Board-to-board connector assembly and connector

A board-to-board connector assembly, comprising:

• a receptacle connector comprising:
• a receptacle-side housing comprising:
• an insular portion having long sides along a first direction and extending along a second direction orthogonal to the first direction;
• and
• receptacle-side long wall portions formed so that a recessed portion is formed between the insular portion and each of the receptacle-side long wall portions along a third direction orthogonal to both of the first direction and the second direction;
• a receptacle-side signal contact comprising a contact portion, the receptacle-side signal contact being retained in the receptacle-side housing so that the contact portion is exposed to an inside of the recessed portion;
• and
• a receptacle-side power contact, which is retained in the receptacle-side housing so as to be arrayed together with the receptacle-side signal contact along the first direction;
• and
• a plug connector comprising:
• a plug-side housing comprising a projecting portion to be inserted into the recessed portion;
• a plug-side signal contact, which is retained in the plug-side housing so as to be exposed to an outside of the projecting portion;
• and
• a plug-side power contact, which is retained in the plug-side housing so as to be exposed to the outside of the projecting portion, and is to be brought into contact with the receptacle-side power contact,
• the plug-side power contact comprising:
• a first flat surface portion having a plate-like shape and being parallel to the first direction and the second direction;
• a second flat surface portion having a plate-like shape and being opposed to a part of the first flat surface portion through intermediation of a component of the plug-side housing;
• and
• a power-contact-side connection portion formed in parallel to the third direction and the first direction and configured to connect the first flat surface portion and the second flat surface portion to each other,
• at least one of the first flat surface portion and the second flat surface portion comprising:
• a stepped portion between a surface opposed in parallel to a surface of another one of the first flat surface portion and the second flat surface portion, and a surface except for the surface opposed in parallel to the surface of the another one of the first flat surface portion and the second flat surface portion;
• and
• a thinned portion that corresponds to a portion having the surface opposed in parallel to the surface of the another one of the first flat surface portion and the second flat surface portion, and has a smaller thickness along the third direction than a thickness of a portion having the surface except for the surface opposed in parallel to the surface of the another one of the first flat surface portion and the second flat surface portion.