Forward voltage reduction and dark light
(1) one is the ohmic contact between the electrode and the luminescent material, but the contact resistance is large, which is mainly caused by the low concentration of the substrate or the defect of the electrode.
(2) one is the non ohm contact between the electrode and the material, which mainly occurs when the first layer of electrode is evaporated during the preparation of the chip electrode.
In addition, the forward pressure reduction may be caused in the encapsulation process, mainly due to the insufficient curing of the silver glue, the contamination of the support or the chip electrode, and the instability of contact resistance or contact resistance.
When the chip is tested on a fixed voltage, the chip has a small current, which shows a dark point, and a dark light phenomenon is that the chip itself has low luminous efficiency and normal pressure drop.
Hard pressure welding
(1) no sticking: mainly due to oxidation or glue on the electrode surface.
(2) contact with the luminescent material is not tight and the thickness of the welding layer is not strong, especially the thickening layer.
(3) wear electrode: usually related to chip material, material brittle and not high strength material easily wear electrode, general GAALAS material (such as high red, infrared chip) is easier to wear than the GAP material.
(4) pressure welding should be adjusted from welding temperature, ultrasonic power, ultrasonic time, pressure, gold ball size and bracket positioning.
Color difference of luminescence
(1) the obvious difference in the color of the same chip is mainly due to the problem of the epitaxial sheet material. The ALGAINP four element material is very thin with quantum structure, and it is difficult to ensure the consistency of the components in each region. The composition determines the forbidden band width and the wavelength of the forbidden band determines the wavelength.
(2) GAP yellow green chip, the luminous wavelength will not be greatly deviate, but because the human eye is sensitive to the color of the band, it is easy to detect yellowish and greenish. Because the wavelength is determined by the epitaxial material, the smaller the area is, the smaller the color deviation concept is. So there is a neighbor selection method in the M/T operation.
(3) some of the red chips of GAP are light orange yellow because of their indirect mechanism. Due to the influence of impurity concentration, when the current density increases, impurity level shifts and luminescence saturation are easily produced, and the luminescence starts to turn orange yellow.
Sluice effect
(1) the LED is unable to conduct at normal voltage, and when the voltage increases to a certain extent, the current changes.
(2) the reason of the phenomenon of brake fluid is that the reverse interlayer appears when the epitaxial piece of the luminescent material is grown. The positive pressure drop of the LED at IF=20MA is hidden. In the process of use, the voltage of the two poles is not big enough and the performance is not bright. The test information instrument can be used to test the curve from the crystal tube diagram, and can also pass through the small curve. The forward voltage drop under current IF=10UA shows that the forward voltage drop under a small current is obviously too large, which may be caused by this problem.
Reverse leakage current IR
Under the limited condition, the reverse leakage current is the basic characteristic of the diode. According to the conventional regulation of LED, it refers to the reverse leakage current of the reverse voltage at 5V. With the improvement of the performance of the LED, the reverse leakage current will be smaller and smaller. IR the smaller the better, the reason is the irregular movement of electrons.
(1) the reason for the quality of the chip itself may be caused by the abnormal cutting of the chip itself.
(2) too much silver glue point, which can cause short circuit when serious. The reverse leakage caused by the epitaxy is mainly caused by the internal structure defects of PN junction. The side corrosion of the chip is not enough or the silvery silk is attached to the surface, and the organic solution is strictly prohibited. To prevent the silver gum from crawling through the capillary phenomenon to the knot area.
(3) electrostatic injury. Epitaxial materials, chip fabrication, device encapsulation, general 5V reverse leakage current is 10UA, and reverse voltage can be fixed under reverse current. The reverse characteristics of different types of LED are large: common green, reverse yellow yellow chips can reach more than 100 volts, and common red chips are between ten and twenty volts.
(4) improper welding line pressure leads to increased IR in the wafer.
Solution：
(1) the amount of silver colloid should be controlled at 1/3 to 1/2 of wafer height.
(2) the static volume of the human body and the machine should be controlled below 50V.
(3) the pressure at the first point of the welding line should be controlled between 30 and 45g.
Dead light phenomenon
(1) the leakage of LED leads to the failure of PN junction and makes the LED lamp not lit. This situation will not affect the work of other LED lamps in general.
(2) the internal connection wire of the LED lamp is disconnected, causing the dead light to produce LED without current. This situation will affect the normal work of other LED lights because of the low working voltage of the LED lamp (red yellow orange LED working voltage 1.8v-2.2v, blue green white LED working voltage 2.8-3.2v), all of which are connected in series and parallel in parallel to adapt to the difference. The work voltage, the more LED lights in series, the greater the impact, as long as there is one of the LED lights inside the line, the whole series of LED lights will not be bright, this situation is more serious than the first situation.
