1. Interconnection in IC Assembly
Level of Interconnection, Wire Bonding, Tape Automated Bonding (TAB), Flip Chip
DMT 243 – Chapter 4
M.Nuzaihan

2. Interconnection in IC Assembly
What is IC Assembly?
Is defined as the process of electrically connecting I/O bond pads on the IC to the corresponding bond pads on the package.
The package : single chip package, multichip package, system level board.
IC assembly process involves 3 interfaces:
1) metallurgical bond pad interface on the package
2) electrical interconnection between these two interfaces
3) metallurgical bond pad interface on the IC
DMT 243 – Chapter 4
M.Nuzaihan

3. Interconnection in IC Assembly
What is IC Assembly?
DMT 243 – Chapter 4
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4. Interconnection in IC Assembly
Purpose of IC Assembly
to enable an IC to be electrically interconnected to the package/system.
to allow that IC to be handled, tested and burnt in to guarantee the quality of the IC.
DMT 243 – Chapter 4
M.Nuzaihan

5. Interconnection in IC Assembly
Requirement for IC Assembly
To provide acceptable electrical properties.
Should provide a low cost solution for electrical interface between the chip and package.
High throughput manufacturing
High reliability
Repairability and replaceability
DMT 243 – Chapter 4
M.Nuzaihan

6. Interconnection in IC Assembly
Levels of Interconnects
Six levels of interconnects:
• Level 1: chip pad to package leads, e.g., wire bonds
• Level 2: components to circuit board, e.g., PLCC socket
• Level 3: circuit board (board-to-board) connector, e.g., edge-board connection
• Level 4: subassembly interconnects, e.g., ribbon cables
• Level 5: subassembly to I/O, e.g., BNC connector
• Level 6: system interconnects, e.g., Ethernet connectors
DMT 243 – Chapter 4
M.Nuzaihan

7. Interconnection in IC Assembly
DMT 243 – Chapter 4
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8. Interconnection in IC Assembly
DMT 243 – Chapter 4
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9. 1st Level Interconnect (Chip pad to package leads)
DMT 243 – Chapter 4
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10. 1s LEVEL INTERCONNECT
DMT 243 – Chapter 4
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11. Example : Combination of Two Types of Interconnection
Interconnection in IC Assembly
Example : Combination of Two Types of Interconnection
DMT 243 – Chapter 4
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12. Interconnection in IC Assembly
Wire Bonding
Chapter 3 - Types of Wire Bonding Process, Important Parameters and Common related Failure Mechanism
DMT 243 – Chapter 4
M.Nuzaihan

13. Wire Bonding Advantages
Highly flexible chip-to-package interconnection process
Low defect rates or high yield interconnection processing ( ppm)
Easily program or taught bonding cycles.
High reliability interconnection structure
Very large industry infrastructure supporting the technology
Rapid advance in equipment, tools and material technology
Disadvantages
Slower interconnection rates due point-to-point processing of each wirebond
Long chip-to-package interconnection lengths, degrading electrical performance
Larger footprint (bond pad) required for chip to package interconnect
Potential for wire sweep during encapsulation overmolding.
DMT 243 – Chapter 4
M.Nuzaihan

14. Interconnection in IC Assembly Wire Bonding
IC Bond Pad Interface
Al is predominant IC bond pad interface for wire bond interconnect. However, Cu metallization is gaining interest due to increase of performance.
Package Bond Pad Interface
Metallized leadframe – most common material are Cu alloys (e.g Cu-Fe, Cu-Cr, Cu-Ni-Si and Cu-Sn) and some instance Fe-Ni or Fe-Ni-Co alloys are also used. Lastly at final it will plated/coated with Ni, Au or Sn.
Metallized chip carrier and PWB – most common conductor is Cu which is plated with Ni and soft or immersion gold for good solderability.
DMT 243 – Chapter 4
M.Nuzaihan

15. Interconnection in IC Assembly
Wire Bonding
DMT 243 – Chapter 4
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16. DMT 243 – Chapter 4
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17. DMT 243 – Chapter 4
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18. Interconnection in IC Assembly
TAB
Tape Automated Bonding (TAB), is the process of mounting a die on a flexible tape made of polymer material, such as polyimide. It is based on the fully automated bonding of one end of the copper beam lead to an IC and the other end of the lead to a conventional package or PWB.
Tape automated bonding (TAB) also known as “gang” bonding technique in which bonds (on the chip or lead frame or substrate) are formed simultaneously.
DMT 243 – Chapter 4
M.Nuzaihan

19. Interconnection in IC Assembly
TAB
There are several TAB tape structures – planar tape, bumped tape, transfer-bumped tape, and ball tape.
DMT 243 – Chapter 4
M.Nuzaihan

20. Interconnection in IC Assembly
TAB
Advantages
Ability to handle small bond pads and finer pitches on the IC.
Elimination of larger wire loops.
Low profile interconnection structures for thin packages.
Improved conduction heat transfer for thermal management.
Improved electrical performance.
Ability to handle high I/O counts.
Ability to burn in on tape before device commitment.
Reduce weight.
DMT 243 – Chapter 4
M.Nuzaihan

21. Interconnection in IC Assembly
TAB
Disadvantages
Basically a peripheral interconnection technique with no active circuitry under the chip bond pads.
Package size tends to increase with larger I/O counts.
Process inflexibility due to hard tooling requirements of the flex circuits, bond head and etc.
Additional wafer processing steps required for bumping
Larger capital equipment investment required.
Difficulty in assembly rework.
Specialty materials and equipment requirements.
DMT 243 – Chapter 4
M.Nuzaihan

22. Interconnection in IC Assembly
TAB
DMT 243 – Chapter 4
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23. Interconnection in IC Assembly
TAB
DMT 243 – Chapter 4
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24. Interconnection in IC Assembly
TAB
DMT 243 – Chapter 4
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25. TAB - IC Bond Pad Interface
Inner Lead Bonding
DMT 243 – Chapter 4
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26. TAB - IC Bond Pad Interface
DMT 243 – Chapter 4
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27. Interconnection in IC Assembly
TAB
Electrical performance – Improved electrical performance, due to short circuit lead lengths between the chip and substrate reducing impedance and signal delays.
Production examples – Tape Ball Grid Array (TBGA), (based on Quad Flat Pack), Pentium TCP.
DMT 243 – Chapter 4
M.Nuzaihan

28. DMT 243 – Chapter 4
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29. DMT 243 – Chapter 4
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30. Interconnection in IC Assembly
Tomorrow
Level of Interconnection, Wire Bonding, Tape Automated Bonding (TAB), Flip Chip
DMT 243 – Chapter 4
M.Nuzaihan