Flying probe tests are the most effective way to solve some of the biggest problems that electrical testers face today. It uses motorized, fast-moving electrical probes instead of bed needles to make electrical measurements and contact pins on devices.
PCB boards are inevitable in production due to external factors such as short circuits, circuit breaker leakage, and other electrical defects. In the future, PCB boards will be more dense, fine-pitch, and multi-layered. If you can’t screen out defective boards quickly, this will result in higher costs.
Electrical testing methods include: dedicated (Dedicated), universal grid (Universal Grid), flying probe type (FlyingProbe), electron beam without contact (E-Beam), adhesive conductive cloth, capacitive (Capacity), and brush (ATG SCANMAN). These tests are often performed with three different types of equipment.
What is the difference between a flying probe test and a test jig? What are their advantages?
Flying probe test: This test uses four to eight probes on a circuit board to test high voltage insulation and low resistance conductivity. Test lines open, and short circuits do not need to make unique test fixtures. The flying probe test is directed to the PCB board mounted on the flying probe test machine, and then the test program can be run. The advantage of flying probe tests is that their test method and operation process are incredibly convenient, saving the cost of testing, reducing the time to make test racks, improving the shipping efficiency, and being suitable for PCB small batch production.
Testing jig
The testing jig can be used to mass-produce PCBs for on-off tests and to make a specific test fixture. The cost of production is higher, but the test efficiency and return order are not charged.
Flying probe tests are currently used for small quantities or samples in electrical test equipment. No matter what PCB board level, the test costs are lower as long as the output reaches certain numbers. They only represent 2–4% of the sale price.
How does the flying probe test work?
Flying probe testers are an improvement over the traditional in-line, automatic, high-voltage PCB board testers that use a needle bed. Instead of using the needle bed, the testers now use a probe.
The UUT is transported by belt or another UUT conveyor to the tester, where the probes are contacted with the test pads and holes via the tester. This allows the components to be tested individually. Test probes are attached to drivers and sensors using a multiplexing device to test components on the unit under test. The probes are shielded so that they cannot interfere with the components of the UUT while one component is under test.
The flying probe tester checks for component values, shorts, and opens. The flying probe tester also has a camera to find missing components. Cameras are used to verify component shapes, such as polarised caps.
Flying probe testers can probe UUTs accurately thanks to their probe positioning accuracy and high repeatability. The flying probe test solves many problems in PCB assembly. For example, test development cycles can take 4-6 weeks.
The flying probe test is a way to check the electrical functionality of a PCB (open and short circuit testing). A flying probe tester can test PCBs within a manufacturing environment. Flying probe testing replaces the bed-of-nails interface used on traditional in-circuit test equipment with four to eight probes controlled independently, moving toward the tested component. The unit under testing (UUT) is transported by belt or another UUT conveyor to the tester. After being fixed, the tester probes will contact the test pads and pass through holes to test each unit component under testing (UUT). Drivers (signal generators and power supplies) are connected to the test probes. Transducers (digital meters, frequency counters, etc.) and drivers (signal generators, power supplies, etc.), are connected to test probes via a multiplexing system. Multiplexing is used to test the components of the UUT. The probe shields the UUT from interference while one component on the UUT is being tested.
1. Charge/discharge time method
The test steps consist of the following: first board, full open circuit test; second board, full short-circuit testing, and network value learning. Finally, the resistance test is used to check the suspected short-circuit location. This test method has the advantage that it is highly accurate and reliable. The disadvantage is that there are many return tests, and the test efficiency does not work well.
2、Inductance measurement method
Inductance measurements are made using large antennas (usually the ground network). Other networks will detect a certain inductance. The tester measures the inductance of each network and compares it to the value. A possible short circuit exists if the values are the same for each network. The tester then performs a test to check for a short circuit. This method can only be used to test the board with a grounding electrical layer if it is unreliable.
3、Capacitance measurement technique
This method is similar to the charge/discharge time method. According to the law governing conductive graphics and capacitance, when you place a reference plane and set the distance L of the conductive graphic and the area A of the conductive graphic, C = eA/L. When there is an open circuit, the area of the conductive graph decreases, and the capacitance decreases. It is shown that there are open circuits; if there are two parts of the conductive graphic connected to the capacitance, the response increases, indicating that there is a short circuit. In the open-circuit test, the capacitance value of the endpoints of the same network should be equal; if not identical, an open circuit exists, and the capacitance value of each network is a comparison of the short-circuit test. This method has the advantage of high test efficiency. The disadvantages are entirely dependent on capacitance. Capacitance is also affected by many factors. Test reliability is lower than resistance methods, particularly the associated or secondary capacitance due to measurement error.
