JP6661290B2 - Ultrasonic probe - Google Patents

Description

  The present invention relates to an ultrasonic probe, and more particularly, to a bonding structure between an electronic circuit chip and a heat conductor disposed in the ultrasonic probe.

  2. Description of the Related Art Ultrasonic diagnostic apparatuses are used in the medical field. An ultrasonic diagnostic apparatus is an apparatus that transmits and receives an ultrasonic wave to and from a subject, and forms an ultrasonic image based on a reception signal obtained thereby. The transmission and reception of the ultrasonic waves are performed by an ultrasonic probe connected to the apparatus body by wire or wirelessly. Some ultrasonic probes are equipped with an electronic circuit chip for channel reduction (reducing the number of signal lines between the apparatus main body and the ultrasonic probe).

  When an ultrasonic probe on which an electronic circuit chip is mounted operates, a large amount of heat is generated in the electronic circuit chip. On the other hand, since the ultrasonic probe is to be brought into contact with the subject, there is a provision that the surface temperature of the portion in contact with the subject must not exceed a predetermined value. Therefore, a technique has been proposed in which heat generated in the electronic circuit chip is dissipated so as not to be transmitted as much as possible to the portion in contact with the subject.

  For example, Patent Literature 1 discloses a backing material formed of a substance having a high thermal conductivity so that heat generated in an electronic circuit chip is transferred to a rear side of the electronic circuit chip, that is, a direction away from a contact surface with a subject. A structure in which a (support block for attenuating acoustic energy) is disposed behind an electronic circuit chip is disclosed.

JP 2014-508022 A

  In order to dissipate the heat generated in the electronic circuit chip, it is preferable that a heat conductor made of a metal having a high thermal conductivity is brought into direct contact with the electronic circuit chip. In this way, more heat can be transferred (absorbed) from the electronic circuit chip to the heat conductor. Then, the heat absorbed by the heat conductor can be transferred in a direction away from the contact surface with the subject.

  On the other hand, an unpackaged chip, that is, a bare chip may be used as an electronic circuit chip in order to improve heat radiation performance or to reduce the size or weight of the ultrasonic probe. The bare chip is one in which the front surface (back surface) of a silicon substrate constituting an electronic circuit is exposed. Thereby, effective heat radiation can be performed from the back surface. As a result, the surface of the electronic circuit chip is conductive.

  When a bare chip is used as an electronic circuit chip, the surface of the electronic circuit chip is conductive, so that a heat conductor, which is a conductor, cannot be directly contacted with the electronic circuit chip. If a certain potential (eg, ground potential) is given to the heat conductor, it cannot be brought into contact naturally, and even if the potential of the heat conductor is uncertain, the heat conductor generally has a high heat absorption. In order to obtain a large volume, if a conductor with a large volume contacts a part of the electronic circuit, the performance of the circuit may be degraded due to fluctuations in the capacitance reactance of the circuit. The body cannot come into direct contact with the electronic circuit chip. On the other hand, since the heat conductor is for absorbing and transferring heat generated in the electronic circuit chip, it is necessary to ensure good thermal conductivity between the electronic circuit chip and the heat conductor.

  It is an object of the present invention to ensure sufficient thermal conductivity between an electronic circuit chip and a heat conductor in an ultrasonic probe while ensuring insulation between the two.

  An ultrasonic probe according to the present invention includes a plurality of vibration elements, and an electronic circuit that processes at least one of a plurality of transmission signals supplied to the plurality of vibration elements and a plurality of reception signals output from the plurality of vibration elements. An electronic circuit chip as a heat source having a chip surface that is at least partially conductive; a heat conductor having a facing surface facing the chip surface; and a heat conductor between the chip surface and the facing surface. And a composite function layer exhibiting a conduction function and an electrical insulation function.

  According to the above configuration, at least a part of the surface (chip surface) is conductive, that is, the heat conduction function and the electrical insulation are provided between the chip surface of the electronic circuit chip which is a bare chip and the facing surface of the heat conductor. A composite functional layer that exerts a function is provided. This makes it possible to preferably transfer the heat generated in the electronic circuit chip to the heat conductor while preventing an electrical short circuit between the chip surface and the opposing surface.

  The electrical insulation function is realized by the insulator included in the composite layer. The electrical insulation function is exhibited by preventing the contact between the chip surface and the opposing surface by the insulator or by preventing the chip surface and the opposing surface from approaching each other to such an extent that dielectric breakdown may occur.

