Laser diode array and method for manufacturing a laser diode array

Abstract

A laser diode arrangement (1) comprises a laser diode chip (2) and a thin-film sensor element (3) for measuring a temperature, wherein the laser diode chip (2) is mounted on the sensor element (3).

Description

The present invention relates to a laser diode arrangement having a laser diode and a sensor element for measuring a temperature.The transmission of data in the form of light is becoming increasingly important for optical communication systems, for example 5 g networks. The transmission is achieved with the aid of laser diodes. The reliability of the transfer is strongly dependent on accurate temperature control. In particular, a constant temperature of the laser diode is necessary in order to enable wavelength stabilization during transmission through an optical fiber.Higher integration density and smaller package sizes make it difficult to achieve constant temperatures for laser diodes. A decisive factor is the accurate measurement of the temperature.In known laser diode arrangements, a laser diode chip is mounted on a chip carrier which in turn is mounted on a larger base carrier which also serves as a heat sink. A thermoelectric cooler is mounted on a TO (Transistor Outline) package head adjacent to a sensor element disposed between the laser diode chip and the thermoelectric cooler. The sensor element can be placed directly on the thermoelectric cooler, but can also be arranged on the base carrier. In both cases, the sensor element cannot measure the temperature of the laser diode chip directly, but only the temperature in the environment.Patent application DE 10 2020 122 923 A1, the content of which is incorporated herein by reference, describes a sensor element for temperature measurement with a thin-film NTC thermistor.It is an object of the present invention to provide an improved laser diode array.According to one aspect, a laser diode arrangement has a laser diode chip and a thin-film sensor element for measuring a temperature of the laser diode chip. The laser diode chip is arranged on the sensor element.By arranging the laser diode chip on the sensor element, in particular directly on the sensor element, the accuracy of the temperature measurement can be improved compared to an arrangement in which the sensor element is located next to the laser diode chip or even at a distance therefrom.The sensor element may have the dual function of a temperature sensor and heat dissipation for the laser diode chip. The sensor element may be arranged on a carrier, such that the sensor element is located between the laser diode chip and the carrier.The sensor element may replace a conventional chip carrier, for example. It is also possible for the sensor element to be provided in addition to a conventional chip carrier. In this case, the sensor element is arranged between the laser diode chip and the chip carrier.In both cases, a larger base support may be present. The contacts of the sensor element and / or of the laser diode chip can be electrically connected to the base carrier via wire bonds.The sensor element may have the same lateral dimensions as the laser diode chip. The sensor element may have a thickness of 500 μm or less. More specifically, the sensor element may have a thickness of 100 μm or less, or even 50 μm or less.The sensor element can have an electrically insulating substrate, a functional layer having a material with a temperature-dependent electrical resistance, wherein the functional layer is arranged on the substrate, and at least two electrodes, wherein the electrodes are formed on or under the functional layer. The electrodes may be formed at the same height of the sensor element. The electrodes are configured to be interlocked. In particular, the electrodes can have interdigitated electrode fingers.The sensor element may have two contact pads. The contact pads may be directly connected to the electrodes. The contact pads may point in the direction of the laser diode chip or in the direction of a carrier. If the contact areas point in the direction of a carrier, the sensor element is referred to as flip-chip mounted.In general, the thin-film sensor element can have all the features of the thin-film sensor element disclosed in DE 10 2020 122 923 A1.The laser diode chip can be connected to one of the contact pads via a conductor track on the sensor element. The conductive path may include a pad on which the laser diode chip is placed and a connection path connecting the pad to one of the contact pads.In particular, the conductor track can connect a cathode of the laser diode chip to a cathode contact pad.The laser diode chip may also be directly electrically connected to a base carrier by a wire bond. In this case, the respective contacts of the laser diode chip and the sensor