CN114171659B - Deep ultraviolet thin film LED with high luminous efficiency and preparation method thereof - Google Patents

Abstract

The invention discloses a deep ultraviolet thin film LED with high luminous efficiency and a preparation method thereof. The deep ultraviolet thin film LED with high luminous efficiency includes a support part; and a strained film-shaped deep ultraviolet LED provided on the support part. LED chip; among them, the support part and the deep ultraviolet LED chip have different thermal expansion coefficients, and the strain is caused by the different thermal expansion coefficients of the support part and the deep ultraviolet LED chip using different temperature changes during the connection process with the deep ultraviolet LED chip. Shrinkage is introduced. As a result, the light emitting mode of the deep ultraviolet LED chip is transformed into the TE mode, thereby greatly improving the light extraction efficiency of the deep ultraviolet thin film LED.

Description

Deep ultraviolet thin film LED with high luminous efficiency and preparation method thereof

Technical field

The present invention relates to the technical field of deep ultraviolet thin film LED, and in particular to a deep ultraviolet thin film LED with high luminous efficiency and a preparation method thereof.

Background technique

As people have more and more demands for sterilization and disinfection in daily life, household sterilization and disinfection devices have attracted more and more attention. Among them, deep ultraviolet light source sterilization and disinfection devices have become popular due to their advantages of energy saving, portability and non-toxicity. The preferred sterilization and disinfection device.

At present, deep ultraviolet solid-state light sources are mainly based on AlGaN-based deep ultraviolet LEDs. However, AlGaN-based deep ultraviolet LEDs have the problem of extremely low light extraction efficiency. The main reason for this problem is that their light extraction efficiency is extremely low.

In order to solve the problem of low light extraction efficiency of LED, the existing technology generally adopts the structure of thin film LED with the substrate peeled off to greatly reduce the total reflection of light in the chip, thereby effectively improving the light extraction efficiency. However, this structure only significantly improves the light extraction efficiency of non-Al (Al-free) InGaN-based blue thin film LEDs and low Al-component AlGaN-based near-UV thin film LEDs. For AlGaN-based deep ultraviolet LEDs, since they use AlGaN with high Al composition as quantum wells, their luminescence mode has been parallel to the easy front-side light extraction of non-Al and low Al composition blue light and near-ultraviolet. The transverse electric (TE) polarized light in the c-axis direction is converted into the transverse magnetic (TM) polarized light perpendicular to the c-axis direction of deep ultraviolet with high Al content and difficult to be extracted by front light. Only the thin film structure is used to improve the deep ultraviolet light extraction efficiency. The improvement is extremely limited.

Contents of the invention

In order to solve the problem of light extraction efficiency of deep ultraviolet thin-film LEDs, the inventor searched a large amount of information and found that applying stress to the quantum wells causes strain in the quantum wells, which can make the light-emitting mode of deep ultraviolet LEDs mainly TE mode, thereby improving the efficiency of deep ultraviolet thin film LEDs. Light extraction efficiency of UV LEDs. However, the inventors encountered some problems when implementing the plan based on this guiding idea: for example, although the method of applying stress on the epitaxial structure can introduce strain into the quantum well, the strain introduced by this operation will seriously degrade the active The crystal quality of the layer will seriously affect the internal quantum efficiency, resulting in a reduction in light extraction efficiency.

To this end, the inventor found that a material with a thermal expansion coefficient that is different from the thermal expansion coefficient of the AlGaN material in the quantum well of the deep ultraviolet thin film LED can remain active while applying a certain stress to the quantum well. The crystal quality of the deep ultraviolet LED layer is adjusted to adjust the light-emitting mode of the deep ultraviolet LED to the TE mode, which greatly improves the light extraction efficiency of the deep ultraviolet LED.

Therefore, according to one aspect of the present invention, a deep ultraviolet thin film LED with high luminous efficiency is provided.

The deep ultraviolet thin film LED with high luminous efficiency includes a support part; and a film-shaped deep ultraviolet LED chip with strain introduced on the support part; wherein the support part and the deep ultraviolet LED chip have different thermal expansion coefficients, and the strain is The support part, which has a different thermal expansion coefficient from that of the deep ultraviolet LED chip, is introduced using different shrinkage rates based on temperature changes during the connection process with the deep ultraviolet LED chip.

Since the thickness of the film-like deep ultraviolet LED chip is thin, and the thermal expansion coefficient of the support portion provided on the film-like deep ultraviolet LED chip is different from that of the deep ultraviolet LED chip, when the support portion is connected to the deep ultraviolet LED chip, During the process, the strain introduced into the deep ultraviolet LED chip due to the different shrinkage rates caused by temperature changes can transform the light-emitting mode of the deep ultraviolet LED chip into the TE mode, thereby greatly improving the performance of deep ultraviolet thin film LEDs. Light extraction efficiency.

In some embodiments, the thickness of the support portion is greater than the thickness of the deep ultraviolet LED chip. This is to ensure that when the support part and the deep ultraviolet LED chip undergo temperature changes, the support part can introduce more strain into the deep ultraviolet LED chip. Preferably, in order to make it easier for the support part to introduce strain to the deep ultraviolet LED chip to change the light-emitting mode of the deep ultraviolet LED chip from the TM mode to the TE mode, the thickness of the deep ultraviolet LED chip is controlled below 10 μm. Preferably, in order to enable the support part to introduce sufficient strain into the deep ultraviolet LED chip so that the light-emitting mode of the deep ultraviolet LED chip changes from the TM mode to the TE mode, the thickness difference between the support part and the deep ultraviolet LED chip is controlled to 90 μm. above. Preferably, the thickness of the holding support part is controlled to be more than 100 μm, so that the deformation of the support part before and after temperature changes can be made smaller.

In a preferred embodiment, the deep ultraviolet LED chip uses AlGaN with high Al composition as the quantum well; the thermal expansion coefficient of the support part is greater than 6×10 ^-6 /k or less than 4×10 ^-6 /k. Therefore, by maintaining a certain gap in the thermal expansion coefficients of the support part and the quantum well, during the connection process, the support part and the deep ultraviolet LED chip have a certain difference in shrinkage rate, so that the deep ultraviolet LED chip can be connected to the deep ultraviolet LED chip. introduce greater strain.

