GB2344564A

GB2344564A - Mobile phone including a lightguide with a spacer element(s) which mounts the guide to a circuit board and includes a cavity to accommodate a light source

Info

Publication number: GB2344564A
Application number: GB9918171A
Authority: GB
Inventors: Karl-Heinz Rademacher; Ernst Macher
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1998-08-06
Filing date: 1999-08-02
Publication date: 2000-06-14
Anticipated expiration: 2019-08-02
Also published as: DE19835664A1; GB2344564B; GB9918171D0; DE19835664C2

Abstract

A luminous body 10 includes a plane lightguide 14 which has a spacer element(s) 16 that mounts the lightguide to a circuit board 12 with a predefined distance therebetween. The spacer element(s) is formed with a cavity 18 (e.g. cone-shaped section 24) to accommodate a light source 20 (e.g. an LED). The luminous body may be fabricated from a material selected from a group comprising polycarbonate, plexiglass, and ABS resin. The surface(s) of the lightguide and the spacer element(s), which covers a hollow space 22 between the body and the circuit board, may be coated with a shielding layer 17 (e.g. metallised Aluminium). The luminous body may be used in a mobile phone assembly wherein the body is arranged between a printed circuit board and a keyboard (Figs.3-5). The different keys (56-1,...56-n,Fig.4) of the keyboard may be arranged into a matrix and the cavities (18,Fig.4) are provided at every centre between four keys to allow for uniform distribution of light via the body to the different keys of the assembly. The arrangement allows for further circuit components to be placed underneath the luminous body on the circuit board without increasing the overall volume of the assembly.

Description

78 492 GB 2344564 Assembly concept for mobile phones

FIELD OF THE INVENTION

The present invention relates to an assembly concept for mobile phones, and in particular to an assembly concept for mobile phones considering the increased demand for placing additional circuit components on the circuit boards of these mobile phones.

TECHNOLOGICAL BACKGROUND

The increasing functionality of mobile phones such as multiband mobile phones requires the placement of additional circuit components on the circuit boards of these mobile phones. However, according to the known assembly concepts free spaces are provided on the printed circuit boards of mobile phones for the keyboards such that the regular arrangement of the keyboard keys almost prohibits the placement of circuit components therebetween.

This may be explained with respect to Fig. 6 showing a crosssectional view of a keyboard part in a known mobile phone. As shown in this Fig. G, the keyboard part 100 is realized with 1 2 a keyboard comprising silicon keypads 102 covered by a keycap 104 for every key. Here, the keycaps 104 are provided for a better contact feeling when pressing the silicon keypad 102.

Further, guiding elements 106 are provided between the silicon keypad parts 102 to maintain an appropriate spacing therebetween. Each silicon keypad part 102 is provided with a contact surface 108. When the silicon keypat 102 is pressed towards a printed circuit board 110, a contact may be closed thereon. For the illumination of the keyboard 100 there are provided lightguides 112 on the printed circuit board 110 to distribute light from a light s ource (not shown) to the different keys via these lightguides 112 and the silicon keypad 102.

As shown in Fig. 6, the provision of the lightguides 112 on the printed circuit board 110 prohibits the placement of larger circuit components in the keyboard area of the printed circuit board 110. Further, this approach is not well adapted to the placement of additional circuit components taking into account that the overall volume of the mobile phone should not be increased considerably through these additional circuit components.

SUMMARY OF INVENTION

In view of the above the object of the invention is to provide an assembly concept for mobile phone units such that space available for the arrangement of functional units is maximized while keeping the overall volume of mobile phone units basically unchanged.

According to the present invention, this object is achieved through a luminous body for a mobile phone assembly, 3 comprising at least one plane light guide element adapted to distribute light within the mobile unit assembly, at least one distance element to mount the plane light guide element to a circuit board with a predefined distance therebetween, wherein the distance element is formed with a cavity to accommodate a light source.

