The Evolution of IC Packaging

Key Takeaways

• The demand for higher pin counts led to the introduction of Pin Grid Array (PGA) and Ball Grid Array (BGA) packages, while miniaturization drove the success of Quad Flat No-leads (QFN) and Wafer Level Chip Scale Package (WLCSP) technologies.

• IC packaging has evolved significantly since the invention of the first semiconductor package, with milestones such as the Dual-in-Line Package and surface mount technology

• The demand for higher pin counts led to the introduction of Pin Grid Array (PGA) and Ball Grid Array (BGA) packages, while miniaturization drove the success of Quad Flat No-leads (QFN) and Wafer Level Chip Scale Package (WLCSP) technologies.

Pin Grid Array (PGA) Closeup

The realm of IC packaging technology has witnessed a remarkable evolution since the introduction of the first semiconductor package. Read on as we embark on a comprehensive exploration of the fascinating evolution of IC packaging. We’ll be delving into the significant trends that have shaped its development, including the drive for  higher pin counts, and pushfor smaller footprints, including modern-day trends of heterogeneous integration

Evolution of IC Packaging by the Decade

Trends in IC Packaging by Decade

One of the first notable milestones in the evolution of IC packaging occurred when Don Forbes, Rex Rice, and Bryant Rogers, engineers from Fairchild, invented the 14-lead ceramic Dual-in-Line Package (DIP) in the 1964. This breakthrough marked the advent of the first real semiconductor package, which featured two rows of pins. Soon thereafter in the 70s the DIP formfactor gained immense popularity. 

The landscape of IC packaging continued to evolve with the introduction of surface mount packaging in the early 1980s. Later on,  a significant advancement followed with the development of area array packages. Unlike previous package types that utilized only the outer perimeter for interconnection terminals, area array packages spread the terminals throughout the entire surface area of the package, enabling a greater number of connections, with examples includings BGAs and PGAs. 

As the 1990s progressed, plastic quad flat pack (PQFP) and thin small-outline packages (TSOP) superseded pin grid array (PGA) packages as the most prevalent choice for high pin count devices. Ball grid array (BGA) packages, although first introduced in the 1970s, underwent further evolution in the 1990s, giving rise to flip-chip ball grid array (FCBGA) packages.

At the change of the millennium and into the modern day, significant developments have focused more on enhancing packaging capabilities by incorporating multiple dies into a single package. This approach, known as System In Package (SiP) or three-dimensional integrated circuit, involves stacking multiple dies on a small substrate, often made of ceramic. Another concept, referred to as Multi-Chip Module (MCM), entails integrating multiple dies onto a common substrate. See the section below about heterogeneous integration trends for more. 

Evolution of IC Packaging Pin Count 

As chips grew larger and incorporated more functionality, semiconductor packaging technology evolved to keep up. The introduction of a chip with 1 million gates led to the need to address the growing number of input/output (IO) connections. 

The focus on accommodating high IO counts was primarily driven by the demand for high-end System-on-Chips (SoCs) used in computing, networking, and storage applications, where extensive data or address buses were required for efficient data transfer. The main focus was striking the right balance between size, power dissipation, and cost. This prompted the emergence of Pin Grid Array (PGA) and Ball Grid Array (BGA) packages, which are in use today.

Initially, both BGA and PGA packages utilized ceramic substrates. However, in modern times, laminates have become the primary choice for both low-cost and high-end applications. Then, with even higher demands for pin-counts in the 1990s, the Chip Scale Package (CSP) was introduced featuring a more compact size compared to previous packaging technologies. This CSP package essentially resembles a smaller version of the BGA package, featuring a reduced ball pitch.

The Push for Smaller Sizes in Semiconductor Packaging 

The 1990s witnessed another major trend in the evolution of IC packaging, focusing on the miniaturization of packages. This shift was primarily driven by the increasing demand for mobile devices such as laptops and mobile phones. These devices required compact packages that closely resembled the size of the integrated circuits (ICs) themselves, aiming to reduce package cost and overall footprint.

To meet these requirements, various packaging technologies were introduced. One notable development was the introduction of the Quad Flat No-leads (QFN) package, which falls under the category of Chip Scale Packages (CSPs). The QFN package quickly gained popularity and emerged as the most successful package type due to its simplicity, performance, and cost-effectiveness.

Another notable advancement that arose from the need for small sizes was the development of the Wafer Level Chip Scale Package (WLCSP), also known as the bumping package. This package type is currently considered the smallest in size, as the package dimensions align with the size of the die itself, resulting in an extremely compact package.

Evolution Into Heterogenous Integration 

Moore's Law observes the doubling of transistor density in an integrated circuit (IC) every two years, but the limitations of 2D integration density have prompted the utilization of 3D techniques —also known as heterogeneous integration. For this reason, there has been significant evolution in IC packages utilizing 3D integration, where multiple layers of the same technology are stacked to increase density.

Heterogeneous integration enables the integration of logic, memory, sensors, and antennas into a single package, driven by power, performance, area, and cost considerations. The convergence of devices, packages, and PCBs leads to diverse advanced packaging solutions tailored for specific systems using a variety of new technologies. Most recently, advancements in heterogeneous integration include interposer technologies, fan-out technologies,  stacking chips and packages, MEMS integration,  utilizing different semiconductor materials, and employing various routing techniques such as through silicon vias and wire-bonding —all in an effort to push computing to the next level.  

In the future, these technologies will be incorporated into the upcoming generation of chips, enabling the creation of even denser and highly optimized chips.

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