Patent Application
20200046210
The present invention relates to an endoscope provided with an image pickup module including a plurality of joints, the image pickup module including the plurality of joints and a manufacturing method for the image pickup module including the plurality of joints.
An image pickup signal outputted by an image pickup device disposed at a distal end portion of an endoscope is subjected to primary processing by an electronic part mounted on a wiring board adjacent to the image pickup device.
Japanese Patent Application Laid-Open Publication No. 2005-334509 discloses an endoscope that transmits an image pickup signal subjected to primary processing by an electronic part mounted on a wiring board to which a lead of an image pickup device is soldered via a signal cable bonded to the wiring board. Heat-resistant sealing resin is used to prevent the soldered lead of the image pickup device from melting, causing the lead to come off and resulting in a connection failure due to heat produced when the signal cable is soldered to the wiring board.
Japanese Patent Application Laid-Open Publication No. 2013-30593 discloses a stacked device in which a plurality of semiconductor devices are stacked and through wirings of the respective semiconductor devices are bonded together in order to accommodate the plurality of semiconductor devices in a small space and reduce parasitic capacitance caused by wiring.
Compared to an image pickup module with an electronic part mounted on a wiring board, an image pickup module using a stacked device can achieve considerable miniaturization and high functionality.
An endoscope according to an embodiment includes an image pickup module, and the image pickup module includes a stacked device that is a rectangular parallelepiped including a light receiving surface, a rear surface on a back side of the light receiving surface and four side surfaces, a plurality of elements including an image pickup device being stacked, adjacent elements being electrically connected together by element joints, a rear surface electrode being arranged on the rear surface; a relay section provided with a first electrode electrically connected to the rear surface electrode of the stacked device by a relay joint and a second electrode electrically connected to the first electrode via a wiring pattern; and a signal cable electrically connected to the second electrode of the relay section by a cable joint, and in the stacked device, of a first region and a second region obtained by dividing the rear surface into two portions, the element joints are arranged only in a first space in which the first region is extended in an optical axis direction and the rear surface electrode is arranged only in the second region.
An image pickup module according to another embodiment includes a stacked device that is a rectangular parallelepiped including a light receiving surface, a rear surface on a back side of the light receiving surface and four side surfaces, a plurality of elements including an image pickup device being stacked, adjacent elements being electrically connected together by element joints, a rear surface electrode being arranged on the rear surface; a relay section provided with a first electrode electrically connected to the rear surface electrode of the stacked device by relay joints and a second electrode electrically connected to the first electrode via a wiring pattern; and a signal cable electrically connected to the second electrode of the relay section by a cable joint, and in the stacked device, of a first region and a second region obtained by dividing the rear surface into two portions, the element joints are arranged only in a first space in which the first region is extended in an optical axis direction and the rear surface electrode is arranged only in the second region.
A manufacturing method for an image pickup module according to a further embodiment includes creating a stacked device that is a rectangular parallelepiped including a light receiving surface, a rear surface on a back side of the light receiving surface and four side surfaces by electrically connecting the adjacent elements via element joints, in a state in which a plurality of elements including an image pickup device are stacked, a rear surface electrode being arranged on the rear surface; electrically connecting, at a second temperature, a signal cable to a second electrode of a relay section where a first electrode and the second electrode connected to the first electrode via a relay wiring pattern are arranged; and electrically connecting the first electrode of the relay section to the rear surface electrode of the stacked device at a third temperature lower than the second temperature.
As shown in
In the following description, note that drawings based on each embodiment are schematic ones and a relationship between thickness and width of each part, thickness ratios among the respective parts and relative angles or the like are different from actual ones, and there are also cases where dimensional relationships and ratios which differ among drawings are included. There may be cases where illustrations of some components and assignment of reference numerals are omitted.
The stacked device 10 is a rectangular parallelepiped having a light receiving surface 10SA, a rear surface 10SB on a back side of the light receiving surface 10SA and four side surfaces 10SS1 to 10SS4 (10SS).
