`
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`
`In re Patent of:
`
`Lebens et al.
`
`U.S. Patent No.:
`
`6,095,661
`
`
`
`Issue Date:
`
`August 1, 2000
`
`Appl. Serial No.:
`
`09/044,559
`
`Filing Date:
`
`March 19, 1998
`
`Title:
`
`METHOD AND APPARATUS FOR AN L.E.D.
`
`FLASHLIGHT
`
`
`PETITION FOR INTER PARTES REVIEW OF UNITED STATES PATENT
`NO. 6,095,661 PURSUANT TO 35 U.S.C. §§ 311–319, 37 C.F.R. § 42
`
`
`Exhibit LG-1017
`
`U.S. Patent No. 5,590,144 (“Kitamura”)
`
`

`

`EURAUS005590
`
`u9;
`United States Patent
`5,590,144
`(11) Patent Number:
`
`[45] Date of Patent: Dec. 31, 1996
`Kitamuraet al.
`
`[54] SEMICONDUCTOR LASER DEVICE
`
`[75]
`
`Inventors: Shoji Kitamura; Yoichi Shindo; Akira
`Amano,all of Kawasaki, Japan
`
`[73] Assignee: Fuji Electric Co., Ltd., Kanagawa,
`Japan
`
`{21] Appl. No.: 289,573
`
`[22]
`
`Filed:
`
`Aug. 12, 1994
`
`Related U.S. Application Data
`
`[60] Division of Ser. No. 43,482, Apr. 6, 1993, Pat. No. 5,444,
`726, which is a continuation-in-part of Ser. No. 788,601,
`Nov. 6, 1991, Pat. No. 5,355,385.
`
`[30]
`
`Foreign Application Priority Data
`
`Japat oe esssssssssssosnseenesseeeee 2-302258
`[JP]
`Nov. 7, 1990
`
`Japan ....
`« 4-85323
`[JP]
`Apr. 1, 1992
`
` Jan. 22,1993 [JP] Japan .... wee 39-8679
`
`
`Mar. 30, 1993
`[JP]
`Japan ......sessessscseserenessnecerseovens 5-70597
`
`Wants Ce ooccececsssssecceseeeneeenes HOI1S 3/04; HO1L 23/48
`(51 ]
`[52] OS. CI. iceecsccssscsssseeesenses 372/36; 257/675; 372/34;
`372/49; 372/109
`(58] Field of Search 200... 372/36, 34, 49,
`372/50, 109; 257/675
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`
`........-esscceeereee 357/17
`1/1987 Althaus et al.
`4,638,343
`
`4,712,127 12/1987 Colomboetal. .
`wee SST/T2
`
`4,852,112
`7/1989 Kagawaetal........
`a. 372/49
`
`4,951,291
`8/1990 Miyauchi etal. ........
`. 372/49
`
`4,951,292
`8/1990 Kuindersmaetal.
`we 372/49
`
`4,962,985 10/1990 LeGrange ......s0
`» 350/96.15
`.....ssssseserseseeesceee 372/49
`4,975,922 12/1990 Sakane et al.
`
`« 437/129
`4,985,370
`1/1991 Ponjceetal. .....
`
`wee SST/T
`5,140,384
`8/1992 Tanaka..........
`+ 257/675
`5,208,188
`5/1993 Newman ...
`5,252,944 10/1993 Caddock, Jr.
`257/675
`5,307,362
`4/1994 Tanaka et al.
`....secssscessesesseeneers 372/50
`5,309,460
`5/1994 Fujimaki et al...ssecssceoeceoeee 372/36
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`5/1990 European Pat. Off..
`0366472
`3/1991
`European Pat. Off.
`.
`416195A2
`1/1992 European Pat. Off.
`.
`0466975A1
`4/1994 European Pat. Off.
`.
`§92746A1
`2127239 10/1972 France.
`4307570A1
`9/1993 Germany .
`58-194381
`11/1983
`Japan .
`60-12782
`1/1985
`Japan .
`60-206185 10/1985
`Japan .
`1-166591
`6/1989
`Japan.
`
`(List continued on next page.)
`OTHER PUBLICATIONS
`
`Patent Abstracts of Japan, vol. 14, No. 507 (E-998) Nov.6,
`1990, abstract, JP 2 209 786, Miyahara Hiroyuki et al.,
`Semiconductor Laser Device.
`
`(List continued on next page.)
`
`Primary Examiner—James W. Davie
`Attorney, Agent, or Firm—Finnegan, Henderson, Farabow,
`Garrett & Dunner, L.L.P.
`
`[57]
`
`ABSTRACT
`
`A semiconductor laser device includes a lead frame for
`electrically controlling a laser diode element having at least
`one end face for emitting a laser beam and for mechanically
`supporting the laser diode element on a planar major surface
`thereof with a support member interposed therebetween. A
`sealing resin layer, transparent to the passage of the laser
`beam, covers at least the laser diode element on the lead
`frame in a sealing manner. To improve the light emitting
`point stability of the laser diode element, when the cross
`section of the planar major surface of the lead frame is
`parallel to the light emitting end face, a horizontal direction
`is the longitudinal direction of the cross section of the lead
`frame, a horizontal center line defines the center of the cross
`section of the lead frame, and a vertical center line defines
`the center as viewed in the vertical direction, the sealing
`resin layer is shaped symmetrically with respect to the
`vertical center line.
`
`9 Claims, 14 Drawing Sheets
`
`35
`
`23
`
`32
`
`Exhibit LG-1017 Page 1
`
`Exhibit LG-1017 Page 1
`
`

