Flexible printed circuit and printed circuit board soldered structure

1. Technical Field

The present invention relates to flexible printed circuit and printed circuit board soldered structure and, more particularly, to a flexible printed circuit and printed circuit board soldered structure for use with high-frequency transmission technology.

2. Description of the Prior Art

In the field of optical communication, data transmission always has a trend toward high speeds. However, high-speed signal transmission is confronted with ever-changing issues. To perform high-speed signal transmission, it is necessary to take account of the integrity of high-frequency signals in the course of signal transmission. When designing a high-frequency circuit, it is necessary to give considerations to the measures taken to reduce signal attenuation with a view to ensuring the integration and matching of characteristic impedance. Therefore, impedance matching design must give considerations to not only adjustment of line width and line spacing but also through hole design. Therefore, persons skilled in the art are eager to solve a problem: how to redesign an appropriate high-frequency package framework which meets the demand for high-frequency circuits in high-speed networks.

The process of soldering a flexible printed circuit to a printed circuit board in the course of electronic product packaging usually requires via holes to be disposed at the end of the flexible printed circuit, so that the flexible printed circuit is connected to lower signal lines through the via holes to solder the lower signal lines to the printed circuit board signal lines from above, thereby effectuating electrical interconnects. However, under a high-frequency transmission framework, the via holes compromise the characteristics and integrity of high-frequency signals, thereby further reducing transmission efficiency.

It is an objective of the present invention to provide a flexible printed circuit and printed circuit board soldered structure which dispenses with the need to provide any through hole on signal lines, so as not to reduce high-frequency signal transmission efficiency.

To solve the foregoing problem, the present invention is to provide a flexible printed circuit and printed circuit board soldered structure, comprising a flexible printed circuit and a printed circuit board. The flexible printed circuit comprises a soft board body, with a first signal pad region disposed on a side of the soft board body, and a first grounding pad region disposed on an opposing side of the soft board body. The first signal pad region comprises a pair of first differential signal transmission lines and two first grounding soldering portions flanking the pair of the first differential signal transmission lines. The first differential signal transmission lines have intact surfaces dispensing with any through hole, wherein ends of the first differential signal transmission lines are flush with an edge of the soft board body. A through hole is disposed on the first grounding soldering portion to electrically connect the first grounding soldering portion and the first grounding pad region, an insulating region is disposed on the first grounding pad region and corresponding in position to the first differential signal transmission lines on a side of the soft board body, and the insulating region extends inward from an edge of the soft board body. The printed circuit board comprises a substrate body, a second signal pad region disposed on a side of the substrate body, and a second grounding pad region disposed on an opposing side of the substrate body. The second signal pad region comprises a pair of second differential signal transmission lines and two second grounding soldering portions flanking the pair of second differential signal transmission lines. The second differential signal transmission lines have intact surfaces dispensing with any through hole, with a through hole disposed on the second grounding soldering portions to electrically connect the second grounding soldering portions and the second grounding pad region. Therein, the flexible printed circuit is disposed on the printed circuit board, the insulating region of the first grounding pad region is disposed above the second differential signal transmission lines to stay away from the second differential signal transmission lines and thus preclude having a short cut with the second differential signal transmission lines, and the ends of the first differential signal transmission lines are soldered to the second differential signal transmission lines from above by a solder to effectuate electrical connection.

Further, a half hole is disposed at the ends of the first differential signal transmission lines to hold a solder.

Further, an end of the first grounding soldering portion is flush with an edge of the soft board body, and the end of the first grounding soldering portion is soldered to the second grounding soldering portions from above by a solder to effectuate electrical connection.

Further, a half hole is disposed at the end of the first grounding soldering portion to hold the solder.

Further, a level sign is disposed on the substrate body of the printed circuit board and beside the second differential signal transmission lines to serve as soldering reference.

Further, a distance between each said level sign and an end of a corresponding one of the second differential signal transmission lines is shorter than or equal to an extension distance by which the insulating region extends inward.

