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Author Topic: Klondike - 16 chip ASIC Open Source Board - Preliminary  (Read 434693 times)
BkkCoins
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May 12, 2013, 01:23:20 AM
 #481


Kinda sucks that these cost 4x as much as the X7R. It's possible to save a little with X5R, and I don't expect > 85C. Blah, better to spend $0.53 extra total and not worry about ceramic popcorn...

Hmm yeah that does suck...but I agree on avoiding the popcorn Tongue. I'm not sure if the X7R/X7S components could also handle higher temperatures during assembly, because there will be a lot of different techniques applied to get them on the board (skillets, IR-ovens, heck maybe even manual soldering). If they do support higher temps, that would be an additional argument for picking them.

I've gone through the nice KiCad files, and noticed that in the stencil (for paste) you've added only a minor blob of solderpaste to the center of each ASIC. Are you sure this would result in adequate heat dissipation to the PCB? I know that in theory the ASIC and PCB should touch, however, there could be minimal spacing which can be resolved with some soldering...
Looking at the bigger picture, the ASICs are designed to dissipate their heat to the PCB and not be actively cooled by a heatsink. Applying a heatsink to the plastic cast of the chip might not take away much heat at all?
I'm sure you've been thinking about this, so I'm probably wrong on the workings of the cooling, but maybe you don't mind putting my mind at ease Smiley?

The underside of the ASIC has thermal vias to transfer heat to the heat sink. Almost all it's heat is dissipated thru the bottom. I still have to change this from 4x4 grid to 5x5 to optimize heat transfer.

The paste layer has not been checked by me yet and it has some changes coming under the ASICs. There actually has to be less paste there, and usually in a cross hatch pattern not just a big blob. The problem is that you can end up with too much solder under the pad and solder doesn't conduct heat that well. Usually under a thermal pad you use a pattern with spaces (cross hatch) to cut down on paste qty. I don't think kicad has support for this so I'll have to figure out what to do. I may have to add several smaller zones there or fix it after in the gerbers.

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May 12, 2013, 01:27:53 AM
Last edit: May 12, 2013, 01:41:21 AM by WynX
 #482

Yes I was aiming for some paste-pattern (not bigger blob). But if its KiCad limitation then you'll surely figure it out. Thanks for clarifying, sounds good Smiley

EDIT: So it seems the center hole per 4 asics will be acting as some sort of heatpipe to the heatsink itself (next to the heatsink sitting directly on the plastic caps).
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May 12, 2013, 01:38:12 AM
 #483

Check the DIY site for the info on that. You should be doing a lot of research on your own for this to decide whether you will either do a the reflow yourself or outsource it. I think most people would be smart to get the boards already populated with components and then find a fab house locally to do the reflow especially having read the specs myself I think you need to get some serious skills and equipment if you are doing multiple boards.

https://www.sparkfun.com/tutorials/59

And more detailed info reflow with QFN chips.

http://www.ti.com/lit/an/sloa122/sloa122.pdf
http://www.ti.com/lit/an/slua271a/slua271a.pdf

Nice links!

reminds me of a video a while back from my fellow countryman Dave Jones from EEVblog.
http://youtu.be/M_rO6oPVsws

he mentions two methods to solder these QFN's and shows one of them. the chip he is soldering is tiny!
You can definitely do this stuff yourself; I hand solder all my stuff but I wouldn't want to do it if i had 100's to assemble. (it also helps that i've had training to solder to class 3 spec)

Part-time Computer Systems Engineering student - Full time Service Assurance (faults) for a large Telco.
sensei
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May 12, 2013, 01:55:50 AM
 #484

The paste under the QFN would be a grid of nine square areas.

See http://www.ti.com/lit/an/sloa122/sloa122.pdf
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May 12, 2013, 03:19:28 AM
Last edit: May 12, 2013, 03:34:05 AM by Bicknellski
 #485

Nice that everyone is pouring over the parts lists and plans for the boards and tacking on more and more information we need that as we can help catch typos etc that BKKcoins may overlook.

Maybe we can work putting together some information into a package for people who are going to do the reflow on their own. Give them an idea of techniques and a rough diy guide although all the videos and pages are great maybe we need something that is specific to the Klondike and given what we know of the design this can be worked on now and edited as BKKcoins reaches the end of the testing. We will need multiple languages. I will do an Indonesian / English version.

I will take all of the posts that BKKcoins and others of a tech nature and edit put that into a working document for us to edit, with that it can be used as reference for the DIYers out there.


Great Video Synapse... the more I see the less I want to try this... but I will be doing this with students this fall. Basically looking to this for a few K16 boards. Looks like I need some equipment.

Quote
Nice links!

reminds me of a video a while back from my fellow countryman Dave Jones from EEVblog.
http://youtu.be/M_rO6oPVsws

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Bicknellski
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May 12, 2013, 03:37:05 AM
Last edit: May 12, 2013, 06:26:53 AM by Bicknellski
 #486

The paste under the QFN would be a grid of nine square areas.

