SUBSTRATE MANUFACTURE

Abstract

The invention relates to a method of forming a void with a circular cross section in a substrate, more particularly to forming through holes electronic substrates The method comprising the steps of causing a laser cutter to traverse in an arc to an intended circumference of the void, traversing the intended circumference of the void at least once, wherein the lead in from the arc to the circumference comprises a radius.

Claims

1. A method of forming a void with a circular cross section in a substrate, said method comprising: causing a laser cutter to traverse in an arc to an intended circumference of the void; and traversing the intended circumference of the void at least once; wherein the lead in from the arc to the circumference comprises a radius.

2. A method according to claim 1, wherein the laser cutter is traversed in a spiral pattern towards the circumference of the void.

3. A method according to claim 1, wherein said substrate is selected from a ceramic, polymer or composite material.

4. A method according to claim 3, wherein the ceramic is aluminium nitride.

5. A method according to claim 1, wherein said laser cutter is a carbon dioxide laser with an assist gas.

6. A method according to claim 1, wherein said laser cutter starts from the centre of the intended circumference of the void.

7. A method according to claim 1, wherein said laser cutter ends at the centre of the intended circumference of the void.

8. A method according to claim 1, wherein the intended circumference of the void is traversed in the range of from 1 to 4 times.

9. A method according to claim 1, wherein the void has an inner wall slope of between 0 and 20 degrees.

10. A method according to claim 9, wherein the void has a frustroconical shape.

11. A method according to claim 1, wherein the intended circumference of the void is traversed in the range of from 2 to 4 times.

12. A method according to claim 1, wherein the intended circumference of the void is traversed in 2 times.

13. A method according to claim 1, wherein said laser cutter starts from the centre of the intended circumference of the void, the method further comprising: at the end of a second or subsequent traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the arc and the second arc have common start and end points, and the radius connects those endpoints.

14. A method according to claim 13, wherein the arc and the second arc form an ellipse shape, and the radius is the major axis of the ellipse shape:

15. A method according to claim 1, wherein said laser cutter starts from the centre of the intended circumference of the void, the method further comprising: at the end of a final traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the arc and the second arc have common start and end points thereby forming a shape having the radius as its major axis.

16. A method according to claim 1, wherein the laser cutter starts from the centre of the intended circumference of the void and is traversed in a spiral pattern towards the circumference of the void, the spiral including the arc, the method further comprising: at the end of the second traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the spiral and the second arc have common start and end points.

17. A method according to claim 1, wherein the laser cutter starts from the centre of the intended circumference of the void and is traversed in a spiral pattern towards the circumference of the void, the spiral including the arc, the method further comprising: at the end of the second or subsequent traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the spiral and the second arc have common start and end points.

18. A method according to claim 1, wherein said laser cutter starts from the centre of the intended circumference of the void, the method further comprising: at the end of a final traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the spiral and the second arc have common start and end points.

19. A method of forming a void with a circular cross section in a substrate, said method comprising: causing a laser cutter to traverse in a first arc from the center of the void arc to an intended circumference of the void; traversing the intended circumference of the void 2 or more times with the laser cutter; and at the end of a final traversal of the intended circumference, causing the laser cutter to traverse in a second arc back to the centre; wherein the first arc and the second arc have common start and end points.

20. The method of claim 19, wherein the circular void inner wall is a frustroconical shape, having an angle in the range from up to 20 degrees, with respect to the axis which is perpendicular to an upper surface of the substrate.

Description

[0025] Exemplary embodiments of the device in accordance with the invention will now be described with reference to the accompanying drawings in which:

[0026] FIG. 1a: Is a schematic of the path taken by the laser cutter during void creation.

[0027] FIG. 1b: Is an alternative schematic of the path taken by the laser cutter during void creation.

[0028] FIG. 2: Is a cross-section of the void creation showing void walls and possible shape.

[0029] Referring to FIG. 1a there is shown a top view of a section of a substrate 16 with a laser cutter 10 focused at the centre of the intended circumference 14a. The void 14 is created by moving the laser cutter 10 from the centre 13 of the substrate 16 in an arc 12a to the intended circumference 14a of the intended void 14. The moving laser cutter 10a travels in a circular fashion around the intended circumference 14a of the void 14, on a cutting path 12. The moving laser cutter 10a travels on the cutting path 12 for a second pass before returning in an arc 12b to the centre of the created void 14.

[0030] Referring to FIG. 1b there is shown a top view of a section of substrate 16 with a laser cutter 10 focused at the centre of the intended circumference 14a. The void 14 is created by moving the laser cutter 10 from the centre 13 of the void 14 in a spiral cutting path 12c to the intended circumference 14a of the intended void 14. The moving laser cutter 10a travels in a circular fashion around the intended circumference 14a of the intended void 14, on a cutting path 12. The moving laser cutter 10a travels on the cutting path 12 for a second pass before returning in an arc 12b to the centre of the intended void 14.

[0031] Referring to FIG. 2 there is shown a cross section of substrate 26 with a laser cutter 20 originally from a laser 21 and an assist gas tube 28 providing a flow of an assist gas 29 following a path of the intended circumference 24a of the intended void 24. The laser cutter 21 is perpendicular to the substrate 26 but focused to create the intended void 24 with a sloping void wall 27 within an acceptable tolerance 27a.