Patent Application
20070163866
1. Field of the Invention
The present invention relates to a printed circuit board (PCB) with thin film switches for a keyboard and more particularly to a PCB with thin film switches for a keyboard and having a stable touching sensitivity.
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
The 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 aligning through hole (31) of the insulating separation (30). When the pressed force applied onto the key is released, the two thin conductive elements (40, 50) are disconnected electronically.
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 between 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 new printed circuit board with thin film switches of a keyboard to overcome the drawback of the conventional thin film switch.
The main objective of the present invention is to provide a printed circuit board (PCB) with thin film switches for a keyboard and having a stable toughing sensitivity.
The PCB has an upper and a lower boards, an insolating separation positioned between the upper and defining multiple holes, and lower boards and the multiple thin film switches mounted to the upper and lower boards. Each thin film switch has two thin film conductive elements respectively formed on the upper and lower board and corresponding to one of the through holes in the insulating separation. Each thin film conductive element has a center conductor, at least two outer conductors formed next to the center conductor, and at least two conductive lines connected to the center and outer conductors.
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 boards (10, 20) respectively have multiple circuit lines (12, 13) (22,23). The insulating separation (30) is positioned between the upper and lower boards (10, 20) and defines multiple through holes (31).
The multiple thin film switches are mounted on the printed circuit board. Each thin film switch corresponds to one of the through holes (31) in the insulating separation (30) and has two thin conductive elements (11,21) respectively formed on the upper and lower board (10, 20). Each thin conductive element (11, 21) has a center conductor (111, 211), at least two outer conductors (112, 212) and at least two conductive lines (113, 213).
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 (12, 13) (22, 23) on 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).
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 film 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 film 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 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.
