JP2007048937A - Semiconductor laser and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser that dispenses with wasteful Au plating and releasing work of a lead after plating, and can reduce the cost, and to provide a method for manufacturing the semiconductor laser. <P>SOLUTION: At least one of leads 13, 15, where the Au plating is performed onto the outermost surface, is fixed to a base 11, where plating is performed on a surface and a planar shape is nearly circular, by an electrically insulating material, and a heat sink 12 is provided at one surface side of the base 11, thus forming a stem 1. A semiconductor laser element 2 is fixed to the heat sink 12, for example, via a submount 3, at least one of the electrodes of the semiconductor laser 2 is connected to the lead 13 by a wire 8. The base 11 and the lead 13, 15 are plated so that Au plating on the outermost surface, performed onto the leads 13, 15, differs from the material of plating performed onto the outermost surface of the base 11 or the thickness of the Au plating. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a semiconductor particularly suitable for use as a light source for pickup such as CD, DVD (digital versatile disk), DVD-ROM, data writable CD-R / RW, DVD-R / RW. The present invention relates to a laser and a manufacturing method thereof. More specifically, the present invention relates to a semiconductor laser having a structure in which a base and a lead are separately plated with a stem type semiconductor laser, and a base that does not require a large Au plating does not need to be wasted Au and a manufacturing method thereof .

  A stem type semiconductor laser used for a conventional CD pickup or the like has a structure as shown in FIG. 3 (see, for example, Patent Document 1). That is, a stem 20 in which a metal material such as iron is formed by a cold forging method, a part of the center portion of the base 21 is raised to form the heat sink portion 22, and the leads 23 and 25 are fixed by a glass 26 or the like is used. The semiconductor laser element 31 is mounted on the heat sink portion 22 via a submount 34 made of a silicon substrate or the like, and one electrode (the back side of the chip 31) is lead by the wire 33 via the relay portion 38 of the submount 34. The other electrode is connected to the submount 34 via the wire 33, and is electrically connected to the common lead 24 via the heat sink 22 and the base 21 via the back surface thereof.

  With this structure, since one electrode of the semiconductor laser element 31 is connected by the lead 23 and the wire 33, it is necessary to perform wire bonding, and it is reliable that the wire bonding portion of the lead is not subjected to sufficient Au plating. It is not possible to perform wire bonding. Therefore, after the leads 23 and 25 are fixed to the base 21, for example, Ni / Au plating is performed by barrel plating or the like, and the Au plating is provided with a thickness of about 0.1 μm. Reference numeral 32 denotes a light-receiving element for monitoring. One electrode is electrically connected to the lead 25 via the wire 33, and the other electrode is electrically connected to the common lead 24 via the submount 34, the heat sink 22 and the base 21. Has been. Then, a cap 35 made of an iron-based material such as Fe—Ni—Co alloy is put on the periphery thereof. A through hole 35 a is provided at the center of the top of the cap 35 so that light emitted from the semiconductor laser element 31 is transmitted, and a glass plate 36 is sealed with a low melting point glass 37.

On the other hand, pick-up light sources such as recent DVD-ROMs, data-writable CD-R / RWs, DVD-R / RWs, etc., have a very high output and generate a large amount of heat. If the heat dissipation is not performed, there is a problem that the life of the semiconductor laser element is reduced, and a device has been devised to improve the heat dissipation by using a copper-based material for the stem. In this case, since a copper-based material is used, the cap cannot be welded, and a structure in which a protective portion is formed by a heat sink without forming a cap has been proposed (for example, see Patent Document 2). That is, as shown in FIG. 4, a heat sink 42 and a protection part 43 are formed integrally with an eyelet 41 made of copper or the like, and leads 44 to 46 are provided on the eyelet 41.
JP 2001-111152 A (FIG. 7) JP 2004-349320 A

  As described above, the conventional stem-type semiconductor laser needs to electrically connect the lead fixed to the base and the electrode of the semiconductor laser element fixed to the heat sink by a wire such as a gold wire. Therefore, it is necessary to apply Au plating of at least about 0.1 μm to the lead. As described above, the plating is performed by barrel plating after the lead is welded to the base with a low melting point glass or the like. Therefore, the plating having the same thickness is formed not only on the lead but also on the base. Since the base is not wire-bonded, thick Au plating is not necessary, but Au plating with the same thickness as the lead adheres, and thick Au plating adheres to both sides of the base that is much larger in area than the lead. There is a problem that the cost will be very high.

