CN118695469A - Flexible circuit board and manufacturing method thereof - Google Patents

Abstract

The present invention provides a flexible circuit board and a manufacturing method thereof. The method includes providing a first flexible circuit substrate and a second flexible circuit substrate; forming a first protective layer and a second protective layer on the top surface and the bottom surface of each of the first flexible circuit substrate and the second flexible circuit substrate respectively; disposing an adhesive layer between the first flexible circuit substrate and the second flexible circuit substrate; disposing a support body in an opening in the adhesive layer; pressing the first flexible circuit substrate, the second flexible circuit substrate, the support body and the adhesive layer; removing the support body to form a cavity between the first flexible circuit substrate and the second flexible circuit substrate; and bending the first flexible circuit substrate so that a portion of the first flexible circuit substrate passes through the cavity. In this way, the advantage of reducing the thickness of the flexible circuit board can be achieved.

Description

Flexible circuit board and manufacturing method thereof

Technical Field

The present invention relates to a flexible circuit board and a manufacturing method thereof, and in particular to a bent flexible circuit board and a manufacturing method thereof.

Background Art

In recent years, due to the development of new energy vehicles (such as electric vehicles), the application of flexible circuit boards in power battery modules has become increasingly important. Flexible circuit boards have the advantages of ultra-thin thickness, softness and lightness, which can help reduce the volume or thickness of power battery modules, thereby reducing the space occupied by power battery modules.

Summary of the invention

One aspect of the present invention provides a method for manufacturing a flexible circuit board, which includes a cavity formed between a first flexible substrate and a second flexible circuit substrate, and a first flexible circuit substrate accommodated in the cavity and bent.

Another aspect of the present invention is to provide a flexible circuit board, which includes a flexible circuit board manufactured by the method of the above aspect.

According to one aspect of the present invention, a method for manufacturing a flexible circuit board is provided. The method includes providing a first flexible circuit substrate and a second flexible circuit substrate; forming a first protective layer and a second protective layer on the top surface and the bottom surface of each of the first flexible circuit substrate and the second flexible circuit substrate respectively; disposing an adhesive layer between the first flexible circuit substrate and the second flexible circuit substrate, wherein the adhesive layer has an opening; disposing a support body in the opening in the adhesive layer; pressing the first flexible circuit substrate, the second flexible circuit substrate, the support body and the adhesive layer so that the adhesive layer and the support body are disposed between the first flexible circuit substrate and the second flexible circuit substrate; shaping and removing the support body to form a cavity between the first flexible circuit substrate and the second flexible circuit substrate; and bending the first flexible circuit substrate so that a portion of the first flexible circuit substrate passes through the cavity.

According to one embodiment of the present invention, the first flexible circuit substrate includes a first flexible substrate and a first circuit layer on the top surface of the first flexible substrate, and the second flexible circuit substrate includes a second flexible substrate and a second circuit layer on the bottom surface of the second flexible substrate.

According to one embodiment of the present invention, before forming the first protective layer and the second protective layer, the method further includes forming a plurality of first conductive holes, wherein the first conductive holes extend from the bottom surface of the first flexible circuit substrate to the first circuit layer; and forming a plurality of second conductive holes, wherein the second conductive holes extend from the top surface of the second flexible circuit substrate to the second circuit layer.

According to one embodiment of the present invention, the step of forming the first protective layer and the second protective layer also includes forming a first opening in the second protective layer of the first flexible circuit substrate so that the first conductive hole protrudes from the second protective layer; and forming a second opening in the first protective layer of the second flexible circuit substrate so that the second conductive hole protrudes from the first protective layer.

According to one embodiment of the present invention, before laminating the first flexible circuit substrate, the second flexible circuit substrate and the adhesive layer, the method further includes forming a plurality of conductive vias in the adhesive layer, wherein the conductive vias respectively connect the first conductive holes and the second conductive holes.

According to an embodiment of the present invention, after bending the first flexible circuit substrate, the method further includes forming a gap between the portion of the first flexible circuit substrate and the second flexible circuit substrate; and filling the gap with a glue layer.

According to another aspect of the present invention, a flexible circuit board is provided, which includes a first flexible circuit substrate, a second flexible circuit substrate, an adhesive layer, and a plurality of conductive vias. The first flexible circuit substrate includes a first straight portion, a second straight portion below the first straight portion, and a bent portion connecting the first straight portion and the second straight portion. The second flexible circuit substrate is disposed below the first flexible circuit substrate, wherein the second straight portion of the first flexible circuit substrate is located between the first straight portion and the second flexible circuit substrate, and the bent portion extends from the first straight portion toward the second flexible circuit substrate to the second straight portion. The adhesive layer is disposed between the first flexible circuit substrate and the second flexible circuit substrate, wherein the second straight portion is surrounded by the first straight portion, the adhesive layer, and the second flexible circuit substrate. The conductive via is disposed between the first flexible circuit substrate and the second flexible circuit substrate, and extends from the first straight portion through the adhesive layer to the second flexible circuit substrate.

