Double-sided cooling of a laser diode
Patent Information
- Application Number
- DE112020002811
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2019-06-11
- Filing Date
- 2020-06-10
- Publication Date
- 2025-10-09
- Estimated Expiration
- 2040-06-10
Smart Images
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Abstract
Description
TECHNICAL FIELD
[0001] The present disclosure relates to double-sided cooling of laser diodes. BACKGROUND
[0002] High-performance semiconductor laser diodes are cooled to keep the junction temperature and carrier leakage low and reliability high. A laser diode may be mounted on a heat sink, which helps reduce thermal impedance.
[0003] Heinemann, S.; et al.: “Advanced chip designs and novel cooling techniques for brightness scaling of industrial, high power diode laser bars”; In: Proceedings of SPIE Vol. 10514 (2018) 105140Y reveals cooling options for laser diodes.
[0004] DE 10 2009 040 835 A1 shows a semiconductor component arrangement which has two heat conducting bodies arranged on opposite sides of the semiconductor component arrangement.
[0005] Heinemann, S.; et al.: “Packaging of high-power bars for optical pumping and direct applications”; In: Proceedings of SPIE Vol. 9348 (2015) 934807 discloses a structure of laser diodes and shows possibilities for thermal management. SUMMARY
[0006] Generally, in some aspects, the subject matter of the present disclosure may be implemented in laser diode devices including: a first heat sink including a first mounting layer, wherein the first mounting layer includes at least two mounting pads that are electrically isolated from each other; a second heat sink including a second mounting layer, wherein the second mounting layer includes at least two mounting pads that are electrically isolated from each other; and a laser diode bar between the first heat sink and the second heat sink, wherein a lower electrical contact of the laser diode bar is attached to the first mounting layer and an upper electrical contact of the laser diode bar is attached to the second mounting layer.
[0007] Implementations of the laser diode devices may include one or more of the following features. For example, in some implementations, the laser diode includes: a first contact bar; and a second contact bar, wherein both the first contact bar and the second contact bar are mounted between the first heat sink and the second heat sink. The first mounting layer may include a first mounting pad and a second mounting pad electrically isolated from the first mounting pad. The second mounting layer may include a third mounting pad and a fourth mounting pad electrically isolated from the third mounting pad. The lower electrical contact of the diode laser bar may be electrically connected to the first mounting pad, and the upper electrical contact of the laser diode bars may be electrically connected to the third mounting pad.A lower surface of the first contact strip may be electrically connected to the first attachment pad of the first attachment layer, and an upper surface of the first contact strip may be electrically connected to the fourth attachment pad of the second attachment layer. A lower surface of the second contact strip may be electrically connected to the second attachment pad of the first attachment layer, and an upper surface of the second contact strip may be electrically connected to the third attachment pad of the second attachment layer. The first contact strip may extend beyond a first edge of the first heat sink and / or the second heat sink, and the second contact strip may extend beyond a second edge of the first heat sink and / or the second heat sink.A shape of the first fastening pad of the first fastening layer may be the same as a shape of the third fastening pad of the second fastening layer, and a shape of the second fastening pad of the first fastening layer may be the same as a shape of the fourth fastening pad of the second fastening layer. The second fastening pad of the first fastening layer may overlap the third fastening pad of the second fastening layer without overlapping the fourth fastening pad of the second fastening layer. The first fastening pad of the first fastening layer may overlap the third fastening pad and the fourth fastening pad of the second fastening layer.
[0008] In some implementations, a height of each of the first contact bar, the second contact bar, and the laser diode between the first heat sink and the second heat sink may be the same.
[0009] In some implementations, the first heat sink includes: a first main body portion including at least one fluid channel; a first electrically insulating layer on the first main body portion; and the first attachment layer on the first electrically insulating layer. The second heat sink includes: a second main body portion including at least one fluid channel; a second electrically insulating layer on the second main body portion; and the second attachment layer on the second electrically insulating layer. Each of the first main body portion, the second main body portion, the first attachment layer, and the second attachment layer may be formed from a metal. The metal is copper or copper-tungsten. Each of the first electrically insulating layer and the second electrically insulating layer may be formed from a ceramic.
