When to use OSP surface finish for PCB? - Page 1
Forum section: electronics / general

author: hal9001
author_rank: Regular Contributor
timestamp: January 17, 2022, 01:32:46 pm
content: Is it ever better to use OSP instead of HASL or other surface finishes?How does it behave in humid conditions during storage?Cheers!

author: tszaboo
author_rank: Super Contributor
timestamp: January 17, 2022, 01:46:03 pm
content: HASL: For everything, except:ENIGL: Fine pitch BGA or other requirements specifically ask for thisOSP: If you cannot afford HASL, or someone accidentally selected this on the order form.

author: hal9001
author_rank: Regular Contributor
timestamp: January 19, 2022, 06:21:45 am
content: Quote from: tszaboo on January 17, 2022, 01:46:03 pmThanks. 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?

author: xavier60
author_rank: Super Contributor
timestamp: January 19, 2022, 08:54:00 am
content: 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.

author: tszaboo
author_rank: Super Contributor
timestamp: January 19, 2022, 12:38:23 pm
content: Quote from: xavier60 on January 19, 2022, 08:54:00 amOSP 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.Quote from: hal9001 on January 19, 2022, 06:21:45 amThat 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.

author: hal9001
author_rank: Regular Contributor
timestamp: January 20, 2022, 02:51:19 pm
content: Quote from: xavier60 on January 19, 2022, 08:54:00 amI have problems with lumpy HASL but from JLCPCB. Any tips how to improve the finish?

author: xavier60
author_rank: Super Contributor
timestamp: January 20, 2022, 09:40:11 pm
content: Quote from: hal9001 on January 20, 2022, 02:51:19 pmNothing 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.

author: Warhawk
author_rank: Frequent Contributor
timestamp: January 21, 2022, 08:57:59 pm
content: 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.

author: xavier60
author_rank: Super Contributor
timestamp: March 10, 2023, 07:19:45 am
content: 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.

author: xavier60
author_rank: Super Contributor
timestamp: March 10, 2023, 09:34:08 am
content: Quote from: karpouzi9 on March 10, 2023, 08:16:51 amIn 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.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 10, 2023, 07:28:35 pm
content: 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.

author: trophosphere
author_rank: Frequent Contributor
timestamp: March 15, 2023, 03:43:15 am
content: 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.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 15, 2023, 03:31:25 pm
content: 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.

author: tchiwam
author_rank: Regular Contributor
timestamp: March 15, 2023, 03:48:13 pm
content: OSL is better than ENIG for RF.ENIG has a very rough surface, don't worry about it until 2-3GHzENEPIG and immersion gold are more expensiveDo a bit of research on this, might not be that important if you build the boards soon after receiving them.

author: xavier60
author_rank: Super Contributor
timestamp: February 04, 2025, 06:32:10 am
content: After 2 years of storage, my OSP treated PCBs show no signs of solderability degradation.

author: wraper
author_rank: Unknown
timestamp: March 05, 2025, 03:54:56 am
content: Quote from: tszaboo on January 17, 2022, 01:46:03 pmSorry, but this is nonsense. OSP is a low cost substitute for ENIG as it also provides excellent flatness. You can use OSP with any parts, including fine pitch BGA, which you cannot do with HASL due to flatness issues. You can often find both ENIG or OSP in different batches of mass produced devices, Raspberry pi for example. But it's quite unlikely you'll find HASL interchanged with OSP.

author: tszaboo
author_rank: Super Contributor
timestamp: March 05, 2025, 04:36:13 pm
content: Quote from: wraper on March 05, 2025, 03:54:56 amI think you should read again what I wrote.

author: wraper
author_rank: Unknown
timestamp: March 05, 2025, 06:33:31 pm
content: Quote from: tszaboo on March 05, 2025, 04:36:13 pmYou presented OSP as something you use if you cannot afford HASL when in fact you go from ENIG straight to OSP if ENIG was actually needed.

author: xavier60
author_rank: Super Contributor
timestamp: March 06, 2025, 01:02:22 am
content: I would like OSP to become a more popular choice. OSP is necessary for many of my PCBs. If not for the higher cost, it would be my only choice.