METHOD OF FABRICATING A GLASS MAGNETIC HARD DRIVE DISK PLATTER USING FILAMENTATION BY BURST ULTRAFAST LASER PULSES

• US 20150118522A1
• Filed: 10/10/2014
• Published: 04/30/2015
• Est. Priority Date: 10/25/2013
• Status: Active Grant

• Current Assignee: Rofin-Sinar Technologies LLC (Coherent Corp.)
• Original Assignee: Rofin-Sinar Technologies Incorporated (Coherent Corp.)
• Inventors: HOSSEINI, S. ABBAS
• Granted Patent: US 10,017,410 B2
• Time in Patent Office: Days
• US Class Current: 428/846.9
• CPC Class Codes: B23K 2103/54 Glass
• CPC Class Codes: B23K 26/0617 and with spots spaced along the common axis
• CPC Class Codes: B23K 26/0622 by shaping pulses
• CPC Class Codes: C03B 33/0222 Scoring using a focussed radiation beam, e.g. laser
• CPC Class Codes: C03B 33/04 Cutting or splitting in curves, especially for making spectacle lenses
• CPC Class Codes: C03B 33/091 using at least one focussed radiation beam, e.g. laser beam C03B33/0955 takes precedence
• CPC Class Codes: G11B 5/8404 manufacturing base layers
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

A non-ablative method and apparatus for making an economical glass hard disk (platter) for a computer hard disk drive (HDD) using a material machining technique involving filamentation by burst ultrafast laser pulses. Two related methods disclosed, differing only in whether the glass substrate the HDD platter is to be cut from has been coated with all the necessary material layers to function as a magnetic media in a computer'"'"'s hard drive. Platter blanks are precisely cut using filamentation by burst ultrafast laser pulses such that the blank'"'"'s edges need not be ground, the platter'"'"'s geometric circularity need not be corrected and there is no need for further surface polishing. Thus the platters can be cut from raw glass or coated glass. As a result, this method reduces the product contamination, speeds up production, and realizes great reductions in the quantity of waste materials and lower production costs.

Claims

1. A method of producing glass hard disk drive platters from a magnetic media coated substrate, using laser machining, comprising the steps of:

providing a planar glass substrate with a layered system of magnetic media coatings, said planar glass substrate includes a top surface and a bottom surface;

providing a laser beam comprising a burst of laser pulses;

providing a laser beam delivery system capable of focusing said laser beam onto said top surface of said planar glass substrate and to enable relative movement between said laser beam and said planar glass substrate;

focusing said laser beam relative to said top surface of said planar glass substrate to form a beam waist external to said top surface of said planar glass substrate, said laser pulses incident on said top surface of said planar glass substrate are focused such that sufficient energy density is maintained within said planar glass substrate to form a continuous laser filament therethrough without causing optical breakdown;

laser ablating a portion of said magnetic media coatings on said top surface of said planar glass substrate;

laser ablating a portion of said magnetic media coatings on said bottom surface of said planar glass substrate;

creating a laser filament that cuts completely through said glass substrate by photoacoustic compression;

enabling relative movement between said focused laser beam and said planar glass substrate moving said laser filament created in said planar glass substrate in circular geometric patterns relative to said glass substrate cutting circular platters from said planar glass substrate.

2. The method of producing glass hard disk drive platters from a magnetic media coated substrate, using laser machining as claimed in claim 1,

wherein said step of providing a laser beam delivery system capable of focusing said laser beam onto said top surface of said planar glass substrate includes passing said laser pulses from a laser source through a selected distributive-focus lens focusing assembly;

wherein said step of focusing said laser beam relative to said top surface of said planar glass substrate to form a beam waist external to said top surface of said planar glass substrate includes adjusting the relative distance and/or angle of said distributive-focus lens focusing assembly in relation to said laser source focusing said laser pulses in a distributed focus configuration creating a principal focal waist and at least one secondary focal waist; and

, adjusting said principal focal waist or said planar glass substrate such that said principal focal waist will not reside on or in said planar glass substrate being cut.

3. The method of producing glass hard disk drive platters from a magnetic media coated substrate, using laser machining as claimed in claim 2,

wherein said step of focusing said laser beam relative to said top surface of said planar glass substrate to form a beam waist external to said top surface of said planar glass substrate further includes:

adjusting said focus such that the spot of laser fluence on said top or bottom surface of said planar glass substrate is located below or above said principal focal waist and has a diameter that is always larger than a diameter of a filamentation that is formed in said planar glass substrate; and

, adjusting the fluence level of said secondary focal waists so that they are of sufficient intensity and number to ensure propagation of a photoacoustic compressive machining through the desired volume of said planar glass substrate; and

,

wherein said step of providing a laser beam comprising a burst of laser pulses further includes applying at least one burst of laser pulses of a suitable wavelength, suitable burst pulse repetition rate and suitable burst pulse energy from said laser source to said planar glass substrate, and wherein the total amount of pulse energy or fluence, applied to said planar glass substrate at a spot where said laser pulses contact said planar glass substrate is greater than the critical energy level required to initiate and propagate photoacoustic compression machining, yet is lower than the threshold critical energy level required to initiate ablative machining; and

stopping said burst of laser pulses when said cutting has been completed.

