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In-circuit test automation: Replacing the human touch

Posted: 21 Oct 2014 ?? ?Print Version ?Bookmark and Share

Keywords:printed-circuit-board assembly? PCBA? PCB? printed-circuit-board assembly? in-circuit tester?

The cost of operators for manufacturing test has been rising continuously for the past decade. That increase has added pressure to the printed-circuit-board assembly (PCBA) line managers' need to bring down costs and compete effectively with cheaper manufacturing economies. One of the new strategies adopted by manufacturers is the replacement of PCBA loading by operators with various automated systems. Unfortunately, sometimes the automated systems need help from the operators they were intended to replace.

I'm often asked about the pros and cons of automation to replace rising labour costs, not to mention challenges of attracting and retaining staff, who are continuously lured away by other job opportunities such as the service industry. Then there is the favourite question of which automated solution is better.

There are two popular automated solutions often considered these days. The first is to integrate a robotic arm with existing in-circuit testers, while the other is to deploy a fully automated inline in-circuit tester on the SMT (surface-mount technology) line.

Not long ago, I visited a PCBA manufacturing line in Thailand that uses an automated robotic arm as a pick-and-place system to load the PCBA onto an ICT (in-circuit tester). The automated robotic arm was almost sandwiched in between two ICTs. Complementing this customised pick-and-place system was a lifter and conveyor used to transfer or transport the trays holding boards to be tested, boards that passed tests, and boards that failed.

Here's a snapshot of how this system works: The robot arm picks the untested board from the bin and loads it onto the fixture. Once the board is loaded, the pneumatic top cover, which is mounted on the fixture, automatically closes and proceeds with barcode scanning. If the board isn't properly placed onto the fixture tooling pin, the board could be damaged when the pneumatic top cover closes. During my visit, I witnessed three occurrences within 15 minutes of boards that failed the robotic arm didn't properly place them. Figure 1 shows a typical robotic arm setup.

Figure 1: A typical robotic arm set up for in-circuit test on the production floor.

To mitigate the potential risk of board damage by misaligned placement, this manufacturer had deployed an operator to manually adjust the board before the top cover closed. I couldn't help but observe an obvious potential pinching hazard that the operator might suffer should he or she be a tad slower than the automated pneumatic cover.

Upon completion of the test, the robotic arm would pick up the board from the ICT system and place it either in the PASS or FAIL bin according to the board test result. At this juncture, I noticed that occasionally, a board would not be correctly placed into the designated bin, triggering the operator to make a quick dash towards the system to make that manual adjustment. It seemed contradictory to have to deploy a full-time operator dedicated to watching over the smooth operation of this automated system, which was installed to reduce operator headcount in the first place.

This automated set-up needed about 15,000 cm² of shop-floor space to house the robotic arm, not including the link conveyors which took up additional space. Overall, this solution took up quite a large area.

Human handling error, ESD, turnover
During yet another recent line tour, this time with an automotive PCBA manufacturer in North America, I saw their automated inline in-circuit test handler. According to the test manager, the company's biggest challenges in the production environment are human handling error, ESD damage, and high operator turnover rate. The test manager believed that an inline ICT system could solve the problems.

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