CN107785471A - The method for packing and UVLED base of ceramic encapsulating structures of a kind of UVLED base of ceramic - Google Patents

Abstract

A method for packaging a UVLED ceramic base and a packaging structure for a UVLED ceramic base, belonging to the field of LED packaging. The packaging method includes: setting a metal layer on the ceramic sintered body substrate to obtain a ceramic metal backing board precursor, the metal layer including a circuit connection part and a package connection part surrounding the circuit connection part; arranging a solder layer on the package connection part, and packaging After the metal frame is attached to the solder layer, it is sealed to obtain the UVLED ceramic base. The UVLED ceramic base packaging structure is packaged by the aforementioned packaging method. The invention realizes the inorganic packaging of the UVLED ceramic base, avoids the use of organic packaging materials, and prolongs the service life of the LED device. On the basis of low temperature, the UVLED ceramic base with good electrical conductivity and thermal conductivity is prepared, and at the same time, it solves the problem of metal The problem of poor bonding between the layer and the ceramic and the frame, thereby improving the stability and reliability of the UVLED ceramic base.

Description

A kind of packaging method of UVLED ceramic base and UVLED ceramic base packaging structure

technical field

The invention relates to the field of LED packaging, in particular to a packaging method for a UVLED ceramic base and a packaging structure for a UVLED ceramic base.

Background technique

With the rapid development of LED technology and the maturity of the visible light field, short-wavelength ultraviolet light-emitting diodes (UV LEDs) have gradually attracted the attention of researchers. Because their spectral bands are concentrated in the ultraviolet range, compared with traditional ultraviolet light sources, they have Unique advantages, including low power consumption, fast luminous response, high reliability, high radiation efficiency, long life, no pollution to the environment, compact structure and many other advantages, so it has broad market application prospects, in screen printing, polymerization Solidification, environmental protection, white light lighting and military detection and other fields have great application value.

At present, the mainstream packaging method of LED is organic packaging, and the main packaging materials are mostly organic materials such as epoxy resin and silicone resin. For ultraviolet LEDs, due to the shorter wavelength of ultraviolet light and high radiation energy, these organic materials are prone to aging when exposed to it for a long time, thereby reducing the luminous efficiency of the LED chip and affecting its performance and life. At present, in order to improve the life and performance of UVLED, the industry mainly improves in the following two ways: one is to delay the aging speed of organic materials from various aspects such as light and heat, and to add light stabilizers, antioxidants and heat to organic packaging materials. However, this method has not completely solved the fundamental problem, and there is still a risk of LED failure. 2. Use inorganic materials for packaging. The existing UVLED ceramic base is mainly realized by co-firing technology, that is, HTCC or LTCC. Although these two methods can avoid the use of organic materials and have better air tightness, there are still some processes in each The disadvantages brought about by the above.

For HTCC technology: Add plasticizer, dispersant, binder and other organic components to the ceramic powder to make a muddy slurry, and make a green body by tape casting; then drill through holes according to the design of each layer , using screen printing metal paste for wiring and hole filling, and finally stacking each green layer, and finally sintering at a high temperature of 1500-1700 ° C to form a ceramic base.

For LTCC technology: similar to HTCC, only 30%-50% low-melting glass frit is mixed into the ceramic powder to reduce the sintering temperature to 850-900°C, so metals such as copper and silver with better conductivity can be used as electrodes and wiring Material.

Contents of the invention

The purpose of the present invention is to provide a packaging method for UVLED ceramic bases. On the basis of realizing the inorganic packaging of UVLED ceramic bases, UVLED ceramic bases with good electrical and thermal conductivity are prepared at low temperature, and the metal layer is solved. The problem of poor bonding with ceramics and frames.

Another object of the present invention is to provide a UV LED ceramic base packaging structure, which can improve the stability and reliability of the UV LED ceramic base.

Embodiments of the present invention are achieved like this:

A packaging method for a UVLED ceramic base, comprising:

A metal layer is arranged on the ceramic sintered body substrate to obtain a ceramic metal liner precursor, the metal layer includes a circuit connection part and a package connection part surrounding the circuit connection part;

providing a solder layer on the package connection; and

After attaching the packaging metal frame to the solder layer, it is sealed.

