DE102012025494B4 - Diode laser module and method for producing a diode laser module - Google Patents

Abstract

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 heat sink (30) thermally connected to the n-side (15) of the laser diode element, 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 comprises at least two joining gaps (41, 42), characterized in that in an optical axis (16) vertical sectional plane of each of the two joining gaps has a taper from the outside inwards, the taper extending in each case over the entire width of the gap. The invention relates to a diode laser module (1) with a laser diode element (10) and two heat sinks (20, 30) with which the waste heat can be dissipated 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 also connected to the first heat sink by means of an electrically insulating joining means. The connection of the second heat sink to the first heat sink comprises at least two joining gaps (41, 42) which at least in sections have a taper from the outside inwards. Furthermore, a method for producing the diode laser module is specified.

Description

The present invention relates to a diode laser module with 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.

Out US20110069731A1 a diode laser is known in which the laser emitters are arranged between two substrates. The substrates have opposite trenches with a triangular cross section. The opposite trenches form diamond-shaped cavities that can be filled with a filler.

In DE 102010042087 A1 describes a diode laser module that contains a laser diode element. This in turn consists of a laser bar, which is connected on the p-side, ie the anode, and the n-side, ie the cathode, each with a heat spreading body. A heat sink is connected to each of these heat spreading bodies. The heat sinks are electrically connected to one side of the laser diode element. During the operation of the diode laser module, a voltage difference occurs between the two heat sinks. A short circuit between the two heat sinks must therefore be avoided. The heat sinks are therefore according to the DE 102010042087 A1 connected to each other by means of an electrically insulating adhesive. Here two equally thick joining gaps are used to the left and right of the laser diode element. The joining gaps lie in a plane parallel to the waveguide of the laser bar, which in 1 of the DE 102010042087 A1 is shown horizontally.

This arrangement has several disadvantages. The two heat sinks can slip against each other during assembly due to tolerances. 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 everywhere and the capillary force in the joint gap has no gradient. Since the capillary forces on the liquid joining agent in the joining gap are the same everywhere, there can be a random distribution of the joining agent during assembly. If the joining agent is underdosed, individual cavities can occur over the length of the joining gap, as a result of which the diode laser module leaks. In addition, the joining agent can even flow away from the joining point, especially when the joining agent is cured at an elevated temperature. If the preassembled diode laser module with the still liquid adhesive is brought to an elevated temperature, the viscosity of the joining agent can temporarily decrease, which favors the flow of the adhesive away from the joint.

The arrangement of the joining gaps near the level of the laser bar means that both heat sinks are approximately the same size and have almost the same cooling capacity. Since most of the waste heat from the laser bar is generated on the p-side of the laser bar, a heat flow between the two heat sinks is necessary. Therefore, a thermal adhesive must be used, for example a ceramic-filled epoxy resin adhesive with a thermal conductivity of over 0.5 W / (m * K). The disadvantage is that inexpensive structural adhesives with good mechanical properties cannot 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 carries particles for cooling that can settle at the joint, the joint must be chosen accordingly thick. However, a thick joint gap exhibits mechanical tension and tends to crack in the hardened jointing agent. This can affect the reliability of the diode laser module.

The object of the invention is to provide a reliable, inexpensive, easy-to-assemble diode laser module with double-sided cooling, in which two heat sinks are used, between which an electrical voltage difference occurs during operation of the laser module. In particular, the distribution of the joining agent in the joining gap should be reproducible, the joining agent should be metered in a manner that is not tolerant of tolerances, a joining agent should be usable without special requirements for thermal conductivity, and the alignment of the heat sinks with respect to one another and with respect to the laser diode element should be easy to accomplish. When the diode laser module is operated, the probability of failure due to a 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 heat sink thermally connected to the p-side (anode) of the laser diode element, a second heat sink thermally connected to the n-side (cathode) of the laser diode element, the second The heat sink is connected to the first heat sink by means of an electrically insulating joining means and the connection of the second heat sink to the first heat sink comprises at least two joining gaps, characterized in that in a sectional plane perpendicular to an optical axis of the laser diode element, each of the two joining gaps has a taper from the outside has inside.

The laser diode element can be, for example, a diode laser bar. A laser bar is a semiconductor chip that has a number of parallel arranged individual edge-emitting emitters contains. If the laser chip contains only one emitter, it is also referred to as a single emitter. In the following, the term laser bar should also include single emitters. A region of the laser diode element which emits laser radiation is referred to as an emitter. Typically, the width of a commercially available laser bar can be approximately 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 also be only 0.4 mm to 1 mm. The laser bar is electrically contacted on the p-side and n-side contact surfaces. These contact areas are the two largest areas of the laser bar, which are arranged opposite one another. The p-side contact area is the anode of the laser diode element, while the n-side contact area is the cathode of the laser diode element.