Another objective of the present invention is to provide a flexible printed circuit and printed circuit board soldered structure, comprising a flexible printed circuit and a printed circuit board. The flexible printed circuit comprises a soft board body, with a first signal pad region disposed on a side of the soft board body, and a first grounding pad region disposed on an opposing side of the soft board body. The first signal pad region comprises a first signal transmission line and two first grounding soldering portions flanking the first signal transmission line. The first signal transmission line has an intact surface dispensing with any through hole, wherein an end of the first signal transmission lines is flush with an edge of the soft board body. A through hole is disposed on the first grounding soldering portion to electrically connect the first grounding soldering portion and the first grounding pad region, and an insulating region is disposed on the first grounding pad region and corresponding in position to the first signal transmission line on a side of the soft board body, and the insulating region extends inward from an edge of the soft board body. The printed circuit board comprises a substrate body, a second signal pad region disposed on a side of the substrate body, and a second grounding pad region disposed on an opposing side of the substrate body. The second signal pad region comprises a second signal transmission line and two second grounding soldering portions flanking the second signal transmission line. The second signal transmission line has an intact surface dispensing with any through hole, with a through hole disposed on the second grounding soldering portions to electrically connect the second grounding soldering portions and the second grounding pad region. Therein, the flexible printed circuit is disposed on the printed circuit board, the insulating region of the first grounding pad region is disposed above the second signal transmission lines to stay away from the second signal transmission lines and thus preclude developing a short circuit together with the second signal transmission lines, and the end of the first signal transmission lines is soldered to the second signal transmission line from above by a solder to effectuate electrical connection.

Further, a half hole is disposed at the end of the first signal transmission lines to hold a solder.

Further, an end of the first grounding soldering portion is flush with an edge of the soft board body, and the end of the first grounding soldering portion is soldered to the second grounding soldering portions from above by a solder to effectuate electrical connection.

Further, a half hole is disposed at the end of the first grounding soldering portion to hold the solder.

Further, a level sign is disposed on the substrate body of the printed circuit board and beside the second signal transmission line to serve as soldering reference.

Further, a distance between the level sign and an end of the second signal transmission line is shorter than or equal to an extension distance by which the insulating region extends inward.

Therefore, the present invention has the following advantages over the prior art:

1. The flexible printed circuit and printed circuit board soldered structure of the present invention not only displays satisfactory high-frequency transmission characteristics, but also dispenses with the need to provide any through hole at the positions of the soldering of signal transmission lines, thereby enhancing the integrity of high-frequency signals during signal transmission.

2. The soldered structure of the present invention is so simple that it is almost the same as the soldering techniques disclosed in the prior art.

FIG. 1 is a perspective view of the first embodiment according to the present invention;

FIG. 2 is an exploded view ( 1 ) of the first embodiment according to the present invention;

FIG. 3 is an exploded view ( 2 ) of the first embodiment according to the present invention;

FIG. 4 is a cross-sectional view of the first embodiment according to the present invention;

FIG. 5 is a top view of the first embodiment according to the present invention;

FIG. 6 is a partial transparent schematic view of the first embodiment according to the present invention;

FIG. 7 is a perspective view of the second embodiment according to the present invention;

FIG. 8 is an exploded view ( 1 ) of the second embodiment according to the present invention;

FIG. 9 is an exploded view ( 2 ) of the second embodiment according to the present invention;

FIG. 10 is a cross-sectional view of the second embodiment according to the present invention;

FIG. 11 is a top view of the second embodiment according to the present invention; and

FIG. 12 is a partial transparent schematic view of the second embodiment according to the present invention.

The technical features and technical solutions of the present invention are hereunder described with reference to accompanying drawings. For illustrative sake, the accompanying drawings are not drawn to scale. The accompanying drawings and the scales thereof are not restrictive of the scope of the present invention.

FIG. 1 , FIG. 2 , and FIG. 3 are a perspective view, an exploded view ( 1 ), and an exploded view ( 2 ) of the first embodiment according to the present invention, respectively. The present invention is described below with reference to the aforesaid diagrams.

The present invention provides a flexible printed circuit and printed circuit board soldered structure 100 which comprises a flexible printed circuit 110 (FPC) and a printed circuit board 120 (PCB).

The flexible printed circuit 110 is tri-layered and comprises, from bottom to top a protective layer 115 , a soft board body 111 , and a protective layer 112 disposed above the soft board body 111 . A first signal pad region 113 is disposed on one side of the soft board body 111 . A first grounding pad region 114 is disposed on the opposing side of the soft board body 111 . Both the first signal pad region 113 and the first grounding pad region 114 are conductive copper foils disposed on the soft board body 111 by wiring layout. Further, the first signal pad region 113 comprises a pair of first differential signal transmission lines 113 A and two first grounding soldering portions 113 B which flank the pair of first differential signal transmission lines 113 A.

