SEMICONDUCTOR DEVICE

• US 20090152696A1
• Filed: 07/05/2006
• Published: 06/18/2009
• Est. Priority Date: 07/08/2005
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Van Driel, Willem Dirk, Tan, Jerry Lutiva, Dimasacat, Jose Joel
• Granted Patent: US 7,838,973 B2
• Time in Patent Office: Days
• US Class Current: 257/676
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/27013 for holding or confining the layer connector, e.g. solder flow barrier
• CPC Class Codes: H01L 2224/29075 Plural core members
• CPC Class Codes: H01L 2224/2929 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/293 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• 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 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/4848 outside the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/48599 Principal constituent of the connecting portion of the wire connector being Gold (Au)
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/83051 Forming additional members, e.g. dam structures
• CPC Class Codes: H01L 2224/83385 Shape, e.g. interlocking features
• CPC Class Codes: H01L 2224/83851 being an anisotropic conductive adhesive
• CPC Class Codes: H01L 2224/85051 Forming additional members, e.g. for "wedge-on-ball", "ball-on-wedge", "ball-on-ball" connections
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 23/3107 the device being completely enclosed
• CPC Class Codes: H01L 23/49503 : characterised by the die pad
• CPC Class Codes: H01L 23/562 : Protection against mechanical damage H01L23/02, H01L23/28 take precedence
• CPC Class Codes: H01L 24/32 : of an individual layer connector
• CPC Class Codes: H01L 24/45 : of an individual wire connector
• CPC Class Codes: H01L 24/48 : of an individual wire connector
• CPC Class Codes: H01L 24/73 : Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 24/83 : using a layer connector
• CPC Class Codes: H01L 24/85 : using a wire connector wire bonding in general B23K20/004
• 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 2924/00011 : Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/01015 : Phosphorus [P]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/0781 : being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15153 : the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 2924/15165 : Monolayer substrate
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/18301 : being an anchoring portion, i.e. mechanical interlocking between the encapsulation resin and another package part
• CPC Class Codes: H01L 2924/3512 : Cracking

Abstract

A semi-conductor device (100) comprises an exposed leadframe (10) with a die pad (11) and a plurality of leads (12). The die pad (11) has a substantially flat bottom surface (14) and a top surface (15). A semi-conductor die (2) is attached to a die attachment portion (31) of the top surface (15). Downbonds (5) connect the die (2) to a downbond attachment portion (32). Standard bonds (4) connect the die (2) to the leads (12). A plastic package (6) encapsulates the die (2), the standard bonds (4) and the downbonds (5). The top surface of the die pad has portions located at different levels, and step-shaped transitions between two adjacent ones of such portions. At least one of such step-shaped transition (36) is located between the die (2) and the downbonds (5). It has been found that such step-shaped transition provides good protection against downbond failure.

Claims

1. Leadframe for a semi-conductor device, comprising a die pad for mounting a semi-conductor die and a plurality of leads for connection with the semi-conductor die, the leads being arranged at a distance from the die pad;

wherein the die pad has a substantially flat bottom surface and a top surface, the top surface having a die attachment portion and a downbond attachment portion for connecting downbonds;

wherein, at least one location between the die attachment surface portion and the downbond attachment surface portion, the top surface of the die pad has at least one third surface portion that is out-of-plane with the die attachment surface portion, and at least one substantially step-shaped surface transition between the die attachment surface portion and said third surface portion.

2. Leadframe according to claim 1, wherein said transition has been formed by etching away a part of the top surface.

3. Leadframe according to claim 1, wherein, at a location between the die attachment surface portion and the downbond attachment surface portion, the die pad has at least one recess in its top surface, wherein said third surface portion is defined by a bottom of said recess, and wherein said step-shaped transition is defined by a wall of said recess.

4. Leadframe according to claim 3, wherein the said recess is formed as a groove directed substantially parallel to a side edge of the die pad.

5. Leadframe according to claim 4, wherein said groove is an annular, endless groove with a substantially rectangular shape, corresponding to the shape of the die pad.

6. Leadframe according to claim 3, wherein the said recess has a substantially rectangular cross-sectional contour.

7. Leadframe according to claim 3, wherein the downbond attachment surface portion is aligned with the die attachment surface portion.