In another preferred embodiment, the laser diode element can comprise a laser bar and a first heat spreading body connected to the p-side of the laser diode element and / or a second heat spreading body connected to the n-side of the laser diode element. The term connection here means an electrical and thermal connection. 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 from the laser bar. In addition, the second heat expansion body can, but need not, be additionally connected to the first heat expansion body by means of an insulation layer. This connection can be a mechanical and / or a thermal connection.

The heat spreaders should have a high thermal conductivity and be electrically conductive. In a preferred embodiment, they can consist, for example, of copper or a metal-diamond composite. For some applications, an expansion-adapted material such as tungsten copper or molybdenum copper must be used. Ceramic thermal conductors are also possible if the required electrical conductivity is produced using a metallic coating. There may be burrs on the edges of the heat spreading bodies to improve the electrical contact with the heat sinks. The two heat spreading bodies are electrically insulated from one another. For this purpose, for example, an insulation layer can be provided between the heat spreading bodies. The p-side contact surface of the laser diode element is the side of the first heat spreading body facing away from the laser bar, which is attached to the anode of the laser bar. The n-side contact surface of the laser diode element is the side of the second heat spreading body facing away from the laser bar, which is attached to the cathode of the laser bar.

Alternatively, the laser diode element can also consist of a laser diode bar, which is provided with only one heat spreading body on the p-side or on the n-side.

A laser bar can contain a number of individual emitters which are designed as edge emitters. The waveguides are designed 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 waveguide and thus also the exit aperture of the laser beams are therefore close to the p-side (anode) of the laser bar. Since most of the heat loss is generated in the epitaxial plane, it is advantageous to attach a first heat sink to the p-side of the laser diode element, which has a higher cooling capacity than the second heat sink attached to the n-side. The main beam directions of the laser radiation from the emitters are parallel. The common plane of the waveguide (waveguide plane) is used below as a reference plane to illustrate advantageous arrangements of the joining gaps. The radiation direction of the emitter closest to the center of the laser bar is defined as the optical axis. The optical axis can lie in the waveguide plane and run perpendicular to the front facet of the laser bar. The laser bar can now have, for example, not just one but several epitaxial structures one above the other, which form a stack of parallel waveguide planes. With such a structure, the middle plane of the individual waveguide planes is considered as the reference plane (waveguide plane). In addition, the laser diode element can also have a stack of individual laser bars. With such a structure, the middle plane of the waveguide planes of the individual laser bars is considered as the reference plane (waveguide plane).

The two heat sinks can preferably be designed as air heat sinks, ie as heat sinks that are operated with air as the cooling medium. For this purpose, they can be equipped with several cooling fins or cooling fingers. Heat sinks with cooling fins can be produced, for example, using extrusion processes, for example from aluminum or an aluminum-based alloy. Particularly good heat dissipation can be achieved if the cooling fins are corrugated. In some cases, however, smooth cooling fins can also be sufficient, which are less expensive to produce. The air flow for cooling is preferably driven by a fan. If the diode laser module has a low power loss, convection cooling without a fan can be sufficient as an alternative. It is advantageous to keep the air flow parallel to the laser beam to lead. It can also be advantageous to direct the air flow antiparallel to the laser beam, ie in the opposite direction. However, it is also possible to provide the air flow with a radial speed component.

The first and / or the second heat sink can have a groove, which comprises a first contact surface and side surfaces, for receiving the laser diode element. It is particularly advantageous if the side surfaces are inclined such that they are at the smallest distance from one another at the cut edges of the contact surface. The groove is then expanded upwards. In particular, the distance between the side surfaces on the contact surface can be selected such that the position of the laser diode element is fixed in at least one direction in such a way that active alignment (adjustment) can be omitted. Such grooves are not absolutely necessary according to the invention, but such grooves are particularly advantageous if the laser diode element comprises one or more heat spreading bodies.

However, the heat sinks can also have channels through which they are cooled with a liquid or a gaseous cooling medium. Such heat sinks can be made, for example, from aluminum or preferably from copper.

The first heat sink has at least two first joining surfaces and the second cooling body has at least two second joining surfaces. The joining agent is located in at least two joining gaps, each of which is delimited by a first joining surface and a second joining surface. In each case, a first joining surface of the first heat sink lies opposite a second joining surface of the second cooling body, the distance between the two surfaces being at least partially bridged by the joining means. The two joining gaps each have a taper at least in sections from the outside inwards. The inside is characterized by being closer to the optical axis than the outside. The inventive tapering of the joint gap from the outside in is defined by the fact that, in a section perpendicular to the optical axis, the distance between the first joint surface and the second joint surface is smaller at a first point than at a second point which is further away from the optical axis than 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 extends over the entire width of the gap. The taper can be wedge-shaped. In this case, the first position can be selected at the inner end of the joint gap and the second position at the outer end of the joint gap. The joining surfaces do not necessarily have to be designed as flat surfaces. Curved surfaces or stepped surfaces are also possible. In any case, the tapering of the joint gaps from outside to inside is essential to the invention.

