EMI Shielding and Thermal Interface Materials for Space Applications - powered by Happy Scribe

Thank you and welcome everyone. My name is Jarrod Cohen. I am the marketing communications manager for Parker Chomerics. This is the thermal interface and EMI shielding materials for space based technology webinar. Thank you for joining us. I see, a few folks are still joining the call, so give us a few seconds and then we'll get started. Thank you. Alright, I think folks have just started to join, so I just wanted to touch on a couple of housekeeping details for everyone before we begin. So please be sure to set yourself on mute if you have not already. After we run through the slides, we will have time for a live question and answer session. So if you have any questions during the presentation, please feel free to type them in that Q and a box. We'll make sure to address them at the end and finally, not to worry if you miss any part of this presentation, the webinar will be recorded and available to view after the call. So with that, let's introduce our speakers.

Hello, everyone. Welcome. My name is Sierra Eidan, and I am the military aerospace market manager for Parker Comerics.

Hi, everyone. My name is Ben Nudelman. I'm a global market manager for Comers, and I've been with the team for four years.

Hi, my name is Keith McDonald. I'm the international director of sales for Europe and Asia, and I've been with Park Chomerics for six years.

All right, so we'll do a quick introduction about who Parker Chomerics is and then we'll get right into the technology and applications for space based requirements, specifically looking at those requirements for thermal interface materials and the EMI shielding materials. And then we'll get right into those all important case studies and applications examples and the Q & A at the end. So like we've said before, if you have any questions or in this presentation, please go ahead and submit them and we'll try to get to them at the end.

So first, just a quick note about who we are. Parker Chomerics is a division of Parker Hannifin Corporation. We are the global leader in the development and application of EMI shielding in thermal interface materials. So our core competencies are in material science and process technology. And Cameron, we really do offer a complete market driven product development cycle. So we feature integrated electronics housings, and we're proud to offer custom engineered solutions in a fully integrated global supply chain. And then we manage that for a lot of our customers worldwide.

Okay, so let's begin with space based technology requirements and precautions when it comes to selecting a thermal interface material and EMI shielding materials.

So what does it mean when we say space based? Space based can be anything from geosynchronous Earth orbit, middle Earth orbit, low Earth orbit or sub orbital or high altitude space applications. These are going to be our primary focus for today's Webinar.

Yes, and Ben, just to clarify, for anyone new to space today, this could be vehicles ranging anywhere from those briefly entering the Earth's atmosphere, like missiles blowing up foreign satellites to vehicles planning on future trips to Mars and beyond. For most of us that have been in the aerospace industry for several or more years, we've seen a tremendous advancement in space exploration technology, with initiatives such as light-weighting uses in composite materials, 3D printing technologies, and transitions and key materials such as metal to plastic conversion. We've also seen electronic get smaller and hotter, creating the need for greater electrical isolation and higher EMI shielding effectiveness.

And probably my favorite space initiative on the list is how much we've seen an overall system cost reduction.

That's right, Sierra. While there have been vast improvements, there are some requirements that have remained tried and true over time, like the critical need for low outgassing to prevent contamination of sensitive optics as well as breathable oxygen. Also, the ability to withstand solar or radiation exposure has always been a factor in design longevity, as well as choosing the correct materials that can withstand exposure to atomic oxygen.

In the US and globally, NASA is the gold standard for aerospace and space-based application specifications, and while we don't want to get into the specifics of each of these standards, we did want to mention that NASA has a number of documents guiding the requirements for material selection in space. There are also several other civil organizations such as SAE, EuroCAE, and RTCA, who publish regulations that are closely tied with EMI and thermal interface material for and please don't forget if you have any questions, go ahead and submit it through the Q and A function, and we will do our best to answer it during the question and answer portion directly after this webinar.

In addition to the NASA and civil regulations, military specs are associated with space systems as well. For example, Mil Standard 461, which is a key driver for EMI shielding requirements in military applications, also applies to space systems and launch vehicles, not only in the military space but also for commercial space systems.

As you can see, many of the requirements for conducted emissions conducted susceptibility, radiated emissions and radiated susceptibility that are needed for ships, ground vehicles and aircraft are also applied to space systems and launch vehicles. Outgassing may be one of the most common drivers for space applications and is critical for several reasons. So we're going to spend some time on this topic, so you understand. So, Ben, what exactly is outgassing and how is it measured?

That's a great question, Sierra. Outgassing is a property of materials in vacuum environments to release their constituent materials. These materials or substances can include water vapor, additives, oil, or any other byproduct of the manufacturing process.

