MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第112页
MIL-STD-883F METHOD 1018.4 18 June 2004 2 (5) Ca libration che ck . The sys tem cal ibrat ion shal l be chec ked on the day of test prior to any tes ting. This shall incl ude check ing the c alibr ation by i n-lett ing a…
MIL-STD-883F
METHOD 1018.4
18 June 2004
1
METHOD 1018.4
INTERNAL WATER-VAPOR CONTENT
1. PURPOSE
. The purpose of this test is to measure the water-vapor content of the atmosphere inside a metal or
ceramic hermetically-sealed device. It can be destructive (procedures 1 and 2) or nondestructive (procedure 3).
2. APPARATUS
. The apparatus for the internal water-vapor content test shall be as follows for the chosen procedure:
2.1 Procedure 1
. (Procedure 1 measures the water-vapor content of the device atmosphere by mass spectrometry.) The
apparatus for procedure 1 shall consist of:
a. A mass spectrometer meeting the following requirements:
(1) Spectra range
. The mass spectrometer shall be capable of reading a minimum spectra range of 1 to 100
atomic mass units (AMUs).
(2) Detection limit. The mass spectrometer shall be capable of reproducibly detecting the specified
moisture content for a given volume package with signal to noise ratio of 20 to 1 (i.e., for a specified limit
of 5,000 ppmv, .01 cc, the mass spectrometer shall demonstrate a 250 ppmv minimum detection limit to
moisture for a package volume of .01 cc). The smallest volume shall be considered the worst case.
(3) Calibration
. The calibration of the mass spectrometer shall be accomplished at the specified moisture
limit (±20 percent) using a package simulator which has the capability of generating at least three known
volumes of gas ±10 percent on a repetitive basis by means of a continuous sample volume purge of
known moisture content ±10 percent. Moisture content shall be established by the standard generation
techniques (i.e., 2 pressure, divided flow, or cryogenic method). The dew point analyzer shall be
recalibrated a minimum of once per year using equipment traceable to NIST or by a suitable commercial
calibration services laboratory using equipment traceable to NIST standards,. Calibration records shall
be kept on a daily basis. Gas analysis results obtained by this method shall be considered valid only in
the moisture range or limit bracketed by at least two (volume or concentration) calibration points (i.e.,
5,000 ppmv between .01 -.1 cc or 1,000 – 5,000 ppmv between .01 - .1 cc). A best fit curve shall e used
between volume calibration points. Systems not capable of bracketing may use an equivalent procedure
as approved by the qualifying activity. Corrections of sensitivity factors deviation greater than 10 percent
from the mean between calibration points shall be required.
NOTE: It is recommended that the percentage of water vapor contained in a gas flowing through the gas
humidifier be compared to the dewpoint sensor reading for accuracy of the sensor. The following
equation may be used to calculate the percent of water vapor contained in a gas flowing through the gas
humidifier.
PaPg
Pv
OH
mmmbmb/psi
mb
/33.1 68.95
)(100
%
2
+
=
, where
P
v
= vapor pressure of water in the GPH based on water temperature in degrees centigrade,
P
g
= gauge pressure in psi, and
P
a
= atmospheric pressure in mm Hg.
(4) Calibration for other gases
. Calibration shall be required for all gases found in concentrations greater
than .01 percent by volume. As a minimum, this shall include all gases listed in 3.1c. The applicable
gases shall be calibrated at approximately 1 percent concentrations as part of the yearly calibration
requirements, with the exception of fluorocarbons, which may use a concentration of approximately 200
ppmv; nitrogen, which may use a concentration of approximately 80 percent or more; helium, which may
use a concentration of approximately 10 percent; and oxygen, which may use a concentration of
approximately 20 percent.
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MIL-STD-883F
METHOD 1018.4
18 June 2004
2
(5) Calibration check
. The system calibration shall be checked on the day of test prior to any testing. This
shall include checking the calibration by in-letting a 5000 ppmv ±20% moisture calibration sample of the
required volumes and comparing the result with the calibration sample. The resulting moisture reading
shall be within 250 ppmv of the moisture level in the calibration sample. Calibration performed on the
day of test prior to any testing may be substituted for the calibration check.
b. A vacuum opening chamber which can contain the device and a vacuum transfer passage connecting the device to
the mass spectrometer of 2.1a. The system shall be maintained at a stable temperature equal to or above the
device temperature. The fixturing in the vacuum opening chamber shall position the specimen as required by the
piercing arrangement of 2.1c, and maintain the device at 100°C ±5°C for a minimum of 10 minutes prior to
piercing.
Note: A maximum 5-minute transfer time from prebake to hot insertion into apparatus shall be allowed. If 5
minutes is exceeded, device shall be returned to the prebake oven and the prebake continued until device reaches
100 °C ±5 °C.
For initial certification of systems or extension of suitability, device temperature on systems using an external
fixture shall be characterized by placing a thermocouple into the cavity of a blank device of similar mass, internal
volume, construction and size. This shall be a means for proving the device temperature has been maintained at
100 °C ± 5 °C for the minimum ten minutes. This also applies to devices prebaked in an external oven but tested
with the external fixture to adjust for any temperature drop during the transfer. These records shall be maintained
by the test laboratory.
c. A piercing arrangement functioning within the opening chamber or transfer passage of 2.1b, which can pierce the
specimen housing (without breaking the mass spectrometer chamber vacuum and without disturbing the package
sealing medium), thus allowing the specimen's internal gases to escape into the chamber and mass spectrometer.
NOTE: A sharp-pointed piercing tool, actuated from outside the chamber wall via a bellows to permit movement,
should be used to pierce both metal and ceramic packages. For ceramic packages, the package lid or cover
should be locally thinned by abrasion to facilitate localized piercing.
