Process and system for quality management and analysis of via drilling

• US 20080011715A1
• Filed: 07/11/2006
• Published: 01/17/2008
• Est. Priority Date: 07/11/2006
• Status: Active Grant

• Current Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Original Assignee: Electro Scientific Industries Incorporated (MKS Instruments Incorporated)
• Inventors: Baldwin, Leo, Matsumoto, Hisashi, Singer, Mark, Howerton, Jeffrey E., Childers, David V.
• Granted Patent: US 7,544,304 B2
• Time in Patent Office: Days
• US Class Current: 216/59
• CPC Class Codes: B23K 2101/42 Printed circuits
• CPC Class Codes: B23K 26/03 Observing, e.g. monitoring, the workpiece
• CPC Class Codes: B23K 26/06 Shaping the laser beam, e.g. by masks or multi-focusing
• CPC Class Codes: B23K 26/389 of fluid openings, e.g. nozzles, jets laser machining of inkjet nozzles B41J2/1634
• CPC Class Codes: H05K 1/0269 for visual or optical inspection
• CPC Class Codes: H05K 2201/09454 Inner lands, i.e. lands around via or plated through-hole in internal layer of multilayer PCB
• CPC Class Codes: H05K 2203/163 Monitoring a manufacturing process
• CPC Class Codes: H05K 3/0035 of blind holes, i.e. having a metal layer at the bottom

Abstract

A process for laser forming a blind via in at least one layer of a circuit substrate having a plurality of capture pads of varying geometry can include, for at least one blind via to be formed in at least one layer of a circuit substrate, evaluating a capture pad geometry value (such as area and/or volume) within a predetermined distance from a drilling location with respect to a blind via geometry value (such as area and/or volume) to be formed at the drilling location. The process can include setting at least one laser operating parameter based on the evaluation in order to obtain a desired capture pad appearance after blind via formation. The process can include imaging a capture pad area defined as an area within a predetermined distance from a blind via drilling location in at least one layer of a circuit substrate, quantifying at least one appearance value for the imaged capture pad area, and determining an acceptability of the imaged capture pad areas based on the quantified appearance value.

Claims

1. A process for laser forming a blind via in at least one layer of a circuit substrate having a plurality of capture pads of varying geometry comprising:

for at least one blind via to be formed in at least one layer of a circuit substrate, evaluating a capture pad geometry value within a predetermined distance from a drilling location with respect to a blind via geometry value to be formed at the drilling location; and

setting at least one laser operating parameter based on a result of the evaluation in order to obtain a desired capture pad appearance after blind via formation.

2. The process of claim 1, wherein the at least one laser process parameter to be set is selected from a group consisting of laser fluence, number of laser pulses, laser pulse width, and any combination thereof.

3. The process of claim 1 further comprising:

comparing a given drill layer to an adjacent drill layer to determine if blind vias are stacked from layer to layer.

4. The process of claim 1 further comprising:

defining a drill layer;

defining a scan area adjacent a drill location in the defined drill layer;

defining a set of ratio ranges, wherein the ratio is defined as the capture pad geometry value within the predetermined distance from the drilling location to the blind via geometry value to be formed at the drilling location; and

selecting a destination layer for drill tools corresponding to each set ratio range.

5. The process of claim 1 further comprising:

analyzing a capture pad appearance after blind via formation.

6. The process of claim 5, wherein analyzing a capture pad appearance after blind via formation further comprises:

imaging a capture pad area defined as an area within a predetermined distance from a blind via drilling location in at least one layer of a circuit substrate;

quantifying an appearance value for the imaged capture pad area; and

determining acceptability of the imaged capture pad area based on the quantified appearance value.

7. The process of claim 6, wherein quantifying the appearance value further comprises:

quantifying a numeric appearance value for the imaged capture pad area to minimize subjectivity in a quality judgment of a laser-formed blind via in the imaged capture pad area.

8. The process of claim 6, wherein quantifying the appearance value further comprises:

performing a fractal dimension analysis on the imaged capture pad area to obtain a numerical value for fractal dimension, where a higher value corresponds to a subjective “

matt”

surface texture and a lower value corresponds to a subjective “

shiny”

surface texture for the imaged capture pad area.

9. The process of claim 6, wherein quantifying the appearance value further comprises:

performing a histogram analysis on the imaged capture pad area to obtain a numerical value for symmetry between populations in the histogram, wherein a value approximating unity corresponds to a subjective “

matt”

surface texture, a value smaller than unity corresponds to a subjective “

shiny”

surface texture, and a value greater than unity corresponds to a subjective “

dark”

surface texture.

10. The process of claim 6, wherein quantifying the appearance value further comprises:

performing a histogram analysis and a fractal dimension analysis on the imaged capture pad area to quantify a numeric appearance value for the imaged capture pad area.

11. The process of claim 6, wherein determining acceptability of the imaged capture pad area based on the quantified appearance value further comprises:

analyzing a relationship between the ratio of capture pad geometry value to blind via geometry value with respect to the quantified appearance value for a plurality of imaged capture pad areas to minimize variance in quality of formed blind via over an entire circuit pattern.

