Flexible printed circuit board

Abstract

A flexible circuit board includes a flexible substrate, a chip, and a patterned circuit layer. The flexible substrate has a surface, which is divided into an operating area and a non-operating area by a cutting line. The chip is arranged in the operating area of ​​the surface, and the patterned circuit layer is arranged on the surface. The patterned circuit layer has multiple signal transmission lines and multiple bypass lines. The bypass lines are not electrically connected to the chip. Each bypass line has a bypass transmission part and an anti-tear part. The bypass transmission part is located in the operating area, and the anti-tear part is located in the non-operating area. A blank area is defined between the anti-tear part and the bypass transmission part. The cutting line passes through the blank area. The spacing between the anti-tear part and the cutting line is between 100um and 400um.

Description

Technical Field

[0001] The present invention relates to a flexible circuit board, and in particular to a flexible circuit board which can prevent circuits from peeling off during a punching process. Background Art

[0002] Flexible printed circuits (FPCs) are packaging structures that incorporate electronic devices and their circuitry onto a flexible substrate. Due to their bendability, thinness, and customizable shape, FPCs are widely used in portable electronic devices. However, their small size and flexibility make individual FPC components difficult to move and process. Therefore, FPCs are typically transported on a reel-to-reel basis through various manufacturing processes (e.g., copper plating, patterning, tin plating, solder mask coating, reflow, chip die-coating, etc.). After completion, FPCs are separated from the reel through a punching process to create the desired dimensions. However, due to the FPCs' small size, the circuitry on them is also quite fine, making it easy for circuits adjacent to the cut lines to peel off from the flexible substrate during the punching process. Therefore, preventing this peeling has become a key issue in improving FPC manufacturing yield. Summary of the Invention

[0003] The main purpose of the present invention is to prevent the bypass transmission part from peeling off during the punching process by providing the anti-tearing part of the bypass line.

[0004] A flexible printed circuit board according to the present invention includes a flexible substrate, a chip, and a patterned circuit layer. The flexible substrate has a surface divided into an active area and a non-active area by a cutting line. The chip is disposed in the active area of ​​the surface, and the patterned circuit layer is disposed on the surface. The patterned circuit layer has a plurality of signal transmission lines and a plurality of bypass lines. The signal transmission lines are electrically connected to the chip, while the bypass lines are not electrically connected to the chip. Each bypass line has a bypass transmission portion and a tear-proof portion. The bypass transmission portion is located in the active area, and the tear-proof portion is located in the non-active area. A blank area is defined between the tear-proof portion and the bypass transmission portion, and the cutting line passes through the blank area. The spacing between the tear-proof portion and the cutting line is between 100 μm and 400 μm.

[0005] Preferably, the bypass transmission portion of the bypass line has a reduced line segment, the reduced line segment is adjacent to the cutting line, wherein a width of the reduced line segment is smaller than a width of other line segments of the bypass transmission portion.

[0006] Preferably, the width of the reduced line segment is the same as the width of the tear-resistant portion of the corresponding bypass line.

[0007] Preferably, the width of the reduced line segment is between 10 um and 150 um.

[0008] Preferably, each of the signal transmission lines has a transmission portion, a reduction portion and a testing portion, the transmission portion is located in the working area, the testing portion is located in the non-working area, the reduction portion is connected between the transmission portion and the testing portion, the cutting line passes through the reduction portion, wherein the width of the reduction portion is smaller than the width of the transmission portion and the testing portion.

[0009] Preferably, the width of the reduced portion is between 8um and 13um.

[0010] Preferably, the signal transmission line has a pre-reduction portion, which is located in the working area and connected between the reduction portion and the transmission portion, wherein the width of the pre-reduction portion is between the width of the reduction portion and the width of the transmission portion.

[0011] Preferably, the width of the testing portion is the same as the width of the corresponding pre-reduction portion.

[0012] Preferably, the width of the pre-shrinkage portion is between 10um and 30um.

[0013] Preferably, the working area has a left side and a right side, a portion of the bypass line is adjacent to the left side, and another portion of the bypass line is adjacent to the right side, and the signal transmission line is located between the bypass lines.

[0014] By means of the above technical solution, the present invention has at least the following advantages and effects: by means of the spacing between the anti-tearing part and the cutting line being between 100um and 400um, the present invention can increase the supporting force of the blank area, thereby preventing the bypass transmission part from peeling off during the punching process, and improving the yield of the overall process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 : A top view of a flexible printed circuit board according to one embodiment of the present invention.

[0016] Figure 2 : A partially enlarged view of the flexible printed circuit board according to one embodiment of the present invention.

