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What does LED chip use in the process of making you "stuck"?
- May 07, 2017 -

1. Forward voltage is reduced, dark light

A: one is the electrode and the luminescent material for the ohmic contact, but the contact resistance, mainly by the material substrate due to low concentration or electrode defects.

B: one is the electrode and the material is non-ohmic contact, mainly occurs in the chip electrode preparation process evaporation of the first layer of the electrode when the extrusion or folder, the distribution of the location.

In addition, the packaging process may also cause the forward pressure is low, the main reason is not full of silver plastic curing, stent or chip electrode contamination caused by large contact resistance or contact resistance instability. Forward voltage drop in the fixed voltage test, the current through the chip is small, so the performance of dark spots, there is a dark phenomenon is the chip itself, low luminous efficiency, positive pressure drop normal.

2. Difficult to pressure welding: (mainly playing non-stick, the electrode off, piercing the electrode)

A: do not stick: mainly because the electrode surface oxidation or glue

B: there is contact with the luminescent material is not strong and thicker layer is not strong, of which the main layer of thickening off.

C: piercing the electrode: usually with the chip material, the material is not broken and the strength of the material is easy to penetrate the electrode, the general GAALAS materials (such as high red, infrared chip) than GAP material easy to wear the electrode.

D: pressure welding debugging should be from the welding temperature, ultrasonic power, ultrasonic time, pressure, the size of the ball, the stent positioning to adjust.

3. Light color difference:

A: The same chip light color is significantly different because of the problem of epitaxial wafer material, ALGAINP four elements of the quantum structure is very thin, the growth is difficult to ensure that the regional components consistent. (The composition determines the forbidden band width, the forbidden band width determines the wavelength).

B: GAP yellow-green chip, the luminous wavelength will not be a big deviation, but because the human eye on this band color sensitive, it is easy to find partial yellow, green. As the wavelength is determined by the epitaxial wafer material, the smaller the area, the smaller the concept of color deviation, so there are adjacent selection methods in the M / T operation.

C: GAP red chip some light color is orange, which is due to its light-emitting mechanism for indirect leap. By the impurity concentration, the current density increases, easy to produce impurity energy level shift and luminescence saturation, light is started to orange.

4. Gate fluid effect:

A: The light-emitting diode can not turn on at normal voltage, when the voltage increases to a certain extent, the current mutation.

B: the cause of the gate fluid phenomenon is the emergence of luminescent materials epitaxial wafers appear when the reverse mezzanine, this phenomenon of LED in the IF = 20MA test when the positive pressure drop is hidden in the use of the process is not enough for the bipolar voltage , The performance is not bright, available test information from the transistor diagram of the instrument test curve can also be a small current IF = 10UA under the forward voltage drop to find the small current under the positive pressure drop significantly larger, it may be The problem.

5. Reverse leakage:

A: Reason: epitaxial material, chip production, device package, the test generally 5V reverse leakage current of 10UA, can also be fixed reverse current test reverse voltage.

B: different types of LED reverse characteristics of a large difference: Pu green, Pu yellow chip can reach more than one hundred reverse thrust, while the general chip is more than ten twenty volts.

C: The reverse leakage caused by the extension is mainly caused by the defects of the internal structure of the PN junction. The side of the chip is not corroded

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