Printed Board Product Questions:
When troubleshooting issues with printed board products, it is important to consider potential problems with the PCB product itself. These problems can manifest as warpage, solder mask issues, and irregular characters.
- Warpage: Sometimes, production planners may skip the hot air leveling process and send the product directly to final inspection. However, if the product is not properly heated, it may experience warpage beyond the allowable range for testing equipment. Therefore, the heat leveling process is essential, and testers should add warpage measurement before testing.
- Solder Mask: Products with more open circuits may be unsatisfactory due to some via holes being blocked by the solder mask layer. During testing, it is important to avoid testing transfer holes (or ensure accurate hole guide passage).
- Characters: Many PCB manufacturers print characters first and then measure them electrically. However, if the characters are slightly offset or the accuracy of the character film is insufficient, they may partially cover fine surface stickers and small holes, leading to open circuits. It is therefore more reasonable to electrically measure PCBs with thin surface mounts, small holes (Φ<0.5), and high density of thin lines before printing characters.
Difference between flying probe test and fixture test:
- A flying probe tester uses the capacitance method and moves quickly point by point on the circuit board to complete the test.
- Standard board learning must be carried out first, and the standard value of the capacitance of each network must be read in.
- Capacitance method is used first, and the resistance method is used for accurate confirmation if the measured capacitance is not within the qualified range.
- Four-wire measurement is possible.
- It is only suitable for testing samples with small batches due to its slow test speed.
Advantages and disadvantages:
Advantages: - High test density, with the minimum pitch reaching 0.05mm or even smaller.
- No fixture cost.
Disadvantages: - Test pins are easily damaged.
- Slow test speed.
- Cannot test withstand voltage, with a greater risk for high-level high-density board tests.
