JP2009212524A - Semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser which has a small external diameter while enhancing heat dissipation property by making a heat sink portion large even when a laser chip has a large chip size and large calorific value, and a thin type optical pickup using the same. <P>SOLUTION: A support portion 12 is provided on the side of one bottom portion (base 11) of a stem 1 where at least two leads 14 and 16 are fixed such that they project from both sides. The heat sink portion 13 is formed such that it extends widely toward the two projecting leads 14 and 16 above the support portion 12. The laser chip 2 is mounted on the heat sink portion 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a small and inexpensive semiconductor laser particularly suitable for use in a pickup light source such as a DVD (Digital Video Disc) or DVD-ROM. More specifically, the present invention relates to a stem-type semiconductor laser that can be formed with a small outer shape even when a laser chip for DVD or the like becomes large.

  A stem type semiconductor laser used for a conventional CD pickup or the like has a structure as shown in FIG. 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 laser chip 31 is mounted on the heat sink part 22 via a submount 34 made of a silicon substrate or the like, and one electrode (the back electrode of the chip 31) is lead by the wire 33 via the relay part 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. 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. And it forms by covering the cap 35 around it. A through hole 35 a is provided at the center of the top of the cap 35 so that light emitted from the laser chip 31 is transmitted, and a glass plate 36 is sealed with an adhesive 37.

  In this structure, although the heat sink portion 22 must be formed between the leads 23 and 25, the leads 23 and 25 must be sealed with glass 26 or the like, so that the diameter of the stem 20 can be reduced. Can not. For this reason, conventionally, only an outer shape of about 5.6 mmφ has been produced.

  On the other hand, as shown in FIG. 8, a plate-like body is drawn to form a ring 27 and a pedestal 28 as a heat sink, and the leads 23 and 25 are directly sealed in the ring 27 by glass 29 or the like. In some types, the stem 20 is formed, and the cap 35 is put on the outer periphery of the stem 20 by press fitting. By adopting such a structure, it is not necessary to directly form a heat sink portion on the base of the stem, and a space for welding the cap is not required, so that a product having a diameter of about 3.3 mmφ is manufactured. In addition, the same code | symbol is attached | subjected to the same part as FIG. 8, and the description is abbreviate | omitted.

  As a light source used for a conventional pickup for a CD or the like, the laser chip has a size of about 0.25 mm square and the operating current is small. Therefore, even if the semiconductor laser having the structure shown in FIG. The amount of laser chip for DVD is as large as about 0.25mm x 0.5mm square, and the operating current is about twice as large as that for CD, and the laser chip will not emit light if the heat dissipation is not enough. There's a problem. Therefore, it is necessary to make the heat sink part as large as possible to improve heat dissipation. Furthermore, in the structure shown in FIG. 8, since the cap is fitted by press-fitting, it is necessary to form a thick solder plating on the stem surface, and the lead also has a thick solder plating, which makes it difficult to perform wire bonding. There is also a problem.

  On the other hand, pickups used to detect signals such as CDs and DVDs are required to be very thin as electronic devices become lighter and thinner as represented by recent notebook personal computers. The semiconductor laser to be used is required to have a small outer diameter, and even if the chip size is increased for the above-mentioned DVD or the like, and the heat radiation needs to be improved, the outer diameter should be about 3.3 mmφ or less. It is rare.

  The present invention has been made in view of such a situation, and provides a semiconductor laser having a small outer diameter while improving heat dissipation characteristics by enlarging a heat sink even in the case of a laser chip having a large chip size and a large amount of heat generation. For the purpose.

  Another object of the present invention is to provide an optical pickup device capable of reducing the thickness of an optical pickup used in a notebook personal computer or the like and achieving a reduction in thickness of an electronic device.

  A semiconductor laser according to the present invention includes a stem that is fixed so that at least two leads protrude on both sides, a support portion provided on one bottom portion (lead fixing portion) side of the stem, and an upper portion of the support portion. The heat sink portion is formed wide so as to extend toward the two protruding leads, and the laser chip is fixed to the heat sink portion.

  Here, the term “widely formed so as to extend to the lead side” means that the support portion provided between the two leads extends in the width direction of the lead, and the support portion provided behind the lead is the front lead. It is meant to include one or both when extending in the direction (perpendicular to the width direction of the lead). The wide portion may be wide so as to cover the top of the lead tip, or may be wide enough to cover the glass portion to which the lead is fixed, although the lead tip is not covered.

