Several factors contribute to the onset of oxidation, including:
1. Environmental Exposure:
– PCBs are often exposed to the air during various stages of manufacturing, shipping, storage, and end use.
The presence of humidity, temperature fluctuations, and pollutants like sulfur or chlorine can accelerate oxidation.
– Moisture and high humidity can create a conductive path across the copper traces, leading to the formation of copper oxide, which negatively impacts conductivity.
2. Heat and Temperature Fluctuations:
– When a PCB is subjected to elevated temperatures during soldering, reflow processes, or operation, the copper may react with oxygen more readily,
forming an oxide layer. Similarly, rapid temperature cycling (e.g., from room temperature to high temperatures) can cause expansion and contraction of materials, leading to microcracks that promote oxidation.
3. Chemical Contamination:
– During the manufacturing process, residues from flux, cleaning agents, or other chemicals can contribute to oxidation. These residues may remain on the surface of the PCB or between components and may accelerate the oxidative process.
4. Aging:
– Over time, even a well-manufactured PCB can begin to show signs of oxidation. As the PCB undergoes long-term exposure to oxygen and environmental factors, oxidation may gradually increase, affecting the performance and appearance of the board.
What does Surface Oxidation do to a circuit board?
The formation of an oxide layer on the copper surfaces of a PCB can have several detrimental effects, including:
1. Impaired Electrical Conductivity:
– Oxide layers, especially those formed on copper traces, can act as an insulator. This can prevent or disrupt electrical connections, leading to poor signal transmission or complete circuit failure.
– If oxidation is significant enough, it can cause increased resistance in the circuit, which can lead to overheating, voltage drops, and malfunctioning components.
2. Poor Solderability:
– Oxidized surfaces are more difficult to solder, as the oxide layer prevents the molten solder from making a strong bond with the underlying copper. This can result in weak or unreliable solder joints, leading to cold solder joints, unreliable connections, or intermittent failures.
– In severe cases, oxidation can cause the solder to ball up rather than spread evenly, creating poor contact points that may compromise the performance of the device.
3. Corrosion and Material Degradation:
– Prolonged oxidation can lead to the formation of copper corrosion, which is more than just surface discoloration. Corroded copper traces or pads can become brittle, leading to cracked or broken traces that cause signal or power interruptions.
– In the long term, oxidation-induced corrosion can cause physical damage to the PCB, necessitating expensive repairs or complete replacement.
4. Aesthetic Concerns:
– While the functional effects of oxidation are the most important, cosmetic issues can also arise. Oxidation can change the color of the PCB from its original bright copper to a dull, dark brown or green hue, which may affect the perceived quality of the final product.