Thermal Gels or Gap Filler Pads? Top 6 Things You Should Know

Thermal interface materials are used to eliminate air gaps or voids from adjoining rough or un-even mating surfaces. Because the thermal interface material has a greater thermal conductivity than the air it replaces, the resistance across the joint decreases, and the component junction temperature will be reduced.

Two principal “gap filler” thermal interface materials prevalent on the market today are thermal gels – also known as dispensable gap fillers – and gap filler pads.

So, which one should you select for your application? Here are the top 6 things you need to know:

1. Conformability

Both thermal gels and thermal gap filler pads are highly conformable, but the maximum configurability of a gap pad is less than that of a gel due to its solid structure. Dispensable gels provide maximum conformability because they can be dispensed in near infinite shapes and patterns.
 

2. Automation  Both thermal gels and gap filler pads offer application via automation, but thermal gels get the significant advantage here because dispensing systems are quite versatile. While pad placement can be automated to an extent, the equipment and fixturing required to do so is typically quite specialized and may not be readily adapted from one job to the next.
  3. Cost When it comes to cost, thermal gap filler pads require less up-front capital because there is no dispensing equipment to invest in. However, our experience with multiple applications suggests that about 5,000 parts per year is the threshold where it becomes more economical to use thermal gels and an automated dispensing system versus pads that are manually applied for the same application. 
  4. Precision Precision and accuracy are important, and the edge might go towards gap filler pads in this instance. Pads can be cut to the exact shape of your part, whereas the thermal gel takes the shape of how it spreads out once it is compressed. But as usual, the specific application will drive the degree of precision required, as well as determine the acceptability of whether the gel material extends beyond the surface of what it is being applied to.
  5. Throughout Speed in production is application-dependent, but recently, one of our customers was considering a switch from pads to gels and ran a test of both materials to gauge the difference in throughput. Their study revealed that it required an operator 18 seconds to apply one pad, including handling the pad, placing it properly and then moving on to the next component. Using a dispensable gel and an automated process, those same steps required only four seconds.
  6. Technology advances

Gap filler pads have long been the go-to choice for many design engineers, but recent advances in thermal gels, which are highly conformable, pre-cured single-component compounds, can provide superior performance, a greater ease of manufacturing and assembly, and a lower cost in certain high-volume applications; particularly as electronic design applications get smaller, more fragile and more complex.

Looking to learn more about thermal gap pads and dispensable gels? Download our new white paper Thermal Interface Materials: Choosing Between Gels and Gap Filler Pads now!

In this white paper, you’ll learn about the two general types of thermal interface materials – gels (or dispensable gap fillers) and gap filler pads – which are used by design engineers for displacing air voids and ensuring proper heat transfer, as well as:

•    Heat transfer fundamentals refresher
•    Intro to gap filler pads and thermal gels
•    Pads vs. gels – understanding key differences
•    Conclusion and recommendations

This white paper analyzes and draws conclusions about key performance and manufacturability characteristics in both gap pads and new advances in gels. Download it today!
 

 

 

 

 

 

 

 

 

 

 

 

 

This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics.

 

 

 

 

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Selecting a Thermal Gel or Thermal Gap Pad – Your Questions Answered (Part I)

Selecting a Thermal Gel or Thermal Gap Pad – Your Questions Answered (Part II)

How to Identify Quality Thermal Gap Fillers in Four Steps

Overcoming Challenges of Fully Autonomous Vehicles

In 1933, Kenworth Motor Truck Co. became the first American truck manufacturer to introduce the Cummins 4 cylinder, 100 hp, HA4 model diesel engine as standard equipment. By 1938 the first two-stroke diesel powered bus was introduced. In 1940, Cummins was the first diesel engine manufacturer to offer a 100,000-mile warranty. By the 1950s, diesel engines had virtually replaced gasoline engines in commercial trucks. Since 1997, engineers of diesel engine manufacturers have risen to the challenges of meeting new and more stringent limits for particulate matter (PM) and nitrogen oxides (NOx) and increasing the fuel efficiency of the engine. 

As the heavy truck and bus market continues to evolve, engineers need to meet new challenges by identifying and adopting innovative technologies. 

 

 

Download our Transportation Trends white paper and learn how Parker is helping heavy truck and bus manufacturers respond to sustainability trends.

 

 

 

Consider the trend of commercial vehicle electrification. Driven largely by concerns over emissions and environmental impact, the vehicle electrification market has grown substantially. And enhanced vehicle battery technologies are the key to driving truck and bus electrification. 

Challenges remain, however, before these systems will prove feasible and practical over the long term.  

Lithium-ion batteries have been the primary solution for electric vehicle manufacturers because they have higher energy densities than lead-acid or nickel-metal hybrid batteries. Li-ion batteries also offer attractive features such as low self-discharge and considerable energy storage, or battery capacity. Yet, there are still many barriers for the vehicle electrification market to overcome. Among these barriers are cost, weight and range, safe storage and thermal management. 

