ElectronicsFabricationGuide

Electronics Fabrication Guide

Introduction

This is a simple guide for people that are new to making circuit boards or soldering.

Soldering

Before you start

Preparing surfaces

The surface we're primarily concerned with is the copper side of the board that you are about to solder, but do make sure your workbench is clear of any crud that may get in your way or adhere to the bottom of the board.

Make sure there is no grease or dirt on the copper. If you're suspicious, wipe it down with a rag and methylated spirits, acetone or similar degreaser. Do not use paper towels - they turn to fluff rapidly.

If the copper is not bright and shiny, rub with very fine silicon carbide paper, or one of those green kitchen scouring pads. You may need to clean with meths again. Allow the board to dry and put the lids on your solvents before commencing soldering.

• Others...

How to solder

Practice. The object of the exercise is to wet the surfaces of both parts you want to join with liquid metal. Once nice and shiny, they are then brought together and enough solder is added to hold them happily together.

When soldering stripboard, always clean it first unless it is brand, spanking new with a mirror finish (see section on stripboard).

Make sure your soldering iron tip is nice and shiny too. Wipe with moist soldering sponge (or wadded paper tissue), and if necessary scrape off accumulated crud with something stiffer like a wire brush, using minimum force. Apply a little more solder if it is not coating, and wipe again to get that beautiful mirror finish.

If the component legs do not have a solder finish, heat up the leg with the soldering iron and push solder onto the other side of the leg. This is good practice for understanding solder's behaviour too. Once you have pushed a coat of solder around the wire, which should take a second at most, remove solder and iron and ditch the excess solder inevitably clinging to the bit.

This process is called "tinning" and two tinned surfaces - say, a couple of wires twisted together - coat with additional solder extremely easily, forming a good electrical connection and a mechanically sound joint.

Now you can start to solder stripboard. You did remember this is a practice run, right? Put the victim part in the holes, and bend it's little legs so it stays put. Bring the soldering iron onto the copper strip near a hole with the component in it, so it touches the copper and the face of the bit is on the component leg. Push the solder in from the side, touching the point of contact between the soldering iron and the copper strip. As soon as the solder melts, divert solder only onto the now hot copper strip. If it doesn't spread around the hole itself, encourage it with the soldering iron tip.

Pull soldering iron and solder away when the solder starts to 'creep' across the copper strip. It is now flowing properly. Allow the solder to cool and set before moving the board - you'll see an obvious phase change.

Trim unwanted wires and legs off short.

When soldering, practice first on something unimportant if you're not sure. If your joints go grey and fuzzy, let the iron get hotter before using it and don't blow on the joint. Re-melt fuzzy or "dry" joints and add a tiny bit more solder so that they go shiny.

Did we mention practicing?

Making stripboard circuits

Stripboard is commonly used for making small runs of simple circuits. It has a matrix of small holes on a 2.5mm grid, connected in stripes on the reverse by lines of copper. It is readily available from electronic hobbyist suppliers worldwide. Maufacturers include Datak and Vero.

The strips on the back of the board need to be "separated" at certain points, to remove undesired connections between components placed on the board. The easiest way to do this is to use a small electric drill with a drill bit around 3-4mm in diameter. Don't drill all the way, just far enough to cut the copper tracks - you may find a 3.5mm drill in a hand-held chuck is easier to control.

The strips then need to be cleaned to ensure oxide and grime accumulated in storage are removed. Methylated spirit and MEK are a good de-greasers. If oxide is a problem, and the copper is not perfectly shiny, run a fine silicon carbide paper over it. No fine paper? Use one of those green scrubbing pads from the kitchen. If spouse disapproves, use "Brasso", wipe down well and replace ruined cleaning pad...

If you should cut a strip in the wrong place, solder a wire jumper over the top. It is a good idea to isolate mounting holes too.

Etching PCBs

Link to some other site?

Heat-shrink Tubing

Anyone ?

-- Main.SimonMcAuliffe - 02 Feb 2006