JP2009158645A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser module capable of relaxing a stress when being implemented even if an intermediate body is not interposed between a laser array and a cooling body. <P>SOLUTION: The laser module 10 includes a laser array 11 comprising a plurality of light emitting parts 13 and a cooling body 12 comprising a laser mounting region where the laser array 11 is mounted. In the laser mounting region of the cooling body 12, a plurality of grooves 21 are provided side by side in the same direction as the plurality of light emitting parts 13. A composite material 22, whose linear expansion coefficient is lower than the component material of the cooling body 12, is embedded in each of the grooves 21. The laser array 11 is positioned above the grooves 21 in which the composite materials 22 are embedded, being implemented on the cooling body 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser module used as a light source.

  High-power semiconductor lasers are used in industrial applications such as high-efficiency solid-state laser excitation light sources because of their high output, high density, extremely sharp peaks in wavelength, and small size. Further, in order to realize further higher output and higher integration, a laser array having a configuration in which semiconductor laser elements such as laser diodes are arranged in an array on one chip is also generalized. However, the laser array generates several tens of watts of heat that is about the same as the output for a chip size of 10 mm × 1 to 2 mm, for example. Since the operating performance and life of semiconductor laser elements depend on the driving temperature, an efficient heat dissipation structure is desired. For this reason, the laser array is used in the form of a laser module in which the laser array is mounted on a cooling body.

  FIG. 11 is a front view showing a configuration of a conventional laser module using a laser array. The laser module 50 mainly includes a laser array 51, an intermediate body 52, and a cooling body 53. The laser array 51 is bonded to the upper surface of the intermediate body 52 using the first solder layer 54. The intermediate body 52 is bonded to the upper surface of the cooling body 53 using the second solder layer 55.

  The laser array 51 is formed by integrally forming a plurality of semiconductor laser elements on the same semiconductor substrate, and is formed in an elongated rod shape. A plurality of light emitting portions 56 are provided on the front end surface of the laser array 51 in a 1: 1 relationship with a plurality of semiconductor laser elements. The intermediate body 52 is provided for the purpose of stress relaxation and is formed in a flat plate shape. The cooling body 53 is for efficiently releasing the heat generated in the laser array 51, and is formed in a quadrangular prism block shape. As this type of laser module 50, for example, the one disclosed in Patent Document 1 is known.

  The laser array 51 having a plurality of semiconductor laser elements is manufactured using a compound semiconductor substrate typified by GaAs (gallium arsenide), whereas the cooling body 53 has high thermal conductivity and is available at a comparatively low price. It is made using a possible metal material such as Cu (copper). The linear expansion coefficient of GaAs is 6.5 ppm / K, while the linear expansion coefficient of copper is 16.5 ppm / K corresponding to 2.5 times that of GaAs. For this reason, in order to relieve the stress due to the difference in linear expansion coefficient between the laser array 51 and the cooling body 53, the intermediate body 52 is made of a material such as AlN (aluminum nitride), SiC (silicon carbide), CuW (copper tungsten), diamond or the like. It is made using.

JP 2006-339511 A (FIG. 1)

  In the conventional module structure, considering the heat exhaust efficiency from the laser array 51 to the cooling body 53, the thickness of the intermediate body 52 is preferably as small as possible. Ultimately, the intermediate body 52 is not interposed, and the laser is not interposed. It is desirable to mount the array 51 directly on the cooling body 53.

  However, when the linear expansion coefficients of the laser array 51 and the cooling body 53 are compared as described above, the difference between the two is large, and when the laser array 51 is simply solder-bonded to the upper surface of the cooling body 53, mounting (solder bonding) May cause problems such as breakage of the laser array 51 and peeling of the solder joint interface. For this reason, in many laser modules 50, the intermediate body 52 is required as one of the module components, and at the same time, an increase in thermal resistance due to the intermediate body 52 is regarded as a problem.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to relieve stress during mounting without interposing an intermediate between the laser array and the cooling body. It is to provide a laser module.

The laser module according to the present invention includes:
A laser array having a plurality of light emitting portions;
A cooling body having a laser mounting area on which the laser array is mounted,
In the laser mounting region of the cooling body, a plurality of groove portions are provided side by side in the same direction as the plurality of light emitting portions, and each groove portion has a material having a smaller linear expansion coefficient than the constituent material of the cooling body Is embedded,
The laser array is located on the plurality of grooves and mounted on the cooling body.