[0017]

Main component symbol description

[0018] 100: Flexible printed circuit board 110: Flexible substrate

[0019] 111: Surface 120: Chip

[0020] 130: Patterned circuit layer 131: Signal transmission line

[0021] 131a: Transmission unit 131b: Reduction unit

[0022] 131c: Testing section 131d: Pre-reduction section

[0023] 132: Bypass line 132a: Bypass transmission unit

[0024] 132b: Anti-tear portion 132c: Reduced line segment

[0025] CL: Cutting line W: Working area

[0026] NW: Non-working area D: Spacing

[0027] RS: right side LS: left side

[0028] B: Blank area W1: Width of the reduced portion

[0029] W2: Width of the transmission part W3: Width of the test part

[0030] W4: Width of the pre-reduction section W5: Width of the reduction line segment

[0031] W6: width of the tear-proof part DETAILED DESCRIPTION

[0032] See also Figure 1 , which is a top view of a flexible circuit board 100 according to an embodiment of the present invention. The flexible circuit board 100 has a flexible substrate 110 , a chip 120 and a patterned circuit layer 130 .

[0033] In this embodiment, the flexible substrate 110 can be made of a material selected from polyimide (PI) or polyethylene terephthalate (PET). The flexible substrate 110 has a surface 111. The surface 111 is divided into an active area W and a non-active area NW by a cutting line CL. The area surrounded by the cutting line CL is the active area W, and the remaining area is the non-active area NW. The punching process is performed along the cutting line CL, leaving the active area W as a driver integrated circuit (IC), and the non-active area NW as waste.

[0034] The chip 120 and the patterned circuit layer 130 are disposed on the surface 111 of the flexible substrate 110 . The chip 120 is located in the working area W, and the patterned circuit layer 130 spans the working area W and the non-working area NW. Figure 1The patterned circuit layer 130 in the figure only reveals its outer outline, but in reality, it is composed of multiple fine circuits. The patterned circuit layer 130 is formed by patterned etching of a copper layer electroplated or rolled on the surface 111. The chip 120 is formed by a core-flipping process, where multiple bumps (not shown) disposed on the chip 120 form a eutectic connection with the patterned circuit layer 130. This allows signals to be transmitted to the chip 120 through the patterned circuit layer 130, or signals generated by the chip 120 to be transmitted externally through the patterned circuit layer 130. The portion where the patterned circuit layer 130 overlaps with the chip 120 is the inner lead portion of the patterned circuit layer 130.

[0035] See also Figure 1 The patterned circuit layer 130 has a plurality of signal transmission lines 131 and a plurality of bypass lines 132. The signal transmission lines 131 are electrically connected to the chip 120, while the bypass lines 132 are not electrically connected to the chip 120. In this embodiment, the working area W has a left side LS and a right side RS. A portion of the bypass lines 132 is adjacent to the left side LS, and another portion of the bypass lines 132 is adjacent to the right side RS, so that the signal transmission lines 131 are located between the bypass lines 132. Since the bypass lines 132 are not electrically connected to the chip 120, the signal can be transmitted directly through the bypass lines 132 without passing through the chip 120.

[0036] See also Figure 2 , which is Figure 1FIG2 is a partial enlarged view of the flexible printed circuit board 100, wherein each signal transmission line 131 includes a transmission portion 131a, a reduction portion 131b, and a testing portion 131c. The transmission portion 131a is located in the working area W, with the inner lead portion and the outer lead portion at either end. The inner lead portion is used to electrically connect to the chip 120, while the outer lead portion is adjacent to the cutting line CL and is electrically connected to the panel or driver circuit board after the flexible printed circuit board 100 is cut from the tape. The testing portion 131c is located in the non-working area NW and is electrically connected to the transmission portion 131a via the reduction portion 131b. Before the flexible printed circuit board 100 is cut from the tape, the testing portion 131c is used for contact with the probes of a probe card to test whether the signal transmission of the transmission portion 131a is correct. The tapered portion 131b is connected between the transmission portion 131a and the testing portion 131c and is located in the region where the cutting line CL passes. The width W1 of the tapered portion 131b is smaller than the widths W2 and W3 of the transmission portion 131a and the testing portion 131c. Since the subsequent punching process is performed along the cutting line CL, the smaller width W1 of the tapered portion 131b can reduce wear of the punching tool used in the punching process. However, to maintain the bonding strength between the tapered portion 131b and the flexible substrate 110, in this embodiment, the width W1 of the tapered portion 131b is between 8 μm and 13 μm to reduce wear of the punching tool. Alternatively, in other embodiments, the width W1 of the tapered portion 131b can be the same as the widths W2 and W3 of the transmission portion 131a and the testing portion 131c. The narrower width W1 of the tapered portion 131b is not a limitation of the present invention.

[0037] Preferably, in this embodiment, the signal transmission line 131 has a pre-reduction portion 131d. The pre-reduction portion 131d is located in the working area W and connected between the reduction portion 131b and the transmission portion 131a. In this embodiment, the width W4 of the pre-reduction portion 131d is between the width W1 of the reduction portion 131b and the width W2 of the transmission portion 131a. The pre-reduction portion 131d can prevent the transmission portion 131a from being directly connected to the reduction portion 131b, thereby preventing current concentration caused by excessive line width changes. The width W3 of the test portion 131c is the same as the width W4 of the corresponding pre-reduction portion 131d, and the width W3 of the test portion 131c and the width W4 of the corresponding pre-reduction portion 131d are between 10 μm and 30 μm.