  Plating is generally performed by barrel plating. In barrel plating, the lead is fixed with the base while stirring, so the leads are easily bent and entangled with each other. There is a problem that the cost increases from this viewpoint.

  The present invention has been made to solve such a problem, and a semiconductor laser having a structure capable of reducing cost by eliminating unnecessary Au plating or disassembling after plating. It aims at providing the manufacturing method.

  Another object of the present invention is to provide a semiconductor laser having a structure that can efficiently dissipate heat generated by a laser element even in a high-power semiconductor laser such as for CD-R / RW and DVD-R / RW. It is to provide.

  The semiconductor laser according to the present invention includes a base having a substantially circular planar shape whose surface is plated, and at least one lead fixed to the base with an electrically insulating material and Au plated on the outermost surface. A semiconductor laser comprising: a heat sink provided on one surface side of the base; a semiconductor laser element fixed to the heat sink; and a wire connecting at least one of electrodes of the semiconductor laser element to the lead, The base and the lead are plated so that the outermost Au plating applied to the lead is different from the plating material or Au plating thickness applied to the outermost surface of the base.

  Here, the substantially circular base does not mean only a complete circular shape, but a positioning slot or the like formed in several places on the peripheral edge of the base, and a part of the peripheral edge of the base is missing. It means to include what is.

  The base and the heat sink are formed of a metal having a higher thermal conductivity than iron, and the heat sink is perpendicular to the mount surface from the end of the mount surface so as to surround a flat mount surface on which the semiconductor laser element is mounted. It is preferable to have a side wall projecting in the direction because a semiconductor laser that easily generates heat with high output can efficiently dissipate heat generated in the laser element.

  Since the lead is fixed to the base via an electrically insulating resin or adhesive, it is not necessary to heat the lead to a high temperature as in the case of welding with glass. In addition, since the lead can be plated before being fixed to the base, the necessary thickness can be plated only on a necessary portion, and the lead is not entangled or bent.

  Since the base and the heat sink are integrally formed of copper, a copper alloy, or aluminum, it is more preferable for heat dissipation because it is further excellent in heat conduction.

  A method of manufacturing a semiconductor laser according to the present invention includes a base having a through hole into which a lead is inserted and a heat sink extending so as to protrude on a surface of the base by forming a metal plate by a cold forging method and having a substantially circular planar shape. Formed integrally, plated with at least Ni on the surface of the base and the heat sink, formed a lead to be inserted into the base, plated to have an Au plated film on at least the outermost surface, A semiconductor laser element is mounted on the heat sink, and an electrode of the semiconductor laser element is electrically connected to the lead by wire bonding. And The stem portion (base and heat sink portion) can be formed by a die casting method using aluminum instead of the cold forging method.

  According to the present invention, since the plating of the base and the lead is performed with different specifications, the thick Au plating necessary for wire bonding can be applied only to the lead, and the thick Au plating is applied to the base portion. There is no need to apply. As a result, the base Au plating having a surface area much larger than that of the lead can be made thinner than the lead, and a significant cost reduction can be achieved. That is, in the conventional semiconductor laser using this type of stem, the stem and the cap are hermetically sealed. Therefore, the window portion of the cap is hermetically sealed with a low melting glass, and the stem and the base are also sealed. The lead was hermetically sealed with low melting point glass or the like. For this reason, if the lead is plated in advance, the plating is violated by heat at the time of glass sealing. Therefore, the plating can be performed only after the glass sealing, and the same amount of plating as the lead has been made on the base. . However, the present invention focuses on using a material with excellent thermal conductivity for the stem so as to efficiently dissipate heat and removes the cap that is difficult to weld to the stem made of copper or the like. Can be fixed to the base at a relatively low temperature with a resin or the like, and the lead is plated in advance, and unnecessary plating such as thick Au plating on the base is reduced, thereby achieving cost reduction.

  In addition, it is not necessary to perform barrel plating after fixing the lead extending in the direction perpendicular to the base to the base by fixing the lead and the base separately after applying desired plating separately to the base. Are not entangled or bent, the subsequent work is very easy, and wire bonding can be performed very reliably. As a result, not only the cost reduction by plating, but also an extra man-hour such as lead extension becomes unnecessary, and a further cost reduction can be achieved. Further, by fixing the lead and the base with a resin, an adhesive, or the like, problems such as a thermal expansion coefficient do not occur so much and the fixing of the lead itself becomes easy. Furthermore, by forming the base, the heat sink and the like with a material having a thermal conductivity superior to that of iron such as copper, a copper alloy, or aluminum, a semiconductor laser having excellent heat dissipation and excellent heat dissipation characteristics can be obtained.