In some embodiments, the deep ultraviolet thin film LED with high luminous efficiency further includes a soldering layer provided between the support part and the deep ultraviolet LED chip. Preferably, the thermal conductivity of the welding layer is greater than 20W/(m·K). This ensures that the heat generated when the deep ultraviolet LED chip is working can be quickly conducted away, thereby effectively reducing the temperature of the deep ultraviolet LED chip and improving its reliability.

In some embodiments, the support part is welded to the bottom of the deep ultraviolet LED chip through a welding layer or welded to the electrode of the deep ultraviolet LED chip. This is to ensure that the strain introduced by the support part into the deep ultraviolet LED chip can be distributed evenly on the quantum well, thereby minimizing local warping of the deep ultraviolet LED chip.

In some embodiments, the soldering layer evenly covers the surface of the deep ultraviolet LED chip facing the support part, the Vickers hardness of the soldering layer is greater than 100HV and the thickness ranges from 500 nm to 5 μm. Since the welding layer is hard and thin, the stress generated when the temperature changes due to the different thermal expansion coefficient of the support part and the deep ultraviolet LED chip can be transmitted to the deep ultraviolet LED chip, thus introducing strain into the deep ultraviolet LED chip. , so that the light-emitting mode of the deep ultraviolet LED chip is mainly TE mode.

In other embodiments, the soldering layer is discontinuously disposed in at least one direction perpendicular to the chip growth direction. To introduce non-isotropic strain in deep ultraviolet LED chips. Since the soldering layer is not continuously provided on the deep ultraviolet LED chip in all directions at this time, in order to ensure the stability of the soldering layer connecting the deep ultraviolet LED chip and the support part, the thickness range of the soldering layer is controlled to 500nm-10μm. . One embodiment in which the soldering layer is discontinuously arranged in at least one direction perpendicular to the chip growth direction is: the soldering layer is arranged to include at least two sets of first groups spaced apart on the surface of the deep ultraviolet LED chip facing the support portion. The thermally conductive solder strip, the first thermally conductive solder strip is made of hard solder with a Vickers hardness greater than 100HV; or the soldering layer includes first thermally conductive solder strips spaced on the surface of the deep ultraviolet LED chip facing the support part and a pair of adjacent thermally conductive solder strips. a second thermally conductive solder strip between adjacent first thermally conductive solder strips, wherein the first thermally conductive solder strip is made of hard solder with a Vickers hardness greater than 100HV, and the second thermally conductive solder strip is made of soft solder with a Vickers hardness less than 100HV Made of solder.

According to one aspect of the present invention, a method for preparing a deep ultraviolet thin film LED with high luminous efficiency is provided, which includes the following steps:

Select film-like deep ultraviolet LED chips and supports with different thermal expansion coefficients;

Connect the deep ultraviolet LED chip and the support part when the two are heated to a temperature greater than 100°C;

Cool the connected deep UV LED chip and support part to room temperature.

Therefore, because the thermal expansion coefficient of the support part is different from that of the deep ultraviolet LED chip, it can introduce strain into the deep ultraviolet LED chip during cooling, causing the light-emitting mode of the deep ultraviolet LED chip to change from the TM mode to the TE mode, thereby greatly improving the deep ultraviolet LED chip. Light extraction efficiency of UV thin film LED. Using the preparation method of the present invention, strain can be introduced into the deep ultraviolet LED chip through heating and cooling, and the operation is convenient and quick.

In some embodiments, before heating the deep ultraviolet LED chip and the support part, it also includes:

Set a welding layer on the deep ultraviolet LED chip or support part. The welding layer at least includes hard solder with a Vickers hardness greater than 100HV, and the thickness of the welding layer ranges from 500nm to 10μm;

Wherein, when the deep ultraviolet LED chip and the supporting part are connected, the deep ultraviolet LED chip and the supporting part are connected through a welding layer.

Since the welding layer is pre-set on the support part or the deep ultraviolet LED chip, when the support part and the deep ultraviolet LED chip are heated, the solder in the welding layer can be in working condition, so that the support part and the deep ultraviolet LED chip can be welded on At the same time, after the welding is completed, as the temperature decreases, the support part can apply stress to the deep ultraviolet LED chip through the welding layer, thereby introducing strain into the deep ultraviolet LED chip, thus achieving a change in the light emission mode of the deep ultraviolet LED chip.

In some embodiments, when selecting a film-like deep ultraviolet LED chip and a support part with different thermal expansion coefficients, the selected deep ultraviolet LED chip is a formal structure or a vertical structure, and the deep ultraviolet LED chip and the support part are connected through a welding layer. To include: connecting the chip bottom of the deep ultraviolet LED chip to the support through a soldering layer; or

When selecting a film-like deep ultraviolet LED chip and a support part with different thermal expansion coefficients, the selected deep ultraviolet LED chip has a flip-chip structure. The connection between the deep ultraviolet LED chip and the support part through the welding layer includes: connecting the deep ultraviolet LED chip and the support part through the welding layer. The surfaces of the two electrodes of the ultraviolet LED chip facing away from the bottom of the chip are connected to the support part.

This ensures that the strain introduced by the support part into the deep ultraviolet LED chip can be distributed evenly on the quantum well, thereby minimizing local warping of the deep ultraviolet LED chip.

