When Considering the Purchase of a Parylene Coating System
What standard process control features should be specified, and do they cover N.F.P.A and O.S.H.A code requirement?
The system should be UL508A Listed and CE Certified.
Each heating zone should have individual manual operating controls, along with separate and redundant manual resettable over-temperature controls. An over-temperature situation should sound an audible alarm and disable power to all heating zones.
The vacuum pump and chamber vacuum pressure should be monitored, and an adjustable alarm should be provided for loss of vacuum, which disables power to the vaporizer if pressure rises beyond the set point.
The cold trap should have local temperature readout, as well as a separate thermocouple and remote control, monitoring the trap temperature. The cold trap should be interlocked with the initial pump start-up, and sound an audible alarm, in the event the cold trap rises above -65 C.
A window or site port should be provided on the chamber, for operator observation of the process.
What are the advantages of a removable "slide on" vaporizer?
The vaporizer can be brought to full set point while resting on its standby cradle; reducing ramp up time during the coating process; allowing minimal run time and increasing runs per shift. Likewise, the vaporizer can be removed from the pyrolysis tube at the end of the cycle, allowing the tube to cool rapidly in preparation for additional coating runs per shift. Therefore, no cooling fans are needed and downtime between production runs is minimized.
Why should I use a removable, closed loop cold trap insert?
A removable insert can be replaced with a clean spare insert, thus minimizing downtime during cold trap maintenance. A “closed loop” insert insures the best achievable vacuum pressure for the chamber with minimal pressure loss.
Why should I use a full pyrolysis tube instead of a tube liner in a metal pyrolysis tube?
Similar to the cold trap insert, the full pyrolysis tube is easily removed and changed with a spare clean tube, minimizing downtime. Because the full pyrolysis tube is clear quartz glass, the dimer can be observed by sliding off the vaporizer. The thermal dissipation of quartz allows for quick change over to the next run.
Maintenance to the tube, which consists of burning off the Parylene film that naturally builds up on the inside surface of the tube during the coating process, is typically done in a separate cleaning furnace (see Paratronix® accessory Burn-Out Furnace). Using a separate furnace for the burn out process, enables the user to replace the original tube with a spare tube to continue operation of the coating system, while the original tube is being cleaned.
Use of metal pyrolysis tube liners is not recommended. They can become jammed in the metal pyrolysis tube if not properly maintained which results in labor intensive delays in removal and replacement with extended system down time.
Why should I use a more expensive Ferro fluidic seal for vacuum sealing, rather than inexpensive O-rings?
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