Thermal relief for through-hole pads in PCB Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a thermal relief pattern with four spokes.

PCB Design

thermal_relief = create_thermal_relief(pad, spokes=[1])

Drag options to blanks, or click blank then click option'

A4

B2

C6

D8

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing too few or too many spokes which can affect soldering quality.

Thermal reliefs commonly use four spokes to balance heat dissipation and solderability.

2fill in blank

medium

Complete the code to set the thermal relief spoke width to 0.2 mm.

PCB Design

thermal_relief.set_spoke_width([1])

Drag options to blanks, or click blank then click option'

A0.1

B0.4

C0.3

D0.2

Attempts:

3 left

💡 Hint

Common Mistakes

Using too narrow spokes that may cause poor heat conduction.

A spoke width of 0.2 mm is a common choice to ensure good solder flow and heat transfer.

3fill in blank

hard

Fix the error in the code to correctly apply thermal relief to a through-hole pad.

PCB Design

apply_thermal_relief(pad, spokes=4, spoke_width=[1])

Drag options to blanks, or click blank then click option'

A'0.2mm'

B2

C0.2

D0.02

Attempts:

3 left

💡 Hint

Common Mistakes

Including units as part of the value causing syntax errors.

The spoke width should be a numeric value without units for correct function.

4fill in blank

hard

Fill both blanks to create a thermal relief with 6 spokes and spoke width 0.15 mm.

PCB Design

thermal_relief = create_thermal_relief(pad, spokes=[1], spoke_width=[2])

Drag options to blanks, or click blank then click option'

A6

B0.1

C0.15

D4

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up spoke count and spoke width values.

Using 6 spokes with 0.15 mm width balances heat and solderability for some designs.

5fill in blank

hard

Fill all three blanks to define a thermal relief with 8 spokes, spoke width 0.1 mm, and spoke gap 0.3 mm.

PCB Design

thermal_relief = create_thermal_relief(pad, spokes=[1], spoke_width=[2], spoke_gap=[3])

Drag options to blanks, or click blank then click option'

A8

B0.1

C0.3

D6

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing spoke gap with spoke width values.

Eight spokes with 0.1 mm width and 0.3 mm gap provide good thermal relief for high-power pads.

Practice

1. What is the main purpose of thermal relief in through-hole pads on a PCB?

easy

A. To prevent any electrical connection

B. To increase electrical resistance

C. To make the pad larger

D. To control heat flow for better soldering

Solution

1. Step 1: Understand thermal relief function

   Thermal relief uses thin copper spokes to connect pads to planes, controlling heat flow.

2. Step 2: Identify the main goal

   This control helps soldering by preventing heat from dissipating too quickly.

3. Final Answer:

   To control heat flow for better soldering -> Option D

4. Quick Check:

   Thermal relief = better soldering heat control [OK]

Hint: Thermal relief balances heat for soldering, not resistance [OK]

Common Mistakes:

• Thinking thermal relief increases resistance
• Assuming it makes pads bigger
• Believing it blocks electrical connection

2. Which of the following correctly describes the copper connection in thermal relief for through-hole pads?

easy

A. Thin copper spokes connecting pad to plane

B. Solid copper plane connection

C. No copper connection at all

D. Thick copper bars around the pad

Solution

1. Step 1: Recall thermal relief design

   Thermal relief uses thin copper spokes, not solid or thick bars, to connect pads.

2. Step 2: Match description to options

   Only thin copper spokes correctly describe the connection method.

3. Final Answer:

   Thin copper spokes connecting pad to plane -> Option A

4. Quick Check:

   Thermal relief = thin spokes connection [OK]

Hint: Thermal relief uses spokes, not solid or thick copper [OK]

Common Mistakes:

• Choosing solid copper connection
• Thinking there is no copper connection
• Confusing thick bars with spokes

3. Given a PCB pad connected to a copper plane with thermal relief, what is the expected effect on soldering time compared to a solid connection?

medium

A. Soldering time decreases due to heat dissipation control

B. Soldering time decreases because of more copper

C. No change in soldering time

D. Soldering is impossible with thermal relief

Solution

1. Step 1: Understand heat flow in thermal relief

   Thermal relief limits heat flow to the plane, slowing heat loss from the pad.

2. Step 2: Relate heat flow to soldering time

   Less heat loss means the pad stays hot longer, allowing solder to melt faster, decreasing soldering time.

3. Final Answer:

   Soldering time decreases due to heat dissipation control -> Option A

4. Quick Check:

   Thermal relief slows heat loss = shorter soldering [OK]

Hint: Thermal relief slows heat loss, so soldering takes shorter [OK]

Common Mistakes:

• Assuming soldering time increases
• Thinking thermal relief has no effect
• Believing soldering is impossible

4. A PCB designer notices that the thermal relief spokes are too thick, causing excessive heat loss during soldering. What is the best fix?

medium

A. Increase the number of spokes

B. Reduce the width of the thermal relief spokes

C. Remove thermal relief and use solid copper

D. Add more vias around the pad

Solution

1. Step 1: Identify problem cause

   Thick spokes conduct more heat, causing excessive heat loss.

2. Step 2: Choose appropriate fix

   Reducing spoke width lowers heat conduction, improving soldering heat retention.

3. Final Answer:

   Reduce the width of the thermal relief spokes -> Option B

4. Quick Check:

   Thinner spokes = less heat loss [OK]

Hint: Thinner spokes reduce heat loss, fix soldering issues [OK]

Common Mistakes:

• Increasing spokes increases heat loss
• Removing thermal relief worsens heat control
• Adding vias does not fix spoke thickness

5. A PCB has a through-hole pad connected to a large ground plane. The thermal relief uses four spokes. If the designer changes to two spokes, what is the likely impact on soldering and electrical performance?

hard

A. No change in soldering; electrical resistance increases greatly

B. Soldering becomes harder; electrical resistance slightly increases

C. Soldering improves; electrical resistance slightly increases

D. Soldering impossible; electrical connection lost

Solution

1. Step 1: Analyze spoke count effect on heat flow

   Reducing spokes from four to two reduces heat conduction paths, retaining more heat in the pad, improving soldering.

2. Step 2: Analyze spoke count effect on electrical resistance

   Fewer spokes slightly increase electrical resistance but usually remain acceptable.

3. Final Answer:

   Soldering improves; electrical resistance slightly increases -> Option C

4. Quick Check:

   Fewer spokes = improved soldering + slight resistance rise [OK]

Hint: Fewer spokes reduce heat flow (improve soldering) and increase resistance slightly [OK]

Common Mistakes:

• Thinking soldering becomes harder with fewer spokes
• Thinking electrical resistance decreases
• Believing electrical connection is lost