When we design PCB board, need to choose the circuit board surface treatment process, now commonly used circuit board surface treatment process HASL (surface tin spraying process), ENIG (gold sink process), OSP (oxidation prevention process), commonly used surface treatment process we how to choose? Different PCB surface treatment process, different fees, the final effect is also different, you can choose according to the actual situation, I will tell you the advantages and disadvantages of HASL, ENIG, OSP these three different surface treatment process.
Tin process is divided into tin with lead and lead-free tin, tin injection for ever in the 1980 s is the most main surface treatment process, but in the present, tin injection for less and less of the circuit board to choose, because circuit board toward the direction of "small and exquisite, tin process can lead to fine components welded with tin beads, tin ball point caused by the bad production, In order to pursue higher process standards and production quality, PCBA processing plants often choose ENIG and SOP surface treatment processes.
Lead tin-spraying advantages: lower price, excellent welding performance, mechanical strength, gloss, etc., better than lead tin-spraying.
Disadvantages of lead spray tin: lead spray tin contains lead heavy metals, production is not environmental protection, can not pass ROHS and other environmental evaluation.
Advantages: low price, excellent welding performance, and relatively environmental protection, can pass ROHS and other environmental evaluation.
Disadvantages: mechanical strength, gloss, etc., not as good as lead-free tin spray.
Common disadvantages of HASL: Not suitable for soldering thin gap pins and too small components due to poor surface flatness of tinjet plates. It is easy to produce tin beads in PCBA processing, and it is easy to cause short circuit to pin components with fine gap.
Gold sinking process is a relatively advanced surface treatment process, mainly used in the surface of the connection functional requirements and a long storage life of the circuit board.
Advantages of ENIG: not easy to oxidize, can be stored for a long time, smooth surface, suitable for welding thin gap pins and components with small solder joints. Reflow soldering can be repeated many times without much loss of solderability. Can be used as the base material of COB wire.
Disadvantages of ENIG: high cost, poor welding strength, due to the use of nickelless plating process, easy to have the problem of black plate. The nickel layer oxidizes over time, and long-term reliability is an issue.
OSP is the chemical formation of an organic skin film on the surface of bare copper. This film has anti-oxidation, heat shock resistance, moisture resistance, to protect the copper surface in the normal environment no longer continue to rust (oxidation or vulcanization, etc.); It is equivalent to an anti-oxidation treatment, but in the subsequent high temperature welding, the protective film must be easy to be quickly removed by the flux, and the exposed clean copper surface can be immediately combined with the molten tin into a strong solder spot in a very short time. The percentage of boards using THE OSP process has increased significantly, because it is suitable for low process boards as well as high process boards, and OSP is the best surface treatment process if there are no functional surface connection requirements or shelf life restrictions.
Advantages of OSP: With all the advantages of bare copper plate welding, expired (three months) boards can also be refinished, but usually only once.
Disadvantages of OSP: Susceptible to acid and humidity. In the case of secondary reflow welding, the time required to complete the second reflow welding is usually poor. If stored for more than three months, it must be resurfaced. Use up within 24 hours after opening the package. The OSP is an insulating layer, so the test point must be printed with solder paste to remove the original OSP layer to contact the needle point for electrical testing. The assembly process needs to undergo major changes. If the detection of raw copper surface is not good for ICT, too sharp ICT probe may damage the PCB, requiring manual guard treatment, limiting ICT testing and reducing test repeatability.
The above is about HASL, ENIG, OSP circuit board surface treatment process analysis, you can choose which kind of surface treatment process according to the actual use of the circuit board.