Description of the drawings

Figure 1 is a schematic structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to a first embodiment of the present invention;

Figure 2 is a schematic structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the first embodiment of the second embodiment of the present invention;

Figure 3 is a schematic cross-sectional structural diagram cut along the soldering layer of the deep ultraviolet thin film LED with high luminous efficiency shown in Figure 2;

Figure 4 is a schematic structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the second embodiment of the present invention;

Figure 5 is a schematic cross-sectional structural diagram cut along the soldering layer of the deep ultraviolet thin film LED with high luminous efficiency shown in Figure 4;

Figure 6 is a schematic cross-sectional structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the third embodiment of the second embodiment of the present invention;

Figure 7 is a schematic cross-sectional structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the fourth embodiment of the second embodiment of the present invention;

Figure 8 is a schematic cross-sectional structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the fifth embodiment of the second embodiment of the present invention;

Figure 9 is a schematic structural diagram of a deep ultraviolet thin film LED with high luminous efficiency according to the sixth embodiment of the second embodiment of the present invention;

Figure 10 is a schematic cross-sectional structural diagram cut along the soldering layer of the deep ultraviolet thin film LED with high luminous efficiency shown in Figure 9;

Figure 11 is a schematic structural diagram of a method for preparing a deep ultraviolet thin film LED with high luminous efficiency according to an embodiment of the present invention, in which welding is provided on the support part;

Figure 12 is a schematic structural diagram of a welding layer formed between a support part and a deep ultraviolet LED chip in a method for preparing a deep ultraviolet thin film LED with high luminous efficiency according to an embodiment of the present invention;

Figure 13 is a schematic flow structure diagram of a method for preparing a deep ultraviolet thin film LED with high luminous efficiency according to an embodiment of the present invention;

Figure 14 is a schematic flow structure diagram of a method for preparing a deep ultraviolet thin film LED with high luminous efficiency according to another embodiment of the present invention;

Reference signs: 20. Deep ultraviolet LED chip; 30. Soldering layer; 32. First thermally conductive solder strip; 33. Second thermally conductive solder strip; 40. Support part; 50. Transfer medium; 60. Heating plate.

Detailed ways

It should be noted that, as long as there is no conflict, the embodiments and features in the embodiments of this application can be combined with each other.

It should also be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations There is no such actual relationship or sequence between them. Furthermore, the terms "comprises" and "comprising" include not only those elements but also other elements not expressly listed or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the statement "comprising..." does not exclude the presence of additional identical elements in a process, method, article, or device that includes the stated element. The terms used in this article are generally terms commonly used by those skilled in the art. If there is any inconsistency with the commonly used terms, the terms in this article shall prevail.

In this article, the term "deep UV" refers to light in the wavelength range of 200nm-300nm.

In this article, the term "quantum well", also known as the active layer, refers to the semiconductor layer provided between the P-type semiconductor layer and the N-type semiconductor layer in the LED chip. The holes provided by the P-type semiconductor layer and the N-type semiconductor layer The provided electrons are combined here to release photons, thereby realizing the LED's luminescence.

In this article, the term "transverse electric (TE)" refers to the transverse electric mode, which refers to the direction of the electric field perpendicular to the direction of propagation.

In this article, the term "transverse magnetic (TM)" refers to the transverse magnetic mode, which refers to the direction of the magnetic field perpendicular to the direction of propagation.

In this article, the term "high Al composition AlGaN" refers to AlGaN with an Al composition in the range of 0.3-1.

In this article, the term "internal quantum efficiency" refers to the ratio of photons generated by the recombination of electron-hole pairs in the quantum well to the total electron-hole pairs when a forward voltage is applied to the LED.

In this article, the term "light extraction efficiency" means that inside the LED, all photons excited by electrical energy are not emitted. Only some photons can leave the device through refraction, and other photons are continuously reflected internally and eventually absorbed. That is, there is a ratio between the light energy actually emitted and the light energy generated. Light extraction efficiency reflects this ratio.

As used herein, the term "hard solder" is a solder having a cured Vickers hardness greater than 100 HV.

As used herein, the term "soft solder" is a solder having a Vickers hardness of less than 100 HV after curing.

In this article, the Vickers hardness of solder (including hard solder and soft solder) refers to the Vickers hardness of the solder in the solidified state at normal temperature (that is, room temperature, generally 25°C).

In this article, a set of thermally conductive solder strips refers to solder blocks made of the same kind of solder (the same kind here means both hard or soft) and connected into one piece.

In this article, the "chip growth direction" refers to the epitaxial growth direction of deep ultraviolet LED chips.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Figure 1 schematically shows a deep ultraviolet thin film LED with high luminous efficiency according to a first embodiment of the present invention.

As shown in Figure 1, the deep ultraviolet thin film LED with high luminous efficiency includes a support part 40 and a strained deep ultraviolet LED chip 20; wherein, the deep ultraviolet LED chip 20 is in a film shape and is disposed on the support part 40; the support The part 40 and the deep ultraviolet LED chip 20 have different thermal expansion coefficients. The strain introduced into the deep ultraviolet LED chip 20 is caused by the support part 40 having a different thermal expansion coefficient from the deep ultraviolet LED chip 20 when it is connected to the deep ultraviolet LED chip 20. It is introduced because temperature changes produce a shrinkage rate different from that of the deep ultraviolet LED chip 20 .

Since the thermal expansion coefficient of the support part 40 is different from that of the deep ultraviolet LED chip 20, and because the thickness of the film-like deep ultraviolet LED chip 20 is thin, when the support part 40 is connected to the deep ultraviolet LED chip 20, The strain introduced into the deep ultraviolet LED chip 20 due to the different shrinkage rates caused by temperature changes can change the polarization mode of the deep ultraviolet LED chip 20 from the TM mode to the TE mode, greatly improving the light extraction efficiency of the deep ultraviolet thin film LED. .

In a preferred embodiment, in order to introduce more strain to the deep ultraviolet LED chip 20 , the thickness of the support portion 40 is set to be greater than the thickness of the deep ultraviolet LED chip 20 . In order to make it easier for the support part 40 to introduce strain to the deep ultraviolet LED chip 20 and to make it easier for the light-emitting mode of the deep ultraviolet LED chip 20 to transition from the TM mode to the TE mode, it is preferred that the thickness of the deep ultraviolet LED chip 20 be controlled below 10 μm. . The deep ultraviolet LED chip 20 at this time can be a chip peeled off from the growth substrate, or a chip on a wafer that has not been peeled off, or a chip transferred to the transfer medium 50 after peeling off, as long as the deep ultraviolet LED chip 20 is peeled off. The thickness of the UV LED chip 20 can be controlled below 10 μm. Existing chip peeling techniques can be used to peel the chip from the growth substrate, such as wet peeling, laser cutting, etc. The present invention specifically addresses chip peeling. The implementation method is not limited. In order to enable the support part 40 to introduce sufficient strain into the deep ultraviolet LED chip 20 so that the light emitting mode of the deep ultraviolet LED chip changes from the TM mode to the TE mode, it is preferred that the thickness of the support part 40 and the deep ultraviolet LED chip 20 are The difference is controlled above 90μm. Preferably, the thickness of the support part 40 is kept above 100 μm, thereby reducing the deformation of the support part 40 caused by temperature changes. In this article, the thickness of a certain structure refers to the distance from the upper surface to the lower surface of the structure along the epitaxial growth direction of the deep ultraviolet LED chip 20 .

