LED inorganic packaging structure and method

Abstract

An inorganic LED packaging structure and method includes a conductive doped silicon wafer, a vertical chip, and a ceramic substrate. Metal brackets are provided around the top of the ceramic substrate, the bottom of the metal brackets being welded to the ceramic substrate. The bottom electrode of the vertical chip is welded to the top of the ceramic substrate and electrically connected to a first electrode at the bottom of the ceramic substrate via a first copper pillar. The top electrode of the vertical chip is electrically connected to the doped silicon wafer. The four edges of the doped silicon wafer are welded to the metal brackets on each side. The bottom of the metal bracket is welded to the ceramic substrate and electrically connected to a second electrode at the bottom of the ceramic substrate via a second copper pillar. By utilizing the electrode properties of the vertical chip and using the conductive doped silicon wafer as an electrical connection component, the top electrode of the vertical chip can be guided to the electrode at the bottom of the ceramic substrate for electrical connection, eliminating the need for wirebonds. This allows for a thinner overall packaging structure and improves product reliability.

Description

Technical Field

[0001] The present invention relates to the field of LEDs, and in particular to an inorganic LED packaging structure and method. Background Art

[0002] Inorganic packaging can be used for ultraviolet LED products, such as the fully inorganic LED lamp and its packaging method, which is published in Chinese Patent Publication No. CN109473512B. The lamp comprises a base and an LED chip. A bowl is provided on the base, and the LED chip is located in the bowl and electrically connected to the base. A glass cover is provided on the bowl to seal the LED chip. Solder is coated on the surface of the bowl, and the glass cover and the bowl are bonded by solder. The above-mentioned packaging uses a positive chip. After the chip is fixed, gold wire needs to be punched for electrical connection. Gold wire is easy to break and has low reliability. In addition, the wire bonding requires a certain amount of space, which results in a thicker overall thickness of the LED lamp bead product. If a flip chip is used for packaging, the bottom of the flip chip is not completely bonded to the substrate, and there is a gap in the flip chip chip, which results in insufficient heat dissipation from the flip chip. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an inorganic LED packaging structure and method, wherein the overall thickness of the packaging structure is thinner and the heat dissipation performance is better.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: an LED inorganic packaging structure, comprising a conductive doped silicon wafer, a vertical chip and a ceramic substrate; metal brackets are provided around the top of the ceramic substrate, and the bottom of the metal bracket is connected to the ceramic substrate by welding. The bottom electrode of the vertical chip is welded to the top of the ceramic substrate and electrically connected to the first electrode at the bottom of the ceramic substrate through a first copper column. The top electrode of the vertical chip is electrically connected to the doped silicon wafer, and the four edges of the doped silicon wafer are respectively welded to the metal brackets around them. The bottom of the metal bracket is welded to the ceramic substrate and electrically connected to the second electrode at the bottom of the ceramic substrate through a second copper column. The present invention is suitable for inorganic packaging of large-size vertical UVLED chips. By utilizing the electrode characteristics of the vertical chip and using a conductive doped silicon wafer as an electrical connection component, the top electrode of the vertical chip can be guided to the electrode at the bottom of the ceramic substrate to achieve electrical connection without the need for welding wires. The overall thickness of the packaging structure can be made thinner, and the product reliability is higher. In addition, the bottom of the vertical chip is completely in contact with the ceramic substrate, and its heat can be transferred to the ceramic substrate and copper pillars for heat dissipation to the maximum extent. The doped silicon wafer on the top can also disperse part of the heat, and the overall heat dissipation effect is better.

[0005] As an improvement, a vapor-deposited gold pad layer is provided in the middle of the bottom of the doped silicon wafer, the top electrode of the vertical chip is welded to the vapor-deposited gold pad layer, solder is provided around the bottom of the doped silicon wafer, and the four sides of the doped silicon wafer are welded to the metal bracket through the solder.

[0006] As an improvement, a groove is provided on the metal bracket, the edge of the doped silicon wafer is placed in the groove, and solder paste is provided in the groove to connect the doped silicon wafer and the metal bracket.

[0007] As an improvement, a V-shaped groove is provided on the surface of the metal bracket for supporting the doped silicon wafer.

[0008] The LED inorganic packaging method of the present invention comprises the following steps:

[0009] (1) Take a conductive doped silicon wafer, form a pad layer in the middle of the bottom of the doped silicon wafer, brush solder around the doped silicon wafer, and heat it to solidify it;

[0010] (2) Fixing the vertical chip on the doped silicon wafer, and electrically connecting the top electrode of the vertical chip to the pad layer;

[0011] (3) Fixing the doped silicon wafer with the vertical chip fixed on the ceramic substrate, pressing the four sides of the doped silicon wafer on the metal bracket on the top of the ceramic substrate, electrically connecting the bottom electrode of the vertical chip to the first pad on the ceramic substrate, and electrically connecting the first pad to the first electrode on the bottom of the ceramic substrate through the first copper column;

[0012] (4) Apply fluid solder paste to the joint between the metal bracket and the doped silicon wafer;

[0013] (5) Through reflow soldering, the solder paste melts with the solder on the doped silicon wafer, so that the doped silicon wafer and the metal bracket are tightly electrically bonded. At the same time, the metal bracket is electrically connected to the second electrode at the bottom of the ceramic substrate through the second copper column.

