2017-01-08 23:20 - Making
In early November, Seeed Studio contacted in regards to my PCB fab comparison post from 2015, asking that I also review them. After a short discussion they agreed to give me a $50 service credit in exchange for a review. This post is that review, of the Fusion PCB Prototyping Service.
I had two boards fabbed, plus a metal solder paste stencil. Let's get into the first board. This is for an incomplete project which I won't describe yet here, instead just covering the quality of the PCB.
They're fully routed, which seems to be common from Chinese fabs. There's one tiny "nipple" of extra FR4 consistently in one spot. I assume this is the very end of the tool path which somehow isn't quite completed. This seems to be common for individually routed boards, as I've seen this sort of issue from three separate (low-cost) fabs.
The good: there's both plated slots and non-plated holes, and they came out as desired.
The bad: a few boards have extra blobs of silkscreen scattered about, see the left two. In consistent locations, and there's two more boards (not pictured) with slightly more faint spots but again in the same locations. Those two I might have missed if it weren't for these very obvious two pointing out the locations. Several of the boards have scratches, more visible in person than in the scanned image here. One of them has a bit of solder mask missing from a spot over one of the traces. There are several blemishes in the solder mask, most too subtle to notice in the scan but one (on the bottom right pictured board) is severe. Perhaps one or two of the ten boards arrived without some form of blemish or scratch.
The ugly: order numbers added to the silkscreen layer. On this board, it's at the top right of the front layer, near the power connector. It seems they put a tiny bit of effort into hiding it under a component, but the presence at all is disappointing. I'd normally check this sort of thing ahead of time, but I selected Seeed because they approached me, not because of my normal evaluation process. I only got to it now that I have the boards and I'm taking the time to write a review. I went looking, and I found as the last entry in their FAQ the Seeed Production Code will be printed on empty space of your PCB page. Certainly could have been more up front with it. I didn't mind when Dirty PCBs did this, they're transparent about it. A way to hint to them where the printing would be least obtrusive would be an improvement. (In this case the fat DIP pads in the middle will be fully covered by a part, and anywhere on the back would be better than almost anywhere on the front.)
This second board is a revision of my environmental sensor project. It's mostly the same, but a USB/UART chip was added along with a few other small tweaks. I'm putting a front and back copy each of the first revision into the picture, for comparison. They're in the bottom right, clearly identifiable as the pair with a different color.
The good: Seeed's blue solder mask is actually blue! More of these boards came out okay: I put four of ten in my defect-free pile, as I was laying the rest on the scanner bed to show. All the issues I've got to bring up next are generally minor.
The bad: Still several defects, including scratches on lots of boards. One, pictured in the mid right, goes across several holes, deep enough to expose copper. Two of the boards, but one really in particular, had a surface finish issue, the whole thing being mottled. The silkscreen shows stippling everywhere on this board. Side-by-side with the rev A board (the bottom-right two) it's nearly unreadable by comparison. One of the boards has a stray speck of metal (solder, surely) sitting off in the middle of nowhere. Thank goodness it's not shorting something. Another has a foreign object in one of the through holes.
The ugly: this board cares about thermal properties, so it has several internal cutouts to help limit heat transfer. The Seeed boards are all routed sloppily. Most of the inner holes have at least one corner where the cut goes a bit too far, creating an extra divot. And still those order numbers in the silkscreen. Again sort of hidden under a part, at least they tried.
A curiosity: Silkscreen between fine pitch pads. Both rev A and B as well as my old prototype include the exact same TSSOP part (U3), with 0.65mm between pins (center to center, 0.40 wide). As best I can tell, the silkscreen gerber specifies one wide empty area across these pins in both revisions. But:
That's the same footprint manufactured thrice by three different fabs. On the left is the prototype by OSH Park, in the middle rev A by Elecrow, and on the right rev B by Seeed. It's the same "Housings_SSOP:TSSOP-8_3x3mm_Pitch0.65mm" default KiCad footprint in all three cases, with no custom clearance setting. The mask clearance ends up overlapping into one large rectangle covering each of the four pins on either side. That's just how OSH and Seeed fabbed it. But Elecrow actually filled in the mask between these pins anyway. I can't fault Seeed for fabbing the board as specified. Overall I'm not excited about the idea of the fab changing the design on my behalf. In this particular case, I like what Elecrow did, however. Perhaps I'd never have noticed if I wasn't scrutinizing the boards for this review, as I never had any trouble soldering them, even completely by hand.
