How to Choose a Reflow Oven - Convection or Vapour Phase?
The reflow oven melts the solder paste in a controlled way and forms the joint. This guide compares convection and vapour phase, explains zone count and the temperature profile per J-STD-020, and shows which oven fits from prototype to volume production.
View reflow ovensConvection or vapour phase - which fits?
Reflow soldering is dominated by two methods: the convection oven using forced hot air or nitrogen, and the vapour phase oven that condenses an evaporating heat-transfer fluid on the board. Both raise the assembly above the solder liquidus, but they differ in process window and repeatability.
Convection is the industry standard for volume: fast throughput, free profile design and good handling of mixed assemblies. Vapour phase physically caps the maximum temperature at the boiling point of the fluid (typically 230 °C, up to 240 °C for lead-free), so overheating is virtually impossible - ideal for sensitive or thermally massive boards.
How many zones and which temperature profile?
The number of zones defines how precisely the profile can be shaped. A profile per IPC/JEDEC J-STD-020 runs four phases: preheat, thermal soak, reflow above liquidus and controlled cooling.
- Preheat: ramp of 1‑3 K/s, gently drives off solvents.
- Soak: 150‑200 °C for 60‑120 s, activates the flux evenly.
- Reflow: above liquidus (lead-free approx. 217 °C), peak 235‑249 °C, time above liquidus 45‑90 s.
- Cooling: controlled up to 4 K/s for a fine grain structure without thermal shock.
As a rule of thumb: 3‑5 zones are enough for prototype and small batch, 6‑8 zones are the volume standard, and 10‑12 zones allow stable profiles at high throughput for mixed or thermally demanding boards. More zones mean more control but also higher cost and energy use.
Prototype, small batch or volume?
Throughput decides between batch and inline design. Batch ovens load one charge, run the profile and open again - affordable, compact and ideal for development and repair. Inline ovens with a conveyor run in step with the SMT line.
For lead-free volume production a nitrogen atmosphere pays off: it reduces oxidation, improves wetting and lowers defect rates. Also check belt width, maximum assembly height and the return of process data for quality assurance.
Frequently asked questions
What peak temperature does lead-free soldering need?
SAC alloys have a liquidus near 217 °C, and the peak is typically set between 235 and 249 °C. The exact limit follows the component classification per J-STD-020.
When is vapour phase better than convection?
Whenever overheating is critical: with large thermal masses, sensitive parts, or when an oxygen-free atmosphere is needed without a nitrogen supply. The trade-off is lower throughput.
How many zones should a volume oven have?
For stable volume profiles 6 to 8 heating zones are common, rising to 10 to 12 at high throughput or with mixed assemblies. More zones allow finer ramps and longer soak phases.
Is a batch oven enough for prototyping?
Yes. A batch reflow oven with 3 to 5 zones is compact, affordable and flexible enough for development, tiny runs and rework. For a takted volume line an inline oven makes more sense.
Looking for the right reflow oven?
From a batch unit for the prototype to an inline oven for volume - we advise on convection, vapour phase, zone count and temperature profile.
Per J-STD-020
Profiles aligned with IPC/JEDEC guidance.
Profile-verified
Real measurement with profiler and thermocouples.
Right-sized
Batch for prototype, inline for volume.
Expert advice
ESD specialists help you choose.