■ "Process → Laminate" and "Laminate → Process" Give Different Results
Each material is die-cut individually.
Then they are aligned and laminated.
Positional accuracy becomes the challenge.
On the other hand,
laminating first and die-cutting at once.
The outer shapes align.
But the difficulty of cutting dissimilar materials simultaneously increases.
In other words, in process design, it is necessary to consider for each project which order is most stable.
■ The More Processes, the More Important Reference Accuracy Becomes
Lamination.
Die-cutting.
Partial adhesion.
Openings.
Further lamination.
The more processes there are, the more likely positional errors are to accumulate.
That is why
reference holes,
marks,
and carriers
are used.
In other words, high-precision lamination must be designed together with the preceding and following processes, not as a standalone process.
■ Foreign Matter Trapped Between Layers Cannot Be Removed
When laminated, foreign matter between materials is sealed inside.
That foreign matter may
lift the interface,
damage the insulating material,
and create local stress.
It is difficult to remove after completion.
In other words, in high-precision lamination, cleanliness before bonding is extremely important.
■ The Thinner the Film, the Greater the Impact of Foreign Matter
A 50 μm film.
30 μm of foreign matter.
This foreign matter becomes a very large step.
In other words, in thin-film lamination, even tiny foreign matter greatly affects interface quality.
That is why
a clean environment,
material cleaning,
and transport control are important.
■ Static Electricity Also Attracts Foreign Matter
The film is peeled.
Static electricity is generated.
It attracts fine particles in the air.
It is laminated in that state.
Foreign matter is sealed inside.
In other words, static electricity control is also important for lamination quality.
■ A Cleanroom Alone Does Not Necessarily Solve It
Even if the environment is clean,
the material itself may shed debris when peeled,
foreign matter may come from blades,
and adhesive may string.
In other words, what matters is not only the cleanliness of the room, but not generating foreign matter from the process itself.
■ In Graphite Lamination, Also Consider Powder Countermeasures
Depending on the material, graphite may shed powder from its edges.
So structures are made such as
sandwiching top and bottom with film,
covering the edges,
and exposing only the necessary parts.
In other words, lamination has the role not only of
heat,
insulation,
and fixing,
but also material protection.
■ In Metal Foil Lamination, Do Not Seal Burrs Inside
There are burrs on copper foil.
An insulating film is applied over it.
It becomes invisible from the outside.
But inside, the burrs keep pressing locally on the film.
In the long term, it may become an insulation risk.
In other words, edge quality before lamination is important.
■ Lamination Can Also Be a Process That Hides Defects
Scratches,
foreign matter,
burrs,
and positional deviations
that were visible before bonding
become hard to see after bonding.
That is why
inspection after completion alone may not be enough.
In other words, in high-precision lamination, assurance in preceding processes is important.
■ Decide What to Inspect at Each Process
Material alone.
Position.
Foreign matter.
Appearance.
Thickness after lamination.
Finished outer shape.
At each process, items that will become invisible later are checked first.
In other words, inspection processes are also designed together with the manufacturing sequence.
■ Positioning Is Sometimes Done with Automatic Image Recognition
Transparent film.
Black graphite.
Metal foil.
Each looks different.
That is why position is corrected using
recognition holes,
marks,
and contours.
In other words, in high-precision lamination, it can also be important to create material shapes that are easy to recognize by imaging.
■ Aligning Transparent Materials with Each Other Is Difficult
Transparent films are stacked.
Contours are hard to see visually.
Contrast is also weak for cameras.
So
recognition marks,
temporary carriers,
printed references,
and so on are used.
In other words, elements not needed in the final product are sometimes provided only during the process.
■ The Value of Laminating on a Carrier
Aligning small components individually is difficult.
If they are laminated while held on a liner or carrier,
position is easier to maintain,
they are easier to transport,
and easier to automate.
In other words, carriers are also process components that support lamination accuracy.
