kmod's blog

24Jul/144

DirtyPCBs and OSH Park: comparison

Long story short, I decided to try out an interesting new PCB-manufacturer, dirtypcbs.com.  I decided to compare it against my current go-to, OSH Park, so I ran a new 4-layer board of mine through both.  The 4-layer service at dirtypcbs was only just launched, and I had to ask Ian to let me in on it, and I think it's important to take that into account.  Here are some quick thoughts:

Price

The easiest thing to compare.

  • OSH Park: $60: $10/in^2 at 6 in^2 (56x70mm), with free shipping.
  • Dirty pcbs: $100: $50 for boards, $25 for rush processing, $25 for fast shipping.  (Note: the prices have changed since then.)

For this size board, OSH Park wins.  I also made a 100x100mm board through dirty pcbs in this same order, which came out to $75 ($50 + $25 for rush processing, got to share shipping charges), vs $155 it would have been on OSH Park.

So not hugely surprising, but due to OSH Park's linear pricing model, they are more price-effective at smaller board sizes.

Turnaround

I ordered both boards on 7/3 before going off for a long weekend.

The OSH Park panel was dated for 7/4, but didn't go out until 7/7; probably good since it seems like the cutoff for getting in on a panel is the day before the panel date.  The panel was returned to OSH Park on 7/16, they shipped by boards that day, and I received them on 7/18.  15 calendar days, which is slightly better than the average I've gotten for their 4 layers (seems to depend heavily on the panelization delay).

dirtypcbs: there were some issues that required some communication with the board factory, and unfortunately each communication round trip takes a day due to time zone issues.  The boards seem to have gotten fabbed by 7/8 -- not quite the "2-3 day" time I had been hoping for, but still way faster than OSH Park.

I didn't end up receiving the dirtypcb boards until 7/22, and I'm not quite sure what happened in between.  Ian was, to his credit, quite forthright about them still figuring out the best processes for working with the new 4-layer fab, which I think delayed the shipment by about a week.  I'm not quite sure where the rest of the delay comes from -- perhaps customs?  DHL reports that the package was shipped on 7/21 -- which is amazing if true, since I received them the next day.

So overall the total time was 19 calendar days, which was a little disappointing given that I had paid extra for the faster processing, but understandable given the situation.  The winner for this round has to be OSH Park, but dirtypcbs clearly has the ability to get the boards to you much faster if they can work out the kinks in their processes.

Board features

Here's a picture of the two boards -- as you can see they both look quite excellent:

2014-07-23 21.51.53

There's a silkscreen ID code on the dirtypcbs board, but they were very considerate and put it under a QFP part where it won't be visible after assembly.

One thing that's nice about going with a non-panelized service is that they can chamfer the board edges for you.  These boards use a PCI-Express card edge connector, for which you're supposed to chamfer the edges (make them slightly angled) in order to make insertion easier.  The dirtypcbs fab ended up doing that for me without it being asked for, though it's quite subtle:

guvcview_image-21

Overall, it's definitely nice to go with a non-panelizing service, since you get clean board edges and potentially-chamfered edges if you need it.  Typically the panel tabs that get left on the OSH Park boards aren't anything more than a visual distraction, but they can actually be quite annoying if you try to apply a solder paste stencil, since it becomes very tricky to hold the board steady.  Also, it makes it very difficult to stencil multiple boards in a row, since they will all break slightly differently.

Another benefit is that dirtypcb gives you the option of different soldermask colors, with anything other than green costing $18 (for their 4-layer options -- for their 2-layer the colors are free).  OSH Park doesn't charge you for color, but your only option is purple.

Dirtypcb only offers HASL finishing for their 4-layer boards whereas OSH Park offers the apparently higher-quality ENIG finish.  I'm not quite sure how that affects things (other than ENIG being lead-free), so I'm not sure how to rate that.

So overall I'd say that dirtypcbs wins this category, due to being non-panelizing: you get clean edges, and you can choose your PCB color.

Board quality

This one's slightly hard for me to judge, since I'm not quite sure what I'm looking for.  OSH Park has better tolerances than dirtypcbs, though since I wanted to have the same board made at both, I used the safer dirtypcbs tolerances.

One thing that I was worried about was this 0.4mm-pitch QFP chip that takes up most of the top side.  Unfortunately, the dirtypcbs fab isn't able to lay soldermask this finely, so the entire pad array is uncovered:

guvcview_image-22

They also don't have any soldermask dams on the 0.5mm-pitch QFN at the top of the photo.

I did, however, specify soldermask there, and OSH Park was able to do it.  The registration between the soldermask and the copper layers are slightly off, by about 2mil, which is a little disappointing but probably nothing to worry about:

guvcview_image-23

 

 

Here's the other tricky section of the board: an 0.8mm-pitch bga:

guvcview_image-24

Both fabs handled it without problems.

guvcview_image-25

 

I haven't electrically tested any of the boards, but these images seem to show that they're both electrically sound.

 

So I'd say that OSH Park edges out dirtypcbs in this category -- the dirtypcb PCBs are definitely high-quality but OSH Park is a slightly better still.

Stencil

I decided to also order a stencil through dirtypcbs, since they offer steel stencils for $30, which is way way cheaper than I've seen them elsewhere.  This is what I got:

2014-07-23 22.17.12

 

That's a huge box!  What was inside?

2014-07-23 22.19.10

A giant stencil!

