The quality of the SMD LED module lies in the use of packaging technology.The key to packaging technology is the packaging of chip materials and the materials required for packaging are directly related to process control. Here are 4 key factors that affects SMD LEDs quality!
With the media industry, advertising industry,and the rapid development of trade exhibition industry, wedding industry and other industries, as the quality of the display screen increases, the requirements for SMD LED panel are getting higher and higher.
The materials used in LED packaging mainly include chips, glue, brackets, packaging glue, bonding wires, etc.
1) LED Display Chip
As the core of the SMD LED screen, the LED chip determines the lifespan and luminous performance of the entire LED display. As the cost of LED chips decreases, the size of LED chips is getting smaller and smaller, which brings a series of performance problems.
There are two main types of encapsulation glue: silicone and epoxy resin.
The silicone phase is cost-effective, excellent in insulation, dielectric and adhesion. The disadvantage is that it is easy to absorb moisture and has weak air tightness. Rarely used in packaging applications for LED devices.
Epoxy resin is easy to age, has poor heat resistance, is susceptible to moisture, and is easy to change color under short-wave light and high temperature.
Epoxy resin has certain toxicity, and the thermal stress matching degree of LED is not high, which greatly affects the performance and life of LED.
3) LED bracket
a. Structural improvements to the stent design.
Because the PPA and the metal are combined physically, the PLCC bracket will have a larger gap after the reflow oven at a high temperature, which will cause moisture to easily enter the device along the metal channel and affect reliability.
b. The role of the stent.
The PLCC (Plastic Leaded Chip Carrier) bracket is the carrier of the SMD LED device, which plays a key role in the reliability and light output of the LED.
Manufacturing process of stents. The PLCC bracket production process mainly includes metal strip punching, electroplating, PPA (polyphthalamide) injection molding, bending, five-sided three-dimensional ink jet and other processes.
Among them, electroplating, metal substrates, plastic materials, etc. occupy the main cost of the stent.
4) Bond wire
Commonly used bonding wires for LED device packaging include gold wires, copper wires, palladium-plated copper wires, and alloy wires, etc.
a. Palladium plated copper wire.
Palladium-plated copper wire, also known as “palladium-plated bonding copper wire”, is used to prevent oxidation of copper wire. Palladium-plated copper wire has the advantages of good welding ball, high mechanical strength and moderate hardness. pin IC package.
b. Gold wire.
Gold wire is the most widely used and has the most mature technology, but it is expensive, which leads to the high cost of LED packaging.
c. Copper wire.
The copper wire is cheap, the heat dissipation is good, and the intermetallic compound grows slowly during the wire bonding process.
Disadvantages of easy oxidation, high hardness and high strain strength. Especially in the process of bonding copper balls, copper is easily oxidized, and the formed oxide film reduces the bonding performance, which puts forward higher requirements for process control in the actual production process
How to judge quality of LED SMDs? Consider this question from above four points than you can know the answer! In a simple word, the bond wire, LED bracket, glue and LED display chip should all be taken into account. Unit LED is a professional LED display factory with experiences of more than 11 years! Just contact us to get free samples, and favorable quotations.