Dissimilar adhesive die attach for semiconductor devices

• US 5,304,842 A
• Filed: 06/26/1992
• Issued: 04/19/1994
• Est. Priority Date: 10/24/1990
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Smith, Rockwell D., Farnworth, Warren M., Moden, Walter L.
• Primary Examiner(s): Crane, Sara W.
• Assistant Examiner(s): WHITEHEAD JR, CARL W
• Application Number:
  US07/904,785
• Time in Patent Office: 662 Days
• Field of Search: 257/666, 257/668, 257/669, 257/674, 257/676, 257/691, 257/735, 257/736, 257/787, 257/788, 257/798, 437/207, 437/208, 437/212, 437/220, 437/915, 437/923
• US Class Current: 257/668
• CPC Class Codes: H01L 2224/2612 Auxiliary members for layer connectors, e.g. spacers
• 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 2224/32245 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 2224/4826 Connecting between the body and an opposite side of the item with respect to the body
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2224/73215 Layer and wire connectors
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2224/83101 as prepeg comprising a layer connector, e.g. provided in an insulating plate member
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/8388 Hardening the adhesive by cooling, e.g. for thermoplastics or hot-melt adhesives
• CPC Class Codes: H01L 23/49506 an insulative substrate being used as a diepad, e.g. ceramic, plastic H01L23/49531 takes precedence
• CPC Class Codes: H01L 23/49558 Insulating layers on lead frames, e.g. bridging members
• 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 24/45 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 24/83 : using a layer 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 2924/00014 : 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 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• 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 2924/01322 : Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• 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 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/3512 : Cracking
• CPC Class Codes: Y10T 29/49121 : Beam lead frame or beam lead device

Abstract

A semiconductor assembly comprises a semiconductor die which is attached by a carrier material to a lead frame. The carrier material is coated on the die side with one type of adhesive and on the lead frame side with a different adhesive. The lead frame has a small surface area to connect to the carrier material, while the semiconductor die has a large surface area to connect to the carrier material. As used with one inventive embodiment, the adhesive between the die and the carrier softens at a low temperature preventing the die from cracking at elevated temperatures. The adhesive on the lead frame side of the carrier material softens at a higher temperature than the adhesive of the die side of the adhesive, thereby firmly connecting the lead frame having a small surface area to the carrier.

Claims

1. A semiconductor assembly, comprising:

a) a semiconductor die having a major surface with bond pads located thereon;

b) a lead frame having lead fingers, each lead finger having an end which terminates proximally to said die;

c) a carrier material having first and second major surfaces;

d) a first adhesive material which attaches said first major surface of said carrier material with said lead frame;

e) a second adhesive material which attaches said second major surface of said carrier material with said die,

wherein after the assembly is assembled said second adhesive softens at a lower temperature than said first adhesive, said softening of said second adhesive relieving stress between said die and said second adhesive, and said first adhesive providing a solid attachment at said second adhesive softening temperature between said lead frame and said carrier material.

2. The semiconductor assembly of claim 1 wherein said second adhesive material is a thermoplastic.

3. The semiconductor assembly of claim 2 wherein said first adhesive material is a thermoplastic.

4. The semiconductor assembly of claim 2 wherein said first adhesive material is a thermoset.

5. The semiconductor assembly of claim 1 wherein said second adhesive material softens below 150°

C.

6. The semiconductor assembly of claim 1 further comprising bond wires to electrically couple said bond pads with said lead fingers.

7. The semiconductor assembly of claim 1 wherein said second adhesive contacts said major surface of said die.

8. The semiconductor assembly of claim 1 wherein said first and second adhesives are less than 4 mils thick.

9. The semiconductor assembly of claim 1 wherein said carrier material is less than 5 mils thick.

10. The semiconductor assembly of claim 1 wherein said assembly is encapsulated after said die and said lead frame are attached to said carrier material.

20. The semiconductor memory device of claim 10 wherein said memory device is a dynamic random access memory.

11. An encapsulated semiconductor memory device, comprising:

a) a semiconductor die having a major surface with bond pads located thereon;

b) a lead frame having lead fingers, each lead finger having an end which terminates proximally to said die;

c) a carrier material having first and second major surfaces;

d) a first adhesive material which attaches said first major surface of said carrier material with said lead frame;

e) a second adhesive material which attaches said second major surface of said carrier material with said die,

wherein after the assembly is assembled said second adhesive softens at a lower temperature than said first adhesive, said softening of said second adhesive relieving stress between said die and said second adhesive, and said first adhesive providing a solid attachment at said second adhesive softening temperature between said lead frame and said carrier material.

12. The semiconductor assembly of claim 11 wherein said second adhesive material is a thermoplastic.

13. The semiconductor memory device of claim 12 wherein said first adhesive material is a thermoplastic.

14. The semiconductor memory device of claim 12 wherein said first adhesive material is a thermoset.

15. The semiconductor memory device of claim 11 wherein said second adhesive material softens below 150°

C.

16. The semiconductor memory device of claim 11 further comprising bond wires to electrically couple said bond pads with said lead fingers

17. The semiconductor memory device of claim 11 wherein said second adhesive contacts said major surface of said die.

18. The semiconductor memory device of claim 11 wherein said first and second adhesives are less than 4 mils thick.

19. The semiconductor memory device of claim 11 wherein said carrier material is less than 5 mils thick.