The challenge
This board conditions the input power for a high-power plasma / laser generator in the 30–60 kW class. It suppresses EMI and provides a controlled startup that limits inrush current.
It uses 6 oz copper (about 210 µm, roughly 8 mil per layer) on a board thicker than 0.100 in. Heavy copper and a thick board turn the whole assembly into a heat sink. The through-hole joints on the large filter parts (chokes, X and Y capacitors and inrush parts) need a lot of heat to wet properly and fill the barrel, without damaging the parts or the laminate.
The board also runs at high voltage. There, flux residues can cause leakage and electrochemical migration, and partial discharge (corona) slowly erodes insulation until it fails.
What BSU did
- Wave solder. BSU soldered the through-hole parts on wave solder with a thermal profile developed for this board, so joints wet and fill despite the copper pulling heat away.
- Cleanliness. Boards were washed and ionic cleanliness was verified by ion chromatography, which identifies the residue species that drive leakage and electrochemical migration.
- Anti-corona coating. An anti-corona coating was applied to suppress partial discharge, which otherwise degrades insulation over time.
Result
More than 100 units built over the past year, in repeat production.
