Method of direct bonding copper foils to oxide-ceramic substrates

• US 4,505,418 A
• Filed: 12/12/1983
• Issued: 03/19/1985
• Est. Priority Date: 09/25/1980
• Status: Expired due to Fees

• Current Assignee: IXYS Corporation (Littelfuse Incorporated)
• Original Assignee: Brown Boveri & CIE AG (ABB Limited)
• Inventors: Wahl, Georg, Neidig, Arno, Berndt, Dietmar, Wittmer, Mark
• Primary Examiner(s): Godici, Nicholas P.
• Assistant Examiner(s): Jordan, M.
• Application Number:
  US06/561,124
• Time in Patent Office: 463 Days
• Field of Search: 228/122, 228/124, 228/198, 228/219, 228/903
• US Class Current: 228/122.1
• CPC Class Codes: B23K 35/38 Selection of media, e.g. special atmospheres for surrounding the working area
• CPC Class Codes: C04B 2235/6581 Total pressure below 1 atmosphere, e.g. vacuum
• CPC Class Codes: C04B 2237/124 based on copper
• CPC Class Codes: C04B 2237/126 wherein the active component for bonding is not the largest fraction of the interlayer
• CPC Class Codes: C04B 2237/343 Alumina or aluminates
• CPC Class Codes: C04B 2237/407 Copper
• CPC Class Codes: C04B 2237/54 Oxidising the surface before joining
• CPC Class Codes: C04B 37/021 in a direct manner, e.g. direct copper bonding [DCB]
• CPC Class Codes: C04B 37/026 consisting of metals or metal salts
• CPC Class Codes: H05K 3/38 Improvement of the adhesion between the insulating substrate and the metal
• CPC Class Codes: H05K 3/4015 using auxiliary conductive elements, e.g. pieces of metal foil, metallic spheres

Abstract

Method for directly bonding copper foils having a copper oxide layer to oxide-ceramic substrates by heating the ceramic substrate covered with the copper foil in an oxygen-containing atmosphere to a temperature above the eutectic temperature of Cu and Cu₂ O, but below the melting temperature of copper in a vacuum furnace at a pressure of not more than 1 mbar while maintaining a furnace atmosphere with a partial oxygen pressure between 0.001 and 0.1 mbar.

Claims

1. Method for the direct bonding of copper foils which carry a copper oxide layer on the surface, to oxide ceramic substrates which comprises disposing a copper foil having a copper oxide layer on the surface on a ceramic substrate with the copper oxide layer in contact with the ceramic substrate, heating the ceramic substrate covered with the copper foil in an oxygen-containing atmosphere to a temperature above the eutectic temperature of Cu and Cu₂ O but below the melting temperature of Cu, in a vacuum furnace at a pressure not more than 1 mbar and maintaining a furnace atmosphere with a partial oxygen pressure between 0.001 and 0.1 mbar, and cooling down the heated ceramic substrate during which cooling-down the partial oxygen pressure is kept below 0.005 mbar.

2. Method according to claim 1, wherein the oxide-ceramic is high-purity aluminum-oxide ceramic with a smooth surface.

3. Method according to claim 1, wherein the oxide-ceramic substrates are moved into the vacuum furnace through a lock and removed from the furnace through a lock.

4. Method according to claim 1, wherein the pressure in the vacuum furnace is at most 0.1 mbar.

5. Method according to claim 2, wherein the pressure in the vacuum furnace is at most 0.1 mbar.