OFweek semiconductor lighting network analysis

1. Forward voltage drops dark light

A: One is that the electrode and the illuminating data are ohmic touches, but the touch resistance is large, which is mainly formed by the low concentration of the data substrate or the electrode defect.

B: One is that the electrode and the data are non-ohmic touches, which mainly occurs in the extrusion printing or the printing of the first layer electrode in the process of preparing the chip electrode, and the orientation is dispersed.

In the other packaging process, the forward voltage drop can also be formed. The primary reason is that the silver gel is insufficiently cured, and the bracket or the chip electrode is stained to form a large touch resistance or the touch resistance is unstable.

When the chip with positive voltage drop is tested at a fixed voltage, the current passing through the chip is small, and then the dark point is reflected. There is also a dark light appearance that the chip itself has low luminous power and the forward voltage drop is normal.

2. Difficult pressure welding: (The first thing is not sticky, the electrode drops, pierce the electrode)

A: It is not sticky: firstly because the electrode is oxidized or has glue

B: There is a lack of contact with the illuminating data and the thickened bonding wire layer is not strong, and the thick layer is mainly dropped.

C: Puncture electrode: usually related to chip data, data brittle and inferior data is easy to penetrate the electrode, usually GAALAS data (such as high red, infrared chip) easier to penetrate the electrode than GAP data,

D: Pressure welding adjustment should be adjusted from welding temperature, ultrasonic power, ultrasonic time, pressure, gold ball size, bracket positioning and so on.

3. Difference in luminous color:

A: There is a significant difference in the luminescent color of the same chip. The first reason is that the epitaxial film has doubts. The ALGAINP four-element data is very thin in quantum layout. It is difficult to ensure that the components of each region are common. (Component resolution band width, band gap width resolution wavelength).

B: GAP yellow-green chip, the wavelength of light will not have a big error, but because the human eye is sensitive to this band color, it is very simple to find yellowish and greenish. Because the wavelength is determined by the epitaxial data, the smaller the area, the smaller the concept of color error, so there is a nearby selection method in the M/T operation.

C: The color of the GAP red chip is orange-yellow, because its light-emitting mechanism is a direct leap forward. Affected by the impurity concentration, when the current density is increased, the impurity level shifts and the luminescence is prone to occur, and the luminescence is turned orange yellow.

4. Brake fluid effect:

A: The LED cannot be turned on under normal voltage. When the voltage is raised to a certain extent, the current suddenly changes.

B: The occurrence of the thyristor surface is caused by the illuminating data epitaxial wafer. When the epitaxial wafer grows, the reverse interlayer is present. The LED with this appearance has a hiding power at the IF=20MA. The application process is due to the voltage of the north and south poles. Large, reflected as not bright, can be used to test the information from the transistor plotter test curve, can also be found through the small current IF = 10UA forward voltage drop, the forward voltage drop under small current is significantly larger, then Can be formed by this question.

5. Reverse leakage:

A: Reason: Epitaxial data, chip manufacturing, equipment packaging, test usually reverse leakage current of 5 UA at 5V, can also be fixed under reverse current to test the reverse voltage.

B: The reverse characteristics of different types of LEDs are quite different: the green color, the reverse breakdown of the yellow chip can reach more than one hundred volts, and the chip is between ten and twenty volts.

C: The reverse leakage formed by epitaxy is mainly formed by the shortcomings of the internal layout of the PN junction. In the process of chip manufacturing, the side surface corrosion is not good or the silver glue wire is attached to the measurement surface. It is strictly forbidden to distribute the silver glue with the organic solution. To avoid the silver glue climbing to the knot area through the capillary appearance

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