Method for attaching a semiconductor die to a leadframe, and a semiconductor device

• US 20090146279A1
• Filed: 12/05/2007
• Published: 06/11/2009
• Est. Priority Date: 12/05/2007
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Griffin, Garrett
• Granted Patent: US 8,105,880 B2
• Time in Patent Office: Days
• US Class Current: 257/676
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2224/05554 being square
• CPC Class Codes: H01L 2224/2612 Auxiliary members for layer connectors, e.g. spacers
• CPC Class Codes: H01L 2224/29012 in top view
• CPC Class Codes: H01L 2224/29082 Two-layer arrangements
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/32014 the layer connector being smaller than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/32245 the item being metallic
• 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 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/75611 Feeding means
• CPC Class Codes: H01L 2224/83101 as prepeg comprising a layer connector, e.g. provided in an insulating plate member
• CPC Class Codes: H01L 2224/83192 wherein the layer connectors are disposed only on another item or body to be connected to the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/83194 Lateral distribution of the layer connectors
• CPC Class Codes: H01L 2224/83851 being an anisotropic conductive adhesive
• CPC Class Codes: H01L 2224/83855 Hardening the adhesive by curing, i.e. thermosetting
• CPC Class Codes: H01L 2224/83856 : Pre-cured adhesive, i.e. B-stage adhesive
• CPC Class Codes: H01L 2224/85 : using a wire connector
• CPC Class Codes: H01L 23/293 : Organic, e.g. plastic
• 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 23/49513 : having bonding material between chip and die pad
• CPC Class Codes: H01L 24/29 : of an individual layer connector
• CPC Class Codes: H01L 24/32 : of an individual layer 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 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 2924/00012 : 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 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/0665 : Epoxy resin
• CPC Class Codes: H01L 2924/07802 : not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/0781 : being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/10161 : with a rectangular active surface
• 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 semiconductor device comprising a leadframe (4) with a carrier pad (3) bonded thereto, and a die (2) bonded to the carrier pad (3) to form a bonded assembly (5) which is encapsulated in a housing (7) with leads (8) of the leadframe (4) extending therefrom is formed by initially bonding the carrier pad (3) which is pre-coated with a thermosetting first adhesive (20) to the leadframe (4). The first adhesive (20) is raised to its thermosetting cure temperature for bonding the carrier pad (3) to the leadframe (4) by heating the leadframe (4) to a temperature just above the thermosetting cure temperature of the first adhesive (20). A thermosetting second adhesive (22) which is liquid at room temperature is applied to a second major surface (19) of the carrier pad (3), and the die (2) is placed on the second adhesive (22) and aligned with the leadframe (4). The second adhesive (22) is raised to its thermosetting cure temperature to bond the die (2) to the carrier pad (3), and in turn form a bonded assembly (5). Bond wires (15) are electrically coupled to contact pads (14) of the die (2) and leads (8) of the leadframe (4) and the bonded assembly (5) is then encapsulated in the encapsulating housing (7).

Claims

1. A method for attaching a semiconductor die to a leadframe, the method comprising:

providing the leadframe with a carrier pad attached thereto, the carrier pad having first and second major surfaces, and a first adhesive bonding the leadframe to the first major surface of the carrier pad,

applying a flowable temperature curable second adhesive to the second major surface of the carrier pad,

placing the die on the second adhesive on the second major surface of the carrier pad for facilitating wire bonding of the die to the leadframe, and

subjecting the second adhesive to a curing temperature for curing thereof to bond the die to the carrier pad.

2. A method as claimed in claim 1 in which the second adhesive is applied to the second major surface of the carrier pad by dispensing the second adhesive through a nozzle.

3. A method as claimed in claim 2 in which the second adhesive is dispensed through the nozzle so that the second adhesive forms a pattern on the second major surface of the carrier pad, and the nozzle is moved during dispensing of the second adhesive therefrom in a common plane of movement in at least one of an X-axis direction and a Y-axis direction for applying the second adhesive on the second major surface of the carrier pad in the form of the pattern.

4. A method as claimed in claim 3 in which the second adhesive is continuously dispensed through the nozzle while the nozzle is being moved in the at least one of the X- and Y-axes directions to form the pattern of the second adhesive as a continuous pattern on the second major surface of the carrier pad.

5. A method as claimed in claim 3 in which dispensing of the second adhesive through the nozzle is periodically disrupted while the nozzle is being moved in the at least one of the X- and Y-axes directions to form the pattern of the second adhesive as a discontinuous pattern comprising a plurality of discrete portions of the adhesive.

