Magnetic Head Wafer Polishing
Wafers used for magnetic tape and hard drive read-write heads are manufactured with very similar front end techniques as used for semiconductor chip manufacturing. The primary difference is that the sustrates used for magnetic head wafer consist of a dual phase ceramic of alumina and titanium carbide, commonly know as AlTiC.
Typical polishing operations consist of diamond stress relief lapping and CMP planarization. At the present time the momentum for hard drive wafer production is towards the manufacturer of perpendicular recording heads. Following this technology is a transition from GMR heads to the more sensitive TMR heads. Likewise the technology for the tape business also continues to evolve, however the challenges for the magnetic tape head wafers is in the manufacturing transition from AMR recording heads to GMR recording heads.
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| Figure 1a. Magnetic hard drive slider | Figure 2a. Magnetic tape head | |
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| Figure 1b. Magnetic pole for HDD head | Figure 2b. Magnetic pole for tape head |
Polishing and planarization of the AlTiC wafers and metal requires tight controls over the polishing abrasive as well as the polishing pad design. Several factor which affect the polishing pad material, include: the pad hardness, porosity, density, nap, surface tension and wetting contact angle of the polishing media.
Magnetic Media Polishing
Polishing and texturizing of the magnetic media or disk requires very tight tolerance for the diamond or alumina polishing abrasives as well as very tight control over the polishing pad surfaces. The BLACKCHEM 2 polishing pad is an excellent polishing pad for polishing with various particles sizes of alumina or diamond.
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| Figure 3. Magnetic Hard Drive Disks polished with fine graded alumina on BLACKCHEM 2 polishing pad. |
Wafer and Media Polishing Pads
NANOFINISH Corporation offers a selection of felt polishing pads comparable to the POLITEX (BLACKCHEM 2), SUBA 500, SUBA V, SUBA IV, GS, SUBA X and natural wool polishing pads that are found in the industrial polishing market today.
BLACKCHEM 2BLACKCHEM 2 is a replacement polishing pad for the POLITEX polishing pad (see comparision table below). Its main application is for CMP polishing with alumina or colloidal silica. The BLACKCHEM 2 also has a very similar and porous structure as the POLITEX pad.
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Properties |
NANOFINISH BLACKCHEM 2 |
RODEL POLITEX |
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Thickness in mm |
1.369 |
1.471 |
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Weight g/m2 |
583.1 |
582.6 |
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Hardness Shore A |
66 |
61 |
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Compressibiity in % |
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Surface resistance in mg |
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Pores volumes of open pores in % |
68.6 |
78.1 |
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Average pore size in um |
40.6 |
55 |
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Wetting angle (against water) |
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| Pore structure for BLACKCHEM 2 (SEM 300X). | Pore structure for POLITEX (SEM 300X). |
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| Cross section for BLACKCHEM 2 (SEM 100X). | Cross section for POLITEX (SEM 100X). |
PC Impregnated Felt Polishing Pads
The PC series of polishing pads are replacement polishing pads for the SUBA series of polishing pads (see comparision table below). There main polishing application is for glass, ceramics, precision optics and other materials where surface finish is critical.
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NANOFINISH |
Replaces |
Specific Gravity |
Durometer Hardness |
Thickness |
Max size |
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PC80 |
SUBA 500 |
0.58 |
>C80 |
0.050" - 1" |
39.5" x 39.5" |
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PC60 |
SUBA V |
0.40 |
>C60 |
0.050" - 1" |
39.5" x 39.5" |
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PC40 |
SUBA IV |
0.34 |
C40 |
0.090" - 1" |
53" x 53" |
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PC55-LD |
SUBA X |
0.32 |
C55 |
0.050" - 1" |
39.5" x 39.5" |
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PC55-HD |
SUBA X |
0.42 |
C55 |
0.050" - 1" |
39.5" x 39.5" |
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PC20 |
Natural wool |
0.31 |
C20 |
1/8" - 1" |
53" x 53" |
Recommended Application
The following is a list of recommendations to maximize the performance of the polishing or lapping operations.
- Match the polishing pad characteristics to the material to be polished
- Charge the abrasive to the polishing surface
- Use a polishing lubricant designed to remove polishing or grinding swarf. This can significantly increase the life and performance of the polishing surface