A UVLED ceramic base packaging structure is packaged by the above-mentioned packaging method.

The beneficial effects of the embodiments of the present invention are:

1. The present invention selects silver or silver-copper alloy with a low melting point and excellent electrical conductivity as the circuit paste layer, and the substrate adopts a ceramic sintered body substrate, without adding too much low melting point glass frit to reduce the sintering temperature and improve thermal conductivity . Therefore, the UVLED ceramic base prepared by the present invention has the advantages of good thermal conductivity and electrical conductivity, and low sintering temperature.

2. The present invention seals the ceramic metal liner with a frame that matches the thermal expansion coefficient of the metal layer and has good ductility, such as silver and copper. After sealing, the residual stress of the ceramic base is small, and the sealing process Through the eutectic liquid phase formed by the metal frame of the middle package and the solder layer, it can be better combined with the ceramic metal liner and form a dense overall structure. The UVLED ceramic base thus prepared has good airtightness, and the bonding force between the metal layer and the frame body and the ceramic sintered body substrate is good, thereby improving the stability and reliability of the UVLED ceramic base.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention,

The accompanying drawings that need to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. Ordinary technicians can also obtain other related drawings based on these drawings without paying creative work.

Fig. 1 is the process flow diagram of the encapsulation method of UVLED ceramic base of the present invention;

Fig. 2 is a schematic structural view of the UVLED ceramic base packaging structure of the present invention;

3 is a partial enlarged view of the ceramic metal liner of the UVLED ceramic base package structure of the present invention;

Fig. 4 is a schematic structural view of the UVLED ceramic base packaging structure of the present invention after setting the LED chip;

Fig. 5 is the picture of the airtightness test of the UVLED ceramic base prepared in Example 1 of the present invention;

Figure 6 is a picture after the bonding force test of the UVLED ceramic base prepared in Example 1 of the present invention, wherein Figure a is the picture after the metal layer and the ceramic bonding force test, and Figure b is the picture after the metal layer and the frame bonding force test.

Icon: 100-UVLED ceramic base packaging structure; 110-ceramic sintered body substrate; 120-metal layer; 121-circuit connection part; 122-package connection part; 123-first metal layer; 124-second metal layer; 130 -solder layer; 140-encapsulation metal frame; 150-ceramic metal lining board; 200-LED chip; 210-conductive wire.

It should be noted that, the metal layer 120 of the present invention is divided laterally on the ceramic sintered body substrate 110, and the metal layer 120 includes a circuit connection part 121 and a package connection part 122; The second metal layer 124 . Therefore, it can also be understood that both the circuit connecting portion 121 and the package connecting portion 122 include the first metal layer 123 and the second metal layer 124 .

Detailed ways

Embodiments of the present invention will be described in detail below in conjunction with examples, but those skilled in the art will understand that the following examples are only for illustrating the present invention, and should not be considered as limiting the scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

The existing UVLED ceramic base manufacturing process is mainly co-firing technology, that is, HTCC or LTCC. The inventor found in research that there are certain problems in the above process.

For example, HTCC technology has disadvantages such as high sintering temperature, huge energy consumption, limited selection of metal conductor materials and poor conductivity. At present, conductor materials are mainly metals such as tungsten, molybdenum, manganese and their alloys with high melting points.

In LTCC technology, due to the relatively low thermal conductivity of the prepared UVLED ceramic base, and the matching problem of the co-fired material, it is easy to deform and crack after sintering, making the bonding force between the metal layer and the ceramic relatively poor (<50N) , which also leads to low reliability in the application of UVLED ceramic bases.

Based on the defects of the prior art, the present invention proposes a process for manufacturing a UVLED ceramic base packaging structure.

