CN103887396A - A light-emitting assembly in which an LED chip is directly welded to the surface of a copper heat sink and a preparation method thereof - Google Patents

Abstract

The invention provides a light-emitting assembly in which LED chips are directly welded to the surface of a copper heat sink. The light-emitting assembly includes a copper heat sink, a ceramic substrate with an LED chip mounting hole in the middle arranged above the copper heat sink, and a ceramic substrate arranged on the ceramic substrate. The positive and negative electrodes on the edge, the LED chip arranged in the chip mounting hole, and the phosphor layer coated on the LED chip; a copper-oxygen eutectic welding layer is arranged between the copper heat sink and the ceramic substrate; the LED chip It is electrically connected with the positive and negative electrodes, and the positive and negative electrodes are connected with the power supply. The light-emitting component of the invention obviously improves the reliability, prolongs the service life, and improves the light efficiency.

Description

A light-emitting component in which an LED chip is directly welded to the surface of a copper heat sink and its preparation method

technical field

The invention belongs to the field of LEDs, in particular to a light-emitting component in which an LED chip is directly welded to the surface of a copper heat sink and a preparation method thereof.

Background technique

Only 15-25% of the electrical energy of the LED chip is converted into light energy, and the rest is converted into heat energy. With the improvement of LED chip manufacturing technology, the power of a single chip continues to increase, and the heat generated also increases. If the increase in heat cannot be dissipated to the surrounding environment in time, the temperature of the chip will increase, the light efficiency will be reduced, and the life of the chip will be attenuated. , color rendering and other performance changes, in order to solve the problem of heat dissipation, has experienced FR-4 printed boards, MCPCB (metal composite substrate), ceramic circuit boards.

For example, the patent CN102263195A mentions that the ceramic ring is connected to the heat sink through a thermally conductive adhesive, the phosphor heat sink and the flexible PCB electrode are bonded on the ceramic surface, and then the chip is directly welded to the heat sink in order to reduce the temperature of the phosphor. Prevents yellowing and color development. Although this patent improves the heat dissipation problem to a certain extent, because each method is different, its limitations are also different. FR-4 and MCPCB boards have a low thermal conductivity of only 0.2-3W/m·K because the intermediate insulating layer is an organic binder, which is only suitable for chips with low power. The thermal conductivity of ceramic substrates is greatly mentioned. For example, alumina ceramics are 25W/m·k. In addition to high thermal conductivity, ceramic materials have a thermal expansion coefficient similar to that of silicon chips, so that chips and substrates, as well as connections can be reduced. Failure due to thermal expansion or contraction between wires. As we all know, metal materials have the highest thermal conductivity due to the movement of free electrons, for example, copper is 386W/m·K. Therefore, in order to further reduce the thermal resistance, people proposed COHS technology, which directly solders the chip to the metal heat sink. However, the thermal expansion coefficient of the metal heat sink is relatively large. For example, the thermal expansion coefficient of copper, which is most commonly used as a heat sink, is 16ppm/k, while the thermal expansion coefficient of the chip is only 4ppm/k. Therefore, how to reduce the expansion coefficient of the metal heat sink becomes the key point of this technology. The essential.

Patent CN102263195A only proposes to directly solder the chip to the heat sink. The focus of this patent is to bond the phosphor powder heat sink on the ceramic surface to guide the temperature of the phosphor powder away and reduce the yellowing of the phosphor powder and the color temperature change. However, it reduces the thermal resistance. Performance is still relatively poor.

Contents of the invention

In order to solve the technical problem of poor thermal resistance reduction performance in the existing light-emitting components, the invention provides a light-emitting component with good thermal resistance reduction performance and a preparation method thereof.

The invention discloses a light-emitting assembly in which an LED chip is directly welded to the surface of a copper heat sink. The light-emitting assembly includes a copper heat sink, a ceramic substrate with an LED chip installation hole in the middle arranged above the copper heat sink, and a ceramic substrate arranged on the ceramic substrate. The positive and negative electrodes on the edge, the LED chip arranged in the chip mounting hole, and the phosphor layer coated on the LED chip; a copper-oxygen eutectic welding layer is arranged between the copper heat sink and the ceramic substrate; the LED chip It is electrically connected with the positive and negative electrodes, and the positive and negative electrodes are connected with the power supply.

