First ebay Minimig sells for £214 (305 EUR / $428 US)

[koaftder]

I'd say someone with some basic skills who is familiar with smt stuff should be able to put together a minimig in about an hour.

I only took me about 5 minutes max to lay down the fpga, and thats the hardest component on the board. As small as the leads may be, you still don't need any magnification or special tools to get it on there.



flux the pads
rake the iron across the pads to build up a layer of solder
center the chip on the pads
tack down two corners
double check the centering
get a tiny solder ball on the tip of the iron, place down the iron at the start of the pad and trace it along the pad until it bumps the lead, you'll see surface tension on the solder work it way up the lead, etc.

For the chip resistors and caps, I smear some paste on both pads and build up a thin layer of solder on both of them. I then center the device on the pad, press down on it and hit one side, then i do the other and then go back and hit the first side again. Actually, I add the solder layer on all the pads for all the device before i start, that way it only takes a few seconds per device to tack them down.

[koaftder]

I don't bother wicking sub mm traces as they don't build up significantly, on larger traces, definitely. One needs to be mindful of using the braid on thin traces as if it is allowed to cool it is very easy to accidentally lift traces off the pcb.

Pre-tinned boards are definitely more convenient.

Flux is definitely important. I always apply flux to the pads  after tinning which helps prevent the part from sliding around as much and much and makes the solder adhere to surfaces much better. I recommend being minimal with the solder and liberal with the flux. It is far easier to remove the excess flux than it is to clean up gobs of solder bridges on a qfp.

One thing I have been wondering about is the method of tinning one pad, tacking it down, and then going to the other pad and applying solder. This method would appear to make sure the part is level with the board.

When I do it, I tin both pads, solder one side, then the other, and go back to the first side again. This is much faster than having to hit one side with the iron and push a wire of solder into the other side.

So the way I do it, when I hit the first side and press down, its going to tack down at a slight angle. When I do the other side it should tension the opposite side right? Thats why I go back to the first pad and hit it again, to make sure it's not in tension. Is this necessary?

[koaftder]

freqmax wrote:
What's the easiest way to program the PIC18 for this project?
(optimized for simplicity and minimum amount of components)

There is a plethora of schematics and free software out there for programming pics with parts you can easily pick up at radio shack, but I use the PicKit 2 from microchip. For $50 dollars, it's well worth it and very easy to use, it even comes with a cd and a demo board. Dennis also uses the pic kit 2.

[koaftder]

wizard66 wrote:

koaftder wrote:
I'd say someone with some basic skills who is familiar with smt stuff should be able to put together a minimig in about an hour.

Impossible with the minimig trust me !!

If you have all your parts laid out and your bom on the table you really can do this in about an hour. How long does it take to lay down the microprocessor? A few minutes at most. I got the fpga on there in about 5 minutes. It only takes a few seconds to lay down a chip resistor or capacitor. Soldering down thru hole dsubs takes less than a minute.

The minimig is not a big board and doesn't have that many parts, the parts it does have are trivial to solder.

[koaftder]

amazing wrote:
@Koaftder
stop the smacktalk..u cant put the minimig together in 1hour
impossible...

u also have to test the 5v circuit..or did u forget about that?

and i suppose u want to have a nice clean board with all components a bit lined out?

I've been slack about ordering the parts. I'll polish it up this evening and when I get the remaining parts I'll video record the process. We should do a minimig assembly speed compo.

[koaftder]

HenryCase wrote:

koaftder wrote:
I don't bother wicking sub mm traces as they don't build up significantly, on larger traces, definitely. One needs to be mindful of using the braid on thin traces as if it is allowed to cool it is very easy to accidentally lift traces off the pcb.

Interesting. I intend to be doing some SMT soldering in the next couple of weeks (I'm upgrading the RAM in my chipped Xbox to 128MB), definitely something I'll bear in mind.

This is the method I will be using:
http://warmcat.com/milksop/soldering.html
Seems pretty straightforward (please bear in mind I have done soldering before, I do realise SMT soldering is a little beyond complete beginner level).

I wouldn't laydown a flat pack like that, though many do. It's just not necessary to make one giant solder bridge across the leads like that. You are dumping heat into the chip unevenly and creating more cleanup work than is necessary.