In a preferred embodiment, the deep ultraviolet LED chip 20 uses AlGaN with high Al composition as the quantum well; the thermal expansion coefficient of the material of the support part 40 is greater than 6×10 ^-6 /k or less than 4×10 ^-6 /k. Therefore, by maintaining a certain difference in the thermal expansion coefficients of the support part 40 and the quantum well, the support part 40 and the deep ultraviolet LED chip 20 undergo temperature changes during the connection process, because there is a certain difference in the shrinkage rates of the two. , introducing larger strain into the deep ultraviolet LED chip 20 . For example, according to the determined thermal expansion coefficient range, copper, aluminum, tin, iron, metal alloys, etc. can be selected as materials for the support portion 40 with a thermal expansion coefficient greater than 6×10 ^-6 /k. Preferably, a material with a thermal expansion coefficient greater than 12×10 ^-6 /k is used as the material of the support part 40 to meet the requirement that the thermal expansion coefficients of the support part 40 and the AlGaN in the quantum well of the deep ultraviolet LED chip 20 have a large difference; General metal materials can meet the requirement of thermal expansion coefficient greater than 12×10 ^-6 /k. For example, the thermal expansion coefficient of iron is 12.2×10 ^-6 /k, the thermal expansion coefficient of copper is 16.5×10 -6 /k, and the thermal expansion coefficient of aluminum is 12.2×10 ^-6 /k. The thermal expansion coefficient is 23×10 ^-6 /k and the thermal expansion coefficient of tin is 26.6×10 ^-6 /k. Therefore, the support part 40 with a large difference in thermal expansion coefficient from the deep ultraviolet LED chip 20 can be used at the same temperature. The changing conditions introduce more strain in the deep UV LED chip 20 . For the material of the support part 40 whose thermal expansion coefficient is less than 4×10 ^-6 /k, silicon, aluminum carbide ceramics, etc. can be selected. Preferably, a material with a thermal expansion coefficient greater than 6×10 ^-6 /k is selected as the material of the support part 40 to introduce compressive strain into the deep ultraviolet LED chip 20 so that the luminescence mode of the deep ultraviolet LED chip 20 can be transformed into TE mode.

2 to 10 schematically show a deep ultraviolet thin film LED with high luminous efficiency according to a second embodiment of the present invention.

As shown in Figures 2, 4 and 9, the deep ultraviolet thin film LED with high luminous efficiency in this embodiment also includes a welding layer 30 based on the first embodiment. The welding layer 30 is provided on the deep ultraviolet LED chip. 20 and the supporting part 40 to connect the deep ultraviolet LED chip 20 and the supporting part 40 through the soldering layer 30 .

In a preferred embodiment, the thermal conductivity of the welding layer 30 is greater than 20 W/(m·K). This ensures that the heat generated when the deep ultraviolet LED chip 20 is working can be quickly conducted away, effectively reducing the temperature of the deep ultraviolet LED chip 20 and improving its reliability.

In some embodiments, the support part 40 is welded to the bottom of the deep ultraviolet LED chip 20 through the welding layer 30 or to the electrode of the deep ultraviolet LED chip 20 . This is to ensure that the strain introduced by the support part 40 into the deep ultraviolet LED chip 20 can be distributed evenly on the quantum well, thereby avoiding local warping of the deep ultraviolet LED chip 20 as much as possible. For example, when the deep ultraviolet LED chip 20 has a formal structure or a vertical structure, the bottom of the deep ultraviolet LED chip 20 (that is, the side of the deep ultraviolet LED chip 20 on which the substrate is disposed) is connected to the support portion 40 through the soldering layer 30 Welding together; when the deep ultraviolet LED chip 20 is a flip-chip structure, the two electrodes of the deep ultraviolet LED chip 20 are welded together with the support part 40 through the welding layer 30 respectively. Preferably, the deep ultraviolet LED chip 20 adopts a flip-chip structure chip, because the thickness of the P-type semiconductor layer is generally thinner than the N-type semiconductor layer, that is, the distance from the quantum well to the P-type semiconductor layer is smaller than the distance directly from the N-type semiconductor layer. , thus making the distance between the support part 40 connected to the chip of the flip-chip structure and the quantum well smaller than the distance between the support part 40 connected to the chip of the regular structure or vertical structure and the quantum well. When the depth of the flip-chip structure is When the shrinkage rate difference (or thermal expansion coefficient difference) between the ultraviolet LED chip 20 and the support part 40 is the same as the shrinkage rate difference (or thermal expansion coefficient difference) between the deep ultraviolet LED chip 20 and the support part 40 in the formal structure or vertical structure, flip-chip The quantum well of the structure will receive greater stress from the support portion 40 , that is, the flip-chip structure of the deep ultraviolet LED chip 20 will receive greater stress. Specifically, the soldering layer 30 may evenly cover the surface of the deep ultraviolet LED chip 20 facing the support part 40 , or may be discontinuously provided in at least one direction perpendicular to the chip growth direction.

In a preferred embodiment, the solder forming the welding layer 30 at least includes hard solder with a Vickers hardness greater than 100HV. By ensuring the hardness of the welding layer 30, it is ensured that the stress generated by the support part 40 can pass through the welding layer 30 when the temperature changes. applied to the deep UV LED chip 20. Preferably, the hard solder uses eutectic solder. Since the eutectic solder is below its melting point, solidification can occur if the temperature drops slightly (less than the temperature of ordinary solder (such as solder)), that is, the solidification of the eutectic solder The speed is greater than the solidification speed of ordinary solder. Therefore, after the deep ultraviolet LED chip 20 and the support part 40 are welded by the eutectic solder, the eutectic solder can quickly solidify to form the solder layer 30, so as to facilitate the cooling of the support part 40 after welding. The stress generated during the process is transmitted to the deep ultraviolet LED chip 20 . For example, the eutectic solder may be gold-tin solder or indium-tin solder. Preferably, the eutectic solder is gold-tin solder.

