The explosive growth of electronic products in recent decades has driven the need for more advanced and efficient integrated circuit (IC) packaging solutions. As devices become smaller, more powerful, and more complex, traditional packaging methods have struggled to keep pace with the demands of modern electronics.
Enter the plastic leaded chip carrier (PLCC), a breakthrough IC packaging technology that has revolutionized the industry. By offering a compact, reliable, and cost-effective solution, PLCCs have enabled manufacturers to create smaller, faster, and more powerful electronic devices. This innovative packaging method has been instrumental in addressing the challenges posed by the rapid evolution of electronic products, from consumer gadgets to automotive systems and aerospace applications.
Understanding Plastic-Leaded Chip Carriers (PLCCs)
What exactly is a PLCC? Simply put, it's a type of surface-mount IC package that uses plastic leads to connect the chip to the printed circuit board (PCB). But there's so much more to this innovative technology!
PLCC (Plastic Leaded Chip Carrier) is a surface-mount package with leads. It has a square shape and typically comes in a 32-pin configuration. The leads are brought out from the four sides of the package in a J-shaped or gull-wing form. PLCC is made of plastic and has a much smaller package size compared to DIP (Dual Inline Package).
PLCC packages are suitable for mounting and routing on PCBs using SMT (Surface Mount Technology). They offer the advantages of small form factor and high reliability. PLCC was first adopted by Texas Instruments in their 64K DRAM and 256K DRAM products.
PLCCs are characterized by their rectangular or square shape, with leads extending from all four sides of the package. These leads are made of a plastic material, typically a high-temperature thermoplastic, which provides excellent electrical insulation and mechanical protection for the delicate chip inside.
Advantages of PLCC Package
One of the key advantages of PLCCs is their compact size. By using a leadless design, PLCCs can achieve a much smaller footprint compared to traditional through-hole packages like dual in-line packages (DIPs). This makes them ideal for space-constrained applications where every millimeter counts.
But size isn't everything! PLCCs also offer superior thermal and electrical performance compared to other packaging methods. The plastic leads provide a low-resistance path for heat dissipation, allowing the chip to operate at higher temperatures without overheating. And because the leads are shorter and more closely spaced than in other packages, PLCCs can achieve faster signal speeds and lower inductance.
Disadvantages of the PLCC Package
Of course, no packaging solution is perfect. PLCCs do have some limitations compared to other methods like ball grid arrays (BGAs) or quad flat packages (QFPs). For example, PLCCs typically have fewer input/output (I/O) pins than BGAs, which can limit their functionality in some applications. And because the leads are exposed on the surface of the PCB, PLCCs may be more susceptible to mechanical damage or contamination than fully encapsulated packages like QFPs.
The Evolution of PLCC Packages
The story of PLCC packages is one of innovation, collaboration, and standardization. It all began in the early 1970s with the introduction of premolded PLCC packages. These early designs used a plastic carrier that was molded around the chip and leadframe before the assembly process. While revolutionary for their time, premolded PLCCs had some limitations, such as higher manufacturing costs and longer lead times.
Enter Texas Instruments (TI), a pioneer in the semiconductor industry. In the late 1970s, TI developed a new type of PLCC package called the postmolded PLCC. Unlike premolded packages, postmolded PLCCs were assembled first and then encapsulated in plastic using a transfer molding process. This innovation brought several advantages, including lower costs, faster production times, and improved reliability.
TI's postmolded PLCC quickly became the industry standard, paving the way for widespread adoption of this packaging technology. Other semiconductor manufacturers soon followed suit, and PLCCs became a common sight in electronic devices of all kinds.
But with popularity came the need for standardization. Enter JEDEC, the Joint Electron Device Engineering Council. This industry organization took on the task of developing standards for PLCC packages to ensure compatibility and interoperability between different manufacturers' products.
JEDEC's efforts culminated in the release of several key standards, including:
JEDEC MS-018: Plastic Leaded Chip Carrier Family (PLCC)
JEDEC MO-047: Plastic Quad Flat Pack (PQFP) and Plastic Leaded Chip Carrier (PLCC) Package Outlines
JEDEC MO-052: Fine Pitch Quad Flat Pack (FPQFP) and Plastic Leaded Chip Carrier (PLCC) Solder Mounting Guidelines
These standards helped to ensure that PLCCs from different manufacturers could be used interchangeably, making it easier for electronics companies to source components and design their products.
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PLCC Package Design and Specifications
When it comes to PLCC package design, one of the most distinctive features is the "J"-shaped leads. But what makes this design so special? Let's take a closer look!
The "J"-lead design gets its name from the shape of the leads, which resemble the letter "J" when viewed from the side. This unique shape offers several advantages over other lead styles, such as "gull-wing" leads found on some other surface-mount packages.
One key benefit of the "J"-lead design is improved mechanical stability. The curved shape of the leads helps to absorb stress and prevent cracking or breaking during handling and assembly. This is especially important for larger PLCC packages with higher pin counts, which can be more susceptible to damage.
