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PCB circuit board reliability identification method and characteristics 时间:【2018-08-21】 共阅【443】次 【打印】【返回

PCB no matter what the internal quality is, it is almost the same on the surface. It is through the surface that differences can be seen, and these differences are critical to the durability and functionality of the PCB throughout its life. It is very important for PCB circuit boards to have reliable performance both in assembly process and in practical use.In addition to the related costs, defects in the assembly process may be brought into the final product by the PCB, and may occur during actual use. The consequences of such failures are unimaginable in all segments of the market, especially those producing products in critical applications. These aspects should be kept in mind when comparing PCB prices. Although reliable, guaranteed and long-lived products have higher initial costs, they are worth it in the long run.


PCB circuit board without welding repair or circuit repair repair.

Benefit

Perfect circuits ensure reliability and safety, no maintenance, no risk.

Risk

If the repair is not proper, the circuit board will be broken. Even if repaired properly, under load conditions (vibration, etc.) there will be a risk of failure, which may occur in actual use.


Cleanliness requirements beyond IPC specification

Benefit

Improving PCB cleanliness can improve reliability.

Risk

The accumulation of residue and solder on PCB will bring risks to the weld-proof layer. Ionic residue will lead to corrosion and contamination of the weld surface, which may lead to reliability problems (bad solder joints/electrical faults) and ultimately increase the probability of actual faults.


25 micron hole wall copper thickness

Benefit

Enhance reliability, including improving the Z shaft's expansion resistance.

Risk

Electrical connectivity problems in the process of blowing or degassing, assembling (inner separation, hole wall fracture), or in actual use under load conditions may occur. IPCClass2 (the standard adopted by most factories) requires less than 20% copper plating.


Strictly control the service life of each surface treatment.

Benefit

Solderability, reliability, and reduce the risk of moisture intrusion.

Risk

As the surface treatment of the old PCB will change the metallographic phase, soldering problems may occur, and moisture intrusion may lead to delamination, inner layer and hole wall separation (circuit breaking) and other problems in the assembly process and/or in actual use.


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

Benefit

Improving reliability and known performance

Risk

Poor mechanical performance means that PCBs fail to perform as expected under assembly conditions, such as delamination, circuit breakage and warpage due to higher expansion performance. The weakening of electrical properties can lead to poor impedance performance.


Copper clad laminate tolerance meets IPC4101ClassB/L requirements.

Benefit

Strict control of dielectric thickness can reduce the expected deviation of electrical performance.

Risk

Electrical performance may not meet the specified requirements, and the output and performance of the same components will be quite different.


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

Benefit

NCAB group recognised "excellent" ink to ensure ink safety and ensure that the solder resist ink meets the UL standard.

Risk

Poor quality ink can cause adhesion, flux resistance and hardness. All these problems will lead to the separation of the solder resist from the PCB and eventually lead to corrosion of the copper circuit. Poor insulation characteristics can cause short circuit due to accidental electrical connectivity / arcing.


Tolerance for defining shape, hole and other mechanical characteristics

Benefit

Strict control of tolerances can improve product size and quality - improve coordination, shape and function.

Risk

Problems in the assembly process, such as alignment / fit (pin press problems are found only when the assembly is complete). In addition, due to the increase of size deviation, there will be problems with loading base.

NCAB specifies the thickness of solder mask, although IPC has no relevant requirements.

Benefit

Improve electrical insulation, reduce the risk of spalling or loss of adhesion, and enhance the ability to withstand mechanical shocks - wherever mechanical shocks occur!

Risk

The thin layer of solder resist can cause adhesion, flux resistance and hardness. All these problems will lead to the separation of the solder resist from the PCB and eventually lead to corrosion of the copper circuit. Due to the thin solder layer and poor insulation, it can cause short circuit due to accidental conduction / arc.


The requirements for appearance and repair were defined, although IPC did not define it.

Benefit

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

Risk

Various abrasions, minor injuries, repairs and repairs - circuit boards can be used but are not good looking. What are the unseen risks, as well as the impact on the assembly, and the risks in actual use, in addition to the apparent problems?


Requirements for depth of plug holes

Benefit

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

Risk

The hole in the hole with holes can remain residue in the process of sinking gold, resulting in solderability. In addition, tin beads may be hidden in the holes. In assembly or practical use, tin beads may splash out, causing a short circuit.


PetersSD2955 specifies the brand and model of stripped blue adhesive.

Benefit

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

Risk

Poor or or inexpensive strippable glue may foam, melt, break or solidify as concrete during assembly, making strippable glue ineffective.


NCAB performs specific approval and order procedures for each purchase order.

Benefit

The execution of the program ensures that all specifications have been confirmed.

Risk

If product specifications are not carefully identified, the resulting deviation may not be detected until assembly or final product, and it is too late.


Do not accept panels with scrap units.

Benefit

Local assembly can help customers improve efficiency without using local assembly.

Risk

Defected boards require special assembly procedures. If the defective boards are not clearly marked out or isolated from the boards, it is possible to assemble the known bad boards, thereby wasting parts and time.

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