As illustrated in FIGS. 2 to 4, the temperature indicating resin 12 includes a resin 110 and a temperature indicating material 111. The temperature indicating material is also called, for example, an indicator material.

The temperature indicating material 111 is embedded in the resin 110. The temperature indicating material 111 reacts at a temperature higher than or equal to a specific temperature higher than room temperatures. For example, the temperature indicating material 111 melts at the temperature higher than or equal to the specific temperature. When the first electronic component 101 generates heat, the heat generated by the first electronic component 101 is conducted to the temperature indicating material 111. The temperature of the temperature indicating material 111 becomes higher than or equal to the specific temperature. Then, the temperature indicating material 111 melts. When the temperature of the temperature indicating material 111 returns to a temperature lower than the specific temperature and the temperature indicating material 111 hardens, the temperature indicating resin 12 visually changes.

The resin 110 is, for example, a polyolefine resin.

The temperature indicating material 111 is, for example, wax.