In the world of industrial automation, we often discuss mechanical failures, failing servo drive bearings, cracked pump shafts, or overheated transistors. However, beneath the surface of every control cabinet, another silent battle is being waged. It's the fight of electronics against its invisible enemies: moisture, chemical fumes, and aggressive production environments. Although PCB boards in automation modules are designed for industrial robustness, their tolerance limits are constantly being pushed.
The reality of production plants often involves dust, chemicals, unstable temperatures, and condensation inside cabinets. As a result, long-term degradation, mistakenly taken for natural wear and tear, leads to sudden and costly downtimes. Understanding the mechanisms by which the environment shortens the life of controllers, inverters, or HMI panels is crucial for maintenance departments. We will show how this silent destroyer works and why professional service fights the cause – corrosion – and not just the effect.
Electrochemical Corrosion and Dendrites
The biggest invisible enemy of industrial electronics is electrochemical corrosion, and its final effect is the formation of dendrites. It starts with moisture, which itself is not the greatest threat. The real problem arises when this water combines with ionic contaminants. These can be residues from improper cleaning, and in industrial environments, primarily salts and acids from the air. This combination creates an electrolyte on the board's surface.
When moisture with contaminants creates a conductive electrolyte on the board, the process of electrochemical corrosion begins. The current flowing through adjacent traces forms a micro-galvanic cell. Metal ions, most often copper, tin, or silver, begin to migrate from an area of higher electrical potential to one of lower potential. In this way, micro-fibers, called dendrites, begin to grow on the surface of the board.
Dendrites are conductive structures resembling miniature tree branches. They grow slowly and continuously. This process can last for months or even years. Eventually, however, dendrites connect two adjacent traces or solder points that should be isolated. This then leads to a micro-short circuit, which causes malfunction or complete failure of the module. This is the most common reason why an element that has been working for years suddenly stops functioning. Professional service must not only replace the damaged component but thoroughly clean the board of these ionic contaminants to stop the growth of dendrites.
Material Degradation
Moisture is dangerous not only because it causes short circuits but also because it physically damages the laminate, which is the material from which the printed circuit board is made. Although industrial laminates are durable, FR-4 material is inherently hygroscopic, meaning it absorbs water like a sponge over time.
When such a moist board is subjected to a rapid temperature increase, for example, during heavy load operation or in an overheated control cabinet, the trapped water expands and evaporates. This causes delamination, which is the separation of connections between laminate layers or the formation of blisters on the surface. This damage is irreversible and can lead to breaks in vias, i.e., holes connecting the layers of the board.
Furthermore, the presence of moisture changes the dielectric parameters and the material's loss tangent. In modern high-speed digital circuits of controllers and drives, this critically affects signal integrity. Communication errors, unstable module operation, or sporadic, difficult-to-diagnose faults often originate from changes in the laminate's electrical characteristics.
Moreover, moisture lowers the glass transition temperature of the laminate. The material then becomes softer and more susceptible to mechanical and thermal stresses. This accelerates the formation of microcracks around solder joints and plated through-holes. This factor is responsible for many component failures whose degradation is undetectable during standard visual inspection.
Chemical Aggression and Industrial Gases
In some specialized environments, the problem is not just water, but the direct action of chemical compounds present in the air. Harmful gases such as hydrogen sulfide, sulfur dioxide, chlorine fumes, or ammonia are common in chemical plants, electroplating facilities, wastewater treatment plants, and paper mills. These gases cause gaseous corrosion.
Aggressive chemicals can penetrate micropores in protective coatings, conformal coatings, and even attack the components themselves. They directly break down protective layers and oxidize copper and other metals on the board. This corrosion often affects contacts and connectors, i.e., elements that must remain unprotected to ensure electrical connection. Corrosion at these points drastically reduces conductivity, leading to increased resistance, voltage drops, and sporadic communication errors, which are a nightmare for maintenance departments.
Although special enclosures are often used, their seals degrade over time, allowing for slow penetration. As a result, chemicals cause pitting corrosion, which can compromise the entire thickness of a trace on the board, leading to a complete break.
How to Defend Yourself?
The conclusions drawn from the analysis of degradation mechanisms are unequivocal. The only defense against these invisible destroyers is proactive action. It is not enough to react to a failure and replace a damaged component.
For maintenance departments, this means the need to monitor environmental conditions in control cabinets and regular preventive maintenance. Only in this way can the life of modules be extended and the risk of costly downtime due to electrochemical corrosion be genuinely minimized.
