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`U3005503016A
`
`1111
`
`145]
`
`Patent Number:
`
`Date of Patent:
`
`5,503,016
`
`Apr. 2, 1996
`
`2720484A1
`60-12750
`63—90774
`“1091111722
`
`1111977
`111985
`411988
`811991
`
`Germany .
`Japan .
`Japan.
`WIPO.
`
`OTHER PUBLICATIONS
`
`“NEC‘s Automative Electronic Condo} Modules", NEC.
`sales brochure, date unknown.
`“Airbags Boom When 1C Accelerometer Sees 50 G", by
`Frank Goodenough, Eiecrmnfc Design. Aug. 8, 1991.
`
`Pfimry Examiner—Heer E. Williams
`Assistant Examiner—Christine K. Oda
`Artemis}; Agent. or Finn—Skjerven, Merrill, MscPherson,
`Frankiin and Fricl; Norman R. Klivans
`
`[5'1]
`
`ABSTRACT
`
`Micro-machined accelerometer chips have a sensitive axis
`perpendicular to the principle surface of the device. In an
`application where the desired sensing direction is in the
`plane of a supporting printed circuit board, the accelerom-
`eter cannot be mounted directly on the printed circuit board
`and instead is mounted on a wait perpendicular to the printed
`circuit board. This requirement to wall-mount the sensor is
`eliminated by using an accelerometer chip packaged with a
`signal conditioning circuit in a multi layer ceramic chip
`carrier. Eiectricai connections are contained within the lay-
`ers of the ceramic and terminate at a side surface of the chip
`carrier. Thus the accelerometer chip sits perpcndicular to the
`printed circuit board and the ceramic chip carrier is attached
`directly thereto.
`
`United States Patent
`Koen
`
`[191
`
`[54] VERTICALLY MOUNTED
`ACCELEROMETER CHIP
`
`['15]
`
`Inventor: Edward F. Keen, Danvilie, Calif.
`
`[73] Assignee:
`
`IC Sensors, Inc., Milpitas, Calif.
`
`[21] Appl. No: 189,948
`
`[22] Filed:
`
`Feb. 1, 1994
`
`
`
`GOIP 1102
`Int. (31.6
`[51]
`731493
`[52] U.S. Cl.
`731493, 431. 777.
`[58] Field of Search
`731756, 8155.5. 204.22, 856; 1141260
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`1011987 Gademann ........
`4,100,973
`311991 Silvermint
`5,012,316
`.
`811991 Stokes et al.
`5,043,791
`.
`911991 Palace et a1.
`5,044,201
`..
`5,060,504 1011991 White etsl.
`5,109,341
`411992 Blackburn etal.
`5,163,325
`1111992 White et a].
`..
`5,221,400
`611993 Staller ct a1.
`.
`5,233,871
`811993 Schwarz eta].
`5,233,873
`811993 Mozgowiec
`5,233,874
`811993 Putty et al.
`5,241,861.
`911993 Hui-sing, 1]
`5,249,465 1011993 Bennett eta].
`5,261,694
`1111993 White et a1.
`..
`5,269,181?
`1211993 Hanson .
`5,394,326
`211995 Liu
`
`
`
`.
`
`35'11'10
`7315113
`“1311 D
`. 11301274
`731517 R
`1561292
`131493
`731493
`. 731517 AV
`731505
`731510
`. 2801135
`131495
`641424.05
`
`FOREIGN PATENT DOCUMENTS
`
`05579171311
`
`911993 European Pat. Off. .
`
`18 Claims, 4 Drawing Sheets
`
`14
`
`44
`
`
`
`—_'fl!/l-
`
`
`. W§I€n 31113 ‘13.; n.
`b -
`
`‘1
`
`
`
`
`54
`
`641
`
`0001
`
`Apple Inc.
`APLl O3 9
`
`US. Patent No. 8,923,941
`
`FITBIT, Ex. 1039
`
`Apple Inc.
`APL1039
`U.S. Patent No. 8,923,941
`
`0001
`
`FITBIT, Ex. 1039
`
`

