When to use OSP surface finish for PCB?

[hal9001]

Is it ever better to use OSP instead of HASL or other surface finishes?
How does it behave in humid conditions during storage?


Cheers!

[tszaboo]

HASL: For everything, except:
ENIGL: Fine pitch BGA or other requirements specifically ask for this
OSP: If you cannot afford HASL, or someone accidentally selected this on the order form.

[hal9001]

HASL: For everything, except:
ENIGL: Fine pitch BGA or other requirements specifically ask for this
OSP: If you cannot afford HASL, or someone accidentally selected this on the order form.

Thanks. A vendor offers only OSP or ENIG for boards under 0.8mm. ENIG is more than two times the expense.
I read OSP finish uses chemicals instead of plating with another metal such as in ENIG or HASL. Does it scratch off if boards are stacked on top of each other for example?

[xavier60]

OSP isn't cheap at all at PCBway, adds about 50% over leaded HASL. Annoying thing is that their HASL used to be acceptable, now it's too lumpy.
They chose to blame my PCB design rather than look for the real cause of the quality loss.
I like the OSP finish, very good solderability. I have yet to see for how long unused boards maintain their solderability.

[tszaboo]

OSP isn't cheap at all at PCBway, adds about 50% over leaded HASL. Annoying thing is that their HASL used to be acceptable, now it's too lumpy.
They chose to blame my PCB design rather than look for the real cause of the quality loss.
I like the OSP finish, very good solderability. I have yet to see for how long unused boards maintain their solderability.

OSP is expensive because it isn't their standard procedure. The process itself is used when you want to save on PCB production, when we are talking about thousands of boards.

HASL: For everything, except:
ENIGL: Fine pitch BGA or other requirements specifically ask for this
OSP: If you cannot afford HASL, or someone accidentally selected this on the order form.

Thanks. A vendor offers only OSP or ENIG for boards under 0.8mm. ENIG is more than two times the expense.
I read OSP finish uses chemicals instead of plating with another metal such as in ENIG or HASL. Does it scratch off if boards are stacked on top of each other for example?

That is a thin board. Usually the reason to go with thinner boards, is because you want to save space (eg smart phone) where everything else is small, and then ENIG is better.
In OSP they just cover the bare copper surfaces with a film, that evaporates during soldering. Kinda like flux.

[hal9001]

OSP isn't cheap at all at PCBway, adds about 50% over leaded HASL. Annoying thing is that their HASL used to be acceptable, now it's too lumpy.
They chose to blame my PCB design rather than look for the real cause of the quality loss.
I like the OSP finish, very good solderability. I have yet to see for how long unused boards maintain their solderability.

I have problems with lumpy HASL but from JLCPCB . Any tips how to improve the finish?

[xavier60]

OSP isn't cheap at all at PCBway, adds about 50% over leaded HASL. Annoying thing is that their HASL used to be acceptable, now it's too lumpy.
They chose to blame my PCB design rather than look for the real cause of the quality loss.
I like the OSP finish, very good solderability. I have yet to see for how long unused boards maintain their solderability.

I have problems with lumpy HASL but from JLCPCB . Any tips how to improve the finish?

Nothing too practical. To save the batch, I heated the boards individually on a hotplate and wiped the solder off with a rag.
The process left the boards with poor solderability.

[Warhawk]

As far as I know OSP has limited shelf life and is used rather for the serial production. It has also brilliant flatness that fine pitch parts benefit from. I personally don't see any reason why a hobbyist or a small manufacturer would decide for it.

[xavier60]

I have just used the last of a batch of PCBs made by PCBWay 18 months ago with OSP finish. I noticed no solderability problems with leaded SMD hand soldering. The PCBs were stored in a closed plastic food storage container.
At the time, OSP and even bare copper were significantly more expensive than HASL, due to lower demand I'm guessing.

 

[xavier60]

Not that I've done it (yet) but if you're sending all of your boards straight to assembly after fabrication, there's no reason to avoid OSP except minimizing cost.

xavier60: did you consider using solder wick to remove the HASL? I've had good success with this for BGA and QFN.

In my case, the lumpy HASL was covering 50mm x 200mm areas of the PCBs that was to mate to heatsinks for LED cooling. They're all gone now, some to the trash bin.
From my experience, there is no need to avoid OSP for any reasons. Except cost.
In the past, ENIG has been associated with Black Pad.

[SiliconWizard]

Yeah, HASL can be pretty lumpy, heavily depends on the manufacturer, so I usually use it only for hand-soldered prototypes, provided there is no fine-pitch or BGA stuff. For any kind of automated assembly, I don't like it. YMMV.

OSP is a non-conductive protective layer, contrary to HASL or ENIG. It does alright for protecting copper, but has to be vaporized during reflow. It thus doesn't give the best finish surface for soldering, and leaves residues that have to be cleaned, even if using no-clean fluxes. I would avoid it unless you had to optimize cost to a high degree and it was ok with your requirements. As already said above, this is actually a cheaper finish, and if it's ever more expensive at a given manufacturer, it's because it's not their standard process, and because you are ordering only low quantities.

Just look at PCBWay for instance, you'll confirm this. If ordering 5-10 pieces, OSP is more expensive, but for larger quantities, it becomes the exact same price as HASL, and past a certain quantity, you can negotiate prices and it will get less expensive.

Additional note is that while it doesn't leave a great surface for soldering, it tends to be a lot less "lumpy" than HASL, so I guess that it might be better for fine-pitch SMD assembly and a low-cost alternative to ENIG, as long as you know the downsides.

[trophosphere]

I've heard of using OSP as an alternative to ENIG when you need the flatness but your PCB also contains microstrip or coplanar wave type transmission line structures carrying millimeter wave RF signals. Because of the skin effect, a large portion of the current will be concentrated in the plating and the Nickel in ENIG happens to have greater conductor loss as opposed to just copper.

[Doctorandus_P]

I stopped the video after 19s. I really did not want to wait for the guy to load up his powerpoint. That is just bad preparation.

[tchiwam]

OSL is better than ENIG for RF.

ENIG has a very rough surface, don't worry about it until 2-3GHz
ENEPIG and immersion gold are more expensive

Do a bit of research on this, might not be that important if you build the boards soon after receiving them.