SURFACE FINISHES COMPARED
OSP or immersion tin: which PCB surface finish?
OSP is the cheaper of the two, at $0.05–0.07 per square inch against $0.08–0.12 for immersion tin. Immersion tin keeps longer before assembly: 6–12 mo against 3–6 mo for OSP.
- Known risk with OSP: Handling.
- Known risk with immersion tin: Whiskers/IMC.
OSP and immersion tin, as published
| Property | OSP | Immersion tin |
|---|---|---|
| Cost, USD per square inch | 0.05–0.07 | 0.08–0.12 |
| Shelf life | 3–6 mo | 6–12 mo |
| Reflow passes | 4–6 | 3–4 |
| Minimum pitch, mm | 0.4 | 0.5 |
| RF performance | Excellent | Good |
| Gold wire bonding | No | No |
| Aluminium wire bonding | No | No |
| Standard | IPC-4555 (draft) | IPC-4554 |
| Known risk | Handling | Whiskers/IMC |
How this was counted
Both columns come from the surface finish table in the MPBxChange material catalogue, as its sources published them. Costs are indicative ranges in US dollars per square inch, not quotations, and move with the gold price and the fabricator. "Not published" means the source gave no value, not that the answer is no.