Via size and drill diameter in PCB Design - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the drill diameter for a via given the via size.

PCB Design

drill_diameter = via_size [1] 0.2

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

A-

B/

C*

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction, which makes the drill diameter too large.

The drill diameter is typically smaller than the via size by a fixed amount, so we subtract 0.2 mm.

2fill in blank

medium

Complete the code to calculate the annular ring width by subtracting drill diameter from via size and dividing by 2.

PCB Design

annular_ring = (via_size [1] drill_diameter) [2] 2

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

A-

B+

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction, or multiplying instead of dividing.

The annular ring is the difference between via size and drill diameter, divided by 2.

3fill in blank

hard

Fix the error in the code to correctly calculate the drill diameter as 0.3 mm less than the via size.

PCB Design

drill_diameter = via_size [1] 0.3

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

A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition which increases drill diameter incorrectly.

Drill diameter should be smaller than via size, so subtract 0.3 mm.

4fill in blank

hard

Fill both blanks to calculate the annular ring width correctly.

PCB Design

annular_ring = (via_size [1] drill_diameter) [2] 2

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

A-

B+

C/

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up addition and subtraction or multiplication and division.

Subtract drill diameter from via size, then divide by 2 to get annular ring width.

5fill in blank

hard

Fill all three blanks to calculate the drill diameter and annular ring width correctly.

PCB Design

drill_diameter = via_size [1] 0.25
annular_ring = (via_size [2] drill_diameter) [3] 2

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

A-

B+

C/

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction, or multiplication instead of division.

Drill diameter is via size minus 0.25 mm. Annular ring is (via size minus drill diameter) divided by 2.

Practice

1. What does the term via size in PCB design usually refer to?

easy

A. The length of the trace connected to the via

B. Only the drill hole diameter

C. The thickness of the PCB

D. The total diameter including drill hole and annular ring

Solution

1. Step 1: Understand via size components

   Via size includes the drill hole plus the annular ring around it.

2. Step 2: Define via size

   Via size = drill diameter + 2 x annular ring width.

3. Final Answer:

   The total diameter including drill hole and annular ring -> Option D

4. Quick Check:

   Via size = drill + 2xannular ring [OK]

Hint: Via size always includes drill plus annular ring twice [OK]

Common Mistakes:

• Confusing drill diameter with via size
• Ignoring annular ring width
• Thinking via size is PCB thickness

2. Which of the following formulas correctly calculates the via size if the drill diameter is D and annular ring width is R?

easy

A. Via size = D + 2 * R

B. Via size = D + R

C. Via size = 2 * (D + R)

D. Via size = D - 2 * R

Solution

1. Step 1: Recall the via size formula

   Via size equals drill diameter plus twice the annular ring width.

2. Step 2: Apply formula to variables

   Via size = D + 2 x R.

3. Final Answer:

   Via size = D + 2 * R -> Option A

4. Quick Check:

   Via size = drill + 2xannular ring [OK]

Hint: Remember annular ring counts twice around drill [OK]

Common Mistakes:

• Adding annular ring only once
• Multiplying drill diameter incorrectly
• Subtracting annular ring width

3. If a PCB designer uses a drill diameter of 0.3 mm and an annular ring width of 0.1 mm, what is the total via size?

medium

A. 0.4 mm

B. 0.6 mm

C. 0.5 mm

D. 0.7 mm

Solution

1. Step 1: Identify given values

   Drill diameter D = 0.3 mm, annular ring R = 0.1 mm.

2. Step 2: Calculate via size

   Via size = D + 2 x R = 0.3 + 2 x 0.1 = 0.3 + 0.2 = 0.5 mm.

3. Final Answer:

   0.5 mm -> Option C

4. Quick Check:

   0.3 + 2x0.1 = 0.5 mm [OK]

Hint: Add drill plus twice annular ring width [OK]

Common Mistakes:

• Adding annular ring once only
• Mixing units or decimal points
• Choosing closest but incorrect option

4. A PCB design rule states the minimum annular ring width is 0.15 mm. A designer sets drill diameter to 0.4 mm and via size to 0.55 mm. What is wrong?

medium

A. Via size is too small for the annular ring requirement

B. Drill diameter is too large

C. Annular ring width is too large

D. Via size is correctly set

Solution

1. Step 1: Calculate required via size

   Minimum annular ring R = 0.15 mm, drill D = 0.4 mm, so via size = 0.4 + 2x0.15 = 0.7 mm.

2. Step 2: Compare with given via size

   Given via size is 0.55 mm, which is less than required 0.7 mm.

3. Final Answer:

   Via size is too small for the annular ring requirement -> Option A

4. Quick Check:

   Via size < required minimum [OK]

Hint: Check if via size ≥ drill + 2xannular ring [OK]

Common Mistakes:

• Ignoring minimum annular ring width
• Assuming drill diameter can be changed
• Thinking via size can be smaller than drill

5. A PCB manufacturer requires a minimum annular ring width of 0.12 mm and a maximum drill diameter of 0.5 mm. If a designer wants a via size of 0.8 mm, what is the largest drill diameter they can use?

hard

A. 0.56 mm or less

B. 0.56 mm

C. 0.56 mm or more

D. 0.56 mm exactly

Solution

1. Step 1: Write the via size formula

   Via size = drill diameter + 2 x annular ring width.

2. Step 2: Substitute known values and solve for drill diameter

   0.8 = drill + 2 x 0.12 -> drill = 0.8 - 0.24 = 0.56 mm.

3. Step 3: Check manufacturer max drill diameter

   Max drill diameter allowed is 0.5 mm, but calculated drill is 0.56 mm, which is too large.

4. Step 4: Interpret largest drill diameter possible

   Designer must use drill diameter ≤ 0.5 mm to meet manufacturer limit, so largest drill diameter is 0.5 mm, less than 0.56 mm.

5. Final Answer:

   0.56 mm -> Option B

6. Quick Check:

   Drill ≤ 0.5 mm and via size = 0.8 mm [OK]

Hint: Solve via size formula, check max drill limit [OK]

Common Mistakes:

• Ignoring max drill diameter limit
• Assuming drill can be larger than max allowed
• Confusing annular ring with drill diameter