  The heat conduction function is realized by making the composite function layer as thin as possible, that is, by bringing the chip surface and the opposing surface as close as possible. Alternatively, an insulating material having a high thermal conductivity may be included in the composite layer. Even in that case, it is preferable that the distance between the chip surface and the opposing surface be as small as possible. The distance between the chip surface and the opposing surface is preferably set to a minimum as long as electrical insulation between them is ensured (that is, no dielectric breakdown occurs between the chip surface and the opposing surface). The distance is determined in consideration of, for example, the dielectric strength of the insulator included in the composite function layer and the potential difference that can occur between the chip surface and the opposing surface. In addition, by the heat conduction function, at least the heat generated in the electronic circuit chip causes the temperature of the subject contact surface of the ultrasonic probe to rise from the electronic circuit chip to an extent that the temperature does not exceed a predetermined value (for example, a temperature determined by regulation). Any heat can be transferred to the heat conductor.

  Preferably, the composite function layer further exhibits an adhesive function of adhering the electronic circuit chip and the thermal conductor.

  When the composite function layer has an adhesive function, the heat conductor can be closely adhered to the electronic circuit chip via the composite function layer. Accordingly, the chip surface and the opposing surface do not unexpectedly separate from each other, so that the heat generated in the electronic circuit chip is more appropriately transferred to the heat conductor.

  Desirably, the composite functional layer further exhibits a shock absorbing function.

  Since the ultrasonic probe is a component that is moved by a human hand, it is susceptible to an impact due to hitting or pulling a cable. In particular, an electronic circuit chip that is a bare chip has lower impact resistance than a package chip. Therefore, it is preferable that the electronic circuit chip is protected from impact. Since the composite functional layer has a shock absorbing function, it is possible to reduce an impact (for example, an impact transmitted from a cable) transmitted to the electronic circuit chip from at least the rear of the ultrasonic probe (the direction opposite to the ultrasonic wave transmitting / receiving surface). it can.

  Preferably, in the composite function layer, the insulation performance of the electrical insulation function is kept constant by distance setting means for setting and maintaining a predetermined distance between the chip surface and the facing surface.

  As described above, from the viewpoint of maintaining high thermal conductivity from the electronic circuit chip to the heat conductor, the distance between the chip surface and the opposing surface is set to a minimum as long as electrical insulation is ensured. If the chip surface and the opposing surface are extremely close to each other, the distance between the chip surface and the opposing surface may be unexpectedly reduced, and an electric short circuit may occur. Therefore, by providing a distance setting means for keeping the distance between the chip surface and the opposing surface constant, the distance between them is kept constant, and the insulation performance of the composite functional layer is kept constant. Of course, by maintaining the distance between the chip surface and the opposing surface, the heat transfer performance of the composite functional layer is also kept constant.

  Preferably, the composite functional layer is a thin-film insulating film formed of an insulator, a first adhesive layer that bonds the insulating film to the electronic circuit, and bonds the insulating film to the thermal conductor. Including a second adhesive layer.

  According to this configuration, the insulating property between the chip surface and the opposing surface is ensured by the insulating film, the first adhesive layer, and the second adhesive layer. That is, the distance between the chip surface and the opposing surface is set to the minimum distance as long as electrical insulation is ensured by the insulating film, the first adhesive layer, and the second adhesive layer. Of course, it is preferable that an insulating adhesive is used for the first and second adhesive layers. Further, by providing a thin insulating film on the composite function layer, the thickness of the composite function layer (that is, the distance between the chip surface and the opposing surface) can be further reduced. Of course, the insulating film is preferably formed of a substance having a high withstand voltage. As a result, the thermal conductivity from the electronic circuit chip to the thermal conductor is kept high. The first and second adhesive layers exhibit an adhesive function.

  Preferably, an elastic modulus of the insulating film is smaller than elastic moduli of the first adhesive layer and the second adhesive layer.

  In order to make the first and second adhesive layers as thin as possible and exhibit high adhesive strength, a hardening type adhesive having a high elastic modulus (that is, hard) must be used in the first and second adhesive layers. May not be. In such a case, it is difficult for the first and second adhesive layers to exhibit a shock absorbing function. Therefore, by using a soft insulating film having a smaller elastic modulus than at least the first and second adhesive layers, the impact on the insulating film can be reduced. It can exhibit an absorption function.

  Preferably, the area of the opposing surface is larger than the area of the chip surface, and the insulating film is provided so as to cover the entire opposing surface.

  When the area of the opposing surface is larger than the area of the chip surface, there is a possibility that an electrical short circuit may occur between the side surface of the electronic circuit chip and the opposing surface due to dielectric breakdown. Since the entire opposing surface is covered with the insulating film, an electrical short circuit between the side surface of the electronic circuit chip and the opposing surface can be prevented.

  ADVANTAGE OF THE INVENTION According to this invention, sufficient thermal conductivity between an electronic circuit chip and a thermal conductor can be ensured in an ultrasonic probe, ensuring both.

