EP0953208A1

EP0953208A1 - Diamond body

Info

Publication number: EP0953208A1
Application number: EP97953665A
Authority: EP
Inventors: Peter Koidl; Christof Wild; Eckhard WÖRNER
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 1997-01-18
Filing date: 1997-12-20
Publication date: 1999-11-03
Also published as: DE19701680A1; DE19701680C2; WO1998032171A1; JP2001508600A; US6536509B1

Abstract

The invention concerns a diamond body designed to enable the thermal contacting with at least one source of heat (30) and presenting at least one recess (13, 15) defining an angular position in relation to the mechanical tensions generated by said or any source of heat (30). Consequently, the mechanical tensions generated at various temperatures, either, for example, by various thermal expansion coefficients of the diamond body (12) or by the source of heat (30) featured by one semi-conductor component, are at least partly compensated, resulting in the possibility to take advantage of the exceptional thermoconductive capacity and insulating characteristics of the diamond, including diamond bodies (12) of a relatively big size.

Description

Diamond body

The invention relates to a diamond body for connection to at least one component.

From the article "Diamond films as thermal conductors and electrical insulators applied to semiconductor power modules" by B. Fiegl, R. Kuhnert, H. Schwarzbauer and F. Koch in Diamond and Related Materials, 3 (1 994), pages 658 to 662 it is known that diamond bodies can advantageously be used as heat sources for dissipating large amounts of heat, for example from semiconductor components, because of the very high thermal conductivity of diamond.

As from the article "Applications of CVD Diamond in Thermal Management" by G. Lu in 2nd International Conference on the Applications of Diamond Films and Related Materials, editors M. Yoshikawa, M. Murakawa, Y. Tzeng and WA Yarbrough, MYU, Tokyo 1 993 known, with diamond plates deposited from the gas phase as diamond bodies, large amounts of heat can also be dissipated quickly with a so-called heat spreading, that is to say an effective spatial distribution of the heat, due to the high thermal conductivity, in particular of point-like heat sources.

However, as is evident from the article "Thermal Stress in Diamond Films" by VG Ralchenko, ED Obraztova, KG Korotooshenko et al. in Applications of Diamond Films and Related Materials: Third International Conference, 1 995, editor A. Feldman, Y. Tzeng, WA Yarbrough et al. known, the problem that due to the very low coefficient of thermal expansion of diamond due to the temperature difference when connecting to other materials such as semiconductors or metals by soldering and in operation at usually room temperatures In some cases, considerable thermally induced mechanical stresses occur, which under certain circumstances can disadvantageously lead to the destruction of the connection or of the diamond body itself.

So far, it has been proposed to reduce such thermal stresses in connection with components that have been applied that a thick soft solder layer be provided when a diamond body is connected to components in order to compensate for the mechanical stresses that are thermally induced in the soldered connection via their elasticity. A disadvantage of this procedure, however, is that the heat resistance increases significantly, so that the heat dissipation is reduced, particularly when heat is spread.

The invention has for its object to provide a diamond body of the type mentioned, in which the risk of loosening a connection to other in particular relatively inelastic materials or the destruction of the diamond body due to thermally induced mechanical stresses is reduced, especially when connected with heat.

This object is achieved in the case of a diamond body of the type mentioned at the outset by introducing at least one elongate recess which extends at an angle to mechanical stresses which are thermally induced from the connection with the or each component.

By providing at least one elongated recess in the diamond body, which is at an angle to at temperature differences, for example when the diamond body is connected to the component under heat application and room temperature, or under certain circumstances also between an operating state with a very high temperature and an idle state. stood, thermally induced mechanical stresses, these are at least partially compensated by the or each obliquely aligned recess by the resulting increase in the mobility of the diamond body, so that the risk of flaking of the diamond body is significantly reduced, the exploited properties of diamond how much however, good electrical insulation behavior or excellent thermal conductivity are essentially retained.