`

`US. Patent
`
`Apr. 2, 1996
`
`Sheet 1 of 4
`
`5,503,016
`
`40
`
`24b
`
`210 m
`
`34
`
`40
`
`FIG 1b
`.
`(prior An)
`
`faIg
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`g5z
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`6
`5
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`55f
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`ACCEL
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`36
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`38a
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`0002
`
`FITBIT, Ex. 1039
`
`

`

`US. Patent
`
`Apr. 2, 1996
`
`Sheet 2 of 4
`
`5,503,016
`
`14
`
`
`
`FIG. 26154
`
`
`
`
`\i?‘ 44
`
`
`
`
`16
`
`52
`
`14
`
`FIG. 2b
`
`FrTBrT.Ex.1039
`
`0003
`
`FITBIT, Ex. 1039
`
`

`

`US. Patent
`
`Apr. 2, 1996
`
`Sheet 3 of 4
`
`5,503,016
`
`44
`
`g»
`
`‘\.‘\\“-‘L
`
`88
`
`66b
`
`FIG. 2c
`
`a6n0
`
`§“REEBRRERSRACE
`
`663
`
`AXIS OF
`ACCEL
`
`FIG. 2d
`
`0004
`
`FITBIT, EX. 1039
`
`0004
`
`FITBIT, Ex. 1039
`
`
`
`
`

`

`US. Patent
`
`Apr. 2, 1996
`
`Sheet 4 of 4
`
`5,503,016
`
`
`
`FIG. 3
`
`FITBIT, EX. 1039
`
`0005
`
`FITBIT, Ex. 1039
`
`

