Method and apparatus for manufacturing LED device

An apparatus and method of manufacturing a light emitting diode (LED) device, and more particularly, an apparatus and method of manufacturing an LED device by dispensing a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin, onto an LED chip. An apparatus and method of manufacturing an LED device, whereby an appropriate amount of fluorescent solution simultaneously in consideration of several factors, such as characteristics of an LED chip and viscosity of the fluorescent solution may be dispensed onto the LED chip, is provided. An apparatus and method of manufacturing an LED device, whereby an appropriate amount of fluorescent solution may be calculated actively in consideration of viscosity of the fluorescent solution, a change in characteristics of an LED chip, or the like, and the appropriate amount of fluorescent solution may be dispensed onto the LED chip, is provided.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2011-0007668, filed on Jan. 26, 2011, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for manufacturing a light emitting diode (LED) device, and more particularly, to a method and apparatus for manufacturing an LED device, whereby a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin is dispensed onto an LED chip.

2. Description of the Related Art

Light emitting diodes (LEDs) are generally manufactured as LED devices by cutting a plurality of LED chips manufactured on a wafer and by mounting the plurality of LED chip on a package. The LED chip each emits blue or red light. When each LED chip is coated with a fluorescent solution including a fluorescent material, color of light generated from an LED device is changed according to the amount of fluorescent material coated. LED devices that emit white light or other color lights may be manufactured by dispensing an appropriate amount of fluorescent solution onto the package on which the LED chips are mounted.

After each LED chip is coated with the fluorescent solution, power is applied to the LED device so that the LED device emits light, and light characteristics of the LED device are tested using a spectroscope. Generally, color coordinates of light emitted from the LED device are measured. The light characteristics of the LED device are represented by values on color coordinates of 1931 international commission on illumination (CIE). Color coordinate values of light generated from the LED chip are changed by the amount of fluorescent material coated. The color coordinate values of the LED device are significant specification of the LED device. When the color coordinate values of the LED device exceed a predetermined range, the LED device is determined as a defective good.

A dispenser for dispensing the fluorescent solution adjusts the amount of fluorescent solution dispensed onto each LED chip, thereby adjusting the color coordinate values of the LED device. In order to adjust the color coordinate values of the LED device by adjusting the amount of fluorescent solution, a dispenser that adjusts the amount of fluorescent solution in a very small unit is required.

Some general dispenser performs test dispensing, measures the weight of a dispensed resin to calculate a dispensing amount (flow rate) for each unit time and then adjusts the dispensing amount by using the calculated dispensing amount (flow rate). However, the minimum unit of weight that may be measured by a scale with a proper price is about 1 to 10 g. Since the minimum unit of weight that may be measured by using a scale is limited, there is a limitation in finely adjusting the amount of fluorescent solution by using general methods.

The fluorescent solution used in a process of manufacturing an LED device is hardened as time elapses, and viscosity of the fluorescent is changed. Viscosity of the fluorescent solution is also changed according to temperature. Since viscosity of the fluorescent solution is changed non-linearly with respect to a factor, such as temperature, or the like, it is very difficult to apply viscosity of the fluorescent solution calculated by a numerical value to the dispenser. The content of the fluorescent material mixed in the fluorescent solution may be changed slightly every time. A dispensing environment is continuously changed due to mechanical characteristics or an unmeasurable factor of the dispenser. General dispensers cannot meet with such a change. In particular, characteristics of the LED chip supplied to a process of dispensing the fluorescent solution are not constant due to a condition of the previous process in which the LED chip is manufactured. Thus, an apparatus and method of manufacturing an LED device that may adjust light characteristics of the LED device in consideration of the circumstances is required.

SUMMARY OF THE INVENTION

The present invention provides an apparatus and method of manufacturing a light emitting diode (LED) device, whereby an appropriate amount of fluorescent solution simultaneously in consideration of several factors, such as characteristics of an LED chip and viscosity of the fluorescent solution may be dispensed onto the LED chip.

