Creating custom footprints in PCB Design - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start defining a new footprint in KiCad.

PCB Design

footprint = pcbnew.Footprint[1]()

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

ACreate

BNew

CAdd

DBuild

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Create' or 'Add' instead of 'New' causes errors.

In KiCad's Python API, pcbnew.FootprintNew() is used to create a new footprint object.

2fill in blank

medium

Complete the code to set the footprint name.

PCB Design

footprint.[1]("Custom_Footprint_01")

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

ASetName

BSetReference

CSetValue

DSetFootprintName

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing footprint name with reference or value.

The method SetName sets the footprint's name in KiCad's API.

3fill in blank

hard

Fix the error in adding a pad to the footprint.

PCB Design

pad = pcbnew.Pad[1]()

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

ACreate

BAdd

CNew

DBuild

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Create' or 'Add' causes runtime errors.

The correct method to create a new pad object is PadNew() in KiCad's API.

4fill in blank

hard

Fill both blanks to set pad properties correctly.

PCB Design

pad.[1](1)
pad.[2](pcbnew.PAD_SHAPE_RECT)

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

ASetNumber

BSetShape

CSetSize

DSetPosition

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up size and shape methods.

SetNumber assigns the pad number, and SetShape defines the pad shape.

5fill in blank

hard

Fill all three blanks to add the pad to the footprint and set its size and position.

PCB Design

footprint.[1](pad)
pad.[2](pcbnew.wxSizeMM(1.5, 1.5))
pad.[3](pcbnew.wxPointMM(5, 5))

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

AAddPad

BSetSize

CSetPosition

DInsertPad

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names like 'InsertPad' instead of 'AddPad'.

AddPad adds the pad to the footprint, SetSize sets pad size, and SetPosition sets its location.

Practice

1. What is the main purpose of creating a custom footprint in PCB design?

easy

A. To match the exact size and shape of a specific part on the PCB

B. To change the color of the PCB

C. To add more layers to the PCB

D. To increase the power supply voltage

Solution

1. Step 1: Understand what a footprint represents

   A footprint is the physical layout on the PCB where a part will be placed, including pads and outlines.

2. Step 2: Identify the purpose of custom footprints

   Custom footprints ensure the pads and outlines fit the exact size and shape of the part for proper placement and soldering.

3. Final Answer:

   To match the exact size and shape of a specific part on the PCB -> Option A

4. Quick Check:

   Custom footprint = exact part fit [OK]

Hint: Custom footprints fit parts exactly on the board [OK]

Common Mistakes:

• Thinking footprints change PCB color
• Confusing footprints with PCB layers
• Assuming footprints affect power supply

2. Which of the following is the correct step to add a pad when creating a custom footprint?

easy

A. Use the text tool to write the pad name

B. Draw a rectangle and fill it with color

C. Select the pad tool, click on the workspace, then set pad size and shape

D. Import a 3D model without setting pad properties

Solution

1. Step 1: Identify how to add pads in footprint editors

   Pads are added by selecting the pad tool and placing them on the workspace.

2. Step 2: Set pad properties after placement

   After placing, you define pad size, shape, and other properties to match the part's pins.

3. Final Answer:

   Select the pad tool, click on the workspace, then set pad size and shape -> Option C

4. Quick Check:

   Pad tool + set size = correct pad addition [OK]

Hint: Use pad tool, then set size and shape [OK]

Common Mistakes:

• Trying to add pads by drawing shapes
• Using text tool instead of pad tool
• Skipping pad property settings

3. Given a custom footprint with 4 pads arranged in a 2x2 grid, each pad 1.5mm square, spaced 2.5mm apart center-to-center, what is the total width of the footprint from outer edge to outer edge horizontally?

medium

A. 7.0 mm

B. 5.5 mm

C. 6.5 mm

D. 4.0 mm

Solution

1. Step 1: Calculate distance between pad centers horizontally

   Two pads spaced 2.5mm center-to-center means distance between centers is 2.5mm.

2. Step 2: Add half pad size on each side for total width

   Each pad is 1.5mm wide, so half width is 0.75mm. Total width = 2.5mm + 0.75mm + 0.75mm = 4.0mm.

3. Step 3: Consider the 2x2 grid arrangement

   Since there are 2 pads horizontally, total width is center-to-center spacing (2.5mm) plus half pad width on each side (0.75mm + 0.75mm) = 4.0mm. But the question asks for total width of the footprint, which includes both rows. The footprint width horizontally is 2 pads spaced 2.5mm apart plus pad widths: 2.5mm + 0.75mm + 0.75mm = 4.0mm.

4. Step 4: Verify if the question expects total width including both rows

   Since pads are arranged in 2x2 grid, horizontally there are 2 pads, so total width is 2.5mm + 0.75mm + 0.75mm = 4.0mm.

5. Final Answer:

   4.0 mm -> Option D

6. Quick Check:

   Center spacing + pad halves = total width [OK]

Hint: Add pad half-widths to center spacing for total size [OK]

Common Mistakes:

• Adding full pad width twice instead of half
• Confusing spacing with edge-to-edge distance
• Ignoring pad size in calculation

4. You created a custom footprint but the pads do not align with the part pins when placed on the PCB. What is the most likely error?

medium

A. Pad sizes are too large

B. Pad positions are incorrect or not matching the part pin layout

C. The footprint name is missing

D. The PCB layer color is wrong

Solution

1. Step 1: Understand alignment issues

   If pads do not align with part pins, the positions of pads in the footprint are likely incorrect.

2. Step 2: Check pad positions against part datasheet

   Verify pad coordinates match the exact pin layout and spacing from the part's datasheet.

3. Final Answer:

   Pad positions are incorrect or not matching the part pin layout -> Option B

4. Quick Check:

   Misaligned pads = wrong pad positions [OK]

Hint: Check pad positions match part pins exactly [OK]

Common Mistakes:

• Blaming pad size instead of position
• Ignoring footprint naming importance
• Focusing on PCB color instead of layout

5. You need to create a custom footprint for a new sensor with 6 pins arranged in a single row, each pin 1.0mm wide, spaced 2.0mm apart center-to-center. You want to add a silkscreen outline 0.5mm larger than the pad area on all sides. What is the total length of the silkscreen outline along the pin row?

hard

A. 12.0 mm

B. 16.0 mm

C. 15.0 mm

D. 13.0 mm

Solution

1. Step 1: Calculate span between pad centers

   6 pins, 5 intervals x 2.0 mm = 10.0 mm.

2. Step 2: Determine pad area length

   Add half pad width (0.5 mm) on each end: 10.0 mm + 1.0 mm = 11.0 mm.

3. Step 3: Apply silkscreen offset

   0.5 mm larger on all sides adds 1.0 mm to length: 11.0 mm + 1.0 mm = 12.0 mm.

4. Final Answer:

   12.0 mm -> Option A

5. Quick Check:

   (n-1)xspacing + pad width + 2xmargin [OK]

Hint: Add pad widths, spacing, then silkscreen margins [OK]

Common Mistakes:

• Confusing center-to-center with edge-to-edge spacing
• Forgetting to add silkscreen margin on both sides
• Ignoring pad width in total length