KR20240011516A - flexible Printed Circuit Board - Google Patents

Abstract

The present invention forms a bending area spaced apart from each other by forming a plurality of cutting holes for bending in the area where the dummy pattern is formed in the base of the flexible circuit board, and the springback phenomenon in the folded area can be minimized regardless of the folding direction. Even if excessive folding occurs, tearing can be prevented and damage to the circuit pattern can be prevented.

Description

Flexible Printed Circuit Board

The present invention relates to a new type of flexible circuit board that minimizes the springback phenomenon at the folded area and prevents damage to the circuit pattern.

In general, a printed circuit board (PCB) is formed in a layered structure of conductors and insulators in the form of a board, and serves to electrically connect various circuit components (e.g., semiconductors, capacitors, resistors, etc.).

Meanwhile, the Flexible Printed Circuit Board (FPCB), a type of printed circuit board (PCB), is a bent and deformed PCB made by forming a thin film circuit in polyimide, a flexible material.

These flexible circuit boards are widely used in small products, vehicle electronics, and battery cells due to their ability to bend and deform.

For example, in the case of the Inter Connection Board (ICB), an electrical component that connects each cell of a high-voltage battery installed in an electric vehicle, the voltage of each cell is measured using the FPCB.

In relation to this, it is as presented in Registration Patent No. 10-1996449, Publication of Patent Publication No. 10-2019-0061378, etc.

Meanwhile, the flexible circuit board provides a plurality of folded portions as needed. In other words, due to the flexible nature of the flexible circuit board, the flexible circuit board is bent depending on the connection position or direction of the circuit, or the flexible circuit board is bent to avoid surrounding components and connect depending on the arrangement of surrounding components.

The folding direction of the flexible circuit board is designed in various ways in consideration of the connection position or direction of the circuit or the arrangement of surrounding components.

In particular, the flexible circuit board is formed to be rounded so that the folded portion has a predetermined radius of curvature (R), thereby preventing damage to the circuit. For this purpose, conventionally, flexible circuit boards are bent using separate bending equipment. In relation to this, it is the same as described in Publication Patent No. 10-2021-0057938.

However, due to the characteristics of polyimide, the flexible circuit board cannot be bent to a preset radius of curvature (R) due to a spring back phenomenon when bent in a round shape. Accordingly, in the past, in consideration of the above-described springback phenomenon, the flexible printed circuit board was bent more than the set curvature radius (R) when bending, and the film portion of the flexible printed circuit board was torn due to excessive bending of the flexible printed circuit board. There was a problem that the circuit pattern formed by the copper plate was damaged.

In the case of Patent Publication No. 10-2021-0150639, it is proposed that a bending groove is formed along the bending area to prevent the springback phenomenon of the flexible circuit board described above.

However, in the case of the method of forming the bending groove described above, there is a high risk that the circuit pattern of the copper foil will be exposed, resulting in damage to the circuit pattern.

Registered Patent No. 10-1996449 Public Patent Publication No. 10-2019-0061378 Public Patent No. 10-2021-0057938 Public Patent No. 10-2021-0150639

The present invention was created to solve various problems according to the prior art described above, and the purpose of the present invention is to minimize the springback phenomenon at the folded portion regardless of the folding direction.

Additionally, the purpose of the present invention is to prevent tearing even if excessive folding occurs and to prevent damage to the circuit pattern.

According to the flexible circuit board of the present invention for achieving the above object, the base of the flexible circuit board is provided with at least one bending area that is bent to extend in a direction different from the formation direction of the base, and the bending The region is characterized in that a plurality of cutting holes for bending are formed to be spaced apart from each other along a direction perpendicular to the bending direction among the directions of the corresponding base.

According to the flexible circuit board of the present invention, the cutting hole for bending is formed to be located in a region where a dummy pattern is formed among each region of the base.

