■ Thermal Management and Noise Countermeasures Are Related
At first glance, heat and noise look like separate problems.
Heat is a temperature problem.
Noise is an electromagnetic wave problem.
In actual products, however, the two are strongly related.
This is because many of the materials used in thermal management are materials that conduct electricity.
For example,
● Copper
● Aluminum
● Graphite
● Metal foil
● Metal plates, and so on.
These conduct heat well.
At the same time, however, they are also electrically conductive.
That is why using conductive materials for thermal management can change noise paths and electrical interference.
■ Materials That Release Heat Become Paths for Noise
In thermal management, heat is released from heat-generating components to enclosures and cooling components.
Metal foil or graphite is sometimes used for this.
However, these materials may also conduct electricity.
Then they can create unintended electrical continuity, pick up noise, or conversely spread noise.
In other words, while you think you have created a path for heat,
you may end up creating a path for noise.
This is the difficulty of heat × noise.
■ In AI Servers, Heat and Noise Increase at the Same Time
In AI servers, GPUs, memory, power supplies, and communications are arranged at high density.
The more computation increases, the more heat generation increases.
At the same time, high-speed signals and large currents also increase.
In other words, in AI servers, heat problems and
noise problems grow at the same time.
In particular, around
● GPUs
● HBM
● Power supply circuits
● High-speed communication lines
● Liquid cooling components
thermal management materials and EMI countermeasure materials may be placed close to each other.
At such times, choosing materials by looking only at heat may worsen noise problems.
■ In EVs, Heat and Noise Are Also Problems at the Same Time
In EVs, motors, inverters, batteries, fast charging, and in-vehicle communications are important.
Because these handle high voltages and large currents, noise problems tend to occur.
At the same time, heat generation is also large.
In other words, in EVs,
releasing heat
insulating
suppressing noise must be considered at the same time.
For example, when metal components are used around batteries, they may be advantageous for heat dissipation, but care is needed regarding electrical continuity and noise paths.
■ Graphite Is Advantageous for Heat but Requires Electrical Care
Graphite is an excellent material for spreading heat in the in-plane direction.
It is also considered in smartphones, wearable devices, and around AI servers.
However, graphite may conduct electricity.
That is why, when it is used near electronic circuits,
● Lamination with insulating films
● Edge treatment
● Checking conduction paths
● Designing the distance from circuits
● Selecting the adhesive layer
are important.
In other words, graphite is a heat spreading material and, at the same time,
a material that requires care in electrical handling.
■ Metal Foil Can Be Used for Both Heat and Noise
Copper foil and aluminum foil are sometimes used not only for thermal management but also for EMI countermeasures.
This is a major advantage.
Metal foil may be able to take on multiple roles, such as
● Spreading heat
● Shielding electromagnetic waves
● Grounding
● Shielding
However, convenient as it is, problems can occur if the design is wrong.
For example,
● Unintended electrical continuity
● Poor grounding design
● Noise coupling
● Risk of short circuits
● Insufficient insulation, and so on.
In other words, metal foil is effective for both heat and noise,
while on the other hand being a material that is dangerous unless heat and noise are designed at the same time.
■ Why Thermal Management Materials Need Insulation
There are often electronic circuits near the places where you want to release heat.
However, when heat dissipation materials are conductive, electrical risks arise.
That is why heat dissipation materials sometimes need an insulating layer.
For example, configurations such as
● Graphite + insulating film
● Metal foil + PET film
● Heat dissipation sheet + insulating layer
● Copper foil + adhesive insulating layer
In other words, actual thermal management components are often not single materials,
but composite configurations of thermal material × insulating material × adhesive material.
■ Noise Countermeasure Materials Can Also Stop Heat
Conversely, prioritizing noise countermeasures can worsen heat problems.
For example, placing EMI absorbers or shielding materials can
● Block the escape route for heat
● Create air layers
● Reduce the heat dissipation area
● Increase thermal resistance
In other words, it can also happen that suppressing noise traps heat.
Here too, what matters is not to think about heat and noise separately.
■ Heat and Noise Change with Placement
For both thermal management materials and noise countermeasure materials, placement is important.
Where to place them.
Over what area to apply them.
In which direction to release heat.
Where to connect to ground.
Where to insulate.
The results change depending on these.
Even with the same materials, if the placement is wrong, there will be adverse effects on both heat and noise.
In other words, with heat × noise, not only material selection,
but also layout design is important.
■ Heat and Noise Are Also Problems at the Edges
When graphite or metal foil is processed, edges can become exposed.
If these edges are conductive, contact with surrounding components can become a problem.
In addition, if particles or burrs come off the edges, they may become foreign matter or a conduction risk.
In other words, with heat × noise, not only the surfaces, but also the edges are subject to design.
This becomes extremely important on the volume production floor.
