CN104226568A - LED (Light emitting diode) fluorescent powder coating method and system based on 3D printing principle - Google Patents

Abstract

The invention relates to a method and system for coating LED fluorescent powder based on the principle of 3D printing. The LED phosphor coating methods used in industry all have the problem of uneven coating thickness, which seriously affects the packaging quality of white LEDs such as thermal resistance dispersion, chromaticity consistency, and light extraction efficiency. In the present invention, by improving the traditional coating process, the vacuum stirring and defoaming device is used to remove the foam of the fluorescent powder glue, and then the piezoelectric coating nozzle is used for heating and constant temperature control, so as to realize the function of reducing and stabilizing the viscosity of the phosphor powder glue, and The piezoelectric coating nozzle based on the 3D printing principle is used to control the size and quantity of the phosphor glue droplets sprayed each time, and the high-precision motion xyz axis motion platform is used to control the coating position of the phosphor glue droplets sprayed each time , to improve the phosphor coating accuracy of high-power white LED chips or chip modules, so as to meet the conformal coating requirements of the phosphor layer thickness and shape in high-power white LED chip modules.

Description

A LED phosphor coating method and system based on 3D printing principle

technical field

The invention relates to the technical field of LED fluorescent powder coating, in particular to a method and system for coating LED fluorescent powder based on the principle of 3D printing.

Background technique

White LED is a new type of semiconductor all-solid-state lighting source. Compared with traditional lighting technology, this new type of light source has leading advantages such as high efficiency and energy saving, long life, small size, easy maintenance, green environmental protection, safe use, and good weather resistance. It is recognized as the first choice for future lighting sources.

White LED packaging is a key process to promote the rapid development of international semiconductor lighting and display, while phosphor coating is currently the mainstream technology for realizing the conversion from blue LED to white LED in the world. The uneven thickness of phosphor powder coating is the main reason for the difference in angular color temperature of white light LEDs. At present, the high-power LED phosphor coating process is mainly realized by two methods: dispensing and spraying, and these two traditional control methods cannot guarantee the amount of phosphor coating each time under large-scale industrial production. Consistency, that is, the coating thickness of the phosphor layer is slightly different every time. As a result, the produced high-power white LEDs cannot effectively improve packaging quality such as thermal resistance dispersion, chromaticity consistency, and light extraction efficiency of the white LED packaging. 3D printing technology is a technology that uses bondable materials such as powdered metal or plastic to construct objects by layer-by-layer printing based on digital model files.

On the basis of the existing coating process, the present invention adds a vacuum stirring and defoaming device to simplify the existing coating process, and effectively removes tiny bubbles contained in the mixed fluorescent powder and glue; adds a nozzle constant temperature control device to control the pressure The electric phosphor nozzle is subjected to constant temperature control to reduce and stabilize the viscosity of the fluorescent powder in the piezoelectric phosphor nozzle; Electrospray head) prints the phosphor layer to the LED chip, so that it overcomes the shortcomings of the traditional coating process and achieves a high-precision and high-uniformity coating effect.

Contents of the invention

One of the purposes of the present invention is to provide a method and system for coating LED phosphor powder based on the principle of 3D printing, which can effectively improve the consistency of phosphor powder coating amount and coating thickness, and improve the light source quality and yield of white LEDs. The specific technical scheme is as follows.

An LED phosphor coating system based on the principle of 3D printing, used to complete the conformal coating process of the thickness and shape of the phosphor layer on the LED chip, including the lower computer system and the upper computer system, the lower computer system includes piezoelectric fluorescent powder spray head and xyz axis motion platform; the upper computer system includes a coating control module and a motion control module; the lower computer system also includes a nozzle constant temperature control device and a vacuum stirring defoaming device, and the upper computer system also includes a defoaming control module; coating The overlay control module is respectively connected to the piezoelectric phosphor nozzle and the nozzle constant temperature control device, the defoaming control module is connected to the vacuum stirring and defoaming device, the motion control module is connected to the xyz axis motion platform, and the piezoelectric phosphor nozzle is installed on the xyz axis motion platform; through The coating control module and the motion control module control the piezoelectric phosphor spray head to coat the phosphor layer on the LED chip based on the 3D printing principle.

