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14 Important Features of the High Reliability PCB

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At first glance, PCB is almost the same regardless of its internal quality. It isthrough the surface that we see differences, which are critical to thedurability and function of the PCB throughout the lifespan.

Whetherit is in the manufacturing assembly process or in actual use, PCB should have areliable performance, which is critical. In addition to the relevant costs, theassembly process defects may be brought into the final product by PCB, in theactual use of the process may occur failure, resulting in claims. Therefore,from this point of view, it can be said without saying that the cost of a pieceof high-quality PCB is negligible. In all segments of the market, especially inthe production of key applications in the market, the consequences of suchfailures will be disastrous. 

Whencomparing PCB prices, these aspects should be kept in mind. Although theinitial cost of reliable, guaranteed and long-life products is high, it isstill good value in the long run. Here's a look at 14 of the most importantfeatures of highly reliable PCB boards:

1. 25 um copper thickness of holewall

Benefits:

Enhancedreliability, including improved the expansion resistance ability of the Z axis.

The risk of not doing it:

Theproblem of electrical connectivity in hole blowing ordegassing, assembly (internal separation, hole wall fracture), or failure mayoccur in actual use under load conditions. IPCClass2 (the standard adopted bymost factories) requires less than 20% copper plating. 

2. No welding repair or open circuitrepair

Benefits:

Perfectcircuitry ensures reliability and safety, no maintenance, no risk

The risk of not doing it

Ifrepaired improperly, the circuit board will be broken. Even if repairedproperly, there will be a risk of failure in the load conditions (vibration,etc.), which may lead to failure in actual use.

3. Beyond the IPC specificationcleanliness requirements

Benefit

ImprovePCB cleanliness can improve reliability.

The risk of not doing it

Theresidue and solder accumulation on the board will bring risks to the SM layer,and the ion residue will lead to the corrosion and pollution risk of thewelding surface, which may lead to the reliability problem (bad solder joint /electrical fault), and finally increase the probability of the actual fault. 

4. Strictly control the service lifeof each surface finish.

Benefit

Solderability,reliability, and reduce the risk of tidal intrusion

The risk of not doing it

Becauseof the metallographic change of the surface finish of the old board, thesolderability may occur, and the moisture intrusion may lead to delamination,inner layer and hole wall separation (circuit breaker) in the assembly processand / or actual use. 

5. The use of internationallyrenowned substrate - does not use the "local" or unknown brand

Benefit

Improvingreliability and known performance

The risk of not doing it

Poormechanical performance means that the board can not perform the desiredperformance under assembly conditions. For example, higher expansionperformance can lead to delamination, open circuit and warpage problems. Theweakening of electrical characteristics leads to poor impedance performance. 

6. Copper clad plate tolerance meetsIPC4101ClassB/L requirements

Benefit

Strictlycontrolling the thickness of dielectric layer can reduce the expected deviationof electrical performance.

The risk of not doing it

Theelectrical performance may not meet the specified requirements, and the outputand performance of the same components will vary greatly. 

7. Define the solder material to meetthe requirements of IPC-SM-840ClassT

Benefit

"Excellent"ink, to achieve the safety of ink, to ensure that the solder resist ink meetsthe UL standard.

The risk of not doing it

Poorquality ink can cause adhesion, flux resistance and hardness. All of theseproblems lead to the separation of the solder layer from the circuit board, andeventually lead to copper circuit corrosion. Poor insulation performance cancause short circuit by the unexpected conduction / arc. 

8. Define tolerances of profile, holeand other mechanical features

Benefit

Stricttolerance control can improve the dimensional quality of products - improvementof fit, profile and function

The risk of not doing it

Assemblyproblems, such as alignment / fit (only when assembly is finished will be foundwith pressure matching pins). In addition, due to the size deviation increases,there will be problems with the base. 

9. The thickness of the solder maskrequirements, although IPC has no relevant provisions

Benefit

Improvethe electrical insulation characteristics, reduce the risk of spalling or lossof adhesion, and strengthen the ability to fight the mechanical impact -regardless of where the mechanical impact occurs!

The risk of not doing it

Solderthin layer can lead to adhesion, flux resistance and hardness problems. All ofthese problems lead to the separation of the solder layer from the circuitboard, and eventually lead to copper circuit corrosion. Because of the thin SMlayer, the insulation property is not good, and the short circuit can be causedby the unexpected conduction / arc. 

10. Define the appearance and repairrequirements, although IPC is not defined

Benefit

Careand careful creat safety in the manufacturing process.

The risk of not doing it

Avariety of scratches, small damage, repair - circuit board can be used, but notgood-looking. 

11. The hole depth requirement

Benefit

Highquality plug hole will reduce the risk of failure in the assembly process.

The risk of not doing it

Chemicalresidue in the process of ENIG remains in the plug-failure hole, resulting insolderability problems. And the hole may also be in possession of solder ball,assembly or actual use, solder may splash out, causing a short circuit. 

12. Specify the brand and model ofPeelable blue mask

Benefit

Thedesignation of Peelable blue mask can avoid the use of "local" orcheap brands.

The risk of not doing it

Inferioror cheap brands can be foamed, melted, broken or solidified like concrete inthe process of assembly, so that the Peelable blue mask can not peel off / notwork. 

13. Perform specific approval andsingle order procedures for each purchase order

Benefit

Theexecution of the program ensures that all specifications have been confirmed.

The risk of not doing it

Ifthe product specifications are not carefully recognized, the resultingdeviation may be found at the end of the assembly or final product, and then itis too late. 

14. Do not accept scrap board

Benefit

Nonlocal assembly can help customers improve efficiency.

The risk of not doing it

Specialassembly procedures are required for defective panels. It is possible toassemble the known broken plate and waste parts and time if it is not clearlyindicated the scrap board (x-out) or is not isolated from the cover plate.


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