Wave Solder Or Reflow Solder: Which Is Better?

By Author: Capital Equipment Exchange
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Capital Equipment Exchange has a range of used wave solder machines and used reflow ovens to help you increase production and solder components to your printed circuit boards (PCB). But which process is better? It depends on the type of PCB assembly and production process you are using. Regardless of the process, precision soldering is necessary for the function of any printed circuit board.

The Wave Soldering Process

As the demand for electronics components increases, manufacturers need to find ways to increase the speed and efficiency of PCB assembly. Wave soldering is a faster process and is used primarily with through-hole printed circuit assembly, but is also used with surface mount technologies.

There are five parts in the wave solder process: preparation, fluxing, pre-heating, wave soldering, and cooling.

Preparation: A solder resist or mask layer is applied to the board to prevent the solder from adhering to any areas where it is not needed.
Fluxing: Solder ...
... flux ensures all parts are clean, any potential corrosion is removed, and protects against damage during the thermal process.
Pre-Heating: During this phase, a PCB will travel along a pre-heated corridor to prepare for the soldering process.
Wave Soldering: Liquid solder paste travels in a wave across the bottom of the PCB and bonds the components in place.
Cooling: The board is cooled to room temperature at a pace that prevents warping or other damage.

Wave Soldering Pros & Cons

Like any process used for printed circuit board assembly, there are pros and cons to the wave solder process. Your manufacturing needs - and the complexity of the board - are both factors to consider.

Pros:

You expose components to heat for a shorter amount of time.
Chances of air exposure and oxidation decrease.
Useful in creating better quality joints.
This process works well for high-volume production.
Perfect for SMT and low-volume production.

Cons:

Can have temperature inconsistencies.
May not work as well for a through-hole technology process.
It requires careful maintenance of the environment.

Soldering With Reflow Ovens

Reflow soldering is the preferred method for surface mount assembly but is also an option for other assembly methods. In this process, solder paste is applied to the PCB, where components will need to be bonded. Pick and place machines add the components to the paste. The assembled board is then conveyed into the reflow oven where the paste melts and creates solder joints.

Reflow soldering works for both single side and double side mounting. There are four stages the board goes through in the reflow oven: preheating, thermal soak, reflow soldering, and cooling.

Pre-Heating: This stage prepares the board for the soldering process and prevents thermal shock, which may damage components or the board.
Thermal Soak: The temperature reaches the correct level to activate the flux within the solder paste.
Reflow Soldering: This is the phase where the paste reaches the correct temperature for the solder to melt and reflow to create the soldered joints
Cooling: The board and solder reach the proper temperature to create the necessary bonds.

Pros & Cons Of Reflow Soldering

SMT reflow ovens have some advantages for the PCB assembly process. This solution is not as fast as wave soldering, so it is not always well-suited for companies with high-volume needs.

Pros:

Reduced thermal shock because components are not immersed directly.
Less solder waste, since the paste is applied precisely where it's needed.
Environmental controls do not need to be as strict.
Perfect for SMT and low-volume production.

Cons:

Temperature control problems can lead to the solder not reflowing properly if too low, or
damaging the board if it’s too high.
Not the best technique for complex boards.
Slower and more expensive than the wave solder process.

Find Used Reflow Ovens & Wave Solder Machines

Deciding which solder process is better is subjective to the needs and demands of your particular assembly process. No matter which method you choose, Capital Equipment Exchange has both used reflow ovens and wave solder machines available for purchase - helping you both save money and boost your production level.