It is an external appearance perspective view of the ultrasonic probe concerning this embodiment. FIG. 2 is an exploded perspective view of the ultrasonic probe according to the embodiment. FIG. 3 is an enlarged view of a transmission / reception unit. It is a perspective view which shows the structure of a rear side heat conductor. It is sectional drawing which shows the example of a composite layer. It is a figure which shows the modification of the composite layer shown in FIG.5 (b). It is a graph which shows the relationship between the thermal resistance of a composite layer, and the temperature rise value of an ultrasonic wave transmitting / receiving surface. FIG. 4 is a cross-sectional view when a composite layer is bonded to an ASIC where warpage has occurred. It is a figure showing an example of a polish amount of ASIC. It is a figure showing an example of a suitable polish direction. FIG. 4 is a cross-sectional view when the ASIC after polishing is bonded to a composite layer.

  Hereinafter, embodiments of the ultrasonic probe according to the present invention will be described. Note that the present invention is not limited to the following embodiments.

  FIG. 1 is an external perspective view of an ultrasonic probe 10 according to the present embodiment. The ultrasonic probe 10 has a shape elongated in the front-rear direction, and transmits and receives ultrasonic waves from an ultrasonic wave transmitting / receiving surface 12 provided at the forefront. That is, the ultrasonic wave transmitting / receiving surface 12 is a surface that comes into contact with the subject. The ultrasonic probe 10 has a front case 14 and a rear case 16 as outer skins for waterproofing or sterilization. The front case 14 and the rear case 16 are integrated by being combined. This constitutes a probe case. It is preferable that the front case 14 and the rear case 16 are made of a substance having high waterproofness, antibacterial property, and insulating property. In the present embodiment, the front case 14 and the rear case 16 are made of resin. A cable 18 connected to the ultrasonic diagnostic apparatus main body extends from the rearmost part of the ultrasonic probe 10. A cable protection boot 20 is provided to protect a joint between the cable 18 and the rear case 16. In the present specification, the short direction of the ultrasonic probe 10 is defined as an x-axis, the longitudinal direction is defined as a y-axis, and the direction orthogonal to the x-axis and the y-axis is defined as a z-axis. The side on which the ultrasonic wave transmitting / receiving surface 12 is provided (positive direction side of the y-axis) is referred to as “front side”, and the opposite direction (negative direction side of the y-axis) is referred to as “rear side”.

  FIG. 2 is an exploded perspective view of the ultrasonic probe 10. The ultrasonic probe 10 includes a wave transmitting / receiving unit 30 including a vibrator and an electronic circuit chip, a front heat conductor 32 for transmitting heat from the vibrator to the front case 14, and a heat for the rear case 16 inside the case. (FPC) 42, which is electrically connected to the electronic circuit chip via a relay board and serves as a path for signals from the ultrasonic diagnostic apparatus main body, and a wire 44 connected to the FPC 42 , And a connector 46 that relays the FPC 42 and the wire 44.

  FIG. 3 is an enlarged view of the transmission / reception unit 30. The transmitting / receiving unit 30 includes a plurality of vibrating elements, a vibrator array 50 for transmitting and receiving ultrasonic waves, electrically connects each vibrating element included in the vibrator array 50 to the ASIC 54, and electrically connects the FPC 42 and the ASIC 54 to each other. Relay substrate 52, ASIC 54 as an electronic circuit chip, backing material 56 for suppressing unnecessary vibration of vibrator array 50, matching of acoustic impedance between vibrator array 50 and subject and reflection of ultrasonic waves And an acoustic lens 60 for suppressing the noise. As shown in FIG. 3, in the transmitting / receiving unit 30, the acoustic lens 60, the acoustic matching layer 58, the vibrator array 50, the backing material 56, the relay board 52, and the ASIC 54 are arranged in this order from the front side.

  The relay board 52 is a board formed of a material such as glass epoxy. The relay board 52 is a multilayer board, and electrical wiring is provided in each layer. The area of the relay board 52 is larger than the area of the ASIC 54. On the back surface 52 a (rear surface), the ASIC 54 is mounted substantially at the center, and a chip component such as a capacitor or a thermistor is surface-mounted around the ASIC 54. I have. A plurality of pads for electrical contact with a plurality of lead wires (described later) provided on the backing material 56 are provided on the front surface (front surface) of the relay board 52.

  The ASIC 54 functions as a transmission sub-beamformer and a reception sub-beamformer. The transmission sub-beamformer generates a plurality of transmission signals having a delay relationship for each vibration element of the transducer array 50. The reception sub-beamformer performs a phasing addition process on a plurality of reception signals obtained from each of the vibration elements to generate a reception signal. The received signal is sent to the main body of the ultrasonic diagnostic apparatus via the FPC 42 or the wire 44, and is processed in the main body of the apparatus to generate one beam data. When the ASIC 54 performs the above-described processing, the number of signal lines between the ultrasonic probe 10 and the apparatus main body is reduced.