Ian was also surprised that they sent something this large :)  I think I have to try using it once but it doesn't seem very easy to use...  It looks very high quality, though, and they also touched up my stencil design for me.  I'm pretty sure all the changes they made were good, but they did things like break up large exposed pads into multiple paste sections.  They also covered up some of the large vias I put in there for hand-soldering the exposed pads -- usually I mark those as "no cream" in Eagle (don't get an opening in the stencil) but I forgot for these.

 

OSH Park doesn't offer stencils, but a similar service OSH Stencils does (no official relation, I believe).  I've used them a few times before and had great experiences with them: they offer cheap kapton stencils, and get them to you fast.  Here's what they look like:

2014-07-23 22.20.39

 

I haven't tried using either set of stencils yet, because unfortunately the circuit is broken :(  I have a lot of these circuit boards now though so maybe even if I don't assemble any more of the boards I'll try out the stencils in the name of science.

Regardless, I think I'm going to stick with OSH Stencils for now :)

 

Conclusion

So that's about it for what I looked at or noticed.  I think I'm going to stick with OSH Park for small boards for now, but the option of getting 10 4-layer 10x10cm boards from dirtypcbs for $50 is pretty crazy, and opens up the possibility of using boards that size.  If dirtypcbs can work out the kinks of their process with the fab, then they also have the potential to deliver circuit boards to you much much faster than OSH Park, and much much more cheaply than places that specialize in fast turnarounds.  So overall I'm glad I ordered from them and I'm sure I will again at some point.

Comments (4) Trackbacks (0)
  1. Thanks kmod, always a pleasure to work with you. In the forum or tossing some PCBs.

    We dug up all the info we could on the order. Here’s what I found:

    Thursday 3 July: Order placed

    Friday 4 July: Sent to board house

    Saturday 5 to Tuesday 8: We did a little dance figuring out the tolerances around some of your tight areas and updated boards a couple times.

    Tuesday 8: Boards accepted to manufacturing

    Wednesday 9: First board arrives from manufacturer (the one without problems)

    Friday/Saturday/Sunday 11/12/13: Second board arrives after logistics stops working for the weekend

    Monday 14: Xiao Tang (Flylin.co does our fulfillment on DirtyPCBs) gets the board and stencil. The stencil is frickin’ huge and we think it’s for another order. I believe we sent the two boards first because the delay was so long. Angry calls were made to the board house, but later we realized the stencil was yours, packaged it separately, and mailed it (I’m not sure if this was Monday or Tuesday).

    Tuesday 15: Logistics sends both packages into the ‘black hole’ between China and Hong Kong. We’re just starting to learn about this. It sits there without tracking updates for 3-4 business days, before popping up on the next Monday (21) night in Hong Kong and is delivered in USA almost exactly 24 hours later. Merry signs for it on Tuesday (22) at 7 pm :) This _barely_ fits the 3-5 (business, in transit) day window advertised by the logistics company.

    As best we can tell, there is some queuing on the China side so the logistics company can get the absolute best bulk rates. We just started DHL service, and today I woke up to 4 emails from people with tracking numbers and no updates in 4 days. It seems this is absolutely normal. The DHL part of the delivery is generally 24hours, but the “black hole” is 3-4 business days. We’ve updated our dirty tracking notice email with some rude bullet points to that effect ;)

    I believe you were our first or second 4 layer board order. This house is slow, slow, slow. They advertise 4-5days for normal service, but we’re finding it takes at least 8 days. The rush service you ordered is much faster and they do meet the advertised 24 or 48 hour turn (minus weekends). The main thing is they’re cheap. Really unbelievably cheap.

    For orders without issues the timeline for non-rush 4layer order is now about 12 days from submit to your doorstep. If you’re willing to cough up for rush service we can reduce that to 5-6 days if it doesn’t straddle two weekends. Additionally, we do have access to UPS/Fedex same/next day service. It’s EXPENSIVE (like 4-8x more), but upon request we can get it there in 48-72 hours if you’re feeling super posh (or have a nice expense account).

    I’ll be posting our adventures in dirty pcbs soon, this will surely be a post :)

    Thanks again for giving us a try and a favorable review despite the delay.

    Best regards,

    Ian

  2. Kevin, Thanks for doing this comparison- I’m always on the hunt for good prototyping houses. I noticed you’re using a card edge connector and that the Dirty PCB is not ENIG finish (HASL? Immersion silver?). You mentioned that the circuit wasn’t working, but if you ended up a non-gold-plated board for the card edge, I’d be interested to hear if there were any issues with signal reliability or wear over time. Thanks!

    • I haven’t ended up plugging either of these cards into anything yet, but I do have another project which uses the same kind of connector with the same PCB process (HASL, I believe; this time through seeedstudio). I think some of those boards have probably accumulated 20 insertions; they’re visibly scratched but I’ve never noticed any issues from that; that project doesn’t do anything high-speed, so I can’t comment on signal reliability. I believe the receptacles are usually only rated for 50 insertion cycles and the boards seem to be roughly approaching that, so so far I feel pretty good about using HASL. If it was something I was expecting to insert+remove a lot I probably wouldn’t go with a card edge connector in the first place. ymmv of course :)

  3. I am so glad you posted this review, because my current project requires specific soldermask colors. I can tolerate slow shipping speed in exchange for this requirement, as long as cost and quality are not compromised relative to OSH Park (which I would normally support if it wasn’t for this color requirement!)

    Thanks,
    Neel


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