`

`5,503,016
`
`1
`VERTICALLY MOUNTED
`ACCELEROMETER CHIP
`
`BACKGROUND OF THE MENTION
`
`1. Field of the Invention
`
`This disclosure relates to sensing variations in velocity
`such as in a motor vehicle, and more particularly to a method
`and structure for mounting an accelerometer on a support.
`2. Description of the Prior Art
`Micro—machined chip accelerometers are well known in
`the art. Examples are disclosed in 11.8. Pat. No. 5,060,504
`issued Oct. 29, 1991 to White, et 31., US. Pat. No. 5,221,400
`issued Jun. 22, 1993 to Staller, and U.S. Pat. No. 5,233,874
`issued Aug. 10, 1993 to Potty et al. As is well known, an
`accelerometer is a device which measures acceleration. or
`more accurately measures force exerted by a body as a result
`of a change in the velocity of the body. A moving body
`possesses an inertia which tends to resist the change in
`velocity. It is this resistance to any change in velocity that is
`the source of the force exerted by the moving body. This
`force is directly proportional to the acceleration component
`in the direction of movement when the moving body is
`accelerated.
`
`10
`
`15
`
`20
`
`In a typical micro-machined accelerometer formed of 7—5
`silicon (a "chip"), a central, typically spherical or rectangu-
`lar shaped mass is suspended by one or more microbridges.
`The bridges are attached to a supporting substrate which
`circumscribes the mass, with a gap provided therebetween.
`The mass is supported within and has free movement
`relative to the supporting substrate. The individual micro-
`bridges witbin e.g. each pair of micro-bridges are positioned
`at opposing edges of the mass such that the pair’s longitu-
`dinal axis constitutes a common axis across the surface of
`the mass.
`
`30
`
`35
`
`2
`The accelerometer chip 14 is electrically connected to the
`ASIC chip to by conductors 18 carrying electrical signals
`between the two chips 14, 16. The metal can 12 is sealed by
`a lid (not shown), while the accelerometer chip l4 and ASIC
`chip 16 are held on a ceramic substrate 20 fixed inside can
`12. Also provided are screws 24a, 24b (and corresponding
`holes not shown} for securing can 12 to a mounting bracket
`[described below].
`The electrical conductive leads which connect chips 14
`and 16 to the remainder of the system (the actual connection
`is not shown for simplicity here) terminate in this case at
`conventional edge clip terminations (pins) 28a, 28b, etc.
`These electrically connect to printed circuit board (PCB) 36
`held by standoifs 38a, 38b on the floor of metal housing 40.
`To better illustrate the structure of FIG. 1A, a side view
`along line A—A of FIG. 1a is shown in FIG. lb. The lid
`which seals [by a weld) can 12 (entitled from FIG. la) is
`designated by reference number 26. FIG. lb also illustrates
`the support structure for the can 12, which is mounted on a
`metal base plate 28 with glass to metal seals. Base plate 28
`in turn is attached by screws 24a, 24b to a mounting bracket
`34. Mounting bracket 34 is a robust structure formed for
`instance of metal, plastic or ceramic. The purpose of mount-
`ing bracket 34 is to properly mount can 12 in a vertical
`orientation on the sidewall of housing 4|). Bracket 34 is held
`onto the sidewall by screws, rivets, or other means (not
`shown). The direction of acceleraan is as shown by the
`arrow labelled “AXIS ofACCEL". Thus the sole purpose of
`base plate 23 and mounting bracket 34 is to vertically mount
`can 12 so that it is perpendicular to PCB 36. Typically in a
`vehicle, PCB 36 is thereby installed in a plane parallel to that
`of the surface of the earth.
`
`. , 283)
`.
`As shown, lead 28a [and the other leads 285, .
`extend from behind metal can 12 (detail not show for
`simplicity) to connect to electrical connectors on PCB 36.
`PCB 3-6 pmvides the connections to the actual air bag firing
`device, typically housed in the steering wheel, whereas the
`housing 40 is typically mounted under the dash board or on
`the floor board of the vehicle. The structure of FIGS. 1a and
`lb functions satisfactorily. However it has the major disad—
`vantages of being relatively bulky and expensive due to the
`rather elaborate mounting structure required to rigidly
`mount
`the accelerometer chip in the desired orientation
`relative to 1) its axis of sensitivity; and 2) the horizontally
`mounted PCB 36. Also,
`the relative complexity of the
`mechanical structure and leads 28 cause reliability prob-
`lems.
`
`Analog Devices has disclosed (Electronic Design, Aug. 8,
`1991, “Airbags Boom When 1C Accelerometer Sees 50G"
`see FIG. 5) a Huerta-machined accelerometer chip whose
`mass moves in the plane of the chip. This chip allows the
`axis of sensitivity to be parallel to the expected acceleration
`phenomenon. However, this is a special accelerometer chip
`apparently available only from this single supplier.
`Thus it would be highly desirable to reduce the cost and
`increase reliability of mounting accelerometer chips in an
`automobile, other vehicle, or other application without the
`need for an expensive and bulky mounting smicture. and
`using a standard accelerometer chip.
`
`40
`
`45
`
`55
`
`The movement of the mass is measured, for instance, by
`measuring a corresponding change in the output of a Wheat-
`stone bridge incorporating beam pierce-resistors formed in
`the micro—bridges.
`Typically such micro-machined silicon chip accelerom-
`eters require external circuitry to process the signal output
`by the accelerometer, for instance for triggering an autumn
`bile air bag deployment system. Such accelerometers hence
`are commonly used in automobiles and other vehicles.
`Accelerometers are constrained in that typically a micro-
`manhined accelerometer as described above has a single axis
`sensitive to acceleration. That is, it can only measure accel-
`eration along a line perpendicular to a plane defined by the
`principal surface of the chip. The principal surface of the
`chip is in the plane of the chips, from which side during
`fabrication various fabrication steps (masking, etching, etc.)
`are performed. For an automobile airbag system the direc~
`tion of acceleration which must be sensed in the event of a
`collision is typically along a line lying in a horizontal plane
`(parallel to the mound).
`Atypical prior art structure for mounting such a micro-
`machined accelerometer chip is shown in a front view in
`FIG. In. Here a conventional metal “can” chip package 12
`defines a central recess 10 in which are conventionally
`mounted the actual accelerometer chip 14 and the associated
`electronic circuitry, here present in ASIC circuit 16. ASIC
`moans Applications Specific Integrated Circuit which is
`typically used, but other types of integrated circuit will also
`perform this function. It is to be understood that in some
`such accelerometers, this circuitry is integrated on the accel-
`erometer chip itself.
`
`SUMMARY OF THE lNVENTlON
`
`65
`
`In accordance with the invention, an accelerometer chip
`whose sensing direction is conventionally perpendicular to
`the plane (principal surface) of the chip is housed in a chip
`carrier and mounted directly on the printed circuit board,
`
`0006
`
`FITBIT, EX. 1039
`
`0006
`
`FITBIT, Ex. 1039
`
`

