Quick answer: Choose SMD busbar thickness by setting the lower limit from continuous current and temperature rise, then checking the upper limit from reflow capability, pad heat spreading and height constraints.
Questions answered on this page
- How should SMD busbar thickness be selected for high-current PCBs?
- Is 40A, 80A or 120A enough to decide thickness?
- Why does a thicker SMD busbar make reflow soldering harder?
- When is a parallel busbar path better than a thicker single part?
Engineering summary
- Thickness is not enough; pad exits and PCB copper bottlenecks often create the first hot spot.
- 0.8mm to 1.2mm is a common evaluation range for many medium/high-current SMD busbar projects.
- Increasing thickness also increases thermal mass, so paste volume, stencil opening and reflow profile must be checked.
Thickness selection logic
SMD busbar thickness is part of the PCB current path, not an isolated copper block. A thicker part lowers resistance, but the solder pad exit, copper thickness, nearby heat sources and reflow process can still become the real limit. For 40A-120A PCB paths, compare thickness, length, pad area and heat spreading together. See the SMD busbar page and SMD busbar category for standard options.
Do not size by cross section only
A heavy busbar can make reflow soldering harder. Check paste volume, stencil opening, coplanarity and inspection method before freezing the drawing.
Decision table
| Item | Check | Risk |
|---|---|---|
| Current | Continuous and peak duration | Oversizing from peak only |
| Temperature rise | Busbar, solder joint, copper exit | Hidden hot spot |
| Reflow | Paste, stencil, thermal mass | Incomplete wetting |
Checklist
- Define continuous current and allowed temperature rise.
- Check pad exit width and PCB copper thickness.
- Validate solder wetting after thickness change.
- Compare standard parts before custom tooling.
FAQ
Is thicker always safer?
No. It can reduce resistance but narrow the soldering process window.
When should parallel paths be used?
When a single thicker part creates soldering or height problems.