  In the laser module according to the present invention, a plurality of groove portions are provided in the laser mounting region of the cooling body, and a material having a smaller linear expansion coefficient than that of the constituent material of the cooling body is embedded in each groove portion. The linear expansion coefficient becomes smaller. For this reason, the stress relaxation at the time of mounting is achieved by mounting the laser array on the cooling body located on the plurality of grooves.

  According to the laser module of the present invention, a plurality of grooves are provided in the laser mounting region of the cooling body, and a material having a smaller linear expansion coefficient than that of the constituent material of the cooling body is embedded in each of the groove portions. The effective linear expansion coefficient can be reduced. Therefore, the stress at the time of mounting can be relieved without interposing an intermediate body between the laser array and the cooling body. As a result, the thermal resistance between the laser array and the cooling body can be greatly reduced as compared with the case where an intermediate is interposed. For this reason, it becomes possible to implement | achieve the laser module excellent in exhaust heat efficiency.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the technical scope of the present invention is not limited to the embodiments described below, and various modifications and improvements have been made within the scope of deriving specific effects obtained by the constituent requirements of the invention and combinations thereof. Also includes form.

  FIG. 1 is a plan view showing the configuration of a laser module according to an embodiment of the present invention, and FIG. 2 is a front view showing the configuration of the laser module. 3 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 4 is a cross-sectional view taken along the line BB in FIG. The illustrated laser module 10 is largely configured to include a laser array 11 and a cooling body 12. Generally, the cooling body 12 is called a heat sink.

  In this specification, due to the configuration of the laser module 10, the direction parallel to the longitudinal direction of the laser array 11 is the X-axis direction, the direction parallel to the short direction of the laser array 11 is the Y-axis direction, and the thickness direction of the laser array 11. The direction parallel to is defined as the Z-axis direction. The X-axis direction, the Y-axis direction, and the Z-axis direction are triaxial directions that are orthogonal to each other. The orthogonal three-axis directions of the X-axis direction, the Y-axis direction, and the Z-axis direction defined here are used as needed to specify the structure and positional relationship of each part throughout the laser module 10. The X-axis direction is divided into an X direction and a −X direction depending on the direction. Similarly, the Y-axis direction is divided into a Y direction and a −Y direction, and the Z-axis direction is divided into a Z direction and a −Z direction.

  The laser array 11 is configured by using a compound semiconductor material such as GaAs, for example, and is formed in a rod-like chip shape as a whole. The dimension (longitudinal dimension) of the laser array 11 in the X-axis direction is set to, for example, 10 mm, and the dimension (short dimension) of the laser array 11 in the Y-axis direction is set to, for example, about 2 mm. The laser array 11 integrally has a plurality of semiconductor laser elements (not shown) arranged in a one-dimensional manner. The plurality of semiconductor laser elements are arranged at a constant pitch in the X-axis direction that is the longitudinal direction of the laser array 11. Therefore, in the arrangement direction (alignment direction) of the semiconductor laser elements, a plurality of light emitting portions (laser light emitting portions) 13 are arranged in the X-axis direction at the same pitch as the plurality of semiconductor laser elements.

  Each light emitting unit 13 is arranged in a horizontal row on one end face (hereinafter referred to as “front end face”) 14 in the Y-axis direction. For this reason, when the laser array 11 is driven, laser light is emitted in the Y direction from the light emitting units 13 arranged in the X-axis direction. Each semiconductor laser element constituting the laser array 11 has a laser resonator inside the element, and the resonator length direction coincides with the Y-axis direction.

