CN102455403A

CN102455403A - Light emitting diode (LED) chip detecting device

Info

Publication number: CN102455403A
Application number: CN 201010512248
Authority: CN
Inventors: 肖海冬
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-10-20
Filing date: 2010-10-20
Publication date: 2012-05-16

Abstract

The invention relates to a noncontact detection system, and provides a light emitting diode (LED) chip detecting device for improving the stability and the anti-interference capability of a system and enlarging the detection object range of the system. The device comprises a singlechip module, a light source, a filter circuit, a detecting circuit, a display circuit, a power supply, an LED to be detected, a current detection unit and an amplifying circuit. The device is structurally characterized in that: the singlechip module is used for controlling the light source and a driving circuit thereof; alternating voltage signals are amplified by a low-noise operational amplifier, filtered by a programmable band-pass filter and detected by the detecting circuit; and the detection signals are acquired and processed by a singlechip.

Description

A kind of led chip pick-up unit

Technical field:

The present invention relates to a kind of non-contact detection system, relate in particular to a kind of led chip pick-up unit.

Background technology:

The continuous development of light emitting diode (LED) chip fabrication techniques makes great power LED get into the general lighting field becomes possibility, and LED holds at high price and becomes restriction it becomes one of principal element of lighting source.Detection to led chip mainly is the detection of P-N knot quality and the Photoelectric Detection of finished product at present, and quality testing exists cost height, inefficient deficiency to the P-N knot, and can't detect bonding wire quality in the encapsulation process; And the detection of finished product can only improve qualification rate, does not have in all senses reducing production costs.The LED bonding technology receives the influence of many parameters such as temperature, pressure and ultrasonic energy, has only these parameters are all coordinated and could produce the up-to-standard chip of bonding wire.Therefore; The bonding wire quality after the pressure welding operation between led chip and support and the quality of chip itself directly influence the qualification rate of LED finished product, and the detection in the LED encapsulation process has been used very important meaning widely to reduction LED production cost, raising yield rate, promotion LED.

The led chip noncontact online test method of based semiconductor photovoltaic effect in led chip, if the LED quality is good, will produce faint photogenerated current in chip, lead-in wire and the support loop with the alternation exciting light vertical irradiation of certain light intensity; Utilize the high magnetic permeability magnetic core of densely packed coil to pass lead-in wire and support loop, magnetic core two ends shunt capacitance, so just the detection with photogenerated current converts the detection to induced potential to, the final detection that realizes bonding wire quality between led chip quality and chip and support.Document 7 has successfully made up the led chip non-contact detection system based on this method, but this system's detection signal-to-noise ratio is low, and receives the interference of external electromagnetic ripple easily.

Summary of the invention:

The present invention is exactly to the problems referred to above, and a kind of stability and antijamming capability that improves system is provided, and enlarges the led chip pick-up unit of the detected object scope of system.

For reaching above purpose; The present invention adopts following technical scheme; The present invention includes one-chip computer module, light source, filtering circuit, detecting circuit, display circuit, power supply, LED to be measured, current detecting unit, amplifying circuit; Its structural feature is that one-chip computer module controls light source and driving circuit thereof; The alternating voltage signal by low noise operational amplifier after, through band-pass filter able to programme and by detecting circuit alternating signal is carried out detection, single-chip microcomputer is gathered, is handled this rectified signal.

The beneficial effect of the invention:

Detection signal-to-noise ratio is the key that the LED non-contact detection system is correctly judged testing result; Noise signal to detection system has been carried out sampling analysis; Found out the same frequency noise that influences detection signal-to-noise ratio; Light source and driving circuit thereof have been carried out shielding processing, reduced influence, made detection signal-to-noise ratio improve 6dB with the frequency noise signal.Utilize the coherent detection principle to calculate the detection signal amplitude, suppressing on the basis of other frequency content noises, the chip of the multiple size of multiple color is detected, the result shows that detection signal-to-noise ratio has improved more than the 20dB under the shielding condition.

Description of drawings:

Fig. 1 is the detection system hardware block diagram.

Embodiment:

The present invention includes one-chip computer module, light source, filtering circuit, detecting circuit, display circuit, power supply, LED to be measured, current detecting unit, amplifying circuit; One-chip computer module is controlled light source and driving circuit thereof; The alternating voltage signal by low noise operational amplifier after; Through band-pass filter able to programme and by detecting circuit alternating signal is carried out detection, single-chip microcomputer is gathered, is handled this rectified signal.

Current detecting unit is required to be open-circuit structure; Light source and driving circuit thereof are shielded; The comprehensive shielded usefulness of shield is to be weighed by the absorption loss of shielding material and reflection loss sum; The frequency of operation of system is low; Electric field wave and magnetic field ripple are also deposited, and shield effectiveness and electromagnetic kind be closely related existing to adopt higher and the metallic aluminium that relative permeability is lower of relative conductivity respectively, relative conductivity is lower and three kinds of shielding materials of iron-nickel alloy, manganese-zinc ferrite that relative permeability is higher shield light source and driving circuit thereof, select suitable shielding material through the signal to noise ratio (S/N ratio) after the shielding relatively.

Noise signal is through coherent detection; Obtain eliminating with the noise of frequency the noise effect of other frequency contents behind the lock-in amplifier with signal; Circuit noise is the principal element that influences testing result under the condition of shielding light source and driving circuit thereof, and the amplitude that the noise signal after the coherent detection reduces is bigger; Utilize the signal value of lock-in amplifier detection and the signal value of related operation gained that less difference is arranged, cause by the signal sampling error; Behind the related operation; Detection signal-to-noise ratio has all had significant raising; All more than 20dB, the signal after the detection is a direct current signal to amplification, even it is carried out level and smooth and rejects thick The noise; In the LED detection system through amplify, the alternating voltage signal band broad of gained behind the filtering circuit, can be through it being carried out related operation handles so that detection signal-to-noise ratio improves more than the 20dB.

Claims

1. led chip pick-up unit; Comprise one-chip computer module, light source, filtering circuit, detecting circuit, display circuit, power supply, LED to be measured, current detecting unit, amplifying circuit; It is characterized in that one-chip computer module controls light source and driving circuit thereof; The alternating voltage signal by low noise operational amplifier after, through band-pass filter able to programme and by detecting circuit alternating signal is carried out detection, single-chip microcomputer is gathered, is handled this rectified signal.

2. according to the said a kind of led chip pick-up unit of claim 1; It is characterized in that current detecting unit is required to be open-circuit structure; Light source and driving circuit thereof are shielded, and the comprehensive shielded usefulness of shield is to be weighed by the absorption loss of shielding material and reflection loss sum.

3. according to the said a kind of led chip pick-up unit of claim 1; It is characterized in that noise signal is through detecting; Obtain eliminating with the noise of frequency the noise effect of other frequency contents behind the lock-in amplifier with signal; Utilize the difference of the signal value of signal value that lock-in amplifier detects and related operation gained, cause by the signal sampling error.