According to the flexible circuit board of the present invention, the cutting hole for bending is formed to be located in a portion of the base where a circuit pattern is not formed.

According to the flexible circuit board of the present invention, the cut hole for bending is characterized in that it is formed as a long hole that is longer in the longitudinal direction than in the width direction.

According to the flexible circuit board of the present invention, the length of the bending cut hole is the same as the length of the bending area or is formed shorter than the length of the bending area.

According to the flexible circuit board of the present invention, the cutting hole for bending is formed to have a width smaller than that of the dummy pattern.

According to the flexible circuit board of the present invention, the bending area is bent to have a preset radius of curvature.

According to the flexible circuit board of the present invention, when the bending area is bent to a set radius of curvature (R), the cutting hole for bending is formed to have a length that does not exceed the radius of curvature provided by the inner surface of the bending area. do.

According to the flexible circuit board of the present invention, both longitudinal ends of the bending cut hole are rounded.

According to the flexible circuit board of the present invention, the bending direction of the bending area is bent in the same direction as the longitudinal direction of the base, or is formed in a direction inclined toward one side from the longitudinal direction of the base. .

According to a flexible circuit board according to another embodiment of the present invention, the base is provided with at least one bending area that is bent to extend in a direction different from the formation direction of the base, and a circuit pattern is formed in the bending area. In the area that is not used, a plurality of cutting holes for bending are formed to be spaced apart from each other along a direction perpendicular to the bending direction among the directions of the corresponding base.

As described above, the flexible circuit board of the present invention has various effects as follows.

The flexible circuit board of the present invention has the effect of being able to accurately perform bending in the bending area by providing a plurality of cutting holes for bending, and minimizing the springback phenomenon after the bending process.

The flexible circuit board of the present invention has the effect of preventing damage to the circuit board because the cutting hole for bending is located in each part of the flexible circuit board where the base circuit pattern is not formed.

The flexible circuit board of the present invention has the effect of preventing the film from lifting because the cutting hole for bending is located in each area of the flexible circuit board where the dummy pattern of the base is formed.

In the flexible circuit board of the present invention, the cutting hole for bending is formed to be equal to or shorter than the length of the bending area, so that when the bending area is bent, it does not exceed the curved surface provided by the bending area. This has the effect of preventing interference, such as pinching of other flexible circuit boards during transportation due to the excessive length of the bending cutout hole, and reducing tearing.

The flexible circuit board of the present invention has the effect of preventing or reducing the lifting phenomenon of the film that may occur at the corners by forming both ends of the bending cutout to be rounded.

The flexible circuit board of the present invention has the effect of minimizing springback when bending the bending area because each bending cutout hole is formed along the bending direction of the flexible circuit board.

1 is a perspective view of a flexible circuit board according to an embodiment of the present invention.
Figure 2 is a plan view of a flexible circuit board according to an embodiment of the present invention.
Figure 3 is an enlarged view of part “A” of Figure 2
Figure 4 is a cross-sectional view taken along line II of Figure 2
Figure 5 is a cross-sectional view taken along line II-II of Figure 2
Figure 6 is an enlarged cross-sectional view of the main portion for explaining in more detail the internal structure of the flexible circuit board according to an embodiment of the present invention.
Figure 7 is a perspective view of the bending state of the flexible circuit board according to an embodiment of the present invention.
Figure 8 is a plan view of the bending state of the flexible circuit board according to an embodiment of the present invention.
Figure 9 is an enlarged view of part “B” of Figure 8
Figure 10 is a side view of the bending state of the flexible circuit board according to an embodiment of the present invention.
Figure 11 is a cross-sectional view taken along line III-III of Figure 8

Hereinafter, some embodiments of the present invention will be described in detail through illustrative drawings. When adding reference numerals to components in each drawing, it should be noted that identical components are given the same reference numerals as much as possible even if they are shown in different drawings. Additionally, when describing embodiments of the present invention, if detailed descriptions of related known configurations or functions are judged to impede understanding of the embodiments of the present invention, the detailed descriptions will be omitted.

