Power module

A power module comprising:

• a power module substrate provided with a circuit layer on one surface of an insulating layer;
• and
• a semiconductor element bonded onto the circuit layer, wherein
• a copper layer composed of copper or a copper alloy is provided on the surface of the circuit layer onto which the semiconductor element is bonded,
• a solder layer formed by using a solder material is formed between the circuit layer and the semiconductor element,
• an alloy layer containing Sn as a main component, 0.5% by mass or more and 10% by mass or less of Ni, and 30% by mass or more and 40% by mass or less of Cu is formed at an interface between the solder layer and the circuit layer,
• a thickness of the alloy layer is set to be within a range of 2 μm or more and 20 μm or less, and
• a thermal resistance increase rate is less than 10% after loading power cycles 100,000 times under the condition where an energization time is 5 seconds and a temperature difference is 80° C. in a power cycle test.