13 test methods commonly used in PCB manufacturing

Printed circuit board (PCB) is widely used in all kinds of electronic equipment. Whether it is mobile phones, computers or complex machines, you can find circuit boards. If the PCB is defective or has a manufacturing problem, it may cause the final product to malfunction and cause inconvenience. In those cases, manufacturers would have to recall the devices and spend additional time and resources fixing the fault.

Therefore, PCB testing has become an indispensable part of the circuit board manufacturing process. It finds the problem in time, assists the staff to deal with it quickly, and ensures the superior quality of PCB.

Here's an Analog Devices-Inc-AD843SQ-883B look at 13 common test methods for PCBS.

1. Online Testing (ICT)

ICT, or Automated Online Testing, is a must-have testing equipment for modern PCB manufacturers and is extremely powerful. It is mainly through the test probe contact PCB layout test points to detect PCBA circuit open, short circuit, all parts of the fault, and definitely inform the staff.

ICT has a wide range of applications, high measurement accuracy, and clear indication of detected problems, making it easy for even workers with average electronic skills to deal with problematic PCbas. The use of ICT can considerably improve production efficiency and reduce production costs.

2. Flying needle test

Flying needle testing is recognized as an effective form of testing along with online testing (ICT), both of which can be effective in detecting manufacturing quality problems, but flying needle testing is proving to be a particularly cost-effective way to improve board standards.

In contrast to the traditional test method, where the test probes are fixed in position, the flying needle test uses two or more independent probes and runs without a fixed test point. The probes are electromechanical and move according to specific software instructions. As a result, the initial cost of flying needle testing is low, and it can be done by modifying the software without changing the fixed structure. By contrast, the initial fixture cost of ICT is higher, thus fly pin testing is cheaper for tiny batch orders, but ICT is faster and less error-prone than fly pin testing, so ICT is still more cost-effective for large batch orders.

3. Functional testing

Functional system test A comprehensive test of the functional modules of the circuit board is performed using special test equipment in the middle and end of the production line to confirm the quality of the circuit board. There are two main functional tests: Final Product Test and Hot Mock-up.

Instead of providing in-depth data (for example, pin location and component-level diagnostics) to improve the process, functional testing typically requires specialized equipment and specially designed testing procedures. Writing functional test programs is complex and therefore not applicable to most circuit board lines.

4. Automatic Optical Inspection (AOI)

AOI uses either a single 2D camera or two 3D cameras to take pictures of the PCB and then compares the board pictures with detailed schematics. If the circuit board does not match the schematic to a certain extent, it will mark the mismatch of the circuit board for inspection by technical personnel, AOI can detect the fault in time.

However, AOI detection will not supply power to the circuit board and cannot detect all components 100%. Therefore, AOI is commonly used in combination with other test methods. Commonly used test combinations are:

AOI and flying needle
AOI and Online Testing (ICT)
AOI and functional testing

5. X-ray test

X-ray test, that is, X-ray test, it uses low-energy X-ray to quickly detect the circuit board open circuit, short circuit, air welding, welding leakage and other problems.

X-ray is mainly used to detect defective circuit boards with ultra-fine spacing and ultra-high density, as well as defects such as bridging, chip missing and dislocation generated during assembly. It can also use tomography to detect internal defects in IC chips. This is the only way to test the bonding quality of the grid array and the solder ball. The main advantage is that BGA solder quality and embedded components can be checked without the cost of fixtures.

6. Laser detection

This is the latest development in pcb testing technology. It scans the printed board with a laser beam, collects all the measurements, and compares the actual measurements with preset acceptance limits. The technology has been proven on bare plates and is being considered for assembly plate testing. That's good enough for a mass production line. ​Quick output, no fixture, visual smooth is its main advantage; ​high initial cost, maintenance and usage problems are the main disadvantages.

7. Aging test

​The Aging test refers to the process of strengthening the corresponding conditions of the aging of the product by simulating various factors involved in the actual use conditions. The purpose is to test the stability and reliability of the product in a specific environment.

According to the design requirements, the product will be placed under the specific temperature and humidity conditions, continuous simulation work 72 hours to 7 days, record the performance data, reverse push the production process to improve, to ensure that its performance to meet the market demand. A burn-in test normally refers to an electrical performance test. Similar tests include drop tests, vibration tests, and salt spray tests.

In addition to the above seven tests, additional testing methods are used to additionally ensure PCB quality based on product requirements. As follows:

8. Solderability test: Ensure the surface is strong and increase the chance of forming a reliable solder joint

9. PCB contamination test: Detect large quantities of ions that can contaminate the board and cause corrosion and other problems

10. Microscopic section analysis: Investigate defects, open circuit, short circuit and other faults

11. Time domain reflectometer (TDR): The fault of high-frequency plate was found

12. Peel test: Find the strength measurement required to peel the laminate from the board

13. Float welding test: Determine the level of thermal stress that PCB holes can resist

PCBA testing is a necessary process that, if done properly, can prevent quality problems from damaging the brand reputation at the time of product launch.

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