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Auger Valves vs. Progressive Cavity Pumps: Best Use for Thermal Paste

It should come as no surprise that electronics manufacturers continue to seek better ways to dissipate heat generated from smaller, more powerful devices that operate at higher temperatures than ever before. Many turn to thermal interface materials (TIM) for electronic systems that require thermal management. So much so that according to recent studies, the global thermal interface materials market, valued at $2.25 billion in 2020, is expected to grow to $4.47 billion by 2027.

Specifically, we are seeing more and more TIM applications for automotive light detection and ranging (LiDAR) systems for autonomous cars and advanced driver assist systems (ADAS). LiDAR sensor reliability is critical to the effectiveness of these systems. As such, sensor manufacturers are increasingly seeking the most reliable method for dispensing thermal interface materials to cover gaps required to reduce the temperature and increase the efficiency and longevity of these electronic components.

So, which dispensing method should you use? Nordson EFD offers several options for applying TIMs, and it varies depending on the type of material and the deposit volume required.

Manual vs. Automated Dispensing

Though manual application is an option, and Nordson EFD offers a number of benchtop fluid dispensers, the operator-to-operator inconsistency can be a challenge when what you need is an accurate dispense, every time. Recent improvements to benchtop dispensers such as the full operator lockout offered by our UltimusPlus dispenser with network connectivity are important to mention here because these dispensers can be used in both manual and automated applications. They can essentially grow with you as you scale production.

However, often we find manufacturers opting for automated dispensing either with a tabletop dispensing robot or an integrated conveyor-fed line since thermal interface material patterns are more and more complex to cover the largest possible area on a part.

Auger Valves vs. Progressive Cavity Pumps

Because thermal interface materials often contain fillers such as ceramic particles, they may be highly viscous and abrasive. And since abrasive materials can harm the inner workings of most mechanical dispensing heads, you should carefully consider the type of thermal compound and dispensing equipment you choose.

In addition to our benchtop fluid dispensers, Nordson EFD offers two main types of dispensing heads for thermal interface materials: auger valves and progressive cavity pumps.

Both operate using rotating geometries that deliver the material from the fluid feeding tube to the dispensing tip. The rotating inner workings of these dispensing heads allow them to deliver the fluid with the least amount of shear possible. Therefore, they allow the TIM to maintain its properties to ensure you will get reliable heat transfer performance.

However, there are key differences between the two dispensing methods to be aware of when trying to decide which one is best for your fluid.

Auger Valves

These dispensing heads use screw feed principles combined with precision time and pressure controls to ensure consistent fluid deposits for high-throughput applications. Our 794-TC auger valve is available with a range of screw gap sizes to ensure the best performance based on your TIM particle size.

Its auger screw is made from tungsten carbide (TC), which provides the best resistance against damage caused by highly abrasive pastes. This ensures a longer dispensing valve life for high-volume production.

Because there are no seals in auger valves, in general, this makes them more resistant to wear since seals wear out faster when abrasive particles rub against them.

However, precisely because these valves have no seals, they are not the right choice for thin or low-viscosity materials. If dispensing fluids with viscosities less than about 30,000 centipoise, you may see fluid dripping or streaming out of the dispense tip attached to the auger valve.

In addition, auger valves are designed specifically for one-part fluids, therefore you would not choose an auger valve for a two-part TIM application.

Progressive Cavity Pumps

Progressive cavity pumps are a volumetric or positive displacement method of dispensing that allows you to set the exact volume you wish to dispense and get that exact volume onto the part, every time. These pumps provide highly precise fluid volume accuracy and repeatability at ± 1%.

Nordson EFD 797PCP Series pump’s modular design is based on the progressive cavity principle where its core components – a rotor and stator – form a perfectly sealed metering chamber. This allows for continuous volumetric dispensing independent of fluid viscosity.

However, for TIM applications because these pumps feature a seal, they are prone to wear out faster than an auger valve. Yet, because of the seal they can dispense a broader range of fluid viscosities.

For two-part TIMs, you would absolutely choose the 797PCP-2K pump because it precisely meters accurate ratios of part A and part B materials through static mixers for highly repeatable dispensing with fluid deposit accuracy at ± 1%.

In addition, because the 797PCP pump comes in a range of sizes it can accommodate nearly any thickness of the dispense pattern required by your application because its flow rate is five times higher than the 794-TC auger valve.

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