 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cover
with Form-in-Place EMI Gasket Eliminates Shielding Cans
|
|
|
|
|
.....In
a digital satellite telephone system, a noisy PCB was shielded
using 12 metal cans. These were mounted into "fences" soldered
onto ground traces. To reduce costs, save board space, and shorten
maintenance times, the manufacturer changed from this shielding
solution to a conductive cover with a form-in-place EMI gasket. |
|
|
|
.....The
cover is an injection molded PC/ABS plastic with a conductive
coating on its inner surface. The shielded cover's internal
ribs provide more than 70 dB of EMI isolation between the 12
separate compartments or circuits on the PCB. Due to flatness
and dimensional tolerances, the cover ribs did not mate perfectly
against the PCB surface. Since the width of each rib was only
about 3 mm, attaching groove-fit or adhesive-mounted EMI gaskets
was impractical. |
|
|
|
|
|
|
|
|
|
|
 |
|
|
.....The
solution was a Cho-Form 3.0 robotically dispensed form-in-place
conductive elastomer. By programming the EMI gasket configuration
on a three-axis dispensing machine, an accurately positioned
"D"-profile gasket bead was formed and cured directly onto the
cover ribs. The plastic easily withstood the 85°C (185°F) in-line
oven cure required for the elastomer material selected. Self-tapping
screws provided sufficient closure force to achieve 20-25% gasket
deflection. |
|
|
.....Cho-Form
technology permits rapid prototyping, design changes and scale-up
at
nominal cost, accommodating batch runs or continuous high-speed
production, from ten to ten million parts. Room temperature
cure materials are also available.
|
|
|
|
|
|
|
|
 |
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
 |
 
|
|