element may be kept separated.If the sensor element is arranged on a chip carrier, which in turn is arranged on a larger base carrier, longer wire bonds are required. Alternatively, the laser diode chip can be electrically connected to a chip carrier by a wire bond and the chip can be electrically connected to a base carrier by a further wire bond. In this case, the chip carrier may have a larger lateral dimension than the sensor element to enable connection by wire bonding.The laser diode chip may be mounted on the sensor element with a conductive paste. Alternatively, the laser diode chip may be mounted on the sensor element by a sintered material. It is also possible to attach the laser diode chip by soldering, for example by using AuSn solder. Other types of mounting are also possible as long as the temperature during mounting is not too high, so that the laser diode chip and the sensitive region of the sensor element are not damaged.The sensor element in turn can be attached to the carrier with a conductive paste, a soldering material or a sintering material.The sensor element may be mounted on the carrier by flip-chip technology. In this case, the contact pads of the sensor element point in the direction of the carrier. The contact pads may be connected to metallizations on the carrier, for example, by soldering bumps or by sintering. It is also possible for the laser diode chip to be mounted on the sensor element in flip-chip technology. In this case, two contacts of the laser diode chip point to the sensor element.According to a further aspect, a method for producing a laser diode arrangement comprises providing a laser diode chip and a thin-film sensor element for measuring a temperature. The laser diode chip is mounted on the sensor element. The laser diode array may include all structural and functional features of the laser diode array as previously described.In a further method step, the thin-film sensor element can be attached to a carrier, wherein this method step can take place before or after the laser diode chip is attached to the thin-film sensor element.The present disclosure encompasses several aspects of an invention. Each feature described with respect to one of the aspects is also disclosed herein with respect to the other aspect, even if the respective feature is not expressly mentioned in connection with the specific aspect.Other features, refinements, and conveniences will become apparent from the following description of the exemplary embodiments in conjunction with the figures. FIG. 1A shows an embodiment of a laser diode arrangement in a schematic cross-sectional view, FIG. 1B shows the laser diode arrangement from FIG. 1A in a schematic plan view, FIG. 2A shows a thin-film sensor element in a schematic cross-sectional view, FIG. 2B shows the thin-film sensor element from FIG. 2A in an exploded perspective view, FIG. 3A shows a further embodiment of a laser diode arrangement in a schematic cross-sectional view, FIG. 3B shows the laser diode arrangement from FIG. 3A in a schematic plan view, FIG. 4A shows a further embodiment of a laser diode arrangement in a schematic cross-sectional view, FIG. 4B shows the laser diode arrangement from FIG. 4A in a schematic plan view, FIG. 5 shows a further embodiment of a laser diode arrangement in a schematic cross-sectional view, FIG. 6 shows a further embodiment of a laser diode arrangement in a schematic cross-sectional view.In the figures, elements of the same structure and / or functionality may be denoted by the same reference numerals. It is understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.FIG. 1A shows a laser diode arrangement 1 with a laser diode chip 2 in a schematic cross-sectional view. FIG. 1B shows the laser diode arrangement 1 in a plan view.The type of laser diode chip 2 may depend on the respective application. For example, it may be a vertical cavity surface emission laser (VCSEL) that is most commonly used for short-range multimode applications, a Fabry-Perot laser (FB) suitable for short to medium transmission range applications below 10Gbit / s, or a distributed feedback laser (DFB) and an electro-absorption modulation laser (EM) that are ideally suited for high speed medium to long range data rates, e.g., for 50Gbit / s and more applications.The laser diode chip 2 is mounted on a sensor element 3 for measuring the temperature of the laser diode chip 2. The sensor element 3 is a thin film NTC thermistor element (TF-NTC). A general configuration of a thin film sensor element 3 is illustrated in FIGS. 2A and 2B (see detailed description below).The laser diode chip 2 is in direct contact with the sensor element 3, which enables accurate detection of temperature changes with a short response time. In addition, the sensor element 3 also functions as a carrier and heat sink for the