Flexible printed circuit and printed circuit board soldered structure

A flexible printed circuit and printed circuit board soldered structure is provided. The structure includes signal transmission lines which dispense with any through hole, thereby enhancing integrity of high-frequency signals. The special design of the signal line structure of the flexible printed circuit and the printed circuit board together provides a satisfactory high-frequency signal transmission interface and enables a soldering technique which is highly practicable and compatible with the flexible printed circuit and printed circuit board soldered structure.

BACKGROUND OF THE INVENTION

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.

SUMMARY OF THE INVENTION

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.

DETAILED DESCRIPTION OF THE 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, andFIG. 3are 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 structure100which comprises a flexible printed circuit110(FPC) and a printed circuit board120(PCB).

The flexible printed circuit110is tri-layered and comprises, from bottom to top a protective layer115, a soft board body111, and a protective layer112disposed above the soft board body111. A first signal pad region113is disposed on one side of the soft board body111. A first grounding pad region114is disposed on the opposing side of the soft board body111. Both the first signal pad region113and the first grounding pad region114are conductive copper foils disposed on the soft board body111by wiring layout. Further, the first signal pad region113comprises a pair of first differential signal transmission lines113A and two first grounding soldering portions113B which flank the pair of first differential signal transmission lines113A.

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 lines113A have intact surfaces which dispense with any through hole. Furthermore, the ends of the first differential signal transmission lines113A are flush with the edge of the soft board body111so that the ends of the first differential signal transmission lines113A can be soldered to second differential signal transmission lines123A of the printed circuit board120below. In a preferred embodiment, a half hole1131A for holding a solder is disposed at each of the ends of the first differential signal transmission lines113A so that the ends of the first differential signal transmission lines113A can be covered with a solder FA (as shown inFIG. 4) and thus soldered to the second differential signal transmission lines123A of the printed circuit board120below.

FIG. 4andFIG. 5are 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 VH1is disposed on the first grounding soldering portion113B to electrically connect the first grounding soldering portion113B and the first grounding pad region114. The edge of the first grounding soldering portion113B and the edge of the soft board body111are flush with each other and thus can be soldered together from above the soft board body111and a second grounding soldering portion123B of the printed circuit board120below. In a preferred embodiment, a half hole1131B is disposed at the end of the first grounding soldering portion113B to hold the solder FA; hence, the end of the first grounding soldering portion113B is covered with the solder FA and thus can be soldered to the second grounding soldering portion123B of the printed circuit board120below. The through hole VH1and the half hole1131B are of any shapes, such as round and square, and the present invention is not limited thereto. The half hole1131A,1131B are optional. In another preferred embodiment, the half hole1131A,1131B 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 portions113B flank and extend along the first differential signal transmission lines113A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the first differential signal transmission lines113A, but the present invention is not limited thereto.

An insulating region A1is disposed on the first grounding pad region114and corresponds in position to the first differential signal transmission lines113A on the soft board body111. The insulating region A1extends inward from an edge of the soft board body111. The insulating region A1is disposed right below the first differential signal transmission lines113A so that the first grounding pad region114does not come into contact with the second differential signal transmission lines123A on the printed circuit board120when the flexible printed circuit110is disposed on the printed circuit board120, so as not to develop any short circuit. The insulating region A1is a naked region (i.e., the soft board body111per se), which dispenses with any copper foil, formed as a result of inward extension of the first grounding pad region114. In another preferred embodiment, the insulating region A1is an insulating layer disposed on the first grounding pad region114, but the present invention is not limited thereto. In another preferred embodiment, the protective layer115below the soft board body111extends and covers the first grounding pad region114from below so that only metal pads with the through holes VH1are exposed from two sides of the first grounding pad region114to prevent the first grounding pad region114from coming into contact with the ends of the second differential signal transmission lines123A, so as not to develop any short circuit.

Referring toFIG. 1,FIG. 2, andFIG. 3, the printed circuit board120is tri-layered and comprises, from bottom to top, a protective layer125, a substrate body121, and a protective layer122disposed above the substrate body121. A second signal pad region123is disposed on one side of the substrate body121. A second grounding pad region124is disposed on the opposing side of the substrate body121. Both the second signal pad region123and the second grounding pad region124are conductive copper foils disposed on the substrate body121by wiring layout. The second signal pad region123comprises a pair of second differential signal transmission lines123A and two second grounding soldering portions123B which flank the pair of second differential signal transmission lines123A.

To prevent through holes from compromising high-frequency characteristics of high-frequency signals, the surfaces of the second differential signal transmission lines123A are intact and dispense with any through hole to maintain the integrity of high-frequency signals being transmitted along the second differential signal transmission lines123A. The end of the printed circuit board120lacks the protective layer122so as to expose the second differential signal transmission lines123A and the second grounding soldering portions123B for use in soldering.

Referring toFIG. 4, a through hole VH2is disposed on the second grounding soldering portions123B to electrically connect the second grounding soldering portions123B and the second grounding pad region124. In another preferred embodiment, the second grounding soldering portions123B flank and extend along the second differential signal transmission lines123A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the second differential signal transmission lines123A, but the present invention is not limited thereto. The through hole VH2is of any shapes, such as round and square, and the present invention is not limited thereto.

