Table Of Contents
Key Points
- There are thousands of materials to choose from when designing a conductive gasket.
- Choosing the correct material for your conductive gasket is critical to the effectiveness of your final product.
- Eliminate headaches by working with Modus Advanced early in the design process.
Designing a conductive gasket is no joke, especially when so many considerations need to be taken into account. One of the most important decisions you’ll make is choosing the right materials for your gasket. There are thousands of gasket materials to choose from, and not all are created equal.
Don’t stress, we’re here to help.
The expert team at Modus has compiled this helpful guide to conductive gasket materials to help you get off on the right foot. Read on to learn more.
Modus Advanced is a leader in custom gasket manufacturing. If you want the best, you need to work with the best. Contact us today.
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What is a Conductive Gasket?
Conductive gasket materials are used to create gaskets used in a variety of applications and industries–everything from aerospace and defense, to medical devices–to provide electromagnetic interference (EMI) shielding, static discharge protection (ESD), and grounding. They can also be used in applications where electrical conductivity is required. They are typically made from materials that have high electrical conductivity, such as copper or silver.
Additionally, conductive gaskets can be used in applications where static electricity needs to be dissipated, such as in fuel systems or in environments where explosive gasses are present–industrial or space applications for example.
Conductive gaskets are available in various forms, including sheets, tapes, dispensed material, and pre-formed gaskets. They can also be combined with other materials, such as elastomers, to create gaskets with specific properties.
Now that you’ve got the quick and dirty of what a conductive gasket is and does, let’s dig into some of the considerations that go into conductive gasket material selection.
Conductive Shielding Gasket Material Questions
The design phase of any part is critical, but careful consideration should be given to the materials you select for your custom conductive shielding gasket. Material selection can quite literally make or break a device, and a failed part can have catastrophic ramifications.
Involving your manufacturing partner early in the design phase can mitigate any hang ups that might occur as they walk you through a robust design for manufacturability (DfM) process.
Use these three questions as a launching point to determine the best-fit materials for your conductive gasket.
What type of filler do you need?
Determining which metal filler you need to use is a large part of the conductive gasket material selection. Prices vary considerably between metals and can be a significant part of your design decisions.
Filler options will vary depending on the type of conductive gasket you are designing. We’ll get into those types a little later on, but in general, your filler options are:
- Silver
- Silver aluminum
- Silver nickel
- Silver copper
- Nickel graphite
Silver will be the most expensive to use, with nickel graphite being the least expensive. Which filler you require will be based on your application, other components in your design, and potential issues with galvanic compatibility.
Further, because of the significant difference in material price, your requirements may help guide you in which manufacturing process is the best fit. For more expensive materials, a low-waste manufacturing process may be the best choice.
Is galvanic compatibility a concern?
Galvanic corrosion happens when there is an exchange of electrons between two metals that have come into contact. Galvanic corrosion is accelerated when in the presence of electrolytes, but even dry air has moisture, which is enough to cause some level of corrosion. Your goal would be to select an EMI shielding material that will not cause galvanic corrosion when in contact with your housing.
If your gasket will be operating in an environment in which electrolytes will be present, you’ll want to carefully select the filler you use to be compatible with any metal used on the housing of your part.
Typically the critical concern is galvanic corrosion between the part’s substrate material, which comes into contact with the EMI gasket. The goal would be to select a filler material that does not corrode the metal of the housing.
Using a galvanic compatibility chart, like the one above allows you to select filler metals that will not cause corrosion in the housing.
If you are bonding to plastic housing, you can usually expect to coat the housing with metal, and thus will want to ensure there are no galvanic compatibility issues between the metal used in coating the housing and the filler you choose.
What are your shielding effectiveness requirements?
An additional consideration is if you must adhere to shielding effectiveness requirements. Shielding effectiveness is a measure of how well a given part reflects or absorbs electromagnetic radiation.
Often in military applications, you will be required to meet MIL-STD-285, the military standard for electromagnetic shielding.
Types of Conductive Gasket Materials
Four primary categories for EMI materials:
- Form-in-Place (FIP) (CNC Dispensed)
- Rubber-Based Sheet or Roll Materials
- Fabric Over Foam
- Beryllium Copper
Keep in mind that his article is meant to provide general guidance only, and there are many materials with different properties and specifications to choose from within each category.
Narrowing down to your final material is something best done with the help of an expert. This guide is designed to help you start the process of material selection, before diving into the nitty-gritty details.
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Learn everything (and more!) about EMI gasket design with this guide!
Form-in-Place (FIP)
Form-in-place (FIP) materials are best fit when you have a very small gasket that would be difficult to die cut and then assemble in your production facility. Very small and thin gaskets are flimsy and difficult to manage, increasing the effort and time that must go into assembly. This is more and more common due to the smaller form factors and space constraints in today’s electronic assemblies.
As such, FIP gaskets are usually selected in an effort to reduce the cost of assembly in these instances. Because the gasket is dispensed directly on the unit, then cured, before being sent back to your production facility, it saves a step (and money) on the assembly process.
In addition, when using custom gaskets for EMI applications, choosing FIP as the method for production can limit waste, thus reducing the cost of more expensive materials. Because of their typical size, FIP materials are commonly used to create an effective seal for electronic devices.
Rubber-Based Materials
Your conductive gasket starts with similar categories of materials as any other solid rubber-based gasket:
- Silicone
- Fluorosilicone
- EPDM
Rubber-based conductive gaskets are typically made from a combination of natural or synthetic rubber and conductive fillers, and can be manufactured in a variety of shapes and sizes to suit the needs of the application.
Form and Fabric Over Foam Solutions
When softer compression forces are required for your design, then foam-based EMI shielding materials may be a fit for your needs. You are much more limited in both material and conductive filler options in this category of materials.
Rather than being filled with particles, foam-based materials are typically made by taking a polyurethane foam and then spraying the foam with copper or nickel. This metal plating will fill the pores of the foam and make it conductive.
Some materials use a fabric or wire mesh wrapped over a low-closure force urethane foam to achieve a similar effect. Fabric over foam solutions typically come in various cross sections (like D-shaped, O-shaped, or C-shaped), with hundreds of different profile offerings.
Keep in mind that EMI materials rarely provide a good seal, particularly against water, so design requirements are a key factor in determining if a foam-based EMI shielding material is even possible to use in your application.
An example of one of the most commonly used foam-based EMI shielding materials is the Parker Chomerics Soft-Shield material family.
Beryllium Copper
Beryllium Copper (BeCu) can be fabricated into specific shapes, the most common we see in EMI shielding applications being “fingers.” A high-performance metal, BeCu provides shielding over a broad range of frequencies and is a good fit when your design requires repeated opening and closing of an enclosure providing an improved compression set.
Getting it Right: Conductive Gasket Material
Without a doubt, the most difficult part of designing a conductive gasket is the material selection. Ensuring your chosen material is cost-effective and meets the design requirements can be a time-consuming endeavor. Getting it right the first time is critical.
Contact us today and work with our expert engineering team to get your custom conductive gasket crafted with speed and precision.