Patent US5451274A successfully refreshed from Google Patents.
US5451274A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reflow of multi-layer metal bumps
Assignee: NXP USA Inc
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Filing: 1994-01-31
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Granted: 1995-09-19
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Expires: 2014-01-31
Abstract
Abstract A method and apparatus for re-flow of multi-layer metal bumps. A multi layer metal bump structure is surrounded by an oxygen poor environment. The topmost layer of the metal bump structure is heated by using infrared light for a predetermined time. The infrared light has a wavelength which is selected such that the top layer is heated more than the underlying layers.
Inventors
- 👤 Debabrata Gupta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 20:01
CPC Classifications
H; H10; H10W; H10W72/00; H10W72/01; H10W72/012; H10W72/20; H10W72/251
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
75 words
A method for re-flow of multi-layer metal bumps, comprising: providing a metal bump structure having a plurality of layers including a tin top layer over a gold layer; placing the metal bump structure in an environmental chamber having an oxygen poor environment; and heating the tin top layer with infrared light from an infrared light source to reflow the multi-layer metal bumps, the infrared light having a wavelength which preferentially heats the tin top layer.
Claim 2
Independent Claim
75 words
A method for re-flow of multi-layer metal bumps, comprising: providing a metal bump structure having a plurality of layers including a tin top layer over a gold layer; placing the metal bump structure in an environmental chamber having an oxygen poor environment; and heating the tin top layer with infrared light from an infrared light source to reflow the multi-layer metal bumps, the infrared light having a wavelength which preferentially heats the tin top layer.
Claim 3
Dependent Claim
47 words
The method for re-flow of multi-layer metal bumps of claim 1 further comprising: continuing the heating until a desired microstructure is formed in the metal bump structure, wherein the desired microstructure includes a eutectic dome having a composition and topography sufficient to bond to a package assembly.
Claim 4
Dependent Claim
38 words
The method for re-flow of multi-layer metal bumps of claim 1, further comprising: reducing oxygen level within the environmental chamber to lower than 2000 parts per million of oxygen before the step of heating the tin top layer.
Claim 5
Independent Claim
122 words
A method for reflowing multi-layer metal structures comprising the steps of: placing a substrate into a chamber, wherein the substrate includes a multi-layer metal bump comprising a gold metal layer and a tin metal layer on top of the gold metal layer; reducing oxygen concentration in the chamber to below approximately 2000 parts per million of oxygen; and exposing the multi-layer metal bump to an infrared heat source having a wavelength that preferentially heats the tin metal layer compared to the gold metal layer, and wherein the substrate is heated for a time that prevents substantial diffusion of the gold metal layer into the tin metal layer and provides a eutectic dome having a thickness sufficient for bonding to an application substrate.
Claim 6
Independent Claim
122 words
A method for reflowing multi-layer metal structures comprising the steps of: placing a substrate into a chamber, wherein the substrate includes a multi-layer metal bump comprising a gold metal layer and a tin metal layer on top of the gold metal layer; reducing oxygen concentration in the chamber to below approximately 2000 parts per million of oxygen; and exposing the multi-layer metal bump to an infrared heat source having a wavelength that preferentially heats the tin metal layer compared to the gold metal layer, and wherein the substrate is heated for a time that prevents substantial diffusion of the gold metal layer into the tin metal layer and provides a eutectic dome having a thickness sufficient for bonding to an application substrate.
Claim 7
Dependent Claim
38 words
The method of claim 4 wherein the step of exposing the multi-layer metal bump to the infrared heat source includes exposing the multi-layer metal bump to an infrared beam having a wavelength between approximately 0.8 and 1.0 micron.
Claim 8
Dependent Claim
42 words
The method of claim 4 wherein the step of exposing the multi-layer bump to the infrared heat source includes exposing the multi-layer bump to a 200 watt infrared heat source for a time less than approximately 15 seconds at 80% lamp power.
Claim 9
Dependent Claim
42 words
The method of claim 4 wherein the step of exposing the multi-layer bump to the infrared heat source includes exposing the multi-layer bump to a 200 watt infrared heat source for a time less than approximately 20 seconds at 60% lamp power.
Claim 10
Dependent Claim
67 words
The method of claim 4 wherein the step of placing the substrate into the chamber includes placing the substrate into an environmental chamber having a window, and wherein the step of exposing the multi-layer metal bump to the infrared heat source includes exposing the multi-layer bump to an infrared heat source external to the environmental chamber, and wherein the infrared heat source is positioned over the window.
References Cited (Backward Citations)
US5250469A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-09-18 | 1999-03-20 | 1999-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-18 | 2003-03-20 | 2003-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-18 | 2007-03-20 | 2007-09-19 | $7700.00 | Window Closed / Lapsed |