According to an aspect of the present invention, there is provided a method of manufacturing a light emitting diode (LED) device by dispensing a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin, onto an LED chip, the method including: (a) dispensing the fluorescent solution onto a plurality of LED chips, respectively, by using a dispenser; (b) measuring light characteristics of light emitted from the plurality of LED chips by applying power to at least a portion of the plurality of LED chips undergoing the operation (a); (c) calculating a representative value of the light characteristics measured in operation (b); (d) determining an amount of fluorescent solution to be dispensed by the dispenser by using the representative value of the light characteristics calculated in operation (c) and feeding back the amount of fluorescent solution to the dispenser; and (e) dispensing the fluorescent solution having the amount determined in operation (d) onto the plurality of LED chips, respectively, by using the dispenser.

According to another aspect of the present invention, there is provided a method of manufacturing a light emitting diode (LED) device by dispensing a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin, onto an LED chip, the method including: (f) dispensing the fluorescent solution onto a plurality of LED chips, respectively, by using a first dispenser; (g) measuring light characteristics of light emitted from the plurality of LED chips by applying power to at least a portion of the plurality of LED chips undergoing the operation (f); (h) calculating a representative value of the light characteristics measured in operation (g); (i) determining an amount of fluorescent solution to be supplemented to the plurality of LED chips by using the representative value of the light characteristics calculated in operation (h) and transferring the amount of fluorescent solution to a second dispenser; and (j) dispensing the fluorescent solution having the amount determined in operation (i) onto the plurality of LED chips, respectively, by using the second dispenser.

According to another aspect of the present invention, there is provided an apparatus for manufacturing a light emitting diode (LED) device by dispensing a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin, onto an LED chip, the apparatus including: a dispenser for dispensing the fluorescent solution onto a plurality of LED chips, respectively, by using a dispenser; a measuring unit for measuring light characteristics of light emitted from the plurality of LED chips by applying power to at least a portion of the plurality of LED chips on which the fluorescent solution is dispensed by the dispenser; a transfer unit for transferring the LED chips from the dispenser to the measuring unit; and a controlling unit for controlling the dispenser to calculate a representative value of light characteristics of the plurality of chips based on the light characteristics measured by the measuring unit and to adjust an amount of fluorescent solution to be dispensed by the dispenser on each LED chip by using the representative value.

According to another aspect of the present invention, there is provided an apparatus for manufacturing a light emitting diode (LED) device by dispensing a fluorescent solution prepared by mixing a fluorescent material with a liquid synthetic resin, onto an LED chip, the apparatus including: a first dispenser for dispensing the fluorescent solution onto a plurality of LED chips, respectively; a measuring unit for measuring light characteristics of light emitted from the plurality of LED chips by applying power to at least a portion of the plurality of LED chips on which the fluorescent solution is dispensed by the first dispenser; a second dispenser for additionally dispensing the fluorescent solution onto the LED chips on which measurement is completed by the measuring unit; and a transfer unit for transferring the LED chips to the first dispenser and the second dispenser sequentially; and a controlling unit for controlling the second dispenser to calculate a representative value of the light characteristics of the plurality of LED chips based on the light characteristics measured by the measuring unit and to adjust an amount of fluorescent solution to be dispensed by the second dispenser on each LED chip by using the representative value.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic view of an apparatus for manufacturing a light emitting diode (LED) device, according to an embodiment of the present invention, andFIG. 2is a partial perspective view of a lead frame used in a method and apparatus for manufacturing an LED device according to the present invention, andFIG. 3is a flowchart illustrating a method of manufacturing an LED device, according to an embodiment of the present invention.

The method of manufacturing an LED device illustrated inFIG. 3is performed using the apparatus for manufacturing an LED device illustrated inFIG. 1.

First, the apparatus for manufacturing an LED device illustrated inFIG. 1will be described below.

The apparatus for manufacturing an LED device illustrated inFIG. 1includes a dispenser110, a measuring unit120, a controlling unit130, and a transfer unit140.