`

`5,590,144
`Page 2
`
`FOREIGN PATENT DOCUMENTS
`
`2-33979
`2-125688
`2-125687
`2-159084
`2-224359
`4-137580
`4-320386
`4-346281
`2005917
`
`Japan .
`2/1990
`Japan .
`5/1990
`Japan .
`5/1990
`Japan.
`6/1990
`Japan .
`9/1990
`Japan.
`5/1992
`Japan .
`11/1992
`Japan .
`12/1992
`4/1979 United Kingdom .
`
`OTHER PUBLICATIONS
`
`Patent Abstracts of Japan, vol. 13, No. 541 (E-854) Dec. 5,
`1989, abstract, JP 1 222 492, Kume Masahiro etal., Semi-
`conductor Laser Device.
`
`Patent Abstracts of Japan, vol. 10, No. 69 (E-389) Mar. 18,
`1986, abstract, JP 60 217 687, Sawai Masaaki, Light-Emit-
`ting Electronic Device.
`
`Patent Abstracts of Japan, vol. 12, No. 486 (E-695) Dec. 19,
`1988, abstract JP 63 200 583, Yano Morichika et al.,
`Semiconductor Laser Device.
`
`Patent Abstracts of Japan, vol. 14, No. 507 (E-998) Nov.6,
`1990, abstract, JP 2 209 785, Miyahara Hiroyuki et al.,
`Optical Semiconductor Device.
`
`Patent Abstracts of Japan, vol. 17, No. 238 (E-1363) relating
`to Japanese Patent document 4364791, published Dec. 17,
`1991, Abstract published May 13, 1993.
`
`Exhibit LG-1017 Page 2
`
`Exhibit LG-1017 Page 2
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 1 of 14
`
`5,590,144
`
`FIG.
`
`TA
`
`Exhibit LG-1017 Page 3
`
`Exhibit LG-1017 Page 3
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 2 of 14
`
`5,590,144
`
`FIG. 2
`
`
`
`
`
`(ym)
`LIGHTEMITTINGPOINTDISPLACEMENT
`
`
`Exhibit LG-1017 Page 4
`
`Exhibit LG-1017 Page 4
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 3 of 14
`
`5,590,144
`
`FIG. 44
`
`|
`
`%
`4Bi
`20b
`
`23/1
`
`"
`4B
`
`20a
`
`20
`
`33
`
`
`
`FIG. SA
`SBt
`
`3
`
`35
`
`40
`
`20¢
`2 158
`°
`
`11
`20b
`
`20
`
`
`
`Exhibit LG-1017 Page 5
`
`Exhibit LG-1017 Page 5
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 4 of 14
`
`5,590,144
`
`
`
`WwOW
`
`dVdOled
`
`é
`
`gL
`
`GZOY
`
`LVYOldd9Oy
`
`Exhibit LG-1017 Page 6
`
`Exhibit LG-1017 Page 6
`
`
`

`

`Dec. 31, 1996
`
`Sheet 5 of 14
`
`5,590,144
`
`U.S. Patent
`
`11
`
`Exhibit LG-1017 Page 7
`
`Exhibit LG-1017 Page 7
`
`
`