Additionally, in describing the components of embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, or order of the component is not limited by the term. When a component is described as being "connected," "coupled," or "connected" to another component, that component may be directly connected or connected to that other component, but there is no need for another component between each component. It should be understood that may be “connected,” “combined,” or “connected.”

Next, a preferred embodiment of the flexible circuit board of the present invention will be described with reference to the attached FIGS. 1 to 11.

The attached Figure 1 is a perspective view of a flexible circuit board according to an embodiment of the present invention, and Figure 2 is a plan view of a flexible circuit board according to an embodiment of the present invention. In addition, Figure 3 is an enlarged view of portion “A” of Figure 2, and Figures 4 and 5 are cross-sectional views of the flexible circuit board according to an embodiment of the present invention seen from different directions.

As shown in these drawings, the flexible circuit board according to an embodiment of the present invention provides a bending area 140 in the base 100 with a cutting hole 141 for bending, thereby providing a spring force when the base 100 is bent. This was done to reduce the number of bags.

The flexible circuit board according to an embodiment of the present invention will be described in more detail for each component as follows.

First, the flexible circuit board according to an embodiment of the present invention includes a base 100. The base 100 is a part that forms the body of the flexible circuit board.

The base 100 includes a bendable film 110. The film 110 forms the outer surface (surface) of the base 100, and the inside of the film 110 has a conductive circuit pattern (120) for transmitting various signals (e.g., sensing signals or control signals, etc.). ) (see attached FIGS. 2, 3, and 6) is provided in thin film form.

As shown in Figure 6 attached, the film 110 may include an upper film 111 and a lower film 112. At this time, the upper film 111 forms the upper surface of the base 100, and the lower film 112 forms the bottom surface of the base 100.

Connectors (not shown) or contact points (not shown) connected to the circuit pattern 120 may be provided at both ends of the base 100, respectively.

The film 110 forming the base 100 is preferably made of a material that is insulating and has ductility. For example, the film 110 may be made of polyimide.

The circuit pattern 120 forming the base 100 may be formed of a thin film made of copper (Cu). At this time, the film 110 is formed to cover the upper and lower surfaces of the circuit pattern 120, respectively.

Additionally, the base 100 has a dummy pattern 130. The dummy pattern 130 may be formed of the same copper thin film as the circuit pattern 120. That is, the dummy pattern 130 is formed to have the same height as the circuit pattern 120.

On the other hand, unlike the circuit pattern 120, the dummy pattern 130 is formed not to transmit signals. That is, the dummy pattern 130 is not a continuously formed circuit, but is formed as a partially disconnected pattern.

The dummy pattern 130 serves to protect the circuit pattern 120, and may be positioned on at least one side of the circuit pattern 120. For example, as shown in Figure 6, the dummy patterns 130 are positioned on both sides of the circuit patterns 120 to prevent the film 110 from sagging between the circuit patterns 120. At this time, an adhesive member 150 may be provided between the circuit pattern 120 and the dummy pattern 130 or between the dummy pattern 130 and the dummy pattern 130.

The dummy patterns 130 are provided in plural numbers and are formed to have a certain length and width. Each of the dummy patterns 130 is positioned to be spaced apart from each other along the length direction, and each of the dummy patterns 130 may be formed to have the same width as the circuit pattern 120 or a wider width.

Meanwhile, the flexible circuit board may include a lead portion 200. The lead portion 200 is connected or branched from the circuit pattern 120 provided on the base 100 and is soldered to, for example, a sensor or a circuit or terminal connected to the sensor to transmit a signal from the sensor.

The lead portion 200 may be provided one or in plurality of two or more. In particular, the lead portion 200 may be provided around at least one side of the base 100 when viewed in its longitudinal direction. For example, one, two or more lead portions 200 may be provided on at least one side of the base 100 in its longitudinal direction.

