Machine Design

How Triz solved a sticky little IC problem

The problematic circuit tester lifts an IC into delicate finger contacts to test the chip.

Innovation Workbench led the engineering team to replace the fragile finger contacts with conductive elastomers that would perform the same function. The larger blob in the center is an elastic material that pushes the IC away from the contact when testing is finished.

After one workshop, engineers with National Semiconductor, Santa Clara, Calif., modified a machine that tests integrated circuits with what they considered innovative solutions to problems that had gobbled up $76,000 in the previous five months of trial-and-error solutions. The testing machine works by first lifting an IC into contact with small leads. When testing completed, the chip was to fall away from the contacts into a sorting bin.

But two problems cropped up. In one, about 1% of the chips would jam against the contactors and not let go. They had to be tapped before they released. And then the delicate contacts began to bend and were pushed aside by the IC leads. Without a sufficient contact, IC tests identified some good parts as being defective.

After an engineering team completed a 16-block problem formulation, Triz-based software responded with 40 possible directions. The most promising suggested eliminating the frail contacts. The software then helped the engineering team identify a conductive elastomer that could function as the fingers.

And to eliminate the sticking or jamming, a spring placed at the center of the contactors compresses when the IC is lifted into place. It also pushes the IC away at the test's end. The innovation here was not a coil spring but a small ball of elastic material that acts like a spring.

Both solutions work well. The consensus among engineers working on the problem is that without guidance from the Triz method, the project would still be hunting for a solution.

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