Fourteen important features of high reliability PCB

Fourteen important features of high reliability PCB

 At first glance, the PCB is similar in appearance regardless of its inherent quality. It is through the surface that we see the differences that are critical to the durability and functionality of the PCB throughout its lifetime.

    Whether it is in the manufacturing assembly process or in actual use, it is essential that the PCB has reliable performance. In addition to the associated costs, defects in the assembly process may be carried into the final product by the PCB, and failure may occur during actual use, resulting in a claim. Therefore, from this point of view, it is no exaggeration to say that the cost of a good quality PCB is negligible.

    In all market segments, especially those that produce products in critical applications, the consequences of such failures are unimaginable.

    These aspects should be kept in mind when comparing PCB prices. Although the initial cost of a reliable, guaranteed, and long-life product is high, it is worth the money in the long run.

    14 most important features of high reliability boards

    1, 25 micron hole wall copper thickness

    Benefits: Enhanced reliability, including improved z-axis resistance to expansion.

    Risk of not doing so

    Blowing or degassing, electrical connectivity problems during assembly (inner layer separation, hole wall fracture), or failure under load conditions in actual use. IPCClass2 (the standard used in most plants) requires 20% less copper plating.

    2, no welding repair or open circuit repair

    Benefits: Perfect circuit ensures reliability and safety, no maintenance, no risk

    Risk of not doing so

    If it is not repaired properly, it will cause the board to open. Even if the repair is 'proper', there is a risk of failure under load conditions (vibration, etc.), which may cause malfunction in actual use.

    3. Exceeding the cleanliness requirements of the IPC specification

    Benefits: Improve PCB cleanliness to increase reliability.

    Risk of not doing so

    Residues and solder deposits on the board pose a risk to the solder mask. Ion residues can cause corrosion and contamination risks on the solder surface, which can lead to reliability issues (bad solder joints/electrical faults) and ultimately increase the actual fault occurrence. Probability.

    4. Strictly control the service life of each surface treatment

    Benefits: solderability, reliability, and reduced risk of moisture intrusion

    Risk of not doing so

    Due to metallographic changes in the surface treatment of old boards, soldering problems may occur, and moisture intrusion may cause delamination, separation of inner layers and walls (opening) during assembly and/or actual use. .

    5. Use internationally renowned substrates – do not use “local” or unknown brands

    Benefits: Improve reliability and known performance

    Risk of not doing so

    Poor mechanical properties mean that the board does not perform as expected under assembly conditions. For example, high expansion performance can cause delamination, open circuit, and warpage problems. Impaired electrical characteristics can result in poor impedance performance.

    6. Cladding tolerance meets IPC4101 Class B/L requirements

    Benefits: Strict control of the dielectric layer thickness can reduce the expected deviation of electrical performance.

    Risk of not doing so

    Electrical performance may not meet the specified requirements, and the output/performance of the same batch of components will vary greatly.

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

    Benefits: NCAB Group recognizes “excellent” inks for ink safety and ensures solder mask inks meet UL standards.

    Risk of not doing so

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

    8. Define tolerances for shapes, holes and other mechanical features

    Benefits: Strict control of tolerances can improve the dimensional quality of the product – improved fit, shape and function

    Risk of not doing so

    Problems during assembly, such as alignment/mating (the problem of press-fitting the needle is only found when the assembly is complete). In addition, there is a problem in mounting the base due to an increase in dimensional deviation.

    9. NCAB specifies the thickness of the solder mask, although IPC has no relevant regulations.

    Benefits: Improve electrical insulation properties, reduce the risk of flaking or loss of adhesion, and strengthen the ability to withstand mechanical impact – no matter where the mechanical impact occurs!

    Risk of not doing so

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

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

    Benefits: Care and careful care in the manufacturing process.

    Risk of not doing so

    A variety of scratches, minor injuries, repairs and repairs – the board can be used but not good looking. In addition to the problems that the surface can see, what are the invisible risks, the impact on assembly, and the risks in actual use?

    11, the requirements for plug depth

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

    Risk of not doing so

    The chemical residue in the immersion gold process may remain in the hole that is not filled with the plug hole, thereby causing problems such as solderability. Moreover, tin beads may be hidden in the holes, and the solder balls may splash out during assembly or actual use, causing a short circuit.

    12, PetersSD2955 specified peelable blue plastic brand and model

    Benefit: The designation of peelable blue glue avoids the use of "local" or cheap brands.

    Risk of not doing so

    Inferior or inexpensive peelable glue may foam, melt, crack or solidify like concrete during assembly, so that the peelable glue cannot be peeled off/inactive.

    13. NCAB performs specific approval and order procedures for each purchase order.

    Benefits: The execution of this program ensures that all specifications have been confirmed.

    Risk of not doing so

    If the product specifications are not carefully confirmed, the resulting deviation may not be discovered until assembly or final product, and it is too late.

    14. Do not accept sets of boards with scrapped units

    Benefits: Failure to use partial assembly can help customers improve efficiency.

    Risk of not doing so

    A defective assembly requires special assembly procedures. If the x-out is not clearly marked or is not isolated from the panel, it is possible to assemble the known bad plate. Waste parts and time.