The global marketplace is constantly evolving. No other industry experiences more change than electronics. New technology becomes available at an alarming rate. In order to remain competitive in the electronics industry, electronics manufacturers must be able to keep up. Electronics companies of all shapes and sizes face quite some challenges.
Keeping up with increasing quality demands, to lower development costs, to lower the production costs, faster service repair times and better ease of use. Puts pressure on all the departments.
Electronics manufacturers are urged to make new products with higher quality at lower costs in shorter time spans. Design For Test (DFT) for printed circuit boards is playing an important role in quality and is imperative to meet high quality and reliability objectives.
What can be done to make the high quality targets obtainable?
The only answer is DFT: Design For Test. Given this starting point, it is clear that every designer should apply DFT. It is of prime importance to understand the quality impact of all aspects of testing, including design for testability and fault coverage targets. Testing alone does NOT add functionality and thus no value to the product as seen from the customer’s point of view. But if DFT is applied, then inherently the chance of failure is diminished and that does add value (read quality) to the product. Thus testing must be advocated or even be made mandatory as an integral part of a design/manufacturing activity and should be considered in the light of customer satisfaction. While it might seem that improving quality costs money, in the long term money is saved through higher yield and fewer customer returns. For this reason time has to be spent on component, board and system inspection, monitoring the manufacturing process for improvements and an overall analysis of the development and production cycle. The analysis may even include the field service costs.
Lower development costs
Testing is necessary to obtain the highest possible product quality. The costs of testing, however, should be low. This is true for the test costs incurred during production as well as for the costs to develop the tests. The amount spent on testing, and the related costs for fault diagnosis and repair, are determined by a product’s design and are thus set at the design phase.
The costs to develop the tests also depend on the product’s design. The better a design is testable, the lower its production test costs and the lower the costs to develop these tests. Hence Design For Test (DFT) is crucial in reducing the cost of test. Use of automated test generation tools keeps costs down and simplifies the development process.
Using JTAG/boundary-scan testability analysis tools early in the product cycle pays off in reduced time to market and improved product quality. The designer will know, prior to prototyping, the level of testablity of that will be attained for the product. If the testablity is deemed to be inadequate, the design can be modified and testablity re-examined, avoiding the delays that every subsequent process step would otherwise encounter. By adopting a policy in which the design phase must include DFT analysis that meets testablity requirements, the organization will avoid wasted layout spins and prototype builds.
Lower production costs
Generate the best test strategy and choose the right tools to use in the production phase.
JTAG/boundary-scan improves production test efficiency in several important ways:
- Boundary-scan based device inter connections tests can run at high speed and are capable of producing pin-level diagnostics.
- Fixturing for board test access can be dramatically simplified, if not eliminated entirely.
- JTAG/boundary-scan can be used as independent station either stand-alone, or in-line.
- The modular nature of JTAG/boundary-scan tools allow them to be combined with other structural test methods, such as in-circuit testing or flying probe, which may already be in use in the factory.
Alternatively JTAG/boundary-scan tools may also be integrated in functional test stations. Boards with faults that are not detected by traditional structural testing are said to “escape” to the functional test stage.
Structural test escape faults are readily detected in traditional functional testing, but are not so easily diagnosed and corrected. Adding JTAG/boundary-scan at the functional stage helps minimize the bone-pile by ensuring that no (or very few) manufacturing defects remain unresolved at this stage. Because of the precise diagnostics from boundary-scan, board repair is usually swift and requires only one action rather than several trial and error attempts to locate the faulty device/pin.
This precision has a positive impact on product quality, and reduction of product to-market times. Savings can also result from reduced product handling, fewer test stations, less floor space, a reduction in training requirements, and use of a familiar, unified GUI for the operator.
The test plan for a product should cover the whole product life-cycle and include: prototype debugging, manufacturing tests and field service repairs. The tools that can be used to locate a problem on a failing Printed Circuit Board Assembly (PCBA) depend on whether design data of the board is available or not, and whether test programs for the board already exist. In all circumstances boundary-scan technology can help to shorten repair times in (field) service and can also be used to-reprogram parts for system upgrades.
What can be done to shorten repair times?
Nobody wants to wait a long time for the repair of a product. JTAG/boundary-scan with ProVision can help to shorten repair times even if no, or only limited, design data is available. It can also be used to re-program parts for system upgrades. Centralized as well as distributed repair facilities can benefit from the same JTAG/boundary-scan-based tests as the factory, helping to quickly analyze test results. Furthermore, because boundary-scan is simple to set-up and connect, the repair department can rapidly switch between target types and versions in high-mix situations.
In summary, if the product has been well planned and incorporates the basic design for test measures required, the enterprise will experience many benefits. Transitions of responsibility from one organization to the next are streamlined, inter- departmental communications are enhanced, and alignment problems are avoided by the use of a common test methodology.
Ease of use
The purpose of any tool is to make a task easier and quicker. It makes sense therefore for tools to be developed by the same people who also use them on a daily basis, allowing intuitive features to be introduced dynamically and progressively as the needs arrive.
Test tools should be reliable and help you with your daily challenges. They should ease your workload, not complicate it.
Some key requirements might be:
- Easy to learn, with minimal knowledge
- Simple to use with application wizards
- Seamless integration
- And easy to pick-up again – after an absence
However, ease of use is not easy to define, as it reaches beyond the daily work of the average user. And, inspite of the fact testing is just one small part of the process, it is still an essential one. As an electronic product moves through its life-cycle, from development through prototyping to manufacturing and finally to the service and support phase, responsibility for the product also migrates through the organization. However, problems can occur at the departmental boundaries where different tools and philosophies can be in use.
If problems are not rapidly understood and resolved, vital aspects such as time-tomarket, repair turnaround time, and product quality and reliability can escalate beyond acceptable limits.