Power module substrate, power module substrate with heat sink, power module, method of manufacturing power module substrate, and copper member-bonding paste
This power module substrate includes a copper plate that is formed of copper or a copper alloy and is laminated on a surface of a ceramic substrate 11 ; a nitride layer 31 that is formed on the surface of the ceramic substrate 11 between the copper plate and the ceramic substrate 11 ; and an Ag—Cu eutectic structure layer 32 having a thickness of 15 μm or less that is formed between the nitride layer and the copper plate.