`

`U.S. Patent
`
`—
`
`Dec. 31, 1996
`
`Sheet 6 of 14
`
`5,590,144
`
`FIG. 12A
`
`Y
`
`12B |
`
`x
`
`HI
`
`29
`
`12B
`
`|
`
`7
`
`_
`
`1
`
`
`Exhibit LG-1017 Page 8
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 7 of 14
`
`5,590,144
`
`FIG. 134
`
`SUB
`
`BEAM
`
`FIG. 13B
`
`PES
`
`Nh’
`
`Exhibit LG-1017 Page 9
`
`Exhibit LG-1017 Page 9
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 8 of 14
`
`5,590,144
`
`FIG. 14
`
`(pum)
`XAXISDISPLACEMENT
`
`POINTDISPLACEMENT4X
`
`LIGHTEMITTING
`
`FIG. 15
`
`TIME
`(min)
`
`LASER
`ON
`
`LASER
`OFF
`
`LASER
`ON
`
`Exhibit LG-1017 Page 10
`
`Exhibit LG-1017 Page 10
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 9 of 14
`
`5,590,144
`
`(O=XP)
`
`
`
`qgt‘Ola
`
`OL
`
`
`
`q9l‘Ola
`
`V9L‘Dla
`
`Y+sfS10
`ULTT005004ODEOZODL00OOFOOe-ODENOT-
`WITT00S004ODE002OOF00O'01-002-00E-004-
`
`1)s‘0
`
`YALN3)ALIAVYS:
`wrf02OL00Ol-02-
`ULOZSLOLSO00S0-0FSTOe
`ENS'0
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`wrtLb0|oLO|
`[aS}
`aa,
`
`
`
`49!‘Old
`
`LSIHS
`
`O9tOld
`
`Exhibit LG-1017 Page 11
`
`Exhibit LG-1017 Page 11
`
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 10 of 14
`
`5,590,144
`
`ALIAVSS
`
`YsaLNA9
`
`wrt,
`
`LAIHS
`
`Th$0
`
`fébt0
`
`AGLOlA
`
`[———adyy
`
`(WWE'O)7+S/)
`
`
`(wiTL=Xp)
`
`wil671—-
`
`LIHS
`
`ALIAVY9
`
`YS1LN4)
`
`OZStObSO00SO0-OL-St02-
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`DILOla
`
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`oY>
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`00S007OOE002OO00ODI002-00E-004-
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`
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`
`LAIHS
`
`
`
`P9l‘Old
`
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`
`H9L‘Old
`
`Exhibit LG-1017 Page 12
`
`OL
`
`in
`
`XV
`
`Exhibit LG-1017 Page 12
`
`
`
`
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 11 of 14
`
`5,590,144
`
`FIG. 17
`
`LIGHT EMITTING CENTER
`DISPLACEMENT (ym)
`% 02 05
`10 Ax
`a)
`
`-10
`
`BEAMSPOTGRAVITYCENTER
`
`
`SHIFT(ym)
`
`FIG.
`
`18A
`
`23 4
`
`FIG. 18B
`
`11
`
`18B
`
`35
`=
`
`20
`
`23
`
`4
`11
`
`20A
`20
`
`20b
`
`20a
`
`Exhibit LG-1017 Page 13
`
`Exhibit LG-1017 Page 13
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 12 of 14
`
`5,590,144
`
`FIG.
`
`719A
`
`20 23
`
`33
`
`11
`
`FIG. 19B
`
`20
`
`11
`
`20b
`
`23
`
`20a
`
`FIG. 19C
`
`
`
`FIG. 19€
`
`FIG.
`
`19E
`
`20 20a
`11
`
`1
`
`23
`
`3B
`
`20b~
`
`—
`
`Exhibit LG-1017 Page 14
`
`

`

`U.S. Patent
`
`Dec. 31, 1996
`
`Sheet 13 of 14
`
`5,590,144
`
`Exhibit LG-1017 Page 15
`
`FIG. 20A
`
`
`FIG. 20B
`
`Poa
`
`~ 3
`
`5
`
`3,
`
`1
`
`32
`
`FIG. 27A
`
`20
`
`|
`
`FIG. 276
`
`20
`
`35
`
`Exhibit LG-1017 Page 15
`
`

`

`U.S. Patent
`
`Dec.
`
`31, 1996
`
`Sheet 14 of 14
`
`5,590,144
`
`FIG. 22
`
`
`
`Exhibit LG-1017 Page 16
`
`