Therefore, according to the present invention there is provided additional placement area on the printed circuit board between the plane lightguide element and the printed circuit board. This additional placement area may be particularly useful for a mobile phone assembly with increased functionality such as multiband operation. Further, also bigger circuit components may be easily placed on the printed circuit board under the plane lightguide element.

According to a preferred embodiment of the present invention, the form of the cavity is determined in the dependence of the positioning of the different distance elements.

Therefore, this preferred embodiment of the invention takes into account that cavities being arranged at, e.g., the boarder line of a keyboard should direct the light in a different direction when being compared to cavities being arranged in the inner part of the keyboard area.

According to yet another preferred embodiment of the present invention, the distance elements are arranged selectively in dependence of circuit components previously being placed on the printed circuit board.

Therefore, this preferred embodiment of the present invention allows to adapt the illumination of the keyboard to placement requirements existing in view of the circuit components. In consequence, restrictions on the placement of circuit 4 components may be almost completely avoided so as to increase the flexibility during the design of the mobile phone assembly.

According to yet another preferred embodiment, the plurality of distance elements are arranged into a matrix and each cavity has the form of a cylindrical hollow body extending in cone form into the plane lightguide element.

Here, the cone form allows for an optimal coupling of the light output by the light source arranged in each cavity into the luminous body and therefore for a very uniform distribution of light through the luminous body.

According to another preferred embodiment of the present invention, a plurality of distance elements are arranged along a circumference of a rectangle and each cavity has the form of a cylindrical hollow body with the side surface being directed towards the plane lightguide element being slanted.

Here, again the coupling of light output by a light source accomodated in the cavity is optimized through slanting a side wall of the cylindrical hollow body. Further, this embodiment allows to minimize the splitting of the placement area covered through the luminous body or, in other words, to provide the placement area covered by the luminous body in a continuous fashion.

According to yet another preferred embodiment of the present invention, the luminous body is fabricated from a material selected from a group comprising polycarbonate, plexiglass, and ABS resin, respectively.

According to this embodiment, the different materials allow for a very effective guidance of light to the different keys 1 5 of the keyboard. Further, these materials also provide sufficient strength to withstand the pressure during actuation of a keyboard mounted on top of the luminous body, e.g., a keypad.

According to yet another preferred embodiment of the present invention, a surface of the plane lightguide element covering a hollow space between the luminous body and the printed circuit board is coated with a shielding layer, e.g.,.a metallization formed of aluminum.

This leads to the further advantage that light guided through the luminous body is not diffused into this hollow space and that further an electromagnetic shielding of the circuit components placed underneath the luminous body may be simultaneously achieved.

According to a second aspect of the present invention, there is provided a mobile phone assembly wherein the luminous body described above is arranged between a printed circuit board and a keyboard.

Therefore, this arrangement allows for further circuit components to be placed underneath the luminous body on the printed circuit board without essentially increasing the overall volume of the mobile phone assembly.

BRIEF DECRIPTION OF DRAWING Preferred embodiments of the present invention will be described with respect to the enclosed drawing in which:

Fig. 1 shows a cross-section of a luminous body according to a first embodiment of the present invention 1 6 being arranged on a circuit board, or a printed circuit board, respectively; Fig. 2 shows a cross-section of a luminous body according to a second embodiment of the present invention being arranged on a printed circuit board, or a printed circuit board, respectively; Fig. 3 shows the arrangement of a keypad on top of.the luminous body according to the first embodiment of the present invention; Fig. 4 shows a mobile phone assembly according to a third embodiment of the present invention; Fig. 5 shows a mobile phone assembly according to a fourth embodiment of the present invention; and Fig. 6 shows a silicon keypad according to the technological background of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a cross-section of a luminous body according to a first preferred embodiment of the present invention. Here, the luminous body 10 is arranged on top of a printed circuit board 12. The luminous body consists of a plane lightguide element 14, a distance element 16 to maintain a predefined distance between the plane lightguide element 14 and the printed circuit board 12. Further, the distance element 16 is formed with a cavity 18 to accomodate a light source 20, e.g., a light emitting diode. Still further, the surface of the plane lightguide element 14 and the distance element 16 covering a hollow space 22 between the luminous body 10 and 1 7 the printed circuit board 12 may be coated with a metallization such as aluminum.