A cover glass 12 is bonded, via a bonding layer 13, to a forefront of the stacked device 10 on which an image pickup device 11 and a plurality of semiconductor devices 21 to 24 are stacked. Note that the cover glass 12 is not any essential component of the image pickup module 1. Contrarily, a rectangular parallelepiped wafer level optical unit composed of a plurality of optical elements including the cover glass 12 may be arranged on the image pickup device 11.
The image pickup device 11 has a light-receiving section 11A composed of a CCD or CMOS image pickup section and the light-receiving section 11A is connected to a through wiring (TSV: through-silicon via) 11H. The image pickup device 11 can be either a front-side illumination type image sensor or a back-side illumination type image sensor.
The image pickup device 11 and the plurality of semiconductor devices 21 to 24 are stacked with sealing resin 25 to 28 being sandwiched therebetween to constitute the stacked device 10.
The semiconductor devices 21 to 24 primarily process an image pickup signal outputted by the image pickup device 11 or process a control signal for controlling the image pickup device 11. For example, the semiconductor devices 21 to 24 include an AD conversion circuit, a memory, a transmission output circuit, a filter circuit, a thin film capacitor and a thin film inductor or the like. The number of devices included in the stacked device 10 including the image pickup device 11 is, for example, 3 or more and 10 or less.
The image pickup device 11 and the plurality of semiconductor devices 21 to 24 include through wirings 11H, 21H to 24H respectively, and adjacent elements facing each other are electrically connected by an element joint B1.
In the image pickup module 1, the element joint B1 is a solder joint made of first solder, a melting point of which is MP1. The first solder is a solder bump using an electric plating method or a solder paste film using printing or the like.
A plurality of rear surface electrodes 20P are arranged on the rear surface 10SB (rear surface of the semiconductor device 24 stacked on the rearmost portion) of the stacked device 10. As shown in
An insulating layer 29, which is a cover layer, is arranged on the rear surface 10SB. The element wiring pattern 21L exposed to the bottom surface of an opening O20P1 of the insulating layer 29 may also be the rear surface electrode 20P.
The rear surface electrode 20P is electrically connected to a first electrode 30P1 of the wiring board 30, which is a relay section, via the relay joint B3. An alignment mark for positioning with the wiring board 30 may be formed on the rear surface 10SB of the stacked device 10.
As will be described later, the relay joint B3 is an ultrasonic joint. In other words, the relay joint B3 is an interface between the rear surface electrode 20P and the first electrode 30P1. The relay joint B3 may also be a thermal ultrasonic joint configured to apply heat as well as ultrasound.
In the image pickup module 1, in the stacked device 10, of a first region 10SB1 and a second region 10SB2 obtained by dividing the rear surface 10SB into two portions of the stacked device 10, the plurality of element joints B1 are arranged only in a first space S1 in which the first region 10SB1 is extended in the optical axis direction and the plurality of rear surface electrodes 20P are arranged only in the second region 10SB2.
In other words, the plurality of element joints B1 are lined up only below the elements 11, 21 to 24, whereas the plurality of rear surface electrodes 20P are lined up only above the opposite side of the arrangement position of the element joints B1. The element joints B1 and the rear surface electrodes 20P are arranged at positions apart from one another.
In the wiring board 30, the first electrode 30P1 is arranged on the front and a second electrode 30P2 connected to the first electrode 30P1 via a relay wiring pattern 31 is arranged in the rear. Note that an electronic part such as a chip capacitor may be mounted on the wiring board 30. The wiring board 30 is a one-side wiring board, and so is inexpensive, but a both-side wiring board or a multilayered wiring board may also be used.
The wiring board 30 is a flexible wiring board based on polyimide or the like, the frontal part of which is arranged parallel to the rear surface 10SB of the stacked device 10, but the rear part of which is inclined with respect to the rear surface 10SB because of the presence of a bent part.
The second electrode 30P2 of the wiring board 30 is electrically connected to the signal cables 40 via cable joints B2. The cable joints B2 are solder joints made of second solder.
Each of the signal cables 40 is a shielded cable including a core wire 41 and a shielded wire 42. A plurality of core wires 41 are bonded to the respective second electrodes 30P2 and the plurality of shielded wires 42 are bonded to a third electrode 30P3, which is one common grounding potential electrode.