  With this structure, the heat sink and the lead (including the glass part to which the lead is fixed) are seen even when the support part is constrained narrowly by the lead interval or the like when viewed in plan (when the stem is viewed from above). Because of the overlapping structure, a sufficient volume of the heat sink can be secured even with a narrow lead interval. As a result, it is possible to provide a heat sink portion that is sufficient for heat dissipation even with a narrow lead interval for an outer diameter of 3.3 mmφ, and even a laser chip that has a large chip size and a large amount of heat, such as a DVD, is small. Can be packaged. That is, in this type of conventional semiconductor laser, the heat sink portion and the support portion are formed with the same width, and the idea is that the heat sink portion and the lead are arranged in a plan view. There is a restriction that the space between the heat sink and the heat sink cannot be enlarged. However, the idea of expanding the heat sink part so that it overlaps with the lead in plan view is large, so even a semiconductor laser for DVD with a small external shape, large chip size and large heat generation has a small external shape of about 3.3 mmφ. Could be formed.

  The stem is formed by fixing the two leads to the through hole of the metallic base via an insulator, the support part is formed integrally with the base, and the heat sink part is formed on the support part. By adopting a structure in which is adhered, a copper material having good thermal conductivity can be used as the heat sink.

  The stem is formed by fixing the two leads to the through hole of the metallic base via an insulator, and the support portion and the heat sink portion are formed integrally with the base, thereby providing dimensional accuracy. And assembly becomes easy.

  Since the support portion and the heat sink portion are integrally formed of a metallic plate material, and the support portion of the integral body is fixed to the base of the stem, the manufacturing process of the stem becomes very easy.

  Even if the stem is formed by sealing the at least two leads through an insulator in a cylindrical ring, the stem is formed wide and provided with a heat sink portion with good heat dissipation. It is also possible to manufacture a semiconductor laser having a laser chip with a large chip size and a large calorific value, such as for DVD.

  An optical pickup device according to the present invention includes a semiconductor laser, a diffraction grating, a beam splitter that separates light emitted from the semiconductor laser and light reflected and returned, and a collimator lens that collimates the beam from the semiconductor laser. A reflector that bends the beam from the semiconductor laser in a right angle direction, an objective lens that focuses the beam on the disk, and a photodetector that detects the reflected light from the disk by separating it with the beam splitter. The semiconductor laser comprises the semiconductor laser according to claim 1.

  According to the present invention, even if a stem having a metallic base formed by a cold forging method is used, a very small semiconductor laser of about 3.3 mmφ can be obtained. In addition, heat dissipation is improved and a highly reliable semiconductor laser can be obtained. Furthermore, by using a stem having a metallic base, the cap can be welded and high airtightness is easily obtained.

  Furthermore, since the heat sink can be formed sufficiently large without being restricted by the interval between the leads, the outer shape of the stem can be increased even with a laser chip having a large chip size or a large calorific value, such as a DVD. Can be mounted without.

  As a result, a very thin pickup can be formed even with a pickup for DVD or the like. In addition, the pickup using the semiconductor laser of the present invention greatly contributes to the thinning of electronic equipment using a laser light source such as a notebook personal computer.

It is explanatory drawing which shows the structure of one Embodiment of the semiconductor laser by this invention. It is explanatory drawing which shows the other structural example which enlarges the heat sink part of FIG. It is explanatory drawing which shows the structure of other embodiment in the semiconductor laser of this invention. It is explanatory drawing which shows the structure of other embodiment in the semiconductor laser of this invention. It is explanatory drawing which shows the structure of other embodiment in the semiconductor laser of this invention. It is explanatory drawing of the structure of the pick-up by this invention. It is explanatory drawing of the structural example in the conventional semiconductor laser. It is explanatory drawing of the structural example in the conventional semiconductor laser.

  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 at least two leads 14 and 16 as shown in FIGS. 1A to 1C, respectively. A support portion 12 is provided on one bottom portion (base 11) side of the stem 1 fixed so as to protrude from both sides. Then, a heat sink portion 13 is formed in a wide width so as to extend toward the above-described two protruding leads 14 and 16 above the support portion 12. The laser chip 2 is mounted on the heat sink portion 13.

  The stem 1 includes a base 11, a support portion 12, a heat sink portion 13, leads 14 and 16 sealed in a through hole provided in the base 11 with a soft glass 17 and the like, and leads provided on the base 11 by direct welding or the like. It consists of 15. In the example shown in FIG. 1, the base 11 and the support portion 12 are integrated, and are formed by, for example, forming an iron plate by using a cold forging method to form a protrusion that forms the support portion 12 at the center thereof. The support portion 12 is a portion sandwiched between the leads 14 and 16 as indicated by a broken line in the plan explanatory view of FIG. 1C, for example, with a thickness of about 1 mm and a diameter of about 3.3 mmφ. In this case, the width is about the same as or slightly narrower than the width sandwiched between the through holes of the base 11 and about 1.1 mm behind the leads 14 and 16 (same as the distance between the centers of the leads 14 and 16). . The diameter of the through hole for fixing the leads 14 and 16 is, for example, about 0.75 mmφ, and the interval is formed to about 1.1 mmφ.

