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Wafering Blades

metallographic precision wafering blades


Process Description ] Selection Guidelines ] Cutting Parameters ] Recommended Procedures ] Trouble Shooting ] Cutting Consumables ]


Metallographic Precision Diamond Wafer Cutting (Click link to print this page)

Precision Cutting

Precision wafer cutting is used for sectioning very delicate samples or for sectioning a sample to a very precise location. Precision wafering saws typically have micrometers for precise alignment and positioning of the sample and have variable loading and cutting speed control.

Metallographic Precision Diamond Wafering Saw
Metallographic precision cutter with cutting table
PICO 155 slow/medium speed wafering saw
PICO 175 fast speed wafering saw

Abrasive Type - In order to minimize cutting damage, precision wafer cutting most frequently uses diamond wafering blades, however for some materials the use of cubic boron nitride (CBN) is more efficient. In addition, optimal wafer cutting is accomplished by maximizing the abrasive concentration aMetallographic wafering bladesnd abrasive size, as well as choosing the most appropriate cutting speed and load. Table I provides some general guidelines and parameters for precision sectioning a variety of materials.

The particle size of fine grit diamond blades is 10-20 microns, or approximately 600 grit. For medium grit diamond wafering blades, the particle size is 60-70 micron, or 220 grit. For these types of wafering blades, the abrasive is mixed with a metal binder and then pressed under high pressure. As will be discussed in the next section, periodic dressing/conditioning of the metal pressed blades is required for optimum cutting performance of the blade.

Wafering Blades Description Characteristic
Fine grit 10-20 micron (600 grit)
Medium grit 60-70 micon (220 grit)
Coarse grit 120 micron (120 grit)
High concentration 100%
Low concentration 50%

In some cases, precision cutting requires a coarser grit wafering blade. Usually the coarsest standard blade uses 120 grit abrasive particles. For metallographic applications, coarse abrasives are mostly associated with electroplated blades. The main characteristic of coarse electroplated blades is that the abrasive has a much higher, or rougher, profile. The advantage of this higher profile is that the blade does not “gum up” when cutting softer materials such as bone, plastics and rubbery types of materials.

Although less common, thin resin-rubber abrasive blades can be used for cutting on precision wafering saws. For cutting with abrasive blades on precision wafer saws, set the speed of the saw to at least 1500 rpm. Note that abrasive blades create significantly more debris which requires changing out of the cutting fluid more frequently.

Electroplated Diamond Blades
Electroplated diamond wafering blade for cutting soft materials

Abrasive Size - Perhaps the most important parameter for precision sectioning is the abrasive size. Similar to grinding and polishing, finer abrasives produce less damage. For extremely brittle materials, finer abrasives are required to minimize and manage the damage produced during sectioning. Sectioning with a fine abrasive wafering blade is often the only way that a specimen can be cut so that the final polished specimen represents the true microstructure. Examples include: silicon computer chips, gallium arsenide, brittle glasses, ceramic composites, and boron-graphite composites. The following figures compare the effects of cutting with a fine grit blade vs. a standard medium grit blade for sectioning a boron graphite golf shaft. As can be seen, the fine grit blade produces significantly less damage to boron fibers.

Metallographic fine grit diamond blade for cutting brittle boron carbide Metallographic medium grit diamond blade for cutting brittle boron carbide

Fine grit diamond cut - golf shaft

Medium grit diamond cut - golf shaft

Metallographic fine grit diamond wafering blade for cutting silicon wafer Metallographic medium grit diamond wafering blade for cutting silicon wafer

Fine grit diamond cut -glass

Medium grit diamond cut - glass

Blade Dressing - The second most important blade characteristic is the abrasive concentration because it directly affects the load which is applied during cutting. For example, brittle materials such as ceramics require higMetallographic wafering blade dressing / conditioningher effective loads to efficiently section; whereas, ductile materials such as metals require a higher abrasive concentration in order to have more cutting points. The result is that low concentration blades are recommended for sectioning hard brittle materials such as ceramics and high concentration blades are recommended for ductile materials containing a large fraction of metal or plastic.

TIP: Minimizing the amount of damage created during sectioning can significantly reduce the amount of time required for grinding and polishing.

The wafering blade bonding matrix can also significantly affect a blade’s cutting performance. Metal pressed wafering blades require periodic dressing in order to maintain performance. A common misconception is that the cutting rates for these blades decrease because the diamond or abrasive is being "pulled out" of the blade. In reality, the metal bond is primarily smearing over the abrasive and "blinding" the cutting edge of the abrasive. With periodic dressing, using a ceramic abrasive encased in a relatively soft matrix, this smeared material is removed and the cutting rate restored. Figure 3-6 shows the effect of dressing a standard grit, low concentration diamond blade for cutting a very hard material such as silicon nitride. Without dressing the blade, the cut rate significantly decreases after each subsequent cut. After dressing the blade, the sample once again cuts like a new blade. Note it is highly recommended that a dressing fixture be used for conditioning or dressing the wafering blades in order to reduce the risk of breaking or chipping the wafering blades. Blade dressing is also accomplished at low speeds (<200 rpm) and at light loads (<100 grams).