  A plurality of electrodes 15 are provided in a 1: 1 relationship with a plurality of semiconductor laser elements on the upper surface of the laser array 11, and a plurality of semiconductor laser elements are also disposed on the lower surface of the laser array 11 on the opposite side (back side). A plurality of electrodes 16 are provided in a 1: 1 relationship. Of the electrodes 15 and 16, the electrode 15 is an n (negative electrode) side electrode, and the electrode 16 is a p (positive electrode) side electrode. In that case, the n-side electrode 15 is formed, for example, by laminating a gold (Au) layer, an alloy layer of gold (Au) and germanium (Ge), and a gold (Au) layer in this order from the semiconductor substrate side. The electrode 16 is formed by laminating, for example, a titanium (Ti) layer, a platinum (Pt) layer, and a gold (Au) layer in this order from the semiconductor substrate side. The laser array 11 is mounted such that the p-side electrode 16 faces the cooling body 12. The plurality of light emitting units 13 described above are provided near (near) the p-side electrode 16 in the Z-axis direction.

  In the X-axis direction, the arrangement pitch of the plurality of semiconductor laser elements constituting the laser array 11 and the arrangement pitch of the plurality of light emitting units 13, the plurality of electrodes 15 and the plurality of electrodes 16 corresponding to the plurality of semiconductor laser elements are as follows: Are set to the same pitch. Therefore, for example, assuming that a plurality of semiconductor laser elements are arranged at a pitch of 400 μm in the longitudinal direction (X-axis direction) of the laser array 11, a plurality of light emitting units 13, a plurality of electrodes 15, and a plurality of semiconductor laser elements are arranged at the same pitch. The electrodes 16 are arranged in the longitudinal direction of the laser array 11. The center positions of the light emitting part 13, the electrode 15 and the electrode 16 of these semiconductor laser elements are set to be the same position in the X-axis direction.

  The laser array 11 is mounted on the upper surface 18 of the cooling body 12. The laser array 11 is joined to the cooling body 12 by a solder layer 17. When soldering the laser array 11 to the cooling body 12, the solder layer 17 is formed by heating and melting a solder material to a predetermined temperature (joining temperature) and then solidifying by a temperature drop. The solder layer 17 is formed on the upper surface 18 of the cooling body 12 so as to protrude outward (X direction, −X direction, −Y direction) from both ends in the longitudinal direction of the laser array 11 and one end in the lateral direction. Has been. It is desirable to form the solder layer 17 as thin as possible so that the thermal resistance between the laser array 11 and the cooling body 12 is reduced.

  The cooling body 12 has high thermal conductivity in terms of heat, and has high conductivity in terms of electricity. The cooling body 12 is configured using, for example, a metal material such as copper, and is formed in a square columnar block shape as a whole. The cooling body 12 is formed to have a larger outer dimension (volume) than the laser array 11. That is, the dimension (width dimension) of the cooling body 12 in the X-axis direction is set larger than the longitudinal dimension of the laser array 11, and the dimension (depth dimension) of the cooling body 12 in the Y-axis direction is short of the laser array 11. It is set larger than the dimension. Further, the dimension (thickness dimension) of the cooling body 12 in the Z-axis direction is set larger than the thickness dimension of the laser array 11.

  The thermal conductivity of the cooling body 12 is a characteristic necessary for efficiently releasing the heat generated in the laser array 11 to the cooling body 12 side and maintaining the driving temperature of the laser array 11 below a predetermined temperature. The conductivity of the cooling body 12 is a characteristic that is necessary to keep the electrical resistance low when supplying current to the laser array 11 through the cooling body 12, for example.

  The upper surface 18 of the cooling body 12 is a surface on which the laser array 11 is mounted (hereinafter referred to as “laser mounting surface”), and the lower surface 19 of the cooling body 12 is the entire laser module 10 including the cooling body 12. This is a reference plane for mounting on a base member (not shown) (hereinafter referred to as “mounting reference plane”).

  In the laser mounting surface 18 of the cooling body 12, there is an area where the laser array 11 is actually mounted (hereinafter referred to as “laser mounting area”). The laser mounting area is an area defined corresponding to the outer dimensions of the laser array 11. For example, if the longitudinal dimension of the laser array 11 is “L1” and the short dimension is “L2”, the laser mounting area is “(L1 + α) × (L2 + β)” within the laser mounting surface 18 of the cooling body 12. It is prescribed by the size of. α and β are positive values set in consideration of the dimensional tolerance of the laser array 11 and the allowable dimension for alignment.

