the online presence for the International Phototool Company, LLC
Design Optimization

With the development of our state of the art Internet Business Center, our goal has become a reality, making it remarkably Quick & Easy for you to order and promptly receive your photoplots and photomasks.  At the Photoplot Store, we continue to scour the world in order to bring you the highest quality products at very reasonable prices.  In order to provide you with the lowest prices possible, and in order for us to deliver our products as quickly as possible, we encourage you to provide us with ready to run plot data that requires an absolute minimum of setup and preparation. In order for you to perform your design work as efficiently as possible, we recommend a number of excellent software and hardware products that you can use to create your own plot files.  With the Gerber editors, you get the added benefit of being able to see exactly what your plot will look like.  Create and optimize your designs, then prepare your data for plotting with your choice of our tested and recommended tools:
Bay Technology's LinkCAD - Really Cool Software!
DraftSight 2D - FREE
CADopia - FREE Downloads!
4D-Technologies - Very useful AutoCAD® & AutoLISP® applications

Downstream Technology's CAM350
Be sure to visit the Cad Portal,
the Internet resource for engineering professionals.

Here are a few DESIGN RULES that we suggest:

| AutoCAD® | Gerber | GDS | EPS | BMP


For further reference, please check out these links, which open up in new windows:

  1. LinkCAD Drawing Design Rules

  2. ASM 3500 Drawing Design Rules for DXF to GDSII

  3. Design Rules for Drawing Masks using AutoCAD -

We accept AutoCAD® DWG and DXF files up to version 2013.

Please construct your designs in Model Space, not Paper Space.

DXF files require less processing on our part, and therefore often go faster through the system. Since DXF files can be rather large, please zip them up before sending them to us. This typically reduces their size by about 70% to 90%.

Use layer 0 only for the insertion of BLOCKs.  Do not draw any entities on layer DEFPOINTS.  Draw all entities on any other layer (except layer 0). Do not turn off layer 0.

Remove all POINT entities.

Remove all LINE, ARC, POINT, and POLYLINE entities that both begin and end at the same point and have no vertices in between - i.e. have zero length.

Remove all LINE, ARC, and POLYLINE entities that do not form, or cannot be readily joined to form, a completely closed boundary or polygon, or which are not otherwise part of the design.

Remove all redundant, duplicate, and/or coincident entities.

Remove all HATCH entities. These are ignored by our data format translators. If you find them necessary to include for illustration purposes, then be sure that the original entities that were used to create the HATCH patterns remain in your drawing.

Purge all unused BLOCKs, LAYERs, and other items from your drawing before sending then to us.

Remove all data that you do not want to appear on your photoplot or photomask; or if it useful reference data, please move it to a layer that is either labeled as "reference", frozen or turned off.

Close all gaps between the endpoints of all the LINE, ARC, or POLYLINE entities that are intended to form a continuous outline - making sure that the endpoint of each entity exactly matches the start point of the next entity.  Using the FILLET command set to a zero radius can help here.

Join all LINE and ARC entities that make up a single continuous boundary into a single closed zero-width POLYLINE outline.  (The PEDIT and BOUNDARY commands are useful for doing this.)

CIRCLE, SOLID/PLANE, and TRACE entities are OK.

We process 2DPOLYLINE and LWPOLYLINE entities in exactly the same way as we do for POLYLINE entities.

Tapered POLYLINES, POLYLINES of varying width, and POLYLINES that double back on themselves or cross themselves can be processed, so long as you make us aware of their presence.  They require special settings to be used during conversion. In addition, they often require extra labor during the data conversion process. Such labor is charged at the consulting rate as posted on our prices page.

SPLINE entities are now accepted.  SPLINES are converted into segmented arcs using straight line segments.  The accuracy of the conversion depends upon the radius tolerance that we use to govern the conversion, which we typically set at 50 nm.

ARC's and curved PLINES are converted to segmented arcs in the same way that SPLINE entities are processed, as described above.

CIRCLE entities are maintained as is.  In other words, they are converted to round pads, defined with a center point and a radius or diameter.

Use BLOCKs (and/or nested BLOCKs) whenever possible in order to conserve file size. All BLOCKS should have a scale factor of 1 in both the X and the Y directions. Mirrored BLOCKs have a scale factor of -1 in one or both directions, and cannot be processed through our data converters. Rotated BLOCKs are usually OK.

