EET Survey of Electronics Chapter 6 – Electric Connections.

Objectives Describe negative effects of poorly formed electric connections Properly remove insulation from a wire Corection install terminal-screw, crimp-on, and mechanical connectors. Explain the principles of soldering Properly insulate wire repairs. Assemble, test, and install cables used as part of electronic interconnection systems.

Why have proper connections Higher than normal resistance –Heat builds at poor connections Potential danger due to heat - may ignite flammable materials (insulation) Loss of power for ‘load’ –Example – poor starting power for automobile.

Wire connections Insulation –PVC –Rubber –Other plastic Wire strippers –Precision tool that avoids nicking the wire –Nick may weaken the wire integrity

Connections Terminal Screw connections –Note direction of screw tightening Crimp Terminals/splices –Butt connector Mechanical connectors –Twist-on mechanical connectors –Lug connectors

Insulating repairs/bare wire Plastic tape (electricians tape) Heat shrink tubing –Heat level needed may vary –Percentage of shrink depends on product –Some types include silicon waterproofing Requires heat gun or other heat source –Matches don’t work very well.

Soldering Solder is a tin-lead allow (may have silver added) –Ratio of 60/40 is normal –Most have flux core Flux cleans connection and allows solder to flow –Prevents oxidation –Resin is the only flux allowed for electrical connections Soldering gun or iron –Gun for higher heat (100W or greater) –Pencil is recommended for electronic work (~27w)

Soldering –Soldering tip must be clean and ‘tinned’ to provide good heat transfer. Note: Soldering involves melting metal and high temperatures. Fumes and spatter may be hazardous

Steps to a good solder connection Make sure metals to be soldered are copper/brass and are clean and free of oil, grease or oxidation –Wire brush or emery cloth may be required –Note – MUST remove chrome plating. Form a good mechanical connection first Heat the joint, not the solder Solder should flow and ‘wick’ into the joint. Finished solder joint should be smooth and shiny.

Cable Connectors IDC connections –Multi-wire ‘Insulation Displacement connections’ Co-axial wire connectors –F-type –BNC –RCA

Other types of wire connections Wire-wrap Prototype boards –Solder-less boards Fiber optic cable –May be a hazardous operation –Many are mechanical/chemical