`

`5,503,016
`
`3
`edge—wise. That is, a side surface of the chip carrier (pack-
`age} is mounted directly on the surface of the PCB.
`The conventional micromachined silicon accelerometer
`chip. packaged with signal conditioning circuitry (cg, an
`ASIC) in e.g. a mold-layer ceramic chip carrier, may he
`hermetically sealed with an 6.3. Kovar lid. Electrical con-
`nections are contained within the layers of the ceramic chip-
`carrier and terminated at
`the bottom (actually the side
`surface) of the chip carrier.
`The flexibility of types of terminations from the ceramic
`chip package olfer a variety of mounting schemes to the
`supporting PCB, such as leadlcss surface mount, or formed
`metal leads such as J-formed leads, S-formed leads, gull
`wings, side brazed with standofl' leads, and others.
`Alternatively,
`the accelerometer chip is packaged in a
`plastic SIP (single in—line package) chip package mounted
`on a lead frame, with the side of the package being mounted
`to the PCB and the leads connecting to the PCB.
`Thus in accordance with the invention a low cost. oom-
`pact, and highly reliable mounting is provided for an aceel-
`erometer chip.
`
`BRIEF DESCRIPTION OF THE. DRAWINGS
`
`FIGS. la and FIG. lb show respectively front and side
`views of a prior art accelerometer mounting structure.
`FIGS. 2a, 2b, 2c and M Show respectively a front view,
`a cross sectional view, a side surface view (when mounted),
`and a second side view of a mounting structure for an
`accelerometer chip in accordance with the invention.
`FIG. 3 shows a cross sectional view of a plastic chip
`carrier for an accelerometer chip in accordance with the
`invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`FIG. 2a shows a front view of aaccelerometer chip 14 and
`a signal conditioning (eg. an ASIC) chip 115 housed in a
`multi-layer ceramic chip carrier 44 of the type well known
`in the art. Conventional accelerometer chip 14 and ASIC
`chip 16 are housed in a recess 54 which is stopped to
`accommodate the dificrent thicknesses of these two devices.
`In FIG. 24. the lid which would normally seal the chip
`carrier 44 is shown removed. Chip carrier 44 is mounted on
`a conventional PCB 42 by solder pads 64a, .
`.
`.
`, 64]" (only
`a ponion of which is shown in FIG. 2a) each of which is
`formed on the underside of chip carrier 44 and thus provide
`a mechanical and electrical attachment to corresponding
`metallized areas on the printed circuit board 42. The actual
`fillets of the two resulting solder bonds are designated by
`reference number 62a, 62b. PCB 42 is the PCB convention-
`ally present in vehicles, as described above, for mechani-
`cally supporting and electrically connecting to an acceler-
`ometer chip.
`PCB 42 is conventionally GIOIFR—4 material, but may be
`other materials as are well known in the art. In this view of
`FIG. 2a, the axis of acceleration is into or out of the page,
`and hence is not illustrated. The principal surface of chip 14
`is illustrated with the conventional protective cap installed.
`Accelerometer chip 14 is connected by wire bonds 52 to
`conductive traces 18 formed on the exposed surface of the
`ceramic chip carrier 44 and hence connects via wire bond 50
`(and others, not shown) to theASIC chip 16. (Accelerometer
`chip 14 also may have one or more electrical connections
`direct to the outside of chip package 44 via traces IS).
`
`10
`
`15
`
`25
`
`35
`
`4G
`
`45
`
`SD
`
`55
`
`60
`
`4
`Typically additional sets of such traces and wire bonds are
`present, but these are not shown here for simplicity. Alter-
`native bonding methods include TAB, flip chip, and others
`known in the art. Also shown are conductive traces 48 to the
