For example, suppose a power semiconductor is to be cooled.

We want to release heat from the semiconductor to a metal cooling plate.

But electrically, we want to insulate it.

In other words,

we want heat to pass.

We do not want electricity to pass.

These are contradictory requirements.

Also, for outdoor equipment,

we want to release heat to the outside.

But we want to seal the enclosure.

A contradiction arises.

In other words, in actual products, thermal management always competes with other functions.

To insulate electrically, an insulating film is added.

Safety then improves.

But the insulating film also becomes part of the heat path.

Making it thicker is advantageous for insulation.

On the other hand, it may be disadvantageous for heat.

In other words,

the more insulation performance is raised, the more heat dissipation performance drops

in some cases.

Conversely, making the insulating film thinner may reduce thermal resistance.

However, the thinner it gets, the more susceptible it becomes to

● Pinholes

● Scratches

● Burrs

● Foreign matter

In other words,

it is made thinner for thermal performance.

But safety becomes more demanding.

This balance is important.

In the material manufacturer’s catalog, there is sufficient insulation performance.

But during processing,

burrs form.

Edges are damaged.

Position shifts.

Metal parts are exposed.

Such things happen.

Then, even if the material alone performs well, the finished component cannot insulate.

In other words, insulation performance is determined not only by material performance but by processing quality.

Copper foil and aluminum foil conduct heat well.

That is why they can be used as heat spreaders.

On the other hand, because they are conductive, they can also be used for EMI shielding.

In other words, a single metal foil is related to both

heat dissipation

and EMI.

This is also an advantage.

But if designed wrongly, it can conversely create noise paths.

For example, a large copper foil is added on a board to release heat.

The heat spreads.

But if that copper foil is near an antenna, it may affect communication characteristics.

Also, depending on the ground design, it can create unwanted current paths.

In other words, heat spreaders also exist electrically.

Metal cannot be placed based on thermal design alone.

Graphite is effective for spreading heat in the in-plane direction.

But it also conducts electricity.

That is why, when used near electronic components or boards,

● Insulating films

● Protective films

● Edge treatment

may be needed.

In other words, even if graphite alone is high-performance, in practice insulating material is added.

Then the laminate thickness and thermal resistance also change.

Metal foil is added as EMI shielding material.

That metal foil may then carry heat in another direction.

This can be good.

But it may also conduct heat to unintended places.

For example,

heat flows from the heat source toward the battery.

Heat flows toward the area around the temperature sensor.

In other words, EMI components are also part of thermal design.

Outdoor equipment and automotive equipment need waterproofing and dustproofing.

That is why the enclosure is sealed.

But when sealed,

internal heat is less likely to escape to the outside via air.

In other words,

the more waterproofing performance is raised, the harder air cooling becomes

in some cases.

If the air inside the enclosure cannot be released outside,

heat must be released to the outside through solids, like

Heat-generating component

↓

TIM

↓

Internal frame

↓

Enclosure

In other words, in waterproof design, rather than dumping heat directly to the outside air, it is important to create

a path that carries heat to the enclosure.

If heat is released to the enclosure, the inside cools.

But in equipment people touch, an enclosure that gets too hot is a problem.

Medical devices.

Robots.

Wearables.

This is especially important in these.

In other words,

we want to cool the inside.

We do not want to make the exterior hot.

A new contradiction arises.

Gaskets and foam seals are inserted for waterproofing.

When this seal material comes between components, the heat path can change.

For example, if metal enclosure parts directly contact each other, heat can be released.

But if a thick foam seal comes between them, heat flows less easily.

In other words, the placement of waterproofing components also affects thermal design.

Making seal materials thinner may be advantageous for heat.

But waterproofing requires a certain amount of compression.

If too thin, problems arise:

steps cannot be absorbed.

Surface roughness cannot be filled.

There is no compression margin.

In other words, the optimal thickness also differs for waterproofing and heat.

Gaskets and foams are used compressed.

Compressing them can improve waterproofing.

On the other hand,

thermal conduction,

thickness,

and repulsive force

also change.

In other words, a single compression condition affects all of

waterproofing,

heat,

and mechanical stress.

In liquid-cooled equipment, coolant flows inside.

Here, it is necessary not only to keep water from getting in from outside, but also

not to leak the internal liquid.

Cold plates.

Piping.

Fittings.

Seal materials.

All are involved.

In other words, in liquid cooling, thermal performance and seal reliability must be established simultaneously.

For example, a large amount of thermally conductive filler is added to seal material.

Thermal conductivity goes up.

But the material becomes harder.

Then conformability to steps worsens, and waterproofing performance may decline.

In other words, raising one function of a material can lower another function.

Double-sided tape is sometimes used for

fixing,

waterproofing,

and sealing.

But if it enters the heat path, it also becomes thermal resistance.

For example, the enclosure is fixed with waterproof double-sided tape.

Waterproofing is high.