FIG. 6is 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 circuit110is disposed on the printed circuit board120. The insulating region A1of the first grounding pad region114is disposed above the second differential signal transmission lines123A to stay away from the second differential signal transmission lines123A and thus preclude developing a short circuit together with the second differential signal transmission lines123A. The ends of the first differential signal transmission lines113A are soldered to the second differential signal transmission lines123A 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 S1is disposed on the substrate body121of the printed circuit board120and beside the second differential signal transmission lines123A to serve as reference for use in the soldering operation. The level signs S1enable the assembly workers or automated machines to confirm the distance between the insulating region A1below the flexible printed circuit110and the ends of the second differential signal transmission lines123A. The distance between each level sign S1and the end of a corresponding one of the second differential signal transmission lines123A is preferably shorter than or equal to an extension distance D1by which the insulating region A1extends 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, andFIG. 9are 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 structure200which comprises a flexible printed circuit210(FPC) and a printed circuit board220(PCB).

The flexible printed circuit210is tri-layered and comprises, from bottom to top, a protective layer215, a soft board body211, and a protective layer212disposed above the soft board body211. A first signal pad region213is disposed on one side of the soft board body211. A first grounding pad region214is disposed on the opposing side of the soft board body211. Both the first signal pad region213and the first grounding pad region214are conductive copper foils disposed on the soft board body211by wiring layout. Therein, the first signal pad region comprises a first signal transmission line213A and two first grounding soldering portions213B which flank the first signal transmission line213A.

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 line213A have an intact surface which dispenses with any through hole. Furthermore, the end of the first signal transmission line213A is flush with the edge of the soft board body211so that the end of the first signal transmission line213A can be soldered to a second signal transmission line223A of the printed circuit board220below. In a preferred embodiment, a half hole2131A for holding a solder FB (shown inFIG. 10) is disposed at the end of the first signal transmission line213A so that the end of the first signal transmission line213A can be covered with the solder FB and thus soldered to the second signal transmission line223A of the printed circuit board220below.

FIG. 10andFIG. 11are 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 VH3is disposed on the first grounding soldering portion213B to electrically connect the first grounding soldering portion213B and the first grounding pad region214. The edge of the first grounding soldering portion213B and the edge of the soft board body211are flush with each other and thus can be soldered together from above the soft board body211and a second grounding soldering portion223B of the printed circuit board220below. In a preferred embodiment, a half hole2131B for holding the solder FB is disposed at the end of the first grounding soldering portion213B so that the end of the first grounding soldering portion213B can be covered with the solder FB and thus soldered to the second grounding soldering portion223B of the printed circuit board220below. The through hole VH3and the half hole2131B are of any shapes, such as round and square, and the present invention is not limited thereto. The half hole2131A,2131B are optional. In another preferred embodiment, the half hole2131A,2131B 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 portions213B flank and extend along the first signal transmission line213A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the first signal transmission line213A, but the present invention is not limited thereto.

An insulating region A2is disposed on the first grounding pad region214and corresponds in position to the first signal transmission line213A on the soft board body211. The insulating region A2extends inward from an edge of the soft board body211. Specifically, the insulating region A2is disposed right below the first signal transmission line213A so that the first grounding pad region214does not come into contact with the second signal transmission line223A on the printed circuit board220when the flexible printed circuit210is disposed on the printed circuit board220, so as not to develop any short circuit. The insulating region A2is a naked region (i.e., the soft board body211per se), which dispenses with any copper foil, formed as a result of inward extension of the first grounding pad region214. In another preferred embodiment, the insulating region A2is an insulating layer disposed on the first grounding pad region214, but the present invention is not limited thereto. In another preferred embodiment, the protective layer215below the soft board body211extends and covers the first grounding pad region214from below so that only metal pads with the through hole VH3are exposed from two sides of the first grounding pad region214to prevent the first grounding pad region214from coming into contact with the end of the second signal transmission line223A, so as not to develop any short circuit.

Referring toFIG. 7,FIG. 8, andFIG. 9, the printed circuit board220is tri-layered and comprises, from bottom to top, a protective layer225, a substrate body221, and a protective layer222disposed above the substrate body221. A second signal pad region223is disposed on one side of the substrate body221. A second grounding pad region224is disposed on the opposing side of the substrate body221. Both the second signal pad region223and the second grounding pad region224are conductive copper foils disposed on the substrate body221by wiring layout. The second signal pad region223comprises a second signal transmission line223A and two second grounding soldering portions223B which flank the second signal transmission line223A.

To prevent through holes from compromising high-frequency characteristics of high-frequency signals, the surface of the second signal transmission line223A is intact and dispenses with any through hole to maintain the integrity of high-frequency signals being transmitted along the second signal transmission line223A. The end of the printed circuit board220lacks the protective layer222so as to expose the second signal transmission line223A and the second grounding soldering portions223B for use in soldering.

Referring toFIG. 10, a through hole VH4is disposed on the second grounding soldering portion223B to electrically connect the second grounding soldering portion223B and the second grounding pad region224. In another preferred embodiment, the second grounding soldering portions223B flank and extend along the second signal transmission line223A and thus effectuate a grounded coplanar waveguide (GCPW) structure together with the second signal transmission line223A, but the present invention is not limited thereto. The through hole VH2is of any shapes, such as round and square, and the present invention is not limited thereto.

FIG. 12is 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 circuit210is disposed on the printed circuit board220. The insulating region A2of the first grounding pad region214is disposed above the second signal transmission line223A to stay away from the second signal transmission line223A and thus preclude developing a short circuit together with the second signal transmission line223A. The end of the first signal transmission line213A is soldered to the second signal transmission line223A 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 S2is disposed on the substrate body221of the printed circuit board220and beside the second signal transmission line223A to serve as reference for use in the soldering operation. The level signs S2enable the assembly workers or automated machines to confirm the distance between the insulating region A2below the flexible printed circuit210and the end of the second signal transmission line223A. The distance between level sign S2and the end of the second signal transmission line223A is preferably shorter than or equal to an extension distance D2by which the insulating region A2extends 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.