On December 24, 2021, Tesla launched a blockbuster update for car owners, the new UI of the car v11 and the FSD Beta V10.8 version, after the update, the owner was pleasantly surprised to find that the light show function was added, in which the headlights hit the "TESLA" pattern, which was very amazing.
Part of the reason is that Tesla did not emphasize this matter in the publicity before, so that people can see this situation, instantly surprised; another part of the reason is that whether it is matrix LED headlights or laser headlights, it is basically a "lamp factory" - Audi's gimmick, due to high costs, the cost of installation is not cheap, it is still far from ordinary consumers, and Tesla is standard in the Model3 and ModelY models that started with two or three hundred thousand, which should be said to be more conscientious. Contrary to the hilarious display in the circle of friends, Tesla is so low-key that it feels that this matter is not simple.
The author has been engaged in the LED industry for many years, out of technical curiosity, through multi-party verification of relevant public information, I hope to restore the technical route of Tesla's front light source.
TESLA headlight effect
According to public information, Tesla's headlights are manufactured by HELLA, a well-known German spare parts supplier, of which the supplier of the light-emitting unit is Samsung Electronics.
"In April 2021, Samsung Semiconductor released a new generation of on-board light source PixCell LED module, which will be applied to smart headlights in automobiles.
Samsung Semiconductor said that the newly developed PixCell LED is an ultra-small LED solution for in-vehicle smart headlights, which can achieve lighting control through a smaller luminous area and chiaroscuro.
In addition, Samsung's products reduce the luminous area to 1/16 of ordinary smart headlights, making the volume of the entire lamp smaller, helping to improve the fuel efficiency of the car, and also increasing the design flexibility of the lamp. ”
PixCell LED module (Image source: Samsung Electronics official website)
Judging from the disassembly analysis released by the domestic research institute - the Light Research Institute, Tesla does use Samsung Electronics' PixCell LED technology. Therefore, it is necessary to dig deeper into the technology.
Tesla car headlights dismantling light source (Image source: Lamp Research Institute)
In order to improve the display effect and prevent crosstalk of adjacent light sources, PixCell LEDs have set up silicon wall partitions between each pixel.
PixCell LED (Image source: Samsung Electronics official website)
From the final display effect, each pixel unit in the PixCell LED achieves a one-sided light output effect. According to previous cognition, the chip segment that can achieve this luminous effect is mainly a thin-film chip, such as a vertical thin-film chip, a flip-chip thin-film chip (TFFC) chip, etc.; the package end can also use flip chip + CSP (Chip Scale Package) technology to block and reflect the light around the chip through the white wall, so that the lateral light is reflected to the front, and the effect of single-sided light can also be realized.
PixCell LED seems to have similarities with CSP technology, but the use of silicon wall to replace the white wall (titanium dioxide and other highly reflective materials), and from the publicity of the schematic, the silicon wall height is higher, the fluorescent film is not covered on the silicon wall. This design actually reduces pixel crosstalk and improves the resolution of pixels.
In order to further understand how the PixCell LED is implemented, we searched many times and finally found a patent recently published by Samsung:
Publication patent number: US17373038
专利名称：LIGHT-EMITTING DEVICES HEADLAMPS FOR VEHICLES AND VEHICLES INCLUDING THE SAME
The patent details the basic design concept of the PixCell LED core light-emitting device:
The basic design idea is to use flip-chip chip technology (TFFC) and wafer-level packaging (WLP) concepts.
Silicon substrate 1000 is formed by corrosion to form a silicon wall 120
And made a reflective layer 72 on the side wall of the silicon wall
The silicon wall is filled with optical transmission material 74 to achieve wafer-level packaging
The actual TFFC's electrodes are led out by leads, a design that goes beyond TFFC's design and takes wafer-level packaging technology one step further.
From the process flow and the final design, Samsung PixCell LED adopts a silicon substrate epitaxial process, the chip architecture adopts a TFFC-like structure with a silicon wall, and a white chip is made of white light chip through wafer-level packaging Wafer Level Package (WLP) technology.
Although the patent is not limited to the silicon substrate, the actual sapphire and silicon carbide substrates are more difficult to have the effect of selective removal of this substrate, and the natural opacity of the silicon substrate is conducive to preventing interference from the adjacent chip string light.
The content presented in this patent is highly innovative and can expand the vision of developers, and the solution may not be as complex as imagined for practitioners who have been engaged in the development of thin-film chips for a long time, but it is indeed relatively new. Of course, to reach the car standard level and break into the pre-loading market, it should take a lot of energy and investment.
Compared with the current mature gallium nitride epitaxy on sapphire and silicon carbide, the GaN-On-Si (gallium nitride on silicon) epitaxy technology used in this scheme has a poor quality due to the large mismatch between gallium nitride and silicon lattice. The difference in crystal quality will be reflected in reliability and performance to a certain extent. Judging from user feedback, Tesla owners have the problem of headlight burning after upgrading the light show, and it is not excluded that it may be related to this.
In a sense, Samsung's PixCell LED can be recognized by the head car companies and break into the automotive front-loading market, which is definitely a milestone event for GaN-On-Si technology based on silicon substrates.
Tesla may know in advance that the GaN-On-Si technology solution has some risks, but it can indeed achieve a smaller luminous area and chiaroscuro. As a result, Tesla's adoption of the technology is in line with its consistent technology-driven style of doing things.
In addition to using GaN-On-Si technology, PixCell LED also combines wafer level package (WLP), Thin Film Flip Chip (TFFC), Drive On Board (DOB) and other technologies, and has evolved and advanced them. PixCell LED is the crystallization of Samsung Electronics' cross-innovation in the field of light-emitting chips and semiconductors, and its innovative vision and innovation ability are worth learning from domestic manufacturers.
Of course, GaN-On-Si technology is not the only way to achieve matrix LED headlights, such as laser peeling technology to achieve TFFC chips, domestic dry photoelectric, Sanan optoelectronics, Yimei core light, etc. in the field of thin-film chips for many years, the use of mature sapphire laser peeling technology, can also have a corresponding program presentation. And in terms of light efficiency and reliability, thin-film chips based on sapphire laser peeling technology will have more advantages than silicon substrate LED technology. (Text: Qu Xiaodong)
Please indicate the source of the reprint! For more LED information, please pay attention to the official website or search for the WeChat public account (LEDinside).