B: One is that the electrode and the material are in non-ohmic contact, which mainly occurs when the first layer electrode is evaporated during the process of preparing the chip electrode.
In addition, the forward pressure drop may also be caused during the packaging process. The main reason is that the silver paste is not cured sufficiently, and the contact resistance or the contact resistance is unstable due to the contamination of the holder or the chip electrode. When the forward voltage is reduced, the chip has a small current flowing through the chip during a fixed voltage test, thereby exhibiting a dark spot. There is also a phenomenon that the light emission efficiency of the chip itself is low and the forward voltage drop is normal.
2. Difficult-to-pressure welding: (mainly non-stick, electrode drop, punching electrode)
A: No sticking: Mainly because the surface of the electrode is oxidized or there is glue B: There is loose contact with the luminescent material and the thickened wire layer is not firm, of which the thick layer is mainly detached.
C: Breakthrough electrode: Usually related to the chip material, the material is brittle and the material with low strength is easy to break through the electrode. Generally GAALAS materials (such as high red and infrared chips) are easier to penetrate the electrode than the GAP material.
D: Pressure welding debugging should be adjusted from welding temperature, ultrasonic power, ultrasonic time, pressure, size of gold ball, positioning of bracket, etc.
3. Glowing color difference:
A: The obvious difference in emission color of the same chip is mainly due to the issue of epitaxial wafer materials. The ALGAINP four-element material adopts a thin quantum structure, and it is difficult to ensure uniform composition of each region in the growth. (Components determine the forbidden band width and the band gap determines the wavelength).
B:GAP yellow-green chip, there will not be a large deviation in the luminous wavelength, but because the human eye is sensitive to the color of this band, it is easy to find yellowish, greenish. Since the wavelength is determined by the material of the epitaxial wafer, the smaller the area, the smaller the concept of color deviation occurs, so there is a proximity selection method in the M/T operation.
C: The red color of the GAP red chip is yellowish orange, which is due to its indirect leap in the luminescence mechanism. Affected by the impurity concentration, when the current density increases, the impurity level shifts and the light emission saturation easily occurs, and the light emission starts to become orange-yellow.
4. The galvanic effect:
A: The light emitting diode cannot be turned on under the normal voltage. When the voltage rises to a certain degree, the current is mutated.
B: The reason for the generation of thyristors is that the reverse sandwich is present when the luminescent material epitaxial wafer grows. The LED with this phenomenon has a hidden forward voltage drop at IF=20MA. In use, the voltage at the two electrodes is not enough. The performance is not bright. Test information instrument can be used to test the curve from the transistor graphic analyzer. It can also be found by the forward voltage drop at a small current of IF=10UA. The forward voltage drop at low current is obviously high, it may be Caused by the problem.
5. Reverse leakage:
A: Reasons: Epitaxial material, chip fabrication, device packaging, and test, the reverse leakage current is generally 10 UA at 5V, and the reverse voltage can also be tested at a fixed reverse current.
B: The reverse characteristics of different types of LEDs have a large difference: In general, the reverse breakdown of a yellow chip can reach over one hundred volts, while the common chip is between ten and twenty volts.
C: The reverse leakage caused by the epitaxy is mainly caused by defects in the internal structure of the PN junction. During the chip manufacturing process, the side etching is not enough or silver paste adheres to the measuring surface. It is forbidden to use organic solutions to mix silver paste. To prevent the silver glue from crawling through the capillary phenomenon to the knot area.
Mild steel, sometimes referred to as carbon steel or ordinary carbon steel, is defined as having a carbon content of no more than 2% and no other perceptible alloy elements.
This steel is produced on a large scale and is the largest part of the steel production industry. You will be able to find it in various applications, fasteners and fasteners.
Generally, this kind of steel has high strength, high hardness and magnetism, and is usually used in motors and electrical appliances - however, their corrosion resistance is poor, and should not be used in corrosive environment without protective coating or coating.
There are some differences between low-carbon steel and steel, because steel has lower toughness and greater brittleness, and low-carbon steel can be further strengthened by adding carbon.
If you need more information or want to order carbon steel products, such as hexagon Bolts, carriage bolts, flange bolts, U-bolts, union bolts, expansion bolts, threaded rods, please contact us.
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