  The ASIC 54 is an unpackaged chip, that is, a bare chip, from the viewpoint of appropriately radiating the heat generated in the ASIC 54 or reducing the size and weight of the ultrasonic probe 10. Therefore, a part of the electronic circuit is exposed on the back surface 54a (rear surface), and a part or all of the back surface 54a is conductive. In this embodiment, a voltage of several tens of volts may be applied to the back surface 54a of the ASIC 54.

  The operation of the ultrasonic probe 10 generates heat in the ASIC 54. Although the vibrator array 50 also generates heat, the calorific value of the ASIC 54 is several times or tens of times greater than the calorific value of the vibrator array 50. Therefore, the main heat source in the ultrasonic probe 10 is the ASIC 54.

  The backing material 56 suppresses unnecessary vibration of each vibrating element included in the vibrator array 50. At the same time, in the present embodiment, since the backing material 56 is provided between the transducer array 50 and the relay board 52, the backing material 56 electrically connects each vibrating element and the relay board 52. And a plurality of lead wires. The backing material 56 has a relatively long front and rear shape. This makes it possible to more suitably suppress the vibration of each of the vibrating elements, and also has the effect of moving the ASIC 54, which is the main heat source, away from the ultrasonic wave transmitting / receiving surface 12 (see FIG. 1), which is the contact surface with the subject. .

  FIG. 4 is a diagram showing the structure of the rear heat conductor 34. The structure of the rear heat conductor 34 will be described with reference to FIG. The rear heat conductor 34 is disposed on the rear side of the wave transmitting / receiving unit 30, that is, on the rear side of the ASIC 54 that is a main heat source. As shown in FIG. 4, the rear heat conductor 34 includes a main frame 36, an upper frame 38, and a lower frame 40. The main frame 36, the upper frame 38, and the lower frame 40 have shapes that can be combined with each other, and the rear heat conductor 34 is configured by combining them. Specifically, the main frame 36 has a structure in which the upper and lower sides are released, and a plate-like upper frame 38 is combined so as to cover an upper release portion of the main frame 36, and a plate-like lower frame 40 is also formed. Are combined so as to cover the lower release portion of the main frame 36.

  In the present embodiment, a convex portion 74 and a concave portion 76 are provided at the rear of the main frame 36. At the rear of the upper frame 38, a concave portion 80 is provided at a position facing the convex portion 74, and a convex portion 78 is provided at a position facing the concave portion 76. The convex portion 74 and the concave portion 80 are fitted into the concave portion 76 and the convex portion 78, respectively. Further, projecting sides 82 are provided on both sides of the upper frame 38. A groove 84 is provided at a position facing the protruding side 82 of the main frame 36. The protruding side 82 and the groove 84 are fitted. With the above structure, the main frame 36 and the upper frame 38 are combined. The lower frame 40 is similarly combined with the main frame 36.

  The rear heat conductor 34 in which the main frame 36, the upper frame 38, and the lower frame 40 are combined has an elliptical xz cross section. Similarly, the xz cross section of the inner peripheral surface of the rear case 16 is also elliptical, and the outer peripheral surface of the rear heat conductor 34 just fits on the inner peripheral surface of the rear case 16. Thereby, the contact area between the rear heat conductor 34 and the rear case 16 is increased, and the heat transmitted to the rear heat conductor 34 can be more efficiently transmitted to the rear case 16. However, the xz cross-sectional profile of the rear heat conductor 34 does not necessarily have to be elliptical, and it is sufficient if at least a portion has an outer peripheral surface that contacts the inner peripheral surface of the rear case 16. Of course, since it is preferable that the contact area between the rear case 16 and the rear heat conductor 34 is large, the shape of the rear heat conductor 34 is a shape conforming to the inner peripheral surface of the rear case 16 as described above. Is preferred.

  The main frame 36 has a front surface 70 facing the rear surface 54 a of the ASIC 54. The area of the front side surface 70 is larger than the area of the back surface 54a of the ASIC 54. When the front side surface 70 comes into indirect contact with the ASIC 54 via a composite layer described later, the heat generated in the ASIC 54 is absorbed by the rear heat conductor 34 and transferred to the rear. This prevents heat from the ASIC 54 from being transmitted to the ultrasonic wave transmitting / receiving surface 12. The joint structure between the front side surface 70 and the back surface 54a will be described later in detail.

  The main frame 36 has a block 72 extending from the front side surface 70 to the rear side. By having the block 72, the rear-side heat conductor 34 has a solid structure rather than a tubular hollow structure, but rather has a solid content. As a result, the heat capacity is increased by increasing the volume of the rear heat conductor 34, thereby improving the heat absorption or heat conductivity of the rear heat conductor 34. In consideration of only the heat absorption coefficient and the heat transfer coefficient, it is preferable that the rear heat conductor 34 has a completely solid structure, and such a mode can be adopted. However, in the present embodiment, a certain amount of space (gap) is left in order to reduce the weight of the ultrasonic probe, or to accommodate the FPC 42, the wire 44, or the connector 46 in the rear heat conductor.

