Flip chip dip coating encapsulant Number:7,150,390 from the United States Patent and Trademark Office (PTO) owispatent A method for underfilling and encapsulating a flip chip in one step is disclosed. The flip chip is immersed in a polymer bath to apply a coating of the polymer to the surface of the flip chip except for the distal end of the conductive projections on the flip chip electrically conductive pads. The coated flip chip is exposed to ultraviolet light or heat (e.g., IR radiation) to surface cure a skin over the polymer coating. The skin-cured flip chip is placed on a substrate which is then heated to reflow the conductive material from the projections and to cause the polymer from the coating to underfill the flip chip and thermally cure to encapsulate and underfill the flip chip.<H encapsulant, coating, Flip, chip, dip, c, 7150390.html, Patent, pto, 7150390

Title: Flip chip dip coating encapsulant

Abstract: A method for underfilling and encapsulating a flip chip in one step is disclosed. The flip chip is immersed in a polymer bath to apply a coating of the polymer to the surface of the flip chip except for the distal end of the conductive projections on the flip chip electrically conductive pads. The coated flip chip is exposed to ultraviolet light or heat (e.g., IR radiation) to surface cure a skin over the polymer coating. The skin-cured flip chip is placed on a substrate which is then heated to reflow the conductive material from the projections and to cause the polymer from the coating to underfill the flip chip and thermally cure to encapsulate and underfill the flip chip.

Patent Number: 7,150,390 Issued on 12/19/2006 to Johnson, et al.

Inventors: Johnson; Farrah J. (Boise, ID), Jiang; Tongbi (Boise, ID)
Assignee: Micron Technology, Inc. (Boise, ID)

Appl. No.: 10/298,337

Filed: November 18, 2002

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
09943481	Aug., 2001	6551863

Current U.S. Class: 228/214 ; 228/180.22; 438/118; 438/127

Current International Class: B23K 1/20 (20060101); B23K 31/02 (20060101); H01L 21/50 (20060101)

Field of Search: 228/123.1,122.1,214,180.22 438/106,108,112,118,127

References Cited [Referenced By]

U.S. Patent Documents


4724613	February 1988	Dale
5496775	March 1996	Brooks
5672393	September 1997	Bachmann et al.
5888850	March 1999	Havens et al.
5933713	August 1999	Farnworth
6063828	May 2000	Ma et al.
6100114	August 2000	Milkovich et al.
6168972	January 2001	Wang et al.
6172141	January 2001	Wong et al.
6245595	June 2001	Nguyen et al.
6248614	June 2001	Kodnani et al.
6255142	July 2001	Babiarz et al.
6365438	April 2002	Ishida et al.
6551863	April 2003	Johnson et al.
6576495	June 2003	Jiang et al.
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6615484	September 2003	Kirsten
6661104	December 2003	Jiang et al.

Primary Examiner: Edmondson; Lynne R.
Attorney, Agent or Firm: Whyte Hirschboeck Dudek SC

Parent Case Text

This application is a continuation of Ser. No. 09/943,481, filed Aug. 30, 2001, now U.S. Pat. No. 6,551,863.

Claims

What is claimed is:

1. A method for encapsulating a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chip in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

2. The method of claim 1 wherein the projections of conductive material are solder balls.

3. The method of claim 1 wherein the polymer bath is ultrasonically vibrated.

4. The method of claim 1 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

5. The method of claim 1 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

6. A method for encapsulating a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, wherein the indentations are in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is immersed in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip wherein the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

7. The method of claim 6 wherein the projections of conductive material are solder balls.

8. The method of claim 6 wherein the polymer bath is ultrasonically vibrated.

9. The method of claim 6 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

10. The method of claim 6 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

11. A method for encapsulating a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and applying ultraviolet light or heat tote coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

12. The method of claim 11 wherein the projections of conductive material are solder balls.

13. The method of claim 11 wherein the polymer bath is ultrasonically vibrated.

14. The method of claim 11 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

15. The method of claim 11 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

16. A method for encapsulating a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

17. The method of claim 16 wherein the projections of conductive material are solder balls.

18. The method of claim 16 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

19. The method of claim 16 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

20. A method for encapsulating a flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

21. The method of claim 20 wherein the projections of conductive material are solder balls.

22. The method of claim 20 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of to distance between the proximate end and the distal end of the projection.

