US4903401A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Leadframe silver bleed elimination
Assignee: NXP USA Inc
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Filing: 1989-04-03
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Granted: 1990-02-27
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Expires: 2009-04-03
Abstract
Abstract A method of making a leadframe useful in packaging semiconductor devices eliminates silver bleed between adjacent leads of the leadframe. This is accomplished by leaving excess leadframe material along the edges of the leads prior to silver plating the flag area and the portion of the leads adjacent to the flag area. After the plating operation, this excess leadframe material is removed thereby leaving silver free leads which will be exposed outside of a resulting encapsulated semiconductor package.
Inventors
- 👤 Brian A. Webb
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 19:07
CPC Classifications
H; H10; H10P; H10P72/00; H10P72/04; H10P72/0446; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49117; Y10T29/49121; Y10T428/00; Y10T428/12; Y10T428/12493; Y10T428/12771; Y10T428/12861; Y10T428/12896
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
102 words
A method to eliminate silver bleed on a leadframe having a flag area, a plurality of leads extending from adjacent the flag area, and a dam bar tieing the leads together a predetermined distance from the flat area, comprising the following steps: providing material to form the leadframe; forming the leadframe including leaving leadframe material along edges of the leads adjacent the dam bar on the flag area side of the dam bar to receive any silver bleed; plating the leads between the dam bar and the flag area with silver; and removing the leadframe material left along edges of the leads.
Claim 2
Independent Claim
102 words
A method to eliminate silver bleed on a leadframe having a flag area, a plurality of leads extending from adjacent the flag area, and a dam bar tieing the leads together a predetermined distance from the flat area, comprising the following steps: providing material to form the leadframe; forming the leadframe including leaving leadframe material along edges of the leads adjacent the dam bar on the flag area side of the dam bar to receive any silver bleed; plating the leads between the dam bar and the flag area with silver; and removing the leadframe material left along edges of the leads.
Claim 3
Dependent Claim
19 words
The method of claim 1 further comprising cutting the plurality of leads to predetermined lengths after the plating step.
Claim 4
Dependent Claim
18 words
The method of claim 1 wherein the material left along edges of the leads extends between adjacent leads.
Claim 5
Independent Claim
139 words
A method to eliminate plating material bleed in a leadframe assembly useful in packaging semiconductor devices and having a plurality of flag areas and a plurality of leads associated with each flat area, a dam bar made from leadframe material interconnects the plurality of leads and is located a short distance from the flag area, comprising the following method: providing material to form the leadframe; forming the leadframe including leaving leadframe material along edges of the leads adjacent to and in contact with the dam bar toward the flag area; selectively plating the leadframe including the material left along the edges of the leads; and removing the material left along the edges of the leads thereby providing a leadframe void of plating material along the edges of the leads near the dam bar to eliminate bleeding between the leads.
Claim 6
Independent Claim
139 words
A method to eliminate plating material bleed in a leadframe assembly useful in packaging semiconductor devices and having a plurality of flag areas and a plurality of leads associated with each flat area, a dam bar made from leadframe material interconnects the plurality of leads and is located a short distance from the flag area, comprising the following method: providing material to form the leadframe; forming the leadframe including leaving leadframe material along edges of the leads adjacent to and in contact with the dam bar toward the flag area; selectively plating the leadframe including the material left along the edges of the leads; and removing the material left along the edges of the leads thereby providing a leadframe void of plating material along the edges of the leads near the dam bar to eliminate bleeding between the leads.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-26 | 1993-08-28 | 1994-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-26 | 1997-08-28 | 1998-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-26 | 2001-08-28 | 2002-02-27 | $7700.00 | Window Closed / Lapsed |