  The laser mounting area is set close to the Y direction end within the laser mounting surface 18. A plurality of groove portions 21 are provided in the laser mounting area, and the laser array 11 is mounted on the laser mounting surface 18 of the cooling body 12 so as to be positioned on the plurality of groove portions 21. Each groove portion 21 is formed in a concave shape when viewed from the Y-axis direction. Each groove portion 21 is embedded with a material 22 having a lower linear expansion coefficient than the constituent material (main material) of the cooling body 12. Specifically, for example, when the cooling body 12 is made of copper, the groove portion 21 is embedded with a material 22 having a lower linear expansion coefficient. The material 22 for embedding the groove portion 21 is preferably a material having a sufficiently low linear expansion coefficient compared to the constituent material of the cooling body 12 (for example, a material having a linear expansion coefficient of ½ or less of copper). In order to embed the material, a high bondability with the cooling body 12 is required so as to form an integral structure with the cooling body 12 in a state where the material is solidified (cured).

  For this reason, in the embodiment of the present invention, as a material having a lower linear expansion coefficient than that of the constituent material of the cooling body 12, the groove portion is formed of the composite material 22 obtained by mixing the SiC particulate material 23 with the AuSn-based solder material 24. A structure in which 21 is embedded is adopted. The AuSn-based solder material has good bondability with copper used as a constituent material of the cooling body 12. For this reason, the embedded portion of the groove portion 21 can be integrated with the cooling body 12 by embedding the groove portion 21 using the composite material 22 obtained by mixing the SiC particulate material 23 with the AuSn-based solder material 24. it can. In this case, for example, when Au20Sn is used as the AuSn solder material, the linear expansion coefficient of SiC is 3.7 ppm / K, whereas the linear expansion coefficient of Au20Sn is 16.2 ppm / K. For this reason, as the composition of the composite material 22, when the mixing ratio of SiC is relatively high, the linear expansion coefficient of the composite material 22 decreases, and when the mixing ratio of SiC is low, the linear expansion coefficient of the composite material 22 increases. . Therefore, the linear expansion coefficient of the composite material 22 can be adjusted using the mixing ratio of the particulate material 23 as a parameter.

  The plurality of groove portions 21 are provided on the element mounting surface 18 of the cooling body 12 in a state of being aligned in the X-axis direction. In addition, each groove portion 21 is provided in a portion excluding the portion immediately below the light emitting portion 13 in the X-axis direction. Therefore, the portion of the laser array 11 except for the portion immediately below the light emitting portion 13 has a structure in which the groove portion 21 is embedded with the composite material 22 as can be seen in the cross-sectional view of FIG. Bonded by a solder layer 17. On the other hand, the portion immediately below the light emitting portion 13 of the laser array 11 has a structure in which the constituent material of the cooling body 12 is present as it is, as can be seen from the sectional view of FIG. Bonded by a solder layer 17.

  The dimension (groove width) W in the X-axis direction of the groove portion 21 is, for example, a condition in which the width of the light-emitting portion 13 is 60 μm and the pitch of the light-emitting portions 13 is smaller than the pitch of the light-emitting portions 13 adjacent in the X-axis direction. It is set to 300 μm when 400 μm, and the dimension (depth dimension) L in the Y-axis direction of the groove 21 is larger than the short dimension of the laser array 11. For example, the short dimension of the laser array 11 is At 1 mm, it is set to 1.5 mm. Further, the dimension (groove depth) D in the Z-axis direction of the groove 21 is set to, for example, 100 μm, and the pitch (groove pitch) P of the grooves 21 adjacent in the X-axis direction is the arrangement of the semiconductor laser elements described above. The same pitch as the pitch is set. However, the center position of the light emitting portion 13 of the semiconductor laser element and the center position of the groove portion 21 are shifted by 0.5 pitch in the X-axis direction.

  Then, the manufacturing method of the laser module which concerns on embodiment of this invention is demonstrated. First, as shown in the plan view of FIG. 5 and the front view of FIG. 6, a plurality of grooves 21 are formed on the upper surface 18 of the cooling body 12 having a quadrangular prism block shape in a line in the X-axis direction. As a method for forming the groove 21, for example, machining or etching can be used. At this time, the depth dimension L of each groove portion 21 is set to be longer than the cavity length of the semiconductor laser elements constituting the laser array 11 (short dimension of the laser array 11). 7 is a cross-sectional view taken along the line CC of FIG. As can be seen from FIG. 7, the adjacent groove portions 21 in the X-axis direction are partitioned by a wall portion 25 made of the constituent material of the cooling body 12. The wall thickness T is set to be larger than the dimension (light emission width) of the light emitting unit 13 in the X-axis direction. For example, if the width of the light emitting portion 13 is 60 μm, the wall thickness T of the wall portion 25 is set to, for example, 100 μm so as to be larger than the light emitting width.