  The leads 14 and 16 are made of, for example, an Fe—Ni alloy rod of about 0.3 mmφ, and are sealed in the through holes of the base 11 by glass beads made of soft glass 17 or the like. The common lead 15 is also made of the same material, but is directly fixed to the base 11 by welding or the like for electrical connection with the base 11.

  In the example shown in FIG. 1, the heat sink portion 13 is formed separately from the support portion 12, and is made of, for example, a copper block, and the plan view is shown in FIG. A wide portion is formed so as to protrude to the side of the leads 14 and 16, the width A in the direction in which the parallel leads 14 and 16 are arranged is formed, for example, about 1.4 mm, and the height B is formed about 1.1 mm. 12 is fixed by brazing or the like. That is, with the support portion 12 alone, the width of the front surface is only about 0.4 mm which is the gap portion of the through hole, but the width of the front surface of the heat sink portion 13 is widened to about 1.4 mm. Therefore, the submount for bonding the laser chip can be securely fixed, and the heat of the laser chip transmitted to the submount can be efficiently dissipated.

  In the example shown in FIG. 1, the width of the heat sink portion 13 is wider than the width of the support portion 12 in the direction (lateral direction) in which the leads 14 and 16 are arranged, but for example, as shown in FIG. The support part 12 may be formed with a wide width on the rear side of 14 and 16, and the heat sink part 13 may be formed wider than the support part 12 on the lead side (C direction in FIG. 2). It may be formed wide in both directions along with the direction in which they are arranged. In short, the area of the heat sink portion 13 as viewed in a plane is formed larger than that of the support portion 12, and the light emitting portion of the laser chip to be mounted is formed with a large area so as to be located at the center of the stem. There are features. In the above-described example, the heat sink portion 13 is formed separately from the support portion 12, but may be formed integrally with the support portion 12 or integrally with the base 11 and the support portion 12 as described later.

  The laser chip 2 is formed so as to emit laser light. The size of the laser chip 2 is about 250 μm × 250 μm for a CD, but increases to about 250 μm × 500 μm for a DVD. However, it is still very small, and is bonded onto the submount 3 made of a silicon substrate or the like of a size of about 0.8 mm × 1 mm in order to facilitate handling and secure heat dissipation. One electrode is connected to the submount 3 by wire bonding such as a gold wire 8 and is connected to the common lead 15 through the conductive adhesive, the heat sink portion 13, the support portion 12 and the base 11 from the back surface. The electrode (back electrode) is connected to the lead 14 by wire bonding such as a gold wire 8 through the connection portion 3 a on the submount 3.

  The submount 3 to which the laser chip 2 is bonded is conveyed by a suction collet and mounted on the heat sink portion 13. Similarly, a light receiving element 4 for monitoring the light emission output of the laser chip 2 is provided on the submount 3, one electrode of which is connected to the common lead 15 via the heat sink portion 13 and the other electrode is made of gold. The lead 16 is electrically connected by wire bonding such as the wire 8. The light receiving element 4 may be provided at a location different from the submount 3.

  A cap (shell) 5 is provided around the laser chip 2 by welding to the stem 1. That is, projections (protrusions) are provided on the bottom surface of the cap 5 (the portion in contact with the stem 11) over the entire circumference, and the entire circumference is hermetically sealed by resistance welding or the like so that current is concentrated on that portion. ing. The cap 5 is preferably made of a material having good heat conductivity such as copper, but may be a metal having good weldability such as iron or cobalt. Further, matte silver plating or the like is preferably applied because it is easy to prevent irregular reflection of light on the inner surface. In addition, a window portion (through hole) 59 through which laser light passes is provided at the center of the top portion of the cap 5, and a transparent plate 6 such as glass is provided in the window portion 5a with an adhesive 7 such as low-melting glass. It is stuck by.

  According to the semiconductor laser of the present invention, since the heat sink portion is formed wider than the support portion, the laser chip can be a large heat sink that can sufficiently dissipate heat even if the stem lead interval is narrow (regardless of the lead interval). Can be mounted. As a result, even a laser chip having a large DVD chip size, large operating current, and large heat generation can be mounted on a stem having a small outer diameter. In addition, in order to form the outer diameter of 3.3 mmφ even with a relatively small chip for a conventional CD and a small calorific value, in the case of a stem type by cold forging, the diameter of the glass to which the lead is fixed or However, a space for forming a portion for welding the cap is required, and the size reduction cannot be achieved, and the size can be reduced only by using a cylindrical ring. Even a stem type by intermediate forging can be manufactured as small as about 3.3 mmφ.

