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Toyo Kohan was the first in the world to develop and practically apply Fine Clad, a highly functional type of dissimilar metallic clad material, using our surface activation bonding process, a new room-temperature bonding technology under vacuum.

Unlike conventional clad materials, Fine Clad is manufactured by pressure bonding at room temperature and under low pressure in a vacuum. This reduces the effects of heat and processing stress on the material, allowing for new applications that are difficult to achieve with conventional clad materials.

Clad material coils
(Copper/nickel, nickel/aluminum, aluminum/stainless steel clad)
Clad material coils
(Copper/nickel, nickel/aluminum, aluminum/stainless steel clad)


Materials can be bonded under low pressure (low load).

No change in material properties (hardness, structure, etc.) after bonding.

  • Excellent thickness precision.
  • Bonding interface is flat.

Foil lamination (from 10 µm) is possible.

  • Thick materials that are difficult to coat with plating can be coated.

Various material combinations are available.

  • Ni/Al, Al/Al, Cu/Al, Al/SUS, etc.

Bonding is performed under vacuum at room temperature.

  • No alloy layer created at the bonding interface.

Clad materials with good workability can be created.

  • Soft materials with good workability can be clad in a way that maintains these properties.

Toyo Kohan’s Fine Clad materials are new composite materials (bimetals) that have never existed before.

Comparison of Fine Clad and conventional clad materials

ItemToyo Kohan
Fine Clad
Conventional clad materials
Interface flatness△ or ×
Interfacial alloy formationNoYes
Foil bonding×
Thickness reduction rate0.1~5.0%30~70%

May vary depending on combination of materials.

Schematic diagram
Schematic diagram

Manufacturing process

A schematic diagram of manufacturing equipment is shown below. The overall setup is a vacuum chamber.
All process of material → surface activation treatment → pressure welding → material rolling are performed under vacuum.

Surface activation bonding method
Surface activation bonding method
Manufacturing process
Manufacturing process


Measurement pointsThickness(mm)MAX.width(mm)
Material A0.015~0.2250
Material B0.05~1.0250
  • May vary depending on properties of materials.
  • Cut sheet (100 x 130 mm) prototypes are also available for trial purposes.

Material combinations (typical examples)

Material AMaterial B
  • Please contact us to discuss any material combinations other than those listed above.

Mechanical properties

Change in mechanical properties after cladding

MaterialThickness(mm)Hardness(Hv)Tensile strength(N/mm2)
Before claddingSUS3040.201170703
Al 1N990.0562459
After claddingSUS3040.200173572

Strength as clad material

As shown in the table above, there is no change in properties before and after cladding.

Processing example

Bending test cross-section
Bending test cross-section


Example of clad material processing
Example of clad material processing

(front view)
Al/mild steel clad
Cu/SUS/Al clad
Ti/Al/SUS clad

Example of stretch forming
Example of stretch forming

SUS/Al clad material (Top surface: SUS)

Example applications

In recent years, as mobile devices such as smartphones have better performance and faster communication speeds (5G), the issue of heat dissipation is becoming increasingly important. On the other hand, installation space available inside devices is limited, and materials that combine multiple functions are required to reduce the component count.
To meet these needs, we have developed heat-dissipating reinforced clad materials (SUS/Cu and SUS/Al clad materials) with excellent heat dissipation and workability, as well as high strength.


  • Excellent heat dissipation
  • High strength
  • Thin and lightweight
  • Great workability


  • Chassis, center frame
  • Shield case
  • Display reinforcing panel

Assessment of heat dissipation

Heat-dissipating reinforcing clad materials show better heat dissipation than either stainless steel alone or stainless steel + graphite sheet.

Graphite sheet can be eliminated, enabling a thinner profile.

Assessment of heat dissipation

The above values were measured by Toyo Kohan, and are not guaranteed values.

Example applications

Recent years have seen multiple graphite sheets layered onto stainless steel to dissipate heat.

In such cases, better heat dissipation can be achieved and the number of graphite sheet layers reduced by attaching a single graphite sheet to heat dissipation reinforced clad materials, instead of stainless steel.

Example applications

The above values were measured by Toyo Kohan, and are not guaranteed values.

Mechanical properties

CompositionClad materialSingle material
Tensile strength (MPa)336408324713253
0.2% proof stress (MPa)209261201
3-point bending strength (MPa)447506495519387
Density (g/cm3)

For a total thickness of 0.3 mm.

The above values were measured by Toyo Kohan, and are not guaranteed values.

Processing example

SUS/Cu clad material
SUS/Cu clad material
SUS/Al/SUS clad material
SUS/Al/SUS clad material

Award History

Awards received for technology and R&D

Year and month of awardDetails
October 2000Received the Technical Development Award from the Japan Institute of Metals and Materials
June 2001Received National Commendation for Invention (Keidanren Chairman’s Prize)
April 2006Received Minister of Education, Culture, Sports, Science and Technology Award for Science and Technology (Development Category)