laser diode chip 2.The sensor element 3 is mounted on a larger base support 4. The connections from the laser diode chip 2 and the sensor element 3 to the base carrier 4 are produced by wire bonds 5 a, 5 b, 5 c. The wire bonds 5 a, 5 b, 5 care, for example, gold wire bonds.The first contact pad 6 ais connected via a first wire bond 5 ato a first metallization 27 aon the base carrier 4. The second contact pad 6 bis connected via a second wire bond 5 bto a second metallization 27 bon the base carrier 4. The first contact pad 6 amay be the cathode and the second contact pad 6 bmay be the anode of the sensor element 3. An upper contact 32 of the laser diode chip 2 is connected via a third wire bond 5 cto a third metallization 27 con the base carrier 4. The upper contact can be the anode of the laser diode chip 2.The cathodes of the thin film sensor element 3 and the laser diode chip 2 are shared, thereby reducing the need for an additional contact pad in the package. The common cathode, i.e. the first contact pad 6 ato which the lower contact 31 of the laser diode chip 2 is connected, is wire-bonded to the first metallization 27 aon the base carrier 4. However, the anodes of the sensor element 3 and the laser diode chip 2 are separated from each other. The different current and voltage requirements of the laser diode chip 2 and of the sensor element 3 can thus be fulfilled.The sensor element 3 may replace a conventional carrier and a heat sink. The sensor element 3 can have the same dimensions as a conventional carrier in a laser diode arrangement. The sensor element 3 may have similar dimensions as the laser diode chip 2, wherein the lateral dimension is larger due to contact pads 6 a, 6 bon an upper side 22 of the sensor element 3.The length and width of the contact pads 6 a, 6 bare, for example, in the range from 400 x 1000 μm 2 up to 20 x 50 μm 2, while the thickness is between 1 μm and 0.01 μm.In particular, the length and width of the contact pads 6 a, 6 bmay be in the range of 250 x 700 μm 2 up to 50 x 150 μm 2 while the thickness may be 0.5 μm or less. In one embodiment, length, width, and thickness are 125 μm, 500 μm, and 0.25 μm. The contact pads 6 a, 6 bmay include a first layer of Ti and a second layer of Au overlying it. The first layer may have a thickness of 0.05 μm and the second layer may have a thickness of 0.2 μm. The thickness of the individual contact pads 6 a, 6 bis the part of the contact pad 6 a, 6 bprotruding from the through hole 23 of the protection layer 21.A connection between the laser diode chip 2 and the sensor element 3 establishes an electrical and thermal contact. The sensor element 3 has a centered temperature sensitive surface on which the laser diode chip 2 is placed.The cathode of the laser diode chip 2 and the cathode (first contact pad 6 a) of the underlying sensor element 3 are electrically connected by a conductor track 7. The material forming the conductive track 7 is applied to a protective layer 21 of the sensor element 3. The conductor track 7 has one or more electrically conductive layers.For the conductive path 7, materials such as Au, Ag, Pt, Cu, Ni, Cr, Ti, Ta, W, Al, Pd, or other metals or compositions thereof may be used. The conductive path 7 may include a first layer of Ti of 0.05 μm and a second layer of Au of 0.2 μm above. The thickness of the conductive path 7 may be between 1 μm and 0.01 μm, and preferably 0.5 μm or less. As a specific example, the conductive path 7 may have a thickness of 0.25 μm, for example.The conductor track 7 has two sections. A first section 8 serves as a contact surface for the laser diode chip 2.The first portion 8 may have dimensions of 260 μm x 200 μm, for example. The lateral dimensions of the first portion 8 and the laser diode chip 2 may be the same. The second portion 9 is a connection path that connects the first portion 8 to the first contact pad 6 a. The connection path may have a width and length of 50 μm x 50 μm. One dimension may be substantially smaller than the other dimension.The maximum width of the conductor track 7 is equal to the size of the sensor element 3, while the maximum length is less than the distance between the two contact pads 6 a, 6 b, so that the conductor track 7 is separated from the second contact pad 6 bto prevent a short circuit. The free space between the conductor track 7 and the second contact pad 6 bmay have a length of at least 5 μm and extend over the entire width of the second contact pad 6 b.The minimum width of the conductor track 7 is 5 μm and the minimum length is the distance between the contact pads 6 a, 6 band the closest edge of the sensitive region of the sensor element 3.The laser diode chip 2 is connected to the conductive path 7 by a conductive material 24, which may be a conductive paste.A distance of at least 1 / 3 of the height of the laser diode