Select Page

MIL-STD 202 Resistance to Solvents Testing:

MIL-STD-202 Resistance to Solvents testing serves a number of purposes. It verifies that markings or color coding will not become illegible or discolored when exposed to solvents. It tests the mechanical and electrical durability of component protective coatings and encapsulant materials when exposed to solvents. These are solvents that may be used to clean solder-flux, fingerprints, and other contaminants from printed-wiring and terminal-board assemblies, et cetera.

Solvents for MIL-202 resistance to solvents are formulated to represent the solvents used in printed wiring assembly processing of electronic components. Processing conditions are also representative of processes used for printed wiring assembly. When this test is referenced, check that conflicting requirements, as far as the properties of the specified finishes and markings are concerned, are not invoked.

Keystone Compliance is a corrosion lab with significant experience in Method 215 of MIL-202 resistance to solvents testing. This knowledge is mainly drawn from MIL-STD-202, but also includes MIL-202G resistance to solvents and MIL-202H resistance to solvents.

The following information is extremely technical in nature. Even though the language is from MIL-STD 202G resistance to solvents, it applies previous versions of the standard. This includes MIL-STD 202H resistance to solvents.

What are the Proper Solvent Solutions For Contamination Testing?

The solvent solutions used in this test shall consist of one of the following:

  • A mixture consisting of one part by volume of isopropyl alcohol, three parts by volume of mineral spirits. Three parts by volume of a mixture of 80 percent kerosene and 20 percent ethylbenzene may be used instead of mineral spirits.
  • A terpene defluxer consisting of a minimum of 90 percent d-limonene and 10 percent surfactant.
  • A mixture consisting of 42 parts by volume water, one part by volume of propylene glycol monomethyl ether one part by volume of monoethanolamine.

The solvent solutions above exhibit some potential for health and safety hazards. Safety precautions as listed in the appropriate manufacturers material safety data sheet shall be observed. All Corrosive atmosphere testing should be performed in a resistance to solvents testing lab.

What Materials Are Needed in a Resistance to Solvents Laboratory?

The vessel for solvent immersion must be a container made of non-reactive material. It must be of sufficient size to permit complete immersion of the specimens in the solvent solutions. A toothbrush, with a handle made of a non-reactive material is also needed.

The brush must have three or four long rows, 1 and 1/8 ±1/8 inch in length, of hard bristles. Each row should contain eight to twelve tufts, the free ends of which shall lie substantially in the same plane. The brush shall be used with a single solvent and when there is any evidence of softening, bending, wear, or loss of bristles, it shall be discarded.

What is the Proper Procedure for This Test?

The specimens subjected to this test shall be divided into three groups of approximately equal size.

The first group:

The solution is maintained at a temperature of 25°C ±5°C, and the specimen is completely immersed for 3 minutes. Immediately following immersion, each specimen is tested. The bristle portion of the brush is dipped in the solution until wet. Then it used with normal hand pressure for ten strokes on the marked portion of the specimen.

Move the brush forward across the surface of the specimen being tested. Immediately after brushing, the procedure is repeated two more times, for a total of three immersions, followed by brushing. After completion of the third immersion and brushing, the specimens are air-blown dry. The specimens shall be inspected to determine the extent, if any, of deterioration that has occurred.

The second group:

The solution is maintained at a temperature of 25°C ±5°C, and the specimen is immersed for 3 minutes in the specified solution. Immediately following immersion, each specimen is tested. The bristle portion of the brush is dipped in the solution until wet. Then, with normal hand pressure, for ten strokes, the specimen is brushed where marked.

Move the brush in a forward direction across the surface of the specimen being tested. Immediately after brushing, the procedure shall be repeated two more times, for a total of three immersions, followed by brushing. After completion of the third immersion and brushing, the specimens are rinsed in approximately 25°C water and all surfaces air-blown dry. The specimens are then inspected to determine the extent, if any, of deterioration that has occurred.

The third group:

The solution is maintained at a temperature of 63°C to 70°C, and the specimen is completely immersed for 3 minutes. Immediately following immersion, each specimen shall be tested. The bristle portion of the brush is dipped in the solution until wet. The specimen is then brushed with normal hand pressure for ten strokes on the portion of the specimen where marking is.

The brush stroke is directed in a forward direction across the surface of the specimen being tested. Immediately after brushing, the procedure is repeated twice, for a total of three immersions, followed by brushing. After completion of the third immersion and brushing, the specimen is rinsed in approximately 25°C water and all surfaces air-blown dry.

There is an optional exposure procedure for the third group. In this procedure the specimen is located on a test surface of a known area which is located 6 ±1 inches below a spray nozzle that discharges solution. The solvent is held at a temperature range of 63°C to 70°C, and the specimen is subjected to this spray for 10 minutes. After completion of the spray exposure, the specimen is thoroughly rinsed in water and all surfaces air-blown dry and inspected.

What is the Procedure of Immersion Testing for Components With Marking Protected By a Sleeve?

Components with a protective sleeve are divided into three groups, and each group is subjected to testing using the solution defined for that group. Each solution is maintained at a temperature of 25°C ±5°C, and the specimens are immersed in it for 3 minutes. Immediately following immersion, each specimen is tested.

The bristle portion of the brush is dipped in the solution until wet. Then the specimen is brushed with normal hand pressure for ten strokes on the sleeve directly above the area of the marking. Immediately after brushing, the procedure is repeated twice for a total of three immersions followed by brushing. Brush forward across the sleeve area above the marking, after the third immersion and brushing, air-blow dry the specimen.

What Happens to Open Construction Parts and Parts Not Intended for PCB Mounting?

Parts of open construction which are susceptible to internal damage by immersion in solvents. Parts not intended for mounting on printed circuit boards, are divided into three groups. Each group is subjected to testing using the solution defined for that group. Each solution is maintained at a temperature of 25°C ±5°C.

The only solution not maintained at this temperature is that consisting of 42 parts water, one part propylene glycol monomethyl ether, and one part monoethanolamine. This is maintained at a temperature range of 63°C to 70°C. Once the proper solution has been acquired each group is tested.

The bristle portion of the brush is immersed in the respective solution for each group until wet. The specimen is immediately brushed with normal hand pressure for ten strokes on the portion where marking has been applied. The test area should not to exceed one-half inch square. Brush forward across the marked surface, this test is repeated twice for a total of three times for each specimen.

Who Should You Trust for Your Resistance to Solvents Certification Needs?

Keystone Compliance has been recognized as one of the best resistance to solvents labs in the country. We employ experienced test engineers, provided with high quality equipment. This ensures the best resistance to solvents testing for your products.

Looking to get resistance to solvents compliance testing done? Our test engineers have an in-depth knowledge of corrosion testing for commercial, military, and aerospace products. Contact us to learn why so many manufacturers rely on Keystone Compliance to meet their compliance testing needs.

Looking for other MIL-STD-202 compliance tests? Click on a link below to learn more about the other test methods.