Selective Soldering Improve the Efficiency of SMT Assembly
In smt assembly, selective soldering is an ideal process that improves the efficiency of SMT production. Its main advantage over the wave soldering technique is that it can process each area of a PCB individually, which results in a better and more uniform quality of the final product. This makes it an ideal method for complex boards that have many SMD components in close proximity to each other and also for boards with both smt assembly and thru-hole components. In addition to that, it has several other benefits over other soldering methods, including near-perfect joints, lower labor and rework costs than manual work, reduced training and staffing costs for skilled hand soldering, and high production efficiency.
Selective soldering machines vary in size, ranging from compact ones that can only process one board at a time to sizable in-line units designed for high volume production. Some can even be configured with two conveyor belts to process a double number of assemblies simultaneously.
The maximum board size you want to process will have a big influence on the machine size you choose, as well as the conveyor width you select and the size of the solder pots. You will also need to consider the type of solder you use, with most assemblers opting for no-clean fluxes that don’t require any post-solder cleaning.
How Does Selective Soldering Improve the Efficiency of SMT Assembly?
Solder nozzles are available in a wide range of sizes, with the thin ones being more precise and ideal for reaching restricted areas. These narrow-diameter nozzles, however, tend to wear out quickly and lengthen the overall processing time. Some selective soldering machines can be configured to vary the nozzle spacing, enabling you to perform multiple dip and drag operations in succession without changing nozzles.
Another important consideration is the amount of dead time you’re willing to tolerate. This is the time spent between each soldering operation and the next, and it’s best to keep this to a minimum to reduce the risk of defects and ensure that the assembly is processed with as few errors as possible. The best way to minimize dead time is to preheat the entire surface of the board before every soldering operation. This prevents flux migration and enables the ionic contamination tester to detect contaminants more accurately.
A good nozzle plate is essential for selecting the right nozzle for each different type of dip or drag operation you’ll be performing. There are myriads of standard designs to choose from, and some manufacturers can even provide specialized nozzle plates for difficult-to-reach areas and for specific applications like swiping tall connectors or lead frames. The nozzle can be directed to the board in various ways, too, with some using jet nozzles that attack the board at an angle, and others delivering a controlled roll-off of solder to the board, returning unused solder back to the pot.