Speaking of pin counts, PLCCs are available in a wide range of sizes to accommodate different chip designs. Common pin counts include 20, 28, 44, 52, 68, 84, and even up to 100 pins or more! The size of the package is typically expressed in terms of the pin pitch (the distance between adjacent pins) and the overall package dimensions.
For example, a 44-pin PLCC package might have a pin pitch of 0.05 inches (1.27mm) and dimensions of 0.785 x 0.785 inches (19.94 x 19.94mm). These dimensions are standardized by JEDEC to ensure compatibility between different manufacturers' products.
But what about heat dissipation? As chips become more powerful and generate more heat, it's increasingly important to have effective thermal management solutions. That's where PLCC packages with heatspreader versions come in!
A heatspreader is a metal plate or slug that is attached to the top of the PLCC package. This plate helps to spread the heat generated by the chip over a larger surface area, making it easier to dissipate into the surrounding environment. Heatspreader versions of PLCC packages are commonly used for high-power applications such as microprocessors, FPGAs, and graphics chips.
Some common heatspreader materials include copper, aluminum, and even advanced composites like copper-tungsten. The choice of material depends on factors such as the thermal conductivity, coefficient of thermal expansion (CTE), and cost.
In addition to heatspreaders, some PLCC packages also feature thermal vias or other enhancements to improve heat transfer. These design elements help to ensure reliable operation and long-term durability, even in demanding environments.
Mounting Options for PLCC ICs
When it comes to mounting PLCC packages onto a PCB, designers have several options to choose from. Each method has its own advantages and considerations, so let's dive in and explore them in more detail!
Through-Hole Mounting
One of the most traditional mounting methods for PLCCs is through-hole mounting. With this approach, the leads of the PLCC package are inserted into plated holes drilled in the PCB. The leads are then soldered to pads on the opposite side of the board.
Through-hole mounting offers several benefits:
Strong mechanical connection between the package and PCB
Easier visual inspection of solder joints
Suitable for high-reliability applications and harsh environments
However, there are also some drawbacks to consider:
Requires drilling holes in the PCB, which adds cost and complexity
Consumes more board space compared to surface-mount options
Slower assembly process due to manual insertion of leads
Surface-Mount Technology (SMT)
In recent years, surface-mount technology (SMT) has become increasingly popular for mounting PLCCs and other packages. With SMT, the leads of the PLCC are soldered directly onto pads on the surface of the PCB, without the need for drilled holes.
SMT offers several advantages over through-hole mounting:
Smaller footprint and higher component density
Faster and more automated assembly process
Lower cost due to fewer drilling and plating steps
Improved high-frequency performance due to shorter lead lengths
However, there are also some challenges to consider with SMT:
Requires precise placement and soldering equipment
More susceptible to thermal stress and cracking during temperature cycling
Visual inspection of solder joints can be more difficult
Socketed Mounting
For applications that require frequent chip replacement or upgrades, socketed mounting is another option to consider. With this method, a socket is soldered onto the PCB, and the PLCC package is inserted into the socket.
Socketed mounting offers several benefits:
Allows for easy chip replacement without soldering
Reduces thermal stress on the package during soldering
Provides a degree of mechanical protection for the chip
However, there are also some drawbacks to socketed mounting:
Adds cost and complexity to the assembly process
Can introduce additional electrical resistance and signal degradation
May not be suitable for high-vibration or shock environments
Ultimately, the choice of mounting method depends on a variety of factors, including:
The specific application and environmental conditions
The size and pin count of the PLCC package
The available board space and component density
- The desired assembly process and cost targets
PLCC vs. LCC Package
Here is a comparison of PLCC (Plastic Leaded Chip Carrier) and LCC (Leadless Chip Carrier) packages:
Feature
| PLCC (Plastic Leaded Chip Carrier)
| LCC (Leadless Chip Carrier) |
|---|
| LCC (Leadless Chip Carrier) | Molded "J"-shaped leads that extend from the package body | Flat contact pads flush with the bottom surface (leadless) |
| Board Mounting | Board Mounting | Contact pads are soldered directly to PCB, requires solder reflow |
| Contact pads are soldered directly to PCB, requires solder reflow | Taller profile due to protruding leads (typically 3-5 mm) | Lower profile, sits flush on PCB (typically 1.5-3 mm) |
| Thermal Performance | Leads create a thermal gap, slightly higher thermal resistance | Leadless design provides better thermal conduction to the PCB |
| Cost | Slightly higher cost due to forming and trimming of leads | Generally lower cost due to simpler leadless design |
| Solder Joint Reliability | Leads provide some mechanical compliance, higher reliability | Joints more rigid, sensitive to PCB flexing and thermal stress |
PLCC (Plastic Leaded Chip Carrier) and LCC (Leadless Chip Carrier) are both surface-mount integrated circuit packages commonly used for devices such as microprocessors. The main difference between them is that PLCC has J-shaped leads extending from the package body, while LCC uses contact pads that are flush with the bottom surface. PLCC leads are soldered to the PCB surface, while LCC is directly reflow soldered to the PCB. PLCC has a higher package height due to the leads, while LCC is lower in profile. LCC provides better thermal performance, while PLCC leads offer some stress buffering. Overall, LCC has a lower cost, but PLCC provides higher mechanical reliability in some applications thanks to its leads.
