PCB material and copper weight basics in PCB Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the copper thickness in micrometers given the copper weight in ounces.

PCB Design

copper_thickness_um = [1] * 35

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

Acopper_weight_g

Bcopper_area

Ccopper_density

Dcopper_weight_oz

Attempts:

3 left

💡 Hint

Common Mistakes

Using copper weight in grams instead of ounces

Using copper area instead of weight

The copper thickness in micrometers is calculated by multiplying the copper weight in ounces by 35.

2fill in blank

medium

Complete the code to calculate the resistance of a copper trace given its length, width, and copper thickness.

PCB Design

resistance = resistivity * (length / (width * [1]))

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

Athickness_um

Bcopper_density

Ccopper_weight_oz

Dthickness_mm

Attempts:

3 left

💡 Hint

Common Mistakes

Using copper weight instead of thickness

Using thickness in millimeters without conversion

The resistance formula uses the copper thickness in micrometers to calculate the cross-sectional area.

3fill in blank

hard

Fix the error in the code to convert copper weight in ounces to thickness in micrometers.

PCB Design

thickness_um = copper_weight_oz [1] 35

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

A*

B+

C-

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using division instead of multiplication

Using addition or subtraction which are incorrect

Multiplying copper weight in ounces by 35 gives the thickness in micrometers.

4fill in blank

hard

Fill both blanks to calculate the copper weight in ounces from thickness in micrometers.

PCB Design

copper_weight_oz = [1] / [2]

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

Athickness_um

B35

Ccopper_density

Dcopper_area

Attempts:

3 left

💡 Hint

Common Mistakes

Using copper density or area instead of thickness

Dividing by wrong number

Dividing thickness in micrometers by 35 converts it back to copper weight in ounces.

5fill in blank

hard

Fill both blanks to calculate the cross-sectional area of a copper trace in square micrometers.

PCB Design

cross_section_um2 = [1] * [2]

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

Awidth_um

Bthickness_um

Clength_um

Dcopper_weight_oz

Attempts:

3 left

💡 Hint

Common Mistakes

Including length in cross-sectional area calculation

Using copper weight instead of thickness

The cross-sectional area is width_um * thickness_um.

Practice

1. Which property of PCB material mainly affects the board's ability to withstand heat?

easy

A. Copper weight

B. Thermal resistance

C. Board thickness

D. Solder mask color

Solution

1. Step 1: Understand PCB material properties

   PCB materials are chosen for their ability to resist heat and mechanical stress.

2. Step 2: Identify the key property for heat resistance

   Thermal resistance measures how well the material withstands heat without damage.

3. Final Answer:

   Thermal resistance -> Option B

4. Quick Check:

   Heat resistance = Thermal resistance [OK]

Hint: Heat resistance relates to material's thermal resistance [OK]

Common Mistakes:

• Confusing copper weight with heat resistance
• Thinking board thickness controls heat tolerance
• Assuming solder mask color affects heat resistance

2. Which of the following correctly describes copper weight in PCB design?

easy

A. Thickness of copper layer measured in ounces per square foot

B. Color of the copper layer

C. Length of copper traces on the board

D. Weight of the entire PCB

Solution

1. Step 1: Define copper weight

   Copper weight refers to the thickness of the copper layer on the PCB, usually measured in ounces per square foot.

2. Step 2: Eliminate incorrect options

   Color, length of traces, and total PCB weight do not define copper weight.

3. Final Answer:

   Thickness of copper layer measured in ounces per square foot -> Option A

4. Quick Check:

   Copper weight = Thickness in oz/ft² [OK]

Hint: Copper weight means thickness in ounces per square foot [OK]

Common Mistakes:

• Confusing copper weight with PCB color
• Thinking copper weight is trace length
• Assuming copper weight is total board weight

3. If a PCB uses 2 oz copper weight instead of 1 oz, what is the main effect on current carrying capacity?

medium

A. It reduces the current carrying capacity by 25%

B. It halves the current carrying capacity

C. It has no effect on current carrying capacity

D. It doubles the current carrying capacity

Solution

1. Step 1: Understand copper weight impact

   Copper weight thickness directly affects how much current the PCB trace can safely carry.

2. Step 2: Compare 1 oz and 2 oz copper

   Doubling copper weight from 1 oz to 2 oz roughly doubles the cross-sectional area, thus doubling current capacity.

3. Final Answer:

   It doubles the current carrying capacity -> Option D

4. Quick Check:

   2 oz copper = double current capacity [OK]

Hint: Double copper weight roughly doubles current capacity [OK]

Common Mistakes:

• Assuming copper weight does not affect current
• Thinking current capacity halves with more copper
• Confusing copper weight with board thickness

4. A PCB designer wrote: "Using 0.5 oz copper weight will increase current capacity compared to 1 oz copper." What is wrong with this statement?

medium

A. 0.5 oz copper weight decreases current capacity compared to 1 oz

B. Copper weight does not affect current capacity

C. 0.5 oz copper weight is thicker than 1 oz

D. Current capacity depends only on board size

Solution

1. Step 1: Analyze copper weight values

   0.5 oz copper is thinner than 1 oz copper, so it carries less current.

2. Step 2: Identify the error in the statement

   The statement incorrectly claims 0.5 oz increases current capacity, which is false.

3. Final Answer:

   0.5 oz copper weight decreases current capacity compared to 1 oz -> Option A

4. Quick Check:

   Less copper = less current capacity [OK]

Hint: Less copper weight means less current capacity [OK]

Common Mistakes:

• Thinking thinner copper carries more current
• Ignoring copper weight effect on current
• Confusing copper weight with board size

5. A PCB project requires high durability and the ability to carry 3 times the current of a standard 1 oz copper PCB. Which combination is best?

hard

A. Use low thermal resistance material with 2 oz copper weight

B. Use standard material with 1 oz copper weight and thicker board

C. Use a high thermal resistance material with 3 oz copper weight

D. Use high thermal resistance material with 0.5 oz copper weight

Solution

1. Step 1: Identify durability requirement

   High durability means choosing a PCB material with high thermal resistance to withstand heat and stress.

2. Step 2: Calculate copper weight for current capacity

   To carry 3 times the current of 1 oz copper, use approximately 3 oz copper weight.

3. Step 3: Match material and copper weight

   Combining high thermal resistance material with 3 oz copper meets both durability and current needs.

4. Final Answer:

   Use a high thermal resistance material with 3 oz copper weight -> Option C

5. Quick Check:

   Durability + 3x current = High thermal resistance + 3 oz copper [OK]

Hint: Match high thermal resistance with needed copper weight [OK]

Common Mistakes:

• Ignoring material thermal resistance for durability
• Using too low copper weight for current needs
• Assuming thicker board replaces copper weight