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Key features of high-reliability PCB
PCB News
Key features of high-reliability PCB

Key features of high-reliability PCB

2021-11-11
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Author:Kavie

      At first glance, regardless of the internal quality of the pcb board, it looks the same on the surface. It is through the surface that we see the differences, and these differences are critical to the durability and functionality of the PCB throughout its life.


PCB


   Whether in the manufacturing assembly process or in actual use, PCB must have reliable performance, which is very important. In addition to related costs, defects in the assembly process may be brought into the final product by the PCB, and malfunctions may occur during actual use, leading to claims. 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 markets that produce products in key application areas, the consequences of such failures are unimaginable.


   When comparing PCB prices, these aspects should be kept in mind. Although the initial cost of reliable, guaranteed, and long-life products is high, they are still worth the money in the long run.


  The 14 most important characteristics of high-reliability circuit boards


  1, 25 microns of hole wall copper thickness


  benefit


   Enhance reliability, including improving the expansion resistance of the z-axis.


   risk of not doing this


  Blowing holes or outgassing, electrical connectivity problems during assembly (inner layer separation, hole wall breakage), or failure under load conditions in actual use. IPCClass2 (the standard adopted by most factories) requires 20% less copper plating.


  2, no welding repair or open circuit repair line repair


  benefit


  Perfect circuit can ensure reliability and safety, no maintenance, no risk


   risk of not doing this


  If repaired improperly, the circuit board will be broken. Even if the repair is ‘proper’, there is a risk of failure under load conditions (vibration, etc.), which may cause failure in actual use.


  3. Cleanliness requirements beyond IPC specifications


  benefit


  Improving PCB cleanliness can increase reliability.


   risk of not doing this


Residues and solder accumulation on the circuit board bring risks to the solder mask. Ionic residues can cause corrosion and contamination risks on the soldering surface, which may lead to reliability problems (bad solder joints/electrical failures) and ultimately increase the occurrence of actual failures Probability.


      4. Strictly control the service life of each surface treatment


  benefit


   Solderability, reliability, and reduce the risk of moisture intrusion


   risk of not doing this


Due to the metallographic changes in the surface treatment of old circuit boards, soldering problems may occur, and moisture intrusion may cause problems such as delamination, separation (open circuit) of the inner layer and the hole wall during the assembly process and/or actual use. .


   5. Use internationally renowned substrates-do not use "local" or unknown brands


  benefit


  Improve reliability and known performance


   risk of not doing this


   Poor mechanical performance means that the circuit board cannot perform the expected performance under assembly conditions, for example: high expansion performance will cause delamination, disconnection and warpage problems. Weakened electrical characteristics can lead to poor impedance performance.


  6, the tolerance of the copper clad laminate meets the requirements of IPC4101ClassB/L


  benefit


   Strictly controlling the thickness of the dielectric layer can reduce the deviation of expected electrical performance.


   risk of not doing this


  The electrical performance may not meet the specified requirements, and the output/performance of the same batch of components will be quite different.


  7. Define solder mask materials to ensure compliance with IPC-SM-840ClassT requirements


  benefit


   NCAB Group recognizes "excellent" inks, realizes ink safety, and ensures that solder mask inks meet UL standards.


   risk of not doing this


   Inferior ink can cause adhesion, flux resistance and hardness problems. All these problems will cause the solder mask to separate from the circuit board and eventually lead to corrosion of the copper circuit. Poor insulation properties can cause short circuits due to unexpected electrical continuity/arc.


   8. Define the tolerances of the shape, hole and other mechanical features


  benefit


   Strict control of tolerances can improve the dimensional quality of products-improve fit, shape and function


   risk of not doing this


   Problems in the assembly process, such as alignment/fitting (the problem of the press-fit pin will only be discovered when the assembly is completed). In addition, due to the increased size deviation, there will be problems when installing the base.


 9. NCAB specifies the thickness of the solder mask, although IPC does not have relevant regulations


  benefit


  Improve electrical insulation properties, reduce the risk of peeling or loss of adhesion, and strengthen the ability to resist mechanical impact-no matter where the mechanical impact occurs!


   risk of not doing this


   Thin solder mask can cause adhesion, flux resistance and hardness problems. All these problems will cause the solder mask to separate from the circuit board and eventually lead to corrosion of the copper circuit. Poor insulation properties due to the thin solder mask can cause short circuits due to accidental conduction/arc.


  10. Appearance requirements and repair requirements are defined, although IPC does not define


  benefit


   In the manufacturing process, we take care and make it safe.


   risk of not doing this


  Various scratches, minor damages, repairs and repairs-the circuit board works but doesn't look good. In addition to the problems that can be seen on the surface, what are the invisible risks, the impact on assembly, and the risks in actual use?


  11、Requirements for plug hole depth


  benefit


   High-quality plug holes will reduce the risk of failure during assembly.


   risk of not doing this


  The chemical residue in the gold deposit process can remain in the hole that is not full of the plug hole, which can cause problems such as solderability. In addition, there may be tin beads hidden in the holes. During assembly or actual use, the tin beads may splash out and cause a short circuit.


  12, PetersSD2955 specifies the brand and model of peelable blue glue


  benefit


The designation of  peelable blue glue can avoid the use of "local" or cheap brands.


   risk of not doing this


   Inferior or cheap peelable glue may foam, melt, crack or solidify like concrete during the assembly process, so that the peelable glue cannot be peeled off/doesn't work.


      13. NCAB implements specific approval and ordering procedures for each purchase order


  benefit


   The execution of this program can ensure that all specifications have been confirmed.


   risk of not doing this


   If the product specifications are not carefully confirmed, the deviations caused by this may not be discovered until the assembly or the final product, and it is too late at this time.


  14, do not accept sets of scrap units


  benefit


   Do not use partial assembly can help customers improve efficiency.


   risk of not doing this


Defective boards require special assembly procedures. If it is not clear to mark the scrap unit board (x-out), or if it is not isolated from the board, it is possible to assemble this known bad board. Waste parts and time.

The above is an introduction to the key features of high-reliability PCBs. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology