US3873428A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preferential gold electroplating
Assignee: AT&T Inc
•
Filing: 1974-02-19
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Granted: 1975-03-25
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Expires: 1994-02-19
Abstract
Abstract Selective soft gold electroplating of noble metal regions on composite surfaces, including exposed titanium regions, is expedited by small lead addition to the electroplating bath. Improvement in selectivity most evident subsequent to the onset of plating permits increasing plating voltage and corresponding increase in plating density. The procedure is applicable to the fabrication of silicon integrated circuits.
Inventors
- 👤 Earl Dallas Winters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 15:34
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/40; H10P14/46; H10P14/47; C; C25; C25D; C25D3/00; C25D3/02; C25D3/48; C25D5/00; C25D5/02; H10W; H10W20/00; H10W20/40; H05; H05K; H05K3/00; H05K3/22; H05K3/24; H05K3/241; H05K3/243; H05K3/244
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
136 words
METHOD OF SELECTIVELY ELECTROPLATING SOFT GOLD ON A NOBLE METAL REGION OF A COMPOSITE SURFACE INCLUDING EXPOSED TITANIUM IN ACCORDANCE WITH WHICH THE SAID SURFACE IS IMMERSED INAN AQUEOUS ELECTROPLATING SOLUTION CONTAINING A SOLUBLE GOLD SALT WITH SAID IMMERSED SURFACE BEING BIASED CATHODICALLY WITH REFERENCE TO AN IMMERSED ANODE, CHARACTRIZED IN THAT THE SAID SOLUTION CONTAINS LEAD WITH THE AMOUNT OF LEAD IN SOLUTION BEING MAINTAINED AT A LEVEL OF FROM ABOUT 20 PPB TO 2 PPM BASED ON THE SAID SOLUTION, IN THAT THE SAID SURFACE IS BIASED AT A LEVEL INTERMEDIATE THE ONSET POTENTIAL FOR THE SAID NOBLE METAL AND TITANIUM, AND IN THAT THE ABSOLUTE VALUE OF THE CATHODE POTENTIAL IS INCREASED TO RESULT IN A CURRENT DENSITY OF AT LEAST 1 MM/CM2 BEFORE ATTAINMENT OF A DEPOSITED GOLD LAYER OF 1 UM.
Claim 2
Dependent Claim
136 words
METHOD OF SELECTIVELY ELECTROPLATING SOFT GOLD ON A NOBLE METAL REGION OF A COMPOSITE SURFACE INCLUDING EXPOSED TITANIUM IN ACCORDANCE WITH WHICH THE SAID SURFACE IS IMMERSED INAN AQUEOUS ELECTROPLATING SOLUTION CONTAINING A SOLUBLE GOLD SALT WITH SAID IMMERSED SURFACE BEING BIASED CATHODICALLY WITH REFERENCE TO AN IMMERSED ANODE, CHARACTRIZED IN THAT THE SAID SOLUTION CONTAINS LEAD WITH THE AMOUNT OF LEAD IN SOLUTION BEING MAINTAINED AT A LEVEL OF FROM ABOUT 20 PPB TO 2 PPM BASED ON THE SAID SOLUTION, IN THAT THE SAID SURFACE IS BIASED AT A LEVEL INTERMEDIATE THE ONSET POTENTIAL FOR THE SAID NOBLE METAL AND TITANIUM, AND IN THAT THE ABSOLUTE VALUE OF THE CATHODE POTENTIAL IS INCREASED TO RESULT IN A CURRENT DENSITY OF AT LEAST 1 MM/CM2 BEFORE ATTAINMENT OF A DEPOSITED GOLD LAYER OF 1 UM.
Claim 3
Dependent Claim
70 words
Method of claim 1 in which the absolute potential of the said surface is first maintained within the range intermediate the onset potentials for the said noble metal and titanium for a period sufficient to result in a visible plating following which such potential is increased to finally attain a bias of a value corresponding with a value at least about -500 mv as measured relative to a calomel electrode.
Claim 4
Dependent Claim
12 words
Method of claim 2 in which the said bias is increased stepwise.
Claim 5
Dependent Claim
12 words
Method of claim 2 in which the said bias is continuously increased.
Claim 6
Dependent Claim
13 words
Method of claim 1 in which the said noble metal region contains platinum.
Claim 7
Dependent Claim
13 words
Method of claim 1 in which the said noble metal region contains palladium.
Claim 8
Dependent Claim
13 words
Method of claim 1 in which the said noble metal region contains gold.
Claim 9
Dependent Claim
26 words
Method of claim 1 in which the said composite surface consists of a pattern of the said noble metal deposited on a continuous layer of titanium.
Claim 10
Dependent Claim
19 words
Method of claim 1 in which the pH of the said solution is from about 5 to about 10.
References Cited (Backward Citations)
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US3380898A
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US3514379A
Cited
US3669852A
Cited
US3700569A
Cited
US3791941A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-24 | 1978-09-23 | 1979-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-24 | 1982-09-23 | 1983-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-24 | 1986-09-23 | 1987-03-25 | $7700.00 | Window Closed / Lapsed |