Further preferably, the piezoelectric phosphor nozzle uses piezoelectric ceramics, and the phosphor glue inside the nozzle is extruded out of the nozzle through deformation of the piezoelectric ceramic for spraying phosphor glue.

Further preferably, the nozzle constant temperature control device includes a heating wire and a thermistor, and the heating wire and the thermistor are installed inside or outside the piezoelectric phosphor nozzle for constant temperature of the piezoelectric phosphor nozzle. control.

Further preferably, the vacuum stirring and defoaming device includes: a phosphor glue container for storing the phosphor glue to be coated; an electric stirring rod, and the electric stirring rod extends into the phosphor glue container from the opening of the phosphor glue container Among them, it is used to stir the phosphor glue; the air valve, the air valve is installed on the opening of the phosphor glue container, and is used to extract the air in the phosphor glue container; through the air valve, the phosphor glue to be coated The air inside the container is pumped out to form a vacuum environment. In the vacuum environment, the electric stirring rod is continuously stirred to stir the bubbles of the phosphor glue in the device from the bottom of the device to the surface of the phosphor glue and finally eliminate them.

Further preferably, the xyz-axis motion platform uses servo motors and linear motors to control the movement of the piezoelectric phosphor nozzle in the xyz-axis direction.

Further preferably, the coating control module is used to control the size of phosphor droplets, the spraying quantity and the constant temperature control device for controlling the piezoelectric phosphor nozzle in the coating process of the piezoelectric phosphor nozzle to control the heating constant temperature of the piezoelectric phosphor nozzle, thereby reducing and stabilizing The viscosity of the fluorescent powder glue inside the nozzle; the motion control module is used to control the xyz axis motion platform to move the piezoelectric phosphor nozzle in the xyz direction; the defoaming control module is used to control the vacuum stirring and defoaming device for rigid The phosphor powder glue that has been mixed is subjected to a defoaming process.

A coating method using the above-mentioned LED phosphor coating system based on the 3D printing principle, wherein the coating control module controls the size and quantity of phosphor glue droplets sprayed by the piezoelectric phosphor nozzle each time; the motion control module passes Control the movement of the xyz-axis motion platform to control the coating position of the phosphor glue droplets sprayed by the piezoelectric phosphor nozzle each time, specifically including the following steps:

4.1 Set the position and size of the LED chip to be coated, the shape and thickness information of the phosphor layer in the host computer system, and then calculate the control of the size and quantity of the phosphor glue droplets sprayed by the piezoelectric phosphor nozzle each time Parameters and control parameters of the phosphor layer 3D printing spraying path of the piezoelectric phosphor nozzle;

4.2 The defoaming control module controls the vacuum stirring and defoaming device to eliminate the bubbles inside the fluorescent powder glue that has just been mixed in the phosphor glue container. At the same time, the coating control module heats the piezoelectric phosphor nozzle to work through the nozzle constant temperature control device. temperature;

4.3 After step 4.2 is completed, the motion control module moves the piezoelectric phosphor nozzle to the top of the LED chip to be coated by controlling the xyz axis motion platform;

4.4 After step 4.3 is completed, using the control parameters calculated in step 4.1, the coating control module and motion control module control the piezoelectric phosphor nozzle to coat the phosphor layer on the LED chip based on the 3D printing principle, specifically The motion control module controls the movement of the xyz-axis motion platform according to the control parameters of the 3D printing spraying path. At the same time, the coating control module controls the piezoelectric phosphor nozzle to print the required fluorescent light on the LED chip according to the control parameters of the size and quantity of phosphor glue droplets. Powder layer;