chip 2 should preferably be maintained between the first section 8 (contact surface) and both sides of the contact pads 6 a, 6 bto prevent overflow of the conductive material 24 during the mounting of the laser diode chip 2. For example, in the case of a laser diode chip 2 having a height of 100 μm, a distance of 100 μm is maintained between the first section 8 (contact surface) and the two contact pads 6 a, 6 bof the sensor element 3 on both sides. The laser diode chip 2 can also have a distance of approximately 100 μm from the lateral edges of the sensor element 3 in the width direction.The sensor element 3 provides the function of a conventional NTC element, which is usually arranged at a lateral distance from the laser diode chip 2, e.g. on the base carrier 4 or a thermoelectric cooler (not shown). In such a conventional arrangement, the sensor element 3 cannot directly measure the temperature of the laser diode chip 2, but measures only the temperature changes in the vicinity thereof. By the direct measurement made possible with the arrangement shown, the temperature control is improved and a constant temperature can be maintained more accurately.The laser diode array 1 can be packaged using various techniques. The most common housings are the TO (Transistor Outline) housing and the 14-pin butterfly housing. In a TO package, the number of pins indicates which components are inside the package. The laser diode arrangement 1 can contain a thermo-electric cooler. The thermoelectric cooler may be placed on the TO package and the base bracket and other fasteners are mounted on the thermoelectric cooler.The laser diode arrangement 1 shown can be a 5-pin arrangement, wherein two pins are provided for the anodes of the laser diode chip 2 and of the sensor element 3, one pin is provided for the common cathode of the laser diode chip 2 and of the sensor element 3 and two pins are provided for the thermoelectric cooler. Without thermoelectric cooling, the arrangement 1 is a 3-pin arrangement.FIG. 2A shows a thin-film NTC sensor element 3 that can be used in the laser diode arrangement 1 of FIGS. 1A and 1B. FIG. 2B shows the thin-film NTC sensor element 3 in an exploded illustration.The sensor element 3 includes an insulating substrate 10. The substrate 10 comprises a main substrate body 11 which has good thermal conductivity and thus serves as a heat sink for the laser diode chip 2. The main substrate body 11 includes, for example, AlN, Si3N4, Al2O3, or other ceramics.The main substrate body 11 has an upper side 12 and a lower side 13, and an insulating film 14 including, for example, SiO2is provided on the upper side 12. The insulating layer 14 is a protective layer for the main substrate body 11.The sensor element 3 has two electrodes 15 a, 15 b. The electrodes 15a, 15b are directly disposed on the insulating layer 14 of the substrate 10. The electrodes 15a, 15b are formed of thin metal layers.The electrodes 15a, 15b are formed as interdigital thin film electrodes. Specifically, the electrodes 15 a, 15 bhave an extended end portion 16 and an electrode finger portion 17, respectively. The electrode finger portion 17 is formed in a central portion of the substrate 10. The electrode fingers 17 extend from the flat end section 16. the two electrodes 15 a, 15 bengage in the region of the electrode fingers 17 in the central region of the substrate 10 and form an interdigital structure there. The electrodes 15 a, 15 bare arranged at the same height in the sensor element 3. At this height, the sensor element 3 can have only electrodes 15 a, 15 b, but no further electrode layers.The sensor element 3 has a functional layer 18 with an upper side 19 and an underside 20. The functional layer 18 is an NTC thin film. The functional layer 18 only partially covers the insulating layer 14 on the upper side 12 of the main substrate body 11. The functional layer 18 is applied at least partially on the electrodes 15 a, 15 b. The electrodes 15 a, 15 bare formed between the substrate 10 and the functional layer 18, in particular the underside 20 of the functional layer 18. The functional layer 18 is arranged directly on the electrode fingers 17.Each of the contact pads 6 a, 6 bof the sensor element 3 is connected to one of the electrodes 15 a, 15 b. The contact pads 6 a, 6 bare arranged at the respective end section 16 of the electrodes 15 a, 15 b.The sensor element 3 has a protective layer 21. The protective layer 21 completely covers an upper side 22 of the sensor element 3 except for the through holes 23 for the contact pads 6 a, 6 b. The contact pads 6 a, 6 bprotrude beyond an upper side 22 of the protective layer 21 for the purpose of electrically contacting the sensor element 3.For example, the total length l and the width b of the thin film sensor element 3 may be in the range of 1000 x 1000 μm 2 