The present invention also provides a method for preparing a light-emitting component in which an LED chip is directly welded to the surface of a copper heat sink, the method comprising the following steps:

S1. Eutectic welding of ceramic and copper heat sink: laminate the ceramic substrate and copper heat sink together for eutectic welding;

S2, on the other side of the ceramic, making positive and negative electrodes;

S3. Weld the LED chip to the surface of the copper heat sink through the mounting hole on the ceramic, and then connect the solder joint of the LED chip to the electrode;

S4, epoxy resin potting, curing, welding power supply.

The present invention reduces the thermal expansion coefficient of the copper heat sink by firmly welding the copper heat sink and ceramics with a low thermal expansion coefficient, realizes the reliable connection between the LED chip and metal copper, and reduces the thermal resistance, thereby reducing the junction temperature of the LED chip and improving the light efficiency. Extended service life.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a light-emitting component.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The invention discloses a light-emitting assembly in which an LED chip is directly welded to the surface of a copper heat sink. The light-emitting assembly includes a copper heat sink, a ceramic substrate with an LED chip installation hole in the middle arranged above the copper heat sink, and a ceramic substrate arranged on the ceramic substrate. The positive and negative electrodes on the edge, the LED chip arranged in the chip mounting hole, and the phosphor layer coated on the LED chip; a copper-oxygen eutectic welding layer is arranged between the copper heat sink and the ceramic substrate; the LED chip It is electrically connected with the positive and negative electrodes, and the positive and negative electrodes are connected with the power supply.

The present invention selects copper with high thermal conductivity as the copper heat sink, and through the copper-oxygen eutectic welding of ceramics and metal copper heat sink copper, the thermal expansion coefficient of copper can be reduced to slightly higher than that of ceramic materials, so that the LED chip can be directly welded to a metal surface with high thermal conductivity.

According to the light-emitting component provided by the present invention, preferably, the LED chip is a sapphire substrate, and the electrodes are on the same side.

According to the light-emitting component provided by the present invention, in order to improve the bonding between the copper heat sink and the ceramic substrate, preferably, the thickness of the copper heat sink is 0.1-1mm, and the thickness of the ceramic substrate is 0.25-0.63mm , the thickness of the copper-oxygen eutectic welding layer is 0.5-10 μm.

According to the light-emitting assembly provided by the present invention, preferably, the thickness of the ceramic substrate is greater than that of the LED chip. This structure has a concave cup structure, which is convenient for potting with epoxy resin.

According to the light-emitting component provided by the present invention, in order to improve safety, preferably, the power supply is an isolated driving power supply.

Preferably, the mounting holes and the surfaces of the positive and negative electrodes are coated with nickel-gold alloy.

The copper heat sink is copper, and the LED chip installation holes in the ceramic substrate can be formed by punching and cutting the ceramic substrate.

The present invention also provides a method for preparing a light-emitting component in which an LED chip is directly welded to the surface of a copper heat sink, the method comprising the following steps:

S1. Eutectic welding of ceramic and copper heat sink: laminate the ceramic substrate and copper heat sink together for eutectic welding;

S2, on the other side of the ceramic, making positive and negative electrodes;

S3. Bond the LED chip to the surface of the copper heat sink through the installation hole on the ceramic, and then connect the LED chip soldering point and the electrode through the gold wire;

S4, epoxy resin potting, curing, welding power supply.

According to the preparation method provided by the present invention, preferably, the surface of the copper heat sink layer is pre-oxidized before eutectic welding. More preferably, the pre-oxidation is: oxidizing the side of the copper heat sink that needs to be welded with the ceramic eutectic at 500-1000°C in an atmosphere with an oxygen content of 50-1000ppm for 10-60min.

According to the preparation method provided by the present invention, preferably, the eutectic welding is carried out at 1065-1080° C. for 10-60 minutes under a nitrogen protective atmosphere.

According to the preparation method provided by the present invention, preferably, nickel-gold alloy is deposited on the surface of the installation hole and the positive and negative electrodes after step S2 and before step S3.

The LED chip mounting holes can be formed when the ceramics are molded, or can be formed after laser drilling and cutting.

