■ Cooling in Prototyping and Cooling in Volume Production Are Different
In prototyping, skilled workers can build things carefully.
They apply materials carefully.
They remove air bubbles.
They adjust positions.
They check pressure.
If there is a problem, they fix it by hand.
That is why good results can come out of prototyping.
In volume production, however, things are different.
It runs on automated machines.
It is applied at a set speed.
It is compression-bonded at a set pressure.
It is repeated under the same conditions.
At this point, if materials and processes are not stable, performance varies.
In other words, prototype success and
volume production success are different things.
■ Thermal Performance Varies Easily
The performance of thermal management components changes with slight differences.
For example,
● Thickness
● Application position
● Pressure
● Air bubbles
● Contact area
● Surface roughness
● Adhesive state
● Material hardness
● Foreign matter, and so on.
Even slight changes in these change thermal resistance.
When thermal resistance changes, temperature changes.
In other words, thermal performance is performance that is easily affected by volume production variation.
■ Thermal Management Is Hard to Judge by Appearance
What is difficult in volume production is that thermal performance is hard to see with the eye.
Externally, it looks fine.
It looks applied.
The shape also looks right.
In reality, however,
● There are air bubbles inside
● Compression bonding is insufficient
● The contact area is insufficient
● The edges are lifting
● The thickness is subtly different
Then thermal performance changes.
In other words, with thermal management components, even if they look the same, their thermal performance is not necessarily the same.
■ Contact State Determines Volume Production Stability
In thermal management, contact is extremely important.
If air layers remain between heat-generating components and heat-dissipating components, heat has difficulty flowing.
That is why, in volume production,
● How stably close contact can be achieved
● Whether pressure is constant
● Whether air bubbles get in
● Whether component tolerances can be absorbed
● Whether contact is maintained after aging
are important.
In other words, with heat × volume production stability, stabilizing the contact state is the central challenge.
■ Thickness Variation Changes Thermal Performance
With thermal management materials, thickness is important.
With TIM and heat dissipation sheets, thermal resistance changes when thickness changes.
In general, the thicker it is, the more thermal resistance tends to increase.
However, if it is too thin, it cannot absorb steps and tolerances, and air layers may remain.
In other words, in volume production, stably maintaining the intended thickness is important.
■ Application Misalignment Changes Performance
When thermal management components are applied in the wrong position, their performance changes.
Off the heat-generating component.
Off the heat dissipation path.
Unable to cover the area to be insulated.
The waterproof line breaks down.
The EMI shield position shifts.
In other words, thermal management components are often related not only to heat but also to insulation, waterproofing, and noise.
That is why application misalignment affects multiple types of performance.
■ Air Bubbles Stop Heat
One of the things to watch out for particularly in volume production is air bubbles.
What is inside an air bubble is air.
Air conducts heat poorly.
That is why, when air bubbles get into heat dissipation sheets or adhesive materials, thermal performance drops.
Moreover, air bubbles can be hard to see from the outside.
In other words, air bubbles become thermal resistance that is hard to see.
■ Foreign Matter Also Affects Thermal Performance and Safety
Foreign matter is also a major problem in volume production.
When foreign matter gets in, it may lead to
● Lifting
● Poor contact
● Uneven thickness
● Insulation defects
● Conduction risk
● Waterproofing defects
Particular care is needed with metal particles, graphite particles, and die-cut scrap.
In other words, with thermal management components, foreign matter management is also part of volume production stability.
■ Material Lot Differences Also Become a Problem
Even with the same material name, slight differences can arise between lots.
For example,
● Hardness
● Adhesive strength
● Thickness
● Peeling force
● Surface condition
● Filler dispersion
● Moisture content, and so on.
When these change, behavior on automated machines and lamination states change.
In other words, in volume production, process design that assumes material lot differences is necessary.
■ In Automated Processes, Reproducibility Is Important
In volume production, automated processes are often used.
In automation, the same operations are repeated.
However, if materials are unstable, equipment conditions are not stable either.
For example, problems such as
● The release liner is hard to peel
● It cannot be picked up by suction
● It stretches during transport
● The application position shifts
● Uneven compression bonding occurs
In other words, the volume production stability of thermal management components is also greatly influenced by whether they run stably in automated processes.
■ In AI Servers, Long-Term Stability Is Important
In AI servers, 24-hour continuous operation is a given.
That is why it is not enough just to cool in the initial state.
It is important that thermal performance does not drop even with long-term use.
For example, if
● TIM pump-out
● Adhesive degradation
● Compression set
● Lifting due to thermal expansion
● Graphite cracking
● Degradation of insulating layers
and so on occur, performance changes over the long term.
In other words, in AI servers,
not only initial performance but also long-term performance is important.
■ In EVs and ESS, Safety Is Involved
In EVs and ESS, volume production stability is directly linked to safety.