[0010] In general, the subject matter of the present disclosure may be implemented in laser diode bar cooling devices including: a first heat sink including a first attachment layer for attachment to a laser diode bar, the first attachment layer including a first attachment pad and a second attachment pad that are electrically isolated from each other; a second heat sink including a second attachment layer for attachment to the laser diode bar, the second attachment layer including a third attachment pad and a fourth attachment pad that are electrically isolated from each other; and a plurality of contact strips for attachment between the first heat sink and the second heat sink.
[0011] Implementations of the laser diode cooling device may include one or more of the following features. For example, in some implementations, a shape of the first mounting pad is the same as a shape of the third mounting pad, and a shape of the second mounting pad is the same as a shape of the fourth mounting pad.
[0012] In some implementations, the shape of the first mounting pad differs from the shape of the second mounting pad.
[0013] In some implementations, when the first heat sink and the second heat sink are aligned with the first attachment layer facing the second attachment layer, the second attachment pad of the first attachment layer overlaps the third attachment pad of the second attachment layer without overlapping the fourth attachment pad of the second attachment layer. In some implementations, when the first heat sink and the second heat sink are aligned with the first attachment layer facing the second attachment layer, the first attachment pad of the first attachment layer overlaps the third attachment pad and the fourth attachment pad of the second attachment layer.
[0014] In some implementations, the first heat sink includes: a first main body portion including at least one fluid channel; a first electrically insulating layer on the first main body portion; and the first attachment layer on the first electrically insulating layer. The second heat sink includes: a second main body portion including at least one fluid channel; a second electrically insulating layer on the second main body portion; and the second attachment layer on the second electrically insulating layer.
[0015] Implementations of the subject matter disclosed herein may have several advantages. For example, in some implementations, the optical output power of a laser diode may be increased through double-sided cooling. In some implementations, segmenting the mounting pads of at least one cooling element surface enables tailored electrical interconnection, such as individually addressable emitters and serial connection of diode laser segments. In some implementations, packaging process costs may be reduced due to component attachment along a single plane.
[0016] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic diagram illustrating an example of double-sided cooling of a laser diode. Fig. Figure 2A is a schematic diagram illustrating a top view of a first electrically insulated cooling element, whereas Fig. 2B a side view of the electrically insulated cooling element through section AA of Fig. 2A is. Fig. Figure 3A is a schematic diagram illustrating a top view of a second electrically insulated cooling element, whereas Fig. 3B a side view of the electrically insulated cooling element through section AA of Fig. 3A is. Fig. 4 and Fig. 5 are schematic diagrams illustrating perspective views of a contact strip and a laser diode attached to a first electrically insulated cooling element. Fig. 6 and Fig. 7 are schematic diagrams illustrating perspective views of a contact strip and a laser diode attached to a second electrically isolated cooling element. Fig. Figure 8 is a schematic diagram showing an exemplary electrically isolated cooling element together with contact strips and a laser diode. DETAILED DESCRIPTION
[0017] The output power of diode lasers is largely limited by heat dissipation, which causes the diode lasers to rise in temperature, which in turn can reduce the diodes' reliability and operating efficiency. Heat sinks with high thermal conductivity, such as copper heat sinks, can be used to keep the diode laser temperature stable during operation. An exemplary electrically isolated heat sink to which laser diodes can be mounted is the ILASCO diode heat sink, which is constructed from a stack of thin copper plates with high thermal conductivity. The individual stacked copper plates define an internal integrated cooling channel through which a coolant is provided. An electrically conductive mounting pad is formed on a top and / or bottom surface of the copper plates. The laser diode can then be directly attached to the electrically conductive mounting pad using solder.For example, the p-side contact of the semiconductor laser diode can be attached directly to the electrically conductive mounting pad. To prevent electrocorrosion of the heat sinks, the coolant paths within such heat sinks can be protected from the electrically conductive mounting pads by providing insulating layers between the electrically conductive mounting pad and the part of the heat sink that forms the cooling channel.
