Designing for Testability: Success Stories from the Field

Hi reader!

If you work in electronics design today, you’re probably building boards that are smaller, denser, faster and packed with more functionality than ever. That’s exciting… but it’s also a real test-access puzzle. BGAs everywhere. Fine-pitch connections everywhere. Fewer test points. More complexity.

But fortunately, we’ve got great news for you. Engineering teams around the world are tackling these challenges, and we’re here to show you the answers!

In this article, we’re going to celebrate what they’ve achieved, and look at how modern test strategies helped unlock smoother bring-ups, faster debug cycles and dramatically higher coverage.

Let’s dive into some of the wins that we’ve seen across the industry, with links to individual case studies giving more details.

High-Density Designs Inspire New Test Approaches

As PCB real estate becomes more crowded with BGAs, fine-pitch devices, and complex interconnects, many teams have creatively expanded their testing toolkits.

• Cicor recognised that each new generation of high-density SMT boards offered an opportunity to rethink coverage strategies. Where traditional test techniques were falling increasingly short, by complementing them with boundary scan, they continued achieving strong test coverage even as physical probe access decreased.

Design For Test: Design For Success

Forward-thinking designers increasingly plan for testability from the outset. Integrating JTAG chains and boundary scan early has led to impressive gains across a range of projects.

• Cicor saw immediate benefits. Boundary scan allowed automatic detection of solder issues and improved assembly parameters on boards too dense for conventional probing.

• PE Fiberoptics leveraged XJTAG to generate interconnect tests directly from CAD netlists, gaining early visibility into potential issues right at the schematic stage.

This proactive mindset enables teams to validate access to nets, pins and power rails before fabrication, ensuring strong coverage and smooth bring-up with no unpleasant surprises later in the process.

Boundary Scan: Unlocking Greater Coverage and Insight

Many engineering groups have expanded their test strategies by integrating boundary scan alongside existing functional or in-circuit methods, often with dramatic results.

• Defence OEM Elettronica achieved a considerable increase in overall test coverage by combining functional tests with boundary scan.

• Flying Test Systems (FTSL) quantified tangible improvements when one board saw a 33% coverage boost over flying probe alone.

• At Seclab, an industrial security appliance team successfully used boundary scan to test FPGAs, DDR, and flash devices that were otherwise impossible to reach using test probes or pins.

Boundary scan continues to prove invaluable for validating connections beneath BGAs, enhancing coverage, and supporting faster diagnosis. By providing visibility into nets that cannot be exercised by probes or functional firmware, it minimises reliance on additional fixtures or manual probing, improving efficiency, accuracy, and overall product reliability.

• Civitanavi Systems reported far greater test coverage and virtual elimination of human errors after integrating boundary scan alongside their bed-of-nails systems.

• Quadient, celebrated discovering how virtual test points allowed them to verify nets under BGAs without mechanical access.

These successes illustrate how boundary scan beautifully complements existing ICT and flying-probe solutions, improving both coverage and speed.

Early Testing Accelerates Development and Saves Money

A growing number of teams have demonstrated that bringing test earlier into the process generates significant savings in time and rework.

• IMSAR dramatically reduced debug time. One issue that would previously have required 40 hours of engineering effort was resolved quickly using boundary scan applied earlier in the workflow.

• Railway systems manufacturer Life Elettronica halved fault-finding time by running boundary scan tests before applying conformal coating.

These examples highlight the value of testing early. Spotting hidden defects sooner, before boards are protected by polymer coatings or enclosed within finished products, means faster fixes. Embedding board-level testing such as boundary scan after population and prior to final assembly can dramatically reduce rework.

• A satellite R&D group located a hidden FPGA solder joint issue within minutes using real-time scan analysis. They’ve since made this step a standard part of each new board’s bring-up.

A strong test-development infrastructure is equally important. With the right tools in place, robust test suites can be established and maintained efficiently.

• FTSL reduced test-setup effort per project from multiple days using competing boundary scan systems to just half a day using XJTAG.

• Elettronica accelerated test generation by reusing existing model libraries and scripts across projects, shortening the test-program learning curve.

• IoT.nxt reduced test-development cycles from months to under a week.

User-friendly test software, reusable libraries, and responsive support empower teams to create tests quickly and confidently.

• Flying Test Systems found XJTAG’s test software makes writing, debugging, and re-using tests straightforward, underpinned by a large library of device models to accelerate test creation. They also remarked that rapid access to expert technical support was a breath of fresh air compared with other vendors.

Advanced scan tool IDEs allow high-level test scripting to cover non-JTAG devices, automatic interconnect checks, and visual fault localisation – features that greatly reduce development time. Project managers should insist on these capabilities and factor in training/support when selecting a test platform.

Programming In A Flash

Many manufacturers have celebrated major throughput gains by modernising their programming strategies and integrating high-speed in-system programming into production.

• MAS Elettronica dramatically reduced programming time by pairing MRAM with XJFlash’s ultra-fast JTAG programmer, avoiding what had previously been a major constraint when programming SPI flash for high-volume production.

• Quadient cut flash programming time by two-thirds with FPGA-based ISP.

• Active Silicon reduced FPGA-accelerated programming time from minutes to just 35 seconds, enjoying “tremendously valuable time savings.”

These successes highlight the value of aligning device selection with a robust in-system programming strategy that prevents flash memory or firmware loading from becoming a production bottleneck.

Advanced programming tools such as XJExpress-FPGA and XJFlash, which can program flash and EEPROM devices directly on the production line, often at the maximum speed the chip supports, enable manufacturers to fully realise the benefits of large FPGAs and high-capacity storage. By ensuring accessible, properly terminated JTAG or programming connections are fitted on each board, planners can take full advantage of high-speed ISP and keep production flowing smoothly.

What Successful Teams Do Differently

Drawing from these proven results in the field, several best practices emerge:

1. Integrate DFT and boundary scan from day one.
   Include a valid JTAG chain in every design and check it with XJTAG DFT Assistant’s Chain Checker.

2. Design PCB layouts with test in mind.
   Add JTAG headers, accessible programming points, and leave room for test fixtures to enable in-circuit programming and probing, as needed. On designs that use BGAs or buried microcontrollers, allow teams to supplement physical access with boundary scan.

3. Automate interconnect testing early.
   Use CAD netlist data to auto-generate pin-toggle tests that detect opens/shorts across the PCB. These can flag solder faults and even unexpected shorts between unrelated signals that functional tests would miss.

4. Use scan tools for fast fault localisation and efficient rework.
   High-level control tools like XJAnalyser give engineers real-time, pin-level visibility and control that can dramatically accelerate debugging. Designers should ensure that sufficient test-points are added to complement boundary scan.

5. Integrate test into manufacturing early.
   Many companies now share their scan test suites with contract manufacturers, ensuring defects are caught before boards are shipped, keeping yields high. Bringing boundary scan (or any board-level test) onto the production line means fewer scrapped assemblies and faster throughput.

In Summary

Across dozens of real-world projects, teams have demonstrated that embracing DFT and boundary scan unlocks faster testing, deeper coverage, and smoother production. These are not cautionary tales, they are success stories showing what’s possible when test strategy is treated as an integral part of the design process, by planning scan chains, selecting programmable devices, and planning automating tests from the start.

As one veteran test manager observed, boundary scan and DFT tools let engineers test connections that cannot be probed. By building these capabilities into their processes, today’s engineering teams are achieving higher yields, fewer surprises, and faster delivery on complex PCB project than ever before.

Got questions or suggestions for future topics? Please get in touch and let us know.

If you enjoyed this update, please forward to a colleague who may find it interesting.