According to the present invention, the luminous body is fabricated from a material such as polycarbonate, plexiglass, and ABS resin, respectively. Therefore, the luminous body does provide both high transparency for the light to be guided therein and high mechanical strength such that a keyboard may be placed thereon and the luminous body may withstand the pressure during the actuation of the different keys.

As shown in Fig. 1, this first embodiment of the present invention operatively allows to distribute light uniformly via the plane lightguide element 14 through accomodating a light source 20 into the cavity 18 of the distance element 16. In case distance elements are arranged in center parts of the printed circuit board, the cavity preferably comprises a cone-formed section 24 extending into the plane lightguide element 14 for an improved coupling of light thereto. Also, the metallized aluminum 17 does not only achieve an electromagnetic shielding of the circuit components placed in the hollow space but also avoids a diffusion of light from the plane lightguide element 14 into this hollow space 22.

Fig. 2 shows the second embodiment of the luminous body according to the present invention being specifically adapted for arranging distance elements at the circumference of the placement area covered through the luminous body.

As shown in Fig. 2, here a further plane lightguide element 26 is fixed onto a further circuit board or printed circuit board 28 with a distance element 30. The distance element is again formed with a cavity 32 wherein a light source 34 is accomodated. As with the embodiment shown in Fig. 1 a 8 shielding layer 36 of metallized aluminum may be provided at those surfaces of the luminous body forming a hollow space 38 for the placement of additional circuit components.

As also shown in Fig. 2, the cavity 32 has the form of a cylindrical hollow body and the side surface 40 of the cylindrical hollow body 32 is slanted towards the plane lightguide element 26 for an improved coupling of light output through the light source 34 thereto. In addition, also the related side surface 42 of the hollow space 38 is slanted such that the part 42 of the metallized aluminum reflects light back to the plane lightguide element 26 to avoid any diffusing into the hollow space 38.

While above different embodiments of the luminous body have been described with respect to Fig. 1 and 2, respectively, in the following the use of these luminous bodies within a mobile phone assembly will be described with respect to Fig. 3 to 5, respectively.

Fig. 3 shows the use of a keypad 44 on top of the luminous body according to the first embodiment. At every key 46 supported through a support element 48, there is provided a pressure element 50 being directed towards the printed circuit board 12. In case the key 46 is pressed, the pressure element exercises a pressure onto the convexity 52 (often referred to as 'dome,) such that a contact on the contact layer 54, e.g., a polyester foil, is closed. As already outlined above, the luminous bodies according to the present invention allow for the placement of additional components also underneath, e.g., the keyboard.

With a top view, Fig. 4 shows the use of the luminous body according to the first embodiment supporting the keypad 44 within a mobile phone assembly.

9 Here, the different keys 56-1,..., 56-n of the keyboard are arranged into a matrix and the cavities 18 are provided at every center between four keys, e.g., 56-1,..., 56-n. Therefore, this arrangement allows for a very uniform distribution of light via the luminous body to the different keys of the mobile phone assembly. However, the placement area underneath the keyboard is split up through the gridlike arrangement of the distance elements in the luminous body.

Fig. 5 shows another embodiment for the use of the luminous body within a mobile phone assembly.

In particular, Fig. 5 relates to the use of the luminous body according to the second embodiment of the present invention within a mobile phone assembly such that light sources are arranged at the circumference of the keyboard between two adjacent rows, respectively. Here, the slanted region 40 shown in Fig. 2 is directed to the interior part of the keyboard to achieve an efficient transfer of light output through the light source 34 via the luminous body to the different keys of the keyboard.

While this embodiment of the mobile phone assembly achieves a slightly less uniform light distribution when compared with the embodiment of the mobile phone assembly shown in Fig. 4, it does not sacrifice for placement space so that also very large circuit components may be easily placed underneath the luminous body.

