fabrication in UK

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ast8346
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fabrication in UK

Postby ast8346 » Tue Mar 03, 2015 11:04 pm

Hello

I need some advice where to print and assemble the board I think I have finished designing. It is AD-DA converter, USB output.

Here I would like to attach a screenshot from Eagle with layout setup, also on background you can see XMOS U8A BGA and how close it is routed, apart from BGA I have also got 2 QFNs

I will provide all components, but essentially I am looking for a place in UK where I can be present during manufacturing process (I am a student and genuinely interested in things).

I live in Manchester area, but I would not mind to travel, to say Bristol or London or anywhere else

To send the board to China or US can also be done, depending on financial benefits of it...

Looking forward for any advice

Thanks a lot!

Anton

edit. just found that OSH Park can do PCB print of it for $133 + VAT & delivery within 12 days, if I do that, I still need a place in UK where I can assemble complex components
Attachments
sshot-1.png
AD-DA Converter
(332.95 KiB) Not downloaded yet
sshot-1.png
AD-DA Converter
(332.95 KiB) Not downloaded yet
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Folknology
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Postby Folknology » Wed Mar 04, 2015 1:05 pm

I was very surprised to see you have used through hole components in your design rather than SMD parts, is there a reason for this?
You would also need to run a DRC check as many of the vias look a little large and will probably have clearance issues, along with many of the BGA tracks. If you don't have an eagle DRU file perhaps use one of PCB pool's (prob the high spec version) for now.

regards
Al
ast8346
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Postby ast8346 » Wed Mar 04, 2015 9:36 pm

Hi Al, thank you for your message
The reason for through hole components is to enable me to easily change them if I want. Say I want to try how does 500 ohm resistor work instead of 1k. That's the main reason. (I guess I could buy SMD soldering station,,)
The other one is to simplify fabrication process, so I can make at least some of the work myself.
That is a prototype, if I will ever get to making it to production, that will be SMD only.
About vias, I was just using some 'safe size', again to simplify fabrication process. Can probably make them smaller. Thank you for the link, I will check it. Eagle has got error check, but it is too strict.
Kind Regards,
Anton
ps. i should probably post the whole thing somewhere on forum :) The board is not quite in the state of sending it to print to be honest (although close to it), but I need to start looking for a place
Hagrid
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Postby Hagrid » Wed Mar 04, 2015 10:46 pm

Using through-hole for resistors (especially vertical ones) is going to drive up your assembly costs and won't necessarily deliver the benefit (swapping out resistors) you want.

The problem is that reworking a board to swap a through hole resistor means you have to clear the existing hole of solder after the old resistor is removed. Even if you have a "professional grade" desoldering system, there is a distinct risk of getting too much heat into the board and delaminating the copper from the board.

It is much easier and safer to swap out SMD chip resistors with a basic hot air station, a good pair of tweezers, a flux pen, and some fine desoldering braid. Just stick to medium size chips like 0603 or 0805.

As you indicated your desire to learn, I encourage you to follow the SMD path.

You might also try hooking up with a local hackerspace to see if they can give you some help. Perhaps https://hacman.org.uk/
ast8346
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Postby ast8346 » Wed Mar 04, 2015 10:58 pm

hmm well I did not think of removing old solder!
yes, that is a very good point. thank you
i tried fab lab manchester, we've made a wooden box for it! the best thing they have in such places is CNC Routing Machine, it is only good for traces like... 30 mil?
For component like BGA, I need some $$$ (£££ in UK!) level gear, I am afraid(
Hagrid
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Postby Hagrid » Thu Mar 05, 2015 9:08 am

Yeah, BGA is not a hot-air friendly device. Needs an oven.

The board you have is quite large (6x4 inch), so gets expensive in the per-square-inch stakes.

I use Hackvana for prototype PCBs (Mitch is an Aussie like me, gets the boards made in China and they send direct world wide). I am guessing that if you reduce the board size by using SMD components, you could significantly lower your cost. Mitch does 10 pieces of 10x10cm double side boards as a "special" for USD$39+postage (I think postage to AU was only about $4). He is also highly interactive in getting your boards just right before they are made (IRC freenode - try http://webchat.freenode.net/?channels=hackvana)
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Folknology
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Postby Folknology » Thu Mar 05, 2015 9:27 am

Hagrid is right, through hole tends to be harder for replacement than SMD I would definitely consider the SMD route it will likely be lower cost less to make both as prototype and manufacture, you can also follow Xmos's layout guides in the U8-64 datasheet.

This worries me :
Thank you for the link, I will check it. Eagle has got error check, but it is too strict.

The DRU checks are there for a very good reason, you use the Design Rules from your manufacture in order to ensure they can actually make your PCB, if you do not comply with these chances are your PCB will not work and it will just be an expensive experiment.

It really is a very good idea to pass all of the DRU checks with the appropriate DRU file or manual settings from your PCB manufacture.


regards
Al
ast8346
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Postby ast8346 » Thu Mar 05, 2015 3:05 pm

Hello
Well, I guess DRC was so strict to me because I didn't change default settings. DRU file is something I need to ask manufacturer to provide then. OK thanks for advice. I will replace TH for SMD then too. Sounds like a lot of work for me! :)
ps. Guys from Newbury electronics gave me £244 quote for PCB print + fine pitch components assembly within 10 days. I will probably do that, unless something else pops up.
Thanks again
ps. Hagrid, what is this hackvana? I have connected, what I am supposed to do next?:)
ast8346
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Postby ast8346 » Thu Mar 05, 2015 6:22 pm

Hi Al

Even after applying PCB Pool high spec rules, I still don't seem to be able to get rid of clearance issues even if changing trace size to 4mil! Please find the picture attached. The thick one on the left is 8mil, then it is 4mil, 8 again, and then 7 and 6mil on the right. All of them give clearance error. What I am doing wrong?

Thank You

Kind Regards

I guess I have to route under pins instead of between?
Attachments
clearance.png
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clearance.png
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Last edited by ast8346 on Thu Mar 05, 2015 7:01 pm, edited 1 time in total.
Hagrid
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Postby Hagrid » Thu Mar 05, 2015 6:48 pm

Hackvana is http://www.hackvana.com/store/

Mitch Davis is a Melbourne-based guy who does PCBs who spent several years in China. The IRC channel is where he hangs out with his customer community. Ask questions about PCB design and you will likely get a good set of responses almost instantly.

You should read his Guide to Hackvana PCBs. This includes a link to his Eagle DRU file

In particular, you can upload your PCB to GerbLook and post a link to them in the IRC channel for others to review and offer advice on issues such as your clearance questions. I am not an Eagle user so cannot advise on Eagle specifics.

The IRC channel is a bit like a virtual hackerspace operating 24/7 with people from all over the planet hanging out there. I am only there occasionally (AndrewDojo) though.

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