Metallographic diamond blade dressing

Metallographic diamond blade dressing

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WAFERING BLADE SELECTION GUIDELINES Wafer cutting guidelines brochure

Material

Characteristic

Speed (rpm)

Load (grams)

Blade (grit/conc.)

Silicon substrate

soft/brittle

<500

<100

Fine/low

Gallium arsenide

soft/brittle

<500

<100

Fine/low

Boron composites

very brittle

1500

250

Fine/low

Ceramic fiber composites

very brittle

2500

500

Fine/low

Glasses

brittle

2500

500

Fine/low

Minerals

friable/brittle

>3000

>500

Fine/low

Alumina ceramic

hard/tough

>3500

>500

Medium / low

Zirconia (PSZ)

hard/tough

>3500

>800

Medium/low

Silicon nitride

hard/tough

>3500

>800

Medium/low

Metal matrix composites

 

>3500

>500

Medium/high

General purpose

 

variable

Variable

Medium/high

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CUTTING PARAMETERS

Most wafer cutting is done at speeds between 50 rpm and 5000 rpm with loads varying from 10-1000 grams. Generally, harder specimens are cut at higher loads and speeds (e.g. ceramics and minerals) and more brittle specimens are cut at lower loads and speeds (e.g. electronic silicon substrates) (see Table IV). It is interesting to note that the cutting efficiency for sectioning hard/tough ceramics improves at higher speeds and higher loads. Figure 3.8 compares the resulting surface finish for sectioning partially stabilized zirconia at a low speed/low load (Figure 3-8a) vs. cutting at a higher load/higher speed (Figure 3-8b). As can be seen, partially stabilized zirconia has less fracturing and grain pull out after sectioning at higher speeds and loads. This observation may seem counter intuitive, however for sectioning hard/tough ceramics, high cutting speeds and loads result in producing a crack that propagates in the direction of the cut instead of laterally into the specimen.

Zirconia sectioned at low speeds and low loads   Zirconia sectioned at high speeds and high loads
Partially stabilized zirconia sectioned at low speeds and low loads   Partially stabilized zirconia sectioned at high speeds and high loads

For wafer cutting it is recommended that a cutting fluid be used. The characteristics of a good cutting fluid include:

- Removes and suspends the cutting swarf
- Lubricates the blade and sample
- Reduces corrosion of the sample, blade and cutting machine parts

In general, cutting fluids are either water-based or oil-based. Water-based cutting fluids are the most common because they are easier to clean, however oil-based cutting fluids typically provide more lubrication.

Metallographic wafer cutting fluidDIACUT oilDIACUT cutting fluid
Oil and water-based cutting fluids

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RECOMMENDED DIAMOND WAFERING PROCEDURES
  • Prior to cutting the sample, condition or dress the wafering blade with the appropriate dressing stick.
  • Clamp the specimen sufficiently so that the sample does not shift during cutting. If appropriate, clamp both sides of the specimen in order to eliminate the cutting burr which can form at the end of the cut.
  • For brittle materials clamp the specimen with a rubber pad to absorb vibration from the cutting operation.
  • Begin the cut with a lower force in order to set the blade cutting kerf.
  • Orient the specimen so that it is cut through the smallest cross section.
  • For samples with coatings, keep the coatings in compression by sectioning through the coating and into the substrate material.
  • Use largest appropriate blade flanges to prevent the blade from wobbling or flexing during cutting.
  • Reduce the force toward the end of the cut for brittle specimens
  • Use the appropriate cutting fluid.

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TROUBLESHOOTING

Symptom

Cause

Action

Chipped or broken blade

  • Improper blade dressing
  • Insufficient clamping of specimen
  • Too high an initial load
  • Use a mechanical dressing fixture
  • Secure specimen with a rubber pad
  • Reduce initial loading to set cutting kerf
  • Excessive blade wobble

  • Too high a cutting load
  • Reduce applied load and/or use larger diameter support flanges
  • Low cutting rates

  • Smeared material on the blade
  • Too low a cutting speed and/or load
  • Redress blade at <100 grams and <200 rpm
  • Increase cutting speeds and loads
  • Rotate specimen to minimize cutting area
  • Excessive specimen damage or chipping

  • Too large an abrasive
  • Excessive vibration
  • Use finer grit diamond blade
  • Secure specimen with rubber mounting pad
  • Burr formation on specimen at end of cut

  • Cutting force or speed too high at end of the cut
  • Excessive vibration
  • Reduce speeds and loads to reduce cutting rate
  • Secure specimen with rubber mounting pads
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    PRECISION WAFER CUTTING CONSUMABLES

    3-inch Diameter (76.2 mm) Wafering Blade, 1/2-inch (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.006-inch

    WB-0030LC

    Metallographic diamond blades

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.006-inch

    WB-0035LC

    Most metal samples

    High

    Medium

    0.006-inch

    WB-0035HC


    4-inch Diameter (102 mm) Wafering Blade, 1/2-inch (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.012-inch

