Aluminum nitride ceramic substrate and light source

Abstract

The utility model discloses an aluminium nitride ceramic substrate and light source relates to LED technical field, including aluminium nitride base layer, circuit layer, reflection coating and bonding pad plating, circuit layer and reflection coating are fixed on the top surface of aluminium nitride base layer, reflection coating is arranged around circuit layer, the top surface of circuit layer is level with the top surface of reflection coating, bonding pad plating has bonding pad plating, the bonding pad plating has bonding pad plating. The bottom surface of the bonding pad plating layer is fixedly arranged on the top surface of the circuit layer, and the top surface of the bonding pad plating layer is used for eutectic soldering with a wafer electrode; according to the utility model, the welding quality can be effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of LED technology, and in particular to an aluminum nitride ceramic substrate and a light source. Background Technology

[0002] The advantages of flip-chip LED packaging compared to conventional LED packaging are mainly reflected in higher heat dissipation efficiency, higher current density, lower signal transmission delay and loss, and higher density integration through miniaturization.

[0003] Currently, the mainstream substrate materials for flip-chip LED packaging include ceramic substrates and aluminum substrates. Compared with metal substrates, ceramic substrates have the following advantages: high thermal conductivity, fast heat dissipation, and low light decay; better insulation, high voltage resistance and electromagnetic interference resistance, and easier to pass UL / GS / EMC certifications; thermal expansion coefficient close to that of the chip crystal, making it more reliable and less prone to lamp failure; and easy to match with non-isolated power supplies, improving power efficiency and reliability.

[0004] Flip-chip substrates are divided into two main categories: flip-chip ceramic substrates and flip-chip aluminum substrates. Flip-chip aluminum substrates require the use of low thermal conductivity insulating layers for circuit design, which is not conducive to heat conduction and heat dissipation and has high thermal resistance. Flip-chip ceramic substrates do not require this, so flip-chip ceramic substrates have higher reliability.

[0005] Currently, the main ceramic substrate materials on the market are alumina and aluminum nitride. Aluminum nitride has a thermal conductivity of over 170 W / (m·K), while the thermal conductivity of alumina is typically around 15–35 W / (m·K). The thermal conductivity of aluminum nitride is more than five times that of alumina. To achieve higher luminous power density in light sources, aluminum nitride ceramic substrates are often chosen in combination with flip-chip technology.

[0006] Aluminum nitride ceramic substrates have low reflectivity, typically only 85%, resulting in low light extraction efficiency. Current methods involve covering the aluminum nitride surface with white ink. However, to improve the light power density of the light source, Au-Sn eutectic bonding of flip chips to aluminum nitride ceramic substrates is often required to achieve higher chip current density. The Au-Sn eutectic bonding process is easily contaminated and interfered with by white ink, leading to numerous bonding voids, poor bonding quality, and ultimately, deterioration of product quality. Utility Model Content

[0007] The purpose of this invention is to provide an aluminum nitride ceramic substrate and a light source to solve the problems existing in the prior art and effectively improve the welding quality.

[0008] To achieve the above objectives, this utility model provides the following solution:

[0009] This utility model provides an aluminum nitride ceramic substrate, including an aluminum nitride base layer, a circuit layer, a reflective coating, and a pad plating layer. The circuit layer and the reflective coating are both fixed on the top surface of the aluminum nitride base layer. The reflective coating is disposed around the circuit layer, and the top surface of the circuit layer is flush with the top surface of the reflective coating. The bottom surface of the pad plating layer is fixed on the top surface of the circuit layer, and the top surface of the pad plating layer is used for eutectic bonding with the wafer electrode.

[0010] Preferably, the reflective coating is a white coating.

[0011] Preferably, the reflective coating is prepared by uniformly mixing silicone and titanium dioxide and then curing it.

[0012] Preferably, the top surface of the reflective coating is a ground and polished surface.

[0013] Preferably, the pad plating is an Au-Sn plating.

[0014] Preferably, the pad plating is a Ni-Au plating.

[0015] Preferably, the circuit layer is a copper circuit layer.

[0016] This invention also provides a light source, including a wafer and an aluminum nitride ceramic substrate as described above, wherein the wafer has wafer electrodes.