The packaging method of a UVLED ceramic base packaging structure 100 of the present invention is a process flow diagram as shown in Figure 1, comprising the following steps:

Step 1: Setting Metal Layer 120

The metal layer 120 is provided on the ceramic sintered body substrate 110 to obtain a precursor of the ceramic metal backing board 150 . The ceramic sintered body substrate can be aluminum nitride ceramics, alumina ceramics or silicon nitride ceramics. Preferably, aluminum nitride ceramics is used as the ceramic sintered body substrate. The shape and thickness of the ceramic sintered body substrate are not limited, as long as it can be used for The metallized ceramic substrate can be prepared. The metal layer 120 includes a circuit connection portion 121 and a package connection portion 122 surrounding the circuit connection portion 121 . Preferably, the metal layer 120 is provided by printing. Wherein, printing can be divided into one or more times, such as two times, three times, four times and more times.

In some examples, printing to set the metal layer 120 is performed twice, and the printing process can be defined as follows.

Firstly, the first printing is performed on the sintered ceramic substrate 110, and the printed metal paste is the first metal paste.

The first metal paste includes a first conductive composition. The first conductive component includes Ag and Cu and an active component for forming a conductive layer on the ceramic sintered body substrate 110 . The active ingredient includes at least one of Ti, Zr and Hf. For example, the active ingredient is Ti, or the active ingredient is Zr, or the active ingredient is Hf, or the active ingredient is a mixture of Ti and Hf, or the active ingredient is a mixture of Ti and Zr, or the active ingredient is a mixture of Zr and Hf, or The active ingredient is a mixture of Ti, Zr and Hf.

The ceramic sintered body substrate 110 used in the present invention is aluminum nitride ceramics, and the active elements Ti, Zr or Hf in the active component react with aluminum nitride to form a bonding layer, for example, aluminum nitride and Ti react to form titanium nitride, so that the metal layer 120 and the ceramic sintered body substrate 110 can be closely bonded. At the same time, if an alumina ceramic sintered body substrate is used, titanium reacts with alumina to generate titanium oxide; a similar embodiment can also be: using a silicon nitride ceramic sintered body substrate, then titanium reacts with silicon nitride to generate titanium nitride and Titanium silicide.

In terms of mass percentage, Ag and Cu account for 95%-98% of the total amount of the first conductive component, and the active component accounts for 2%-5% of the total amount of the first conductive component. According to the first metal paste formed according to the ratio and the first metal layer 123 formed by the first metal paste, the active components in the metal layer can directly react with the ceramic sintered body substrate 110 at high temperature to form a bonding layer, thereby ensuring The metal layer is tightly combined with the ceramic sintered body substrate. In addition to the above-mentioned first conductive component and active component, the first metal paste also includes other organic components such as an organic binder and an organic solvent.

Then, the second printing is performed on the first metal paste, and the printed metal paste is the second metal paste.

The viscosity of the second metal paste is smaller than the viscosity of the first metal paste, so that the fluidity of the second metal paste on the ceramic sintered body substrate 110 is greater than the fluidity of the first metal paste on the ceramic sintered body substrate 110, thereby The small pits formed on the ceramic sintered body substrate 110 by the first metal paste are made up, so that the surface of the entire metal layer 120 is smoother and more even. The second metal paste includes a second conductive composition. The second conductive composition includes Ag and Cu. The silver-to-copper mass ratio of the second conductive component is greater than the silver-to-copper mass ratio of the first conductive component. That is to say, the weight percentage of silver in the second conductive component is larger than that in the first conductive component. In addition to the above-mentioned second conductive component, the second metal paste also includes other organic components such as an organic binder and an organic solvent.

Therefore, the metal layer 120 formed according to the above method substantially includes two layers after vacuum sintering, namely, the first metal layer 123 formed by the first metal paste and the second metal layer 124 formed by the second metal paste. As shown in FIG. 3 , the first metal layer 123 made of the first metal paste is disposed on the surface of the sintered ceramic substrate 110 . The second metal layer 124 made of the second metal paste is disposed on the surface of the first metal layer 123 .

Step 2: setting the solder layer 130 and the package metal frame 140

A solder layer 130 is provided on the package connection portion 122 of the metal layer 120 . The solder layer 130 is also provided by printing. The solder layer 130 is made of silver copper paste. The solder layer 130 includes 72-77% of Ag and 23-28% of Cu in mass percentage.

