MIL-STD-202H.pdf - 第38页

MI L - S TD - 202 - 10 6 M E TH O D 1 0 6 M O I S T URE RE S I S T A NCE 1. SCOPE 1. 1 P urpose . The mo i s t ur e r e s i s t an c e t e s t i s per f or m ed f or t he pur pos e of ev al ua t i ng , i n a n accelerate…

MIL-STD-202-106

CONTENTS

PARAGRAPH PAGE

FOREWORD…………………………………………………………. ii

1. SCOPE 1

1.1 Purpose………………………………………….……..…………. 1

2. APPLICABLE DOCUMENTS 1

3. DEFINTIONS 1

4. GENERAL REQUIREMENTS 1

4.1 Apparatus ……………………………………………..…………. 1

4.1.1 Chamber………………………………………………………….. 1

4.1.1.1 Opening of the chamber door………………………………….. 1

4.1.1.2 Water……………………………………………………………… 1

4.2 Procedure………………………………………………………… 2

4.2.1 Mounting………………………………………………………….. 2

4.2.2 Initial measurements……………………………………………. 2

4.2.3 Number of cycles………………………………………………… 3

4.2.4 Subcycle of step 7……………………………………………….. 3

4.2.4.1 Step 7a……………………………………………………………. 3

4.2.4.2 Step 7b (when applicable)……………………………………… 3

4.2.5 Polarization and load. …………………………………………… 3

4.3 Final measurements……………………………………………… 3

4.3.1 At high humidity…………………………………………………… 3

4.3.2 After high humidity……………………………………………….. 3

4.3.2 After high humidity………………………………………………. 3

4.3.3 After drying period……………………………………………….. 3

5. DETAILED REQUIREMENTS 4

5.1 Summary……………..…………………………..………………. 4

6. NOTES 4

6.1 Supersession data………………………………………………. 4

FIGURE PAGE

1. Graphical representation of moisture-resistance test.…………….. 2

iii

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MIL-STD-202-106

METHOD 106

MOISTURE RESISTANCE

1. SCOPE

1.1 Purpose. The moisture resistance test is performed for the purpose of evaluating, in an accelerated manner,

the resistance of component parts and constituent materials to the deteriorative effects of the high-humidity and heat

conditions typical of tropical environments. Most tropical degradation results directly or indirectly from absorption of

moisture vapor and films by vulnerable insulating materials, and from surface wetting of metals and insulation. These

phenomena produce many types of deterioration, including corrosion of metals, physical distortion and decomposition

of organic materials, leaching out and spending of constituents of materials; and detrimental changes in electrical

properties. This test differs from the steady-state humidity test (method 103 of this standard) and derives its added

effectiveness in its employment of temperature cycling, which provides alternate periods of condensation and drying

essential to the development of the corrosion processes and, in addition, produces a "breathing" action of moisture

into partially sealed containers. Increased effectiveness is also obtained by use of a higher temperature, which

intensifies the effects of humidity. The test includes low temperature and vibration subcycles (when applicable, see

4.2.4.2) that act as accelerants to reveal otherwise indiscernible evidence of deterioration since stresses caused by

freezing moisture and accentuated by vibration tend to widen cracks and fissures. As a result, the deterioration can

be detected by the measurement of electrical characteristics (including such tests as dielectric withstanding voltage

and insulation resistance) or by performance of a test for sealing. Provision is made for the application of a polarizing

voltage across insulation to investigate the possibility of electrolysis, which can promote eventual dielectric

breakdown. This test also provides for electrical loading of certain components, if desired, in order to determine the

resistance of current-carrying components, especially fine wires and contacts, to electro-chemical corrosion. Results

obtained with this test are reproducible and have been confirmed by investigations of field failures. This test has

proven reliable for indicating those parts which are unsuited for tropical field use.

2. APPLICABLE DOCUMENTS

This section not applicable to this standard.

3. DEFINTIONS

This section not applicable to this standard.

4. GENERAL REQUIREMENTS

4.1 Apparatus

4.1.1 Chamber. A test chamber shall be used which can meet the temperature and humidity cycling specified on

figure 1. The material used to fabricate the platforms and standoffs, which support the specimens, shall be non-

reactive in high humidity. Wood or plywood shall not be used because they are resiniferous. Materials shall not be

used if they contain formaldehyde or phenol in their composition. Provisions shall be made to prevent condensate

from the chamber ceiling dripping onto the test specimens.

4.1.1.1 Opening of the chamber door. During the periods when the humidity is ascending or descending, the

chamber door should not be opened. If the chamber door must be opened, it should be opened during the 16th hour

through the 24th hour of an individual cycle. While the chamber is at 25°C (77°F), and the relative humidity tolerance

must be maintained, the chamber door should be opened only for a short period of time.

4.1.1.2 Water. Steam, or distilled and demineralized, or deionized water, having a pH value between 6.0 and 7.2

at 23°C (73.4°F) shall be used to obtain the specified humidity. No rust or corrosive contaminants shall be imposed

on the test specimens by the test facility.

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MIL-STD-202-106

4.2. Procedure.

4.2.1 Mounting. Specimens shall be mounted by their normal mounting means, in their normal mounting position,

but shall be positioned so that they do not contact each other, and so that each specimen receives essentially the

same degree of humidity.

4.2.2 Initial measurements. Prior to step 1 of the first cycle, the specified initial measurements shall be made at

room ambient conditions, or as specified.

NOTES:

1. Allowance of 100 percent RH is intended to avoid problems in reading values close to 100 percent RH, but

actual chamber operation shall be such so as to avoid condensation.

2. Unless otherwise specified, the steady state temperature tolerance is ±2°C at all points within the immediate

vicinity of the specimens and the chamber surfaces.

3. Rate of change of temperature is unspecified; however, specimens shall not be subjected to radiant heat from

chamber-conditioning processes.

4. Circulation of air in the chamber shall be at a minimum cubic rate per minute equivalent to 5 times the volume

of the chamber.

FIGURE 1. Graphical representation of moisture-resistance test.

INITIAL CON-

DITIONING IN A

DRY OVEN 24

HOURS

HUMIDITY

UNCONTROLLED

INITIAL MEASRUEMENTS

AS SPECIFIED IN 4.2.2

END OF FINAL CYCLE

MEASUREMENTS AS

SPECIFIED IN 4.3

VIBRATE IS 15

MINUTES AS

SPECIFIED IN

4.2.4.2

90-100% RH

100% RH

80-100%

+10°C

-2°C

VOLTAGE APPLIED AS SPECIFIED IN 4.2.5

STEPS 7a & 7b (IF APPLICABLE) SHALL BE

PERFORMED A MINIMUM OF 5 OF THE 10

CYCLES. HUMIDITY IS UNCONTROLLED

DURING STEPS 7a & 7b ONLY

STEP 7b

STEP 7a

PRIOR TO FIRST CYCLE

UNLESS OTHERWISE

SPECIFIED

STEP 1 STEP 2

STEP 3

STEP 4

STEP 5

STEP 6 STEP 7

ONE CYCLE 24 HOURS. REPEAT AS SPECIFIED IN 4.2.3

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