[0038] See also Figure 2Each bypass line 132 has a bypass transmission portion 132a and an anti-tear portion 132b. The bypass transmission portion 132a is located in the working area W, and the anti-tear portion 132b is located in the non-working area NW. Since the bypass transmission portion 132a of the bypass line 132 is not connected to the chip 120 and does not need to be tested, there is a blank area B between the anti-tear portion 132b and the bypass transmission portion 132a. The cutting line CL passes through the blank area B. The blank area B is used to further reduce the wear of the punching head during punching.

[0039] See also Figure 2 In this embodiment, the bypass transmission portion 132a of the bypass line 132 has a reduced line segment 132c, which is adjacent to the cutting line CL, wherein a width W5 of the reduced line segment 132c is smaller than the widths of the remaining line segments of the bypass transmission portion 132a, and the width W5 of the reduced line segment 132c is the same as the width W6 of the corresponding anti-tear portion 132b of the bypass line 132, and the width W5 of the reduced line segment 132c and the width W6 of the anti-tear portion 132b are between 10um and 150um. Since the width W5 of the reduced line segment 132c is small, the bonding force between the reduced line segment 132c and the flexible substrate 110 is weak, and since the reduced line segment 132c is not connected to the anti-tear portion 132b, it is more susceptible to the influence of the cutting line CL during punching. Preferably, the distance D between the anti-tear portion 132b and the cutting line CL is between 100um and 400um, so that the anti-tear portion 132b can provide support force, reduce the deformation of the blank area B during punching, and prevent the reduced line segment 132c of the bypass transmission portion 132a from peeling off during the punching process.

[0040] In other embodiments, the reduction line segment 132c may also have a bypass reduction portion and a bypass pre-reduction portion (not shown) like the signal transmission line 131. The bypass reduction portion is located between the bypass pre-reduction portion and the blank area B. Since the width of the bypass reduction portion is narrower than that of the bypass pre-reduction portion, it is more susceptible to punching, so that the anti-tearing effect of the anti-tearing portion 132b on the reduction line segment 132c can be more significant.

[0041] In the present invention, the distance D between the anti-tearing portion 132b and the cutting line CL is between 100um and 400um, thereby increasing the support force of the blank area B, preventing the bypass transmission portion 132a from peeling off during the punching process, and improving the yield of the entire process.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A flexible printed circuit board, characterized in that: Include: A flexible substrate having a surface, the surface being divided into a working area and a non-working area by a cutting line; a chip disposed in the working area of ​​the surface; as well as A patterned circuit layer is arranged on the surface, and the patterned circuit layer has multiple signal transmission lines and multiple bypass lines. The signal transmission lines are electrically connected to the chip, and the bypass lines are not electrically connected to the chip. Each of the bypass lines has a bypass transmission portion and an anti-tear portion. The bypass transmission portion is located in the working area, and the anti-tear portion is located in the non-working area. There is a blank area between the anti-tear portion and the bypass transmission portion, and the cutting line passes through the blank area, wherein the spacing between the anti-tear portion and the cutting line is between 100um and 400um.

2. The flexible printed circuit board according to claim 1, wherein The bypass transmission portion of the bypass line has a reduced line segment adjacent to the cutting line, wherein a width of the reduced line segment is smaller than a width of other line segments of the bypass transmission portion.

3. The flexible printed circuit board according to claim 2, wherein: The width of the reduced line segment is the same as the width of the tear-resistant portion of the corresponding bypass line.

4. The flexible printed circuit board according to claim 2 or 3, wherein: The width of the reduced line segment is between 10um and 150um.

5. The flexible printed circuit board according to claim 1, wherein Each of the signal transmission lines has a transmission portion, a reduction portion and a testing portion, the transmission portion is located in the working area, the testing portion is located in the non-working area, the reduction portion is connected between the transmission portion and the testing portion, the cutting line passes through the reduction portion, wherein the width of the reduction portion is smaller than the width of the transmission portion and the testing portion.

6. The flexible printed circuit board according to claim 5, wherein: The width of the reduced portion is between 8um and 13um.

7. The flexible printed circuit board according to claim 6, wherein: The signal transmission line has a pre-reduction portion located in the working area and connected between the reduction portion and the transmission portion, wherein the width of the pre-reduction portion is between the width of the reduction portion and the width of the transmission portion.

8. The flexible printed circuit board according to claim 7, wherein: The width of the testing portion is the same as the width of the corresponding pre-reduction portion.

9. The flexible printed circuit board according to claim 7 or 8, wherein: The width of the pre-shrink portion is between 10um and 30um.

10. The flexible printed circuit board according to claim 1, wherein The working area has a left side and a right side, a portion of the bypass line is adjacent to the left side, and another portion of the bypass line is adjacent to the right side, and the signal transmission line is located between the bypass lines.

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