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PCB/PCBA knowledge
5 Methods To Teach You How To Waterproof Your PCBA Boards(1)

A PCBA board fails to take effect has several reasons. Among those reasons, water vapor and humidity are also one of key factors. The insulation resistance performance can be greatly impacted if the circuit board is placed and saved in the environment with serious water vapor and humidity conditions. Even worse, it might intensifies the process of corrode conductors and circuit board components.

Thus, in this passage, we are going to introduce 5 methods to waterproof for PCBA boards.

Table of Contents

Before showing 5 methods to waterproof PCBA boards, we can know something about waterproof PCB first.

Through coating the PCB with a water-resistant sealant, waterproof printed circuit board (PCB) is able to withstand extreme temperatures and humidity, and even chemical exposure. There are 5 ways to waterproof the PCBA boards.

Tip for how to waterproof the circuit boards
Tip for how to waterproof the circuit boards

structural waterproofing

As the initial method used for PCBA waterproof in the electronics industry, its main waterproof concept is “hydrophobic”, that is, engineers think of strengthening the airtightness of its own shell, so that it can be effectively isolated from the internal components, and prevent water vapor, molecules, ions, etc. from entering the interior. The design of the abrasive tool of the product needs to spend more thought on its sealing. In the structural design of natural products, the selection of materials must be carefully considered. Its cost will inevitably increase accordingly.

  • Practical analysis

Different types of products require corresponding structures to open molds separately. The general mold opening fee is not cheap, which further increases the cost. For some small companies, the order quantity of a single product is small, and then open The cost burden accounts for a large proportion, and the gain outweighs the gain.

Moreover, if a specific waterproof structure is applied to some areas with large temperature difference between morning and evening and high humidity, and the principle of thermal expansion and contraction, the gap between the appearance of the waterproof shell will be deformed accordingly, and water vapor will more easily enter the interior, causing damage to the circuit board. corrosion.

  • Advantages and disadvantages of circuit board structure waterproof

Advantages: The structure of the product used in ordinary environments has a good waterproof effect.

Disadvantages: The structure has the risk of being deformed. It is more susceptible to environmental influences in harsh environments such as acids, alkalis, and neutral salt spray.

Potting waterproof

Potting waterproof -Epoxy resin potting glue
Potting waterproof -Epoxy resin potting glue

Epoxy resin potting glue is commonly used to potting waterproof, which is used to pot electronic product modules, and wrap the entire PCBA board. Make the circuit board waterproof, moisture-proof, acid-base salt corrosion-proof, mold-proof, and can also play the role of shock resistance and external impact. It can be used in combination with the waterproofing of the product structure, and can play a double protective role in some specific application environments.

  • Practical analysis

With good thermal thermal conductivity of the potting compound, it is beneficial for heat dissipation of power type circuit board after potting. However, after the circuit board is potted, it might make the EMI conductive shielding materials become larger.

In terms of electricity, the engine, power system module, brake system module, and various connectors of automotive electronics can play their role, and can also be used in the power supply industry.

  • Advantages and disadvantages of potting waterproof

Advantages: good waterproof effect, excellent thermal conductivity

Disadvantages: expensive, not easy to repair; not suitable for precision components

Nano-waterproof liquid coating

Nano-waterproof liquid coating - simple operation, curing at room temperature
Nano-waterproof liquid coating – simple operation, curing at room temperature

The nano-waterproof liquid coating forms an ultra-thin ultra-hydrophobic waterproof gas film on the surface of the PCBA of electronic products, which can penetrate the nano-liquid into the tiny gaps of electronic components by soaking to achieve complete coverage and encapsulation. Then the whole PCBA board can get a comprehensive and three-dimensional waterproof effect.

  • Advantages and disadvantages of circuit board nano-waterproof liquid coating method

Advantages: simple operation, curing at room temperature, no need to increase equipment investment, no vacuum environment

shortcoming:

1) Suggestion: The choice of nano-waterproofing liquid is very important. The price of various nano-waterproofing coatings on the market varies greatly, and of course the performance also varies greatly. This requires our manufacturers to test more products of the same type, compare performance, and choose quality Excellent nano coating.

