WO2014095065A1

WO2014095065A1 - Diode laser module and method for producing a diode laser module

Info

Publication number: WO2014095065A1
Application number: PCT/EP2013/003856
Authority: WO
Inventors: Ulrich RÖLLIG; Petra Hennig; Matthias Schröder; Dalibor Dadic
Original assignee: Jenoptik Laser Gmbh
Priority date: 2012-12-21
Filing date: 2013-12-19
Publication date: 2014-06-26
Also published as: DE102012025494B4; DE102012025494A1

Abstract

The present invention relates to a diode laser module (1) comprising a laser diode element (10) and two heat sinks (20, 30), which can be used to dissipate the waste heat from the laser diode element on both sides. The first heat sink is thermally connected to the p‑side of the laser diode element, and the second heat sink to the n‑side. The second heat sink is additionally connected to the first heat sink by means of an electrically insulating joining medium. The connection of the second heat sink to the first heat sink comprises at least two joining gaps (41, 42) having at least in sections a tapering from the outer region inwards. Furthermore, a method for producing the diode laser module is specified.

Description

Diode laser module and method of making a diode laser module

description

The present invention relates to a diode laser module having a laser diode element and two heat sinks, with which the waste heat of the laser diode element can be dissipated on both sides according to the preamble of claim 1.

DE 102010042087 A1 describes a diode laser module which contains a laser diode element. This in turn consists of a laser bar located at the p-side, i. the anode, and the n-side, i. the cathode is connected to a respective heat spreader. At each of these heat spreader each a heat sink is connected. The heat sinks are electrically connected to one side of the laser diode element. In operation of the

Diode laser module occurs a voltage difference between the two heat sinks. Therefore, a short circuit between the two heatsinks should be avoided. The heat sinks are therefore connected to each other according to DE 102010042087 A1 by means of an electrically insulating adhesive. Here are two evenly thick joining gaps left and right take the laser diode element used. The joining gaps lie in a plane parallel to the waveguide of the laser bar, which is shown horizontally in FIG. 1 of DE 102010042087 A1. This arrangement has several disadvantages. The two heat sinks can slip during assembly due to tolerances against each other. The horizontal joint gaps do not represent a self-aligning geometry. Furthermore, the distribution of the liquid adhesive during assembly is indefinite, since the joint gap is the same thickness everywhere and the capillary force in the joint gap has no gradient. Since the capillary forces on the liquid joining agent in the joint gap are the same everywhere, there may be a random distribution of the joining agent during assembly. If the joining agent is underdosed, individual voids may occur over the length of the joining gap, causing the diode laser module to leak. In addition, the joining agent can even flow away from the joint, in particular when the joining agent is cured at elevated temperature. Namely, if the preassembled diode laser module is brought to an elevated temperature with the still liquid adhesive, the viscosity of the joining agent may temporarily decrease, which favors the passage of the adhesive from the joint.

The arrangement of the joint gap near the plane of the laser bar causes both

Heat sinks are about the same size and have almost the same cooling capacity. Because the

BESTÄTiGÜNGS OPtE Waste heat of the laser bar for the greater part on the p-side of the laser bar is obtained, a heat flow between the two heat sinks is necessary. Therefore, a Wärmeleitkleber must be used, for example, a ceramic-filled epoxy adhesive with a

Thermal conductivity of over 0.5 W / (m * K). The disadvantage is that inexpensive structural adhesive with good mechanical properties can not be used because of their low thermal conductivity. Another disadvantage is that the joint gap must be relatively thick in order to avoid short circuits between the two heat sinks, especially on the outside. Since the air flow for cooling carries particles that can settle at the joint gap, the joint gap must be selected thick accordingly. However, a thick joint gap has mechanical tension and tends to crack in the cured joining agent. As a result, the reliability of the diode laser module can be impaired.

The object of the invention is to provide a reliable, inexpensive, easy to install

To provide diode laser module with double-sided cooling, in which two heat sinks are used, between which an electrical

Voltage difference occurs. In particular, the distribution of the joining agent in the joint gap should be reproducible, the joining agent must be tolerant to dosing, a joining agent without special requirements for thermal conductivity be used, and the alignment of the heat sink to each other and the laser diode element should be easy to accomplish. During operation of the diode laser module, the probability of failure due to short circuit should be minimized, in particular in the case of air cooling.

The object is achieved by a diode laser module according to claim 1, comprising a laser diode element, a first with the p-side (anode) of the laser diode element thermally connected heat sink, a second thermally connected to the n-side (cathode) of the laser diode element heat sink, wherein the second Heatsink is connected to the first heat sink by means of an electrically insulating joining means and the connection of the second heat sink with the first heat sink at least two joining gaps, characterized in that in a plane perpendicular to an optical axis of the laser diode element cutting plane each of the two joining gaps at least partially a taper of outside inwards.