    WB-0040LC

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.012-inch

    WB-0045LC

    Most metal samples

    High

    Medium

    0.012-inch

    WB-0045HC


    5-inch Diameter (127 mm) Wafering Blade, 1/2-inch (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.015-inch

    WB-0050LC

    Metallographic diamond wafering blades

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.015-inch

    WB-0055LC

    Most metal samples

    High

    Medium

    0.015-inch

    WB-0055HC


    6-inch Diameter (153 mm) Wafering Blade, 1/2-inch (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.020-inch

    WB-0060LC

    Metallographic diamond wafering blades

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.020-inch

    WB-0065LC

    Most metal samples

    High

    Medium

    0.020-inch

    WB-0065HC


    7-inch Diameter (153 mm) Wafering Blade, 1/2-inch (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.020-inch

    WB-0070LC

    Metallographic diamond wafering blades

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.020-inch

    WB-0075LC

    Most metal samples

    High

    Medium

    0.020-inch

    WB-0075HC


    8-inch Diameter (153 mm) Wafering Blade, 1/-inch" (12.7 mm) Arbor

    Application

    Conc.

    Diamond size

    Thickness

    Catalog
    Number

     

    Brittle materials (microelectronic materials, friable ceramics, minerals)

    Low

    Fine

    0.020-inch

    WB-0080LC

    Metallographic diamond wafering blades

    Hard/tougher ceramics (Si3N4, ZrO2)

    Low

    Medium

    0.020-inch

    WB-0085LC

    Most metal samples

    High

    Medium

    0.020-inch

    WB-0085HC


    Electroplated Diamond Wafering Blades, 1/2" (12.7 mm) Arbor

    Application

    Blade Diameter

    Catalog
    Number

     

    4-inch Electroplated Diamond blade for soft gummy materials such as plastics, rubber, PCB's and other soft materials

    4-inch

    EPD-0040

    Electroplated Diamond Blades

    5-inch Electroplated Diamond blade for soft gummy materials such as plastics, rubber, PCB's and other soft materials

    5-inch

    EPD-0050

    6-inch Electroplated Diamond blade for soft gummy materials such as plastics, rubber, PCB's and other soft materials

    6-inch

    EPD-0060

    7-inch Electroplated Diamond blade for soft gummy materials such as plastics, rubber, PCB's and other soft materials

    7-inch

    EPD-0070

    8-inch Electroplated Diamond blade for soft gummy materials such as plastics, rubber, PCB's and other soft materials

    8-inch

    EPD-0080


    CBN Wafering Blades, 1/2" (12.7 mm) Arbor

    Application

    Conc.

    Grit size

    Thickness

    Catalog
    Number

     

    4-inch CBN wafering blade (medium grit, high concentration

    High

    Medium

    0.012"

    WCBN-0045

    Metallographic CBN blades

    5-inch CBN wafering blade (medium grit, high concentration

    High

    Medium

    0.015"

    WCBN-0055

    6-inch CBN wafering blade (medium grit, high concentration

    High

    Medium

    0.020"

    WCBN-0065

    7-inch CBN wafering blade (medium grit, high concentration

    High

    Medium

    0.020"

    WCBN-0075

    8-inch CBN wafering blade (medium grit, high concentration

    High

    Medium

    0.020"

    WCBN-0085


    CBN/Diamond Hybrid Wafering Blades, 1/2" (12.7 mm) Arbor

    Application

    Conc.

    Grit size

    Thickness

    Catalog
    Number

     

    4-inch CBN/Diamond hybrid Wafering Blade (medium grit, high conc.)

    High

    Medium

    0.012-inch

    WCBND-0045

    Metallographic CBN blades

    5-inch CBN/Diamond hybrid Wafering Blade (medium grit, high conc.)

    High

    Medium

    0.015-inch

    WCBND-0055

    6-inch CBN/Diamond hybrid Wafering Blade (medium grit, high conc.)

    High

    Medium

    0.020-inch

    WCBND-0065

    7-inch CBN/Diamond hybrid Wafering Blade (medium grit, high conc.)

    High

    Medium

    0.020-inch

    WCBND-0075


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    CUTTING FLUID

    Description

    Quantity

    Catalog Number

     

    Water-based wafer cutting fluid

    16 oz (0.47l)
    32 oz (0.94l)

    WL-3000-16
    WL-3000-32

    Metallographic wafer cutting fluid

    Water-based wafer cutting fluid with corrosion inhibitor

    16 oz (0.47l)
    32 oz (0.94l)

    WL2-3000-16
    WL2-3000-32

    Oil-based wafer cutting fluid
    16 oz (0.47l)
    32 oz (0.94l)
    OL-3000-16
    OL-3000-32

    MISCELLANEOUS

    Description

    Quantity

    Catalog Number

     

    Dressing sticks (medium grit)

    each

    DRES-0010

    Dressing stick

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