Semiconductor devices with improved lead frame structures

• US 6,265,761 B1
• Filed: 05/07/1999
• Issued: 07/24/2001
• Est. Priority Date: 05/07/1999
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Ghai, Ajay K.
• Primary Examiner(s): Williams, Alexander O.
• Application Number:
  US09/307,095
• Time in Patent Office: 809 Days
• Field of Search: 257/666, 257/669-674, 257/676, 257/684, 257/696, 257/784, 257/692, 257/735, 174/52.4, 174/52.2, 438/123, 438/124, 438/127
• US Class Current: 257/666
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/32014 the layer connector being smaller than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/85439 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 23/49503 characterised by the die pad
• CPC Class Codes: H01L 23/4951 Chip-on-leads or leads-on-chip techniques, i.e. inner lead fingers being used as die pad
• CPC Class Codes: H01L 23/49541 Geometry of the lead-frame
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/207 : Diameter ranges

Abstract

A lead frame to support a semiconductor die within an encapsulating package. The lead frame includes a first rail and a second rail in a first plane, with the second rail parallel to and spaced apart from the first rail by more than the length of the package. A first bar and a second bar are connected perpendicularly to the first and second rails, with the second bar spaced apart from the first bar by more than the width of the package. A lead is connected perpendicularly to the first bar with an unconnected lead end extending toward the second bar and located to extend under the supported semiconductor die. A first support tab is connected perpendicularly to the first rail with a first unconnected tab end extending toward the second rail and located to extend under the supported semiconductor die. A second support tab is connected perpendicularly to the second rail with a second unconnected tab end extending toward the first rail and located to extend under the supported semiconductor die.

Claims

1. A lead frame to support a semiconductor die within an encapsulating package, consisting essentially of:

a first rail and a second rail in a first plane, said second rail parallel to and spaced apart from the first rail by more than the length of the encapsulating package;

a first bar and a second bar connected perpendicularly to the first and second rails, said second bar spaced apart from the first bar by more than the width of the encapsulating package;

a first plurality of leads connected perpendicularly to the first bar, each of the first plurality of leads having an unconnected lead end extending toward the second bar, said unconnected lead end located to extend under the supported semiconductor die;

a second plurality of leads connected perpendicularly to the second bar, each of the second plurality of leads having an unconnected lead end extending toward the first bar, said unconnected lead end located to extend under the supported semiconductor die;

a first support tab connected perpendicularly to the first rail with a first unconnected tab end extending toward the second rail, said first unconnected tab end located to extend under the supported semiconductor die;

a second support tab connected perpendicularly to the second rail with a second unconnected tab end extending toward the first rail, said second unconnected tab end located to extend under the supported semiconductor die.

2. The lead frame of claim 1, where the portions of the lead and the first and second support tabs that extend under the supported semiconductor die are in a second plane parallel to and spaced downwardly from the first plane.

3. The lead frame of claim 2, where a space between the first plane and the second plane is at least one-half the thickness of the semiconductor die.

4. The lead frame of claim 2, where a space between the first plane and the second plane is about the same as the thickness of the semiconductor die.

5. The lead frame of claim 2, where the portion of the lead in the first plane and the portion of the lead in the second plane are connected by a portion of the lead forming an angle of not less than about forty-five degrees to the first and second planes.

6. The lead frame of claim 5, where the connecting portion of the lead forms an angle of not more than about seventy degrees to the first and second planes.

7. The lead frame of claim 1, where the lead extends under the supported die by at least one-tenth of the semiconductor die width.

8. The lead frame of claim 1, where the distance between the edge of the semiconductor die and the encapsulating package is less than about seven-tenths of a millimeter.

9. The lead frame of claim 1, where the portion of the lead inside the encapsulating package is wider than the portion of the lead outside the encapsulating package.

10. The lead frame of claim 1, where a selected portion of the lead inside the encapsulating package and not under the semiconductor die is plated with metal.

