Thermosonic bonding

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Thermosonic bonding is a method used to form reliable electrical connections to silicon integrated circuit chips. Alexander Coucoulas introduced and invented it in 1966. [1][2] [3][4][5] These chips are the mainstay of computers and a myriad of other electronic devices which is why a reliable connection is paramount.

Wires connected to a chip with thermosonic bonding

Thermosonic bonding is akin to Friction welding since it also creates a scrubbing action at the contact points between the deforming lead wire and the metallized pads of the chip though Thermosonic bonding transmits ultrasonic waves in a pre-heated lead wire to produce these results. As a result, Thermosonic bonding allows materials with high melting points, such as gold, and lower cost aluminum and copper lead wires, to be reliably bonded well below their melting points using relatively low bonding forces and therefore does not expose the chip to damaging high temperatures and mechanical stresses.

History[edit]

Earlier wire bonding methods were Thermocompression bonding,[6] which used heat and pressure and ultrasonic bonding,[7] 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.[8] [9]


Ongoing Development[edit]

Thermosonic bonding is now used in the Flip Chip process.

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[10](DCSQUID).

Light-emitting diodes can be connected using thermosonic bonding, which can improve their performance.[11]

Summary[edit]

At present, the majority of connections to the silicon integrated circuit chip are made using Thermosonic bonding[12] 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.

See also[edit]

. https://sites.google.com/site/thermosonicbonding/

References[edit]

  1. ^ 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#_
  2. ^ Coucoulas, A., Trans. Metallurgical Society Of AIME, “Ultrasonic Welding of Aluminum Leads to Tantalum Thin Films”, 1966, pp. 587–589. abstract
  3. ^ 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
  4. ^ https://sites.google.com/site/thermosonicbonding/
  5. ^ Coucoulas, A., US patent|3507033, (filed in 1966), Apr. 1970.
  6. ^ 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. 
  7. ^ Carlin, B., Ultrasonics, McGraw-Hill Book Co., 1960.
  8. ^ Coucoulas, A., Trans. Metallurgical Society Of AIME, “Ultrasonic Welding of Aluminum Leads to Tantalum Thin Films”, 1966, pp. 587–589. abstract
  9. ^ 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
  10. ^ 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
  11. ^ 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
  12. ^ Harman, G., Wire Bonding In Microelectronics], McGraw-Hill, Chapt. 2, pg.36