Mounting hole placement in PCB Design - Cell-by-Cell Formula Trace

Sample Data

This data shows mounting hole IDs with their X and Y positions on a PCB board. Board dimensions and calculated center coordinates are included. The distance from hole H1 to the board center is calculated.

Cell	Value
A1	Hole ID
B1	X Position (mm)
C1	Y Position (mm)
A2	H1
B2	10
C2	5
A3	H2
B3	90
C3	5
A4	H3
B4	10
C4	45
A5	H4
B5	90
C5	45
A6	Board Width (mm)
B6	100
A7	Board Height (mm)
B7	50
A8	Center X
B8	=B6/2
A9	Center Y
B9	=B7/2
A10	Distance H1 to Center
B10	=SQRT((B2-B8)^2+(C2-B9)^2)

Formula Trace

=SQRT((B2-B8)^2+(C2-B9)^2)

Step 1: B6/2

Step 2: B8

Step 3: B7/2

Step 4: B9

Step 5: (B2-B8)

Step 6: (B2-B8)^2

Step 7: (C2-B9)

Step 8: (C2-B9)^2

Step 9: (B2-B8)^2 + (C2-B9)^2

Step 10: SQRT(2000)

Cell Reference Map

    A       B       C
1 | Hole ID | X Pos  | Y Pos  
2 |   H1    |  10    |   5    
3 |   H2    |  90    |   5    
4 |   H3    |  10    |  45    
5 |   H4    |  90    |  45    
6 | Board W |  100   |        
7 | Board H |  50    |        
8 | CenterX |  =B6/2 |        
9 | CenterY |  =B7/2 |        
10| Dist H1 | =SQRT((B2-B8)^2+(C2-B9)^2) |

Arrows:
B8 <- B6
B9 <- B7
B10 <- B2, B8, C2, B9

This map shows the cells used in the formula for distance calculation. Center X (B8) depends on Board Width (B6). Center Y (B9) depends on Board Height (B7). Distance (B10) depends on hole H1's X (B2), Y (C2), and center coordinates (B8, B9).

Result

    A       B       C
1 | Hole ID | X Pos  | Y Pos  
2 |   H1    |  10    |   5    
3 |   H2    |  90    |   5    
4 |   H3    |  10    |  45    
5 |   H4    |  90    |  45    
6 | Board W |  100   |        
7 | Board H |  50    |        
8 | CenterX |  50     |        
9 | CenterY |  25     |        
10| Dist H1 | 44.72   |        

The final result shows the calculated center coordinates of the board (50 mm, 25 mm) and the distance from hole H1 to the center as approximately 44.72 mm.

Sheet Trace Quiz - 3 Questions

What is the value of Center X (cell B8)?

A 100

B 50

C 25

D 10

Key Result

Distance from a point to center is calculated using the Pythagorean theorem: SQRT((X - CenterX)^2 + (Y - CenterY)^2).

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