High reliability PCB circuit board has 14 obvious characteristics

Date：2022-04-08 15:02:40Views：850

Whether in the manufacturing and assembly process or in practical use, PCB should have reliable performance, which is very important. In addition to the relevant costs, the defects in the assembly process may be brought into the final product by the PCB, and faults may occur in the actual use process, resulting in claims. No matter what the internal quality of PCB is, it is almost the same on the surface. It is through the surface that we can see the differences, and these differences are crucial to the durability and function of PCB in the whole life. Let's take a look at the 14 obvious features of high reliability PCB circuit board:

1. 25 micron hole wall copper thickness

Benefits: increased reliability, including improved expansion resistance of the z-axis.

Risks of not doing so:

Electrical connectivity problems during hole blowing or degassing and assembly (inner layer separation, hole wall fracture), or faults may occur under load conditions during actual use.

Ipcclass2 (the standard adopted by most factories) requires 20% less copper plating.

2. No welding repair or open circuit repair

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

Risks of not doing so:

If not repaired properly, the circuit board will be open circuit.

Even if the repair is' proper ', there is a risk of failure under load conditions (vibration, etc.), which may occur in actual use.

3. Exceeding the cleanliness requirements of IPC specification

Benefits: improving PCB cleanliness can improve reliability.

Risks of not doing so:

The residue and solder accumulation on the circuit board will bring risks to the anti welding layer, and the ion residue will lead to the risk of corrosion and pollution on the welding surface, which may lead to reliability problems (bad solder joint / electrical failure) and finally increase the probability of actual failure.

4. Strictly control the service life of each surface treatment

Benefits: Solderability, reliability, and reduced risk of moisture intrusion.

Risks of not doing so:

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

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

Benefits: improved reliability and known performance.

Risks of not doing so:

Poor mechanical performance means that the circuit board cannot perform as expected under assembly conditions.

For example, high expansion performance will lead to delamination, open circuit and warpage. The weakening of electrical characteristics can lead to poor impedance performance.

6. The tolerance of copper clad laminate shall meet the requirements of ipc4101classb / L

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

Risks of not doing so:

The electrical performance may not meet the specified requirements, and there will be great differences in output / performance of the same batch of components.

7. Define welding resistance materials to ensure compliance with ipc-sm-840classt requirements

Benefits: NCAB Group recognizes "excellent" ink, realizes ink safety, and ensures that the solder resist ink meets UL standards.

Risks of not doing so:

Poor quality inks can cause adhesion, flux resistance and hardness problems.

All these problems will lead to the separation of the solder resist from the circuit board and eventually lead to copper circuit corrosion.

Poor insulation characteristics can cause short circuits due to unexpected electrical connectivity / arcing.

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

Benefits: strict tolerance control can improve the dimensional quality of products - improve fit, shape and function.

Risks of not doing so:

Problems during assembly, such as alignment / fit (the problem of press fit needle will be found only when the assembly is completed).

In addition, due to the increase of dimensional deviation, there will be problems in installing the base.

9. NCAB specifies the thickness of solder resist layer, although IPC has no relevant provisions

Benefits: improved electrical insulation properties, reduced risk of spalling or loss of adhesion, and enhanced resistance to mechanical impact – wherever mechanical impact occurs.

Risks of not doing so:

Thin solder resist layer can lead to adhesion, flux resistance and hardness problems.

All these problems will lead to the separation of the solder resist from the circuit board and eventually lead to copper circuit corrosion.

Poor insulation characteristics due to thin resistance welding layer can cause short circuit due to accidental conduction / arc.

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

Benefits: careful care and care in the manufacturing process create safety.

Risks of not doing so:

A variety of scratches, minor injuries, repairs and repairs - circuit boards work but don't look good.

In addition to the problems that can be seen on the surface, what are the invisible risks, the impact on the assembly and the risks in actual use

11. Requirements for plug hole depth

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

Risks of not doing so:

Chemical residues in the gold precipitation process may remain in the holes with insufficient plug holes, resulting in problems such as weldability.

In addition, there may be tin beads hidden in the hole, which may splash out during assembly or actual use, resulting in short circuit.

12. Specify the brand and model of peelable blue glue

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

Risks of not doing so:

Inferior or cheap strippable glue may bubble, melt, crack or solidify like concrete during assembly, so that the strippable glue cannot be peeled off / ineffective.

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

Benefits: the implementation of this procedure can ensure that all specifications have been confirmed.

Risks of not doing so:

If the product specification is not carefully confirmed, the resulting deviation may not be found until the assembly or final product, and then it is too late.

14. Sheathed plates with scrapped units are not acceptable

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

Risks of not doing so:

Special assembly procedures are required for defective sheathed boards. If the scrapped unit board (x-out) is not clearly marked or isolated from the sheathed board, it is possible to assemble this known bad board, thus wasting parts and time.

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