■ Adhesives Also Have Thickness
Adhesives look thin.
But when stacked, they affect the overall thickness.
Furthermore, if adhesive enters the heat path, it also becomes
thermal resistance.
In other words, there are the requirements:
you want it thin.
But you want to fix things.
You want it to conform to steps.
■ The Concept of Partial Adhesion
When there is no need to put adhesive across the entire surface,
placing adhesive
● Only on the outer periphery
● Only in some areas
may reduce
● Weight
● Thickness
● Thermal resistance
In other words,
where to place the adhesive also becomes thermal design.
■ Integrating Components Can Reduce Assembly Processes
For example, suppose
graphite,
insulating film,
and adhesive
are applied separately.
If these are laminated in advance
and supplied as a single component,
the customer only needs to apply it once.
In other words,
making composite functional components can reduce assembly processes.
■ Smart Devices Are a Good Match for Integration
The narrower the inside of the product,
the more you want to reduce the number of parts.
You want to reduce application processes.
That is why integrated components such as
heat + insulation + adhesion
heat + EMI + fixing
are a good match.
This has a strong connection with OTIS’s processing technologies.
■ However, Adding Just One Layer Makes It Thicker
Integration is convenient.
However, every time
an insulating film is added,
an adhesive layer is added,
or a protective layer is added,
thickness increases.
In smart devices,
an increase of 50 μm
can itself become a design problem.
In other words, with integration, it is necessary to consider
not the number of functions, but the minimum necessary stacking.
■ There Is a Lot of Irregular-Shape Processing
The inside of a smart device
is not just perfect rectangles.
Avoiding cameras.
Avoiding connectors.
Avoiding antennas.
Avoiding screws.
As a result,
● Openings
● Notches
● Narrow sections
● Complex outer shapes
increase.
In other words, not only material performance, but
being able to precisely process irregular shapes becomes important.
■ In Narrow Sections, Both Thermal Performance and Processability Become Problems
Suppose a long, narrow graphite shape is made to release heat to the enclosure.
Making it narrow lets it pass through narrow gaps.
However, there are problems such as
● It tears easily
● It deforms easily when peeled
● The cross-section through which heat passes also becomes smaller
In other words, there is the trade-off that
making it narrower makes it easier to place.
But heat flows less easily, and processing becomes harder.
■ Automated Supply Is Also Important
Smart devices are mass-produced.
Applying large quantities of thin-film components by hand one at a time is not realistic.
That is why
● Reel supply
● Automated peeling
● Automated pick-up
● High-precision application
are important.
In other words, components must not only have good thermal performance,
but also be handleable by automated machines.
■ The Thinner the Component, the Harder Automated Pick-Up Becomes
Thin graphite.
Thin films.
Soft TIM.
These may
● Warp
● Sag
● Stick due to static electricity
● Deform during pick-up
That is why it is necessary to consider even
● Carriers
● Release liners
● Pick-up surfaces
● Component arrangement
■ Static Electricity Is Also a Problem
When handling thin films and release liners, static electricity may be generated.
Static electricity may cause
● Components to re-adhere
● Foreign matter to be attracted
● Transport posture to be disturbed
In smart devices, components are small, so even small foreign particles become a problem.
■ Appearance Quality Is Also Strict
Smartphones and wearables are products that ordinary consumers look at directly.
Even internal components, if they affect the exterior through
● Squeeze-out
● Lifting
● Warping
lead to appearance defects.
In other words,
not only thermal performance, but also product appearance is governed by processing accuracy.
■ The Researcher's Perspective: The Heat Problem of Smart Devices Tends to Be a Problem of "Space" Rather Than "Amount of Heat"
Even with the same amount of heat, large equipment can hold large heat sinks.
Smart devices cannot.
In other words,
there is little room to increase cooling capacity.
That is why heat must be designed across the entire product, such as
● Spreading heat
● Changing heat source positions
● Making the enclosure a heat path
● Controlling power consumption
■ The Shop-Floor Perspective: A 0.1 mm Component Change Alters Both Heat and Assembly
Make the TIM 0.1 mm thicker.
Then it conforms more easily to steps.
But thermal resistance may increase.
Make the insulating film thinner.
Then it saves space.
But processing and insulation reliability become harder.
In other words, in smart devices,
design changes of tens of μm
simultaneously affect
heat, strength, assembly and safety.
■ Things to Check at the Design Stage
In thermal management for smart devices, at least the following need to be checked.
Heat sources
● How much heat does the SoC generate?
● How does it change during communication?
● What about during fast charging?
● Is there thermal interference with the camera or battery?
Heat spreading
● Where will heat be spread?
● Is graphite suitable?
● Is metal foil suitable?
● Is a vapor chamber needed?
Human body and exterior
● Which surfaces do people touch?
● Will the surface temperature become high?
