Modeling Kirkendall Vacancy Flux in Ternary SAC Solder Interfaces
Modelling vacancy transport in ternary SAC interfaces enables precise prediction of Kirkendall microvoid growth, preventing latent failure in high-reliability packaging.
OSP Copper
Meaning
Surface protection measured against the oxidation resistance of exposed circuitry ensures solderability during the assembly of electronic components on a printed circuit board. Bare boards treated as osp copper require controlled storage environments because the organic film degrades when exposed to high humidity or multiple heat cycles. This finish consists of a thin organic layer that is chemically bonded to the copper pads to prevent tarnishing before they are soldered.
It is a cost-effective alternative to metallic finishes like gold or silver.
Protective Film
The coating is applied in a liquid bath where the organic molecules selectively react with the copper surface. In a high-volume manufacturing environment, osp copper provides a temporary barrier that is easily removed by the flux during the soldering process.
Storage Limitation
Because the film is only a few hundred nanometers thick, it is susceptible to mechanical scratches and chemical degradation.
Soldering Compatibility
The absence of a metallic barrier means that the solder reacts directly with the copper, which creates a strong metallurgical bond. However, if the board goes through multiple reflow cycles, the organic film on the un-soldered pads can evaporate and leave the copper vulnerable to oxidation. Quality teams monitor the color of the pads to detect any breakdown of the protection.
This finish is preferred for applications where a flat pad surface is necessary for high-density component placement.