Solder mask expansion in PCB Design - Dashboard Guide

Dashboard Mode - Solder mask expansion

Dashboard Goal

Understand how solder mask expansion affects PCB manufacturing quality and yield by analyzing expansion values and defect rates.

Sample Data

PCB_ID	Solder Mask Expansion (µm)	Defect Count	Total Pads	Yield (%)
PCB001	50	2	100	98
PCB002	70	5	120	95.8
PCB003	40	1	110	99.1
PCB004	80	7	130	94.6
PCB005	60	3	115	97.4
PCB006	55	2	105	98.1

Dashboard Components

• KPI Card: Average Solder Mask Expansion
  Formula: Average = SUM([Solder Mask Expansion (µm)]) / COUNT([PCB_ID])
  Result: (50+70+40+80+60+55)/6 = 59.17 µm
• KPI Card: Average Defect Rate (%)
  Formula: Defect Rate per PCB = (Defect Count / Total Pads) * 100
  Average Defect Rate = AVERAGE((Defect Count / Total Pads) * 100)
  Calculations:
  PCB001: 2/100*100=2%
  PCB002: 5/120*100=4.17%
  PCB003: 1/110*100=0.91%
  PCB004: 7/130*100=5.38%
  PCB005: 3/115*100=2.61%
  PCB006: 2/105*100=1.90%
  Average = (2+4.17+0.91+5.38+2.61+1.90)/6 = 2.83%
• Line Chart: Solder Mask Expansion vs Yield
  X-axis: Solder Mask Expansion (µm)
  Y-axis: Yield (%)
  Shows how yield changes with expansion values.
• Bar Chart: Defect Count per PCB
  X-axis: PCB_ID
  Y-axis: Defect Count
  Highlights which PCBs have higher defects.
• Table: Detailed PCB Data
  Shows all columns for detailed inspection.

Dashboard Layout

+----------------------+----------------------+
|  KPI: Avg Expansion   |  KPI: Avg Defect Rate |
|      (59.17 µm)       |       (2.83 %)        |
+----------------------+----------------------+
|                                              |
|      Line Chart: Expansion vs Yield           |
|                                              |
+----------------------+----------------------+
|  Bar Chart: Defect Count  |  Table: PCB Details  |
|       per PCB             |                      |
+----------------------+----------------------+
    

Interactivity

A filter slider for Solder Mask Expansion allows selecting a range (e.g., 40 to 70 µm).
When adjusted, the KPI cards, line chart, bar chart, and table update to show data only for PCBs within that expansion range.
This helps analyze how defect rates and yield behave for specific expansion values.
The table supports sorting by any column for deeper analysis.

Self Check

If you add a filter to show only PCBs with Solder Mask Expansion <= 60 µm, which components update and what changes occur?

• KPI Cards recalculate averages only for PCBs with expansion ≤ 60 µm (PCB001, PCB003, PCB005, PCB006).
• Line chart redraws to show yield for these PCBs only.
• Bar chart shows defect counts only for these PCBs.
• Table filters to show only these PCBs.

This helps focus on lower expansion values and their quality impact.

Key Result

Dashboard analyzing solder mask expansion impact on PCB defect rates and yield.

Practice

1. What is the main purpose of solder mask expansion in PCB design?

easy

A. To adjust the size of mask openings around pads

B. To change the thickness of the PCB substrate

C. To increase the number of layers in the PCB

D. To modify the copper trace width

Solution

1. Step 1: Understand solder mask expansion function

   Solder mask expansion changes the size of openings around pads to control soldering quality.

2. Step 2: Identify the correct purpose

   Adjusting mask openings prevents solder bridges or insufficient coverage during assembly.

3. Final Answer:

   To adjust the size of mask openings around pads -> Option A

4. Quick Check:

   Solder mask expansion = Adjust mask openings [OK]

Hint: Think about mask openings size control [OK]

Common Mistakes:

• Confusing mask expansion with PCB thickness
• Mixing mask expansion with copper trace width
• Assuming it changes PCB layers

2. Which of the following is the correct way to specify a solder mask expansion value to increase the mask opening size by 0.05 mm?

easy

A. solder_mask_expansion = -0.05

B. solder_mask_expansion = 0

C. solder_mask_expansion = 0.05

D. solder_mask_expansion = +0.00

Solution

1. Step 1: Understand sign convention for expansion

   Positive values increase mask opening size; negative values decrease it.

2. Step 2: Choose the positive value for increasing size

   0.05 mm positive value means mask opening grows by 0.05 mm.

3. Final Answer:

   solder_mask_expansion = 0.05 -> Option C

4. Quick Check:

   Positive value increases opening size [OK]

Hint: Positive value means bigger opening [OK]

Common Mistakes:

• Using negative value to increase size
• Using zero which means no change
• Confusing plus sign usage

3. Given a pad size of 1.0 mm and a solder mask expansion of -0.1 mm, what will be the effective mask opening size?

medium

A. 0.8 mm

B. 1.1 mm

C. 1.0 mm

D. 0.9 mm

Solution

1. Step 1: Understand the effect of negative expansion

   Negative expansion reduces the mask opening size by the given amount.

2. Step 2: Calculate effective mask opening

   1.0 mm pad size minus 0.1 mm expansion = 0.9 mm opening.

3. Final Answer:

   0.9 mm -> Option D

4. Quick Check:

   Pad size + expansion = opening size [OK]

Hint: Add expansion (negative) to pad size [OK]

Common Mistakes:

• Adding negative expansion instead of subtracting
• Ignoring sign of expansion
• Using pad size without adjustment

4. A designer sets solder mask expansion to 0.0 mm but notices solder bridging on the PCB. What is the most likely error?

medium

A. Expansion value is too small, should be positive

B. Expansion value is too large, should be negative

C. Expansion value syntax is incorrect

D. Expansion value has no effect on solder bridging

Solution

1. Step 1: Analyze effect of zero expansion

   Zero expansion means mask opening matches pad size exactly, no extra clearance.

2. Step 2: Understand solder bridging cause

   Without extra clearance (positive expansion), solder can bridge between pads.

3. Final Answer:

   Expansion value is too small, should be positive -> Option A

4. Quick Check:

   Positive expansion prevents bridging [OK]

Hint: Use positive expansion to avoid bridging [OK]

Common Mistakes:

• Thinking zero expansion is enough
• Assuming negative expansion prevents bridging
• Ignoring solder mask role

5. A PCB has pads of 0.8 mm size. To ensure no solder bridging but avoid excessive mask exposure, the designer wants the mask opening to be 0.9 mm. What solder mask expansion value should be set?

hard

A. -0.1 mm

B. 0.1 mm

C. 0.9 mm

D. -0.9 mm

Solution

1. Step 1: Calculate required expansion

   Desired opening (0.9 mm) minus pad size (0.8 mm) = 0.1 mm expansion.

2. Step 2: Confirm sign of expansion

   Since opening is larger than pad, expansion must be positive 0.1 mm.

3. Final Answer:

   0.1 mm -> Option B

4. Quick Check:

   Opening - pad size = positive expansion [OK]

Hint: Expansion = desired opening - pad size [OK]

Common Mistakes:

• Using negative expansion when opening is larger
• Confusing pad size with opening size
• Setting expansion equal to opening size