12. The process of claim 11 further comprising:

adjusting at least one laser process parameter based on feedback from the relationship between the ratio of capture pad geometry value to blind via geometry value corresponding to the quantified appearance value for a plurality of imaged capture pad areas with a laser-formed blind via located in the imaged capture pad area.

13. The process of claim 5, wherein setting at least one laser parameter further comprises:

adjusting at least one laser process parameter based on feedback from a relationship between the ratio of capture pad geometry value to blind via geometry value corresponding to an analyzed capture pad appearance for a plurality of capture pad areas with laser-formed blind via located in the plurality of capture pad areas.

14. The process of claim 1, wherein evaluating a capture pad geometry value within a predetermined distance from a drilling location with respect to a blind via geometry value to be formed at the drilling location for at least one blind via to be formed in at least one layer of a circuit substrate further comprises:

calculating a ratio of the capture pad geometry value within the predetermined distance from the drilling location with respect to the blind via geometry value to be formed at the drilling location for each blind via to be formed in at least one layer of the circuit substrate.

15. A process for laser forming a blind via in at least one layer of a circuit substrate having a plurality of capture pads of varying geometry comprising:

imaging a capture pad area defined as an area within a predetermined distance from a blind via drilling location in at least one layer of a circuit substrate;

quantifying an appearance value for the imaged capture pad area; and

determining acceptability of the imaged capture pad area based on the quantified appearance value.

16. The process of claim 15, wherein imaging the capture pad area further comprises:

imaging a capture pad area with a laser-formed blind via located in the capture pad area.

17. The process of claim 15, wherein quantifying the appearance value further comprises:

quantifying a numeric appearance value for the imaged capture pad area to minimize subjectivity in a quality judgment of a laser-formed blind via in the imaged capture pad area.

18. The process of claim 15, wherein quantifying the appearance value further comprises:

performing a fractal dimension analysis on the imaged capture pad area to obtain a numerical value for fractal dimension, where a higher value corresponds to a subjective “

matt”

surface texture and a lower value corresponds to a subjective “

shiny”

surface texture for the imaged capture pad area.

19. The process of claim 15, wherein quantifying the appearance value further comprises:

performing a histogram analysis on the imaged capture pad area to obtain a numerical value for symmetry between populations in the histogram, wherein a value approximating unity corresponds to a subjective “

matt”

surface texture, a value smaller than unity corresponds to a subjective “

shiny”

surface texture, and a value greater than unity corresponds to a subjective “

dark”

surface texture.

20. The process of claim 15, wherein quantifying the appearance value further comprises:

performing a histogram analysis and a fractal dimension analysis on the imaged capture pad area to quantify a numeric appearance value for the imaged capture pad area.

21. The process of claim 15, wherein determining acceptability of the imaged capture pad area based on the quantified appearance value further comprises:

analyzing a relationship between a ratio of capture pad geometry value to blind via geometry value with respect to the appearance value for a plurality of imaged capture pad areas to minimize variance in quality of formed blind via over an entire circuit pattern.

22. The process of claim 21 further comprising:

optimizing at least one laser process parameter based on the relationship between the ratio of capture pad geometry value to blind via geometry value with respect to the appearance value for a plurality of imaged capture pad areas with a laser-formed blind via located in the imaged capture pad area.

23. The process of claim 15 further comprising:

optimizing at least one laser process parameter based on a relationship between a ratio of capture pad geometry value to blind via geometry value with respect to the appearance value for a plurality of imaged capture pad areas with a laser-formed blind via located in the imaged capture pad area.

24. The process of claim 23, wherein the at least one laser process parameter to be optimized is selected from a group consisting of laser fluence, number of laser pulses, laser pulse width, and any combination thereof.

25. The process of claim 23 further comprising:

comparing a given drill layer to an adjacent drill layer to determine if blind vias are stacked from layer to layer.

26. The process of claim 15 further comprising:

defining a drill layer;

defining a scan area adjacent a drill location;

defining a set of ratio ranges, wherein the ratio is defined as the capture pad geometry value to blind via geometry value to be formed in the capture pad area; and

selecting a destination layer for drill tools corresponding to each set ratio range.

27. The process of claim 15 further comprising:

for at least one blind via to be formed in at least one layer of a circuit substrate, evaluating a capture pad geometry value within a predetermined distance from a drilling location with respect to a blind via geometry value to be formed at the drilling location.

28. The process of claim 27, wherein evaluating a capture pad geometry value within a predetermined distance from a drilling location with respect to a blind via geometry value to be formed at the drilling location for at least one blind via to be formed in at least one layer of a circuit substrate further comprises:

calculating a ratio of the capture pad geometry value within the predetermined distance from the drilling location with respect to the blind via geometry value to be formed at the drilling location for each blind via to be formed in at least one layer of the circuit substrate.

29. The process of claim 27 further comprising:

setting at least one laser operating parameter based on results of the evaluation in order to obtain a desired capture pad appearance after blind via formation.

30. The process of claim 15 further comprising:

setting at least one laser operating parameter based on the quantified appearance value in order to obtain a desired capture pad appearance after blind via formation.