Flexural stress can occur due to incorrect handling during manual picking and placing of THT components on assemblies which have already undergone SMD soldering. This leads to damage and breakage of sensitive SMD components.

Schnaidt know-how can offer effective assistance. The variable pick and place support not only enables support of the assembly in its marginal areas, but also permits the movement of freely positionable assembly support pads to support it in areas in which picking and placing takes place and, as a result, prevent deflection.

The assembly support pads are held magnetically in their positions.  The firmly applied coordinate system enables assigning of the support pad configuration pattern to the assemblies undergoing picking and placing.

The inclination angle of the entire system can be adjusted, enabling stress-free working in individually configured pick and place workstations.

Small series of assemblies also demand harmonised and reproducible processes.

However, investments in automated soldering systems frequently do not pay off in complex soldering tasks. To counter the risk of a failure to meet quality requirements through purely manual production of these small batches, manual soldering fixtures offer an ideal alternative to process support. The assembly is fixed and aligned here in the carrier and, additionally, important process techniques are already integrated in the fixture.

As a consequence, the operator can concentrate completely on the soldering process and produce the quality demanded of the soldering point.

If complex procedures in final installation of the complete PCB assembly are to be designed to ensure greater process reliability and reproducibility, these must ensure production results independently of a worker and avoid assembly errors.

If, as in our example, the assembly needs to undergo several handling stages prior to installation in the final casing, support fixtures can offer assistance.

The panel joints are first removed, as depicted in the flowchart, and the assembly is folded, aligned and pushed into the final casing.

All these procedures are predefined with absolute accuracy in our handling fixture, thus avoiding any damage to the assembly or deviations from module specifications due to errors in the sequence. Moreover, these handling fixtures are ergonomically designed to ensure that the operator does not suffer from fatigue, even after long periods spent executing repetitive working steps.

The problem

The experience of our customers indicates that more than half the problems encountered in the SMD process occur as the result of uneven application of solder paste during stencil printing.

In particular, assemblies with large outer dimensions can shift during the stencil printing process, resulting in misalignment during printing.

In many cases, the process parameters which can effectively counter this are limited, and increasingly smaller components and pitch distances add to the rejection rate.

In contrast to the methods frequently employed which involve the checking of product quality on completion of printing using increasingly more sophisticated measurement systems, our stencil printing support intervenes directly in the process.

The solution

Assemblies are supported during the printing process by our stencil printing support, with deflection of the assemblies being ruled out as a result.

The option to add negative contours to the support plate means that this can even be ensured during two-sided SMD picking and placing.

A further advantage is the achievement of a considerable weight reduction and, consequently, simplified storage when compared to the familiar aluminium support blocks available on the market through the use of glass fibre plates with a thickness of only 10mm and universal ESD protection.

Linear holding strips enable rapid conversion of the printing support plates, thus benefiting setup management in low volume and high mix production.