  Next, the semiconductor laser of the present invention will be described with reference to the drawings. The semiconductor laser according to the present invention has a planar shape in which the surface is plated, as shown in the perspective view of FIG. 1 and the exploded view of the stem portion in FIG. At least one lead 13, 15 whose outermost surface is plated with Au is fixed to a circular base 11 with an electrically insulating material, and a heat sink 12 is provided on one surface side of the base 11, whereby the stem 1 is provided. Is formed. The semiconductor laser element 2 is fixed to the heat sink 12 via, for example, a submount 3, and at least one of the electrodes of the semiconductor laser element 2 is connected to the lead 13 and the wire 8. In the present invention, the base 11 and the leads 13 and 15 are plated so that the outermost Au plating applied to the leads 13 and 15 is different from the plating material applied to the outermost surface of the base 11 or the thickness of the Au plating. Is given. In the example of FIG. 1, there are two leads 13 and 15, but if there is no need for a light receiving element, there may be one or three. That is, in other words, the base 11 and the leads 12 and 13 are separately plated, and each has a desired plating thickness with a desired plating thickness.

  The base 11 and the heat sink 12 are formed such that, for example, a copper plate is formed by a cold forging method so that the heat sink 12 protrudes integrally with the plate-like base 11 as shown in FIG. In the heat sink, a flat bonding surface 12a perpendicular to the surface of the base 11 is formed at the center of the substantially circular base, and side walls 12b are formed on both sides so as to cover the bonding surface 12a from both sides. When viewed, it is formed in a letter 3 shape. The heat sink 12 has a height of, for example, about 2 mm. As a result, the sides of the pair of leads 13 and 15 are surrounded by the side wall portion 12b and can be protected from the tentacles of workers from the side, and the wire bonding portion and the semiconductor laser device 2 described later are protected. can do.

  The material constituting the base 11 and the heat sink 12 is preferably a material with good thermal conductivity, such as copper shown in this example. In addition to copper, the alloy contains copper at least 50 at% with a copper alloy such as phosphor bronze. A copper-based material can be used. Moreover, even if it is not a copper-type material, if it is a material with better thermal conductivity than iron, such as aluminum, it can be used. For example, in the case of aluminum, the base 11 and the heat sink 12 can be integrally molded by die casting, and if only the portion that becomes the reference surface of the mount surface 12a or the surface of the base 11 is dimensioned by machining, the heat dissipation performance An excellent stem portion can be obtained at low cost.

  In the example shown in FIG. 1, the heat sink 12 has a mounting surface 12 a at the center and side walls 12 b on both sides thereof, so that the top view is formed in a letter 3 shape. Is not limited. By mounting the semiconductor laser element 2 on the mount surface 12a of the heat sink 12, the laser beam emitted from the semiconductor laser element 2 is formed so as to be emitted upward from the center of the stem 1 (perpendicular to the base surface). If it is, it can be formed into a free shape later and can be designed into a shape with good heat dissipation. However, as shown in FIG. 1, it is preferable to form the semiconductor laser element 2 and its wire bonding portion so as to protect them from the tentacles of an operator or the like. In the example shown in FIG. 1, the base 11 and the heat sink 12 are integrally formed. However, the heat sink 12 may be manufactured separately from the base 11 and fixed to the base 11.

  The base 11 has a thickness of, for example, about 1.2 mm and a diameter of about 5.6 mmφ. As shown in a sectional view before the leads 13 and 15 are inserted in FIG. A through hole 11a for inserting 15 is formed, and positioning grooves 11b and 11c are formed on the outer periphery. Further, in front of the central mount surface 12a, a concave portion 11d having an inclined surface for mounting the light receiving element 4 is formed. The diameter of the through hole into which the leads 13 and 15 are inserted is, for example, about 1 mmφ, and the interval is formed to be about 2 mm. A lead 14 as a common lead is fixed to the back surface of the base 11 by brazing or the like. After these processing and forming, although not shown, the entire surface is plated with, for example, Ni of about 2 μm and Au of about 0.008 μm.

  The leads 13 and 15 are made of, for example, an Fe—Ni alloy rod having a diameter of about 0.45 mmφ or Kovar (registered trademark). Since a wire such as a gold wire, which will be described later, is bonded to the leads 13 and 15, Au plating of about 0.1 μm is required to improve the familiarity with the gold wire.

