From bump chip carriers (BCCs) to quad flat packs (QFPs), there are a lot of different types of surface mounted packages (SMDs) out there. However, one of the most common is the plastic leaded chip carrier (PLCC).
Before you learn about soldering, It’s important to understand how integrated circuits (IC) work and which is the most effective method of mounting them on your PCB.
Nevertheless, this guide will explain what a PLCC package is and what makes it different from other SMDs. From this, you will be able to see how it can be beneficial for you to use.
What are PLCCs?
As you should know, PLCC stands for plastic leaded chip carrier. It is a surface mount device package type. It houses an integrated circuit (or chip) in a rectangular/square. The PLCC is a more price-effective improvement over the ceramic leadless chip carrier (CLCC).
It is one of the most common chip carriers today. It originally came out in 1976 but didn’t receive much mainstream adaptation until the early 80s.
You get two types of packages: a square package (MO-047 standard) and a rectangular package (MO-052). The categorization for the square package came out in 1984, while the standard for the rectangular package came in 1985. The PLCC uses a J-shaped lead instead of the gull wing-shaped leads you might find on some flat-pack SMDs.
There are two form factors you may encounter with PLCCs. You get a heat spreader and a non-heat spreader version. Both versions are almost identical-looking.
The lead’s J shape allows you to sell the PLCC directly onto the PCB or mount it on a socket. This allows you to replace the PLCC without reworking the board. Nowadays, you get PLCCs made from green material and leadless chip carriers. We will go in-depth about LCCs in the next section.
PLCC Packages– What is an LCC Package
You might consider the LCC as the next evolution in plastic-leaded chip carriers. LCC stands for leadless chip carriers. Instead of leads, LCCs have pins at the bottom near the edges of the package. LCCs can either be plastic or ceramic.
Design and Construction of PLCC Package
PLCC packages typically have rectangular or square-shaped bodies that (mostly) consist of a thermoset plastic. The PLCC package’s leads extend equally from each side.
Each lead connects to the PLCC package via a lead frame, which secures the leads and connects them to an integrated circuit (IC) inside. The leadframe can either consist of pure copper or a blended copper alloy.
Manufacturers etch or mark the top of each PLCC package. These markings contain the manufacturer’s name, the PLCC package’s part number, and the date.
Types and Sizes of PLCC Package
PLCC packages come in a host of different shapes and sizes. You can identify the type of PLCC package by the park number. In addition to having different space requirements, PLCC types differ in the number of pins they can have (pin counts). The most common PLCC packages and their pin counts are as follows:
- Standard PLCC: 20 to 84 pins
- Thin PLCC: Can accommodate the same number of pins as the standard PLCC. However, it has a thinner body and, consequently, a lower profile.
- Quad PLCC: 44 to 84 pins
- Miniature PLCC: 16 to 52 pins.
- Enhanced PLCC: Features the same pin count as the Standard and Thin PLCC. However, it also features a heat sink that helps keep the IC chip inside the package cool.
- Ceramic PLCC: Another variation of the standard PLCC. However, instead of a plastic body, it uses a ceramic one. This material allows it to manage and dissipate heat, making it suitable for usage under high temperatures.
PLCC Packages– PLCC vs. LCC Package
The key difference between these two packages is that the PLCC package has leads while the LCC package does not. Instead, the LCC package uses vertically recessed metal pads at the outer edges.
LCCs are extremely popular because they are lightweight and versatile, and you can use them in situations where you may want to mount and unmount the IC (like a microprocessor) instead of completely soldering it onto the board.
Much like PLCCs, LCCs are either square or rectangular. In addition to this, you can get them with either plastic or ceramic bodies. Once again, LCCs are surface mounted, but you cannot solder them to the board. PLCCs are more versatile, as you can solder them on or surface-mount them to a socket.
How to Troubleshoot and Repair PLCC Packages
The size and design of PLCC packages can make them hard to troubleshoot and repair. Their integrated circuits and tightly packed pins make it harder to maneuver around and find faults. This is especially true if you’ve already soldered the package onto your PCB. There are a few steps you can take to make the process of troubleshooting and repair a bit easier.
- Visually examine the PLCC and its connections: The first step is to visually examine the PLCC package for any faults or defects. Make sure you inspect the package for any discoloration, noticeable cracks or breakages. If you’ve already soldered the package to the PCB, you’ll also need to inspect the connections. Check for any damage or breaks in the solder joints. You must also ensure the package’s leads/pins aren’t broken or bent.
- Inspect and Test the IC: Once you’ve ascertained that the PLCC’s physical package isn’t damaged, you’ll need to ensure the IC is functional. Using a multimeter to test the IC is one of the most common methods.
- Replace the PLCC package: If the IC is functional and the connections seem intact, your only other resort is to replace the package entirely. This will require you to remove the package from the PCB and rework a new one into it.
It’s always best to consult a professional when working with electronic components for advanced circuits – especially if you’re a novice. This is something else you must consider when trying to fix a faulty PLCC package.
Pros of PLCC Packages
What are some of the advantages of using PLCC SMD packages?
- They are cheaper to produce than ceramic leadless chip carriers (CLCC).
- You can sell the PLCC on the board’s surface or connect it to a socket. If your PLCC houses a programmable logic device (PLD chip), you can program it independently and connect it to the board. This allows you to test and troubleshoot the system, especially in circumstances where onboard programming is unavailable.
- Thanks to its J-shaped lead, the PLCC is more space-efficient than the outward L-shape and gull-wing leads of SMDs like the quad flat pack. While QFP leads fold outwards into a toe, PLCC leads fold into a heel.
- Since you can connect the PLCC to a socket, you can avoid damaging the chip inside the carrier. You will not have to directly solder it onto the board, which allows you to avert using heat near the chip.
Cons of PLCC Packages
As we discussed in the previous section, PLCC packages have many advantages. However, as with most components, they have disadvantages too. The most obvious con is their limited space for leads/pins. Since PLCC packages are small, they don’t have a lot of room for pins.
PLCC packages exhibit poor thermal performance, especially compared to other packages such as Ball Grid Arrays and Quad Flat Packages. This can make PLCC packages a little less reliable than their alternatives.
Because of their limited pin counts and long signal paths, the PLCC package also exhibits unsatisfactory signal speeds. Thus, this package is unfit in instances that require a balance of high performances mixed with good heat dissipation.
You have numerous IC mounting options out there. In this guide, we explored what plastic-leaded chip carriers are. We defined their advantages and compared them to leadless chip carriers. This should inform your next decision on which type of SMD to integrate with your PCB.
Nevertheless, we hope you have enjoyed reading this guide and found it helpful. As always, thank you for reading.