Lap & Polish

 

Our lapping and polishing experience dates to the late ‘70’s when flat substrates were required for mirror coatings used in copy machines and printing presses. We have since pace with rapidly developing technologies in display, photo lithography, biotechnologies and other industries requiring precision optical glass components. Today, the Coresix lapping and polishing processes have evolved to meet the highest standards of thickness, flatness, roughness and cosmetic specifications.

 

Common Terms for Lapping

  • Flatness
    Of a surface is the degree to which the surface approximates a mathematical plane. Flatness is typically specified in microns, waves or fringes (half waves).

  • Bow (& Warp)
    The deviation of the center point of the median surface of a free, unclamped wafer from the median surface reference plane established by three points equally spaced on a circle with a diameter a specified amount less than the nominal diameter of the wafer.  Bow is typically measured in microns.
     
  • Roughness
    Is a measurement of the small-scale variations in the height of a physical surface. A common measure of surface roughness is the rms (root-mean-square) height h of the surface bumps.

  • Warp
    The difference between the maximum and minimum distances of the median surface of a free, unclamped wafer from a reference place.

     
  • Waviness
    This refers to the irregularities which are outside the roughness width cut off values. Waviness height is the peak to valley distance of the surface profile, measured in microns.
     
  • TTV
    Total Thickness Variation – expresses the maximum peak to valley measurement within a given part or from one part to the next.
     
  • Super Polish
    This is an advanced polishing process designed to eliminate polishing micro-structure in the surface of the glass and produce roughness to <3Ǻ.


Coresix Capabilities

Lapping Minimum Maximum Tolerance
Flatness 1/10 Wave NA NA
Bow/Warp <1um/Inch NA NA
TTV <2um   NA +/-1um
Thickness 200um NA +/-5um
Size 10mm  300mm +/-0.10mm


Polish Minimum Maximum Tolerance
Flatness 1/10 Wave NA NA
Bow/Warp <1um/Inch NA NA
TTV <2um   NA +/-1um
Thickness 200um NA +/-5um
Size 10mm  300mm +/-0.10mm


Metrology Equipment Used At Coresix

  • Measures flatness, line profile, radius and other surface parameters to accuracy of 50nm Zygo
     
  • Interferometer 
    Quickly measures surface roughness and flatness Smart Scope (OGP, Inc.): an optical CMM system for accurate dimensional measurements.




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Common Flatness Measurements

  • Power & Irregularity
    As expressed over a defined aperture (ex. 12/12/4 = 12 fringes of power and 12 fringes of irregularity over a four-inch aperture) is measured in newton rings on an interferometer.
     
  • Fringes
    Measured by interferometer, a fringe is a distortion in the surface relative to an optical plane (1 fringe = ½ wave)
     
  • Waves
    Another way of expressing flatness as defined by the number of Newton rings measured over a given area.  (1 wave = 2 fringes)
     
  • Microns
    Defines flatness in peak to valley measurement over a given area.
     
  • Arc Minutes and Seconds
    Parallelism of top of one surface to another in degrees (1 arc min = 1' = 1/60 deg, 1 arc sec = 1" = 1/60 arc min) 
  • TIR
    Total indicator reading is the maximum focal plane deviation relative to a known reference plane.

     

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