When these materials are released and condensed on nearby surfaces, they can be detrimental to high sensitivity optical equipment and other electronics. Now I'm going to go put Ben to the test. Ben, can you tell us more about how outgassing is tested and measured?

Yeah, so outgassing is tested using the steps in ASTM Spec E595. During this test, materials are placed in a vacuum environment and held at a constant temperature of 125 degrees Celsius for a 24 hours period after the vacuum and heat exposure. There are two primary factors that are measured. Total math loss referred to by the acronym TML and collected volatile condensable materials referred to by the acronym CBCM. Sierra, do you know the difference between these two measurements is, yeah.

So total mass loss is the percentage of the original mass the material has lost during the 24 hours testing period. So for a material to qualify as low outgassing by NASA, it must have a TML of less than 1 /% meaning it is lost less than 1% of its total weight. CVCM is the percentage of total weight of the material that has condensed on a specially designed condensing plate and must be less than zero 1% of the initial material mass.

Before testing, some materials can undergo a process known as post baking to help them pass out gassing. Basically, the materials are exposed to higher temperatures, such as 150 degrees C in order to Bake out materials before the official 24 hours test period.

Examples of material that pass slow outgassing requirements that are often used in space applications are conductive elastomers, thermal gels and gap pads, metal mesh gaskets conductive heat shrink tubing, and copper foil tapes, both with and without pressure sensitive adhesive. So luckily for us, there are a few resources for determining outgassing qualities of materials. Parker Chomerics publishes a document of all of our materials that pass NASA low outgassing requirements whether there are any post baking steps required and the associated NASA reference number. This database was established around 1997 and is based in and around the ASTM E 100 and 559 or the standard test method for contamination outgassing characteristics of spacecraft materials.

So NASA also publishes a document of all materials that have been submitted to them for testing is important to note that they publish the results whether the materials pass the low outgassing metrics of 1% and .1% or not, so this document should be closely watched. It's also important to note that many accredited test labs conduct the ASTM E 595 tests individually, and there are plenty of materials that pass low outgassing requirements but will not show up on the NASA website. The NASA website is outgassing NASA.gov and the code for Parker Chomerics is CHO. TEC is a code for legacy Tecknit products which are manufactured by Chomerics as well. Let's talk about another huge initiative in space and space flight: lightweighting. Lightweighting has been a popular topic of discussion in recent years with the introduction of carbon composites, 3D printing and advancements and electrically conductive plastics.

Whether your space vehicle is launching satellites into orbit on the wing of a Boeing 747 or using propellants to boost into low Earth orbit. It takes a tremendous amount of force to reach outside of the atmosphere, so any reduction and weight can be critical to the launch. A lower weight satellite, for example, can mean that a greater number of satellites can be sent into orbit with each launch. Likewise, lower weight on launch with vehicle components can be lower fuel costs or higher payload capacity. It's a balancing act.

Ben, can you tell us some examples of materials that could be used for light weighting?

Yeah, absolutely. For example, electrically conductive heat shrink tubing is an alternative to metal cable braids. Foil laminates can be a great replacement for machined metal board shields or lightweight grounding straps. Electrically conductive plastics are being used to replace metal housings to provide 65% weight savings and conductive coatings. Can metalize traditional plastics to add shielding to those areas of concern, let's shift to talking about radiation exposure now at various levels of orbit and remove from protection at several atmosphere layers. Space-based applications may have to deal with exposure to different types of radiation.

Internal components, such as thermal interface materials that are located within housings and cavities, can often be protected from UV rays and charged particles by Otter materials on the vehicle or spacecraft. However, thermal interface material still need to withstand prolonged exposure to gamma radiation. Metal based materials can experience an embrittling process, and a similar reaction can be observed in some silicone based materials. Thermal interface materials with high levels of ceramic fillers are able to stand up better to high radiation, even up to 100 megarad.

When we think about corrosion, we tend to think of electrolytic corrosion, which is due to the presence of water. But in space there are different types of electrolytes, and metals tend to degrade significantly, depending on the chemicals that they're exposed to. Exposure to atomic oxygen can lead to corrosion in many different metals.

That's right Sierra, silver, for example, will corrode when exposed to atomic oxygen, which can lead to foreign object debris or FOD as a result of the silver oxide flaking off. Silver oxide is relatively conductive but can still have a negative impact on conductivity or grounding performance. Another phenomenon that occurs in metals is whiskering surface layers or solder joints made of tin when exposed to vacuum environments, may form microscopic crystalline strands or whiskers.

