Remember when the evaluation of a flying prober purchase began with a study of the actual benefits of this type of test equipment, then included a verification of mechanical reliability, repeatability of probe positioning, and effectiveness in the context of an electronic board manufacturing and test environment? Today, the evolution of electronic components, board downsizing, and the continuous and fast diversification of products introduced at all levels in the electronics market have shown how useful it is, or rather essential, to obtain a flying prober to increase the quality of newly-manufactured boards, meet all the technological and financial bounds of the in-circuit test, to date, reserved exclusively to high volumes.
The increase in performance of flying probe test over the years has certainly been helped along by comparison to in-circuit test, that is, to bed of nails testers; the gap between the two test techniques has decreased to the point that, in many cases, flying probe test is definitely preferred over a bed of nails. In fact, since their introduction, albeit with an initial cost considerably higher than that of a bed of nails system, flying probers have attracted users because they eliminate test fixtures, the cost of which is hard to justify in many cases, particularly for low manufacturing volumes.
On the other hand, the test times achievable by the first flying probe test systems were significantly longer than those of conventional in-circuit testers. For this reason, bed of nails systems have continued to find many advocates, even though flying probers offer a much higher degree of flexibility toward product modifications and considerably lower test setup times and, above all, are more adaptable to the frenetic pace of the modern global market, which not only consumes large quantities of product, but requires continuous evolution and customization.
Analyzing different ratios, such as price/performance, setup time/test time, initial price/operating cost, normally used by decision-makers, flying probers have gained ground with respect to bed of nails testers primarily as a result of the miniaturization of electronic components, which is an ongoing challenge to board designers who have to find room for the notorious “test points.” Due to the ability to contact objects much smaller (order of magnitude 0.1 mm) than those accessible via a bed of nails fixture (requiring a minimum TP of around 0.8 mm), flying probers are definitely preferred where the boards are not equipped with specific test points and require contact directly on SMD components to achieve enough test coverage to meet current quality standards.
When a board is not designed according to “design for testability” criteria and, by choice or necessity, the test points are not all distributed on one side of the board, it is immediately understandable how essential it is to have a tester capable of accessing both sides of the PCB simultaneously to contact all of the components and to gain access to all of the nets of the circuit under test. In this case, many flying probers are significantly limited, since many of the systems currently on the market offer only single-side probing, which considerably limits test capability and forces the user to create two test programs for the same board (one for each side) with consequent waste of time, money and loss of test automation capabilities.