4.5 Judging whether the next LED chip needs to be coated, if so, go to step 4.3; if finished, then end.

On the basis of the traditional dispensing method and spraying method, the present invention adds a vacuum stirring and defoaming device to simplify the existing coating process and effectively remove the tiny air bubbles contained in the mixed phosphor powder and glue; The constant temperature control device of the nozzle is used for constant temperature control of the piezoelectric phosphor nozzle to reduce and stabilize the viscosity of the fluorescent powder in the piezoelectric phosphor nozzle, and adopts the piezoelectric coating nozzle control based on the principle of 3D printing The size and quantity of phosphor glue droplets sprayed each time, using a high-precision motion xyz axis motion platform to control the coating position of phosphor glue droplets sprayed each time, to achieve precise control of high-power white LED chips or chip molds The phosphor powder coating process of the group, so as to meet the conformal coating requirements of the thickness and shape of the phosphor layer in the high-power white LED chip module.

Compared with the prior art, the present invention has the following advantages and beneficial effects: the present invention adopts the phosphor coating method based on the 3D printing principle, uses the piezoelectric phosphor nozzle as the phosphor print head, and prints out The required phosphor coating can be applied to the phosphor coating and packaging process of high-power white LED or LED chip modules, and can also be applied to wafer-level chip coating, which can precisely control the coating of various viscosities The amount of glue applied, the thickness of the coating and the shape of the layer greatly improve the coating accuracy of the phosphor coating and ensure the consistency of the coating thickness.

Description of drawings

Fig. 1 is a block diagram of an LED phosphor coating system based on the principle of 3D printing provided by the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

An LED phosphor coating system based on the principle of 3D printing in this example is shown in FIG. 1 , including an upper computer system 11 and a lower computer system 10 . The lower computer system includes a piezoelectric phosphor nozzle 12 and an xyz axis motion platform 14; the upper computer system includes a coating control module 16 and a motion control module 17; the lower computer system also includes a nozzle constant temperature control device 13 and a vacuum stirring and defoaming device 15. The host computer system also includes a defoaming control module 18; the coating control module is respectively connected to the piezoelectric phosphor nozzle and the constant temperature control device of the nozzle, the defoaming control module is connected to the vacuum stirring and defoaming device, and the motion control module is connected to the xyz axis motion platform. The piezoelectric phosphor nozzle is installed on the xyz axis motion platform; the piezoelectric phosphor nozzle is controlled by the coating control module and the motion control module based on the 3D printing principle to coat the phosphor layer on the LED chip

Preferably, the piezoelectric phosphor nozzle 12 uses piezoelectric ceramics, and the phosphor glue inside the nozzle is extruded out of the nozzle through the deformation of the piezoelectric ceramics for spraying phosphor glue; the nozzle constant temperature control device 13 includes A heating wire and a thermistor, the heating wire and a thermistor are installed inside or outside the piezoelectric phosphor nozzle 12 for constant temperature control of the piezoelectric phosphor nozzle 12; the vacuum stirring and defoaming device 15 includes a phosphor glue container for storing the phosphor glue to be coated; an electric stirring rod, which extends into the phosphor glue container from the opening of the phosphor glue container for stirring the phosphor glue; an air valve , the air valve is installed in the opening of the phosphor glue container, and is used to extract the air in the phosphor glue container; through the air valve, the air inside the phosphor glue container to be coated with phosphor glue is drawn out to form a vacuum environment. Under the vacuum environment, the electric stirring rod is continuously stirred, and the bubbles of the phosphor glue in the device are stirred from the bottom of the device to the surface of the phosphor glue and finally eliminated; the xyz axis motion platform 14 uses servo motors and linear motors to control the piezoelectric The phosphor spray head 12 moves in the xyz axis direction.

The coating control module 16 is used to control the size of the phosphor droplet, the spraying quantity, and the constant temperature control device 13 to control the heating and constant temperature of the piezoelectric phosphor nozzle 12 during the coating process of the piezoelectric phosphor nozzle 12, thereby reducing and stabilizing The viscosity of the fluorescent powder glue inside the nozzle; the motion control module 17 is used to control the xyz axis motion platform 14 to move the piezoelectric phosphor nozzle 12 in the xyz direction; the defoaming control module 18 is used to control the vacuum stirring and removing The bubble device 15 performs a defoaming process on the phosphor glue that has just been mixed.