We do not recommend using "convoluted", or self-intersecting POLYLINEs.  ("Butterfly" targets are often the culprit here.)  Each section of such entities should be separated into its own closed zero-width POLYLINE outline.

Processing TEXT:

  • We can now process MTEXT, SIMPLENOTE and NOTE entities!

  • Windows, OpenType, and TrueType fonts may be used in addition to the standard SHX fonts.

  • Numerous regular and outlined SHX fonts are available. Free versions of these may be found by searching online. These are particularly useful for labeling photomasks.

  • We can now process proprietary fonts such as Helvetica.

If you have features that are completely surrounded by other features on the same layer, the plotter will typically overwrite the inner features - unless something is done to prevent this. This process is called Polygon De-Embedding (described here).  As part of our standard procedures, we will typically run our own de-embedding routines on your data, which also help to identify duplicate entities.

Please specify the data units with your order.  We recommend using at least 5 or 6 decimal places if working in inches, and 4 to 6 decimal places if working in millimeters. Of course, 6 decimal places in mm is 25.4 times more accurate than 6 decimal places in inches.  Our photoplotter accepts data having up to 6 decimal places in inches or in mm.  We can process data in just about any units, so long as you tell us what those units are. We usually send data the to plotter with 6 decimal places in mm.

Data Extents: Please keep all data within +/- 55 inches (+/- 1400 mm) of the X/Y origin.

Layer names should not exceed 15 characters, and shall have no spaces or special characters other then underscores or dashes.

Whenever possible, please use a 1:1 scale for all inserted blocks.  Other scale factors often have a adverse affect on the conversion of curved features to the segmented arcs that we use for plotting.

LINE thickness is ignored. POLYLINE Width is typically maintained.

The following entities are ignored by our converters: SHAPE, POINTS, 3DPOLY, ATTDEF, 3DFACE, HATCH, MLINE, RAY, RTEXT, TOLERANCE, WIPEOUT, POLYFACE MESH and XLINE.

Gerber Data

We recommend the use of 274-X data format, which includes embedded apertures.

For advanced designers only: Subfigures (Step and Repeat data) can be employed with just about any size and shape, as compared to custom apertures must fit within about a 1" to 2" inch square area.  Subfigures may be generated from panelized Gerber data, inserted DWG/DXF BLOCK entities, or from GDSII structures or cell placements. For F9000/MDA data, the limit of arrayed subfigure placements is about 50,000. There is no known limit for arrayed subfigure placements in DPF data, except that we must convert DPF data to 274-X data prior to plotting, depending upon the type of plotter used.

We highly recommend that the designer preview their own Gerber data in a Gerber Viewer such as ViewMate, in order to make sure that the data looks exactly like what it is intended to look like - before it is sent to us. This is especially true if the Gerber data file was not created by a Gerber editor to begin with, but by a data conversion program such as LinkCAD or ASM500.  There are several free software packages available on the market that can be used just for this purpose. We highly recommend the free Pentalogix ViewMate product for this purpose.


For further reference, please check out these links, which open up in new windows:

  1. LinkCAD Drawing Design Rules

  2. ASM 3500 Drawing Design Rules for DXF to GDSII

  3. Design Rules for Drawing Masks using AutoCAD -

We can process polygons/boundaries without a limit to the number of vertices on each. The old 200 vertex limit is now obsolete.

We can process a nearly unlimited number of cell placements and nested cells in each data file.

Circles, arcs and other curves created from AutoCAD design files will be converted to segmented entities before creating the photomask or photoplot.  Please specify the tolerance on the radius or entity width that you need for us to meet.  Unless otherwise specified, we will use a 100 nm radius tolerance on films, 50 nm radius tolerance on glass masks.

Donuts created from DWG/DXF data will not close properly at the start/end point.  Please use a closed zero-width boundary/polyline instead, as roughly shown here.

If you have features that are completely surrounded by other features on the same layer, the plotter or laser writer will typically overwrite the inner features - unless something is done to prevent this. This process is called Polygon De-Embedding (described here).

For data that is on several layers which are intended to be combined into a composite image or photoplot, please specify the order in which the layers are to be processed, and whether or not each layer should be clear or dark.


We recommend exporting your design to EPS v3.0.

PostScript is the industry standard for sending documents to high-resolution printers. LinkCAD's PostScript-compatible export has been optimized for producing low-cost masks using high-resolution laser printers. The PostScript export can also be used to generate photoplot and photomask data.

