Stainless Steel Stencil Laser Performance Information
Sparks Laser Services (SLS) have invested in three of the highest specification laser
machines available today. We believe that this enables us to consistently produce
stencils and laser cut components to the highest quality levels and tightest tolerances
possible. Detailed below is the technical data for the machines that we use, our
internal quality criteria on stencil parameters and the areas of potential advantage over
alternative stencil technologies.
Technical Data
Cutting Performance
Up to 8000 aps/hr in standard mode
Up to 15000 aps /hr for BGA’s with ‘turbo-cut’ engaged
Material Thickness
Up to 600m
Axial Precision
(X/Y axis)
+/- 3m on full working area
Right angle precision
Less than 2 angular seconds
Repeatability
+/- 1m
Quality Control and Stencil Characteristics
Aperture Sizes (typical)
Better than +/- 0.00025”
Aperture Taper (typical)
0.0004 – 0.0006” dependant upon material thickness
Pre-Production test cuts are taken and checked from each machine on a daily basis.
‘Scancheck’ System. SLS are in the unique position of being able to offer additional quality control on
100% of the stencils manufactured through our Scancheck system. This 12000dpi resolution scanner
compares the stencils directly against the gerber data and will identify any error on :
Aperture presence
Positional accuracy
Aperture size
Aperture shape
Each stencil will also have sample apertures measured from the PCB (non-squeegee) side of the stencil
using high magnification microscopes.
Comparison With Alternative Premium Stencil Technologies
Production Speed:
Historically one of the key advantages nickel electroformed stencils had, was the ease of
accommodating very high aperture counts when compared with the laser cutting option. The time taken
for early laser machines to produce high aperture count stencils could be a problem for production
scheduling. This was particularly emphasised for BGA work where machines could not easily cope
with the requirements to produce perfect rounds whilst still achieving acceptable production speeds.
The latest generation of laser cutting equipment armed with high speed linear drives and increased laser
lamp pulse rate (up to 5Khz) now mean that any image can be produced quickly while still enabling us
to cut perfectly shaped apertures.
Material Thickness:
One of the inherent characteristics of the electroforming process is that it produces considerable
variations in material thickness that are obviously not present on stainless steel stencils. Variations of
20m would not be uncommon within an electroformed stencil with the thickness in any particular
region being determined by the image density.
Positional Accuracy:
The latest generation of laser machines cut directly from the co-ordinates within the gerber data and as
such are extremely accurate. Other technologies rely upon the vagaries of photo mech operations to
produce filmwork photo-tooling. The accuracy of this photo-tooling is dependant upon the photo
plotter used and is also subject to change through environmental factors such as humidity and
temperature. Further down the production cycle the Electroform process also requires the careful
balance of chemicals within the plating bath to control the growth / shrinkage of the finished product.
Aperture Taper:
The amount of aperture taper for stencils produced from any technology will be largely dependant upon
the material thickness but the shape and consistency of the taper is superior with laser cut stencils as
there is no photo resist exposure stage. However both chemically etched and Electroformed products
rely upon the exposure of photo resist material from a central light source. This results in a taper that
becomes more biased as the apertures progress away from the centre of the exposed image.
Aperture Wall Quality:
Nickel stencils have always been promoted on the strength of the paste release qualities due to the
smooth aperture walls achieved through the plating process. However this has now been largely
negated due to the increase of the lamp frequency from the original 1KHz standard. These are now
adjustable up to 5 KHz and also produce excellent quality aperture walls.
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