The polarity and orientation of each photoplot must be specified when ordering. Read the below Definition if you are placing order first time.

Definitions

  • A phototool is a photoplot made of flexible photographic film or a photomask made of a coating applied to a glass or quartz substrate.
  • Data areas are those containing text, vectors, or filled areas as drawn in the CAD program.
  • Field areas are non-data areas; these are the empty spaces outside the figures drawn in the CAD program. The field extends to the edge of the mask, or nearly so.
  • The emulsion side is the image surface on silver-halide films and plates.
  • The chrome side is the image surface on chrome-on-quartz masks.
  • Positive phototools (photoplots and masks) are dark (opaque) in the data areas and clear (transparent) in the field areas.
  • Negative phototools are clear (transparent) in the data areas and have a dark (opaque) field.
  • Right-reading means that text or other figures inserted into the CAD database in normal, left-to-right reading fashion appear in the same orientation on the phototool as they do when viewing in the CAD system using the conventional viewpoint. The conventional CAD system viewpoint is a view from above, looking down and through the image layer or layers.
  • Emulsion/chrome Up phototools are right-reading when the image surface faces toward you.
  • Emulsion/chrome Down phototools are right-reading when the image surface faces away from you.
  • Negative-acting photoresist cross-links upon exposure to UV light, so it becomes resistant to attack from the development chemicals where the photomask or photoplot is transparent. This means the photoresist remains after development wherever the photomask is clear. Dark areas of the photomask prevent cross-linking, so the photoresist is removed upon development.
  • Positive-acting resist decomposes (long polymer molecules break apart) upon exposure to UV light, so the resist is removed during development wherever the phototool is transparent. Dark areas of the phototool prevent exposure to UV light, so those areas remain after development.

Phototool Type Designations

PCBkey  Designation Image Examples Phototool Polarity Image Surface Purpose
CAD Image Phototool Image Polarity Data Areas Field Areas Orientation Mirrored
 PU  cad image positive emulsion up   P ositive Dark Clear  U p No silkscreen master; exposure on bottom side of substrate coated with positive-acting resist
 PD  cad image positive emulsion up   P ositive Dark Clear  D own Yes exposure on top side of substrate coated with positive-acting resist
 NU  cad image positive emulsion up   N egative Clear Dark  U p No exposure on bottom side of substrate coated with negative-acting resist
 ND  cad image positive emulsion up   N egative Clear Dark  D own Yes exposure on top side of substrate coated with negative-acting resist
  • Green areas in the CAD image column are data areas.
  • Light blue areas in CAD image column are non-data (field) areas.
  • All graphics in the Phototool Image column indicate how the phototool will appear with the emulsion or chrome (image surface) facing you.
  • The white areas in the Phototool Image column are transparent on the phototool.
  • The black areas in the Phototool Image column are opaque on the phototool.
  • The Polarity, Data Areas, Field Areas, Orientation, and Mirrored columns indicate how the phototool will appear with the emulsion or chrome (image surface) facing you.

Example 1 -- top-side of wafer using positive-acting resist

You have a silicon wafer you are going to pattern with metal twice using a spin-on positive-acting photoresist. The CD (critical dimension) is 20um. This means no lines or spaces are smaller than 20um on the phototool. Very-High-Resolution (8000 DPI or 1/8 mil resolution) is a good choice for this scenario.

Your order form should look something like this:

  PCBkey Photoplot order form:

  file #      file name        plot type        quantity
  ------ -------------------  -----------      ----------
    1     metal1.gbr             VPD               1 
    2     metal2.gbr             VPD               1 

 Note: H = high resolution, V = very high resolution
       N = negative, P = Positive
       U = right reading emulsion up, D = right reading emulsion down

Example 2 -- two-sided subtractively etched PCB

You have a two-sided through-hole PCB you are going to print and etch using the standard subtractive process and want to order one set of working film. High-Resolution (4000 DPI or 1/4 mil resolution) is adequate because your minimum feature size is more than 5 mils. The solder mask is the LPI (Liquid Photo Imageable) type, applied to both sides with the same pattern, and you are going to apply a conventional screen-printed legend to the top side. Negative-working photoresist is typically used for this application.

Your order form should look something like this:


  PCBkey Photoplot order form:

  file #      file name        plot type        quantity
  ------ -------------------  -----------      ----------
    1     trace_top.gbr          HND               1 
    2     trace_bot.gbr          HNU               1 
    3     silk_top.gbr           HPU               1 
    4     smask.gbr              HPD               1 
    4     smask.gbr              HPU               1 

 Note: H = high resolution, V = very high resolution
       N = negative, P = Positive
       U = right reading emulsion up, D = right reading emulsion down