Technical parameters of production
Manufacturing method
Stencil manufacturing with laser cutting uses CAD/CAM data as a source including information about land patterns of surface mounted components. After data conversion to GERBER format (if needed), specialized software calculates laser (or rather plasma ball formed by laser in the material) movement coordinates taking in account width of the beam itself, that allowing to form holes of different shapes and sizes in the metal sheet.
Therefore, by making changes in the source file you will get openings in the metal corresponding to those set in the file with high level of accuracy.
Due to such accuracy of replication you have unlimited opportunities in selection of optimized stencil aperture type and size to match well your technical requirements.
Process parameters
- Laser spot diameter – 0.025-0.040 mm (depending of laser model)
- Minimum cut line width – 0,050 mm
- Minimum gap of material between neighboring apertures – not less than 0.100 mm
- Machine positional accuracy - ±0.001 mm
- Maximum machine working area - 740 x 620 mm
- Openings tapering to the trapeze base - 0.01-0.04 mm
Tapering is the difference between tapered opening sizes at the top and bottom side of material. Openings tapering allows easier solder paste release from stencil apertures.
Stencil is always cut from the side applied to PCB. Therewith, tapered aperture size increases towards PCB. While cutting, cone is arranged with its wide side up, which is just a feature of cutting process.
For laser cut stencils all dimensions are measured on the side, solder paste is applied to, and the printer squeegee travel along (that is you see in the file).
Aperture sizes on the PCB side of stencil are 0.01-0.04 mm larger due to the aperture tapering.
Fiducials and text engraving are always made on the stencil side facing PCB.
- Maximum treated material thickness – 0.2 mm
- Laser frequency – up to 5 kHz and above. The higher pulse repetition frequency, the smoother aperture side walls, which allows easier solder paste pass through them.
Equipment
Figure 1 Laser cutting machine for SMT stencils LPKF StencilLaser G 6080
Quality control
Figure 2 View of stencil apertures made with laser cutting in 0.15 mm thick stainless steel sheet. (100X magnification)
During cutting process all stencils pass sampling verification of cutting quality by specialized portable microscope with high optical magnification.
Finally all orders pass verification by specialized Automated Optical Inspection (AOI) system. Each order has verification results report authenticated by stamp and signature of our production engineer.