Abstract: A vapor deposition apparatus includes an insert within which a material is deposited on the surface of a film. A cassette includes end plates each having a rib that edgewise receive a spiral wrapping of a film at least 300 mm wide. Spaces between turns of the wrapping define a gas flow channel and spaces between adjacent turns of one rib define inlet openings that communicate with the channel. Each rib has a predetermined width dimension, a predetermined average thickness dimension, and a width-to-thickness aspect ratio of at least 2:1. The spacing between end plates is at least 300 mm and is also greater than the film width at deposition temperature. The width dimension of each rib is between about 0.5% to about 2.0% of the end plate spacing. A diverging flow director contacts one end plate to directing gaseous fluid toward the inlet openings in that end plate.