At the first glance of PCB, regardless of the intrinsic quality, from the surface they are similar. It is through the surface, we see the differences, and these differences are very crucial to the durability and function of PCB in the whole life
Whether in the PCB manufacturing process and assembly process or in actual use, PCB should have a reliable performance, which is crucial. In addition to theassociated costs , the defects in assembly process may be brought into the final product by the PCB, and can cause failure in actual use and then lead to the claim. Therefore, from this point of view, it is no exaggeration to say that the cost of a high-quality PCB is negligible. In all market segments, especially the market production of key application areas, the consequences of such a failure would be unthinkable and terrible.
Compare PCB price, we should keep in mind these aspects. Although initial cost of reliable, guaranteed , long-life products is higher, but it’s worthy in the long term or value. Here take a look at top 10 of the most important features of high reliability printed circuit boards:
1. Hole wall copper thickness 25 um
Benefits:
Enhance reliability, including the ability to improve the resistance to expansion of the z-axis.
The risk of not doing so:
Electrical connectivity problems (inner layer separation, the hole walls rupture) in the assembly process , or being damaged in actual use under load conditions. IPC Class2 (most PCB manufacturers apply this standard) prescribs to 20% less with 20um.
2. No weld repair or line breaking up repair
Benefits:
Perfect circuits ensure reliability and security, no maintenance, no risk
3. Beyond the IPC cleanliness requirements specification
Benefit:
The improvement of PCB cleanliness can improve the reliability.
The risk of not doing so
The residue on the circuit board, the solder resist accumulation would pose a risk to the welding surface, ionic residues can cause solder surface corrosion and contamination risks, which may lead to reliability problems (bad solder joint / electrical failures) and eventually increase the probability of actual fault.
4. Strict control of the life of every kind of surface treatment
Benefit:
Solderability, Reliability, and reduce the risk of moisture intrusion
The risk of not doing so
Since the surface treament of the old circuit board occurs metallurgical changes, which is possible to cause soldering problems, and moisture intrusion may lead to delamination, the separation (disconnection) of inner layer and the hole wall, and other issues during the PCB assembly process.
5. Use internationally renowned base material but local or unknown brand
Benefit:
Improve the reliability and known performance
The risk of not doing so
Poor mechanical properties mean that the circuit board can not play the expected performance in the assembled condition, such as: high expansion will lead to delamination, breaking and warping problems. Weaken the electrical characteristics can lead to poor impedance performance.
6. CCL tolerances in accordance IPC4101ClassB / L requirements
Benefit
Strict control of the thickness of the dielectric layer can reduce the expected value deviation of the the electrical performance.
The risk of not doing so
Electrical performance may not meet requirements, the same batch of components will have a quite difference in the output and performance.
7. Defining solder resistance material, to ensure compliance with the requirements of IPC-SM-840 Class T
Benefit
NCAB Group has endorsed the “excellent” ink, to ensure that the solder resist ink according to UL standards.
The risk of not doing so
Poor quality ink can cause adhesion, hardness and resistance to anti-flux problem. All of these issues will lead to the printed circuit board from the solder resist layer, and eventually lead to corrosion of the copper circuit. Poor insulation characteristics can cause a short circuit due to accidental electrical connectivity / arc.
8. Defining the tolerance of the shape, holes and other mechanical characteristics
Benefit
Strictly control the size tolerances can improve PCB product quality – Improve fitness, outline and function
The risk of not doing so
Assembly process problems, such as alignment / fitness (only when assembled will find press-fit pin problems). Further, since the size deviation is increased, there will be problems of loading dock.
9, Specify the thickness of solder resist layer, although no relevant provisions of IPC
Benefit
Improved electrical insulating properties, reducing the risk of peeling or loss of adhesion to strengthen the ability to against the wherever mechanical impact force
The risk of not doing so
Thin solder can lead to adhesion, hardness and resistance to anti-flux problem. All of these issues can result in solder resist layer seperated from the printed circuit board, and eventually lead to corrosion of the copper circuit. and also cause poor insulation properties.
10. Specify the plug hole depth requirements
Benefit
High quality hole plug will reduce the risk of failure in the PCB assembly process.
The risk of not doing so
The unfilled plug holes may remain chemical residues in the immersion gold process, resulting in weldability and other issues. And the holes may contain tin balls, during the assembly or practical use, the solder balls may splash out and cause short circuits.