MIL-STD 883 Method 1002 Immersion Testing
The purpose of immersion testing to MIL-STD 883 is to determine the effectiveness of the seal of microelectronic devices. The immersion of the part under evaluation into liquid at widely different temperatures subjects it to thermal and mechanical stresses. These events can readily detect a defective terminal assembly, or a partially closed seam or molded enclosure.
These types of defects can result from faulty construction or from mechanical damage such as might be produced during physical or environmental tests. This immersion test is generally completed immediately following environmental testing because this testing will tend to aggravate any incipient defects. These defects can occur in seals, seams, and bushings.
This test is essentially a laboratory test condition. This test procedure is intended only as a measurement of the effectiveness of the seal following this test. The choice of fresh or salt water as a test liquid is dependent on the nature of the component part under test. The immersion test lab can offer either liquid for testing. Electrical measurements are made after immersion cycling to obtain evidence of leakage through seals. The use of a salt solution instead of fresh water will facilitate detection of moisture penetration.
The MIL-STD 883 immersion test provides a simple and ready means of detection of the migration of liquids. Effects noted can include lowered insulation resistance, corrosion of internal parts, and appearance of salt crystals. This is a destructive test and shall not be used as a 100 percent test or screen.
This ingress protection enclosure test consists of successive cycles of immersions. Each cycle consists of immersion in a hot bath of fresh (tap) water at a temperature of 65°C +5°C, -0°C, followed by immersion in a cold bath. The number of cycles, duration of each immersion, and the nature and temperature of the cold bath are indicated in the applicable test condition.
The transfer of specimens from one bath to another shall be accomplished as rapidly as practicable. In no case shall the transfer time exceed 15 seconds. After completion of the final cycle, specimens are to be thoroughly and quickly washed in fresh (tap) water or distilled water. All surfaces are to be wiped or air-blasted clean and dry. Unless otherwise specified, measurements shall be made at least 4 hours, but not more than 48 hours, after completion of the final cycle.
Upon completion of the electrical measurements and external visual examination, the device shall be dissected and examined. All evidence of corrosion of internal elements or the appearance of salt crystals should be identified. Where this test is performed as part of a group or subgroup of tests, the post-test measurements or inspections need not be performed specifically at the conclusion of this test. Instead, it may be performed once at the conclusion of the group or subgroup.
|Test Condition||Number of Cycles||Duration of Each Immersion||Immersion Bath||Temperature of Cold Bath|
|A||2||15||Fresh or Tap Water||25⁰ C (+10,-5)|
|B||2||15||Saturated Solution of Sodium Chloride and Water||25⁰ C (+10,-5)|
|C||5||60||Saturated Solution of Sodium Chloride and Water||0⁰ C +3|
|D||5||60||Parts by Volume:||0⁰ C +3|
|Water -48 parts|
|Methanol 1-50 parts|
|Morpholine -1 part|
|3.5-dimenthyl- 1-hexyn-3-o1-1 part|
|Stannous chloride – 5 grams|
Unless otherwise specified, the measurements shall include pin-to-pin resistance, pin-to-case resistance and full electrical test of all device characteristics or parameters listed in the applicable acquisition document. Final evaluation shall include external visual examination for legibility of device markings and for evidence of discoloration or corrosion of package and leads.
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