Wiring structure of flexible printed circuit board

Abstract

A wiring structure for a flexible printed circuit board includes a flexible substrate, a chip, and a circuit layer. The upper surface of the flexible substrate has a chip placement area and a circuit placement area. The chip is placed in the chip placement area. A first bump and a second bump of the chip are spaced apart, and no other bump is present between the first bump and the second bump. A first inner lead bonding segment, a second inner lead bonding segment, a first redundant circuit, and a second redundant circuit of the circuit layer are located in the chip placement area. The first inner lead bonding segment is electrically connected to the first bump. The first redundant circuit is connected to the first inner lead bonding segment and is adjacent to the first bump. The second inner lead bonding segment is electrically connected to the second bump. The second redundant circuit is connected to the second inner lead bonding segment and is adjacent to the second bump.

Description

Technical Field

[0001] The present invention relates to a flexible circuit board, and in particular to a wiring structure of the flexible circuit board. Background Art

[0002] See also Figure 1 , is a top view of a conventional flexible printed circuit board 200. The flexible printed circuit board 200 comprises a flexible substrate 210, a chip 220 and a circuit layer 230. The flexible substrate 210 has an upper surface 211. The chip 220 and the circuit layer 230 are located on the upper surface 211. The circuit layer 230 is composed of a plurality of fine circuits to provide electrical connection between the chip 220 and external electronic components. Figure 2 , is a partial enlarged view of the flexible printed circuit board 200. The horizontal line marked 220 in the figure represents the edge of the chip 220. The chip 220 has a first bump 221 and a second bump 222. The circuit layer 230 has a first inner lead bonding section 231 and a second inner lead bonding section 232. The first inner lead bonding section 231 and the second inner lead bonding section 232 are electrically connected to the first bump 221 and the second bump 222, respectively. When the distance between the first bump 221 and the second bump 222 is large and there is no other bump, a blank area will appear between the two bumps 221 and 222, as shown in the figure, resulting in a lack of support. This can cause the first inner lead bonding section 231 and the second inner lead bonding section 232 to be stretched due to excessive temperature changes when the chip 220 is flip-chipped onto the flexible substrate 210, resulting in creases or fractures. Summary of the Invention

[0003] The main purpose of the present invention is to provide support by connecting the first inner lead bonding segment and the second inner lead bonding segment to prevent the first inner lead bonding segment and the second inner lead bonding segment from being creased or broken during chip flipping.

[0004] A wiring structure of a flexible circuit board of the present invention includes a flexible substrate, a chip, and a circuit layer. The flexible substrate has an upper surface, the upper surface has a chip setting area and a circuit setting area, the circuit setting area surrounds the chip setting area, the chip is set in the chip setting area, the chip has a first bump and a second bump, there is a space between the first bump and the second bump, the space is greater than 200um, and there is no other bump between the first bump and the second bump, the circuit layer has a first inner lead bonding section, a second inner lead bonding section, a first redundant circuit, a second redundant circuit, a transmission portion, and a stress release portion, the first inner lead bonding section, the second The inner lead bonding section, the first redundant circuit and the second redundant circuit are located in the chip setting area, the first inner lead bonding section is electrically connected to the first bump, the first redundant circuit is connected to the first inner lead bonding section and is adjacent to the first bump, the second inner lead bonding section is electrically connected to the second bump, the second redundant circuit is connected to the second inner lead bonding section and is adjacent to the second bump, the transmission part and the stress release part are located in the circuit setting area, the transmission part is electrically connected to the first inner lead bonding section and the second inner lead bonding section, the stress release part is connected to the transmission part, and the stress release part is located between the transmission part and the edge of the chip, wherein the stress release part is a comb-shaped structure.

[0005] Preferably, the first redundant circuit and the second redundant circuit are not connected to any bump.

[0006] Preferably, the first redundant circuit and the second redundant circuit are located between the first inner lead bonding section and the second inner lead bonding section.