7. A glass hard disk drive platter coated with magnetic media made by the method of claim 1.

4. A method of producing glass hard disk drive platters using laser machining, comprising the steps of:

providing a planar glass substrate;

providing a laser beam comprising a burst of laser pulses;

providing a laser beam delivery system capable of focusing said laser beam onto said planar glass substrate and to enable relative movement between said laser beam and said planar glass substrate;

focusing said laser beam relative to said planar glass substrate to form a beam waist at a location external to said planar glass substrate, said laser pulses focused such that a sufficient energy density is maintained within said planar glass substrate to form a continuous laser filament therethrough without causing optical breakdown;

creating a laser filament that pierces completely through said planar glass substrate by photoacoustic compression; and

,

moving said laser filament in circular geometric patterns in and relative to said planar glass substrate with said laser beam delivery system cutting circular hard disk drive platters from said planar glass substrate by photoacoustic compression.

5. The method of producing glass hard disk drive platters using laser machining as claimed in claim 4,

wherein said step of providing a laser beam delivery system capable of focusing said laser beam onto said top surface of said planar glass substrate includes passing said laser pulses from a laser source through a selected distributive-focus lens focusing assembly;

wherein said step of focusing said laser beam relative to said top surface of said planar glass substrate to form a beam waist external to said top surface of said planar glass substrate includes adjusting the relative distance and/or angle of said distributive-focus lens focusing assembly in relation to said laser source focusing said laser pulses in a distributed focus configuration creating a principal focal waist and at least one secondary focal waist; and

, adjusting said principal focal waist or said planar glass substrate such that said principal focal waist will not reside on or in said planar glass substrate being cut.

6. The method of producing glass hard disk drive platters using laser machining as claimed in claim 5,

wherein said step of focusing said laser beam relative to said top surface of said planar glass substrate to form a beam waist external to said top surface of said planar glass substrate further includes:

adjusting said focus such that the spot of laser fluence on said top or bottom surface of said planar glass substrate is located below or above said principal focal waist and has a diameter that is always larger than a diameter of a filamentation that is formed in said planar glass substrate; and

, adjusting the fluence level of said secondary focal waists so that they are of sufficient intensity and number to ensure propagation of a photoacoustic compressive machining through the desired volume of said planar glass substrate; and

,

wherein said step of providing a laser beam comprising a burst of laser pulses further includes applying at least one burst of laser pulses of a suitable wavelength, suitable burst pulse repetition rate and suitable burst pulse energy from said laser source to said planar glass substrate, and wherein the total amount of pulse energy or fluence, applied to said planar glass substrate at a spot where said laser pulses contact said planar glass substrate is greater than the critical energy level required to initiate and propagate photoacoustic compression machining, yet is lower than the threshold critical energy level required to initiate ablative machining; and

stopping said burst of laser pulses when said cutting has been completed.

8. A glass hard disk drive platter made by the method of claim 4.

9. A method of producing glass hard disk drive platters using laser machining, comprising the steps of:

providing a planar glass substrate;

providing a laser beam comprising a burst of laser pulses;

providing a laser beam delivery system capable of focusing said laser beam onto said planar glass substrate and to enable relative movement between said laser beam and said planar glass substrate;

focusing said laser beam relative to said planar glass substrate to form a beam waist at a location external to said planar glass substrate, said laser pulses focused such that a sufficient energy density is maintained within said planar glass substrate to form a continuous laser filament therethrough without causing optical breakdown;

creating a laser filament that pierces completely through said planar glass substrate by photoacoustic compression; and

,

moving said laser filament in circular geometric patterns in and relative to said planar glass substrate with said laser beam delivery system cutting circular hard disk drive platters from said planar glass substrate by photoacoustic compression.

10. A method of producing glass hard disk drive platters using laser machining, comprising the steps of:

providing a planar glass substrate;

providing a laser beam comprising a burst of laser pulses;

providing a laser beam delivery system capable of focusing said laser beam onto said planar glass substrate and to enable relative movement between said laser beam and said planar glass substrate in a first circular pattern and a second circular pattern;

focusing said laser beam relative to said planar glass substrate to form a beam waist at a location external to said planar glass substrate, said laser pulses focused such that a sufficient energy density is maintained within said planar glass substrate to form a continuous laser filament therethrough without causing optical breakdown;

creating a laser filament that pierces completely through said planar glass substrate by photoacoustic compression; and

,

cutting circular hard disk drive platters from said planar glass substrate.

11. The method of producing glass hard disk drive platters using laser machining, as claimed in claim 10 wherein said laser beam delivery system is:

radially adjustable enabling said first circular pattern to be cut in and through said glass substrate; and

,

radially adjustable enabling said second circular pattern to be cut in and through said glass substrate.

12. A glass hard disk drive platter made by the method of claim 10.