What problems are often encountered during the use of LED injection molding module chips? How should it be solved? How did these problems arise? With these questions, let's discuss together.

1. Forward voltage decreases, dark light

A: One is that the electrode and the light-emitting material are in ohmic contact, but the contact resistance is large, which is mainly caused by the low concentration of the material substrate or the electrode defect.

B: One is that the electrode and the material are in non-ohmic contact, which mainly occurs in the extrusion or pinching of the first layer of electrode during the preparation of the LED injection module chip electrode, and the distribution position.

In addition, the forward voltage may also be reduced during the packaging process. The main reasons are that the silver glue is not fully cured, and the bracket or LED injection module chip electrodes are stained, resulting in high contact resistance or unstable contact resistance. When the LED injection molding module chip with reduced forward voltage is tested at a fixed voltage, the current passing through the chip is small, thus showing dark spots. Another dark light phenomenon is that the luminous efficiency of the chip itself is low, and the forward voltage drop is normal.

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

A: Non-stick: mainly because the electrode surface is oxidized or glued

B: The contact with the luminescent material is not strong and the thickened wire layer is not strong, and the thickened layer is mainly peeled off.

C: Piercing electrode: usually related to the chip material of the LED injection molding module. Materials with brittle materials and low strength are easy to penetrate the electrode. Generally, GAALAS materials (such as high red, infrared chips) are easier to penetrate electrodes than GAP materials.

D: Pressure welding debugging should be adjusted from welding temperature, ultrasonic power, ultrasonic time, pressure, gold ball size, bracket positioning, etc.

3. Lighting color difference:

A: The obvious difference in the luminous color of the same chip is mainly due to the problem of the epitaxial wafer material. The ALGAINP four-element material adopts a very thin quantum structure, and it is difficult to ensure that the composition of each region is consistent. (The composition determines the band gap, and the band gap determines the wavelength).

B: GAP yellow-green chip, the light-emitting wavelength will not vary greatly, but because the human eye is sensitive to the color of this band, it is easy to detect yellowish and greenish. Since the wavelength is determined by the epitaxial wafer material, the smaller the area, the smaller the concept of color deviation, so there is a neighboring selection method in the M/T operation.

C: Some of the light-emitting color of the GAP red chip is orange-yellow, which is due to its light-emitting mechanism being an indirect jump. Affected by the impurity concentration, when the current density increases, the impurity energy level shift and luminescence saturation are easy to occur, and the luminescence begins to turn orange-yellow.

4. Thyristor effect:

A: The light-emitting diode cannot be turned on under normal voltage. When the voltage is increased to a certain level, the current will change abruptly.

B: The reason for the thyristor phenomenon is that there is a reverse interlayer during the growth of the luminescent material epitaxial wafer. The LEDs with this phenomenon have hidden forward voltage drop when tested at IF=20MA. During the use process, the voltage between the two poles is not large enough. , the performance is not bright, you can use the test information instrument to test the curve from the transistor diagram meter, or you can find out by the forward voltage drop under the small current IF=10UA, the forward voltage drop under the small current is obviously larger, it may be caused by this problem.

5. Reverse leakage:

A: Reason: Epitaxial materials, chip fabrication, device packaging, the reverse leakage current is generally 10UA under 5V, and the reverse voltage can also be tested under a fixed reverse current.

B: The reverse characteristics of different types of LED injection molding modules are quite different: the reverse breakdown of common green and common yellow chips can reach more than one hundred volts, while the common chips are between ten and twenty volts.

C: The reverse leakage caused by epitaxy is mainly caused by the internal structural defects of the PN junction. During the chip fabrication process, the side corrosion is insufficient or there is silver glue attached to the measurement surface. It is strictly forbidden to use organic solutions to prepare silver glue. In order to prevent the silver glue from climbing to the junction area through capillary phenomenon.