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The LED chip used in the process of what makes you "stuck"?
Release date:2015-12-21 11:02

The LED chip used in the process of what makes you "stuck"?



1. The forward voltage is reduced, dim light


A: is A kind of electrode and the luminescent material for the ohmic contact, but contact resistance is big, mainly caused by the low substrate concentration or electrode material defect.


B: one kind is electrode and materials for non-ohmic contacts, mainly in the first layer electrode chip electrode preparation process of evaporation of extrusion is printed or clip, distribution position.


Encapsulation process also may cause a positive pressure is reduced, the main reason with silver adhesive curing insufficient, bracket or chip electrode contact resistance caused by contamination such as large and unstable contact resistance.

Low forward voltage chip in a fixed voltage test, by the chip's current is small, which show dark spots, and a dim light phenomenon is the chip itself luminous efficiency is low, positive pressure drop to normal.


2. Hard bonding (mainly are not sticky, electrode loss, wear electrode).


A: didn't stick: mainly because the electrode surface oxidation or glue


B: do you have contact with the luminescent material not firm and upset welding line layer is not firm, which is given priority to with thickening layer falls off.


C: through electrode, is often associated with chip material, material brittle and strength is not high to break through the electrode, general GAALAS materials (such as high, infrared chips) more easily through the electrode GAP materials.


D: bonding debugging should from the welding temperature, ultrasonic power, ultrasonic time, pressure, golden ball size, to adjust the bracket positioning etc.


3. The light color difference:


Emitting light colors have obvious differences: A same chip problems, mainly because of epitaxial wafer materials ALGAINP four element material using quantum structure is very thin, it is hard to guarantee the regional growth components. (component decided to forbidden band width, forbidden band width wavelength).


B: GAP yellow green chip, light wavelength does not have a large deviation, but due to the human eye is sensitive to the band color, it is easy to find out yellow and green. Because the wavelength is determined epitaxial wafer materials, the smaller the area, a concept of color deviation is smaller, so the adjacent selection method in M/T work.


C: GAP some glowing red chip color is orange

Color, this is due to its luminescence mechanism is indirectly by leaps. Influenced by impurity concentration, current density increased, easy to produce the impurity level offset and glowing saturation, light is turning into a orange.


4. The brake fluid effect:


A: is the light emitting diode to conduction in the normal voltage, when the voltage is raised to A certain extent, current mutations.


B: brake fluid phenomenon causes is luminescent material in growth of epitaxial wafer reverse intercalation, there is the phenomenon of the LED in the IF = 20 ma test positive pressure drop when the hidden, in use process is out of the poles voltage is not big enough, the show is not bright, available test instrument inion from transistor curve tracer test, but can be by small current IF = 10 ua under positive pressure drop to found that small electrical flow of large, positive pressure drop may be due to the problem.


5. Reverse leakage:


A: reason: epitaxial material, chip production, device packaging and testing under the general 5 v reverse leakage current of 10 ua, can also be fixed reverse current flow reverse voltage test.


B: different types of LED control IC reverse characteristics differ big: green,, yellow chip reverse breakdown can reach more than one hundred v, and a chip is between a decade or two v.


C: denotation caused by reverse leakage caused by main p-n junction structure defects, chip production process side corrosion or have enough silver silk touch attached to the test surface, it is forbidden to use the organic solution deployment of silver sol. In order to prevent the silver glue by capillarity climb to the junction area.


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