The dispenser110dispenses a fluorescent solution onto an LED chip30. The fluorescent solution is prepared by mixing a fluorescent material with a liquid synthetic resin, such as epoxy, silicon, or the like. If a predetermined amount of time elapses after the fluorescent solution is dispensed onto the LED chip30, the fluorescent solution is hardened and is in a solid state. Due to the fluorescent material included in the fluorescent solution, color of light generated from the LED chip30is changed, and the light is irradiated towards the outside. In addition, the fluorescent solution is hardened and serves to stably support and protect the LED chip30. It is very significant in adjusting light characteristics of the LED device40to precisely adjust the amount of fluorescent solution.

The dispenser110dispenses a constant amount of fluorescent solution onto the LED chip30. The dispenser110is configured to move forward and backward, right and left, and upward and downward, if necessary.

A plurality of LED chips30are disposed on the dispenser110at regular intervals. A set of the plurality of LED chips30supplied to the apparatus for manufacturing an LED device illustrated inFIG. 1so as to be processed as in one unit in this way is referred to as an LED array. A representative LED array may be a lead frame50illustrated inFIG. 2. The lead frame50is configured by disposing a formation material (package20) having a synthetic resin shape on a metal thin plate at regular intervals. The LED chips30are bonded to each package20, and a positive electrode and a negative electrode of each LED chip30are bonded to an electrode pad of the package20via a wire21and are electrically connected to the electrode pad of the package20. The lead frame50is supplied to the apparatus for manufacturing an LED device illustrated inFIG. 1by using a device, such as a general loader. If an operation of supplying the lead frame50to the apparatus for manufacturing an LED device illustrated inFIG. 1is completed, the lead frame50is discharged from the apparatus for manufacturing an LED device illustrated inFIG. 1.

The dispenser110dispenses a predetermined amount of fluorescent solution onto each LED chip30of the lead frame50. The lead frame50having other structures than the lead frame50illustrated inFIG. 2may be used. The above-described LED array is not limited to the shape of the lead frame50. An LED array having a palette shape on which a plurality of ceramic packages are disposed, may also be used.

Referring toFIG. 1, after power is applied to the LED chip30onto which the fluorescent solution is dispensed by the dispenser110and the LED chip30emits light, the measuring unit120measures light characteristics of the LED chip30. The light characteristics of the LED chip30include luminous intensity, brightness, light temperature, and the like. In the present embodiment, the case where color coordinate values (CIE rank) of 1931 international commission on illumination (CIE) are measured by the measuring unit120will be described.

Light characteristics of the LED device40mounted on the lead frame50may be measured when a positive electrode51and a negative electrode52of a power terminal of the lead frame50are electrically isolated from each other, as illustrated inFIG. 2. The measuring unit120may be configured in various ways. However, in the present embodiment, a probe121is in contact with the LED device40in a downward direction of the lead frame50, as illustrated inFIG. 1, and power is applied to the LED device40, and light is generated from the LED device40, and a light receiving unit disposed on an upper portion of the lead frame50receives the light, and the measuring unit120measures light characteristics of the LED device40.

The transfer unit140transfers the lead frame50from the dispenser110to the measuring unit120and conveys the lead frame50from the measuring unit120back to the dispenser110, if necessary. The measuring unit120may measure light characteristics of each LED device40while moving forward and backward and right and left when the lead frame50is fixed, so as to measure light characteristics of the plurality of LED devices40of the lead frame50, respectively. Alternatively, the measuring unit120may measure light characteristics of each LED device40while the transfer unit140allows the lead frame50to move forward and backward and right and left when the measuring unit120is fixed.

The controlling unit130calculates a representative value of light characteristics of the plurality of LED devices40based on a light characteristic value of each LED device40measured by the measuring unit120. The representative value is a statistical term that means a value for representing a center of statistical data. The representative value includes a mean value, a median, a value having the most frequency (mode), and the like. In the present embodiment, the case where a mean value of color coordinate values of each LED device40is calculated as the representative value will be described. A standard deviation of each LED device40may also be additionally calculated.

Significant specification of the LED device40is color coordinate values of light that is generated from the LED device40. The specification of such color coordinate values is generally defined by a target value of the color coordinate values and a lower limit value and an upper limit value based on the target value.FIG. 4illustrates reference distribution R having a target value of color coordinate values.