A number of recesses is preferably provided, which are preferably arranged at right angles to mechanical stresses. It is expedient for the recesses to be oriented at a small angle to heat flow directions determined by the geometry of the diamond body and the arrangement of heat sources or heat sinks formed, for example, by the or each component. It is particularly advantageous if a number of recesses run essentially at right angles to mechanical stresses and essentially parallel to the directions of heat flow.

In one embodiment, a number of recesses are designed as internal slots that are open to two surfaces of the diamond body. In other configurations, the recesses are designed as slots which are open to three surfaces, the respective residual material thickness on an edge side adjacent to the slot end being smaller than the depth of each slot. This results in a particularly high compensation of thermally induced mechanical stresses in connection with narrow elongate components, in which case it is expedient for good heat spreading that slots arranged parallel to one another are provided oriented transversely to an elongated heat source or heat sink. In the case of a grid-like arrangement of a plurality of punctiform heat sources or heat sinks as components, it is advantageous to arrange the recesses extending between adjacent heat sources and to enclose each heat source in order to spread the heat generated over a larger area on the one hand and mechanical ones generated in the area of each heat source on the other To compensate tensions locally.

With diamond bodies designed in this way, components to be connected with solder, in particular at a relatively high temperature, such as semiconductor lasers or computing modules, can be applied without there being a great risk of detachments, breaks and / or deformations of the applied components or of diamond bodies, advantageously due to the Compensation of the mechanical stresses through the recesses, a very thin solder layer with a correspondingly low thermal resistance can be used.

Further expedient refinements and advantages of the invention are the subject of the subclaims and the following description of exemplary embodiments with reference to the figures of the drawing. Show it:

1 is a flattened cuboid diamond body with recesses made on the edge and inside in a perspective view,

2 is a perspective representation of a flattened cuboid diamond body with recesses made from two edge sides and oriented parallel to one another,

3 shows a flattened cuboid diamond body with parallel, parallel to each other introduced from two cover sides other aligned recesses in a perspective view,

4 a circumferential and longitudinally arranged recesses in a round diamond body in a top view,

5 shows the arrangement of heat sources as components in a diamond body according to FIG. 1 in a perspective view and

6 shows a perspective view of a diamond body according to FIG. 2 as a heat spreader arranged between a laser diode bar and a microchannel cooler.

1 shows a perspective illustration of a diamond body 1 made from one piece, which has a flattened cuboid shape. The diamond body 1 has a first edge side 2, a second edge side 3 opposite the first edge side 2, a third edge side 4 extending between the first edge side 2 and the second edge side 3, and a fourth edge side 5 opposite the third edge side 4 form the peripheral surface of the diamond body 1 all around. Furthermore, the diamond body 1 has a first cover side 6 visible in the illustration according to FIG. 1 and a second cover side 7 opposite the first cover side 6, which form the cover surfaces of the diamond body 1.

The diamond body 1 shown in FIG. 1, as the first group of recesses, has a number of short edge slots 8 which extend between the cover sides 6, 7 and are each open to one of the edge sides 2, 3, 4, 5. The short edge slots 8 are elongated and aligned substantially perpendicular to the edge side 2, 3, 4, 5 to which they are open. As a second group of elongated recesses, first inner slots 9, each parallel to one another, are introduced into the diamond body 1 shown in FIG. 1, only a few of which are provided with reference numerals for reasons of clarity. Furthermore, the diamond body 1 has elongated second inner slots 10 aligned at right angles to the first inner slots 9, of which only a few are provided with the relevant reference numerals for reasons of clarity. The inner slots 9, 10 extend open between the cover sides 6, 7 and are closed at their ends facing the edge sides 2, 3, 4, 5. The first inner slots 9 are aligned in groups in parallel to the first edge side 2 and the second edge side 3 and are regularly spaced. Every second inner slot 10 is arranged between two adjacent first inner slots 9 and runs parallel to the third edge side 4 and the fourth edge side 5, each in alignment with its second inner slots 10, which are adjacent in the longitudinal direction.

