DIRECT BOND COPPER

Controlled Atmosphere Furnaces for Attachment and Oxidation

Direct Copper Bonding (DBC) is the direct mating of two dissimilar electronic materials (Copper and Ceramic). The interface between the pure copper and the ceramic is very reliable. The DBC process takes advantage of the copper – oxygen eutectic where the melting point is lower than that of pure copper or oxide ceramic. At the melting temperature the eutectic is the only liquid present, it wets and bonds to both surfaces.

At 1065°C – a liquid copper-oxygen eutectic will form on the surface of the copper. The liquid is a mixture of Cuprous Oxide(Cu₂O) formed from the Cupric Oxide (CuO) and liquid copper. The Cu₂O first wets to the Al₂O₃, forming small concentrations of copper aluminates (CuAl₂O₄ and CuAlO₂). As the system is cooled, Cu2O becomes segregated as crystals within the interfacial layer, bonding to pure copper, alumina, and copper aluminates. This interfacial layer bonds the pure copper metal to alumina.

Thermal process requirements for oxidation and attachment in Direct Copper Bonding:

• Oxidation atmosphere must be precisely controlled
• Attachment atmosphere must be <5ppm O₂ for good Copper surfaces
• Clean flow of 99.999% Nitrogen Tight Temperature Control
• +/- 2°C Across belt for good uniformity
• +/-2°C Along soak for controlled eutectic flow
• Ceramic substrates require controlled cooling

BTU Controlled Atmosphere Muffle Furnaces (TCA) are optimized for DBC processing. The furnaces are fully customizable to meet varying process/production requirements. Key features include:

• Muffle construction for high purity N₂ atmosphere operation
  • <2ppm O₂ Inert atmosphere
  • National Fire Protection Association NFPA 86, NFPA-79 and UL508a safe atmosphere compliant
  • Made in the USA with high quality materials for maximum reliability
• Left Center Right Trim
  • Improves part uniformity and yield
  • Uniform eutectic across plates
• Gas Barrier*
  • Superior atmosphere separation
  • <2ppm O2 Inert atmosphere
• Cooling Eductors*
  • Shorter foot prints
  • Controlled cooling of heavy loads

*May only be required for most demanding applications based on load/profile