1. Among the requirements for non-electrolytic nickel coating on PCB board, the coating should serve a number of functions.
2. One of these functions is to facilitate the deposition of gold on the surface.
3. The primary objective of the circuit is to establish a strong physical and electrically conductive connection between the PCB board and the components.
4. However, if the surface of the PCB contains oxides or contaminants, the use of modern weak fluxes would prevent the desired solder connection from forming.
Gold naturally precipitates on top of nickel and does not oxidize during long-term storage. However, gold does not precipitate on oxidized nickel, so the nickel must remain pure between the nickel bath and the dissolution of the gold. A requirement for nickel is to remain free of oxidation long enough to allow precipitation of gold. Components developed chemical immersion baths to allow 6-10% of nickel in the precipitation phosphorus content. This phosphorus content in the electroless nickel coating is considered a careful balance of bath control, oxide, and electrical and physical properties.
Hardness is important for electroless nickel-coated surfaces used in applications requiring physical strength, such as bearings in automotive transmissions. PCB board requirements are less stringent, but some stiffness is still important for wire-bonding, touch pad contact points, edge-connectors, and handling sustainability. Wire bonding requires a certain hardness of nickel. If the lead deforms the deposit, a loss of friction can occur, causing the lead to “melt” onto the substrate. SEM pictures showed no penetration into the planar nickel/gold or nickel/palladium (Pd)/gold surfaces.
Copper is the preferred metal for circuit formation due to its ease of fabrication and excellent electrical conductivity. Gold also has good electrical conductivity and is ideal for outer metal layers. The electrical properties of most production boards are not affected by the nickel layer, but the nickel can impact the electrical properties of high frequency signals. Signal losses on microwave PCBs can exceed designer specifications, which is proportional to the thickness of the nickel.
Contact resistance is important for maintaining conductivity to external contacts after prolonged environmental exposure. Antler’s 1970 study highlighted the contact requirements for nickel/gold surfaces in different end-use environments. A nickel barrier layer is not required for low temperature environments, but as the temperature increases, more nickel is needed to prevent nickel/gold transfer on PCB boards.
2. One of these functions is to facilitate the deposition of gold on the surface.
3. The primary objective of the circuit is to establish a strong physical and electrically conductive connection between the PCB board and the components.
4. However, if the surface of the PCB contains oxides or contaminants, the use of modern weak fluxes would prevent the desired solder connection from forming.
Gold naturally precipitates on top of nickel and does not oxidize during long-term storage. However, gold does not precipitate on oxidized nickel, so the nickel must remain pure between the nickel bath and the dissolution of the gold. A requirement for nickel is to remain free of oxidation long enough to allow precipitation of gold. Components developed chemical immersion baths to allow 6-10% of nickel in the precipitation phosphorus content. This phosphorus content in the electroless nickel coating is considered a careful balance of bath control, oxide, and electrical and physical properties.
Hardness is important for electroless nickel-coated surfaces used in applications requiring physical strength, such as bearings in automotive transmissions. PCB board requirements are less stringent, but some stiffness is still important for wire-bonding, touch pad contact points, edge-connectors, and handling sustainability. Wire bonding requires a certain hardness of nickel. If the lead deforms the deposit, a loss of friction can occur, causing the lead to “melt” onto the substrate. SEM pictures showed no penetration into the planar nickel/gold or nickel/palladium (Pd)/gold surfaces.
Copper is the preferred metal for circuit formation due to its ease of fabrication and excellent electrical conductivity. Gold also has good electrical conductivity and is ideal for outer metal layers. The electrical properties of most production boards are not affected by the nickel layer, but the nickel can impact the electrical properties of high frequency signals. Signal losses on microwave PCBs can exceed designer specifications, which is proportional to the thickness of the nickel.
Contact resistance is important for maintaining conductivity to external contacts after prolonged environmental exposure. Antler’s 1970 study highlighted the contact requirements for nickel/gold surfaces in different end-use environments. A nickel barrier layer is not required for low temperature environments, but as the temperature increases, more nickel is needed to prevent nickel/gold transfer on PCB boards.
