Why design rules prevent manufacturing defects in PCB Design - Dashboard Impact

Dashboard Mode - Why design rules prevent manufacturing defects

Business Question

How do design rules in PCB design help reduce manufacturing defects and improve product quality?

Sample Data: PCB Design Rule Checks and Defect Counts

Design Rule	Rule Description	Violations Found	Defects After Manufacturing
Minimum Trace Width	Trace width must be at least 6 mil	5	3
Minimum Spacing	Spacing between traces at least 6 mil	3	2
Via Size	Via diameter at least 10 mil	2	1
Annular Ring	Annular ring width at least 5 mil	4	2
Silkscreen Clearance	Clearance from pads at least 3 mil	1	0
Component Placement	Components must not overlap	0	0
Test Point Access	Test points accessible for probes	1	0
Overall	Total violations and defects	16	8

Dashboard Components

• KPI Card: Total Violations
  Shows total design rule violations found before manufacturing.
  Formula: SUM of 'Violations Found' column = 16
• KPI Card: Total Defects
  Shows total defects found after manufacturing.
  Formula: SUM of 'Defects After Manufacturing' column = 8
• Bar Chart: Violations vs Defects by Rule
  X-axis: Design Rule
  Y-axis: Count
  Two bars per rule: Violations Found and Defects After Manufacturing
  Shows how violations relate to defects per rule.
• Table: Detailed Rule Data
  Shows all columns from sample data for detailed inspection.

Dashboard Layout

+----------------------+----------------------+
|  KPI: Total Violations |  KPI: Total Defects  |
+----------------------+----------------------+
|                                              |
|      Bar Chart: Violations vs Defects         |
|                                              |
+----------------------------------------------+
|                                              |
|           Table: Detailed Rule Data           |
|                                              |
+----------------------------------------------+
  

Interactivity

A filter dropdown allows selecting one or more Design Rules.
When a rule is selected, the KPI cards update to show totals only for those rules.
The bar chart and table also update to show data filtered by the selected rules.
This helps focus on specific design rules causing most defects.

Self Check

If you filter the dashboard to show only the "Minimum Trace Width" rule:
- What is the total number of violations?
- What is the total number of defects?
- How do the bar chart and table update?
(Answer: Violations = 5, Defects = 3, bar chart and table show only that rule's data.)

Key Result

Dashboard shows how PCB design rule violations relate to manufacturing defects by rule.

Practice

1. Why are design rules important in PCB manufacturing?

easy

A. They prevent defects like shorts and opens in the PCB.

B. They make the PCB look more colorful.

C. They reduce the cost of raw materials.

D. They increase the speed of the soldering process.

Solution

1. Step 1: Understand the purpose of design rules

   Design rules set limits on layout features to avoid manufacturing problems.

2. Step 2: Identify the main benefit of following design rules

   Following design rules prevents defects such as shorts and opens that cause PCB failure.

3. Final Answer:

   They prevent defects like shorts and opens in the PCB. -> Option A

4. Quick Check:

   Design rules prevent defects = A [OK]

Hint: Design rules stop errors before production starts [OK]

Common Mistakes:

• Thinking design rules only affect appearance
• Confusing cost savings with defect prevention
• Assuming design rules speed up soldering

2. Which of the following is a correct design rule syntax for minimum trace width in a PCB design tool?

easy

A. MinTraceWidth = 0.15mm;

B. min_trace_width: 0.15;

C. traceWidthMin = '0.15mm'

D. MinTraceWidth 0.15mm

Solution

1. Step 1: Identify correct syntax style for design rules

   Design rules often use key-value pairs with assignment and units, ending with semicolon.

2. Step 2: Compare options to this style

   MinTraceWidth = 0.15mm; uses assignment '=', unit 'mm', and semicolon ';' correctly.

3. Final Answer:

   <code>MinTraceWidth = 0.15mm;</code> -> Option A

4. Quick Check:

   Correct syntax uses '=' and ';' = D [OK]

Hint: Look for '=' and ';' with units for correct syntax [OK]

Common Mistakes:

• Omitting semicolon at end
• Using colon instead of equal sign
• Missing units or quotes around values

3. Given a PCB layout with a trace width of 0.1mm but the design rule requires minimum 0.15mm, what will a design rule check report?

medium

A. No issues found, trace width is acceptable.

B. Error: Trace width below minimum allowed.

C. Warning: Trace width is larger than maximum.

D. Error: Trace width missing units.

Solution

1. Step 1: Compare actual trace width to minimum rule

   The trace is 0.1mm but minimum allowed is 0.15mm, so it is too narrow.

2. Step 2: Determine design rule check result

   The tool reports an error because the trace width violates the minimum width rule.

3. Final Answer:

   Error: Trace width below minimum allowed. -> Option B

4. Quick Check:

   Trace 0.1mm < 0.15mm = Error B [OK]

Hint: Check if actual value meets minimum rule [OK]

Common Mistakes:

• Assuming no error if value is close
• Confusing minimum and maximum rules
• Ignoring units in comparison

4. A PCB design rule check script has this line: MinSpacing = 0.2mm but the tool reports a syntax error. What is the likely cause?

medium

A. Spacing value is too small.

B. Incorrect unit; should be 'mil' not 'mm'.

C. Variable name cannot start with uppercase letter.

D. Missing semicolon at the end of the line.

Solution

1. Step 1: Check syntax rules for design statements

   Each statement must end with a semicolon to be valid syntax.

2. Step 2: Identify missing semicolon as error cause

   The line lacks a semicolon at the end, causing syntax error.

3. Final Answer:

   Missing semicolon at the end of the line. -> Option D

4. Quick Check:

   Statements need ';' at end = A [OK]

Hint: Look for missing semicolon in error lines [OK]

Common Mistakes:

• Blaming units instead of syntax
• Thinking variable names are case-sensitive errors
• Confusing value size with syntax error

5. A PCB has a via hole diameter of 0.3mm but the design rule requires a minimum of 0.4mm to avoid mechanical defects. Which combined action best prevents manufacturing defects?

hard

A. Ignore the rule since 0.3mm is close enough and save cost.

B. Keep via diameter at 0.3mm but add more vias to compensate.

C. Increase via diameter to 0.4mm and run design rule check before production.

D. Change the design rule to 0.3mm to match the via size.

Solution

1. Step 1: Identify the violation and its risk

   The via diameter is smaller than minimum, risking mechanical defects during manufacturing.

2. Step 2: Choose the best corrective action

   Increasing via size to meet the rule and running a design rule check ensures defects are caught early.

3. Final Answer:

   Increase via diameter to 0.4mm and run design rule check before production. -> Option C

4. Quick Check:

   Fix violation + check early = C [OK]

Hint: Fix violations and run checks before production [OK]

Common Mistakes:

• Ignoring rules to save cost
• Changing rules to fit design instead of design to rules
• Adding more vias without fixing size