See http://www.ti.com/lit/an/sloa122/sloa122.pdf


http://www.actel.com/documents/QFN_AN.pdf <--- More QFN porn

http://www.youtube.com/watch?v=IhUGXEom6IM <--- Stencil Mate... hmmm might be interested if you are going to reflow yourself.

http://www.photostencil.com/pdf/Mastering-QFN-Challenges.pdf <--- Stencil for solder

http://www.solder.net/product <--- Website Order Stencils Here

http://www.pcb-devboards.de/catalog/product_info.php?cPath=66_71_75&products_id=10037 <--- Website Order Stencils Here

http://www.soldertools.net/product_images/PDFs/Reworking%20QFNs%20Newly%20Developed%20Cost%20Effective%20Approach.pdf <--- More info on QFN stencils and rework

http://www.soldertools.net/categories/Solder-Training-Kits/ <--- Need practice before the boards and chips arrive?

http://www.proto-advantage.com/store/product_info.php?products_id=2220077 <--- Buy Stencils

http://www.solder.net/products/stencilmate/evaluation-kit <-- Free Evaluation Kit for Stencil Mate.

http://www.proto-advantage.com/store/product_info.php?products_id=3000029{2}6 <------ QFN48 Stencil Kit

http://www.proto-advantage.com/store/datasheets/AN0001.pdf <---- Nice how to use of the Stencil Kit and equipment required.

http://hobbybotics.com/projects/hobbybotics-reflow-controller-v8-03/ <--- DIY Reflow Oven

Just asking... not sure if you have the time BKKcoins... just put it on the back burner if you get time later but can we get stencils for the solder mask for both the chips for bumping and for those who want to use masks on the PCBs one for a K16 board or just a a 4 chip quadrant.

Checking thickness of the solder info from a few pdf's on QFN 48 7 x 7 chips.

Quote
For 0.5 mm pitch parts, a stencil thickness of 0.125 mm is recommended. Also, to improve the paste release, a stainless steel stencil with electro-polished trapezoidal walls is recommended.

For the paste, it is recommended to use “No Clean”, Type 3 paste. Since the pads on the package are plated with 100% matte Sn, the package can be soldered using either Pb-free or SnPb solder paste.

Quote
Stencil screening the solder onto the PCB board is commonly used in the industry. The recommended stencil thickness used is 0.075 mm to 0.127 mm (0.003 in to 0.005 in) and the sidewalls of the stencil openings should be tapered approximately 5 degrees to facilitate the release of the paste when the stencil is removed from the PCB.

Can we get stencil templates?

1. For stenciling solder on the Avalon chips so we can bump the Avalon chip ourselves?
2. For stenciling solder to the entire K16 or one quadrant on the K16 (4 chip pads)?

Might be something that I can get fabricated in metal and if people are interested I can ship out once the boards are ready to be mass produced.

http://www.paceusa.com/sites/default/files/10072048.pdf

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May 12, 2013, 03:37:21 AM
 #487

Will we be able to use cgminer with the Klondike 16?
If so any idea how much effort will be involved with firmware & drivers.
It seems the current Avalon driver interfaces with the FPGA chip.
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May 12, 2013, 03:46:19 AM
 #488

Quote from: SebastianJu
I have read the recommendations about avalon miners and found this psu: Seasonic Platinum 1000
It seems to be a nice piece or work, you only need to put in the cables you need and it gets highest values in benchmarks. I think i will get one of these and hope it will be enough to run many or all diy-miners. Maybe, if needed, with y-cables. Unfortunately this psu never is sold cheap at ebay... i have an email alarm since a month without results... Smiley

The PSU is arguably the best investment you can make. Don't cheap out. Well-regarded brands (Corsair, Antec, Enermax) are popular for a reason: they don't die under heavy loads. Most of these have multiple 12V rails you can use, rated to a certain current (say 18A). It'll be important to not overload individual rails.

The Lepa 1600-MA is $288 at Amazon. I bought one. Four 30A rails, two 20A rails, 1600 watts total. 20mV ripple on combined 12V rails under full load with 87% efficiency (according to one review). Yeah, she'll drive a lot of boards nicely Cool
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May 12, 2013, 04:16:29 AM
 #489

Will we be able to use cgminer with the Klondike 16?
If so any idea how much effort will be involved with firmware & drivers.
It seems the current Avalon driver interfaces with the FPGA chip.
I'll be modifying the cgminer avalon driver to suit. Pretty much changing how it communicates with the board to use my own command set, but still acting as a serial port over USB. Unlike the Avalon it won't just blindly dump data to the chips. It will have an API to query the K16, send work, and whatever.

I started working on the firmware but have paused that while I finish the board now. I've had to move a bunch of caps around so this is taking a bit longer than just laying down data signals. And yesterday/today had some commitments to drive people around so some delays.