6. A method as claimed in claim 3 in which the common plane of movement of the nozzle in the X- and Y-axes directions lies substantially parallel to a plane defined by the second major surface of the carrier pad.

7. A method as claimed in claim 1 in which the die is pressed into engagement with the second adhesive on the second major surface of the carrier pad, and is manoeuvred thereon for aligning electrically conductive contact pads of the die with corresponding leads of the leadframe for facilitating subsequent wire bonding of contact pads of the die and the leads of the leadframe.

8. A method as claimed in claim 1 in which the second adhesive is a thermosetting electrically non-conductive adhesive.

9. A method as claimed in claim 1 in which the second adhesive has a cure temperature in the range of 80°

C. to 250°

C.

10. A method as claimed in claim 9 in which the second adhesive has a cure temperature of approximately 175°

C.

11. A method as claimed in claim 1 in which the second adhesive is liquid at room temperature.

12. A method as claimed in claim 1 in which the carrier pad is of a flexible and an electrically non-conductive material.

13. A method as claimed in claim 1 in which the carrier pad is of polyimide material stable at the cure temperature of the second adhesive.

14. A method as claimed in claim 1 in which the area of the carrier pad in plan view is substantially similar to the area of the die in plan view.

15. A method as claimed in claim 1 in which the die and the carrier pad are attached to the leadframe so that the die overlays proximal ends of at least some of the leads of the leadframe.

16. A method as claimed in claim 1 in which the die comprises a first major surface adjacent which an integrated circuit is formed therein, and a second major surface remote from the integrated circuit and defined by a substrate on which the integrated circuit is formed, and the die is placed on the second adhesive with one of the first and second major surfaces of the die abutting the second adhesive.

17. A method as claimed in claim 1 in which the method further comprises wire bonding the die to the leadframe, and encapsulating the die, the leadframe and the carrier pad bonded together in an encapsulating housing of a mouldable thermosetting material, with distal ends of leads of the leadframe extending from the encapsulating housing.

18. A method as claimed in claim 1 in which the first adhesive is a temperature curable adhesive.

19. A method as claimed in claim 1 in which the first adhesive has a cure temperature in the range of 120°

C. to 250°

C.

20. A method as claimed in claim 19 in which the first adhesive has a cure temperature of approximately 200°

C.

21. A method as claimed in claim 1 in which the first adhesive is an electrically non-conducting thermosetting adhesive.

22. A method as claimed in claim 1 in which the first adhesive is pre-coated onto the first major surface of the carrier pad, and is partially cured thereon.

23. A method as claimed in claim 1 further comprising bonding the carrier pad to the leadframe prior to bonding the die to the carrier pad.

24. A method as claimed in claim 23 in which the carrier pad is placed on the leadframe with the first adhesive on the first major surface thereof abutting the leadframe, and the leadframe is heated for in turn at least partially curing the first adhesive.

25. A semiconductor device comprising:

a carrier pad having first and second major surfaces,

a leadframe bonded to the first major surface of the carrier pad by a first adhesive,

a semiconductor die bonded to the second major surface of the carrier pad by a second adhesive, the second adhesive being a flowable temperature curable adhesive, and having been applied to the second major surface of the carrier pad in flowable form for facilitating alignment of electrically conductive contact pads of the die with leads of the leadframe during placement of the die on the carrier pad.

26. A semiconductor device as claimed in claim 25 in which the second adhesive is an electrically non-conductive thermosetting adhesive.

27. A semiconductor device as claimed in claim 25 in which the carrier pad is electrically non-conductive.

28. A semiconductor device as claimed in claim 25 in which the carrier pad is of polyimide material.

29. A semiconductor device as claimed in claim 25 in which the first adhesive is an electrically non-conductive thermosetting adhesive.

30. A semiconductor device as claimed in claim 25 in which the carrier pad comprises a carrier pad pre-coated with the first adhesive on the first major surface thereof.

31. A semiconductor device as claimed in claim 25 in which the area of the carrier pad in plan view is substantially similar to the area of the die in plan view, and the die and the carrier pad overlay a proximal portion of at least some of the leads of the leadframes.

32. A semiconductor device as claimed in claim 25 in which the die comprises a first major surface adjacent which an integrated circuit is formed therein, and a second major surface remote from the integrated circuit defined by a substrate in which the integrated circuit is formed, the die being attached to the carrier pad with the second major surface of the die adjacent the second major surface of the carrier pad.

33. A semiconductor device as claimed in claim 25 in which the die, the carrier pad and the leadframe bonded together are encapsulated in an encapsulating housing of a mouldable thermosetting material, distal portions of the respective leads of the leadframe extending from the encapsulating housing.