[0007] Preferably, the first redundant circuit has a first line segment and a second line segment, the first line segment and the second line segment are connected to the first inner lead bonding segment, the first line segment is located between the first inner lead bonding segment and the second line segment, wherein the first inner lead bonding segment, the first line segment and the second line segment are arranged in parallel.

[0008] Preferably, the first inner lead bonding segment has a first side, the second line segment of the first redundant circuit has a second side, and the distance between the first side and the second side is less than 0.1 mm.

[0009] Preferably, the second redundant circuit has a third line segment and a fourth line segment, the third line segment and the fourth line segment are connected to the second inner lead bonding segment, the third line segment is located between the second inner lead bonding segment and the fourth line segment, wherein the second inner lead bonding segment, the third line segment and the fourth line segment are arranged in parallel.

[0010] Preferably, the stress release portion has a plurality of finger-shaped circuits, and a pitch is provided between each of the finger-shaped circuits, and the pitch is not less than 16 μm.

[0011] Preferably, the finger circuits do not extend into the chip arrangement area.

[0012] Preferably, the first redundant circuit and the second redundant circuit have a first width, the first inner lead bonding section and the second inner lead bonding section have a second width, and the first width is 0.5 to 3 times the second width.

[0013] The present invention provides support for the first inner lead bonding section and the second inner lead bonding section by means of the first redundant circuit and the second redundant circuit, and reduces the influence of the transmission section by means of the stress release section, thereby preventing the first inner lead bonding section and the second inner lead bonding section from being creased or broken during the flip chip process, thereby improving the process qualification rate of the flexible printed circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : A top view of a conventional flexible printed circuit board.

[0015] Figure 2 : A partial enlarged view of the conventional flexible printed circuit board.

[0016] Figure 3 : An auxiliary diagram of a flexible printed circuit board according to one embodiment of the present invention.

[0017] Figure 4 : A partially enlarged view of the flexible printed circuit board according to one embodiment of the present invention.

[0018]

Main component symbol description

[0019] 100: Flexible circuit board 110: Flexible substrate

[0020] 111: Upper surface 111a: Chip setting area

[0021] 111b: Line setting area 120: Chip

[0022] 121: first bump 122: second bump

[0023] 130: Circuit layer 131: First inner lead bonding section

[0024] 132: Second inner lead bonding section 133: First redundant circuit

[0025] 133a: first line segment 133b: second line segment

[0026] 134: second redundant line 134a: third line segment

[0027] 134b: fourth line segment 135: transmission section

[0028] 136: stress release portion 136a: finger-shaped circuit

[0029] S: interval P: spacing

[0030] S1: first side S2: second side

[0031] D:DistanceE:Edge

[0032] 200: Flexible circuit board 210: Flexible substrate

[0033] 220: Chip 221: First bump

[0034] 222: second bump 230: circuit layer

[0035] 231: first inner lead bonding section 232: second inner lead bonding section DETAILED DESCRIPTION

[0036] See also Figure 3 , which is a top view of a flexible printed circuit board 100 according to an embodiment of the present invention. The flexible printed circuit board 100 includes a flexible substrate 110, a chip 120, and a circuit layer 130. The chip 120 and the circuit layer 130 are disposed on the upper surface 111 of the chip 120. The area of ​​the upper surface 111 where the chip 120 is disposed is defined as a chip placement area 111a, and the remaining area is defined as a circuit placement area 111b. The circuit placement area 111b surrounds the chip placement area 111a.

[0037] See also Figure 4 The chip 120 is disposed on the flexible substrate 110 by a flip-chip process using thermal compression and eutectic bonding with the circuit layer 130. The chip 120 has a first bump 121 and a second bump 122. A space S is provided between the first bump 121 and the second bump 122. The space S is greater than 200 μm, and there is no other bump between the first bump 121 and the second bump 122.

