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Frequently asked questions (FAQ)

LED chip use process often problems and analytic solution - (AddTime : 2013-01-16)

1. The forward voltage is reduced, dark

A: one kind is electrode and luminescent material for ohmic contact, but contact resistance is big, mainly by the material base of low concentration or defect caused by electrode.
B: one kind is electrode and materials for non-ohmic contacts, mainly in chip electrode preparation process evaporation first layer electrode of extrusion printing or clamp seal, distribution position. Another encapsulation process can also cause positive pressure drop, the main reason is the silver glue curing is not full, the support or chip electrode contamination caused by contact resistance, such as big or contact resistance is not stable. Positive pressure to reduce the chip in the fixed voltage test, through the chip of the current small to show dark spot, and a dark phenomenon is chip itself luminous efficiency is low, the positive pressure drop to normal.

2. Difficult pressure welding: (main have not sticky, electrode wear electrode) play off,
A: can't stick: mainly for electrode surface oxidation or glue
B: with luminescent material contact not firm and upset welding wire layer not firm, in which thickening layer is off.
C: play wear electrode: usually and chip material related, material embrittlement and strength is not high material easy play wear electrode, general GAALAS materials (such as,, infrared chip) a GAP material easy play wear electrode,
D: pressure welding welding temperature, ultrasonic testing should be power, ultrasonic time, pressure, golden ball size, support positioning adjustment.

3. Luminous color difference:
A: with A chip emitting light colors have obvious difference is mainly because epitaxial wafer materials, ALGAINP the four elements materials used in the quantum structure is very thin, growth is difficult to ensure regional component consistent. (component decided to forbidden band width, forbidden band width decided to wavelength).
B: GAP yellow green chip, luminescent wavelength does not have a large deviation, but because the human eye to the band color sensitive, it is easy to find out yellow, slant green. Due to the wavelength is epitaxial wafer materials decision, the smaller the area, there are color deviation concept is smaller, so in the M/T work in adjacent selection method.
C: GAP red chip some luminous color is partial orange, this is because of its luminescent mechanism for indirect leap forward. Influence by the impurity concentration, current density increased, easy generation impurity level migration and luminous saturation, luminous is to start into orange.

4. Brake fluid effect;
A: is the light emitting diode in normal voltage can't conduction, when voltage heightening to A certain degree, the current mutate.
B: produce brake fluid phenomenon reason is luminescent material epitaxial wafer growth appeared when reverse sandwich, there is the phenomenon of 200W led Flood light in IF = and ma test when the positive pressure drop have to conceal a gender, in use process is out of polar voltage is not big enough, for the performance of the not bright, available test instrument information from transistor tracer test curve, also can through the small current = 10 ua IF the positive pressure drop to discover, small electric flow pressure drop is obviously too large, it may be caused by the problem.

5. Reverse leakage:
A: reason: epitaxial material, chip production, device packaging, testing generally 5 v reverse leakage current under 10 ua, can also fixed reverse current flow test reverse voltage.
B: different types of 200W led Flood light reverse characteristics differ big: general green, general yellow chip reverse breakdown can reach more than one hundred v, and general chip is in more than a dozen twenty between v.
C: denotation caused by the reverse leakage is mainly composed of p-n junction internal structure defect chip production process side corrosion is not enough or silver glue wire with attached to the test surface, it is strictly prohibited to use organic solution deployment silver glue. In order to prevent the silver glue through the capillarity climbed to the junction area.