But when one wants to release heat from the heat source to the enclosure, that tape may become the bottleneck of the heat path.

With full-surface adhesion,

fixing strength

and waterproofing

are easy to raise.

But thermal resistance may increase.

With partial adhesion, it is easier to secure the heat path.

But the waterproof line may be broken.

In other words,

where to bond and where not to bond

also becomes multifunctional design.

With gaskets and adhesive seals, if the perimeter is not connected all the way around, water may get in.

If along the way there are

breaks,

steps,

chips,

or misalignment,

waterproofing is lost.

In other words, even when integrating thermal management components and seal components,

a shape that does not break the seal line is needed.

For example, adhesive is applied to an insulating film and it is attached to a metal enclosure.

Then a single sheet may handle

insulation,

waterproofing,

and fixing.

This leads to fewer parts.

But at the same time,

thermal resistance,

air bubbles during application,

and edge shape

also become important.

In other words, the more multifunctional it becomes, the more design conditions increase.

A single component handles

insulation,

waterproofing,

thermal conduction,

and fixing.

In this case, one component can reduce many processes.

But a defect in one place may lose all of

heat,

insulation,

and waterproofing.

In other words, in multifunctional components, the quality responsibility of a single sheet becomes large.

Openings are made for heat dissipation.

Air is made to flow.

Vents are provided.

Thermally advantageous.

But waterproofing goes down.

In other words,

air cooling performance and waterproofing performance fundamentally compete

in some cases.

That is why other countermeasures, such as vent membranes or special structures, may be needed.

A metal enclosure is used for EMI countermeasures.

Metal also conducts heat well.

That is why it is advantageous for enclosure heat dissipation.

On the other hand, problems with

weight,

insulation,

and electrical paths

increase.

In other words, even a single metal enclosure affects all of

heat,

EMI,

weight,

and insulation.

Metal is made thinner.

It is replaced with resin.

Weight can be reduced.

But

it becomes harder to spread heat.

EMI shielding performance goes down.

This may happen.

That is why combined countermeasures are needed, such as

placing thin metal foil partially,

using conductive paint,

and adding graphite.

In EV batteries,

we want to cool the cells.

We want to insulate high voltage.

We do not want to leak coolant.

We also do not want water to get in from outside.

Furthermore, during thermal runaway, we do not want heat to spread.

In other words, EVs are a typical example of combined challenges.

Components cannot be selected by looking at heat alone.

In EV batteries under normal conditions,

we want to release heat from the cells to the cooling plate.

But in abnormal conditions, we do not want heat to transfer to the adjacent cell.

In other words,

heat dissipation in normal conditions.

Thermal insulation in abnormal conditions.

There is this contradiction.

This is hard to solve with a single material.

Thermally conductive materials and thermal insulation materials must be used differently by location.

GPUs.

HBM.

High-speed communication.

Optical communication.

Power supplies.

These become denser.

Then heat sources and high-frequency circuits come closer together.

Heat dissipation metal,

EMI shielding,

and insulation

must be established in the same narrow space.

In other words, the higher the density, the harder heat-only design becomes.

In smartphones,

we want to spread SoC heat.

But it is hard to place metal around antennas.

Furthermore, we want to waterproof the enclosure.

And we want to make it thin.

In other words, all of

heat,

radio waves,

waterproofing,

and thinness

must be established at the same time.

In such markets, multifunctional components have high value.

In wearable medical devices,

we want to cool electronic components.

We do not want too much heat to flow to the human body.

We want to insulate electricity.

We do not want sweat or moisture to get in.

In other words,

heat,

insulation,

waterproofing,

and wearability

must be considered at the same time.

In robots,

motors,

AI boards,

and batteries

generate heat.

Furthermore,

waterproofing,

EMI,

weight reduction,

and mobility

are also needed.

Installing a large metal heat sink will cool it.

But it gets heavier.

Sealing it makes it waterproof.

But heat builds up.

In other words, it is necessary to find the optimal point among multiple requirements.

For example, only thermal evaluation is performed.

The temperature passes.

But the insulation test fails.

The EMI test shows increased noise.

The waterproof test shows leaks.

Such things happen.

In other words, when changing materials or structures, multiple related evaluations must be performed.

The TIM is changed.

Metal foil is added.

The insulating film is made thinner.

The adhesive is changed.

Such changes do not affect just one function.

When heat is improved, it is necessary to see what happens to

insulation,

noise,

waterproofing,

and durability.

In other words, a change in thermal management is a system change.

To spread local heat, copper foil was added.

The temperature went down.

But it worsened in EMI evaluation.

The metal foil had created unintended electrical coupling.

In other words,

as a result of adopting it after checking only thermal performance,

electrical performance was broken.

To lower thermal resistance, the insulating film was made thinner.

Component temperature went down.

But after volume production, insulation failures occurred in some units.

The cause was the effect of metal burrs and foreign matter.

Small protrusions that were not a problem with thick material became apparent due to thinning.