[0038] The circuit layer 130 is formed by patterning and etching a copper layer laminated or electroplated on the flexible substrate 110. In this embodiment, the circuit layer 130 includes a first inner lead bond segment 131, a second inner lead bond segment 132, a first redundant circuit 133, and a second redundant circuit 134. The first inner lead bond segment 131, the second inner lead bond segment 132, the first redundant circuit 133, and the second redundant circuit 134 are located in the chip arrangement area 111a. The first inner lead bond segment 131 is electrically connected to the first bump 121. The first redundant circuit 133 is connected to the first inner lead bond segment 131 and is adjacent to the first bump 121. The second inner lead bond segment 132 is electrically connected to the second bump 122. The second redundant circuit 134 is connected to the second inner lead bond segment 132 and is adjacent to the second bump 122. Preferably, the first redundant circuit 133 and the second redundant circuit 134 are located between the first inner lead bonding section 131 and the second inner lead bonding section 132 to fill the gap between the first inner lead bonding section 131 and the second inner lead bonding section 132 .

[0039] See also Figure 4 Since the first redundant circuit 133 and the second redundant circuit 134 are not connected to the bumps, they are less likely to be affected by the thermal compression process of the flip chip, thereby reducing the deformation of the flexible substrate 110 near the first inner lead bonding section 131 and the second inner lead bonding section 132, thereby preventing the first inner lead bonding section 131 and the second inner lead bonding section 132 from being creased or broken during the flip chip process.

[0040] In this embodiment, the first redundant circuit 133 has a first line segment 133a and a second line segment 133b. The first line segment 133a and the second line segment 133b are connected to the first inner lead bonding segment 131. The first line segment 133a is located between the first inner lead bonding segment 131 and the second line segment 133b. The first inner lead bonding segment 131, the first line segment 133a, and the second line segment 133b are arranged in parallel. The first inner lead bonding segment 131 has a first side S1, and the second line segment 133b of the first redundant circuit 133 has a second side S2. Preferably, a distance D between the first side S1 and the second side S2 is less than 0.1 mm, so that the first redundant circuit 133 is adjacent to the first inner lead bonding segment 131 and has a better support effect. The second redundant circuit 134 includes a third line segment 134a and a fourth line segment 134b. The third line segment 134a and the fourth line segment 134b connect to the second inner lead bonding segment 132. The third line segment 134a is located between the second inner lead bonding segment 132 and the fourth line segment 134b. The second inner lead bonding segment 132, the third line segment 134a, and the fourth line segment 134b are arranged in parallel. The distance between the side of the second inner lead bonding segment 132 and the side of the fourth line segment 134b is also less than 0.1 mm. This ensures that the second redundant circuit 134 is adjacent to the second inner lead bonding segment 132 and has a better support effect.

[0041] In addition, the first redundant circuit 133 and the second redundant circuit 134 have a first width W1, and the first inner lead bonding section 131 and the second inner lead bonding section 132 have a second width W2. The first width W1 is 0.5 to 3 times the second width W2, which can further increase the supporting force of the first redundant circuit 133 and the second redundant circuit 134.

[0042] See also Figure 4 In this embodiment, the first redundant circuit 133 and the second redundant circuit 134 respectively provide support to the first inner lead bonding section 131 and the second inner lead bonding section 132. This can resist the pulling of the first inner lead bonding section 131 and the second inner lead bonding section 132 when the chip 120 is flip-chipped on the flexible substrate 110, thereby preventing the first inner lead bonding section 131 and the second inner lead bonding section 132 from being creased or broken.

[0043] See also Figure 4The flexible printed circuit board 100 of this embodiment has a transmission portion 135 and a stress relief portion 136. The transmission portion 135 and the stress relief portion 136 are located in the circuit arrangement area 111b. The transmission portion 135 electrically connects the first inner lead bonding segment 131 and the second inner lead bonding segment 132. The stress relief portion 136 connects the transmission portion 135 and is located between the transmission portion 135 and the edge E of the chip 120. The stress relief portion 136 has a comb-like structure. In this embodiment, the stress relief portion 136 further relieves stress accumulated in the first inner lead bonding segment 131 and the second inner lead bonding segment 132, thereby preventing stress concentration on the first inner lead bonding segment 131 and the second inner lead bonding segment 132, which could lead to fracture.

