Patent Application
20070165387
1. Field of the Invention
The present invention relates to a multi-layer printed circuit board (PCB) and more particularly to a multi-layer PCB for a keyboard.
2. Description of Related Art
A keyboard includes a base having an upper opening, a top cover, a printed circuit board (PCB), and multiple keys. The multiple keys are mounted on the top cover and the top cover is mounted over the upper opening of the base. The PCB is mounted in the base and has multiple thin film switches corresponding to the multiple keys on the top cover. Therefore, when one key is pressed, the pressed key will touch the corresponding thin film switch on the PCB, and then the PCB will output an electronic signal to a computer connected to the keyboard.
With reference to
Multiple thin film switches are mounted between the upper board (10) and the lower board (20), but only one thin film switch is shown in
The two thin conductive elements (40, 50) are separated by the insulting separation (30) and aligned with the corresponding through hole (31). When one key on the top cover of the keyboard is pressed, the two conductive elements (40, 50) corresponding to the pressed key touches with each other and are connected electronically through the through hole (31) in the insulating separation (30). When the pressed force applied onto the key is released, the two thin conductive elements (40, 50) are disconnected electronically. Therefore, a thickness of the insolating separation determines the sensitivity of touching a key. Many types of keyboards having different sensitivity of touch are produced, since the isolating separations with different thickness are used in the PCBs of the keyboards. Accordingly, the factory for fabricating the multi-layer PCB has to prepare many different insolating separations to fabricate the keyboards having different sensitivity of touch.
Further, since the thin conductive elements (40, 50) are formed on the upper and lower boards (10, 20), exposure surfaces of the thin conductive elements (40, 50) are easily shrunk to form to an uneven face in a curing procedure of fabricating the upper or lower board (10, 20). Thus, the uneven faces decrease a touching area of the thin conductive elements (40, 50) to make the touching sensitivity of the thin film switch is not stable.
Therefore, the present invention provides a multi-layer PCB for a keyboard to overcome the drawback of the conventional multi-layer PCB.
The main objective of the present invention is to provide a multi-layer printed circuit board (PCB) for a keyboard.
A multi-layer printed circuit board of a keyboard has an upper and lower layers, an insolating separation positioned between the upper and lower layers, multiple thin film switches having two thin conductive element respectively formed on the upper and lower layer, and multiple spacers positioned between one of the upper and lower layer and the insolating layer. Since each spacer can be selectively formed on the upper layer, lower layer or insolating separation and corresponds to the through holes of the insolating separation, the spacers increase a distance between the two thin conductive element of each thin film switch. Therefore, sensitivity of touch of the multi-layer PCB can be adjusted by different arrangements of the spacers.
The second objective of the present invention is to provide a thin film switch of the PCB of a keyboard and having a stable toughing sensitivity.
Each thin conductive element of the each thin film switch has a center conductor, at least two outer conductors formed adjacent to the center conductor, and at least two conductive lines connected to the center and outer conductors. With such an arrangement, the area of the center and outer conductors will be reduced, surfaces of the conductors are even in the curing procedure of fabricating upper or lower board to keep a stable touching sensitivity.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
With reference to
The upper and lower layers (10, 20) respectively have multiple circuit lines (12, 13) (22,23). The upper layer (10) has a bottom (101), and the lower layer (20) has a top (201).
The insulating separation (30) is positioned between the upper and lower layers (10, 20), defines multiple through holes (31) and has two opposite sides (301, 302).
Each thin film switch has two thin conductive elements (11, 21) respectively formed on the upper and lower board (10, 20). The two thin conductive elements (11, 21) are aligned with one of the through holes (31) in the insolating separation (30).
The multiple spacers (40) are positioned between one of the upper and lower layers (10, 20) and the insolating separation (30), and corresponding respectively to the through holes (31) in the insolating separation (30).
In the first embodiment, with reference to
With reference to
With reference to
Each spacer (40) can comprise multiple curved protrusions. The multiple curved protrusions are arranged to a circular shape.
Furthermore, to provide a stable touching sensitivity to the PCB, with reference to
The center conductor (111, 211) is aligned with the corresponding through hole (31) in the insolating separation (30).
The at least two outer conductors (112, 212) are symmetrically formed adjacent to the center conductor (111,211) and also aligned with the corresponding through hole (31). Each outer conductor (112, 212) is further connected to the circuit lines (112, 13) (22, 23) of the upper or lower board (10, 20).
The at least two conductive lines (113, 213) are respectively connected to the outer conductors (112, 212) and are connected to the center conductor (111, 211).
Based on the forgoing description, the multi-layer PCB in accordance with the present invention uses the spacers (40) to increase a distance between thin conductive elements (11, 21) of each thin film switch of PCB to fabricate different senses of touch of PCB of keyboard.
The center conductor (111, 211) is formed of a circular shape and each outer conductor (112, 212) is formed of a curved shape. When the conductive lines (113, 213) are connected to the center conductor (111, 211) and the outer conductors (112, 212), the thin conductive element (11, 21) is formed to an invert-S shape.
Since the center conductor (111, 211) and the outer conductor (112, 212) have smaller areas than that of the conventional thin conductive element in accordance with the prior art, surfaces of the center and outer conductors (111, 211) (112, 212) are hardly shrunk to an uneven face in the curing procedure of fabricating upper or lower board. Therefore, the center and outer conductors (111, 211) (112, 212) have even faces, the touching sensitivity of the thin film switch is stable.
Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
