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Reducing Electromagnetic interference in EV Applications

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As technology advances, weight reduction in electronics – from compact handheld consumer devices to electronic vehicles – is a primary focus. Polymer Science began considering how thermal management materials will meet the performance requirements of today’s EV design and embraced the approach of less is more.

Less Is More

A primary example role materials fill within weight reduction is found in passenger electric vehicles. These vehicles have weights ranging from 600kg to 2600kg with nearly 20% of the overall weight coming from the EV battery alone. It has been estimated Every 7 kg of overall weight reduction adds nearly 1 additional mile of range to an electric vehicle, so weight reduction in all aspects of EV design is critical to improvements in the technology. Reducing the weight of materials throughout vehicles and within advanced batteries is crucial to improving performance.

Thermal Management Solutions

At Polymer Science, thermal management material refers to thermal pads, gap fillers, phase change materials, heat spreader, heat pipes and many other alternatives. Choosing one over another relies on a range of requirements. A key factor is: energy requirements are staying the same or rising, resulting in increased energy density. This makes thermal management more challenging. With these two key points of focus, overall weight reduction and managing increased energy density, Polymer Science endeavors to derive higher thermal performance from less material.

Less Is More from Gap Fillers

Nearly all electrical components, specifically in advanced batteries and EV, but throughout aerospace, phones, computers and many products components are becoming smaller, thinner or otherwise less in some way. A 2-part dispensable gap filler offers a lower weight, smaller gap and lower impedance for better heat flow. Where a thermal gap pad thickness begins at 0.25mm, 2-part dispensables achieve 25 micron, 50 micron and 100 micron thickness bondlines. By comparison, many may immediately assume dispensables will replace pads. There are distinct advantages and disadvantages to both gap fillers, especially within manufacturing processes.

Types of Gap Fillers

A brief consideration of all the types of gap fillers reveals why you might choose dispensables versus pads. In general, there are two primary categories: solid gap fillers and liquid gap fillers. There are silicone and non-silicone types of solid and liquid gap fillers. Within liquid dispensables, there are non-curables like grease and curable liquid gap fillers including 2-part dispensable and single-part dispensables. Other thermal management types are heat spreaders, both foil and graphite types, phase change materials and thermally conductive electrical insulator pads. Polymer Science is launching PS-2811, PS-2812 and PS-2813, 1 W, 2 W and 3 W/m K 2-part silicone based dispensables that will provide great options for many manufacturers in EV and beyond. These products specifically address heat dissipation with thin bond lines and lower weight materials.

So What Is a 2-Part Dispensable Gap Filler?

A 2-part dispensable is a material that is applied as a liquid and cures to a solid. Polymer Science uses 2-part platinum cure chemistry. As the name implies, 2-part dispensables are dispensed then compressed in a liquid state and allowed to cure in place. Polymer Science designs our 2-part dispensables to cure at room temperature. Time of cure and conditions can be tuned to meet the process application conditions. This quality of curing in place and tuning cure time is an important argument for the applications of 2-part dispensables. As materials heat, they expand so non-curing greases are susceptible to thermal pumping. The loss of material reduces the efficient heat transfer. Solid materials and curable dispensables resolve the issues related to thermal pumping.

