Route planning for two-layer board in PCB Design - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Layer Usage in Two-Layer PCB Routing

In a two-layer PCB, how are the layers typically used for routing signals?

A Top layer for horizontal traces, bottom layer for vertical traces

B Top layer for power, bottom layer for ground only

C Both layers used interchangeably without any specific pattern

D Top layer for ground, bottom layer for signals

💡 Hint

Think about how to minimize crossing and simplify routing.

Typically, the top layer routes horizontal signals and the bottom layer routes vertical signals to reduce crossing and simplify routing.

❓ dax_lod_result

intermediate

Calculate Total Trace Length per Layer

Given a dataset of trace segments with their lengths and layer info, which DAX measure correctly calculates the total trace length on the top layer?

PCB Design

TraceData = DATATABLE(
  "TraceID", INTEGER,
  "Length_mm", FLOAT,
  "Layer", STRING,
  {
    {1, 10.5, "Top"},
    {2, 5.0, "Bottom"},
    {3, 7.2, "Top"},
    {4, 3.3, "Bottom"}
  }
)

A TotalTopLength = CALCULATE(SUM(TraceData[Length_mm]), FILTER(TraceData, TraceData[Layer] = "Top"))

B TotalTopLength = CALCULATE(SUM(TraceData[Length_mm]), FILTER(TraceData, TraceData[Layer] = "Bottom"))

C TotalTopLength = SUM(TraceData[Length_mm]) WHERE TraceData[Layer] = "Top"

D TotalTopLength = SUMX(FILTER(TraceData, TraceData[Layer] = "Top"), TraceData[Length_mm])

💡 Hint

Remember that CALCULATE requires filter expressions or FILTER function for conditions.

Option D uses SUMX with FILTER to sum lengths only where Layer is 'Top'. Option D is valid syntax but less efficient than A. Option D is invalid syntax. Option D sums bottom layer lengths, not top.

❓ visualization

advanced

Best Visualization for Layer Trace Length Comparison

You want to compare total trace lengths on top and bottom layers visually. Which chart type best shows this comparison clearly?

A Pie chart showing percentage of total trace length per layer

B Line chart showing trace length over time per layer

C Scatter plot with trace length on X-axis and layer on Y-axis

D Stacked bar chart showing total length per layer stacked by trace type

💡 Hint

Think about showing parts of a whole clearly.

A pie chart clearly shows the proportion of total trace length per layer, making it easy to compare their shares. Stacked bar is more complex and better for multiple categories. Line chart is for trends over time. Scatter plot is less intuitive here.

🔧 Formula Fix

advanced

Identify the Error in Routing Layer Assignment Logic

Review this pseudocode for assigning routing layers based on signal direction. What is the error?

if signal_direction == "horizontal":
    assign_layer = "Top"
elif signal_direction == "vertical":
    assign_layer = "Bottom"
else:
    assign_layer = "Top" or "Bottom"

A The elif condition should check for diagonal signals instead of vertical

B The else statement uses 'or' which returns a boolean, not a layer string

C The assign_layer variable is not declared before use

D The if statement should use '==' for assignment, not '='

💡 Hint

Check what 'or' returns in Python expressions.

The expression '"Top" or "Bottom"' evaluates to 'Top' always, so it does not assign both layers or a choice. It returns a string, but the use of 'or' here is misleading and may cause confusion. The code should explicitly assign one layer or handle the else case differently.

🎯 Scenario

expert

Optimizing Trace Routing on a Two-Layer Board with High-Density Components

You have a two-layer PCB with many components close together. You need to optimize routing to minimize crosstalk and signal interference. Which approach is best?

A Use the top layer for all signal traces and the bottom layer exclusively for ground plane

B Use only one layer for routing and leave the other layer empty to reduce complexity

C Route horizontal signals on the top layer and vertical signals on the bottom layer, adding ground fills on both layers

D Route signals randomly on both layers to balance trace density, without ground fills

💡 Hint

Think about signal integrity and layer usage patterns.

Routing horizontal signals on top and vertical on bottom reduces crossing and crosstalk. Adding ground fills on both layers improves shielding and reduces interference. Using one layer only or random routing increases interference risks.