Futureproofing Automated Test

​1. Abstract

​An automated unified test system for printed circuit boards and assemblies is designed around a test hardware and software platform to improve performance, increase throughput, reduce maintenance costs and reduce the amount of test systems required to test a company’s product portfolio.

2. Problem statement

In today’s world of ever-increasing technology advancement, printed circuit boards (PCB’s) continue to become more complex with advanced chips being an integral part of board design. Following manufacture of such boards, they must be tested to ensure they are functionally correct and fit for purpose.
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With the drive to increase first pass yield (FPY), increase test throughput and reduce PCB costs overall, legacy test systems as described above no longer provide a viable test platform to meet these objectives and a new approach is needed.

3. Background

For many years, test systems have been created specifically to test a particular device under test (DUT) or assembly.  These systems usually have a requirements specification created and owned by the product group responsible for the DUT without any regard to a companywide test strategy, if indeed one exists.  They are often bespoke designed to meet the requirements of a single DUT.

This leads to many test systems incurring:
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• A high value of assets.
• Increased cost of maintenance.
• High levels of real estate required at the contract manufacture.
• Test systems being continually designed and built from the ground up.
• Large NRE costs and long build lead times.

Assets like the above tend to be used long after the depreciation period due to cost replacement. This leads to the frustration of management with very high costs being involved to maintain systems.

The lack of a companywide test strategy was, my experience whilst working as a test engineer for a previous global company for 23+ years.

When a new DUT was developed, the responsible product group created the test system requirement based on tests used for design verification. Whilst these tests are somewhat justified for new product introduction (NPI) they will not necessarily be correct for the production environment.

For New Product Development (NPD), focus is given to the DUT’s design validation and verification (V&V), where-as production tests revolve around ensuring that the product has been assembled correctly, catches infant mortality, functions as expected, maximizes the first pass yield (FPY) target rate and minimizes test execution time.

A companywide test strategy provides:
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• Increased agility, a single hardware/software test platform that can be utilized on many different types of DUT’s.
• Ease of use by system operators with comprehensive documentation.
• Involvement of test engineering within DUT design development process. 
• Ability to test multiple DUT’s in batch mode within the same test cycle.
• Reduction in the amount of floor space required to test the DUT portfolio.
• Auto uploading of test logs for analysis and data mining.
• Reduction of NRE costs.
• Reduced time to market. 
• Eliminate test bottlenecks.
• Reduction and ease of maintenance tasks due to a common platform.
• Access by remote test engineers to perform upgrades and fault diagnosis.
• Reduce the overall cost of test.

By removing product groups from the test system design process and creating a test strategy managed by a test management team, manufacturing test issues can be overcome and streamlined.

4. Solution

The use of NI hardware and software is pivotal to creating a quality unified test system. PXI based modular instrumentation hardware together with the LabVIEW and TestStand software, provide an ideal platform to create systems that are both powerful and flexible in nature.

With collaboration between Amfax, NI and the customer, a NI core config rack system was developed that was not only unified in nature, it allowed for many different types of DUT to be tested at production levels. Up to 16 DUTS of the same type can be tested in TestStand batch mode (where applicable) significantly reducing the amount of time required per DUT test.

As much NI instrumentation as possible was used within the system to enable global calibration and support by NI.
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Increased performance between systems was realized due to the high-quality instrumentation used and the reduced amount of wiring required by utilizing the benefits that a MacPanel interface and Interface cards (DAKS) provide. This provided good quality test results no matter which system was used to perform the test.

​5. Conclusion

Unified test systems can be a far more cost-effective solution even though the initial outlay will be more expensive. The ability to test several DUT’s of the same type concurrently dramatically reduces the test time of each DUT and fits perfectly with the batch production methods of DUT manufacturing.

Test assets are expensive and need to have the agility to test many different types of DUT so they operate and provide great performance at all times.
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Maintenance and calibration costs are significantly reduced due to the ease of regular maintenance of a common system together with a significantly reduced number of assets requiring calibration.
Operators become more knowledgeable of a common system and requiring less training.