material as the metal pattern layer.
According to claim 1,
The conductive pattern of the pattern fuse is a flexible printed circuit board, characterized in that curved portions and straight portions are formed alternately.
According to claim 2,
The conductive pattern of the pattern fuse is a flexible printed circuit board, characterized in that the intersection angle of a virtual line connecting both ends of the conductive pattern and a virtual line connecting the two most protruding parts of the conductive pattern is 30° or less.
The method according to any one of claims 1 to 3,
A flexible printed circuit board, wherein the air gap is formed by removing the adhesive layer.
The method according to any one of claims 1 to 3,
a tape disposed on the upper surface of the pattern fuse;
It further includes,
The air gap is a flexible printed circuit board, characterized in that formed between the tape and a side of the pattern fuse.