MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第50页

MIL-STD-883F METHOD 1009.8 22 March 1989 2 3. PROCEDURE . 3.1 Maint enance and condi tioning of test chamber . The purpos e of the c leaning c ycle i s to as sure t hat all materi als whi ch could adver sely af fect the …

MIL-STD-883F

METHOD 1009.8

22 March 1989

METHOD 1009.8

SALT ATMOSPHERE (CORROSION)

1. PURPOSE

. This test is proposed as an accelerated laboratory corrosion test simulating the effects of seacoast

atmosphere on devices and package elements.

1.1 Terms and definitions

1.1.1 Corrosion

. Corrosion is the deterioration of coating or base metal or both by chemical or electrochemical action.

1.1.2 Corrosion site

. A corrosion site is the site at which the coating or base metal or both is corroded. The location of

corrosion.

1.1.3 Corrosion product (deposit)

. The effect of corrosion (i.e., rust or iron oxide, nickel oxide, tin oxide, etc.). The

product of corrosion may be at the corrosion site, or may flow or run (due to action of liquid carrier of salt) so as to cover

noncorroded areas.

1.1.4 Corrosion stain

. Corrosion stain is a semitransparent deposit due to corrosion products.

1.1.5 Blister

. A blister is a localized swelling and separation between the coating(s) and base metal.

1.1.6 Pinhole

. A pinhole is a small hole occurring in the coating as an imperfection which penetrates entirely through the

coating.

1.1.7 Pitting

. Pitting is the localized corrosion of coating or base metal or both, confined to a point or small area, that

takes the form of cavities.

1.1.8 Flaking

. Flaking is the separation of small pieces of coating that exposes the base metal.

2. APPARATUS

. Apparatus used in the salt-atmosphere test shall include the following:

a. Exposure chamber with fixtures for supporting devices. The chamber and all accessories shall be made of

material (glass, plastic, etc.) which will not affect the corrosiveness of the salt atmosphere. All parts within the

test chamber which come in contact with test specimens shall be of materials that will not cause electrolytic

corrosion. The chamber shall be properly vented to prevent pressure build-up and allow uniform distribution of

salt fog.

b. Salt solution reservoir adequately protected from the surrounding ambient. If necessary, auxiliary reservoirs may

be used for long duration tests in accordance with test conditions C and D (see 3.2).

c. Means for atomizing the salt solution, including suitable nozzles and compressed air or a 20 percent oxygen, 80

percent nitrogen mixture (the gas entering the atomizers shall be free from all impurities such as oil and dirt).

d. Chamber-heating means and controls.

e. Means for humidifying the air at temperature above the chamber temperature.

f. Air or inert gas dryer.

g. Magnifier(s) 1X to 3X, 10X to 20X and 30X to 60X.

MIL-STD-883F

METHOD 1009.8

22 March 1989

3. PROCEDURE

3.1 Maintenance and conditioning of test chamber

. The purpose of the cleaning cycle is to assure that all materials which

could adversely affect the results of the subsequent tests are removed from the chamber. The chamber shall be cleaned by

operating it at 95°F ±5°F (35°C ±3°C) with deionized or distilled water as long as necessary. The chamber shall be cleaned

each time the salt solution in the reservoir has been used up. Several test runs therefore could be run before cleaning,

depending on the size of the reservoir and the specified test condition (see 3.2). When long duration conditions (test

conditions C and D, see 3.2) are required, the reservoir may be refilled via auxiliary reservoirs so that the test cycle shall not

be interrupted. After the cleaning cycle, on restarting the chamber, the reservoir shall be filled with salt solution and the

chamber shall be stabilized by operating it until the temperature comes to equilibrium, see 3.1.4. If operation of the chamber

is discontinued for more than one week, the remaining salt solution, if any, shall be discarded. Cleaning shall then be

performed prior to restarting the test chamber. Intermittent operation of the chamber is acceptable provided the pH and

concentration of the salt solution are kept within limits defined in 3.1.1.

3.1.1 Salt solution

. The salt concentration shall be 0.5 to 3.0 percent by weight in deionized or distilled water as required

to achieve the deposition rates required by 3.1.4. The salt used shall be sodium chloride containing on the dry basis not

more than 0.1 percent by weight of sodium iodide and not more than 0.3 percent by weight total impurities. The pH of the

salt solution shall be maintained between 6.5 and 7.2 when measured at 95°F ±5°F (35°C ±3°C). Only CP grade (dilute

solution) hydrochloric acid or sodium hydroxide shall be used to adjust the pH.

3.1.2 Preconditioning of leads

. Unless otherwise specified, the test specimens shall not be preconditioned. If required

(see 4.c.), prior to mounting specimens for the salt atmosphere test, the device leads shall be subjected to the bending

stress initial conditioning in accordance with test condition B1 of method 2004. Where the specific sample devices being

subjected to the salt atmosphere test have already been subjected to the required initial conditioning, as part of another test

employing the same sample devices, the lead bend need not be repeated.