`left ofASIC 16, which points through the multi-layers of
`chip carrier 44, and emerge at the side surface (here shown
`as a lower portion) of chip carrier 44 at solder pads 64a, . .
`. , 64].
`Both ASIC 16 and accelerometer chip 14 are housed in
`stepped recess 54 in chip carrier 44.
`A cross section through line 3—3 of FIG. 2a is shown in
`FIG. 25, showing the chip carrier 44, recess 54, chips 14 and
`16 and the Kovar cap 60 which seals the chip carrier package
`44. Kovar cap 60 has formed on its inner surface a conven-
`tional solder sealing ring of tin and gold which mates to
`corresponding ring 72 of layered, tungsten, nickel. and gold
`on chip package 44. Also shown are wire bonds 50, 52. The
`ASIC 16 is considerably thinner than the accelerometer chip
`14 and hence is housed in a shallower portion of stepped
`recess 54, so as to achieve coplanarity for easier wire
`bonding. (This detail is not critical.)
`FIG. 2c shows a "bottom" view of a chip carrier 44 Le.
`shows the side surface 68 of chip carrier44 in FIG. 20 which
`is in intimate contact with PCB 42 as shown in FIG. 2a. Here
`the PCB 42 is not shown for illustrative purposes. Mechani-
`cal mounting solder pads 66a, 66.!) on the side surface 63 of
`chip carrier 44 extend the length of each end of the side
`surface 68 to achieve firm mechanical mounting to the
`underlying PCB 42. Pads 66a. 66!; are optional. The elec—
`trical and mechanical contact solder pads 64a. 64f (and
`others not marked by reference numbers) are, as described
`above. in electrical contact with the accelerometer chip l4
`and the circuitry of ASIC 16.
`FIG. 25! shows a side view of chip carrier 44 with the cap
`60 in place and again showing the actual solder fillet 62a to
`solder pad 66a as in FIG. 2a. Dimensions 3, h node in FIGS.
`2d. 2d are in one embodiment respectively 0.5 inch, 0.125
`inch, and 0.29 inch. These dimensions are illustrative only,
`as are the materials described herein, and are not intended to
`be limiting.
`The accelerometer chip 14 used in accordance with the
`invention may he conventional (piers-electric, piezoresis-
`Live, capacitive) or of other types. The ASIC chip 16 of
`course is dispensed with if its functions are integrated on
`accelerometer chip 14. Advantageuusly the strucuire in
`accordance with the invention having its axis of sensitivity
`being parallel to the plane of the PCB reduces the overall
`size of the package, reduces the number of components,
`makes fabrication easier, and eliminates interconnections
`(electrical and mechanical) which are typically a source of
`failures. Thus reliability is increased while cost of materials
`and assembly is decreased over the prior art. As described
`above, the actual connections to the printed circuit board
`may be of various types in addition to the leadless surface
`mount type shown in FIGS. 2a and 2:1. For instance, formed
`metal leads of various types could be attached to pads 64a,
`.
`. . ,64fforcontact toPCB 42.
`In an alternate embodiment, accelerometer chip and sig-
`nal conditioning chip 115 are stacked up and connected in a
`flip—chip configuration, then held in chip carrier 44.
`Another embodiment shown in FIG. 3 in cross section in
`a side view has accelerometer chip 14 on suppon (die attach
`lead frame portion} 74 mounted in an SIP plastic chip carrier
`'76. The side surface of chip carrier 76 is then mounted to
`PCB 82. Conductor ’73 from chip 14 contacts lead 80 other
`leads and conductors (not shown) which connects to PCB
`
`0007
`
`FITBIT, EX. 1039
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`0007
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`FITBIT, Ex. 1039
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`