The controlling unit130calculates distribution11of the color coordinate values by calculating a color coordinate mean value and a standard deviation of the LED device40of the lead frame50and compares the distribution11with the reference distribution R, as illustrated inFIG. 4. Since the color coordinate values of the LED device40are most affected by the amount of fluorescent solution, the color coordinate values of the LED device40may be changed by adjusting the amount of fluorescent solution to be dispensed by the dispenser110.

The controlling unit130calculates a value of the fluorescent solution required for moving the mean value of the color coordinate values of the lead frame50in this way and transfers the calculated value to the dispenser110, thereby adjusting the amount of fluorescent solution. A correlation between the amount of fluorescent solution and the color coordinate values of the LED device40may be summarized by using a method, such as an experiment, or the like, in advance and may be made as a database, and the controlling unit130may calculate a value of the fluorescent solution to be dispensed to correct the color coordinate values by inquiring the database.

The controller unit130may adjust the color coordinate values of the LED device40largely by using two methods. The first method is to dispense a little insufficient amount of fluorescent solution by using the dispenser110, to calculate a mean value of the color coordinate values and then to calculate a value of the fluorescent solution to be additionally dispensed, thereby performing supplementary dispensing.

The second method is to dispense a fluorescent solution of which amount is determined as the most appropriate amount by using a method, such as an experiment, or the like, onto a first LED array and to measure color coordinate values of the first LED array, thereby calculating a mean value of the color coordinate values. The operation on the first LED array is completed, and the first LED array is discharged. After the mean value of the color coordinate values of the first LED array and the color coordinate target value of the first LED array are compared, a value of the fluorescent solution to be added or reduced so as to remove a difference between the mean value of the color coordinate values of the first LED array and the color coordinate target value of the first LED array is calculated by the controlling unit130. The dispenser110dispenses the fluorescent solution having a corrected amount on the next LED array (second LED array) by reflecting the value calculated by the controlling unit130. This is to correct an error between a target value and color coordinate values of each LED array measured in real-time.

Hereinafter, the method of manufacturing an LED device illustrated inFIG. 3will be described by using the apparatus for manufacturing an LED device, having the above structure illustrated inFIG. 1.

First, the fluorescent solution is dispensed onto the lead frame50by using the dispenser110(operation (a); S110). The fluorescent solution is dispensed onto all LED chips30of the lead frame50, respectively. In this regard, the dispenser110dispenses the fluorescent solution having a little smaller amount than the amount of fluorescent solution required in consideration of further correction.

The transfer unit140transfers the lead frame50to the measuring unit120, and the measuring unit120measures color coordinate values by applying power to each LED device40of the lead frame50sequentially (operation (b); S120). In this regard, the measuring unit120may measure color coordinate values of all LED devices40of the lead frame50and may perform measurement only on some LED device40that are randomly selected from among all LED devices40so as to reduce a process time, if necessary.

The color coordinate values measured by the measuring unit120are transferred to the controlling unit130, and the controlling unit130calculates a mean value of the measured color coordinate values (operation (c); S130).

Referring toFIG. 4, the controlling unit130calculates a difference between the mean value of measured color coordinate values11of the LED devices40and a color coordinate target value based on reference distribution R. The controlling unit130calculates the amount of fluorescent solution required to coincide the mean value of the color coordinate values11of the LED devices40with the color coordinate target value, thereby feeding back the calculated amount of fluorescent solution to the dispenser110(operation (d); S140). In this regard, a database that is made by summarizing a correlation between the amount of fluorescent solution and the color coordinate values, as described above, may be used.

The transfer unit140conveys the lead frame50back to the dispenser110, and the dispenser110additionally dispenses the fluorescent solution onto each LED device40of the lead frame50based on the value transferred by the controlling unit130(operation (e); S150). By performing additional dispensing in this way, distribution12of color coordinate values of the lead frame50is close to the reference distribution R, as illustrated inFIG. 5. That is, the controlling unit130controls the dispenser110to additionally dispense the fluorescent solution so that the mean value of the color coordinate values of the lead frame50is close to a central value of the reference distribution R.