to 50 x 50 μm 2. The thickness d may be, for example, 500 μm or less. In particular, the thickness may be 150 μm or less. The thickness d can be measured without a part of the contact surfaces 6 a, 6 bprotruding from a protective layer of the sensor element 3. Specifically, the sensor element 3 may have a length and width of 700 x 700 μm 2 to 150 x 150 μm 2 with a thickness d of 300 μm or less. An example is a length l of 650 μm, a width b of 550 μm, and a thickness d of 280 μm.The sensor element 3 can be produced by the following method. The main substrate body 11 is formed. A material of the main substrate body 11 may include Si, SiC, or glass. Alternatively, the material can also comprise AlN or Al2O3. The main substrate body 11 has an upper side 12 and a lower side 13.Two electrodes 15a, 15b are formed on the substrate 10. The application can be effected by a PVD method ("physical vapor deposition"), a CVD method ("chemical vapor deposition") or galvanically. In a further process step, the electrodes 15 a, 15 bmay be structured. The electrodes 15 a, 15 bengage with one another in the form of interdigital structures. The electrodes 15 a, 15 bmay be formed to be spaced apart from an edge portion of the substrate 10.The functional layer 18 is applied to a partial region of the electrodes 15 a, 15 b, for example by sputtering on a functional material. Specifically, the functional layer 18 is formed to be spaced apart from the edge portion of the insulating substrate 10 and formed on the finger interdigital structures portion of the electrodes 15 a, 15 b. The functional layer 18 can be deposited as a full-surface thin film and structured in a further process step, for example by means of lithography.The functional material may comprise an NTC ceramic based on an oxidic material having a perovskite or spinel structure. Alternatively, the functional material can also be based on a carbide or nitride material or on vanadium oxide or SiC.After deposition, the functional layer 18 has not yet crystallized. The functional layer 18 is then sintered to obtain the NTC properties. The sintering process can be carried out at temperatures of up to 1000° C.It is also possible for the functional layer 18 to be initially formed on a partial surface of the substrate 10 and for the electrodes 15 a, 15 bto then be formed on an upper side of the functional layer 18.The protective layer 21 is applied to the upper side 19 of the functional layer 18. The protective layer 21 completely covers the upper side 22 except for two through holes 23. The subareas are arranged above the extended end sections 16 of the electrodes 15 a, 15 b, to which the contact pads 6 a, 6 bcan be applied in a subsequent process step. For structuring, the protective layer 21 can either be applied over the whole area and the free subareas produced by a subsequent process such as lithography or laser structuring or can be structured directly by using a mask during the deposition process.The contact pads 6 a, 6 bare formed through the protective layer 21 and serve for the electrical contacting of the sensor element 3. Each of the contact pads 6 a, 6 bcontacts an extended end section 16.The contact pads 6 a, 6 bmay include Cu, Au, Ni, Cr, Ag, Ti, W, Pd or Pt as material. In a specific example, the contact pads 6 a, 6 bare formed of Cu. Preferably, the contact pads 6 a, 6 bhave a thickness of >5 μm. Alternatively to the contact pads 6 a, 6 b, bumps or thin electrodes can also be provided.The sensor element 3 can be manufactured from a larger component, which is then divided into individual, discrete sensor elements 3. The separation in the longitudinal and width directions can be effected by plasma etching or sawing and notching. From the lower side 13, a grinding process may be performed to remove material of the insulating substrate 10 to a defined final component thickness.FIGS. 3A and 3B show a further embodiment of a laser diode arrangement 1 in a cross-sectional view and a plan view. As in FIGS. 1A and 1B, a laser diode chip 2 is mounted directly on a thin film sensor element 3. The thin film sensor element 3 may be like the sensor element 3 of FIGS. 2A and 2B.The difference from FIGS. 1A and 1B is that a conventional chip carrier 26 is provided, wherein the sensor element 3 is arranged between the laser diode chip 2 and the chip carrier 26. Accordingly, both the sensor element 3 and the chip carrier 26 function as carrier for the laser diode chip 2.The sensor element 3 may be attached to the chip carrier 26 with a conductive paste. As examples, Ag screen printing or other means such as AuSn solder may be used.The sensor element 3 may have a smaller thickness d than the sensor element 3 of FIGS. 1A and 1B, since the chip carrier 26 also takes over the function of a heat sink. The thickness d of the sensor element 3 may be, for