[0018] Cooling on both sides of a laser diode, rather than a single side, can further improve the stability and operating efficiency of a laser diode. However, establishing electrical contact with a laser diode cooled on two sides can be complicated, as it may be difficult to access the contact pads coupled to the diode. Furthermore, double-sided cooling can lead to damage to the laser diode resulting from forces applied during the attachment process.
[0019] Fig. 1 is a schematic diagram illustrating a perspective view of an example of double-sided cooling of a laser diode. The example device 100 includes a first heat sink 104, a second heat sink 106, and a laser diode device 102 mounted between the first heat sink 104 and the second heat sink 106. The device 100 further includes a first contact bar 108 and a second contact bar 110, with both the first and second contact bars 108, 110 being mounted between the first heat sink 104 and the second heat sink 106. Further, each contact bar 108, 110 provides a contact for electrically connecting to a different electrode of the laser diode 102.For example, the device 100 may be configured and arranged such that the contact strip 108 provides electrical contact with the p-type electrode of the laser diode 102, whereas the device 100 may also be configured and arranged such that the contact strip 110 provides electrical contact with the n-type electrode of the laser diode 102.
[0020] For example, each of the first heat sink 104 and the second heat sink 106 may include an integrated cooling element device having one or more integrated internal cooling channels, as well as an electrically conductive mounting layer separated from the integrated cooling channels by an insulating layer. For example, the first heat sink 104 is formed from a main body portion 114 and an electrically insulating layer 118 on the main body portion 114. In some implementations, the first heat sink 104 also includes a second electrically insulating layer 116 on a backside of the main body portion 114, opposite the side on which the insulating layer 118 is formed.For example, the main body portion 114 may include an internal cooling channel through which a coolant may flow to absorb heat generated by the laser diode 102 and transfer the heat away to maintain the laser diode at a constant temperature.
[0021] Likewise, the second heat sink 106 is formed from a main body portion 124 and an electrically insulating layer 128 on the main body portion 124. The main body portion 124 of the second heat sink 106 may also include its own internal cooling channel through which a coolant may flow to absorb heat generated by the laser diode 102 and transfer the heat away to maintain the diode 102 at a constant temperature. In some implementations, the second heat sink 126 may include a second electrically insulating layer 128 on a back side of the main body portion 124 opposite the side on which the insulating layer 118 is formed.
[0022] To provide high heat transfer from the laser diode 102, the main body portions 114, 124 and the layers 118, 128 are formed from materials with high thermal conductivity. However, to reduce electrocorrosion on the main body portions 114, 124, the material of the insulating layers 118, 128 may also have high electrically insulating properties. For example, the main body portions 114, 124 may be formed from a metal such as copper, which has a thermal conductivity of about 385.0 W / m*K at about room temperature, or copper-tungsten. In contrast, the electrically insulating layers 118, 128 may be formed from aluminum nitride, which has a thermal conductivity of about 140 W / m*K and an electrical resistivity of greater than about 10 14Ohm*cm at about room temperature, or diamond, which has a thermal conductivity of greater than about 1800 W / m*K and an electrical resistivity of greater than about 10 16 Ω*cm at approximately room temperature. In some cases, the main body portions 114, 124 may be formed from a stack of plates, such as copper or copper-tungsten plates, each etched to define a different portion of the cooling channels.
[0023] In some cases, each heat sink 104, 16 also includes an opening into which the coolant can be provided into the cooling channels, and therefore serves as a coupling region. For example, as in Fig. 1, the heat sink 106 includes openings 113 that extend through the electrically insulating layer 126 and into the main body portion 102. The openings 113 are connected to the at least one cooling channel formed within the main body portion 124. Similarly, the heat sink 104 may also include one or more openings that are coupled to internal cooling channels within the main body portion 114 and thus serve as a coupling region.