And just to elaborate, there are examples of elemental materials that can grow whiskers as well as some alloys like zinc, cadmium, indium, and lead. The Whiskers can grow as long as several millimeters and become electrically conductive FOD, causing short circuits and failures. So keep this point in mind when choosing surface finishes. Metal substrates as well as the metalized coatings like conductive paint. Pure tin is the most common material to experience whiskering, but alloys such as tin lead that have 97% or less tin will avoid that whiskering.

Coefficient of thermal expansion or a CTE is the measure of the expansion and contraction of materials as a result of temperature changes, parts will inherently grow in, shrink in size as a result of significant fluctuations during launch orbit and reentry of space vehicles. Choosing a thermal material to dissipate heat as well as one with a similar coefficient of thermal expansion to the substrate can help mitigate these types of issues. Hollow conductive elastomer profiles can take up large tolerance ranges and are very effective in maintaining their shape and electrical properties during these compression cycles.

TG, also known as the glass transition temperature, is the temperature at which the material transitions to a brittle state where cracking can occur along with loss of functionality of the material altogether. So you want to avoid using materials that are not rated into that low temperature range.

Okay, now that we've reviewed some critical requirements that need consideration for space vehicle design, let's talk about some of the thermal interface materials that can be used to meet these requirements.

Thermal interface materials need to meet the combination of the requirements we just mentioned and should be down selected based on all of these factors, the space vacuum environment leads to the need for low outgassing and limiting FOD that may float around in zero gravity situations. Because of vacuum exists, the only true mechanism for heat transfer is conduction through direct contact rather than convection and airflow.

Other requirements of inherent properties of thermal interface material, such as high thermal connectivity or low thermal resistance. Most thermal interface materials that are used in space utilize ceramic fillers in a silicone or acrylic binder so as to provide electrical isolation and high heat transfer capabilities

With the exception of a few of our materials, most thermal pads, thermal gels, thermally conductive attachment tapes, and even standard grease products will meet that CVCM and TML limit for NASA low outgassing. Thermal gap pads also have the advantage of conformability and can be applied on a number of carriers, which encourage the material to retain cohesive properties and not break apart under compression.

Nearly all of our thermal gels, including silicone and on silicone based ones alike, will pass low outgassing requirements and have high thermal conductivity up to seven five Watts per meter kelvin. Thermal gels were originally developed for the automotive industry, and as such, will pass stringent shock and vibration testing that can translate to launch applications. Once again, the cohesive strength of the material is high and will allow the material to stay together when undergoing compression and decompression.

And lastly, thermally conductive adhesive tapes are often used to apply heat sinks to PCBs or heat generating components. While there is limited airflow, thermal heat spreaders are also used to pull heat away from these chips, and the adhesive tapes can actually reduce weight by replacing screws and other mechanical fasteners.

We wanted to separately mention the use of thermally conductive electrical insulator pads because of their position as a workhorse for decades. In satellite applications selected and tested by organizations such as NASA and Sandia National Labs. CHOTHERM 1671 has undergone long-term thermal cycling and radiation exposure testing to prove its effectiveness. Mechanical factors such as part puncture resistance limit FOD risks, and enhanced durability for long-term applications in orbit. Widely used on power transistors, thermal insulator pads can be die cut to specific sizes and shapes for all kinds of power conversion units and electrical assemblies.

Don't forget if you have any questions, go ahead and submit them through the Q and A function, and we will do our best to answer them during the question and answer portion at the end of this webinar. Now let's move on from thermal materials into electrically conducted materials used in space.

As with the thermal interface material, the EMI shielding materials also need to meet a range of general industry requirements for space, as well as program specific shielding and environmental requirements. So once again, FOD is a concern. So we often see calls for the use of durable conductive elastomer gaskets that can withstand damage of a result of over compression. Conductive elastomers may often be needed between subsystems rather than within the confines of an electronics package.

Electrically conductive elastomers have been used in military and aerospace applications since the early 1960s, when we developed a silver plated, copper filled silicone material called CHOSEAL 1215. As we briefly showed on the outgassing slide, the NASA website clearly list the times and temperatures used to outgas Chomerics elastomers. In general, Florosilicones tend to outgas less than their silicone counterparts with identical conductive particle filters. EPDM gaskets can emit compounds when heated and rarely pass low outgassing requirements. Conductive form in place gaskets use additives to aid in the dispensing process of the product and also do not pass outgassing without significant post baking.

We also wanted to mention that the standard pressure sensitive adhesive that comes with elastomer gaskets is by itself low outgassing rated. Sierra, have you ever seen outgassing pass with the material not on the list?

