"Flip Chip + Chip Scale Package" is a perfect match

This article mainly introduces the evolution and future trends of chip-level LED packaging technology. With the continuous development of LED, the cost will be the main obstacle for LEDs to be widely used in various fields such as general illumination, TV backlight and mobile phone backlight. Integration of upstream and downstream technologies through the industry chain is one of the effective ways to reduce costs.

In this paper, the combination of the chip process and the packaging process implemented by flip chip technology is introduced to simplify the LED manufacturing process. The white light chip LED of the technology is directly mounted on the substrate and has better heat dissipation effect and smaller volume. With the maturity of the LED lighting market and the development of other application markets, chip-level LED packaging technology has a bright future.

background

At present, a large number of white LEDs are mainly realized by exciting yellow phosphors by blue LEDs. The technical route of blue LED chips in the industry includes three technical directions: formal structure, vertical structure and flip-chip structure.

The process of manufacturing the chip is relatively simple, but the heat dissipation effect is not as good as the vertical and flip-chip structure, and the packaging process requires gold wire to realize electrical connection, which is more suitable for medium and small power chip packaging, and is often used for indoor lighting tubes, ceiling lamps and the like.

Due to the electrode bonding and epitaxial substrate stripping process, the vertical structure of the chip is relatively complicated and costly. The packaging process still needs gold wire interconnection, but its heat dissipation effect is good, and it is suitable for medium and high power LED products. .

Flip-chip is relatively moderate in process state. Because it directly conducts heat and heat through large-area metal electrodes, the heat dissipation effect is very good, and the gold-free wire interconnection is completely realized, which makes the work reliability significantly improved, which is very suitable for medium and high power LED applications. For high-end lighting and direct-lit TV backlights and other high-demand occasions.

The luminous efficiency, cost and reliability of LED devices are three major issues that LED products need to solve in the field of lighting.

The improvement of the luminous efficiency of LED power devices requires efforts to improve the luminous efficiency of devices from materials, epitaxial layer structures, chip designs, and packaging processes. At present, the luminous efficiency of LEDs has exceeded the light efficiency level of light sources (such as fluorescent lamps and energy-saving lamps) used in the market. The low cost has become the most important force to promote the market share of LEDs. However, while the cost is reduced, it is necessary to ensure high reliability. Sex and other qualities are prerequisites.

The traditional LED industry includes the extension, chip, package and lighting industry chain links. The current industrial development trend shows mergers and acquisitions and vertical integration of the industry chain to reduce costs. By vertically integrating the technical aspects of the chip and packaging, the cost can be further reduced. Therefore, the chip-level package concept in the traditional IC field is introduced into the LED field, that is, the combination of the LED chip and the package, that is, the chip-scale package technology provides a good technical way for the vertical integration of the LED industry. With the rapid increase in market demand and increasing pressure on price decline, the development of Chip Scale Package (hereinafter referred to as "CSP") has become an inevitable trend.

In the three LED chip technology routes, flip chip is suitable for chip-level packaging because it does not need gold wire interconnection and can be directly mounted on various substrate surfaces (PCB, ceramics, etc.) (it is completed directly in the chip manufacturing stage). White light package), forming a chip-level white LED device. Because flip chip heat dissipation, high reliability, and high current drive, it has a high cost performance, so "flip chip + chip scale package" has become the perfect combination, in terms of LED white light device cost and reliability Has a strong advantage, in the past two years has become the hot spot of the LED industry research and the mainstream direction of development.

Chip-level packaging development

CSP refers to a package component with a package size that is no more than 120% of the chip size and is fully functional. The advantage of CSP devices is that the packaging of individual devices is simple and miniaturized, minimizing the material cost of each device. The production capacity of CSP mass production is very large, so as to meet the demand of explosive growth in the market, and the cost of the device is lowered by the large-scale production effect. Chip-scale LED packaging technology brings challenges to packaging technology due to the smaller package size. In particular, LEDs as optical devices require uniform light conversion layers to achieve uniform optical components and ensure packaged devices. Reliability.

Since 2013, package-free packaging has definitely been a hot topic in the LED industry. The so-called package-free package does not really eliminate the packaging process, but advances some packaging processes to the chip process stage, which is actually chip-level packaging. LED companies in Taiwan, Japan, South Korea, Europe and the United States have released similar chip-scale packaged LED products. The common features of each enterprise product are based on the flip chip, which makes the package smaller, optical and thermal performance better. At the same time, the steps of the lead frame and the wire are omitted, which makes the subsequent process more convenient.

There are three main technical solutions for the chip-scale packaging process .

First, the LED wafer is first diced, and then the flip chip is mounted on the substrate material on which the circuit has been fabricated, and then other packaging processes are performed. Finally, the dicing and splicing obtain single or multiple LED modules, which is currently The more popular way is also a more mature process.

