​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.

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.

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.

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.

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. 

With expertise in more than 120 countries, our client designs and maintains products globally, often requiring numerous bespoke test solutions throughout their portfolio. They sought to:

• decrease cost of ownership,
• maximise the use of common resources to test different units, and
• reduce downtime through easier replaceability and maintenance.

The major requirements were as follows:

• ability to test multiple units and different types of units at the same time with one test solution,
• enabling parallel testing of both identical and eventually different types of units and
• be modular in design to quickly enable replacement when required.

​The team at Amfax worked with the client during the early concept ideas, exploring existing solutions and understanding the long-term needs of the client.

The common test rack involves an NI core rack, expanded with additional resources and switching functionality. A mass interconnect system is installed, using direct access kits for connectivity to PXI cards and a custom hybrid module for all other rack resources. The system contains:

Within each port module is an identifying code that the common rack can interpret to indicate the variant of port module installed. Internal port module current sensors enabled individual supplies to be monitored in real time and internal relays provided 2nd layer switching allowing sophisticated signal routing to be performed.

​Amfax designed a detailed top-level block diagram early in the project that formed the basis of collaborative design discussions with the client. Later, the initial commissioning of the test system used this block diagram as the primary source of information to identify signal path connectivity during software development.

​To make it easy for the client to take ownership of all drawings after project closures, Amfax used the clients preferred drawing and document packages such that the client could port these into their own documentation management system to provide the flexibility for them to maintain the design in the future. This includes using Altium Designer for electrical schematics, step files and DWG files for mechanical drawings, and Microsoft Office programmes for other supporting documents, test procedures, and manufacturing build documents.

If there are any issues in-service, the extended modularity reduces downtime by enabling operators to swap out a failed module (i.e. the port module), and replace with a spare and/or send the module off for repair.

After successful commissioning at a clients’ contract manufacturer, over a 2 year period, a further 8 systems were produced as “Build to Print” and deployed at all the clients contract manufacturers globally.

All new DUTS are now tested on these systems with a program in place to convert the testing of all DUTs to the new system. This requires only DUT cassettes to be designed and manufactured along with new software.

The overall impact is that the client now sees a significant reduction in the cost of test. In their own words:

For our client, it’s now accepted as the global test station; all new product must be designed to be tested on it.