[0024] Both the heat sink 104 and 106 include a corresponding mounting layer to which the laser diode 102 and the contact strips are attached. For example, as shown in Fig. 1, the heat sink 104 includes a first attachment layer formed from the attachment pads 120, 122. The attachment pads 120, 122 are formed on the electrically insulating layer 118 of a material with high electrical conductivity (e.g., a metal such as copper or copper-tungsten) to provide electrical contact with the semiconductor laser diode 102 and / or with the contact strips 108, 110. The heat sink 106 may also include an attachment layer formed from a plurality of attachment pads, similar to the heat sink 104.
[0025] Fig. Figure 2A is a schematic diagram showing a top view of the heat sink 104 with the laser diode 102, the contact strips 108, 110 and the heat sink 106 removed. Fig. Figure 3A is a schematic diagram showing a bottom view of the heat sink 106 with the laser diode 102, the contact strips 108, 110, and the heat sink 104 removed. That is, Fig. Figure 3A provides a view of the surface of the heat sink 106 facing the laser diode 102 and the contact strips 108, 110. Fig. Figure 2B is a schematic diagram showing a side view of the first heat sink 104 through the Fig. 2A shown cross section AA-illustrated. Fig. Figure 2B is a schematic diagram showing a side view of the second heat sink 106 through the Fig. 3A shown cross section AA-illustrated. In some implementations, as in the Fig. 2A-3B, both the heat sink 104 and the heat sink 106 have an identical configuration and arrangement of the main body portion, the electrically insulating layers, and the attachment layers.
[0026] As explained herein and in Fig. 2B, the first heat sink 104 includes the main body portion 114, the first electrically insulating layer 118, the second electrically insulating layer 116, and a mounting layer including a plurality of mounting pads 120, 122. In some cases, the first heat sink 104 also includes a metal layer 201 on an opposite side of the heat sink on which the mounting layer is formed. Similarly, as in Fig. As shown in Figure 3B, the second heat sink 106 includes the main body portion 124, the first electrically insulating layer 128, the second electrically insulating layer 126, and a mounting layer including a plurality of mounting pads 320, 322. In some cases, the second heat sink 104 also includes a metal layer 301 on an opposite side of the heat sink on which the mounting layer is formed.
[0027] With reference to the Fig. 2A-2B, each of the attachment pads 120, 122 may be electrically isolated from each other within the attachment layer of the first heat sink 104. To electrically isolate the attachment pads from each other, the attachment pads may be separated by a physical gap. For example, the first attachment pad 120 is physically and electrically separated from the second attachment pad 122 by a gap 200. Because the attachment pads 120, 122 are also formed on the electrically insulating layer 118, there is little to no electrical conduction between the pads through the layer 118. Likewise, with reference to the Fig. 3A-3B, each of the attachment pads 320, 322 may be electrically isolated from each other within the attachment layer of the second heat sink 106. For example, the first attachment pad 320 is physically and electrically separated from the second attachment pad 322 by a gap 300. Because the attachment pads 320, 322 are also formed on the electrically insulating layer 128, there is little to no electrical conduction between the pads through the layer 128.
[0028] The plurality of contact pads (e.g., pads 120, 122 or pads 320, 322) of each heat sink may be formed by first providing a layer of an electrically conductive material (e.g., copper or copper-tungsten) on a surface of the electrically insulating layer of the heat sink. For example, a layer of copper may be deposited directly onto the surface of the electrically conductive layer 118, while a layer of copper may be deposited directly onto a surface of the electrically insulating layer 128. Standard deposition techniques such as, among others, physical vapor deposition, electron beam deposition, or electroplating may be used to form the electrically conductive material. The electrically conductive material may be formed to have a thickness in the range of, for example, between about 50 nm and about several tens of micrometers.