The LED phosphor coating method based on the 3D printing principle of this example includes the following steps and contents:

Step (1) In the coating control module 16, set the position and size of the LED chip to be coated, the shape and thickness of the ideal phosphor layer and other information, and then calculate the phosphor powder sprayed out of the piezoelectric phosphor nozzle each time. Coating control parameters such as the control parameters of the size of the glue droplet and the ideal phosphor layer 3D printing spray path control parameters of the piezoelectric phosphor nozzle, the algorithm is as follows:

αV _t = NV _r

Among them, V _t is the amount of phosphor glue theoretically required by the conformal coating method for the LED chip to be coated, which can be calculated from the length, width, height and thickness of the phosphor layer of the LED chip to be coated. V _r is the glue amount of the fluorescent powder micro-droplets that need to be ejected each time actually by the piezoelectric phosphor nozzle 12. It needs to obtain the actual optimum micro-droplet glue amount through experiments according to different LED chip sizes and phosphor layer thicknesses ( For example: for a high-power LED chip with a side length of 1.5 mm, the measured optimal amount of micro-droplet glue is 16 picoliters; for a high-power LED chip with a side length of 1.0 mm, the measured optimal amount of micro-droplet glue is 13 picoliters; for a high-power LED chip with a side length of 0.83 mm, the measured optimum micro-droplet volume is 10 picoliters), or the minimum micro-droplet volume that can be sprayed directly using a piezoelectric phosphor nozzle (8 picoliters); α is the conversion coefficient between the theoretical value and the actual value, and the best conversion coefficient needs to be obtained through experiments according to different viscosities of phosphor glue; N is the LED chip to be coated using the 3D printing principle. The number of droplets coated can be calculated from the known parameters V _t , V _r , α. The control voltage of the piezoelectric phosphor nozzle 12 and the position offset coordinate of the next phosphor droplet to be ejected in the 3D printing track of the current LED chip can be calculated through V _r and the viscosity of the phosphor glue;

Step (2) Use the vacuum stirring and defoaming device 13 to eliminate the bubbles inside the fluorescent powder glue that has just been mixed in the device, and at the same time, heat the piezoelectric phosphor nozzle 12 to the working temperature through the nozzle constant temperature control device 15;

Step (3) After step (2) is completed, the piezoelectric phosphor nozzle 12 is moved to the top of the LED chip to be coated through the xyz axis motion control device 14;

Step (4) After step (3) is completed, use the coating control parameters calculated in step (1) to control the piezoelectric phosphor nozzle to eject multiple or one phosphor droplet (micro The number of drops depends on the needs of the user. If you need to improve production efficiency, reduce the number of single-chip LED chips coated with phosphor droplets; if you need to improve the accuracy of phosphor coating, increase the number of single-chip LED chip coated phosphor droplets The number of drops), to complete the current LED chip-based phosphor coating work;

Step (5) judging whether the next LED chip needs to be coated, if necessary, then go to step (3); if finished, then end.

Claims (7)

