High frequency, low temperature thermosonic ribbon bonding process for system-level applications

• US 5,894,983 A
• Filed: 01/09/1997
• Issued: 04/20/1999
• Est. Priority Date: 01/09/1997
• Status: Expired due to Fees

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Wilson, Steven E., Beck, Donald J., Hillman, Kelly V., Deju, Hector, Rief, Gary A., Buschor, Thomas K., Nichols, James B., Pigon, Brett A., Whybrew, Walter M.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): Knapp, Jeffrey T.
• Application Number:
  US08/781,541
• Time in Patent Office: 831 Days
• Field of Search: 228/1.1, 228/110.1, 228/180.5
• US Class Current: 228/110.1
• CPC Class Codes: H01L 2224/05624 Aluminium [Al] as principal constituent
• CPC Class Codes: H01L 2224/05644 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/45014 Ribbon connectors, e.g. rectangular cross-section
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48455 Details of wedge bonds
• CPC Class Codes: H01L 2224/48472 the other connecting portion not on the bonding area also being a wedge bond, i.e. wedge-to-wedge
• CPC Class Codes: H01L 2224/48624 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/48644 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/78313 Wedge
• CPC Class Codes: H01L 2224/78318 inside the capillary
• CPC Class Codes: H01L 2224/85099 Ambient temperature
• CPC Class Codes: H01L 2224/85205 Ultrasonic bonding
• CPC Class Codes: H01L 2224/85207 Thermosonic bonding
• 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 24/78 Apparatus for connecting with wire connectors
• 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 2924/00014 : 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 2924/01027 : Cobalt [Co]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01039 : Yttrium [Y]
• 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 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/15787 : Ceramics, e.g. crystalline carbides, nitrides or oxides
• CPC Class Codes: H01L 2924/20102 : Temperature range 0 C=<T<60 C, 273.15 K =<T< 333.15K
• CPC Class Codes: H01L 2924/20103 : Temperature range 60 C=<T<100 C, 333.15 K =< T< 373.15K
• CPC Class Codes: H01L 2924/20305 : Ultrasonic frequency [f] 100 Khz=<f< 125 KHz
• CPC Class Codes: H01L 2924/20306 : Ultrasonic frequency [f] 125 Khz=<f< 150 KHz
• CPC Class Codes: H01L 2924/206 : Length ranges
• CPC Class Codes: H01L 2924/20752 : larger or equal to 20 microns less than 30 microns
• CPC Class Codes: H01L 2924/3011 : Impedance

Abstract

A thermosonic ribbon bonding process uses a combination of a relatively low temperature and a high frequency to bond a ribbon conductor to conductive bonding sites of a system level support structure, such as a space/airborne antenna, containing circuit components whose characteristics might otherwise be degraded at an elevated temperature customarily used in device-level thermosonic bonding processes. By relatively low temperature is meant a temperature no greater than the minimum temperature that would potentially cause a modification of the circuit parameters of at least one of the system'"'"'s components. Such a minimum temperature may lie in a range on the order of 25-85° C., while the ultrasonic bonding frequency preferably lies in a range of from 122 KHz to 140 KHz. For gold ribbon to gold pad bonds, this high frequency range achieves the requisite atomic diffusion bonding energy, without causing fracturing or destruction of the gold ribbon or its interface with the gold pad.

Claims

1. A method of bonding a ribbon conductor to conductive bonding sites of a plurality of components of a support structure, said components having characteristics which become degraded at a temperature above a prescribed temperature, comprising the steps of:

(a) heating said support structure to a temperature no greater than said prescribed temperature;

(b) bringing a respective section of said ribbon conductor into contact with a respective one of said conductive bonding sites, and ultrasonically vibrating said respective section of said ribbon conductor to effect a thermosonic bond of said respective section of said ribbon conductor to said respective one of said conductive bonding sites; and

(c) repeating step (b) for additional ones of said conductive bonding sites.

2. A method according to claim 1, wherein step (b) comprises ultrasonically vibrating said respective section of said ribbon conductor at a frequency that will achieve atomic diffusion bonding, but will not cause fracturing or destruction of said ribbon conductor or its interface with an associated bonding sites.

3. A method according to claim 1, wherein step (b) comprises ultrasonically vibrating said respective section of said ribbon conductor at a frequency above 120 KHz.

4. A method according to claim 1, wherein step (a) comprises heating said structure including said conductive bonding sites to a temperature no greater than 100°

C.

