This paper briefly introduces the 14 important features of PCB.

PCB, regardless of internal quality, is similar on the surface, and it is through the surface that we see the difference, which is critical to the durability and function of the PCB throughout its life.

Here are 14 of the most important features of a highly reliable circuit board:

1. The hole wall of 25 microns is thick.

Benefits: enhanced reliability, including improved z-axis capacity for expansion.

The risk of not doing so: the problem of electrical connectivity in the blow hole or degassing, the assembly process (the inner separation, the fracture of the hole wall), or the possibility of failure in the actual use of the load condition.IPCClass2 (the standard used in most factories) requires less than 20% copper plating.

2. No welding repair or circuit repair.

Benefits: the perfect circuit ensures reliability and safety, no maintenance, no risk.

The risk of not doing so: if the repair is not correct, the circuit boards will be broken.Even if properly repaired, there is a risk of failure in the load condition (vibration, etc.), which may cause a failure in actual use.

3. Exceed the cleanliness requirements of the IPC specification.

Benefits: increased PCB cleanliness improves reliability.

Do not risk: residue on the PCB, solder accumulation will pose a risk to prevent welding layer, ionic residue can lead to welding surface corrosion and pollution risks, which could cause reliability problems (poor solder joints/electrical fault), and eventually increase the probability of actual fault.

4. Strictly control the service life of each surface treatment.

Benefits: solder, reliability, and reduce the risk of moisture intrusion.

Do not risk: because the old circuit board surface treatment metallographic happens, possible soldering problem, while the moisture intrusion can lead to and/or in the actual use in the assembly process layer, the inner layer and separation of hole wall (break).

5. Use international famous materials -- do not use "local" or unknown brands.

Benefits: improved reliability and known performance.

The risk of not doing this: poor mechanical performance means that the PCB fails to perform the desired performance under assembly conditions, for example, high expansion performance leads to layering, breaking and warping.Weak electrical characteristics can lead to poor impedance performance.

6. Copper plate tolerance meets the requirements of IPC4101ClassB/L.

Advantages: strict control of dielectric thickness can reduce the expected deviation of electrical performance.

Risk of not doing this: electrical performance may not meet the required requirements, and the same batch of components will differ greatly in output/performance.

7. Define resistance welding materials to ensure compliance with ipc-sm-840classt requirements.

Advantages: "fine" ink, to realize the ink security, to ensure that the soldering layer ink meets the UL standard.

Risk of not doing this: poor quality ink can cause adhesion, flux resistance and hardness.All of these problems lead to the separation of the solder layer and the circuit board, and eventually lead to the corrosion of the copper circuit.The insulation characteristics may be short circuited due to unexpected electrical connectivity/arc.

8. Define the tolerance of appearance, hole and other mechanical characteristics.

Advantage: strict control tolerance can improve the product's dimension quality - improve coordination, appearance and function.

The risk of not doing this: problems in the assembly process, such as alignment/coordination (only when the assembly is complete will you find the problem of pressing the needle).In addition, due to the larger size deviation, mount the base will also have problems.

9. The thickness of the resistance welding layer is required, although the IPC has no relevant provisions.

Benefits: improve electrical insulation, reduce the risk of flaking or loss of adhesion, and enhance the ability to resist mechanical impact - no matter where the mechanical impact occurs!

The risk of not doing this is that the resistance of the soldering layer can lead to adhesion, flux resistance and hardness.All of these problems lead to the separation of the solder layer and the circuit board, and eventually lead to the corrosion of the copper circuit.The insulation property is not good due to the thin layer of resistance welding, which can cause the short circuit due to unexpected conduction/arc.

10. The appearance requirements and repair requirements are defined, although IPC is not defined.

Benefits: carefully and carefully molded in the manufacturing process.

The risk of not doing this: multiple abrasions, minor injuries, repairs and repairs - the circuit boards can be used but not pretty.In addition to the seemingly obvious issues, what are the unseen risks, the impact on assembly, and the risks in actual use?

11. Requirements for plug depth.

Benefits: high quality plug holes reduce the risk of failure during assembly.

The risk of not doing this: the chemical residues in the process of sinking gold can be found in the perforated hole of the plug hole, resulting in solderability and other problems.It may also contain tin beads, which can be splatched and short-circuited during assembly or actual use.

12. Specify the brand and model of the blue glue.

Benefits: the designation of bluestone can avoid the use of "local" or cheap brands.

The risk of not doing this: poor or cheap removable glue can bubble, melt, break, or solidify like concrete in the process of assembly, thus making it impossible to peel and unpeel.

13. Perform specific approval and ordering procedures for each purchase order.

Benefits: the execution of this program ensures that all specifications have been identified.

The risk of not doing so: if the product specification is not carefully identified, the resulting deviation may be found only when the assembly or final product is assembled, and then it is too late.

14. Do not accept sets of scrap units.

Benefits: not using local assembly can help customers improve efficiency.

Don't do that: the risk of defective boards require special assembly procedures, if not clearly indicate the scrapped unit board (x - out), or is not isolated from the set of samples, it could be assembled this known bad board, thereby waste parts and time.

It is important that PCB has reliable performance, whether in manufacturing assembly processes or in actual use.In addition to the relevant costs, defects in the assembly process may be brought into the final product by PCB, which may fail during actual use, leading to claims.Therefore, from this point of view, it can be said that the cost of a high-quality PCB is negligible.In all segments of the market, particularly in the production of key applications, the consequences of such failures are dire.