Wave Soldering Basics - How Does the Process Work?
Wave soldering is the classic method for THT series production, in which the board passes over a standing wave of molten solder. This guide explains the three process stages of fluxing, preheating and the solder wave, gives typical temperatures and weighs the pros and cons against reflow soldering.
View soldering guidesHow does wave soldering work step by step?
In wave soldering the populated board rides on transport fingers through three consecutive zones: fluxer, preheat and solder wave. The underside touches a standing wave of molten solder while the components on top stay dry. In a single pass, hundreds of joints are formed at once.
The process is designed for leaded components (THT, Through Hole Technology) and solders whole assemblies in series. The parameters are set once and stay constant across the batch, which delivers high repeatability.
What happens during fluxing, preheating and in the wave?
Each of the three zones has a clearly defined job. The flux cleans and activates the metal surfaces, the preheat drives off solvents and reduces thermal shock, and the wave forms the actual solder joint.
- Fluxing: A thin, even film of flux (usually no-clean or VOC-free) removes oxides and improves wetting.
- Preheating: The flux solvent evaporates, the board reaches 100‑130 °C and the temperature gap to the 250 °C wave is reduced.
- Solder wave: The molten solder rises as a standing wave, wets pad and lead and fills the plated through hole by capillary action.
- Cooling: After leaving the wave the solder solidifies within a few seconds into a solid joint.
What temperatures lead-free and leaded solders require.
Read the guideWave soldering or reflow - which fits when?
Wave soldering and reflow soldering do not exclude each other, they complement one another. Reflow is the standard for SMD parts, while wave soldering plays to its strength with leaded components and rugged connectors. Many assemblies pass through both processes in turn.
- Wave soldering pros: high throughput for THT, mechanically strong joints, cost-efficient for large runs.
- Cons: only suits the underside, bridging and shadowing risk with dense SMD, high solder and energy consumption.
- Reflow wins on fine SMD pitches, wave soldering on connectors, transformers and terminals.
Frequently asked questions
What is wave soldering used for?
Mainly for series soldering of leaded THT components such as connectors, electrolytic capacitors and terminals. In one pass every joint on the underside is formed at once, which makes high volumes economical.
Why must the board be preheated before the wave?
Preheating to about 100‑130 °C evaporates the solvent in the flux and shrinks the temperature step to the roughly 250 °C wave. That reduces thermal shock, delamination and warping of the board.
What is the difference between wave soldering and reflow?
In wave soldering the underside of the board touches a wave of molten solder and solders leaded components. In reflow, solder paste is printed and the whole assembly is melted in an oven - the standard for SMD.
What solder temperature is common for lead-free wave soldering?
Lead-free SAC solders usually run at 250 to 265 °C in the wave, leaded solder about 20‑30 °C cooler. Contact time is typically 2 to 4 seconds.
Questions about soldering for your series?
From flux to preheat to the right solder alloy - we help you choose the consumables and equipment for your THT series production.
Process reliable
Matched fluxes and solders for clean wetting.
Temperature stable
Materials tested for lead-free wave processes.
Series ready
Consumables for high volumes in stock.
Expert advice
Soldering specialists support your selection.