  As described above, in a state where the main frame 36 is combined with the upper frame 38 and the lower frame 40, between the block 72 and the upper frame 38, between the block 72 and the lower frame 40, and A gap is formed at a portion behind the rear end. The FPC 42, the connector 46, and the wire 44 are arranged in the gap. Accordingly, the FPC 42, the connector 46, and the wire 44 are also disposed inside the rear heat conductor 34, so that the contact between the rear heat conductor 34 and the rear case 16 by the FPC 42, the connector 46, and the wire 44 is achieved. Is not disturbed.

  The rear heat conductor 34 is preferably formed of a material having good heat conductivity. For example, it is formed of a metal such as copper, aluminum, or magnesium or an alloy thereof, or a carbon material. From the viewpoint of reducing the weight of the ultrasonic probe 10, in the present embodiment, aluminum having a relatively low specific gravity is used as the material of the rear heat conductor 34. As described above, the rear heat conductor 34 is made of metal or the like, and thus is conductive. In the present embodiment, the rear heat conductor 34 is connected to a ground sheath or the like included in the cable 18 and has a ground potential.

  Hereinafter, a composite layer that is provided between the ASIC 54 and the rear heat conductor 34 and that exhibits a heat conduction function, an electrical insulation function, and other functions will be described. As described above, the ASIC 54 is a bare chip, and part or all of the back surface 54a is conductive. Further, the rear heat conductor 34 is conductive. Therefore, the back surface 54a of the ASIC 54 and the front surface 70 of the rear heat conductor 34 cannot be brought into direct contact. Therefore, in the present embodiment, a composite layer is provided between the two.

  FIG. 5 shows four structures that can be used as composite layers. 5A to 5D, the upper side is the front side of the ultrasonic probe 10, the lower side is the rear side of the ultrasonic probe 10, the relay board 52, the ASIC 54, the composite layers 90a to 90d, and the rear side. An xy sectional view of the heat conductor 34 is shown.

  The composite layer 90a shown in FIG. 5A includes an adhesive 92 and a filler 94.

  As the adhesive 92, an insulating adhesive is used. Therefore, only by providing the adhesive 92 between the rear surface 54a of the ASIC 54 and the front surface 70 of the rear heat conductor 34, insulation between the rear surface 54a and the front surface 70 can be realized. However, if the thickness of the adhesive 92 is made very small in order to increase the thermal conductivity of the composite layer 90a (that is, transfer more heat generated in the ASIC 54 to the rear thermal conductor 34), locally, When the back surface 54a and the front side surface 70 come into contact with or approach each other to cause insulation breakdown, an electrical short circuit may occur between them.

  Therefore, in the composite layer 90a, a plurality of insulating and spherical fillers 94 are mixed with the adhesive 92. The diameter of the plurality of fillers 94 is determined in consideration of the dielectric strength of the filler 94 or the adhesive 92 and the potential difference that can occur between the back surface 54a and the front surface 70. That is, the distance between the back surface 54a and the front side surface 70 is set to be equal to the distance at which the dielectric breakdown does not occur. In the present embodiment, the diameter of the filler 94 is set to 40 μm. By mixing the plurality of fillers 94 into the adhesive 92, the distance between the back surface 54a and the front side surface 70 does not become smaller than the diameter of the filler 94, that is, the insulation between them is ensured, In addition, the distance becomes the minimum as long as the insulation is ensured, that is, the thermal conductivity of the composite layer 90a is maintained high.

  The filler 94 is formed of a member having insulating performance equivalent to that of the adhesive 92 and having a high (at least higher than that of the adhesive 92) thermal conductivity. For example, it is formed of aluminum nitride (aluminum nitride) or aluminum oxide (alumina). Thus, the heat generated in the ASIC 54 can be transferred to the rear heat conductor 34 via the filler 94 having good heat conductivity. That is, the filler 94 plays a role of ensuring the insulation between the back surface 54a and the front side surface 70 and improving the thermal conductivity of the composite layer 90a.

  Further, in the composite layer 90a, the adhesive 92 exerts an adhesive function for adhering and fixing the ASIC 54 and the rear heat conductor 34. Thereby, the positional relationship between the ASIC 54 and the rear heat conductor 34 is fixed, that is, the distance between the two does not exceed the diameter of the filler 94, and the suitable thermal conductivity is maintained.

  The composite layer 90b shown in FIG. 5B has a thin film 96, a front adhesive layer 98 for bonding the film 96 and the ASIC 54, and a bonding layer 98 for bonding the film 96 and the rear heat conductor 34. It is configured to include the rear adhesive layer 100.

  The film 96, the front adhesive layer 98, and the rear adhesive layer 100 are all formed of an insulating material. Since these insulating materials are sandwiched between the back surface 54a and the front side surface 70, insulation between them is ensured.