The joining gaps can lie in the plane of the waveguide of the laser diode element. However, it is more advantageous if the joining gaps do not lie in this plane, but are spaced apart from the waveguide plane and are located in the half space of the n side of the laser diode element. Then the first heat sink can be easily dimensioned by an enlarged surface with a higher cooling capacity than the second heat sink. It is particularly advantageous if, in addition, the joining gaps have a greater distance from the reference plane (waveguide plane) on the outside than on the inside. This manifests itself, for example, in that the outer surfaces of the joining agent are further away from the waveguide plane than the inner surfaces of the joining agent. If the joining surfaces are at least partially flat, it can be achieved that an angle between two first joining surfaces is less than 180 °. Angles between 60 ° and 120 ° are advantageously provided, particularly advantageously between 80 ° and 100 °. As a result, the joining gaps are neither designed to be mirror-symmetrical to the waveguide plane, nor to a plane parallel to the waveguide plane. In this advantageous embodiment considered, the center planes of the individual joining gaps are thus inclined relative to the waveguide plane.

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

The tapering of the joining gaps from the outside inwards according to the invention can be achieved in a preferred embodiment in that an angle is provided between two second flat joining surfaces which is smaller than the angle between two first flat joining surfaces. The angle between the second joining surfaces is preferably chosen to be 2 ° to 20 ° smaller than the angle between the first joining surfaces. In the case of joining gaps which are only tapered in sections, this consideration applies accordingly to the corresponding sections of the joining surfaces which limit the tapering of the adhesive gaps.

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 that lies in the middle of the middle emitter of the laser bar and can run in the direction of the resonator. The joining gaps are then to the left and right of the laser diode element. It is advantageous to choose the spacing of the joining gaps to be larger on the inside than the width of the laser diode element.

The first heat sink, which is attached to the p-side of the laser diode element, can be dimensioned such that it has a higher cooling capacity than the second heat sink, which is attached to the n-side of the laser diode element. Since the laser diode element emits more waste heat on the p-side than on the n-side, this advantageous dimensioning of the heat sink reduces the heat flow between the two heat sinks. Ideally, there is little or no heat flow between the two heat sinks. Therefore, an inexpensive joining agent can be used which does not have to meet high thermal conductivity requirements. The thermal conductivity can be less than 0.3W / (m * K) or even less than 0.1W / (m * K). Said heat sink dimensioning can be designed such that the first heat sink has a larger surface for heat exchange than the second heat sink. For this purpose, the first heat sink can be equipped with more cooling fins and / or with cooling fins having a larger area overall.

The laser diode element can, for example, be shorter than the first and / or the second heat sink, the length dimension being considered in the direction of the optical axis. It is also possible for the laser diode element to protrude or be set back in the direction of the optical axis with respect to the front edge of the first or second heat sink. A backset has the advantage that the laser diode element is better protected against mechanical damage.

1. a) Bereitstellen eines Laserdiodenelements, eines ersten Kühlkörpers und eines zweiten Kühlkörpers,
2. b) Verbinden des ersten Kühlkörpers mit der p-Seite des Laserdiodenelements,
3. c) Verbinden des zweiten Kühlkörpers mit der n-Seite des Laserdiodenelements,
4. d) Verbinden des zweiten Kühlkörpers mit dem ersten Kühlkörper mittels eines elektrisch isolierenden Fügemittels.

Dabei umfasst die Verbindung des zweiten Kühlkörpers mit dem ersten Kühlkörper wenigstens zwei Fügespalte, wobei jeder der zwei Fügespalte in einer zu einer optischen Achse senkrechten Schnittebene jeweils eine Verjüngung von außen nach innen aufweist.A method for producing a diode laser module according to the invention can include the following steps:

1. a) providing a laser diode element, a first heat sink and a second heat sink,
2. b) connecting the first heat sink to the p-side of the laser diode element,
3. c) connecting the second heat sink to the n side of the laser diode element,
4. d) connecting the second heat sink to the first heat sink by means of an electrically insulating joining means.

The connection of the second heat sink to the first heat sink comprises at least two joining gaps, each of the two joining gaps each having a taper from the outside inward in a sectional plane perpendicular to an optical axis.