3.1.3 Mounting of test specimens

. The test specimens shall be mounted on the holding fixtures (plexiglass rods, nylon or

fiberglass screens, nylon cords, etc.) in accordance with the applicable orientation(s) below. Specimens shall also be

positioned so that they do not contact each other, so that they do not shield each other from the freely settling fog, and so

that corrosion products and condensate from one specimen does not fall on another.

a. Dual-in-line packages with leads attached to, or exiting from, package sides (such as side-brazed packages and

ceramic dual-in-line packages): Lid upward 15° to 45° from vertical. One of the package sides on which the leads

are located shall be oriented upward at an angle greater than or equal to 15° from vertical (see figure 1009-1a).

b. Packages with leads attached to, or exiting from the opposite side of the lid (such as TO cans, solid sidewall

packages, and metal platform packages): Lid 15° to 45° from vertical. One-half of the samples shall be tested

with the lid upward; the remaining samples shall be tested with the leads upward (see figure 1009-1b). For

packages with leads attached to, or exiting from the same side as the lid, only one orientation (lid and leads

upward) is required.

c. Packages with leads attached to, or exiting from package sides, parallel to the lid (such as flatpacks): Lid 15° to

45° from vertical. One of the package sides on which the leads are located shall be oriented upward at an angle

greater than or equal to 15° from vertical. For packages with a metal case, one-half of the samples shall be

tested with the lid upward; the remaining samples shall be tested with the case upward. All other packages shall

be tested with the lid upward (see figure 1009-1c).

d. Leadless and leaded chip carriers: Lid 15° to 45° from vertical. One-half of the samples shall be tested with the lid

upward; the remaining samples shall be tested with the lid downward (see figure 1009-1d).

e. Flat specimens (e.g., lids only and lead frames only): 15° to 45° from vertical.

MIL-STD-883F

METHOD 1009.8

22 March 1989

NOTE: In cases where two orientations are required for testing, the specified sample size shall be divided in half (or as

close to one-half as possible). In all cases, inspections following the test in accordance with 3.4 shall be

performed on all package surfaces.

NOTE: Precautions may be used to prevent light induced photovoltaic electrolytic effects when testing windowed UV

erasable devices.

3.1.4 Chamber operation

. After conditioning of test chamber in accordance with 3, a salt fog having a temperature of

95°F minimum (35°C minimum) shall be passed through the chamber for the specified test duration (see 3.2). The exposure

zone of the chamber shall be maintained at a temperature of 95°F ±5°F (35°C ±3°C). The fog concentration and velocity

shall be so adjusted that the rate of salt deposit in the test area is between 20,000 and 50,000 mg/m

/24 hours. Rate of salt

deposit may be determined by either volumetric, gravimetric, or other techniques at the user's option. The salt solution

collecting at the bottom of the chamber shall be discarded.

3.2 Length of test

. The minimum duration of exposure of the salt atmosphere test shall be specified by indicating a test

condition letter from the following table. Unless otherwise specified, test condition A shall apply:

Test condition

Length of test

A 24 hours

B 48 hours

C 96 hours

D 240 hours

3.3 Preparation of specimens for examination

. Upon completion of the salt exposure test, the test specimens shall be

immediately washed with free flowing deionized water (not warmer than 100°F (38°C) for at least 5 minutes to remove salt

deposits from their surface after which they shall be dried with air or inert gas, and subjected to the inspections below.

3.4 Failure criteria

. All inspections shall be performed at a magnification of 10X to 20X, unless otherwise specified in this

procedure (see 3.4.1b and 3.4.1c).

NOTES:

1. Corrosion stains shall not be considered as part of the defective area of 3.4.1a.

2. Corrosion products resulting from lead corrosion that deposit onto areas other than the lead shall not be

considered as part of the defective area of 3.4.1a.

3. Corrosion at the tips of the leads and corrosion products resulting from such corrosion shall be disregarded.

4. Portions of leads which cannot be further tested in accordance with 3.4.1b, due to geometry or design (such as

standoffs on pin grid arrays or the brazed portion of leads on side-brazed packages), shall be subject to the failure

criteria of 3.4.1a.

3.4.1 Finished product

. No device is acceptable that exhibits:

a. Corrosion defects over more than 5 percent of the area of the finish or base metal of any package element other

than leads such as lid, cap, or case. Corrosion defects to be included in this measurement are: Pitting, blistering,

flaking, and corrosion products. The defective area may be determined by: Comparison with charts or

photographs of known defective areas (see figure 1009-2), direct measurement using a grid or similar measuring

device, or image analysis.