What is solder mask expansion in PCB design?
Solder mask expansion is the amount by which the solder mask opening is larger or smaller than the copper pad underneath. It controls how much of the copper pad is exposed for soldering.
Why is controlling solder mask expansion important?
It ensures good solder joint quality by exposing enough copper for soldering while preventing solder bridges and shorts between pads.
What happens if solder mask expansion is too large?
If solder mask expansion is too large, too much copper is exposed, increasing the risk of solder bridges and short circuits between pads.
What is the typical range for solder mask expansion values?
Typical solder mask expansion values range from -0.05 mm (mask opening smaller than pad) to +0.15 mm (mask opening larger than pad), depending on manufacturing capabilities.
How does solder mask expansion affect automated optical inspection (AOI)?
Proper solder mask expansion helps AOI systems detect soldering defects by clearly defining pad boundaries and preventing false positives from solder bridging.
What does a positive solder mask expansion value mean?
A positive solder mask expansion means the mask opening is larger than the copper pad, exposing more copper.
What risk increases if solder mask expansion is too large?
Too large solder mask expansion exposes more copper, increasing the chance of solder bridges between pads.
What is the main purpose of solder mask on a PCB?
Solder mask protects copper traces and prevents solder from bridging between pads during assembly.
Which value is a typical solder mask expansion?
Typical solder mask expansion values are around +0.1 mm, allowing slight extra opening over the pad.
How does solder mask expansion affect solder joint quality?
Solder mask expansion controls how much copper is exposed, which affects solder joint quality.
Explain solder mask expansion and why it matters in PCB manufacturing.
Describe what could happen if solder mask expansion is set too small or too large.