Solder School

The board is laid out as four levels, left to right, and each one shrinks.

Level 1 — big pads. Twelve 1.00 mm holes with generous copper rings. These are the joints where you learn what a good one looks and sounds like: the iron heats pad and lead together, the solder flows in and makes a shiny cone, and you move on. Almost impossible to get wrong, which is the point.

Level 2 — medium pads. Twenty-four joints at 0.80 mm. The same technique, less margin. This is where most people stop burning the board.

Level 3 — the header grid. Forty holes on a 2.54 mm pitch in an 8 × 5 block. Standard header pitch, the same spacing you will meet on every Arduino, every Raspberry Pi hat, every breakout board you ever buy. Solder a 40-pin strip here and you have done the single most common job in electronics.

Level 4 — surface mount. Twenty-four SMD lands in two rows: six larger 1206 pairs, then six smaller 0805 pairs. No holes to hold anything. You tin one pad, slide the part in with tweezers, then solder the other side. It feels impossible for about ten minutes and then it feels routine.

Level 4 — the chip. An SO-8 footprint, 1.27 mm pin pitch, eight pads of 0.60 × 2.00 mm. Soldering an IC is the moment beginners think they cannot do electronics. You can. The land pattern is drawn to IPC-7351B with 0.67 mm of clear mask between pads, so drag-soldering and wick clean-up both behave the way the tutorials say they should.

Below the practice levels is the finish line: three LEDs, three resistors, a buzzer, a tact switch and a CR2032 holder — a small circuit that is genuinely wired up. Twenty more joints, and they are the only ones on the board that matter electrically.

Hold the button down. All three LEDs should light and the buzzer should sound at the same time. One LED dark means one cold joint, and you know exactly which one to reflow. Nothing at all means the battery, switch or ground side needs a look. It is the cheapest test equipment there is: a circuit simple enough that its failure modes teach you something.

The button gates the whole circuit, so standby current is zero. The cell only feeds the board while your finger is on the button. Leave the board in a drawer for a year and the battery will still be good — no flat CR2032 waiting for you the way it is with every always-on trainer board.

Work left to right, one level at a time. Set the iron to about 330 °C, wipe the tip on the sponge and melt a little solder onto it before your first joint. Every through-hole joint is the same four moves: hold the iron on the pad and the lead together for 1–2 seconds, feed solder into the joint (not onto the iron), take the solder away, then take the iron away. A good joint is a smooth, shiny cone that hugs the lead.

Level 1 — big pads (12 joints)

1. Bend a spare lead or wire link into a U so both ends drop into two neighbouring holes.
2. Push it flat against the board, turn the board over and splay the ends slightly so it cannot fall out.
3. Solder both ends, then trim the leads just above the joint with flush cutters.
4. Repeat until all 12 pads are done. Check each one: shiny cone, no ball sitting on top, no gap around the lead.

Level 2 — medium pads (24 joints)

1. Same method, same links. The smaller pads need less solder and less time — about one second of heat is enough.
2. If the board around a pad starts to darken, you are holding the iron on too long.
3. Trim and inspect as before. Too much solder bridges neighbouring pads here; if it happens, clean it off with desoldering wick.

Level 3 — header grid (40 joints)

1. Use the round-pin headers supplied. Standard square header pins are too thick for these holes — do not force them.
2. Break the strips into lengths that match the rows of the grid and push them in from the front.
3. Turn the board over and rest it on the table so the header sits flat. Solder one end pin only, check the header is straight, re-melt that pin to adjust if needed, then solder the rest.
4. Do not trim header pins. Look closely for bridges between neighbouring pins — 2.54 mm is close.

Level 4 — surface mount (24 joints)

1. Start with the larger 1206 pads, then move to the smaller 0805 ones.
2. Melt a small blob of solder onto one pad of a pair only.
3. Hold the resistor with tweezers, re-melt the blob and slide the part in flat against the board. Take the iron away first, then let go.
4. Solder the other end, then touch the first end again so both joints are smooth. These pads are practice only, so the resistor values do not matter.

Level 4 — the SO-8 chip (8 joints)

1. Line up the dot on the chip (pin 1) with the pin-1 mark on the footprint, with all eight legs centred on their pads.
2. Tack one corner pin, check the alignment, then tack the opposite corner.
3. Solder the remaining pins one at a time — or, with a little flux, drag the iron along each row.
4. If two pins bridge, add flux and pull the excess off with wick.

Finish line — the working circuit (20 joints)

These are the only joints that carry current, so take your time. Fit the parts lowest first, so each one stays flat when you turn the board over.

1. Resistors (R). Stand each 1 kΩ resistor upright: bend one lead down alongside the body so both leads fit the holes. Resistors can go either way round. Solder and trim.
2. LEDs. The short leg — the flat side of the LED — goes into the hole marked K. Push each LED down, solder, trim. Red or yellow LEDs only.
3. Tact switch (SW). Line its legs up with the holes and press until it sits flat on the board, then solder every leg.
4. Buzzer (BZ). The longer leg, or the one marked +, goes to BZ+. If the buzzer has a paper seal on top, peel it off after soldering.
5. CR2032 holder. Fit it as shown by the CELL THIS SIDE mark and solder both pins. Skip this step if the holder is already fitted.
6. Test. Only now, with the iron away, fit a CR2032 cell as the holder shows. Hold the button: all three LEDs should light and the buzzer should sound.

If something does not work: one LED dark — check that its short leg is in K, then reflow that LED and its resistor. Nothing at all — check the cell is the right way up, then reflow the switch, the buzzer and the holder.

Every pad in Levels 1 to 4 is deliberately isolated. There is no hidden net, no short waiting to happen, nothing you can damage. Solder whatever you like into them, desolder it, do it again. The silkscreen states this on the board itself so nobody wastes an evening looking for a fault that was never there.

This is not a cheap single-sided offcut. It is a proper 2-layer FR-4 board, 1.6 mm thick, on Kingboard KB-6164 laminate (UL file E123995) with a measured Tg of 140 °C and a UL94 V-0 flammability rating. The measured copper peel strength is 1.60 N/mm against a 1.05 N/mm specification, and the laminate survives more than 240 seconds of 288 °C thermal stress where the spec asks for ten. In plain terms: a beginner leaning on the iron for far too long is not going to lift a pad or scorch the substrate.

The pads are ENIG — immersion gold over nickel. Gold does not oxidise, so the board solders as cleanly on the day you open it as it would have on the day it was made, and it stays that way through however many sessions it takes. The mask is white with black legend, so the printed instructions and component markings are easy to read under a desk lamp.

Four 3.2 mm mounting holes on a 92 × 72 mm pattern let you screw it to a stand or a desk if you want it held still while you work.

The full build instructions are on the back silkscreen — no lost leaflet, no tab left open. Component markings on the front tell you where each part goes and which way round: R, LED with the K cathode flat, BZ+ and BZ−, CR2032, SO-8. A QR code on the back takes you to the online build guide at diykit.ae for the step-by-step version with photos.

There is one warning printed on the back, and it is worth repeating here: fit the cell last, and never solder with it in.

Every part the board needs to work, except the battery. The CR2032 coin cell is not included — use any standard 3 V CR2032, and fit it last, after all soldering is done.

A single 40-pin strip is 101.6 mm long — longer than the board — which is why Level 3 ships as two 20-pin strips.