The laser diode element may, for example, be a diode laser bar. A laser bar is a semiconductor chip that contains a number of individual edge emitting emitters arranged in parallel. If the laser chip contains only one emitter, it is also used as a single emitter designated. In the following, the term laser bars should also include single emitters. An emitter is a laser-emitting region of the laser diode element. Usually, the width of a commercially available laser bar can be about 10 mm, the length 1 mm to 6 mm and the height 0.05 mm to 0.2 mm. In the case of a laser bar with only one emitter (single emitter), the width can be only 0.4 mm to 1 mm. The laser bar is electrically contacted on the p-side and the n-side contact surface. These contact surfaces are the two largest surfaces of the laser bar, which are arranged opposite one another. The p-side contact surface is the anode of the laser diode element, while the n-side contact surface is the cathode of the laser diode element.

The laser diode element may in another preferred embodiment a

Laser bar as well as connected to the p-side of the laser diode element first heat spreader and / or connected to the n-side of the laser diode element second heat spreader. Under connection here is an electrical and thermal connection to understand. The electrical connection must be able to carry the operating current of the laser bar. The thermal connection must be able to dissipate the waste heat of the laser bar. In addition, but not necessarily, the second can

Heat spreader be connected to the first heat spreader by means of an insulating layer. This compound can be a mechanical and / or a thermal

Be connected.

The heat spreaders should have a high thermal conductivity and be electrically conductive. In a preferred embodiment, they may for example consist of copper or of a metal-diamond composite material. For some applications, an expansion-adapted material such as tungsten-copper or molybdenum-copper should be used. Ceramic heat conducting bodies are also possible if the required electrical conductivity is produced by means of a metallic coating. At the edges of the heat spreader burrs can be present to improve the electrical contact with the heat sinks. The two heat spreader are electrically isolated from each other. For this purpose, for example, an insulating layer between the

Heat spreader be provided. The p-side contact surface of the laser diode element is the laser bar side facing away from the first heat spreader, which is attached to the anode of the laser bar. The n-side contact surface of the laser diode element is the laser bar side facing away from the second heat spreader, which is attached to the cathode of the laser bar. Alternatively, the laser diode element but also consist of a laser diode bar, which is provided with only a heat spreader on the p-side or on the n-side.

A laser bar may contain a number of individual emitters designed as edge emitters. The waveguides are formed as a flat epitaxially produced structure and lie in one plane. The p-side of the laser bar is the epitaxial side while the n-side is the substrate side. The waveguides and thus the exit aperture of the

Laser beams are thus close to the p-side (anode) of the laser bar. Since most of the heat loss occurs in the epitaxial plane, it is advantageous to be on the p-side of the

Laser diode element to install a first heat sink having a higher cooling capacity than the attached to the n-side second heat sink. The main beam directions of the laser radiation of the emitter are parallel. The common plane of the waveguides

(Waveguide plane) is used in the following as a reference plane for illustrating advantageous arrangements of the joining gap. The optical axis defines the emission direction of the emitter closest to the center of the laser bar. The optical axis can lie in the waveguide plane and run perpendicular to the front facet of the laser bar. Now, for example, the laser bar can not just one, but several

Epitaxy structures on top of each other, which is a stack of parallel

Form waveguide planes. In such a structure, the central plane of the individual waveguide planes is considered as the reference plane (waveguide plane). In addition, the laser diode element may also comprise a stack of individual laser bars. In such a structure, the central plane of the waveguide planes of the individual laser bars is considered as a reference plane (waveguide plane). The two heat sinks may preferably be used as air cooling bodies, i. be designed as a heat sink, which are operated with air as the cooling medium. For this purpose, they can each be equipped with a plurality of cooling fins or cooling fingers. Cooling bodies with cooling fins can be produced, for example, using extrusion processes, for example, of aluminum or of an aluminum-based alloy. A particularly good heat dissipation can be achieved if the cooling fins are corrugated. In some cases, however, smooth cooling fins can be sufficient, which are less expensive to produce. The airflow for cooling is preferably driven by a fan. For small power losses of the diode laser module, convection cooling without a fan can alternatively suffice.

It is advantageous to guide the air flow parallel to the laser beam. It may also be advantageous to guide the air flow antiparallel to the laser beam, ie in opposite directions Direction. But it is also possible, the air flow with a radial

Provide speed component.

The first and / or the second heat sink may have a groove, which includes a first contact surface and side surfaces for receiving the laser diode element. It is particularly advantageous if the side surfaces are inclined in such a way that they have the smallest distance from one another at the cutting edges of the contact surface. The groove is then extended upwards. In particular, the spacing of the side surfaces on the abutment surface can be selected such that the laser diode element is fixed in position in at least one direction such that an active alignment (adjustment) can be dispensed with. Such grooves are not necessarily required according to the invention, but such grooves are particularly advantageous when the laser diode element one or more

Heat spreader comprises. However, the heat sink can also have channels through which they are cooled with a liquid or a gaseous cooling medium. Such heatsink can be made for example of aluminum or preferably of copper.