 

Electric vehicle battery technology 

A lot of research is being conducted to identify alternative battery chemistries and reduce the use of cobalt. Although cobalt is ideal for rechargeable batteries because of its thermal stability and high energy density, a problem is that it is almost exclusively mined in the Democratic Republic of Congo, an unstable country that has been charged with numerous human rights violations. 

Increased ethics concerns and growing costs have universities, private companies and the U.S. military aggressively researching alternatives to cobalt. 

• The U.S. Army is focusing on a new electrolyte design using silicon particle anodes in conjunction with lower cost transitional fluorides. The solid polymer electrolyte provides greater stability, even at higher temperatures, overcoming previous heat concerns. 
• IBM is researching a cobalt- and nickel-free cathode material and a safe liquid electrolyte with a high flash point. 
• Research at Washington University in St. Louis on potassium-air batteries has shown that the effective selection of the electrolyte in battery chemistries can double their capacity.  
• Engineers at the McKelvey School of Engineering also have developed a borohydride fuel cell that operates at double the voltage of conventional hydrogen fuel cells.  
   

Battery safe storage 

Since it is critical to protect the integrity of a battery from dirt and water, proper sealing is a key design consideration. Electric vehicle battery covers pose unique sealing challenges due to the significant size of the perimeter of the battery, as well as the aggressive performance requirements. Batteries are assigned Ingress Protection (IP) ratings to specify the degree of environmental protection from solids and water that might otherwise enter the enclosure and cause damage. Sealing products from Parker O-ring and Engineered Seals and electronic materials from Parker Lord prevent ingress between battery covers and housings—for both serviceable and non-serviceable batteries.   

 

Watch this webinar to learn more:

View our webinar on Serviceability of EV Battery Packs

 

Electromagnetic interference (EMI) 

Electromagnetic interference is a concern because electric vehicles have multiple battery cells, converters and powered electronics (ADAS, LiDAR and infotainment screens). The signals from one could interfere with those of another. The good news is that special EMI shields now exist to help contain the magnetic signals within the components. 

Among them are seals that are made of electrically conductive elastomers and form-in-place (FIP) conductive gaskets and even plastic pellet materials for housings 

 

Thermal management 

Thermal management tops the list of priority concerns. Parker offers several material innovations in this area that can stand up to excessively high temperatures and are flame-retardant to prevent a catastrophic thermal event, including thermally conductive gap filler pads and thermally conductive structural adhesives  

In addition, there are air ventilation panels that dissipate heat and provide EMI shielding. 

 

 

  Conclusion 

Electric vehicle battery technology is a significant, trending topic in the bus and commercial vehicle market. While lithium-ion is currently the most dominant type of EV battery, engineers are driven by concerns over emissions and environmental impact to find a higher performing alternative. Reduced weight, improved storage, and better thermal management are among the features that engineers are hoping to work into EV batteries.  

 

To learn more about how Parker is helping heavy truck and bus manufacturers respond to sustainability trends, read our Transportation Trends White Paper.

 

This article was contributed by Christopher Overmyer, Senior Field Application Engineer, Parker Engineered Materials Group 

 

 

 

 

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Clean energy consultancy Gladstein, Neandross and Associates, in its recent report on sustainable fleets¹, predicts another decade of diesel-powered heavy trucks leading long-haul. Diesel efficiency and emissions reductions are important areas of research as broader trends toward sustainable fleet adoption accelerate. 

One new technology to the diesel market is cylinder deactivation (CDA). This technology has been commercially applied to the automotive sector as “Displacement on Demand” to improve fuel economy in V-8 engines. In the diesel market, CDA not only helps with fuel economy, but it also helps to increase exhaust temperatures and reduce engine-out nitrogen oxides (NOx).  

 

 

Read our Transportation Trends White Paper to learn more about how Parker is helping heavy truck and bus manufacturers evolve to sustainability trends,

 

 

 

 

CDA would be used when the diesel engine runs below its normal operating temperatures, such as in a cold start or when the engine is under light loads (i.e., idling or cruising at highway speeds). In these conditions, the system deactivates some of the cylinders to increase the load on the remaining cylinders. When this occurs, more fuel per injection is required and this produces more heat in the engine block. This, in turn, raises the exhaust gas temperature to an appropriate operating level to activate the diesel particulate filter (DPF) burn off cycle. Successful development and commercialization of CDA technology would help the industry meet 2024 emissions standards. 

Another major advancement has been in the development of ducted fuel injectors. Developed by Sandia National Laboratory’s Combustion Research Facility, the ducted fuel injectors offer many benefits. They clean emissions like soot (another potent climate change chemical second only to carbon dioxide) from vehicle fuel, and they represent an inexpensive transition by working well with conventional diesel fuels. They can easily be retrofitted into existing engines, require no after-treatment systems, and have the potential to lengthen oil change intervals. 

The ducts are small tubes that are mounted to the underside of the cylinder head near the injector nozzle. Researchers continue to search for appropriate high-temperature alloys for those tubes without substantially increasing costs. 