It is expedient to arrange the inner slots 9, 1 0 so that they have regular distances and thus a highly symmetrical structure. The length of the edge slits 8 and inner slits 9, 10 is set up in such a way that the respective remaining material thickness 1 1 at selected locations with reference characters to an inner slit 9, 10 adjacent to the respective slit end is smaller than the length of the edge slits 8 or inner slits 9, 10 .

The diamond body 1 shown as an exemplary embodiment in FIG. 1 is particularly suitable for connection to point-shaped heat sources or heat sinks as components which are each symmetrically surrounded by two pairs of inner slots 9, 10. The diamond body 1 can also advantageously be connected to components which extend through a plate which extends essentially over the entire surface of the diamond body 1 is formed, which is connected to the diamond body 1 by point-shaped connections enclosed by inner slots 9, 10 and has a considerable temperature difference of, for example, a few 100 degrees in two operating states, the diamond body 1 being used primarily as an electrical insulator in this case. By providing the inner slots 9, 10 and also the edge slots 8, the mechanical stresses caused in the diamond body 1 due to the temperature difference in the two operating states of the component are compensated to such an extent that deformations, damage or breaks in the component and / or the diamond body 1 are avoided .

FIG. 2 shows a perspective illustration of a further exemplary embodiment of a flattened cuboid diamond body 1 2 with edge sides 2, 3, 4, 5 and cover sides 6, 7 aligned in pairs parallel to one another. The diamond body 1 2 shown in FIG. 2 is the first group of elongated recesses first long edge slots 1 3, which extend from the first edge side 2 parallel to the third edge side 4 and fourth edge side 5 in the direction of the second edge side 3 opposite the first edge side 2 and are open to both edge sides 6, 7. The remaining material thickness 1 4 remaining between the end of the first long edge slots 1 3 facing the second edge side 3 and the second edge side 3 is many times smaller than the length of the first long edge slots 1 3. The first long edge slots 1 3 are regularly spaced apart and parallel to one another aligned.

In the middle between two adjacent first long edge slots 1 3, starting from the second edge side 3, in the direction of the first edge side 2, as the second group of elongate recesses to both cover sides 6, 7, open second long edge slots 1 5, with the end facing the first edge side 2 second long edge slots 1 5 also one compared to the length of the second long edge slots 1 5 remains a much smaller second residual material thickness 1 6. In order to impart different compensation properties to the diamond body 1 2 on the first edge side 2 and the second edge side 3, it is expedient that the long edge slots 1 3, 1 5 each have different lengths, so that different residual material thicknesses 14, 1 6 remain in each case.

The diamond body 1 2 shown in Fig. 2 can also be worked out from a single piece and has a meandering structure which, when applied transversely to the course of the long edge slots 1 3, 1 5 or elongated heat sources or heat sinks as components for a particularly effective compensation of thermal induced mechanical stresses.

FIG. 3 shows a perspective illustration of a further exemplary embodiment of a flattened cuboid diamond body 17 with edge sides 2, 3, 4, 5 and cover sides 6, 7 formed in accordance with the diamond bodies 1, 1 2 shown in FIGS. 1 and 2 The diamond body 1 7 shown in FIG. 3 is a first group of elongate recesses, a number extending from the first cover side 6 in the direction of the second cover side 7, parallel to the third edge side 4 and the fourth edge side 5 and to the first edge side 2 and the second edge side 3 open first slot slots 1 8 introduced. The first slot slots 18 are regularly spaced and have a depth which is greater than the first residual material thickness 19 remaining between their slot end facing the second cover side 7 and the second cover side 7.

Furthermore, in the diamond body 1 7 shown in FIG. 3, a number of extending from the second cover side 7 in the direction of the first cover side 6, parallel to the third edge side 4 and the center between adjacent first groove slots 1 8 as a second group of elongate recesses fourth Edge slot 5 extending and to the first edge side 2 and the second edge side 3 open second slot slots 20 are introduced. The depth of the regularly spaced second slot slots 20 is also set so that it is greater than the second residual material thickness 21 remaining between the slot end of the second slot slots 20 facing the first cover side 6 and the cover side 6.