According to an embodiment of the present invention, the first flexible circuit substrate comprises a first flexible substrate, a first circuit layer disposed on the top surface of the first flexible substrate, a first protective layer disposed on the top surface of the first flexible substrate and covering the first circuit layer, and a second protective layer disposed on the bottom surface of the first flexible substrate. The second flexible circuit substrate comprises a second flexible substrate, a second circuit layer disposed on the bottom surface of the second flexible substrate, a second circuit layer disposed on the bottom surface of the second flexible substrate, and a fourth protective layer disposed on the bottom surface of the second flexible substrate and covering the second circuit layer.

According to an embodiment of the present invention, the conductive via extends from the first circuit layer to the second circuit layer.

According to an embodiment of the present invention, the thickness of the adhesive layer is greater than the thickness of the first flexible circuit substrate, and the thickness of the adhesive layer is greater than the thickness of the second flexible circuit substrate.

By using the flexible circuit board and the manufacturing method thereof of the present invention, a supporting cavity is formed inside the circuit board so that a portion of the flexible circuit substrate passes through the cavity. Therefore, when manufacturing a longer circuit board, the additional increase in the overall thickness can be avoided, thereby achieving the advantage of reducing the thickness of the circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, as is standard practice in the industry, many features are not drawn to scale. In fact, for the sake of clarity of discussion, the dimensions of many features may be arbitrarily scaled.

1A to 1D are cross-sectional views of intermediate stages of a method for manufacturing a flexible printed circuit board according to some embodiments of the present invention.

FIG. 2 is a cross-sectional view of the flexible printed circuit board at an intermediate stage of the process according to FIG. 1C .

FIG. 3 is a top view of an intermediate stage of a process for producing a flexible printed circuit board according to some embodiments of the present invention.

FIG. 4 is a cross-sectional view of a flexible printed circuit board according to some embodiments of the present invention.

DETAILED DESCRIPTION

The present invention provides many different embodiments or examples to implement different features of the invention. The specific examples of components and configurations described below are intended to simplify the present invention. These are of course only examples and are not intended to be limiting. For example, the description of a first feature formed on or above a second feature includes an embodiment in which the first feature and the second feature are in direct contact, and also includes an embodiment in which other features are formed between the first feature and the second feature, so that the first feature and the second feature are not in direct contact. In addition, the present invention repeats component symbols and/or letters in various specific examples. The purpose of this repetition is to simplify and clarify the description and does not indicate a relationship between the various discussed embodiments and/or configurations.

Furthermore, spatially relative terms, such as "beneath," "below," "lower," "above," "upper," etc., are intended to facilitate description of the relationship of a part or feature depicted in the drawings to other parts or features. Spatially relative terms encompass different orientations of the element in use or operation in addition to the orientation depicted in the drawings. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may be interpreted so.

The existing manufacturing method of the flexible circuit board used in the power battery module makes the circuit board into a plurality of straight sections, wherein two straight sections are connected by a folding section, which is fixed by using adhesive tape in the folding notch of the folding section. However, this method requires folding the straight section more than twice, and its fixing method will increase the overall thickness of the circuit board, so it is not conducive to the manufacture of a thin and light flexible circuit board. Therefore, the present invention provides a flexible circuit board and a manufacturing method thereof, which utilizes the formation of a supporting cavity inside the circuit board so that a part of the flexible circuit substrate passes through the cavity, thereby avoiding an additional increase in the overall thickness, so as to achieve the advantage of reducing the thickness of the circuit board, thereby further reducing the occupied space of the power battery module.

FIG. 1A to FIG. 1D illustrate cross-sectional views of intermediate stages of a method for manufacturing a flexible circuit board according to some embodiments of the present invention. First, referring to FIG. 1A , a first flexible circuit substrate 110 and a second flexible circuit substrate 120 are provided. The first flexible circuit substrate 110 includes a first flexible substrate 111 and a first circuit layer 113, and the second flexible circuit substrate 120 includes a second flexible substrate 121 and a second circuit layer 123. In some embodiments, the first circuit layer 113 is disposed on a top surface 111A of the first flexible substrate 111, and the second circuit layer 123 is disposed on a bottom surface 121B of the second flexible substrate 121. In some embodiments, the first circuit layer 113 and the second circuit layer 123 can be formed by patterning metal layers (not shown) on the first flexible substrate 111 and the second flexible substrate 121, respectively, wherein the patterning method can be photolithography and etching.

