Solder pillar bumping and a method of making the same
View Patent ↗A method of forming flip chip bumps includes forming a plurality of metallization pads on a die. In another step, a structured layer having pores is formed on the die and metallization pads where the pads on the die are exposed through the pores. In yet another step, the die is transferred to a chamber having a liquid metal bath. In another step, a first pressure is created within the chamber followed by dipping the die in the liquid metal bath. In another step, a second pressure is created within the chamber such that liquid metal fills portions of the pores thereby forming metal pillars connected to the pads.
1. A method of forming a flip chip bump, the method comprising:
forming a plurality of metallization pads on a die;
forming a structured layer having pores on the die and metallization pads, thereby exposing the pads on the die through the pores;
transferring the die to a chamber having a liquid metal bath therein;
creating a first pressure within the chamber;
dipping the die in the liquid metal bath; and
creating a second pressure within the chamber such that liquid metal fills portions of the pores thereby forming metal pillars connected to the pads.
2. The method of claim 1 further comprising removing the structured layer.
3. The method of claim 1 further comprising preheating the semiconductor to a desired temperature.
4. The method of claim 1 further comprising:
removing portions of the structured layer such that a portion of the metal pillars is exposed; and
forming a solder sphere from the exposed portion of the metal pillars.
5. The method of claim 1 further comprising:
forming a low melting point solder cap on the metal pillars;
melting the solder cap to form a solder sphere; and
removing the structured layer.
6. The method of claim 1 further comprising:
removing the structured layer; and
melting the metal pillar to form a solder sphere on the metallization pad.
7. The method of claim 1 further comprising:
forming the structured layer to have a free standing area thereby exposing areas of the die without pads; and
removing portions of the structured layer such that a portion of the metal pillars is exposed.
8. The method of claim 1 further comprising:
forming a second structured layer having pores on the first structured layer such that the second structured layer pores are aligned with the first structured layer pores, thereby exposing the pads on the die through both sets of pores, the second structured layer pores having a different diameter than the first structured layer pores; and
removing a portion of the second structured layer such that a portion of the metal pillars is exposed.
9. The method of claim 1 further comprising planarizing the combined layer of metal pillars and structured layer.
10. The method of claim 1 wherein the metal comprises at least one of the following materials: tin (Sn), lead (Pb), copper (Cu), silver (Ag), bismuth (Bi), indium (In), and antimony (Sb).
11. The method of claim 1 wherein the metallization pads comprise at least one of the following materials: copper (Cu), nickel (Ni), gold, (Au), and aluminum (Al).
12. The method of claim 1 wherein the structured layer comprises at least one of the following materials: SU-8, epoxy, silicone, silica epoxy based photoresist, polymer resist, silicone backbone resist, PMMA, benzocyclobutene and silica.
13. The method of claim 1 wherein the forming the structured layer step comprises:
forming a layer of photosensitive material on the die and metallization pads;
exposing the layer of photosensitive material to radiation at predetermined areas corresponding to the pads; and
removing portions of the layer that are exposed to radiation to form pores in the layer, thereby exposing the pads on the die through the pores.
14. The method of claim 1 wherein the aspect ratio of the metal pillars is at least about 1.
15. The method of claim 1 wherein the aspect ratio of the metal pillars is at least about 5.
16. The method of claim 1 wherein the aspect ratio of the metal pillars is at least about 10.
17. The method of claim 1 wherein the die comprises at least one of the following materials: semiconductor, glass, ceramic, and polymer.
18. A method of assembling a semiconductor package, the method comprising:
forming a plurality of metallization pads on a die;
forming a structured layer having pores on the die and metallization pads, thereby exposing the pads on the die through the pores;
transferring the die to a chamber having a liquid metal bath therein;
creating a first pressure within the chamber;
dipping the die in the liquid metal bath;
creating a second pressure within the chamber such that liquid metal fills portions of the pores thereby forming metal pillars connected to the pads;
removing at least a portion of the structured layer;
placing the die on a second component having a respective solder depot on each of a plurality of metallization pads such that the pillars are aligned with the solder depots; and
connecting the pillars to the solder depots.
