LASER-BASED MATERIAL PROCESSING APPARATUS AND METHODS

• US 20110240617A1
• Filed: 03/01/2011
• Published: 10/06/2011
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Shah, Lawrence, Sohn, Jin Young, Cho, Gyu Cheon, Xu, Jingzhou
• Granted Patent: US 9,321,126 B2
• Time in Patent Office: Days
• US Class Current: 219/121.72
• CPC Class Codes: B23K 2103/16 Composite materials , e.g. fibre reinforced
• CPC Class Codes: B23K 26/00 Working by laser beam, e.g. welding, cutting or boring
• CPC Class Codes: B23K 26/0624 using ultrashort pulses, i.e. pulses of 1ns or less
• CPC Class Codes: B23K 26/38 by boring or cutting
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

Various embodiments may be used for laser-based modification of target material of a workpiece while advantageously achieving improvements in processing throughput and/or quality. Embodiments of a method of processing may include focusing and directing laser pulses to a region of the workpiece at a pulse width sufficiently short so that material is efficiently removed by nonlinear optical absorption from the region and a quantity of heat affected zone and thermal stress on the material within the region, proximate to the region, or both is reduced relative to a quantity obtainable using a laser with longer pulses. In at least one embodiment, an ultrashort pulse laser system may include at least one of a fiber amplifier or fiber laser. Various embodiments are suitable for at least one of dicing, cutting, scribing, and forming features on or within a composite material.

Claims

1. A method of scribing, dicing, cutting, or processing to remove material from a region of a workpiece having a composite material comprising at least two non-metallic materials having different optical properties, said method comprising:

directing laser pulses toward said composite material of said workpiece, the laser pulses having at least one pulse width in the range from tens of femtoseconds to about 500 picoseconds and a pulse repetition rate in the range from a few tens of kHz to about 10 MHz;

focusing said laser pulses into laser spots having spot sizes (1/e²) in a range from a few microns to about 100 μ

m, wherein at least one said laser pulse provides a power density above a threshold for nonlinear absorption in said composite material at a wavelength of said at least one laser pulse; and

positioning said laser spots relative to said workpiece in such a way that a spatial overlap between adjacent focused spots (1/e²) for removal of said composite material is sufficient for scribing, dicing, cutting or processing said workpiece at said wavelength, pulse width, repetition rate, and power density,

wherein said method controls heat accumulation within one or more materials of said workpiece region, while limiting accumulation of unwanted material about said region.

2. The method of claim 1, wherein said composite material of said workpiece comprises a material structure and its host material.

3. The method of claim 1, wherein said workpiece further comprises non-composite material disposed in contact with said composite material, and said method further comprises removing at least a portion of said non-composite material.

4. The method of claim 3, wherein said non-composite material comprises metal.

5. The method of claim 3, wherein said non-composite material comprises a polymer.

6. The method of claim 1, wherein an energy density of a pulse impinging said non-composite material is above a single shot ablation threshold corresponding to linear absorption at the wavelength.

7. The method of claim 1, wherein said wavelength is in a range from about 0.5 μ

m to about 2 μ

m.

8. The method of claim 1, wherein said wavelength is in a range from about 1 μ

m to about 1.5 μ

m.

9. The method of claim 1, wherein said wavelength is in a range from about 0.9 μ

m to about 1.1 μ

m.

10. The method of claim 1, wherein said workpiece further comprises at least two layers of non-composite material, and said composite material is disposed between said at least two layers of non-composite material, and said method further comprises removing at least a portion of said non-composite material from at least one layer of the non-composite material.

11. The method of claim 1, wherein a thickness of said workpiece is less than about 1000 μ

m.

12. The method of claim 1, wherein a fluence of at least one pulse is in a range from about 0.01 J/cm² to about 10 J/cm², and said positioning comprises moving said composite material relative to said focused spots at a speed in the range from about 1 mm/sec to about 0.5 m/sec.

13. The method of claim 1, wherein at least one laser pulse has a pulse energy in a range from about 0.1 μ

J to about 500 μ

J, wherein said pulse energy is determined, at least in part, by said spot size and said repetition rate.

