Some solutions for intermittent problems

Intermittent field problems are among the most expensive warranty issues to handle. It can take years to find the root cause, then figuring out a solution to eliminate the problem can be difficult.

So it’s pretty wise to take steps to avoid problems that cause sporadic failures. One of these, tin whiskers, has been vexing electronics providers since the 1940s. It’s become a bigger problem since the ban on lead, which is one of the most effective mitigation technologies. The growths grow not only on tin, they also sprout from zinc and cadmium, according to Dave Hillman, principal materials and process engineer at Rockwell Collins.

He’s spent years working on this issue, among others, and he’s pretty open about sharing his experiences. In a recent IPC webinar, Hillman stressed that design and manufacturing engineers should use a mitigation system rather than a single solution.

Conformal coating is one of the best solutions. Coatings trap whiskers so they can’t cause problems, so thicker coatings work better than thin ones. Pre-tinning of leads and terminations also helps reduce the growth of tin whiskers, as does solder dipping.

Hillman also suggests that companies use assessment tools that let users  know whether their processes are at high, medium or low risk. These tools help users determine whether a step like adding conformal coatings makes a large enough improvement to justify the cost.

Hillman’s webinar is one of a series of online IPC presentations that address many of the challenges facing circuit board producers, including testing, cleaning and prototyping. For those who want to focus more on tin whiskers, IPC is offering a conference in Texas next week, April 17-19, in Fort Worth, Texas.

More information: IPC Tin Whiskers Conference, Sponsored by Lockheed Martin Corporation, April 17–19, 2012, Ft. Worth, Texas, www.ipc.org/tin-whiskers

 

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