Clad material for cooler, cooler for heat-generating device, and method of producing cooler for heat-generating device

A method of producing a cooler for a heat-generating device, characterized by comprising:

• executing production of a tensile strain of 3 to 10% or a rolling process at a finish rolling ratio of 10 to 25% on a clad raw material that has a core material, a sacrificial material layer that covers one side of the core material, and a brazing filler metal layer that covers the other side of the core material, thereby obtaining a clad material for a cooler;
• and
• brazing the clad material for a cooler to other members that constitute the cooler, with the sacrificial material layer side disposed on a fluid passage side, wherein:
• the core material is formed of an aluminum alloy that contains Mn, Cu, and Si in contents given below and contains at least one or two or more selected from Fe, Ti, and Zr in contents given below, with the balance being made of Al and unavoidable impurities
• Mn:
• 0.4 to 1.5 mass %
• Cu:
• 0.05 to 0.8 mass %
• Si:
• 0.05 to 1.0 mass %
• Fe:
• 0.05 to 0.5 mass %
• Ti:
• 0.05 to 0.20 mass %
• Zr:
• 0.05 to 0.15 mass %;
• the sacrificial material layer is formed of an Al alloy sacrificial material that contains Zn in a content given below and contains at least one or two or more selected from Si, Fe, Mn, Ti, and Zr in contents given below, with the balance being made of Al and unavoidable impurities
• Zn:
• 0.5 to 5.0 mass %
• Si:
• 0.05 to 1.0 mass %
• Fe:
• 0.05 to 0.5 mass %
• Mn:
• 0.05 to 1.1 mass %
• Ti:
• 0.05 to 0.20 mass %
• Zr:
• 0.05 to 0.15 mass %;
• the brazing filler metal layer is formed of an aluminum alloy brazing filler metal that contains Si in a content given below, with the balance being made of Al and unavoidable impurities
• Si:
• 6.5 to 12.6 mass %;
• prior to the brazing the clad material for a cooler to the other members that constitute the cooler, the clad material for a cooler has an elongation of at least 10%, an average crystal grain diameter of the core material is 10 to 100 μm, and an average grain diameter (equivalent circle diameter) of Si grains present in the brazing filler metal layer is less than 1.8 μm;
• and
• after the brazing the clad material for a cooler to the other members that constitute the cooler, a potential difference between the core material and a surface of the sacrificial material layer is at least 50 mV and a proportion t1/T (%) of a thickness of the core material to a total thickness of the clad material for a cooler satisfies the following Expression:
• t1/T (%)≧85% Expression
• T:
• total thickness of the clad material for a cooler
• t1:
• thickness of the core material.