Thermosonic bonding

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Thermosonic bonding is the most widely used wire bonding method to electrically connect silicon integrated circuits.[1]Alexander Coucoulas, The Father of Thermosonic Bonding,[2] introduced and invented it in 1966 (Figure 1).[3] [4][5][6] Due to the well-proven reliability of a Thermosonic bond, it is extensively used to connect the all important Central Processing Unit (CPU) which are encapsulated integrated circuits that serve as the mainstay and "brains" of the computer.

Wires connected to a silicon integrated circuit using thermosonic bonding

Thermosonic bonding is a akin to Friction welding since it creates a scrubbing action at the contact points between the pre-heated deforming lead-wire and the metallized pads of the silicon integrated circuit. In addition, it produces a temporary ultrasonic or acoustic softening in the lead-wire which facilitates its deformation to form the desirable contact area at relatively low temperatures and forces. As a result of the frictional action and acoustic softening induced in the lead wire during the bonding cycle, Thermosonic bonding can be used to reliably bond high melting point metals lead wires, (such as gold, and lower cost aluminum and copper) with relatively low bonding parameters. This ensures that the fragile and costly silicon integrated circuit “chip” used to form Central Processing Units (CPU) for computers are not exposed to damaging high temperatures or mechanical stresses during the bonding process.

History[edit]

Earlier wire bonding methods were Thermocompression bonding,[7] which used heat and pressure and ultrasonic bonding,[8] which used vibratory energy and pressure. Thermosonic bonding improved upon the reliability of the earlier processes by preheating the lead wire and metallized chip prior to introducing the ultrasonic cycle. It resulted in eliminating the incidences of cracking in the fragile and costly silicon chip. The improvement occurred because pre-heating the lead-wire softened it which facilitated its deformation in forming the required contact area during the ultrasonic bonding cycle. Under these conditons, the onset of recrystallization (metallurgy) or hot working of the deforming wire tends to occur while it is forming the required contact area. Due to hot working during the bonding cycle, the final deformed-bonded wire would be in a relatively soft and stable state. If the wire was ultrasonically deformed at room temperature, it would tend to strain hardened (cold working)and therefore tend to transmit damaging mechanical stresses to the silicon chip. Thermosonic bonding, initially referred to as Hot Work Ultrasonic Bonding, was found to work on bonding aluminum and copper wires to tantalum and palladium thin films on aluminum oxide and glass substrates which simulated the metallized chip.[9] [10]


Ongoing Development[edit]

Thermosonic bonding is now used in the Flip Chip process which is an alternate method of electrically connecting silicon integrated circuits.

Josephson Effect and superconducting interference (DCSQUID) devices use the Thermosonic bonding process as well. In this case, other bonding methods would degrade or even destroy YBaCuO₇ microstructures, such as microbridges, Josephson junctions and superconducting interference devices[11](DCSQUID).

When electrically connecting Light-emitting diodes with thermosonic bonding techniques, an improved performance of the device has been shown.[12]

Background Of Alexander Coucoulas (Inventor)[edit]

Alexander Coucoulas Father Of Thermosonic Bonding

Alexander Coucoulas retired from AT&T Bell Labs as a Member Of The Technical Staff in 1996 where he pioneered research in the areas of electronic/photonic packaging and optical fibers which resulted in: producing numerous publications and presentations; co-authoring several technical books and; obtaining more than 30 patents. He was twice awarded best paper-publication and presentation at the 20th and 43rd IEEE Electronic Components Conference for “Compliant Bonding” in 1970, and AlO Bonding in 1993 (Figure 2)[13] both of which were his patented inventions.[14]

His Greek immigrant parents were Ionians who were born in the biblical port-city of Smyrna, situated on the western coast of Asia Minor, which was the birthplace of Homer. His father, Demetrios Koukoulas, was rescued (as a maimed Smyrnaean Greek soldier) in the Aegean Sea by a Japanese naval cruiser during the Fire of Smyrna in September 1922 and brought to Pereaus, Greece.[15][16] He immigrated to the United States on the SS King Alexander that same year.

His son, Alexander Coucoulas, served in the US Army as a combat engineer in the Far East Command in the early 1950s and was awarded the National Defense Service Medal for the Korean War (1950-1954).[17] After serving in the US Army, he obtained his undergraduate and graduate degrees in Metallurgical Engineering and Material Science at New York University which was financed by the GI Bill, a graduate scholarship and part-time jobs in the New York Metropolitan area. His graduate thesis, included in a co-authored paper,[18] was under the tutelage of dr. Kurt Komarek who later became the President of the University Of Vienna and presently is professor-emeritus.[19]

Summary[edit]

At present, the majority of connections to the silicon integrated circuit chip are made using Thermosonic bonding[20] because it employs lower bonding temperatures, forces and dwell times than thermocompression bonding, as well as lower vibratory energy levels and forces than ultrasonic bonding to form the required bond area. Therefore the use of Thermosonic Bonding eliminates damaging the relatively fragile silicon integrated circuit chip during the bonding cycle. The proven reliability of Thermosonic bonding has made it the process of choice, since such potential failure modes could be costly whether they occur during the manufacturing stage or detected later, during an operational field-failure of a chip which had been connected inside a computer or a myriad of other microelectronic devices.