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(1) one is the ohmic contact between the electrode and the luminescent material, but the contact resistance is large, which is mainly caused by the low concentration of the substrate or the defect of the electrode.
(2) one is the non ohm contact between the electrode and the material, which mainly occurs when the first layer of electrode is evaporated during the preparation of the chip electrode.
In addition, the forward pressure reduction may be caused in the encapsulation process, mainly due to the insufficient curing of the silver glue, the contamination of the support or the chip electrode, and the instability of contact resistance or contact resistance.
When the chip is tested on a fixed voltage, the chip has a small current, which shows a dark point, and a dark light phenomenon is that the chip itself has low luminous efficiency and normal pressure drop.
Hard pressure welding
(1) no sticking: mainly due to oxidation or glue on the electrode surface.
(2) contact with the luminescent material is not tight and the thickness of the welding layer is not strong, especially the thickening layer.
(3) wear electrode: usually related to chip material, material brittle and not high strength material easily wear electrode, general GAALAS material (such as high red, infrared chip) is easier to wear than the GAP material.
(4) pressure welding should be adjusted from welding temperature, ultrasonic power, ultrasonic time, pressure, gold ball size and bracket positioning.
Color difference of luminescence
(1) the obvious difference in the color of the same chip is mainly due to the problem of the epitaxial sheet material. The ALGAINP four element material is very thin with quantum structure, and it is difficult to ensure the consistency of the components in each region. The composition determines the forbidden band width and the wavelength of the forbidden band determines the wavelength.
(2) GAP yellow green chip, the luminous wavelength will not be greatly deviate, but because the human eye is sensitive to the color of the band, it is easy to detect yellowish and greenish. Because the wavelength is determined by the epitaxial material, the smaller the area is, the smaller the color deviation concept is. So there is a neighbor selection method in the M/T operation.
(3) some of the red chips of GAP are light orange yellow because of their indirect mechanism. Due to the influence of impurity concentration, when the current density increases, impurity level shifts and luminescence saturation are easily produced, and the luminescence starts to turn orange yellow.
Sluice effect
(1) the LED is unable to conduct at normal voltage, and when the voltage increases to a certain extent, the current changes.
(2) the reason of the phenomenon of brake fluid is that the reverse interlayer appears when the epitaxial piece of the luminescent material is grown. The positive pressure drop of the LED at IF=20MA is hidden. In the process of use, the voltage of the two poles is not big enough and the performance is not bright. The test information instrument can be used to test the curve from the crystal tube diagram, and can also pass through the small curve. The forward voltage drop under current IF=10UA shows that the forward voltage drop under a small current is obviously too large, which may be caused by this problem.
Reverse leakage current IR
Under the limited condition, the reverse leakage current is the basic characteristic of the diode. According to the conventional regulation of LED, it refers to the reverse leakage current of the reverse voltage at 5V. With the improvement of the performance of the LED, the reverse leakage current will be smaller and smaller. IR the smaller the better, the reason is the irregular movement of electrons.
(1) the reason for the quality of the chip itself may be caused by the abnormal cutting of the chip itself.
(2) too much silver glue point, which can cause short circuit when serious. The reverse leakage caused by the epitaxy is mainly caused by the internal structure defects of PN junction. The side corrosion of the chip is not enough or the silvery silk is attached to the surface, and the organic solution is strictly prohibited. To prevent the silver gum from crawling through the capillary phenomenon to the knot area.
(3) electrostatic injury. Epitaxial materials, chip fabrication, device encapsulation, general 5V reverse leakage current is 10UA, and reverse voltage can be fixed under reverse current. The reverse characteristics of different types of LED are large: common green, reverse yellow yellow chips can reach more than 100 volts, and common red chips are between ten and twenty volts.
(4) improper welding line pressure leads to increased IR in the wafer.
Solution：
(1) the amount of silver colloid should be controlled at 1/3 to 1/2 of wafer height.
(2) the static volume of the human body and the machine should be controlled below 50V.
(3) the pressure at the first point of the welding line should be controlled between 30 and 45g.
Dead light phenomenon
(1) the leakage of LED leads to the failure of PN junction and makes the LED lamp not lit. This situation will not affect the work of other LED lamps in general.
(2) the internal connection wire of the LED lamp is disconnected, causing the dead light to produce LED without current. This situation will affect the normal work of other LED lights because of the low working voltage of the LED lamp (red yellow orange LED working voltage 1.8v-2.2v, blue green white LED working voltage 2.8-3.2v), all of which are connected in series and parallel in parallel to adapt to the difference. The work voltage, the more LED lights in series, the greater the impact, as long as there is one of the LED lights inside the line, the whole series of LED lights will not be bright, this situation is more serious than the first situation.
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