EUTECT Lösungskompetenz

Tag: selective-soldering

When does special soldering automation make sense for selective soldering tasks?

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.

When does special soldering automation make sense for selective soldering tasks?

What needs to be considered when developing a workpiece carrier?

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.

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.

Do you have too little flux on the solder joint but too much on the circuit board?

Always check, even when fluxing:

Often the devil is in the details when it comes to precision fluxing. If you can adjust the flux application that applies the flux to the board, you can control the result quite accurately, even if the flux is applied quite quickly. New smartphones, in combination with a flashlight, are able to record videos at 60fps (frames per second). When a flashlight is used to illuminate the flux stream, you can detect it quite easily and see where it is applied.

In order to keep the assembly clean, you can also hold a thermal paper or sandwich paper in between. This paper clearly shows the direction of the flux stream. A small glass panel can also be used.

The positions can then be optimized and the performance parameters of the dispenser should be adjusted. This is done via the software of the machines. The ratio of speed, time and power of the dispenser is important. The simplest way to control the flux is the automatic module for flux stream control, which under certain circumstances can also be retrofitted in an Eutect systems.

Choosing the right selective soldering process for my end product?

It depends on many different factors

Components used ( SMD/THT?), number of assemblies and solder joints, cycle times, PCB design and number of changes of soldering profile and finally the budget. These parameters are looked at in an evaluation, which takes place in the EUTECT technical centre. All wave and nozzle soldering processes as well as the laserthermode, induction, piston soldering and laser knife processes can be used at this facility. In accordance with the customer’s specifications and economic requirements, we develop solutions which are refined in further steps with all necessary pre- and post-processing. Starting with the machine cell, kinematics, fluxing and quality control, highly efficient systems are created. The modules that are optimal for the task in terms of process technology and economy are selected and combined to form proven stand-alone, rotary transfer or inline production concepts.

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