In the image pickup module 1, the signal cables 40 are not directly soldered to the stacked device 10. In other words, the signal cables 40 are soldered to the wiring board 30, which is a relay section, and the wiring board 30 is bonded to the stacked device 10. Even for the stacked device 10 having the narrow rear surface 10SB, constraints on the number and the outer diameter of signal cables 40 and connection difficulties are alleviated.
Furthermore, in the stacked device 10, the rear surface electrodes 20P of the relay joint B3 are arranged at positions apart from the element joints B1. For this reason, the load, vibration and heat applied when the first electrode 30P1 is ultrasound-bonded to the rear surface electrodes 20P are not directly transmitted to the element joints B1. In this way, the image pickup module 1 exhibits high reliability without the risk of damaging the stacked device 10 during ultrasonic bonding.
Note that the insulating layer 29 does not cover the whole surface of element wiring pattern 21L, and there is opening O20P2 in the insulating layer 29 above part of the element wiring pattern 21L. The opening O20P2 is for an inspection terminal 20P2, the element wiring pattern 21L of which is exposed to the bottom surface. The stacked device 10 is manufactured by cutting a stacked wafer as will be described later. The inspection terminal 20P2 is used to grasp characteristics of the stacked device 10 in a state of the stacked wafer.
In an inspection using a prober, the surface contacted by a prober needle may be damaged. Then, scratches may have an adverse influence during bonding, and reliability of the image pickup module may be lowered. The image pickup module 1 with the inspection terminal 20P2 in the same connection state as the rear surface electrode 20P does not damage the rear surface electrode 20P even after the inspection, and so the reliability never deteriorates.
As shown in
Thus, the stacked device 10 and the wiring board 30 can be easily bonded via the relay joints B3 in the image pickup module 1. Since the element joints B1 can define the arrangement interval (inter-electrode pitch) with photolithography accuracy in the semiconductor manufacturing step, it is possible to easily achieve narrow pitch and secure a wide circuit region in the element by reducing the inter-electrode pitch. On the other hand, since the wiring board 30, which is the relay section, is formed, for example, in a printed circuit board manufacturing step, the accuracy of inter-electrode pitch of the relay joints B3 is inferior to the accuracy of inter-electrode pitch of the element joints B1. Therefore, when the relay joints B3 are arranged with the same inter-electrode pitch as the inter-electrode pitch of the element joints B1, strict positioning accuracy is required, and so there is a high difficulty in bonding. By widening the inter-electrode pitch of the relay joints B3, it is possible to relax requirements for the positioning accuracy of the wiring board 30 and facilitate bonding.
Note that even if the element joints B1 are not solder joints, but are, for example, hybrid bonding joints in which an insulating film and a conductive film formed on the same surface are directly bonded together, the load and vibration applied when the first electrode 30P1 is ultrasonically bonded are never directly transmitted to the element joints B1, and so there is no risk of damaging the stacked device 10.
Note that the relay section is not limited to the flexible wiring board 30, but the relay section may be a MID solid wiring board, a Si interposer, a TAB tape with a flying lead, a ceramic wiring board or a glass wiring board or a combination of those elements.
In the image pickup module 1, a dimension (external dimension) of the image pickup device 11 orthogonal to the optical axis O is a 1 mm or less square, for example, 600 μm×600 μm. External dimensions of the wiring board 30 and the stacked device 10 are designed to be equal to or less than the external dimension of the image pickup device 11. In other words, the wiring board 30 is accommodated within the second space S2 in which the image pickup device 11 is extended in the optical axis direction. The image pickup module 1 is an ultra-small image pickup module specialized for an endoscope.
A manufacturing method for an image pickup module will be described briefly according to a flowchart in
An image pickup device wafer including the image pickup device 11 and a plurality of semiconductor device wafers each including the semiconductor devices 21 to 24 are manufactured.
For example, regarding the image pickup device wafer, a plurality of light-receiving sections 11A or the like are arranged on a silicon wafer or the like using a publicly known semiconductor manufacturing technique. A peripheral circuit configured to primarily process an output signal of the light-receiving section 11A or process a drive control signal may be formed on the image pickup device wafer. A cover glass wafer for protecting the light-receiving section 11A is preferably bonded to the image pickup device wafer before forming the through wiring 11H from the rear surface.