[0017] The present invention achieves the following technical advantages over the prior art:

[0018] The aluminum nitride ceramic substrate and light source provided by this utility model have a top surface of the circuit layer flush with the top surface of the reflective coating, and a bottom surface of the pad plating layer fixedly disposed on the top surface of the circuit layer. The top surface of the pad plating layer is used for eutectic bonding with the wafer electrode. This ensures that the top surface of the pad plating layer is above the top surface of the reflective coating, making the pad plating layer higher than the reflective coating. This avoids the wafer from resting on the reflective coating during eutectic bonding due to the reflective coating being higher than the pad plating layer, thus preventing the reflective coating from causing contamination and interference to the eutectic bonding process. It can reduce bonding voids in the subsequent eutectic bonding process, making it more stable and controllable, improving bonding quality, increasing light extraction efficiency, and improving product quality. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1A schematic diagram of the aluminum nitride ceramic substrate and the light source provided by this utility model;

[0021] In the diagram: 1-aluminum nitride base layer, 2-circuit layer, 3-reflective coating, 4-pad plating, 5-wafer, 6-wafer electrode, 7-polished surface. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] The purpose of this invention is to provide an aluminum nitride ceramic substrate and a light source to solve the problems existing in the prior art and effectively improve the welding quality.

[0024] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] like Figure 1 As shown, this embodiment provides an aluminum nitride ceramic substrate, including an aluminum nitride base layer 1, a circuit layer 2, a reflective coating 3, and a pad plating layer 4. The circuit layer 2 and the reflective coating 3 are both fixedly disposed on the top surface of the aluminum nitride base layer 1. The reflective coating 3 is disposed around the circuit layer 2. The top surface of the circuit layer 2 is flush with the top surface of the reflective coating 3. The bottom surface of the pad plating layer 4 is fixedly disposed on the top surface of the circuit layer 2. The top surface of the pad plating layer 4 is used for eutectic bonding with the wafer electrode 6.

[0027] The aluminum nitride ceramic substrate provided in this embodiment has the top surface of the circuit layer 2 flush with the top surface of the reflective coating 3, and the bottom surface of the pad plating layer 4 is fixedly disposed on the top surface of the circuit layer 2. The top surface of the pad plating layer 4 is used for eutectic bonding with the wafer electrode 6. This ensures that the top surface of the pad plating layer 4 is located above the top surface of the reflective coating 3, making the pad plating layer 4 higher than the reflective coating 3. This avoids the wafer 5 from resting on the reflective coating 3 during eutectic bonding due to the reflective coating 3 being higher than the pad plating layer 4. It also avoids the reflective coating 3 from causing contamination and interference to the eutectic bonding process, thereby reducing bonding voids in the subsequent eutectic bonding process, making it more stable and controllable, improving bonding quality, increasing light extraction efficiency, and improving product quality.

[0028] As a preferred embodiment of this invention, the reflective coating 3 is a white coating that can improve the reflectivity of the aluminum nitride ceramic substrate from 85% to approximately 92%.

[0029] As a preferred embodiment of this invention, the reflective coating 3 is prepared by uniformly mixing and curing silicone and titanium dioxide. It possesses high reliability, excellent heat resistance, and is suitable for gold-tin eutectic processes. Furthermore, it does not yellow, blacken, or crack during long-term use of the light source, thus improving the reliability of the light source. Specifically, transparent silicone and titanium dioxide are mixed in a certain proportion to form a white reflective coating. The mixing ratio can be adjusted according to the viscosity of the adhesive (the reference ratio is a titanium dioxide weight ratio greater than 50%). The white reflective coating is applied to the aluminum nitride substrate 1 on which the circuit layer 2 has been installed. During application, it is important to ensure the amount of white reflective coating used is sufficient to ensure that the overall thickness after baking is higher than the thickness of the circuit layer 2. The transparent silicone can be a commonly used high-temperature resistant A / B two-component methyl silicone for LEDs. Mix component B evenly according to the adhesive specifications (e.g., A:B = 1:1). Take the specified weight of titanium dioxide and pour it into the mixed transparent silicone (the weight of titanium dioxide accounts for 50%-80% of the total weight of titanium dioxide and silicone). After mixing, put it into a container with agate balls and place it in a vacuum centrifugal mixer to mix the silicone and titanium dioxide evenly. White reflective coating application method: Use damming adhesive (a common material for mirror aluminum COB) to make a dam around the area to be coated. The height of the dam should be higher than the circuit layer 2. Then, pour the white reflective coating evenly into the dam, controlling the amount of white reflective coating poured into the dam to be slightly higher than the damming adhesive. Place it in an oven to dry, forming a slightly convex white reflective plane that completely covers the circuit layer 2 (the auxiliary dam at the process edge can be removed by water jet cutting).