2) Common liquid coating materials include polyurethane, epoxy resin, UV glue, silicone, and acrylic. These liquid coatings form a protective layer on the surface of the workpiece by spraying or artificial brushing.

In the process, it is easy to block the small pores, generate air bubbles, thicker thickness, uneven thickness, etc., so that it cannot be changed. Good to achieve the effect of three defenses.

Three anti-paint waterproof

Three anti-paint waterproof - coating and curing a layer of adhesive film on the board
Three anti-paint waterproof – coating and curing a layer of adhesive film on the board

Conformal paint is also called insulating paint, and moisture-proof paint. Through coating and curing a layer of adhesive film on the PCBA to prevent moisture and corrosion. However, the film is formed by three anti-paint waterproof can only protect moisture. So, if the circuit board is completely immersed under the water, it definitely fails to normal work.

Three anti-paint waterproof is not resistant to falling and vibration, and easy to peel off under the external impact. Under some situation, its protection function for PCBA is limited. And it is hard to check whether it is evenly coated.

  • Advantages and disadvantages of circuit board three anti-paint

Advantages: low cost
Disadvantages: uneven thickness of anti-paint film, insufficient coverage of the edge part, unbearable shrinkage pressure of thermal hardening, not environmentally friendly

Parylene nano-coating protection

Parylene nano-coating - a good moisture-proof, mildew-proof, anti-salt spray coating materials
Parylene nano-coating – a good moisture-proof, mildew-proof, anti-salt spray coating materials

The parylene coating film is made by a unique vacuum vapor deposition process. It is kind of conformal polymer film coating that is constructed by active small molecules on the substrate surface. The 0.1-100 micron film coating prepared by deposition at room temperature is uniform in thickness, dense and pinhole-free, transparent and stress-free. Beside, it also has excellent electrical insulation and protection. It is a good moisture-proof, mildew-proof, anti-salt spray coating materials.

  • Advantages of Parylene nano-coating protection

(1)Because it is formed under vacuum conditions, it can be applied to different shapes surface, such as edges with sharp angle and cracks.

Since it is formed under vacuum conditions, the biggest feature of this process is “pervasive”, which can be applied to surfaces of various shapes, including sharp edges, cracks and inner surfaces.

2)Provide pinhole-free parylene coating protection layer
The parylene deposition process is to heat and vaporize the xylene ring dimer and then crack it into free gas phase molecules at high temperature, and instantly adsorb on the substrate to form a film under vacuum and room temperature conditions. Then it can form a nice airtight protective film.

Solvent fails to be contained in paint that it can better solve the drawback which inevitably leave fine pinholes because of the solvent volatilization during the drying process. Thus, it can provide the pinhole-free protective film.

3)Independent protection performance + overall protection performance
Under the room temperature, the parylene coating film is deposited with active monomers and double radicals. The monomers sink and attach to the substrate in advance, then each monomer of active bonds are bonded. At last, they forms a whole film layer.

Coating layer plays as an independent protection point. When some part of the coating layer is damaged, the protection performance of its surrounding layers won’t be greatly affected. At the same time, each point of the coating layer passes through Chemical bonds link together to form a whole, which enhances its protective performance.

Difference in film thickness uniformity between parylene coating and common coating

Difference in film thickness uniformity between parylene coating VS common coating
Difference in film thickness uniformity between parylene coating VS common coating
Differences/Types Ordinary coating Parylene nano coating
Film thickness The thickness of the film is uneven and the shape changes. The film thickness is uniform and the shape is the same.
Coverage area The edge part, the coverage area is not enough. Good coverage around
Shrinkage pressure The shrinkage pressure of thermal hardening cannot bear. Constant room temperature without any shrinkage pressure.

Conclusion

To sum up, the waterproof technology of several mainstream PCBA boards in the market can enhance the durability of electronic products through effective waterproof technology, greatly prolong the service life of electronic products, and enhance the market competitiveness of products.

FAQ

Water causes short circuits in electronics and changes the connectivity among circuits.

  1. Epoxy (commonly used)
  2. Silicone
  3. Urethane 
  4. Acrylic
  5. Para-xylylene 
  6. Fluoropolymer 
  1. The nature of the product, your budget, and your requirements.
  2.  A decent PCB design is needed. And PCB designers should strictly check to ensure the circuit complies with best practices. 

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