Figures 2 and 3 show a first embodiment of the solder layer 30, which exemplarily shows the structure of the solder layer 30 evenly covering the surface of the deep ultraviolet LED chip 20 facing the support portion 40, as shown in Figures 2 and 3 As shown in FIG. 3 , the soldering layer 30 evenly covers the surface of the deep ultraviolet LED chip 20 facing the supporting part 40 , that is, the soldering layer 30 completely covers the surface of the deep ultraviolet LED chip 20 facing the supporting part 40 , and the soldering layer The thickness is the same everywhere. Therefore, the quantum well of the deep ultraviolet LED chip 20 is subjected to the same stress in the x direction and the y direction (the x direction and the y direction are perpendicular to the chip growth direction, and the y direction is perpendicular to the x direction). That is, at this time, the quantum well is subjected to biaxial stress. stress. In order that the deep ultraviolet LED chip 20 and the support part 40 with the soldering layer 30 added between them can still introduce strain in the deep ultraviolet LED chip 20 due to temperature changes, in this embodiment, the Vickers hardness of the soldering layer 30 is controlled to In the range greater than 100HV. Preferably, the thickness range of the soldering layer 30 is controlled between 500 nm and 5 μm to ensure that the soldering layer 30 can transfer the stress of the supporting part 40 to the deep ultraviolet LED chip 20; and at the same time ensure that the supporting part 40 and the deep ultraviolet LED chip 20 are welded well. Stability prevents welding failure due to warping of the support part 40 and the deep ultraviolet LED chip 20 .

Figures 4 to 10 show the second to sixth embodiments of the soldering layer 30, which exemplarily show various implementations of the soldering layer 30 that is discontinuously arranged in at least one direction perpendicular to the chip growth direction. . At this time, in order to ensure that the soldering layer 30 can stably connect the deep ultraviolet LED chip 20 and the supporting part 40, the thickness of the soldering layer 30 needs to be controlled in the range of 500 nm-10 μm. It can be specifically divided into two implementation methods: In one of the implementation methods, as shown in FIGS. 5 to 8 , the soldering layer 30 is provided at intervals on the surface of the deep ultraviolet LED chip 20 facing the support part 40 There are at least two sets of first thermally conductive solder strips 32, and the first thermally conductive solder strips 32 are made of hard solder with a Vickers hardness greater than 100HV. Wherein, each group of first thermally conductive solder strips 32 can be continuously arranged along at least one direction perpendicular to the chip growth direction (as shown in FIGS. 5 to 7 ). Specifically, each group of first thermally conductive solder strips 32 can be arranged along the same direction. Continuously arranged on the support part 40 (the structure of the second embodiment of the soldering layer 30 shown in Figure 5); there may also be at least two sets of first thermally conductive solder strips 32 continuously arranged along different directions perpendicular to the chip growth direction, That is, a grid structure is formed on the surface of the soldering layer 30 facing the deep ultraviolet LED chip of the supporting part 40 (the structure of the third embodiment of the soldering layer 30 shown in Figure 6 and the structure of the soldering layer 30 shown in Figure 7 The structure of the fourth embodiment), in the third embodiment of the soldering layer 30, the angle between the first thermally conductive solder strips 32 continuously arranged in different directions on the support part 40 is 90°, and during the soldering In the fourth embodiment of the layer 30, the angle between the first thermally conductive solder strips 32 continuously arranged in different directions on the support part 40 is not 90°. For example, at least one group of the first thermally conductive solder strips 32 is arranged along x The direction is continuously arranged, and at the same time, at least one group of first thermally conductive solder ribbons 32 is continuously arranged along the m direction, and the angle between the x direction and the m direction is not 90°; each group of first thermally conductive solder ribbons 32 can also be grown perpendicular to the chip. The directions are discontinuous (as shown in the structure of the fifth embodiment of the soldering layer 30 in FIG. 8 ), which can be realized by disposing the first thermally conductive solder strips 32 on the supporting part 40 in a lattice structure. In another implementation, the soldering layer 30 includes first thermally conductive solder strips 32 spaced apart on the surface of the deep ultraviolet LED chip 20 facing the support portion 40 and disposed between adjacent first thermally conductive solder strips 32 . The second thermally conductive solder strip 33, wherein the first thermally conductive solder strip 32 is made of hard solder with a Vickers hardness greater than 100HV, and the second thermally conductive solder strip 33 is made of soft solder with a Vickers hardness less than 100HV. Specifically, The soldering layer of this implementation can be obtained by arranging a second thermally conductive solder strip 33 between the first thermally conductive solder strips 32 on the basis of the second to fifth embodiments of the soldering layer 30 , for example, in the soldering layer 30 On the basis of the second embodiment, second thermally conductive solder strips 33 are disposed between the first thermally conductive solder strips 32, and the structure of the sixth embodiment of the soldering layer 30 as shown in Figure 10 can be obtained. The thus obtained quantum well of the deep ultraviolet LED chip 20 is subject to greater strain in the direction in which the first thermally conductive solder strip 32 continues to grow, and less strain in other directions, that is, the quantum well is subject to uniaxial strain at this time.

No matter which embodiment is used to realize the solder layer 30 in the deep ultraviolet thin film LED with high luminous efficiency of the second embodiment, it at least includes hard solder with a Vickers hardness greater than 100HV, and its thickness range is controlled within 500nm- 10μm. Since the welding layer 30 disposed between the support part 40 and the deep ultraviolet LED chip 20 has the characteristics of both thinness and hardness, the support part 40 and the deep ultraviolet LED chip 20 have different thermal expansion coefficients when the temperature changes. The generated stress can be conducted to the deep ultraviolet LED chip 20 through the soldering layer 30 .

According to one aspect of the present invention, a method for preparing a deep ultraviolet thin film LED with high luminous efficiency is provided, which includes the following steps:

Select film-like deep ultraviolet LED chips 20 and support parts 40 with different thermal expansion coefficients;

Connect the deep ultraviolet LED chip 20 and the support part 40 when the two are heated to a temperature greater than 100°C;

The connected deep ultraviolet LED chip 20 and the support part 40 are cooled to room temperature.