The method of manufacturing an LED device illustrated inFIG. 3includes performing preparatory dispensing the fluorescent solution onto one lead frame50and performing additional dispensing the fluorescent solution after measurement.

If necessary, the method of manufacturing an LED device illustrated inFIG. 3may be implemented by dispensing the fluorescent solution having the most appropriate amount onto a first-supplied lead frame50(first LED array) and completing measurement and then by dispensing the fluorescent solution having a value corrected according to the result of measurement onto the next lead frame50(second LED array).

That is, operations (a), (b), and (c) are performed on the first LED array, and in operation (d), the controlling unit130calculates the amount of fluorescent solution that is the most appropriate when the fluorescent solution is dispensed onto a new LED chip30based on the result of operation (c). In this way, the dispenser110dispenses the fluorescent solution having the corrected amount onto the next lead frame50(second LED array) according to the calculated values (operation (e); S150).

In such a method, the amount of fluorescent solution may be corrected by increasing or decreasing the amount of fluorescent solution. That is, when the distribution13of color coordinate values of the first LED array is as illustrated inFIG. 6, by decreasing the amount of fluorescent solution to be dispensed onto the second LED array, the distribution12of color coordinate values of the second LED array may be adjusted, as illustrated inFIG. 5. The amount of fluorescent solution to be dispensed onto the following lead frame50may also be increased or decreased based on the result of dispensing onto the preceding lead frame50.

Since a liquid synthetic resin of the fluorescent solution stored in the dispenser110is hardened as time elapses, viscosity of the fluorescent solution is not constant and is continuously changed. In addition, an optimum value of the fluorescent solution to be dispensed may be finely changed according to various factors, such as ambient temperature, characteristics of the LED chip30bonded to the lead frame50, and the like. If necessary, a mixture ratio of the synthetic resin of the fluorescent solution with respect to the fluorescent material may be changed according to situations. The most appropriate amount of fluorescent solution according to several factors that are changed in real-time may be inferred from color coordinate values measured from the lead frame50dispensed immediately before.

Meanwhile, stock of all LED devices40may be managed by managing a mean value of light characteristics of a plurality of LED devices40, as described above. For example, in a state where LED devices40having a mean value that is smaller than a color coordinate target value of the reference distribution R, as illustrated inFIG. 4, are manufactured, the LED devices40are additionally manufactured by configuring distribution13of color coordinate values of the LED devices40to intentionally have a greater mean value than the color coordinate target value, as illustrated inFIG. 6so that a mean value of the distribution12of all stocks may coincide with the color coordinate target value of the reference distribution R, as illustrated inFIG. 5. By introducing the concept of the color coordinate mean value to the LED device40manufactured by dispensing the fluorescent solution, the quality of all LED devices40may be controlled, and stock may be reduced.

Operation (e) may include adjusting the fluorescent solution so that a measured color coordinate mean value of LED chips30coincides with a color coordinate target value. However, the amount of fluorescent solution may be adjusted so that the color coordinate mean value is intentionally greater than or smaller than the color coordinate target value so as to coincide the whole mean value of the first LED array and the second LED array with the target value.

In addition, color coordinate values of each LED device40of two or more lead frames50on which dispensing and measurement have been completed, are accumulated to calculate a mean value of the color coordinate values, and the amount of fluorescent solution of the next lead frame50to be dispensed may be adjusted based on the mean value of the color coordinate values.

The amount of fluorescent solution is not adjusted in units of each LED device40, as described above, but is adjusted using a mean value of light characteristics of the plurality of LED devices40. By using the method described above, the present invention may manage statistically and may improve the quality of all LED devices40statistically in consideration of the effect of various error occurrence factors.

In particular, a white LED device that is mainly used for lighting generally constitutes one lighting by combining a plurality of LED devices. Thus, a mean value of color coordinate values of a plurality of LED devices and a standard deviation thereof, as well as color coordinate values of each LED device, are significant. The amount of fluorescent solution of each LED device may be adjusted using the concept of a representative value of light characteristics like in the present embodiment so that the quality of all LED devices may be more effectively controlled.