Pros and Cons of a 2-part Dispensable Gap Filler

There are a number of reasons manufacturers might favor solid materials in lieu of 2-part dispensables. Among the cons of 2-part dispensables are the permanence, mess and high cost of entry. More permanent – Gap pads are reworkable. If placed in the wrong spot, the material can easily be adjusted. Once dispensed and cured, 2-part dispensables must be removed to correct mistakes such as alignment issues. There is an argument in favor of this quality. Defect rates may be reduced by precise positioning of dispensables. More Messy – Pads do not create any mess during application. With dispensables, there is the opportunity for drips and application to areas where thermal management material is not desired. More capital expenditure – Initially, the cost of entry for dispensables is higher than pads. Dispensing equipment can cost from tens of thousands of dollars to hundreds of thousands depending upon the level of robotics and automation used in the dispensing process. This initial barrier to entry is offset by the return on investment through lowering scrap cost. Since no die cutting is required, there is another potential benefit by reducing a manufacturing step. There is a strong potential reduction of component sealing and gasketing costs through automation. Less material is usedThe first clear advantage of dispensables is the low, thin bond lines. Compared to thicker gap fillers or pads, dispensables provide thermal protection at a much lower weight. For example, assuming a battery module size of 157cm x 119cm, applying a dispensable such as PS-2813, a 3 W/m K dispensable at 100 micron thickness would result in a thermal management layer weight of 5.45 kg. A 0.25mm thickness gap pad such as PS-1593, which is also 3 W/m K for this same battery, would weigh 13.22 kg, which is significantly more. In a passenger EV vehicle, this increase would have about a 1 mile range implication for this specific battery. Less Waste – Another clear advantage of dispensables is less waste is created. More waste is created when solid gap fillers are cut. Waste from yield is derived from the input width of the rolls and scrap from trim. Dispensables are applied precisely for the application. Less AdjustmentsCure in place is a key quality of 2-part dispensables. Dispensables cure at room temperature so there is no requirement to be put into an oven during manufacturing. This means less disruption in the manufacturing process. Less Fixed and More Tuneable – Dispensables can be tuned to suit the manufacturing process. The ability to tune viscosity and curing times is beneficial when considering applications and how to use dispensables. Lower compression forces – In comparison to solid gap fillers, dispensables are applied as a bead, and two mating surfaces are put together. Lower impedance – Finally, when a material’s thermal impedance is lower, the material is a better thermal conductor. As a liquid, the material will flow into microscopic cracks and crevices to promote better heat flow, offering more thermal protection than a solid gap filler pad.

How to Choose

Polymer Science works carefully with our business partners to find the customized solution. Assuming a 2-part dispensable is most beneficial to your application, choosing from the products within Polymer Science requires further consideration.

Functional Properties

Functional properties should always be your first consideration when determining a thermal management material. The higher the thermal load, the higher thermal conductivity material needs to be considered. Preliminary calculations can determine what type of heat load you have to keep the system within an optimal operational range. After functional requirements are addressed, your manufacturing process will determine the physical properties of what the 2-part dispensable needs to look like from a viscosity and cure point perspective. As previously noted, dispensables can be tuned to fit into the manufacturing process. So too, viscosity can be adjusted to suit the manufacturing process. Polymer Science works with our business partners to consider whether the application will occur horizontal or if surfaces rotate prior to mattering. If applying vertically or where movement is a concern, viscosity should be considered, or the use of a thixotropic dispensable will be required so it stays where applied.

Considering the Cure Point

The speed of cure is temperature dependent. Polymer Science’s technical data sheets show our 2-part dispensables are designed to cure at a specific rate based at room temperature. Heat generated within the manufacturing process can be used to accelerate the curing process. Time is a factor as well. If there is a long dwell before the mating component will be introduced for the assembly, a delayed cure may be desirable whereas an inhibited dispense system can be developed and used.

Applications

EV and Advanced Battery applications

Dispensables are invaluable between the individual battery cells as a vehicle for thermal dissipation as well as secondarily, a vibration dampener. Then there’s within the module. A 2-part dispensable can be used between the individual cells and the module housing. Dispensables can even be used between the module housing and the external portion of the pack itself. You have to get heat clear from that cell to the outside so it doesn’t run into some kind of resistance. Excess heat within an individual cell can trigger a thermal runaway event, so allowing for the efficient transfer of heat from the cell to the heat sink or atmosphere is very important. In addition to the batteries themselves, EV power converters take the stored energy within the batteries and transforms it to usable energy within the vehicle.

General Electrical Components

Both in EV and conventional automotive, there are electrical components including small computers throughout vehicles that need temperature control.

LED Lighting

Many of these components are small and require temperature control.

Phones

There’s a weather proofing quality added when 2-part dispensables are used around the casing.

Circuit boards

Thermally conductive and electrically insulative, dispensables can be poured across a circuit board without short circuiting. This is useful because designs often have a conductive surface on the other side. You can transfer heat from the circuit board as well.

General Applications

Anywhere where you might be producing heat, you can use these products to manage heat, limit space requirements and reduce weight. Polymer Science’s 2-part dispensables benefit aerospace, consumer electronics, computers and many more industries.

Working with Polymer Science

At Polymer Science, we see thermal management as both a challenge and an opportunity. Increasing energy density is occurring in all of these industries. In the present and the future, thermal management is helping to move innovation forward. Two-part dispensable gap fillers offer a lower weight, fill smaller gaps, cure in place and provide lower impedance for better heat flow. In short, 2-part dispensables deliver more from less.