Slide 1

SOLDERING

Making a sound electrical and mechanical joint.What Is Soldering?Soldering is a method of applying an alloy (filler metal), of lower melting point, to join metal parts together. The filler metal having a lowermelting pointthan the adjoining metal.Unlikewelding, soldering does not involve melting the work pieces.

It consists of a copper bit attached to iron rod at its one end, and a handle at the other end. It is used to melt the filler metal and paste it to make the joint. Soldering IronThe soldering iron must be placed into the specially designed stand, when not in use. These usually incorporate a sponge for keeping the bit clean. Electric solder iron is heated by passing electric current through it.

Solders

Solder is a filler metal made from an alloy (mixture) of tin (60%) and lead (40%) which acts as a bonding agent during the solder process. Having the lowest possible melting point minimizes heat stress on electronic components during soldering.

FluxCopper oxidizes very quickly in air. The transfer of heat is restricted by this oxidation layer.

Soldering to oxidized copper is very difficult, and you may damage the circuit board and/or components by having to hold the iron on the joint for long periods trying to get the solder to flow.

So a soldering flux, usually a rosin compound, is applied to the joint first to clean the joint and allow the solder to flow.

The most common type of flux used in electronics (soft soldering) wasrosin -based, using the rosin from selectedpine trees.Printed Circuit Boards

Perfboard(Perforated PCB)

PCB Stripboards

Copper Clad PCB

Soldering: Step-by-Step Guide

STEP 1 : Work PreparationWork pieces which are to be joined together should be perfectly clean. There should not be any dirt, dust, rust, paint or grease. Cleaning is done with the help of a file or sandpaper.

STEP 2 : Preparation of JointTo wet the metals of the base joint, the metals have to be clean. If the metals are not clean, the solder will not wet uniformly, and this fact will be hidden under a blob of solder.

STEP 3 : FluxingFlux is applied to the joint with the help of a brush before soldering.

STEP 4 : Tinning

In this step of soldering procedure, the bit of solder iron is cleaned Allow soldering iron to heat up. Clean the tip of iron on sponge. Feed 1/2cm solder onto the tip. Wipe tip on sponge again.

STEP 5 : Place the components

Fit them onto the PCB and push them down carefully. Bend the leads apart carefully to prevent it from falling apart.Make sure the part is pushed flat against the boardSTEP 6 : Soldering

Heat the joint

Heat the joint with the tip of the iron. Be sure to heat both the solder pad and the component lead or pin.

Apply the solder

Touch the end of the solder to the joint so that it contacts both the solder pad and the component lead or pin. It should melt and flow smoothly onto both the pin and the pad. If the solder does not flow, heat the joint for another second or twoand try again.Let It FlowKeep heating the solder and allow it to flow into the joint. It should fill the hole and flow smoothly onto both the solder pad and the pin or component lead.

Let It CoolOnce enough solder has been added to the joint and it has flowed well onto both the component lead and the solder pad, remove the iron from the joint and allow it to cool undisturbed.Trim the LeadUse your diagonal cutters to trim the lead close to the boardFixing mistakes

Place the soldering iron on the solder joint to be removed and allow the solder to become molten. Place the solder extractor next to the solder joint.Push the button and the solder will be removed

Good And Bad Joints

Never touch the end of the soldering iron. Hold wires to be heated with tweezers or clamps. Never solder a live wire.Always return the soldering iron to its stand when not in use. Work in a well-ventilated area. The smoke formed is mostly from the flux which can be irritatingGive any soldered surface a minute or two to cool down before you touch it.Never leave flammable items (such as paper) near your soldering iron.