Editor's Note: This article originally appeared in the March 2012 issue of SMT Magazine.
Since the day high-volume electronic manufacturing began, along
with the proliferation of surface-mount devices (SMDs) on the printed circuit board assembly (PCBA), the in-circuit tester (ICT) has been the default manufacturing test system. In-circuit test methods make use of bed-of-nails fixtures to get access to the device under test via test probes and test points (see Figure 1) and also utilize the complex analog and digital capabilities offered by the tester to accurately measure component values, voltages, and frequencies, as well as simulate the functional operation of digital devices to detect open/shorted pins.
Figure 1: In-circuit test method with a bed-of-nails fixture.
Flying Probers (FP)
The flying probe tester uses a moving mechanical head where
a probe is attached to get in contact with the target component pins and test points on the PCBA. Flying probe has been mostly used for prototyping and new product introduction (NPI) due to its shorter program development time and the system does not require a bed-of nails fixture to test a PCBA.
Technological advancements to the flying probe are limited: The ability to include more probes for better throughput, allowed testing between top and bottom sides of the PCBA, lack of new capabilities to run powered (analog and digital), and boundary scan tests. The high system cost, limited test coverage, and lower throughput compared to in-circuit testers (see Graphs 1 and 2) are the main reasons why flying probes are still confined to prototype and NPI testing work only.