Applications of PLCC Packages
PLCC packages have found widespread use across a variety of industries and applications. From consumer gadgets to mission-critical systems, these versatile packages offer a compelling combination of performance, reliability, and cost-effectiveness. Let's explore some of the key areas where PLCCs have made their mark!
Consumer Electronics
One of the most prominent applications for PLCC packages is in the world of consumer electronics. These devices, which include everything from smartphones and laptops to gaming consoles and smart home devices, rely on high-density packaging to deliver ever-increasing functionality in smaller and more affordable form factors.
PLCCs are particularly well-suited for consumer applications due to their:
Compact size and low profile
Ability to accommodate high pin counts
Compatibility with automated assembly processes
Cost-effectiveness compared to other packaging options
Automotive Electronics
Another major application area for PLCC packages is in the automotive industry. Modern vehicles are packed with electronic systems, from engine control units and infotainment systems to advanced driver assistance features and autonomous driving capabilities.
In this demanding environment, PLCCs offer several key benefits:
Robust mechanical and thermal performance
Resistance to vibration and shock
Compatibility with high-reliability manufacturing processes
Ability to operate over a wide temperature range
Aerospace Industry
PLCCs have also found a home in the aerospace industry, where they are used in a variety of applications ranging from avionics and communication systems to satellites and spacecraft. In these mission-critical environments, reliability and durability are paramount.
PLCCs are well-suited for aerospace applications due to their:
Hermetic sealing options for enhanced environmental protection
Compatibility with high-reliability testing and screening processes
Ability to withstand extreme temperature, vibration, and radiation conditions
Track record of successful use in space-qualified components
Read-Only Memory (ROM) Devices
One specific application where PLCC packages have proven particularly popular is in read-only memory (ROM) devices. These non-volatile memory chips, which retain their contents even when power is removed, are used to store firmware, lookup tables, and other fixed data.
PLCCs are an ideal choice for ROM devices due to their:
High pin counts to accommodate parallel data interfaces
Compact size and low profile for space-constrained applications
Compatibility with low-cost PCB manufacturing processes
Proven reliability and data retention performance
Conclusion
The PLCC package is a milestone in the history of electronic packaging. It introduced a surface-mount design with J-shaped leads, which significantly increased interconnect density compared to previous through-hole packages, while the leads also provided stress relief and reliability advantages. The widespread use of PLCC has promoted the miniaturization, cost reduction, and manufacturing efficiency improvement of electronic devices. Although new packaging forms such as BGA and QFP have been developed today, PLCC continues to be used in some applications due to its unique advantages. Its important historical position and far-reaching impact cannot be ignored.
T0 92 Transister Package FAQ
1. What is a PLCC package?
A PLCC (Plastic Leaded Chip Carrier) is a surface-mount integrated circuit package with a rectangular plastic housing. It has leads that emerge from all four sides of the package in a J-shape or gull-wing shape for surface mounting on printed circuit boards (PCBs). PLCC packages offer high interconnect density, reliability, and a small footprint.
2. What is the difference between LCC and PLCC package?
The main difference between LCC (Leadless Chip Carrier) and PLCC (Plastic Leaded Chip Carrier) is that LCC packages do not have leads, while PLCC packages have leads extending from the package sides. LCCs have metal pads on the bottom for soldering directly to the PCB. PLCCs have formed leads that provide stress relief and are surface mounted. Additionally, LCCs typically have a ceramic housing, while PLCCs use a plastic housing.
3. What is an LCC package?
An LCC (Leadless Chip Carrier) is a surface-mount package with a ceramic housing and no leads. Instead of leads, it has metal pads on the bottom surface that are directly soldered to the PCB. LCCs provide a compact, low-profile package with good thermal and electrical characteristics.
4. What does PLCC do?
PLCC packages provide a means of encapsulating and protecting integrated circuits while enabling surface mounting on PCBs. The PLCC package's J-shaped or gull-wing leads allow for reliable soldering and stress relief. PLCCs are used to package various types of ICs, such as microcontrollers, memory chips, and ASICs. They offer a space-saving, cost-effective, and surface-mountable solution for electronic devices.
5. When was PLCC package invented?
The PLCC (Plastic Leaded Chip Carrier) package was originally released in 1976. It was developed as a lower-cost alternative to the ceramic leadless chip carrier (CLCC) package. The PLCC package was first adopted by Texas Instruments for their 64K and 256K DRAM products.
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