KR20080098289A - Keypad assembly for mobile communication terminal with flexible printed circuit board - Google Patents

Abstract

The present invention relates to a keypad assembly of a mobile communication terminal having a flexible printed circuit board, and more particularly, a key top provided with a plurality of key buttons; Light emitting means disposed under the key top and emitting light with the key button; A flexible printed circuit board having a plurality of contacts provided at positions corresponding to the key buttons, respectively, and a plurality of dome switches covering the respective contacts; And a plurality of protrusions disposed at a lower side of the flexible printed circuit board and formed at positions corresponding to the contacts so that when the key button is pressed downward, the dome switch can be pressed in the direction of contact with the contacts. It relates to a keypad assembly of a mobile communication terminal having a flexible printed circuit board including a sheet member.

Description

Keypad assembly of mobile communication terminal embedding with flexible printed circuit board

1 is an exploded perspective view of a conventional mobile communication terminal.

2 is a cross-sectional view of the main part of FIG.

Figure 3 is an exploded cross-sectional view of the keypad assembly according to an embodiment of the present invention.

4 is a view showing a state in which the keypad assembly of FIG. 3 is coupled.

5 shows an example of operation in which the keypad assembly of FIG. 4 operates.

6 is a view showing that light is emitted from the light emitting means in FIG.

7 is an exploded cross-sectional view of a keypad assembly according to another embodiment of the present invention.

8 is a cross-sectional view of a keypad assembly according to another embodiment of the present invention.

<Brief Description of Drawings>

10 ... Keypad Assembly 20 ... Keytop

21 ... key button 30 ... light-emitting means

31 ... light guide sheet 32 ... light source

33 ... Adhesive 34 ... Reflective layer

341 ... base 342 ... reflective particles

40 ... flex circuit board 41 ... contact

42 ... Dome switch 50 ... Seat member

51 ... overhang

The present invention relates to a keypad assembly of a mobile communication terminal incorporating a flexible printed circuit board, and more particularly, to a keypad assembly of a mobile communication terminal incorporating a flexible printed circuit board that enables slimming of the mobile communication terminal. .

Mobile communication terminals have been widely used to date because they are easy to carry and have various functions in addition to wireless communication. Figure 1 is a perspective view of a mobile communication terminal according to the prior art, Figure 2 is a cross-sectional view of the main part of the mobile communication terminal of FIG.

The mobile communication terminal 100 includes a main body 110 and a folder 120. The main body is composed of an upper frame 111 and a lower frame 112, the keypad assembly 130, the light emitting sheet 143, the printed circuit board 140 between the upper frame 111 and the lower frame 112 It is provided in a laminated structure.

The keypad assembly 130 includes a key top 131 and a key base 133.

The key top 131 is provided with a plurality of key buttons 132 on which various numbers, letters and symbols are printed. The key base 133 is attached to the rear of the key top 131. A plurality of protrusions 134 are provided on the rear surface of the key base 133. The protrusion 134 is positioned to correspond to each key button 132.

The light emitting sheet is provided between the keypad assembly 130 and the printed circuit board 140. Specifically, an El sheet is used.

The printed circuit board 140 is for driving and controlling the mobile communication terminal 100, and a contact 141, a dome switch 142, and a top tape 144 are provided on an upper surface thereof.

The contact points 141 are provided at positions corresponding to the key buttons 132, respectively. The dome switch 142 is provided in plural to cover the contact 141. When the key button 132 of the key top 131 is pressed downward, when the central portion of the dome switch 142 contacts the contact point 141 by the protrusion 134, the mobile communication terminal 100 is predetermined. Electrical operation is performed.

The top tape 144 is provided on the outer circumference of the dome switch to fix the dome switch on a printed circuit board, and a film of synthetic resin material is used.

Recently, many efforts have been made to reduce the overall thickness of the mobile communication terminal.

To this end, it is also considered to reduce the thickness of the key top and key base, but if the thickness of the key top and key base is reduced below a certain amount, there is a problem that the click feeling of pressing the key button is significantly reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a keypad assembly of a mobile communication terminal with a flexible circuit board which maintains a feeling of clicking a key button while reducing the overall thickness of the mobile communication terminal. The purpose.

