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What is the Best Selective Solder Machine?

Selective soldering refers to the “picky” or “individualized” method of applying solder to electronic components. The reasons for the selectiveness range from soldering only specific components and speeding up the process via automation.

You need to use a selective solder machine to achieve this – and there are several options out there. In this article, you will find out the function of the machine and how to choose one.

What is the Function of a Selective Solder Machine?

It is the machine that enables automated process of soldering electronic components onto a Printed Circuit Board (PCB).

It is the major reason why selective soldering is preferred over the other soldering processes – because of the automation it offers.

 The choice of a selective soldering machine often boils down to core factors like price and the overall performance. Understanding how the machine works can also aid in the selection process.

How the PCB Components Interface with the Machine

Ordinarily, the electronic components used in a PCB cannot be deemed completed in terms of the placement if they have not been soldered.

For these parts to be soldered with the machine, they have to follow a set of procedures. The simplest explanation is that the parts are loosely attached to the circuit board. The PCB would then be placed inside the selective solder machine where it will be soldered, as per the dedicated process the machine uses.

Types of Selective Solder Machines


Different companies manufacture different kinds of machines for selective soldering. Examples of such companies are Manncorp, SEIKA Machinery Inc., Hentec Industries and Kurtz Ersa. Out of the list, the machines manufactured by Kurtz Ersa are one of the most popular.

The Ersa Versaflow 3/45 and Ersa Versaflow 4/55 are the most popular. In the next paragraphs, we will discuss the distinct features of these machines.


This is the “first in-line selective soldering machine” from the manufacture and it offers a mix of higher throughput and flexibility. It also features dual track transport and can be used even in the smallest of spaces.

Here are some of the machine’s attributes:

Modular Design

The basis on a modular platform allows for the maximization of different approaches. At the core of the performance is the support for the following integrations:

  • Solder modules
  • Additional flux and;
  • Preheat modules

Higher Configuration Options

You could also “stylize” the machine as you want. Thanks to the configurability, you will be able to achieve the following:

  • Further expansion of the throughput. This is subject to the preheaters’ segmentation.
  • Multi-Module Support: the VERSAFLOW 3/45 selective solder machine supports multiple modules, provided it has been tuned to the maximum configuration level. Up to 3 modules are supported and two out of this can be configured to support two, mini-wave solder baths.
  • You could also substitute the single-wave bath with the multi-wave bath.

Product Changes

The machine supports changes in the product, without having to subject the same to loss in production time. For the best results, use the multi-wave soldering process for this purpose.

Parallel Soldering Process

The VERSAFLOW 3/45 machine also supports parallel processing. It uses a combination of soldering cycle, flux separation and preheating cycle for this purpose.

Flexibility Meets Voluminous Production

You can get the best of both worlds – flexibility and higher production. On the one hand, the use of the multi-wave soldering process allows for the production of higher volumes, while the mini-wave soldering process supports flexible productions.

High-End Soldering

The machine also has a high-end soldering system that easily integrates into the in-line manufacturing concepts.

The VERSAFLOW 3/44 selective solder machine also has the following features:

  • The support for the installation of up to 6 mini-wave soldering baths. Each of the solder modules can also be preceded by a preheat unit.
  • It uses a Computer-Aided-Design (CAD)-Assistant for offline programming functions.
  • Supports up to 4 flux spray heads.
  • Uses a secure process control that monitors the entire selective soldering processes.


This is another selective solder machine from Kurtz Ersa. It is best described as the “ultimate in selective soldering” – and this is due to the enhancements it brings to the in-line selective soldering process.

As a leading selective solder machine, the VERSAFLOW 4/55 provides unlimited configuration options, offers the highest specifications for throughput and flexibility.

Here are some of the features:

  • Increased process flexibility
  • The modular design enables flexibility of the system’s configurations.
  • The multi-wave soldering process comes in handy when preparing the high-volume applications.
  • It uses link for traceability systems required for process control.
  • It supports up to 20-inch by 20-inch processable area.
  • The VERSAFLOW 4/55 selective solder machine is ideally used for linking either the peripheral equipment or manual workstations.
  • It supports the following variables: fluxer y-variable and Versaflex soldering module X/Y/Z variable.
  • It utilizes power convection for the optimal homogenous preheats.

