There are various reasons for using special soldering automation for selective soldering. It is often the complexity of the assembly that prevents the use of standard soldering systems. If the available degrees of freedom of a standard soldering system are not sufficient or if the solder joints differ too much in position and geometry, EUTECT soldering automation systems are used. However, even if individual solder joints of an assembly require separate soldering parameters or individual “movements” are necessary for individual solder joints, for example for a different break-off angle to avoid solder bridges, the use of a special solution is unavoidable.

Hardware may also require the use of a special solution. For example, if special workpiece carriers or masks are used in the production process to protect adjacent, closely positioned components, access to the soldering point may be difficult. In these cases, specific process components, kinematics and automation solutions are required. The same applies to soldering in cavities, such as in housings or similar. If different solder joints require different soldering processes or specific nozzle geometries are required for mini wave soldering, special solutions must also be considered.

Roughly summarized, it can be concluded that whenever not all solder joints of an assembly have the same properties and can be soldered identically, special soldering automation in selective soldering becomes necessary. The reason for different soldering processes can be the shape, position, metallurgy and access to the solder joint, e.g. for products with high added value. Another factor is the quantity to be produced. If this is high with low cycle times, automation must also be considered in order to avoid unnecessary process steps or manual activities.

The development of customized workpiece carriers requires careful planning and consideration of various factors to ensure that the carriers meet the customer’s requirements and fit the selected soldering process so that it works efficiently. Based on the characteristics of the customer’s product, the cycle time and the requirements of a soldering process for an assembly, we develop customized workpiece carriers that solve all the given tasks and at the same time provide all the necessary functions.

We include customer requirements such as component identification or placement queries as well as the integration of specific soldering masks which are integrated directly into the carrier.

We also develop satellite workpiece carriers. Since special requirements for a workpiece carrier often cannot be adapted by standard carrier systems, or because only standard carriers are used in the process cells due to standardized belts, we also develop so-called satellite workpiece carriers. These are taken from the basic workpiece carrier for the soldering process in order to carry out the respective processes. We use robots or other kinematics for this purpose.

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:

1ppm=0.0001%
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.