23. The method of claim 20 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

24. A method for encapsulating a flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

25. The method of claim 24 wherein the projections of conductive material are solder balls.

26. The method of claim 24 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

27. The method of claim 24 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

28. The method of claim 24 wherein the coated flip chip is positioned on the substrate board such that the projections align with electrically conductive pads on the substrate board.

29. A method for encapsulating a flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the tip having indentations corresponding to the projections on the flip chip, wherein small holes are defined within the indentations; positioning the tip in contact with, or close proximity to, the flip chip such that the indentations align with the projections; applying a vacuum through the indentations such that the flip chip is secured to the tip and the indentations partially cover the projections; repositioning the tip such that the flip chip secured to the tip is immersed in a polymer bath, the flip chip being immersed to a point between the proximate end of the projections and the distal end of the projections such that the distal ends of the projections are not in contact with the polymer, the polymer bath being vibrated ultrasonically to facilitate wetting of the chip around the balls, the polymer bath having a viscosity sufficiently high such that the polymer is not pulled into the vacuum; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chip such that an outer layer of the coating cures to form a skin-cured coating on the flip chip.

30. The method of claim 29 wherein the projections of conductive material are solder balls.

31. The method of claim 29 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

32. The method of claim 29 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

33. A method for encapsulating a flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises solder balls attached to a surface of the flip chip, the solder balls having a distal section and having a height above the surface of the flip chip; contacting the flip chip with a pick-up tip, the pick-up tip comprising indentations adapted to fit the solder balls on the flip chip, the indentations further comprising holes in fluid communication with a vacuum source; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip and the indentations at least partially cover the distal portion of the solder balls; immersing the flip chip secured to the pick-up tip in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the solder balls, up to about one-half the height of the solder balls, extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip except for the distal ends of the solder balls; and exposing the flip chip to ultraviolet light or heat such that a portion of the polymer coating cures to form a cured outer skin.

34. The method of claim 33 wherein the projections of conductive material are solder balls.

35. The method of claim 33 wherein the flip chip is immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

36. The method of claim 33 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

37. A method for encapsulating a batch of flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chips substantially simultaneously in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips having the distal ends of the projections uncoated; and applying ultraviolet light or heat to the coated flip chips such that an outer layer of each coating cures to form a skin-cured coating on the flip chips.

38. The method of claim 37 wherein the projections of conductive material are solder balls.

39. The method of claim 37 wherein the polymer bath is ultrasonically vibrated.

40. The method of claim 37 wherein the flip chips are immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projections.

41. The method of claim 37 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

42. A method for encapsulating a batch of flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing at least one pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chips, wherein the indentations are in fluid communication with a vacuum source; positioning the at least one pick-up tip in contact with, or close proximity to, the flip chips such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chips are secured to the at least one pick-up tip; repositioning the at least one pick-up tip such that the flip chips secured to the pick-up tip are substantially simultaneously immersed in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips wherein the distal ends of the projections are uncoated; and applying ultraviolet light or heat to the coated flip chips such that an outer layer of the coatings cure to form a skin-cured coating on the flip chip.

43. The method of claim 42 wherein the projections of conductive material are solder balls.

44. The method of claim 42 wherein the polymer bath is ultrasonically vibrated.

45. The method of claim 42 wherein the flip chips are immersed in the polymer bath to a point approximately one-half of the distance between the proximate end and the distal end of the projection.

46. The method of claim 42 wherein the projections of conductive material are in contact with electrically conductive pads on the flip chip.

47. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chip in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections uncoated; and curing a portion of the polymer coating.

48. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chip in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

49. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, wherein the indentations are in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is immersed in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip wherein the distal ends of the projections are uncoated; and partially curing the polymer coating.

50. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, wherein the indentations are in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is immersed in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

51. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and curing a portion of the polymer coating.

52. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

53. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and partially curing the polymer coating.

54. A method for forming a coated flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

55. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and partially curing the polymer coating.

56. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

57. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and partially curing the polymer coating.

58. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

59. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the tip having indentations corresponding to the projections on the flip chip, wherein small holes are defined within the indentations; positioning the tip in contact with, or close proximity to, the flip chip such that the indentations align with the projections; applying a vacuum through the indentations such that the flip chip is secured to the tip and the indentations partially cover the projections; repositioning the tip such that the flip chip secured to the tip is immersed in a polymer bath, the flip chip being immersed to a point between the proximate end of the projections and the distal end of the projections such that the distal ends of the projections are not in contact with the polymer, the polymer bath being vibrated ultrasonically to facilitate wetting of the chip around the balls, the polymer bath having a viscosity sufficiently high such that the polymer is not pulled into the vacuum; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and partially curing the polymer coating.

60. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the tip having indentations corresponding to the projections on the flip chip, wherein small holes are defined within the indentations; positioning the tip in contact with, or close proximity to, the flip chip such that the indentations align with the projections; applying a vacuum through the indentations such that the flip chip is secured to the tip and the indentations partially cover the projections; repositioning the tip such that the flip chip secured to the tip is immersed in a polymer bath, the flip chip being immersed to a point between the proximate end of the projections and the distal end of the projections such that the distal ends of the projections are not in contact with the polymer, the polymer bath being vibrated ultrasonically to facilitate wetting of the chip around the balls, the polymer bath having a viscosity sufficiently high such that the polymer is not pulled into the vacuum; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

61. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises solder balls attached to a surface of the flip chip, the solder balls having a distal section and having a height above the surface of the flip chip; contacting the flip chip with a pick-up tip, the pick-up tip comprising indentations adapted to fit the solder balls on the flip chip, the indentations further comprising holes in fluid communication with a vacuum source; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip and the indentations at least partially cover the distal portion of the solder balls; immersing the flip chip secured to the pick-up tip in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the solder balls, up to about one-half the height of the solder balls, extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip except for the distal ends of the solder balls; and partially curing the polymer coating.

62. A method for forming a coated flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip situated thereon, wherein the flip chip comprises solder balls attached to a surface of the flip chip, the solder balls having a distal section and having a height above the surface of the flip chip; contacting the flip chip with a pick-up tip, the pick-up tip comprising indentations adapted to fit the solder balls on the flip chip, the indentations further comprising holes in fluid communication with a vacuum source; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip and the indentations at least partially cover the distal portion of the solder balls; immersing the flip chip secured to the pick-up tip in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the solder balls, up to about one-half the height of the solder balls, extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip except for the distal ends of the solder balls; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured, thereby forming a coated chip.

63. A method for forming a batch of coated flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chips substantially simultaneously in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips having the distal ends of the projections uncoated; and partially curing the polymer coating.

64. A method for forming a batch of coated flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chips substantially simultaneously in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips having the distal ends of the projections uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

65. A method for forming a batch of coated flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing at least one pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chips, wherein the indentations are in fluid communication with a vacuum source; positioning the at least one pick-up tip in contact with, or close proximity to, the flip chips such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chips are secured to the at least one pick-up tip; repositioning the at least one pick-up tip such that the flip chips secured to the pick-up tip are substantially simultaneously immersed in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips having the distal ends of the projections are uncoated; and partially curing the polymer coating.

66. A method for forming a batch of coated flip chips, the method comprising the steps of: providing two or more flip chips, each flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing at least one pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chips, wherein the indentations are in fluid communication with a vacuum source; positioning the at least one pick-up tip in contact with, or close proximity to, the flip chips such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chips are secured to the at least one pick-up tip; repositioning the at least one pick-up tip such that the flip chips secured to the pick-up tip are substantially simultaneously immersed in a polymer bath, wherein the polymer bath covers the flip chips and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chips from the polymer bath such that a coating of polymer adheres to each flip chip and the part of the projections covered by the polymer bath to form coated flip chips having the distal ends of the projections are uncoated; and exposing the coated flip chip to ultraviolet light or heat such that a portion of the polymer coating is cured.