The joining agent can preferably be an adhesive, particularly preferably an epoxy resin adhesive, which can be cured thermally at elevated temperature, at room temperature or chemically. The joining agent can, however, also be of an inorganic nature, for example a cement or a silicate-based joining agent. The joining agent can be viscous before curing and have high strength after curing. It is therefore a solidifiable joining agent. The diode laser module can be produced in such a way that an electrically insulating joining agent is applied to the joining surfaces of the first and / or the second cooling body before the two cooling bodies are joined together. In the viscous state, the joining agent can preferably be applied as a bead, for example as an adhesive bead. The height of the joining agent applied, for example the bead, can be greater than the predetermined mean thickness of the joining gap. The two heat sinks are joined together with the laser diode element, which is at least partially arranged between the two heat sinks. The joining gaps, which are located between two opposing joining surfaces, are bridged by the joining agent. When the heat sinks are joined together, pressure can be exerted on the previously applied joining agent. By joining the heat sink as a result of the tapering of the joining gap according to the invention, which is ventilated from the outside inwards, joining means can be essentially pressed outwards. Essentially, here means that the joining agent can also be pressed inwards, but because of the smaller hydraulic diameter caused by the tapering of the joining gap, it flows more slowly on the inside than on the outside, so that the joining agent preferably escapes to the outside. This means that the joining agent is pressed outwards in an adhesive gap when the movement of the joining agent is averaged over the joining agent volume. This advantageous effect is particularly pronounced when a medium or highly viscous joining agent is used, i.e. the viscosity of the joining agent is greater than 1000 cP. A thixotropic joining agent can be particularly advantageous. The thixotropy of the joining agent can prevent the joining agent from running before joining the heat sinks and can additionally promote the advantageous escape of the joining agent to the outside when joining. After joining, the outer surface of the joining agent can form either in the joining gap itself or in a cavity adjacent to the outside of the joining gap.

Alternatively, the heat sink with the laser diode element can also initially be assembled without a joining agent. The joining agent can be in In this case, after assembly, be introduced from the outside into the joint gap. To do this, it may be sufficient to dose the joining agent into a cavity provided on the outside of the joining gap, from which it penetrates into the joining gap as a result of the capillary forces. This type of filling of the joint gap can be accomplished particularly advantageously, since the tapering of the joint gap according to the invention, described below, increases the capillary forces on the liquid joining agent from the outside inwards. As a result, the liquid joining agent is preferably distributed to the inside of the joining gap and a reproducible distribution of the joining agent is achieved, which does not depend on random factors. In addition, the geometry of the joining gaps according to the invention means that the joining agent cannot flow away from the joining point, in particular not even if the viscosity of the joining agent temporarily drops during a curing process at elevated temperature. In a preferred embodiment, a space for receiving excess adhesive can be provided on the inside of the joint gap, which has at least one extension in cross section. This means that the liquid joining agent no longer capillates in the direction of the laser bar. This space can also hold a small amount of excess joining agent, so that a certain overdosing of the joining agent is not critical. Since the respectively opposing joining surfaces of both cooling bodies form a joining gap, free surfaces of the joining agent can be formed on the inside and outside. The inner surface of the joining agent can either lie in the joining gap, ie between the joining surfaces, or outside the joining gap, for example in the abovementioned inner cavity. It is even possible that the joining agent reaches as far as the laser diode element and then no free joining agent surface is formed on the inside. This can be the case in particular if, in a further embodiment, no internal cavity is provided, but the joining gaps reach as far as the laser diode element. The outer surface of the joining agent can either lie in the joining gap, ie between the joining surfaces, or outside the joining gap, for example in the adjacent outer cavity. Even if the joining agent is underdosed, it is distributed evenly over the entire length of the joining gap, promoted by the tapering of the joining gap. Because of the gradient of the capillary force in the joint gap, there is a uniform distance between the inner and outer surface of the jointing agent, the joint gap is practically filled uniformly and reproducibly from the inside.

A thermal conductor can advantageously be introduced between the p-side connection surface of the laser diode element and the corresponding contact surface of the first heat sink, as well as between the n-side connection surface 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 agent can be designed, 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, a heat-conducting film, for example a carbon film, can also be used. Alternatively, such a heat-conducting agent can also be formed as a metallic coating, for example made of tin, lead, indium, cadmium or gold, which is applied at least to the contact surface of the first and / or the second heat sink. Such a coating can additionally or alternatively be applied to the n-side and / or the p-side contact surface of the laser diode element. A heat-conducting agent can, however, also be a further joining agent, for example a heat-conducting adhesive. If the contact surfaces and contact surfaces are sufficiently flat, a heat-conducting agent can also be dispensed with. The first heat sink can therefore 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-conducting agent or without a heat-conducting agent. The first heat sink can additionally be mechanically connected to the p-side of the laser diode element and / or the second heat sink can be mechanically connected to the n side of the laser diode element. A mechanical connection can be form-fitting, material-fitting or force-fitting, and a combination of several of these types of connection is also possible. The use of the above Another joining means is, for example, an integral mechanical connection, while a contact pressure, which can arise, for example, 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. Through the above Forming a groove in one or both heat sinks can also be a positive connection.