The lead portion 200 is formed to have a narrower width than the base 100. For example, the lead portion 200 is formed to be thinner than the base 100.

In addition, at least a portion of the lead portion 200 is bent or curved. As a result, shock or vibration transmitted from the soldered area can be prevented from being buffered in the corresponding lead portion 200 and transmitted as is to the base 100.

Next, the flexible circuit board according to an embodiment of the present invention is configured to include a bending area 140.

The bending area 140 is a region that is bent to extend to a direction or location different from the formation direction (longitudinal direction) of the base 100.

The bending area 140 may be provided in at least one location of the base 100.

The bending area 140 is bent to have a preset radius of curvature (R) (see attached FIG. 11). That is, when the flexible circuit board is completely folded, there is a risk of cracks occurring or short circuiting in the circuit pattern 120 despite the presence of the film 110. Considering this, the flexible circuit board is bent to have a preset minimum radius of curvature (R) rather than being completely folded. The radius of curvature (R) may be determined by considering the width, thickness, bending direction, etc. of the flexible printed circuit board.

In addition, the length (L1) of the bending area 140 is determined by considering the radius of curvature (R). For example, when the radius of curvature is R, the length L1 of the bending area 140 may be determined to be πR or more.

Meanwhile, the bending area 140 may be formed along the length direction of the base 100, the width direction of the base 100, or a direction inclined toward one side of the base 100. That is, the bending area 140 may be formed in a direction crossing the two long sides of the base 100, a direction crossing the two short sides, or a direction obliquely crossing the two long sides.

A plurality of cutting holes 141 for bending are formed in the bending area 140.

This cutting hole 141 for bending serves to reduce the springback phenomenon when bending the bending area 140. That is, the bending area of the bending area 140 is reduced by the amount of the bending cutout hole 141, thereby reducing the springback phenomenon.

The cutting holes 141 for bending may be arranged to be spaced apart from each other along a direction perpendicular to the bending direction (or longitudinal direction) among the respective directions of the base 100. For example, each bending cut hole 141 may be formed to be spaced apart from each other along the width direction of the base 100.

The cutting hole 141 for bending may be formed to be located in a portion of the base 100 where the dummy pattern 130 is formed. That is, the cutting hole 141 for bending is formed to avoid the circuit pattern 120, thereby preventing damage to the circuit pattern 120.

In particular, the width W1 of the bending cut hole 141 is narrower than the width W2 of the dummy pattern 130. That is, the bending cut hole 141 is formed to penetrate only the dummy pattern 130, and its position and size are such that it does not damage the circuit pattern 120 or the adhesive member 150 provided between each dummy pattern 130. is decided. As a result, it is possible to prevent the problem of the film 110 lifting due to damage to the adhesive member 150, which may occur when the bending incision 141 is formed in the area where only the film 110 is located. It is possible to prevent tearing of the film 110 in advance.

In addition, the cutting hole 141 for bending is formed as a long hole that is longer in the length (L2) direction than in the width (W1) direction. At this time, the longitudinal direction is the same as the longitudinal direction of the base 100 (or the longitudinal direction of the bending area).

Both longitudinal ends of the bending cut hole 141 are rounded. That is, by ensuring that the cutting hole 141 for bending does not have corners, tearing or opening of the film 110, which mainly occurs at the corner areas, can be minimized.

Additionally, the length L2 of the bending cut hole 141 may be equal to the length L1 of the bending area 140 or may be shorter than the length L1 of the bending area 140.

Of course, the length L2 of the bending incision 141 may be equal to the length L1 of the bending area 140 or may be longer than the length L1 of the bending area 140. However, in this structure, since the bending cutout hole 141 is long, there is a risk that other flexible circuit boards may be caught during transportation of the flexible printed circuit board, and there is a risk that the bending cutout hole 141 may be torn. It is not desirable because there are

Meanwhile, the separation distance L3 between each bending cut hole 141 is formed to be larger than the width W1 of the bending cut hole 141.