`

`5,503,016
`
`5
`82. Here lead 80 is part of the lead frame on which chip l4
`(and a signal conditioning chip, not shown, if needed) is
`mounted. Alternatively, the lead frame terminations (leads)
`are staggered for additional support (not shown).
`In accordance with the invention not only an accelerom—
`eter may be so mounted, but so may other force or other
`sensors (transducers) which have a single axis of sensitivity.
`This disclosure is illustrative and not limiting; further
`modifications will be apparent to one of ordinary skill in the
`art in light of this disclosure and are intended to fall within
`the scope of the appended claims.
`I claim:
`1. A transducer assembly comprising:
`a transducer chip having an axis of sensiLivity, the axis of
`sensitivity being perpendicularto a principal surface of
`the transducer chip;
`3 chip package housing the transducer chip; and
`a circuit board, wherein a side surface of the chip package
`is mounted directly to a surface of the circuit board, the
`side surface of the package being perpendicular to the
`principal surface of the transducer chip, so that the axis
`of sensitivity lies parallel to a plane defined by the
`surface of the circuit board.
`2. The assembly of claim 1. wherein the transducer chip
`is a micro-machined accelerometer.
`3. The assembly of claim 1 wherein the chip package is a
`multi—Iayer ceramic chip carrier defining an interior recess in
`which the transducer chip is fixed.
`4. The assembly of claim 1, further comprising a plurality
`of conductive elements connected to the transducer chip and
`extending through the chip package to a side surface thereof
`perpendicular to the principal surface of the transducer chip,
`the conductive elements connecting to contact pads on the
`circuit board.
`5. The assembly of claim 4. wherein the conductive
`elements each include a conductive pad formed on the side
`surface of the package.
`6. The assembly of claim 1, firrther comprising a plurality
`of attachment pads fomled on the side surface of the
`package, the attachment pads being bonded to the surface of
`the circuit board.
`7. The assembly of claim 3. further comprising a lid
`located over the recess and attached to the package.
`8. The assembly of claim 3, further comprising an inte—
`grated circuit mounted in the recess in the package. the
`integrated circuit being electrically cemented to the trans-
`ducer chip.
`9. The assembly of claim 1. wherein the chip package is
`a plastic lead frame package in which the transducer chip is
`alfixed.
`
`10
`
`15
`
`‘20
`
`30
`
`35
`
`45
`
`SD
`
`6
`10. A method of mounting a transducer on a circuit board.
`comprising the steps of:
`providing a transducer having an axis of sensitivity per-
`pendicular to a principal surface of the transducer;
`providing a package having conductive traces extending
`on a side surface of the package;
`fixing the transducer in the package. so that the axis of
`sensitivity lies parallel to a plane defined by the side
`surface of the package and the principal surface of the
`transducer is perpendicular to the side surface of the
`package; and
`mounting the package on a surface of the circuit board,
`the side surface of the package being in direct contact
`with the surface of the circuit board, and the conductive
`traces being in electrical contact with associated traces
`on the surface of the circuit board.
`11. A transducer assembly for mounting on acircuit hoard
`comprising:
`a transducer chip having an axis of sensitivity perpen-
`dicular to a principal surface thereof;
`a chip package in which the transducer chip is affixed. the
`chip package having a side surface lying in a plane
`parallel to the axis of sensitivity and being perpendicu—
`lar to the principal surface of the transducer chip; and
`a plurality of attachment points on the side surface of the
`chip package adapted to mounting the side surface
`directly to the circuit board.
`12. The assembly of claim 11, wherein the transducer chip
`is a micro-machined accelerometer.
`13. Tire assembly of claim 11, wherein the chip package
`is a mold-layer ceramic chip carrier defining an interior
`recess in which the transducer chip is fixed.
`14. The assembly of claim 11. further comprising a
`plurality of conductive elements contacting the transducer
`chip and extending through the chip package to the side
`surface thereof, the conductive elements adapted to contact-
`ing contact pads on the circuit board.
`15. The assembly of claim 14, wherein the conductive
`elements each include a conductive pad for-tried on the side
`surface of the chip package.
`16. The assembly of claim 13, further comprising a lid
`located over the recess and attached to the chip package.
`17. The assembly of claim 13, further comprising an
`integrated circuit mounted in the recess in the chip package,
`the integrated circuit being electrically connected to the
`transducer chip.
`18. The assembly of claim 11, wherein the chip package
`is a plastic lead frame package.
`assess
`
`0008
`
`FITBIT, EX. 1039
`
`0008
`
`FITBIT, Ex. 1039
`
`