When assembling the heat sink provided with the joining agent, a first joining surface comes to lie opposite a second joining surface and the joining agent 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 agent is applied as described above only after the heat sinks have been assembled. The wetting of the joining surfaces does not have to take place over the entire area, but the joining agent can also be slightly underdosed, so that the entire first and second joining areas are not wetted over the entire area. Overdosing is also possible, the joining agent can then collect in the cavities provided for this purpose, which adjoin the interior of the joint gaps. For reliable electrical insulation, a certain joint gap thickness is required between the first heat sink and the second heat sink, particularly on the outside. This distance can be determined by the laser diode element, which then has the function of a spacer due to its fixed thickness. In addition, but not necessarily, further spacers made of an electrically insulating material can be introduced as spacers between the heat sinks. The use of at least one spacer is advantageous if the laser diode element has a shorter length in the direction of the optical axis than the heat sinks, ie the laser diode element is shorter than the heat sinks. In particular if the laser diode element does not comprise a heat spreading body 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 on 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 for supplying current to the laser diode element.

The envelope of the outer edges of the cooling fins of the heat sink can advantageously be circular in cross section. 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 can also have a flattened shape (D shape) and / or be oval or rectangular. Other shapes are also possible. Flattening has the advantage that the diode laser module can be safely placed on it during installation or storage.

The diode laser module can further comprise an outer jacket which surrounds the heat sink at least in sections. This outer jacket has the effect that the air flow for cooling the diode laser module cannot escape radially in the surrounding section, but is instead guided in the spaces between the cooling fins or cooling fingers. This is advantageous because it improves the cooling of the diode laser module. In addition, an air stream can also be generated on the exit side of the laser beam, which simultaneously cools optical elements in the laser beam path and / or the target region of the laser beam. This air flow can be partially parallel to the optical axis and can be either blowing or sucking on the exit side of the laser beam. The outer jacket can advantageously be adapted to the enveloping outer edges of the cooling fins, so that it surrounds the diode laser module at a certain distance in cross section. A distance of the outer jacket to the outer edges of the cooling fins is particularly advantageous, which does not exceed the average hydraulic diameter of the air channels between the cooling fins. In particular, the outer jacket can be circular or oval in cross-section, with or without lateral flattening, or rectangular.

The diode laser module according to the invention has reliable electrical insulation between the heat sinks. An inexpensive joining agent can be used for the production. The requirements for the manufacturing tolerances are less demanding compared to the prior art, so that the manufacture of the module is more cost-effective. The inventive design of the joining gap enables particularly reliable and precise positioning of the heat sinks with respect to one another even without complex positioning devices. The heat sinks can be positioned passively in the correct position to each other during assembly. The joint gap is filled evenly over the entire length with the jointing agent, so that there are no voids in the jointing gap even if the jointing agent is underdosed. The design of the joining gap according to the invention can also achieve that, prior to joining the heat sinks, joining agent applied to the joining surfaces is preferably pressed outward in the joining gap when joining, so that the laser bar cannot be contaminated with joining agent. This can even tolerate an overdosing of the joining agent. Another advantage of the diode laser module is that the cooling air is guided effectively. This allows the flow rate of the cooling air to be reduced, so that fewer particles are carried along, which can settle on the outer surface of the joint gap. As a result, the likelihood of a short circuit is further reduced in connection with the joining gap according to the invention.

Further advantageous embodiments are the subject of the respective subclaims.

• 1 zeigt ein erfindungsgemäßes Diodenlasermodul in der Vorderansicht
• 2 zeigt den in 1 gekennzeichneten Ausschnitt in vergrößerter Darstellung
• 3 zeigt das Diodenlasermodul in seitlicher Schnittdarstellung
• 4 zeigt einen ersten Kühlkörper, einen zweiten Kühlkörper und ein Laserdiodenelement in Vorderansicht zur Veranschaulichung der Bezeichnung der einzelnen Flächen
• 5 zeigt ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Diodenlasermoduls in Vorderansicht
• 6 zeigt einen Klebspalt, bei dem die Verjüngung abschnittsweise ausgebildet ist

The invention is described in more detail below with reference to the figures.

