If your application requires limits in electromagnetic and/or electrostatic interference, shielding may be required. Shields are material around a conductor or group of conductors that limit these factors.
These materials are normally produced with a drilling process and therefore the coverlay is limited in its features and characteristics. The coverlay openings typically must be round and oval holes and cannot have square cornered or dense features. Both polyester and polyimide coverlay can be punched or blanked in lieu of the drilling process and is normally done for large coverlay openings.
|Via Hole||Covered with coverlay|
|Component Hole||.005″ (.127mm) minimum per side larger than the copper pad|
|Feature Definition||.008″ (.20mm) minimum|
Photoimagable Coverlay & Soldermask (Covercoat)
Both photoimagable coverlay and soldermask are produced by a photo controlled process and are used for tight pad spaces. This process enables unique shapes to be applied anywhere on the circuit. Photoimagable coverlay is usually not used with 2 oz. copper or above. Due to the thickness of the copper, photoimagable coverlay and soldermask will not conform around the area of some copper features.
|Via Hole||Covered with soldermask|
|Component Hole||.003″ (.076mm) minimum per side larger than the copper pad|
|Feature Definition||.005″ (.127mm) minimum|