The structure of the produced deep ultraviolet thin film LED with high luminous efficiency is shown in Figure 1.

Preferably, AlGaN with a high Al composition is selected as the quantum well of the deep ultraviolet LED chip 20; a component with a thermal expansion coefficient greater than 6×10 ^-6 /k or less than 4×10 ^-6 /k is selected as the support part 40 .

Preferably, a component with a thickness greater than that of the deep ultraviolet LED chip 20 is selected as the support portion 40 . Further, a deep ultraviolet LED chip 20 with a thickness less than 10 μm is selected. Furthermore, the support portion 40 with a thickness greater than 100 μm is selected.

Specifically, the heating temperatures of the support part 40 and the deep ultraviolet LED chip 20 need to be controlled below their failure temperatures to ensure that failure will not occur after the two are connected in a heated state.

Therefore, due to the different thermal expansion coefficients of the support part 40 and the deep ultraviolet LED chip 20, the support part 40 can have a large difference in size change with the deep ultraviolet LED chip 20 after a large temperature change, so that the deep ultraviolet LED chip 20 Introducing strain into the film changes the light emitting mode of the deep ultraviolet LED chip from the TM mode to the TE mode, thereby greatly improving the light extraction efficiency of the deep ultraviolet thin film LED. Using the preparation method of the present invention, strain can be introduced into the deep ultraviolet LED chip 20 by heating and cooling, and the operation is convenient and quick.

According to another aspect of the present invention, a method for preparing a deep ultraviolet thin film LED with high luminous efficiency is provided, which further includes the following steps based on the previous preparation method:

Before heating the deep ultraviolet LED chip 20 and the support part 40, it also includes:

A welding layer 30 is provided on the deep ultraviolet LED chip 20 or the support part 40. The welding layer 30 at least includes hard solder with a Vickers hardness greater than 100HV, and the thickness of the welding layer 30 ranges from 500 nm to 10 μm;

When the deep ultraviolet LED chip 20 and the supporting part 40 are connected, the deep ultraviolet LED chip 20 and the supporting part 40 are connected through the soldering layer 30 .

Since the soldering layer 30 is provided, when the supporting part 40 and the deep ultraviolet LED chip 20 are heated, it is necessary to ensure that the solder in the soldering layer 30 can reach the operating temperature during heating, so that the supporting part 40 and the deep ultraviolet LED chip 20 can be connected through the soldering layer 30 The UV LED chips 20 are soldered together.

Preferably, a thermal conductive solder with a thermal conductivity greater than 20 W/(m·K) is selected to prepare the soldering layer 30 .

Preferably, the hard solder uses eutectic solder, so that the eutectic solder can quickly solidify to form the solder layer 30 after welding the deep ultraviolet LED chip 20 and the support part 40, so that the support part 40 can be cooled down after welding. The generated stress is transferred to the deep ultraviolet LED chip 20 . For example, the eutectic solder may be gold-tin solder or indium-tin solder. It is further preferred that the eutectic solder uses gold-tin solder with a eutectic temperature of nearly 280°C, and the heating temperature when the deep ultraviolet LED chip 20 is connected to the support part 40 is controlled to be above 280°C, and at the same time, the melting point is selected to be much greater than 280°C. The support part 40 is made of material (such as aluminum alloy). Therefore, the deep ultraviolet LED chip 20 and the support part 40 can be welded by eutectic welding, and the support part 40 is cooled to room temperature after the welding is completed at this temperature. Due to the large temperature difference, the support part 40 is The deformation is large, and thus large strain can be introduced into the deep ultraviolet LED chip 20 . Furthermore, a metal material with a thermal expansion coefficient greater than 12×10 ^-6 /k is selected as the material for making the support part 40 , so that the support part 40 with a large difference in thermal expansion coefficient relative to the deep ultraviolet LED chip 20 , during the cooling process, Due to the large temperature difference, greater strain is introduced into the deep ultraviolet LED chip 20. The strain introduced into the deep ultraviolet LED chip 20 by the support part 40 through cooling can be calculated according to the following formula:

For example, the average Al composition of AlGaN in the quantum well of the deep ultraviolet LED chip 20 is 0.4, and the corresponding linear interpolation thermal expansion coefficient is 5.034×10 ^-6 /k; the support part 40 is made of metallic copper, and its thermal expansion coefficient is 17.5× 10 ^-6 /k; The deep ultraviolet LED chip 20 and the copper support part 40 are welded at 280°C. When cooled to room temperature (25°C), the strain introduced by the copper support part 40 into the deep ultraviolet LED chip 20 (Thermal mismatch) can be calculated by the previous formula:

ε=(17.5-5.034)×10 ^-6 /k×(280-25)=0.0032≈0.3%.

Figure 13 schematically shows one embodiment of a method for preparing a deep ultraviolet thin film LED with high luminous efficiency, which includes the following steps:

S100: Select the film-shaped deep ultraviolet LED chip 20 and the support part 40 with different thermal expansion coefficients;

S200: Set the welding layer 30 on the deep ultraviolet LED chip 20 or the support part 40. The welding layer 30 at least includes hard solder with a Vickers hardness greater than 100HV, and the thickness of the welding layer 30 ranges from 500 nm to 10 μm;

S300: When the deep ultraviolet LED chip 20 and the support part 40 are heated to a temperature greater than 100°C, connect the two through the soldering layer 30;

S400: Cool the connected deep ultraviolet LED chip 20 and the support part 40 to room temperature.

The structure of the produced deep ultraviolet thin film LED with high luminous efficiency is shown in Figures 2, 4 and 9.

Figure 14 schematically shows another embodiment of a method for preparing a deep ultraviolet thin film LED with high luminous efficiency, which includes the following steps:

S101: Select a film-like deep ultraviolet LED chip 20 and set a welding layer 30 on the deep ultraviolet LED chip 20. The welding layer 30 at least includes hard solder with a Vickers hardness greater than 100HV, and the thickness range of the welding layer 30 is 500nm- 10μm;

S201: Select the support part 40 that has a different thermal expansion coefficient from that of the film-like deep ultraviolet LED chip 20;

S300: When the deep ultraviolet LED chip 20 and the support part 40 are heated to a temperature greater than 100°C, connect the two through the soldering layer 30;

S400: Cool the connected deep ultraviolet LED chip 20 and the support part 40 to room temperature.