  In the state where the plated leads 13 and 5 are inserted into the through holes 11a of the base 11 thus plated and aligned to a predetermined dimension, for example, epoxy resin or the like is placed in the through holes 11a. Can be fixed by applying a thermosetting resin of, for example, baking at about 200 to 300 ° C. for about 10 to 200 minutes. Even if the temperature rises to this level, the plating applied to the base 11 and the leads 13 and 15 is not affected at all. As the resin for fixing the lead, in addition to the epoxy resin, a thermoplastic resin such as a polyphenylene sulfide resin, a polyphthalamide resin, and a liquid crystal polyester resin, or a silicone resin mixed with silica powder can be used. These resins can mechanically bond the leads 13 and 15 and can be electrically insulated. In addition to the resin, an epoxy-based or two-component adhesive can also be used.

  The semiconductor laser element 2 is formed so as to emit laser light, and is mounted on the heat sink 12 via the submount 3 in a bare chip state, but its size is about 250 μm × 250 μm for CD reproduction. For DVD playback, it is about 250 μm × 350 μm, and for CD-R / RW, it is about 250 μm × 900 μm. However, even this largest chip is very small, and in order to facilitate its handling and secure heat dissipation, as described above, a silicon substrate or AlN (aluminum nitride) usually having a size of about 0.8 mm × 1 mm. ) And the like on the submount 3. 1 and 2, one electrode is connected to the submount 3 by wire bonding such as a gold wire 8, and the common lead 14 is connected from the back surface of the electrode via a heat sink 12 and a base 11 by a conductive adhesive. The other electrode (back surface electrode) is connected to the lead 13 by wire bonding such as a gold wire 8 through a connection portion (not shown) on the submount 3.

  The submount 3 to which the semiconductor laser element 2 is bonded is conveyed by a suction collet and mounted on the heat sink 12. A light receiving element 4 for monitoring the light emission output of the semiconductor laser element 2 is mounted in a recess 11d formed on the surface of the base 11, and one electrode thereof is connected to the common lead 14 via the base 11, and the other These electrodes are electrically connected to the leads 15 by wire bonding such as gold wires 8. The light receiving element 4 may be provided on the submount 12 or outside the semiconductor laser.

  According to the semiconductor laser of the present invention, since the base 11 and the leads 13 and 15 are separately plated, thick Au plating is performed only on the leads that require thick Au plating for wire bonding. The base that is not performed can be plated or omitted as much as necessary, which greatly contributes to cost reduction. Furthermore, by plating before joining the base and the lead, the lead is not entangled or bent even if barrel plating is performed, and the working process can be greatly simplified. Furthermore, in the present invention, since it has a structure in which the side wall is formed continuously with the heat sink while having a structure that eliminates the cap, all of these can be composed of a material having excellent thermal conductivity such as copper, Heat generated in the semiconductor laser element is transmitted to the side wall and base of the heat sink and can be dissipated by heat radiation from each, and a high output semiconductor laser element such as a CD-R / RW or DVD-R / RW Even if the amount of heat generated is large, heat can be dissipated quickly, and the reliability of the semiconductor laser element can be improved.

  In addition, although there is no cap, since the side wall is formed on the heat sink, the semiconductor laser element and the wire bonding part are located inside the side wall, and the wire bonding part is damaged by unexpected tentacles, etc. Can be prevented.

  Next, a method for manufacturing this semiconductor laser will be described. As described above, the semiconductor laser manufacturing method of the present invention does not perform plating after the leads are fixed to the base, but separately performs plating before that to form the necessary plating for each of the necessary thicknesses. There is a special feature. As a result, the base 11 can be made of Au plating much thinner than the lead.

  Specifically, first, a metal plate such as a copper plate is formed by a cold forging method so that the planar shape is substantially circular, and has a through hole 11a into which a lead is inserted and protrudes on the surface of the base 11. The extending heat sink 12 is integrally formed. At this time, as described above, the heat sink 12 is formed so that the flat mounting surface 12a is formed so that the semiconductor laser element 2 can be mounted at substantially the center of the circular base 11, and both of the two are formed. It is preferable to form the side wall 12b on the side. Further, the base 11 is simultaneously formed with through holes 11a into which the leads 13 and 15 are inserted, and concave portions 11b and 11c for positioning and the like at the peripheral ends. Further, the common lead 14 is formed on the surface of the base 11 opposite to the surface on which the heat sink 12 is provided by brazing or the like, and then Ni plating and Au plating are performed to form a plating film. Au plating can be formed very thin, about 0.008 μm.