In the following, the manufacturing process of the flexible circuit board according to the above-described embodiment of the present invention will be described in detail.

First, to manufacture a flexible circuit board according to an embodiment of the present invention, a circuit pattern 120 and a dummy pattern 130 made of a thin copper plate are respectively prepared.

The prepared circuit pattern 120 and the dummy pattern 130 are coated (thermo-compressed) by a compression process so that the upper and lower surfaces are in contact with the upper and lower films 111 and 112, respectively. At this time, an adhesive member 150 for adhering the upper film 111 and the lower film 112 is provided between each circuit pattern 120 or between the circuit pattern 120 and the dummy pattern 130.

In addition, the flexible circuit board manufactured through the pressing process has unnecessary parts removed through a punching process, and the base 100 and the lead portion 200 are formed separately.

In particular, during the above-described punching process, a plurality of cutting holes 141 for bending are formed together. That is, each bending cut hole 141 is formed in the punching process.

And, the flexible circuit board on which the punching process has been completed is partially bent through a bending process.

The bending process can be performed using a thermal forming device that bends while applying constant heat.

In the bending process, the bending area 140 of the flexible circuit board is bent. At this time, the bending area 140 is bent by heat applied to the jig (not shown) in close contact with the surface of a jig (not shown) formed roundly to have a predetermined outer diameter.

The bending process may be completed once, or may be completed repeatedly two or more times. For example, if there are two or more bending areas, each bending area (bending area) may be bent at the same time, or each bending area may be bent sequentially.

The bending process may be terminated by stopping the provision of heat to the jig after a preset period of time has elapsed and the jig is separated from the flexible circuit board.

The attached Figures 8 to 11 show the state of the flexible printed circuit board in each direction after the bending process has been completed.

On the other hand, when the bending process is completed and the flexible printed circuit board is taken out from the thermal forming device, the flexible printed circuit board experiences a springback phenomenon in which the bent portion attempts to recover to its original position to a certain extent due to the self-restoring force of the film 110 and the copper thin film. occurs.

However, since a plurality of bending cut-out holes 141 are formed in the bending area 140, the elastic restoring force is reduced by the area where each bending cut-out hole 141 is formed, thereby minimizing the springback phenomenon. .

In this way, the flexible circuit board of the present invention can be accurately bent in the bending area 140 by providing a plurality of bending incision holes 141, and the springback phenomenon can be minimized after the bending process.

In addition, in the flexible circuit board of the present invention, the cutting hole 141 for bending is located in each part of the flexible circuit board where the circuit pattern 120 of the base 100 is not formed, thereby preventing damage to the circuit pattern 120. can be prevented.

In addition, in the flexible circuit board of the present invention, the cutting hole 141 for bending is located in each part of the flexible circuit board where the dummy pattern 130 of the base 100 is formed, thereby preventing the film 110 from lifting. It can be.

In addition, in the flexible circuit board of the present invention, the cutting hole 141 for bending is formed to be equal to or shorter than the length of the bending area 140, so that the curved surface provided by the bending area 140 is formed when the bending area 140 is bent. It will not exceed. As a result, interference such as getting caught in other flexible circuit boards during transportation due to the excessive length L2 of the bending cutout hole 141 can be prevented, and tearing can also be reduced.

In addition, in the flexible circuit board of the present invention, both ends of the bending incision 141 are rounded, so that the lifting phenomenon of the film 110 that may occur at the corner area can be prevented or reduced.

In addition, in the flexible circuit board of the present invention, each bending cutout hole 141 is formed along the bending direction of the flexible circuit board, so that springback during bending of the bending area 140 can be minimized.

Meanwhile, the flexible circuit board according to an embodiment of the present invention may be formed in a structure without the dummy pattern 130.