The structure of the produced deep ultraviolet thin film LED with high luminous efficiency is shown in Figures 2, 4 and 9.

In other embodiments, the support part 40 can also be selected first as needed, and the welding layer 30 is provided on the support part 40. The welding layer 30 at least includes hard solder with a Vickers hardness greater than 100HV, and the thickness of the welding layer 30 ranges from 500nm-10μm; then select a film-like deep ultraviolet LED chip 20 with a different thermal expansion coefficient from the support part 40 . That is, the deep ultraviolet LED chip 20 and the supporting part 40 in steps S101 and S201 are replaced with each other.

In step S200 or step S101, the soldering layer 30 may be provided on the support part 40 or the deep ultraviolet LED chip 20 by sputtering, evaporation or electroplating. Specifically, the soldering layer 30 may have a uniform thickness and completely cover the surface of the support part 40 facing the deep ultraviolet LED chip 20 , or may have a uniform thickness and completely cover the surface of the deep ultraviolet LED chip 20 facing the support part 40 , and remain The thickness of the soldering layer 30 ranges from 500 nm to 5 μm (the structure of the soldering layer 30 is shown in Figure 3); the soldering layer 30 can also be discontinuously arranged in at least one direction perpendicular to the chip growth direction (the structure of the soldering layer is shown in Figure 5 to Figure 8 and Figure 10).

Exemplarily, the discontinuous arrangement of the welding layer 30 in at least one direction perpendicular to the chip growth direction can be achieved in the following manner:

In the first implementation, on the surface of the support part 40 or the deep ultraviolet LED chip 20, the first thermally conductive solder strip 32 is continuously provided only in one direction perpendicular to the chip growth direction, that is, the first thermally conductive solder strip 32 It is arranged discontinuously in other directions. The first thermally conductive solder strip 32 is made of hard solder with a Vickers hardness greater than 100HV. The thickness of the first thermally conductive solder strip 32 ranges from 500nm to 10μm; the first thermally conductive solder strip 32 can be along the x direction. , y direction or other directions; at least two sets of first thermally conductive solder strips 32 are provided, and all the first thermally conductive solder strips 32 are of equal thickness and are arranged at intervals to form the welding layer 30 (the structure of the welding layer 30 is shown in Figure 5 ). At this time, the soldering layer 30 has a larger strain in its continuous arrangement direction, and the strain introduced into the deep ultraviolet LED chip 20 is also along the continuous arrangement direction of the first thermally conductive solder strip 32. That is, the soldering layer 30 in this embodiment has Uniaxial strain is introduced into the deep ultraviolet LED chip 20 .

In the second implementation, on the surface of the support part 40 or the deep ultraviolet LED chip 20, the first thermally conductive solder strips 32 are continuously provided only in two directions perpendicular to the chip growth direction, that is, the first thermally conductive solder strips 32 It is arranged discontinuously in other directions. The first thermally conductive solder strip 32 is made of hard solder with a Vickers hardness greater than 100HV. The thickness of the first thermally conductive solder strip 32 ranges from 500nm to 10μm; the first thermally conductive solder strip 32 can be along the x direction. and y direction, continuously set along the x direction and the m direction, or continuously set along the y direction and the m direction, where the angle between the x direction and the y direction is 90°, and between the x direction or the y direction and the m direction The included angle is not 90°, and all the first thermally conductive solder strips 32 are of equal thickness and are spaced apart to form a grid-like soldering layer 30 (the structure of the soldering layer 30 is shown in Figures 6 and 7).

In the third implementation, a discontinuous first thermally conductive solder strip 32 is provided on the surface of the support part 40 or the deep ultraviolet LED chip 20 along any direction perpendicular to the chip growth direction, and the first thermally conductive solder strip 32 is made of For hard solders with a Vickers hardness greater than 100HV, the thickness of the first thermally conductive solder strip 32 ranges from 500nm to 10μm; at least two sets of first thermally conductive solder strips 32 are provided, and all the first thermally conductive solder strips 32 are of equal thickness and together constitute the welding The layer 30 is, for example, a lattice-shaped solder layer 30 on the surface of the support part 40 or the deep ultraviolet LED chip 20 (the structure of the solder layer 30 is shown in FIG. 8 ).

In the fourth implementation manner, on the basis of any one of the first to third implementation methods, soft solder with a Vickers hardness less than 100HV is filled between adjacent first thermally conductive solder strips 32 to form a second The thickness range of the thermally conductive solder tape 33, the first thermally conductive solder tape 32 and the second thermally conductive solder tape 33 is 500nm-10μm; all the first thermally conductive solder tape 32 and the second thermally conductive solder tape 33 together form the soldering layer 30 (soldering layer The structure of 30 is shown in Figure 10. From this, it can be understood that the discontinuous arrangement of the soldering layer 30 described in the present invention in a certain direction does not guide the thermal soldering strip (including the first thermally conductive solder strip 32 and the second thermally conductive solder strip). The discontinuous arrangement of the strip 33) is that the thermally conductive solder strips in this direction are not prepared with the same kind of solder, that is, the thermally conductive solder strips in this direction are at least two different solders arranged at intervals).

Among them, it is easy to understand that the method for preparing a deep ultraviolet thin film LED with high luminous efficiency of the present invention can also be used to prepare the structure of any of the aforementioned embodiments of a deep ultraviolet thin film LED with high luminous efficiency as needed.

In the above implementation manner, for simplicity of expression, "on the surface of the support part 40 or the deep ultraviolet LED chip 20" respectively refers to the surface of the support part 40 facing the deep ultraviolet LED chip 20 or on the deep ultraviolet LED chip. 20 on the surface facing the support portion 40 .

In the present invention, the discontinuous arrangement of the soldering layer 30 in at least one direction perpendicular to the chip growth direction is not limited to the foregoing implementation. The first thermally conductive solder strip 32 can also be continuously arranged in three or more directions as needed. .

