A surface finish offers a coating on the external coating copper that helps prevent oxidation and an electrically conductive surface. This surface has two generic practical requirements: to give a solderable surface allowing you to connect components with solder and also to attach an element without soldering, like a wire relationship or press-fit connector.
Organic Solderability Preservative (OSP)- This technique coats an extremely slim coating of a natural materials that inhibits copper oxidation. It really is so thin that it's almost impossible to see and measure.
The organic materials is removed by the solder flux used during PCB assembly. PCBs which have been OSP covered will have shiny copper pad coloration. Probably the most common OSP is ENTEK CU-106A. This coating is utilized for PCB assemblies that will proceed through multiple assembly procedures. PCB’s which have multiple surface coatings can also use the CU-106A(By) finish.
Immersion Tin (ImSn)- This technique coats a slim level of tin on the surface of the copper surface. The tin produces an exceptionally flat work surface for installation of surface attach components with ultra
fine-pitch components. This coating also offers a thicker, standard surface that delivers lubrication for press-fit pins.
Immersion Metallic (ImAg)- This technique plates a slim layer of metallic directly on the surface of the copper surface.Much like the other immersion surface surface finishes, the finished product produces an extremely flat work surface; it is perfect for fine pitch components. This surface finish has the capacity to maintain high solderability after multiple warmth cycles. This may also be used as an aluminium wire bondable surface. It really is appropriate for no-clean assembly procedures. That is becoming popular as a heat solder leveling (HASL) alternative to lead-free soldering applications. This surface finish produces a boring tarnished looking surface. There is certainly significant industry data displaying that the dullness will not impact solderability or reliability.
Other Finishes- Other coatings include hot-air solder leveling and immersion nickel-gold (ImNiAu).
Desk 1, from a 2003 Surface Attach Technology Association (SMTA) paper, summarizes the characteristics of every PCB finish.
hdi pcb. printed circuit. circuit board. electroless nickel. immersion tin. high density. hdi board. solder mask. density interconnect. hdi technology. pcb surface. immersion gold. pcb manufacturing. shelf life. leadfree hasl. highdensity interconnect. pcb technology. hdi printed. stacked vias. immersion silver. smaller components. lead free. sequential lamination. buried via. hot air. via fill. nickel immersion. hard gold. hdi microvia. board thickness. electrical performance. pitch bga. laser drill. air solder. using hdi. interconnect pcb. annular ring. aspect ratio. hole fill. controlled impedance. signal integrity.