[0030] As a preferred embodiment of this example, the top surface of the reflective coating 3 is a polished surface 7. After the white reflective coating is baked and cured at high temperature, the cured reflective coating 3 is polished by a grinding machine until the top surface of the circuit layer 2 is completely exposed, and then the surface of the polished surface is polished and cleaned.

[0031] As a preferred embodiment of this invention, the pad plating layer 4 is an Au-Sn plating layer, and the plating thickness can be adjusted accordingly based on the plating thickness of the metal layer on the back of the flip chip 5.

[0032] As a preferred embodiment of this invention, the pad plating layer 4 is a Ni-Au plating layer, and the plating thickness can be adjusted accordingly based on the plating thickness of the metal layer on the back of the flip chip 5.

[0033] Eutectic bonding of pad plating 4 and wafer electrode 6 is achieved through processes such as gold-tin eutectic solder / flux / ultrasonic hot pressing: gold or gold-tin electrode flip wafer 5 achieves eutectic bonding with pad plating 4 on the substrate through gold-tin solder in a high-temperature vacuum eutectic furnace; gold-tin electrode flip wafer 5 achieves eutectic bonding with pad plating 4 on the substrate through flux in a high-temperature vacuum eutectic furnace; gold-tin electrode flip wafer 5 achieves eutectic bonding with pad plating 4 on the substrate through ultrasonic hot pressing.

[0034] As a preferred embodiment of this invention, the circuit layer 2 is a copper circuit layer, which has good thermal conductivity and a long service life.

[0035] Example 2

[0036] This embodiment provides a light source, including a wafer 5 and an aluminum nitride ceramic substrate as described in Embodiment 1. The wafer 5 has wafer electrodes 6.

[0037] The light source provided in this embodiment has the top surface of the circuit layer 2 flush with the top surface of the reflective coating 3, and the bottom surface of the pad plating layer 4 is fixedly disposed on the top surface of the circuit layer 2. The top surface of the pad plating layer 4 is used for eutectic bonding with the wafer electrode 6. This ensures that the top surface of the pad plating layer 4 is located above the top surface of the reflective coating 3, making the pad plating layer 4 higher than the reflective coating 3. This avoids the wafer 5 from resting on the reflective coating 3 during eutectic bonding due to the reflective coating 3 being higher than the pad plating layer 4. It also avoids the reflective coating 3 from causing contamination and interference to the eutectic bonding process, thereby reducing bonding voids in the subsequent eutectic bonding process, making it more stable and controllable, improving bonding quality, increasing light extraction efficiency, and improving product quality.

[0038] This utility model uses specific examples to illustrate its principles and implementation methods. The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the idea of ​​this utility model. In summary, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. An aluminum nitride ceramic substrate, characterized in that: The device includes an aluminum nitride substrate, a circuit layer, a reflective coating, and a pad plating layer. The circuit layer and the reflective coating are both fixed on the top surface of the aluminum nitride substrate. The reflective coating surrounds the circuit layer, and the top surface of the circuit layer is flush with the top surface of the reflective coating. The bottom surface of the pad plating layer is fixed on the top surface of the circuit layer, and the top surface of the pad plating layer is used for eutectic bonding with the wafer electrode.

2. The aluminum nitride ceramic substrate according to claim 1, characterized in that: The reflective coating is white.

3. The aluminum nitride ceramic substrate according to claim 2, characterized in that: The reflective coating is prepared by uniformly mixing silicone and titanium dioxide and then curing it.

4. The aluminum nitride ceramic substrate according to claim 1, characterized in that: The top surface of the reflective coating is a polished surface.

5. The aluminum nitride ceramic substrate according to claim 1, characterized in that: The pad plating is an Au-Sn plating.

6. The aluminum nitride ceramic substrate according to claim 1, characterized in that: The pad plating is a Ni-Au plating.

7. The aluminum nitride ceramic substrate according to claim 1, characterized in that: The circuit layer is a copper circuit layer.

8. A light source, characterized in that: It includes a wafer and an aluminum nitride ceramic substrate as described in any one of claims 1-7, wherein the wafer has wafer electrodes.

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