SOLDERING TECHNIQUES
AIM- To Study soldering technique & practice it.
REQUIREMENTS- Soldering Iron (25W), solder wire, P.C.B, connecting wires, De-soldering pump, etc.
INTRODUCTION- components are connected together in circuits by soldered joints, solder is basically an alloy of lead & tin the proportions varying according to the application for electronic work a mixture of 60% tin & 40% lead is usual. Solder joints provide high electrical conductivity & good mechanical strength. Solder has a low melting point, lower than that of either tin or lead. The melting point varies according to the exact composition of the solder but ordinary 60-40 tin-lead solder melts at 188˚c. The bit or tip of the soldering iron is heated electrically to between 300˚c & 420˚c.
The temperature required to melt the solder is also sufficient to oxidize many metals, forming a layer of oxide that will prevent the solder “sticking” to the surface. Solder intended for electrical work is therefore made in the form of a hollow wire, with one or more cores of resin flux, a chemical mixture that will dissolve the oxide film at soldering temperatures.
Metals which can be soldered easily include Gold, Silver, Tin, and Copper & Lead. Typical bad joints are caused by insufficient heat, dirty surfaces, insufficient solder or persistent reheating of joint in an attempt to get it to stick. Soldering is something of an art, & needs to be practiced.
Proper soldering is most important to learn, since 90% of all service problems are due to bad solder connections.
To make a good solder connections follow these simple rules:-
CAUTIONS :-
PROCEDURE: -
A) SOLDERING
B) DESOLDERING:- If solder is accidently bridged between two foils, it should be cleared of carefully. Also to remove the components , which are already soldered on P.C.B without any damage & plugged holes can be cleared very easily with de-soldering pump. For efficient use of it perform the following steps:-
C) CONNECTING WIRES –: A jumper wire is a flexible wire for connecting two different points . To solder a jumper wire use following method –
1) Cut the wire to required length . Strip or remove 4 mm. insulation from both the ends with a blade or the wire stripper .
2) Twist the small strands of wire together, at each end. Then melt a small amount of solder on each exposed lead to form a thin layer on it. This is called ‘Tinning’.
3) Connect the wire from the component side and solder it on the copper foil side.
REQUIREMENTS- Soldering Iron (25W), solder wire, P.C.B, connecting wires, De-soldering pump, etc.
INTRODUCTION- components are connected together in circuits by soldered joints, solder is basically an alloy of lead & tin the proportions varying according to the application for electronic work a mixture of 60% tin & 40% lead is usual. Solder joints provide high electrical conductivity & good mechanical strength. Solder has a low melting point, lower than that of either tin or lead. The melting point varies according to the exact composition of the solder but ordinary 60-40 tin-lead solder melts at 188˚c. The bit or tip of the soldering iron is heated electrically to between 300˚c & 420˚c.
The temperature required to melt the solder is also sufficient to oxidize many metals, forming a layer of oxide that will prevent the solder “sticking” to the surface. Solder intended for electrical work is therefore made in the form of a hollow wire, with one or more cores of resin flux, a chemical mixture that will dissolve the oxide film at soldering temperatures.
Metals which can be soldered easily include Gold, Silver, Tin, and Copper & Lead. Typical bad joints are caused by insufficient heat, dirty surfaces, insufficient solder or persistent reheating of joint in an attempt to get it to stick. Soldering is something of an art, & needs to be practiced.
Proper soldering is most important to learn, since 90% of all service problems are due to bad solder connections.
To make a good solder connections follow these simple rules:-
- Use the right type of soldering iron [About 10to 25 watts with 1/8 or1/4 tip is ideal for P.C.B. work.]
- Keep the hot tip of the soldering iron on a piece of metal so that excess heat is dissipated.
- Clean the component leads wires, lugs etc. with a blade or knife to remove the rust & dust before soldering.
- Use just enough solder to cover the lead & the copper foil area. Excess solder can bridge across from one foil paths to another foil & cause a short circuit.
- Use sufficient heat to allow the solder to spread freely. If the solder barely melts& forms a round ball of rough flaky solder, the heat is not enough. A good solder joint will look smooth, shinning & solder spreaded, for that hold the iron firmly.
- Larger metal surfaces take longer time to heat e.g:- clamps of I.F.T’s, gang lugs, power transistor, etc.
- Keep the soldering iron tip clean, wipe it often with a damp sponge or cloth.
- The soldering time for circuit board connection is about 2to 3 seconds.
CAUTIONS :-
- Do not use excess solder
- Do not use or spread solder on copper lines of the P.C.B. as these lines functions as connection wire.
- Position the work so that gravity tends to keep the solder where you want it.
- Do not over heat the components or the P.C.B. as it may spoil the P.C.B or damage the components.
- The P.C.B or components should not vibrate while soldering otherwise you will have a dry or cold joint.
- In case of dry solder, re-weld the joint to get a shinny bright finish.
- Do not uses flux as solder supplied contains flux.
- Never use sand paper or other cleaning material on the Board.
- Do not bend the leads flat against the foil path. Bend them at a 450 angle with the P.C.B.
- Avoid solder bridges. A solder bridge may occur if you accidentally touch an adjacent previously soldered connection, if you use too much solder or if you ‘drag’ the soldering iron across other foils as you remove it from the connection.
PROCEDURE: -
A) SOLDERING
- Insert the components leads in to the P.C.B. holes. Bend the leads at a 450 angle to the P.C.B
- Push the clean & hot soldering iron tip against both the lead & the circuit board foil. Heat both for two or three seconds.
- Touch the solder tip to the other side of the connection. Let the heated lead & the circuit board foil melt the solder. Do not touch the solder directly on to the soldering iron tip.
- Remove the solder as soon as it begins to melt. Allow it to flow around the connection. Then remove the iron & let the connection cool.
- After the solder has hardened , clip off the wire close to the P.C.B. foil.
B) DESOLDERING:- If solder is accidently bridged between two foils, it should be cleared of carefully. Also to remove the components , which are already soldered on P.C.B without any damage & plugged holes can be cleared very easily with de-soldering pump. For efficient use of it perform the following steps:-
- Hold the de-soldering pump in your palm with its tip on the P.C.B .
- Depress the shaft of the pump with your thumb till it stays in the locked position .
- Place the tip of pump right on the spot to be de-soldered with your thumb on release button .
- Melt the solder connection thoroughly with a soldering iron .
- As soon as the solder melts completely remove the soldering iron and depress the release button of the pump immediately. You should have a perfectly de-soldered point.
- In case you have de-soldered the connection properly repeat the above procedure to get best result .
C) CONNECTING WIRES –: A jumper wire is a flexible wire for connecting two different points . To solder a jumper wire use following method –
1) Cut the wire to required length . Strip or remove 4 mm. insulation from both the ends with a blade or the wire stripper .
2) Twist the small strands of wire together, at each end. Then melt a small amount of solder on each exposed lead to form a thin layer on it. This is called ‘Tinning’.
3) Connect the wire from the component side and solder it on the copper foil side.