The diamond bodies 1, 1 2, 1 7 shown in FIGS. 1 to 3 are preferably made of synthetically produced polycrystalline diamond disks with a thickness of a few 100 micrometers between the cover sides 6, 7 and edge lengths of the edge sides 2, 3, 4, 5 of made up to a few centimeters. The width of the recesses 8, 9, 1 0, 1 3, 1 5, 1 8, 20 is in the range of a few tens of micrometers, the distance between adjacent short-edge slots 8, inner slots 9, 10, long-edge slots 1 3, 1 5 and slot slots 1 8, 20 is in the range of a few 100 micrometers. Typical values for the residual material thicknesses 1 1, 14, 1 6, 1 9, 21 are also in the range of a few 1 00 micrometers.

FIG. 4 shows a top view of a flattened, disc-shaped diamond body 22 which has a cylindrical edge side 23 and a first cover surface 24 visible in the illustration according to FIG. 4 and a second cover surface 25 opposite the first cover surface 24 and running parallel to it. The diamond body 22 shown in FIG. 4 has, as a first group of elongate recesses, annular slits 26 arranged on concentrically nested circular circumferential lines, each of which extends in sections along five circular circumferences in the diamond body 22 shown in FIG. 4. In this case, ring slots 26 arranged in each case next to the circumference of the circle extend in the same ring slot angle segment, the individual ring slot angle segments being separated from one another with the same spacing angle. Furthermore, the diamond body 22 shown in FIG. 4, as a second group of elongate recesses, has a number of radial radial slots 27, each arranged between adjacent ring slots 26, which are arranged centrally on the concentrically arranged circumferential lines along which the ring slots 26 extend are, wherein the radial slots 27 arranged on the circumferential line with the largest diameter are open to the edge side 23.

The diamond body 22 shown in FIG. 4 is provided in particular as a heat spreader for use with a centrally arranged heat source or heat sink as a component and with a metal ring attached to the edge side 23 for heat dissipation or heat supply.

FIG. 5 shows a perspective illustration of the diamond body 1 according to FIG. 1 when used with periodically arranged heat sources 28 positioned centrally between the inner slots 9, 10 or the edge sides 2, 3, 4, 5 and short edge slots 8 as components with locally opposite surrounding temperatures. The heat sources 28 are, for example, surface-emitting laser arrays, the electrical contacting of which is not shown in FIG. 5 for reasons of clarity. The heat sources 28 are provided on their sides opposite the diamond body 1 with a cover 29 which extends over the heat sources 28 and which together form a structural unit with a coefficient of thermal expansion different from diamond.

The thermally induced mechanical stresses that occur due to the temperature differences along the connection between two adjacent heat sources 28 when the structural unit formed by the heat sources 28 and the cover 29 is applied to the diamond body 1 by applying heat, for example during soldering, are due to the intermediate ones Inner slits 9, 10 and short-edge slits 8, which extend partly at right angles, partly at 45 degrees between adjacent heat sources 28, are largely compensated for by reducing the risk of damage, the inner slits 9, 10 due to their essentially oblique orientation to those of the heat sources 28 are oriented radially pointing heat flow directions, so that a relatively good heat dissipation is ensured to a heat dissipation element, not shown in FIG. 5, arranged on the side of the diamond body 1 opposite the heat sources 28.

FIG. 6 shows a perspective illustration of the diamond body 1 2 according to FIG. 2, to which a laser diode bar 30, adjacent to the second edge side 3, is applied by, for example, brazing at a relatively high temperature. Due to the long edge slots 1 3, 1 5 extending at right angles to the second edge side 3 with the resulting meandering structure, mechanical stresses are due to the different thermal expansion coefficients of the semiconductor material of the laser diode bar 30 and the diamond body 1 2 when the mechanical connection is carried out equalizable, so that the risk of damage to the laser diode bar 30 is significantly reduced.