[0029] The contact pads (e.g., pads 120, 122 or pads 320, 322) of each heat sink can then be defined by forming the gap in the as-provided electrically conductive material. For example, the gaps 200, 300 can be formed by performing ion etching or chemical etching of the electrically conductive material in only the region where the gap 200 is to be defined. This process can, for example, involve depositing a resist as a mask and then defining the gap region in the resist mask using lithography before performing the ion etching or etching. Other suitable techniques for defining the gaps can be used instead. In some cases, the gaps 200, 300 can be formed, for example, by punching the electrically conductive material.As a result of the etching process, a plurality of electrically isolated attachment pads, each having the same thickness, may be formed directly in contact with the surface of the underlying electrically insulating layer (e.g., layer 118 or layer 128). In some implementations, forming the gaps 200, 300 may expose the underlying electrically insulating layers. A width of the gaps 200, 300 between facing edges of the first attachment pad (e.g., pad 120 or pad 320) and the second attachment pad (e.g., pad 122 or pad 322) may be less than about 1.5 mm. For example, the width of the gaps 200, 300 may be about 1.25 mm or less, 1 mm or less, 0.75 mm or less, or 0.5 mm or less.
[0030] In some implementations, each gap between the mounting pads is empty (e.g., only air is present in the gap between each mounting pad). In other implementations, the gaps may be filled with an electrically insulating material. For example, gaps 200, 300 may be filled with a dielectric, a polymer, an epoxy, or an adhesive.
[0031] In some implementations, the main body portions (e.g., 114, 124) include openings to which a fluid coupling may be attached. For example, as in Fig. 1, the main body portion 124 includes openings 113 extending from an exterior to an interior region of the heat sink. One of the two openings 113 is used to supply a cooling fluid (e.g., water) to the interior of the main body portion 124, whereas the other of the two openings 113 is provided for removing the cooling fluid from the heat sink. The main body portion 124 may include internal fluid channels fluidly coupled to the openings 113 and through which the cooling fluid propagates to enable cooling of the heat sink during operation of the device. Although in Fig. 1, the main body portion 114 may also include inlet and outlet openings 113 for receiving and removing cooling fluid in a similar manner to the main body portion 124. Each of the main body portions may also include one or more mounting holes for securing the heat sinks. For example, Fig. 1, the main body portion 124 includes a mounting hole 112 located between the fluid inlets and outlets 113. Examples of the mounting holes 112 are also shown in the Fig. 2A and Fig. 3A, in which the opening 112 extends into the main body portion of the heat sink. To provide access to the openings 112 and 113, at least some of the electrically insulating layers (e.g., layers 118, 128) and a portion of the attachment layer (e.g., portions of pads 120, 122 and / or portions of pads 320, 322) are removed.
[0032] Fig. 4 is a schematic diagram showing a perspective view of the exemplary first heat sink 104, with the second heat sink 106 and the first contact strip 108 omitted for a simplified view. As in Fig. 4, the laser diode 102 is attached to the first attachment pad 120. For example, the laser diode 102 may include a first electrode (e.g., a p-type contact) on a first or bottom surface that is electrically connected to the first attachment pad 120. The laser diode 102 may be physically and electrically connected to the first attachment pad 120 using a solder connection, e.g., a first solder layer 400 between the attachment pad 120 and the laser diode 120. For example, the laser diode 102 may be soldered to the first attachment pad 120 using an AuSn solder layer. During manufacturing, the solder layer 400 onto which the laser diode 102 is placed may be provided by a solder preform. For example, the solder may have a predefined shape (e.g., rectangular prism) made of solid material. The footprint of the solder preform 400 may be the same as the footprint of the laser diode 102.The solder preform may have a thickness in a range of about 10 micrometers to 40 micrometers, including, for example, between about 15 micrometers to about 35 micrometers, between about 20 micrometers to about 30 micrometers, or about 25 micrometers, among others. The solder preform 400 is placed between the bottom surface of the laser diode 102 and the mounting pad 120. When the second heat sink 106 is attached to the top surface of the laser diode 102, the solder preform 400 may be heated, allowing the solder to melt and join the diode 102 to the mounting pad 120.
[0033] Separately, the second contact strip 110 is also attached to the mounting pad 120. The second contact strip 110 provides an electrical contact area to which the first electrode (e.g., the p-type contact) of the bottom surface of the laser diode 102 can be electrically connected. That is, an electrically conductive path can be established from the bottom electrode of the laser diode 102 via the mounting pad 120 to the contact strip 110. The contact strip 110 extends outward beyond the edge of the heat sink 104, so that when both heat sinks 104, 106 are used, it is possible to easily access the surface of the contact strip 110 and establish an electrical connection. The external electrical connection to the edge of the contact strip 110, which protrudes from the edge of the heat sink, can be established, for example, by wire bonding, clamping, tape bonding, or soldering, among other types of electrical connections.