Next, referring to FIG. 1B , a first conductive hole 132 is formed in the first flexible circuit substrate 110 so that the first conductive hole 132 extends from the bottom surface 111B of the first flexible substrate 111 to the top surface 111A to electrically contact the first circuit layer 113; and a second conductive hole 134 is formed in the second flexible circuit substrate 120 so that the second conductive hole 134 extends from the top surface 121A of the second flexible substrate 121 to the bottom surface 121B to electrically contact the second circuit layer 123. In some embodiments, the first conductive hole 132 and the second conductive hole 134 can be formed by laser drilling to form a blind hole and then filled with metal paste. In other embodiments, the first conductive hole 132 and the second conductive hole 134 can be formed by mechanical drilling and then electroplating to fill the hole.

Then, please continue to refer to Figure 1B, a first protective layer 115 is formed on the top surface 111A of the first flexible circuit substrate 110, and a second protective layer 117 is formed on the bottom surface 111B of the first flexible circuit substrate 110, wherein the first protective layer 115 covers the first circuit layer 113, and the second protective layer 117 has an opening so that the first conductive hole 132 protrudes from the bottom surface 111B, that is, the top surface of the first conductive hole 132 is higher than the second protective layer 117.

Similarly, a first protective layer 125 is formed on the top surface 121A of the second flexible circuit substrate 120, and a second protective layer 127 is formed on the bottom surface 121B of the second flexible circuit substrate 120, wherein the second protective layer 127 covers the second circuit layer 123, and the first protective layer 125 has an opening so that the second conductive hole 134 protrudes from the top surface 121A, that is, the top surface of the second conductive hole 134 is higher than the first protective layer 125.

Referring to FIG. 1C , the adhesive layer 140 is disposed between the first flexible circuit substrate 110 and the second flexible circuit substrate 120, and the support body 150 is disposed in the opening (not shown) of the adhesive layer 140. Then, the adhesive layer 140, the support body 150, the first flexible circuit substrate 110, and the second flexible circuit substrate 120 are pressed together. In some embodiments, the thickness T1 of the adhesive layer 140 may be greater than the total thickness T2 of the first flexible circuit substrate 110, the first protective layer 115, and the second protective layer 117. In some embodiments, the thickness T1 of the adhesive layer 140 may be greater than the total thickness (not shown) of the second flexible circuit substrate 120, the first protective layer 125, and the second protective layer 127. In some embodiments, the support body 150 must be a material that is not easily deformed under high temperature and high pressure, and is preferably a material that is not bonded to the second protective layer 117 of the first flexible circuit substrate 110 and the first protective layer 125 of the second flexible circuit substrate 120. In some embodiments, the material of the support body 150 may be a cured thermosetting resin or a metal block with a surface roughness less than 5 μm.

In some embodiments, before the lamination step, a conductive via 145 is formed in the adhesive layer 140, wherein the position of the conductive via 145 corresponds to the position of the first conductive via 132 and the second conductive via 134, so as to electrically connect the first conductive via 132 and the second conductive via 134. It should be noted that the conductive via 145 is a through hole filled with a metal conductive paste.

Please refer to FIG. 2 , which illustrates another cross-sectional view of the intermediate stage of the process of the flexible printed circuit according to FIG. 1C . The flexible printed circuit may have more than one set of first conductive holes 132 , second conductive holes 134 and conductive vias 145 , and may have multiple sets of first conductive holes 132 , second conductive holes 134 and conductive vias 145 according to actual application requirements. In some embodiments, the support 150 is disposed between the two conductive vias 145 and the adhesive layer 140 .

Next, referring to FIG. 1D , the support body 150 (refer to FIG. 1C ) is formed and removed to form a cavity O1 between the first flexible circuit substrate 110 and the second flexible circuit substrate 120, and the cavity O1 is surrounded by the adhesive layer 140. In some embodiments, the cavity O1 is formed between the second protective layer 117 of the first flexible circuit substrate 110 and the first protective layer 125 of the second flexible circuit substrate 120. It should be noted that the aforementioned forming is a step of cutting the circuit board to a required size or processing the finished part into a specific shape during the manufacturing process of the circuit board, which can be performed by, for example, mechanical forming, water jet cutting or laser forming, which is well known to those skilled in the art and will not be described in detail here.