`

`2
`on an n-type GaAssubstrate 2. An electrode 7 is selectively
`formed on the obverse side of the laser diode element in an
`opened portion of the p-type cap layer 6. An electrode 8 is
`formedonthe rear side of the substrate 2. End-face destruc-
`tion preventing layers 10 (FIG. 10) are respectively formed
`on the light emitting end facesof the laser diode element and
`are irradiated with laser beams. The end-face destruction
`preventing layers 10 are made of organic resin, which
`exhibits high heat resistance and low absorption coefficient
`in the wavelength region of the emitted laser beams.
`Asbest illustrated in FIG.11, the laser diode element1 is
`mounted on a photo diode 23 serving also as a submount
`layer and a radiatorplate. The photo diode 23 is mounted on
`the top end portion of the center lead frame of laterally
`arrayed lead frames 20. The photodiode 23 and the p-type
`cap layer 6 are connected to the respective lead frames 20 by
`bonding wires, for example, gold wires (not shown). The
`laser diode element 1, connected to those lead frames 20,is
`A semiconductorlaser device of the can-type as shown in
`enclosed by resin 11, such as transparent epoxy resin, in a
`FIGS. 6 and 7 is known in the art. As shownin FIG.6,a laser
`sealing manner. The semiconductor laser device of the
`diode element1 is soldered to a radiator 62 supported on a
`mold-type, which includes the laser diode element 1 having
`stem 61. A cap 63 with a glass window 64 is soldered to the
`the end-face destruction preventing layers 10, is low in cost
`stem 61. In the semiconductor laser device shown in FIGS.
`and good in endurance.
`7A and 7B, a laser diode element 1 is mounted to a submount
`In the semiconductor laser device of the mold-type, as
`provided by a photo diode 23, which is then mounted on a
`shown in FIGS. 12A and 12B, the laser diode element 1 is
`radiator 62 extending upwardly from the stem 61. The photo
`positioned at or near the center the sealing resin layer 11,
`diode 23 submountalso serves as a radiator plate. The laser
`which is designated by intersection point 27 of the X axis 25
`diode element 1 is covered with a cap 63 also fastened to the
`and the Y axis 26, as in the semiconductorlaser device of the
`stem 61. The combination of the radiator 62 and the photo
`can-type. The center 28 of the lead frame 20 is displaced by
`diode 23 are positioned so that the laser diode element 1 is
`distance AX,, (or offset 29), from the intersection point 27
`located at the center of the glass window 64 in cap 63, as
`of the sealing resin layer 11, because of the total thickness
`viewed from the front; the center being designated by an
`of the laser diode element1, the photo diode 23 and the lead
`intersection point 27 of a horizontal center line 25 (at a right
`frame 20.
`angle to the major surface of the radiator 62, or an X-axis
`Those semiconductor laser devices are assembled into
`direction) and a vertical centerline 26 (parallel to the major
`various types of optical systems. A typical example of the
`surface of the radiator 62, or a Y-axis direction).
`optical system is a pick-up device for an optical disc as
`Another semiconductor laser device of a resin sealing or
`schematically illustrated in FIG. 13A.
`mold-type has been developed. This type of laser device is
`In the pick-up device illustrated, a laser beam emitted
`less expensive and can be shaped more flexibly than the
`from the laser diode element 1 passes through a diffraction
`can-type laser device disclosed above. The mold-type laser
`grating 51, turned 90° by a half mirror 52, and focused on
