Corrosives on a PCB – Protect your PCB

Corrosion is one of the major enemies of all things made of metal. Everything from Cars, to satellites orbiting Earth, to printed circuit boards are affected by corrosion. Whether you are on ground level, under it, or even in space, corrosion will prove to be a problem for anything made of certain metals. Corrosion occurs when oxygen and metal bond with each other, this process is called oxidation. This produces rust and it also causes the metal to lose its chemical properties which over times breaks it down. Printed circuit boards are mostly made of metal and like everything else around us, they are exposed to oxygen. Eventually, like most metals, printed circuit board’s will corrode. At Bittele Electronics, we work hard to assist our customer to keep their boards rust free and functioning at high levels for as long as possible.

There are several methods in which corrosion can affect your printed circuit boards. These types of corrosions are known as Atmospheric, Fretting, Galvanic, and Electrolytic. Atmospheric corrosion is the most common and standard type of corrosion that occurs. Metals that are exposed to moisture cause the metal ions to bind with oxygen atoms. Copper is one of those metals that is highly susceptible to atmospheric corrosion due to its chemical structure. This is a problem for copper's electrical conductivity which makes it a big issue for printed circuit boards in the long run. Fretting corrosion occurs when the surface oxide layer is removed by the action of closing solder-plated switches, and this will allow the layer beneath to oxidize. Galvanic corrosion is caused by electrolyte being present between two different types of metals in the presence of it. This method of corrosion affects metal that is more resistant to rust than it does metals that are traditionally more susceptible. For example, when gold is in contact with tin in the presence of an electrolyte, the gold will corrode faster than usual, despite gold being one of the more rust resistive material. Electrolytic corrosion is the type of corrosion when there is metal degradation. Metal degradation occurs when metal slivers are created by traces experiencing dendrite growth when ionic contaminated moisture infects the electrical voltage between the traces. Metal slivers can result in short circuits.

Unfortunately, it is impossible to avoid corrosion all together, but you can delay it and extend the life of your printed circuit board. There are several steps you can take to assist you in the battle against rust. The first and most important step is to keep your printed circuit boards clean and dry. This will help ensure you avoid ionic contamination. Printed circuit board components being exposed to moisture with ionic contamination is one of the most common causes of corrosion in printed circuit boards. Sealed enclosures or regular maintenance should be considered to ensure your board stays clean and dry.

Another important step to consider is how your PCBs are fabricated. Ensure your fabricators will operate in a dry and clean environment. The quality and care the fabricator provides your board will play a major role in its potential life. That is why it is important to work with printed circuit board fabricators such as Bittele Electronics who take quality and care of your board seriously. Using a manufacturer who guarantees quality, clean and dry environment is an important step in finding a manufacturer partner that will deliver you a printed circuit board that won’t be hindered from the start.

There are PCBs being designed specifically for environments where keeping them clean and dry won’t be possible. Some boards are being manufactured for agricultural, under water, automotive, or other uses where the boards will be regularly exposed to moisture and dirt regularly. In these situations, it is difficult to maintain boards cleanliness and reduce moisture contact. If possible, consider a sealed enclosure to ensure board and components have as much protection as possible.

HASL and Gold Immersion (ENIG) are two of the most common finishes used for printed circuit boards. HASL uses a corrosive flux to prepare the surface, which will not help corrosion susceptibility. Gold does not react with oxygen, which means it will not rust or corrode over time. Gold Immersion (ENIG) will protect your printed circuit boards surface. Gold Immersion (ENIG) also makes for a higher quality finish and look. Another advantage for Gold Immersion (ENIG) surface finish is, it is easy to clean and maintain. RO water rinsing will typically be sufficient enough in cleaning and maintaining boards with Gold Immersion (ENIG) finishes. Unfortunately, most printed circuit board manufacturers choose to charge customers additional charge to upgrade to Gold Immersion (ENIG) from HASL. At Bittele Electronics, we do not charge our customers extra for Gold Immersion (ENIG) finish.

Another option for boards that will be exposed is a conformal coating. Conformal coating can provide great protection but If it is not applied perfectly, it will increase corrosion probability. Conformal coating needs to be applied with perfect coverage. Any bubbles, cracks, or breaks will significantly increase corrosion probability for your board and components. This is where once again, having a manufacturer with high quality and one that is dependable becomes important again. There 4 commonly used conformal coating types, they are Acrylic Resin, Epoxy, Polyurethane, Silicone Type. You need to know or ensure your manufacturer is aware of the proper coating for your board, based on the material, components, and environment it will be exposed to. By selecting the proper conformal coating, applying it consistently and error-free will ensure your board gets the protection it needs.

Keeping printed circuit board’s corrosion free varies from simply keeping your boards clean and dry, Gold Immersion (ENIG) surface finish, or to a more serious measures such as enclosures and conformal coating. Taking these steps doesn’t guarantee your board will never be affected by corrosion but rather extend the life of your board. Bittele Electronics can provide you with an excellent print circuit board that is manufactured to highest quality standards and will give you the advantage you need in your efforts to prolong the life of your printed circuit board.


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