[0034] The contact strip may have a length in the range of about 5 mm to about 30 mm, a width in the range of about 0.5 mm to about 20 mm, and a height or depth in the range of about 0.1 mm to about 5 mm. An exemplary dimension of the contact strip is 17.5 mm long, 4.5 mm wide, and 1.75 mm deep. The contact strip 110 may include a material with high electrical conductivity, such as copper or copper-tungsten. The contact strip 110 may be physically and electrically connected to the mounting pad 120 using a solder connection, e.g., a solder layer between the mounting pad 120 and the contact strip 110. For example, the contact strip 110 may be soldered to the mounting pad 120 using an AuSn solder layer. During manufacturing, the solder layer onto which the contact strip 110 is placed may be provided by a solder preform 402. For example, the solder can have a predefined shape (e.g.The solder preform 402 is placed between the bottom surface of the contact strip 110 and the mounting pad 120. When the second heat sink 106 is attached to the top surface of the contact strip 110, the solder preform 402 can be heated, allowing the solder to melt and join the contact strip 110 to the mounting pad 120.
[0035] Both the contact strip 110 and the laser diode are also bonded to the second heat sink 106. To provide the bond connection for the contact strip 110, a second solder connection, e.g., a solder layer 502, is applied between the contact strip 110 and the mounting pad 322 (see Fig. 5) of the second heat sink 106. For example, the contact strip 110 can be soldered to the mounting pad 322 using an AuSn solder layer. During manufacturing, the additional solder layer 502 can be applied to the top side of the contact strip 110 in the form of a solder preform (see Fig. 5). The solder preform 502 is placed between the top surface of the contact strip 110 and the attachment pad 322 of the second heat sink 106. When the second heat sink 106 is attached to the top surface of the contact strip 110, the solder preform 502 may be heated, allowing the solder to melt and join the contact strip 110 to the attachment pad 322. The solder preform 502 may have a footprint that conforms to at least a portion of the footprint of the contact strip 110.
[0036] Similarly, a solder layer 500 may be used to bond a second or upper surface of the laser diode 102 to the other mounting pad 320 of the upper heat sink 106 (see Fig. 5). For example, the laser diode 102 may include a second electrode (e.g., an n-type contact) on the second surface that is electrically connected to the mounting pad 320. The second surface may be the surface of the diode 102 opposite the first or bottom surface of the diode 102. The laser diode 102 may be physically and electrically connected to the mounting pad 320 using a solder connection, e.g., a solder layer between the mounting pad 320 and the laser diode 102. For example, the laser diode 102 may be soldered to the mounting pad 320 using an AuSn solder layer. During manufacturing, the solder layer 500 on the top surface of the laser diode 102 may be formed by a solder preform (see Fig. 5). For example, the solder may have a predefined shape (e.g., a rectangular prism) made of solid material. The solder preform 500 may have the same footprint as the footprint of the laser diode 102. The solder preform 500 is placed between the top surface of the laser diode 102 and the mounting pad 320. When the second heat sink 106 is attached, the solder preform 500 may be heated, allowing the solder to melt and join the diode 102 to the mounting pad 320.
