PCB board EMC design should be part of any comprehensive electronic devices and systems design , it attempts to make the product reach than other methods of EMC 's more cost effective . EMC design key technology is the study of sources of electromagnetic interference from electromagnetic interference electromagnetic emission control at the source is the ultimate solution . Control emission sources of interference , in addition to the mechanism from sources of electromagnetic interference generated by working to reduce its level of electromagnetic noise generated , the need to shield widely used (including isolation ) , filtering and grounding techniques.
EMC's key design techniques include electromagnetic shielding method , filtering circuit and grounding components should pay particular attention to the lap of the grounding design .
A , PCB board EMC design pyramid
First, the good foundation EMC design is a good application of electrical and mechanical design principles. This includes reliability considerations , such as to meet the design specifications are within acceptable tolerances , a good method of assembling and testing various technologies are being developed .
In general , today's device driver you want to install electronic equipment on the PCB. These devices are constituted by a potential source of interference and electromagnetic energy having sensitive components and circuits. Therefore , PCB EMC EMC design is the design of the next most important issue. Matching position of the active components, traces of traces , impedance grounding circuit filter design and EMC should be considered in the design . Some devices also need to be shielded PCB .
Again, internal cables used to connect the PCB or other internal sub- components. Therefore , the method including the alignment of internal cables and shielding design of the overall EMC EMC any given device is very important.
After EMC PCB design and completion of the internal cable design , special attention should be shielded enclosure design and processing methods all gaps , perforations and cables through holes.
Finally , consideration should also focus on the issue of input and output filtering power and other cables.
Second, the electromagnetic shielding
The main use of a variety of conductive shielding materials, manufacturing into a variety of housing and connected to the earth, to cut off electromagnetic noise through electrostatic coupling space , inductively coupled alternating electromagnetic field coupling or form of transmission, the main use of isolation relays or opto- isolation transformer isolation devices such as electromagnetic noise is cut in the form of conductive pathways , the ground system characterized by two separated parts of the circuit , the cut may be coupled through an impedance .
The effectiveness of the shield with the shielding effectiveness (SE) to represent the shielding effectiveness is higher, the greater the degree of difficulty for each additional 20dB of . Chassis consumer devices generally require only about 40dB shielding performance, and military equipment enclosure generally require more than 60dB shielding effectiveness .