High-frequency signals passing through a through hole are likely to produce parasitic capacitance and thus compromise signal integrity and high-frequency characteristics while high-frequency signal transmission is taking place; hence, the first differential signal transmission lines 113 A have intact surfaces which dispense with any through hole. Furthermore, the ends of the first differential signal transmission lines 113 A are flush with the edge of the soft board body 111 so that the ends of the first differential signal transmission lines 113 A can be soldered to second differential signal transmission lines 123 A of the printed circuit board 120 below. In a preferred embodiment, a half hole 1131 A for holding a solder is disposed at each of the ends of the first differential signal transmission lines 113 A so that the ends of the first differential signal transmission lines 113 A can be covered with a solder FA (as shown in FIG. 4 ) and thus soldered to the second differential signal transmission lines 123 A of the printed circuit board 120 below.

FIG. 4 and FIG. 5 are a cross-sectional view and a top view of the first embodiment according to the present invention, respectively. The present invention is described below with reference to the aforesaid diagrams.

A through hole VH 1 is disposed on the first grounding soldering portion 113 B to electrically connect the first grounding soldering portion 113 B and the first grounding pad region 114 . The edge of the first grounding soldering portion 113 B and the edge of the soft board body 111 are flush with each other and thus can be soldered together from above the soft board body 111 and a second grounding soldering portion 123 B of the printed circuit board 120 below. In a preferred embodiment, a half hole 1131 B is disposed at the end of the first grounding soldering portion 113 B to hold the solder FA; hence, the end of the first grounding soldering portion 113 B is covered with the solder FA and thus can be soldered to the second grounding soldering portion 123 B of the printed circuit board 120 below. The through hole VH 1 and the half hole 1131 B are of any shapes, such as round and square, and the present invention is not limited thereto. The half hole 1131 A, 1131 B are optional. In another preferred embodiment, the half hole 1131 A, 1131 B are dispensed with, and the solder is attached to the surface of a metal film to effectuate electrical interconnects. In another preferred embodiment, the first grounding soldering portions 113 B flank and extend along the first differential signal transmission lines 113 A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the first differential signal transmission lines 113 A, but the present invention is not limited thereto.

An insulating region A 1 is disposed on the first grounding pad region 114 and corresponds in position to the first differential signal transmission lines 113 A on the soft board body 111 . The insulating region A 1 extends inward from an edge of the soft board body 111 . The insulating region A 1 is disposed right below the first differential signal transmission lines 113 A so that the first grounding pad region 114 does not come into contact with the second differential signal transmission lines 123 A on the printed circuit board 120 when the flexible printed circuit 110 is disposed on the printed circuit board 120 , so as not to develop any short circuit. The insulating region A 1 is a naked region (i.e., the soft board body 111 per se), which dispenses with any copper foil, formed as a result of inward extension of the first grounding pad region 114 . In another preferred embodiment, the insulating region A 1 is an insulating layer disposed on the first grounding pad region 114 , but the present invention is not limited thereto. In another preferred embodiment, the protective layer 115 below the soft board body 111 extends and covers the first grounding pad region 114 from below so that only metal pads with the through holes VH 1 are exposed from two sides of the first grounding pad region 114 to prevent the first grounding pad region 114 from coming into contact with the ends of the second differential signal transmission lines 123 A, so as not to develop any short circuit.

Referring to FIG. 1 , FIG. 2 , and FIG. 3 , the printed circuit board 120 is tri-layered and comprises, from bottom to top, a protective layer 125 , a substrate body 121 , and a protective layer 122 disposed above the substrate body 121 . A second signal pad region 123 is disposed on one side of the substrate body 121 . A second grounding pad region 124 is disposed on the opposing side of the substrate body 121 . Both the second signal pad region 123 and the second grounding pad region 124 are conductive copper foils disposed on the substrate body 121 by wiring layout. The second signal pad region 123 comprises a pair of second differential signal transmission lines 123 A and two second grounding soldering portions 123 B which flank the pair of second differential signal transmission lines 123 A.

To prevent through holes from compromising high-frequency characteristics of high-frequency signals, the surfaces of the second differential signal transmission lines 123 A are intact and dispense with any through hole to maintain the integrity of high-frequency signals being transmitted along the second differential signal transmission lines 123 A. The end of the printed circuit board 120 lacks the protective layer 122 so as to expose the second differential signal transmission lines 123 A and the second grounding soldering portions 123 B for use in soldering.