Processing PostScript Data

Our LinkCAD converter relies on two external tools to import PostScript: pstoedit and Ghostscript. These tools are distributed under the GNU General Public License.

EPS files may contain either vector data or raster data, or both.  Vector data may be processed quite readily, while raster data cannot be processed with LinkCAD!

We strongly suggest that you download and install the program called GSView, which is the graphical interface for Ghostscript.  This viewer will enable you to see exactly what your data will look like as it goes through the conversion to Gerber format.  If the results don't look exactly like what you've created using Adobe's Illustrator or other such program, then you might want to make some changes to see what works and what doesn't.

EPS files can also be viewed with Acrobat.

If there is any text in your design, we highly recommend that you explode all the text into paths/polygons/outlines before exporting the data to an EPS file.  In Adobe Illustrator, the command sequence is to first select all text, then choose "create outlines -crtl-shft-O" from the Type menu.  Using this method creates outstanding text quality and appearance on your photomask.  If you are using another design tool and do not have the capability to explode the text, then please embed the font when you export your data to EPS format.  Also, please use one of the system or TrueType or OpenType fonts (such as Arial, Courier, Times New Roman, etc.), while avoiding any of the proprietary fonts (such as Helvetica, Myriad, and Monotype fonts).

Image Resolution of EPS Data:

The database resolution of our LinkCAD data conversion program is always 0.001 microns, or 25,400,000 dpi (dots per inch). There are, however, several factors that prevent you from achieving such a high resolution for your PostScript generated masks:

PostScript calculates in 72 dpi units. To convert from nanometers to 1/72 inches, LinkCAD instructs the PostScript processor to multiply the units by 2.83464566929E-6. The calculation is done with very High Resolution and the actual limiting factor is the printer's resolution. If the printer has a resolution of 4800 dpi, the maximum error would be approximately 5.29 microns.

Be careful, however, if you are working with repeated structures (comb structures) such as alignment masks. Because 1/4800 dpi is not an integer multiple of 0.001 microns, you get an interference pattern, which offsets your structure by 5.29 microns at every wavelength,.

We suggest that you set your EPS output resolution to the highest setting possible in order to maintain the best possible image quality.


To create a bitmap image for photoplotting, simply set the pixel size to the minimum feature size that you want on your film.

For instance, if you want the smallest features to be 7 microns in size, then set the pixel size to 7 microns. This is equivalent to 3628.57143 DPI.

If the smallest feature size is to be 25.4 microns (0.001"), then simply set the pixel size to 25.4 microns. This is equivalent to 1000 DPI.

BMP, PNG, JPG, and GIF files are nearly equivalent in terms of what our data format converter can read.

Please note that any features that are anything other than white will be plotted as black. White pixels in a bitmap image will be clear on your film, unless we reverse the polarity of the entire image. Our plotter does not do grayscale imaging, only high-contrast half-tone imaging.

Terminology conventions used by IPC:

Please click here for a graphical description of the terms we use on our online order forms..

"Field" refers to everything but the entities (or digitized data).

Digitized Dark (Clear Field) = opaque entities (pads, boundaries, etc.).
Digitized Clear (Dark Field) = clear entities (pads, boundaries, etc.).

RRCU (Right Reading Chrome Up) = Not Mirrored by IPC.
RREU (Right Reading Emulsion Up) = Normal; Not Mirrored by IPC.
RRCD (Right Reading Chrome Down) = Mirrored by IPC.
RRED (Right Reading Emulsion Down) = Reversed; Mirrored by IPC.

(Note: These definitions will apply whether there is text or not, and especially applies if there is text that reads both ways on the same photomask [and yes, we've seen this happen].  These will be verified by the customer's examination of check plots prior to manufacturing.)

Information to help you determine your Photomask Specifications for...

Photomask Inspection Criteria

Photomask Defect & Repair Criteria





LinkCAD (, from Bay Technology, Inc. is a robust, powerful, and very easy to use data format translation utility capable of importing and exporting GDSII, DXF, CIF, LASI, Gerber RS274-X, and IE3D files.  It can import Compass files, and it can also export  EPS Postscript files to drive the world's most accurate plotters.  A viewer may be purchased that is very useful for visual confirmation of the design and to help identify problem areas.

Click on these links to register for a FREE, Fully Functional Trial Version of LinkCAD for Windows, Linux, Sun Solaris(TM).

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