The first heat sink has at least two first joining surfaces and the second heat sink has at least two second joining surfaces. The joining means is located in at least two joining gaps, which are delimited by a respective first joining surface and a second joining surface. In each case, a first joining surface of the first heat sink faces a second joining surface of the second heat sink, wherein the distance between the two surfaces is at least partially bridged by the joining means. The two joining gaps each have a taper at least in sections from outside to inside. The inside is characterized by being closer to the optical axis than the outside. The inventive taper of the joining gap from outside to inside is defined by the fact that in a section perpendicular to the optical axis, the distance of the first joining surface to the second joining surface is smaller at a first location than at a second location, which is farther from the optical axis as the first place. In a preferred

Embodiment, the first joining surfaces and the second joining surfaces are each designed as flat surfaces. Then the taper can each extend over the entire width of the gap. The taper may be wedge-shaped. In this case, the first position can be chosen at the inner end of the joining gap and the second position at the outer end of the joining gap. The joint surfaces do not necessarily have to be flat Be formed surfaces. Curved surfaces or stepped surfaces are also possible. Essential to the invention, however, in any case, the taper of the joint gap from outside to inside. It is sufficient if the joining gaps are tapered in sections in cross section. In a further preferred embodiment, for example, at least the first or the second joining surfaces may have a bend in the considered section. Then the taper can be present only over a certain portion of the gap. This section may have a wedge-shaped taper. In another section, the joint gap may be formed as a parallel gap or even have an extension from the outside to the inside.

The joining gaps may lie in the plane of the waveguides of the laser diode element.

It is more advantageous, however, if the joining gaps are not in this plane, but are spaced from the waveguide plane and in the half-space of the n-side of the

Laser diode element are located. Then, namely, the first heat sink is to be dimensioned in a simple manner by an enlarged surface with a higher cooling capacity than the second heat sink. It is particularly advantageous if, in addition, the joint gaps have a larger distance to the reference plane (waveguide plane) than inside. This manifests itself, for example, in the fact that the outer joining surfaces are further away from the

Waveguide plane are removed as the inner joint surfaces. If the joining surfaces are at least partially planar, it can be achieved that an angle between two first joining surfaces is less than 180 °. Advantageously, angles between 60 ° and 120 °, particularly advantageously provided between 80 ° and 100 °. As a result, the joining gaps are each formed neither mirror-symmetrically to the waveguide plane, nor to a plane parallel to the waveguide plane. The middle planes of the individual joining gaps are therefore arranged inclined in this advantageous embodiment considered against the waveguide plane.

The first and / or the second heat sink may preferably be designed to be translationally symmetrical. The symmetry direction. the translation symmetry may be in the direction of the optical axis of the diode laser module. The joining gaps may also preferably be translationally symmetrical with respect to the optical axis of the diode laser module.

The tapering of the joint gap according to the invention from outside to inside can be achieved in a preferred embodiment by providing an angle between two second planar joining surfaces which is smaller than the angle between the first two even joining surfaces. Preferably, the angle between the second joining surfaces is selected to be smaller by 2 ° to 20 ° than the angle between the first joining surfaces. At only

Sectionally tapered joining gaps, this consideration applies accordingly for the corresponding sections of the joining surfaces, which limit the taper of the adhesive gap. Two joining gaps can be arranged mirror-symmetrically with respect to a plane that is perpendicular to the waveguide plane and parallel to the optical axis of the laser radiation. The optical axis represents a straight line which lies in the middle of the middle emitter of the laser bar and can run in the resonator direction. The joining gaps are then located to the left and right of the laser diode element. It is advantageous to also choose the distance of the joining gap inside larger than the width of the laser diode element.

The first heat sink attached to the p-side of the laser diode element may be dimensioned to have a higher cooling power than the second heat sink attached to the n-side of the laser diode element. Since the laser diode element emits more heat at the p-side than at the n-side, the heat flow between the two heat sinks is reduced by this advantageous dimensioning of the heat sink. Ideally, no or only a small heat flow occurs between the two heat sinks. Therefore, a low-cost joining agent can be used, to which no requirements for high thermal conductivity must be made. The thermal conductivity can be less than 0.3W / (m * K) or even less than 0.1 W / (m * K). Said heat sink dimensioning can be carried out such that the first heat sink has a larger surface for heat exchange than the second heat sink. The first heat sink can be equipped for this purpose with more cooling fins and / or with overall larger cooling fins. The laser diode element may for example be shorter than the first and / or the second heat sink, wherein the length dimension is in this case considered in the direction of the optical axis. It is also possible that the laser diode element protrudes in the direction of the optical axis relative to the front edge of the first and second heat sink or is set back. A return offset has the advantage that the laser diode element against mechanical

Damage is better protected.

A method for producing a diode laser module according to the invention may comprise the following steps:

a) providing a laser diode element, a first heat sink and a second heat sink, b) connecting the first heat sink to the p-side of the laser diode element, c) connecting the second heat sink to the n-side of the laser diode element,

d) connecting the second heat sink to the first heat sink by means of an electrically insulating joining means.

In this case, the connection of the second heat sink to the first heat sink comprises at least two joining gaps, wherein each of the two joining gaps in a section plane perpendicular to an optical axis in each case at least partially has a taper from outside to inside.

