Communications: radio wave antennas – Antennas – With housing or protective covering
Reexamination Certificate
2000-05-25
2003-09-02
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With housing or protective covering
C343S702000
Reexamination Certificate
active
06614405
ABSTRACT:
OBJECT OF THE INVENTION
The object of the invention is a frame structure according to the preamble of claim
1
. The invention relates to frame structures, particularly to mobile stations and other small-sized portable equipment operating at high frequencies.
BACKGROUND OF THE INVENTION
Mobile phones utilize frame structures, to which the printed circuit board of the phone is fixed, whereby the frame structure is generally manufactured by casting, typically die casting, by deep drawing, by bending a metal sheet, or from metal coated plastic. Usually the frame structure comprises partitions which separate the components or component groups mounted on the device's printed circuit board from each other, whereby the partitions also form an RF shield in order to reduce the power of the radio frequency radiation received or emitted by said component or component group. Typically the partitions also make the frame more rigid.
The purpose of the frame structure is typically to protect the internal components of the device and in addition to support the printed circuit board or boards and other components of the device, as well as to reduce any interfering radiation generated by device from spreading into the environment. A purpose of the frame is also to protect the device's components from external electromechanical interference sources or signals being coupled to the components.
Previously there are many known ways to fasten components, such as printed circuit boards or corresponding, to the frame structure. Threadings can be made in the frame structure, particularly it its partitions or in pins made separately in the frame structure, so that the fastening can be made with screws. As the frame structures are often made very thin in order to minimize the weight of the device the partitions must often be equipped with bulges around the threadings so that there will be sufficiently material around the threads in order to achieve a firm fastening. One such solution is presented in the application publication EP-391 020, which presents a mobile phone frame structure. In the solution presented by the publication partitions are formed in connection with the frame structure so that the partitions have thickened places in partition corners and ends which enable fastening with screw. In a solution of this kind the components are fixed to the frame with the aid of screws, which complicates the manufacture of the frame structure and the assembly of the equipment. First the frame must be cast, after which the required threadings must be formed in different places of the structure. In the assembly phase the printed circuit board must be positioned accurately, so that the fastening holes in the printed circuit board are accurately registered with the threadings, and then the screws must be individually screwed. All this will result in a large number of work steps, which causes substantial costs in mass production.
The use of screws to fasten printed circuit boards and other components means that their corresponding threads require extra space in the frame structure and a corresponding space also on the printed circuit board which shall be fastened at that place, so that a component fastened on the printed circuit board will not be clamped between the printed circuit board and the fixing point. Thus a screw fastening consumes a substantial area on the printed circuit board.
In the mass production of mobile stations and corresponding devices it is essential that there is a minimum number of work steps and that they can be performed as fast as possible. Further, a maximally efficient use of the printed circuit board area is of primary importance in small-sized devices. Such devices must also be as light as possible, whereby it is an object to manufacture the components of the device of materials which are as thin and light as possible, but in spite of this the resulting device must be as rigid as possible and withstand blows, wear and torsion. Frame structures have been made for instance of plastics, on the surface of which a thin metal film is formed in order to obtain electrical protection characteristics. Plastic is a light material, but a problem is the low rigidity of plastic structures. In such cases the rigidity can be increased with the aid of partitions, but then the size of the device must be increased due to the space required by such extra reinforcing structures.
Magnesium has also been used as material for frame structures. Advantages of the magnesium is its lightness, the rigidity of structures made of it, and a possibility to realize versatile forms. Disadvantages of the magnesium are on the other hand a low resistance against corrosion and the high costs, and the threading bores also cause strength problems. Further a frame made of magnesium must be coated, which causes an extra work step. The coating also impairs the electrical characteristics of the magnesium frame, because the coating causes losses.
SHORT DESCRIPTION OF THE INVENTION
The object of the present invention is to eliminate the above mentioned disadvantages. An object of the invention is also a simple, cheap and durable structure. A further object of the invention is to realize a frame structure which is suitable to be used in mobile stations and other corresponding devices utilizing high frequencies, in which the frames must have a robust and rigid structure which acts as an efficient barrier against electromagnetic radiation and to which the device's components can be fixed in a simple, easy and reliable manner.
The objects of the invention are attained by forming the frame structure by extrusion, and by forming the fixing means required for fastening the components during the extrusion. Such fixing means are preferably pin-like projections, which can be compressed into a rivet fixing the component. Such fixing means can also be strip-like clamping edges which are bent over the edges of the component. With the aid of fixing means of this type it is at the same time possible to form both a mechanical fixing and a good electrical contact between the component and the frame structure. During the extrusion it is also possible to fix parts made of other materials to the frame structure, such as fixing means of different types and other components, such as antennas.
The frame structure according to the invention is characterized in what is said in the characterizing clause of the independent claim concerning the frame structure. The invention also relates to a device, which is characterized in what is said in the characterizing clause of the independent claim concerning the device. Further the invention relates to a method, which is characterized in what is said in the characterizing clause of the independent claim concerning the method. The dependent claims represent other preferred embodiments of the invention.
According to a preferred embodiment of the invention a rivet fixing can act as the fixing mechanism which replaces the screw fastening. Then the rivets are extruded in connection with the partitions belonging to the structure, whereby the rivets are made as projections directed upwards from the partitions and having a thickness, which can be the same as that of the partition. In connection with the fixing of the printed circuit board the free area of the compartments separated by the partitions is not reduced due to the fixing means, and the area of the printed circuit board can be utilized more effectively for components, compared to the conventional use of screws. A separate work step to enable the fixing, for instance threading, is avoided because the fixing means are formed already during the extrusion. The use of rivets integrated in the frame also facilitates the assembly phase, because there is no need to mount separate fastening means. Compressing a rivet is also a rapid step compared to the turning of a screw. One of the means formed during the extrusion can also be left so short that it is not thicker than the printed circuit board, whereby this means acts only as an registering means. The
Lohtander Kari
Mikkonen Esa
Pesonen Kalevi
Darby & Darby
Dinh Trinh Vo
Filtronic LK OY
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