fabrication | coating | dicing | packaging

APPLICATION NOTES (Considerations in Specifying Micro Optics)

Material

The selection of material is dependent on the application. The most common substrate material, hence best price/performance trade-off is listed below with important design specifications.

                                 Transmission Range | Index of Refraction | Thermal Coefficient

Fused Silica                    185-2200nm          1.45847 (546.1nm)    0.57 ppm/K (0-200°C)
Bk-7                              340-2100nm          1.51680 (546.1nm)    8.3x10-6/°C (20-300°C)
Silicon                          1200-7000nm           3.4289 (4 micron)    2.55x10-6/°C (25°C)
Sapphire                        210-3500nm           1.7708 (546.1nm)    7.7x10-6/°C (0-500°C)

Other materials such as ceramic or specialty glass are considerations based on thermal properties and index of refraction requirements.

Fabrication (top)

The fabrication process of taking raw material and shaping and polishing it to the final substrate requires multiple steps. The traditional process of grinding and polishing is cost effective. However, due to the nature of micro optics, development is required to control tolerances on a micro scale. The development cost in this case is usually associated with engineering of the tooling.

Coating (top)

For Micro Optix™ applying the coating is a batch process. The cost associated with a given part is the average of the entire coating run. With the exception of metal and single layer antireflective coatings, the process will require a test run to maintain adequate process control. This assures that when the coating run is performed it will meet the design specifications. After repeated coating runs of the same design without interruptions, tolerances can be tightened.

Dicing (top)

The final step of dicing can be performed using two methods of blocking. The least expensive is by using tape to hold the substrate in place. This method works well when the thickness of the final part is less than 1/5 of the overall surface area. If the thickness is greater than this value, then the best method is to wax the substrate to a glass carrier. The tradeoff in using the tape method on thicker parts is that chipping will increase and detachment of parts during dicing is likely.

Packaging (top)    

Clean room grade packaging which can hold the parts in a stationary location is ideal. Gel and membrane packages work best. Avoid packaging where the parts are in constant motion such as envelopes, tubes and bags, as this may lead to chipping.