1, what is the LED chip manufacturing process?
LED chip manufacturing is mainly in order to make effective and reliable low ohmic contact electrode, and can meet the minimum pressure drop between can contact materials and provide the pressure pad of welding line, at the same time the light as much as possible. Crossing the membrane process generally by vacuum evaporation method, the main in 1.33 x 10? 4 pa under high vacuum, resistance heating or electron beam bombardment melt material, heating method and under low pressure into a metal vapor deposition in the surface of the semiconductor material. P type used in the general contact metal including AuBe, AuZn alloy, N the contact metal AuGeNi alloy is often used. Alloy layer is formed after coating also need light emitting area as much as possible by lithography process, make to stay alloy layer can meet effective reliable low ohmic contact electrode and the requirement of the welding line pressure pad. After the photolithography process through alloying process, alloying is usually carried out under the aegis of the H2 or N2. Alloying time and temperature are usually based on factors such as semiconductor material properties and alloy furnace form decision. If blue, green, etc, of course, the chip electrode process more complex, need to increase the passivation film growth, such as plasma etching process.
2, LED chip manufacturing process, which has the important influence of the photoelectric performance?
In general, the LED epitaxial production after completion of her main performance has already set, chip manufacturing does not produce the 甞 nuclear nature to change, but in the process of coating, alloying inappropriate bad conditions can cause some electrical parameters. Such as alloying is low or high temperature can cause ohmic contact undesirable, poor ohmic contact is made in the chip is the main reason for the high pressure drop VF. After cutting, if some of the corrosion process was carried out on the edge chip, to improve the chip reverse leakage current will be a good help. This is because with the diamond wheel blade after cutting, edge chip will remain more debris powder, these if at the p-n junction of LED chips will cause leakage, even has a breakdown phenomenon. In addition, if the chip surface photoresist stripping is not clean, will result in positive welding line with virtual welding, and so on and so forth. If the back is also causes the pressure drop is on the high side. In the process of chip production through the way such as surface coarsening, formatted with inverted trapezoidal structure can improve the light intensity.
3, why the LED chip is divided into 8 mil, such as 9 mil,... 40 mil, 13 ∽ 22 mil, such as different size? The size of LED photoelectric performance what effect is there?
The LED chip size according to the power can be divided into low power chip, the power and high power chip. According to customer requirements can be divided into single pipe, digital, dot matrix, and decorative lighting and other categories. As for the chip specific size is according to the actual production level of different chip manufacturers, no specific requirements. As long as the process pass, chip xiaoke improve unit of output and reduce the cost, photoelectric performance is not fundamental change will happen. Chip using current actually associated with density current through the chip, chip using current small, big chip using current, and their basic unit current density. If 10 mil chip is the use of the current 20 ma, then 40 mil chip using current can increase 16 times in theory, which is 320 ma. But considering the heat dissipation is the main problem of the big electricity flow, so its luminous efficiency is lower than the small current. On the other hand, due to the area increases, the body resistance of the chip will reduce, so are to the voltage will be dropped.
4, what's the area of high power LED chips generally refers to the chip? Why is that?
Commonly used in high-power white light LED chip in the market can be seen all around 40 mil, the use of the so-called high power chip power generally refers to the electric power in more than 1 w. Due to the quantum efficiency is generally less than 20% most of the electricity will be converted into heat energy, so it's very important to high power chip cooling, chip has a larger area.
5, manufacturing GaN epitaxial material chip technology and processing equipment compared with GaP, GaAs, InGaAlP what are the different request? Why is that?
Ordinary LED red, yellow, and highlighting four yuan red yellow chip substrate are in compound semiconductor materials such as GaP, GaAs, generally used as the N type substrate. Lithography with wet process, and finally with emery wheel blade cut into chips. Blue and green chips of GaN material is used of the sapphire substrate, due to the sapphire substrate is insulation, so can't as one of the LED, must through the dry etching process at the same time making P/N on the epitaxial two electrodes and by some of the passivation process. Because sapphire is very hard, with emery wheel blade difficult to cross into a chip. It processes more general than GaP, GaAs materials LED and complex.
6, the transparent electrode chip structure and its characteristic is what?
So-called a transparent electrode is to be able to conduct electricity, 2 it is to be able to pervious to light. This material is now the most widely used in LCD production technology, its name is called indium tin oxide, ITO abbreviations, but it cannot be used as welding pad. Making the first ohmic electrodes to do well in the chip surface, and then in the covered a layer of ITO in the ITO surface plating a layer of solder pad. This down from the lead of the current through the ITO layer evenly distributed to the various ohmic contact electrode, at the same time ITO because refractive index between air and epitaxial material refractive index, can improve the light Angle, luminous flux can be increased.
7, used in chip of semiconductor lighting technology development is the mainstream?
With the development of semiconductor LED technology, its application in the field of lighting also more and more, especially the emergence of white LED is becoming a hot spot of semiconductor lighting. But the key chip, encapsulation technology needs to be improved, in terms of the chip to the high power, high photosynthetic efficiency and reduce the thermal resistance in terms of development. Improve power means the use of the chip current increasing, the most direct way is to increase the chip size, now widespread high power chips are 1 mm * 1 mm or so, using the current 350 ma. Due to the use of current increased, heat dissipation problems become prominent question, now, through the method of flip chip basically solved the problem. With the development of LED technology, its application in the field of lighting will face an unprecedented opportunities and challenges.
8, what is "Flip Chip (Flip Chip)"? How about its structure? What are the advantages?
Blue leds usually adopt Al2O3 substrate, Al2O3 substrate hardness is very high, low thermal conductivity and electrical conductivity, if USES the formal structure, on the one hand, will bring antistatic problem, on the other hand, under the condition of high current heat will become the main problem. Due to the positive electrode up at the same time, will cover part of the light, luminous efficiency is reduced. High power blue LED by flip chip technology can be more effective than traditional packaging technology out of the light.
Now the mainstream of the inversion structure is: was prepared in the first place is suitable for the large size eutectic welding electrode blue LED chip, at the same time was better than blue LED chip slightly larger silicon substrate, and produced for eutectic solder on the gold conductive layer and the lead wire (ultrasonic gold ball solder joints). Then, using eutectic welding equipment to high power blue LED chip with silicon substrate welded together. This structure is characteristic of epitaxial layer directly in contact with the silicon substrate, thermal resistance and much lower than the sapphire substrate of silicon substrate, so the heat dissipation problem well solved. Due to the sapphire substrate after flip up, become smooth, sapphire is transparent, so the light problem is solved.
