PCB Technical - ​PCBA processing products, PCB product testing methods

The current PCB product testing methods mainly include the following five types:

1. Manual visual test

Manual visual testing is to confirm the placement of electronic components on the PCB circuit board through human vision and comparison. This technology is one of the most widely used online testing methods. But with the increase in output and the shrinking of PCB circuit boards and electronic components, this method is becoming less and less applicable. Low upfront cost and no test fixture are its main advantages; at the same time, high long-term cost, discontinuous defect detection, difficulty in data collection, no electrical testing and visual limitations are also the main disadvantages of this method.

2. Automated Optical Inspection (AOI)

This test method is also called automatic visual test. It is usually used before and after reflow. It is a newer method of confirming manufacturing defects. It has a better effect on the polarity of components and the existence of components. It is a non-electrical, fixture-free online technology. Its main advantages are easy follow-up diagnosis, easy program development, and no fixtures; the main disadvantages are poor short-circuit recognition, and it is not an electrical test.

3. Functional Test

Functional testing is the earliest automatic testing principle. It is a basic testing method for a specific PCB or a specific unit, which can be completed with various test equipment. Functional testing mainly includes final product test (Final Product Test) and the latest entity model (Hot Mock-up).

4. Flying-Probe Tester

Flying probe tester is also called probe tester, and it is also a commonly used test method. Due to advances in mechanical accuracy, speed, and reliability, it has been generally welcomed in the past few years. In addition, the current requirements for a test system with fast conversion and no fixture capabilities required for prototype manufacturing and low-volume manufacturing make flying probe testing the best choice. The main advantage of the flying probe tester is that it is the fastest Time To Market tool, with automatic test generation, no fixture cost, good diagnosis and easy programming.

5. Manufacturing Defect Analyzer (MDA)

MDA is a good tool for only diagnosing manufacturing defects in high-volume/low-mix environments. The main advantages of this PCB test method are low initial cost, high output, easy follow-up diagnosis and fast and complete short-circuit and open-circuit tests; the main disadvantage is that functional tests cannot be carried out, usually there is no test coverage indication, fixtures must be used, and test costs higher.

Disadvantages of FPC soft and hard composite board

After the supplier’s introduction, it is generally understood that if the "flexible and rigid composite board" is simply compared with the "flexible board + circuit board + connector", the biggest disadvantage is that the "flexible and rigid composite board" is more expensive. It is possible that the price of the original "soft board + hard board" will be nearly doubled, but if the price of the connector or the cost of HotBar is deducted, the price may tend to be the same, and the detailed cost may have to be Only after actuarial calculations will have a clearer outline. Another disadvantage is that smt patching and heating may need to use a carrier to support the part of the soft board, which virtually increases the assembly cost of SMT.

Advantages of FPC soft and hard composite board

In addition to the price, the use of Rigid-flex Board has many advantages, as listed below:

1. It can effectively save the space on the circuit board and eliminate the use of connectors or HotBar processes

Because the soft and hard boards have been combined, the space that originally needed to use the connector or HotBar process can be saved. For some boards with high-density requirements, losing a connector space is like picking up It's like a piece of treasure.

In this way, it also saves the cost of parts using the connector or the cost of the HotBar process. In addition, the space between the two boards can be made tighter by eliminating the need for connectors.

2. The signal transmission distance is shortened and the speed is increased, which can effectively improve the reliability

The traditional signal transmission through the connector is "circuit board-connector-soft board-connector-circuit board", while the signal transmission of the flexible and hard composite board is reduced to "circuit board-soft board-circuit board", signal transmission The distance between different media is shortened, and the problem of signal transmission attenuation between different media is also reduced. Generally, the circuit on the circuit board is made of copper, while the contact terminal of the connector is gold-plated, and the solder pin is fully tin-plated. Moreover, solder paste is required to be soldered on the circuit board, and the signal transmission between different media will inevitably be attenuated. If you switch to a flexible and hard composite board, these media will become less and the signal transmission ability can be relatively improved., For some products that require higher signal accuracy, it helps to improve their reliability.

3. Simplify product assembly and save assembly man-hours

The use of flexible and hard composite boards can reduce the man-hours for SMT parts, because the number of connectors is reduced. It also reduces the man-hours for assembly of the whole machine, because it eliminates the assembly action of inserting the soft board into the connector, or eliminates the HotBar manufacturing process. It also reduces the cost of parts management and inventory, because the BOM is reduced, so the management becomes less.