An electrically continuous, grounded conformal EMI protective shield and methods
for applying same directly to the surfaces of a printed circuit board. The EMI
shield adheres and conforms to the surface of the components and printed wiring
board. The shield takes the shape of the covered surfaces while adding little to
the dimensions of the surfaces. The EMI shield includes low viscosity, high adherence
conductive and dielectric coatings each of which can be applied in one or more
layers using conventional spray techniques. The conductive coating prevents substantially
all electromagnetic emissions generated by the shielded components from emanating
beyond the conformal coating. The dielectric coating is initially applied to selected
locations of the printed circuit board so as to be interposed between the conductive
coating and the printed circuit board, preventing the conductive coating from electrically
contacting selected components and printed wiring board regions. A high viscosity,
non-electrically-conductive filler material is applied to printed circuit board
regions that have surfaces that are cavitatious and/or which have a highly variable
slope. The filler material can be used in conjunction with conformal EMI shield
board level coating. The high viscosity, electrically non-conductive filler material
substantially covers each cavity such that the covered cavity is inaccessible and
that the covered region of the printed circuit board has a contiguous, contoured
surface. A pre-manufactured non-electrically-conductive component cover can be
mounted over a corresponding component and secured to the printed wiring board.
The component cover and printed wiring board surround the component, forming a
sealed enclosure. The component cover has a thin cross-section and an interior
surface that follows closely the surface of the component. This minimizes the volume
enclosed by the component cover. In addition, the exterior surface of the component
cover has a low profile, and prevents the conformal EMI shield from physically
contacting the covered component. Instead, the exterior surface of the component
cover is coated with the EMI shield.