It should be understood that while two embodiments of the mobile phone assembly have been described with respect to Fig. 4 and 5, respectively, both approaches clearly may be combined in an appropriate way to optimize the criteria available placement space and light distribution simultaneously.

Also, while specific forms for the cavity in the distance element have been explained with respect to Fig. 1 and 2, respectively, it should be appreciated that the form of this cavity is generally determined in dependence of the position of the distance elements on the printed circuit board. In particular, the form of the cavity must be chosen such that the light coupling is optimized while minimizing the space requirements for the distance elements to increase the available placement area. Also, while the shielding layer has been described as metallized aluminum layer, equivalently any reflecting material such as, e.g., white paper or any other metallization may be easily used to that purpose, whatever is appropriate.

11

Claims

1. Luminous body for a mobile phone assembly, comprising:

a) at least one plane light guide element (14; 26) adapted to distribute light within the mobile phone assembly, b) at least one distance element (16; 30) to mount the plane light guide element (14; 26) to a circuit board (12; 28) with a predefined distance therebetween; wherein c) the distance element (16; 30) is formed with a cavity (18; 32) to accommodate a light source (20; 34)

2. Luminous body according to claim 1, characterized in that the form of the cavity is determined in dependence of the positioning of the at least one distance element (16; 30).

3. Luminous body according to claim 1 or 2, chax-acterized in that a plurality of distance elements are arranged at positions on the circuit board (12; 28) selected in dependence of circuit components placed on the circuit board (12; 28).

1 12

4. Luminous body according to claim 1, characterized in that a plurality of distance elements (16) are arranged into a matrix.

5. Luminous body accordin! to claim 4, characterized in that each cavity (18) has the form of a cylindrical hollow body extending in cone form into the plane light guide element (14).

6. Luminous body according to claim 1, characterized in that a plurality of distance elements (30) are arranged along the circumference of a rectangle.

7. Luminous body according to claim 6, characterized in that each cavity (32) has the form of a cylindrical hollow body and that the side surface (40) of the cylindrical hollow body being directed towards the plane light guide element (26) is slanted into the plane light guide element (26).

8. Luminous body according to one of the claims 1 to 7, characterized in that the luminous body is fabricated from a material selected from a group comprising polycarbonate, plexiglass, and ABS resin, respectively.

9. Luminous body according to one of the claims 1 to 8, characterized in that surfaces (42) of the plane light guide element (14; 26) and the distance element (16; 30) covering a hollow space (22; 38) between the luminous body and the circuit board (12; 28) are coated with a shielding layer (17; 36).

10. Luminous body according to claim 9, characterized in that the shielding layer (17; 36) consists of metallized aluminum (Al).

1 13

11. Mobile phone assembly, comprising:

a) a circuit board (12; 28) for the placement of functional circuit elements of the mobile phone assembly, b) a luminous body (10; 25) according to one of the claims 1 to 10 arranged with a predefined distance above the circuit board, and C) a keyboard with a plurality of keys (56-1, 56-n) being supported through the luminous body (10; 25).

12. Mobile phone assembly according to claim 11, cha.racte.rized in that the keys are arranged into a matrix and that the luminous body is provided with a cavity at least at one center of four keys (56-1, 56-n), respectively.

13. Mobile phone assembly according to claim 11 or 12, characte.rized in that the keys are arranged into a matrix and that the luminous body is provided with at least one cavity (32) between at least two adjacent key rows of the matrix and at the circumference of the matrix.

14. Assembly method for a mobile phone, comprising the steps:

a) placing the electronic circuit components and a display unit of the mobile phone on a circuit board (12; 28), 1 14 b) mounting a luminous body (10; 25) according to one of the claims 1 to 10 onto the circuit board, C) mounting a keyboard (44) onto to the luminous body (10; 25), and d) fixing the circuit board (12; 28) with the luminous body (10; 25) and the keyboard (44) mounted thereto in a housing.

15. Luminous body for a mobile phone assembly substantially as described above with reference to Fig. 1 to 3 of the accompanying drawings.

16. Mobile phone assembly as described above with reference to Fig. 4 and 5 of the accompanying drawings.