DSpace SMT kit Build Instructions


This is a kit intended for someone who wants to learn to do some serious surface mount component (SMT) soldering - we assume you have a reasonable skill at soldering normal through-hole components.

The kit builds a clone of the Arduino Leonardo with a bunch of RGB LEDs at one end - if you just want a Leonardo please buy one from the Arduino guys, their boards are more reliable, more solidly built, and probably cheaper than what you will get when you build this kit - besides we all owe them for creating such a cool infrastructure for us all to play with - please buy their stuff.

You will need ...


Checking your kit

Your kit should contain a circuit board, some fine lead-free solder, a pair of tweezers and a bunch of components. Before you start make sure all your parts are present and that you can identify them, don't remove them from the tape until just before you are about to solder them to the board

Check that all the parts in your kit are present, they're small, tiny even, lay them out on a clean well lit table (with solid coloured surface), don't lose any - note that resistors tend to be black or occasionally light blue, while capacitors are beige/brown, there are different numbers of each type of part. Capacitors also tend to be square in cross section while resistors are flatter. There will be 1 extra of each of the .1uF, 1k and 10k parts just in case you lose one.

Parts List

C1-10,14,18-1913+1.1uFcapacitor 0603
C11-13310uFcapacitor 0805
C15-16218pFcapacitor 0603
C1711uFcapacitor 0603
D11protection diode
F11PTCFUSE-1812 (larger fuse)
F21PTCFUSE-1206 (smaller fuse)
IC113.3V3.3v voltage regulator (5 pins)
IC21ATMEGA32U4-AUCPU (44 pins)
IC31NCP1117-5.05V VOLTAGE REGULATOR (2-3 pins plus pad)
IC41LM358op amp (8 pins)
LED1-2,43yellow LED 0603
LED31red LED 0603
P11power jack
Q11FDN340Ptransistor (3 pins)
R1,7-83+110kresistor 0603
R2-3222 ohmsresistor 0603
R4-6,94+11kresistor 0603
RGB0-1516WS2812RGB LED
SW11reset switch
USB-B1USB connector

SMT part sizes are often given by numbers like 0603, 0805, 1208 and 1812 - 0603s are the smallest we use here.

Board Alignment

The base board looks like this, components only go on the top. Turn the board so the text is the right way up, the USB connector is to the left, the LED array to the right - like this:

when we refer to "top", "left", right", "below" etc in the document below it will be about the board in this alignment.

Identifying Components

Components come in tape with a transparent layer holding them in place, you peel back the transparent layer to remove the components, don't do this until you're just about to solder them in place.

By design you can recognise the components from the number of parts on each piece of tape, the exception are the 18pF capacitors and 22 ohm resistors - there are two of each. As mentioned above capacitors are usually beige with a square cross section, resistors are black or occasionally (as in this case) light blue and flatter).

Soldering Technique

The board has been tinned with lead-free solder, you can choose to use lead free or leaded solder - use the finest solder you can find, some fine lead free solder is included in the kit.

Prepare your soldering iron - if you have a fine tipped iron just clean it and tin it well. Otherwise pull out a file and file the tip of your iron to a fine point (remember you may be filing lead dust off of it) carefully tin the result.

Find a good clear surface to work on - otherwise if you drop a part finding it will be hard

Tip: read through the instructions below, if you can find an old dead circuit board with some surface mount parts on it, if you have a hot air rework station available to you use it to remove some parts - just point the hot air at a component for a minute or so then gently lift it off with the tweezers. Then solder them back on. Now try it with a chip (be gentle about removing it so you don't damage the PCB traces). If you don't have hot air you can still remove small components by lying the iron down beside them so that both ends get hot and remove them with tweezers.

When you pick up a component with tweezers grab it by the narrow side, if you grab it from the long ends it's more likely to go 'ping' and be lost to the other side of the room. For the same reason avoid squeezing your tweezers too tightly.


We're going to solder a simple large component (a fuse) first, then an easy chip.

Next we'll do the CPU - we want to do this before we do the rest of the components to leave room to move around it

Then we'll solder all the small resistors, capacitors and small LEDs

The larger parts - fuses, large LEDS, the reset switch and crystal

Finally we'll do the through hole parts, the power connector and USB connector

Soldering simple components

Simple components like resistors, capacitors, leds, fuses etc are easy:

Do this as quickly as you can so you don't damage the board

Here's a YouTube video that shows you how to do it, there are lots of these check out a few before you start.

So for a first attempt look for one of the two poly fuses - F1 - the larger of the two fuses - it goes in the bottom left of the board just above one of the mounting holes and to the left of the holes for mounting for the power plug. Tin one pad, bring the fuse in and solder that end, wait until it cools the solder the other end. Normally when you are soldering small components you want to have your iron temperature in the range 370-390C - but for large components, like this fuse, being soldered to large lands on the PCB you may like to raise the temperature a bit until the solder flows well.

Soldering chips

It's easier to solder complex chips if the area around them is clear - for this reason we solder them first. Let's start with an easy part - IC4 the 8-pin LM358 goes just to the right of the fuse you just soldered.

