Sintered diamond having high thermal conductivity and method for producing the same and heat sink employing it

A method for producing a high thermal conductivity diamond sintered compact comprising 60 vol. % to 90 vol. % of diamond grains on the whole sintered compact basis and the balance of substantially copper, which is substantially free from pores inside and has a diamond grain size distribution peak in a range of from 5 μm to 100 μm, at least two of the diamond grains constructing the sintered compact being directly bonded with each other, the copper forming the sintered compact substantially not being oxidized and the quantity of oxygen in the sintered compact being at most 0.025 weight %, the method comprising:

• arranging a powder body of diamond grains having a grain size distribution of 5 μm to 100 μm in contact with an oxygen free copper sheet and one or more metal sheet selected from the Group IVa and Va metals in contact with the copper sheet in a metal capsule;
• sealing the metal capsule in vacuum or in an inert gas or reducing gas;
• applying pressure of 1 GPa to 6 GPa to the sealed metal capsule at a temperature of 1100° C. to 1500° C. to infiltrate the melted copper into the diamond powder body;
• lowering the temperature to at most 900° C. to solidify the copper while maintaining the pressure at 1 GPa to 6 GPa;
• and
• lowering the pressure and temperature to ambient pressure and temperature to produce a sintered compact.

A method for producing a high thermal conductivity diamond sintered compact comprising 60 vol. % to 90 vol. % of diamond grains on the whole sintered compact basis and the balance of substantially copper, which is substantially free from pores inside and has a diamond grain size distribution peak in a range of from 5 μm to 100 μm, at least two of the diamond grains constructing the sintered compact being directly bonded with each other, the copper forming the sintered compact substantially not being oxidized and the quantity of oxygen in the sintered compact being at most 0.025 weight %, the method comprising:

• mixing diamond powder having a grain size distribution in a range of from 5 μm to 100 μm and high purity copper powder with a purity of at least 99.9%;
• arranging the mixed powder body in a metal capsule;
• sealing the metal capsule in vacuum or in an inert gas or reducing gas;
• applying pressure of 1 GPa to 6 GPa to the sealed metal capsule at a temperature of 1100° C. to 1500° C. to infiltrate the melted copper into the diamond powder body;
• lowering the temperature to at most 900° C. to solidify the copper while maintaining the pressure at 1 GPa to 6 GPa;
• and
• lowering the pressure and temperature to ambient pressure and temperature to produce a sintered compact.