The joining means may preferably be an adhesive, more preferably one

Epoxy resin adhesive, which can be thermally cured at elevated temperature, at room temperature or chemically. However, the joining agent can also be of an inorganic nature, for example a cement or a silicate-based joining agent. The joining agent may be viscous before curing and have a high strength after curing. It is therefore a solidified joining agent. It is possible to produce the diode laser module in such a way that the joining surfaces of the first and / or the second heat sink before the

Assembling the two heat sink an electrically insulating compound is applied. The joining agent can be applied in the viscous state, preferably as a bead, for example as a bead of adhesive. The height of the applied joining means, such as the bead, may be greater than the predetermined average thickness of the joint gap. The two heat sinks are joined together with the laser diode element, which is arranged at least partially between the two heat sinks. The joining gaps, which are in each case between two opposite joining surfaces, are bridged by the joining agent. When assembling the heat sink, a pressure on the previously applied joining agent can be exercised. By can when joining the heat sink due to

according to the invention tapering of the joint gap, which runs from outside to inside,

Joining means are essentially pushed outwards. Essentially means here that although joining means can be pressed inwards, but this flows inside because of the tapering of the joint gap smaller hydraulic diameter inside slower than outside, so that the joining means preferably escapes to the outside. This means that the joining agent in an adhesive gap, if the movement of the joining agent over the

Mean volume of agent mediates, is pushed outward. This advantageous effect is particularly pronounced when a medium or high viscosity compounding agent is used, ie the viscosity of the joining agent is greater than 1000 cP. Particularly advantageous may be thixotropic joining agent. The thixotropy of the joining agent may cause the

Prevent jointing before joining the heat sink and the beneficial

Dodge the joining agent to the outside when assembling additionally convey. In this case, the outer joint surface can form after joining either in the joint gap itself or in a cavity adjacent to the outside of the joint gap.

Alternatively, the heat sink with the laser diode element also initially without

Joining means are assembled. The joining agent can in this case after the

Assembly be introduced from the outside into the joint gap. For this purpose, it may be sufficient to meter the joining agent into a cavity provided on the outside of the joint gap, from which it penetrates into the joint gap as a result of the capillary forces. This type of filling of the joint gap is particularly advantageous to accomplish, as described by the invention described below tapering of the joint gap from outside to inside

Capillary forces on the liquid joining agent increase from the outside inwards. As a result, the liquid joining agent preferably spreads to the inside of the joint gap and achieves a reproducible distribution of the joining agent, which does not depend on random factors.

In addition, the joining gap according to the invention has the effect that the joining means can not flow away from the joint, in particular not even when the viscosity of the joining agent temporarily decreases during a curing process at elevated temperature. On the inside of the joint gap can be in a preferred

Embodiment, a space for receiving excess adhesive may be provided, which has at least one extension in cross-section. As a result, it can be achieved that the liquid joining agent does not continue to be capped in the direction of the laser bar. This space can also absorb a small amount of excess joining agent, so that a certain overdose of the joining agent is not critical. Since the respective opposite joining surfaces of both

Heat sink form a joint gap, can form inside and outside each free surfaces of the joining agent. The inner joint surface may either be in the joint gap, i. lie between the joint surfaces or outside of the joint gap, for example, o.g.

adjacent inner cavity. It is even possible that the joining agent reaches as far as the laser diode element and then forms no free joint surface on the inside. This may be the case, in particular, if, in a further embodiment, no inner cavity is provided, but the joining gaps extend as far as the laser diode element. The outer joint surface can either lie in the joint gap, ie between the joint surfaces or outside of the joint gap, for example in the adjacent outer cavity. Even with an underdosing of the joining agent, this spreads, promoted by the taper of the joint gap, on the entire length of the joint gap evenly. Due to the gradient of the capillary force in the joint gap turns

uniform distance between the inner and outer joint surface, the joint gap is practically uniformly and reproducibly filled from the inside.

Between the p-side pad of the laser diode element and the corresponding contact surface of the first heat sink can advantageously be introduced a heat conduction, as well as between the n-side pad of the laser diode element and the corresponding contact surface of the second heat sink. This serves to improve the thermal connection. Such a heat conducting means may be formed, for example, as a metal foil, for example made of tin, lead, indium, cadmium or an alloy of two or more of these metals. However, it is also possible to use a heat-conducting foil, for example a carbon foil. Alternatively, such a heat conduction agent can also be formed as a metallic coating, for example made of tin, lead, indium, cadmium or gold, which is at least on the contact surface of the first and / or the second

Heat sink is applied. Such a coating may additionally or alternatively be applied to the n-side and / or the p-side contact surface of the laser diode element. However, a heat conducting agent can also be a further joining agent, for example a

Thermal adhesive, be. If the contact surfaces and contact surfaces are made sufficiently flat, can also be dispensed with a heat conduction. The first heat sink may thus be thermally connected to the p-side of the laser diode element and the second heat sink to the n-side of the laser diode element either with a heat conduction or without a heat conduction. The first heat sink may additionally be connected to the p side of

Laser diode element and / or the second heat sink with the n-side of

Be connected mechanically laser diode element. A mechanical connection can be positive, cohesive or non-positive, whereby a combination of several of these types of connection is possible. The use of the o.g. Another joining means, for example, represents a cohesive mechanical connection, while a contact force, which may for example arise from the fact that the laser diode element is clamped between the first and the second heat sink, realizes a non-positive mechanical connection. Both types of mechanical connection can also be present at the same time. By the o.g. Forming a groove in one or both heat sinks can also be made a positive connection.