Variation in thermal management components may change
● Temperature differences between cells
● Propagation suppression performance during thermal runaway
● Insulation performance
● Waterproofing performance
● Long-term reliability
In other words, in EVs and ESS, volume production variation
can lead to safety variation.
■ In Smartphones and Wearables, It Becomes a Difference in How It Feels
In smartphones and wearable devices, volume production variation can show up in the user experience.
One unit does not feel hot.
Another unit feels hot.
One unit’s battery degrades quickly.
Another unit has no problem.
When such differences occur, they lead to quality problems.
In other words, in small devices, variation in thermal performance
becomes variation in perceived quality.
■ Heat × Volume Production Stability Is a Combined Challenge
Thermal management components often do not have a single function.
Not only heat dissipation but also
● Insulation
● Waterproofing
● Adhesion
● Noise countermeasures
● Weight reduction
● Automation
● Cost
are required at the same time.
In other words, volume production stability is not stabilizing only thermal performance.
It is stabilizing multiple functions at the same time.
This is what is difficult.
■ The Researcher's Perspective: Thermal Performance Should Be Evaluated Including Post-Mounting Variation
In research and development, the thermal conductivity and thermal resistance of materials alone are often evaluated.
In volume production, however, that alone is not enough.
In reality, evaluation is needed all the way to
● Thickness after mounting
● Contact state after mounting
● Compression bonding conditions
● Changes over time
● Lot differences
● Changes after thermal cycling
In other words, in future thermal management, not only material performance, but also
post-mounting performance
post-volume-production performance will be important.
■ The Shop-Floor Perspective: In Volume Production, Design That Does Not Vary Is Important
On the shop floor, not varying can be more important than peak performance.
A material that stably lowers temperature by 3°C in volume production can be more valuable than a material that lowers the maximum temperature by 5°C in a prototype.
This is because, in volume production, stability is quality.
In other words, reproducible performance is more important than peak performance.
■ Problems That Tend to Occur for Heat × Volume Production Stability
In volume production processes, the following kinds of problems can occur.
● Application misalignment
● Air bubbles
● Thickness variation
● Uneven compression bonding
● Foreign matter contamination
● Peeling
● Material lot differences
● Automated machine stoppages
● Curl from winding
● Particle shedding
● Changes over time
● Performance degradation after thermal cycling
These affect not only thermal performance but also insulation, waterproofing, noise, reliability, and yield.
In other words, with heat × volume production stability,
component design
processing design
process design must be considered at the same time.
■ OTIS's Perspective
OTIS is not a company that develops materials themselves.
However, we may be able to contribute in the area of processing thermal management materials into a form that can be used stably in volume production.
What matters from OTIS’s perspective is
● High-precision die-cutting
● Microfabrication
● High-precision lamination
● Lamination of dissimilar materials
● Reel supply
● Supply formats for automated processes
● Release liner design
● Dimensional stability
● Lamination accuracy
● Reducing variation in volume production
Thermal management materials do not work just by choosing good materials.
It is important that they can be supplied to volume production processes stably and in the same condition.
■ What OTIS Can Do
At OTIS, through
● Heat dissipation sheet processing
● Graphite processing
● Insulating material processing
● Adhesive material processing
● EMI material processing
● Metal foil processing
● High-precision die-cutting
● Microfabrication
● High-precision lamination
● Stacking of irregular shapes
● Reel supply
● Designing supply formats for automated processes
and more, we may be able to contribute to bringing thermal management components closer to a state in which they can be used stably in volume production.
Especially in AI servers, EVs, ESS, smartphones, and wearable devices, not only thermal performance but also volume production reproducibility is important.
■ Outside OTIS's Expertise
On the other hand, OTIS is not a company that specializes in
● Development of materials themselves
● Quality assurance design for entire finished products
● Dedicated thermal simulation analysis
● Cooling equipment design
● Equipment design for customers’ entire lines
However, in the area of making thermal management materials work stably in volume production processes,
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
★★★★★ Smartphones
★★★★★ Wearable devices
★★★★☆ Robots
★★★★☆ Communication equipment
■ Summary
Thermal management is completed not in prototyping but in volume production
Thermal management is not finished once it cools in prototyping.
What truly matters is cooling the same way in volume production.
Thermal performance changes with thickness, application position, air bubbles, pressure, foreign matter, and contact state.
And these tend to vary in volume production.
That is why, with heat × volume production stability, material selection alone is not enough.
Processing accuracy.
Lamination accuracy.
Supply format.
Automation suitability.
Process reproducibility.
Long-term reliability.
Only by including all of this does thermal management work.
Future heat problems cannot be solved by materials manufacturers alone.
What is needed is technology that delivers good materials to volume production processes in good condition and with the same quality.
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.
