Soldering Basics

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Overview Introduction

Definition Equipment

Procedure Preparation Execution Finishing

Specific Techniques Desoldering Tinning

Conclusion References

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Introduction – Definition Unite two base metal items Add filler metal (solder)

Typ. < 842°F (450°C) melting point

Metal flows via capillary action

Metal bonds via wetting action

Metallurgical joint exhibits Fair mechanical strength Excellent electrical

conductivity Watertightness

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Introduction – Common Usage Electronics Plumbing Stained glasswork Jewelry Orthodontics

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Introduction – Equipment Solder

Joint filler metal Metallic alloy

Sn/Pb Typ. 60/40 or 63/37 mix 60/40 melts @ 374°F (190°C) 60/40 melts @ 364°F (183°C)

Pb-free EU RoHS compliance Typ. Sn/Ag/Cu alloy Melts @ 422–433°F (217–223°C)

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Introduction – Equipment Flux

Removes base, filler metal oxides Aids wetting process Rosin-based flux Availability

Separate paste Flux-in-core solder

Primary fume component…

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Introduction – Equipment Soldering Iron

Solder melting heat source Power rating

Higher power ≠ higher tip temp Higher power heat larger joints 15-35W for electronic work

Various tips available Conical, chisel types Tip width ~ 70-90% contact width

Never use ‘cold heat’ irons on electronics!

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Introduction – Equipment Solder wick

Braided copper strands Flux impregnated Absorbs solder when heated Remove excess solder Desolder components

Solder stand + sponge Always return iron when

unused Always clean tip

Remove burnt flux Remove excess solder

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Introduction – Equipment Heat sink

Protect heat sensitive components Clip between component body and

iron Substitution

alligator clips Hemostat

99% alcohol + brush Clean joint residual flux Purity important

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Procedure – Preparation Clean components

Remove dirt, grease, oxidation Causes unwettability Solder tend to bead up Component leads bright, shiny Solder pads bright copper color Fine steel wool, emery cloth

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Procedure – Preparation Prepare iron

Plug in iron Dampen sponge Clean tip w/ sponge Apply solder to iron tip (tinning) Wipe excess solder Tip should be have silvery sheen

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Procedure – Execution Place component

Bend leads to fit hole pattern

Insert component through correct holes

Clinch leads slightly outward to hold in place

Attach heat sink if needed

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Procedure – Execution Solder component

Wipe iron w/ sponge Apply tiny solder amount

to iron tip Not solder to form joint Helps conduct heat

properly Touch tip side to BOTH

pad and lead Add bit more solder to

form heat bridge Wait for joint to be heated

(~1-2 sec)

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Procedure – Execution Solder component (cont.)

Feed small solder amount from opposite side

Molten solder should spread and fill joint

Move solder away first Move iron away quickly Return iron to stand

Entire process ≤ 5 sec Wait additional 3-5 sec for

joint cooling

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Procedure – Inspection Inspect joint quality

Good joint Shiny Bright Smooth Concave solder fillet Good wetting

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Procedure – Inspection Inspect joint quality (cont.)

Bad joints Balled up or spiked Dull color Crystalline or grainy

looking Convex solder fillet Dewetted

Causes Dirty leads, pads Movement during cooling Overheating

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Procedure – Finishing Return iron to stand Cut excess lead length Clean residual flux w/

alcohol Prevent future oxidation Prevent unwanted

electrical shorts

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Techniques - Desoldering Repair bad joints Remove solder bridges

Excess solder connects two pads, leads Unwanted electrical connection formed

Remove components Both require old solder removal

Place solder wick against solder joint Heat wick opposite side from joint Solder should wick up braid Remove braid first Remove and return iron to stand

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Techniques – Wire Tinning Must tin wires before

soldering to components, board Attach heat sink just below

insulation Heat wire end Touch solder to wire

opposite iron tip Solder should wick up wire Too much heat damages

wire insulation

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Conclusion Introduction

Definition Equipment

Procedure Preparation Execution Finishing

Specific Techniques Desoldering Tinning

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References www.curiousinventor.com/guides/How_To_Solder www.aaroncake.net/electronics/solder.htm www.qsl.net/n9zia/solder.html www.solderinguide.com itp.nyu.edu/physcomp/Tutorials/SolderingAPerfBoard www.modchipworld.co.uk www.drmsmetals.com/data/electronic/erzin.html www.hsl.gov.uk/capabilities/rosin.htm www.sparkfun.com www.howardelectronics.com www.ladyada.net www.uelectronics.info us.geocities.com/steves_workshop www.theavenuestaineglass.com