The image pickup device wafer to which the cover glass wafer is bonded via the bonding layer 13 and the plurality of semiconductor device wafers each including the semiconductor devices 21 to 24 are stacked, thermally treated at a first temperature T1 which is equal to or higher than the melting point MP1 of the first solder of the element bonding B1 to manufacture a stacked wafer in which the semiconductor devices 21 to 24 are electrically connected. The melting point MP1 and the first temperature T1 are less than the heat-resisting temperature of the semiconductor devices 21 to 24, for example, 200° C. to 250° C.
The sealing resin 25 to 28 may be injected from a side surface of the stacked wafer after bonding or arranged during lamination.
The stacked wafer is cut so that the four sides of the substantially rectangular light-receiving section 11A of the image pickup device 11 are parallel to the four sides of the rectangular cross section orthogonal to the optical axis O of the stacked device respectively, and divided into individual rectangular parallelepiped stacked devices 10. Therefore, the four side surfaces 10SS of the stacked device 10 are cut surfaces. Note that corners parallel to the optical axis O may be chamfered after cutting the stacked device 10, the cross section in the direction orthogonal to the optical axis may be made hexagonal or the corners may be made curved surfaces.
In other words, the stacked device 10 is a perfect rectangular parallelepiped, but the “rectangular parallelepiped” in the present invention also includes a substantially rectangular parallelepiped, corners of which are chamfered or a surface of which is curved.
The wiring board 30, which is the relay section, where the first electrode 30P1 and the second electrode 30P2 connected to the first electrode 30P1 via the relay wiring pattern 31 are arranged and the signal cables 40 are manufactured.
The core wire 41 of the signal cable 40 is electrically connected to the second electrode 30P2 of the wiring board 30 via the cable joint B2 made of second solder. A second temperature T2 in the present second bonding step is higher than a melting point MP2 of the second solder. For example, when the melting point MP2 is 140° C. to 190° C., the second temperature T2 is 150° C. to 200° C.
Note that the first bonding step may be performed after cutting the element wafer into elements.
The first electrode 30P1 of the wiring board 30, which is the relay section, is electrically connected to the rear surface electrode 20P of the stacked device 10. As has already been described, since this bonding step (second bonding step) is a relatively low temperature ultrasonic bonding step, the step temperature (third temperature T3) is, for example, less than 150° C. and is lower than the first temperature T1 and the second temperature T2.
In other words, in the image pickup module having a plurality of joints, the processing temperature of the bonding processing, which is performed later, is lower than the processing temperature of the bonding processing, which is performed before. In other words, the third temperature T3 is lower than the second temperature T2, and further the second temperature T2 is lower than the first temperature T1.
Therefore, in the third bonding step, there is no risk of the element joints B1 and the cable joints B2 having poor contact.
According to the manufacturing method of the above-described order, the connection operation in step S13 (cable bonding step) is performed on the wiring board 30 with high handling performance to which the stacked device 10 is not bonded. Moreover, this is particularly preferable since the element joints B1 are never affected during cable bonding.
However, step S14 (stacked device bonding step) may be performed before step S13 (cable bonding step).
In this case, the second solder having the melting point MP2 lower than the melting point MP1 of the first solder is used for the cable joints B2. In other words, when the signal cables 40 are bonded to the wiring board 30 (with relay joints B3) to which the stacked device 10 is bonded, the melting point MP2 of the second solder of the cable joints B2 is lower than the melting point MP1 of the first solder of the element joints B1. For this reason, the temperature in the step of bonding the signal cables 40 can be set to be lower than the melting point MP1. Therefore, reliability of the element joints B1 never deteriorates. Note that the melting point MP2 is preferably lower than the melting point MP1 by 10° C. or more and particularly preferably 20° C. or more.