■ Continuous Lamination with Reel-to-Reel
As volume production quantities increase,
applying one sheet at a time
is not productive enough.
So roll materials are laminated continuously.
This allows processing at
high speed,
continuously,
and under constant conditions.
However,
tension,
meandering,
pitch,
and rollers must be controlled.
■ With Long Runs, Slight Positional Deviations Accumulate
A single positional deviation is 0.05 mm.
For short runs, no problem.
But in long-run processing, feed errors and meandering accumulate.
That is why in continuous lamination, position is maintained using
sensors,
imaging,
meandering correction,
and so on.
In other words, maintaining accuracy over the entire length becomes volume production technology.
■ Lamination of Materials with Different Widths Is Also Difficult
Narrow graphite is partially applied to a wide film.
In this case, both
widthwise position
and lengthwise pitch
must be aligned.
In other words, high-precision placement of partial materials is more difficult than simple full-surface lamination.
This is where the value of high-precision lamination emerges.
■ In Multi-Row Processing, Accuracy Between Rows Is Also Important
To increase material yield, multiple rows are arranged within one roll width.
Then
each row position,
pitch between rows,
and feed direction
must be controlled.
In other words, the more volume production efficiency is raised, the more complex positional control becomes.
■ Balancing High Precision and Yield
Spacing between materials is made wide.
Easy to process.
But material yield is poor.
Spacing is made narrow.
Yield is good.
But positional deviation and waste stripping become difficult.
In other words, in high-precision lamination,
quality,
material cost,
and productivity must be considered simultaneously.
■ Prototype Lamination and Volume Production Lamination Are Different
In prototyping,
positions can be aligned by hand,
bonded slowly with a roller,
and redone if there are air bubbles.
In volume production,
it must be made at high speed,
continuously,
and under the same conditions.
In other words, prototype success alone does not mean volume production lamination is established.
■ In Prototyping, People Are Relieving Stress
When people apply it, they naturally make corrections such as
pulling slightly,
easing back slightly,
and changing the angle.
For automated equipment, this must be designed as process conditions.
In other words, in automating lamination, converting human feel into equipment conditions is important.
■ In Volume Production, Material Lot Differences Also Have an Effect
Adhesive strength,
hardness,
thickness,
and surface roughness
change slightly by lot.
As a result, even with
the same pressure
and the same speed,
air bubbles and peeling can change.
In other words, volume production lamination needs process margin that holds up within material tolerances.
■ Create a Stable Range Rather Than an Optimal Point
At a pressure of 100 N
and a speed of 10 m/min,
the appearance is best.
But if conditions shift slightly, defects occur.
This is unstable for volume production.
Look for a range where quality can be maintained even if conditions change somewhat.
In other words, it is important to create a stable process window, not a single point of highest quality.
■ The State Also Changes During Storage After Lamination
Right after bonding, there is no problem.
One day later.
One week later.
The adhesive wets out.
Or it warps due to internal stress.
In other words, it may be necessary to look not only at evaluation right after lamination, but also after time has passed.
■ Some Adhesives Need Dwell Time
Depending on the adhesive, it does not reach its final adhesive strength right after pressing.
The bonded area increases over time.
In other words,
adhesive strength right after processing
and final adhesive strength
may differ.
In volume production evaluation, it is necessary to understand material properties.
■ Lamination Interfaces Move with Thermal Cycling
High temperature
and low temperature
are repeated.
Each material expands and contracts.
Stress is applied to the interface.
As a result,
lifting,
delamination,
and warping
may appear.
In other words, for lamination quality, what matters is not right after bonding, but being able to maintain the laminated state even after long-term use.
■ Micro-Delamination Directly Affects Thermal Performance
The interface between graphite and TIM lifts slightly.
It is almost invisible.
But air enters that area, and thermal resistance increases.
In other words, the lamination interface is a mechanical joint and at the same time a thermal interface.
■ Integrating Heat, Insulation and EMI
For example,
copper foil,
insulating film,
and adhesive
are laminated.