In other words, the thermal improvement had cut into the safety margin.

To raise the waterproofing performance of outdoor equipment, openings were reduced and the enclosure was sealed.

It passed the waterproof test.

But in continuous operation, the internal temperature rose greatly.

This was because the air-cooling path was gone.

In other words,

the waterproofing countermeasure broke the heat path.

To ensure waterproofing and fixing, full-surface adhesive tape was added.

Water no longer got in.

But that adhesive layer entered the heat path, and component temperature rose.

In other words, a single adhesive material was

a plus for waterproofing

and a minus for heat.

Minimize thermal resistance.

Maximize insulation thickness.

Maximize seal pressure.

Maximize EMI shielding.

Each looks correct on its own.

But in a product, not everything can be maximized.

What matters is, within the range that satisfies the required performance,

finding the overall optimal point of multiple functions.

The temperature is high.

Change the TIM.

Trying to solve it with that alone may break other functions.

For example, combine multiple small improvements, such as

TIM change,

contact improvement,

enclosure heat spreading,

airflow path improvement,

and power control.

That may make improvement possible without disrupting overall performance.

To solve multiple challenges, multiple functions are sometimes combined into a single component, such as

Graphite ＋ Insulating film ＋ Adhesive

or

Metal foil ＋ Insulating material ＋ Seal material

This may reduce

the number of parts,

application processes,

and misalignment.

Laminating multiple materials increases functions.

But

thickness,

thermal resistance,

warping,

delamination,

and processing difficulty

also increase.

In other words, multifunctional components require

designing the interference between functions, not just adding functions together.

Insulating material over the entire surface.

Adhesive over the entire surface.

Metal foil over the entire surface.

This makes it thicker than necessary.

So functions are placed only where needed, such as

TIM only directly above the heat source.

Insulation only at the high-voltage area.

Waterproof adhesive only on the perimeter.

Metal foil only around noise sources.

In other words, the value of partial processing and partial lamination emerges.

For example, a structure is made where

the center dissipates heat,

the perimeter is waterproof,

and only part is insulated.

Assembling this from separate components increases misalignment.

If laminated in the required positions in advance, assembly processes can be reduced.

In other words, a processing company can create not the material itself, but

the arrangement of functions.

When OTIS processes thermal management materials,

looking only at

TIM

and graphite

is not enough.

Actual customer challenges are often

heat + insulation,

heat + waterproofing,

heat + EMI,

heat + adhesion.

In other words, what OTIS should aim for is the area of

not “We can process heat dissipation materials,” but “We can establish multiple functions as volume production components.”

OTIS does not need to develop all materials.

Insulating material manufacturers.

Graphite manufacturers.

Adhesive manufacturers.

Seal material manufacturers.

Their respective high-performance materials are combined.

OTIS designs

shape,

position,

lamination,

and supply format.

In other words, it plays the role of integrating material manufacturers’ expertise into a single volume production component.

For example, there is a consultation:

“This component gets hot, and it also needs waterproofing.”

Rather than immediately looking for a single material, we break it down:

Where should heat be released?

Where should it be sealed?

Is electrical insulation needed?

Is there EMI?

Is fixing needed?

Then the necessary functional materials are combined.

In other words, thinking in terms of functions, not product names, is important.

At OTIS, through

● TIM processing

● Graphite processing

● Copper foil and aluminum foil processing

● Insulating film processing

● EMI material processing

● Adhesive processing

● Gasket and seal material processing

● Foam processing

● High-precision die-cutting

● Thin-film processing

● Partial lamination

● High-precision lamination

● Lamination of dissimilar materials

● Half-cutting

● Opening processing

● Reel-to-reel processing

● Conversion into multifunctional components

● Supply formats for automatic application

we can contribute to volume production of components that have not only thermal functions but multiple functions.

OTIS is not a company that specializes in

● Developing thermal materials themselves

● Formulation development of insulating materials themselves

● Dedicated EMI analysis

● Design of entire waterproof structures

● Electrical design of entire products

As needed, we work with material manufacturers, analysis companies and customers’ design departments.

Within this, OTIS plays the role of turning multiple functional materials into a single component that can actually be assembled.

In thermal management, lowering component temperature is important.

But products also need other functions, such as

insulation,

waterproofing,

EMI,

fixing,

and durability.

If, as a result of improving heat,

insulation gets worse,

waterproofing gets worse,

noise increases,

or it peels,

then it has not improved as a product.

That is why, in thermal management,

rather than maximizing a single number, the whole product must be established.

Where should heat flow?

Where should heat be stopped?

Where should electricity be stopped?

Where should water be stopped?

Where should noise be stopped?

Organize each of these, and place the required functions in the required places.

This is what matters.

Good thermal management is not the structure that cools best.

It is a structure that lowers heat without breaking other necessary functions.

And those multiple functions are brought together into a form that is thin, precise and mass-producible.

That is where a processing company delivers great value in thermal management.

 

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.