67. The method of claim 47, wherein the step of curing comprises forming a skin-cured polymer coating.

68. The method of claim 47, further comprising the steps of attaching the flip chip to a substrate and applying heat to reflow the polymer coating to full a gap between the flip chip and the substrate.

69. A method of forming a coated flip chip, comprising the steps of: providing a flip chip having conductive contacts situated on a surface of the flip chip, the contacts having an end proximate to the surface of the flip chip and a distal end; coating the conductive contacts with a polymer material such that the distal ends of the conductive contacts are uncoated with the polymer material; and partially curing the polymer coating.

70. The method of claim 69, wherein the step of coating comprises immersing the flip chip in a polymer solution.

71. The method of claim 70, further comprising ultrasonically vibrating the polymer solution.

72. The method of claim 69, wherein the step of partially curing the polymer coating comprises exposing the coating to ultraviolet light or heat.

73. The method of claim 69, wherein the polymer coating is cured to form a skin-cured coating.

74. The method of claim 69, further comprising, prior to the step of coating the conductive contacts, the step of securing the distal ends of the contacts to a pick-up device.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to semiconductor manufacturing, and more specifically to methods and apparatus for applying an encapsulant to a flip chip.

Typically, in flip chip packaging, one or more integrated circuits (IC) chips are mounted on a substrate to form an electronic substrate. Solder balls (also known as solder bumps), which are mounted on the electrical connection pads of the flip chip are aligned with the corresponding electrical connection pads on the substrate. The flip chip and the substrate are then heated to cause the solder to melt (or "reflow") and wet the electrical connection pads of the substrate. The substrate and flip chip are then cooled to solidify the solder thereby forming the desired electrical connections.

As with any IC chip mounted on a substrate surface, differences in the thermal expansion coefficients between the chip and the surface can cause stress and fatigue in these connections as the substrate is subjected to further heat/cool cycles during subsequent processing. A common method of reducing this stress, and providing better adhesion, is to fill the gap between the chip and the mounting surface with a suitable polymeric underfill resin.

Furthermore, IC chips mounted on substrates are frequently coated with a polymeric encapsulation resin to protect the IC chip from outside contamination and mechanical stress. However, separate application of the underfill and the encapsulant requires extra process steps. Additionally, the encapsulant may not be compatible with the underfill.

Known methods which apply the underfill and the encapsulant simultaneously typically require extra steps for masking the electrical contact area of the solder balls or else require etching steps to remove encapsulant from these areas. Therefore, a method for simultaneously underfilling and encapsulating an IC chip without masking or removal steps is desirable.

BRIEF SUMMARY OF THE INVENTION

In one preferred embodiment, the invention is a method for encapsulating and underfilling a flip chip, the method comprising the steps of providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; immersing the flip chip in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections uncoated; applying ultraviolet light or heat (e.g., IR radiation) to the coated flip chip such that an outer layer of the coating cures to form a skin-cured flip chip; placing the skin-cured flip chip on a substrate board to form an assembly; heating the assembly such that: (i) the conductive material forms an electrical junction between the flip chip and the substrate; (ii) the polymer from the polymer coating on the flip chip underfills and encapsulates the flip chip; and, (iii) the polymer from the coating cures.

In another preferred embodiment, the invention is a method for encapsulating and underfilling a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, wherein the indentations are in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the projections; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is immersed in a polymer bath, wherein the polymer bath covers the flip chip and part of the projections up to a point between the proximate end of the projection and the distal end of the projection; removing the flip chip from the polymer bath such that a coating of polymer adheres to the flip chip and the part of the projections covered by the polymer bath to form a coated flip chip having the distal ends of the projections are uncoated; applying ultraviolet light or heat (e.g., IR radiation) to the coated flip chip such that an outer layer of the coating cures to form a skin-cured flip chip; releasing the skin-cured flip chip from the pick-up tip; placing the skin-cured flip chip on a substrate board to form an assembly; heating the assembly such that: (i) the conductive material forms an electrical junction between the flip chip and the substrate; (ii) the polymer from the polymer coating on the flip chip underfills and encapsulates the flip chip; and, (iii) the polymer from the coating cures.

