A method for the joining of ceramic pieces includes applying a layer of titanium on a first ceramic piece and applying a layer of titanium on a second ceramic piece; applying a layer of nickel on each of the layers of titanium on the first ceramic piece and the second ceramic piece; applying a layer of nickel phosphorous to each of the layers of nickel on the first ceramic piece and the second ceramic piece; assembling the first ceramic piece and the second ceramic piece with the layers of titanium, nickel, and nickel phosphorous therebetween; pressing the layer of nickel phosphorous of the first ceramic piece against the layer of nickel phosphorous of the second ceramic piece; heating the first ceramic piece and the second ceramic piece to a joining temperature in a vacuum; and cooling the first ceramic piece and the second ceramic piece. A hermetic seal is formed between the first ceramic piece and the second ceramic piece.

A sintered body includes a crystal grain containing silicon nitride, and a grain boundary phase. If dielectric losses of the sintered body are measured while applying an alternating voltage to the sintered body and continuously changing a frequency of the alternating voltage from 50 Hz to 1 MHz, an average value ε.sub.A of dielectric losses of the sintered body in a frequency band from 800 kHz to 1 MHz and an average value ε.sub.B of dielectric losses of the sintered body in a frequency band from 100 Hz to 200 Hz satisfy an expression |ε.sub.A−ε.sub.B|≤0.1.

A bonded body of the present invention includes a ceramic member formed of ceramics and a Cu member formed of Cu or a Cu alloy. In a bonding layer formed between the ceramic member and the Cu member, an area ratio of a Cu.sub.3P phase in a region extending by up to 50 μm toward the Cu member side from a bonding surface of the ceramic member is equal to or lower than 15%.

A bonded body of the present invention includes a ceramic member formed of ceramics and a Cu member formed of Cu or a Cu alloy. In a bonding layer formed between the ceramic member and the Cu member, an area ratio of a Cu.sub.3P phase in a region extending by up to 50 μm toward the Cu member side from a bonding surface of the ceramic member is equal to or lower than 15%.

An aluminum alloy member is made of an aluminum alloy having a Mg concentration set in a range of 0.4 mass % or more and 7.0 mass % or less and a Si concentration set to less than 1 mass %, the aluminum alloy member and a copper member are bonded to each other through solid-phase diffusion, and a compound layer made up of a first intermetallic compound layer that is disposed on the aluminum alloy member side and made of a θ phase of an intermetallic compound of Cu and Al, a second intermetallic compound layer that is disposed on the copper member side and made of a γ.sub.2 phase of an intermetallic compound of Cu and Al, and a Cu—Al—Mg layer provided between the first intermetallic compound layer and the second intermetallic compound layer is provided in a bonding interface between the aluminum alloy member and the copper member.

A method is provided for producing an insulating circuit substrate with a heat sink including an insulating circuit substrate and a heat sink, the insulating circuit substrate including a circuit layer and a metal layer that are formed on an insulating layer, and the heat sink being bonded to the metal layer side. The method includes: an aluminum bonding layer forming step of forming an aluminum bonding layer formed of aluminum or an aluminum alloy having a solidus temperature of 650° C. or lower on the metal layer; and a heat sink bonding step of laminating a copper bonding material formed of copper or a copper alloy between the aluminum bonding layer and the heat sink and bonding the aluminum bonding layer, the copper bonding material, and the heat sink to each other by solid phase diffusion bonding.

A method of manufacturing a ceramics-metal bonded body according to the present invention is a method of manufacturing a ceramics-metal bonded body in which a metal layer is bonded to at least one surface of a ceramics substrate, and comprises: a groove-forming step of forming a groove extending across a bonding region of a ceramics substrate to which a metal layer is bonded; and a bonding step of, after the groove-forming step, forming a metal layer by stacking, in the bonding region of the ceramics substrate, a metal plate of an aluminum or aluminum alloy with a thickness of less than or equal to 0.4 mm, via an Al—Si based brazing material foil, and bonding the metal plate to the bonding region by heating while applying load in a stacking direction.

A bonded body is formed to configured to join a ceramic member formed of a Si-based ceramic and a copper member formed of copper or a copper alloy, in which, in a joint layer formed between the ceramic member and the copper member, a crystalline active metal compound layer formed of a compound including an active metal is formed on the ceramic member side.

A power module substrate according to the present invention is a power module substrate in which a copper sheet made of copper or a copper alloy is laminated and bonded onto a surface of a ceramic substrate (11), an oxide layer (31) is formed on the surface of the ceramic substrate (11) between the copper sheet and the ceramic substrate (11), and the thickness of a AgCu eutectic structure layer (32) is set to 15 m or less.

A bonded body of the present invention includes a ceramic member formed of ceramics and a Cu member formed of Cu or a Cu alloy. In a bonding layer formed between the ceramic member and the Cu member, an area ratio of a Cu.sub.3P phase in a region extending by up to 50 m toward the Cu member side from a bonding surface of the ceramic member is equal to or lower than 15%.