Loaded film cassette for gaseous vapor deposition

A film cassette for a gaseous vapor deposition process, the cassette comprising:

• a central shaft having an axis therethrough;
• a first and a second end plate, each end plate being mounted to the shaft, each end plate comprising a central hub from which radiate a plurality of angularly spaced spokes,
• the spokes of each end plate having an interior surface that lies on a reference plane oriented substantially perpendicular to the axis of the shaft,
• each end plate having a spiral rib mounted to the interior surface thereof,
• each spiral rib having a predetermined number of uniformly spaced turns and a predetermined pitch associated therewith,
• the spaces between adjacent turns of the spiral rib defining a spiral groove on each end plate,
• a film substrate having first and second edges thereon and having a predetermined width dimension greater than three hundred millimeters (300 mm),
• each edge of the film substrate being received within the spiral groove on one of the end plates to define a spiral wrapping of film having a plurality of turns,
• spaces between adjacent turns of the spiral film wrapping cooperating to define a gas flow channel extending axially across the cassette between the end plates,
• each rib having a cross sectional configuration in a radial plane containing the axis of the shaft, the cross sectional configuration exhibiting substantially linear major edges,
• each rib having a predetermined width dimension measured from the interior surface of the spoke on which the rib is mounted in a direction parallel to the axis of the shaft, a predetermined average thickness dimension measured in a radial direction with respect to the axis of the shaft, and a width-to-average-thickness aspect ratio of at least 2:1, wherein
• the interior surface of the spokes is spaced a distance greater than the width dimension exhibited by the film substrate at a gaseous deposition temperature, and
• the width dimension of the rib on each end plate is between about 0.5% to about 2.0% of the spacing between the interior surface of the spokes;
• and
• the spaces between adjacent turns of the spirally mounted rib disposed between adjacent spokes on one end plate define a plurality of inlet openings for a gaseous fluid,
• the spaces between adjacent turns of the spirally mounted rib extending between adjacent spokes on the other end plate defining a plurality of outlet openings for a gaseous fluid,
• the inlet and the outlet openings communicating with the gas flow channel.