Selective soldering machines are a compromise solution in modern PCB Assembly (PCBA)processes. Despite the advancements in surface mount technology (SMT), electronic components still rely on traditional Through-Hole Technology (THT) due to cost or material constraints.

Even though most components on PCBs can be assembled using SMT, some electronic parts still require THT processes. While techniques like Past-In-Hole (PIH) or Pin-In-Paste (PIP) allow through-hole components to be used in SMT assembly or use selective mask wave soldering process, limitations persist due to component technology. As a result, selective soldering machines have emerged.

Selective soldering machines differ slightly from traditional wave soldering machines. They use small soldering nozzles that can be easily moved. The PCB is fixed in place, and the soldering nozzle is moved to apply solder to the through-hole component terminal pins, achieving soldering.

The soldering nozzle of a selective soldering machine resembles a fountain, with molten solder flowing from it, similar to the chip wave or call turbulent wave in wave soldering. This method ensures excellent soldering of through-hole component pins, with nearly 100% solder filling in hole. Additionally, components do not need to withstand the high temperatures required for reflow soldering. However, a drawback is the space required to accommodate the soldering nozzle.

Here are the pros and cons of Selective Soldering Machines:

Pros/advantage:

• No Special Fixtures or Soldering Carrier Required: Unlike traditional wave soldering, selective soldering doesn’t need special fixtures or wave soldering carrier during soldering.

• Regular Wave Soldering Conditions: Through-hole components don’t require materials that can withstand the high temperatures of reflow soldering. Regular wave soldering conditions are sufficient.

• Better Soldering Quality and Solder Filling Rate in Hole: Selective soldering offers higher-quality soldering and better solder filling rates in hole for through-hole components.

• Energy Efficient: It saves energy since it doesn’t need a large solder pot like wave soldering machines or long heating zones like reflow ovens.

• Cost Savings: Compared to wave soldering, it doesn’t require as much solder bar.

• Smaller Keep Out Area: The keep out area required for selective soldering is smaller compared to creating an carrier for wave soldering.

• Less PCB Warping: PCBs are less likely to bend or deform due to high temperatures.

• Time Saving: It saves time compared to traditional wave soldering and SMT processes.

Cons/disadvantage:

• Additional Equipment Needed: You have to purchase an additional soldering machine.

• Larger Clearance Area Required: Compared to SMT processes, you need to reserve a larger clearance area.

• Programming Required: It requires programming, which can be time-consuming initially. However, once programmed, it can be reused.

YouTube: Selective soldering machine introduction:

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