5. A method according to claim 1, wherein step (a) comprises heating said structure including said conductive bonding sites to a temperature lying in a range of from 25°

C. to 100°

C., and step (b) comprises ultrasonically vibrating said respective section of said ribbon conductor at a frequency lying in a range of from a frequency above 120 KHz to 140 KHz.

6. A method according to claim 1, wherein step (a) comprises heating said structure including said conductive bonding sites to a temperature lying in a range of from 25°

C. to 85°

C., and step (b) comprises ultrasonically vibrating said respective section of said ribbon conductor at a frequency lying in a range of from 122 KHz to 140 KHz.

7. A method according to claim 1, wherein step (a) comprises heating said support structure by way of convective heat flow from a convection heat source, so as to bring said bonding sites to said temperature no greater than said prescribed temperature.

8. A method according to claim 1, further including the step (c) of coating a respective thermosonically formed ribbon conductor bond with a conductive adhesive so as to increase the strength of said bond against mechanical stress.

9. An apparatus for bonding a ribbon conductor to conductive bonding sites of a plurality of components of a support structure, said components having characteristics which become degraded at a temperature above a prescribed temperature, comprising:

a heat source which is operative to heat said support structure to a temperature no greater than said prescribed temperature;

a bonding head assembly, which is operative to bring a respective section of said ribbon conductor into contact with a respective one of said conductive bonding sites, and imparts ultrasonic energy to said respective section of said ribbon conductor at a frequency that effects a thermosonic bond of said respective section of said ribbon conductor to said respective one of said conductive bonding sites.

10. An apparatus according to claim 9, wherein said bonding head assembly is operative to impart ultrasonic energy to said respective section of said ribbon conductor at a frequency above 120 KHz.

11. An apparatus according to claim 9, wherein said heat source is operative to heat said structure including said conductive bonding sites to a temperature no greater than 100°

C.

12. An apparatus according to claim 9, wherein said heat source is operative to heat said structure including said conductive bonding sites to a temperature lying in a range of from 25°

C. to 100°

C., and said bonding head assembly is operative to ultrasonically vibrate said respective section of said ribbon conductor at a frequency lying in a range of from a frequency above 120 KHz to 140 KHz.

13. An apparatus according to claim 9, wherein said heat source is operative to heat heating said structure including said conductive bonding sites to a temperature lying in a range of from 25°

C. to 85°

C., and said bonding head assembly is operative to ultrasonically vibrate said respective section of said ribbon conductor at a frequency lying in a range of from 122 KHz to 140 KHz.

14. An apparatus according to claim 9, wherein said heat source comprises a convective heat source which is operative to heat said support structure by way of convective heat flow, so as to bring said bonding sites to said temperature no greater than said prescribed temperature.

15. An apparatus according to claim 9, wherein said bonding head assembly is supported and controllably positioned by a three-dimensional translation system.

16. An apparatus according to claim 9, wherein said bonding head is operative to impart said ultrasonic energy to said respective section of said ribbon conductor for a prescribed period of time.

17. An apparatus according to claim 16, wherein said bonding head is operative to impart ultrasonic energy in a frequency range on the order of 122 KHz to 140 KHz for a duration lying in a range on the order of from 15 to 1200 milliseconds.

18. An apparatus according to claim 9, wherein said bonding head assembly comprises a tool support arm, having a distal end supporting a bonding tool in an orientation that is generally orthogonal to a longitudinal vibrational axis of said tool support arm, said tool support arm having a second end thereof coupled to receive an ultrasonic compressional wave launched by an ultrasonic wave emitting transducer, and wherein said ribbon conductor is fed through said bonding tool into engagement with a respective bonding site, such that said ultrasonic compressional wave launched by said transducer propagating through said tool support arm to said distal end thereof causes ultrasonic vibrational translation of a distal end of said bonding tool and a ribbon conductor captured thereby, so as to effect an atomic diffusion bond between said ribbon conductor and a respective bonding site.

19. An apparatus according to claim 18, wherein said bonding tool has a bore through which said ribbon-configured conductor is fed by a controlled clamp member, which is operative to controllably grip and urge said ribbon conductor inwardly or outwardly through said ribbon feed bore of said bonding tool.

20. An apparatus according to claim 19, wherein said bonding head assembly is operative to exert a prescribed pressure between the ribbon conductor and said respective bonding site.

21. An apparatus according to claim 20, wherein said prescribed bonding pressure lies within a range on the order of 90 to 136 grams.