When assembling the cooling body provided with joining means, in each case a first joining surface of a second joining surface comes to lie opposite and the joining means now bridges the distance between the first and the opposite second joining surface and wets both joining surfaces. The same result is obtained if the joining means as described above is applied only after the assembly of the heat sink. The wetting of the joining surfaces does not have to take place over the entire surface, but the joining agent can also be easily underdosed, so that not the entire first and second joining surfaces are wetted over the entire surface. It is also an overdose possible, the joining agent can then collect in the above-mentioned cavities, which connect to the inside of the joining gaps. For reliable electrical insulation, a specific joint gap thickness between the first heat sink and the second heat sink is required especially outside. This distance can be determined by the laser diode element, this then has the function of a spacer due to its fixed thickness. In addition, but may not be, further spacers made of an electrically insulating material as a spacer between the heat sinks may be introduced. The use of at least one spacer is advantageous if the laser diode element in the direction of the optical axis has a shorter length than the heat sink, the laser diode element is thus shorter than the heat sink. In particular, if the laser diode element comprises no heat spreader, but only a laser bar, which is usually not longer than 5 millimeters, a spacer may be required.

The laser diode module can advantageously be electrically contacted to the first and / or the second heat sink, for example by screw contacts, plug contacts, welded contacts or spring contacts. For this purpose, the first heat sink must be electrically connected to the p side of the laser diode element and / or the second heat sink must be electrically connected to the n side of the laser diode element. Then, the first and / or the second heat sink can serve as a connection contact to the power supply to the laser diode element.

The envelope of the outer edges of the cooling fins of the heat sink can be advantageous in

Cross-section be circular. Then you can arrange the diode laser module in a tube, which can serve as an outer jacket for guiding a cooling air flow. Alternatively, the envelope may also have a flattening (D-shape) and / or be oval or rectangular. Other shapes are possible. A flattening has the advantage that the

Diode laser module can be turned off during assembly or storage. The diode laser module may further comprise an outer sheath which surrounds the heat sink at least in sections. This outer jacket causes the air flow for cooling the diode laser module in the surrounding portion can not escape radially, but is guided in the interstices of the cooling fins or cooling fingers. This is advantageous since the cooling of the diode laser module is thereby improved. In addition, in addition to the output side of the laser beam, an air flow can be generated, which simultaneously cools optical elements in the laser beam path and / or the target area of the laser beam. This air flow may be partially parallel to the optical axis and be performed either blowing or sucking on the exit side of the laser beam. The outer jacket may advantageously be adapted to the envelope of the outer edges of the cooling fins, so that it surrounds the diode laser module in a certain distance in cross section.

Particularly advantageous is a distance of the outer jacket to the outer edges of the cooling fins, which does not exceed in the mean hydraulic diameter of the air channels between the cooling fins. In particular, the outer sheath may be circular or oval in cross-section, with or without a lateral flattening, or rectangular.

The diode laser module according to the invention has a reliable electrical insulation between the heat sinks. For production, a low-cost joining agent can be used. The demands on the manufacturing tolerances are less demanding than the prior art, so that the production of the module is less expensive. The inventive design of the joint gap is a particularly reliable and accurate positioning of the heat sink to each other even without consuming

Positioning devices possible. The heat sinks can passively position themselves in the correct position during assembly. The joint gap is filled evenly over the entire length with a joining agent, so that even with underdosing of the joining agent, no voids in the joint gap occur. By the invention

Forming of the joint gap can also be achieved that before joining the heat sink applied to the joining surfaces joining agent is preferably pressed in the joint gap during assembly, so that it can not come to contamination of the laser bar with joining agent. This can even overdose of the

Fügemittel be tolerable. Another advantage of the diode laser module is that the cooling air is effectively guided. This can reduce the flow rate of the cooling air, so that fewer particles are carried along, which are at the outer

Settling surface of the joining gap. As a result, the short circuit probability is further reduced in connection with the joint gap according to the invention. Further advantageous embodiments are the subject of the respective subclaims.

The invention will be described in more detail below with reference to the figures. 1 shows a diode laser module according to the invention in a front view

Fig. 2 shows the marked in Fig. 1 section in an enlarged view

3 shows the diode laser module in a lateral sectional view

Fig. 4 shows a first heat sink, a second heat sink and a laser diode element in front view to illustrate the designation of the individual surfaces

5 shows a further embodiment of a diode laser module according to the invention in front view

Fig. 6 shows an adhesive gap, in which the taper is formed in sections

A first embodiment is shown in FIGS. 1, 2 and 3. 1 shows a view in the direction opposite to the laser beam direction on the front side of the diode laser module 1. The joining means 40) is shown hatched in FIG. This merely serves to emphasize that the marked surfaces 40 in FIG. 1 represent viewing surfaces, not cutting surfaces. FIG. 2 shows a section of FIG. 1 in order to reveal the first joining gap 41 in an enlarged view. 3 shows the diode laser module 1 in cross section. The cutting plane is perpendicular to the waveguide plane along the optical axis. The laser diode element 10 comprises a laser bar 1 1, a first heat spreader 12 and a second heat spreader 13, wherein the laser bar 1 1 is arranged between the first and the second heat spreader. The heat spreaders 12, 13 are formed longer in the direction of the optical axis 16 than the laser bar 1 first The leading edges of the

Heat spreaders are flush with the beam exit aperture of the laser bar while extending rearwardly beyond the back facet of the laser bar.