  Next, as shown in the plan view of FIG. 8 and the front view of FIG. 9, each of the groove portions 21 is filled with a composite material 22 generated by mixing the particulate material 23 with the solder material 24 in advance, and then soldered by heating. All the grooves 21 are filled with the composite material 22 by melting the material 24 and solidifying the solder material 24 by a temperature drop (such as natural cooling). When Au20Sn is used for the solder material 24, the solder material 24 is melted by heating to a temperature equal to or higher than its melting point (280 ° C.). In this case, it is desirable that the upper surface of the composite material 22 in which the groove portion 21 is embedded is formed so as to be flush with the laser mounting surface 18 so that the laser mounting region of the cooling body 12 is not uneven. Further, when the width W of the groove 21 is narrow, the molten composite material 22 does not flow out of the groove 21 due to a capillary phenomenon. When the groove portion 21 is wide, the composite melted by applying and curing a solder resist on the front portion of the cooling body 12 or pressing a film-like solder resist, a heat-resistant polyimide film or the like against the front portion of the cooling body 12. It is necessary to prevent the material 22 from flowing out of the groove 21.

  Thereafter, the laser array 11 is soldered to the laser mounting surface 18 of the cooling body 12 using a solder material (material of the solder layer 17) having a melting point lower than that of the solder material 24 in the laser mounting area of the cooling body 12. At this time, as shown in FIG. 2, the laser array 11 and the cooling body 12 are aligned in the X-axis direction so that the groove 21 is not disposed immediately below the light emitting portion 13 of the laser array 11, and the laser array 11 The laser array 11 and the cooling body 12 are aligned in the Y-axis direction so that the front end face 14 is flush with the Y-direction end face of the cooling body 12. In solder joining, the laser array 11 is solder-joined to the cooling body 12 while the composite material 22 is solidified by setting the heating temperature to a temperature lower than the melting point of the solder material 24. As a solder material used as the material of the solder layer 17, for example, a low melting point solder material mainly containing In (indium) can be used.

  In the laser module 10 according to the embodiment of the present invention, a plurality of grooves 21 are formed in the laser mounting region of the cooling body 12, and the plurality of grooves 21 are composite materials having a lower linear expansion coefficient than the constituent material of the cooling body 12. 22 is embedded. For this reason, the effective linear expansion coefficient in the laser mounting area (hereinafter referred to as “effective linear expansion coefficient”) is smaller than when the groove 21 is not provided in the laser mounting area of the cooling body 12. The effective linear expansion coefficient in the laser mounting region varies depending on the mixing ratio of the particulate material 23 in the composite material 22 and the dimensions (particularly, the groove width) of the groove 21.

  FIG. 10 is a diagram showing the correlation between the mixing ratio of the particulate material and the effective linear expansion coefficient in the laser mounting region. In the figure, the curve indicated by □ indicates the result of simulation under the condition of the groove width of 200 μm and the groove pitch of 400 μm, and the curve indicated by Δ indicates the result of simulation under the condition of the groove width of 300 μm and the groove pitch of 400 μm. Is shown. In this simulation, it is assumed that the groove 21 is embedded with a composite material 22 using SiC for the particulate material 23 and Au20Sn for the solder material 24. With reference to this simulation result, for example, by setting the groove width of the groove 21 to 300 μm and the mixing ratio of the SiC particulate material 23 to about 50%, the effective linear expansion coefficient of the laser mounting region is set to 1 of copper. Can be reduced to about 8 ppm / K corresponding to / 2.