[0014] As an improvement, the doped silicon wafer is formed by cutting.

[0015] As an improvement, the pad layer is formed by evaporating gold.

[0016] As an improvement, the vertical chip is fixed on the doped silicon wafer by eutectic or solder.

[0017] As an improvement, the bottom electrode of the vertical chip is electrically connected to the first pad of the ceramic substrate through eutectic or solder.

[0018] The beneficial effects brought about by the present invention compared with the prior art are:

[0019] By utilizing the electrode characteristics of the vertical chip and using a conductive doped silicon wafer as an electrical connection component, the top electrode of the vertical chip can be guided to the electrode at the bottom of the ceramic substrate to achieve electrical connection without the need for bonding wires. The overall thickness of the packaging structure can be made thinner, and the product reliability is higher. In addition, the bottom of the vertical chip is completely in contact with the ceramic substrate, and its heat can be transferred to the ceramic substrate and copper pillars for heat dissipation to the maximum extent. The doped silicon wafer on the top can also disperse some of the heat, resulting in better overall heat dissipation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the packaging structure of the present invention.

[0021] Figure 2 It is a schematic diagram of the packaging process of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] like Figure 1Figure 1 shows an inorganic LED packaging structure comprising a conductive doped silicon wafer 2, a vertical chip 3, and a ceramic substrate 1. The doped silicon wafer 2 used for packaging is square and has both light-transmitting and conductive properties. In this embodiment, the doped silicon wafer 2 is cut from a single large silicon wafer 12. A vapor-deposited gold pad layer 13 and a solder brush 9 are pre-placed at corresponding locations on the large silicon wafer 12 before being cut into individual doped silicon wafers 2 for packaging. This improves production efficiency. The top of the ceramic substrate 1 is surrounded by metal brackets 4, which are connected to form a rectangular frame. The bottom of the metal bracket 4 is connected to the ceramic substrate 1 by welding. The metal bracket 4 is L-shaped and includes a horizontal portion and a vertical portion. An arc-shaped groove 11 is provided at the hinge between the vertical portion and the horizontal portion. The horizontal portion is used to support the doped silicon wafer 2. The edge of the doped silicon wafer 2 is placed in the arc-shaped groove 11 and has a certain gap with the inner side of the vertical portion. The gap is connected to the arc-shaped groove 11. The gap and the arc-shaped groove 11 can be filled with solder paste 10, thereby welding the doped silicon wafer 2 to the metal bracket 4. The top of the ceramic substrate 1 is provided with a first and a second pad in the crystal bonding area. The bottom of the ceramic substrate 1 is provided with a first electrode 6 and a second electrode 7 at corresponding positions. The first pad is electrically connected to the first electrode 6 via a first copper column 5, and the second pad is electrically connected to the second electrode 7 via a second copper column 8. The bottom electrode of the vertical chip 3 is soldered to the first pad on the top of the ceramic substrate 1 and electrically connected to the first electrode 6 on the bottom of the ceramic substrate 1 via a first copper pillar 5. The top electrode of the vertical chip 3 is electrically connected to the pad layer of the doped silicon wafer 2 and to the metal support 4 via the doped silicon wafer 2. The bottom of the metal support 4 is soldered to the ceramic substrate 1 and electrically connected to the second electrode 7 on the bottom of the ceramic substrate 1 via a second copper pillar 8. The metal support 4 has a V-shaped groove on its surface for supporting the doped silicon wafer 2. Molten solder can flow into the V-shaped groove, increasing the contact area between the metal support 4 and the doped silicon wafer 2 and improving the reliability of the bonding between the doped silicon wafer 2 and the metal support 4.