Keypad assembly of a mobile communication terminal of the present invention for achieving the above object, the key top is provided with a plurality of key buttons; Light emitting means disposed under the key top and emitting light with the key button; A flexible printed circuit board disposed below the light emitting unit, the flexible printed circuit board having a plurality of contacts provided at positions corresponding to the key buttons and a plurality of dome switches covering the respective contacts; And a plurality of protrusions disposed at a lower side of the flexible printed circuit board and formed at positions corresponding to the contacts so that when the key button is pressed downward, the dome switch can be pressed in the direction of contact with the contacts. And a sheet member.

In a keypad assembly of a mobile communication terminal in which the flexible printed circuit board is embedded, the light emitting means includes: a light-transmitting light guide sheet; A light source disposed outside one edge of the light guide sheet to allow light to enter the light guide sheet; An adhesive for separating the light guide sheet from the key top and the flexible printed circuit board; And a diffuse reflection layer that diffusely reflects the light passing through the light guide sheet toward the key button and is provided on a lower surface of the light guide sheet.

In the keypad assembly of the mobile communication terminal in which the flexible printed circuit board is embedded, the light emitting means is preferably embedded in the flexible printed circuit board, characterized in that the El sheet.

In the keypad assembly of the mobile communication terminal in which the flexible printed circuit board is embedded, the protrusion of the sheet member is preferably formed on the lower surface of the sheet member.

In the keypad assembly of the mobile communication terminal in which the flexible printed circuit board is embedded, the sheet member is preferably attached to the lower surface of the flexible printed circuit board.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is an exploded cross-sectional view of the keypad assembly according to an embodiment of the present invention, Figure 4 is a view showing the combination of the keypad assembly of Figure 3, Figure 5 shows an operation example of the keypad assembly of Figure 4 operates. 6 is a view showing that light is emitted from the light emitting means in FIG.

The keypad assembly 10 of the mobile communication terminal according to the present embodiment includes a key top 20, a light emitting means 30, a flexible printed circuit board 40, and a sheet member 50.

The key top 20 is provided with a plurality of key buttons 21, the letters, numbers, symbols, etc. are printed on the key button 21. The key top 20 is a plastic injection or plastic film, metal sheet or the like is used.

The light emitting means 30 includes a light guide sheet 31, a light source 32, an adhesive 33, and a diffuse reflection layer 34.

The light guide sheet 31 is disposed between the key top 20 and the key button 21, and it is preferable to use polycarbonate (PC) or polyurethane (PU), but polymethacrylic acid As long as it is excellent in light transmittance, such as acrylic resin, such as methyl and a methacryl- styrene copolymer, it can be used. When the light is incident from the light source 32 to be described later, the incident light is totally reflected from the upper and lower surfaces of the light guide sheet 31 to travel from one edge of the light guide sheet 31 toward the other edge. In this case, the reason why the light is totally reflected on the upper and lower surfaces of the light guide sheet 31 is that the refractive index of air in contact with the upper and lower surfaces of the light guide sheet 31 is considerably smaller than that of the silicon material forming the light guide sheet 31. to be. Due to such a difference in refractive index, the light traveling through the light guide sheet 31 is easily totally reflected when only a predetermined angle of incidence is exceeded.

The light source 32 is disposed outside one side edge of the light guide sheet 31 to inject light into the light guide sheet 31. The distance between the light source 32 and the light guide sheet 31 has a sufficient distance to allow light incident on the light guide sheet 31 to travel with a predetermined angle of incidence between an upper surface and a lower surface. As the light source 30 emits light when electricity is supplied, a light emitting diode or the like may be used. The light source is provided in the keypad assembly to prevent the light from leaking to the periphery to reduce the overall failure rate, and does not require a separate light source.

The adhesive 33 is to separate the light guide sheet 31 from the key top 20 and the flexible printed circuit board 40 by a predetermined distance, between the key top 20 and the light guide sheet 31, and The light guide sheet 31 and the flexible circuit board 40 are respectively provided.