Description of the drawings:

As shown in Fig. 1, the light-emitting assembly includes a copper heat sink 1, a ceramic substrate 2 with an LED chip mounting hole 6 in the middle arranged above the copper heat sink 1, positive and negative electrodes 3 arranged on the edge of the ceramic substrate 2, and arranged on the chip The LED chip 4 in the mounting hole 6 is coated on the phosphor layer 5 on the LED chip 4; the copper heat sink 1 and the ceramic substrate 2 are connected by a copper-oxygen eutectic welding layer 7; the LED chip 4 and The positive and negative electrodes 3 are welded by welding wires, and the positive and negative electrodes are connected to a power supply. Nickel-gold alloy 8 is deposited on the surface of the installation hole and the positive and negative electrodes.

The present invention will be described in further detail below through specific examples.

Example 1

1. Use laser to drill and cut ceramics with a thickness of 0.1mm to form a ceramic substrate with LED mounting holes;

2. Pre-oxidize a copper sheet with a thickness of 0.1mm: oxidize for 60min at 800°C in an atmosphere with an oxygen content of 100ppm;

3. Lay the pre-oxidized copper sheet and the cut ceramics together, keep them warm at 1072°C for 30 minutes in a nitrogen protective atmosphere, and then cool to room temperature;

4. Then screen-print copper electrodes on the other side of the ceramic, and sinter at 800 ° C for 10 minutes in a nitrogen protective atmosphere; 5. Finally, deposit Ni-Au on the LED mounting holes and electrode surfaces;

6. The LED chip with a power of 2W is welded to the surface of the copper heat sink through the die-bonding process;

7. Connect the chip and ceramic surface electrodes through gold wires;

8. Potting fluorescent powder and epoxy resin in the mounting hole, interconnecting the isolated drive power supply and electrodes, and finally installing it into the heat dissipation system to obtain product A1.

Example 2

1. Use laser to drill and cut ceramics with a thickness of 2mm to form a ceramic substrate with LED mounting holes;

2. Pre-oxidize the copper sheet with a thickness of 100mm: oxidize in an atmosphere with an oxygen content of 100ppm at 800°C for 60min;

3. Lay the pre-oxidized copper sheet and the cut ceramics together, keep them warm at 1072°C for 30 minutes in a nitrogen protective atmosphere, and then cool to room temperature;

4. Deposit a layer of copper on the other side of the ceramic by physical vapor deposition, cover with photosensitive ink, expose, develop, electroplate and thicken the exposed line to a certain thickness, remove the ink, and then put it into the copper etching solution to the non-plated thickened part the copper disappears;

5. Finally, Ni-Au is deposited on the LED mounting hole and electrode surface;

6. The chip with a power of 2W is placed on the surface of the copper heat sink through the crystal bonding process;

7. Connect the chip and ceramic surface electrodes through gold wires;

8. Potting phosphor powder and epoxy resin in the mounting hole, interconnecting the isolated drive power supply and electrodes, and finally installing it into the heat dissipation system to obtain product A2.

Comparative example 1

1. Use laser drilling and cutting to form a ceramic substrate with LED mounting holes;

2. Print copper electrodes on one side of the ceramic, then sinter at 800°C in a nitrogen atmosphere for 10 minutes, and cool to room temperature;

3. Bond the other side to the copper heat sink with thermal conductive adhesive;

4. Then screen-print copper electrodes on the other side of the ceramic, and sinter at 800 ° C for 10 minutes in a nitrogen protective atmosphere; 5. Finally, deposit Ni-Au on the LED mounting holes and electrode surfaces;

6. The 2W chip is placed on the surface of the copper heat sink through the solid crystal process;

7. Connect the chip and ceramic surface electrodes through gold wires;

8. Potting fluorescent powder and epoxy resin in the mounting hole, interconnecting the isolated drive power supply and electrodes, and finally installing it into the heat dissipation system to obtain product B1.

Comparative example 2

1. Form lines on the surface of double-sided ceramic copper-clad (DBC) boards through filming, exposure, development, etching and other processes;

2. Finally, Ni-Au is deposited on the LED mounting hole and electrode surface;

3. The 2W chip is mounted on the surface of the DBC copper clad laminate through the die-bonding process;

4. The copper surface on the other side of the unmounted chip is soldered to the surface of the copper heat sink through eutectic brazing;

5. Connect the chip and ceramic surface electrodes through gold wires;

6. Make a retaining wall to prevent epoxy resin from overflowing, potting fluorescent powder and epoxy resin in the retaining wall, interconnecting the isolated drive power supply and electrodes, and finally installing it into the heat dissipation system to obtain product B2.