  The film 96 may be formed of, for example, polyimide (PI), polyethylene terephthalate (PET), or polyphenylene sulfide (PPS). These substances have a relatively high dielectric strength, and can secure the insulation between the back surface 54a and the front side surface 70 even when the film 96 is thinned to, for example, about 4 μm. Of course, the material of the film 96 is preferably a material having a high thermal conductivity.

  In the composite layer 90b, the front adhesive layer 98 and the rear adhesive layer 100 exhibit an adhesive function. Of course, the front adhesive layer 98 and the rear adhesive layer 100 are preferably as thin as possible as long as the adhesive function can be exhibited. The front adhesive layer 98 and the rear adhesive layer 100 are formed as thin as possible and use a hardening adhesive (for example, epoxy or the like) having a strong adhesive force in order to exhibit a reliable adhesive function.

  In this way, by using the film 96 that can ensure insulation even if it is extremely thin, the distance between the back surface 54a and the front surface 70 can be reduced to about several μm (that is, the thickness of the composite layer 90b is reduced to several μm). The thickness can be reduced to about μm). Thereby, the thermal conductivity of the composite layer 90b is kept high.

  The film 96 preferably has a relatively low elastic modulus and is formed of a relatively soft material. It is preferable to be formed of a material that is at least formed of a curable adhesive and has a relatively large elastic modulus (that is, hard) and is softer than the front adhesive layer 98 and the rear adhesive layer 100. Thus, the film 96 functions as a shock absorber between the ASIC 54 and the rear heat conductor 34.

  The ASIC 54 that is a bare chip has relatively low impact resistance because it is not packaged. Further, in the case of an ultrasonic probe, such as the ultrasonic probe 10, which is connected to the apparatus main body by the cable 18, the cable 18 is caught or pulled during use, so that the rear side of the ultrasonic probe 10 is May be shocked. Therefore, in the present embodiment, the film ASIC is formed of a relatively soft material and has a function as a shock absorbing material, thereby protecting the ASIC 54, which is a bare chip that is vulnerable to shock, from a shock from behind.

  In consideration of insulation properties and shock absorption properties, it is preferable that the film 96 be made of polyimide having excellent insulation properties, a relatively small elastic modulus, and a relatively soft polyimide.

  As shown in FIG. 5B, the area of the front side surface 70 is larger than the area of the ASIC 54, and the film 96 is provided so as to cover the entire front side surface 70. The rear adhesive layer 100 is also provided so as to cover the entire front side surface 70 so that the film 96 is adhered to the entire front side surface 70. This effect will be described with reference to FIG.

  FIG. 6A shows a composite layer 90e which is a modification of the composite layer 90b shown in FIG. 5B. In the composite layer 90e, the area of the xz plane of the film 96, the front adhesive layer 98, and the rear adhesive layer 100 is the same as the rear surface 54a of the ASIC 54. That is, the film 96 does not cover the entire front side surface 70, and the front side surface 70 has the exposed portion 70a.

  Since the insulating film 96 is also provided in the composite layer 90e, the composite layer 90e can exhibit a suitable insulating function and heat conduction function between the back surface 54a and the front side surface 70. Actually, the mode of the composite layer 90e can be adopted. However, since the thickness of the composite layer 90e is reduced to about several μm, as shown in FIG. 6A, the distance between the side surface 54b of the ASIC 54 and the exposed portion 70a of the front side surface 70 is considerably short. In this state, if a relatively large potential difference occurs between the side surface 54b and the exposed portion 70a, dielectric breakdown may occur and an electrical short circuit may occur between the two.

  In this regard, according to the composite layer 90b shown in FIG. 5B, since the entire front side surface 70 is covered with the film 96, there is no exposed portion 70a on the front side surface 70. There is no danger of an electrical short between them. The film 96 does not necessarily need to cover the entire front side surface 70, but may cover the front side surface 70 to some extent in the vicinity of the ASIC 54 so that dielectric breakdown does not occur between the side surface 54 b of the ASIC 54 and the front side surface 70. .

  As shown in FIG. 6B, in the bonding step between the ASIC 54 (wave transmitting / receiving unit 30) and the rear heat conductor 34 in the composite layer 90e, the front bonding layer 98 and the front bonding layer 98 are pressed together. It is conceivable that the rear adhesive layer 100 protrudes laterally from the side edge of the film 96, and the front adhesive layer 98 and the rear adhesive layer 100 are bonded on the side of the film 96. In such a case, the front adhesive layer 98 and the rear adhesive layer 100 formed of a curable adhesive such as epoxy are integrated with each other, and an impact from behind is transmitted to the ASIC 54 via the joint. . That is, the shock absorbing function of the film 96 cannot be suitably exhibited.

