A spiral EMI gasket is a metal spring that keeps every seam, connector and vent electrically closed. We match it to your enclosure, so it passes its test and keeps passing for the life of the system.
Lab booked? Tell us the date. Not the EMI expert? You don't need to be.
Spiral EMI gaskets for aerospace, defense, space and semiconductor equipment.
Qualified at leading prime contractors and equipment makers as their go-to EMI source.
EMI rarely has an owner while an enclosure is being designed. Then a review flags the seams, or the finished system fails at the lab, and shielding lands on whoever built the box.
With a retest already booked, the fast answer is whatever gasket ships today. It gets you through the test.
A year or two later, it's often back on your desk. The quick fix has broken, corroded or gone flat, and now there is a redesign, a retest and a second round of cost.
The gasket was never the thing at risk.
The electronics behind it were.
So choose the gasket for the life of the system, not for the lab date. You don't have to become an EMI expert to do it.
Why enclosures leak (EMI 101, lesson 1) →
The best EMI shield is a welded metal box. Nothing gets in. Nothing gets out.
But you can't service a welded box. So a real enclosure gets a lid, a door, connectors and vents, and every one of those openings is a gap interference can pass through.
An EMI gasket closes that gap electrically, so the opening behaves like solid metal again.
You probably know fingerstock and conductive elastomers. You may not have seen a spiral EMI gasket. It is a spiral of spring metal that sits in the joint and presses against both surfaces along the full length of the seam. Close the lid and it compresses. Open the lid and it springs back.
Because it's a spring, its force is something you can calculate. It comes in three force classes, about 30, 10 and 1.5 pounds per inch of gasket, so it suits a stiff cast housing as well as a thin sheet-metal door. And if the joint also has to keep out rain or dust, a requirement that tends to show up late, one part can shield and seal.
That is what a Spira gasket does. It makes every seam, connector and vent on a box you can open act like a welded metal box again.
Why the spiral →
Show us where your box opens. That's where it leaks. It usually comes down to three places.
The long joints where covers meet the chassis. A spiral EMI gasket runs the full length of the seam: in a groove where there's room for one, on the surface where there isn't.
Shield a seam, door or lid →Every connector is a hole cut through the enclosure wall. A spiral EMI gasket closes the gap at the connector, in a thin frame for flange-mounted MIL connectors or as an O-ring for jam-nut connectors.
Shield a connector →Cooling air has to get through. Interference doesn't. Honeycomb vent and fan filters pass the air and are sealed to the panel with a spiral EMI gasket.
Shield a vent or fan →Not sure where it's leaking? Send us the drawing.
Talk to an EMI engineerA quick fix has to get through one test. A gasket you design in has to work every time the enclosure is opened, for as long as the system is in service. Three things make a spiral EMI gasket worth designing in.
The reason is the spring. A spiral recovers when the joint opens instead of staying flat, and because it is one continuous piece, there is nothing to break off inside your electronics. Seat it in a dovetail groove, and the groove holds the gasket in place and keeps it from being over-compressed. There are options that resist galvanic corrosion and salt fog.
You design it in once. No mid-life replacement. No requalification.
Bring the problem, not the theory. Every design starts with the same questions. Is there room for a groove, or does it need to surface mount? How large is the opening? Where are the fasteners, and how is it clamped? What environment will it live in? How much shielding do you need?
From your answers we choose the spiral, the force class, the material and the seal for that joint. We'll also raise the things most engineers don't expect a gasket supplier to ask about: whether a dovetail groove makes sense, what the environment will do to the joint, and whether the same part should seal out weather.
One source covers the whole enclosure: seams, connectors and vents, plus parts made to your drawing.
Shielding electronics since 1978, and founded by the engineer who wrote Shielding of Electromagnetic Waves (Springer). Prime contractors and equipment makers qualify Spira as their go-to EMI source, and about three-quarters of our business is repeat programs. Every gasket is made in San Fernando, California, under AS9100 and ISO 9001, and classified EAR99.
Fingerstock, wire mesh, conductive elastomer and fabric over foam are each the right call somewhere. See where each one works, and where a spiral EMI gasket is worth designing in.
EMI shows up late and lands on whoever built the box. We get that call a lot.
You don't have to become an expert to answer it. Send us what you're working on, and an engineer who can read your drawing takes it from there. Want to understand the why? We'll teach you. Just need it solved? We'll solve it.