In step S300, when the deep ultraviolet LED chip 20 and the support part 40 are heated to a temperature greater than 100°C, connecting the two through the welding layer 30 may include: disposing the support part 40 on one of the heating plates 60 , and place the deep ultraviolet LED chip 20 on another heating plate 60 through the thermally conductive transfer medium 50, and heat the support part 40 and the deep ultraviolet LED chip 20 through the heating plate 60. Since the soldering layer 30 is pre-disposed on the supporting part 40 or the deep ultraviolet LED chip 20, when the supporting part 40 and the deep ultraviolet LED chip 20 are heated, the solder in the soldering layer 30 can be in working condition, so that the supporting part 40 can be The deep ultraviolet LED chip 20 is welded together through the welding layer 30. After the welding is completed, along with the cooling, the support part 40 can apply stress to the deep ultraviolet LED chip 20 through the welding layer 30, thereby introducing strain into the deep ultraviolet LED chip 20. As a result, the light emitting mode of the deep ultraviolet LED chip 20 is changed.

In step S300, the soldering layer 30 is connected to different positions of the deep ultraviolet LED chip 20 according to the structure of the deep ultraviolet LED chip 20 selected in step S100 or step S101. For example, when the selected deep ultraviolet LED chip 20 When it is a formal structure or a vertical structure, the connection between the deep ultraviolet LED chip 20 and the support part 40 through the welding layer 30 includes: connecting the chip bottom of the deep ultraviolet LED chip 20 and the support part 40 through the welding layer 30; for another example, if When the deep ultraviolet LED chip 20 is in a flip-chip structure, the connection between the deep ultraviolet LED chip 20 and the support part 40 through the soldering layer includes: using the soldering layer 30 to connect the two electrodes of the deep ultraviolet LED chip 20 away from the bottom of the chip. The surface is connected to the support part 40. This ensures that the strain introduced by the support part into the deep ultraviolet LED chip can be distributed evenly on the quantum well, thereby minimizing local warping of the deep ultraviolet LED chip.

What is described above are only some embodiments of the present invention. For those of ordinary skill in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (14)

1. The deep ultraviolet thin film LED with high light extraction efficiency is characterized by comprising:

a support part;

a film-shaped deep ultraviolet LED chip having a strain introduced therein, the strain causing a light emission mode of the film-shaped deep ultraviolet LED chip to be changed from a TM mode to a TE mode; and

the welding layer is arranged between the supporting part and the deep ultraviolet LED chip, and the deep ultraviolet LED chip is connected with the supporting part through the welding layer;

wherein the support part and the deep ultraviolet LED chip have different thermal expansion coefficients, and the strain is introduced by the support part having the different thermal expansion coefficients with the deep ultraviolet LED chip by using different shrinkage rates caused by temperature change in the process of connecting with the deep ultraviolet LED chip;

the soldering layer comprises at least hard solder with Vickers hardness greater than 100HV, and the thickness of the soldering layer is 500nm-10 μm.

2. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 1, wherein the thickness of the support is greater than the thickness of the deep ultraviolet LED chip.

3. The deep ultraviolet thin film LED with high light extraction efficiency of claim 2, wherein the thickness of the deep ultraviolet LED chip is less than 10 μιη; the thickness of the support portion is greater than 100 μm.

4. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 1, wherein the deep ultraviolet LED chip uses AlGaN of high Al composition as a quantum well.

5. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 1, wherein the thermal expansion coefficient of the support portion is greater than 6 x 10 ^-6 K or less than 4X 10 ^-6 /k。

6. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 2, wherein the thermal conductivity of the solder layer is greater than 20W/(m-K).

7. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 1, wherein the support portion is soldered to the bottom of the deep ultraviolet LED chip or to an electrode of the deep ultraviolet LED chip through the soldering layer.

8. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 7, wherein the soldering layer uniformly covers the surface of the deep ultraviolet LED chip facing the support portion.

9. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 7, wherein the solder layer is discontinuously disposed in at least one direction perpendicular to the direction of chip growth.

10. The deep ultraviolet thin film LED with high light extraction efficiency of claim 9, wherein the solder layer comprises at least two sets of first thermally conductive solder strips spaced on the surface of the deep ultraviolet LED chip facing the support, the first thermally conductive solder strips being made of a hard solder with a vickers hardness greater than 100 HV.

11. The deep ultraviolet thin film LED with high light extraction efficiency according to claim 9, wherein the soldering layer comprises first heat conductive solder strips arranged on a surface of the deep ultraviolet LED chip facing the support portion at intervals and second heat conductive solder strips arranged between adjacent first heat conductive solder strips, wherein the first heat conductive solder strips are made of hard solder with a vickers hardness of more than 100HV and the second heat conductive solder strips are made of soft solder with a vickers hardness of less than 100 HV.

12. The preparation method of the deep ultraviolet thin film LED with high light-emitting efficiency is characterized by comprising the following steps of:

arranging a welding layer on the selected film-shaped deep ultraviolet LED chips or the supporting parts with different thermal expansion coefficients, wherein the welding layer at least comprises hard solder with the Vickers hardness of more than 100HV, and the thickness range of the welding layer is 500nm-10 mu m;

When the deep ultraviolet LED chip and the supporting part are heated to the temperature of more than 100 ℃, connecting the two through the welding layer;

the connected deep ultraviolet LED chip and support portion were cooled to room temperature.

13. The method for manufacturing a deep ultraviolet thin film LED having high light extraction efficiency according to claim 12, wherein when selecting a film-like deep ultraviolet LED chip and a support portion having different thermal expansion coefficients, the selected deep ultraviolet LED chip is of a front-mounted structure or a vertical structure, and the connection between the deep ultraviolet LED chip and the support portion is realized by a solder layer comprising: and connecting the bottom of the deep ultraviolet LED chip with the supporting part through the welding layer.

14. The method for manufacturing a deep ultraviolet thin film LED with high light extraction efficiency according to claim 12, wherein when selecting a film-shaped deep ultraviolet LED chip and a support part having different thermal expansion coefficients, the selected deep ultraviolet LED chip is of a flip-chip structure, and the connection between the deep ultraviolet LED chip and the support part is realized by a solder layer comprising: and connecting the surfaces of the two electrodes of the deep ultraviolet LED chip, which are away from the bottom of the chip, with the supporting part through the welding layer.