1. An LED phosphor coating system based on the principle of 3D printing, which is used to complete the conformal coating process of the thickness and shape of the phosphor layer on the LED chip, including the lower computer system and the upper computer system. The lower computer system includes a press Electroluminescent powder nozzle and xyz axis motion platform; the host computer system includes a coating control module and a motion control module; it is characterized in that the lower computer system also includes a nozzle constant temperature control device and a vacuum stirring defoaming device, and the host computer system also includes a defoaming device Control module; the coating control module is respectively connected to the piezoelectric phosphor nozzle and the constant temperature control device of the nozzle, the defoaming control module is connected to the vacuum stirring and defoaming device, the motion control module is connected to the xyz axis movement platform, and the piezoelectric phosphor nozzle is installed on the xyz axis movement On the platform: the piezoelectric phosphor spray head is controlled by the coating control module and the motion control module based on the 3D printing principle to coat the phosphor layer on the LED chip. 2. The LED phosphor coating system based on the principle of 3D printing according to claim 1, wherein the piezoelectric phosphor spray head uses piezoelectric ceramics, and the phosphor powder inside the spray head is glued by deformation of the piezoelectric ceramics. Squeeze out the outside of the nozzle for spraying phosphor glue. 3. The LED phosphor coating system based on 3D printing principle according to claim 1, characterized in that, The nozzle constant temperature control device includes a heating wire and a thermistor installed inside or outside the piezoelectric phosphor nozzle for constant temperature control of the piezoelectric phosphor nozzle. 4. The LED phosphor coating system based on the principle of 3D printing according to claim 1, wherein the vacuum stirring and defoaming device comprises: a phosphor glue container for storing phosphor glue to be coated; An electric stirring rod, the electric stirring rod extends from the opening of the phosphor glue container into the phosphor glue container for stirring the phosphor glue; an air valve, the air valve is installed at the opening of the phosphor glue container for extracting the phosphor The air in the glue container; through the air valve, the air inside the phosphor glue container to be coated with phosphor glue is drawn out to form a vacuum environment. Stir from the bottom of the unit until the surface of the phosphor glue is finally eliminated. 5. The LED phosphor coating system based on 3D printing principle according to claim 1, characterized in that, the xyz axis motion platform adopts servo motor and linear motor to control the piezoelectric phosphor nozzle in the xyz axis direction move up. 6. The LED phosphor coating system based on 3D printing principle according to claim 1, characterized in that, The coating control module is used to control the size of the phosphor droplet, the spraying quantity and the constant temperature control device of the piezoelectric phosphor nozzle during the coating process of the piezoelectric phosphor nozzle, so as to reduce and stabilize the phosphor inside the nozzle. the viscosity of the glue; The motion control module is used to control the xyz axis motion platform to move the piezoelectric phosphor nozzle in the xyz axis; The defoaming control module is used to control the vacuum stirring and defoaming device to perform a defoaming process on the newly mixed phosphor glue. 7. A coating method using the LED phosphor coating system based on the 3D printing principle of claim 1, wherein the coating control module controls the phosphor glue droplets ejected by the piezoelectric phosphor nozzle each time The size and quantity; the motion control module controls the coating position of the phosphor glue droplets sprayed by the piezoelectric phosphor nozzle each time by controlling the movement of the xyz axis motion platform, which specifically includes the following steps: 4.1 Set the position and size of the LED chip to be coated, the shape and thickness information of the phosphor layer in the host computer system, and then calculate the control of the size and quantity of the phosphor glue droplets sprayed by the piezoelectric phosphor nozzle each time Parameters and control parameters of the phosphor layer 3D printing spraying path of the piezoelectric phosphor nozzle; 4.2 The defoaming control module controls the vacuum stirring and defoaming device to eliminate the bubbles inside the fluorescent powder glue that has just been mixed in the phosphor glue container. At the same time, the coating control module heats the piezoelectric phosphor nozzle to work through the nozzle constant temperature control device. temperature; 4.3 After step 4.2 is completed, the motion control module moves the piezoelectric phosphor nozzle to the top of the LED chip to be coated by controlling the xyz axis motion platform; 4.4 After step 4.3 is completed, using the control parameters calculated in step 4.1, the coating control module and motion control module control the piezoelectric phosphor nozzle to coat the phosphor layer on the LED chip based on the 3D printing principle, specifically The motion control module controls the movement of the xyz-axis motion platform according to the control parameters of the 3D printing spraying path. At the same time, the coating control module controls the piezoelectric phosphor nozzle to print the required fluorescent light on the LED chip according to the control parameters of the size and quantity of phosphor glue droplets. Powder layer; 4.5 Judging whether the next LED chip needs to be coated, if so, go to step 4.3; if finished, then end.