INTRODUCTION

The production of small optical components and subassemblies, in order to meet their typical low cost objectives, must use processes that are fast and convenient. Of particular significance in the production sequence is the step that provides the required polished surfaces for light transmission, reflection or refraction.

Ultra Tec's equipment meets these objectives of speed and ease, providing a smooth process flow from the initial preparation to the final polish. Perhaps the key element in this is an unique workholding configuration, in which mounted components pass from one process step to the next, using ULTRA TEC's 'Quick-Release' interface, avoiding time-consuming transferring and remounting.

TECHNICAL CONSIDERATIONS

The materials used in the optics industry require consideration of the following characteristics:

• The material may be soft, friable, or delicate
• The item may have a complex shape
• Surfaces may require precise angular alignment
• If expensive or unique materials are being used, material loss needs to be minimized
• The resulting surface quality must be excellent.

These considerations are important when selecting and cutting, lapping, and polishing equipment. The equipment's versatility and precision of work-holding are crucial in supporting both R&D and Production operations which may require the movement from one type of workpiece to another, allowing the flexible planning, performance and equipment utilization.

PRECISION CUTTING - SECTIONING

A motorized table work feed provides high control and versatility in comparison with other techniques. ULTRASLICE 6000 allows long and dicing cuts to be performed. The workpiece is adjusted to its X, W, and Z positions, and the cutting traverse is made in the Y direction-the extent of the Y traverse being settable. For production operations, indexed fixturing devices are prepared to minimize repeat setup times.

Speed and feed rates are fully controllable to provide optimized cutting parameters for materials from soft polymeric materials up to the hardest crystals. The feed rate at which the table advances is infinitely variable to adjust to the needs of the particular application. The blade rotational speed is variable up to 6000rpm.

The Saw accepts all standard blades, including special dicing blades-the blades most typically being diamond, available in a variety of matrices. In many low-kerf applications, and where the initial cutting action must produce a good finish, such as for fiber optics, special blades are available.

GRINDING, LAPPING AND POLISHING

The preparation process uses abrasives of decreasing size to remove surface irregularities until the final quality is achieved. Using abrasive films for lapping and polishing is more convenient, cleaner, and less subject to variability than the more traditional loose-abrasive slurry techniques. In some specific applications, however, use of slurry can optimize final polish. The ULTRAPOL Series Polisher accommodates both film and slurry techniques.

Film abrasives and polishes are available in a variety of materials, including diamond, silicon carbide, aluminum oxide, cerium oxide. With a large range of particle sizes, from those appropriate for grinding to the finest of final-polishing steps. These are available in non-adhesive or pressure sensitive adhesive backing (PSA).

Slurries are available, including ULTRAPOL B Suspension which, in conjunction with fine-particle films, has yielded the highest polishes on optical devices. The ULTRAPOL 1200 Series Polishers use 8 inch diameter films. The systems allow for high precision holding of the samples in radial, axial and Z (height) directions. 

Crucial for optical components, the microp[ositioner head is oscillated across the polishing plate to improve surface finish. This, in conjunction with only the relatively small surface area of the sample being in contact with the plate during processing, makes ppreparation times short. 

The system also allows for end-point of a lapping or polishing operation to be signaled to the user. This is effected by an LED, coupled with a controllable end-stop.

METHODS

The component to be prepared is mounted into a 'quick release' workholder specific for its size and orientation. These in most cases are designed to hold the specimen 'dry', without the need for waxes or cements. The workholder is then mounted onto a 'quick release' clamp on the the Saw, for initial sectioning. Optical materials benefit from moderate speed and feed rates to maintain surface integrity.

After sectioning, the workholder is removed and mounted onto ULTRAPOL for  subsequent lapping and polishing. The various optical materials require differing speed and loading conditions which are provided by ULTRA TEC on supply of the system. After polishing, the specimen is removed from the workholder and cleaned, ready for use.

SUMMARY

ULTRA TEC provides cutting, grinding and polishing solutions to the optic, fiber-optic, electro-optic, materials, semiconductor and failure analysis industries.

ULTRA TEC systems allow for fast, convenient, cost-effective preparation of a wide variety of sample types for production and research applications. Samples are mounted and transferred between instruments with the use of "Quick Release Workholders" which allow for minimized downtime, high reproducibility of results and high productivity.

REFERENCES

1."Cutting and Polishing Optical and Electonic Materials". 2nd Ed. GVV Fynn and WJA Powell. Publ. Adam Hilger

2. "Fiber Polishing Equipment Plays a Role in FDA Approved Dental Laser Photonics Spectra Article. (pending publication, October 1997)

3. "Positron Emission Mammography (PEM): A Promising Technique for Detecting Breast Cancer" CJ Thompson et al. IEEE Transactions on Nuclear Science, Vol. 42, No. 4 (August 1995)