In the early years, back-end packaging and testing procedures for wafers were comparatively straightforward. Although they only made up 15% of an integrated circuit's total cost, silicon wafer packages were dependable and reasonably priced.
In recent years, though, silicon wafer manufacturing processes have undergone significant changes in response to the increasing demands technological demands. One of the areas that has experienced the most innovation is back-end wafer packaging. To help you understand these changes and their benefits, we created this article.
The two primary phases of semiconductor manufacturing are front-end (wafer fabrication) and back-end (packaging and testing).
Packaging can be made of glass, ceramic, plastic, or metal, and it serves to link the wafer to their surroundings while shielding them from environmental factors like light, heat, and impacts.
Outsourced semiconductor assembly and test companies (OSATs) handle the majority of packaging. These companies compete primarily based on low labor costs rather than other differentiators.
Initially, silicon producers used simple back-end packaging techniques. While the fundamental purposes of these techniques have not changed, the increasing demand for digital devices has led to growth in the variety and complexity of package types over time.
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Packaging and testing procedures have had to change to keep up with chips' increasing size, power, and versatility. Due to this evolution, advanced packaging technologies have emerged, requiring capabilities and precision processes far surpassing those of traditional or mainstream packaging solutions.
Wire-bond technology is an interconnection method created in the 1950s and is still used today. It uses thin metal wires and solder balls to join the printed circuit board (PCB) to the die, the silicon square that houses the integrated circuit.
It can connect relatively distant points and takes up less space than packaged chips, but it can fail in high temperatures, high humidity, and temperature cycling. Moreover, each bond must be formed sequentially, which adds complexity and can slow manufacturing.
The wire-bonding market is predicted to be worth $16 billion by 2031.
The first significant advancement in packaging technology in the mid-1990s was flip-chip packaging. These employ a face-down die with all of its surface area utilized for interconnection through solder "bumps" that fuse the PCB with the die.
This leads to a higher signal-propagation rate, the speed at which signals travel from the transmitter to the receiver, and a smaller form factor or hardware size.
Flip-chip packaging is the most widely used and least expensive technology, primarily for radio-frequency system-in-package solutions, smartphones, and central processing units. The flip-chip market is worth about $27 billion at the moment.
Wafer-level packaging creates the electrical connections and molding at the wafer level before using a laser to cut the silicon wafer into individual chips. This contrasts with traditional packaging, which first "dices" the silicon wafer into individual chips before attaching the chips to the PCB and creating the electrical connections.
There are two categories of wafer-level packaging: fan-in and fan-out.
There are three varieties of fan-out packaging: core, high density, and ultrahigh density.
Wafer Level Chip Scale Packaging, or stacked WLCSP, is a specific type of wafer level packaging. Electrical connections are made by applying solder bumps and redistributing the I/O pads to a wider pitch. Unlike traditional packaging, WLCSP produces a package size equivalent to the die size.
Both memory-chip stacking and heterogeneous bonding—which combines logic and memory chips—make it possible to have multiple integrated circuits in a single package. In 2.5-D stacking, an interposer joins one die to another as two or more chips are arranged side by side.
Advanced packaging, first introduced around 2000, is currently gaining traction as the next big development in semiconductor technology. It allows for the combination of several chips and parts to create highly functional, integrated subsystems.
As a result of utilizing many of the manufacturing processes utilized in wafer fabrication, advanced packaging has blurred the distinction between front-end and back-end processes.
These technologies facilitate direct stacking without intermediary layers (3D), such as die-to-die, die-to-wafer, or wafer-to-wafer stacking, or side-by-side placement of chips and chipsets using a silicon bridge or interposer (2.5D).
This approach allows for:
To take advantage of this convergence, major semiconductor industry players are investing heavily. TSMC is one of the most notable players dedicated to this change, making multibillion-dollar investments in Taiwan's cutting-edge packaging facilities.
TSMC currently controls the majority of advanced packaging manufacturing at scale worldwide thanks to its 3DFabric system, which includes the SoIC series for stacking technologies, chip-on-wafer-on-substrate (CoWoS) integration, and InFO fan-out packaging technologies.
Significant challenges remain in semiconductor packaging and testing, but these challenges also offer opportunities for innovation and growth. With the right vision and determination, they can inspire groundbreaking solutions.
The convergence of front-end and back-end processes in semiconductor manufacturing is reshaping the industry, opening abundant opportunities across the value chain. As we move forward, integrating these traditionally separate domains promises to redefine what is possible in semiconductor design.
At Wafer World, we believe following these changes is crucial to improving the efficiency of our processes and ensuring the quality of our products. If you’d like to learn more about the wafer manufacturing process, reach out!