In this case, the cutting hole 141 for bending may be formed in a portion of the bending area 140 where the circuit pattern 120 is not formed.

Additionally, the flexible printed circuit board according to an embodiment of the present invention may be formed in a structure in which the width W2 of the dummy pattern 130 is extremely narrow.

In this case, the cutting hole 141 for bending is formed to have a width (W1) larger than that of the dummy pattern 130 in the bending area 140 and is formed in an area where the circuit pattern 120 is not formed (an area spaced apart from the circuit pattern). ) can be formed.

Of course, even if the width W2 of the dummy pattern 130 is not narrow, the width W1 of the bending cut hole 141 may be larger than the width W2 of the dummy pattern 130. In this case as well, the bending cutout 141 is formed to be spaced apart from the circuit pattern 120.

In the above, even though all the components constituting the embodiment according to the present invention have been described as being combined or operated in combination, the present invention is not necessarily limited to this embodiment. That is, as long as it is within the scope of the purpose of the present invention, all of the components may be operated by selectively combining one or more of them. In addition, terms such as “include,” “comprise,” or “have” described above mean that the corresponding component may be present, unless specifically stated to the contrary, and thus do not exclude other components. Rather, it should be interpreted as being able to include other components. All terms, including technical or scientific terms, unless otherwise defined, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Commonly used terms, such as terms defined in a dictionary, should be interpreted as consistent with the contextual meaning of the related technology, and should not be interpreted in an idealized or overly formal sense unless explicitly defined in the present invention.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but rather to explain it, and the scope of the technical idea of the present invention is not limited by these examples. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be construed as being included in the scope of rights of the present invention.

100. Base 110. Film
111. Upper film 112. Lower film
120. Circuit pattern 130. Dummy pattern
140. Bending area 141. Cutting hole for bending
150. Adhesive member 200. Lead part

Claims (11)

It includes a base formed by forming a circuit pattern for signal transmission inside a bendable film and a dummy pattern that protects the circuit pattern and does not transmit the signal,
The base is provided with at least one bending area that is bent to extend to a different direction or position than the forming direction of the base, and the bending area includes a direction perpendicular to the bending direction among the directions of the base. A flexible circuit board characterized in that a plurality of cutting holes for bending are formed to be spaced apart from each other. According to claim 1,
A flexible circuit board, characterized in that the cutting hole for bending is formed to be located in a region where the dummy pattern is formed. According to claim 2,
A flexible circuit board, wherein the bending cut hole is formed to have a width smaller than that of the dummy pattern. According to claim 1,
A flexible circuit board, characterized in that the cutting hole for bending is formed to be located in a region where the circuit pattern is not formed. According to claim 1,
A flexible circuit board, characterized in that the bending area is bent to have a preset radius of curvature. According to claim 5,
A flexible circuit board, wherein the bending cut hole is formed as a long hole that is longer in the longitudinal direction than the width direction. According to claim 6,
A flexible circuit board, characterized in that the length of the bending cut hole is equal to the length of the bending area or is formed shorter than the length of the bending area. According to claim 6,
A flexible circuit board, characterized in that both longitudinal ends of the bending cut hole are rounded. According to claim 1,
A flexible circuit board, characterized in that the bending direction of the bending area is bent in the same direction as the longitudinal direction of the base or is formed to be inclined in a direction from the longitudinal direction of the base. It includes a base formed by forming a circuit pattern for signal transmission inside a bendable film,
The base is provided with at least one bending area that is bent to extend to a different direction or position than the formation direction of the base, and a cutting hole for bending is formed in a part of the bending area where the circuit pattern is not formed. is formed,
A flexible circuit board, wherein a plurality of cutting holes for bending are provided and spaced apart from each other along a direction perpendicular to the bending direction among the directions of the base. According to claim 10,
A flexible circuit board, wherein the bending cut hole is formed as a long hole that is longer in the longitudinal direction than the width direction.

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