`device is described in detail
`in Published Unexamined
`the surface of a disc 54 through an objective lens 53. The
`Japanese Patent Application No. Hei. 2-125687. In this
`laser beam is separated into a main beam and a subbeam by
`device, as shown in FIG. 8 herein, a laser diode element 1
`the diffraction grating 51. The subbeam is used for tracking
`is mounted on a submount 23 and then sealed in a sealing
`servo purposes. The laser beam, reflected by the disc, 54
`resin layer 11 comprised of transparent epoxy resin, for
`passes through the objective lens 53 and the half mirror 52
`example. The element1 is electrically powered through lead
`against and is projected onto the light sensor 55. The sensor
`frames 20 and a gold wire 21. The semiconductor laser
`transforms the received laser beam into a corresponding
`device of the mold-type has been knownasalight emitting
`electrical signal.
`device of low light density per unit area, analogous to an
`The light sensor 55 consists of six photo diodesA to F, as
`LED.
`shown in FIG. 13B. The main beam is incident on the
`quartered diodes A to D. The laser beam experiences astig-
`matism as it passes throughthe half mirror 52, and the shape
`of the main beam changesas indicated by the dotted lines in
`FIG. 13B, depending on the location of the photo diodes.
`The focusing servo mechanism positions the objective
`lens 53 so that (A+C)—(B+D)=0 where A, B, C and D are
`outputs of the photo diodes A, B, C and D. The “gravity
`center of beam on the photo diodes”, to be discussed later is
`defined as
`
`This is a division of application Ser. No. 08/043,482,
`filed Apr. 6, 1993, U.S. Pat. No. 5,444,726, which is a
`continuation-in-part of application Ser. No. 07/788,601,
`filed Nov. 6, 1991, U.S. Pat. No. 5,355,385.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`invention relates to semiconductor laser
`The present
`devices of the mold-type in which a laser diode elementis
`encapsulated in a sealing resin layer, and more particularly
`to a semiconductor laser device that experiences minimal
`displacementofits light emitting point during continuously
`operation and/or during changing ambient conditions.
`2. Discussion of the Prior Art
`
`The laser device of the mold-type is advantageous
`because of low manufacturing cost and the resin sealing
`layer can be of a wide variety of shapes. Additionally, the
`laser diode element can be used in high light density
`applications without any characteristic deterioration owing
`to light damage if an end face destruction preventing layer
`is used. A semiconductor laser device incorporating an
`end-face destruction preventing layer is described in detail
`in commonly assigned U.S. application Ser. No. 07/788,601,
`filed Nov. 6, 1991, U.S. Pat. No. 5,355,385.
`One example of the laser device disclosed in patent
`application Ser. No. 07/788,601, U.S. Pat. No. 5,355,385,
`will be described with reference to FIGS. 9 through 12. The
`laser diode element1 is illustrated as having a DH (double
`heterodyne junction) structure. As shown, an n-type clad
`layer 3 made of AlGaAs, an active layer 4, a p-type clad
`layer 5, and a p-type cap layer 6 made of GaAsare layered
`
`1
`SEMICONDUCTOR LASER DEVICE
`
`5,590,144
`
`10
`
`15
`
`25
`
`30
`
`35
`
`40
`
`50
`
`55
`
`60
`
`1X, YI=[{(A+B)-(C+D)}/(A+-B+C+D), {(A+D)-(B+C)(AtB+C+
`D)]
`
`65
`
`In the semiconductorlaser device of the mold-type, it has
`been discoveredthat the light emitting point, i.e., the origin
`of the emitted laser beam, shifts location when the laser
`
`Exhibit LG-1017 Page 17
`
`Exhibit LG-1017 Page 17
`
`

