Table of Contents
Advertisement
Environmental Requirements
Air Quality
Corrosive Contaminants
Particulate
Contaminants
Viscid Contaminants
Chapter 1
The air quality, temperature and humidity requirements for the system are
described below.
As a rule, good air quality is as important for the reliability of your test
system as it is for your production process. The presence of airborne
contaminants at the site will contribute to system degradation, resulting in
lower reliability and higher operating costs. Three types of airborne
contaminants are discussed below.
Corrosion is a complex form of material deterioration or destruction by
chemical or electrochemical reaction. The presence of corrosive
contaminants (gases) in the atmosphere is very common in industrial
environments. If ignored, corrosion can eventually degrade system
performance by its effects on high-impedance circuits and low-impedance
interfaces. It can also deteriorate most plastics including software storage
media. The effects of corrosive contaminants are usually accelerated at high
humidities or high temperatures.
Corrosives generally cannot be filtered out of the air by normal filtration
methods, and the techniques that must be used for their removal are complex
and costly. If the source of corrosive contaminants cannot be eliminated, the
system should be installed in an enclosed environment with a fresh air
supply at positive pressure.
Particulate contaminants (hard particles) consist of smoke, dust, hair, lint,
fibers and miscellaneous organic and inorganic materials. The presence of
these contaminants in the air can cause system degradation, especially where
disk drives, test fixtures, and low-impedance interfaces are concerned.
Particulate contaminants can be filtered from the air, and appropriate filters
should be included with any air conditioning installation. Also consider
installing "No Smoking" signs in the area. Tobacco smoke is a well-known
factor in fixture contact contamination. It causes false failures leading to
unnecessary device under test/test system repairs, and higher production
costs.
Viscid contaminants are oily or sticky airborne substances that can be
deposited on the system's electronic and mechanical parts. Besides
contributing directly to system degradation, viscid contaminants collect and
hold particulate contaminants and make cleaning very difficult. Viscid
contaminants can be removed from the air by filtration, but it is preferred
that the source of viscid contaminates be identified and the contaminates be
eliminated at their source.
Site Preparation
15
Advertisement
Table of Contents
