Reliable deposition of thin parylene

A parylene deposition system comprising:

• a vaporizer configured to vaporize a polymer dimer into a dimeric gas;
• a pyrolysis tube connected to the vaporizer and configured to pyrolize the dimeric gas into a monomeric gas;
• an outer deposition chamber connected to the pyrolysis tube and having an interior configured to receive the monomeric gas;
• and
• a core deposition chamber placeable in and removable from the outer deposition chamber and configured to effuse the monomeric gas from interior of the outer deposition chamber into an interior of the core deposition chamber, the core deposition chamber comprising:
• a base,
• a removable cover configured to mate and seal with the base and define the interior of the core deposition chamber, and
• a conduit through a top of the cover and about a center of the top of the cover, the conduit defined at least in part by a first fixed portion of the cover and a second fixed portion of the cover, the first fixed portion spaced apart from the second fixed portion by a distance between 50 μm and 6000 μm, the conduit having a lumen connecting the interior of the core deposition chamber to the interior of the outer deposition chamber, the lumen having a length and a cross-section, the cross-section having a width equal or smaller to the distance between the first fixed portion and the second fixed portion of the cover, the length being less than 140 times the cross-section width.