9018-18076.pdf.pdf - 第29页
Keysight i3070 Series 5 In-Circuit Test System Site Preparation 5 Environmental Requirements Air Quality Requir ements 5-2 Air Temperatur e Requirements 5-3 Humid ity Requir ements 5-4
4-4 Site Preparation
4 RF Attenuation Requirements
Table 4-6 Determining Available Site Attenuation with a site allowance or a different wall
attenuation
Parameter Value
R; Required Site Attenuation (dB)
n; Number of Walls
W; Attenuation per wall
R – n *W ; Remaining Attenuation Requirement (dB)
D; Distance from Equipment to Real Estate Border (m)
5-2 Site Preparation
5 Environmental Requirements
Air Quality Requirements
As a rule, good air quality is as important for the reliability of your Medalist ICT system as it is for your
production process. Three types of airborne contaminants are discussed below. The presence of any
of these contaminants at the site will contribute to system degradation, resulting in lower reliability
and higher operating costs.
Corrosive Contaminants
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
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 DUT repairs and higher production costs.
Viscid Contaminants
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 the elimination of their source, if possible,
is preferable.