  Also in this regard, according to the composite layer 90b shown in FIG. 5B, since the film 96 covers the entire front side surface 70, even if the front adhesive layer 98 slightly protrudes from the side end of the ASIC 54, , It does not bond with the rear adhesive layer 100. That is, since the film 96 is always sandwiched between the front adhesive layer 98 and the rear adhesive layer 100, the composite layer 90b can suitably exert the shock absorbing function. In this respect, also from this viewpoint, the film 96 does not necessarily cover the entire front side surface 70, and the front side surface 70 is formed to some extent near the ASIC 54 to the extent that the protruding portion of the front adhesive layer 98 and the rear adhesive layer 100 are not bonded. You only need to cover it.

As described above, the thermal conductivity of the composite layer 90b is determined by the thickness of the composite layer 90b. FIG. 7 is a graph showing the relationship between the thermal resistance of the composite layer 90b and the temperature rise value of the ultrasonic wave transmitting / receiving surface 12. The thermal resistance is a value indicating the difficulty in transmitting the temperature. That is, if the thermal resistance of the composite layer 90b is large, the heat generated in the ASIC 54 is less likely to be transmitted to the composite layer 90b side, and the corresponding heat is transferred to the front side, that is, the ultrasonic transmitting / receiving surface 12, so that the ultrasonic transmitting / receiving surface 12 The temperature rise value increases. It is assumed that the rising temperature of the ultrasonic wave transmitting / receiving surface 12 needs to be suppressed to 10 ° C. or less due to various conditions (the amount of heat generated by the ASIC 54 and the amount of heat radiation in other structures) in the ultrasonic probe 10. In this case, from the graph shown in FIG. 7, it is necessary to set the thermal resistance of the composite layer 90b to 2 × 10 ⁻⁴ [K · m ² / W] or less. In the present embodiment, when the thickness of the composite layer 90b is about 40 μm, the thermal resistance of the composite layer 90b is about 2 × 10 ⁻⁴ [K · m ² / W], so the thickness of the composite layer 90b is 40 μm. It is set as follows.

  Of course, if the composite layer 90b is too thin, the insulating function and the shock absorbing function of the film 96 or the adhesive function of the front adhesive layer 98 and the rear adhesive layer 100 may not be sufficiently exhibited. There is naturally a lower limit to the thickness. That is, the thickness of the composite layer 90b is determined in consideration of thermal conductivity, insulation, shock absorption, and adhesiveness.

  In the present embodiment, in consideration of the thermal conductivity, insulation, shock absorption, and adhesiveness of the composite layer 90b, the possible range of the thickness of the composite layer 90b is 5 to 40 μm (in this case, the film is The thickness of the film 96 can take 4 to 35 μm), a desirable range is 7 to 20 μm (the thickness of the film 96 can take 4 to 15 μm at this time), preferably 8 to 10 μm (the thickness of the film 96 at this time is 4 μm). ).

  The composite layer 90c shown in FIG. 5C has an insulating oxide film 102 formed on the front surface 70 of the rear heat conductor 34 and an adhesive bonding the oxide film 102 and the back surface 54a of the ASIC 54. Agent 104 is included.

  The oxide film 102 is formed, for example, by alumite treatment when the rear heat conductor 34 is aluminum. Since alumite has high insulating properties, the oxide film 102 exhibits an insulating function. Further, since the thermal conductivity of the metal oxide is generally relatively high, the thermal conductivity of the composite layer 90c is kept high even if the oxide film 102 is provided. Of course, it is preferable that the thickness of the oxide film 102 be as thin as possible as long as the insulation is ensured.

  In the composite layer 90c, the adhesive 104 exerts an adhesive function for adhering and fixing the ASIC 54 and the rear heat conductor 34. Of course, the adhesive 104 is preferably as thin as possible from the viewpoint of thermal conductivity as long as the adhesive 104 can exhibit an adhesive function.

  The composite layer 90d shown in FIG. 5D includes a plurality of spacers 106 sandwiched between the ASIC 54 and the rear heat conductor 34, and an insulating adhesive 108.

  Since the plurality of spacers 106 are sandwiched between the ASIC 54 and the rear heat conductor 34, the distance between the back surface 54a of the ASIC 54 and the front side surface 70 of the rear heat conductor 34 becomes constant (spacer thickness). Will be kept. Thereby, insulation between the back surface 54a and the front side surface 70 is ensured. Of course, the spacer 106 is formed of an insulating material. The thickness of the spacer 106 is also determined in consideration of the dielectric strength of the spacer 106 or the adhesive 108 and the potential difference between the back surface 54a and the front surface 70.

  Further, the spacer 106 is formed of a material having high thermal conductivity. As a result, heat generated in the ASIC 54 is transferred to the rear heat conductor 34 via the plurality of spacers 106. That is, the spacer 106 plays a role of improving the thermal conductivity of the composite layer 90d. The spacer 106 is formed of aluminum nitride (aluminum nitride), aluminum oxide (alumina), or the like having relatively high thermal conductivity and relatively high insulating properties.