■ The Faster Things Get, the Tougher Noise Becomes
In AI servers, communication equipment, and automotive equipment, high-speed signals are increasing.
As signals become faster, noise countermeasures become more difficult.
At the same time, higher speeds also lead to increased heat generation.
In other words, in future industries,
higher speed
higher heat generation
higher density advance at the same time.
As a result, heat and noise will become challenges that are increasingly impossible to separate.
■ The Researcher's Perspective: Heat and Noise Are a Multiphysics Problem
In research and development, heat and noise are often treated as separate fields of expertise.
In actual products, however, both occur at the same time.
Heat is a problem of the temperature field, and noise is a problem of the electromagnetic field.
However, materials, shapes, placement, and contact states affect both in common.
In other words, heat × noise is
a multiphysics problem.
In future high-density electronic devices, thermal analysis alone or EMI analysis alone may become insufficient.
■ The Shop-Floor Perspective: Thermal Management Components Can Cause Noise Defects
On the volume production floor, adding thermal management components can cause other defects.
For example,
● Conductive materials too close to circuits
● Insulating films shifting
● Burrs on metal foil
● Graphite particles falling off
● Lamination misalignment creating conduction risks
● Adhesive layers too thin, resulting in insufficient insulation distance, and so on.
In other words, thermal management components must not be evaluated on heat alone.
■ Problems That Tend to Occur in Volume Production for Heat × Noise
In volume production processes, the following kinds of problems can occur.
● Burrs on metal foil
● Graphite particle shedding
● Positional misalignment of insulating films
● Adhesive squeeze-out
● Exposed edges
● Lamination misalignment
● Contamination by conductive foreign matter
● Positional variation in automated processes
● Minute electrical continuity that is hard to find in inspection
These affect not only thermal performance but also noise performance and electrical safety.
In other words, with heat × noise,
processing accuracy
lamination accuracy
edge management
foreign matter management are important.
■ OTIS's Perspective
OTIS is neither a thermal materials manufacturer nor an EMI materials manufacturer.
However, we may be able to contribute in the area of processing thermal management materials and noise countermeasure materials into a form that can be used in volume production processes.
What matters from OTIS’s perspective is
● Graphite processing
● Metal foil processing
● EMI material processing
● Lamination with insulating films
● Lamination with adhesive materials
● Edge management
● Fine die-cutting
● Lamination of dissimilar materials
● Reel supply
● Designing supply formats for automated processes
When heat and noise are considered at the same time, the result is often not a single material but a composite component.
This is where the importance of processing technology increases.
■ What OTIS Can Do
At OTIS, through
● Graphite sheet processing
● Copper foil and aluminum foil processing
● Processing of EMI absorbers and shielding materials
● High-precision lamination with insulating films
● Stacking with adhesive materials
● Irregular-shape processing
● Fine die-cutting
● Reel supply
● Designing supply formats for automated processes
and more, we may be able to contribute to bringing heat × noise countermeasure components closer to a state in which they can be used in volume production.
Especially in AI servers, communication equipment, EVs, and robots, heat, noise, insulation, and thinness must be considered at the same time.
■ Outside OTIS's Expertise
On the other hand, OTIS is not a company that specializes in
● Development of EMI materials themselves
● Development of thermal materials themselves
● Circuit design
● Antenna design
● Dedicated EMI analysis
● Dedicated thermal analysis
However, in the area of making thermal management materials and noise countermeasure materials into composite components that work in volume production processes,
we may be able to play an important role.
■ Industries Where This Technology Will Be Important
★★★★★ AI servers
★★★★★ Data centers
★★★★★ Communication equipment
★★★★★ EVs and electrical components
★★★★☆ Robots
★★★★☆ 3D semiconductors
★★★★☆ Medical devices
■ Summary
Materials that release heat can create noise problems
In thermal management, conductive materials such as copper, aluminum, and graphite are often used.
These conduct heat well.
At the same time, however, they also have electrical effects.
That is why, while you think you have created a path for heat,
you may end up creating a path for noise.
This is the difficulty of heat × noise.
From now on, the more high density, high speed, and high heat generation advance in AI servers, EVs, communication equipment, robots, and so on, the more heat and noise will become challenges that cannot be separated.
That is precisely why thermal management materials must not be chosen on heat alone.
They must be designed including noise, insulation, edges, lamination, and mass producibility.
Thermal management is not the selection of a single material, but design that makes combined challenges work in volume production.
Column Supervisor: Koji Kakumoto (President, OTIS Co., Ltd.)
After studying abroad and working in planning and development at a trading company, he joined OTIS Co., Ltd. in 2011. While primarily working in the Corporate Planning Department, he has also served concurrently in manufacturing and technical divisions, and since 2018 has served as President, working to drive business growth and strengthen the organization.
This article is a general technical explanation intended for educational purposes and does not refer to any specific company, product, or technology.