Please refer to FIG3, which is a top view of an intermediate stage of the process of a flexible circuit board according to some embodiments of the present invention. The flexible circuit board shown in FIG3 can be obtained by bending the first flexible circuit substrate 110, the first protective layer 125 and the second protective layer 127 in FIG1D into the cavity O1. The cross-sectional views of FIG1A to FIG1D can be drawn according to the cross-sectional line A-A' of FIG3; and the cross-sectional view of FIG2 can be drawn according to the cross-sectional line B-B' of FIG3.

Please refer to FIG. 4, which illustrates a cross-sectional view of a flexible printed circuit board 200 according to some embodiments of the present invention, wherein FIG. 4 is drawn along the horizontal line section in FIG. 3, and this horizontal line overlaps with the horizontal line segment of the section line A-A'. Therefore, FIG. 4 does not depict the adhesive layer 140 and the conductive via 145. The flexible printed circuit board 200 can be, for example, made by bending the first flexible circuit substrate 110, the first protective layer 125, and the second protective layer 127 in FIG. 1D into the cavity O1. It should be understood that the thickness of the cavity O1 is the thickness T1 of the adhesive layer 140 (refer to FIG. 1C), so the first flexible circuit substrate 110, the first protective layer 125, and the second protective layer 127 can be bent into the cavity O1.

As shown in FIG4 , the flexible circuit board 200 includes a first flexible circuit substrate 210 , a second flexible circuit substrate 220 , an adhesive layer (not shown) and a plurality of conductive vias (not shown). The second flexible circuit substrate 220 is disposed below the first flexible circuit substrate 210 . In some embodiments, the first flexible circuit substrate 210 includes a first flexible substrate 211, a first circuit layer 213 on a first surface 211A of the first flexible substrate 211, a first protective layer 215 on the first surface 211A of the first flexible substrate 211 and covering the first circuit layer 213, and a second protective layer 217 on the second surface 211B of the first flexible substrate 211; similarly, the second flexible circuit substrate 220 includes a second flexible substrate 221, a second circuit layer 223 on the second surface 221B of the second flexible substrate 221, a third protective layer 225 on the first surface 221A of the second flexible substrate 221, and a fourth protective layer 227 on the second surface 221B of the second flexible substrate 221 and covering the second circuit layer 223.

The first flexible circuit substrate 210 includes a first straight portion 210A, a second straight portion 210B and a bent portion 210C. The first straight portion 210A and the second straight portion 210B both extend along the direction X. The second straight portion 210B is located between the first straight portion 210A and the second flexible circuit substrate 220, and the second straight portion 210B is adjacent to the adhesive layer. In other words, the second straight portion 210B is surrounded by the first straight portion 210A, the adhesive layer (not shown) and the second flexible circuit substrate 220. Referring to FIG. 2 , the second straight portion 210B replaces the support body 150 in FIG. 2 . The bent portion 210C connects the first straight portion 210A and the second straight portion 210B, and the bent portion 210C extends from the first straight portion 210A toward the second flexible circuit substrate 220 (i.e., toward the direction Y) to the second straight portion 210B.

In some embodiments, a gap O2 is defined between the second straight portion 210B and the second flexible circuit substrate 220 , and a glue layer may be selectively filled in the gap O2 to fix the second straight portion 210B.

As described above, the present invention provides a flexible circuit board and a method for manufacturing the same, which utilizes lamination of multiple flexible circuit substrates and forms a cavity between the flexible circuit substrates so as to bend one of the flexible circuit substrates once into the cavity, thereby obtaining a longer flexible circuit board without increasing the thickness of the circuit board, thereby further reducing the space occupied by the power battery module.

Although the present invention has been disclosed as above with several embodiments, they are not intended to limit the present invention. Those skilled in the art to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the definition of the attached claims.

【Explanation of symbols】

110: first flexible circuit substrate

111: first flexible substrate

111A: Top surface

111B: Bottom surface

113: First circuit layer

115: First protective layer

117: Second protective layer

120: Second flexible circuit substrate

121: Second flexible substrate

121A: Top surface

121B: Bottom surface

123: Second circuit layer

125: First protective layer

127: Second protection layer

132: first conductive hole

134: Second conductive hole

140: Adhesive layer

145: Conductive via

150: support body

200: Flexible printed circuit board

210: first flexible circuit substrate

210A: First straight line portion

210B: Second straight line portion

210C: Bending part

211: first flexible substrate

211A: First surface

211B: Second surface

213: First circuit layer

215: First protective layer

217: Second protective layer

220: Second flexible circuit substrate

221: Second flexible substrate

221A: First surface

221B: Second surface

223: Second circuit layer

225: The third protective layer

227: The fourth protection layer

A-A’, B-B’: hatching line

O1: Cavity

O2: Gap

T1, T2: thickness

X,Y: direction.

