Benzotriazole To Protect Copper

Question:

We have tried various concentrations of benzotriazole from 0.5 percent to 1.5 percent and have concluded benzotriazole makes no difference in the surface protection on our copper-plated lead frames. What are the critical parameters of operating such a system?

Answer:

There is much information as to the efficacy of using benzotriazole as a protective coating over copper. The use of this material over U.S. pennies is common knowledge. The fact that your tests show little difference in the surface protection of parts tested in solutions of various concentrations of benzotriazole suggests you may not be applying the coating properly or there is a problem associated with the preplate or plating bath itself. Porosity in the copper deposit as a result of improper preplate techniques is the most common cause of black spots on copper-plated parts. The proper method for the application of a benzotriazole coating is as follows: copper plate; activate and rinse well; immerse in a solution of benzotriazole with a concentration of 0.1 to 0.5 weight percent for at least 30 sec. The pH of the solution should be between 7.0 and 8.5 at a temperature of at least 140 F. A free-rinsing, non-ionic surfactant should be used to increase the surface contact of the solution.