• 1 shows an inventive diode laser module in front view
• 2 shows the in 1 marked section in an enlarged view
• 3 shows the diode laser module in a side sectional view
• 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
• 6 shows an adhesive gap in which the taper is formed in sections

A first embodiment is in the 1 . 2 and 3 shown. 1 shows a view looking towards the laser beam direction on the front of the diode laser module 1 , The joining agent 40 is) 1 hatched. This only serves to highlight the marked areas 40 in 1 represent visible surfaces, not cut surfaces. 2 shows a section of the 1 to the first joint gap 41 to reveal in an enlarged view. 3 shows the diode laser module 1 in cross section. The cutting plane runs perpendicular to the waveguide plane along the optical axis. The laser diode element 10 includes a laser bar 11 , a first heat spreading body 12 and a second heat spreading body 13 , the laser bar 11 is arranged between the first and the second heat spreading body. The heat spreaders 12 . 13 are in the direction of the optical axis 16 trained longer than the laser bar 11 , The front edges of the heat spreading bodies are arranged flush with the beam exit aperture of the laser bar, while they extend rearward beyond the rear facet of the laser bar. Between the two heat spreaders 12 . 13 there is no direct electrical contact since an insulation layer (not shown) is provided between them. The heat spreaders 12 . 13 have a high thermal conductivity. You can for example consist of copper or a metal-diamond composite. For some applications, an expansion-adapted material such as tungsten copper or molybdenum copper can be used to advantage. There may be burrs on the edges of the heat spreading bodies to improve the electrical contact with the heat sinks. The p-side contact area 14 of the laser diode element 10 is the laser bar 11 opposite side of the first heat expansion body 12 that is on the anode of the laser bar 11 is appropriate. The n-sided contact surface 15 of the laser diode element is the side of the second heat spreading body facing away from the laser bar 13 that is on the cathode of the laser bar 11 is appropriate.

The laser bar 11 contains here, for example 49 single emitter (not shown), which is designed as an edge emitter and across the width of the laser bar 11 are evenly distributed. The waveguides are designed as a flat, epitaxially produced structure and lie in one plane 80 , The p side of the laser bar is the epitaxial side, while the n side is the substate side. The waveguides and thus also the exit aperture of the laser beams are close to the p-side. Since most of the heat loss is generated in the epitaxial plane, it is advantageous, as shown in the exemplary embodiment, on the p-side of the laser diode element 10 a first heat sink 20 which has a higher cooling capacity than that on the n side 15 attached second heat sink 30 Has. The main beam directions of laser radiation 16 the emitters are parallel. The level of the waveguide 80 is used below as a reference level for illustration.

The laser diode element 10 is between the heat sinks 20 . 30 arranged. The laser diode element is, as in 3 shown in the direction of the optical axis 16 considered shorter than the heat sinks ( 20 . 30 ). The length of the laser diode element corresponds to the length of the heat spreading body 12 . 13 , The distance of the heat sink 20 . 30 is on the one hand by the laser diode element 10 itself, as well as through an additional spacer 60 certainly. This spacer 60 is electrically insulating and ensures that the joint gap thickness is maintained over the entire length of the heat sink, even if the heat spreading body 12 . 13 of the laser diode element 10 are shorter than the heat sink. The laser diode element is also in the direction of the optical axis opposite the front edges of the heat sink ( 20 . 30 ) set back. The back offset has the advantage that the laser diode element is protected against mechanical damage. The second heat sink 30 is with the first heat sink 20 by means of an electrically insulating joining agent 40 connected. The joining agent is in two joining gaps 41 . 42 , each with a first joining surface 22a . 22b and a second joining surface 33a . 33b be limited. Thereby lies the areas 22a of the first heat sink 20 the area 33a of the second heat sink 30 opposite, the distance between both surfaces by the joining agent 40 is bridged. The first joint gap defined thereby 41 is in 1 completely with joining agent 40 filled and has a taper from the outside in, which is wedge-shaped. Furthermore, the area lies 22b the first heat sink of the surface 33b opposite of the second heat sink, the distance between the two surfaces by the joining means 40 is bridged. The second joint gap defined thereby 42 also has a taper from the outside in. The taper according to the invention is characterized, as in 2 for the first joining gap, characterized in that the distance of the first joining surface is in a section perpendicular to the optical axis 22a to the second joining surface 32a on one place 47 is smaller than elsewhere 48 which is farther from the laser diode element than the location 47 , The same applies to the distance between the first joining surface 22b to the second joining surface 32b ,