As such, the light guide sheet 31 is spaced apart from the key top 20 and the flexible printed circuit board 40 by a predetermined distance by using the adhesive 33. The light guide sheet 31 is the key top 20 or the flexible printed circuit board. This is because most of the light is incident on the key top 20 or the flexible printed circuit board 40 without being totally reflected on the upper and lower surfaces of the light guide sheet 31 when it contacts 40. In general, total reflection occurs well when the refractive indices between the two media in contact with each other are large as described above. As shown in the present embodiment, the light guide sheet 31, the key top 20, and the flexible printed circuit board 40 When the materials are similar to each other and the refractive indices are similar, total reflection does not easily occur and is mostly incident. (Because total reflection occurs only when the angle of incidence is 90 ° when the mediums of similar refractive index are in contact with each other, almost all of the light is incident without total reflection in this embodiment.)

The diffuse reflection layer 34 diffuses the light passing through the light guide sheet 31 toward the key button 21 while totally reflecting it. The diffuse reflection layer 34 is provided on the lower surface of the light guide sheet 31 by a conventional printing method. Specifically, screen printing, offset printing, pad printing, or the like is used. The diffuse reflection layer 34 is composed of a resin 341 and reflective particles 342.

The resin 341 has a light transmitting property, and the liquid containing the reflective particles 342 is hardened. In printing, a volatile solvent is applied to the lower surface of the light guide sheet together with the resin and the reflective particles, but during printing and drying, the solvent is volatilized 100% so that it is not left in the diffuse reflection layer 50. 341.

The reflective particles 342 have good reflecting properties and are used for printing light-emitting pigments of fine powder made of phosphorescent material, and specifically, white pigments or fluorescent pigments emitting by changing wavelength band of light may be used. The fluorescent pigment may be made of sulfides such as zinc, strontium, barium, and other various materials may be used. Fluorescent pigments need these fluorescent pigments when it is necessary to selectively reflect light and emit light in various colors.

As shown in FIG. 6, some of the light incident on the light guide sheet 31 is totally reflected between the upper surface and the lower surface, but part of the light is incident on the diffuse reflection layer 34. At this time, light incident on the diffuse reflection layer 34 is incident through the base portion 341, and then is incident from the surface of the diffuse reflection particle 342. Light that is diffusely reflected from the diffuse reflection particle 342 is diffusely reflected at various reflection angles according to the incident angle thereof. Meanwhile, the designer may adjust the density and size of the diffuse reflection particle 342 so that most of the diffusely reflected light may be directed toward the key button 21.

The flexible printed circuit board 40 is disposed below the light emitting sheet, and provides a plurality of contacts 41 and a plurality of dome switches 42 on the bottom surface of the flexible printed circuit board 40. The flexible printed circuit board 40 is a printed circuit board 40 made of a polyimide resin and a metal thin plate, and is a flexible printed circuit board 40 having excellent bending resistance. As the flexible printed circuit board 40 is provided in the keypad assembly 10, when the user presses the key button 21 downward, the key top 20, the light emitting means 30, and the sheet member 50 to be described later and Can be bent freely together.

The contact 41 is provided in a position corresponding to each of the plurality of key buttons 21, and has the same configuration as the contacts 41 mentioned in the prior art, detailed description thereof will be omitted.

The dome switch 42 is provided on the lower surface of the flexible printed circuit board 40 to cover each of the contacts 41, and has the same configuration as the dome switch 42 mentioned in the prior art. Will be omitted.

Although not shown, the flexible printed circuit board 40 may include an electronic component that may perform various electrical functions on an upper surface or a lower surface.

The sheet member 50 is disposed below the flexible printed circuit board 40 and covers an outer circumference of the dome switch 42. The sheet member 50 is preferably made of a synthetic resin film similar to the top tape in the prior art. As the sheet member 50 is disposed on the flexible printed circuit board 40 to cover the outer circumference of the dome switch 42, the dome switch 42 is fixed on the flexible circuit board 40 in position. On the other hand, the sheet member 50 is provided with a plurality of protrusions (51). The protruding portion 51 is preferably made of a different material from the sheet member 50, and specifically, a material having elasticity is used.

