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EMI Shielding Tips and FAQs

 

 EMI/RFI Shielding Management Tips and FAQs
 

1.What are the most important factors that effect EMI/RFI shielding?

The following components comprise an effective EMI/RFI management solution:

        • A complete Faraday Cage over the EMI/RFI transmitting components that are tied to a true ground.
        • The EMI/RFID shielding cans or lids are the last resort and can always be relied on if the circuit
          design cannot take care of the EMI/RFI noise. 
        • A good EMI/RFI gasket made of compressible metal springs or a conductive rubber is the solution
          when a large area inside a cabinet must be addressed. 
        • If a see through window is required, a blackened mesh over a transparent window is a good
          solution. 
        • If there is still EMI/RFI leakage, a good conductive caulk will take care of it. 
        • Conductivity of the shielding materials is directly related to the shielding effectiveness of the
           solution, then followed by the thickness of the shielding materials.
        • Ventilation holes along the top surfaces are currently the only solution when heat must be
           removed for the components inside the shielding can.
         
Some of the potential pit-falls after implementing the solutions listed above:

        • There is always a potential resonance at some higher frequency that is generated by the size and
           shape of the shielding can or lid that can put the compliance out of order. 
        • Potentially oxidation and galvanic corrosion can occur whenever there are two different metals
           used (including filled conductive gasket, adhesive, coating and caulks). 
        • Soldering of the lids while providing the best and most consistent shields, can be costly to remove
           to rework any of the components.

2. Besides soldering the EMI/RFI lid or cover, is there a better way?

        • With the lead-free soldering requirements on most commercial devices, the EMI/RFI shielding
           cans/covers must be soldered at the same time as the other components are being attached.
           This process makes the subsequent visual inspection almost impossible.
        • Since the processing temperature is as high as 250-300°C, making repairs by removing the
           covers/cans that much more difficult and detrimental to the components on the board.
        • AIT has a solution that can be directly placed on the shielding cans/lids without soldering. The lids
          or cans are pre-coated with a pressure-sensitive conductive adhesive that forms both mechanical
          attachment bonding and electrical grounding using the same geometric shape.       

 
3. What can I do if I need to remove more heat from the components inside the EMI/RFI cans/lids besides adding more ventilation holes and fans?

        • Adding ventilation holes and fans outside of the EMI/RFI shielding can/cover can only achieve
          a basic level of heat removal of less than a watt. Higher power chips that are now used in
          communication may require much better thermal management along with EMI/RFI shielding. 
        • AIT has a patented thermal solution of a compressible phase-change pad that can be pre-applied
          onto the EMI/RFI shielding can/cover before attachment to the circuit board. For best results, heat
          the lids to above 60°C before placement onto components or modules that need both thermal and
          EMI shielding requirements. This temperature permits good flow to minimize any trapped air gaps.

4.Is dispensing and curing a conductive rubber caulk or gasket compound the most cost effective method for covers of cellular phones and other devices? 

       • Traditionally the form-in-place method of placing a gasket is the most cost effective method in
          terms of materials but may be more costly in terms of manufacturing. 
        • AIT can provide a pre-form shaped-gasket to specific engineering drawings with conductive
          pressure-sensitive adhesive as a high volume alternative to the form-in-place EMI/RFI gaskets.
        • Use of pre-form gaskets can be extremely cost effective and faster in manufacturing for
          larger volumes. 
         
5. What can I do when traditional copper tape shielding relaxes and does not make proper electrical contact lossing the shielding effectiveness? 

        • The problem when using most of the copper tapes on the market today is that they provide
           short-term compliance and are a temporary solution to the problem but lack long-term
           reliability. 
        • Conductive EMI/RFID caulking material can be applied over the shim areas that are currently
           in place. 
        • If you are doing it new or designing for a new project, you may want to use an intrinsically
           conductive pressure sensitive copper tape such as those available from AIT. AIT uses a
           proprietary Z-axis conductive pressure sensitive tape to provide better Emi/RFI shielding.
           The XY discontinuity may help minimize the chance of residual resonance noise that may occur.

 

03/09/2010 09:06

EPAK
Latest  News:
09.08.2010

BV9000 Videos Added & Epak Electronics YouTube video channel online

03.08.2010

Comco Celebrate 45th Year Anniversary

Started in 1965 Comco Inc have been in business selling microblasters for 45 years. Epak Electronics Ltd have been Comco's UK representative since 1970 - and have built up a wealth of information and experience in micro abrasive blasting over the last 40 years.

21.07.2010

RPS ANTHEM lead dipping, twin solder bath solderability system now shipping. With dynamic solder bath or wave nozzles, single or double static or dynamic flux baths and available with optional rotary head for QFP packages. Epak have already shipped and installed the first Anthem in the UK.

   

 

09.07.2010

NEW UV-C Intensity Labels Available. Now a label is available specifically to target UV-C intensity measurement. Available now.

MORE DETAILS

09.03.2010 

Read Our Technical Article on Micro-Abrasive Applications in Micromachining in the latest Commercial Micro Manufacturing Magazine.

21.10.09 Epak Custom Large Fossil Blast Cleaning Cabinet

18.09.09 Epak BV9000 Wafer Beveller Installed

Our latest custom project to build a larger scale Wafer beveller based around the Comco BV8003 has been delivered and installed.

Designed to take from 30mm to 150mm (6") wafers. 

       27.10.08       SPT RTR-D2/D3 series  Special Pickup Tips for thin or fragile components
14.10.08 Safe-T-Stain : We are able to source all the Safe-T-Stains again in 8oz bottles. 
18.04.08 NEW from AI Technology : COOL-SILVERTM CPU Thermal Grease gives 2-3 degree centigrade lower  temperatures over the industry "standards" even for a medium performing CPS for longer life of the processors and electronic devices. 
19.03.08 : New  Website Launched

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