Making test lean again.(DESIGN FOR TEST)(Lean manufacturing)

Circuit board test, like any step in the PCB assembly process, benefits from lean manufacturing practices that continually improve process steps. If lean manufacturing principles were applied to circuit board test, what would a lean test strategy and test platform look like? A viable option is an efficient implementation of lean board test that uses an open platform board test (OPBT) architecture.

The End of the In-Circuit Era

The need to get more done with fewer resources has driven important strategic shifts through the history of circuit board test. In the late 1970s and early 1980s, increasingly complex boards populated with early microprocessors began outstripping the capabilities of digital functional testers. By the mid-1980s, in-circuit testers with their lower capital cost, much simpler programming, and fault coverage aligned to common manufacturing faults had supplanted digital functional testers in the PCB assembly process.

As component and board technology advanced, so did in-circuit tester capability--and complexity. By the mid-1990s, in-circuit test (ICT) platforms were chockablock with capabilities like backdrive digital vector test and variants such as combinational test that eventually made in-circuit testers as expensive, complicated, and costly to deploy as their digital functional predecessors. Once again, developing and debugging test programs took weeks, and maintenance and support costs grew as well.

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Today, these capable but expensive traditional ICT platforms make up the majority of the worldwide in-circuit installed base. Regardless of the complexity or cost, most test engineers consider ICT a solved problem and have turned their attention elsewhere.

But current economic and technical realities are bringing the era of traditional in-circuit testers to an end as surely as the digital functional testers they once replaced. Here's why:

Loss of Electrical Access to Circuit Nodes

Increasingly complex components are packed more densely into shrinking board dimensions. The price of miniaturization is ever decreasing electrical accessibility by ICT bed-of-nails test fixtures, leading to reduced fault coverage.

The Shift in the Manufacturing Fault Spectrum

Even as board technology has grown in complexity, automated assembly and improved component quality have increased manufacturing yields and changed the traditional proportions of component and assembly process defects. For example, while improved device quality has made digital defects almost nonexistent, relatively more mechanical and solder-quality defects now occur. …

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