The joining column 40 . 41 lie above the waveguide level, ie in the half-space in which there is also the n-side contact surface 15 of the laser diode element is located. On the outside are the distances of the joining gaps to the reference plane 80 bigger than inside. This makes it possible to use the first heat sink 20 a larger number of cooling fins 27 to be provided as on the second heat sink 30 which has a smaller number of cooling fins 37 contains. The heat sink 20 . 30 are translationally symmetric with respect to the main beam direction (optical axis) 16 trained, as well as the joining gaps 41 . 42 ,

The tapering of the joint gaps from the outside in is achieved by the in 1 . 2 shown wedge-shaped construction of the joining gaps 41 . 42 causes. In 4 are the components of the first heat sink 20 , second heat sink 30 and laser diode element 10 shown individually one above the other to show the position of the designated areas and to illustrate the formation of the wedge shape of the adhesive gaps. To form the wedge-shaped adhesive gap is between the first joining surfaces 22a and 22b an angle 23 provided by 90 °, while the angle between the second joining surfaces 32a and 32b an angle 33 of 75 ° is provided. The joint gap has a thickness on the inside 41 from 0.05mm on while it's a thickness outside 42 of 0.5mm. In 1 and 2 however, it is shown thicker overall for illustration. It is particularly advantageous to choose the thickness of the joint gap on the inside between 0.02mm and 0.2mm and on the outside between 0.1mm and 2mm.

The first heat sink 20 contains a groove for receiving the laser diode element 10 that from the first contact surface 21 and two side faces 25 is formed. The side faces 25 are inclined so that they are on the cut edges of the contact surface 21 have the smallest distance from each other. The groove is then expanded upwards. The width of the groove is on the contact surface 25 only slightly wider than the first heat spreading body 12 , namely so wide that it reliably fits into the groove taking the tolerances into account. As a result, the horizontal position of the laser diode element relative to the first heat sink is fixed, so that active alignment (adjustment) can be dispensed with. The second heat sink 30 also contains a groove for receiving the laser diode element 10 that from the first contact surface 31 and two side faces 35 is formed. The width of the groove is on the contact surface 35 only slightly wider than the second heat spreading body 13 , namely so wide that it reliably fits into the groove taking the tolerances into account. 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 set for the first 20. Such grooves are not absolutely necessary according to the invention, but such grooves are particularly advantageous if the laser diode element 10 comprises one or more heat spreading bodies.

The two heat sinks 20 . 30 are designed as air heatsinks. For this purpose they are each equipped with several cooling fins 27 . 37 fitted. The cooling fins are used to achieve particularly good heat dissipation 27 . 37 corrugated. In some cases, however, smooth cooling fins can also be sufficient, which are less expensive to produce. The airflow 70 is preferably driven by a fan. If the diode laser module has a low power loss, convection cooling without a fan can be sufficient as an alternative. The diode laser module also includes an outer jacket 50 with a circular cross section representing the heat sink 23 . 30 surrounds at a distance from the outer edges of the cooling fins, which is in the order of the distance of the cooling fins. The airflow 70 is like in 3 shown, parallel and in the same direction as the laser beam 16 guided. Alternatively, it would also be possible for the air flow to be antiparallel, that is to say in the opposite direction from the illustration in FIG 3 , respectively. The air flow is driven by a fan, not shown. This can be installed behind the module on the side facing away from the laser bar and can be operated by blowing or suction. The air is inside the outer jacket 50 guided. It is sufficient if the outer jacket surrounds the heat sink in sections. The heat sinks protrude slightly from the outer jacket, as shown in this first embodiment.

Another embodiment is in 4 shown. In this example there is the laser diode element 10 only from a laser bar 11 , There are no heat spreaders. The laser bar 11 is right here between the first heat sink 20 and the second heat sink 30 arranged. The p-side contact area 14 the laser bar lies on the first contact surface 21 that was previously coated with indium. The n-sided contact surface 15 the laser bar lies on the second contact surface 31 that was previously coated with indium.

The first and second joining surfaces 22 . 32 are not designed 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 center lines of curvature of the first 22 and second 33 Joining surfaces can be reached.

The diode laser module has a round outer contour with a flattening on the top of the second heat sink 30 on. You can see that in the illustration in 4 because the outer edges of some cooling fins lie in one plane. As a result, the module can be placed on this flat surface without it tipping. Another advantage is that there is no twisting if you place the module in an appropriately shaped outer jacket 50 introduces.

