PCB News - 14 important features of high-reliability PCB​

14 important features of high-reliability PCB

Regardless of the internal quality of the PCB, the surface is almost the same. 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.

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 failures 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 those that produce products in key application areas, the consequences of such failures are disastrous.

These aspects should be kept in mind when comparing PCB prices. 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 micron hole wall copper thickness

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

Risks of not doing so: blow 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

Benefits: perfect circuit can ensure reliability and safety, no maintenance, no risk

The risk of not doing this: If the repair is not done properly, it will cause the circuit board to open. 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. Exceeding the cleanliness requirements of IPC specifications

Benefit: Improving PCB cleanliness can increase reliability.

The risk of not doing so: 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 Eventually increase the probability of actual failure.

4. Strictly control the service life of each surface treatment

Benefits: solderability, reliability, and reduce the risk of moisture intrusion

The risk of not doing this: due to the metallographic changes in the surface treatment of the old circuit boards, soldering problems may occur, and moisture intrusion may cause delamination, inner layers and hole walls during the assembly process and/or actual use Separation (open circuit) and other issues.

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

Benefit: Improved reliability and known performance

The risk of not doing so: 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

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

The risk of not doing this: the electrical performance may not meet the specified requirements, and there will be large differences in output/performance of the same batch of components.

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

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

The risk of not doing so: 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 accidental electrical continuity/arc.

8. Defining the tolerances of shapes, holes and other mechanical features

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

The risk of not doing this: problems in the assembly process, such as alignment/fitting (only when the assembly is completed will the press-fit needle problem be found). 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

Benefits: Improve the 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!

The 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

Benefits: Careful care and carefulness in the manufacturing process create safety.

The risk of not doing this: multiple scratches, minor injuries, 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 the depth of the plug hole

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

The risk of not doing so: The chemical residue in the gold deposit process can remain in the hole that is not full of the plug hole, which will 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

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

Risk of not doing so: Inferior or cheap peelable glue may blisters, 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

Benefits: The implementation of this program can ensure that all specifications have been confirmed.

The risk of not doing this: If the product specifications are not carefully confirmed, the resulting deviation may not be discovered until the assembly or the final product, and it will be too late at this time.

14. Do not accept boards with scrapped units

Benefits: Not using partial assembly can help customers improve efficiency.

Risk of not doing so: All defective boards require special assembly procedures. If the scrap unit board (x-out) is not clearly marked, or it is not isolated from the board, it is possible to assemble this board. Known bad board, thus wasting parts and time. (Explained by PCB manufacturer)