Secondly, after the LED wafer is metallized, the flip-chip LED chip is fabricated by dicing, and then the front side and the four sides of the flip-chip LED chip are coated with a fluorescent layer material to achieve the purpose of packaging, which can be directly downstream. Lighting customer application. This method is currently the more common practice on the market, and the direction of each LED factory competing for development.

Third, after the LED epitaxial wafer is completed by the metallized electrode, the phosphor coating is directly performed at the wafer level, and the chip-level packaging is realized after cutting and splitting. The process route is technically difficult, and is still in the early stage of industrialization.

Combining the three methods, the key prerequisite for implementing the chip-level packaging is the development of flip chip.

In China, Jingke Electronics launched the first generation of chip-scale light source products in 2012, which realizes mass production and sales, which is called “chip-level gold-free package”. The upgraded third-generation chip-level light source products are shown in the figure. 1. Based on the flip-chip technology process platform, Jingke Electronics has taken advantage of the technological advantages of chip development and mass production, and combined with advanced packaging technology, has realized the development and mass production of chip-level white LEDs, namely the white light chip. Show.

Chip-level package product applications

The chip-level white LED, which is realized by flip chip, is a white light chip, which can be directly mounted on the PCB board, eliminating the bracket or the substrate, saving the solid crystal and the wire bonding process in the process, and greatly simplifying the link of the LED industry chain. Downstream customer applications, saving costs. Figure 3 below compares the process flow difference between white light chip application and traditional LED application. It is obvious that the application of white light chip is simple.

The white light chip has excellent heat dissipation performance, as shown in FIG. 4, comparing the heat transfer path diagram of the conventional SMD package device and the white light chip on the PCB board. Traditional SMD devices require heat dissipation via chip->solid glue->substrate->solder paste layer->PCB. The heat dissipation path of the white light chip is chip->metal layer->PCB, and the former is 50% higher than the latter by thermal resistance test.

The white light chip is a chip-scale horizontal package, and its package size is not more than 120% compared with the chip size, and has a significant volume advantage. Compared with the traditional LED light source device, the white light chip releases enough space for the secondary optical design for the secondary light distribution, and the volume of the secondary optical component used with the white light chip will be greatly reduced. As shown in FIG. 5, the white light chip is attached to the PCB board, and the secondary optical lens is used for the TV backlight strip, which can make the TV thinner. In addition, as shown in FIG. 6, the white light chip is directly mounted on the substrate, and the arrangement pitch can be controlled, and the high density integration is easy. At the same time, the white light chip can be arranged in a variety of color temperature specifications on the same substrate and achieve color control as shown in Figure 7, to meet the needs of the illumination color temperature diversity.

Figure 7. Two-color temperature COB source realized by white light chip device

The application of CSP white LED devices places higher demands on the accuracy of SMT directly attached to the PCB, although the existing SMT equipment cannot be satisfied. However, some new high-precision SMT devices on the market can meet their accuracy requirements. It is believed that the promotion and application of CSP white LED devices will not be a big problem.

Conclusion and Outlook

From the current market trend, Japan, South Korea, Europe, the United States, Taiwan and other companies have successively launched flip-chip LED chips and chip-scale package products, further demonstrating the future development potential and outstanding technology of chip-level package products realized by flip chip. Advantage. As the LED lighting market gradually matures and other various application markets come, it is believed that there will be a large market space for chip-scale packaged LED products in the future.

The environmentally friendly braided sleeve is made of one or more PET, nylon, copper or cotton threads, PP yarn, nylon, and low-elastic yarn. It can be exported to all countries in the world through environmental protection certification.
The environmentally friendly braided sleeve is mainly used in computer power cords, audio video cables, automobiles, aviation, wire and cable industries, etc. It plays a protective and beautifying role and has certain shielding performance. It is most suitable for the audio medical industry, economical and easy to organize. At the same time, it has very good wear and corrosion resistance, suitable for wire harness protection, wear, corrosion, decoration and storage in various mechanical and electronic industries.
The environmentally friendly braided sleeve is made of one or more PET, nylon, copper or cotton threads, PP yarn, nylon, and low-elastic yarn. It can be exported to all countries in the world through environmental protection certification.

Properties: Excellent flexibility, can be loosely, easy to lead wires, excellent contractility, elasticity and abrasive resistance.
   

Specifications of Halogen Free PET Eexpandable Braided Sleeving 

Automotive Braided Sleeving

Pet Tube Braided Sleeve,Wire Pet Sleeving,Electrical Wire Sleeving ,Wire Cable Sleeve

Shenzhen Huiyunhai Tech.Co.,Ltd , https://www.hyhbraidedsleeve.com