Reduced stress LOC assembly including cantilevered leads

• US 5,872,398 A
• Filed: 01/11/1996
• Issued: 02/16/1999
• Est. Priority Date: 01/11/1996
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Corisis, David J., Kinsman, Larry D., Brooks, Jerry M., King, Jerrold L.
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): KELLEY, NATHAN K
• Application Number:
  US08/584,738
• Time in Patent Office: 1,132 Days
• Field of Search: 257/666, 257/691, 257/735, 257/668, 257/674, 257/694, 257/690
• US Class Current: 257/735
• CPC Class Codes: H01L 2224/04042 Bonding areas specifically adapted for wire connectors, e.g. wirebond pads
• CPC Class Codes: H01L 2224/05556 in side view
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/06136 Covering only the central area of the surface to be connected, i.e. central arrangements
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• 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 2224/4826 Connecting between the body and an opposite side of the item with respect to the body
• 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 2224/48599 Principal constituent of the connecting portion of the wire connector being Gold (Au)
• CPC Class Codes: H01L 2224/48647 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/48699 Principal constituent of the connecting portion of the wire connector being Aluminium (Al)
• CPC Class Codes: H01L 2224/48747 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/73215 Layer and wire connectors
• CPC Class Codes: H01L 2224/85447 Copper (Cu) as principal constituent
• 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 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/06 of a plurality of bonding areas
• 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 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 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01014 : Silicon [Si]
• CPC Class Codes: H01L 2924/0102 : Calcium [Ca]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01075 : Rhenium [Re]
• 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 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/181 : Encapsulation

Abstract

An LOC die assembly including a die dielectrically adhered to the underside of a lead frame. The adhesive is applied over a minimum cross-sectional area and number of attachment points to maximize flexure of leads extending over the active surface of the die. In this manner, flexure of the leads to accommodate filler particles lodged between the leads and the active surface of the die during transfer molding of a plastic encapsulant is maximized, and the point stresses on the active surface caused by the filler particles are reduced by the lead flexure.

Claims

1. A semiconductor die assembly, comprising:

a semiconductor die having a periphery and an active surface;

a lead frame including a plurality of lead elements, at least some of which extend from beyond said die periphery inwardly over said active surface of said die; and

at least one adhesive segment disposed between and adhering an underside of a portion of said lead frame and said active surface to support said die from said lead frame underside;

wherein a majority of said inwardly extending lead elements extend in a cantilevered manner for the majority of each of their respective lengths over said active surface.

2. The die assembly of claim 1, wherein a plurality of said inwardly extending lead elements are adhered to said active surface proximate the periphery of said die.

3. The die assembly of claim 2, wherein said periphery is in part defined by opposing sides, and said adherence of said lead frame to said die is provided by first and second substantially parallel elongated adhesive segments lying adjacent and parallel to said opposing sides of said die, and substantially transverse to orientations of said inwardly extending lead elements to which said segments are adhered.

4. The die assembly of claim 1, wherein said semiconductor die periphery is defined by opposing ends and opposing sides, and said lead frame is adhered to said active surface only proximate each end of said die, and said inwardly extending lead elements extending over said active surface from the sides of said die are unadhered to said active surface throughout their extents thereover.

5. The die assembly of claim 4, wherein said adhesive segments are disposed between said active surface and lead frame elements extending over said active surface from the ends of said die.

6. The die assembly of claim 1, wherein said periphery is defined in part by opposing ends and said lead frame further includes at least one bus element extending over said active surface from one end of said die to another, and said adherence of said lead frame to said die is provided by said at least one adhesive segment in an elongated configuration disposed between said at least one bus element and said active surface for a majority of an extent of said at least one bus over said active surface.

7. The die assembly of claim 6, wherein said at least one elongated adhesive segment lies between said at least one bus element and said active surface for substantially all of the extent of said at least one bus over said active surface.

8. The die assembly of claim 6, wherein said at least one bus element comprises a first bus element and a second bus element extending in mutually parallel relationship over said active surface, and said at least one elongated adhesive segment comprises first and second adhesive segments, one disposed between each of said first and second bus elements and said active surface.

9. The die assembly of claim 1, wherein said adhesive segment comprises a dielectric adhesive segment.

10. The die assembly of claim 1, wherein said at least one adhesive segment is of a size and shape corresponding to the portion of said lead frame to which it is adhered.

11. The die assembly of claim 1, wherein said at least one adhesive segment comprises the smallest plurality of adhesive segments required to support said die from the underside of said lead frame.

12. The die assembly of claim 1, wherein said at least one adhesive segment comprises the smallest cross-sectional area of adhesive required to support said die from the underside of said lead frame.

13. The die assembly of claim 1, wherein said at least one adhesive segment comprises a plurality of adhesive segments disposed at the fewest laterally spaced locations on said active surface required to support said die from the underside of said lead frame.

14. The die assembly of claim 1, wherein said at least one adhesive segment comprises a plurality of adhesive segments sized and configured to provide the least direct adherence between said lead frame and said die required to support said die from said lead frame.

15. The die assembly of claim 1, wherein said periphery is defined by opposing ends, and opposing sides, and at least one adhesive segment comprises a plurality of segments, at least one of which is disposed proximate each end of said die and at least another of which is disposed proximate a center of said active surface, and at least one of said inwardly extending lead elements is secured to said at least another segment.

16. The die assembly of claim 15, wherein said at least another segment comprises two segments disposed proximate a center of said active surface, and at least one inwardly extending lead element extends from each opposing side of said die and is secured to one of said two segments.

17. The die assembly of claim 1, wherein at least one of said inwardly extending lead elements includes an enlarged inner end, to which said at least one adhesive segment is secured.