Double Probe vs Flying Probe Test Method
The flying probe test method does not rely on a fixed pin pattern on a fixture or bracket. Instead, it utilizes two or more probes mounted on a magnetic head that can freely move on the x-y plane. Test points are generated directly from CADI Gerber data control.
Advantages of Flying Probe Testers
- Probes can move independently within a 4 mil distance, without limits to proximity.
- Tester is based on capacitance measurement, detecting short or open circuits.
- Flexible testing approach suitable for complex circuit boards with lower yields.
Factors to Consider in Tester Selection
- Test speed: Needle bed tester is faster for testing thousands of points simultaneously.
- Cost: Needle bed tester may cost 20-30% less for single-sided testing.
- Efficiency: Flying probe tester handles only two or four test points at a time.
Testing Equipment for PCB Boards
For bare board testing, specific instruments are available. Using a general-purpose instrument initially more expensive than a dedicated one can reduce individual configuration costs in the long run.
Grid Selection for Test Pads
- Standard Grid: 2.5mm grid for boards with pin components and surface mount equipment.
- Imm Grid: Test pads larger than 0.7mm are recommended to prevent damage to test needles.
Combining a universal tester with a flying probe tester ensures accurate and economical inspection of high-density circuit boards. Another method is using a conductive rubber tester to detect grid deviations, although varying pad heights may affect test point connections.
Testing Levels
- Bare board inspection
- Online testing
- Function detection
Universal testers can accommodate various circuit board styles and special applications, making them versatile for different testing needs.