As the protrusion 51 is provided on the sheet member 50, the thickness of the entire keypad assembly may be reduced by removing the key base (reference numeral 133 of FIG. 2) mentioned in the related art. In general, the key base is provided in the lower portion of the key top to form a protrusion protruding to a predetermined thickness. As the protrusion is provided in the sheet member, the key base does not need to exist in the present embodiment. Therefore, in the present embodiment, it is possible to reduce the thickness of the keypad assembly of the entire mobile communication terminal by removing the key bay.

On the other hand, the protrusion 51 is formed on the lower surface of the sheet member 50, a plurality of protrusions protrude downward. These protrusions 51 are formed at positions corresponding to the plurality of contacts 41, respectively. The protrusion 51 presses the dome switch 42 in a direction of contacting the contact 41 when the key button 21 is pressed downward by a user, and a detailed operation thereof will be described later.

3 and 4, reference numeral 112 denotes a lower case of the mobile communication terminal. The lower case 112 is provided to contact the protrusion 51 of the sheet member 50, or is provided at a slight distance from the protrusion 51. Since the lower case 112 is the same configuration as the lower case 112 mentioned in the prior art, a detailed description thereof will be omitted.

Hereinafter, the operation of the keypad assembly 10 of the present embodiment having the above-described configuration will be described.

When the key button 21 is pressed downward under predetermined conditions, the light emitting means 30, the printed circuit board 40, and the sheet member 50 provided below the key button 21 pressed as shown in FIG. ) Is sequentially pressed downwards. At this time, since the protruding portion 51 of the sheet member 50 is in contact with the lower case 112, it does not move downward and presses the dome switch 42 in the direction of contact with the contact 41. When the pressurized dome switch 42 contacts the contact 41, an electrical operation desired by the user is performed. That is, an electrical operation corresponding to the pressed key button 21 is performed.

Meanwhile, in the present embodiment, the light emitting means 30 is provided above the flexible printed circuit board 40. If the light emitting means 30 is provided below the flexible printed circuit board 40, the circuit pattern engraved on the printed circuit board 40 and the other printed circuit board 40 when the light emitting means 30 emits light. This is because the light is blocked by the electronic components mounted on the panel, and thus the desired key button 21 cannot be illuminated.

On the other hand, the operation of the light emitting means 30 will be briefly described. When it is necessary to illuminate the key button 21, electricity is supplied to the light emitting diode 321 constituting the light source 32. When electricity is supplied, light is emitted from the light emitting diode 321, and the emitted light travels directly toward the light guide sheet 31. As described above, the light incident from one side edge of the light guide sheet is totally reflected from the upper and lower surfaces of the light guide sheet and proceeds toward the other edge of the light guide sheet. On the other hand, the light incident on the reflective layer is reflected from the surface of the diffuse reflection particle 342 made of a metal material is directed toward the key button 21. The diffusely reflected light illuminates the key button 21 so that the user can identify each key button 21 even in a dark place.

The keypad assembly 10 of the mobile communication terminal according to this embodiment has the following effects.

First, in the present embodiment, a protrusion is provided on the sheet member corresponding to the top tape of the prior art. Accordingly, since the key base is removed as described above, the thickness of the keypad assembly of the overall mobile communication terminal can be reduced.

On the other hand, in order to reinforce the structural rigidity of the keypad assembly which is reduced as the key base is removed, the light guide sheet is positioned below the key top. In other words, if the key base is removed, the structural rigidity of the keypad assembly is reduced, and thus, the user feels no click feeling when the user presses the key button. In this embodiment, since the light guide sheet is disposed in place of the key base, the structural rigidity is reduced. It can be maintained as is to maintain the user's click feeling.

In addition, in the present embodiment, the thickness of the key top can also be reduced at the same time. In other words, in the related art, when the thickness of the key top is reduced, the user does not have a feeling of click as described above. However, in the present embodiment, a flexible printed circuit board (a printed circuit board in which a dome switch has been directed to an upper side is flipped upside down in this embodiment so that the dome switch can face to a lower side in the lower part of the light guide sheet. (Replaced with a flexible printed circuit board), the structural rigidity generated as the thickness of the key top is reduced allows the flexible printed circuit board to remain intact.

