EUTECT Lösungskompetenz

Tag: mini-wave-soldering

Which soldering process achieves the best, high quality results?

To start with, this topic is a mere theoretical analysis. The facts listed here are only feasible if working in a perfect production environment, with pre-products without tolerances etc. This is de facto not in accordance with reality. In all process variants of packaging and connectivity, the final soldering quality depends on optimal layout of the assemblies, pin-pad component and wetting-friendly metallization of all components involved. In addition, the corresponding fluxes and soldering materials as well as the overall soldering automation concept must be considered.

Nevertheless, we still address the question of which soldering process delivers the best, high-quality results from the merely technical side. The following soldering process comparisons are based on a basic physical qualities as a first orientation. First of all, the process capability index Cpk or the parts per million (ppm) are to be evaluated independently and thus independently from the manufacturer of the soldering automation. Whereby the real ppm tolerance range is very much dependent on the core competence and professionalism of the soldering automation manufacturer.

The quality key figures of Cpk, ppm and percentage rejects are based on the following conversions:

0.3 as Cpk corresponds to 32% corresponds to 320,000 ppm
1.00 as Cpk corresponds to 2.7% corresponds to 2700 ppm
1.33 as Cpk corresponds to 0.0063% corresponds to 63 ppm

The ranking of the quality-comparative soldering processes is as follows:

Mini wave soldering process with inert gas: 0.01 to 0.05 %: 100 to 500 ppm
Laser soldering process: 0.1 to 3% = 1,000 to 30,000 ppm
Piston soldering process: 0.9 to 7% = 9,000 to 70,000 ppm
Thermode soldering process: 0.3 to 3% = 3,000 to 30,000 ppm
Induction brazing process: 0.3 to 3% = 3,000 to 30,000 ppm

For comparison:

Reflow soldering process: 0.005 to 0.030%: 50 to 300 ppm

With this approach, all selective soldering processes can be evaluated in relation to each other and put into an overall economic understanding together with the additional boundary conditions. For a project-oriented quality assessment, a process evaluation under real process conditions is therefore essential. This procedure offers the possibility of being able to make the planned investment decision with full confidence.

Due to the fundamentally physically sound process factors, the mini wave soldering process in its professional application is the first qualitative choice of possible selective soldering processes.

Do you desolder your SMD-components during selective soldering?

How to minimize the risk of desoldering SMD-components?

If this is the case, the heat input for the solder joints of the SMD-components positioned in the proximity of the THT component is usually too high. These SMD-components must be protected from excessive heat with a mask, unless a layout adjustment of the assembly is possible. Especially with high packing densities and increasing miniaturization, desoldering can be a challenge.

What to consider when using a solder mask?

However, the use of solder masks requires that some factors be taken into account already during the design of the PCB:

Ensure your THT solder joint is surrounded with at least 1.5 mm space and that high components are not positioned in the immediate vicinity. With the optimal solder mask, you can achieve a process window with maximum reproducibility. However, if you have unchangeable and narrow spaces, please do not hesitate to contact us, because we have a wealth of experience and special solutions for various problems.

Which solder mask types are available ?

There are many different types of solder masks for selective soldering. These can be manufactured in different dimensions and from different materials, additional these masks can also be used for large wave soldering. There are specific soldering masks for the selective soldering process only, that perform in combination with the right material and the appropriate soldering nozzle. In addition, masks can also be used for laser and induction soldering as well as piston soldering. In this case, they also protect the PCBA and its surroundings from reflections as well as solder and flux splashes.

For further information and your individual solder mask do not hesitate to contact us.

Lacking hole fill during THT-soldering?

What options support hole fill during your soldering process?

With THT-soldering it can happen that the hole fill does not form properly. In this case the solder does not completely perforate the hole and the counterminiscus is not formed 100%.

First check that the diameter of the hole in relation to the pin ratio and the joint geometry are correctly selected. If this is the case, you have the following options to optimize the process:

Mini wave or selective soldering:

  • Increase the temperature of the solder bath and check for the desired temperature at the process point.
  • Increase contact time between mini-wave and product
  • Increase preheating temperature, activation or preheating time
  • Check the optimal flux quantity
  • Verify that the correct flux is used in accordance to solids and other activators
  • More about the EUTECT IW1 & 2 module

Laser solderings

  • Use of a preheater to apply heat to the joints, thus facilitating hole fill
  • Position of the laser focus in the right angle and in relation to the product geometry, solder feed and overall product geometry
  • Test feeding speed of the solder wire
  • Additional energy input after fusing of wire
  • Test the optimal flux content and the correct alloy in the solder wire
  • More about EUTECT laser soldering


If you still have problems with hole fill, please contact us, we will help you to optimize your soldering process.

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