Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K9/00—Screening of apparatus or components against electric or magnetic fields
  • H05K9/0007—Casings
  • H05K9/002—Casings with localised screening
  • H05K9/0022—Casings with localised screening of components mounted on printed circuit boards [PCB]
  • H05K9/0024—Shield cases mounted on a PCB, e.g. cans or caps or conformal shields
  • H05K9/0032—Shield cases mounted on a PCB, e.g. cans or caps or conformal shields having multiple parts, e.g. frames mating with lids

Definitions

• the present invention generally relates to shields protecting electronic components from radio frequency and/or electromagnetic interferences Background of the invention
• a p ⁇ ted circuit board may interfere with the operation of an antenna
• One manufacturing challenge is to eliminate electromagnetic interference radiating from the PCB or from the electric components assembled on it
• the known solution for interference elimination is to use a shield protecting components situated inside the shield and/or components situated outside the shield from radio frequency interference (RFI) and/or electromagnetic interference (EMI)
• RFID radio frequency interference
• EMI electromagnetic interference
• US6180876 describes an apparatus and a method for shielding discrete areas of a PCB from electromagnetic interference
• This apparatus includes a frame and separate shielding lids
• the frame is soldered onto the solder tracks of the PCB
• the frame provides fencing dividing the PCB into discrete areas
• the shielding lids are placed on top of the frame so that each lid shields a separate discrete area
• the lids are of different heights depending on the height of the components contained in the respective discrete areas of the PCB
• FIG 1 shows two prior art EMI shields accordant to US6180876
• a frame 101 is placed on the top of a PCB 102 and lids 103 and 104 are placed on top of the frame 101
• the fences of the frame define two discrete areas 105 and 106 covered by the lids
• the PCB, the frame, and the two lids form the two EMI shields
• the lids can be considered as boxes which are open towards the frame
• the interior surfaces of the lid 103, the frame 101 , and the PCB 102 comprise one of the EMI shields shown in the figure [005]
• the shields are usually composed of several components such as shielding lids, which complicates assembling
• the second drawback of the pnor art RFI/EMI shields is that they are relatively costly to assemble
• One objective of the invention is to solve the drawbacks of RFI/EMI shields in the prior art
• Another objective of the invention is to provide a RFI/EMI shield especially suitable for a mobile phone and other small-sized devices equipped with a display
• the objectives of the invention are achieved by placing a frame on the top of a printer circuit board (PCB) and a display on top of the frame so that the intenor surfaces of the display, the frame, and the PCB comp ⁇ se an RFI/EMI shield
• lids are omitted from the RFI/EMI shield according to the invention This saves space inside the device in which the shield is assembled
• the invention compnses the RFI/EMI shield and the arrangement for protecting electric components from RFI/EMI
• FIG 1 shows two of the prior art EMI shields
• FIG 2 shows the EMI shield according to the invention
• FIG 3 shows the electromagnetic shielding arrangement in a device having at least one display
• FIG 4 shows a display partly covering a frame
• Radio frequency interference can be considered a certain type of electromagnetic interference (EMI)
• EMI electromagnetic interference
• the term “electromagnetic shield” or simply “shield” refer to the shield that is intended to protect a device and its components from EMI and/or RFI.
• FIG. 2 shows the electromagnetic shield in accordance with the invention.
• the shield is especially intended for mobile phones and other small- sized devices that include at least one display.
• the shield is composed of: a frame 201 , a printed circuit board 202, and a display 203.
• the frame has fencing that divides the area of the PCB 202 into two discrete areas 204 and 205.
• the continuous fencing 206 extends in an outward direction from the surface of the PCB and surrounds the discrete area 204 of the PCB.
• the dis- play 203 of a device is assembled on the frame 201.
• the back plane of the display is assembled on the frame so that the face of the display 207 is usable.
• FIG. 3 shows the electromagnetic shielding arrangement according to the invention. This figure is a cross-section of the electromagnetic shielding.
• the arrangement comprises: a frame 301 , a printed circuit board 302, and a display 303 having continuous fencing surrounding a discrete area of the PCB.
• a plurality of electric components 304-306 is situated in the discrete area of the PCB 302.
• the frame 301 is grounded to the PCB 302, for example, by soldering, screwing, or gluing, or by using clips.
• the display 303 is grounded to the frame, for example, by soldering, screwing, or gluing, or by using clips.
• the grounding between the display and the frame can be achieved by using metal springs, conductive adhesive, or some other conductive elastomer.
• the back plane of the display is preferably made of conductive material such as metal or metalized plastic. As shown in FIG.
• the plurality of electric components 304-306 is encapsulated inside the display 303, the frame 301 , and the PCB 302.
• This encapsulation 307 is illustrated with a dashed line.
• the encapsulation operates as electromagnetic shielding.
• the encapsulation/shielding 307 protects the components of the PCB 302 from the RFI/EMI originating outside of the encapsulation.
• the component 304 situated inside the encapsulation is a radiation source
• the encapsulation/shielding also protects elect ⁇ c components situated outside of the encapsulation
• the antenna of a mobile phone needs to be protected against RFI [015]
• an appropriate display is assembled to a frame so that the display, the frame, and a certain area of the PCB surrounded by the frame encapsulate at least one component situated in the said area of the PCB
• the arrangement saves space in inside a device in which the shield is assembled
• the ar- rangement and the shield according to the invention offer the following benefits First, the arrangement makes it easier to pre-test the display with the shield Secondly, it makes it easier to maintain a device containing the PCB, especially when the display is assembled on the frame by screwing or by using clips Thirdly, the display efficiently attenuates RFI and thus protects the operation of elect ⁇ c components
• a frame does not need to surround the whole surface of a PCB
• the surface of the display i e the back plane of the display
• the display may be larger than the area of the PCB surrounded by the frame, because also in this case the display operates as a part of the RFI/EMI shield
• FIG 4 shows a display partly covenng a frame
• the shielding comprises the frame 401 , the PCB 402, and the display 403
• the display 403 only partly covers the frame 401 and the PCB 402 under it
• the shape of the frame 401 is such that the frame covers the component 406
• the other components 404 and 405 situated on the PCB are covered by the display 403
• the components 404-406 are encapsulated 407 by the shielding
• a frame is a part of the outer covering of a device Plastic or metalized plastic is especially useful material for this purpose
• the outer covenng of a mobile phone is usually composed of two pieces a piece which is situated on the same side as the display and another piece which is situated on the opposite side
• the piece situated on the opposite side of the display may be formed so that it contains the frame that is a part of an RFI/EMI shield

Landscapes

• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
• Telephone Set Structure (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8566096

Family Applications (1)

Country Status (3)

Families Citing this family (1)

Family Cites Families (3)

• 2003
  • 2003-05-13 FI FI20030708A patent/FI20030708A/fi not_active Application Discontinuation
• 2004
  • 2004-05-07 EP EP04731644A patent/EP1625779A1/de not_active Withdrawn
  • 2004-05-07 WO PCT/FI2004/050060 patent/WO2004103049A1/en active Application Filing

Non-Patent Citations (1)

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