Referring to FIG. 4 , a through hole VH 2 is disposed on the second grounding soldering portions 123 B to electrically connect the second grounding soldering portions 123 B and the second grounding pad region 124 . In another preferred embodiment, the second grounding soldering portions 123 B flank and extend along the second differential signal transmission lines 123 A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the second differential signal transmission lines 123 A, but the present invention is not limited thereto. The through hole VH 2 is of any shapes, such as round and square, and the present invention is not limited thereto.

FIG. 6 is a partial transparent schematic view of the flexible printed circuit and printed circuit board soldered structure of the present invention. The present invention is described below with reference to the aforesaid diagram.

The flexible printed circuit 110 is disposed on the printed circuit board 120 . The insulating region A 1 of the first grounding pad region 114 is disposed above the second differential signal transmission lines 123 A to stay away from the second differential signal transmission lines 123 A and thus preclude developing a short circuit together with the second differential signal transmission lines 123 A. The ends of the first differential signal transmission lines 113 A are soldered to the second differential signal transmission lines 123 A by the solder FA to effectuate electrical connection.

To render it easy for assembly workers or automated machines to perform a soldering operation and reduce the likelihood soldering failures, a level sign S 1 is disposed on the substrate body 121 of the printed circuit board 120 and beside the second differential signal transmission lines 123 A to serve as reference for use in the soldering operation. The level signs S 1 enable the assembly workers or automated machines to confirm the distance between the insulating region A 1 below the flexible printed circuit 110 and the ends of the second differential signal transmission lines 123 A. The distance between each level sign S 1 and the end of a corresponding one of the second differential signal transmission lines 123 A is preferably shorter than or equal to an extension distance D 1 by which the insulating region A 1 extends inward.

The second embodiment of the present invention is described below. The second embodiment differs from the first embodiment mainly in the quantity of the signal transmission lines.

FIG. 7 , FIG. 8 , and FIG. 9 are a perspective view, an exploded view ( 1 ), and an exploded view ( 2 ) of the second embodiment according to the present invention, respectively. The present invention is described below with reference to the aforesaid diagrams.

The second embodiment provides a flexible printed circuit and printed circuit board soldered structure 200 which comprises a flexible printed circuit 210 (FPC) and a printed circuit board 220 (PCB).

The flexible printed circuit 210 is tri-layered and comprises, from bottom to top, a protective layer 215 , a soft board body 211 , and a protective layer 212 disposed above the soft board body 211 . A first signal pad region 213 is disposed on one side of the soft board body 211 . A first grounding pad region 214 is disposed on the opposing side of the soft board body 211 . Both the first signal pad region 213 and the first grounding pad region 214 are conductive copper foils disposed on the soft board body 211 by wiring layout. Therein, the first signal pad region comprises a first signal transmission line 213 A and two first grounding soldering portions 213 B which flank the first signal transmission line 213 A.

High-frequency signals passing through a through hole are likely to produce parasitic capacitance and thus compromise signal integrity and high-frequency characteristics while high-frequency signal transmission is taking place; hence, the first signal transmission line 213 A have an intact surface which dispenses with any through hole. Furthermore, the end of the first signal transmission line 213 A is flush with the edge of the soft board body 211 so that the end of the first signal transmission line 213 A can be soldered to a second signal transmission line 223 A of the printed circuit board 220 below. In a preferred embodiment, a half hole 2131 A for holding a solder FB (shown in FIG. 10 ) is disposed at the end of the first signal transmission line 213 A so that the end of the first signal transmission line 213 A can be covered with the solder FB and thus soldered to the second signal transmission line 223 A of the printed circuit board 220 below.

FIG. 10 and FIG. 11 are a cross-sectional view and a top view of the second embodiment according to the present invention, respectively. The present invention is described below with reference to the aforesaid diagrams.

A through hole VH 3 is disposed on the first grounding soldering portion 213 B to electrically connect the first grounding soldering portion 213 B and the first grounding pad region 214 . The edge of the first grounding soldering portion 213 B and the edge of the soft board body 211 are flush with each other and thus can be soldered together from above the soft board body 211 and a second grounding soldering portion 223 B of the printed circuit board 220 below. In a preferred embodiment, a half hole 2131 B for holding the solder FB is disposed at the end of the first grounding soldering portion 213 B so that the end of the first grounding soldering portion 213 B can be covered with the solder FB and thus soldered to the second grounding soldering portion 223 B of the printed circuit board 220 below. The through hole VH 3 and the half hole 2131 B are of any shapes, such as round and square, and the present invention is not limited thereto. The half hole 2131 A, 2131 B are optional. In another preferred embodiment, the half hole 2131 A, 2131 B are dispensed with, and the solder is attached to the surface of a metal film to effectuate electrical interconnects. In another preferred embodiment, the first grounding soldering portions 213 B flank and extend along the first signal transmission line 213 A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the first signal transmission line 213 A, but the present invention is not limited thereto.