The distances between optically active areas of the laser diode bar 30, from which laser radiation 31 can be emitted with arrows, and between the second long edge slots 15 which are open to the second edge side 3 and the intermediate first long edge slots 13 are for effective heat spreading by those which are optically active Areas generated as heat sources are matched to each other so that each optically active area is arranged on sections of the diamond body 1 2 extending between two long edge slots 1 3, 1 5. A microchannel cooler 32 is attached to the cover side 7 of the diamond body 1 2 opposite the laser diode bar 30. Inflow lines 33 aligned parallel to one another with microchannels 34 open to the second cover side 7 of the diamond body 1 2 and outflow lines 35 adjoining the inflow lines 33 are aligned parallel to the long edge slots 1 3, 1 5. This results in a heat flow during operation of the laser diode bar 30 essentially parallel to the long edge slots 1 3, 1 5, while mechanical stresses occur transversely thereto, so that on the one hand there is an effective heat spreading and on the other hand an effective compensation of the mechanical stresses.

Claims

PATENT CLAIMS

Diamond body for connection to at least one component, characterized in that at least one elongate recess (8, 9, 10, 1 3, 1 5, 1 8, 20, 26, 27) is introduced, which is at an angle to the connection with the or each component extends thermally induced mechanical stresses.

2. Diamond body according to claim 1, characterized in that a number of recesses (8, 9, 1 0, 1 3, 1 5, 1 8, 20, 26, 27) are at least obliquely to one by at least one heat source (28, 30) and / or at least one heat sink induced heat flow direction is arranged extending.

3. Diamond body according to claim 2, characterized in that a number of recesses (8, 9, 1 0, 1 3, 1 5, 1 8, 20, 26, 27) with respect to the or each heat source

(28, 30) and / or the or each heat sink is aligned such that the alignment angles to the mechanical stresses are greater than the alignment angles to the directions of heat flow.

4. Diamond body according to one of claims 1 to 3, characterized in that a number of recesses (8, 9, 10, 1 3, 1 5, 1 8, 20, 26, 27) are arranged extending at right angles to mechanical stresses is.

5. Diamond body according to one of claims 2 to 4, characterized in that a number of recesses (8, 9, 10, 1 3, 1 5, 1 8, 20, 26, 27) are substantially parallel to one through or any heat source (28, 30) and / or the or each heat sink-induced heat flow direction is arranged to extend.

6. Diamond body according to one of claims 1 to 5, characterized in that a number of mutually parallel recesses (8, 9, 1 0, 1 3, 1 5, 1 8, 20) is provided.

7. Diamond body according to one of claims 1 to 6, characterized in that a number of mutually perpendicular recesses (8, 9; 8, 10; 9, 10) is provided.

8. Diamond body according to claim 6 and claim 7, characterized in that in two mutually perpendicular

Directions Recesses (9, 10) with alternating alignments follow one another.

9. Diamond body according to one of claims 1 to 6, characterized in that a number on at least one

Recesses (26, 27) arranged circumferentially are provided.

10. Diamond body according to claim 9, characterized in that a number of recesses (27) extending transversely to the or each circumferential line is arranged.

1 1. Diamond body according to Claim 9 or Claim 10, characterized in that a number of recesses (26) are arranged to extend along the or each circumferential line.

1 2. Diamond body according to one of claims 1 to 1 1, characterized in that a number of recesses closed internal edges (9, 10, 26, 27), which extend from a cover side (6, 24) of the diamond body (1, 22) to a cover side (7, 25) opposite this cover side (6, 24).

13. Diamond body according to one of claims 1 to 12, characterized in that a number of recesses (8, 13, 15, 18, 20, 27) on three sides (2, 6, 7; 3, 6, 7; 4, 6, 7; 5, 6, 7; 2, 3, 6; 2, 3, 7; 23, 24, 25) are open, with the respective residual material thickness (11, 14, 16, 19, 21) on the closed side the slots (2, 6, 7;

3, 6, 7; 4, 6, 7; 5, 6, 7; 2, 3, 6; 2, 3, 7; 23, 24, 25) is smaller than the depth of each recess (8, 13, 15, 18, 20, 27).

14. Diamond body according to one of claims 1 to 13, characterized in that it is a cuboid or cylinder flattened in one dimension.