Meanwhile, after all LED chips30of the lead frame50are dispensed (operation (a); S110), light characteristics of the LED chips30of the lead frame50are measured (operation (b); S120), as described above. However, dispensing and measurement may also be sequentially performed on each LED chip30of the lead frame50.

Various well-known methods of adjusting the amount of fluorescent solution by using the dispenser110may be used. After the amount (flow rate) of the fluorescent solution coated by the dispenser110for a unit time is set constant, a dispensing amount may be adjusted using a length of time when a nozzle of the dispenser110is opened. The dispensing amount may also be adjusted by adjusting the number of times when the nozzle of the dispenser110is opened, using a valve.

Next, an apparatus for manufacturing an LED device, according to another embodiment of the present invention will be described with reference toFIG. 7.

The apparatus for manufacturing an LED device illustrated inFIG. 7is characterized by including two dispensers210and250, such as a first dispenser210and a second dispenser250. A measuring unit220is disposed between the first dispenser210and the second dispenser250. A transfer unit240transfers a lead frame50to the first dispenser210, the measuring unit220, and the second dispenser250, sequentially.

A controlling unit230adjusts the amount of fluorescent solution to be dispensed by the first dispenser210and the second dispenser250based on light characteristic values of the LED device measured by the measuring unit220.

For example, the first dispenser210dispenses the fluorescent solution having a smaller amount than the amount of fluorescent solution required to have a light characteristic target value, and the second dispenser250additionally dispenses the amount of fluorescent solution required to have a light characteristic target value based on a value determined by the controlling unit230, thereby adjusting light characteristics of the LED device.

Hereinafter, a method of manufacturing an LED device, according to another embodiment of the present invention by using the apparatus for manufacturing an LED device illustrated inFIG. 7will be described.

FIG. 8is a flowchart illustrating a method of manufacturing an LED device, according to another embodiment of the present invention.

Referring toFIG. 8, the method of manufacturing an LED device according to the present embodiment includes, first, dispensing a smaller amount of fluorescent solution than a required amount onto each LED device of the lead frame50by using the first dispenser210(operation (f); S210).

The transfer unit240transfers the lead frame50to the measuring unit220, and the measuring unit220allows a probe221to be in contact with each LED chip of the lead frame50and applies power to the LED chip, thereby measuring color coordinate values of the LED chip (operation (g): S220).

The controlling unit230calculates a mean value of the color coordinate values of each LED device of the lead frame50based on the value measured by the measuring unit220(operation (h); S230).

By considering a difference between a color coordinate target value of reference distribution R and the mean value of color coordinate values11of each LED device, as illustrated inFIG. 4, the amount of fluorescent solution to be supplemented to LED devices of the lead frame50is determined and is transferred to the second dispenser250(operation (i); S240).

The transfer unit240transfers the lead frame50to the second dispenser250, and the second dispenser250dispenses the fluorescent solution of which amount is adjusted by the controlling unit230, on each LED device of the lead frame50(operation (j); S250).

In the apparatus for manufacturing an LED device illustrated inFIG. 7and the method of manufacturing an LED device illustrated inFIG. 8, while the second dispenser250performs correction dispensing, dispensing may be performed by the first dispenser210onto a new lead frame50so that a working time may be reduced and productivity may be improved.

Various modified methods of the apparatus for manufacturing an LED device illustrated inFIG. 1and the method of manufacturing an LED device illustrated inFIG. 3may be applied to the apparatus for manufacturing an LED device illustrated inFIG. 7and the method of manufacturing an LED device illustrated inFIG. 8.

As described above, in an apparatus and method of manufacturing an LED device according to the one or more embodiments of the present invention, an appropriate amount of fluorescent solution may be calculated actively in consideration of viscosity of the fluorescent solution, a change in characteristics of an LED chip, or the like, and the appropriate amount of fluorescent solution may be dispensed onto the LED chip.