MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第88页

MIL-STD-883F METHOD 1014.11 18 June 2004 8 TABL E III. Test lim its for radio isot ope fine l eak method . Volu me of Q S package cc < 0.0 1 1 x 10 -8 > 0.01, < 0. 4 5 x 10 -8 > 0.4 5 x 10 -7 3.2. 6 Personnel…

MIL-STD-883F

METHOD 1014.11

18 June 2004

3.2.2 Determination of counting efficiency (k)

. The counting efficiency (k) of equation (1) shall be determined as follows:

a. Five representative units of the device type being tested shall be tubulated and the internal void of the device shall

be backfilled through the tubulation with a known volume and known specific activity of krypton-85 tracer gas and

the tubulation shall be sealed off.

b. The counts per minute shall be directly read in the shielded scintillation crystal of the counting station in which the

devices are read. From this value, the counting efficiency, in counts per minute per microcurie, shall be calculated.

3.2.3 Evaluation of surface sorption

. All device encapsulations consisting of glass, metal, and ceramic or combinations

thereof, including coatings and external sealants, shall be evaluated for surface sorption of krypton-85 before establishing

the leak test parameters. Representative samples of the questionable material shall be subjected to the predetermined

pressure and time conditions established for the device configuration as specified by 3.2.1. The samples shall then be

counted every 10 minutes, with count rates noted, until the count rate becomes asymptotic with time. (This is the point in

time at which surface sorption is no longer a problem.) This time lapse shall be noted and shall determine the "wait time"

specified in 3.2.4.

3.2.4 Procedure

. The devices shall be placed in radioactive tracer gas activation tank. The activation chamber may be

partially filled with inert material to reduce pumpdown time. The tank shall be evacuated to 0.5 torr. The devices shall be

subjected to a minimum of 2 atmospheres absolute pressure of krypton-85/dry nitrogen mixture for a minimum of 12

minutes. Actual pressure and soak time shall be determined in accordance with 3.2.1. The R value in counts per minute

shall not be less than 600 above background. The krypton-85/dry nitrogen gas mixture shall be evacuated to storage until

0.5 to 2.0 torr pressure exists in the activation tank. The storage cycle shall be completed in 3 minutes maximum as

measured from the end of the activation cycle or from the time the activation tank pressure reaches 60 psia if a higher

bombing pressure is used. The activation tank shall then immediately be backfilled with air (air wash). The devices shall

then be removed from the activation tank and leak tested within 1 hour after gas exposure with a

scintillation-crystal-equipped counting station. Device encapsulations that come under the requirements of 3.2.3 shall be

exposed to ambient air for a time not less than the "wait time" determined by 3.2.3. In no case will the time between removal

from the activation chamber and test exceed 1 hour. This exposure shall be performed after gas exposure but before

determining leak rate with the counting station. Device encapsulations that do not come under the requirements of 3.2.3 may

be tested without a "wait time." (The number of devices removed from pressurization for leak testing shall be limited such

that the test of the last device can be completed within 1 hour.) The actual leak rate of the component shall be calculated

with the following equation:

(ACTUAL READOUT IN NET COUNTS PER MINUTE) X Q

Q =

Where Q = Actual leak rate in atm cc/s, and QS and R are defined in 3.2.1.

NOTE: CAUTION. Discharge of krypton 85 into the atmosphere must not exceed limits imposed by local and Federal

regulations.

3.2.5 Failure criteria

. Unless otherwise specified, devices that exhibit a leak rate equal or greater than the test limits of

table III shall be considered as failures.

NOTE: CAUTION. Devices which do not exhibit a leak rate sufficient to fail seal test, may retain radioactive tracer gas in

sufficient concentration to cause soft errors in complex, small geometry devices.

MIL-STD-883F

METHOD 1014.11

18 June 2004

TABLE III. Test limits for radioisotope fine leak method

Volume of Q

package

< 0.01 1 x 10

-8

> 0.01, < 0.4 5 x 10

-8

> 0.4 5 x 10

-7

3.2.6 Personnel precautions

. Federal, some state and local governmental regulations require a license for the

possession and use of krypton-85 leak test equipment. In the use of radioactive gas, these regulations and their maximum

permissible exposure and tolerance levels prescribed by law should be observed.

3.3 Test condition C

or C

, perfluorocarbon gross leak. Test condition C

is a fixed method with specified conditions that

will ensure the test sensitivity necessary. Test condition C

has been replaced by C

. Test condition C3 is a fixed method

that uses a vapor detection system instead of an indicator bath.