[0037] Fig. 6 is a schematic diagram showing a perspective view of the exemplary second heat sink 106, with the first heat sink 104, the second contact strip 110, and the laser diode 102 omitted for a simplified view. As shown in Fig. 6, the first contact bar 108 is attached to the mounting pad 320. The first contact bar 108 provides an electrical contact area to which the second electrode (e.g., the n-type contact) of the top surface of the laser diode 102 can be electrically connected. That is, an electrically conductive path can be established from the top electrode of the laser diode 102 via the mounting pad 320 to the first contact bar 108. The contact bar 108 extends over the edge of the heat sink 106 and beyond, so that when both heat sinks 104, 106 are used, it is possible to easily access the surface of the contact bar 108 and establish an electrical connection. The contact bar 108 can comprise a material with high electrical conductivity, such as copper or copper-tungsten. The contact bar 108 can be connected using a solder connection, e.g.,a solder layer between the attachment pad 320 and the contact strip 108, physically and electrically connected to the attachment pad 320. For example, the contact strip 108 may be soldered to the attachment pad 320 using an AuSn solder layer. During manufacturing, the solder layer onto which the contact strip 108 is placed may be provided by a solder preform 600. For example, the solder may have a predefined shape (e.g., rectangular prism) made of solid material. The solder preform 600 is placed between the contact strip 108 and the attachment pad 320. When the first heat sink 104 is attached to the contact strip 108, the solder preform 600 may be heated, allowing the solder to melt and join the contact strip 108 to the attachment pad 320.
[0038] Fig. Figure 7 is a schematic diagram showing a perspective view of the exemplary second heat sink 106, with the first heat sink 104 omitted for clarity. Dashed outlines of the laser diode 102, the second contact strip 110, and the solder preforms 402, 502 are included to illustrate the position of these features relative to the contact pads 320, 322 of the second heat sink 106 in the finished device.
[0039] As in Fig. As shown in Figure 7, to provide the bond for the contact strip 108 to the mounting pad 122 of the first heat sink 104, an additional solder connection, e.g., a solder layer 700, is provided on the contact strip 108. For example, the contact strip 108 may be soldered to the mounting pad 122 using an AuSn solder layer. During manufacturing, the additional solder layer 700 may be provided on the contact strip 108 in the form of a solder preform. The solder preform 700 is placed between the contact strip 108 and the mounting pad 122 of the first heat sink 104. When the first heat sink 104 and the second heat sink 106 are attached, the solder preform 700 may be heated, allowing the solder to melt and join the contact strip 108 to the mounting pad 122.As explained herein, a solder preform 500 may be used to bond a first surface of the laser diode 102 to the other attachment pad 320 of the upper heat sink 106 (see . Fig. 6-7), and another solder preform 400 can be used to bond a second surface of the laser diode 102 to the mounting pad 120 of the lower heat sink 104 (see Fig. 4-5) to bond.
[0040] As in Fig. 7, the gap 300 between the mounting pad 320 and the mounting pad 322 provides electrical isolation of the contact strip 110 from the electrode of the laser diode 102, which is in contact with the mounting pad 320. When the lower heat sink 104 is bonded in place, the contact strip 110 provides a direct electrical connection to the electrode of the laser diode 102, which is in contact with the mounting pad 120. For example, Fig. 8 is a schematic diagram illustrating the upper heat sink 106 together with both contact strips 108, 110 and the laser diode 102. In Fig. 8 also shows an outline of the mounting pad 120 and the mounting pad 122 of the heat sink 104, illustrating their position relative to the contact strips and the laser diode 102 when both heat sinks are mounted (e.g., as shown in Fig.1). Contact strip 110 is directly electrically connected to the electrode on the lower surface of laser diode 102 via mounting pad 120 (and solder layers 400, 402). However, the electrode on the lower surface of laser diode 102 does not form a short circuit with the electrode on the upper surface of the laser diode due to the gap 200 present between mounting pads 120 and 122, as well as the gap 300 between mounting pads 320 and 322. Similarly, contact strip 108 is directly electrically connected to the electrode on the upper surface of laser diode 102 via mounting pad 320 (and solder layers 500, 600). However, the electrode on the top surface of the laser diode 102 does not form a short circuit with the electrode on the bottom surface of the laser diode in view of the gap 300 present between the mounting pads 320 and 322 and the gap 200 between the mounting pads 120 and 122.The thickness of each of the contact strips 108, 110, the solder preforms (400, 402, 500, 502, 600, 700) and the laser diode 102 can be set so that when both heat sinks are attached, the distance between the lower heat sink and the upper heat sink is uniform. That is, the total thickness (as measured from the surface of pad 120 to the surface of pad 322) of solder preform 402 (after reflow), contact strip 110, and solder preform 502 (after reflow) is the same as the total thickness (as measured from the surface of pad 122 to the surface of pad 320) of solder preform 700 (after reflow), contact strip 108, and solder preform 600 (after reflow), which in turn is the same as the total thickness (as measured from the surface of pad 120 to the surface of pad 320) of solder preform 400, laser diode 102, and solder preform 500.
