Abstract: The invention provides a power module substrate with a heat sink, which includes a power module substrate provided with an insulating substrate, a circuit layer provided on one surface of the insulating substrate and a metal layer provided on the other surface of the insulating substrate. The heat sink is bonded to the power module substrate via a bonding layer (30) to a surface on an opposite side to the insulating substrate of the metal layer. Bonding layer is a sintered body of silver particles, a porous body having a relative density in a range of 60% or more and 90% or less, and having a thickness in a range of 10 ?m or more and 500 ?m or less.

Abstract: A power module substrate with a heat sink (10) includes a power module substrate (20) provided with an insulating substrate (21), a circuit layer (22) provided on one surface of the insulating substrate (21) and a metal layer (23) provided on the other surface of the insulating substrate (21); and a heat sink (40) bonded via a bonding layer (30) to a surface on an opposite side to the insulating substrate (21) of the metal layer (23) of the power module substrate (20), in which the bonding layer (30) is a sintered body of silver particles, a porous body having a relative density in a range of 60% or more and 90% or less, and has a thickness in a range of 10 ?m or more and 500 ?m or less.