`

`5,590,144
`
`3
`device is continuously operated and/or ambient conditions
`change. Shifting or displacementofthe light emitting point
`is graphically represented in FIG. 14. To plot the graph ofthe
`figure, a mold-type semiconductorlaser device was operated
`at room temperature while being fed with an operating
`current of 50 mA.In the graph, the abscissa represents time
`in minutes, and the ordinates represents the extend of
`displacement in the X-axis direction (normal to the lead
`frame surface. As seen from the graph, after about two
`minutes of laser emission,
`the light emitting point was
`displaced 0.5 um in the —X-axis direction (i.e., toward the
`lead frame 20). After the device was turned off for about two
`minutes, the light emitting point returned to the original
`center point (moved in the +X-axis direction, or toward the
`laser diode). When the semiconductor laser device is
`assembled into a pick-up device, the extend of displacement
`of the gravity center of the beam on the photo diodes
`dependson the duration of continuouslaser device operation
`and/or changes in ambient temperature.
`The semiconductor laser device was operated at an output
`power of 3 mW at ambient temperatures from —10° C.to 60°
`C. The gravity center of beam on the photo diodes was found
`to be displaced 10 um or more. Minimization of the dis-
`placementofthe light emitting point is essential in order that
`the semiconductor laser devices of the mold-type, which has
`many advantages,
`acquire the
`excellent performance
`achieved by can-type semiconductor laser devices.
`Turning to FIG. 15, there is shown a simulation model of
`the influence of light emitting point displacement when the
`laser device operates in a pick-up device. In the simulation,
`a one-dimensional optical system was utilized, in which a
`laser beam from a laser diode LD1,located on theleft side,
`passes through a convex lens 79, separated from the diode
`LD1bya distance d1, and thelaser beam,reflected by a disc
`73, then passes through another convexlens 80 to be focused
`on a photo diode (PD) 69. The one-dimensional system was
`treated as a double Fourier transform optical system. A light
`intensity distribution U2 on the convex lens 79, a light
`intensity distribution U3 on the disc 73, a complex ampli-
`tude U4 on the convex lens 80, and a light
`intensity
`distribution U5 +A were calculated using Fresnel’s diffrac-
`tion formula, with the assumption that the light intensity
`distribution U1 onthe laser diode element1 is rectangular in
`shape, is centered at AX and has a width of 2 um. The AX
`corresponds to the extent of displacement of the light
`emitting point of the laser diode. The results of the calcu-
`lations using the parameters in Table 1 are shown in FIGS.
`16A -16].
`FIGS. 16A-16Eare graphical representations of the light
`distributions U1, U2, U3, U4 and U5+AX=0, and FIGS.
`16F-16J are graphical representations of the same when
`AX=1 um. A beam spot gravity center on the photo diode can
`be calculated using the light intensity distribution (U5+A) on
`the photo diode. When the displacement quantity AX of the
`light emitting point was 1 ym, a shift of the beam spot
`gravity point, when calculated, was 7.9 ym. Similar calcu-
`lations were repeated for other quantities of the displace-
`ment. The results of the calculation showedthe relationship
`between the quantity of displacementof the light emitting
`point and the quantity of shift of the beam spot gravity center
`on the photo diode, as shownin FIG. 17. Thus, in an pick-up
`optical system, 1 um displacementof the light emitting point
`produces a 7.9 times larger shift in the beam spot gravity
`center on the surface of the photo diode. This value is
`defined as a coupling magnification M between the laser
`diode element and the photo diode. The coupling magnifi-
`cation M is determined by the magnification of the lens
`
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`4
`system andthe distance of the optical path betweenthe light
`emitting point of the laser diode element 1 and the signal
`detection, divided photo diode. Accordingly, the coupling
`magnification M differs with the construction of the optical
`pick-up device.
`
`TABLE 1
`
`Ax
`al
`f
`d2
`lens diameter
`A
`
`1.0 um
`25.0 pm
`3.9 pm
`4.6 pm
`4.0 pm
`0.3 pm
`
`In the conventional semiconductorlaser device, the extent
`of the shift of the beam spot on the photo diode 69 can
`exceed a tolerable value. Accordingly, a mechanism to
`adjust the displacement of the light emitting point or a
`mechanism to follow the shift of the beam spot gravity
`center is required for the conventional semiconductorlaser
`device.
`Thus, the semiconductor laser device of the mold-type is
`advantageous in that it is inexpensive and can be flexibly
`shaped. However, when it
`is utilized in an application
`requiring good light emitting point stability, an additional
`adjusting mechanism is required. This negates the advan-
`tages of laser devices of the mold-type.
`
`SUMMARYOF THE INVENTION
`
`Thepresent invention has been made in view of the above
`circumstances and has an object to provide a semiconductor
`laser device of the mold-type which has less displacement of
`the light emitting point, and henceis directly applicable for
`devices requiring goodstability of the light emitting point,
`such as a pick-up device in an optical system for a compact
`disk.
`
`To solve the problems of conventional semiconductor
`laser devices the inventors carefully studied the relationship
`between the lead frame supporting the laser diode element
`and the sealing resin layer for sealing the lead frame and the
`laser diode element and have succeeded in minimizing the
`shift of the lead frame, which is caused by the sealing resin
`layer.
`According to the present invention, a semiconductor laser
`device, having a lead frame for electrically controlling a
`laser diode element having at least an end face for emitting
`a laser beam and for mechanically supporting the laser diode
`element on the planar major surface thereof with a support
`memberinterposed therebetween, and a sealing resin layer
`allowing the laser beam to pass therethrough and covering at
`least the laser diode element on the lead frame in a sealing
`manner, is improved in that the sealing resin layer is shaped
`symmetrically with respect to the lead frame. When the
`cross section of the lead frameis parallel to the light emitting
`end face, the laser diode element is supported at the center
`of the lead frame when viewed in the horizontal direction,
`and the sealing resin layer is shaped symmetrically with
`respect to the vertical center line. While the resin layer
`portion sealing the lead frame and laser diode is, in accor-
`dance with the invention, substantially symmetrical,
`the
`external form of the remainingportion ofthe resin layer may
`be tubular, rectangular or trapezoidal.
`In the semiconductor laser device having the sealing resin
`layer, lead frame fixing means are employedto affix the lead
`frame to an external fixing board, with the laser diode
`
`Exhibit LG-1017 Page 18
`
`Exhibit LG-1017 Page 18
`
`

