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Diffusion Bonding

Summary

Diffusion Bonding

Diffusion Bonding

Diffusion bonding is a technology to bond materials together by applying heat and force to the materials, using diffusion of atoms. Without melting the materials it could be join together.

Diffusion binding is technology to bond plane surface by layer by layer. Also it could bond different metal (incl. ceramics) each other with no interlayer metals. (Metal-to-metal bonding)

Able to produce fluid device which has tiny fluid channels, or precise 3D hollow structures.

Please ask WELCON which new materials create complex shapes cannot be made machining conventional way.
We provide from conceptual design to trial prototype.

Categorizing bonding method

Solid phase bonding - Diffusion bonding Use atoms diffusion by load and temperature

About Diffusion Bonding

Diffusion bonding is a technique which has been widely used for aerospace and military industry.  In recent years, technology for mass production has been developed by manufactures.  Diffusion bonding can bond different materials, which is difficult to use binding with melting method.(such as brazing, welding and using glue or adhesives)

Therefore, it is applied, for example, to driving shafts of vehicle so that expensive material can be used for minimum usage. It is also used for like a thermocouple, which uses different materials in one parts.

  • Aerospace
  • IT related, antenna
  • Automobile
  • Food process equipment
  • Analysis, Measurement instrument
  • Electronics, Electronic component
  • Semiconductor equipment
  • Industrial machine, Automated transport machinery
  • Mold
  • Other: Diffusion bonding is spreading to new field.

Technical term

What is diffusion

Take milk poured into coffee, for example. Milk becomes admixed evenly relatively in a short time. In air or fluid, it is easily observed that the difference of concentration gets lost. This phenomena occurs in a solid form very slowly.  Diffusion is a phenomena that a substance moves in a solvent and becomes admixed evenly.

 Movement of atom in a solid form differs according to the size.  Like oxygen or carbon, small atom can proceed into other substance easily, whereas atom with certain size cannot move unless atomic vacancy exist next to it. When temperature rises, the environment becomes suitable for diffusion bonding since energy of atom becomes larger and activated, and also, the probability of atomic vacancy existence is larger.

The phenomena of diffusion consists of two laws of Fick. Fick’s first law illustrates that the flux of solute moves from regions of high concentration to regions of low concentration, and the flux is proportional to the concentration gradient.

The law, which illustrates that the amount of solute per unit area per unit time

Where C is the concentration of solute, and X is the position of gradient.

Fick’s second law shows how the concentration changes with time as follows;

One of the example is controlled atmosphere heat treatment, such as oxidization of metal or carburizing, diffusion occurs in one direction and the concentration of boundary surface does not change according to time.  In this case, the law can be illustrated as:

The concentration of solute (“C”) is:

 c=Ax+B

Where X is the thickness of oxidized film or carburized layer, the growth of reactive layer is depend on the speed of diffusion of metal ion towards reactive layer, and the speed of growth is proportional to the flux of metal ion.  In this case, the gap of the concentration of metal ion on the surface of both reactive layer is constant.

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