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Frequently Asked Questions
When Considering A Parylene Coating System
- What standard process control features should be considered, and do they cover N.F.P.A and O.S.H.A code requirement?
- What are the advantages of a removable "slide on" vaporizer?
- Why should I use a removable closed loop cold trap insert?
- Why should I use a full pyrolysis tube instead of a tube liner in a metal pyrolysis tube?
- Rotary feed through "O" ring type or "ferro fluid" type?
- What should be included in a Parylene Coating System Operation and Maintenance Manual?
- At Paratronix Inc. we earn our living operating our own machines.
Here are several aspects that we find are important to the success of a parylene operation.
- 1. What standard process control features
should be considered, and do they cover N.F.P.A and O.S.H.A code requirement?
- A main power disconnect which disables all electrical
power in the event access is required inside control panels should be installed.
All heating zones 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 a local temperature readout,
as well as a separate thermocouple and remote control, which monitors the
trap temperature. It should be interlocked with the initial pump start-up
and sound an audible alarm, should the cold trap rise above -65 C.
Some type of window or site port should be provided on
the chamber, for operator observation of the process.
An adjustable speed control should be provided to control
rotation speed during the coating cycle.
The system should be provided with a main power connecter
and start/stop switch, which provides for a manual reset in the event of
electrical power loss. This also allows the operator to set and hold constant,
all process variables such as vaporizer temperature; providing "load
and go" coating process day after day. These specifications comply
with N.F.P.A. machine wiring and O.S.H.A. regulations.
- 2. 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; thus reducing ramp up time during 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.
- 3. Why should I use a removable closed
loop cold trap insert?
- If the insert is removable, it 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.
- 4. 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 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 is done in a separate cleaning
furnace (see Paratronix Inc. accessory Burn-Out Furnace) and does not tie
up the system pyrolysis furnace; thus leaving it available for production
use. Tube liners, if not properly maintained, can become jammed in the
metal pyrolysis tube and removal can be time consuming, with high downtime
to production.
- 5. Rotary feed through "O"
ring type or "ferro fluid" type?
- The ferro fluid type, although initially more expensive,
will provide the best vacuum seal available, and requires no maintenance.
Ferro fluid types are not subject to virtual leaks that "O" ring
type seals demonstrate. "O" ring seal rotary feed through requires
the addition of silicon grease to provide adequate sealing, and are prone
to wear over time. A quality ferro fluid seal will provide 8-10 years life
in a parylene coater, where as the rotary "O" ring type needs
attention at least every six (6) months. Parylene coaters operate at medium
vacuum and ferro fluid seals are designed for use in high vacuum equipment;
thus the integrity of the seal is superior to the "O" ring type.
Side by side tests demonstrate faster pump down rates and lower vacuum
levels with the ferro fluid rotary seal.
- 6. What should be included in a Parylene
Coating System Operation and Maintenance Manual?
- A comprehensive manual should include as a minimum:
- Warranty Statement, which includes a full one (1) year
warranty. An overview of the Parylene Process. Process Documentation, which
explains parts preparation, priming, masking and demasking procedures,
and any equipment needed to control the Parylene process. Start-up and
Operating Procedures for a Parylene coating system, which outlines proper
vacuum levels and temperature parameters. System Trouble Shooting for both
process and machine equipment.
- Complete wiring Schematic and fuse list in accordance
with N.F.P.A. 79 Electrical Standard for for Electrical Machinery. Suggested
Spare Parts List A list of Regular and Preventative Maintenance Required.
Machine Specifications, which outline space, utility and ambient temperature
requirements. A Comprehensive Appendix which includes all O.E.M. equipment
manuals and contact phone numbers.
- Paratronix Inc. supplies all of the above in a comprehensive
Operating & Maintenance Manual. The manual is reviewed thoroughly during
our "machine training program". Most machine concerns can be
settled quickly by using the manual while contacting our Technical Service
Department.
- 7. At Paratronix Inc. we earn our living operating our own machines.
We find several aspects that are important to the success of a parylene operation:
-
- Achieve the maximum amount of customer product per cycle.
- Minimize the dimer charge.
- Reduce the time between cycles, unload and reload in shortest time.
- Satisfy the above three with the highest quality coating.
FAQ Copyright © 1997 Paratronix Inc., all rights reserved.
Data compiled by L. Habershaw and J. Monaghan with over 30 years combined experience
in the design and operation of Parylene coating systems.
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