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Offline LukeZ

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Assembling Boards by Hand
« on: August 09, 2017, 12:24:46 PM »
I know several people are planning or have mentioned building boards by hand, and I've gotten several messages on this topic. I think we need a public place to discuss this.

Most people are not going to want to attempt hand builds, but for those that do here is a place to discuss your experiences and ask questions. It doesn't matter if you are building the TCB, Scout or Sound Card, post here and I will try to help as best I can.

Good luck!

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Offline Thor91172

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Re: Assembling Boards by Hand
« Reply #1 on: August 10, 2017, 11:19:23 AM »
Hopefully this will help others.  Please double check for errors.

John
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scout_top.pdf
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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #2 on: August 10, 2017, 02:24:36 PM »
John that looks good. R1 is named "P1" but otherwise it looks about right.

When I assemble these, I usually set out before hand all the components, and the small things like resistors and capacitors I've written on the tape their values. For that reason when I assemble it is usually faster for me just to know what value goes where, than what part number, at least for the resistors and small caps. Larger items of course you can tell where they go just by looking.

Here is an alternate version with values listed for most parts, and part numbers for others. Maybe this will be useful as well.
Scout_v1r10_Placement.jpg
Assembling Boards by Hand Scout_v1r10_Placement.jpg
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Scout_v1r10_Placement.pdf
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Offline dannydeleon

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Re: Assembling Boards by Hand
« Reply #3 on: August 11, 2017, 02:19:27 PM »
Hi Luke,

I have ordered the PCBs for both the Scout and the Sound card from OSH Park. I see that the Scout have U1, U2, Q1 and Q2 with solder pads under them while the Sound Card only has C6. Will a hot air rework station suffice to solder these or do I have to use a reflow oven for both or can I just use the hot air station for the sound card?

Thanks,
Danny

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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #4 on: August 11, 2017, 03:20:36 PM »
Hi Danny, I've never owned or used a hot air station so I can't say how it compares to a hot plate/oven. My impression has been that hot air is used for re-working individual components rather than for bulk assembly but again, I have no experience with them so what do I know.

I'm inclined to say a hot plate is going to be easier and more consistent, but regardless you're going to have to use something other than a soldering iron. And if you're going to reflow any of it, just reflow all of it, it will be much easier.

Also - C6 on the sound board is just a regular capacitor. The two components that can't be soldered by hand on that one are actually U1 (the amp) and the SD card adapter.
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Offline johnnyvd

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Re: Assembling Boards by Hand
« Reply #5 on: August 12, 2017, 01:03:09 AM »
I would recommend using a reflow oven. The temperature profile of the solder is quite precise. And the SMD components need some time to "settle".

Currently i'm building a reflow controller for a infrared oven. Here's the blog of the guy that developed it: http://andybrown.me.uk/2015/07/12/awreflow2/

10 PCB's are on the way from https://www.seeedstudio.com/fusion_pcb.html most of the parts can be easily aquired at ebay or aliexpress.

I will post updates in this thread, but because of shipping times these will take some time  ;)

I have added the BOM for the Reflow controller as the one on Andy's website is not very "complete"..
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Andy Workshop Reflow.xlsx
(17.46 kB ~ Downloads: 14)
pcb_built_large.jpg
Assembling Boards by Hand pcb_built_large.jpg
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schematic.pdf
(100.24 kB ~ Downloads: 20)
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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #6 on: August 12, 2017, 10:26:15 AM »
Reflow ovens are great and the DIY controllers are very cool and fun. However, you don't need all that stuff if you don't have the time or money. I've assembled all my boards on hot plate that cost less than $20 at the grocery store or Amazon.

For a temperature controller I use my thumb and forefinger on the knob. I try not to let the temp get above 200* Celsius because it's easy to remember and the paste I use melts at 183* (Mechanic MCN-300 for a few bucks on eBay).

I've used a cheap IR thermometer to monitor temps. It works ok. Later I "upgraded" to a thermocouple on my multimeter. On the cheap plates I've used, somewhere around the "Low" setting is all you need, they get pretty hot. If you're not paying attention you can burn your board.

Heat it up, wait till everything flows, then unplug and let it cool. We're not building anything especially delicate or complicated, so the crude approach works just fine.

If you can do it better then by all means! But for others not inclined, the quick and dirty method works too.
ThreeScouts.jpg
Assembling Boards by Hand ThreeScouts.jpg
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Offline jhamm

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Re: Assembling Boards by Hand
« Reply #7 on: August 12, 2017, 11:52:50 AM »
Luke,
i am impressed
On such a simple solution I would not have come!

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Offline johnnyvd

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Re: Assembling Boards by Hand
« Reply #8 on: August 12, 2017, 01:47:19 PM »
Check this overview of reflow possibilities: https://www.sparkfun.com/tutorials/59 get your fryingpan ready for some reflowing!
* E-75 / E-100 PAK44 "monster" - in progress
* Sturmjagdtiger PAK44 - in progress
* pz.kpfw KV-2 754(r) - in progress
* T-34 88mm "Kurland Tiger" - in progress

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Offline fuchstraumer

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Re: Assembling Boards by Hand
« Reply #9 on: August 16, 2017, 09:58:26 AM »
I've been looking at assembling some of these boards by hand: it is fortuitous that I have two tanks to refurb, since OSH park requires 3 boards... and clearly that 3rd board is a sign I should order another tank (been thinking about getting a Leopard and working on some kind of stabilizer)

Anyways, Digikey is pretty critically out of one component in particular: BAT54S-FDICT-ND, the diode for the recoil trigger. I've not been able to find any alternates: any similar models have the wrong diode configuration. Any go-to alternates? Next best option I found was https://www.digikey.com/product-detail/en/diodes-incorporated/BAT54STA/BAT54SCT-ND/243050, or the BAT54SCT-ND. Its got twice the leakage current, but should that really be a tremendous design concern in this case?

