Optimizing Your Test Strategy Print E-mail
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Written by Stacy Kalisz Johnson   
Saturday, 31 January 2009 19:00

Microsoft’s Xbox is a shining example of the economy of maintenance.

Consumers are electing not to fill prescriptions and are skipping doctor visits in hopes of saving money, a recent article said. Result: Uncontrolled health issues are getting worse and requiring more advanced treatment, which in turn costs more over the long run.

Drivers are leaving their cars to similar fates. Maintenance is being skipped in an effort to save cash, but over time leads to costly breakdowns and more days lost in the shop, costing more than the routine checks would have! It recalls the saying, an ounce of prevention is worth a pound of cure.

The parallels one can draw from consumer behaviors to the PCB test industry in an economic crisis are remarkable. During the recession, users may choose not to implement test and inspection in the same way as in a recovery. New products are not getting the same level of test and inspection added because of the upfront burden of the capital investment. I cringe when I converse with customers who are reducing resources by lessening the test and inspection focus, in some cases by leaving inline systems in pass-through mode. Just as with the examples above, short-term savings are more favored by management in the current economic scenario, but the big picture is being overlooked. It is clear there is still a lack of understanding of the return on investment on test and inspection tools. Another saying sums up this situation nicely: We can’t see the forest for the trees.

Look at the warranty repair numbers found in the public domain and it will not take long to conclude that catching defects before they leave the door to customers clearly is cheaper than a warranty repair/return. The Microsoft Xbox example has been used many times to illustrate this. Microsoft spent some $1 billion to extend its warranty from 90 days to three years.1 It is also well documented and accepted that the farther up the production line a defect is found, the less expensive it will be to repair. Fixing a paste print defect will cost orders of magnitude less than fixing a defect found at electrical test.

These economic times leave no room for a $1 billion warranty extension. It is critical to have defect containment procedures to prevent defects from reaching customers. That said, this economy also means scrutiny on the value of test, especially with management. Therefore, a review of test economics and a renewed commitment to defect prevention and detection is critical for all of us. In fact, I would argue now is the best time to revisit your test strategy; those who do will have lower repair costs and a better bottom line to present to their management team.

It’s no secret margins are being squeezed and competition is fierce. The current economic uncertainty is taking this to all-time new levels. Defect prevention and detection lower rework cost by reducing or eliminating post reflow defects, therefore improving product margins. Also, by reducing the work in progress or inventory being held for rework (i.e., unshipped boards where money is sunk in materials, but not able to collect payment from customers), the overall cash flow picture will improve.

For the best results, optimize the test strategy. To do this, understand the difference between faults, defects, process indicators and potential defects (Figure 1). Collect accurate data on defect levels and defect spectrums. Defect levels are typically higher than normally acknowledged in the industry. To have accurate data on test effectiveness of different test and inspection solutions, it is recommended each test engineering department conduct studies of their lines to understand their test systems' efficacy at catching defects. Determine where in the manufacturing process different defects are introduced and where they can be detected. If possible, gather data from field returns and estimate different test strategies and their respective impact on warranty cost. Be sure to have a holistic view of the test strategy from a process improvement or defect prevention perspective – including defect containment – and include the board’s complexity in the test strategy selection process. It is important both the defect prevention and defect containment pieces be present.


For process control with shorter feedback loops, the test and inspection systems should be placed early in the manufacturing process (post print or post reflow, or both). For optimal defect containment, test and inspection should be performed after the board has been manufactured.

In summary, strive for continuous improvement in data gathering for optimal test strategy selection, and the economics will continue to favorably change. Start small: The data will speak for themselves and will help justify the ongoing investment in your test strategy.


1. Colleen Taylor, “Microsoft Extends Xbox 360 Warranty at $1B Cost,” Electronic News, July 2007.

Last Updated on Tuesday, 24 March 2009 16:01


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