Copper foil has the role of
heat spreading
and EMI.
Insulating film has the role of
electrical safety.
Adhesive has the role of
fixing.
In other words, high-precision lamination can integrate multiple functions into a single component.
■ The Value of Reducing Customer Processes
The customer
applies graphite,
applies insulating film,
and applies adhesive,
performing three processes.
If integrated on the processing company’s side,
the customer may need only one process.
This leads to
reduced man-hours,
reduced positional deviation,
and reduced operator variation.
In other words, lamination can contribute not only to component performance but also to customer productivity.
■ Reducing Processes Also Stabilizes Quality
With three application processes, there are three opportunities for defects.
Combining them into one may reduce opportunities for defects.
In other words, converting to composite components leads not only to cost reduction, but also to stabilization of volume production quality.
■ However, Combining Too Much Also Increases Risk
Many functions are put into a single component.
Convenient.
But if part of it is defective, the entire component becomes defective.
Material costs also rise.
Rework is also difficult.
In other words, it is necessary to consider how far to integrate.
■ Choose Processes Worth Integrating
Positional accuracy is important.
Customer work is difficult.
Foreign matter risk is high.
Difficult to automate.
It is highly valuable for the processing manufacturer to integrate such processes.
Conversely, there is no need to force integration of things that can easily be done in the customer’s process.
In other words, high-precision lamination is a technology to be used while looking at the customer’s entire process.
■ Failure Example: The Dimensions of Each Material Are Correct, but the Lamination Position Shifts
Graphite.
Insulating film.
Both passed drawing dimensions.
But the lamination position shifted by 0.5 mm.
The graphite edge was exposed.
An insulation failure risk arose.
In other words, it was not the accuracy of each material alone, but the relative position between materials that was the functional quality.
■ Failure Example: Bonding at High Pressure Caused Adhesive to Squeeze Out
Lamination pressure was raised to counter air bubbles.
Air bubbles decreased.
But adhesive squeezed out from the edges.
It stuck to the equipment.
A foreign matter problem also arose.
In other words, improving one defect created another.
■ Failure Example: Full-Surface Lamination Worsened Thermal Performance
To improve fixing strength, adhesive was added to the entire graphite surface.
Assembly became easier.
But the adhesive layer became thermal resistance, and the expected thermal performance was not achieved.
In other words, improving assemblability worsened the heat path.
■ Failure Example: Flat at Room Temperature, Warped in High-Temperature Evaluation
Dissimilar materials were laminated cleanly.
Initial appearance was good.
When a high-temperature test was performed, warping occurred.
Part of the interface lifted.
Thermal performance also changed.
In other words, the failure was judging lamination quality only by appearance right after processing.
■ Failure Example: Manual Application Succeeded in Prototyping, Wrinkles in Volume Production Roll Lamination
In prototyping, an engineer applied one sheet at a time.
No problem.
In volume production, it was changed to continuous lamination.
Wrinkles occurred due to the tension difference between the upper and lower materials.
In other words, even if the bonded materials are the same, a change in processing method makes it a different condition.
■ The Researcher's Perspective: Lamination Is "a Technology for Creating Interfaces"
Material A.
Material B.
One looks only at the performance of each.
But the moment they are laminated, a new interface is created.
That interface takes on properties such as
thermal resistance,
adhesion,
stress,
and electrical insulation.
In other words, lamination can also be called not a technology for stacking materials, but a technology for designing new functional interfaces.
■ The Shop-Floor Perspective: Look Not Only at the Finished Product, but Peel It Apart
A lamination defect occurs.
The cause cannot be determined from appearance alone.
Peel it apart once and look at
contact marks,
air bubble marks,
adhesive distribution,
and foreign matter.
Then it may become clear
where there is no contact
and where there was stress.
In other words, interface problems require looking at the interface itself.
