■ Materials That Release Heat Also Tend to Conduct Electricity
Well-known thermal management materials include
● Copper
● Aluminum
● Graphite
● Metal plates, and so on.
These conduct heat well.
At the same time, however, they often also conduct electricity.
In other words, they are advantageous for heat.
They have the characteristic of being disadvantageous for electricity.
■ Insulating Materials Tend to Stop Heat
On the other hand,
● PET
● PI
● Foams
● General resins
and so on hardly conduct electricity.
In other words, they are advantageous for insulation.
However, they also conduct heat poorly.
In other words, they are advantageous for insulation.
They have the characteristic of being disadvantageous for heat.
■ Heat and Insulation Are Essentially Contradictory
This is what makes thermal design difficult.
When you try to release heat, you want to use conductive materials.
However, using conductive materials makes insulation difficult.
Conversely, if you emphasize insulation, heat will not escape.
In other words, heat and insulation tend to be essentially a trade-off.
■ What Is Happening in AI Servers
In AI servers, GPUs and CPUs generate large amounts of heat.
That is why you want to release heat to the cooling equipment as efficiently as possible.
At the same time, however, there is high-density wiring inside the server.
If a heat dissipation material conducts electricity, it could lead to a serious failure.
That is why, in AI servers, materials that simultaneously satisfy
high heat dissipation
high insulation are required.
■ What Is Happening in EVs
In EVs, things are even more severe.
Batteries handle voltages in the hundreds of volts.
At the same time, heat generation is also large.
In other words, you want to release heat.
But electrical leakage is absolutely not allowed.
What is required here is insulated heat dissipation.
■ The Same Challenge Arises in ESS
ESS are becoming larger.
The greater the amount of energy stored, the greater the amount of heat generated.
And voltages also become higher.
In other words, just as with EVs, both heat dissipation and insulation must be achieved.
In recent ESS fire countermeasures as well, thermal design and insulation design can no longer be separated.
■ Why Ceramics Are Attracting Attention
A typical material that solves this challenge is
ceramic-based materials.
For example,
● Alumina
● Aluminum nitride
● Boron nitride, and so on.
These hardly conduct electricity while conducting heat to a certain extent.
In other words, they have the property of letting heat flow while stopping electricity.
■ However, Materials Alone Do Not Solve the Problem
There is an important misconception here.
Using ceramics is not the end of the story.
In reality, the structure is
Heat-generating body
↓
Heat dissipation material
↓
Insulating layer
↓
Cooling component
At this point, if the contact state is poor, heat will not flow.
In other words, not only insulation performance but also contact thermal resistance is important.
■ Dielectric Breakdown Happens Suddenly
Heat problems often worsen gradually.
Dielectric breakdown, however, is different.
It happens suddenly at a certain moment.
That is why insulation design requires designing with margin.
In particular, in
AI servers
EVs
ESS, long-term reliability is important.
■ Thermal Expansion Can Also Break Insulation
When heat is generated, materials expand.
However,
metals
resins
ceramics differ in how much they expand.
Then stress occurs at the interfaces.
When this is repeated over long periods,
● Cracks
● Delamination
● Insulation degradation
can occur.
In other words, heat problems cause insulation problems.
■ It Becomes Even More Difficult in 3D Semiconductors
In 3D semiconductors, chips are stacked vertically.
Then heat density rises.
However, insulation distances become shorter.
In other words, higher heat dissipation performance and
higher insulation performance are required at the same time.
This is one of the major challenges of 3D semiconductors.
■ It Also Becomes Important in Robots
In robots that come into contact with people,
motors
batteries
control boards generate heat.
However, the risk of electric shock must be avoided.
In other words, they must release heat while protecting people.
The more robots increase in the future, the more important heat × insulation will become.
■ The Same Goes for Wearable Devices
In devices close to the human body,
not only heat generation but also safety is important.
In wearable devices, heat and insulation cannot be separated.
The closer the distance to the human body, the harder it is to achieve both.
■ The Researcher's Perspective: Insulated Heat Dissipation Is a Central Theme of Future Materials
In recent materials development,
rather than simple high thermal conductivity materials,
investment in insulating heat dissipation materials is increasing.
This is because
AI servers
EVs
ESS
3D semiconductors all require them.
■ The Shop-Floor Perspective: Insulation Performance Is Broken by Processing
On the shop floor, there is something more frightening than material performance.
That is processing defects.
For example,
● Burrs
● Foreign matter
● Pinholes
● Lamination misalignment
● Exposed edges
Even if a material is insulating in the catalog, its performance changes depending on the state of processing.
In other words, insulation is not determined by the material alone.
■ Problems That Tend to Occur in Volume Production for Heat × Insulation
In volume production processes,
● Misalignment of insulating films
● Exposed metal foil
● Foreign matter contamination
● Uneven compression
● Thickness variation
● Delamination
● Cracks, and so on can occur.
These affect not only thermal performance but safety itself.
■ OTIS's Perspective
OTIS is not an insulating materials manufacturer.
Nor is it a heat dissipation materials manufacturer.
However, in the area of combining
heat dissipation materials
insulating materials
adhesive materials
metal foils
and processing them into structures that work in volume production, we may be able to contribute.
In particular, we may be able to deliver value in
● High-precision lamination
● Microfabrication
● Lamination of dissimilar materials
● Heat dissipation structures with insulating layers
● Automated supply
■ What OTIS Can Do
At OTIS, through
● Insulating material processing
● Heat dissipation material processing
● High-precision lamination
● Lamination of dissimilar materials
● Fine die-cutting
● Reel supply
● Design for automation
and more, we may be able to contribute to making components that achieve both heat dissipation and insulation.
■ Outside OTIS's Expertise
On the other hand, OTIS is not a company that specializes in
● Development of insulating materials themselves
● Ceramic development
● High-voltage design
● Power supply design
● Dedicated insulation analysis
However, in the area of making structures that achieve both heat dissipation and insulation work in volume production,
we may be able to play an important role.
■ Industries Where This Technology Will Be Important
★★★★★ AI servers
★★★★★ EVs and batteries
★★★★★ ESS and energy storage systems
★★★★★ 3D semiconductors
★★★★☆ Robots
★★★★☆ Wearable devices
★★★★☆ Communication equipment
■ Summary
You want to release heat. But you don’t want electricity to flow
This is the essence of heat × insulation.
In future industries, just releasing heat is not enough.
At the same time, it is necessary to insulate, protect safety, and ensure long-term reliability.
That is why thermal management does not end with choosing materials.
Only when everything works, including structure, contact, processing, and volume production, does it become true insulated heat dissipation design.
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.
