introduction to soldering electronic circuits lab 2...

Introduction to Soldering

Electronic Circuits

Department of Electrical and

Computer Engineering

Kettering University

Mark G. Thompson, IME-100, 2002

Soldering Tools and Supplies

• Good quality pencil-type soldering iron

• Small gauge resign core solder

• Damp sponge

• Safety glasses

• Needle nose pliers/wire cutters

• Bench top vise for extra hands

• Braided de-soldering wick


Soldering Safety

• Always wear safety glasses

• Solder on a fire resistant surface (never directly on a bench or desk top)

• Never leave a hot iron unattended

• Use caution when laying down or picking up a hot iron (tip temperatures are 700 – 800 degrees F)

• Use a soldering iron stand if available

• Replace the cord if it becomes worn or burnt

• Do not overload electrical outlets


A clean tip is important

• A clean tip assures

good thermal contact

between iron and

component

• Clean the tip regularly

by wiping on a damp

sponge


Holding the soldering iron

• Hold the soldering

iron in a relaxed

position, like holding a

pen

• Steady your arm by

resting it on the work

surface


Correct component placement

• Place the components through the holes on the top side of board

• Check the alignment of polarized components

• Components should be nearly flush with the board surface

• Bend the leads outward on the bottom side to hold components in place while soldering


Incorrect component placement

• Here the components

are not placed flush

with the board surface

• See the previous slide

for correct, flush

component placement


Tin the tip

• Melt a small amount

of solder on the tip

before beginning;

called “tinning the tip”

• This procedure

reduces oxidation on

the tip and improves

heat transfer to the

component


Soldering technique

• The component lead should be between the iron and the solder

• Heat the component lead and the PCB trace for a short time (max. 2-3 seconds)

• Touch the solder to the component lead (not the tip of the iron)


Soldering technique (cont.)

• Feed a small amount of molten solder to the joint

• Some solder will be drawn up into hole, the rest will form a cone around the lead

• Pull the solder away first, then pull the iron away


Good solder joint

• A good solder joint should be shiny and cone shaped

• Wiggle the component slightly to test for good mechanical connection

• Trim the excess lead length with wire cutters


Bad solder joint

• A bad (cold) solder joint will be dull and glob-like

• The board may be discolored from over-heating

• These symptoms will lead to unreliable electrical and mechanical connection


De-soldering

• If you make a mistake,

solder can be removed

from a connection

using braided de-

soldering wick


De-soldering

• Place the braided de-soldering wick on the solder to be removed

• Heat the wick to melt and draw the solder into the wick

• Continue to use fresh wick until all solder is removed and component lead is free


Completed board

• This is an example of

the top side of a

completed board

• Components are neatly

aligned with correct

polarity and placed

flush with the board

surface


Completed board

• This is an example of the bottom side of a completed board

• Solder joints are shiny and cone shaped

• Board is not discolored from over-heating

• Excess leads are neatly trimmed off

• There are no unwanted solder bridges between connections


Finishing Up

• Before finishing, invest some time in checking over your work. It could save you hours of trouble-shooting and re-work later.

• Look for solder bridges between connections, cold solder joints, missed connections, and reversed polarity on components.

• Touch up any solder connections that seem less than perfect.

• Once power is applied….it may be too late!


introduction to soldering electronic circuits lab 2...

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