Orbital Welding of
Semiconductor Process Gas Lines
BARBARA K. HENON, PH.D.
A discussion of the advances in semiconductor welding
that meet standards and contribute to better, cleaner,
and more repeatable welds
Introduction
Beneath the floor of every microchip manufacturer there is a basement or“subfab” with miles of stainless teel tubing transporting gases used in production.
Some of these gases are highly toxic at very low concentrations, some are pyrophoric, bursting into flames on contact
with air, and some are highly corrosive. Not only must the
piping be corrosion resistant and leak free, but the joining
technology must maintain the integrity and corrosion
resistance of the system. Furthermore, gases at the parts
per billion purity range must be able to pass through
the piping systems without accumulating particulates,
moisture or other contaminates.
Orbital Welding Technology
Orbital welding technology, by consistently delivering
welds of the highest quality, is essential for achieving the
high yields of semiconductor devices that might otherwise be compromised by the least amount of particulate
contamination. Orbital welding, by definition, is “
automatic or machine welding of tubes or pipes in-place with
the electrode rotating (or orbiting) around the work.” 1
The welding process is called Gas Tungsten Arc Welding
(GTAW) or Tungsten Inert Gas (TIG), which for semiconductor applications is a fusion or autogenous weld, but
for other applications wire can be added. The tungsten
electrode is unconsumed, thus autogenous GTAW is a very
clean process in that nothing is added to the weld.
Orbital welding was developed for the aerospace
industry in the 1960s and was adopted for use by the
semiconductor industry in the early 1980s. Since that
time millions of orbital welds have been made to join
semiconductor process gas lines. While orbital welding of
semiconductor process gas lines reached its peak about
10 years ago, it is still a major application of orbital tube
welding (see Figure 1, 2).
SEMI Standards
Prior to 1993, standards for semiconductor gas lines
relied primarily on company specifications. Practices or
standard operating procedures (SOPs) were developed
by installing contractors to meet the stringent purity standards set by the industry. SOPs are written procedures to
assure that all welding operations are performed in the
Figure 1. Orbital welding of semiconductor tubing in
a cleanroom with the AMI Model 207 power supply
(left) and Model 107 power supply (right); pipe stands
are used to support tubing assemblies during welding.
(Photo courtesy of Murray Co.)