[0041] A number of embodiments of the invention have been described. Nevertheless, it should be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
Claims
[1] A laser diode device comprising: a first heat sink (104) comprising a first mounting layer, wherein the first mounting layer comprises at least two mounting pads (120, 122), namely a first mounting pad (120) and a second mounting pad (122) electrically insulated from the first mounting pad (120); a second heat sink (106) comprising a second mounting layer, wherein the second mounting layer comprises at least two mounting pads (320, 322), namely a third mounting pad (320) and a fourth mounting pad (322) electrically insulated from the third mounting pad (322); and a laser diode bar (102) between the first heat sink (104) and the second heat sink (106), wherein a lower electrical contact of the laser diode bar (102) is attached to the first attachment layer and an upper electrical contact of the laser diode bar (102) is attached to the second attachment layer; a first contact strip (108); and a second contact strip (110), wherein both the first contact strip (108) and the second contact strip (110) are attached between the first heat sink (104) and the second heat sink (106); wherein the lower electrical contact of the laser diode bar (102) is electrically connected to the first mounting pad (120), and the upper electrical contact of the laser diode bar (102) is electrically connected to the third mounting pad (320); wherein a lower surface of the first contact strip (110) is electrically connected to the first attachment pad (120) of the first attachment layer, and an upper surface of the first contact strip (110) is electrically connected to the fourth attachment pad (322) of the second attachment layer; wherein a lower surface of the second contact strip (108) is electrically connected to the second attachment pad (122) of the first attachment layer, and an upper surface of the second contact strip (108) is electrically connected to the third attachment pad (320) of the second attachment layer; wherein the second fastening pad (122) of the first fastening layer overlaps the third fastening pad (320) of the second fastening layer without overlapping the fourth fastening pad (322) of the second fastening layer; wherein the first fastening pad (120) of the first fastening layer overlaps the third fastening pad (320) and the fourth fastening pad (322) of the second fastening layer. [2] Laser diode device according to claim 1, wherein the first contact strip (110) extends beyond a first edge of the first heat sink (104) and / or the second heat sink (106), and the second contact strip (108) extends beyond a second edge of the first heat sink (104) and / or the second heat sink (106). [3] The laser diode device according to claim 1, wherein a shape of the first mounting pad (120) of the first mounting layer is the same as a shape of the third mounting pad (320) of the second mounting layer, and wherein a shape of the second mounting pad (122) of the first mounting layer is the same as a shape of the fourth mounting pad (322) of the second mounting layer. [4] The laser diode device according to claim 1, wherein a height of each of the first contact bar (110), the second contact bar (108) and the laser diode is the same between the first heat sink (104) and the second heat sink (106). [5] The laser diode device according to claim 1, wherein the first heat sink (104) comprises: a first main body part (114) comprising at least one fluid channel; a first electrically insulating layer (118) on the first main body part (114); and the first attachment layer on the first electrically insulating layer (118); and wherein the second heat sink (106) comprises: a second main body portion (124) comprising at least one fluid channel; a second electrically insulating layer (128) on the second main body portion (124); and the second attachment layer on the second electrically insulating layer (128). [6] The laser diode device according to claim 5, wherein each of the first main body part (114), the second main body part (124), the first fixing layer and the second fixing layer are formed of a metal. [7] A laser diode device according to claim 6, wherein the metal is copper or copper-tungsten. [8] A laser diode device according to claim 6, wherein both the first electrically insulating layer (118, 126) and the second electrically insulating layer (116, 128) are formed of a ceramic.
Citation Information
Patent Citations
Method for thermally contacting opposing electrical terminals of a semiconductor device array
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