What is underfill material?
An underfill is a composite material made up of an epoxy polymer with significant amounts of filler. Additional components added to the underfill formulation are flow agents, adhesion promoters, and dyes. Although primarily used for flip-chip devices, underfills can also be used with ball-grid arrays (BGAs) and CSPs.
What is flip-chip semiconductor?
Flip chip (also known as direct chip attach) is the process whereby a semiconductor die is attached bond pad side down to a substrate or carrier. The electrical connection is made by means of a conductive bump on the die bond pad. Flip chip bonding can offer a number of advantages over other interconnection processes.
What is flip-chip device?
1 Flip-chip devices. Flip-chip devices have solder bumps, other metal bumps, or even conductive adhesive bumps on the face of the device for I/O connections. During assembly, the devices are flipped face down, then mated and bonded to corresponding solder or metal pads on the package or interconnect substrate.
Why is underfill needed?
Why is underfill applied? Underfill provides a strong mechanical bond between the chip and the PCB’s connection, protecting the solder joints from mechanical stress. It also helps transfer heat. Underfill softens the mismatch between the coefficient of thermal expansion (CTE) between the chip and the board.
What underfill means?
1 : a rolled or forged member (as of steel) that is imperfect because of insufficient material. 2 : an incompletely filled can or container.
How are underfills used in flip chip devices?
An underfill is a composite material made up of an epoxy polymer with significant amounts of filler. Additional components added to the underfill formulation are flow agents, adhesion promoters, and dyes. Although primarily used for flip-chip devices, underfills can also be used with ball-grid arrays (BGAs) and CSPs.
Which is the correct definition of flip chip?
Flip chip, also known as controlled collapse chip connection or its abbreviation, C4, is a method for interconnecting dies such as semiconductor devices, IC chips, integrated passive devices and microelectromechanical systems (MEMS), to external circuitry with solder bumps that have been deposited onto the chip pads.
How is the viscosity of flip chip underfill measured?
Underfill viscosity is measured on a TA rheometer with constant shear rate at 25°C and at 90°C. Gel time is measured on a conventional Sunshine Gel Timer at 150°C.
What kind of material is an underfill made of?
Underfills are epoxy-based materials that are typically dispensed between the die and the substrate after chip joining. S.L. Buchwalter, in Encyclopedia of Materials: Science and Technology, 2001