19. The method of claim 18 further comprising preheating the die to a desired temperature.
20. The method of claim 18 further comprising planarizing the combined layer of metal pillars and structured layer.
21. The method of claim 18 wherein the forming the structured layer step comprises:
forming a layer of photosensitive material on the die and metallization pads;
exposing the layer of photosensitive material to radiation at predetermined areas corresponding to the pads; and
removing portions of the layer that are exposed to radiation to form pores in the layer, thereby exposing the pads on the die through the pores.
22. The method of claim 18 further comprising planarizing the combined layer of metal pillars and structured layer.
23. The method of claim 21 further comprising encapsulating the die.
24. The method of claim 18 further comprising forming an undermold between the die and the second component.
25. The method of claim 18 further comprising forming a liquid underfill between the die and the second component.
26. The method as in claim 18 wherein the second component comprises a substrate.
27. The method as in claim 18 where in the second component comprises a die.
28. The method of claim 18 wherein the metal comprises at least one of the following materials: tin (Sn), lead (Pb), copper (Cu), silver (Ag), bismuth (Bi), indium (In), and antimony (Sb).
29. The method of claim 18 wherein the metallization pads comprise at least one of the following materials: copper (Cu), nickel (Ni), gold, (Au), and aluminum (Al).
30. The method of claim 18 wherein the structured layer comprises at least one of the following materials: epoxy based photoresist, polymer resist, silicone backbone resist, PMMA, benzocyclobutene (BCB) and silica.
31. The method of claim 18 wherein the aspect ratio of the metal pillars is at least about 1.
32. The method of claim 18 wherein the aspect ratio of the metal pillars is at least about 5.
33. The method of claim 18 wherein the aspect ratio of the metal pillars is at least about 10.
34. The method of claim 1 wherein the die comprises at least one of the following materials: semiconductor, glass, ceramic, and polymer.
35. A method of assembling a semiconductor package, the method comprising:
forming a plurality of metallization pads on a die;
forming a structured layer having pores on the die and metallization pads, thereby exposing the pads on the die through the pores;
transferring the die to a chamber having a liquid metal bath therein;
creating a first pressure within the chamber;
dipping the die in the liquid metal bath;
creating a second pressure within the chamber such that liquid metal fills portions of the pores thereby forming metal pillars connected to the pads;
forming a respective solder sphere on an end of each of the metal pillars;
placing the die on a second component having a plurality of metallization pads such that the solder spheres are aligned with the metallization pads of the second component; and
connecting the solder spheres to the metallization pads of the second component.
36. The method of claim 35 further comprising preheating the die to a desired temperature.
37. The method of claim 35 wherein the forming the structured layer step comprises:
forming a layer of photosensitive material on the die and metallization pads;
exposing the layer of photosensitive material to radiation at predetermined areas corresponding to the pads; and
removing portions of the layer that are exposed to radiation to form pores in the layer, thereby exposing the pads on the die through the pores.
38. The method of claim 35 wherein the forming a solder sphere step comprises:
removing portions of the structured layer such that a portion of the metal pillars is exposed; and
forming a solder sphere on an end of the exposed metal pillars.
39. The method of claim 35 wherein the forming a solder sphere step comprises:
forming a low melting point solder cap on the metal pillars; and
melting the solder cap to form a solder sphere.
40. The method of claim 35 further comprising planarizing the combined layer of metal pillars and structured layer.
41. The method of claim 35 further comprising encapsulating the die.
42. The method of claim 35 further comprising forming an undermold between the die and the second component.
43. The method of claim 35 further comprising forming a liquid underfill between the die and the second component.
44. The method as in claim 35 wherein the second component comprises a substrate.
45. The method as in claim 35 wherein the second component comprises a die.
46. The method of claim 35 wherein the metal comprises at least one of the following materials: tin (Sn), lead (Pb), copper (Cu), silver (Ag), bismuth (Bi), indium (In), and antimony (Sb).
