Via size and drill diameter in PCB Design - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the relationship between via size and drill diameter

In PCB design, the via size is closely related to the drill diameter. Which statement correctly describes this relationship?

A The drill diameter is always larger than the via size to ensure clearance.

B The drill diameter and via size are always equal for precision.

C The drill diameter is always smaller than the via size to allow for plating.

D The drill diameter is unrelated to the via size and can be any value.

💡 Hint

Think about how the plating process reduces the hole size.

The drill diameter is larger than the finished via size because plating adds copper thickness to the walls, reducing the final hole size.

🎯 Scenario

intermediate

Selecting drill diameter for a given via size

You need to design a via with a finished size of 0.4 mm. The plating thickness is 0.025 mm on each side of the hole. What drill diameter should you specify?

A 0.35 mm

B 0.30 mm

C 0.40 mm

D 0.45 mm

💡 Hint

Add twice the plating thickness to the finished via size.

Drill diameter = via size + 2 * plating thickness = 0.4 + 2*0.025 = 0.45 mm.

❓ dax_lod_result

advanced

Calculate average drill diameter per via size category

Given a dataset of vias with columns 'ViaSize' and 'DrillDiameter', which DAX measure correctly calculates the average drill diameter for each via size category?

PCB Design

Average Drill Diameter = AVERAGEX(VALUES(Vias[ViaSize]), CALCULATE(AVERAGE(Vias[DrillDiameter])))

A Average Drill Diameter = CALCULATE(AVERAGE(Vias[DrillDiameter]), ALLEXCEPT(Vias, Vias[ViaSize]))

B Average Drill Diameter = AVERAGEX(VALUES(Vias[ViaSize]), CALCULATE(AVERAGE(Vias[DrillDiameter])))

C Average Drill Diameter = AVERAGE(Vias[DrillDiameter])

D Average Drill Diameter = SUM(Vias[DrillDiameter]) / COUNTROWS(Vias)

💡 Hint

Use AVERAGEX over distinct via sizes to get average per category.

Option B uses AVERAGEX over distinct ViaSize values and calculates average DrillDiameter per group, correctly computing average per category.

❓ visualization

advanced

Best visualization to compare via sizes and drill diameters

You want to create a dashboard that shows the distribution of via sizes and their corresponding drill diameters across multiple PCB layers. Which visualization type is best suited for this purpose?

A Stacked bar chart showing total drill diameters per layer

B Pie chart showing percentage of each via size

C Scatter plot with Via Size on X-axis and Drill Diameter on Y-axis, colored by PCB layer

D Line chart showing drill diameter trends over time

💡 Hint

Consider how to show relationship between two numeric variables and categories.

A scatter plot effectively shows the relationship between via size and drill diameter, with color differentiating PCB layers.

🔧 Formula Fix

expert

Identify the error in drill diameter calculation measure

Consider this DAX measure intended to calculate the drill diameter for a given via size by adding plating thickness twice:

Drill Diameter = Vias[ViaSize] + 2 * Vias[PlatingThickness]

Why does this measure produce incorrect results when used in a report?

A It uses direct column references without aggregation, causing row context issues.

B It incorrectly multiplies plating thickness by 2 instead of adding.

C It should use SUM instead of subtraction for drill diameter calculation.

D It lacks a FILTER function to limit rows to the current via size.

💡 Hint

Think about how DAX handles row context in measures.

Measures cannot use direct column references without aggregation because they lack row context, leading to errors or incorrect results.