Process for forming cone shaped solder for chip interconnection
First Claim
1. A process for forming non-spherical shapes in solder interconnects on the surface of a substrate or a semiconductor die comprising the steps of:
- a)depositing a first layer of solder onto a surface;
b)plating a second layer of solder over said first layer of solder; and
c)forming said first and second layers of solder into a non-spherical shape wherein the non-spherical shape of said solder interconnects facilitate joining between two surfaces.
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Abstract
A method of forming non-spherically shaped solder interconnects, preferably conical, for attachment of electronic components in an electronic module. Preferably, the solder interconnects of the present invention are cone shaped and comprise of depositing a first solder followed by a second solder having a lower reflow temperature than the first solder. Warm placement of the electronic component at a somewhat elevated temperature than room temperature but less than the solder reflow temperature reduces the force required during placement of a semiconductor chip to a substrate. After warm placement, reflow of the module occurs at the lower reflow temperature of the second solder. The conical shape of the solder interconnects are formed by a heated coining die which may also coin a portion of the interconnects with flat surfaces for stand-offs. The ability of the cone shaped solder interconnects to meet the opposing surface of a chip or substrate at different heights accommodates the camber typically associated with chip and substrate surfaces.
58 Citations
71 Claims
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1. A process for forming non-spherical shapes in solder interconnects on the surface of a substrate or a semiconductor die comprising the steps of:
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a)depositing a first layer of solder onto a surface;
b)plating a second layer of solder over said first layer of solder; and
c)forming said first and second layers of solder into a non-spherical shape wherein the non-spherical shape of said solder interconnects facilitate joining between two surfaces. - View Dependent Claims (2, 3, 4, 5)
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6. A process for forming non-spherical shapes in solder interconnects comprising the steps of:
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(a) providing a semiconductor wafer and a substrate for mounting said wafer;
(b) applying a masking layer to said wafer or to said substrate;
(c) patterning and developing a plurality of openings in said masking layer;
(d) forming a plurality of solder interconnects by plating a layer of solder into said plurality of openings in said masking layer; and
(e) molding said plurality of solder interconnects into a non-spherical shape, wherein the non-spherical shape of said plurality of solder interconnects facilitates joining of said wafer and said substrate in a non-planar environment. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. A process for forming cone shaped solder on a semiconductor wafer or a substrate for use in controlled chip collapse connections comprising the steps of:
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(a) providing a first surface;
(b) applying a bond pad for a connection to said surface;
(c) applying a seed layer over said surface;
(d) applying and patterning a masking layer over said seed layer to form an opening in said masking layer exposing said seed layer;
(e) plating a metal solder into the opening of said masking layer;
(f) stripping said masking layer;
(g) removing said seed layer not covered by said solder; and
(h) molding said solder to form a cone shape. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59)
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60. A method of joining semiconductor chips and substrates in a non-planar environment using non-spherically shaped solder comprising the steps of:
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(a) providing a semiconductor chip and a substrate for mounting said chip;
(b) forming a plurality of non-spherical solder interconnects on a surface of said chip or substrate;
(c) forming standoffs on a surface of said chip or said substrate; and
(d) contacting said chip with said substrate, whereby the placement force is reduced and said standoffs limit the extent of collapse of said solder interconnects. - View Dependent Claims (61, 62, 63, 64, 65, 66, 67, 68, 69)
(a) plating a first solder on a surface of said chip or said substrate; and
(b) plating a second solder over said first solder; and
molding said solders with a heated coining die comprising a rigid, non-solder wettable plate having an array of non-spherically shaped cavities such that said heated coining die deforms said second solder to form said non-spherical shape.
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63. The process according to claim 62, wherein said first layer of solder comprises a higher melting point solder than said second layer of solder.
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64. The process according to claim 62, wherein said first layer of solder comprises a Lead-tin alloy and said second layer of solder comprises a tin alloy.
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65. The process according to claim 60, wherein said contacting of said chip to said substrate occurs at an elevated temperature greater than room temperature but less than said solder reflow temperature.
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66. The process according to claim 60, wherein said non-spherical shape is conical.
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67. The process according to claim 66, wherein said conical shape of said solder interconnect having a base angle of about 75 to 80 degrees.
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68. The process according to claim 60, wherein said plurality of solder interconnects and said standoffs are formed on a surface of a chip.
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69. The process according to claim 60, wherein said plurality of solder interconnects and said standoffs are formed on a surface of a substrate.
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70. A method of joining semiconductor chips and substrates in a non-planar environment using non-spherically shaped solder comprising the steps of:
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(a) providing a semiconductor chip and a substrate for mounting said chip;
(b) forming a plurality of non-spherical solder interconnects on a surface of said chip;
(c) forming standoffs on a surface of said chip or substrate; and
(d) contacting said chip with said substrate, whereby the placement force is reduced and said standoffs limit the extent of collapse of said solder interconnects.
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71. A method of joining semiconductor chips and substrates in a non-planar environment using non-spherically shaped solder comprising the steps of:
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(a) providing a semiconductor chip and a substrate for mounting said chip;
(b) forming a plurality of non-spherical solder interconnects on a surface of said substrate;
(c) forming standoffs on a surface of said chip or said substrate; and
(d) contacting said chip with said substrate, whereby the placement force is reduced and said standoffs limit the extent of collapse of said solder interconnects.
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Specification