In another preferred embodiment, the invention is a method for encapsulating and underfilling a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; securing the flip chip to a pick-up tip by means of a vacuum; positioning the pick-up tip such that the flip chip attached thereto is partially immersed in a polymer bath to a level between the proximate end and the distal end of the projections; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; applying ultraviolet light or heat (e.g., IR radiation) to the coated flip chip such that an outer layer of the coating cures to form a skin-cured flip chip; releasing the skin-cured flip chip from the pick-up tip; placing the skin-cured flip chip on a substrate board to form an assembly; heating the assembly such that: (i) the conductive material forms an electrical junction between the flip chip and the substrate; (ii) the polymer from the polymer coating on the flip chip underfills and encapsulates the flip chip; and, (iii) the polymer from the coating cures.

In another preferred embodiment, the invention is a method for encapsulating and underfilling a flip chip, the method comprising the steps of: providing a flip chip having projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the pick-up tip having indentations corresponding to the projections on the flip chip, the indentations in fluid communication with a vacuum source; positioning the pick-up tip in contact with, or close proximity to, the flip chip such that the indentations align with and partially cover the solder balls; applying a vacuum through the indentations such that the flip chip is secured to the pick-up tip; repositioning the pick-up tip such that the flip chip secured to the pick-up tip is partially immersed in a polymer bath such that the immersed chip is fully wetted by the polymer, the flip chip being immersed to a point such that the pick-up tip and the distal ends of the projections extend above the polymer bath, wherein the polymer bath is ultrasonically vibrated and the polymer bath has a viscosity sufficiently high such that the polymer bath is not pulled above the desired immersion point by the vacuum securing the flip chip to the pick-up tip; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; applying ultraviolet light or heat (e.g., IR radiation) to the coated flip chip such that an outer layer of the coating cures to form a skin-cured flip chip; releasing the skin-cured flip chip from the pick-up tip; placing the skin-cured flip chip on a substrate board to form an assembly; and applying thermal energy to the assembly, wherein the thermal energy causes the solder and the polymer to flow and also cures the polymer.

In another preferred embodiment, the invention is a method for encapsulating and underfilling a flip chip, the method comprising the steps of: providing a wafer having an upper surface, the upper surface having at least one flip chip arrayed thereon, wherein the flip chip comprises projections of conductive material on one side of the flip chip, the projections having a proximate end attached to the flip chip and a distal end opposite the proximate end; providing a pick-up tip, the tip having indentations corresponding to the projections on the flip chip, wherein small holes are defined within the indentations; positioning the tip in contact with, or close proximity to, the flip chip such that the indentations align with the projections; applying a vacuum through the indentations such that the flip chip is secured to the tip and the indentations partially cover the projections; repositioning the tip such that the flip chip secured to the tip is immersed in a polymer bath, the flip chip being immersed to a point between the proximate end of the projections and the distal end of the projections such that the distal ends of the projections are not in contact with the polymer, the polymer bath being vibrated ultrasonically to facilitate wetting of the chip around the balls, the polymer bath having a viscosity sufficiently high such that the polymer is not pulled into the vacuum; removing the flip chip from the polymer bath such that a coating of the polymer remains in contact with the flip chip such that the distal ends of the projections are uncoated; applying ultraviolet light or heat (e.g., IR radiation) to the coated flip chip such that an outer layer of the coating cures to form a skin-cured flip chip; releasing the skin-cured flip chip from the pick-up tip; placing the skin-cured flip chip on a substrate board to form an assembly; and applying thermal energy to the assembly, wherein the thermal energy causes the solder and the polymer to flow and also cures the polymer to encapsulate the coated chip.

In another preferred embodiment, the