[0024] like Figure 2 As shown, the LED inorganic packaging method of the present invention includes the following steps:

[0025] (1) Take a large conductive silicon wafer, evaporate a gold pad layer 13 and a solder brush 9 at the corresponding position of the large silicon wafer, and heat the solder to solidify it;

[0026] (2) Cutting the large silicon wafer into a separate doped silicon wafer 2, the evaporated gold pad layer is located in the middle of the bottom of the doped silicon wafer 2, and the solder is located around the doped silicon wafer 2;

[0027] (3) Fixing the vertical chip 3 on the doped silicon wafer 2 by eutectic or soldering, and electrically connecting the top electrode of the vertical chip 3 to the pad layer;

[0028] (4) The doped silicon wafer 2 with the vertical chip 3 fixed thereon is fixed on the ceramic substrate 1, and the four sides of the doped silicon wafer 2 are pressed on the metal bracket 4 on the top of the ceramic substrate 1. The bottom electrode of the vertical chip 3 is electrically connected to the first pad of the ceramic substrate 1 through the eutectic or solder, and the first pad is electrically connected to the first electrode 6 at the bottom of the ceramic substrate 1 through the first copper pillar 5;

[0029] (5) Apply fluid solder paste to the connection between the metal bracket 4 and the doped silicon wafer 2;

[0030] (6) Through reflow soldering, the solder paste and the solder on the doped silicon wafer 2 melt, so that the doped silicon wafer 2 and the metal bracket 4 are tightly electrically bonded. At the same time, the metal bracket 4 is electrically connected to the second electrode 7 at the bottom of the ceramic substrate 1 through the second copper column 8.

[0031] (7) Spectroscopy and packaging.

[0032] The present invention is suitable for inorganic packaging of large-size vertical UVLED chips. By utilizing the electrode characteristics of the vertical chip 3 and using the conductive doped silicon wafer 2 as an electrical connection component, the top electrode of the vertical chip 3 can be guided to the electrode at the bottom of the ceramic substrate 1 to achieve electrical connection without the need for welding wires. The overall thickness of the packaging structure can be made thinner and the product reliability is higher. In addition, the bottom of the vertical chip 3 is completely in contact with the ceramic substrate 1, and its heat can be transferred to the ceramic substrate 1 and copper pillars for heat dissipation to the maximum extent. The doped silicon wafer 2 on the top can also disperse part of the heat, and the overall heat dissipation effect is better.

Claims

1. An inorganic LED packaging structure, characterized in that: It includes a conductive doped silicon wafer, a vertical chip and a ceramic substrate; metal brackets are provided around the top of the ceramic substrate, the bottom of the metal bracket is connected to the ceramic substrate by welding, the bottom electrode of the vertical chip is welded to the top of the ceramic substrate and electrically connected to the first electrode at the bottom of the ceramic substrate through a first copper column, the top electrode of the vertical chip is electrically connected to the pad layer of the doped silicon wafer, the four edges of the doped silicon wafer are respectively welded to the metal brackets around them, the bottom of the metal bracket is welded to the ceramic substrate and electrically connected to the second electrode at the bottom of the ceramic substrate through a second copper column.

2. The LED inorganic packaging structure according to claim 1, characterized in that: A vapor-deposited gold pad layer is provided in the middle of the bottom of the doped silicon wafer, the top electrode of the vertical chip is welded to the vapor-deposited gold pad layer, solder is provided around the bottom of the doped silicon wafer, and the four sides of the doped silicon wafer are welded to the metal bracket through the solder.

3. The LED inorganic packaging structure according to claim 1, characterized in that: The metal support is provided with a groove, the edge of the doped silicon wafer is placed in the groove, and solder paste connecting the doped silicon wafer and the metal support is provided in the groove.

4. The LED inorganic packaging structure according to claim 1, characterized in that: The metal bracket is used to support the doped silicon wafer and is provided with a V-shaped groove on its surface.

5. A method for inorganic LED packaging, characterized in that: The following steps are involved: (1) Take a conductive doped silicon wafer, form a pad layer in the middle of the bottom of the doped silicon wafer, brush solder around the doped silicon wafer, and heat it to solidify it; (2) Fixing the vertical chip on the doped silicon wafer, and electrically connecting the top electrode of the vertical chip to the pad layer; (3) Fixing the doped silicon wafer with the vertical chip fixed on the ceramic substrate, pressing the four sides of the doped silicon wafer on the metal bracket on the top of the ceramic substrate, electrically connecting the bottom electrode of the vertical chip to the first pad on the ceramic substrate, and electrically connecting the first pad to the first electrode on the bottom of the ceramic substrate through the first copper column; (4) Apply fluid solder paste to the joint between the metal bracket and the doped silicon wafer; (5) Through reflow soldering, the solder paste melts with the solder on the doped silicon wafer, so that the doped silicon wafer and the metal bracket are tightly electrically bonded. At the same time, the metal bracket is electrically connected to the second electrode at the bottom of the ceramic substrate through the second copper column.

6. The LED inorganic packaging method according to claim 5, characterized in that: The doped silicon wafer is formed by cutting.

7. The LED inorganic packaging method according to claim 5, characterized in that: The pad layer is formed by evaporating gold.

8. The LED inorganic packaging method according to claim 5, characterized in that: The vertical chip is fixed on the doped silicon wafer by eutectic or solder.

9. The LED inorganic packaging method according to claim 5, characterized in that: The bottom electrode of the vertical chip is electrically connected to the first pad of the ceramic substrate through eutectic or solder.

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