[0044] In this embodiment, the stress relief portion 136 includes a plurality of finger-shaped circuits 136 a. Each finger-shaped circuit 136 a has a pitch P between them that is no less than 16 μm. This pitch P reduces the copper layer area adjacent to the edge E of the chip 120, thereby relieving stress. Preferably, the finger-shaped circuits 136 a do not extend into the chip placement area 111 a to avoid affecting the flow of underfill between the chip 120 and the upper surface 111.

[0045] The present invention provides support for the first inner lead bonding section 131 and the second inner lead bonding section 132 by means of the first redundant circuit 133 and the second redundant circuit 134, and reduces the influence of the transmission section 135 by means of the stress release portion 136, thereby preventing the first inner lead bonding section 131 and the second inner lead bonding section 132 from being creased or broken during the flip chip process, thereby improving the process yield of the flexible printed circuit board 100.

[0046] 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 wiring structure of a flexible printed circuit board, characterized in that: Include: The flexible substrate has an upper surface, wherein the upper surface has a chip setting area and a circuit setting area, and the circuit setting area surrounds the chip setting area; A chip is disposed in the chip arrangement area, the chip having a first bump and a second bump, a gap between the first bump and the second bump being greater than 200 μm, and no other bump being disposed between the first bump and the second bump; and A circuit layer comprising a first inner lead bonding section, a second inner lead bonding section, a first redundant circuit, a second redundant circuit, a transmission portion, and a stress release portion, wherein the first inner lead bonding section, the second inner lead bonding section, the first redundant circuit, and the second redundant circuit are located in the chip arrangement area, the first inner lead bonding section is electrically connected to the first bump, the first redundant circuit is connected to the first inner lead bonding section and is adjacent to the first bump, the second inner lead bonding section is electrically connected to the second bump, the second redundant circuit is connected to the second inner lead bonding section and is adjacent to the second bump, the transmission portion and the stress release portion are located in the circuit arrangement area, the transmission portion is electrically connected to the first inner lead bonding section and the second inner lead bonding section, the stress release portion is connected to the transmission portion, and the stress release portion is located between the transmission portion and an edge of the chip, wherein the stress release portion is a comb-shaped structure; The first redundant circuit and the second redundant circuit are located between the first inner lead bonding section and the second inner lead bonding section.

2. The wiring structure of the flexible printed circuit board according to claim 1, wherein: The first redundant circuit and the second redundant circuit are not connected to any bump.

3. The wiring structure of the flexible printed circuit board according to claim 1, wherein: The first redundant circuit has a first line segment and a second line segment, the first line segment and the second line segment are connected to the first inner lead bonding segment, the first line segment is located between the first inner lead bonding segment and the second line segment, wherein the first inner lead bonding segment, the first line segment and the second line segment are arranged in parallel.

4. The wiring structure of the flexible printed circuit board according to claim 3, wherein: The first inner lead bonding segment has a first side, the second segment of the first redundant circuit has a second side, and a distance between the first side and the second side is less than 0.1 mm.

5. The wiring structure of the flexible printed circuit board according to claim 3 or 4, characterized in that: The second redundant circuit has a third line segment and a fourth line segment, the third line segment and the fourth line segment are connected to the second inner lead bonding segment, the third line segment is located between the second inner lead bonding segment and the fourth line segment, wherein the second inner lead bonding segment, the third line segment and the fourth line segment are arranged in parallel.

6. The wiring structure of the flexible printed circuit board according to claim 1, wherein: The stress release portion has a plurality of finger-shaped circuits, and a spacing is provided between each of the finger-shaped circuits, and the spacing is not less than 16 μm.

7. The wiring structure of the flexible printed circuit board according to claim 6, wherein: The finger circuits do not extend into the chip arrangement area.

8. The wiring structure of the flexible printed circuit board according to claim 1, wherein: The first redundant circuit and the second redundant circuit have a first width, the first inner lead bonding section and the second inner lead bonding section have a second width, and the first width is 0.5 to 3 times the second width.

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