A package metal frame 140 is attached to the solder layer 130 . The packaging metal frame 140 can be made of silver or copper, and the metal frame is preferably set to be Cu, especially oxygen-free copper. It is a good sealing match to the precursor of the ceramic metal liner 150 . Before the packaging metal frame 140 is attached to the solder layer 130, the packaging metal frame 140 is pretreated, and the pretreatment includes degreasing and deoxidizing steps to remove oil stains and surface oxides on the packaging metal frame 140 surface.

Step 3: Packaging the metal frame 140 and the precursor of the ceramic metal liner 150 for vacuum sealing

After the above steps are completed, the precursor of the ceramic metal backing board 150 and the packaging metal frame 140 are sealed together under vacuum conditions. The sealing temperature is 780°C-950°C, and the sealing time is 10min-60min. The vacuum condition is that the degree of vacuum is higher than 5×10 ^-2 Pa, that is, the pressure is lower than 5×10 ^-2 Pa.

During the sealing process, the solder layer 130 and the packaging metal frame 140 can form a eutectic liquid phase, so that the packaging metal frame 140 passes through the solder layer 130 disposed on the precursor of the ceramic metal backing board 150 and the precursor of the ceramic metal backing board 150 A good contact is obtained, and a dense overall structure is formed, so that the prepared UVLED ceramic base packaging structure 100 has the advantages of excellent air tightness and excellent bonding force between each part.

The UVLED ceramic base packaging structure 100 prepared according to the above packaging method is shown in FIG. Wherein, the ceramic metal liner 150 includes a ceramic sintered body substrate 110 and a metal layer 120 . The metal layer 120 is disposed on both sides of the sintered ceramic substrate 110 by printing. The solder layer 130 is disposed on the package connection portion 122 of the metal layer 120 . The encapsulating metal frame 140 is disposed on the solder layer 130 to form a frame structure for encapsulating the LED chip 200 .

Referring to FIG. 3 , divided vertically, the metal layer 120 includes a first metal layer 123 formed by the above-mentioned first metal paste and a second metal layer 124 formed by the second metal paste. The first metal layer 123 is provided on both surfaces of the ceramic sintered body substrate 110, and the second metal layer 124 is provided on the surface of the first metal layer 123.

Referring to FIG. 4 , the LED chip 200 is disposed on the circuit connection portion 121 of the metal layer 120 , and the LED chip 200 is connected to the circuit connection portion 121 of the metal layer 120 through a conductive wire 210 . The LED chip 200 is an ultraviolet LED chip.

It should be noted that the metal layer 120 of the present invention is not a continuous layer structure disposed on the ceramic sintered body substrate, but presents a circuit pattern according to the required circuit pattern. Therefore, the circuit connection part 121 of the metal layer 120 is connected to the package. The portion 122 may be continuous or discontinuous, and the present invention is not limited thereto. The circuit connection portion 121 of the metal layer 120 mainly refers to the portion of the metal layer 120 where the LED chip 200 and the conductive wire 210 are disposed. The package connection part 122 of the metal layer 120 mainly refers to the part of the metal layer 120 where the solder layer 130 and the package metal frame 140 are disposed.

The UVLED ceramic base through the above packaging method has good airtightness, and has the advantages of low sintering temperature, good electrical conductivity and thermal conductivity, and good bonding force between the metal layer and the frame body and the ceramic sintered substrate. The stability and reliability of its subsequent application.

Below in conjunction with embodiment the present invention is further described.

Example 1

An aluminum nitride ceramic sintered body substrate 110 with a size of 114.3mm×114.3mm is selected for use after ultrasonic cleaning treatment is performed on its surface. The first metal paste is printed on the surface of the sintered ceramic substrate 110 through the first printing to form the first metal layer 123 . The second metal paste is printed on the first metal layer 123 formed of the first metal paste by the second printing to form the second metal layer 124 . Through the first printing and the second printing, the metal layer 120 is provided on the ceramic sintered body substrate 110 , thereby obtaining a precursor of the ceramic metal backing plate 150 .

A solder layer 130 is provided on the package connection portion 122 of the metal layer 120 . The setting of the solder layer 130 is also by printing, wherein the solder layer 130 includes 72% Ag and 28% Cu by mass percentage.

