WO2009054592A1

WO2009054592A1 - Capacitive switch module

Info

Publication number: WO2009054592A1
Application number: PCT/KR2008/003640
Authority: WO
Inventors: Sang-Chuel Lee; Jae Hong Joo; You-Hee Seo
Original assignee: Ad Semicondictor Co., Ltd.
Priority date: 2007-10-23
Filing date: 2008-06-25
Publication date: 2009-04-30
Also published as: KR100952905B1; TW200919964A; TWI352504B; CN101861635B; CN101861635A; KR20090041176A

Abstract

A capacitive switch module is disclosed, which is capable of achieving simplification of fabricating process and miniaturization, preventing deterioration of sensitivity and reducing the possibility of malfunction, and further capable of reducing inferior goods caused by impacts applied during the transportation. The most distinctive feature of the capacitive switch module according to the present invention is in an integrated structure of a metal plate serving as a sensing electrode, a base serving as a bracket, and a capacitive sensor IC chip. Also, a lower cover capable of relieving an impact applied from a lower part to the capacitive sensor IC chip is optionally mounted.

Description

Description CAPACITIVE SWITCH MODULE

Technical Field

[1] The present invention relates to a capacitive switch module, and more particularly to a capacitive switch module capable of achieving simplification of fabricating process and miniaturization, preventing deterioration of sensitivity and reducing the occurrence possibility of malfunction, and further capable of reducing inferior goods caused by impacts applied during the transportation.

[2]

Background Art

[3] Recently, as more and more mobile devices such as a cell phone are employing a touch sensor, popularity of those mobile devices is amazingly soaring. Since the touch sensor came to be in common use in the mobile market, the market of a capacitive switch module, which is a component part of the touch sensor, is accordingly growing, rather than being limited to home appliances in applicable fields. A capacitive switch is advantageous in many respects including visual design, structural superiority, semipermanent life, durability and the likes, in comparison with a conventional mechanical switching system. As the capacitive switch market is being activated, the market of the capacitive switch module is also growing and technical demand of customers about the capacitive switch module is increasing. For improvement in convenience and reliability of the product demanded by the customers of a capacitive sensor integrated circuit (IC), modularization needs to be performed. However, lots of time and cost are necessitated for the modularization since it requires a surface mount device (SMD) process including other additional processes and various parts.

[4] More specifically, the conventional modularization comprises processes of ® printed circuit board (PCB) SMD of the touch sensor IC and RC parts, © insertion of lead pins for power supply and signal output, © plastic covering of an outside of the touch sensor IC and molding of the touch sensor IC, and ® insertion of a bracket and a gasket. Here, the required parts include the touch sensor IC and the RC parts, the lead pins, the plastic cover, and the brackets. In a case where a manufacturer of the touch sensor parts supply the parts to the customer, herein corresponding to a final manufacturer of a product such as a cell phone, and the customer manufactures the final product using the touch sensor parts, the above processes have to be separately performed by the touch sensor parts manufacturer and the final product manufacturer. Especially, the insertion of brackets should be performed by the final product manufacturer. Therefore, increased processing time and cost are imposed to the final product manufacturer, corresponding to the customer.

[5] In order to solve this problem, the touch sensor parts manufacturer is making an effort for the final product manufacturer to save the processing time and the manufacturing cost, by modularizing the capacitive switch which is used in the touch sensor. An example of a thus -developed capacitive switch module is disclosed in Korean Patent Registration No. 528680.

[6] Fig. 1 is an exploded perspective view of a capacitive sensing switch disclosed in

