Frequently Asked Questions about
our Analytical Testing Process
1. What is the relative humidity
inside my package?
The relative humidity of air is
the percentage of moisture contained in the air relative to the
fully saturated state of the air and is a function of both pressure
For a finite volume (such as a
semiconductor package) we can look up the low temperature, saturated
steam tables in the Handbook of Physics and Chemistry and determine
the vapor pressure of water at a given temperature. However, finding
information on the equilibrium characteristics of the environment
may prove difficult. It is possible, for example, to have a closed
environment maintain 100% RH over a wide temperature and pressure
range and yet never have a liquid condensate present. The materials
used in modern semiconductor devices can include epoxies,
polyamides, desiccants, adhesives, and other materials which can
take up or release water and maintain equilibrium with the closed
environment over a broad range of pressures and temperatures. The
concept of relative humidity is difficult to apply to a closed
2. How do I relate dewpoint, relative humidity,
and ppm of moisture?
Let's begin with the definition
of dew point that is the temperature to which the air would have to
be cooled (at constant pressure and constant water vapor content) in
order to reach saturation.
In a finite or closed
environment, such as a semiconductor package, we do not have the
proper conditions that permit the definition of dew point to be
valid. As we cool the package, both the internal pressure and the
moisture content change. So perhaps dew point is not a relevant term
when trying to describe the moisture content of a hermetically
sealed semiconductor package.
The measurement of moisture
per the Mil-Std in a semiconductor package is expressed in per cent
per unit volume (where 10,000 ppmv = 1.0%) following a specific
measurement recipe. Measurements made following the same recipe can
be compared. Other recipes (such as tests conducted at 37C for
medical devices) only produce data which is relevant to themselves.
When comparing moisture measurements made at different laboratories,
it is essential that the recipe for calibration is considered as
well as the recipe for measurement.
3. Why is my
package full of water?
When a manufacturer offends
the Moisture Gods, bedlam is sure to follow. The Pernicka
Corporation has been in constant negotiation with the Moisture Gods
over the past 40 years and has developed numerous approaches to
quelling their anger. We provide
consulting services to try to help appease the
Moisture Gods and allow a manufacturer to produce dry packages.
4. How can I convert percent per unit volume to
1.0% per unit volume = 10,000 ppmv.
5. How accurate is my data?
Pernicka Corporation our mass spectrometers are checked daily to
ensure that the following accuracy for standard analytical
procedures, traceable to NIST, is routinely maintained:
Measurements in the ppbv
range and at higher accuracy are optionally available.
- For non-condensable species, the larger of +/- 1.0% of
measured value or +/- 10 ppmv.
- For condensable species, the larger of +/- 1.0% of measured
value or +/- 100 ppmv.
6. How is the equipment calibrated and to what
Our laboratory calibration system meets
all the requirements of Mil-Std 45662A. We have maintained
suitability to conduct measurements per Mil-Std 883/750 since 1978.
In addition, both our laboratory and our manufacturing facility are
ISO 9002 certified.
For a thorough explanation, please
download the white paper, Advancements in Calibration
Techniques and Moisture Measurements .