An insulating region A 2 is disposed on the first grounding pad region 214 and corresponds in position to the first signal transmission line 213 A on the soft board body 211 . The insulating region A 2 extends inward from an edge of the soft board body 211 . Specifically, the insulating region A 2 is disposed right below the first signal transmission line 213 A so that the first grounding pad region 214 does not come into contact with the second signal transmission line 223 A on the printed circuit board 220 when the flexible printed circuit 210 is disposed on the printed circuit board 220 , so as not to develop any short circuit. The insulating region A 2 is a naked region (i.e., the soft board body 211 per se), which dispenses with any copper foil, formed as a result of inward extension of the first grounding pad region 214 . In another preferred embodiment, the insulating region A 2 is an insulating layer disposed on the first grounding pad region 214 , but the present invention is not limited thereto. In another preferred embodiment, the protective layer 215 below the soft board body 211 extends and covers the first grounding pad region 214 from below so that only metal pads with the through hole VH 3 are exposed from two sides of the first grounding pad region 214 to prevent the first grounding pad region 214 from coming into contact with the end of the second signal transmission line 223 A, so as not to develop any short circuit.

Referring to FIG. 7 , FIG. 8 , and FIG. 9 , the printed circuit board 220 is tri-layered and comprises, from bottom to top, a protective layer 225 , a substrate body 221 , and a protective layer 222 disposed above the substrate body 221 . A second signal pad region 223 is disposed on one side of the substrate body 221 . A second grounding pad region 224 is disposed on the opposing side of the substrate body 221 . Both the second signal pad region 223 and the second grounding pad region 224 are conductive copper foils disposed on the substrate body 221 by wiring layout. The second signal pad region 223 comprises a second signal transmission line 223 A and two second grounding soldering portions 223 B which flank the second signal transmission line 223 A.

To prevent through holes from compromising high-frequency characteristics of high-frequency signals, the surface of the second signal transmission line 223 A is intact and dispenses with any through hole to maintain the integrity of high-frequency signals being transmitted along the second signal transmission line 223 A. The end of the printed circuit board 220 lacks the protective layer 222 so as to expose the second signal transmission line 223 A and the second grounding soldering portions 223 B for use in soldering.

Referring to FIG. 10 , a through hole VH 4 is disposed on the second grounding soldering portion 223 B to electrically connect the second grounding soldering portion 223 B and the second grounding pad region 224 . In another preferred embodiment, the second grounding soldering portions 223 B flank and extend along the second signal transmission line 223 A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the second signal transmission line 223 A, but the present invention is not limited thereto. The through hole VH 2 is of any shapes, such as round and square, and the present invention is not limited thereto.

FIG. 12 is a partial transparent schematic view of the second embodiment according to the present invention. The present invention is described below with reference to the aforesaid diagram.

The flexible printed circuit 210 is disposed on the printed circuit board 220 . The insulating region A 2 of the first grounding pad region 214 is disposed above the second signal transmission line 223 A to stay away from the second signal transmission line 223 A and thus preclude developing a short circuit together with the second signal transmission line 223 A. The end of the first signal transmission line 213 A is soldered to the second signal transmission line 223 A by the solder FB to effectuate electrical connection.

To render it easy for assembly workers or automated machines to perform a soldering operation and reduce the likelihood soldering failures, a level sign S 2 is disposed on the substrate body 221 of the printed circuit board 220 and beside the second signal transmission line 223 A to serve as reference for use in the soldering operation. The level signs S 2 enable the assembly workers or automated machines to confirm the distance between the insulating region A 2 below the flexible printed circuit 210 and the end of the second signal transmission line 223 A. The distance between level sign S 2 and the end of the second signal transmission line 223 A is preferably shorter than or equal to an extension distance D 2 by which the insulating region A 2 extends inward.

In conclusion, a flexible printed circuit and a printed circuit board soldered structure of the present invention not only displays satisfactory high-frequency transmission characteristics, but also enhances the integrity of high-frequency signals during signal transmission owing to dispensing with the need to provide any through hole at the positions of the soldering of signal transmission lines. Furthermore, the soldered structure of the present invention is so simple that it is almost the same as the soldering techniques disclosed in the prior art.

While example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of example embodiments of the present application, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.