SMT & Inspection | March 15, 2009

Aeroflex in the UK utilises Boundary Scan and is happy

One of Aeroflex’s offices is located in Slough, Berkshire/UK, where small numbers of specially designed boards are manufactured. In particular, mobile phone protocol testers are manufactured and tested. These solutions are sold to the big names in the communication business.

Gary Brightman, test engineer, is responsible for production testing of the boards. He has been dealing with test technologies for quite a long time. In the early 1990s he utilised a Marconi test system. On legacy products it is still in use today, but it was a ot of work to program. Furthermore, the system had limited functionality and no further enhancements were possible. Before Aeroflex started dealing with alternative test technologies such as JTAG/Boundary Scan, they utilised a mixture of In-Circuit Test (ICT) and Functional Test (FT).

Gary Brightman remembers: “Getting a good fault diagnostics from functional test was impossible.” Consequently, test engineers at Aeroflex decided to have a closer look at Boundary Scan as a challenging, but obviously promising test technology. The benefits of Boundary Scan were at hand:

• good diagnostics capability, especially for interconnections
• lots of new components occurred on the market, e.g. BGA components, that could only be tested with Boundary Scan
• Boundary Scan was also applicable without additional labour or financial efforts after possible design changes

In 2000, the analysis of the market narrowed possibilities to JTAG Technologies, ASSET Intertech, CORELIS and GOEPEL electronic. Aeroflex decided on a final comparison between JTAG Technologies and GOEPEL electronic with hardware and development systems loaned from both - free to use for them in a trial period. In the end, the final decision was made in favour of the system from GOEPEL electronic. Aeroflex wanted a program to run everything, a coherent solution, not bits of solutions in many sub programs. Another criterion was the ease of the program – in the GOEPEL electronic system there were more features integrated into one package.

But the integration side of the system as the ultimate value for the decision, because Aeroflex looked for Boundary Scan that could be integrated into an existing test station. The system from the German supplier could be used further on. “The GOEPEL system was the most developed”, says Gary Brightman. “Our in-house software could deal with the software easiest and lots of functions could be transformed. Additionally, the ability for tests to be executed under customer software control was possible”. Finally, the ICT was replaced by a Boundary Scan system.

Aeroflex uses a PXI rack, in which a Boundary Scan controller is included, with fixture to external connectors. The engineers in Slough had special interfaces and designed their own interface boards to maximise the advantage of GOEPEL’s Boundary Scan solution. They’re trying to keep the connection to the PC as minimal as possible, thus they use the PXI rack including GPIB boards and PXI cards, among them a Boundary Scan controller from GOEPEL electronic.

Because Aeroflex manufactures small volumes, “speed is not a big issue for us”, argues Gary Brightman. Test time is less critical, but test coverage and board level tests are important. As most boards are about 75% digital – and that percentage has been increasing over a very short time – Boundary Scan has a good reputation, providing a test coverage of 80-90%. The test engineers execute most commonly known Boundary Scan test types such as Infrastructure Test, Interconnection Test, Cluster Test to test non-Bscan components plus a functional test setup with JTAG, measured externally. But the goal is to completely avoid a functional tes,t because of its incredible time consumption.

In the case of multi board modules - once assembled it is extremely expensive to strip, fix and rebuild. The aim is zero defects at this point. Especially in the case of design changes, Boundary Scan fits best as test technology. The methodology is only applied in the production stage due to the timing of the interface fixtures. As soon as a board is available, it gets tested. But in contrast to various other board design and manufacturing companies, Aeroflex doesn’t execute a prototype test.

Boundary Scan gives good fault diagnostics and isolation with node location that wouldn’t be possible with FT or ICT. In particular the number of BGA components and fine pitched devices has always been critical for utilising Boundary Scan. Aeroflex’ entire test system consists of four different ATE systems:

Parallel to test executions, programming of Flash devices (e.g. FPGA’s) is done as part of the testing, with the test code being loaded before the final code is loaded. Gary Brightman adds: “One of the exciting features of GOEPEL’s Boundary Scan software is CASLAN that gives us nearly unlimited opportunities in Flash programming”. CASLAN is a powerful programming language. GOEPEL’s software philosophy is to automate the generation of tests were ever possible, this is achieved with a huge device library of models. However Aeroflex, like most of GOEPEL’s customers, always wants to do something unique. This is where CASLAN comes in, allowing the user to modify models, create new ones, essentially what ever they want using a clear and easy to understand language.

Once decided for Boundary Scan technology, Aeroflex does not even think about changing this situation. They’re more than happy with the technology and the GOEPEL electronic system in particular. They need absolutely no fixtures, no physical contact. Especially in terms of increasingly higher density where physical access is limited, no test points must be designed in. And Gary Brightman smiles when talking about testing analog devices: “Tests of boards with not a single Boundary Scan device are possible - and we’ve done it!” In these cases, they’ve used external Boundary Scan devices stimulating the UUT.

Asked if he’d still pick GOEPEL again if he could turn back time, Gary Brightman doesn’t think for a second. “Definitely!”. No further words are needed.

Gary Brightman (Aeroflex) with Karl Miles (GOEPEL electronics Ltd, UK)

Aeroflex Incorporated is a well-known, multi-faceted high technology company that designs, develops, and manufactures a diverse range of microelectronic and test and measurement products. The Company’s products are in worldwide use, supporting communication systems, networks and automatic test systems.

This article was written by Goepel electronics.


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