What PCB surface finishes are offered in Seeed Fusion?

Seeed Fusion standard PCB service offers four surface finish options from the popular HASL to high quality ENiG finishes to suit different applications. A surface finish is applied to the exposed copper pads to protect them and prevent oxidation until assembly, which would strongly inhibit the copper's ability to bond with molten solder.

HASL - Hot Air Solder Levelling
For HASL finishes, the boards are dipped in a bath of molten solder and then passed through a conveyor of hot air knives that brush the excess solder off. Essentially, the copper pads are pre-tinned with the thinnest layer of solder possible, and the tinning protects the bare copper underneath. This gives the boards good shelf-life and the existing layer of solder makes the molten joints much easier to join. The HASL surface finish is the simplest and most common surface finish and sufficient for most projects. However, it is not ideal for fine pitch components since, the thin layer of solder still leaves a rounded surface and the components will not lie completely flat against the surface of the pad.

HASL Lead Free - Lead Free Hot Air Soldering Levelling
In order to be RoHs compliant, regular lead solder cannot be used and this includes as a surface finish. Therefore, Seeed Fusion offers a Lead Free option as well for those intending on commercial distribution. However, lead free solder has a higher melting point, so it may not be ideal for the average hobbyist with regular soldering equipment.

ENIG - Electroless Nickel / Immersion Gold
In the ENIG plating process, the copper pads are protected by a coating of nickel, and then the nickel is protected with a fine layer of gold particles. This offers superior corrosion resistance compared to HASL due to the high corrosion resistance of gold. In addition, the excellent surface planarity of the nickel/gold finish allows components to be soldered flat onto the pad, making it ideal for BGA pads and other fine pitch components. The disadvantages include the higher cost and soldering is not as easy compared to HASL, since there is no pre-tinned surface. Solderability is still good, however.

Hard Gold
Similar to ENIG, the pads are plated with nickel but then with a much thicker layer of gold. Hard gold is reserved for gold fingers which require durability and excellent resistance to corrosion. It is not suitable for soldering due its poor solderability and the high cost of gold. If you select the Hard Gold option, we will plate the entire board with Hard Gold. If your boards have gold fingers and you would like the rest of the pads to have an ENIG finish, please use the Advanced PCB service.

The following options are only available in the Advanced PCB service.

OSP - Organic Solderability Preservative
A thin layer of a water soluble organic compound is applied to the surface of the boards, which then selectively adheres to the copper surfaces, forming an almost undetectable protective layer. This makes it ideal for fine pitched devices but the shelf life is relatively short - up to one year, so it is more suited to batch assembly rather than prototyping. It is also clear in color, making it difficult to inspect the coverage of the compound. It is the most environmentally friendly of all the available finishes.

Immersion Tin
Tin is deposited onto the surface of the copper via a displacement reaction which removes some of the surface copper in the process. The resulting finish has excellent planarity and the reliability is comparable to ENIG. The thickness of the tin layer is also much easier to control, but the process involves the use of a carcinogen and the boards must be handled carefully to avoid contamination.

Immersion Silver
Similar to immersion tin, immersion silver produces exceptionally flat surfaces, has great solderability and can serve as an ENIG alternative but it also has a poor shelf life and does not respond well to handling. The immersion silver process however, does not use highly toxic chemicals and does not affect the final diameter of plated holes. Due to a high friction coefficient, immersion silver surface finishes are not suited for pin insertion or press-fit machines.

Hard Gold + ENIG
Select this option if your board has gold fingers and you would like the rest of the pads to have ENIG finish.

Fusion Technical Support

  1. What is Gerber file?
  2. What are the PCB panelization rules?
  3. How to generate the Gerber (manufacturing) files?
  4. What is the correct way to draw the silkscreen on the bottom side?
  5. My PCB does not require Solder Mask, what should I do?
  6. My PCB does not require Drill Holes, what should i do ?
  7. Which layer should I use in EAGLE for milling?
  8. What is the depth and width of the v-cuts/grooves?
  9. I don't want silkscreen on my PCBs, how can I proceed with a PCB Assembly order?
  10. What are the dimensions for Dielectric Separation thickness?
  11. What is the thickness of the inner copper layers?
  12. What are Blind and Buried Vias?
  13. What is the The Min Track/Spacing for 1oz./2oz./3oz. Copper weight
  14. What are Plated Half-Holes/Castellated Holes?
  15. How do I design non-plated through holes/slots?
  16. What PCB materials are available in Seeed Fusion?
  17. What is the thickness of Fusion PCB?
  18. What PCB surface finishes are offered in Seeed Fusion?
  19. What color options are available for the solder mask/resist?
  20. What is the PCB copper weight?
  21. What is Impedance Control?
  22. PCB quantity
  23. How do plated through holes/slots shows on the Gerber?
  24. How to generate Gerber files from PCBE
  25. How to generate Gerber files in Altium Designer
  26. How to generate Gerber files from CircuitMaker
  27. How to generate Gerber and Drill files from Eagle
  28. How to generate Gerber and drill files from KiCad
  29. How to generate Gerber files from DipTrace
  30. How to generate Gerber files from Proteus
  31. How to generate Gerber files from DesignSpark
  32. How to convert drilling layer from Gerber to Excellon format in CAM350
  33. Recommend size for BGA
  34. Solder Mask Dam
  35. What is the difference between Fusion standard PCB and Fusion Advanced PCB?
  36. What should I do if my Gerber files are too big (over 4MB)?

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