Mounting hole placement in PCB Design - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Mounting Hole Placement Importance

Why is precise mounting hole placement critical in PCB design?

A To ensure the PCB fits correctly in the enclosure and avoids mechanical stress

B To increase the electrical conductivity of the PCB

C To reduce the number of components on the PCB

D To improve the thermal performance of the PCB

💡 Hint

Think about the physical fit and mechanical stability of the PCB.

Mounting holes must be placed accurately to ensure the PCB fits properly in its enclosure and to prevent mechanical stress that could damage components or the board itself.

❓ data_modeling

intermediate

Calculating Mounting Hole Coordinates

You have a rectangular PCB of 100mm width and 80mm height. Mounting holes should be placed 5mm from each edge. What are the X and Y coordinates of the top-left mounting hole assuming origin (0,0) is at the bottom-left corner?

A (5, 75)

B (5, 5)

C (95, 75)

D (95, 5)

💡 Hint

Remember the origin is bottom-left, so Y increases upwards.

The top-left hole is 5mm from the left edge (X=5) and 5mm from the top edge (Y=80-5=75).

❓ dax_lod_result

advanced

DAX Measure for Counting Mounting Holes by Type

Given a table 'MountingHoles' with columns 'HoleType' and 'Diameter', which DAX measure correctly counts the number of mounting holes with diameter greater than 3mm?

PCB Design

Measure = CALCULATE(COUNTROWS(MountingHoles), FILTER(MountingHoles, MountingHoles[Diameter] > 3))

A Measure = SUMX(MountingHoles, IF(MountingHoles[Diameter] > 3, 1, 0))

B Measure = COUNTROWS(FILTER(MountingHoles, MountingHoles[Diameter] > 3))

C Measure = COUNT(MountingHoles[Diameter] > 3)

D Measure = CALCULATE(COUNTROWS(MountingHoles), FILTER(MountingHoles, MountingHoles[Diameter] > 3))

💡 Hint

Consider the correct use of CALCULATE and FILTER functions in DAX.

Option D uses CALCULATE with FILTER correctly to count rows where Diameter is greater than 3mm.

❓ visualization

advanced

Best Visualization for Mounting Hole Distribution

Which visualization best shows the spatial distribution of mounting holes on a PCB layout?

A Bar chart showing count of holes by diameter

B Pie chart showing percentage of hole types

C Scatter plot with X and Y coordinates of holes

D Line chart showing hole diameter over time

💡 Hint

Think about showing positions on a 2D plane.

A scatter plot with X and Y coordinates effectively shows where holes are placed on the PCB.

🔧 Formula Fix

expert

Debugging Mounting Hole Placement Calculation

Given this SQL snippet to select mounting holes within 5mm of PCB edges (width=100, height=80):

SELECT * FROM Holes WHERE X < 5 OR X > 95 OR Y < 5 OR Y > 75;

Which issue will cause incorrect results?

A Coordinates comparison values are off by 1mm

B Strict inequalities (<, >) exclude holes exactly at 5mm or 95mm

C Using OR instead of AND causes holes not near edges to be included

D The query should use BETWEEN instead of inequalities

💡 Hint

Consider if holes exactly at 5mm from edges should be included using the given inequalities.

The query uses strict inequalities (< 5, > 95, < 5, > 75), which exclude holes positioned exactly 5mm from the edges (e.g., X=5, X=95, Y=5, Y=75), typical for mounting holes.

Practice

1. What is the main purpose of mounting holes on a PCB?

easy

A. To cool down the PCB components

B. To securely fix the PCB inside a device

C. To provide electrical connections

D. To increase the PCB size

Solution

1. Step 1: Understand mounting hole function

   Mounting holes are designed to hold the PCB in place inside a device.

2. Step 2: Differentiate from other PCB features

   Electrical connections and cooling are done by traces and heat sinks, not mounting holes.

3. Final Answer:

   To securely fix the PCB inside a device -> Option B

4. Quick Check:

   Mounting holes = Secure fixing [OK]

Hint: Mounting holes hold the board physically [OK]

Common Mistakes:

• Confusing mounting holes with electrical vias
• Thinking holes cool components
• Assuming holes increase PCB size

2. Which of the following is the correct way to specify a mounting hole position on a PCB?

easy

A. Using x and y coordinates on the board

B. Using the hole diameter only

C. Using the color of the hole

D. Using the number of pins

Solution

1. Step 1: Identify position parameters

   Mounting holes are placed by specifying their x and y coordinates on the PCB layout.

2. Step 2: Exclude irrelevant options

   Hole diameter defines size, color and pin count are unrelated to position.

3. Final Answer:

   Using x and y coordinates on the board -> Option A

4. Quick Check:

   Position = x,y coordinates [OK]

Hint: Positions need x and y coordinates [OK]

Common Mistakes:

• Confusing hole size with position
• Using color or pins to locate holes
• Ignoring coordinate system

3. Given a PCB with mounting holes at coordinates (10, 20), (50, 20), (10, 60), and (50, 60), what is the distance between the two holes at (10, 20) and (50, 20)?

medium

A. 30 units

B. 60 units

C. 50 units

D. 40 units

Solution

1. Step 1: Identify coordinates of the two holes

   The holes are at (10, 20) and (50, 20), so they share the same y-coordinate.

2. Step 2: Calculate horizontal distance

   Distance = |50 - 10| = 40 units since y is the same.

3. Final Answer:

   40 units -> Option D

4. Quick Check:

   Distance = 50 - 10 = 40 [OK]

Hint: Subtract x values when y is equal [OK]

Common Mistakes:

• Calculating vertical distance instead
• Adding coordinates instead of subtracting
• Mixing x and y values

4. A PCB designer placed mounting holes at (15, 25), (15, 75), (65, 25), but forgot one hole to complete the rectangle. Which coordinate should be added to complete the mounting hole placement?

medium

A. (65, 75)

B. (15, 50)

C. (40, 75)

D. (65, 50)

Solution

1. Step 1: Identify existing hole coordinates

   Holes are at (15, 25), (15, 75), and (65, 25). Two share x=15, two share y=25.

2. Step 2: Find missing corner to form rectangle

   The missing corner must have x=65 and y=75 to complete the rectangle.

3. Final Answer:

   (65, 75) -> Option A

4. Quick Check:

   Opposite corner = (65, 75) [OK]

Hint: Complete rectangle with missing opposite corner [OK]

Common Mistakes:

• Choosing midpoint instead of corner
• Mixing x and y values incorrectly
• Ignoring rectangle shape

5. You need to place four mounting holes on a PCB sized 100x80 units. The holes must be 5 units from each edge. What are the correct coordinates for the holes?

hard

A. (5, 0), (95, 0), (5, 80), (95, 80)

B. (0, 0), (100, 0), (0, 80), (100, 80)

C. (5, 5), (95, 5), (5, 75), (95, 75)

D. (10, 10), (90, 10), (10, 70), (90, 70)

Solution

1. Step 1: Calculate hole positions from edges

   Each hole is 5 units from left/right edges (x=5 and x=100-5=95) and top/bottom edges (y=5 and y=80-5=75).

2. Step 2: List all four corner coordinates

   Holes are at (5,5), (95,5), (5,75), and (95,75).

3. Final Answer:

   (5, 5), (95, 5), (5, 75), (95, 75) -> Option C

4. Quick Check:

   Edges minus 5 units = hole coords [OK]

Hint: Subtract 5 from edges for hole positions [OK]

Common Mistakes:

• Using 0 or full edge coordinates
• Adding 10 units instead of 5
• Mixing x and y values