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Outdoor p5 big screen pros and cons identification lamp method
LEDp5 display
LEDp5 equipment accounts for about 40% to 70% of the LEDp5 display cost, and the LEDp5 display cost is greatly reduced due to the decline in the cost of LEDp5 equipment. The quality of the LEDp5 package has a great influence on the quality of the LEDp5 display. The key to package reliability includes the selection of chip data, the selection of package materials, and process control. Other, severe reliability specifications are also the key to checking high quality LEDp5 equipment.
With the LEDp5 display gradually infiltrating into high-end shopping malls, the quality requirements for LEDp5 display equipment are also getting higher and higher. This article discusses the high- performance LEDp5 display device packaging experience, and discusses the key technologies for ending high-quality LEDp5 display equipment.
LEDp5 display device packaging status
SMD (Surface Mounted Devices) refers to the surface mount package structure LEDp5, which mainly has LEDp5 (ChipLEDp5) with PCB structure and LEDp5 (TOP LEDp5) with PLCC structure. This article is the first to discuss TOP LEDp5, the SMD LEDp5 mentioned in the following refers to TOP LEDp5.
The primary materials used in the LEDp5 display device package include brackets, chips, die attach adhesives, bond wires and encapsulants. The following is a brief introduction of the current situation of some domestic developments in terms of packaging materials.
1, LEDp5 bracket
(1) The role of the stent. The PLCC (Plastic Leaded Chip Carrier) bracket is the carrier of SMD LEDp5 equipment, which plays a key role in the reliability and light output of LEDp5.
(2) The production process of the stent. The PLCC stent production process mainly includes metal strip punching, electroplating, PPA (polyphthalamide) injection molding, bending, and five-sided three-dimensional inkjet. In the meantime, electroplating, metal substrates, plastic materials, etc. occupy the primary cost of the stent.
(3) Structural improvement planning of the bracket. The PLCC bracket is physically combined because of the combination of PPA and metal. After the over-temperature reflow oven, the gap will become larger, and then the water vapor will simply enter the interior of the equipment along the metal channel and affect the reliability.
For the high-quality LEDp5 flashing equipment for the reliability of the products to meet the needs of high-end shopping malls, some of the packaged factories have improved the structural planning of the brackets. For example, Foshan Guoxing Optoelectronics Co., Ltd. selects advanced waterproof structure planning, bending and stretching, etc. The method is to extend the water vapor inlet path of the bracket, and add a waterproofing method such as a waterproof groove, a waterproof step, a water discharge hole and the like inside the bracket, as shown in the figure. The plan not only saves the cost of packaging, but also travels to product reliability, and is now widely used in outdoor LEDp5 display products. After the sealing of the LEDp5 bracket of the bending structure of the SAM (Scanning Acoustic Microscope) and the airtightness of the normal bracket, it can be found that the product with the bent structure is better in airtightness, as shown in the figure.
2, chip
LEDp5 chip is the center of LEDp5 equipment, and its reliability selects the lifespan and luminous function of LEDp5 equipment and even LEDp5 display. The cost of LEDp5 chips accounts for the largest total cost of LEDp5 equipment. With the decline in cost, the standard cut of LEDp5 chips is getting smaller and smaller, and together they bring a series of reliability problems. The structure of the LEDp5 blue-green chip is shown in the figure.
As can be seen from the above figure, following the standard reduction, the pad of the P electrode and the N electrode is also reduced. The reduction of the electrode pad directly affects the quality of the wire. In the process of packaging and application, the gold ball is detached and the electrode itself is separated. After all, Invalid. Together, the interval a between the two pads will also shrink, which will cause the current density at the electrode to increase excessively, and the current is partially concentrated at the electrode, and the uneven current is seriously affected by the function of the chip, so that the chip has a partial temperature. Excessively high, uneven brightness, simple leakage, off-electrode, and even low-level illumination power, after all, led to a decline in the reliability of the LEDp5 display.
3, bonding wire
The bonding wire is one of the key data of the LEDp5 package. Its function is to end the electrical connection between the chip and the pin, and play the role of current introduction and derivation of the chip and the outside world. Common bonding wires for LEDp5 equipment packages include gold wire, copper wire, palladium-plated copper wire and alloy wire.
(1) Gold wire. The gold wire is the most widely used, the oldest process, but the price is expensive, resulting in the LED p5 package cost is too high.
(2) Copper wire. The replacement of gold wire by copper wire has the advantages of low cost, good heat dissipation, and slow growth of intermetallic compounds in the process of wire bonding. The defect is that copper has an easy oxidation, high hardness and high strain strength. Especially in the heating environment of the bonding copper ball burning process, the copper surface is easily oxidized, and the formed oxide film reduces the bonding function of the copper wire, which puts higher requirements on the process control in the process of production.
(3) Palladium-plated copper wire. In order to prevent copper wire oxidation, palladium-bonded copper wire has gradually attracted the attention of the packaging industry. Palladium-bonded copper wire has the advantages of high mechanical strength, moderate hardness, good soldering and ball bonding, and is very suitable for high-density, multi-pin integrated circuit packages.
4, glue
Now, the glue of LEDp5 display equipment package mainly includes epoxy resin and silicone.
(1) Epoxy resin. Epoxy resin is easy to age, easy to be wet, and has poor heat resistance. Short-wave illumination and simple discoloration at high temperature have certain toxicity in the case of colloid. Thermal stress and LEDp5 do not match very well, which will affect the reliability and life of LEDp5. number. Therefore, the epoxy resin is generally attacked.
(2) Silicone. Compared with silicone, epoxy resin has high cost performance, excellent insulation, dielectric properties and adhesion. However, the defect is that the airtightness is poor and it is easy to absorb moisture. Therefore, it is rarely used in the packaging of LEDp5 display equipment.
Other, high-quality LEDp5 displays also have special requirements for flashing effects. Some packaging plants use additives to improve the stress of the glue and reach the matte matte side together.