Mounting hole placement in PCB Design - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the primary purpose of mounting holes in PCB design?

Mounting holes are used to securely attach the PCB to its enclosure or chassis, preventing movement and mechanical stress.

beginner

Name two common types of mounting holes used in PCB design.

Common types include plated mounting holes (with metal plating for grounding) and non-plated mounting holes (just mechanical support).

intermediate

Why is it important to consider the placement of mounting holes relative to components?

To avoid interference with components and traces, ensuring mechanical stability without damaging electrical parts.

intermediate

What is a typical clearance recommendation around mounting holes?

A clearance of at least 1mm to 2mm around mounting holes is recommended to avoid electrical shorts and mechanical damage.

advanced

How can mounting holes contribute to grounding in PCB design?

Plated mounting holes can be connected to the ground plane, helping reduce electromagnetic interference and improve signal integrity.

What is the main function of mounting holes on a PCB?

A To store components

B To route electrical signals

C To cool down the PCB

D To attach the PCB securely to a case or chassis

Mounting holes are designed to fix the PCB mechanically, not for electrical or thermal functions.

Which type of mounting hole can help with grounding?

A Non-plated hole

B Thermal pad

C Plated hole

D Blind via

Plated mounting holes have metal plating that can connect to the ground plane.

What is a good clearance distance around mounting holes to avoid shorts?

A 1-2mm

B 0.5mm

C 0.1mm

D 5mm

A clearance of 1-2mm is typical to prevent electrical shorts and mechanical damage.

Why should mounting holes be placed away from components?

A To avoid mechanical interference and damage

B To increase signal speed

C To reduce manufacturing cost

D To improve soldering

Placing holes away from components prevents mechanical stress and interference.

Which of the following is NOT a purpose of mounting holes?

A Mechanical support

B Routing power signals

C Electrical grounding (if plated)

D Fixing PCB in enclosure

Mounting holes are not used for routing power signals.

Explain why mounting hole placement is important in PCB design.

Think about both mechanical and electrical aspects.

Describe the difference between plated and non-plated mounting holes and their uses.

Consider electrical connectivity and mechanical function.

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