example, 50 μm or less.The length and width may be the same as described for the sensor element 3 in the preceding example. For example, the sensor element 3 may have a length and width of 700 x 700 μm 2 to 150 x 150 μm 2 and a thickness d of 50 μm or less. A specific example is a length l of 650 μm±10 μm, a width b of 550 μm±10 μm, and a thickness d of 50 μm±10 μm.The thickness of the chip carrier 26 may be greater than the thickness of the sensor element 3. The thickness of the chip carrier 26 may be at least three times as great as the thickness of the sensor element 3.As in FIGS. 2A and 2B, the cathode of the laser diode chip 2 and the cathode (first contact pad 6 a) of the underlying sensor element 3 are electrically connected by a conductor track 7 having a first section 8 and a second section 9.The first contact pad 6 ais connected via a first wire bond 5 ato a first metallization 27 aon the base carrier 4. The second contact 6 bis connected via a second wire bond 5 bto a second metallization 27 bon the base carrier 4. The anode of the laser diode chip 2 is connected via a third wire bond 5 cto a third metallization 27 con the base carrier 4. Due to the greater total thickness of sensor element 3 and chip carrier 26, longer wire bonds 5 b, 5 care required.FIGS. 4A and 4B show a further embodiment of a laser diode arrangement 1 in a cross-sectional view and in a plan view. The arrangement 1 differs from the arrangement 1 of FIGS. 3A and 3B only in the electrical connection of the anode of the laser diode chip 2 to the third metallization 27 con the base carrier 4.In this embodiment, the anode of the laser diode chip 2 is not directly connected via a wire bond to the third metallization 27 con the base carrier 4, but via a wire bond 5 cto a metallization 28 on the chip carrier 26. In this case, two shorter wire bonds 5 c, 5 dmay be used.The chip carrier 26 is larger in a lateral dimension than the sensor element 3, so that space is provided for the metallization 28. The length and width of the sensor element 3 may be, for example, in the range from 1000 x 800 μm 2 down to 50 x 30 μm 2. The thickness may be 150 μm or less. As an example, the length and width of the sensor element 3 may be 700 x 500 to 150 x 100 μm 2 with a thickness of 50 μm or less. As a specific example, the sensor element 3 has dimensions of 650 μm±10 μm, a width b of 300 μm±10 μm, and a thickness d of 50 μm±10 μm.The length and width of the contact pads 6 a, 6 bare, for example, in the range from 400 x 800 μm 2 down to 20 x 50 μm 2, while the thickness is between 1 μm and 0.01 μm. In particular, the length and width of the contact pads 6 a, 6 bmay be in the range from 250 x 500 μm 2 down to 50 x 150 μm 2 or 50 x 100 μm 2 while the thickness may be 0.5 μm or less. As a specific example, a sensor element 3 has dimensions l, b, d of 125 μm, 300 μm and 0.25 μm.The chip carrier 26 may have the same length as the sensor element 3 and a greater width than the sensor element 3. Thus, the chip carrier 26 has a width of 550 μm, for example, while the sensor element 3 has a width of 300 μm.A sufficient distance is required between the contact tracks of the sensor element 3 and the metallization 28 on the chip carrier 26 in order to prevent a short circuit due to overflow of the conductive paste during the mounting. As an example, a lateral distance ranging from 700 μm down to 10 μm is sufficient. In a specific example, the distance is 125 μm.According to a further embodiment, the cathode contacts for the sensor element 3 and the laser diode chip 2 are also separated. In this case, the cathode of the laser diode chip 2 can be directly connected via a wire bond to a metallization on the base carrier 4, as is shown for the anode in FIGS. 3A and 3B. In this case, the laser diode array 1 may be a 6-pin array. It is also possible for the cathode of the laser diode chip 2 to be connected via a wire bond to a metallization on the chip carrier 26 and for the metallization to be connected via a further wire bond to a metallization on the base carrier 4, as illustrated for the anode in FIGS. 4A and 4B.FIG. 5 shows a cross-sectional view of a further embodiment of a laser diode arrangement 1. In this embodiment, the sensor element 3 is mounted in flip-chip technology.Here, too, the laser diode chip 2 is mounted directly on the thin-film sensor element 3. The sensor element 3 may be mounted on a chip carrier 26 which in turn may be mounted on a larger base carrier 4. It is also possible for the sensor element 3 to be mounted directly on a larger base carrier 4. The sensor element 3, the chip carrier 26 and the base carrier 4 can be formed as in the preceding embodiments.In the illustrated embodiment, the contact pads 6 a, 6 bare configured for connection by solder bumps 29 for a soldering process. The contact pads 6 a, 6 bare soldered