The Selective Soldering Machine Process


Utilizing the right process can make a lot of differences in how you get to use the selective solder machine.

For this reason, here are some of the processes you can utilize:

1.    Selective Aperture Tooling Over Wave Solder

The areas on the PCB that have been soldered in the SMT reflow soldering procedure are masked off or removed here.

The aperture tooling over wave solder process also involves the following:

  • Only the PCB areas meant to be soldered are exposed. They are exposed to the tool’s window or aperture.
  • A pool of molten solder is used to drag the circuit board through a wave of solder.
  • The other PCB areas that aren’t meant to be soldered are then masked.

2.    Laser Selective Soldering System

This is not as popular as the selective aperture or miniature wave soldering systems. Although it is relatively new, the laser selective soldering system supports the importation of Computer-Aided-Design (CAD)-based circuit board layouts.

The data derived from the import directs the positioning of the laser to make an accurate soldering of the PCB.

3.    Mass Selective Dip Solder Fountain

It is a variant of the selective-aperture selective soldering process. The selective dip solder fountain requires the use of specialized tools that allow for the pumping of solder through the apertures.

The following processes define the selective dip solder fountain:

  • It involves the placement of solder fountains at the specific areas of the PCB meant to be soldered.
  • The circuit board is then dipped into the selective-solder fountain.
  • All the selective soldering components of the board are then simultaneously soldered in the correct locations. The other parts are left untouched.

4.    Miniature Wave Select Solder Fountains

The soldering process here requires the usage of a round, miniature pumper solder wave. The miniature wave select solder fountain is often preferred due to the accuracy – but at the expense of speed.

Unlike the other selective solder machine processes, it neither uses masking nor tooling.

The mini wave soldering process also supports the circuit board’s manipulation, as this enables the soldering in the right places. The following are some of the modifications to the soldering process:

  • Board Articulation: the circuit board can be articulated over a fixed wave. It can also be articulated over a solder bath. Once the articulation or positioning is made, the board will undergo the selective soldering process.
  • Circuit Board Fixture: the PCB can also be fixated at a spot. In this case, the wave-solder pot will be moved below the circuit board for the selective soldering process to take place.

The Benefits of Selective Soldering

In addition to simplifying the process of applying solder pastes to a PCB, the selective-soldering process also has a lot of other benefits.

Reduced Heat

The selective soldering process doesn’t require the excessive application of heat on the circuit board. Doing so often exposes the PCB to damages, especially when used in higher temperatures.


From the ERSA VERSAFLOW 3/45 to the ERSA VERSAFLOW 4/55; the process offers multiple customization options. This makes it possible to integrate unique brand features and different component parameters into the PCB.

It is Ideal for Compact Real Estate

The selective soldering process is also a reliable option for circuit boards manufactured with the Through-Hole Technology (THT) process. Most especially, it is the best for boards that due to the limited size, do not support the wave soldering process.

Excellent Selectivity

If you are looking for a selective method of applying to PCB components, the selective-soldering process usually comes first.

The excellence of the selectivity is enhanced by the limitations of the masks to the board areas needing soldering.

Zero Attachments

Specific attachments like glues, solder and excessive flux are not required for the selective-soldering process.

Final Words: Selective Soldering vs. Wave Soldering

Both selective soldering and wave soldering offer excellent options for applying solder to a PCB. When it comes to choosing between the two, you have to look at the speed, repeatability, cost and the types of materials required.

On the one hand, selective soldering is less likely to require rework, can be repeated, and requires less cleaning.

On the other hand, the wave soldering process cannot be repeated, requires additional cleaning and is not always repeatable.

To balance the two, selective soldering trumps with the less material requirements, repeatability and less cleaning, but costs more and requires a complicated setup.

We will help you maximize the potentials of a selective solder machine to produce multiple circuit boards in a short time – and this could help you save money!




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