Spira Manufacturing Corporation - Surface Mounting Techniques

Application Information

View Mounting Techniques datasheet in pdf format.

Surface Preparation
Minimal surface preparation is required with Spira EMI gaskets. A clean surface will encourage the highest level of shielding attainable. For environmental sealing a 32 micron finish is recommended.
Adhesion
We recommend you do not use conductive sealants with Spira EMI gaskets. Our shielding is achieved through the metal-to-metal contact between the spiral and joint surfaces. Conductive sealants will merely get in the way of this. To apply gaskets that do not have adhesive backing, you can use either super glue, epoxy or RTV. Be careful to apply the adhesive only to the rubber portion of the gasket. Do not get glue on the spiral as it will degrade the shielding.

Fastener Placement

Fasteners may be placed on either side of the gasket. Care should be taken to avoid puncturing the spiral. To maintain the integrity of the EMI bond it is important that each fastener is referenced to the chassis by making good metal-to-metal contact.

When using the gasket to achieve an environmental seal, care must be taken to ensure that the fastener placement does not compromise this seal.

Excellent Design Screw makes EMI bond with chassis. Screw going through rubber elastomer maintains the integrity of the environmental seal.		Excellent Design: Gasket held in place with screw and nutplate.
Good Design The risk of moisture leak is minimized by the use of a rubber washer. The metal nutplate ensures that the screw will be referenced to the chassis to maintain the integrity of the EMI seal.		Good Design: Gasket held in place with screw, nutplate and one rubber washer.
Poor Design The use of two rubber washers insulates against environmental leakage, but also prevents the screw from being referenced to the chassis. This creates an EMI "hole" and can significantly degrade the shielding quality of the joint.		Poor Design: Gasket held in place with screw, nutplate and two rubber washers.
Poor Design Moisture can leak through the screw hole, compromising the environmental seal.		Poor Design: Gasket held in place with screw and nutplate.

The following gaskets can be surface mounted:

Information for other gaskets is available in Groove Mounting Techniques.