to metallizations 28 a, 28 bon the chip carrier 26.The design and the material of the contact pads 6 a, 6 bare designed for a soldering method. The minimum size of the contact pads 6a, 6b is the size of a solder bump 29, which typically has a diameter from 400 down to 1 μm. A bump 29 has a diameter of 150 μm or less, for example. The maximum size of the contact pads 6 a, 6 bis the same as described in the previous embodiments.It is also possible to arrange the protrusions in the form of a grid on the contact pads 6 a, 6 b. In the case of more than one solder bump 29, a distance of 150 μm or less must be maintained between each solder bump 29 in the arrangement.The height of the solder bumps 29 may range from 250 μm down to 1 μm, preferably 50 μm or less. Materials such as Cu, Au, Ni, Sn, Co, SAC (SnAgCu), or other backing materials or compositions thereof may be used. In order to ensure good adhesion of the solder bumps, under bump metallization (UBM) may also be used. For the UBM, materials such as Ni, Cr, Ti, Ta, Pt, Pd, W, Cu, Al, Au, or other metals or compositions thereof are used. The dimensions of the UBM may cover the entire contact pad 6 a, 6 bof the sensor element 3 or may be at least the dimensions of the base of the solder bumps 29.Optionally, an epoxy-based, SiO2-based or other polymer-based underfill is applied to the contact pads 6 a, 6 band subsequently cured to improve the reliability of the solder bumps.In order to ensure the contactability of the laser diode chip 2, a rear-side metallization 30 is applied to the sensor element 3. The material of the back side metallization 30 may be the same as that of the contact pads 6 a, 6 bdescribed in the previous embodiments.The insulating substrate 10 of the sensor element 3 is located between the laser diode chip 2 and the functional layer 18 of the sensor element 3, and the further components of the sensor element 3, such as the protective layer 21 and electrodes 15 a, 15 bare not shown here. The sensor element 3 can be formed as illustrated in FIGS. 2A and 2B.The sensor element 3 can have the same geometrical dimensions as in the preceding embodiments.The laser diode chip 2 has a first (lower) contact 31 and a second (upper) contact 32. The first contact 31 is directly connected to the back side metallization 30. The backside metallization 30 may be connected to a metallization on a base carrier by wire bonding. The upper contact 32 of the laser diode chip 2 can be connected to a further metallization on the base carrier.Here too, one of the contacts of the laser diode chip 2 and of the sensor element 3 can be common and the other contact can be separate. The back side metallization 30 may be connected to the second metallization 28 bon the chip carrier 26 by wire bonding, for example. The second metallization can be connected to the base carrier via a wire bond. It is also possible for the rear-side metallization 30 to be connected to a metallization on the base carrier via a wire bond, wherein the sensor element 3 is connected to the same metallization. The back side metallization 30 may be connected to the cathode of the laser diode chip 2.It is also possible to keep the positive and negative contacts disconnected. Accordingly, either a 5-pin or 6-pin design with a thermoelectric cooler or a 3-pin or 4-pin design without a thermoelectric cooler is possible.In an alternative embodiment, the laser diode chip 2 may be mounted on the sensor element 3 by flip-chip technology instead of screen printing. In this case, two lower contacts are provided on the laser diode chip 2. The back side metallization 30 may then be replaced by two metallizations 30 that are not electrically connected to each other. The distance between the metallizations can be, for example, 50-250 μm. One of the contacts of the laser diode chip 2 is connected to one of the metallizations and the other contact is connected to the other metallization. Each of the metallizations can then be connected to the base carrier by a wire bond.FIG. 6 shows a cross-sectional view of a further embodiment of a laser diode arrangement 1. Here, too, the sensor element 3 is mounted by means of flip-chip technology.The difference from the preceding embodiment is that the sensor element 3 is fixed to metallizations 28 a, 28 bon the chip carrier 26 by a sintering method. The contact pads 6 a, 6 bof the sensor element 3 are designed for a sintering method, in particular for a silver (pressure) sintering method. The material of the contact pads 6 a, 6 bis Ag- or Au-based.The thickness of the contact pads 6 a, 6 bmust be sufficiently larger than the thickness of the functional layer 18.In order to ensure that the laser diode chip 2 can be contacted, a rear-side metallization 30 is applied to the sensor element 3. The material of this rear side metallization 30 can be the