Patent Application
20100246143
Electromagnetic interference (EMI) is an unwanted disturbance that affects an electrical device due to either electromagnetic conduction or electromagnetic radiation emitted from an external source. The disturbance may interrupt, obstruct, or otherwise degrade or limit the effective performance of the electrical device. EMI can also be referred to as radio frequency interference (RFI). The Federal Communications Commission (FCC) has developed standards for EMI immunity for consumer electronic devices.
Electromagnetic shielding can be used to limit the penetration of electromagnetic fields into a space by blocking them with a barrier made of conductive material. Typically, the barrier is implemented as an enclosure that separates electrical devices from the outside world. Electromagnetic shielding used to block radio frequency electromagnetic radiation is also known as RF shielding. Typical materials used for electromagnetic shielding include sheet metal, metal mesh, and metal foam. Any holes in the shield must be significantly smaller than the wavelength of the radiation that is being kept out, or the enclosure will not be effective.
Conventionally, certain electrical components on a printed circuit board within a portable electronic device housing are often EMI shielded to reduce EMI emissions and/or EMI disruptions. The EMI shielding is conventionally done with an EMI can (or RF can) that is a metal container that is placed over the certain electrical components and mounted onto the surface of the printed circuit board. Often, the EMI shield is made from a metal sheet having openings or from a metal mesh. The openings can allow thermal heat to better dissipate through the EMI shield. Unfortunately, however, as compact portable electronic devices become increasingly more compact, the availability of space within a housing for a compact electronic device becomes more limited. Accordingly, given the constrained geometries and tight tolerances of compact portable electronic devices, such as handheld portable electronic devices, it is increasingly difficult to provide EMI shielding without causing a significant area increase penalty to housing designs for compact electronic devices.
Thus, there is a need for improved techniques for providing EMI shielding to one or more electrical components within a housing of a portable electronic device.
The invention pertains to improved approaches for providing electromagnetic interference (EMI) shielding to one or more electrical components within a housing of a portable electronic device. According to one aspect of certain embodiments of the invention, an electromagnetic shield can be attached to one or more edges of a substrate (e.g., printed circuit board) provided within a housing of a portable electronic device. Advantageously, this allows the substrate space to be efficiently utilized such that relatively wide electrical components can be provided on the substrate without having to further increase the width of the substrate to provide space for an EMI shielding structure and its attachment to the substrate. The housing of the portable electronic device can be compact, such as a low profile housing.
The invention may be implemented in numerous ways, including, but not limited to, as a system, device, apparatus, or method. Example embodiments of the present invention are discussed below.
As an electronic apparatus, one embodiment of the invention can, for example, include at least: a substrate having a top surface, a bottom surface and a plurality of side surfaces, the substrate being configured to support one or more electronic components coupled to the top surface or the bottom surface; and a metal structure secured proximate to the top surface or the bottom surface of the substrate over and around at least one of the one or more electronic components, wherein at least one side of the metal structure is attached to a corresponding at least one side surface of the side surfaces of the substrate.
As an electronic device, one embodiment of the invention can, for example, include at least: a printed circuit board (PCB), the PCB having a plurality of layers, and the PCB having a top surface, a bottom surface and a plurality of side surfaces; at least one electrical component mounted on the top surface the PCB; and an electromagnetic interference (EMI) shield mounted on the top surface of the PCB over and around the at least one electrical component, wherein at least one side of the EMI shield is attached to at least one corresponding side surface of the side surfaces of the PCB.
As a method for providing electromagnetic interference (EMI) shielding for an electronic device, one embodiment of the invention can, for example, include at least the acts of: forming or obtaining an EMI shield having at least a top surface and a plurality of side surfaces; receiving a substrate having at least one electrical component mounted thereon that is to be EMI shielded; and attaching the EMI shield to the substrate over and around the at least one electrical component with respect to the substrate, such that at least one side surface of the EMI shield connects to a corresponding side of the substrate.
Various aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, in which:
The invention pertains to improved approaches for providing electromagnetic interference shielding to one or more electrical components within a housing of a portable electronic device. According to one aspect of certain embodiments of the invention, an electromagnetic shield can be attached to one or more edges of a substrate (e.g., printed circuit board) provided within a housing of a portable electronic device. Advantageously, this allows the substrate space to be efficiently utilized such that relatively wide electrical components can be provided on the substrate without having to further increase the width of the substrate to provide space for an EMI shielding structure and its attachment to the substrate.
The housing of the portable electronic device can be compact, such as a low profile housing. The portable electronic device can pertain to a portable digital media player, a mobile telephone, personal digital assistant, handheld computing devices, etc.
Embodiments of the invention are discussed below with reference to
According to one embodiment, when the EMI shielding structure 104 is attached to a surface 106 (e.g., top surface) of the substrate 102, at least one side 108 of the EMI shielding structure 104 is placed against a corresponding side surface 110 of the substrate 102. Advantageously, the substrate 102 does not have to made larger to accommodate the EMI shielding. As a result, the substrate 102 can be thinner than would be conventionally provided since surface space on the surface 106 of the substrate 102 need not be provided for placing and attaching the side 108 of the EMI shielding structure 104 to the surface 106 of the substrate 102.
The EMI shielding arrangement 100 is well suited for use with portable electronic devices and, more particularly, compact portable electronic devices. For example, the compact portable electronic device can be a handheld electronic device. A housing for a compact portable electronic device housing tends to be internally filled with high density construction, such that there is very little unoccupied space. The housing for the portable electronic device can be of any material or combination of materials, such as metals, plastics, or ceramics.