In this embodiment, the packaging metal frame 140 is made of oxygen-free copper. Pretreatment is performed on the packaging metal frame 140 . Specifically, the pretreatment successively includes degreasing and deoxidizing treatment, that is, degreasing treatment is first performed on the packaging metal frame 140 with a heavy oil cleaning agent. Secondly, at room temperature (20°C-30°C), soak in a sulfuric acid solution with a mass fraction of 10wt% for 3 minutes for deoxidation treatment to remove oxides on the surface of the copper foil, and then blow dry to remove impurities on the surface of the copper foil. Then, the package metal frame 140 made of oxygen-free copper after pretreatment is attached to the solder layer 130 .

Finally, the precursor of the ceramic metal backing board 150 and the packaging metal frame 140 are sealed under vacuum conditions. The sealing temperature is 850°C, the sealing time is 30 minutes, and the vacuum degree is 1×10 ^-3 Pa.

Thus, the UVLED aluminum nitride ceramic base packaging structure of the present invention was prepared, and then related tests were performed on it. The test results are shown in Table 1.

Example 2

Except that the packaging metal frame is an Ag frame, 3-5g of high-mesh aluminum oxide polishing powder is added to the heavy oil cleaning agent in the pretreatment process, and the degreasing and deoxidizing treatment are realized at the same time, the others are the same as in Example 1. Thus, the UVLED aluminum nitride ceramic base packaging structure of the present invention was prepared, and then related tests were performed on it. The test results are shown in Table 1.

Example 3

Except that the material of the ceramic sintered body substrate is alumina, the others are the same as in Embodiment 1.

Thus, the UVLED ceramic base packaging structure of the present invention was prepared, and then related tests were performed on it. The test results are shown in Table 1.

Comparative example 1

Except that the packaging metal frame is an iron-nickel alloy frame, and the pretreatment process only includes the degreasing step, the others are the same as in Embodiment 1.

In this way, the UVLED aluminum nitride ceramic base was prepared, and then related tests were carried out. The test results are shown in Table 1.

Comparative example 2

The commercially available low temperature co-firing technology (LTCC) was used to prepare the UVLED alumina ceramic base, and then related tests were carried out on it. The test results are shown in Table 1.

Comparative example 3

The commercially available UVLED alumina ceramic base prepared by high-temperature co-firing technology (HTCC) was selected, and then relevant tests were carried out on it. The test results are shown in Table 1.

Evaluation of UVLED ceramic base:

1) Air tightness evaluation:

At room temperature, drip red ink in the UVLED ceramic base package frame. When titrating, it is necessary to ensure that the red ink is in contact with the inner wall of the frame and prevent it from overflowing from the upper surface of the frame. After dripping the red ink, let it stand for 2 hours to observe its penetration. .

2) Evaluation of binding ability

a. Metal layer and ceramic sintered body substrate

Use a solder sheet (Φ2mm) to weld the T-pin and the metal layer square (2*2mm), and then use an electronic universal tensile testing machine (Xinhong XDL-500N) to pull the T-pin off the ceramic gold substrate. Tensile force value (N), and observe its separation phenomenon, the sample test quantity is 20pcs. If the metal layer is separated from the ceramics, the bonding strength is NG, and the evaluation is "×"; if the metal layer and the ceramics are mixed and separated, the bonding force is OK, and the evaluation is "○". Then count the number of each separation state as the evaluation result.

b. Metal layer and frame

After the frame was peeled off, its separation state from the ceramic sintered body substrate was observed with a stereo microscope, and the number of samples tested was 100pcs. If the frame is separated from the metal layer on the sintered ceramic substrate, the bonding force between the metal layer and the frame is poor, and the evaluation is "×"; When the bonding force between the layer and the frame was excellent, it was evaluated as "◯". If both of the above two separation states exist, the binding force is average, and the evaluation is "△", and then the number of each separation state is counted as the evaluation result.

3) Evaluation of cold and heat shock resistance

Using the model TSG-71S-A temperature shock test chamber, the UVLED ceramic base sample was raised from -40°C to 125°C for 6 minutes, then dropped from 125°C to -40°C for 4 minutes, and then the sample was raised from -40°C The temperature is raised to 125°C for 6 minutes, and this cycle is repeated, and the sample is visually observed for cracks or peeling every 50 cycles.

