Description And Reasons of Poor Plating During PCB Electroplating:
11. Recess plating. Sparse and dense irregular cavities on the coating surface (different from pinholes) create a “ceiling face” coating. This phenomenon can occur in two situations. Firstly, some units use glass bead spray to remove flash. However, if the air pressure is too high during spraying, the kinetic energy inertia of the glass beads can impact the coated surface, creating small pits. If the coating is too thin and the pits are not filled, a “ceiling face” coating is formed. Secondly, when the metallographic phase of the base material alloy is not uniform, selective corrosion can occur during the pre-plating process. In this case, the more active metal is etched first to form cavities. If these cavities are not filled after electroplating, a “ceiling face” coating is the result. For example, Ni42Fe base material may exhibit uneven alloy metallurgy on its surface due to incomplete mixing of Ni and Fe during the metallurgical process. As a result, during pre-plating, Fe being more active than Ni, is selectively etched to form pits. If the plating layer fails to flatten the pits, a “ceiling face” plating layer is created. Similarly, zinc brass can also exhibit this phenomenon if the copper-zinc metallographic phase is uneven, leading to selective corrosion of zinc before copper during pre-plating.
12. Loose dendritic coating. A dirty plating solution with high main metal ion concentration, low complexing agent and additives, anodes positioned too close, and high current density can result in the formation of a loose dendritic coating. This type of coating, resembling foam plastic, has uneven dendrites and can easily be wiped off with fingers.
13. Double-layer plating. Double-layer plating often occurs when the plating solution’s operating temperature is high. When the workpiece is lifted out of the plating tank and re-plated, salt frost may precipitate on the workpiece due to evaporating water, resulting in a double-layer coating if not dissolved before re-plating. To prevent double-layer plating, shake the workpiece in the plating solution before re-plating for a few seconds to ensure the dissolution of salt frost.
14. Blackened coating. High metal and organic impurities in the plating solution, especially in low current density areas, can cause blackening of the coating. Insufficient additives can also lead to black coating in large plated areas. If ions’ temperature is too low and the current is high, a gray-black plating layer may form. To address metal impurities, use a corrugated board as the cathode and carry out 0.1-0.2A/dm2 electrolysis. To tackle organic pollution, use 3-5 g/l activated carbon, preferably granular, and wash with pure water before use.
15. Passive peeling. Ni42Fe alloy is prone to passivation. Inadequate oxidation or delayed oxide dissolution during the activation process can lead to oxide residues on the plated surface, resulting in peeling or roughness of the coating.
16. Replacement peeling. When different materials are present on the same workpiece, such as copper substrate with a nickel-plated surface, exposed copper may lead to replacement peeling if copper ions in a strong corrosion tank reach a limit. This can result in a replacement copper layer forming on the nickel layer, causing the tin layer to peel after tinning. Frequent updates of the corrosion potion can prevent replacement peeling.
17. Peeling due to oil pollution. Failure to remove oil during pre-plating treatment can prevent plating in the oil-contaminated area. Even if the plating covers the area, it lacks bonding force with the base material, resulting in pseudo-plating.
18. Dark round spot coating. In the case of a large area to be plated, such as a pipe’s heat sink, impurities or insufficient additives in the plating solution can lead to the formation of a gray-black dark round spot plating layer in the center of the heat sink, resembling plaster. This occurs as the center is a low current area, leading to the concentration and precipitation of impurities. Additionally, insufficient additives may decrease the plating solution’s depth capability.
19. Uneven gloss and thickness of the coating are visibly uneven due to the recent addition of additives, which have not fully dispersed, resulting in uneven bath characteristics. Once the additives are evenly dispersed, this issue naturally disappears.
20. Chemical fiber contamination of the plating solution can result in visible traces of chemical fiber embedded in the plating layer. This can be resolved by using an anode bag made of PP cloth with a soldering iron.
11. Recess plating. Sparse and dense irregular cavities on the coating surface (different from pinholes) create a “ceiling face” coating. This phenomenon can occur in two situations. Firstly, some units use glass bead spray to remove flash. However, if the air pressure is too high during spraying, the kinetic energy inertia of the glass beads can impact the coated surface, creating small pits. If the coating is too thin and the pits are not filled, a “ceiling face” coating is formed. Secondly, when the metallographic phase of the base material alloy is not uniform, selective corrosion can occur during the pre-plating process. In this case, the more active metal is etched first to form cavities. If these cavities are not filled after electroplating, a “ceiling face” coating is the result. For example, Ni42Fe base material may exhibit uneven alloy metallurgy on its surface due to incomplete mixing of Ni and Fe during the metallurgical process. As a result, during pre-plating, Fe being more active than Ni, is selectively etched to form pits. If the plating layer fails to flatten the pits, a “ceiling face” plating layer is created. Similarly, zinc brass can also exhibit this phenomenon if the copper-zinc metallographic phase is uneven, leading to selective corrosion of zinc before copper during pre-plating.
12. Loose dendritic coating. A dirty plating solution with high main metal ion concentration, low complexing agent and additives, anodes positioned too close, and high current density can result in the formation of a loose dendritic coating. This type of coating, resembling foam plastic, has uneven dendrites and can easily be wiped off with fingers.
13. Double-layer plating. Double-layer plating often occurs when the plating solution’s operating temperature is high. When the workpiece is lifted out of the plating tank and re-plated, salt frost may precipitate on the workpiece due to evaporating water, resulting in a double-layer coating if not dissolved before re-plating. To prevent double-layer plating, shake the workpiece in the plating solution before re-plating for a few seconds to ensure the dissolution of salt frost.
14. Blackened coating. High metal and organic impurities in the plating solution, especially in low current density areas, can cause blackening of the coating. Insufficient additives can also lead to black coating in large plated areas. If ions’ temperature is too low and the current is high, a gray-black plating layer may form. To address metal impurities, use a corrugated board as the cathode and carry out 0.1-0.2A/dm2 electrolysis. To tackle organic pollution, use 3-5 g/l activated carbon, preferably granular, and wash with pure water before use.
15. Passive peeling. Ni42Fe alloy is prone to passivation. Inadequate oxidation or delayed oxide dissolution during the activation process can lead to oxide residues on the plated surface, resulting in peeling or roughness of the coating.
16. Replacement peeling. When different materials are present on the same workpiece, such as copper substrate with a nickel-plated surface, exposed copper may lead to replacement peeling if copper ions in a strong corrosion tank reach a limit. This can result in a replacement copper layer forming on the nickel layer, causing the tin layer to peel after tinning. Frequent updates of the corrosion potion can prevent replacement peeling.
17. Peeling due to oil pollution. Failure to remove oil during pre-plating treatment can prevent plating in the oil-contaminated area. Even if the plating covers the area, it lacks bonding force with the base material, resulting in pseudo-plating.
18. Dark round spot coating. In the case of a large area to be plated, such as a pipe’s heat sink, impurities or insufficient additives in the plating solution can lead to the formation of a gray-black dark round spot plating layer in the center of the heat sink, resembling plaster. This occurs as the center is a low current area, leading to the concentration and precipitation of impurities. Additionally, insufficient additives may decrease the plating solution’s depth capability.
19. Uneven gloss and thickness of the coating are visibly uneven due to the recent addition of additives, which have not fully dispersed, resulting in uneven bath characteristics. Once the additives are evenly dispersed, this issue naturally disappears.
20. Chemical fiber contamination of the plating solution can result in visible traces of chemical fiber embedded in the plating layer. This can be resolved by using an anode bag made of PP cloth with a soldering iron.
