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PCB manufacturing PLCC package

The production history of ceramic package components is earlier than that of plastic package components in pcb manufacturing industry. When forming a surface form, the terminal electrodes are usually printed or sintered on the side or bottom surface of the carrier. When the board is assembled and connected, there is no buffering effect between the carrier electrode and the substrate pad, so the connection portion is susceptible to assembly stress. At the same time, the production process of ceramic package components is high and the price is much higher than that of plastic package components in pcb manufacturing industry. Based on this, around the 1980s, plastic components quickly rose in the SMT market with their excellent cost performance, and were widely used. However, ceramic package components also have superiority. It is a sealed component with good thermal conductivity and corrosion resistance, and can work reliably in harsh environments.

PCB manufacturing PLCC package

PCB manufacturing PLCC package

The leaded plastic chip carrier PLCC is also evolved from DIP, which is a relatively inexpensive form of chip carrier compared to ceramic chip carriers in pcb manufacturing industry. PLCC is almost a package that must be replaced by a plastic package DIP with a pin count greater than 40. The latter is impractical due to the large footprint. The PLCC is a J-shaped pin bent under the package with a pitch of 0.05 in. Such packages are commonly found in logic circuits, microprocessor arrays, and standard units.

 

In 1981, JEDEC established a special working group to register PLCC. The PLCC for square packages, known as the JEDEC form factor for MO-047, specifies the number of terminals 20, 28, 44, 52, 68, 84, 100 and 124. This form factor is used for most digital circuits and linear circuits, the total pin count is equally divided on four sides, the number is equal in pcb manufacturing industry. The memory chip is preferably rectangular in shape to match the geometry of the silicon wafer.

 

The second registration is the JEDEC form factor of the MO-052 for rectangular packages with pins 18, 22, 28 and 32. The 18-pin PLCC is available in two sizes, the shorter one for 64KB dynamic randomization memory, longer for 265KB of dynamic random access memory in pcb manufacturing industry. The 28 and 32-pin packages are used in electrically erasable programmable read-only memory (E2PROM).

 

The PLCC uses a J-shaped short pin that has a lower bend around the package. Since the PLCC is assembled on the surface of the circuit board and does not have to withstand the insertion and extraction force, it is generally made of a copper material, which can reduce the thermal resistance of the pin. When the component is heated, it can effectively absorb the stress caused on the solder joint due to the inconsistent thermal expansion coefficient between the components and the substrate, and prevent the solder joint from breaking in pcb manufacturing industry. However, after the packaged IC is soldered to the PCB, it is difficult to detect the solder joint. The number of pins of the PLCC is generally from tens to hundreds. This package is generally used in computer micro-processing unit ICs, application-specific integrated circuit ASICs, and gate array circuits.

 

Each PLCC surface has a mark positioning for judging the direction during smt process. Pay special attention to the order of the pins when using PLCC in pcb manufacturing industry. Unlike SOIC, PLCC has no pin identification on the surface of the package, and its logo is usually an oblique angle. Generally, this flag is placed on the left-hand side. If the pin on each side is odd, the center line is pin 1. If the pin on each side is even, the left pin of the center two pins. It is No. 1. The start and end of the pin is usually calculated from the mark.

 

The pins of the PLCC are plastic to absorb the stress of the solder joints and thus avoid cracking of the solder joints in pcb manufacturing industry. Since the J-shaped pins are designed with the plasticity of the pins in mind, make sure that the pins and edges are not in contact with the plastic case. A concern in PLCC is that when the pin is bent and hits the plastic case, the movement of the pin is limited and becomes non-plastic. This can happen if the pins are bent during shipping or handling.

 

 

PLCC mainly uses reflow and gas phase welding, of which gas phase welding is more suitable. In this way, the PLCC pin is protected from inert gas and is not easily oxidized, and the soldering temperature can be accurately controlled to improve reliability. Since PLCC is a J-shaped pin, it can be packed in strips and rods on the packaging, which is more conducive to transportation and patching in pcb manufacturing industry.

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