Notes
Slide Show
Outline
1
Basic Soldering
2
History of Soldering
  • Developed by the Egyptians.


  • Most electronic equipment failures are caused by bad solder joints.


  • Space program required high reliability soldering techniques.
3
Advantages of Soldering
  • Mechanical Fasteners


  • Questionable electrical contact


  • Mechanical shock (movement) loosens connection.


  • Exposed surface to oxidize
  • Solder Connections


  • Continuous electrical path.


  • No loosening by movement.



  • No surfaces to oxidize.
4
Nature of Solder
  • Alloy of tin (Sn) and Lead (Pb).


  • Low melting point.
    • Sn = 450 ° F
    • Pb = 621 ° F
    • Solder = 361 ° F



  •                                                                                   (OVH 1)
5
Eutectic Solder
  • 63 % Sn, 37 % Pb; Melts completely at 361 ° F.


  • Other percentages begin melting at        361 ° F, but go through a plastic stage.


  • Movement during plastic stage causes cold solder joints.
6
Wetting Action
  • Solder is a metal solvent, not a glue.


  • Solder forms a new alloy with the copper joint.


  • Wetting action forms a metallic bond.


  • Surface must be clean and at the correct temperature.
  •                                                                                   (OVH 2)
7
Flux
  • The joint oxidizes rapidly when heating.


  • Flux removes light oxides during the soldering process.


  • Use only rosin flux in electronic soldering.


  •                                                                                   (OVH 3)
8
Soldering Irons

  • Soldering irons have 3 parts:
  • 1. Heating Unit
  • 2. Heater Block (Heat Reservoir)
  • 3. Tip


  • 25 W or 30 W pencil-type is good for most electronic work.


  •                                                                                                      (OVH 4)
9
Controlling Heat at the Joint
  • The Heat Cycle:


  • How fast the joint gets hot.


  • How hot the joint gets.


  • How long the joint stays hot.
10
Controlling Heat at the Joint
  • Relative Thermal Mass:
  • Mass of work compared to mass of tip & reservoir.
  • Controls the speed of heat flow.
  • Use large tip for heavy work.
  • Use small tip for light work.
  • Controls the amount of heat available.
  • Use large reservoir for heavy work.
  • Use small reservoir for light work.
11
Controlling Heat at the Joint
  • Surface Condition:
    • Contaminants and oxides block heat flow.

  • Thermal Linkage:
    • Contact area between tip and joint.
    • Increase contact area with a small amount of solder.


    •                                                                             (OVH 5)
12
Controlling Heat at the joint
  • Apply heat for no more than 2 seconds.


  • Apply heat to the joint – not to the solder.
13
Handling a Soldering Iron
  • Preparation of plated & unplated tips:
    • Cleaning and tightening threads.
    • Shaping with file (unplated only).
    • Tinning.


  • Keep a small amount of solder on the tip to prevent oxidation and improve thermal linkage.
14
Applying Solder
  • Relative Thermal Mass:
    • Select correct size solder and iron.
  • Surface Condition:
    • Remove oxides and contaminants from joint.
  • Thermal Linkage:
    • Keep a small amount of solder on the tip.  (This also prevents oxidation of the tip.)
  • Wetting Action:
    • Raise the joint to the liquidous point – never melt solder with the tip.
    •                                                                             (OVH 6)
15
Examples
  • Properly Applied solder wets well.
  • (OVH 7)
  • Use the proper amount of solder.
  • (OVH 8, OVH 9)
16
Soldering Demonstration