An HVAC Controller may include a first sub-assembly and a second sub-assembly releasably engageble with the first sub-assembly. The first sub-assembly may include a first housing and a printed circuit board capable of being secured relative to the first housing and capable of providing one or more signals. The second sub-assembly may include a second housing and a second printed circuit board capable of being secured relative to the second housing and capable of receiving the one or more signals from the first printed circuit boards when the first sub-assembly is releasably engaging the second sub-assembly. The first printed circuit board and the second printed circuit board each may have one or more component mounted on sides facing one another, the components each extending a distance. The sum of the distances may be greater than a distance spacing the facing sides of the printed circuit boards.