PCB News - Features of high reliability PCB

Features of high reliability PCB

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

benefit

Improve 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.

2. 25 micron hole wall copper thickness

benefit

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

The risk of not doing so

Blow holes or degassing, 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 PCB factories) requires 20% less copper plating.

3. No welding repair or open circuit patching repair

benefit

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

The risk of not doing so

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.

4. Requirements for the depth of the plug hole

benefit

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

The risk 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, 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.

5. Cleanliness requirements beyond 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 ultimately increase the occurrence of actual failures Probability.

6. Implement specific approval and order procedures for each purchase order

benefit

The execution of this procedure ensures that all specifications have been confirmed.

The risk of not doing so

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

7. Strictly control the service life of each surface treatment

benefit

Solderability, reliability, and reduce the risk of moisture intrusion

The risk of not doing so

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. .

8. 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 the expected electrical performance.

The risk of not doing so

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

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

benefit

Recognize "excellent" inks, realize ink safety, and ensure that solder mask inks meet UL standards.

The risk 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. Poor insulation properties can cause short circuits due to accidental electrical continuity/arc.

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

benefit

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

The risk of not doing so

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 into the base.

11. Lianshuo Circuits specifies the thickness of the solder mask, although IPC does not have relevant regulations

benefit

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 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. Poor insulation properties due to the thin solder mask can cause short circuits due to accidental conduction/arc.

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

benefit

Careful care and carefulness in the manufacturing process create safety.

The risk of not doing so

Various 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?

13. Do not accept boards with scrapped units

benefit

Not using partial assembly can help customers improve efficiency.

The risk of not doing so

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.

14. 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.

The risk of not doing so

Inferior or cheap peelable glue may foam, melt, crack or solidify like concrete during the assembly process, making the peelable glue unable to peel off/not working