● Is heat flowing toward the battery?
● In AR/VR, is heat coming toward the face?
Insulation and EMI
● Is the insulation of metal foil sufficient?
● Does it affect antenna characteristics?
● Can EMI materials and heat-spreading materials be combined?
Thin films
● What is the total stack thickness?
● Can each layer be made thinner?
● Are there wrinkles or warping?
● Can irregular shapes be processed?
Adhesion and fixing
● Is full-surface adhesion needed?
● Is partial adhesion possible?
● Will it shift at high temperature?
● Is the adhesive layer becoming thermal resistance?
Waterproofing
● Does sealing trap heat?
● Is the seal material placement appropriate?
● Can heat be released to the exterior?
Volume production
● Can it be supplied on reels?
● Can it be automatically peeled?
● Can thin-film components be picked up stably?
● Can multiple materials be integrated?
In smart devices, it is necessary to consider
heat, thinness, weight, electrical design, waterproofing and volume production at the same time.
■ OTIS's Perspective: Smart Devices Are One of the Markets Where the Value of "Thin-Film Processing" Is Most Visible
OTIS is
not a smartphone manufacturer.
Not an SoC manufacturer.
Not a vapor chamber manufacturer.
However, many thin-film materials are used inside smart devices, such as
● Graphite
● Copper foil
● Aluminum foil
● TIM
● Insulating films
● EMI materials
● Adhesives
● Seal materials
Moreover, there are the requirements of being
thin
small
complex in shape
high-precision
mass-produced
This is a good match for OTIS.
■ Where OTIS Should Aim
Not the finished smartphone itself.
What to target is the thin-film functional components around high-heat components.
For example,
● TIM around SoCs
● Graphite heat-spreading components
● Copper and aluminum foil heat-spreading components
● Insulating materials around batteries
● Thermal insulation and heat dissipation components around cameras
● EMI + heat dissipation components
● Waterproof seal materials
● Flexible thermal management components for wearables
■ "Cutting Materials" Alone Is Not Enough Value
Buying graphite from a material manufacturer.
Cutting it per the drawing.
That alone easily turns into price competition.
For OTIS to deliver value,
Graphite
＋
Insulating material
＋
Adhesive
are laminated with high precision.
Only the necessary parts are made adhesive.
It is made into a reel form that can be applied automatically.
In other words, it is necessary to go as far as
turning materials into parts that can be used in the customer’s process.
■ What OTIS Can Do
At OTIS, through
● Graphite processing
● TIM processing
● Copper foil processing
● Aluminum foil processing
● Insulating film processing
● EMI material processing
● Adhesive processing
● Seal material processing
● High-precision die-cutting
● Microfabrication
● Thin-film processing
● Irregular-shape processing
● High-precision lamination
● Lamination of dissimilar materials
● Partial lamination
● Half-cutting
● Reel-to-reel processing
● Supply formats for automated application
● Integration of multiple functional materials
we may be able to contribute to
turning high-performance thin-film materials used in smart devices into parts that can be mass-produced.
■ Outside OTIS's Expertise
OTIS is not a company that specializes in
● Smartphone body design
● SoC design
● Antenna design
● Design of vapor chambers themselves
● Battery cell development
● Thermal design of entire smart devices
As needed, collaboration with material manufacturers, device manufacturers and cooling component manufacturers is necessary.
■ Markets Where This Technology Will Be Important
★★★★★ Smartphones
★★★★★ AR, VR and XR devices
★★★★★ Smartwatches
★★★★★ Wearable devices
★★★★☆ Tablets
★★★★☆ Small edge AI devices
★★★★☆ Wireless earphones
★★★★☆ Handheld game consoles
■ Summary
The heat problems of smart devices begin with “having no space for cooling”
Smart devices
are becoming higher-performing.
However,
they are becoming thinner.
Lighter.
Waterproof.
Batteries are also becoming larger.
In other words,
heat is increasing, yet the space available for thermal management is decreasing.
That is why methods such as
adding large heat sinks
or installing large fans
are hard to use.
Instead,
spreading heat with graphite,
diffusing heat with vapor chambers,
guiding heat with metal foils,
insulating toward the human body and battery,
and achieving insulation and EMI at the same time:
thermal design on the scale of a few tens of μm to a few mm becomes important.
And those components
must not merely be thin.
They must be processable into complex shapes.
Be correctly positioned.
Not warp.
Not peel.
Be applicable automatically.
Be mass-producible.
In other words, in smart devices, material performance and microfabrication technology cannot be separated.
What OTIS should target is not the smart device itself.
It is the common challenges inside it:
heat, thin films, insulation, EMI, adhesion, waterproofing, microfabrication and automation.
The thinner products become,
what remains in the end
is the design question of “how to use these tens of μm.”
And that is
one of the places where a precision processing company can most easily deliver value.
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.
