The stepped stencil is a special variant of the SMD stencil. What makes it special is that it provides for different material strengths in partial areas.
Special demands in manufacture require the use of a stepped stencil. Unlike a standard stencil, a stepped stencil is capable of providing the correct amount of paste for every component without producing steps.
The component mixture comprising connectors, large
and small components, µBGA and QFN together on
one PCB results in the requirement for different stencil strengths. This can only be achieved by stepped technology.
In view of the growing percentage of mixed assemblies, the significance of stepped stencils in electronic componentry manufacture has increased. Mixed assemblies are variants that provide for the assembly of both very big and very delicate components on the same PCB. Big components require more, while small components require less solder paste volumes. Where paste application can no longer be controlled to a sufficient degree by adapting the pad sizes, step stencils are used for optimal adjustment of the solder paste volumes.
Another area in that stepped stencils are used is the adjustment of excessive via hole pluggings. In this process, plugs that are not absolutely level with the PCB surface are covered by a recess on the stencil bottom side. This prevents the formation of artificial jumps in the printing process and associated smearing of the print.
Any number of recesses of different depths can be implemented in the stepped stencil.
The development of an innovative, patented manufacturing process permits precise and efficient design of the steps in a stepped stencil. First, the stainless steel blank is manufactured. In the process, different plug recesses, step heights or depths can be placed on the squeegee and/or the PCB side. Next, the integrated camera system of the cutting laser accurately positions the blank, after which the stepped stencil is cut and undergoes further processing. Another advantage offered by solid material stepped stencils is achieved by the smooth gradient between the steps, which prevents paste deposits and hardening.
As the technological and market leader in the fabrication of high-precision metal stencils in Europe, Christian Koenen GmbH offers its customers not only a precision tool but also extensive process support. The company is the only stencil manufacturer to operate its own in-house laboratory for research and development – the Application Center. The Application Center is furnished with sophisticated printing and measuring equipment designed by experienced process engineers. New technologies are developed, existing products are perfected, and customers receive support during process evaluation. In addition, the company conducts fundamental research for technical printing. Customers and partners thus have a platform for training, printing tests and research tasks at their disposal.
Already the stencil printing stage involves far more than twenty parameters that have an impact on the quality and the performance of the manufacturing line. In the manufacture of electronic modules, the printing process might cause up to 65 % of the faults. An adapted layout combined with optimum release properties is crucial for the production process, as only a stably running manufacturing line is an economic manufacturing line. The technical facilities provide the customers with the option of outsourcing the research and development work to improve the printing process. Valuable production time can thus be gained as the performance of the manufacturing line is not affected. At Christian Koenen GmbH, customers can benefit from sound process advice provided by experts: The experts adapt the processes in accordance with the customer parameters and materials. Continuous further development of the products ensures that the customers have a long-term edge over the competition.
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Europe's largest manufacturer of SMD metal Stencils.