The taper can extend over the entire width of the gap or only over a certain section of the gap. Such a further exemplary embodiment of a joining gap is shown in 6 shown. The first joint surface 22 is a flat surface. The second joining surface 32 is not a flat surface, but consists of two flat partial surfaces. Are the two joining surfaces 22 . 32 in this third exemplary embodiment, the joining gap shown results with a taper formed in sections from the outside inwards. This taper is in the section 81 , another section during the joint gap 82 has no taper. The taper is here only in the tapered section 81 to determine. The sections with 81 or without 82 Rejuvenation are in 6 shown as arrows pointing inwards from the outside. The taper according to the invention is as in 6 for the first joining gap, characterized in that the distance of the first joining surface is in a section perpendicular to the optical axis 22 to the second joining surface 32 at one point 47 is smaller than elsewhere 48 which is farther from the laser diode element than the location 47 ,

In a further embodiment, not shown, the laser diode element 10 from a laser diode bar 11 exist with only one heat spreading body 12 or 13 is provided.

In a further exemplary embodiment, the laser bar can have, for example, not just one but a plurality of epitaxial structures one above the other, which form a stack of parallel waveguide planes. With such a structure, the middle plane of the individual waveguide planes is used as the reference plane (waveguide plane 80 ) considered. In addition, the laser diode element can also have a stack of individual laser bars. With such a structure, the middle plane of the waveguide planes of the individual laser bars is used as the reference plane (waveguide plane 80 ) considered.

LIST OF REFERENCE NUMBERS

1

diode laser module

10

laser diode element

11

laser bars

12

first heat spreading body

13

second heat spreading body

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 joining surface

33

Angle between two second joining surfaces

34

second receiving groove

35

Side surface of the second receiving groove

40

joining means

41

first joint gap

42

second joint gap

43

inner joint surface

44

outer joint surface

45

internal cavity for taking up excess joining agent

46

outer cavity

47

first place to measure the thickness of the joint gap

48

second place for measuring the thickness of the joint gap

50

outer sheath

60

spacer

70

airflow

80

Waveguide level of the laser diode element

81

Taper from outside to inside, section of the adhesive gap with taper

82

Section of the adhesive gap without taper

Claims (20)

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 heat sink (30) thermally connected to the n-side (15) of the laser diode element, 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 comprises at least two joining gaps (41, 42), characterized in that in an optical axis (16) vertical sectional plane of each of the two joining gaps has a taper from the outside inwards, the taper extending in each case over the entire width of the gap. Diode laser module after Claim 1 , characterized in that the first heat sink (20) has a higher cooling capacity than the second heat sink (30). Diode laser module after 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 of this waveguide plane. Diode laser module after Claim 1 or 2 , characterized in that in the sectional plane perpendicular to the optical axis (16) the two joining gaps (41, 42) are wedge-shaped at least in sections. Diode laser module after Claim 1 . 2 or 4 , characterized in that the joining gaps (42, 43) each open at least in sections into a cavity (45) which is at least partially provided for receiving excess joining agent. Diode laser module according to one of the preceding claims, 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. Diode laser module according to one of the preceding claims, 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) is connected. Diode laser module after Claim 7 , characterized in that the first and / or the second heat sink serves as a connection contact for supplying current to the laser diode element (10). Diode laser module according to one of the preceding claims, characterized in that the laser diode element comprises a laser bar (11) and a first heat spreading body (12) connected to the p-side of the laser diode and / or a second heat spreading body (13) connected to the n-side of the laser diode. includes. Diode laser module after Claim 9 , characterized in that the second heat expansion body is connected to the first heat expansion body by means of an insulation layer. Diode laser module according to one of the preceding claims, characterized in that the joining means (40) has a thermal conductivity of less than 0.3 W / (m * K). 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). Diode laser module according to one of the preceding claims, characterized in that the first and the second cooling body (20, 30) are designed as air cooling bodies. Diode laser module after Claim 13 , characterized in that the first and the second heat sink are provided with smooth or corrugated cooling fins (27, 37). Diode laser module after Claim 14 , characterized in that it further comprises an outer jacket (50) which surrounds the first and second heat sinks (20, 30) at least in sections. Diode laser module after Claim 15 , characterized in that the distance between the outer casing (50) and the outer edges of the cooling fins (27, 37) is smaller than the average hydraulic diameter of the air channels between the cooling fins. 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 to the first heat sink by means of an electrically insulating joining means (40), characterized in that the connection of the second heat sink to the first The heat sink comprises at least two joining gaps (41, 42), and each of the two joining gaps each has a taper from the outside inwards in a section plane perpendicular to an optical axis (16), the taper extending in each case over the entire width of the gap. Procedure according to Claim 17 , characterized in that before the joining of the two heat sinks, the electrically insulating joining means (40) is applied to the joining surfaces of the first and / or the second heat sink. Procedure according to Claim 18 , characterized in that the joining means (40) is essentially pressed outwards in the joining gaps when the cooling bodies (20, 30) are joined together. Procedure according to Claim 17 , characterized in that the electrically insulating joining means (40) is introduced into the joining gap from the outside after the two heat sinks have been joined together.

Images