Integrated-circuit lead-frame package with failure-resistant ground-lead and heat-sink means

• US 5,289,344 A
• Filed: 10/08/1992
• Issued: 02/22/1994
• Est. Priority Date: 10/08/1992
• Status: Expired due to Term

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Panaccione, Paul J., Gagnon, Jay J.
• Primary Examiner(s): Tolin, Gerald P.
• Application Number:
  US07/958,496
• Time in Patent Office: 502 Days
• Field of Search: 165/80.3, 165/185, 174/51, 174/52.2, 174/52.4, 257/675, 257/688, 361/386, 361/387, 361/388, 361/389, 361/421, 361/814, 361/704, 361/707, 361/712
• US Class Current: 361/712
• CPC Class Codes: H01L 2224/05553 being rectangular
• CPC Class Codes: H01L 2224/05554 being square
• CPC Class Codes: H01L 2224/05599 Material
• 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 2224/45147 Copper (Cu) 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 2224/484 Connecting portions
• CPC Class Codes: H01L 2224/48599 Principal constituent of the connecting portion of the wire connector being Gold (Au)
• CPC Class Codes: H01L 2224/48699 Principal constituent of the connecting portion of the wire connector being Aluminium (Al)
• CPC Class Codes: H01L 2224/48799 Principal constituent of the connecting portion of the wire connector being Copper (Cu)
• CPC Class Codes: H01L 2224/49112 the connectors connecting a common bonding area on the semiconductor or solid-state body to different bonding areas outside the body, e.g. diverging wires
• CPC Class Codes: H01L 2224/85399 Material
• CPC Class Codes: H01L 23/49562 for devices being provided for in H01L29/00
• CPC Class Codes: H01L 23/49568 specifically adapted to facilitate heat dissipation
• 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 24/49 : of a plurality of wire connectors
• 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 2924/00015 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed as prior art
• CPC Class Codes: H01L 2924/01005 : Boron [B]
• 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 2924/01023 : Vanadium [V]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15747 : Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2924/181 : Encapsulation

Abstract

The lead-frame in an integrated circuit package, a standard package designated SOT-89, has a plurality of leads of which at least one is an extension of a die-attach pad. At least one ground wing is formed as an extension of a peripheral portion of the die-attach pad and extends upward to approximately the plane of the top of the die. The ground wing has an upstanding portion and a horizontal portion that are at an angle to each other so as to lock the distal end of the wing in the body of encapsulating resin. An integrated circuit die having at least one electrical connection which is grounded electrically via a terminal and wire bonded to the distal part of the ground wing. A contact surface near the distal end of wing is positioned approximately in the plane of the top of the die. This ground circuit can parallel and can be redundant to a ground circuit through the die via the conductive bond that attaches the bottom of the die to the die-attach pad. The ground lead that is an extension of the die-attach pad serves both to remove heat from the die and to provide an electrical ground connection. The contact surface of the wing provides a point of ground-wire attachment that does not move relative to the encapsulating resin as do other peripheral parts of the die attach pad during temperature cycling and mechanical stress. Thus, a common failure mode, which is called heal-cracking, is substantially eliminated.

Claims

1. An integrated-circuit package comprising:

(a) a semiconductor integrated-circuit die having two major faces, a top face and a bottom face, said die having at least one electrical circuit ground terminal on the top face and at least one electrical signal terminal on the top face,

(b) a lead frame comprising;

(i) a die-attach pad, having a top face, a bottom face, a front side, a back side, a right side, and a left side, the bottom die face of the die being bonded to the top face of said die-attach pad to provide a physical and thermal connection between said die and said pad,

(ii) at least one ground lead extending away from the front side of said die-attach pad, said lead having a proximal end attached to said pad and a distal end, and

(iii) at least one ground wing, separate from the ground lead, and extending from said pad, said wing having a proximal end attached to said pad, a distal end, and a contact surface spaced from the proximal end of the wing,

(c) at least one wire forming a direct electrical connection between the contact surface of said ground wing and said electrical ground terminal on said top die face, and

(d) a solid electrically insulating body encapsulating said die, the proximal end of said ground lead, the distal end of said ground wing, and said at least one wire, so that said ground lead is enabled to function as heat-sink ground tab conducting heat and electrical current from said die to the outside of said body.

2. The integrated-circuit package of claim 1, wherein the point of attachment of said wire to said ground wing lies on a top-surface of said wing near the distal end of said ground wing.

3. The integrated-circuit package of claim 1, wherein the point of attachment of said wing to said pad lies on one of the side edges of the pad.

4. The integrated-circuit package of claim 1, wherein the wing has a distal portion adjacent the distal end of the wing, said distal portion having a top surface, and said at least one wire is electrically connected to the top surface.

5. The integrated-circuit package of claim 1, wherein a top face of said die and said top face of said contact surface of said distal end of said wing lie approximately in one plane.

6. The integrated-circuit package of claim 1, wherein the wing includes a standup portion which routes the wing from the point where its proximal end contacts the pad approximately up to the plane of the top face of the die.

7. The integrated-circuit package of claim 1, wherein two wings are provided.

8. The integrated-circuit package of claim 1, wherein two wings are provided and attached to opposite edges of the pad.

9. The integrated-circuit package of claim 1, additionally comprising a plurality of conductive wire forming electrical connections between said proximal ends of some of said leads and several circuit terminals, respectively, on said top die face.