`

`5,590,144
`
`5
`element mounted on a planar majorsurface of the lead frame
`by way of an interposed support member.
`For the fixing means,
`the surface of the lead frame
`opposite to the surface to which the laser diode elementis
`mounted, may be used as a mounting surface to be placed,
`for mounting, against an external fixing board.
`In the semiconductor laser device in which the end face of
`the lead frame lies in a plane containing the light emitting
`end face, a horizontal direction is defined for the center of
`the horizontal center line, and a vertical direction is defined
`for the center of the vertical center line, the planar mounting
`surface of the sealing resin layer is uniformly separated from
`the surface of the lead frameparallel to the horizontal center
`line or the vertical center line by a distance AX1 that is
`defined by the following formula
`.
`
`AX1S(AL/M)I(axAT),
`
`Q)
`
`where © is the linear expansion temperature coefficient of
`the sealing resin layer;
`ATis the change in ambient temperature;
`AL is the tolerable shift of the beam spot on the divided
`photo diode of a pick-up device and a semiconductor laser
`device is used as a reproduction light source in an optical
`disc system; and
`M is the image forming magnification of a lens system
`including at least one lens, which is located along the
`distance of an optical path between a light emitting point of
`a laser diode element and the divided photo diode of a
`pick-up device.
`There are many causes producing displacement of the
`light emitting point of a laser diode element. The inventors
`of the present patent application paid particular attention to
`the thermal expansion of the sealing resin layer, which
`results from the heat generated when the laser diode element
`operates. In the present invention, the displacement of the
`lead frame, which is most sensitive to thermal expansion of
`the sealing resin layer, is minimized in order to obtain less
`displacement of the light emitting point.
`Also in the present invention, the sealing resin layer is
`shaped symmetrically with respect to the lead frame. Con-
`sequently, forces exerted on the lead frame resulting from
`horizontal and vertical thermal expansion of the sealing
`resin layer can be distributed uniformly. As a result, distor-
`tion of the lead frame owing to differences in thermal
`expansion is considerably reduced. Hence, less displace-
`mentof the light omitting point is obtained.
`fixing the lead frame to an external fixing board can
`remove the influence of thermal expansion of the sealing
`resin layer and minimize light emitting point displacement.
`The lead frame fixing means may include an uncovered
`surface of the lead frame, which provides a mounting
`surface for placement against the external fixing board.
`When the mounting surface is the uncovered surface ofthe
`lead frame, the heat generated whenthe laser diode element
`operatescan beeffectively transferred from the resin sealing
`layer through the lead frame to the external fixing board.
`Therefore, thermal expansion of the sealing resin layer is
`reduced to minimize the influence of thermal expansion on
`the lead frame.
`The fixing means may include at least one through-hole
`formed in the uncovered lead frame. In this case, fasteners
`of low thermal expansion are inserted into the through-hole
`to affix the lead frame to an external fixing board.
`To gain less displacementof the light emitting point, the
`thickness of the sealing resin layer, that is, the separation or
`
`6
`distance of the resin layer form the external fixing board,
`maybeselected so that displacementof the lead framefalls
`within a tolerable range.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanying drawings, which are incorporated in
`and constitute a part of this specification, illustrate embodi-
`ments of the invention and, together with the description,
`serve to explain the objects, advantages andprinciples of the
`invention.
`
`In the drawings:
`FIG. 1Ais across sectional view of a semiconductorlaser
`device according to a first embodiment of the present
`invention, which is taken along line 1A—1Ain FIG. 1B;
`FIG.1B is across sectional view taken along line 1B—1B
`of FIG. 1A;
`FIG.2 is a graph comparatively showing variations of the
`extent of displacement of a light emitting point versus
`operating time in a conventional laser device and the laser
`device of FIG. 1;
`FIG. 3 is a perspective view of a rectangularly shaped
`semiconductor laser device, which is manufactured using
`the same technique as for the laser device of FIG. 1;
`FIG. 4A is a side view, partially in cross section, of a
`semiconductor laser device according to a second embodi-
`ment of the present invention;
`FIG.4B is across section view taken along line 4B—4B
`of FIG. 4A;
`FIG. 5A is a side view showing a semiconductor laser
`device according to a third embodiment of the present
`invention;
`FIG. 5B is a cross section view taken along line 5B—5B
`of FIG. 5A;
`FIG.6 is a perspective view, partially broken away, of a
`conventional semiconductor laser device of the can-type;
`FIG.7Ais a front view of the semiconductor laser device
`shown in FIG. 6;
`FIG.7Bis a cross sectional view taken along line 7B—7B
`in FIG. 7A;
`FIG. 8 is a perspective view of a semiconductor laser
`device of the mold-type;
`FIG. 9 is a perspective view showing the structure of a
`laser diode element used in the semiconductor laser device
`of FIG. 8;
`FIG. 10is a cross sectional view taken along line 10—10
`of FIG.9;
`FIG.11is a cross sectional view of a semiconductor laser
`device of the mold-type;
`FIG. 124Ais a plan view of the semiconductorlaser device
`shownin FIG.8;
`FIG. 12B is a cross sectional view taken along line
`12B—12Bof FIG. 12A;
`FIG. 13Ais a perspective view showing an optical system
`of a pick-up device for an optical disc, which uses a
`semiconductor laser device;
`FIG. 13B is an explanatory diagram showing the con-
`struction of a light sensor containedin the optical system of
`FIG. 13A;
`FIG. 14 is a graph showing displacement of the light
`emitting point of a semiconductor laser device in the X
`direction versus device operating time;
`
`10
`
`15
`
`20
`
`25
`
`35
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`40
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`45
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`30
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`60
`
`65
`
`Exhibit LG-1017 Page 19
`
`Exhibit LG-1017 Page 19
`
`