As described above, the present embodiment allows the key top, the light guide sheet, the flexible circuit board, and the sheet member to be stacked in order to reduce the overall thickness but maintain the click feeling.

In addition, in the present embodiment, as the light guide sheet is provided between the key top and the flexible circuit board, the overall luminous efficiency can be increased. In the conventional mobile communication terminal, the light emitting sheet emitting light is located between the key base and the dome switch, and the light emitted from the light guide sheet has to pass through both the key base and the key top. As the transmission distance increases and the loss of light increases while passing through the key base and the key top, the amount of light transmitted to the user is reduced. However, since the key base was removed and the light guide sheet was disposed below the key top as in the present embodiment, the amount of light emitted from the light guide sheet to the outside was dramatically increased to maximize light utilization efficiency.

The keypad assembly 10 according to the present invention can be modified as follows.

First, in the above-described embodiment, the light guide sheet 31, the light source 32, the pressure-sensitive adhesive 33, and the diffuse reflection layer 34 are used as the light emitting means 30. However, as shown in FIG. It is also possible.

The EL sheet has a structure in which a phosphor is coated between a transparent conductive electrode and a back electrode, and when the alternating voltage is applied to both electrodes, light is generated while charging and discharging are repeated. The EL sheet is made of a flexible material, and when the key button 21 is pressed downward, the EL sheet moves downward together with the key button 21.

In addition to the above-described light emitting means 30, it is also possible to use a light emitting diode 321 mounted on the printed circuit board 40. At this time, the light emitting diode 321 is mounted on the upper surface of the flexible printed circuit board 40, and when the light is emitted to illuminate the key button 21 provided on the upper side.

In addition, although the protrusion 51 of the sheet member 50 is formed on the lower surface of the sheet member 50 in the above-described embodiment, it is formed on the upper surface of the sheet member 50 as shown in FIG. It is also possible. At this time, the protrusion 51 protrudes upward from the upper surface.

Although the present invention has been described in detail with reference to the embodiments and various modifications, the present invention is not necessarily limited to these embodiments and modifications, and various modifications can be made without departing from the spirit of the present invention. Can be.

The keypad assembly of a mobile communication terminal having a flexible printed circuit board according to the present invention as described above can reduce the thickness of the mobile communication terminal by the thickness of the embedded printed circuit board, thereby dramatically slimming the mobile communication terminal.

Claims (5)

A key top provided with a plurality of key buttons; Light emitting means disposed under the key top and emitting light with the key button; A flexible printed circuit board disposed below the light emitting unit, the flexible printed circuit board having a plurality of contacts provided at positions corresponding to the key buttons and a plurality of dome switches covering the respective contacts; And It is disposed below the flexible printed circuit board, and provided with a plurality of protrusions formed at positions corresponding to the contacts so as to press the dome switch in the direction of contact with the contact when the key button is pressed downwards. A keypad assembly of a mobile communication terminal having a flexible printed circuit board including a sheet member. The method of claim 1, The light emitting means is a light-transmissive light guide sheet; A light source disposed outside one edge of the light guide sheet to allow light to enter the light guide sheet; An adhesive for separating the light guide sheet from the key top and the flexible printed circuit board; And A diffused reflection layer including a plurality of diffuse reflection particles to diffuse the light passing through the light guide sheet toward the key button, the diffuse reflection layer is provided on the lower surface of the light guide sheet of the mobile communication terminal with a flexible printed circuit board Keypad assembly. The method of claim 1, And the light emitting means is an EL sheet. The method of claim 1, The protrusion of the sheet member is a keypad assembly of a mobile communication terminal with a flexible printed circuit board, characterized in that formed on the lower surface of the sheet member. The method of claim 1, The sheet member is a keypad assembly of a mobile communication terminal with a flexible printed circuit board, characterized in that attached to the lower surface of the flexible printed circuit board.

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