Test Method for Cleanliness of PCB Assemblies by Electrolytic Reaction


Select a printed board assembly and a location for test with two terminations approximately 0.010" apart.

Apply one drop of distilled water across the two terminations. The distilled water should be confirmed at 1meg H2O.

Connect a power supply to the two terminations with a 3-5 volt supply. A lower or higher voltage may be used if the products being assessed normally use a different voltage. All tests should be conducted at a single voltage to aid comparison.

The circuit board cleanliness may be based on the growth of copper dendrites across the terminations or by monitoring the current and should be <300 micro amp's after 1 min. Using a 5-10X magnification the reaction if any may be observed between the adjacent terminals.

When the test is complete the water and any reaction products may be removed. The circuit board may then be used in an undamaged state.

Repeat the test on another area of the board.

The test may be used on bare boards, soldered and cleaned boards, con formally coated boards or boards using a no clean process.

The test is very sensitive and is an ideal method of assessment but it does not currently relate and can not be compared to existing cleanliness standards. The tests may be conducted and then compared with long term SIR tests or ionic contamination measurements. It is possible to conduct the different tests and compare the results and then set an internal reference criteria.

Test method developed from material from Motorola and GEC Marconi.