Viewport Safety Bulletin

Viewport Safety Bulletin
Safety Bulletin Ref: OIPT/SafetyBull/2014/001
Release Date: 01 May 2014
Oxford Instruments Plasma Technology (OIPT) Confidential - For External Use
This recommended improvement notice applies to all systems using an
RF mesh and a bonded Perspex assembly at viewport windows, OIPT
part number 94-MD81D14211. This applies to the majority of OIPT
products. Equipment: View Port 94-MD81D14211
Concern:
It has come to our attention that the
Perspex disc can become detached.
If the protection components are
missing or damaged:
Do not look through the viewport at the plasma.
Note: Viewports intended to transmit UV light are also used, particularly with optical
emission endpoint detectors. These do not have the Perspex protection disc, and should
not be used for direct viewing of the plasma.
Design
Some plasmas emit possibly harmful amounts of UV light, and the Perspex blocks at least
99.9% of the ultra-violet light. The part has been in use since before 1992. Since 2008,
tools which use this part also have this label:
OIPT/SafetyBull/2014/001
Safety Bulletin
Oxford Instruments Plasma Technology (OIPT) Confidential - For External Use
Improvement
The window components will in future be assembled with the RF mesh / Perspex part
reversed , so that the Perspex is retained by the mesh even if the bonding fails. It is
recommended, but not essential, to make this change on existing equipment when next
venting the tool for maintenance. The tool is safe to use in its original condition, provided
the mesh and Perspex are still present.
The exploded views on following pages provide details for this assembly.
Note: there is some risk of tearing the wire mesh when reassembling the window. If the
mesh is old or showing signs of wear, use a new component 94-MD81D14211
The assembly method to minimise risk of tearing is:
1. Place the window flange MD84D16140
face down (air side to the bench)
5.
Place the window glass M0651D01 on
the gasket
2. Place the UV filter (mesh + Perspex
piece) MD81D14211into the window
flange, mesh side down
6.
Place the modified KF40 O-seal
94-MA00D14711 on the flange
7.
Offer the assembly to the chamber port
and secure with four M6 x25mm cap
head screws
3. Gently push the Perspex disc into window
flange, so that the wire mesh is drawn
around the edges of the Perspex
4.
Place the window gasket M4175D01
into the window flange, over the wire
mesh
If the parts are assembled without step 3,
then there is a risk that the mesh is severed
by the edges of the Perspex when the parts
are compressed together.
OIPT/SafetyBull/2014/001
Safety Bulletin
Oxford Instruments Plasma Technology (OIPT) Confidential - For External Use
OIPT/SafetyBull/2014/001
Safety Bulletin
Oxford Instruments Plasma Technology (OIPT) Confidential - For External Use