In order for our SMD stencils to deliver the best possible print result for your application, various properties of the stencil must be configured and manufactured to fit precisely.  

Based on the component shapes of a PCB assembly to be used, the correct stencil material thickness must be selected. Due to the constantly increasing demands on the functional range of electronic devices, new and smaller designs are emerging at ever shorter intervals. This trend towards miniaturization, as well as the packing density of the circuit board, decisively determine the film thickness of the SMD stencil. The aim is to achieve a perfect soldering result for every type of board. If the material thickness is too thick, there is a risk of short circuits, solder bridges or solder beads, which can also cause the board to fail later. At Becktronic we tune the paste application not only by surface manipulation but also by the right material thickness selection. These material thicknesses are available in 10µm steps from 30µm to 300µm.

The same thought process also plays a role in the design of the opening sizes of the pads. These pads should correspond in origin to the SMD land area and thus to the copper layer.

Ideally, the pad openings are then manipulated in such a way that no "misprints" occur in the first place. Should errors nevertheless accumulate after the first printing processes, we can identify possible sources of error on the basis of the printing result and make modifications to your stencil. Often, however, the fault does not lie with the stencil; inferior boards can also lead to irregular and faulty printing results. In addition to planarity problems of the LP, the pad areas do not necessarily always have the size according to the CAD data, or the solder stop is not in the place or thickness as desired.

Another aspect is the material selection for your SMD stencil. Nowadays, high-quality and very flat stainless steel sheets are used as the base material. These are extremely durable and can withstand up to 300,000 squeegee cycles when used ideally. Appropriate finishing and post-treatment can reduce the internal wall roughness of the pads or further increase the paste-repellent properties of the substrate side. Other high-quality alloys such as FineGrain or stencils made of nickel are also available. The properties of these materials mean that the inner walls of the pads are smoother from the outset after laser cutting and require less to no post-treatment. 

Finally, it is a matter of the correct alignment of the stencils. In order to achieve clean and, above all, reproducible printing results, the stencils are provided with certain marks. These so-called register marks are found both on the board to be assembled and on the SMD stencil. In this way, the stencil can always be precisely aligned with the layout of the board during each printing process, resulting in identical solder paste printing.