Figure 2. AlO Bonding: A Method Of Joining Oxide Optical Components To Aluminum Coated Substrates”1993 IEEE Electronic Components Conference double Click squares to read full resolution.
Figure 1, ”Hot Work Ultrasonic (Thermosonic) Bonding” 1970 IEEE Electronic Components Conference. Double click squares to read full resolution

See also[edit]

References[edit]

  1. ^ https://www.google.com/search?output=search&sclient=psy-ab&q=thermosonic+wire+bonding&btnK=
  2. ^ Harman, G., Wire Bonding In Microelectronics], McGraw-Hill, Chapt. 2, pg.36 also search Coucoulas at http://www.amazon.com/WIRE-BONDING-MICROELECTRONICS-3-E/dp/0071476237/ref=sr_1_1?s=books&ie=UTF8&qid=1354948679&sr=1-1&keywords=wire+bonding+in+microelectronics#_
  3. ^ Coucoulas, A., Trans. Metallurgical Society Of AIME, “Ultrasonic Welding of Aluminum Leads to Tantalum Thin Films”, 1966, pp. 587–589. abstract
  4. ^ Coucoulas, Alexander, Hot Work Ultrasonic (Thermosonic) Bonding, Proceedings 1970 20th Electronic Components Conference, pp.549- 556. 1970. Hot Work Ultrasonic (Thermosonic) Bonding 549-556.pdf (file) http://en.wikipedia.org/wiki/File:Hot_Work_Ultrasonic_(Thermosonic)_Bonding_549-556.pdf
  5. ^ https://sites.google.com/site/thermosonicbonding/
  6. ^ Coucoulas, A., US patent|3507033, (filed in 1966), Apr. 1970.
  7. ^ Anderson, O. L.; Christensen, H.; Andreatch, P. (1957). "Technique for Connecting Electrical Leads to Semiconductors". Journal of Applied Physics 28: 923. doi:10.1063/1.1722893. 
  8. ^ Carlin, B., Ultrasonics, McGraw-Hill Book Co., 1960.
  9. ^ Coucoulas, A., Trans. Metallurgical Society Of AIME, “Ultrasonic Welding of Aluminum Leads to Tantalum Thin Films”, 1966, pp. 587–589. abstract
  10. ^ Coucoulas, Alexander, Hot Work Ultrasonic (Thermosonic) Bonding, Proceedings 1970 20th Electronic Components Conference, pp.549- 556. 1970. Hot Work Ultrasonic (Thermosonic) Bonding 549-556.pdf (file) http://en.wikipedia.org/wiki/File:Hot_Work_Ultrasonic_(Thermosonic)_Bonding_549-556.pdf
  11. ^ L. Burmeister, D.Reimer and M. Schilling, “Thermosonic bond contacts with gold wire to YBa2Cu3O7 microstructures” , Superconductor Science and Technology Journal, Vol 7, number 8, August, 1994.http://iopscience.iop.org/0953-2048/7/8/006/ doi:10.1088/0953-2048/7/8/006
  12. ^ Seck-Hoe Wong,Mooi,Guan Ng,Mee-Lee Yong, Noorais, (Phillips Company) “Packaging Of Power LEDs Using Thermosonic Bonding Of Au-Au Interconnects”, Surface Mount Technology Association International Conference, 9-24-2006. http://www.smta.org/knowledge/proceedings_abstract.cfm?PROC_ID=2053
  13. ^ A.Coucoulas, Benzoni, A.M., Dautartas, M.F., Dutta, R., Holland, W.R., Nijander, C.R., Woods, R.E., AlO Bonding: A Method Of Joining Oxide Optical Components to Aluminum Coated Substrates, pp 471-481, Proceedings of the 43rd Electronic Components and Technology Conference, 1993 http://www.researchgate.net/publication/3565139_AlO_bonding_a_method_of_joining_oxide_optical_components_toaluminum_coated_substrates
  14. ^ http://www.google.com/patents/US5178319
  15. ^ http://www.worldnavalships.com/edgar_quinet_class.htm
  16. ^ Dobkin, Marjorie Housepian. Smyrna 1922: The Destruction of a City. New York: Harcourt Brace Jovanovich, 1971; 2nd ed. Kent, Ohio: Kent State University Press, 1988, pp.102,174,117-121.
  17. ^ National Defense Service Medal
  18. ^ K.L.Komarek,A.Coucoulas,and N.Klinger, Journal Of The Electrochemical Society,V.110,No.7,July 1963 https://www.researchgate.net/publication/233854987_thesispublication
  19. ^ http://translate.google.com/translate?hl=en&sl=de&u=http://de.wikipedia.org/wiki/Kurt_Komarek&prev=/search%3Fq%3Dkurt%2Bkomarek%2Bwikipedia%26hl%3Den%26biw%3D1507%26bih%3D702&sa=X&ei=-CpLUe7MNZG-4APgpYD4CQ&sqi=2&ved=0CDcQ7gEwAA
  20. ^ Harman, G., Wire Bonding In Microelectronics], McGraw-Hill, Chapt. 2, pg.36