  On the other hand, a rod of about 0.45 mmφ made of Fe—Ni alloy or the like is prepared, and Ni and Au plating is performed on the surface thereof. In this case, the Au plating ensures a thickness of about 0.1 μm. The leads 13 and 15 are inserted into the through hole 11a of the base 11, the insertion height is aligned and held at the center of the through hole 11a, and a resin paste such as epoxy resin is poured into the through hole 11a, Heat to about 200-300 ° C. to cure.

  After that, as in the conventional semiconductor laser manufacturing, the semiconductor laser element 2 is die-bonded, for example, a submount 3 made of a silicon substrate is attracted by a collet, and conductive at a predetermined position on the mount surface 12a of the heat sink 12. Bonding is performed using an adhesive or In. The light receiving element 4 is also bonded to a predetermined place with a conductive adhesive or the like, and one electrode of each of the semiconductor laser element 2 and the light receiving element 4 is electrically connected to the leads 13 and 15 using a wire such as a gold wire 8. Connect to. The electrical connection is made in consideration of the fact that the electrode of the semiconductor laser element 2 and the lead 13 are not directly wire-bonded but may be wire-bonded via the submount 3 or the like. In the present invention, the manufacturing of the semiconductor laser is completed by this wire bonding, and the cap is not put thereon.

  In the above example, the base portion and the heat sink stem portion are formed by processing a copper plate or the like by the cold forging method. For example, the base 11 and the heat sink 12 having the same structure as described above are formed by die casting using aluminum. A stem portion can be formed. In this case, for example, the mounting surface 12a and the outer periphery of the surface of the base 11 are required to have a dimensional accuracy, and therefore it is preferable that the dimensions are obtained later by machining. The other manufacturing steps are the same as in the above example, and details are omitted.

It is a perspective explanatory view of one embodiment of a semiconductor laser by the present invention. FIG. 2 is an exploded cross-sectional explanatory view of a stem portion of the semiconductor laser of FIG. 1. It is sectional explanatory drawing which shows an example of the conventional semiconductor laser. It is perspective explanatory drawing which shows the other structural example of the conventional semiconductor laser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stem 2 Semiconductor laser element 3 Submount 4 Light receiving element 8 Gold wire 11 Base 12 Heat sink 13 Lead 13a Ni / Au plating 14 Common lead 15 Lead 15a Ni / Au plating

Claims (6)

  A base having a substantially circular planar shape to be plated on the surface, at least one lead fixed to the base with an electrically insulating material and plated with Au on the outermost surface, and one surface of the base A semiconductor laser comprising: a heat sink provided; a semiconductor laser element fixed to the heat sink; and a wire connecting at least one of electrodes of the semiconductor laser element to the lead, wherein the outermost surface is applied to the lead A semiconductor laser in which the base and the lead are plated so that the Au plating differs from the plating material applied to the outermost surface of the base or the thickness of the Au plating.   The base and the heat sink are formed of a metal having a higher thermal conductivity than iron, and the heat sink is perpendicular to the mount surface from the end of the mount surface so as to surround a flat mount surface on which the semiconductor laser element is mounted. 2. The semiconductor laser according to claim 1, wherein the semiconductor laser is formed to have side walls protruding in the direction.   3. The semiconductor laser according to claim 1, wherein the lead is fixed to the base via an electrically insulating resin or adhesive.   4. The semiconductor laser according to claim 1, wherein the base and the heat sink are integrally formed of copper, a copper alloy, or aluminum.   A metal plate is formed by a cold forging method to form a base having a substantially circular planar shape and having a through hole into which a lead is inserted and a heat sink extending so as to protrude on the surface of the base. The surface of the substrate is plated with at least Ni, the lead to be inserted into the base is formed, the plating is performed so that at least the outermost surface has an Au plating film, and the lead is electrically insulated in the through hole of the base. A method for producing a semiconductor laser, comprising: fixing with a conductive resin or an adhesive; mounting a semiconductor laser element on the heat sink; and electrically connecting an electrode of the semiconductor laser element to the lead by wire bonding.   By a die casting method using aluminum, a base having a substantially circular planar shape and having a through hole into which a lead is inserted and a heat sink extending so as to protrude on the surface of the base are integrally formed, and the lead to be inserted into the base is formed. After forming and plating so as to have an Au plating film on at least the outermost surface, the lead is fixed in the through hole of the base with an electrically insulating resin or adhesive, and the semiconductor laser device is mounted on the heat sink And an electrode of the semiconductor laser element is electrically connected to the lead by wire bonding.

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