PCB News - Some features of PCB reliability

Some features of PCB reliability

At first glance, the PCB board looks the same regardless of its quality. It is through appearance that we can see the differences, and these differences are crucial to the durability and function of the PCB throughout the lifetime. Whether in the production assembly process or in practice, PCB must have a reliable function, which is very important. In addition to related costs, shortcomings in the assembly process may be brought into the final product by the PCB, and faults may occur in the process of practical application, leading to claims. Therefore, from this point of view, it can be said without exaggeration 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 this type of failure 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 still worth the money in the long run. Let's take a look at the 14 most important features of high-reliability circuit boards:

1. 25 micron hole wall copper thickness

advantage:

Enhance the reliability, including the ability to improve the swelling resistance of the z-axis.
The dangers of not doing this:
Hole blowing or degassing, electrical connectivity problems in the assembly process (inner layer separation, hole wall fracture), or problems may occur under load conditions during practical use. IPCClass2 (the norm used by most factories) rules copper plating to be 20% less.

2. No welding repair or open circuit repair line repair

advantage:
Perfect circuit can ensure reliability and safety, no repair, no danger
The danger of not doing so
If the correction is improper, the circuit board will be broken. Even if the correction is ‘appropriate’, under load conditions (oscillations, etc.) there will be a risk of malfunction, and then malfunctions may occur in practice.

3. Exceeding the cleanliness requirements of IPC specifications

advantage
Improving the cleanliness of PCB printed boards can improve reliability.
The danger of not doing so
Residues and solder accumulation on the circuit board will bring dangers to the solder mask. Ionic residues will cause corrosion and contamination of the soldering surface, and then may cause reliability problems (bad solder joints/electrical problems), and eventually add practical problems. Probability.
4. Strictly control the service life of each appearance treatment
advantage
Solderability, reliability, and reduce the risk of moisture invasion
The danger of not doing so
Because the surface treatment of old circuit boards will undergo metallographic changes, soldering problems may occur, and moisture aggression may cause problems such as delamination, inner layer and hole wall separation (open circuit) during the assembly process and/or practical application. .
5. Use world-famous substrates-do not use "local" or do not know the brand
advantage
Improved reliability and known functions
The danger of not doing so
Poor mechanical performance means that the circuit board cannot perform its expected function under assembly conditions. For example, high swelling function can cause delamination, disconnection and warpage problems. Weakened electrical characteristics can lead to poor impedance performance.
6. The public service of copper clad laminate meets the requirements of IPC4101ClassB/L
advantage
Strictly controlling the thickness of the dielectric layer can reduce the error of the expected value of the electrical function.
The danger of not doing so
Electrical functions may not meet the requirements of the rules, and the same batch of components will have large differences in output/function.
7. Define solder mask materials to ensure compliance with IPC-SM-840ClassT requirements
advantage
"Excellent" ink, complete the ink safety, ensure that the solder mask ink meets UL specifications.
The danger of not doing so
Inferior inks 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. Under-insulation properties can cause short circuits due to accidental electrical continuity/arc.
8. Defining the shape, holes and other mechanical features of the public service
advantage
Strict control of public service can improve the scale and quality of products-improve cooperation, appearance and function
The danger of not doing so
Problems in the assembly process, such as alignment/cooperation (the problem of pressing the needle will only be discovered when the assembly is completed). In addition, because of the increased dimension error, it will be problematic to install the base.
9. Requirements for the thickness of the solder mask, although IPC has no relevant rules
advantage
Improve the electrical insulation characteristics, reduce the risk of falling off or loss of adhesion, and strengthen the ability to resist mechanical impact-no matter where the mechanical impact occurs!
The danger of not doing so
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. Due to the thin solder resist layer, the insulation characteristic is insufficient, which can cause a short circuit due to accidental conduction/arc.
10. Appearance requirements and repair requirements are defined, although IPC does not define
advantage
Careful care and careful care during the production process ensure safety.
The danger of not doing so
A variety of scratches, minor injuries, repairs and repairs-the circuit board can be used but not beautiful. In addition to the problems that can be seen on the outside, what are the invisible dangers, the impact on the assembly, and the dangers in practical use?
11. Requirements for the depth of the plug hole
advantage
High-quality plug holes will reduce the risk of failure in the assembly process.
The danger of not doing so
The chemical residues in the gold-immersion process can remain in the hole that is not full of the plug hole, and then problems such as solderability can be caused. In addition, tin beads may be hidden in the holes. In assembly or practical use, the tin beads may splash out and form a short circuit.

12. Specify the brand and type of peelable blue glue

advantage
The designation of peelable blue glue prevents the use of "local" or cheap brands.
The danger of not doing so
Inferior or cheap peelable glue may foam, melt, crack or solidify like concrete during the assembly process, and then make the peelable glue unable to peel off/not working.
13. Perform specific approval and ordering procedures for each acquisition order
advantage
The implementation of this procedure can ensure that all specifications are now recognized.
The danger of not doing so
If the product specifications are not carefully recognized, the resulting errors may not be discovered until the assembly or the final product, and then it is too late.
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