What should you know about conformal coatings applied to PCB

2018-11-23 17:54Writer: qyadminReading:

    What is Conformal Coating?

  Conformal coating is a type of coating with special ingredients, used to protect circuit boards and concerning equipment from erosion finally to prolong products' shelf life and guarantee Printed Circuit Boards' (PCBs) security and reliability. Conformal coating features high capability withstanding high temperature and low temperature. It'll become a transparent protective film after solidification, featuring excellent merits including insulation, moistureproof, anti-creeping, shakeproof, dust proof, anti-corrosion, anti-aging, corona resistance etc.
  The reason for the existence of conformal coating lies in the fact that PCB boards possibly suffer from issues like erosion, softening, deformation or mould in practical environment that perhaps embraces chemical, vibration, high-dust, salt fog, moisture and extremely high temperature all of which will possibly lead circuit boards to suffer from defects or failure.

 Why is Conformal Coating a Must-Be for PCBs?

  Based on the definition and brief introduction on conformal coating, it is easy to summarize that the key role conformal coating plays in PCB manufacturing process lies in its protective function as moisture resistance, waterproof, insulation etc. The reason why conformal coating is a must-be for PCBs is so obvious but a little complex since it is related with so many elements and a couple of them will be discussed in detail in this part.

  a. Moisture

  Moisture is the commonest and destructive factor causing damage to PCB boards. Too much moisture will dramatically decrease insulation resistance and the value of Q, accelerate high-speed decomposition, and get conductors eroded. It's common for us to see metal parts that have been assembled on PCB board is covered with a layer of green copper just because chemical action just takes place between copper and water vapor and oxygen.

  b. Pollutant

  It's hardly believe that hundreds of pollutants can be found on the surface of printed circuit boards when conformal coating isn't applied on them. Those pollutants are equivalently hazardous to the reliability and functionality of PCBs. Similar with moisture or high humidity, pollutants contaminated on circuit boards can also lead to bad results such as electronic failure, conductor erosion, or even irretrievable shortcuts. Majority of contaminants left on circuit boards derive from residues during manufacturing process including flux, solvent parting agent, clipped wire and marking ink. Moreover, some contaminants result from manual residue when boards are touched by operating people including human oil, finger print, cosmetics and food residue. Plus, lots of pollutants even come from operating environment, such as salt spray, sand soil, fuel, acid and other erosive vapor and mould.
  Nevertheless, those pollutants can be greatly cut by effective measures that can be made during PCB fabrication process. New technologies can be used to optimize manufacturing process to cut down the number of chemical residues on circuit boards. Rigorous operating principles can be set up and conformed to and operation engineers are trained to be compatible with all requirement of scientific manufacturing. For example, when operators are required to wear gloves when holding boards in hand, no fingerprints will be left on them.
  When conformal coating is used on the surface of circuit board or components, if negative factors in operation environment take the leading role, conformal coating is capable of reducing or eliminating electronic operating deterioration. As long as conformal coating is able to take hold for such a satisfying time period like longer than life time of final products, conformal coating will be believed to take its full responsibilities. Even though conformal coating is just a thin layer, it is able to excellently withstand mechanical vibration, thermal shock and high-temperature operations.
  One point should be noticed that it's a myth that conformal coating is capable of making components being with stronger mechanical strength or sufficient conductivity. Fixation of components depends on mechanical method with joint mixture while conformal coating won't help.

 
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