Otherwise I've been able to source alternates for the sound card, and I'm going to get a digikey cart/csv sheet for the scout later today. I've not done SMD stuff in a long time, but I'll probably be able to use the reflow oven at work (hopefully, working on space-grade stuff here means there's some red tape and regs about personal projects)

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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #10 on: August 16, 2017, 10:09:59 AM »
For reference this is D13 on the schematic, here is the original part specified in the BOM: BAT54S-7-F.

The alternative you linked to would work, but DigiKey is also showing it as 0 stock.

Instead I would use this direct replacement, over 165k in stock: BAT54S.

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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #11 on: August 16, 2017, 10:37:59 AM »
I updated the TCB bill of materials on the Downloads page with the in-stock diode.
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Offline Lotuswins

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Re: Assembling Boards by Hand
« Reply #12 on: August 22, 2017, 09:09:52 PM »
Luke,

What is the white disk material (and square clear) between the hot plate and the boards?? Is it to disperse the heat, making it more even over the boards?  And where do you measure the temperature? on the board, the white, or?? 

thanks, Jerry

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Offline LukeZ

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Re: Assembling Boards by Hand
« Reply #13 on: August 22, 2017, 10:22:43 PM »
Jerry, that's just a piece of aluminum foil. Absolutely not required and it does nothing to help distribute the heat.

The solder paste is a mixture of flux and solder balls. As it melts the flux often finds its way through holes in the board (called vias) and can stain your hot plate, and leave unsightly marks on the bottom of your PCBs as it burns (it will leave unsightly marks anyway, but not so bad with the foil). I put aluminum foil down to keep things clean in case I want to use that hot plate for food some day. :)

If you are using an IR thermometer you can point the beam at the board surface since that is the relevant temperature to measure. Since I have taken to using a thermocouple I just put it on the hot plate surface since obviously it can't go on the boards.

You will quickly realize there is nothing precise about this process. Temperature control on these hot plates is very crude. As long as you don't overheat things, you will be fine. You can easily see with your eyes when the solder begins to flow, at that point you know you don't need it any hotter. 

The best way to prevent burning is to bring the temperature up gradually. The hot plate will heat up much faster than the boards sitting on its surface, and the hot plate also cools down very slowly (the heating surface is typically made of cast iron which holds heat for a very long time). What this means is that while you can always make the plate hotter, once it reaches a given temperature you can not reduce the temperature anytime soon. If it gets too hot you are in a bad situation, and if you don't watch the temp closely it can easily get away from you and there is no way to bring it back down. The boards will be too hot to touch so you won't be able to remove them by hand, and anyway jostling them could cause your components to come loose.

So turn on the hot plate for a short bit, then off. Monitor the temp. Let it go up slowly. Turn the adjustment knob to a low enough setting that it is cycling itself below your target temperature, and only increase the setting gradually.

It doesn't matter how quickly or slowly the temp rises, but doing it slowly helps you keep things under control and makes it less likely you will overshoot and burn something.

As I say, when the solder starts to reflow you will clearly see it. That usually happens around 200* celsius. At that point you don't need it any hotter. Just maintain that temp until every contact has reflowed (turned shiny) and you're done.

After you do this once you will understand how easy it is. Trying to explain it in words makes it sound more difficult than it really is.

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Re: Assembling Boards by Hand
« Reply #14 on: November 19, 2017, 10:51:16 AM »
Good afternoon. First congratulate Luke for this great job. I ordered some scout pcb (rev.10) to seed, soldered the components with a hot plate as recommended. Burned the 328p atmega through the isp using an arduino nano and the arduino ide as (arduino as isp) then with the same arduino as cable ftdi and uploaded the program with open panzer. I think it went up well since it did not No error message. But a doubt arises when I connect the scout to the tcb by the serial port following the letters of the tcb and the scout (tx-rx- gnd) these are not in the same order on the two plates. as the plates mark, the red LED lights up intermittently and does not respond to any order of the control. but if I connect the cables in the same order as shown in the tcb, the blue led lights steadily, but does not respond to the movement of the stick, but if I move a wheel of the station to which I am assigned in a position the lights and in another cannon shot. When I put the firing position (if I have the airsoft gun disconnected) one of the engines moves a little towards a direction. If I have the gun connected it shoots and at the same time tries to move the engine but much less than if it is not connected and when this happens the blue led of the scout turns off and the red one turns on 4 times. I have to say that I do not have sbus or ibus station. if not a ppm adapter that transforms the signal from my standard receiver to ppm. the movement of the tower works and the lights on and off. if you can tell me if it's a problem with the station or the scout. a greeting sorry for the billet