14 important features of high reliability PCB

- May 15, 2020-

14 important features of high reliability PCB

 

At first glance, PCB is almost the same on the surface regardless of its internal quality. It is through the surface that we see the differences that are critical to the durability and functionality of the PCB throughout its life.

 

Whether in the manufacturing and assembly process or in actual use, PCB must have reliable performance, which is very important. In addition to the related costs, defects in the assembly process may be brought into the final product by PCB, and faults may occur in the actual use process, leading to claims. Therefore, from this point of view, it can be said that the cost of a high-quality PCB is negligible. In all segments, especially those producing products in key application areas, the consequences of such failures are unimaginable.

 

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

 

Benefits:

 

Increased reliability, including improved z-axis expansion resistance.

 

Risk of not doing so:

 

Electrical connectivity problems (inner layer separation, hole wall fracture) in the process of blowing or degassing and assembly, or failure may occur under load conditions in actual use. Ipcclass2 (the standard used in most factories) requires less than 20% 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, the circuit board will open. Even if the repair is "proper", there will be a risk of failure under load conditions (vibration, etc.), which may lead to failure in actual use.

 

3. Exceeding the cleanliness requirements of IPC

 

benefit

 

Improving PCB cleanliness can improve reliability.

 

Risk of not doing so

 

The accumulation of residue and solder 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 joints / electrical faults), and ultimately increase the probability of actual faults.

 

4. Strictly control the service life of each surface treatment

benefit

 

Solderability, reliability and reduced risk of moisture intrusion

 

Risk of not doing so

As the surface treatment of the old circuit board will change metallographically, there may be solderability problems, while moisture intrusion may lead to delamination, inner layer and hole wall separation (open circuit) and other problems in the assembly process and / or actual use.

 

5. Use of internationally renowned base materials - do not use "local" or unknown brands

benefit

Improve reliability and known performance

 

Risk of not doing so

 

Poor mechanical performance means that the circuit board cannot perform its expected performance under assembly conditions. For example, high expansion performance may cause delamination, open circuit and warpage problems. The weakening of electrical characteristics can lead to poor impedance performance.

 

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

 

benefit

 

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

 

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 greatly different.

 

7. Define welding materials to ensure they meet the requirements of ipc-sm-840classt

 

benefit

 

"Excellent" ink to achieve ink safety and ensure that the solder mask ink meets UL standard.

 

Risk of not doing so

 

Poor quality ink can lead to adhesion, flux resistance and hardness problems. All of these problems will lead to solder mask separation from the circuit board, and eventually lead to copper circuit corrosion. Poor insulation can cause short circuits due to unexpected electrical continuity / arcing.

 

8. Tolerances defining shapes, holes and other mechanical features

 

benefit

 

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

 

Risk of not doing so

 

Problems during assembly, such as alignment / fit (press fit pins will only be found after assembly). In addition, as the size deviation increases, there will be problems in mounting the base.

 

9. Thickness requirements for solder mask, although not specified by IPC

 

benefit

 

Improve electrical insulation, reduce the risk of flaking or loss of adhesion, and enhance the ability to resist mechanical impact - no matter where it occurs!

 

Risk of not doing so

 

Thin solder mask can cause adhesion, flux resistance and hardness problems. All of these problems will lead to solder mask separation from the circuit board, and eventually lead to copper circuit corrosion. Poor insulation due to thin solder mask, short circuit due to unexpected conduction / arc.

 

10. Visual and repair requirements are defined, although IPC does not

 

Benefit

 

In the manufacturing process, we carefully care and carefully create safety.

 

Risk of not doing so

 

A variety of scratches, minor injuries, repairs and repairs - circuit boards work but don't look good. Besides the problems that can be seen on the surface, what are the risks that can't be seen, as well as the impact on the assembly, and the risks in actual use?

11. Requirements for plug hole depth

 

benefit

 

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

 

Risk of not doing so

 

If the plug hole is not enough, the chemical residue in the process of gold deposition can be left in the hole, resulting in solderability and other problems. In addition, tin beads may be hidden in the hole. During assembly or actual use, tin beads may splash out, causing short circuit.

 

12. Specify the brand and model of peelable blue glue

 

benefit

 

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

 

Risk of not doing so

 

Poor or cheap peelable adhesive may blister, melt, crack or set like concrete during assembly, so that the peelable adhesive will not peel / work.

 

13. Perform specific approval and order placement procedures for each purchase order

 

benefit

 

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

 

Risk of not doing so

 

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

 

14. Sheathing with scrap units is not acceptable

 

benefit

 

Not using partial assembly can help customers improve efficiency.

 

Risk of not doing so

Special assembly procedures are required for the defective cover plate. If the x-out is not clearly marked or it is not isolated from the cover plate, it is possible to assemble the known damaged plate, thus wasting parts and time.

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