47. The method of claim 35 wherein the metallization pads comprise at least one of the following materials: copper (Cu), nickel (Ni), gold, (Au), and aluminum (Al).
48. The method of claim 35 wherein the structured layer comprises at least one of the following materials: epoxy based photoresist, polymer resist, silicone backbone resist, PMMA, benzocyclobutene and silica.
49. The method of claim 35 wherein the aspect ratio of the metal pillars is at least about 1.
50. The method of claim 35 wherein the aspect ratio of the metal pillars is at least about 5.
51. The method of claim 35 wherein the aspect ratio of the metal pillars is at least about 10.
52. The method of claim 35 wherein the die comprises at least one of the following materials: semiconductor, glass, ceramic, and polymer.
53. A method of assembling a semiconductor package, the method comprising:
forming a plurality of metallization pads on a die;
forming a structured layer having pores on the die and metallization pads thereby exposing the pads on the die through the pores;
transferring the die to a chamber having a liquid metal bath therein;
creating a first pressure within the chamber;
dipping the die in the liquid metal bath;
creating a second pressure within the chamber such that liquid metal fills portions of the pores thereby forming metal pillars connected to the pads;
removing portions of the structured layer such that a portion of the metal pillars is exposed;
placing the die on a second component having a plurality of metallization pads such that the metal pillars are aligned with the metallization pads of the second component; and
connecting the metal pillars to the metallization pads of the second component.
54. The method of claim 53 further comprising preheating the die to a desired temperature.
55. The method of claim 53 wherein the forming the structured layer step comprises:
forming a layer of photosensitive material on the die and metallization pads;
exposing the layer of photosensitive material to radiation at predetermined areas corresponding to the pads; and
removing portions of the layer that are exposed to radiation to form pores in the layer, thereby exposing the pads on the die through the pores.
56. The method of claim 53 further comprising planarizing the combined layer of metal pillars and structured layer.
57. The method of claim 53 further comprising encapsulating the die.
58. The method of claim 53 further comprising forming an undermold between the die and the second component.
59. The method of claim 53 further comprising forming a liquid underfill between the die and the second component.
60. The method of claim 53 wherein the second component comprises a substrate.
61. The method of claim 53 wherein in the second component comprises a die.
62. The method of claim 53 wherein the metal comprises at least one of the following materials: tin (Sn), lead (Pb), copper (Cu), silver (Ag), bismuth (Bi), indium (In), and antimony (Sb).
63. The method of claim 53 wherein the metallization pads comprise at least one of the following materials: copper (Cu), nickel (Ni), gold, (Au), and aluminum (Al).
64. The method of claim 53 wherein the structured layer comprises at least one of the following materials: epoxy based photoresist, polymer resist, silicone backbone resist, PMMA, benzocyclobutene and silica.
65. The method of claim 53 wherein the aspect ratio of the metal pillars is at least about 1.
66. The method of claim 53 wherein the aspect ratio of the metal pillars is at least about 5.
67. The method of claim 53 wherein the aspect ratio of the metal pillars is at least about 10.
68. The method of claim 53 further comprising:
forming the structured layer to have a free standing area thereby exposing areas of the die without pads.
69. The method of claim 53 further comprising:
forming a second structured layer having pores on the first structured layer such that the second structured layer pores are aligned with the first structured layer pores, thereby exposing the pads on the die through both sets of pores, the second structured layer pores having a different diameter than the first structured layer pores; and
removing portions of the second structured layer such that a portion of the metal pillars is exposed.
70. The method of claim 53 wherein the die comprises at least one of the following materials: semiconductor, glass, ceramic, and polymer.