■ OTIS's Perspective: High-Precision Lamination Is "a Technology That Turns Multiple Materials into a Single Functional Component"
Materials OTIS handles include
TIM,
graphite,
insulating materials,
metal foil,
adhesives,
and foams.
Processing them one sheet at a time also has value.
But if they can be laminated with high precision in the required positions,
multiple functions such as
heat,
insulation,
EMI,
fixing,
and sealing
can be combined into a single component.
This is where the great value of high-precision lamination lies.
■ OTIS Is Not "a Company That Bonds" but "a Company That Creates Functional Arrangements"
Lamination appears to be just
bonding material A and material B.
But in reality,
where,
with what area,
at what thickness,
with what positional accuracy,
and in what order
it is bonded is what matters.
In other words, what OTIS provides is not simple bonding.
It is processing that places functional materials where they are needed.
■ Combining the Strengths of Material Manufacturers into One Sheet
Graphite from material manufacturer A.
Insulating film from material manufacturer B.
Adhesive from material manufacturer C.
Each has excellent materials.
OTIS laminates them with high precision and turns them into a single functional component.
In other words, OTIS can play the role of integrating the strengths of multiple material manufacturers into customer components.
■ Creating Value Through Material Combinations, Not Material Manufacturer Competition
Which graphite is best?
Which adhesive is best?
There is no need to compete only on these.
The optimal material differs by application.
OTIS does not make the materials themselves, but
combines materials suited to the application.
In other words, value can be created through material selection + processing + lamination.
■ What the Customer Wants Is Not Lamination Technology Itself
Customers often do not say,
“We want high-precision lamination.”
What customers want is
to make components thinner,
to lower heat,
to insulate,
to reduce application processes,
and to automate.
High-precision lamination is used as a means to solve those challenges.
In other words, proposing based on customer challenges rather than processing technologies is important.
■ What OTIS Can Do
At OTIS, by combining
● High-precision lamination
● Thin-film lamination
● Partial lamination
● Lamination of dissimilar materials
● TIM lamination
● Graphite + insulating material lamination
● Metal foil + insulating material lamination
● Adhesive lamination
● Foam lamination
● High-precision die-cutting
● Microfabrication
● Half-cutting
● Opening processing
● Slit processing
● Tension control
● Positional accuracy control
● Carrier design
● Reel-to-reel processing
● Image inspection
● Supply formats for automation
● Development from prototyping to volume production conditions
we can turn multiple functional materials into a single mass-producible component.
■ Outside OTIS's Expertise
OTIS is not a company that specializes in
● Formulation development of adhesives themselves
● Development of graphite materials themselves
● Development of insulating materials themselves
● Manufacturing of metal foil itself
● Thermal design of customers’ entire products
We work with the respective specialist material manufacturers and customers’ design departments.
What OTIS takes on is the area of combining different high-performance materials into a single volume production component in the required positional relationship.
■ Summary: High-Precision Lamination Is Not Adding Materials Together
Graphite.
Insulating film.
TIM.
Metal foil.
Adhesive.
Each is a high-performance material.
But simply stacking them does not make a high-performance component.
Position,
thickness,
pressure,
tension,
air bubbles,
foreign matter,
warping,
and thermal expansion
must be controlled.
Furthermore, it is decided
which material to place where,
where to make adhesive,
which part to insulate,
and where to let heat flow.
In other words, high-precision lamination is
not a technology for stacking materials, but a technology for stacking functions.
And in volume production, it is not enough to bond one sheet cleanly.
Even if material lots change,
even if speed changes,
no matter how many tens of thousands are made,
the same position,
the same thickness,
the same contact,
and the same performance
must continue to be created.
What material manufacturers make is high-performance material, sheet by sheet.
What OTIS should make is a state in which they function simultaneously in the correct places.
Where heat passes.<br>Where electricity is stopped.<br>Where it is fixed.<br>Where it is protected.
Placing these accurately within tens of μm to a few mm.
Reproducing that laminated state in volume production.
That is the value of high-precision lamination at OTIS.
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.