  Thus, even when the laser array 11 is directly mounted on the cooling body 12 without using an intermediate body called a submount, the plurality of grooves 21 provided in the laser mounting area of the cooling body 12 are embedded with the composite material 22. Thus, by reducing the effective linear expansion coefficient in the laser mounting region, it is possible to relieve stress during mounting. For this reason, compared with the case where an intermediate body is used, the thermal resistance between the laser array 11 and the cooling body 12 is significantly reduced. Therefore, heat can be efficiently released from the laser array 11 to the cooling body 12. Further, since it is not necessary to use an intermediate body, when current is supplied to the laser array 11 through the cooling body 12, it is possible to avoid generation of Joule heat in the intermediate body and reduce power consumption.

  Further, since the groove portion 21 is provided in a portion of the laser array 11 excluding the portion immediately below the light emitting portion 13, the wall made of the constituent material of the cooling body 12, particularly immediately below the light emitting portion 13 where the heat generation during laser driving becomes significant. There is a portion 25 (see FIG. 7), and the heat of the light emitting portion 13 can be quickly released to the cooling body 12 through the wall portion 25. For this reason, the exhaust heat efficiency from the laser array 11 to the cooling body 12 can be further improved.

  In the embodiment of the present invention, SiC is used for the particulate material 23 to be mixed with the solder material 24 in obtaining the composite material 22. However, the present invention is not limited to this. For example, invar material or silicon oxide (SiO 2) Diamond or the like can also be used. Furthermore, instead of the solder material 24, an epoxy resin may be used to form the composite material. In that case, the groove part 21 mentioned above will be embedded by the composite material formed by mixing the particulate material 23 with a smaller linear expansion coefficient than the constituent material of the cooling body 12 in an epoxy resin.

  In the embodiment of the present invention, the laser array 11 is soldered to the cooling body 12 using a low melting point solder material different from the solder material 24 used for embedding the groove 21. It is also possible to solder the laser array 11 to the cooling body 12 using the solder material 24 described above. Specifically, for example, after forming the plurality of grooves 21 in the cooling body 12, the laser mounting is performed so that the groove 21 is slightly raised from the laser mounting surface 18 of the cooling body 12 at the stage of filling the respective grooves 21 with the composite material 22. The region is covered with the composite material 22, the laser array 11 is placed thereon and heated, and the solder layer 17 made of the same material as the composite material 22 is used to solder the laser array 11 to the cooling body 12. do it.

It is a top view which shows the structure of the laser module which concerns on embodiment of this invention. It is a front view which shows the structure of the laser module which concerns on embodiment of this invention. It is AA arrow sectional drawing of FIG. It is BB arrow sectional drawing of FIG. It is a top view which shows the state which formed the groove part in the cooling body in the manufacturing process of the laser module. It is a front view which shows the state which formed the groove part in the cooling body in the manufacturing process of the laser module. It is CC sectional view taken on the line of FIG. It is a top view which shows the state which embedded the material in the groove | channel of the cooling body in the manufacturing process of the laser module. It is a front view which shows the state which embedded the material in the groove | channel of the cooling body in the manufacturing process of the laser module. It is a figure which shows the correlation of the mixing ratio of a particulate material, and the effective linear expansion coefficient of a laser mounting area | region. It is a front view which shows the structure of the conventional laser module.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Laser module, 11 ... Laser array, 12 ... Cooling body, 13 ... Light emission part, 18 ... Laser mounting surface, 21 ... Groove part, 22 ... Composite material, 23 ... Particulate material, 24 ... Solder material

Claims (4)

A laser array having a plurality of light emitting portions;
A cooling body having a laser mounting area on which the laser array is mounted,
In the laser mounting region of the cooling body, a plurality of groove portions are provided side by side in the same direction as the plurality of light emitting portions, and each groove portion has a material having a smaller linear expansion coefficient than the constituent material of the cooling body Is embedded,
The laser array is mounted on the cooling body and positioned on the plurality of grooves. The laser module according to claim 1, wherein the groove is provided in a portion except for a portion directly below the light emitting portion of the laser array. The laser module according to claim 1, wherein the groove is embedded with a composite material obtained by mixing a particulate material having a smaller linear expansion coefficient than the constituent material of the cooling body with a solder material. The laser module according to claim 1, wherein the groove is embedded with a composite material obtained by mixing a particulate material having a smaller linear expansion coefficient than that of the constituent material of the cooling body with an epoxy resin.

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