Test Method and Results

1. Reliability test

Put the products A1, A2, B1 and B2 made in the examples and comparative examples into the ice-water mixture at 0°C for 5 minutes, then quickly take them out and put them into boiling water at 100°C for 5 minutes, and then carry out the cold and heat shock test reciprocatingly. Ice water and boiling water gauge one cycle at a time. The results are shown in Table 1.

2. LED junction temperature Tj test

Place the temperature measuring point of the K-type thermocouple on the cooling pad, and measure the temperature of the cooling pad as Tc, because Tj=Rjc·P+Tc (Rjc is the thermal resistance parameter of the chip, and P is the power converted into heat), so The junction temperature Tj can be obtained. The higher the junction temperature, the lower the luminous efficiency and the shorter the lifetime. The results are shown in Table 1.

Table 1

the A1 A2 B1 B2 Hot and cold shock (times) >100 >100 50 >100 Tj (℃) 52 53 52 122

It can be seen from Table 1 that the light-emitting assembly of the present invention has high thermal shock resistance and good reliability; at the same time, the junction temperature of the light-emitting assembly of the present invention is lower than 60°C, and the light-emitting assembly of the present invention has high luminous efficiency and long service life . Although the light-emitting component of Comparative Example 1 has good luminous efficiency and service life, its reliability is low, and the light-emitting component of Comparative Example 2 has good reliability, but its luminous efficacy is low and its service life is short. To sum up, the light-emitting component of the present invention obviously improves the reliability, prolongs the service life, and improves the light efficiency.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (11)

1. a LED chip is welded direct to the luminescence component of copper heat sink surface, it is characterized in that, there is the ceramic substrate of LED chip installing hole the centre that described luminescence component comprises that copper is heat sink, be arranged on the heat sink top of copper, be arranged on the positive and negative electrode at the edge of ceramic substrate, be arranged on the LED chip in chip installing hole, be coated in the phosphor powder layer on LED chip; Described copper is heat sink and ceramic substrate between be provided with copper oxygen eutectic weld layer; Between described LED chip and positive and negative electrode, be electrically connected, described positive and negative electrode is connected with power supply.

2. luminescence component according to claim 1, is characterized in that, described LED chip is the LED chip of Sapphire Substrate, electrode homonymy.

3. luminescence component according to claim 1, is characterized in that, the thickness that described copper is heat sink is 0.1-100mm, and the thickness of described ceramic substrate is 0.1-2mm, and the thickness of described copper oxygen eutectic weld layer is 0.01-100 μ m.

4. luminescence component according to claim 1, is characterized in that, the thickness of described ceramic substrate is greater than the thickness of LED chip.

5. luminescence component according to claim 1, is characterized in that, described power supply is isolation drive power supply.

6. luminescence component according to claim 1, is characterized in that, described installing hole and positive and negative electrode surface deposition have nickel billon.

7. LED chip is welded direct to a preparation method for the luminescence component of copper heat sink surface, it is characterized in that, the method comprises the following steps:

Eutectic welding that S1, pottery and copper are heat sink: ceramic substrate and heat sink being superimposed together of copper are carried out to eutectic welding;

S2, at ceramic opposite side, make positive and negative electrode;

S3, LED chip is welded to copper heat sink surface by the installing hole on pottery, afterwards LED chip solder joint is connected with electrode;

S4, epoxy resin encapsulated, solidify the source of welding current.

8. preparation method according to claim 7, is characterized in that, before eutectic welding, copper heat-sink shell is carried out to surface preoxidizing.

9. preparation method according to claim 8, is characterized in that, described pre-oxidation is: by the one side of heat sink copper needs and the welding of ceramic eutectic, at 500-1000 ℃, oxygen content is oxidized 10-60min in the atmosphere of 50-1000ppm.

10. preparation method according to claim 7, is characterized in that, described eutectic welding is at 1065-1080 ℃, to be incubated 10-60min under nitrogen protection atmosphere.

11. preparation methods according to claim 7, is characterized in that, after step S2, before S3 at installing hole and positive and negative electrode surface deposition nickel billon.

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