 

Thermal energy recovery systems 

A desire to improve energy efficiency and cut greenhouse gas emissions has led to considerable interest and research in various waste heat recovery techniques. Topping the list of options are thermoelectricity and Rankine Cycle. Rankine Cycle offers the greatest potential due to its higher cycle efficiency. 

Rankine Cycle is not a new concept. It has been widely employed in large-scale power plants for years. But it has yet to be fully implemented for heavy-duty trucks and buses.  

The cycle works by recovering wasted heat from the engine through an intermediate heat transfer loop that is filled with a working fluid. The fluid captures some of the energy from the waste heat source. The fluid is often water, but with organic Rankine cycles, a higher molecular mass fluid with a lower boiling point is used to reduce the amount of heat needed for energy recovery.  

Despite its tremendous potential, some challenges remain, such as limitations of heat available in the heat source, heat rejection constraints, backpressures during the recovery process, and safety and environmental impacts of the chosen working fluid.  

The beauty of this form is that its heat source--exhaust waste heat--exists on all current engines on the market. 

 

Creating a more aerodynamic truck 

Today there is a large array of aerodynamic aids available for heavy-duty trucks and trailers, all designed to increase efficiency by reducing drag and fuel consumption by as much as 12%. 

Some of the more popular options include front and underbody deflectors, side skirts, rear diffusers and boat tails. Companies have experimented with the specific design and rigidity of such aids to further enhance aerodynamic performance. While all of these can provide some benefit, the key is to identify the right combination of aids that provides enough fuel savings to offset the added costs. 

Low-rolling resistance tires also improve truck aerodynamic performance by reducing resistance caused by the tires rolling on the highway’s surface, often through tread depth and design. To date, however, while more fuel-efficient truck tires have garnered interest because of their ability to minimize energy and boost fuel economy, their lower life cycles cause concerns for bottom line-oriented owners and operators.  

Another trend in commercial trucking is the replacement of dual tires with super single tires. The advantage of reducing the number of tires on a large rig is minimized friction and resistance. However, safety concerns arising from what happens when a tire blows are keeping most fleets from making the switch. 

 

Alternative fuel sources 

Electric (battery or fuel cell) is not the only alternative energy source being explored, as companies continue to research the potential of various renewable fuels, like renewable natural gas (RNG), biodiesel and renewable diesel (RD) which are efficient as fuel sources while producing inherently lower greenhouse gas emissions. 

California leads the way in renewable energy research with herds of dairy cows already powering fleets, homes and factories throughout the state. An especially promising development is the recycling of dairy cow waste to produce methane--an option that creates a negative carbon footprint. Known as biomethane, it is an attractive tool for battling climate change.  

Beyond dairy waste, RNG can come from other sources of manure, landfills, as well as wastewater. The advantage is that it can be easily exchanged with natural gas drilled out of the ground, minimizing the need to overhaul natural gas engine designs.  

Biodiesel (B) and renewable (R) diesel, both of which can be made from similar feedstocks, recycled cooking oil (i.e., oil used to make French fries), oil from algae, soybeans, and other oilseed crops, are also attractive alternatives for existing diesel engines. Not only are they carbon neutral, but, like RNG, their use does not necessitate a diesel engine modification. However, biodiesel blends above 20 percent (B20) will require use of higher performance fluorocarbon sealing compounds. Learn more in our Seal Materials for Biodiesel blog.

One of the concerns for renewable diesel is the choice of which feedstock is used. Palm oil feedstock, for example, has been linked to significant land use impacts, including deforestation, which results from allocating land to grow and farm the palm oil. 

Yet another alternative fuel is ethanol. One company recently completed tests showing that its system matched the torque and power of a commercial diesel engine using ethanol instead of diesel fuel, delivering over 500 hp and 1850 ft lb. of torque without additional aftertreatment. 

There are several points of concern for fleets that operate Class 4 through Class 8 vehicles with multiple power sources, i.e., some diesel, some natural gas, some electric, etc. Among other things, they will face “right to repair” and maintenance challenges as technicians must be sufficiently trained in the repair of multiple power-source vehicles. For example, mechanics working with electric systems need to be well-versed on sensors and how to properly ground them to avoid serious injuries. In addition, a wide variety of parts may need to be inventoried to maintain an array of engine types.  

Another point of concern is the training of first responders—not only the emergency responders, but also tow/salvage operators. Diesel, natural gas, and electric engines require different approaches to putting out fires in a roadway vehicle crash or in a facility where electric vehicles are charged.  

 

Conclusion 

When considering options for lessening environmental impact, total cost of ownership still plays a role in ultimately determining which technologies will be adopted and to what extent. The ability to make these innovations affordable, safe, reliable, and sustainable is the key to the future of a sustainable transportation model. 

 

To learn more about how Parker is helping heavy truck and bus manufacturers evolve to sustainability trends, read our Transportation Trends White Paper.

 

This article was contributed by Christopher Overmyer, Senior Field Application Engineer, Parker Engineered Materials Group 

 

¹ Cision PR Newwire - State of Sustainable Fleets Report Released, Finds Sustainable Vehicle Technologies and Fuels Are Growing Across All Sectors

 

 

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