It's all we've done since 1978. That year an EMC engineer named George Kunkel founded Spira. He wrote Shielding of Electromagnetic Waves (Springer), published more than 100 papers on EMC design, and chaired the IEEE EMC Society's Technical Committee on Interference Control for 17 years.
George Kunkel wrote the book on shielding.
We made it simple.
Today Spira's engineers do that work one drawing at a time, and the customer service team you'll reach includes people who have been here since 2002, 2003 and 2015.
Your name goes on the drawing. Our job is to make the gasket the one part of it you never have to think about again.
Send a drawing, or describe the seam, connector or vent in your own words. An EMI engineer reviews it and tells you where it's leaking and why.
We choose the gasket, size the groove or surface mount with you, and send a sample to test in your own enclosure.
The part number goes on your drawing, and we supply the program for as long as it runs. From then on, a reorder is a part number and a date.
Tell us the joint and we'll send the sample that fits it. Compress it between your fingers and let go. You're holding a spring. Then put it in your enclosure and take it to the lab. It's how most new designs start here: a sample, a test, then a part number on the drawing.
Request a samplePrograms here run 5 to 20 years, and some systems can never be serviced at all. Spiral EMI gaskets close the seams, MIL connectors and vents on enclosures that have to meet MIL-STD-461, DO-160 or a customer's own requirement, in salt fog, vibration, temperature extremes and vacuum. Made in California under AS9100. Classified EAR99.
Tool enclosures are opened for service again and again. A spiral EMI gasket springs back after every opening and does not vary from batch to batch. Leading equipment makers already approve Spira. Show us your build plan early and we'll plan capacity around it.
The product names you already order by are all here.
Choose this when you have room for a groove. The groove holds the gasket and keeps it from being over-compressed.
Choose this when there is no room for a groove, or the hardware already exists.
Choose this when the leak is at a connector.
Choose this when the opening has to pass air.
When the catalog part doesn't fit, send a drawing. Custom diameters from .034 inch to 1.5 inch, custom rings, die-cut gaskets from 15 pieces, and parts made to your print.
Not sure which family? The product selector asks a few questions about your joint and points you to one.
Open the product selectorMore application stories →
Some engineers want to understand the why. Some just need it solved. Either works, and you never have to learn EMI to get our help.
Five short lessons: why enclosures leak, how to shield a seam, a connector and a vent, and how to choose an EMI gasket. When you want to go deeper, the groove and mounting rules, the fastener spacing calculator, the test data and the technical papers are all there, with no form to fill in.
Start with lesson 1A drawing, a sketch, a failed test report. An EMI engineer takes it from there.
Talk to an EMI engineer5 Questions to Ask Before Choosing an EMI Gasket is a short guide to choosing a gasket before the design is locked.
Show us your plan now. The earlier we see it, the faster we can respond.
A spiral of spring metal that sits in the joint between two parts of an enclosure and keeps that joint electrically closed, so interference can't get in or out through the gap.
The best EMI shield is a welded metal box, but you can't service one. Every lid, door, connector and vent is a gap. An EMI gasket closes each gap, so the enclosure still opens and still shields.
No. Send a drawing or describe the opening, and an engineer takes it from there. If you'd like to learn the why, EMI 101 covers it in plain language.
A groove when there's room for one, because it holds the gasket and controls how far it compresses. Surface mount when there isn't room, or when the hardware already exists. It's the first thing we ask on every design.
Yes. Request a sample and test it in your own enclosure.
It is designed to last the life of the system. Seated in a dovetail groove, one gasket can serve an enclosure that is opened and closed for 10 years or more.
Tell us the date when you get in touch, and an engineer will look at what's possible. If the lead time on a quote doesn't fit your schedule, tell us your date and we'll see what can be done.
No. We support the test method your program requires. Tell us the spec and we'll work to it.
No. Fingerstock, wire mesh, conductive elastomer and fabric over foam each have a place, and we'll tell you when one of them suits your joint better.
Compare it over the life of the system, not by the foot. A gasket you design in once isn't bought again at a service interval, and the joint isn't retested or requalified because of it.
In San Fernando, California, under AS9100 and ISO 9001. Products are classified EAR99.
Upload a drawing or describe the problem in your own words. An EMI engineer replies within one business day. Lab date coming up? Tell us when.
Design it in once.