Here's a great YouTube example of this technique

Next solder the CPU IC2 - it's a 44-pin chip with finer pitched pins. Use the same technique to start: solder one pin to align the chip, align it carefully so all the pins are over their pads, notice the round circle on the board (under the chip) align the index mark on the chip with that corner, and then solder an opposite pin to hold it all down.

At this point it will help if you spread some flux on the pins you're about to solder

Now you have a couple of options:

Now solder the 3.3v regulator IC1, and the 5v regulator IC3 - IC3 has a tab which must be soldered and 2 or 3 pins depending on the make (solder the pins first before the tab, it makes alignment easier). Note: the first generation of boards has a bug - the pads for IC3 are slightly wrong, gently bend down the 2 pins on the component so that they are straight, solder the tip of the tab to the pad (use a hot iron) and then the 2 other pins.

Finally solder the 3-pin transistor Q1

General components

Now we solder the resistors and capacitors - since the parts are not marked when yopu normally work swith SMT components you need to build up a good discipline, I remove parts from their packaging (usually a marked plastic bag), solder all the parts of one type, and putting them back in their packaging before moving to the next part - the last thing you want to end up with is two tapes of components on your desk and not be able to remember which values they are.

In this kit the parts don't come in individual plastic bags, but do the same thing, remove one piece of tape, identify it, solder all the components on it to the board.

These parts are tiny, be careful, don't squeeze on the tweezers too hard or they will go 'ping', if you do lose something get in touch and we'll see if we can help you - we've added an extra of some of the more common parts.

Install these parts in this order:

There are 4 small LEDs on the left hand side of the board - LED3, the power LED is red - look very closely at the LEDs, one end is marked, often with a green spot - that end the cathode and should face to the left of the board. These components are made pf a plastic that is very easily melted - be carefull.

D1 is a larger diode - note that the cathode is marked with a band, look at the marking on the board

Q2 is a crystal above the CPU, it doesn't matter which way around it goes

SW1 the reset switch on the left hand side can also go in either way around

RGB0-15 - the RGB LEDs have to go in the right way around, notice the chamfered corner and the marking on the board - these parts are made of a low temperature plastic you have to be careful about overheating them when soldering

Finally you can solder the through hole components, the power connector and the USB connector

Some parts are not included in the kit:

Using a reflow oven

This is an alternate operation to hand soldering the components, it's quicker and does a more profession looking job, of course you wont learn as much. You will need some solder paste and a reflow oven (or a converted toaster oven with a good thermostatic control designed for reflow) - I don't reccomend using a hot plate, your normal oven or a plain toaster oven - you will melt the RGB LEDs into slag.

Load up the solder paste into a dispenser (usually a syringe with a small tip). Under magnification drop a little paste onto each pad on the board, start in a far corner and carefully work towards yourself so you don't have to work over the top of paste you've already placed. Don't put any paste on the through hole parts (power connector and USB connector, we'll solder them by hand at the end. If you drop paste between pads especially on fine pitched components don't get too worried, surface tension during the reflow process will likely fix things up, but you can use a clean scalpel, or fine knife to separate pads if you like.

Add the parts to the board - do it in the same order as above, be careful about alignment (get the chips the right way around, watch out as you lean over the board to place parts, you don't want to smear the paste, you may want to roll your sleeves up.

When you're done go over the board with tweezers carefully looking for parts that may need realigning after being bumped during placement

Choose a reflow profile to match the solder paste you are using, run the board through the oven and take it out when it has cooled.

Under magnification check all the components, look for shorts between pins, and 'tombstoned' or missing parts (ones that are sticking up on end) rework those with you soldering iron

Finally hand solder in the USB and power connectors

Bring up and testing

Here's a finished board:

The simplest test is to plug your board into a USB connector and see what happens, rather than plugging it directly into a computer the first few times try and use a USB hub, just in case something bad happens. The first time you do it hold your finger on fuse F2, if it gets hot unplug it immediately. The red LED should light.

If the LED doesn't light or the fuse gets hot use a mutimeter to look for shorts - is the top pin of Q1 at 5v? is the bottom right one?

Don't solder things while they are plugged into the USB!

You computer should see the device - on Linux type 'dmesg' and see if it has logged being plugged in, on Windows check out the system control panel

If you don't see a device grab an oscilloscope and check the crystal leads for a 16MHz signal (set the voltage range to ~100mV/div) if it's not there looks for shorts on the crystal and the crystal pins on the CPU), then check the 4 power supply pins on the CPU for 5v - also look at R2/R3 and the soldering under the USB connectorEventually we'll ship these pre-programmed, the first few will need to be programmed after they have been built - talk to Paul.


The device is an Arduino Leonardo clone - program it in the Arduino development as if it were a Leonardo.

The 16 LEDs are what Ada calls NeoPixels - they are connected to Arduino digital pin 16 - using Ada's libraries you initialise it this way:

	#define PIN 16
	Adafruit_NeoPixel strip = Adafruit_NeoPixel(16, PIN, NEO_GRB + NEO_KHZ800);

The 16 LEDS are numbered left to right, top to bottom, you can extend them using the pins next to them

The simple strandtest Arduino program can be used to turn on the LED array and make it do pretty things


The 1.1/1.0 versions of the board have one known bug - the SCL/SDA pins (next to the Aref pin) are reversed from expected