There is no direct electrical contact between the two heat spreaders 12, 13 since an insulating layer (not shown) is provided between them. The

Heat spreader 12, 13 have a high thermal conductivity. For example, they can be made of copper or of a metal-diamond composite material. For some applications, an expansion-adapted material such as

Tungsten-copper or molybdenum-copper advantageous to use. At the edges of the heat spreader burrs can be used to improve the electrical contact with the

Heat sinks may be present. The p-side contact surface 14 of the laser diode element 10 is the side facing away from the laser bar 1 1 of the first heat spreader 12, which at the Anode of the laser bar 1 1 is mounted. The n-side contact surface 15 of the laser diode element is the side of the second side facing away from the laser bar

Heat spreader 13, which is attached to the cathode of the laser bar 1 1. The laser bar 1 1 contains here, for example, 49 individual emitters (not shown), which are formed as edge emitter and distributed uniformly over the width of the laser bar 1 1. The waveguides are designed as a flat epitaxially produced structure and lie in a plane 80. The p-side of the laser bar is the epitaxial side, while the n-side is the substrate side. The waveguides and thus also the exit aperture of the laser beams are thus close to the p-side. Since most of the heat loss occurs in the epitaxial plane, it is advantageous, as shown in the exemplary embodiment, to attach a first heat sink 20 to the p-side of the laser diode element 10, which has a higher cooling power than the second heat sink 30 attached to the n side 15 Has. The main beam directions of the laser radiation 16 of the emitter are parallel. The plane of the waveguides 80 will be used hereinafter as reference plane for illustration.

The laser diode element 10 is arranged between the heat sinks 20, 30. The

As shown in FIG. 3, the laser diode element is shorter in the direction of the optical axis 16 than the heat sinks (20, 30). The length of the laser diode element here corresponds to the length of the heat spreader 12, 13. The distance of the heat sink 20, 30 is determined on the one hand by the laser diode element 10 itself, as well as by an additionally introduced spacer 60. This spacer 60 is electrically insulating and ensures compliance with the joint gap thickness over the entire heat sink length, even if the

Heat spreader 12, 13 of the laser diode element 10 are formed shorter than the heat sink. Also, the laser diode element is recessed in the direction of the optical axis with respect to the leading edges of the heat sinks (20, 30). The return offset has the advantage that the laser diode element is protected against mechanical damage. The second heat sink 30 is connected to the first heat sink 20 by means of an electrically insulating

Joining agent 40 connected. The joining means is located in two joining gaps 41, 42, which are delimited by a respective first joining face 22a, 22b and a second joining face 33a, 33b. Here, the surfaces 22a of the first heat sink 20 of the surface 33a of the second heat sink 30 opposite, wherein the distance between the two surfaces is bridged by the joining means 40. The thus defined first joint gap 41 is completely filled in Fig. 1 with joining means 40 and has from the outside to the inside a taper, which is wedge-shaped. Furthermore, the surface 22b of the first heat sink is the surface 33b of the second heat sink opposite, wherein the distance between the two surfaces is bridged by the joining means 40. The thus defined second joint gap 42 also has from the outside to the inside

Rejuvenation on. The tapering according to the invention is characterized, as shown in FIG. 2 for the first joining gap, by the fact that in a section perpendicular to the optical axis the distance of the first joining surface 22a to the second joining surface 32a is smaller at one point 47 than at another Point 48, which is farther away from the laser diode element than the point 47. The same applies to the distance of the first joining surface 22b to the second joining surface 32b. The joining gaps 40, 41 are above the waveguide plane, i. in the half-space, in which there is also the n-side contact surface 1 5 of the laser diode element. On the outside, the distances between the joining gaps and the reference plane 80 are greater than the inside. This makes it possible to provide a larger number of cooling fins 27 on the first heat sink 20 than on the second

Heat sink 30, which contains a smaller number of cooling fins 37. The heat sinks 20, 30 are translationally symmetrical with respect to the main beam direction (optical axis) 16, as well as the joining gaps 41, 42.