The assembly process 200 can initially obtain 202 an EMI shield having at least a top surface and a plurality of side surfaces. In one implementation, the EMI shield is a can like structure having a top surface and four sides. Next, a substrate can be received 204. In one implementation, the substrate can include a top surface, a bottom surface, and a plurality of side surfaces. The substrate can have at least one electrical component that is to be EMI shielded mounted on the top surface of the substrate. Examples of electrical components that may require shielding are integrated circuits, transistors, capacitors, inductors, etc.
Thereafter, the EMI shield can be attached 206 to the substrate over and around the at least one electrical component with respect to the substrate. Typically, the EMI shield together with the substrate enclose the at least one electrical component. Here, the EMI shield is attached 206 such that at least one side of the EMI shield connects to a corresponding side of the substrate. Those sides of the EMI, if any, that are not attached to the sides of the EMI shield can be attached 206 to the top surface of the substrate. After the EMI shield has been attached 206, the assembly process 200 can end since the EMI shield has been attached 206. Other processing (not shown) can then be performed to further assemble the electronic device.
Advantageously, to support a compact, low profile design for the housing 302 of the portable electronic device 320, the EMI Shield 322 can fit over and couple to one or more sides of the substrate 304. More particularly, in the case of the electrical component 308 there is insufficient space between the edge of the electrical component 308 and the edge of the associated side of the substrate 304 to attach the EMI shield 322 on the top surface of the substrate 304. Hence, for at least one side of the substrate 304 where there is insufficient space on the top surface of the substrate 304, the EMI Shield 322 can fit over and couple to a corresponding side of the substrate 304.
In the embodiment illustrated in
To support a compact, low profile design for the housing 402 of the portable electronic device 420, the EMI shield 422 can fit over and couple to portions of two sides of the substrate 404 in the vicinity of the electrical component 408. Here, in the case of the electrical component 408 there is insufficient space between the edge of the electrical component 408 and the edge of the associated side of the substrate 404 to attach the EMI shield 422 on the top surface of the substrate 404. Hence, for the two sides of the substrate 404 where there is insufficient space on the top surface of the substrate 404 to attach the EMI shield 422 on the top surface of the substrate, the EMI shield 422 can fit over and couple to the corresponding sides of the substrate 404. However, on all of the other sides (or portions thereof), the EMI shield 422 can be attached to the top surface of the substrate 404 since there is space on the top surface of the substrate 404.
In the various embodiments noted above, an EMI shield can connect to a primary (e.g., top or bottom) surface of a substrate (e.g., printed circuit board). Alternatively or additionally, the EMI shield can attach to one or more side surfaces of the substrate. The connections between the EMI shield and the substrate can be solder connections. For example, at predetermined intervals the sides of the EMI shield can be connected to the top, bottom or side surface of the substrate. In the case where the EMI shield is attached to the sides, at least one electrical component can be placed very close to the edge of the substrate. In one example, the at least one electrical component can be placed within not more than 0.7 millimeters from the nearest edge of the substrate. In another example, the at least one electrical component can be placed within 0.2-1.0 millimeters from the nearest edge of the substrate.
Given that layout of electrical components and EMI shields on substrates (e.g., printed circuit boards) is subject to minimum spacings, conventionally the electrical components are placed more than 1.2 millimeter in from each board edge when EMI shielding is provided by a EMI shielding can attached to the top surface of the substrate. As a result, use of EMI shielding conventionally results in use of wider circuit boards. The wider circuit boards cause the resulting electronic device to be wider. In contrast, with several embodiments of the invention, the minimum spacings are substantially reduced where the EMI shield can attaches to the side surface of the substrate. For example, the electrical components can be placed at about 0.5 millimeters in from each board edge when EMI shielding is provided by an EMI shielding can be attached to a side surface of the substrate. Hence, in this example, the invention can provide a savings is about 0.5 millimeters at each of the edges where the EMI shielding attaches to a side surface of the substrate. For example, with two sides of the EMI shield can being attached to the side surface of the substrate, the space savings provided by the invention is about 1.0 millimeters.
The lid 508 is attached to or integral with the frame 506. In the embodiment shown in
With this design, the width of the printed circuit board 502 is able to remain smaller at the central portion of the frame 506 since the lid 508 extends across the full width of the printed circuit board 502 and is able to couple to the corresponding sides of the printed circuit board. Consequently, EMI shielding is provided to those one or more electrical components (including the electrical component 510) attached to the printed circuit board 502 that are now covered by the integrated frame and lid arrangement 504 together with one or more caps.
A portable electronic device as discussed herein may be a hand-held electronic device. The term hand-held generally means that the electronic device has a form factor that is small enough to be comfortably held in one hand. A hand-held electronic device may be directed at one-handed operation or two-handed operation. In one-handed operation, a single hand is used to both support the device as well as to perform operations with the user interface during use. In two-handed operation, one hand is used to support the device while the other hand performs operations with a user interface during use or alternatively both hands support the device as well as perform operations during use. In some cases, the hand-held electronic device is sized for placement into a pocket of the user. By being pocket-sized, the user does not have to directly carry the device and therefore the device can be taken almost anywhere the user travels.
The advantages of the invention are numerous. Different embodiments or implementations may, but need not, yield one or more of the following advantages. One advantage of certain embodiments of the invention is that electrical components within a portable electronic device housing can be EMI shielded in a space efficient manner. As a result, portable electronic devices can be thin and compact. Another advantage of certain embodiments of the invention is that EMI shields can be attached to one or more sides of a substrate. Advantageously, substrates internal to portable electronic device housings can be made smaller and more compact when EMI shielding can be attached to a side surface as opposed to a top surface of the substrate.
The various aspects, features, embodiments or implementations of the invention described above can be used alone or in various combinations.
The many features and advantages of the present invention are apparent from the written description. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.