I've laser cut my own stencils out of plastic before, but they've only worked okay. For roughly $20, and with a $50 coupon, I decided to order a metal one to see what that was like. Board two has several surface mount parts, and I added a QFN part in this revision.
There's not actually a lot to say here. The measurements were listed online in the order page (28 x 30 cm) but it was a case of ordering sight unseen over the internet and not truly understanding the size. I ended up cutting it down to make it practical to use by hand, and then it worked very well.
I have now used it once, and it was a fine experience. Especially including the narrow pitch QFN leads, which worked great the first time. But then, once I was done, I whipped the board under the microscope to check my joints. The soldering was fine, but up close, the silkscreen's quality issues were clearly revealed. Was the inkjet under-extruding? I can see that it's a bunch of separate dots, which do not connect to form any sort of line. The upper case letter "I" in "IO" is especially bad, sometimes one-and-a-half sometimes just one row of dots not quite making a line. (This is visible in the comparison shot of U3 above, as well.)
The order I made for everything reviewed above was two PCBs, 10 qty each, and one metal stencil. That's $9.90 x 2 plus $19.90 which seemed a reasonable $39.70. But that weight/size came to $84.20 total after shipping (!). If I try again without the stencil I get $34.89 total. The same no-stencil order comes out $32.84 at Elecrow.
For an order of just board one, Seeed quotes $9.90 for a basic board (1.6mm FR-4, 2 layer, qty 10, green mask, HASL, 1 oz copper). Great. But go through checkout and you'll discover that the cheapest shipping is $12.68, for 10-18 day service (3-5 day costs $19.43). Elecrow charges $11.50 for their 5x10cm service with otherwise identical specs, but they have a shipping option at only $6.60 (their 2-3 day costs $18.05). If you're patient that's $22.58 from Seeed, or $18.10 from Elecrow, and a wider difference if you're impatient. And if I were ordering there, I'd have squeezed into 5x5cm and saved another $2.
Which is another subtler issue. Elecrow puts their size-based pricing right up front. I've definitely designed to a 5x5 or 5x10 cm envelope before. But Seeed just has you type in your size and only then tells you the cost. It might be that this gives you more/better choice for what to do and what it will cost, but it's very hard to know what your board will cost ahead of time, or to know how to focus the design phase to optimize cost. Where is the line? Let's compare some known prices at Elecrow to what Seeed would charge:
A lot of data to say that they're both competitive, always within a few dollars of each other. When I use Elecrow's size increments. I've got another practical board in progress, it's 41 x 130 mm and external concerns force this particular size. At Elecrow I'd need to buy the 5x15 cm service at $23.48 for five copies. For five copies at this size Seeed charges $16.84, which is a significant difference (roughly 28%). But since Seeed will only tell me the final cost of a board after selecting all options, it's hard for me to take advantage of these possible savings.
For this review I've pulled out another set of two boards I ordered from Elecrow in late 2015. (A failed (suspended?) project which I won't go into...) They're of similar sizes to the Seeed boards reviewed here, and when looking at them with as critical an eye as I did when I started writing this detailed review, I did find two small scratches, out of eleven boards. But I did not find any other issues, most importantly no order numbers added to the silkscreen. The prices are very similar, and I can predict the price easily ahead of time.
If I don't need more than three and my boards are small, I'll definitely go for OSH Park. If I've got bigger boards or I want more than three copies though, Seeed probably won't be my go to in the future.