`

`5,590,144
`
`7
`FIG. 15 is a diagram of a one-dimensional simulation for
`examining displacement of the light emitting point in a
`pick-up device for a compact disc;
`FIG. 16A-16Eare graphical representations of simulated
`pick-up device light distributions U1, U2, U3, U4 and U5+A
`when AX=0;
`FIG. 16F-16J are graphical representations of simulated
`pick-up device light distributions as in FIGS. 16A—16E,
`when AX=1 um;
`FIG.17 is a graph showingthe relationship between shifts
`of the gravity center of a beam spot and displacementsofthe
`light emitting point, which result from the simulations of
`FIGS. 16A-16];
`FIG. 18A is a side view showing a semiconductor laser
`device according to a second embodimentofthe invention,
`in which a sealing resin layer covers only a laser diode
`element and a photo diode;
`FIG. 18B is a cross sectional view taken along line
`18B—18B of FIG. 18A;
`FIGS. 19A to 19E are cross sectional views showing
`specific examples of fixing means used for a semiconductor
`laser device;
`FIG. 20A is a side view showing a semiconductorlaser
`device according to a third embodiment of the present
`invention;
`FIG. 20B is a cross sectional view taken along line
`20B—20B of FIG. 20A;
`FIG. 21A is a side view, partly in cross section, showing
`a structure for fixing the laser device of FIGS. 20A and 20B
`to a fixing board;
`FIG. 21B is a side view, partly in cross section, showing
`another structure for fixing the laser device of FIGS. 20A
`and 20B to a fixing board;
`FIG. 22 is a view showing a semiconductor laser device
`according to a second embodimentof the invention where
`the lead frame is not covered by the sealing resin layer; and
`FIG.23 is a perspective view showing the semiconductor
`laser device according to the second embodiment wherethe
`lead frame is not covered by the sealing resin layer.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`FIGS. 1A and 1B cooperate to show the construction of a
`semiconductorlaser device accordingto a first embodiment
`of the present invention, which is of the mold-type already
`generally described with reference to FIG. 12.
`Asshown, a laser diode element 1, which has end-face
`destruction preventing layers 10, as best seen in FIG.10, is
`securedto a lead frame 20, with a photo diode 23 interposed
`therebetween. The lead frame 20 mechanically supports and
`electrically controls the laser diode element 1 and the photo
`diode 23. The photo diode 23 also serves as a submount and
`a radiator plate for laser diode element 1. The assembly of
`the laser diode element 1, the photo diode 23, and the lead
`frame 20 is encapsulated with a sealing resin layer 11 made
`of transparent epoxyresin. Like or equivalent portions of the
`laser device of FIG. 1 will be designated by like reference
`numerals used in the drawingsillustrating the conventional
`laser devices and other embodiments of the invention.
`
`It is to be noted that an intersection point 27 of a center
`line 25 of the sealing resin layer 11, which extends in the
`horizontal direction (perpendicular to the lead frame major
`planar surface, and referred to as an X-axis direction and a
`
`10
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`35
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`8
`center line 26 in the vertical direction (parallel to the plane
`of the lead frame major planar surface, and referred to as a
`Y-axis direction) is coincident with a center 28 of the lead
`frame 20. However, as noted earlier, the center 27 of the
`sealing resin layer 11 is displaced from the center 28 of the
`lead frame 20 by an offset 29 (FIG. 12A). Specifically, in the
`cross section of FIG. 1B, which is parallel to the light-
`emitting end face of the laser diode element 1 on which the
`end-face destruction preventing layer 10 is formed, the Y
`axis 26 defining the vertical direction and the X axis 25
`defining the horizontal direction, respectively, are coincident
`with the horizontal and vertical center lines of the sealing
`resin layer. Thus,
`the sealing resin layer 11 is formed
`symmetrically with respect to the X axis 25 and the Y axis
`26. Therefore, the thickness of the sealing resin layer 11
`around the lead frame 20 is uniform, i.e., the resin sealing
`layer is symmetrical abovethe lead frame. Consequently,the
`distribution of thermal stresses or forces on the lead frame
`20, which are caused by heat generated by the laser beam
`emission, are balanced and generally cancelled out. Accord-
`ingly, displacement of the lead frame 20 may be limited by
`the shapes of the lead frame 20, the photo diode 23 and the
`laser diode element 1. Therefore, displacement of the lead
`frames 20 can be markedly reduced as compared to con-
`ventional devices. Hence, displacementof the light emitting
`point of the laser diode element 1 mounte