Why Mounting hole placement in PCB Design? - Purpose & Use Cases

The Big Idea

What if one tiny misplaced hole could ruin your entire device assembly?

The Scenario

Imagine you are designing a circuit board and need to place mounting holes manually by measuring and marking each position on paper or a simple drawing.

You try to guess the exact spots for screws to fit the case, but it's hard to be precise without a clear system.

The Problem

Manually placing mounting holes is slow and prone to mistakes.

One wrong measurement can cause the board not to fit the case, leading to costly rework or wasted materials.

It's also hard to keep track of hole sizes and positions consistently across multiple designs.

The Solution

Using a systematic mounting hole placement method in your PCB design software automates accurate hole positioning.

This ensures holes are correctly sized and precisely located according to your case or enclosure requirements.

You save time, reduce errors, and improve the reliability of your final product.

Before vs After

✗ Before

Measure hole positions with ruler and mark on paper

✓ After

Use PCB software commands to place mounting holes at exact coordinates

What It Enables

It enables fast, precise, and repeatable mounting hole placement that fits perfectly with your product's mechanical design.

Real Life Example

A hardware engineer designs a new device enclosure and uses mounting hole placement tools to ensure the PCB fits securely inside without drilling new holes or modifying the case.

Key Takeaways

Manual hole placement is slow and error-prone.

Automated placement ensures precision and consistency.

Accurate holes improve product fit and reduce rework.

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