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Brunnecker F.,LPKF Laser and Electronics AG | Geiger R.,LPKF Laser and Electronics | Pump C.,LPKF Laser and Electronics
Kunststoffe International | Year: 2010

Laser staking, a sturdy and matured basic technology of laser transmission welding offering reliability for use in automated production, is a new method for positive connection of two components by plastic deformation of one of the two components. The process uses the easily dosed energy input of the laser and combines aspects of laser transmission welding for a reliable process for the fixing of printed circuit boards. A material bond between the two joining members is obtained under the influence of a defined pressing force which is introduced by joining zone by a suitable pressing device. The welding path at 0.37 mm is reached at the point in time when the laser is switched off after 0.49 s. If the particular energy distribution is advantageous for the process, the power density distribution of the laser beam can also be adapted to the applications using additional beam-forming components. Source


Oosterhof A.,HTS in Leeuwarden | Schmidt S.,LPKF Laser and Electronics
SMT Surface Mount Technology Magazine | Year: 2012

The quality of a stencil may be measured a number of ways: Smoothness of the cut wall, material quality, thickness and thickness uniformity of the material, proper aperture location, and proper aperture size. Here, through the testing of a dozen stencils acquired and manufactured using different equipment and methods, the authors show that significant variability exists in aperture size precision between various stencil manufacturing sources. Source


Oosterhof A.,Eastwood Consulting | Schmidt S.,LPKF Laser and Electronics
IPC APEX EXPO 2012 | Year: 2012

Many articles have been published indicating that 60 to 75% of all board assembly problems stem from solder paste printing. The important outcome from the printing process is to get the correct amount of solder deposited in the right place. A significant part of that solution is the stencil and its correctness depends on how well its manufacturing process is controlled using proper machines, materials, methods and manpower. The quality of the stencil can be measured a number of ways: smoothness of the cut wall, material quality, thickness and thickness uniformity of the material, proper aperture location, proper aperture size. This report will show that significant variability exists in aperture size precision between various stencil manufacturing sources. Source


Oosterhof A.,Oosterhof Consulting | Schmidt S.,LPKF Laser and Electronics
Printed Circuit Design and Fab/Circuits Assembly | Year: 2011

Parameters that influence positional accuracy are studied on a number of laser-formed stencils. The machine used to cut the stencils consists of two systems, the laser and the moving mechanism. The metal used for laser cutting has typically been stainless steel, type 302 or type 304, produced in a rolling mill. The resulting sheets are very uniform in thickness, but the specified thickness can typically vary by about 12 μm. Stencils fabricated using the electroforming (EF) process consist of pure nickel. The EF process starts with a film that represents the aperture pattern to be manufactured. Making the film introduces additional process steps with their inherent possibility of errors, as film material is temperature- and moisture-sensitive. Most stencil manufacturers produce stencils in air-conditioned rooms where the temperature is about 20°C. When printing on a board with components that have large pads and large spaces between pads, a significant alignment error between the stencil apertures and board pads may not cause serious issues. Source

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