Table 1. Test Results

It can be seen from the above table that the ceramic base prepared in the embodiment of the present invention has no red ink penetration after 2 hours, that is, the airtightness is all OK, see Figure 5 for details. However, the red ink permeated the ceramic base prepared in Comparative Example 1 after 2 hours. This is mainly because the frame is made of Kovar alloy, which has relatively poor thermal expansion coefficient matching and ductility with the metal layer. It is easy to generate large residual stress during sintering, which leads to poor bonding with the ceramic metal lining. It affects the airtightness and reliability of the UVLED ceramic base.

The bonding strength of each group of ceramic bases was tested. After the metal layer was peeled off from the ceramic substrate and the frame, except for Comparative Example 1, the separation states of the other groups were all mixed and separated. In addition, it can also be seen that compared with the ceramic bases prepared in Comparative Examples 2 and 3, the tensile force value after the metal layer of the ceramic base prepared in the embodiment of the present invention is peeled off from the ceramic substrate is relatively large, and the values are all much greater than 100N, indicating that the metal layer of the present invention Excellent bonding force with ceramic substrate and frame, see Figure 6 for details.

The thermal shock resistance test was carried out on each group of ceramic bases, and the results showed that the thermal shock resistance of the ceramic bases prepared in each example was better than 2000 times, while the ceramic bases prepared in other comparative examples were less than 800 times. It shows that the reliability of the UVLED ceramic base prepared by the present invention is high.

In addition, the present invention uses silver-copper alloy as the circuit paste layer, which has a lower melting point and higher conductivity than the tungsten paste used in Comparative Example 3. Secondly, in the preparation process of the ceramic base of Comparative Example 2, the sintering of the green sheet and the metal paste is carried out at the same time. In order to reduce the sintering temperature of the green body, it is often necessary to add too much low-melting glass frit in the green body, which will greatly Reduce the thermal conductivity of the ceramic base. However, the substrate selected in the present invention is a ceramic sintered body substrate, that is, the sintering of the green sheet and the metal paste is carried out successively, and there is no need to add low-melting point glass frit to the green body, and its thermal conductivity is higher. Therefore, it can be concluded that the UVLED ceramic base of the present invention has the advantages of high electrical conductivity and thermal conductivity, and low sintering temperature.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A packaging method for a UVLED ceramic base, characterized in that it comprises: A metal layer is arranged on the ceramic sintered body substrate to obtain a ceramic metal backing board precursor, the metal layer includes a circuit connection part and a packaging connection part surrounding the circuit connection part; providing a solder layer on the package connection; and Sealing is performed after attaching the package metal frame to the solder layer. 2. The packaging method of the UVLED ceramic base according to claim 1, wherein the ceramic sintered body substrate is aluminum nitride ceramics, alumina ceramics or silicon nitride ceramics. 3. The packaging method of the UVLED ceramic base according to claim 1, wherein the metal layer is provided on the ceramic sintered body substrate by printing. 4. The packaging method of the UVLED ceramic base according to claim 3, wherein printing the metal layer on the ceramic sintered body substrate comprises first printing and second printing. 5. The packaging method of the UVLED ceramic base according to claim 1, characterized in that, the solder layer is provided on the packaging connection part by printing. 6. The packaging method of the UVLED ceramic base according to claim 1, wherein the components of the metal layer and the solder layer both include silver or a silver-copper alloy. 7. The packaging method of the UVLED ceramic base according to claim 1, wherein the packaging metal frame is made of silver or copper. 8. The method for packaging UVLED ceramic bases according to any one of claims 1 to 7, wherein the solder layer comprises 72-77% Ag and 23-28% Cu by mass percentage. 9. The encapsulation method of UVLED ceramic base according to claim 1, is characterized in that, the sealing between the encapsulation metal frame that is arranged on the described solder layer and the ceramic metal liner precursor is carried out under vacuum condition , and the sealing temperature is 780°C-950°C, and the sealing time is 10min-60min. 10. A UVLED ceramic base packaging structure, characterized in that the UVLED ceramic base packaging structure is packaged by the packaging method according to any one of claims 1 to 9.