3.3.1 Procedure applicable to fixed (C

) method. The devices shall be placed in a vacuum/pressure chamber and the

pressure reduced to 5 torr or less and maintained for 30 minutes minimum. The vacuum cycle may be omitted for packages

with an internal volume >

0.1 cm

. A sufficient amount of type I detector fluid shall be admitted to cover the devices. When

the vacuum cycle is performed, the fluid will be admitted after the minimum 30 minute period but before breaking the

vacuum. The devices shall then be pressurized in accordance with table IV. When the pressurization period is complete

the pressure shall be released and the devices removed from the chamber without being removed from a bath of detector

fluid for greater than 20 seconds. A holding bath may be another vessel or storage tank. When the devices are removed

from the bath they shall be dried for 2 ±1 minutes in air prior to immersion in type II indicator fluid, which shall be maintained

at 125°C ±5°C. The devices shall be immersed with the uppermost portion at a minimum depth of 2 inches below the

surface of the indicator fluid, one at a time or in such a configuration that a single bubble from a single device out of a group

under observation may be clearly observed as to its occurrence and source. The device shall be observed against a dull,

nonreflective black background though the magnifier, while illuminated by the lighting source, from the instant of immersion

until, expiration of a 30-second minimum observation period, unless rejected earlier.

For packages greater than 5 grams, the effects of package thermal mass shall be determined by evaluating each package

family with known leakers and measuring the time for bubbles to be observed. If the evaluation time exceeds the 30

seconds required for the observation time, then the observation time shall be extended to take into account the package

thermal mass effect. Alternate methods may be used to meet this intent provided the method is documented and made

available to the preparing or acquiring activity upon request.

3.3.1.1 Test condition C

, fixed method. Allowable fixed method conditions shall be as shown in table IV, herein.

TABLE IV. Condition C pressurization conditions

Pressure

psia (min)

Minimum pressurization

time (hour)

30 23.5 12

45 8 4

60 4 2

75 2 1

90 1 0.5

105 0.5 N/A

MIL-STD-883F

METHOD 1014.11

18 June 2004

3.3.2 Failure criteria

. A definite stream of bubbles or two or more large bubbles originating from the same point shall

be cause for rejection.

CAUTION: When the leak is large, the operator may notice a stream of liquid exiting the package without the release of

bubbles. This condition shall result in the package being rejected.

3.3.3 Test condition C

, perfluorocarbon vapor detection.

3.3.3.1 Procedure

. The devices shall be placed in a vacuum/pressure chamber and the pressure reduced to 5 torr and

maintained for 30 minutes minimum. A sufficient amount of type I detector fluid shall be admitted to the pressure chamber

to cover the devices. The fluid shall be admitted after the 30 minute minimum vacuum period but before breaking the

vacuum. The devices shall then be pressurized in accordance with table IV. The pressure shall be maintained for a period

of 30 minutes minimum. Upon completion of the pressurization period, the pressure shall be released, the devices removed

from the pressure chamber without being removed from a bath of detector fluid for more than 20 seconds and then retained

in a bath of perfluorocarbon fluid. When the devices are removed from the fluid they shall be air dried for a minimum of 20

seconds and a maximum of 5 minutes prior to the test cycle. If the type I detector fluid has a boiling point of less than 80°C,

the maximum drying time shall be 3 minutes.

The devices shall then be tested with a perfluorocarbon vapor detector that is calibrated in accordance with 2.3h and 2.3i.

"Purge" time shall be in accordance with table V. Test time shall be a minimum of 3.5 seconds (unless the device is rejected

earlier) with the perfluorocarbon vapor detector purge and test chambers at a temperature of 125 ±5°C, or 2.5 seconds

minimum with the purge and test chambers at a temperature of 150 ±5°C.

NOTE: Air dry, purge and test limits for each device shall be complied with in all cases, including stick to stick handling.

NOTE: Test temperature shall be measured at the chamber surface that is in contact with the device(s) being tested.

Device orientation within the test cell should maximize heat transfer from the heated chamber surface to the cavity

of the device within the capability of the equipment.

3.3.3.2 Failure criteria

. A device shall be rejected if the detector instrumentation indicates more than the equivalent of

0.167 or 1/6 microliter of type I detector fluid in accordance with table I.

TABLE V. Purge time for condition C

Package with internal Purge time

free volume

(CM

) (seconds)

<0.01 < 5

>0.01 <0.10 < 9

>0.10 < 13

NOTE: Maximum purge time can be determined by cycling a device with a 0.02 to 0.05 inch hole and measuring the

maximum purge time that can be used without permitting the device to escape detection during the test cycle.