  In the composite layer 90d, the adhesive 108 exhibits an adhesive function for adhering and fixing the ASIC 54 and the rear heat conductor 34. The adhesive 108 also has a function of fixing the positions of the plurality of spacers 106.

  According to each of the composite layers described above, heat conduction from the ASIC 54 to the rear heat conductor 34 is maintained while electrical insulation is maintained between the back surface 54a of the ASIC 54 and the front side surface 70 of the rear heat conductor 34. Is maintained at a high level. In other words, according to each of the composite layers, even when a bare chip is provided as the ASIC 54, the heat generated in the ASIC 54 is preferably applied to the rear side (that is, the side opposite to the ultrasonic wave transmitting / receiving surface 12 which is the contact surface with the subject). ).

  Hereinafter, a process performed when the ASIC 54 is warped when the ASIC 54 is soldered to the relay board 52 by the reflow process will be described with reference to FIGS. 8 to 11.

  FIG. 8 is a cross-sectional view showing a case where the relay board 52 and the ASIC 54 that have been warped by the reflow process are joined to the rear heat conductor 34 via the composite layer 90a. As shown in FIG. 8, when the relay substrate 52 and the ASIC 54 are bonded to the rear heat conductor 34 via the composite layer 90a in a warped state, the distance between the rear surface 54a and the front side surface 70 becomes different in the xz plane. Will differ in location. As a result, the thickness of the composite layer 90a becomes excessively large and a suitable thermal conductivity cannot be maintained, or the distance between the back surface 54a and the front side surface 70 becomes less than the distance required for insulation. There is a possibility that a portion may be formed and dielectric breakdown may occur.

  In the present embodiment, when the ASIC 54 is warped, the warped back surface 54a is flattened so that the processed back surface is parallel to the front side surface 70, and then the ASIC 54 and the rear heat conductor 34 are combined. Bonded through layers. For example, referring to FIG. 9, the back surface of the ASIC 54 is flattened by shaving off a portion of the ASIC 54 warped by the reflow process, which is behind the dashed line.

  The flattening is performed using, for example, a dicing device or a surface grinder. In the flattening process, the grinding direction is set to a direction different from the cleavage direction of the ASIC 54 in order to prevent chip cracking. Referring to FIG. 10, in the ASIC 54, assuming that the x-axis direction and the z-axis direction are the cleavage directions, the direction of the arrow avoiding these directions is defined as the grinding direction.

  FIG. 11 shows a state in which the ASIC 54 after the planarization process is bonded to the rear heat conductor 34 via the composite layer 90a. As shown in FIG. 11, even if the ASIC 54 is warped by the reflow process, the flattening process does not cause the ASIC 54 to be warped, and the back surface 54 a of the ASIC 54 and the rear heat transfer The distance from the front side surface 70 of the body 34 can be suitably maintained.

  The embodiment according to the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Reference Signs List 10 ultrasonic probe, 12 ultrasonic wave transmitting and receiving surface, 14 front case, 16 rear case, 18 cable, 20 cable protection boot, 30 transmitting and receiving unit, 32 front heat conductor, 34 rear heat conductor, 36 main frame, 38 upper frame, 40 lower frame, 42 FPC, 44 wires, 46 connector, 50 transducer array, 52 relay board, 54 ASIC, 54a back surface, 54b side surface, 56 backing material, 58 acoustic matching layer, 60 acoustic lens, 70 Front side, 70a Exposed portion, 72 blocks, 74, 78 convex portion, 76, 80 concave portion, 82 projecting side, 84 groove portion, 90a, 90b, 90c, 90d, 90e Composite layer, 92, 104, 108 adhesive, 94 filler , 96 film, 98 front adhesive layer, 100 rear adhesive layer, 10 Oxide film, 106 a spacer.

Claims (3)

A plurality of vibrating elements,
An electronic circuit for processing at least one of a plurality of transmission signals supplied to the plurality of vibration elements and a plurality of reception signals output from the plurality of vibration elements, and a chip surface at least partly of which is conductive An electronic circuit chip as a heat source,
A heat conductor having a facing surface facing the chip surface,
A composite functional layer that exhibits a heat conduction function and an electrical insulation function between the chip surface and the facing surface,
With
The composite functional layer is made of an insulating adhesive mixed with an insulating filler for setting and maintaining a predetermined distance between the chip surface and the facing surface ,
The filler depends on the dielectric strength of the filler or the adhesive, and the potential difference that can occur between the chip surface and the opposing surface, in order to ensure insulation between the chip surface and the opposing surface. Having a diameter of
An ultrasonic probe, characterized in that: The composite functional layer further exhibits an adhesion function of adhering the electronic circuit chip and the heat conductor,
The ultrasonic probe according to claim 1, wherein: The composite functional layer further exerts a shock absorbing function,
The ultrasonic probe according to claim 1, wherein: