The new high-end EKRA E4 stencil printer sets milestones in the industry-wide price-performance ratio

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 1 April 2000




(2000), "The new high-end EKRA E4 stencil printer sets milestones in the industry-wide price-performance ratio", Soldering & Surface Mount Technology, Vol. 12 No. 1.



Emerald Group Publishing Limited

Copyright © 2000, MCB UP Limited

The new high-end EKRA E4 stencil printer sets milestones in the industry-wide price-performance ratio

The new high-end EKRA E4 stencil printer sets milestones in the industry-wide price-performance ratio

Keywords: EKRA, Stencil printers

The EKRA E4 in-line stencil printer with its innovative machine concept fulfils high requirements in accuracy and reliability. The low-cost version of the fully automated high-end model E5 is a complete system that offers an excellent price-performance ratio. The standard version already features programmable conveyor and stencil wiper, vision alignment system and a pneumatically controlled print head. The integrated EVA system (the patented EKRA vision alignment) uses two high-resolution CCD cameras on a very precise XY gantry with glass-scale reading, for the alignment of the PCB in regard to the fixed stencil. This closed-loop linear decoder system performs with an outstanding resolution of±1 micron within a field of view of 10 x 8mm that can be moved across the entire PCB. Moreover, the alignment of the print nest is provided with a resolution of±0.5 micron. The print system is specified with a high accuracy of±25 micron and a repeatability of±12.5 micron (at 4-sigma).

The integrated stencil wiper system commences wet and dry cleaning actions in freely programmable production steps, and it allows for additional vacuum cleaning through the cleaning paper. The compact printing system occupies a footprint on the shop floor of only 975 x 1,200mm, and is aimed at in-line board assembly with stringent demands on precision and reliability in higher volume manufacturing. The E4 supports both Siemens and SMEMA interfaces.

The E4 is based on a similar machine concept as the successful high-end printer family E5 and features the same rigidly welded steel frame which is engineered and optimized by the finite-element method. This assures excellent long-term stability and reliability. The printer accepts stencil frames ranging from 406 x 406mm up to 737 x 737mm without any additional mechanical adaptation, whereby the PCB size can vary from 80 x 50 mm up to 355 x 355mm. This very flexible technique allows product changeovers within 3min., promising a very high up-time and in turn an optimum throughput. For PCB support during printing, five magnetic bars in different lengths and ten magnetic support pins are provided.

The squeegee speed is programmable between 0-240mm/sec., and the squeegee pressure up to 320N. PCBs with a thickness between 0.4 and 6mm can be processed. The conveyor speed can be programmed up to 400mm/sec. An edge clearance of 2.5mm (0.1in) is necessary. For double-sided board assemblies, the board clearance is 18mm. The bi-directional conveyor with automatic width adjustment permits easy integration into very different manufacturing environments. The PCBs are fixed by rail clamping or knife edge steel blades from the top side.

The 2 1/2D inspection system and EKRA Crossflow print head technology are two options that can optimize the E4 performance even further. In contrast to conventional 2D inspection, the EKRA 2 1/2D system has no difficulties with different PCB surfaces or fiducials or markings on a substrate. It monitors the printing process, the stencil underside and eventually the formation of paste bridges. The 2 1/2D system clearly measures the paste volume on pads. For teaching the inspection parameter, the real stencil will be used as master, instead of less than ideal CAD data or an unreliable PCB. After printing, with the 2 1/2D system, paste volume and precision of the print can be carefully inspected and misprints avoided. The system also inspects the stencil: if too much dirt is detected, it automatically starts a wiping cycle.

For more information please contact: Ilka Wissling, EKRA Eduard Kraft GmbH, Zeppelinstrasse 16, D-74357 BÖnnigheim. Tel: +49 (0) 7143 8844 0; Fax: +49 (0) 7143 8844 2; E-mail:

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