PCBMASTER ------ A Deep Dive into the Application and Challenges of Bead Probe Technology in the PCB Process

Author: Jack Wang

1. PCBA electronics manufacturing trends

In the field of PCBA (Printed Circuit Board Assembly) electronic product manufacturing, electronic devices are developing towards miniaturization and high performance. The component density on circuit boards is increasing, and the space is becoming more compact. Take the mobile phone board as an example. Test points with no practical functions are often abandoned. Some enterprises believe that if the circuit board assembly quality is good, subsequent power testing is not necessary. At the same time, the integrated circuit packaging technology is constantly innovating. After BGA (Ball Grid Array) packaging, new packaging forms such as QFN (Quad Flat No - leads) have emerged. The communication module is often integrated on a small circuit board, and the finished product factory solders it to the main circuit board as an SMT (Surface Mount Technology) component.

2. Comparison between traditional ICT and beaded probe technology

Traditional ICT (In - Circuit Test) uses pointed probes to contact circular test points to form a test loop. The test points need to occupy a large area, have high requirements for positioning accuracy, and take up a lot of circuit board space.

In contrast, the bead probe technology works in the opposite way. By printing solder paste on the test points to make them protrude higher, and using large - diameter flat - head probes (50, 75, 100 mils) to increase the contact probability, similar to hammering a nail, it can efficiently achieve test connections.

3. Practical application of bead probe technology

However, this technology has many problems in practical applications. The residual magnetic flux of PCB wiring is likely to cause poor contact between the probe and the test point. Therefore, many probe manufacturers have developed new - type probes specifically for the bead probe technology to improve the contact performance. The accuracy of the solder - paste printing process is crucial. Compared with tin - lead solder paste, lead - free solder paste has poor cohesion, which puts forward higher requirements for solder - paste printing. Because the amount of solder paste printed on the test point directly determines the solder height. If the solder height is insufficient, the misjudgment rate of ICT testing will increase significantly. The deviation of solder - paste printing thickness should be controlled within ±5μm. The width of PCB wiring also has an impact. If the wiring width is too small, the wiring is likely to be accidentally pushed away due to insufficient adhesion when the probe contacts or is affected by other external forces. It is generally recommended that the minimum wiring width be more than 5 mils. Although there are successful cases of 4 - mil wiring, due to its small width, the false - alarm rate of ICT testing is relatively high. To improve reliability, the wiring width can be appropriately increased, and green solder mask can be used to cover it to enhance the firmness of the wiring. In terms of high - frequency performance, whether the application of bead probe technology will introduce capacitance effects or antenna effects, thereby affecting the high - frequency performance of electronic products, is a highly concerned issue.

Currently, neither tests nor customer feedback have shown such problems. However, as the working frequency of electronic products continues to increase, continuous attention and in - depth research are still needed. In terms of reliability, no obvious problems have been found after 200 - cycle tests, which to some extent proves the reliability of this technology under normal use conditions. However, considering the complex use environment of electronic products and the requirements for long - term stability, more environmental simulation tests and long - term reliability research still need to be carried out.

In conclusion, the bead probe technology brings new ideas to PCB testing. However, to achieve wide application, the above - mentioned technical problems need to be solved.

If you are troubled by the application of bead probe technology, PCBMASTER can provide you with professional solutions. We have an experienced technical team that can accurately address problems such as PCB wiring and solder - paste printing, and customize efficient testing solutions for you, helping you break through technical bottlenecks and improve production efficiency and product quality.

Author: Jack Wang