How to control the quality of pcb

n the entire production process of the PCB circuit board, there are many quality control points. If it is not rigorous, the quality problem of the PCB line board is endless. This is also a headache, because there is only one of them, so big, so big, so big Most devices are not available. Next, introduce the 9 major quality problems and solutions of the PCB board.

1. [Layers]

Stratification is the difficulty of the boss of PCB, ranking first in common problems. The cause of it may be roughly as follows:
(1) Improper packaging or preservation, moisture;
(2) The preservation time is too long, exceeding the preservation period, and the PCB board is tide;
(3) Supplier’s materials or process issues;
(4) Design materials and copper surfaces are not well distributed.

2. [Poor weld]
Weldability is also one of the more serious issues, especially batch problems. The possible cause is plate surface pollution, oxidation, black nickel, nickel thick abnormalities, anti -welding SCUM (shadow), too long storage time, moisture absorption, PAD on the anti -welding, too thick (repair). The pollution and hygroscopic problems are relatively easy to solve, and other problems are more troublesome, and there is no way to find it through feeding inspection. At this time, it is necessary to pay attention to the process capacity and quality control plan of the PCB board factory. For anti -welding PAD and poor repairs, you need to understand the standards of PCB suppliers on the formulation of maintenance. Inspectors and inspectors have a good assessment system, and at the same time, it is clear that the dense area of the pads cannot be repaired.

3. [Board bending plates]
The reasons that may cause the plate bending plates are: supplier selection problems, abnormal production processes, poor control of heavy labor, improper transportation or storage, not strong enough design of the broken hole, and the differences in copper area of each layer are too large. In the last 2 points, the design of the design needs to be avoided in the early stage. At the same time, the PCB factory simulation stickers IR conditions can be required to test, so as not to occur in the back of the furnace. For some thin plates, you can need to add a wooden slurry plate to the packets when the packaging is used to avoid subsequent deformation. At the same time, add a fixture to prevent the device from overweighting the curved plate.

4, [scrape, dew copper]
Scratches and bronze are the defects that test the management system and execution of the PCB plant. This problem is not serious, but it will indeed bring quality concerns. Many PCB companies will say that this problem is difficult to improve. The author once promoted the improvement of scratches of many PCB factories, and found that many times it is not that it is not good, but whether to change it or not to change it. All PCB factories that seriously promote the project have improved significantly.

5. [Poor impedance]
Impedance is an important indicator of the radio frequency performance of the mobile phone board. Generally, the common problem is that the impedance differences between the PCB batches are relatively large. Since the current impedance test bar is generally on the side of the PCB, it will not ship with the board, so the supplier can pay the batch of impedance strips and test reports for each time they ship. Comparison data of the edge line diameter and the inner line diameter.

6. [BGA welding empty hole]
BGA welded cavities may cause poor main chip function, and may not be found in the test that hidden risks are high. So many patch factories now have X-Ray for inspection after the part. The cause of this kind of bad may occur is the residual liquid or impurities in the PCB hole, vaporization after high temperature, or poor laser hole type on the BGA pad. Therefore, many HDI boards now require electroplating pores or half -filled holes to avoid this problem.

7. [Foam/Show off for anti -welding]
Such problems are usually abnormal in the control of the PCB welding process, or the use of anti -welding ink is not suitable (cheap goods, non -chemical inks, not suitable for installing welded welds), or may be too high in patch and heavy work. To prevent batch problems, PCB suppliers need to formulate corresponding reliability test requirements and control them at different stages.

8. 【Poor Confucius】
Poor holes are mainly caused by insufficient technical capabilities of the PCB plant or simplified technology. Its manifestations are not full of plug holes. It may cause insufficient welding volume, short circuit with patch or assembly devices, and residual impurities in the hole. This problem can be found in the appearance inspection, so it can be controlled by the feeding inspection and requires the PCB plant to improve.

9. [Poor size]
There are many possible reasons for the poor size. It is easy to shrink in the PCB production process. Suppliers have adjusted the drilling program / graphics ratio / molding CNC program, which may cause problems such as biased bias and poor structural parts. Because it is difficult to check such problems, it can only be controlled by the supplier’s good process, so special attention needs to be paid to it when choosing the supplier.