The tapering of the joining gap from outside to inside is effected by the wedge-shaped construction of the joining gaps 41, 42 shown in FIGS. 1, 2. In Fig. 4, the components of the first heat sink 20, second heat sink 30 and laser diode element 10 are shown individually superimposed to represent the location of the designated areas and to illustrate the emergence of the wedge shape of the adhesive gap. To form the wedge-shaped adhesive gaps, an angle 23 of 90 ° is provided between the first joining surfaces 22a and 22b, while the angle between the second joining surfaces 32a and 32b is an angle 33 of 75 °

is provided. The joint gap has a thickness 41 of 0.05 mm on the inside, while it has a thickness 42 of 0.5 mm on the outside. In Fig. 1 and 2, however, it is shown for illustrative purposes thicker overall. It is particularly advantageous to choose the thickness of the joining gap inside between 0.02mm and 0.2mm and outside between 0.1mm and 2mm. The first heat sink 20 includes a groove for receiving the laser diode element 10, which is formed from the first contact surface 21 and two side surfaces 25. The side surfaces 25 are inclined so that they have at the cutting edges of the contact surface 21 the smallest distance from each other. The groove is then extended upwards. The width of the groove is only slightly wider on the contact surface 25, than the first heat spreader 12, namely so wide that it reliably fits into the groove, taking into account the tolerances. This is the result set horizontal position of the laser diode element to the first heat sink, so that an active alignment (adjustment) can be omitted. The second heat sink 30 also includes a groove for receiving the laser diode element 10, which is formed from the first contact surface 31 and two side surfaces 35. The width of the groove is only slightly wider on the contact surface 35 than the second heat spreader 13, namely so wide that it reliably fits into the groove, taking into account the tolerances. As a result, the horizontal position of the

Laser diode element 10 to the second heat sink 30 and thus also the horizontal

Alignment of the second heat sink 30 to the first 20 set. Such grooves are not necessarily required according to the invention, but such grooves are particularly advantageous when the laser diode element 10 comprises one or more heat spreader.

The two heat sinks 20, 30 are formed as air cooling body. For this purpose, they are each equipped with a plurality of cooling fins 27, 37. To be a particularly good

To achieve heat dissipation, the cooling fins 27, 37 are designed wavy. In some cases, however, smooth cooling fins can be sufficient, which are less expensive to produce. The airflow 70 is preferably driven by a fan. In small

Power losses of the diode laser module can alternatively be sufficient convection cooling without fan. The diode laser module additionally includes an outer sheath 50 having a circular cross-section surrounding the heatsinks 23, 30 at a distance from the outer edges of the cooling fins that is on the order of the distance of the cooling fins. The air flow 70 is, as shown in Fig. 3, parallel and in the same direction as the laser beam 16 out. Alternatively, it would also be possible the air flow antiparallel, ie in

opposite direction compared to the illustration of FIG. 3, lead. Of the

Air flow is driven by a fan, not shown. This can be mounted behind the module on the side facing away from the laser bar and operated by blowing or sucking. The air is guided inside the outer jacket 50. It is sufficient if the outer jacket surrounds the heat sink in sections. The heatsink are a piece over the outer shell, as shown in this first embodiment.

Another embodiment is shown in Fig. 4. In this example, the laser diode element 10 consists of only one laser bar 1 1. Heat spreaders are not available. The laser bar 1 1 is arranged here directly between the first heat sink 20 and the second heat sink 30. The p-side contact surface 14 of the laser bar is applied the first contact surface 21, which was previously coated with indium to. The n-side

Contact surface 15 of the laser bar is located on the second contact surface 31, which was previously coated with indium to. The first and second joining surfaces 22, 32 are not embodied as flat, but as curved surfaces. The tapering of the joining gaps from outside to inside can be achieved, for example, by means of different radii of curvature and / or by means of different curvature center lines of the first 22 and second 33 joining surfaces. The diode laser module has a round outer contour with a flattening on the upper side of the second heat sink 30. It can be seen in the illustration in Figure 4 that the outer edges of some cooling fins lie in a plane. This allows you to put the module on this flattening, without it tipping. Another advantage is that it can not be twisted, if you put the module in a corresponding

adapted outer jacket 50 introduces.

The taper can extend over the entire width of the gap or even over a certain portion of the gap. Such a further inventive design of a joint gap is shown in Fig. 6. The first joining surface 22 is a flat surface. The second joining surface 32 is not a flat surface, but consists of two flat partial surfaces. If the two joining faces 22, 32 face each other in this third exemplary embodiment, the illustrated joining gap results with a section-wise tapering from outside to inside. This taper is located in section 81, while the joint gap has another section 82 that does not taper. The taper is to be determined here only in the tapered section 81. The sections with 81 or without 82

Rejuvenation is shown in FIG. 6 as arrows pointing from outside to inside. The tapering according to the invention is characterized, as shown in FIG. 6 for the first joint gap, by the fact that in a section perpendicular to the optical axis the distance of the first joining surface 22 to the second joining surface 32 is smaller at a point 47 than at another point 48, which is farther from the laser diode element than the location 47.