Korean Patent Registration No. 528680. Referring to Fig. 1, although not shown, a sensor IC for sensing capacitance varied according to contact with a human body, and active and passive elements are mounted on a bottom surface of a PCB 20 constituting the capacitive sensing switch 10, and these are in connection with a plurality of input and output terminals 23a, 23b and 23c. A conductor patterned sensing surface 21 is formed on an upper surface of the PCB 20. Also, on the upper surface of the PCB 20, one or more light emitting diodes (LEDs) 25 are mounted to emit light for a user to recognize the operation state of the capacitive sensing switch 10. The above structured PCB 20 is mounted in an outer case 50 which is opened upward. A diffusion epoxy material (not shown) which evenly diffuses the light generated from the LEDs 25 fills the upper part of the PCB 20. In addition, a sensing plate 60 has a case form which is opened downward and formed with a light emitting surface 62, which is light- transmittable, on an upper surface thereof. A plurality of fixing pieces 61 are formed at a lower end of the sensing plate 60 to fix the sensing plate 60 to the PCB 20. Corresponding to the fixing pieces 61, a plurality of mounting holes 26 are formed on the PCB 20. According to this structure, the sensing plate 60 can be electrically connected with the PCB 20 by inserting the fixing pieces 61 of the sensing plate 60 in the mounting holes 26 of the PCB 20, and fixing the fixing pieces 61 and the mounting holes 26 to each other, for example, by soldering.

[7] Meanwhile, the above- structured capacitive sensing switch module has some drawbacks as follows. First, if a space exists between the sensing plate 60 and a cover of a product applying the capacitive sensing switch module, sensitivity may be deteriorated due to an air gap, thereby bringing about the possibility of malfunction.

[8] Second, the capacitive sensing switch module may be applied with some impacts during the transportation thereof. When the PCB 20 is mounted to the outer case 50 having an integrated structure and fixed by the epoxy (not shown), external impacts may be applied directly to susceptible electronic elements mounted to the PCB 20, such as the sensing IC, the active and the passive elements. In this case, although being manufactured in the normal state, the capacitive sensing switch module may cause inferior goods when being actually applied after the transportation.

[9] Third, since the required parts including the touch sensor IC, the active and the passive elements are all separately mounted to the PCB 20, the pin insertion process and the epoxy molding process are necessarily performed, thereby complicating the whole manufacturing process and also making miniaturization of the elements difficult.

[10]

Disclosure of Invention Technical Problem

[11] Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a capacitive switch module capable of preventing deterioration of sensitivity and generation of malfunction caused by an air gap although there exists a space between a sensing plate of the capacitive switch module and a cover of a product applying the capacitive switch module.

[12] It is another object of the present invention to provide a capacitive switch module capable of reducing inferior goods caused by external impacts applied thereto during the transportation.

[13] It is still another object of the present invention to provide a capacitive switch module capable of simplifying the manufacturing process by omitting pin insertion and molding processes, and also achieving a compact size thereof.

[14]

Technical Solution

[15] In accordance with an aspect of the present invention, the above and other objects can be accomplished by the provision of a capacitive switch module comprising a base formed as a case holding a hollow space and opened to upper and lower sides thereof; a capacitive sensor IC chip formed by molding to integrally include a sensor IC for sensing capacitance, an active element, a passive element, and signal input and output pins, and received in the hollow space of the base; and a metal plate mounted to an upper part of the capacitive sensor IC chip and electrically connected with the signal input pin of the capacitive sensor IC chip to thereby serve as a sensing terminal.

[16] Preferably, the capacitive switch module may further comprise a lower cover connected to the base as supporting a lower part of the capacitive sensor IC chip, to be movable within a predetermined gap maintained relative to the base.

[17] The capacitive switch module may further comprise a mounting plate horizontally mounted across the hollow space in the base, wherein the metal plate is seated on the mounting plate.

[18] A conductive gasket may be mounted in contact with an upper surface of the metal plate so as to transmit a touch-input signal to the metal plate. Here, the conductive gasket is preferably made of an elastic material. [19] The capacitive switch module may further comprise a plurality of extension protrusions extended from a lower part of the base.

[20] Any one of the lower cover and the base may have a connection protrusion whereas the other one has a recess formed in a vertical direction for engagement with the connection protrusion.

[21] The capacitive switch module may further comprise an insulating tape interposed between the metal plate and the conductive gasket in order for detailed adjustment of sensitivity. Here, the insulating tape may be in the form of a double-sided adhesive tape.

