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smithsinterconnect.com
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Filter Capacitor Comparison
The heart of the filter connector is the capacitor array. Smiths Interconnect uses
monolithic ceramic capacitor array on both thick and thin film technology. Using a dry
process to laminate the layers of X7R ceramic tape, Smiths Interconnect is capable of
achieving capacitance values from 100pF to 100nF on the same array. Our extensive
filtering capability allows for unique applications and arrangements not engineered
elsewhere in the connector world. This may include mixed contact sizes, new insert
arrangements, or high voltage applications up to 2000VDC Dielectric Withstand Voltages
(DWV).
The planar array is much more complex and versatile in its design. The planar uses
the same X7R material as the tubular capacitor, however the electrodes run
perpendicular to the contact. This allows higher capacitance and higher voltage
ratings, as the pin to pin spacing does not affect the design as much. With the
electrodes running perpendicular to the contact, we can stack more electrodes thus
increasing capacitance and at the same time, thicken the dielectric between
electrodes to increase withstanding voltages.
The planar array also has the advantage of strength. As the layers of ceramics are stacked
perpendicular to the contact, we can increase the planar thickness to about .100" to
withstand high vibration scenarios as in the EFA. This far outweighs the .015" found in the
Tubular capacitor. Because the capacitor is ceramic, it is relatively brittle in comparison to
the other components of a connector (metal, rubber, and plastic). Therefore, the internal
construction of the filter connector must isolate the capacitors from mechanical stress.
Smiths Interconnect uses a thin wall ground plane to house the filter elements. The
ground plane is captured between halves of the connector shell to provide mechanical
retention as well as electrical contact. Thermal stress from the connector shell is not
transferred to the capacitor arrays due to a gap between the outside diameter of the
ground plane and the inside of the shell. Stress from the contacts is eliminated through
the use of a block of epoxy on either side of the capacitors. Smiths Interconnect further
isolates the capacitors with a proprietary expansion barrier between the epoxy and the
capacitors. EMI/RFI and EMP protection can both be integrated into a connector with
only a small increase in length over the non-filtered version. Smiths Interconnect’s design
approach for diode connectors is unique. Smiths Interconnect mounts the diodes around
the outside of the contact arrangement on a multilayer circuit board within the
connector.