Why libraries ensure correct component mapping in PCB Design - Formula Trace Breakdown

Sample Data

This table shows components on a PCB and how each is linked to a library part and its correct footprint for manufacturing.

Cell	Value
A1	Component ID
B1	Library Part Name
C1	Mapped Footprint
A2	R1
B2	Resistor_0603
C2	0603_Footprint
A3	C1
B3	Capacitor_0402
C3	0402_Footprint
A4	U1
B4	Microcontroller_QFP
C4	QFP_Footprint

Formula Trace

IF(B2 = 'Resistor_0603', '0603_Footprint', IF(B2 = 'Capacitor_0402', '0402_Footprint', IF(B2 = 'Microcontroller_QFP', 'QFP_Footprint', 'Unknown')))

Step 1: LibraryPartName = 'Resistor_0603' for R1

Step 2: Return '0603_Footprint' for R1

Step 3: LibraryPartName = 'Resistor_0603' for C1

Step 4: LibraryPartName = 'Capacitor_0402' for C1

Step 5: Return '0402_Footprint' for C1

Step 6: LibraryPartName = 'Resistor_0603' for U1

Step 7: LibraryPartName = 'Capacitor_0402' for U1

Step 8: LibraryPartName = 'Microcontroller_QFP' for U1

Step 9: Return 'QFP_Footprint' for U1

Cell Reference Map

    A           B                 C
1 |Component ID|Library Part Name |Mapped Footprint|
2 |    R1     | Resistor_0603    | 0603_Footprint|
3 |    C1     | Capacitor_0402  | 0402_Footprint|
4 |    U1     | Microcontroller_QFP | QFP_Footprint|

Arrows: B2->C2, B3->C3, B4->C4

The formula uses the Library Part Name in column B to determine the correct footprint in column C for each component in column A.

Result

    A           B                 C
1 |Component ID|Library Part Name |Mapped Footprint|
2 |    R1     | Resistor_0603    | 0603_Footprint|
3 |    C1     | Capacitor_0402  | 0402_Footprint|
4 |    U1     | Microcontroller_QFP | QFP_Footprint|

The footprints in column C are correctly assigned based on the library part names in column B.

This shows the final mapping of each component to its correct footprint, ensuring the PCB design uses the right physical parts.

Sheet Trace Quiz - 3 Questions

What footprint is assigned to component R1?

A 0603_Footprint

B 0402_Footprint

C QFP_Footprint

D Unknown

Key Result

Nested IF statements check library part names to assign correct footprints for components.