A Comprehensive Guide to Flying Probe Electrical Testing

As a PCB testing engineer, it is imperative to ensure that the PCBA boards are thoroughly tested for quality and reliability prior to being deployed in electronics. One of the most effective testing options available is the flying probe test (FPT), which is utilized during both the PCB manufacturing and assembly stages. In this article, we will delve into the intricacies of this testing method and explore its benefits in detail.

To begin with, let us first gain a brief understanding of the flying probe test by watching a YouTube video. However, it is important to note that this testing method requires a high level of technical expertise and precision in order to achieve accurate results.

What is a Flying Probe Test

Flying Probe Test (FPT) is an electrical testing method that is utilized to detect any potential defects in PCBs. This method is an improved version of traditional nail bed testing and is considered a reliable and efficient way to test PCBs. During the testing process, a clip is used to hold the PCB in place, and a series of pins on the clip are connected to the test points on the PCB.

FPT uses a pair of programmable probes that move around the PCB to verify circuit continuity, which is why it is known as “flying” probe testing. The probes are not controlled manually but rather by a programmed sequence that ensures greater accuracy and precision. The computer transmits the program as commands to each point, and a complete test can be conducted in approximately 15 minutes.

Flying probe test PCB is a cost-effective testing method that does not require specialized fixtures, making it an ideal option for low-volume projects. Its non-invasive nature also ensures that there is no risk of damaging the circuit board during the testing process.

How the Flying Probe Test System Works

  1. Flying Probe Programming: The FPT programs are generated using the Test Program Generator on an offline computer that requires Gerber, BOM, and ECAD files. The program is then uploaded to the tester machine, where the main board, values, test points, component formats, and offsets of the component under test are defined, quantified, debugged, and finalized for the test program’s design.
  2. PCB Preparation: Once the program is uploaded, the board is transported by the conveyor belt to the area where the probe is performed to access the test points. The test points are probed using a series of pins connected to the PCB.
  3. Probe Movement: The flying probe system performs the test on the probing points. The probe on the tester moves at high speed on the surface of the PCB according to a predetermined program and then reads the measured value.
  4. Test Results: The FPT system generates a comprehensive report, including the results of each test point. Any PCB failure or deviation from the established plan and expectations will indicate that the unit has continuity, short circuit, open circuit, and other manufacturing defects. This report will provide valuable information for debugging and further improvement in the manufacturing process.

Why Choose Flying Probe Electrical Testing Service

Features of flying probe test

The wider flying probe test coverage can be used to detect various potential defects on the board such as open circuits, short circuits, capacitance, inductance, impedance, tolerance, polarity, direction, misalignment, and more. It is considered a safer testing method since it does not require physical contact with the board, minimizing the risk of damage.

In PCBA projects, the flying probe testing services are a cost-effective option for rapid prototyping as it does not require specific test clips. However, it may not be suitable for mass production due to longer testing times and higher unit costs compared to in-line tests (ICT).

One of the advantages of the FPT is the real-time fault location identification on the circuit board, allowing for faster corrective actions. The system’s accuracy is achieved through the use of a mechanical arm and programming, which ensures precise probing.

However, the flying probe test has limitations. Skilled technicians are required to set up the test procedures and interpret the results. The system is unable to test analog components such as operational amplifiers and transistors that require dynamic signal testing. Furthermore, components with high pin counts or high-density boards with fine-pitch components may not be tested as probes may not reach all test points.

What other testing methods are there besides the flying probe?

  • Bed of nails testing: This method requires jigs that use a range of spring pins specifically designed for the board used in the project.
  • In-circuit testing: ICT is used to detect individual component or connection defects.
  • Automated optical inspection: AOI inspection system relies on comparison to detect missing components, wrong orientation, or solder joint problems on the PCBA board.
  • X-ray inspection: This method is used to inspect the internal connections and solder joint quality of invisible components.
  • Functional test: This test checks the overall function of the PCBA board by testing the electrical signal and input/output of the circuit board under simulated operating conditions.
  • Additional methods: Other testing methods include boundary scan testing, power-off testing, environmental testing, and reliability testing.

Types of FPT testers

According to the test object

  • Bare PCB: Involves evaluating the connectivity, open circuits, and short circuits on a board without electronic components. This type of testing can help identify any issues that may arise during the design and manufacturing process.
  • PCBA: Involves evaluating circuit boards with electronic components installed. The main objective is to verify the accuracy, performance, and quality of component installation to ensure that there are no problems during the assembly process.

According to function

  • Manual machine: This type of equipment requires manual operation, making it suitable for small-batch and low-frequency testing.
  • Automatic machine: This model uses an automated robotic arm to control the probe for testing and is suitable for mass production and high-frequency testing.
  • Equal-length tester: This type uses probes of the same length for testing. Although it can improve the test accuracy, it slows down the PCB test process.
  • Non-isometric tester: Different lengths of the probes allow for increased testing accuracy while maintaining testing speed.
  • Multi-point tester: The device can test different points on the PCB at the same time, which improves the test efficiency and accuracy.
  • High speed device: This type uses a high-speed flying probe to test, which improves test speed while ensuring accuracy.
  • Rotary device: The flying probe in the circuit test adopts a rotating mechanism to realize more complex test operation and high-efficiency test.

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