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

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

Interconnection in IC Assembly What is IC Assembly? DMT 243 – Chapter 4 M.Nuzaihan

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

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

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

Interconnection in IC Assembly DMT 243 – Chapter 4 M.Nuzaihan

Interconnection in IC Assembly DMT 243 – Chapter 4 M.Nuzaihan

1st Level Interconnect (Chip pad to package leads) DMT 243 – Chapter 4 M.Nuzaihan

1s LEVEL INTERCONNECT DMT 243 – Chapter 4 M.Nuzaihan

Example : Combination of Two Types of Interconnection Interconnection in IC Assembly Example : Combination of Two Types of Interconnection DMT 243 – Chapter 4 M.Nuzaihan

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

Wire Bonding Advantages Highly flexible chip-to-package interconnection process Low defect rates or high yield interconnection processing (40-1000 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

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

Interconnection in IC Assembly Wire Bonding DMT 243 – Chapter 4 M.Nuzaihan

DMT 243 – Chapter 4 M.Nuzaihan

DMT 243 – Chapter 4 M.Nuzaihan

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

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

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

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

Interconnection in IC Assembly TAB DMT 243 – Chapter 4 M.Nuzaihan

Interconnection in IC Assembly TAB DMT 243 – Chapter 4 M.Nuzaihan

Interconnection in IC Assembly TAB DMT 243 – Chapter 4 M.Nuzaihan

TAB - IC Bond Pad Interface Inner Lead Bonding DMT 243 – Chapter 4 M.Nuzaihan

TAB - IC Bond Pad Interface DMT 243 – Chapter 4 M.Nuzaihan

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), TapePak@ (based on Quad Flat Pack), Pentium TCP. DMT 243 – Chapter 4 M.Nuzaihan

DMT 243 – Chapter 4 M.Nuzaihan

DMT 243 – Chapter 4 M.Nuzaihan

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