[22]

Advantageous Effects

[23] As described above, a capacitive switch module according to the embodiment of the present invention is capable of saving a bracket insertion process that has been imposed to a final product manufacturer, that is, a customer of the capacitive switch module. Also, the manufacturing process for a sensor parts manufacturer who produces the capacitive switch module is simplified. That is, the simplified manufacturing process is beneficial to both the manufacturer and the customer. More specifically, since a metal plate serving as a sensing electrode, a base serving as a bracket, and a capacitive sensor IC chip are all integrally structured, the manufacturing process and the structure can be greatly simplified, thereby improving the marketability. Furthermore, by achieving miniaturization of the product and simplifying the process for both the sensor parts manufacturer and the customer, demands of much more customers can be satisfied. Here, the simplification of the process not only means mere improvement of the process but also means that manufacturing of the capacitive switch module can be mechanized and automated by saving lots of secondary processes including outsourcing and manual labor. Accordingly, in addition, the miniaturized products enable a greater variety of designs and further enable entry into more new and variable fields of industry.

[24] Recently, the IC industry is getting more competitive as well as other industrial fields. Although there is accordingly growing competition for lower price, customers are demanding more and more technological innovation. The capacitive switch module according to the present invention would be really competent to meet the customers various demands by its lower price, simplified structure and process, and improved convenience in use. Moreover, the miniaturization improves entry into various markets.

[25] Additionally, according to the present invention, deterioration of sensitivity of the capacitive switch module can be prevented, thereby reducing malfunction rate. Also, in- feriority generated by external impacts can be prevented from occurring. [26]

Brief Description of the Drawings

[27] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[28] Fig. 1 is an exploded perspective view of a conventional capacitive sensing switch disclosed in Korean Patent Registration No. 528680;

[29] Fig. 2 is an exploded perspective view of a capacitive switch module according to a first embodiment of the present invention; and

[30] Fig. 3 is an exploded perspective view of the capacitive switch module according to a second embodiment of the present invention.

[31]

Best Mode for Carrying Out the Invention

[32] Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description, since the same reference numerals refer to the same elements throughout the drawings, explanation about the same elements will not be repeated.

[33] Fig. 2 is an exploded perspective view of a capacitive switch module according to a first embodiment of the present invention. Referring to Fig. 2, a base 140 serving as a bracket in the conventional technology is in the form of a hollow cubic case which is opened upward and downward. A mounting plate 144 is horizontally mounted in the hollow space of the base 140. Two opposite sides among four sides of the mounting plate 144 are formed with a recess, thereby forming penetrable slits 143 together with an inner wall of the base 140. A protruded piece 132 of a metal plate 130 having a sensing electrode is passed through the penetrable slits 143 and fixed. Accordingly, the metal plate 130 is mounted as put on the mounting plate 144. A capacitive sensor integrated circuit (IC) chip 150 is inserted in a lower space of the base 140 with respect to the mounting plate 144. Here, the protruded piece 132 of the metal plate 130 is in electric connection with an input pin of the capacitive sensor IC chip 150. According to this embodiment, the capacitive sensor IC chip 150 is implemented by a 8-pin dual in-line package (DIP) IC chip comprising 8 pins including, for example, a voltage supplying (VDD) pin, a ground (GND) pin, an output pin, a sensitivity adjusting pin, and four input pins 155 being cut short for efficient contact with the protruded piece of the metal plate. However, the present invention is not limited to this embodiment. When the capacitive sensor IC chip 150 is fitted and fixed to the metal plate 130, the four input pins 155 are electrically connected with the protruded pieces 132 of the metal plate 130, which are extended toward the input pins 155. Since the capacitive sensor IC chip 150 integrally includes a sensor IC, an active element, a passive element, and signal input and output pins by molding, a pin insertion process and an epoxy molding process, which have been conventionally performed, can be omitted. Therefore, the whole manufacturing process can be simplified and also, reduced size of the elements can be achieved. Meanwhile, a plurality of extension protrusions 149 are extended from a lower part of the base 140. Here, the extension protrusions 149 have substantially the same length as a lead wire of the capacitive sensor IC chip 150. Therefore, when the capacitive switch module according to the embodiment of the present invention is inserted in a printed circuit board (PCB), being applied to a product, cohesion between the capacitive switch module and the PCB can be enhanced before the lead wire is soldered, thereby improving user s convenience. In addition, at a lower part of the capacitive sensor IC chip 150, a lower cover 160 is mounted to enclose the capacitive sensor IC chip 150. Two opposite sides among four sides of the lower cover 160 are provided with a connection piece 162, respectively. A slit 164 is formed at each of the connection pieces 162 in a vertical direction so that a locking protrusion 148 formed at an outer wall of the base 140 is hooked in the slit 164. The connection piece 162 of the lower cover 160 has a corresponding shape to a guiding recess 146 formed at the outer wall of the base 140. According to the drawing, a bottom 166 of the lower cover 160 is chamfered such that the lead wires of the capacitive sensor IC chip 150 are passed through the chamfered parts. However, the lower cover 160 of the present invention is not limited to this structure but may have the bottom 166 of other various types depending on position of the lead wire of the capacitive sensor IC chip 150. Here, the slit 164 formed at the connection piece 162 is a bit longer than the locking protrusion 148. With this structure, although an impact is applied to the bottom 166 of the lower cover 160 in a direction toward the capacitive sensor IC chip 150, since the lower cover 160 moves maintaining a little gap relative to the base 140, the impact can be absorbed in the gap without being directly transmitted to the capacitive sensor IC chip 150. As a result, impacts applied to the capacitive switch module during the transportation can be relieved.