8. Leadframe according to claim 3, wherein the die pad has at least one further recess in its top surface, at a location between the downbond attachment surface portion and a side edge of the die pad.

9. Leadframe according to claim 1, wherein, at a location between the die attachment surface portion and the downbond attachment surface portion, the die pad has at least one ridge on its top surface, wherein said third surface portion is defined by a top of said ridge, and wherein said step-shaped transition is defined by a wall of said ridge.

10. Leadframe according to claim 9, wherein said ridge has been formed by etching away parts of the lead frame base material to form the die attachment surface portion and the downbond attachment surface portion, respectively.

11. Leadframe according to claim 1, wherein the die attachment surface portion and the downbond attachment surface portion are out-of-plane with each other, wherein said step-shaped transition is defined by a transition between the die attachment surface portion and the downbond attachment surface portion.

12. Leadframe according to claim 11, wherein the said third surface is at the same level as the downbond attachment surface portion.

13. Leadframe according to claim 11, wherein the downbond attachment surface portion is located closer to the bottom surface of the die pad than the die attachment surface portion.

14. Leadframe according to claim 13, wherein said step-shaped transition has been formed by etching away a part of the lead frame base material to form the downbond attachment surface portion.

15. Leadframe according to claim 11, wherein the die attachment surface portion is located closer to the bottom surface of the die pad than the downbond attachment surface portion.

16. Leadframe according to claim 15, wherein said step-shaped transition has been formed by etching away a part of the lead frame base material to form the die attachment surface portion.

18. Semi-conductor device according to claim 16, wherein the leadframe is exposed.

17. Semi-conductor device, comprising:

a leadframe comprising a die pad for mounting a semi-conductor die and a plurality of leads for connection with the semi-conductor die, the leads being arranged at a distance from the die pad;

wherein the die pad has a substantially flat bottom surface and a top surface, the top surface having a die attachment portion and a downbond attachment portion for connecting downbonds;

wherein, at least one location between the die attachment surface portion and the downbond attachment surface portion, the top surface of the die pad has at least one third surface portion that is out-of-plane with the die attachment surface portion, and at least one substantially step-shaped surface transition between the die attachment surface portion and said third surface portion;

a semi-conductor die attached to the die attachment portion of the die pad, the semi-conductor die comprising an integrated circuit;

a plurality of standard bonds connecting said integrated circuit to respective leads;

a plurality of downbonds connecting said integrated circuit to the downbond attachment portion of the die pad; and

a plastic package encapsulating at least the semi-conductor die, the standard bonds and the downbonds.

19. Semiconductor device according to claim 17,

wherein, at a location between the die attachment surface position and the downbond attachment surface portion, the die pad has at least one recess in its top surface, wherein said third surface portion is defined by a bottom of said recess, and wherein said step-shaped transition is define d by a wall of said recess;

and

wherein said at least one recess is entirely filled plastic material of the package.

20. Method for manufacturing a semi-conductor device, the method comprising the steps of:

providing a base leadframe strip;

using an etching process, defining at least one leadframe, comprising a die pad and a plurality of leads, wherein the die pad has a substantially flat bottom surface and a top surface, the top surface having a die attachment portion and a downbond attachment portion for connecting downbonds;

using an etching process, etching away at least a portion of the top surface of the die pad, at least one location between the die attachment surface portion and the downbond attachment surface portion, to define at least one third surface portion that is out-of-plane with the die attachment surface portion, and at least one substantially step-shaped surface transition between the die attachment surface portion and said third surface portion;

attaching a semi-conductor die to the die attachment portion of the die pad, the semi-conductor die comprising an integrated circuit;

connecting standard bonds to said integrated circuit and to respective leads;

connecting downbonds to said integrated circuit and to the downbond attachment portion of the die pad;

applying molten plastic material on the top surface of the die pad, for encapsulating at least the semi-conductor die, the standard bonds and the downbonds.

21. Method according to claim 20, wherein at least one groove is etched into said the top surface of the die pad, and wherein the step of applying molten plastic material is applied such as to ensure that the molten plastic material fully fills said at least one groove.