Assembly and harness assembly

An assembly comprising a circuit board structure and a plurality of connection portions, wherein:

• the circuit board structure has a main circuit board and a supplemental circuit board;
• the main circuit board has an upper surface and a lower surface in an up-down direction;
• the main circuit board is formed with an accommodating portion;
• the accommodating portion is recessed downward in the up-down direction from the upper surface of the main circuit board;
• the main circuit board has a plurality of upper main conductive portions;
• the upper main conductive portions are formed on the upper surface of the main circuit board;
• the supplemental circuit board has an upper surface and a lower surface in the up-down direction;
• the supplemental circuit board has a plurality of upper supplemental conductive portions;
• the upper supplemental conductive portions are formed on the upper surface of the supplemental circuit board;
• the supplemental circuit board is, at least in part, accommodated in the accommodating portion;
• each of ones of the connection portions connects a respective one of the upper main conductive portions and a respective one of the upper supplemental conductive portions with each other;
• the accommodating portion pierces the main circuit board in the up-down direction;
• the main circuit board has a plurality of lower main conductive portions;
• the lower main conductive portions are formed on the lower surface of the main circuit board;
• the supplemental circuit board has a plurality of lower supplemental conductive portions;
• the lower supplemental conductive portions are formed on the lower surface of the supplemental circuit board;
• and
• each of ones of the connection portions connects a respective one of the lower main conductive portions and a respective one of the lower supplemental conductive portions with each other.