Industry news

2016August

Analysis of problems encountered in the use of LED chip

From: www.szbako.com Data:31/08/2016

Decline in

1. forward voltage a dark

: A is the electrode and luminescent materials is the ohm touch, but touch resistance big, basically formed by the data of low substrate concentration or electrode incomplete of. B

: one is the electrode and material for non ohmic touch, mainly in the process of preparing the chip electrode in the process of evaporation of the first layer of the squeeze printing or printing, spread.

other encapsulation process also can form positive pressure drop, main reason is silver glue curing is not sufficient, the stent or chip electrode contamination formed touch resistance or touch the resistance is not stable.

the forward voltage drop of the chip in the fixed voltage test, after chip current small, and then reflect scotoma. There is a dark appearance is chip self luminous low power, forward voltage is normal. <2. difficult to pressure welding: (primary beat the non stick, drop electrode penetrated electrode)

A: not stick: first because the electrode surface oxidation or gum C: penetrated electrode: usually with the related data of chip, data and brittle strength of easy wear electrode, usually GAALAS (such as red and infrared chip) data is gap data easy to hit the electrode wear, 3. luminous color difference: a

: with a chip light-emitting color there is significant difference between the first is because of the epitaxial wafer data queries, ALGAINP four element data selected quantum layout is very thin, the growth is very difficult to ensure the regional groups together. (the resolution of the band gap width and the width of the forbidden band is decided. Yellow and green B:GAP


C:GAP red chip light-emitting color is orange yellow, this is because the luminescence mechanism for leap directly. Affected by the concentration of impurities, the current density increases, the impurity level shift and the emission is easy to occur, and it is the beginning of orange yellow luminescence.

4. Brake fluid effect: a

: light emitting diode in the normal voltage not conducting, when the voltage booster to a certain degree of current occurs sudden change.

b: brake fluid appearance of reason is luminous material epitaxial film growth, it has inverse sandwich, led this representation in the IF=20MA forward voltage drop of test have to hide, in the use process is for polar voltage is not high, which is not bright, available information of test instrument from transistor tracer test curve, also can through the forward voltage drop of small current IF=10UA found, small current, and the forward voltage drop significantly larger, is formed by the question.

5. The reverse leakage current: a

: Reason: epitaxial material, chip manufacturing, equipment package, test usually 5V reverse leakage current 10UA and can also be fixed reverse current test reverse voltage.

b: no big difference between the types of LED reverse characteristics: Pu green, Huang Pu chip reverse breakdown can be reached more than 100 volts, and general chip in their teens and 20 volts between.

C: the formation of epitaxial reverse leakage current of the first formed by the PN junction of the internal layout shortcomings of, chip manufacturing process side surface corrosion not or a colloidal silver wire sticking in measuring surface, prohibited the use of organic solution distribution of silver colloid. In order to avoid the silver glue through the capillary surface to climb to the junction area

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