What factors affect SMD LED panel package reliability?

August 22, 2024

The cost of LED display, a highly efficient display technology, is largely influenced by the LED device, which accounts for 40% to 70% of the total cost. As the cost of LED devices decreases, the overall cost of LED displays also decreases. the quality and reliability of LED displays depend largely on the quality and reliability of their packaging. Key factors include the selection of chip materials, encapsulation materials, and the fine control of the process. With the gradual expansion of LED display to the high-end market, the quality of the device requirements are also rising.

LED display device encapsulation materials: LED display device encapsulation materials mainly include bracket, chip, solid crystal adhesive, bonding wire and encapsulation adhesive, etc. This article will focus on surface mount type encapsulation materials. In this article, we will focus on the discussion of surface-mounted package structure LED (SMD Grid Transparent LED panel), especially the PLCC structure of the LED (TOP LED).

I. LED bracket

1. Role: PLCC bracket as a carrier for SMD LED devices, the reliability of the LED and light performance plays a crucial role.

2. Production process: including metal strip punching, plating, PPA injection molding, bending, five-sided three-dimensional inkjet process. Plating, metal substrate and plastic materials are the main components of the stent cost.

3. Structural improvement design: In order to improve product reliability, some encapsulation factories have improved the structural design of the stent, such as the use of waterproof structure, bending and stretching methods to extend the path of water vapor into the stent, and increase the stent inside the waterproof groove, waterproof steps and water release holes and other multiple waterproof measures. These designs not only reduce the cost of packaging, but also improve the reliability of the product, and has been widely used in Outdoor Led Display products.

LED Chip

1. Core status: LED chip is the core of LED device, its reliability directly affects the life and luminous performance of LED device and display.

2. Cost and size: With the reduction of cost, the size of LED chip is getting smaller and smaller, which reduces the cost, but also brings the reliability problem. The reduction of chip size leads to electrode pad shrinkage, affecting the quality of the welding line, which may lead to gold ball detachment or electrode itself detachment, and ultimately failure. At the same time, the reduction of the distance between the pads increases the current density at the electrodes, resulting in uneven current distribution, affecting chip performance and reducing the reliability of the LED display.

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Bonding wire

1. Function: Bonding wire is the key material to realize the electrical connection between the chip and the pin, and plays the role of current import and export.

2. Material selection:

Gold wire: widely used, mature technology, but expensive, increasing the cost of packaging.

Copper wire: has the advantages of low cost and good heat dissipation, but it is easy to oxidize, high hardness, and requires high process control.

Palladium-plated copper wire: to prevent oxidation of copper wire, with high mechanical strength, moderate hardness and good welding into the ball, suitable for high-density, multi-pin integrated circuit package.

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IV. Encapsulation Adhesive

Main types:

Epoxy resin: easy to aging, susceptible to moisture, poor heat resistance, may be in the short-wave light and high temperature discoloration. Usually need to be modified to improve its performance (SMD Stadium Perimeter LED billboard using epoxy resin encapsulation adhesive).

Silicone: has a high cost-effective, excellent insulation and dielectric properties, but the airtightness is poor, easy to absorb moisture, less used in LED display device packaging.

V. Testing and quality control

In order to ensure the quality and reliability of LED display devices, packaging plants usually carry out strict testing and quality control. For example, through the SAM (Scanning Acoustic Microscope) to test the bending structure design of the LED bracket encapsulation of airtightness to ensure that it is better than ordinary bracket. In addition, the encapsulation factory will also use additives to improve the stress of the glue, while achieving a matte matte effect to enhance the display effect.

Author:

Mr. Alex

E-mail:

alexrgbdance@gmail.com

Phone/WhatsApp:

8613267107880