Relay joints B3 of an image pickup module 1A according to modification 1 shown in
A melting point MP3 of the third solder is lower than the melting point MP1 of the first solder and the melting point MP2 of the second solder. Furthermore, in the stacked device 10, the rear surface electrodes 20P of the relay joints B3 are arranged at positions away from the element joints B1. For this reason, the heat applied when the first electrode 30P1 is soldered to the rear surface electrode 20P is never directly transmitted to the element joints B1. For this reason, the image pickup module 1 provides high reliability without the risk of damaging the stacked device 10 during solder bonding.
For this reason, the third temperature T3 in the third bonding step by the relay joints B3 can be set to be lower than the melting point MP1 and the melting point MP2. For this reason, the reliability of the element joints B1 and the cable joints B2 never deteriorates.
In other words, in the case of the image pickup module having a plurality of solder joints, a material having a melting point lower than the melting point of the solder subjected to the bonding processing before is used as the solder for the joints to be subjected to bonding processing later.
In an image pickup module 1B of the present modification, relay joints B3 correspond to the solder joints as in the case of the image pickup module 1A. As shown in
Since the image pickup module 1B is an ultra-small module, the relay joints B3 are extremely small, for example, 20 μm to 50 μm. Furthermore, an arrangement interval of the plurality of relay joints B3 is extremely narrow, for example, 50 μm to 200 μm.
In the image pickup module 1B, the third solder of the relay joints B3 is melted and bonded by laser heating. Laser heating allows local heating of only a micro region. This prevents other surrounding relay joints B3 from being adversely affected.
Furthermore, since heat is applied to the electrode 30P1 via the heat transfer terminal 36 and the through conductor 35, bonding can be performed more efficiently than heat transfer via the substrate (resin) of the wiring board 30.
An image pickup module 1C of the present modification is similar to the image pickup module 1B and has the same effects.
As shown in
The region where the heat transfer terminal 36 is arranged is an unnecessary region after the relay joints B3 is bonded. For this reason, as shown in
Since the heat transfer terminal 36 is on the upper side, the wiring board 30C can be easily irradiated with laser. Furthermore, since no heat transfer terminal 36 is present in the opposite region of the first electrode 30P1, the wiring board 30C has a high degree of freedom of the design, and allows, for example, an electronic part to be mounted in the opposite region.
As shown in
The insertion portion 90 is constructed of a distal end portion 90A where the image pickup module 1 or 1A to 1C (hereinafter referred to as an “image pickup module 1” or the like) are arranged, a bending portion 90B which is continuously provided on the proximal end side of the distal end portion 90A and which is freely bendable, and a flexible portion 90C which is continuously provided on the proximal end side of the bending portion 90B. The bending portion 90B is curved through operation of the operation portion 91. Note that the endoscope 9 may be a rigid endoscope or also a capsule type endoscope.
The operation portion 91 provided with various buttons to operate the endoscope 9 is provided on the proximal end side of the insertion portion 90 of the endoscope 9.
The light source apparatus 81 has, for example, a white color LED. Illumination light emitted from the light source apparatus 81 is guided to the distal end portion 90A via the universal cord 92 and a light guide (not shown) that is inserted through the insertion portion 90 to illuminate the subject.
The endoscope 9 includes the insertion portion 90, the operation portion 91 and the universal cord 92, and transmits an image pickup signal outputted from the image pickup module 1 or the like arranged at the distal end portion 90A of the insertion portion 90 using the signal cable 40 that is inserted through the insertion portion 90.
Since the image pickup module 1 or the like is an ultra-small module, the distal end portion 90A of the insertion portion 90 of the endoscope 9 has a small diameter and is minimally invasive. In the image pickup module 1 or the like, since an image pickup signal outputted from the image pickup device is primarily processed by the stacked device 10 disposed nearest to the image pickup device, the endoscope 9 displays images of high quality. Furthermore, in the image pickup module 1 or the like, solder does not re-melt during manufacturing, and so the endoscope 9 provides high reliability.
The present invention is not limited to the aforementioned embodiments or the like, but can be changed or modified in various ways without departing from the spirit and scope of the present invention.
This application is a continuation application of PCT/JP2017/015662 filed on Apr. 19, 2017, the entire contents of which are incorporated herein by this reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2017/015662 | Apr 2017 | US |
| Child | 16656648 | US |
