How Much Do You Know About Flying Probe Test

What is Flying Probe Test?

Actually, flying probe test can be regarded as the upgrading of bed of nails fixture test in that flying probe tester takes advantage of probes to replace bed of nails. Four headers are equipped on flying probe tester along X-Y axis and can move at a high speed.

As a flying probe tester is working, unit under test (UUT) will be first transported to the internal tester through conveyor belt or other UUTs. Then, probes will have contact with test pads and vias so that defects of UUTs can be found out. Probes are connected with drivers (such as signal generators, power supply etc.) through multiplexing system and sensors (such as digital multimeter, frequency counters etc.), through which components belonging to UUTs can be tested. When a component is being tested, other components on the same UUT will be shielded from test to stop reading from being disturbed.

Flying probe tester is capable of testing shorts, opens and component values. Additionally, a camera is equipped on the flying probe tester to help to find out missing components and to inspect component polarity. As positioning accuracy and repeatability of probes reach a scope between 5μm and 15μm, flying probe tester can accurately test the fabrication situation of UUT.

How does Flying Probe Tester Work?

Flying probe tester carries out programming more easily and more quickly than traditional ICT (in-circuit test) systems, flying probe test for example.

To implement flying probe test programming, testing staff should first transform CAD (computer aided design) data provided by engineers into applicable file. Then, the newly-generated file will be run through a test program with new files with corresponding formats generated. Last, all the files will be created catering to UUT test demands and requirement.

As soon as test programming is finished, the authentic flying probe test is around the corner. A testing item should be determined first, shorts for example. Then, data of reference points conforming to UUT should be picked up from CAD data. As soon as UUT is fixed on the platform, the programming will be carried out to inspect the fabrication or assembly issues.

It’s necessary to point out that debugging should be done prior to official testing. What’s more, debugging of flying probe test can be completed within shorter time compared with conventional ICT test.

Advantages of Flying Probe Test

Based on the definition and working principles mentioned above, flying probe test features the following advantages:

• Short test development cycle;

• Relatively low test cost;

• High conversion flexibility;

• Rapid feedback provided to PCB design engineers at prototyping period.

Therefore, compared with conventional ICT, flying probe test calls for shorter overall test time. When it comes to PCB assembly, manufacturing can be started just a couple of hours after CAD file arrives. Thus, prototyping PCB assemblies can be tested a couple of hours after being assembled, which differs a lot from conventional ICT that usually spends even a couple of months on test alone. Besides, owing to low difficulty on setting, programming and test, ordinary technicians are able to operate.

Disadvantages of Flying Probe Test

Each coin has two sides. Apart from obvious advantages, flying probe test simultaneously features some disadvantages.

Since flying probes have direct physical contact with vias and test pads and small pits are easily caused on board surface, some OEMs will regard them as fabrication defects. Nowadays, however, as science and technology make constant progress, this will be overcome through the advent of upgrading flying probe testers.

Sometimes, when flying probe tester is working on components without test pad, it's possible that probes have contact with component leads so that loose leads or leads with badly-performed soldering may be missed.

In spite of the disadvantages mentioned, flying probe test is still regarded as a significant test method as far as PCB fabrication and PCB assembly are concerned and will always play a crucial role in leading electronic products to excellent performance and high reliability.