same as in the case of the contact pads 6 a, 6 b, such that the laser diode chip 2 can also be mounted by silver (printing) sintering.Alternatively, the rear side metallization 30 is the same as in the above-described contact pads 6 a, 6 bfor the conventional mounting of the laser diode chip 2.The connection to a base carrier can be effected as described in the embodiment in FIG. 5.Reference numbers1 Laser diode arrangement 2 Laser diode chip 3 Sensor element 4 Base carrier 5 a Drahtbond 5 b Drahtbond 5 c Drahtbond 5 d Drahtbond 6 aFirst contact pad 6 bSecond contact pad 7 Conductive track 8 First section (contact surface) 9 Second section (connection path) 10 Insulating carrier 11 Main substrate body 12 Upper side 13 Lower side 14 Insulating layer 15 First electrode 15 bSecond electrode 16 End section 17 Electrode finger 18 Functional layer 19 Upper side 20 Lower side 21 Protective layer 22 Upper side 23 Through hole 24 Conductive material 25 Overflow 26 Chip carrier 27 aFirst metallization (base carrier) 27 bSecond metallization (base carrier) 27 cThird metallization (base carrier) 28 Metallization (chip carrier) 28 aFirst metallization (chip carrier) 28 bSecond metallization (chip carrier) 29 Solder bump 30 Rear side metallization 31 first contact (of the laser diode chip) 32 second contact (of the laser diode chip) l length b width d thicknessReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 122 923 A1 [0005, 0015]

Claims

Laser diode arrangement (1) comprising a laser diode chip (2) and a thin-film sensor element (3) for measuring a temperature, wherein the laser diode chip (2) is mounted on the sensor element (3).Laser diode arrangement (1) according to claim 1, wherein the sensor element (3) comprises a functional layer (18) comprising a material having a temperature-dependent electrical resistance, an insulating substrate (10) and two electrodes (15a, 15b), wherein the electrodes (15a, 15b) are formed on or under the functional layer (18), and wherein the electrodes (15a, 15b) are formed at the same height and engage in one another.Laser diode arrangement (1) according to one of the preceding claims, wherein the thickness of the sensor element (3) is 500 μm or less.Laser diode arrangement (1) according to one of the preceding claims, wherein the sensor element (3) is mounted on a carrier (4, 26) in such a way that the sensor element (3) is arranged between the laser diode chip (2) and the carrier (4, 26).Laser diode arrangement (1) according to Claim 4, wherein the sensor element (3) and / or the laser diode chip (2) is electrically connected to the carrier (4, 26) via wire bonds (5a, 5b, 5c, 5d).Laser diode arrangement (1) according to one of the preceding claims, wherein the sensor element (3) has two contact pads (6a, 6b) for the electrical connection of the sensor element (3).Laser diode arrangement (1) according to Claim 6, wherein the laser diode chip (2) is connected to one of the contact pads (6a, 6b) via a conductor track (7) on the sensor element (3).Laser diode arrangement (1) according to one of claims 6 or 7, wherein the contact pads (6a, 6b) are electrically connected to a base carrier (4) by wire bonds (5a, 5b).Laser diode arrangement (1) according to one of the preceding claims, wherein the laser diode chip (2) is directly electrically connected to a base carrier (4) by a wire bond (5d).Laser diode arrangement (1) according to one of the preceding claims, comprising a chip carrier (26) on which the sensor element (3) is mounted and a base carrier (4) on which the chip carrier (26) is mounted, wherein the laser diode chip (2) is electrically connected to the chip carrier (26) by a wire bond (5c) and the chip carrier (26) is electrically connected to the base carrier (4) by a further wire bond (5d).Laser diode arrangement (1) according to one of the preceding claims, wherein the laser diode chip (2) is attached to the sensor element (3) by a conductive paste, by a sintered material or by soldering material.Laser diode arrangement (1) according to one of the preceding claims, wherein the sensor element (3) is attached to the carrier (4, 26) by a conductive paste, by a soldering material or by a sintering material.Laser diode arrangement (1) according to one of the preceding claims, wherein the sensor element (3) is mounted in flip-chip technology.Laser diode arrangement (1) according to one of the preceding claims, wherein one contact of the sensor element (3) and of the laser diode chip (2) is shared and the other contact is separated.Method for producing the laser diode arrangement (1) according to one of the preceding claims, comprising the steps A) providing the laser diode chip (2) and the thin-film sensor element (3) and B) mounting the laser diode chip (2) on the thin-film sensor element (3).

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