A wafer stage includes a first evaporator where a refrigerant circulates. These modules are simple and inexpensive to manufacture, and versatile. In this embodiment, a spring is disposed in the second chamber and configured to apply a biasing force on a first piston disposed within the first chamber. The asset includes an intellectual asset and a product. The second contact module includes a second housing and a number of second contacts insert molded in the second housing. The upper frame has a locating opening, and the locating block is embedded in the locating opening.