  Since this metallic stem can be used, the cap can be provided on the stem by resistance welding as described above. As a result, confidentiality can be greatly improved, solder plating required for press-fitting is not required, and solder plating cannot be applied to the leads, so that the wire bonding property is greatly improved.

  In the above-described example, the heat sink portion 13 is manufactured separately from a material different from the support portion 12 and is fixed to the support portion 12 by brazing or the like. If formed by such a separate body, it is preferable because a copper block having particularly good heat conduction can be used. However, as shown in the perspective view of the stem portion in FIG. Thus, the heat block portion 13 can be formed integrally with the base 11 and the support portion 12. If formed integrally, there is an advantage that the heat block portion 13 does not need to be fixed and can be manufactured with high accuracy.

  As another example, as shown in a perspective explanatory view of a similar stem portion in FIG. 4, the support portion 12 and the heat block portion 13 are integrally formed by punching and bending a copper plate, and The support portion 12 may be fixed to the base by welding or brazing. As shown in FIG. 4, by bending the heat sink portion, the surface area can be increased in a limited space, and the heat dissipation characteristics can be improved. The other parts are the same as in the above example, and the same parts are denoted by the same reference numerals and the description thereof is omitted.

  FIGS. 5A and 5B are explanatory diagrams showing still another example in a cross-section in a right angle direction, in which a large laser chip for DVD or the like can be mounted in a conventional small package of 3.3 mmφ. This is an example in which a wide heat sink is provided. That is, the cylindrical ring 18 is formed by drawing processing such as the copper plate as described above, and the stem 1 is formed by sealing the leads 14 and 16 with the glass 19 or the like in the ring 18. The support portion 12 and the common lead 15 are integrally formed. The heat sink portion 13 formed wider than the support portion is fixed on the support portion 12. Other parts other than the stem 1 are the same as in the example shown in FIG. 1, and the same parts are denoted by the same reference numerals and description thereof is omitted. Although the light receiving element is not shown in FIG. 5, it is provided in the same manner as in the above example.

  FIG. 6 is an explanatory diagram showing an outline of an example in which a thin pickup is constructed using the semiconductor laser having a small outer diameter. That is, the semiconductor laser 50 is disposed sideways, and the light from the semiconductor laser is diffracted by the diffraction grating 51. For example, in the three-beam method, the laser beam is divided into three, and the beam splitter 52 that separates the emitted light and the reflected light. The collimator lens 53 converts the beam into a parallel beam, the prism mirror (reflecting mirror) 54 bends the beam at 90 ° (z-axis direction), and the objective lens 55 focuses the surface of a disk 56 such as a DVD or CVD. The reflected light from the disk 56 is detected by the photodetector 58 via the beam splitter 52, the concave lens 57, and the like. In FIG. 6, the semiconductor laser 50 and the photodetector 58 are substantially in the same plane (xy plane).

  In this way, by arranging the semiconductor laser 50 in a horizontal direction and detecting irregularities on the surface of a DVD or the like while emitting a laser beam in a direction parallel to a DVD or the like, the optical pickup can be made thinner. Depending on the outer diameter of the optical pickup, a very thin optical pickup can be configured by reducing the outer diameter. As described above, an optical pickup having a thickness of about 5 mm was obtained by using the semiconductor laser according to the present invention having an outer diameter of 3.3 mmφ.

DESCRIPTION OF SYMBOLS 1 Stem 2 Laser chip 11 Base 12 Support part 13 Heat sink part 14 Lead 15 Common lead 16 Lead

Claims (6)

A stem fixed so that at least two leads protrude on both sides, a support portion provided on one bottom side of the stem, and extending to the two lead sides protruding above the support portion A semiconductor laser comprising a heat sink portion formed wide and a laser chip fixed to the heat sink portion. The stem is formed by fixing the two leads to the through hole of the metallic base via an insulator, the support part is formed integrally with the base, and the heat sink part is formed on the support part. 2. The semiconductor laser according to claim 1, wherein is bonded. 2. The stem is formed by fixing the two leads to a through hole of a metallic base via an insulator, and the support portion and the heat sink portion are formed integrally with the base. Semiconductor laser. 2. The semiconductor laser according to claim 1, wherein the support portion and the heat sink portion are integrally formed of a metallic plate material, and the support portion of the single piece is fixed to the base of the stem. 2. The semiconductor laser according to claim 1, wherein the stem is formed by sealing the at least two leads through an insulator in a cylindrical ring. A semiconductor laser, a diffraction grating, a beam splitter that separates light emitted from the semiconductor laser and reflected light, a collimator lens that collimates the beam from the semiconductor laser, and a beam from the semiconductor laser A reflecting mirror that bends the light beam in a right angle direction, an objective lens that focuses the beam on the disk, and a photodetector that detects the reflected light from the disk by separating it with the beam splitter. An optical pickup device which is a semiconductor laser according to claim 1.

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