2.2 Procedure 2
. (Procedure 2 measures the water-vapor content of the device atmosphere by integrating moisture
picked up by a dry carrier gas at 50°C.) The apparatus for procedure 2 shall consist of:
a. An integrating electronic detector and moisture sensor capable of reproducibly detecting a water-vapor content of
300 ±50 ppmv moisture for the package volume being tested. This shall be determined by dividing the absolute
sensitivity in micrograms H
2
0 by the computed weight of the gas in the device under test, and then correcting to
ppmv.
b. A piercing chamber or enclosure, connected to the integrating detector of 2.2a, which will contain the device
specimen and maintain its temperature at 100°C ±5°C during measurements. The chamber shall position the
specimen as required by the piercing arrangement. The piercing mechanism shall open the package in a manner
which will allow the contained gas to be purged out by the carrier gas or removed by evacuation. The sensor and
connection to the piercing chamber will be maintained at a temperature of 50°C ±2°C.
2.3 Procedure 3
. (Procedure 3 measures the water-vapor content of the device atmosphere by measuring the response
of a calibrated moisture sensor or an IC chip which is sealed within the device housing, with its electrical terminals available
at the package exterior.) The apparatus for procedure 3 shall consist of one of the following:
a. A moisture sensor element and readout instrument capable of detecting a water-vapor content of 300 ±50 ppmv
while sensor is mounted inside a sealed device.
b. Metallization runs on the device being tested isolated by back-biased diodes which when connected as part of a
bridge network can detect 2,000 ppmv within the cavity. The chip shall be cooled in a manner such that the chip
surface is the coolest surface in the cavity. The device shall be cooled below dew point and then heated to room
temperature as one complete test cycle.
NOTE: Suitable types of sensors may include (among others) parallel or interdigitated metal stripes on an oxidized
silicon chip, and porous anodized-aluminum structures with gold-surface electrodes.
MIL-STD-883F
METHOD 1018.4
18 June 2004
3
Surface conductivity sensors may not be used in metal packages without external package wall insulation. When used, the
sensor shall be the coolest surface in the cavity. It should be noted that some surface conductivity sensors require a higher
ionic content than available in ultraclean CERDIP packages. In any case, correlation with mass spectrometer procedure 1
shall be established by clearly showing that the sensor reading can determine whether the cavity atmosphere has more or
less than the specified moisture limit at 100°C.
3. PROCEDURE
. The internal water-vapor content test shall be conducted in accordance with the requirement of
procedure 1, procedure 2, or procedure 3. All devices shall be prebaked for 16-24 hours at 100°C ±5°C prior to hot insertion
into apparatus. External ovens shall have a means to indicate if a power interruption occurs during the prebaking period and
for how long the temperature drops below 100 ±5°C. Devices baked in an external oven which loses power and whose
temperature drops below 100 ±5°C for more than 1 hour shall undergo another prebake to begin a minimum of 12 hours
later.
Note: It is recommended that samples submitted to the labs shall include information about the manufacturing process
including sealing temperature, sealing pressure, sealing gas, free internal cavity volume, lid thickness at puncture site, lid
material, and the location of the puncture site.
3.1 Procedure 1
. The device shall be hermetic in accordance with test method 1014, and free from any surface
contaminants which may interfere with accurate water-vapor content measurement. The internal water-vapor content
laboratory is not required to test for hermeticity in accordance with Test Method 1014 of MIL-STD-883.
After device insertion, the device and chamber shall be pumped down and baked out at a temperature of 100°C ±5°C until
the background pressure level will not prevent achieving the specified measurement accuracy and sensitivity. After
pumpdown, the device case or lid shall be punctured and the following properties of the released gases shall be measured,
using the mass spectrometer:
a. The increase in chamber pressure as the gases are released by piercing the device package. A pressure rise of
less than 50 percent of normal for that package volume and pressurization may indicate that (1) the puncture was
not fully accomplished, (2) the device package was not sealed hermetically, or (3) does not contain the normal
internal pressure.
b. The water-vapor content of the released gases, as a percent by unit volume or parts per million volume (ppmv) of
the total gas content.
c. The proportions (by volume) of the other following gases: N
2
, He, Mass 69 (fluorocarbons), O
2
, Ar, H
2
, CO
2
, CH
4
,
NH
3
, and other solvents, if available. Calculations shall be made and reported on all gases present greater than
.01 percent by volume. Data reduction shall be performed in a manner which will preclude the cracking pattern
interference from other gas specie in the calculations of moisture content. Data shall be corrected for any system
dependent matrix effects such as the presence of hydrogen in the internal ambient.
3.1.1 Failure criteria
.
a. A device which has a water-vapor content greater than the specified maximum value shall constitute a failure.
b. A device which exhibits an abnormally low total gas content, as defined in 3.1a, shall constitute a failure, if it is not
replaced. Such a device may be replaced by another device from the same population; if the replacement device
exhibits normal total gas content for its type, neither it nor the original device shall constitute a failure for this cause.
3.2 Procedure 2
. The device shall be hermetic in accordance with test method 1014, and free from any surface
contaminants which may interfere with accurate water-vapor content measurement.
After device insertion into the piercing chamber, gas shall be flowed through the system until a stable base-line value of the
detector output is attained. With the gas flow continuing, the device package shall then be pierced so that a portion of the
purge gas flows through the package under test and the evolved moisture integrated until the base-line detector reading is
again reached. An alternative allows the package gas to be transferred to a holding chamber which contains a moisture
sensor and a pressure indicator. System is calibrated by injecting a known quantity of moisture or opening a package of
known moisture content.
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