Method for coating semiconductor device using droplet deposition
View Patent ↗Methods and systems for coating of semiconductor devices using droplets of wavelength conversion or phosphor particles in a liquid medium. A plurality of nozzles delivers a controlled amount of the matrix material to the surface of the semiconductor device, with each of said nozzles having an opening for the matrix material to pass. The opening has a diameter wherein the diameter of the phosphor particles is less than or approximately equal to one half the diameter of the opening. The phosphor particles are also substantially spherical or rounded. The nozzles are typically arranged on a print head that utilizes jet printing techniques to cover the semiconductor device with a layer of the matrix material. The methods and systems are particularly applicable to covering LEDs with a layer of phosphor materials.
1. A method for depositing a uniform layer of phosphor material on a semiconductor device comprising;
providing a semiconductor device;
providing a print head with a plurality of nozzles, each of said nozzles capable of depositing a droplet of matrix material on said semiconductor device, said matrix material comprising a phosphor in a liquid medium;
depositing a layer of matrix material droplets from said nozzles on said semiconductor device with a uniform pitch between adjacent droplets;
allowing said droplets to spread and flow together under gravity or surface tension to form a layer of matrix material on said semiconductor device; and
allowing said liquid medium to dry leaving a substantially uniform layer of phosphor particles on the semiconductor device.
2. The method of claim 1 , wherein said layer of phosphor particles has a thickness, said thickness being increased by depositing one or more additional droplet layers.
3. The method of claim 1 , wherein said liquid medium is a volatile liquid medium.
4. The method of claim 1 , wherein said semiconductor device is a light emitting diode (LED).
5. The method of claim 1 , wherein said phosphor particles are substantially rounded.
6. The method of claim 1 , wherein said nozzle comprises a nozzle opening and wherein said phosphor particles have a diameter that is less than or approximately equal to one half the diameter of said nozzle opening.
7. A method for depositing a layer of phosphor material on an LED, comprising:
providing an LED;
providing a reservoir of matrix material comprising substantially spherical wavelength conversion particles in a liquid medium;
forming said matrix material into droplets; and
depositing said droplets on said LED, said droplets forming a conformal layer of phosphor particles on said LED such that emission from said LED is substantially uniform.
8. The method of claim 7 , wherein said wavelength conversion particles comprise phosphor particles.
9. The method of claim 7 , wherein said matrix material is formed into droplets by a plurality of nozzles.
10. The method of claim 9 , wherein said nozzle has an opening, and wherein said wavelength conversion particles have a diameter that is less than or approximately equal to one half the diameter of said nozzle opening.
11. The method of claim 7 , wherein said liquid medium comprises a volatile, non volatile or curable liquid.