An interconnection for flex circuit boards used, for instance, in a quantum computing system are provided. In one example, the interconnection can include a first flex circuit board having a first side and a second side opposite the first side. The interconnection can include a second flex circuit board having a third side and a fourth side opposite the third side. The first flex circuit board and the second flex circuit board are physically coupled together in an overlap joint in which a portion of the second side for the first flex circuit board overlaps a portion of the third side of the flex circuit board. The interconnection can include a signal pad structure positioned in the overlap joint that electrically couples a first via in the first flex circuit board and a second via in the second flex circuit board.