[34] Additionally, a conductive gasket 110 is mounted in an inner space 142 of the base

140 above the metal plate 130 to safely transmit a touch-input signal to the metal plate 130 serving as a sensing electrode cap. By this, in spite of an air gap existing between the metal plate 130 of the capacitive switch module and an outer cover of the product, the metal plate 130 and the outer cover can be brought into close contact with each other, accordingly preventing deterioration of sensitivity, that may be caused by the air gap, and malfunction. The conductive gasket 110 may be made of an elastic material, for example, a conductive rubber formed by distributing conductive particles such as carbon black on rubber to have conductivity. Conventionally, mounting of the gasket has been performed by the customer who is supplied with the capacitive switch module. Therefore, according to the embodiment of the present invention, the customer s satisfaction can be greatly improved by omitting the gasket mounting process.

[35] An insulating tape 120 may be interposed between the metal plate 130 and the conductive gasket 110, optionally. The main function of a insulating tape 120 is to improve the ESD(electrostatic discharge), and independently from the sensitivity adjusting pin in the capacitive sensor IC chip 150, the insulating tape 120 may be used for detailed adjustment of the sensitivity by being adjusted in thickness thereof. In case that the insulating tape 120 is in the form of a double-sided adhesive tape, cohesion between the metal plate 130 and the conductive gasket 110 can be enhanced.

[36] Thus, according to the embodiment of the present invention, since the metal plate

130 having the function of the electrode cap also serves as a sensing terminal, a dedicated sensing electrode is not required. In addition, the base 140 serves as the bracket required to guide the capacitive switch module in the conventional art, by being integrally formed with the metal plate 130 and the capacitive sensor IC chip 150. In the conventional capacitive switch module, the parts serving as the electrode cap are formed at a bare PCB. However, according to the embodiment of the present invention, the improved capacitive sensor IC chip 150 is capable of functioning as the sensing terminal by disposing the conductive metal plate 130 at an upper part of the capacitive sensor IC chip 150 and electrically connecting the metal plate 130 to the short input pins 155 of the capacitive sensor IC chip 150 through the protruded pieces 132.

