Selective Solder vs Wave Solder

Wave Solder

The simplified process of using a wave solder machine:

1. First, a layer of flux is sprayed to the underside of the target board. The purpose of the flux is to clean and prepare the components and PCB for soldering.
2. To prevent thermal shock the board is slowly preheated before soldering.
3. The PCB then passes through a molten wave of solder to solder the boards.

Selective Solder

The simplified process of using a selective solder machine:

1. Flux is applied to the components that need to be soldered only.
2. To prevent thermal shock the board is slowly preheated before soldering.
3. Instead of a wave of solder a small bubble/fountain of solder is used to solder the specific components.

Depending on the situation or project certain soldering techniques are better than others.
Although wave soldering is not suited to the very fine pitches required by many of the boards today, it is still an ideal method of soldering for many of the projects that have conventional through-hole components and some larger surface mount components. In the past wave soldering was the primary method used in the industry due to the larger PCBs of the time period as well as most components being through-hole components that were spread out over the PCB.

Selective soldering, on the other hand, allows for the soldering of finer components on a much more densely populated board. Since each area of the board is soldered separately the soldering can be more finely controlled to allow for the adjustment of various parameters such as component height and different thermal profiles. However, a unique program must be created for each different circuit board being soldered.

In some cases, a combination of multiple soldering techniques is required for a project. For example, larger SMT and through-hole components can be soldered by a wave solder and then the fine pitch SMT components can be soldered through selective soldering.

We at Bittele Electronics prefer to primarily use Reflow Ovens for our projects. For our reflow soldering process we first apply solder paste using a stencil on the PCB, then parts are placed onto the pads through the use of our pick and place machine. The next step is to actually use our reflow ovens to melt the solder paste thus soldering the components. For projects with through-hole components, Bittele Electronics uses wave-soldering. Through a mixture of wave soldering and reflow soldering we can meet the needs of almost all projects, in the cases where certain components require special handling, such as heat sensitive components, our trained assembly technicians will hand solder the components.