Substrate unit and electronic device

A substrate unit which is inserted into and attached to a first rack type housing including a first substrate attachment portion or a second rack type housing including a second substrate attachment portion different from the first substrate attachment portion, and in which a first direction vertical to a front direction as an inserting direction with respect to the first rack type housing or the second rack type housing and a second direction as a direction opposite to the first direction are width directions, comprising:

• an electronic circuit substrate which includes a first width dimension portion, and a second width dimension portion continuous with the front direction side of the first width dimension portion, a first concave portion which is concave in the second direction from the second width dimension portion being formed on the first direction side of the first width dimension portion, a second concave portion which is concave in the first direction from the second width dimension portion being formed on the second direction side of the first width dimension portion in the electronic circuit substrate, and holes being formed at a first direction side end portion of the electronic substrate and at a second direction side end portion of the electronic substrate;
• an electronic component installed on the electronic circuit substrate;
• and
• a heat sink which includes a first side frame portion fixed to the first width dimension portion of the electronic circuit substrate from the first concave portion, a second side frame portion fixed to the first width dimension portion of the electronic circuit substrate from the second concave portion, and a sink main body portion continuous from the first side frame portion to the second side frame portion, heat generated by the electronic component being configured to be conducted to the heat sink;
• and
• fixation members each of which is inserted into the corresponding hole so that the first side frame and the second side frame are fixed to the electronic circuit substrate.