[37] As aforementioned, the conventional capacitive switch module is manufactured through steps of ® PCB SMD of a touch sensor IC and RC parts, © insertion of lead pins for power supply and signal output, © plastic covering of an outside of the touch sensor IC and molding of the touch sensor IC, and ® insertion of a bracket and a gasket. Here, the required parts include the touch sensor IC and the RC parts, the lead pins, the plastic cover, and the brackets. However, according to the embodiment of the present invention, main processes and parts of the conventional method can be simplified. First of all, the first and second processes, that is, ® PCB SMD of a touch sensor IC and RC parts and © insertion of lead pins for power supply and signal output can be omitted by using the improved capacitive sensor IC chip 150. In other words, since the conventional PCB process, the pin insertion, the covering and the molding are all completed by applying the improved capacitive sensor IC chip 150, no additional processes are required. Furthermore, the third and fourth processes of the conventional art, that is, © plastic covering of an outside of the touch sensor IC and molding of the touch sensor IC and ® insertion of a bracket and a gasket can be achieved by structuring the metal plate 130, the base 140 and the capacitive sensor IC chip 150 as an integrated body. The metal plate 130, made of a conductive material, not only functions as the sensing electrode but also lifts the capacitive sensor IC chip 150 and the base 140 by being inserted in the upper space of the base 140 and connected with the base 140. Moreover, through the molding process that has been performed to relieve the impacts applied to the capacitive sensor IC chip parts and improve reliability, holes or apertures formed in the base 140 can be designed to help a more efficient connection between the metal plate 130 and the short input pins 155 formed in the middle of the IC chip 150.

[38] Fig. 3 is an exploded perspective view of a capacitive switch module according to a second embodiment of the present invention. Comparing Fig. 3 with Fig. 2, the most distinctive feature of the second embodiment is in omission of the lower cover employed in the first embodiment. Such a structure may be considered in a case where omission of the lower cover is more advantageous depending on a surface structure of the product. According to this, the penetrable slit 143, the guiding recess 146 and the locking protrusion 148 necessarily provided in Fig. 2 are not shown in Fig. 3. Additionally, according to the second embodiment shown in Fig. 3, the mounting plate 144 needs to be disposed at a relatively lower position. Also, through-holes 200 for passing the lead pins of the capacitive sensor IC chip 150 therethrough are formed at four corners of the mounting plate 144.

[39] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[I] A capacitive switch module comprising: a base formed as a case holding a hollow space and opened to upper and lower sides thereof; a capacitive sensor IC chip formed by molding to integrally include a sensor IC for sensing capacitance, an active element, a passive element, and signal input and output pins, and received in the hollow space of the base; and a metal plate mounted to an upper part of the capacitive sensor IC chip and electrically connected with the signal input pin of the capacitive sensor IC chip to thereby serve as a sensing terminal.

[2] The capacitive switch module according to claim 1, further comprising a lower cover connected to the base as supporting a lower part of the capacitive sensor IC chip, to be movable within a predetermined gap maintained relative to the base.

[3] The capacitive switch module according to claim 1, further comprising a mounting plate horizontally mounted across the hollow space in the base, wherein the metal plate is seated on the mounting plate.

[4] The capacitive switch module according to claim 1, wherein a conductive gasket is mounted in contact with an upper surface of the metal plate so as to transmit a touch-input signal to the metal plate.

[5] The capacitive switch module according to claim 4, wherein the conductive gasket is made of an elastic material.

[6] The capacitive switch module according to claim 1, further comprising a plurality of extension protrusions extended from a lower part of the base.

[7] The capacitive switch module according to claim 1, wherein any one of the lower cover and the base has a connection protrusion whereas the other one has a recess formed in a vertical direction for engagement with the connection protrusion.

[8] The capacitive switch module according to claim 4, further comprising an insulating tape interposed between the metal plate and the conductive gasket in order for improving the ESD and detailed adjustment of sensitivity.

[9] The capacitive switch module according to claim 8, wherein the insulating tape is in the form of a double-sided adhesive tape.

[10] The capacitive switch module according to claim 1, wherein the metal plate includes a protruded piece which is extended toward the input pin of the capacitive sensor IC chip and electrically connected to the input pin of the capacitive sensor IC chip.

[I I] The capacitive switch module according to claim 10, wherein the capacitive sensor IC chip is implemented by a 8-pin dual in-line package (DIP) IC chip comprising a voltage supplying (VDD) pin, a ground (GND) pin, a sensitivity adjusting pin, an output pin, and four input pins, the four input pins being cut short for efficient contact with the protruded piece of the metal plate.