Alloy: Tin (99%), Silver (0.3%), Copper (0.7%)
Melting point: 217-227°C
Flux core: Built-in cleaning agent
Strength: Strong mechanical and electrical bond

Soldering iron: 25-60W (30W typical for small robots)
Solder: 1mm diameter, rosin-core
Flux: Optional (usually in solder)
Wet sponge: Cleans iron tip
Wick/solder sucker: Desolders mistakes
Heat-shrink tube: Insulation after soldering
Safety: Ventilation, eye protection

1. Tin the iron tip
   └─ Touch iron to wet sponge
   └─ Apply small amount of solder to tip
   
2. Position components
   └─ Hold wire and connector together
   └─ Keep steady (use helping hands tool)
   
3. Heat the joint (not solder!)
   └─ Touch iron to both wire and connector
   └─ Hold for 2-3 seconds
   └─ Iron should heat metal, not solder
   
4. Apply solder
   └─ Touch solder to hot joint (not iron tip)
   └─ Solder flows onto joint
   └─ Use just enough (25mm / 1 inch)
   
5. Remove solder first
   └─ Stop feeding solder
   
6. Remove iron
   └─ Let cool for few seconds
   └─ Don't move joint while cooling
   
7. Inspect
   └─ Should be shiny and smooth
   └─ Not dull (cold joint) or lumpy

Visual:
✓ Shiny, smooth appearance
✓ Slightly convex (rounded) at edges
✓ No voids or gaps
✓ Solder flows smoothly onto wire

Electrical:
✓ Resistance < 0.1 Ω
✓ Low inductance
✓ Can carry full current

Visual:
✗ Dull, grainy appearance
✗ Concave (indented)
✗ Solder doesn't properly connect

Electrical:
✗ High resistance (intermittent failures)
✗ Can fail under vibration
✗ Heat cycling degrades further

1. Touch iron tip to joint
2. Let heat warm old solder
3. Solder should flow and become shiny
4. Looks much better now!

Steps:
1. Place wick on bad joint
2. Hold soldering iron on top of wick
3. Wick absorbs molten solder
4. Lift wick and iron when done

Result: Joint mostly cleaned

Steps:
1. Heat joint with iron
2. Place solder sucker tip over joint
3. Press trigger to suck up molten solder
4. Remove iron

Result: Joint quickly cleared

Cost: $30-50 (worth it for frequent repairs)
Advantage: Fastest, cleanest
Best for: Production, frequent repairs

1. Strip 5mm of insulation from wire
2. Tin wire end (coat with thin solder)
3. Insert into connector terminal
4. Heat connection point
5. Apply solder until it flows
6. Remove iron and cool
7. Cover with heat shrink

1. Insert component leg through PCB hole
2. Bend leg slightly to hold component
3. Apply iron to connection (very brief, PCB can heat)
4. Add solder and remove iron
5. Trim excess leg with snips

Modern approach: Surface mount (SMD) requires hot air or oven
Traditional approach: Dip ICs
  - Use sockets when possible (easy replacement)
  - Solder socket carefully
  - Insert IC after soldering

Wire ──[Crimp]── Wire
      └─ Connects two wires end-to-end

Wire ──[Spade crimp] → Slides onto pin
      └─ Fast connector to terminal

Wire ──[Ring crimp]
       └─ Slips over bolt for ground

1. Choose correct size crimp for wire gauge
2. Strip 5-6mm of insulation from wire
3. Insert wire into crimp barrel
4. Use crimping tool (calibrated for wire/crimp size)
5. Squeeze firmly until crimp seats
6. Tug test: Pull hard, should not slide out
7. Apply heat shrink over crimp for insulation

Manual tool: $10-30 (basic)
├─ Works for small quantities
├─ Requires strength
├─ Many different crimp sizes fit

Ratcheting crimper: $30-60 (semi-professional)
├─ Auto-stops at proper compression
├─ Better consistency
├─ Worth it if doing many crimps

Powered crimper: $200+ (professional)
├─ Fast, consistent
├─ For high-volume production

Uncovered solder: Exposed, can short circuit
With heat shrink: Insulated, protected from moisture

Heat shrink ID should be 1.5-2× the insulation OD

Example:
Wire insulation OD: 2.5mm
Choose heat shrink: 4mm or 5mm ID

Too small: Won't fit over joint
Too large: Won't insulate properly

1. Slide tubing over wire before soldering
2. Solder joint
3. Slide tubing over joint
4. Use heat gun or lighter to shrink
5. Tubing shrinks ~50% when heated
6. Result: Insulated, protected joint

Layout:
├─ Soldering iron (right side if right-handed)
├─ Solder spool (left side)
├─ Wet sponge (iron cleaning)
├─ Helping hands tool (holds components)
├─ Heat shrink dispenser
├─ Desoldering tools (nearby)
└─ Fume extractor (behind work area)

Lighting: Bright overhead + task light

Ventilation: Fume extractor pulls solder fumes away

Fumes: Flux residue (can irritate lungs)

Solution:
✓ Open window for air circulation
✓ Use fume extractor with carbon filter
✓ Never breathe fumes directly
✓ Work in well-ventilated area

For sensitive individuals:
✓ Wear respirator mask
✓ Take frequent breaks

Before use:
☐ Joint shiny or dull?
☐ Solder smooth or lumpy?
☐ Any cracks visible?
☐ Wire fully inserted?
☐ Insulation intact?

Tug test: Pull gently (not hard)
├─ Should not budge
├─ If moves, probably cold joint
└─ Re-solder

Bend test: Gently flex wire
├─ Should remain solid
├─ If crackles, likely fracture
└─ Too much heat, re-solder

Continuity test:
├─ Multimeter on resistance mode
├─ Should read < 0.1 Ω
├─ If high resistance, bad joint
└─ Dry joint, re-solder

Current test (under load):
├─ Monitor during operation
├─ If joint gets hot, bad connection
└─ Resistance generates heat