Claims (10)

1. A manufacturing method of a flexible circuit board is characterized by comprising the following steps:

Providing a first flexible circuit substrate and a second flexible circuit substrate;

forming a first protective layer and a second protective layer on the top surface and the bottom surface of each of the first flexible circuit substrate and the second flexible circuit substrate respectively;

Arranging an adhesive layer between the first flexible circuit substrate and the second flexible circuit substrate, wherein the adhesive layer is provided with an opening;

Disposing a support within the opening in the adhesive layer;

Pressing the first flexible circuit substrate, the second flexible circuit substrate, the supporting body and the bonding layer to enable the bonding layer and the supporting body to be arranged between the first flexible circuit substrate and the second flexible circuit substrate;

Forming and removing the support body to form a cavity between the first flexible circuit substrate and the second flexible circuit substrate; and

And bending the first flexible circuit substrate so that a part of the first flexible circuit substrate passes through the cavity.

2. The method of claim 1, wherein the first flexible circuit substrate comprises a first flexible substrate and a first circuit layer on the top surface of the first flexible substrate, and the second flexible circuit substrate comprises a second flexible substrate and a second circuit layer on the bottom surface of the second flexible substrate.

3. The method of manufacturing a flexible printed circuit according to claim 2, further comprising, before forming the first protective layer and the second protective layer:

forming a plurality of first conductive holes, wherein the first conductive holes extend from the bottom surface of the first flexible circuit substrate to the first circuit layer; and

Forming a plurality of second conductive holes, wherein the second conductive holes extend from the top surface of the second flexible circuit substrate to the second circuit layer.

4. The method of manufacturing a flexible printed circuit according to claim 3, wherein the step of forming the first protective layer and the second protective layer further comprises:

forming a first opening in the second protective layer of the first flexible circuit substrate so that the first conductive hole protrudes out of the second protective layer; and

Forming a second opening in the first protective layer of the second flexible circuit substrate so that the second conductive hole protrudes out of the first protective layer.

5. The method of manufacturing a flexible printed circuit according to claim 3, further comprising, before bonding the first flexible printed circuit, the second flexible printed circuit, and the adhesive layer:

and forming a plurality of conductive through holes in the bonding layer, wherein the conductive through holes are respectively connected with the first conductive holes and the second conductive holes.

6. The method of manufacturing a flexible circuit board according to claim 1, further comprising, after bending the first flexible circuit board:

forming a gap between the portion of the first flexible circuit substrate and the second flexible circuit substrate; and

And the filling glue layer is arranged in the gap.

7. A flexible circuit board, comprising:

A first flexible circuit substrate, wherein the first flexible circuit substrate comprises:

a first straight line portion;

A second straight line portion below the first straight line portion; and

A bending portion connecting the first straight portion and the second straight portion;

the second flexible circuit substrate is arranged below the first flexible circuit substrate, wherein the second linear part of the first flexible circuit substrate is positioned between the first linear part and the second flexible circuit substrate, and the bending part extends from the first linear part to the second flexible circuit substrate to the second linear part;

an adhesive layer disposed between the first flexible circuit substrate and the second flexible circuit substrate, wherein the second linear portion is surrounded by the first linear portion, the adhesive layer, and the second flexible circuit substrate; and

And a plurality of conductive through holes arranged between the first flexible circuit substrate and the second flexible circuit substrate and extending from the first linear part to the second flexible circuit substrate through the bonding layer.

8. The flexible circuit board of claim 7, wherein the first flexible circuit substrate comprises:

A first flexible substrate;

the first circuit layer is arranged on the top surface of the first flexible substrate;

the first protective layer is arranged on the top surface of the first flexible substrate and covers the first circuit layer; and

A second protective layer arranged on the bottom surface of the first flexible substrate,

And the second flexible circuit substrate comprises:

a second flexible substrate;

the second circuit layer is arranged on the bottom surface of the second flexible substrate;

a third protective layer disposed on the top surface of the second flexible substrate; and

And the fourth protective layer is arranged on the bottom surface of the second flexible substrate and covers the second circuit layer.

9. The flexible circuit board of claim 8, wherein the conductive via extends from the first circuit layer to the second circuit layer.

10. The flexible circuit board of claim 7, wherein the thickness of the adhesive layer is greater than the thickness of the first flexible circuit substrate and the thickness of the adhesive layer is greater than the thickness of the second flexible circuit substrate.