Yes, but unfortunately, these were all very customer specific, like baking their elastomer in a vacuum at logo temperature for multiple days. So just keep in mind that exposing these materials to temperatures beyond or below their limits can affect the electrical properties of the conductive elastomer, causing resistance to rise, shielding to decrease, and even degradation of the gasket itself. So try to stick to the materials with history.

Often used as a band aid solution or for additional grounding, electrically conductive foil tapes and fabric tapes are used across interfaces and joints to provide additional shielding with minimal weight gain. Something to keep in mind, however, is that these materials can be plated or metal-based, so a pure tin plating can exhibit whiskering and should not be used for space or high altitude applications. Copper foil tapes are often used for high conductivity and low outgassing needs. And considering the vacuum environment, do not have galvanic corrosion concerns as with other applications.

Yeah, Ben and piggyback backing on your topic of weight savings. Electrically conductive heat shrink tubing serves as the perfect alternative to cable wrapping and braiding with metal meshes. Not only does electrically conductive heat shrink tubing support cable management, but with a 40% weight savings across hundreds or even thousands of feet of wiring and the associated connector boots. The heat shrink tubing served as a significant cost driver and weight decreaser. Electrically conductive heat shrink tubing uses a specifically formulated flexible paint that will not crack or Flake during the shrinking process.

Okay, now, my favorite part of these webinars is sharing with you some specific examples that we've worked on to help you get a better idea of how you might use these products and technologies.

The first application we would like to discuss is the seal for two halves of a faring on a rocket ship. The faring is the nose cone that provides the first layer of defense of the rocket payload and is often built in two parts. With a seal running the entire length of the faring, sometimes more than 50ft tall. We've developed multiple types of sealing solutions, and because they are very specific to our customers requirements, we wanted to speak in general terms about some of the requirements. These Rockets see extreme shock, vibration, and thermal expansion and contraction, all leading to the need for a very durable solution that can take up large tolerance gaps and withstand numerous compression cycles.

Conductive or nonconductive fabric reinforcement is meant to hold the gasket together. In severe cases where the gasket needs an additional support layer. The gasket profile you see in the bottom right hand corner is not for a specific rocket faring application, but gives you an idea of the potential sizing in inches, some of them ranging between two and four inches in height and width. Many of these application requirements also incorporate the high levels of EMI shielding and corrosion resistance that are inherent in many conductive elastomers.

The next example is a high altitude missile application. Our customers missile needed to withstand high temperatures for a low duration of time and the electronics needed to pass stringent requirements for radiated immunity and susceptibility. Multiple components were initially made of machined aluminum, and a metal to electrically conductive plastic conversion was investigated, so you have to remember to consider the upfront, cost and time for building an injection molding tool. In this case, the weight took cost benefit were analyzed, and the electrically conductive plastic a product called PREMIER PEI 140, was chosen as it reduced weight, maintained high levels of EMI shielding, and even had some RF absorption properties.

And while the plastic pieces were not necessarily as strong as aluminum, they were strong enough for the application. Also, to note, the base polymer polyetherimide passes outgassing as well as the requirements for low smoke density. It has good dielectric properties and has low thermal expansion.

CHOTHERM 1671, an insulator pad product, which we mentioned earlier is typically used on power transistors. However, this application was for a large box that was used to house and support sensitive satellite electronics for NASA. The GPS system was placed inside a double wall box and the CHOTHERM 1671 was layered in between the two walls to maintain electrical isolation during deployment. It also has excellent mechanical strength for protection from damage of the thermal gasket from temperature swings that create thermal expansion and contraction during transport.

And finally, this application was one where our electrically conductive heat shrink tubing, known as CHO-SHRINK 1061, solved multiple issues for the customer. So during EMI testing they noticed that their cables were emitting EMI. They had a very complex cabling system, and the lab recommended metal cable wrap to help solve the problem. However, not only was the braided metal cable shields stiff and inflexible, preventing them from wrapping and bending these cables into the desired positions, but the amount of braided cable necessary actually put them over their weight limit.

So actually, after we talked with them and listen to their issues, the need for low outgassing weight reduction, the need for 70 to 80 dB of shielding. We sampled them our electricity conductive heat shrink tubing as well as the maiting grommets for the connector body, and this customer was able to utilize their existing heat srink setup in line during manufacturing, which was great and there's also for a lower electrical conductivity or shielding needs our CHO-SHRINK 1121 is the silver plated copper version and can be used as that commercial alternative.

And with that, we'll now get into some of my questions you all have submitted.