Patent US4978423A successfully refreshed from Google Patents.
US4978423A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Selective solder formation on printed circuit boards
Assignee: Nokia Bell Labs
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Filing: 1988-09-26
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Granted: 1990-12-18
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Expires: 2008-09-26
Abstract
Abstract Disclosed is a method of providing solder on selected portions of a printed circuit board. Solder is first electroplated over copper conductor patterns on the board by means of a first photoresist layer. After stripping the first photoresist, a second photoresist layer is laminated over the board and developed to expose selected portions of the solder. The exposed portions are selectively stripped. The copper exposed by the selective stripping is then subjected to a scrubbing while the photoresist protects the remaining solder, and the second photoresist is removed.
Inventors
- 👤 Roy K. Durnwirth, Jr.
- 👤 John E. George
- 👤 Kim L. Morton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 19:49
CPC Classifications
H; H05; H05K; H05K3/00; H05K3/30; H05K3/32; H05K3/34; H05K3/3465; H05K3/3473; H05K3/02; H05K3/06; H05K3/061; H05K3/062; H05K3/3452; H05K2201/00; H05K2201/09; H05K2201/09818; H05K2201/099; H05K2203/00; H05K2203/03; H05K2203/0361; H05K2203/04; H05K2203/043; H05K3/10; H05K3/108
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
96 words
A method of fabricating printed circuit boards comprising the steps of: forming a pattern of conductive material over an insulating substrate; depositing a layer of solder over the pattern of conductive material; depositing a photoresist mask layer by vacuum lamination over the resulting structure and developing the layer so as to expose areas of solder to be removed; selectively removing the exposed areas of solder to expose portions of the conductive material; and pumice scrubbing the portions of conductive material exposed by the selective removal of the solder while the photoresist mask protects the remaining solder.
Claim 2
Independent Claim
96 words
A method of fabricating printed circuit boards comprising the steps of: forming a pattern of conductive material over an insulating substrate; depositing a layer of solder over the pattern of conductive material; depositing a photoresist mask layer by vacuum lamination over the resulting structure and developing the layer so as to expose areas of solder to be removed; selectively removing the exposed areas of solder to expose portions of the conductive material; and pumice scrubbing the portions of conductive material exposed by the selective removal of the solder while the photoresist mask protects the remaining solder.
Claim 3
Dependent Claim
13 words
The method according to claim 1 wherein the conductive material comprises electroplated copper.
Claim 4
Dependent Claim
18 words
The method according to claim 2 wherein the thickness of the copper is within the range 25-50 μm.
Claim 5
Dependent Claim
13 words
The method according to claim 1 wherein the solder comprises tin and lead.
Claim 6
Dependent Claim
15 words
The method according to claim 1 wherein the solder thickness is at least 7.5 μm.
Claim 7
Dependent Claim
18 words
The method according to claim 1 wherein the thickness of the photoresist is within the range 75-100 μm.
Claim 8
Dependent Claim
18 words
The method according to claim 1 wherein the solder is removed by applying a solution comprising hydrogen peroxide.
Claim 9
Dependent Claim
21 words
The method according to claim 1 wherein the conductive material pattern includes strips which have a pitch less than 625 μm.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-12-17 | 1994-06-18 | 1994-12-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-17 | 1998-06-18 | 1998-12-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-17 | 2002-06-18 | 2002-12-18 | $7700.00 | Window Closed / Lapsed |