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May 12, 2013, 09:04:55 AM
 #490

I've heard alot of talk of the K16 unit but what's the status on the K1 units now? How many do you plan on making? I just wanna have a slight idea on how much I should save of my BTC for a few units and how many other people I have to contend with as I'm sure there will be a good demand for the K1's.
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May 12, 2013, 09:06:54 AM
 #491

I've heard alot of talk of the K16 unit but what's the status on the K1 units now? How many do you plan on making? I just wanna have a slight idea on how much I should save of my BTC for a few units and how many other people I have to contend with as I'm sure there will be a good demand for the K1's.

How many Avalon chips do you have?

Don't you need 4 layer?
Yes.

My tentative plans were to offer 6 products:
Board Only and Board w/Parts kit.

For each,

Klondike 1  - thumb size
Klondike 16 - 10x10cm
Klondike 64 - 20x20cm

Once I have a working prototype I'll start an "OpenBitcoinstore" site to take pre-orders. That way I know how big a PCB batch to run, and how many components. I'll have a bulk order rate for assemblers who want to source everything needed (but ASICs) the easy way.

I may offer an pre-assembled "Klondike 1" as well since I figure that's not beyond my means to build here. The rest I'm looking at shipping parts to my home in Canada, packing kits and shipping from both there and across the border in WA state (because Canada Post is too costly for x-border).

At least that's my thinking now unless I get talked into some better idea.

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May 12, 2013, 09:16:38 AM
 #492

I've got zero chips so far as I'm only interested in buying finished units and from what I read bkk is making the K1 units from his own chip stocks, I'd just like to know how many he's planning to make and an idea how much a finished unit would cost(Chip and all)
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May 12, 2013, 09:34:22 AM
 #493

I think Bkkcoins is assembling the K1 miners but you need to send him your asic chips.
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May 12, 2013, 09:57:36 AM
 #494

I've got zero chips so far as I'm only interested in buying finished units and from what I read bkk is making the K1 units from his own chip stocks, I'd just like to know how many he's planning to make and an idea how much a finished unit would cost(Chip and all)

You would have to have your own chips for these boards or any boards he makes. He does not supply chips from what I have read through in this thread. His supply is limited and I believe was even considering taking Avalon chips from people in trade for boards. There are number of chip buys right now... or maybe wait for others to use his designs to make singles later might be possible.

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May 12, 2013, 10:38:10 AM
 #495

I've got zero chips so far as I'm only interested in buying finished units and from what I read bkk is making the K1 units from his own chip stocks, I'd just like to know how many he's planning to make and an idea how much a finished unit would cost(Chip and all)

You would have to have your own chips for these boards or any boards he makes. He does not supply chips from what I have read through in this thread. His supply is limited and I believe was even considering taking Avalon chips from people in trade for boards. There are number of chip buys right now... or maybe wait for others to use his designs to make singles later might be possible.


And Terrahash is making full retail products out of these boards with case and offering hosting if needed etc.
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May 12, 2013, 10:40:18 AM
 #496

Point is I think if you want K1's you need to give chips to BKKcoins so he could do them for you. We are a few months away I think from that so keep following the thread.

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May 12, 2013, 10:45:14 AM
 #497

I've got zero chips so far as I'm only interested in buying finished units and from what I read bkk is making the K1 units from his own chip stocks, I'd just like to know how many he's planning to make and an idea how much a finished unit would cost(Chip and all)

You would have to have your own chips for these boards or any boards he makes. He does not supply chips from what I have read through in this thread. His supply is limited and I believe was even considering taking Avalon chips from people in trade for boards. There are number of chip buys right now... or maybe wait for others to use his designs to make singles later might be possible.
That's right - I have limited chips coming and the ones I have I'll be putting to work mining once the testing is done. I just don't have the capital resources to order lots of chips.

For the K1 I don't mind trading chips for assembly. It's actually helpful because I can't mine fast enough now to buy many chips. So maybe people will send me two chips and get one assembled K1 in return, or something like that.

I'll be limited in how many I can produce and it sounds like the demand will outstrip what I can do on my own here, so it may well be that K1's are also produced and sold by a licensed third party who is actually set up and in the business of making things, bypassing the investment in design and prototyping. We'll see soon enough.

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May 12, 2013, 11:16:06 AM
 #498

im also looking for a complete board , with everything included
but max $300 for every 5gh
Bicknellski
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May 12, 2013, 02:10:50 PM
 #499

im also looking for a complete board , with everything included
but max $300 for every 5gh

Try BFL.

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May 12, 2013, 02:22:35 PM
 #500

I only have enough chips for my own boards, but I will have the facilities to place them on the boards for any one who wants to send them my way.

Actually I was not impressed with the video of the QFN being placed on the PS board in an earlier post. I don't think the guy doing the work was really happy with it either. While he got theleads to flow, the was no real effort to get the heat sink to flow. He played with the edges.
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