11. A semiconductor device consisting essentially of:

an capsulating body with roughly a first rectangular solid shape having a package width, lenght, and thickness;

a semiconductor die with approximately a second rectangular solid shape having a die width, lenght, and thickness;

a plurality of leads adhesively attached directly to a bottom surface of the semiconductor die an extending outwardly beyond the package width;

a wire bond coupling each of a plurality of pads on a top surface of the semiconductor die to the plurality of leads at points on the leads between the die width and the package width;

a first and second support tabs adhesively attached directly to the bottom surface of the semiconductor die and extending outwardly in opposite directions to about the package lenght.

12. The semiconductor device of claim 11, where the portions of the lead and the first and second support tabs that extend beyond the semiconductor die are offset toward the top surface of the semiconductor die and extend in a plane parallel to the bottom surface of the semiconductor die and a point where the wire bond is coupled to the lead is substantially on the plane.

13. The semiconductor device of claim 12, where the plane is about at or above a midplane of the semiconductor die.

14. The semiconductor device of claim 12, where the plane is about at the top surface of the semiconductor die.

15. The semiconductor device of claim 12, where the adhesive is an electrically insulating adhesive.

16. The semiconductor device of claim 11, where the lead is plated with a metal around the point where the wire bond is coupled to the lead.

17. The semiconductor device of claim 16, where the metal is silver.

18. The semiconductor device of claim 11, where the portion of the lead attached to the bottom surface of the semiconductor die covers at least one-tenth of the width of the semiconductor die.

19. The semiconductor device of claim 11, where a distance between the semiconductor die and the encapsulating body is less than about seven-tenths of a millimeter.

20. The semiconductor device of claim 11, where the portion of the lead inside the encapsulating body is wider than the portion of the lead outside the encapsulating body.

21. A method of assembling a semiconductor die in an encapsulating package, comprising:

forming a lead frame, consisting essentially of

a first rail and a second rail in a first plane, said second rail parallel to and spaced apart from the first rail by more than the length of the encapsulating package,

a first bar and a second bar connected perpendicularly to the first and second rails, said second bar spaced apart from the first bar by more than the width of the encapsulating package,

a first plurality of leads connected perpendicularly to the first bar, each of the first plurality of leads having an unconnected lead end extending toward the second bar, said unconnected lead end located to extend under the supported semiconductor die,

a second plurality of leads connected perpendicularly to the second bar, each of the second plurality of leads having an unconnected lead end extending toward the first bar, said unconnected lead end located to extend under the supported semiconductor die;

a first support tab connected perpendicularly to the first rail with a first unconnected tab end extending toward the second rail, said first unconnected tab end located to extend under the supported semiconductor die,

a second support tab connected perpendicularly to the second rail with a second unconnected tab end extending toward the first rail, said second unconnected tab end located to extend under the supported semiconductor die;

attaching a bottom surface of the semiconductor die directly to the unconnected lead end;

connecting an electrically conductive wire to the lead and to a bonding pad on a top surface of the semiconductor die;

encapsulating the semiconductor die, the support tabs, the lead, and the electrically conductive wire with a circuit package; and

trimming away the rails and the bars.

22. The method of claim 21, further comprising offsetting the unconnected end of the lead and the unconnected ends of the support tabs downwardly into a second plane parallel to the first plane.

23. The method of claim 21, where a portion of the lead that is encapsulated is wider than a portion of the lead that is not encapsulated.

24. The method of claim 21, further comprising applying metal plating to the lead in the area where the electrically conductive wire is connected.

25. The method of claim 21, wherein said attaching includes attaching at least one-tenth of the width of the semiconductor die to the unconnected lead end.

26. The method of claim 21, wherein said attaching includes adhesively bonding with an electrically insulating adhesive.

27. The method of claim 21, where said attaching further comprises adhesively bonding the bottom surface of the semiconductor die to the support tabs.

28. The method of claim 21, where said lead frame further includes a tie bar connected to the rails and to the lead, and said trimming further comprises trimming away the tie bar.