In a further embodiment, not shown, the laser diode element 10 may consist of a laser diode bar 1 1, which is provided with only one heat spreader 12 or 1 3. For example, in another embodiment, the laser bar may have not one but a plurality of epitaxial structures stacked on top of each other that form a stack of parallel waveguide planes. In such a structure, the central plane of the individual waveguide planes is considered to be the reference plane (waveguide plane 80). In addition, the laser diode element may also comprise a stack of individual laser bars. In such a structure, the central plane of the waveguide planes of the individual laser bars is considered as a reference plane (waveguide plane 80).

designations

1 diode laser module

10 laser diode element

1 1 laser bar

12 first heat spreader

13 second heat spreader

14 p-side contact surface (anode)

15 n-side contact surface (cathode)

16 laser beam (main beam direction); optical axis

20 first heat sink

21 first contact surface

22 first joining surface

23 angle between two first joining surfaces

25 side surface of the first receiving groove

27 cooling fins

30 second heat sink

31 second contact surface

32 second joint surface

33 angle between two second joining surfaces

34 second receiving groove

35 side surface of the second receiving groove

40 joining agents

41 first joint gap

42 second joint gap

43 inner joint surface

44 outer joint surface

45 inner cavity for holding excess joining agent outer cavity

first place to measure the thickness of the joint gap

second point for measuring the thickness of the joint gap

outer sheath

spacer

airflow

Waveguide plane of the laser diode element

Rejuvenation from outside to inside, section of the gluing gap with rejuvenation section of the gluing gap without rejuvenation

Claims

claims

A diode laser module (1) comprising a laser diode element (10), a first heat sink (20) thermally connected to the p side (14) of the laser diode element, a second thermally connected to the n side (15) of the laser diode element

Heat sink (30), wherein the second heat sink is connected to the first heat sink by means of an electrically insulating joining means (40) and the connection of the second heat sink to the first heat sink at least two joining gaps (41, 42), characterized

in that, in a sectional plane perpendicular to an optical axis (16), each of the two joining gaps has, at least in sections, a taper from outside to inside.

2. diode laser module according to claim 1, characterized in that the first

Heatsink (20) has a higher cooling capacity than the second heat sink (30).

3. diode laser module according to claim 2, characterized in that the two

Joining gaps (41, 42) are each formed asymmetrically with respect to the waveguide plane (80) of the laser diode element and / or are arranged outside this waveguide plane.

4. diode laser module according to claim 1 or 2, characterized in that in a plane perpendicular to the optical axis (16) cutting plane, the two joining gaps (41, 42) are at least partially wedge-shaped.

5. diode laser module according to claim 1, 2 or 4, characterized in that the

Joining gap (42, 43) inside at least partially into a cavity (45) open, which is at least partially provided for receiving excess joining agent.

6. diode laser module according to one of the preceding claims, characterized

characterized in that the two joining gaps (41, 42) are arranged mirror-symmetrically with respect to a plane which is perpendicular to the waveguide plane and parallel to the optical axis of the laser radiation.

7. diode laser module according to one of the preceding claims, characterized

characterized in that the first heat sink (20) is electrically connected to the p-side (anode) of the laser diode element (10) and / or the second heat sink (30) is electrically connected to the n-side (cathode) of the laser diode element (10) ,

8. diode laser module according to claim 7, characterized in that the first and / or the second heat sink as a terminal contact to the power supply to

Laser diode element (10) is used.

9. diode laser module according to one of the preceding claims, characterized

in that the laser diode element comprises a laser bar (1 1) and a first heat spreader (12) connected to the p side of the laser diode and / or a second heat spreader (13) connected to the n side of the laser diode.

10. diode laser module according to claim 9, characterized in that the second

Heat spreader is connected to the first heat spreader by means of an insulating layer.

1 1. Diode laser module according to one of the preceding claims, characterized

characterized in that the joining means (40) has a thermal conductivity of less than 0.3 W / (m * K).

12. diode laser module according to one of the preceding claims, characterized

in that the laser diode element (10) serves as a spacer for adjusting the thickness of the joining gaps (41, 42).

13. diode laser module according to one of the preceding claims, characterized

characterized in that the first and the second cooling body (20, 30) are formed as air cooling body.

14. diode laser module according to claim 13, characterized in that the first and the second heat sink with smooth or corrugated cooling fins (27, 37) are provided.

15. diode laser module according to claim 14, characterized in that it further comprises an outer jacket (50) which surrounds the first and second heat sink (20, 30) at least in sections.

16, diode laser module according to claim 15, characterized in that the distance of the outer jacket (50) to the outer edges of the cooling fins (27, 37) is smaller than the average hydraulic diameter of the air ducts between the cooling fins.

17. A method for producing a diode laser module (1) comprising

a) providing a laser diode element (10), a first heat sink (20) and a second heat sink (30)

b) connecting the first heat sink (20) to the p-side (14) of the laser diode element c) connecting the second heat sink (30) to the n-side (15) of the

laser diode element

d) connecting the second heat sink with the first heat sink by means of a electrically insulating joining means (40),

characterized in that the connection of the second heat sink to the first heat sink comprises at least two joining gaps (41, 42),

and each of the two joining gaps in a section plane perpendicular to an optical axis (16) has at least in sections a tapering from outside to inside.

18. The method according to claim 17, characterized in that before the joining of the two heat sink, the electrically insulating joining means (40) is applied to the joining surfaces of the first and / or the second heat sink.

19. The method according to claim 18, characterized in that the joining means (40) during assembly of the heat sink (20,30) is pressed in the joining gaps in each case substantially to the outside.

20. The method according to claim 17, characterized in that the electrically insulating joining means (40) is introduced after the joining of the two heat sink from the outside into the joint gap.