14. The method of claim 1, wherein said laser pulses are output by an ultrashort pulsed laser system.

15. The method of claim 1, wherein said power density is at least about 10¹² W/cm².

16. The method of claim 1, wherein said power density is in the range from about 10¹² W/cm² to about 10¹⁴ W/cm².

17. The method of claim 1, wherein a pulse width in the range from tens of femtoseconds to about 1 ps.

18. The method of claim 1, wherein said pulses comprise a series of pulses and at least two corresponding laser spots have a spatial overlap of at least about 50%, wherein said series of pulses provide depthwise removal of about 30-300 μ

m when positioned to impinge at least a portion of said composite material of said workpiece, wherein said spot sizes are in the range from about 10-100 μ

m.

19. The method of claim 2, wherein said material structure and its host material enhances a mechanical property of said workpiece.

20. The method of claim 19, wherein said mechanical property comprises rigidity of the workpiece.

21. The method of claim 2, wherein said material structure and its host material comprises a woven glass.

22. The method of claim 2, wherein said material structure and its host material comprises matte glass.

23. The method of claim 2, wherein said material structure and its host material comprise cotton paper.

24. The method of claim 2, wherein said host material comprises epoxy.

25. The method of claim 2, wherein said host material comprises polymer.

26. The method of claim 1, wherein said composite material of said workpiece is selected from the group consisting of FR-4, FR-5, FR-6, G-10, CEM-1, CEM-2, CEM-3, CEM-4, and CEM-5.

27. The method of claim 1, wherein said composite material of said workpiece is selected from the group consisting of (a) woven glass and epoxy, (b) matte glass and polyester, (c) cotton paper and epoxy, and (d) woven glass and polyester.

28. The method of claim 1, wherein said workpiece comprises a printed circuit board.

29. The method of claim 1, wherein a patterned metal layer is deposited on said workpiece.

30. The method of claim 1, wherein said workpiece comprises a thin layer of polymer for protecting said composite material of said workpiece.

31. The method of claim 1, wherein said workpiece comprises a layer of low-k material.

32. The method of claim 1, wherein the energy density of a laser pulse impinging said composite material of said workpiece is less than a single-shot ablation threshold corresponding to linear absorption at the laser wavelength, and said energy density reduces or avoids heat accumulation in said composite material.

33-44. -44. (canceled)

45. A method of processing a workpiece having a composite material comprising at least two different materials with different properties and functionalities, said different materials comprising at least one of a dielectric material and a metal material, said method comprising:

irradiating said composite material of said workpiece with a series of laser pulses, at least two pulses of the series having different characteristics that are applied to different materials of said workpiece, said series of laser pulses comprising at least one pulse providing a power density above a threshold for nonlinear absorption at a wavelength of said at least one laser pulse; and

controlling heat-affected zone (HAZ) such that at least one HAZ generated during removal of at least one of the dielectric material and the metal material is increased depthwise relative to at least one HAZ generated during removal of a portion of said composite material of said workpiece.

46. A laser-based system for scribing, dicing, cutting, or processing a workpiece having a composite material comprising at least two different materials with different properties and functionalities, the laser-based system comprising:

a source of optical pulses, at least one pulse having a wavelength longer than a linear absorption edge of said composite material of said workpiece;

an optical amplification system configured to amplify a pulse from said source to a pulse energy of at least about 1 μ

J and to generate output optical pulses having at least one pulse width in a range from about 10 fs to a few hundred picoseconds;

a modulation system, comprising at least one optical modulator, configured to adjust a repetition rate of said output optical pulses to be within a range from a few kHz to about 10 MHz;

a beam delivery system configured to focus and deliver pulsed laser beams to the workpiece, wherein a pulsed beam is focused into a spot size (1/e²) in a range from about 10 μ

m to about 100 μ

m, said focused beam providing a peak power density above a threshold for nonlinear absorption at a wavelength of said laser pulse;

a positioning system configured to position said beams relative to said workpiece at a rate in a range from about 1 mm/sec to about 20 m/sec; and

a controller configured to be coupled to at least said positioning system, said controller configured to control a spatial overlap between adjacent focused beams during processing of the workpiece at said repetition rate.

47-76. -76. (canceled)