Question: We have a switch that gets wave soldered during the assembly process, but it does not always stay flush with the printed circuit board. Is there a specification that describes how to measure flushness or what the acceptability requirements are for this type of part?
Possible Solution: The final criterion for any component is in the final assembly process and how it fits into the box assembly. There is a requirement 7.1.6 Component Mounting on page 7-15 of IPC-A-610 which describes the spacing between the board and the component. Also check the note which states that components cannot be tilted due to mating requirements with enclosures or panels, for example toggle switches, potentiometers, LCDs and LEDs.
To keep the component flush to the board could also be an issue. Please check 7.1.4 Hole Obstruction on page 7-12, which may be a problem when considering the solder joint and such. If the switch has standoffs beneath it may help solve the problem. If not then some sort of standoff may be required.