Impedance-controlled traces in PCB Design - Real Business Scenario

Scenario Mode

👤 Your Role: You are a PCB design engineer working for an electronics manufacturing company.

📋 Request: Your manager wants you to analyze the impedance-controlled traces on recent PCB designs to ensure signal integrity and reduce signal loss. They want a report showing the trace impedance values, deviations from target impedance, and recommendations for improvement.

📊 Data: You have a dataset containing PCB trace measurements including Trace ID, Layer, Target Impedance (Ohms), Measured Impedance (Ohms), Trace Width (mils), and Dielectric Thickness (mils).

🎯 Deliverable: Create a dashboard report showing each trace's impedance, the deviation from target, a summary of how many traces meet the target impedance within tolerance, and visual charts highlighting traces with impedance issues.

Sample Data

Trace ID	Layer	Target Impedance (Ohms)	Measured Impedance (Ohms)	Trace Width (mils)	Dielectric Thickness (mils)
T1	Top	50	48	6	5
T2	Top	50	52	5.8	5
T3	Inner1	75	80	4	6
T4	Inner1	75	74	4.2	6
T5	Bottom	50	55	5.5	5
T6	Bottom	50	49	6	5
T7	Top	50	51	5.9	5
T8	Inner1	75	73	4.1	6

1

Step 1: Import the PCB trace data into your BI tool.

Load the table with columns: Trace ID, Layer, Target Impedance, Measured Impedance, Trace Width, Dielectric Thickness.

Expected Result

Data table with 8 rows and 6 columns loaded successfully.

2

Step 2: Create a calculated column 'Impedance Deviation' to find the difference between Measured and Target Impedance.

Impedance Deviation = [Measured Impedance (Ohms)] - [Target Impedance (Ohms)]

Expected Result

New column showing deviations: T1=-2, T2=2, T3=5, T4=-1, T5=5, T6=-1, T7=1, T8=-2.

3

Step 3: Create a measure 'Within Tolerance' to count traces with absolute deviation less than or equal to 2 Ohms.

Within Tolerance = COUNTROWS(FILTER(Table, ABS([Impedance Deviation]) <= 2))

Expected Result

Count of traces within tolerance = 6.

4

Step 4: Create a bar chart showing each Trace ID on the X-axis and Measured Impedance on the Y-axis, with a line for Target Impedance.

Configure bar chart: X-axis = Trace ID, Y-axis = Measured Impedance; Add constant line at Target Impedance per trace.

Expected Result

Bar chart visualizes measured impedance per trace with target impedance line for comparison.

5

Step 5: Create a table visual listing Trace ID, Layer, Target Impedance, Measured Impedance, Impedance Deviation, and a status column 'Meets Target' showing 'Yes' if deviation <= 2, else 'No'.

Meets Target = IF(ABS([Impedance Deviation]) <= 2, "Yes", "No")

Expected Result

Table clearly shows which traces meet impedance targets.

6

Step 6: Add a summary card showing total traces, traces within tolerance, and percentage within tolerance.

Total Traces = COUNTROWS(Table); Percentage Within Tolerance = DIVIDE([Within Tolerance], [Total Traces]) * 100

Expected Result

Summary card shows: Total Traces=8, Within Tolerance=6, Percentage=75%.

7

Step 7: Add recommendations text box explaining that traces with deviation greater than 2 Ohms should be reviewed for trace width or dielectric thickness adjustments.

Static text: 'Review traces T3 and T5 for impedance correction by adjusting trace width or dielectric thickness.'

Expected Result

Dashboard includes clear recommendations for improvement.

Final Result

PCB Trace Impedance Report

Trace ID | Layer  | Target | Measured | Deviation | Meets Target
--------------------------------------------------------------
T1       | Top    | 50     | 48       | -2        | Yes
T2       | Top    | 50     | 52       | 2         | Yes
T3       | Inner1 | 75     | 80       | 5         | No
T4       | Inner1 | 75     | 74       | -1        | Yes
T5       | Bottom | 50     | 55       | 5         | No
T6       | Bottom | 50     | 49       | -1        | Yes
T7       | Top    | 50     | 51       | 1         | Yes
T8       | Inner1 | 75     | 73       | -2        | Yes

Summary:
Total Traces: 8
Within Tolerance (±2 Ohms): 6
Percentage Within Tolerance: 75%

Recommendations:
- Review traces T3 and T5 for impedance correction by adjusting trace width or dielectric thickness.
- Maintain current design for traces meeting target impedance.

✓6 out of 8 traces meet the target impedance within ±2 Ohms tolerance.

✓Traces T3 and T5 have deviations of +5 Ohms, indicating potential signal integrity issues.

✓Adjusting trace width or dielectric thickness can help bring impedance closer to target.

✓Overall, 75% of traces meet impedance control requirements.

Bonus Challenge

Create a scatter plot showing the relationship between Trace Width and Measured Impedance to identify patterns affecting impedance control.

Show Hint

Plot Trace Width on X-axis and Measured Impedance on Y-axis; use color to indicate if trace meets target impedance.