Here is my first surface mount board with the ATMEGA328P-AU. I am shooting for small scale manufacturer. The V1.x version of this board sold a large quantity over the past several years. I attached the board top and bottom. Can you help me check for "Design for manufacture" aspect?
I know I should add fuducial points but I don't know where and with what rule. Any suggestion is appreciated.
Since the board is simple, I was trying to use EAGLE autoroute. But the router made a bunch of vias to route all IC pins on the bottom (not bottom layer) and used bottom layers. Made no sense. So I hand routed most connections.
You have some traces on the red layer that are awfully thin, I would fix those. Looks like maybe remnants of autorouting with default settings.
Edit:NetClasses, check the width setting for the traces, clearances around traces.
When you're ready to make cards, contact cbas-usa.com in CA for assembly quote. You drop ship parts & boards & a check (no plastic last time I ordered), they send boards back using your FedEx account.
Thank you for the comments. Yes those thin traces (0.006") were done by auto router. I can increase them to 0.01", same width as the ones that I routed. Do you think 0.01" for signal is decent?
I have two net classes: default set at 0mil for width, drill and clearance. The other one is power, 14mil for width and 0mil for drill and clearance.
I am using Laen's DRU (OSH park). In his DRU, all clearances are set to 6mil. I guess this is the reason my autorouted traces are all 6mils (overriding 0mil default?)
Thanks. I made the changes. I had to reduce clearance to 6mils otherwise there is not enough space to route the GND and 5V pins on the chip. Also the SMD pads on the IC are too closely spaced for 10mil clearance and I got 72 design rule errors if I don't reduce clearance to 6mil The pads seem to be spaced out 0.01". This part came from Seeedstudio open parts library.
So about assembly, for something this simple, do you have a ball-park estimate from your past interactions with cbas-usa? I poked around seeedstudio's propagate service. Their minimal order is 100, and costs maybe $7.5 (including printing the board).
e-mail them & ask. If just a couple they'll probably suggest doing by hand, there are so few parts. If a lot, they'l quote you for a solder paste stencil, pick & place programming, and the actual assembly. I've only done larger boards, hard to say with this few components.
The autorouter has put a bunch of tracks about 6mil from nearby pads, since you've told it that that's OK.
Just because it's OK, doesn't mean it's the best idea; when I autoroute a PCB I then spend quite a bit of time pushing around the tracks (and resizing them) to make the board less prone to manufacturing and user errors.
On the blue side there's a couple of traces at the bottom that go below the big connector right to the edge of the board that could easily be rerouted more directly and wholly inside the connector footprint. Same goes for the connector on the right hand edge to a lesser extent.
Thanks. Marvin, do you mean LCD pin 2 should be routed more directly? I can see that. It is 5v that I can get from right side of the mcu.
Westfw, I later adjusted the default net class as CR advised and now minimal trace is 10mil. I am still learning EAGLE. There must be a way to have auto router do a few traces at a time.
Here you go - Tracks in orange are simplified routing
Also the connections between orange 1-1 and 2-2 could be done on the top layer to remove necessity for vias and also help with simplifying bottom layer more.
(Caveat - I can't 100% guarantee this is ok because some of the traces are obscured in the screenshots)
So I am ready to submit this board order. I've found most of the SMD parts and purchased them. One part still eluded my hands/mouse clicks, the 16MHz 5032 crystal with 2 contacts:
Scroll to the very end. Only one crystal is listed. I searched ebay and only found 4-pad crystals. They put together this library with parts that can be hand soldered. Maybe that's why they picked this one? Any source of this part?
I was using seeedstudio open parts library for EAGLE. They can assemble small quantities of boards if I use their parts. I thought they used it to help hand soldering. I will ask them though. Do you think "hand soldering" argument makes some sense?
The pads seem to be spaced out 0.01". This part came from Seeedstudio open parts library.
