Abstract: An assembling device and method for mounting a second plate to a first plate is described. The assembling device is an alignment jig includes a first carrier plate having a first air channel and a first carrier area and a second carrier plate having a second air channel and a second carrier area. The first air channel is linked to the first carrier area and the first plate is on the first carrier area. The second carrier plate and the first carrier plate are joined together through a pivot and the second carrier plate is stacked over the first carrier plate. The second air channel is linked to the second carrier area. The second plate is over the second carrier area. The second carrier plate or the first carrier plate has a third air channel and the corresponding second or third plate has an opening exposing the third air channel.