Advanced semiconductor package interconnect technology

Research

Advanced semiconductor package interconnect technology

Wire bonding

Wire bonding is an interconnection technology that uses thin metal wires (usually gold or aluminum) to connect integrated circuits (ICs) or other electronic components to a board or other device.

Introduction

Wire bonding is the oldest and most widely used traditional 1st level packaging interconnection method, which is applied to various electronic components. Its applications include connecting power semiconductors in automobiles, connecting LED devices in lighting, and recently, it has also been used for stacking and connecting memory semiconductor devices. The metals commonly used as wire bonding materials are gold (Au), copper (Cu), aluminum (Al), and silver (Ag), with gold (Au) wire being widely used among them. Wire bonding methods are broadly divided into ball bonding and wedge bonding, and they are joined using heat or ultrasonic pressure.

유세훈 수석연구원, yoos@kitech.re.kr

Flip chip bonding

Flip-chip bonding is a method of flipping a microchip and connecting it directly to a circuit board using small solder bumps. It is a bonding technology that improves electrical performance, especially through high-density interconnection

Introduction

Flip-chip bonding is an advanced bonding method that has evolved from traditional wire bonding. In comparison to wire bonding, which utilizes the chip's periphery for bonding, Flip-chip bonding offers the advantage of significantly increasing the number of input and output terminals by using solder bumps. Moreover, this method allows for easy dissipation of heat generated by the chip through solder(metal), providing thermal management benefits. It serves as a fundamental bonding approach for the fabrication of advanced packages and can be broadly classified into two processes: Mass Reflow (MR) using the Controlled Collapse Chip Connection (C4) method and Thermal Compression Bonding (TCB) that utilizes heat and pressure.

유세훈 수석연구원, yoos@kitech.re.kr

Underfill process

Underfill refers to the epoxy material coated between the chip and the carrier or package and PCB substrate, serving to protect electronic products by providing a protective layer

Introduction

The underfill is an epoxy material and protects the semiconductor package from chemical and physical shocks such as drop and impact. As the electronic package mounting technology develops and the performance of packages increases, the reliability of solder joints is becoming more important. Underfill is applied between chip and carrier or between semiconductor package and PCB substrate. By evenly distributing and relieving the stress concentrated in the solder joints due to the difference in thermal expansion coefficient (CTE), the underfill improves the reliability of the semiconductor packages.

고용호 수석연구원, yonghoko@kitech.re.kr

Laser assisted bonding (LAB)

Laser-assisted bonding is a technology that bonds chips or components within a few milliseconds by irradiating a rectangular area laser beam that has passed through a homogenization optical system

Introduction

The commonly used semiconductor package bonding method, Mass Reflow process, has limitations such as extended process time leading to thermal damage (substrate warpage) and low uniformity in heat transfer. To address these challenges, Laser Assisted Bonding (LAB) process, utilizing homogeneous laser beams, is introduced as an alternative bonding method to replace the Mass Reflow process. LAB process offers high selective energy (heat) transfer and rapid processing, gaining attention in the field. In the advanced electronics industry, semiconductor components are increasingly thin and miniaturized, resulting in substrate warpage in thinning chips and substrates. Consequently, one effective method to mitigate this issue is utilized.

유세훈 수석연구원, yoos@kitech.re.kr

Hybrid bonding

Hybrid bonding is a process to create a permanent bond between heterogeneous or homogeneous die. “Hybrid” refers to the fact that both dielectric-to-dielectric and metal-to-metal bonds are formed between the two surfaces

Introduction

Hybrid bonding has emerged as a viable alternative that eliminates the need for traditional bumps by utilizing small copper-to-copper connections to interconnect dies within packages. This innovative approach enables the achievement of pitches as small as 10µm and below. By leveraging hybrid bonding, interconnect density is significantly improved, allowing for the creation of advanced memory cubes and 3D-like packages. The bonding process involves the permanent combination of a dielectric bond (SiOx) with embedded metal (Cu) to establish interconnections. Referred to as direct bond interconnect (DBI) in the industry, hybrid bonding enhances fusion bonding by incorporating embedded metal pads in the bond interface, facilitating direct face-to-face connections between wafers.

박지용 수석연구원, j.park@kitech.re.kr

Advanced Packaging Integration Center

Research