JP2010075367A - Medical array-type ultrasonic probe and medical ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the pitch variation when a plurality of channels are formed by cutting a piezoelectric element and at least two acoustic matching layers, to effectively join a first control signal substrate to the piezoelectric element, and to effectively secure the conductivity between the members. <P>SOLUTION: The ultrasonic probe includes: a packing material; the first control signal substrate formed on the packing material; the plurality of channels formed by layering the piezoelectric element and the at least two acoustic matching layers on the first control signal substrate and by dicing from the uppermost acoustic matching layer to the surface of the first control signal substrate; and a second control signal substrate formed on these channels. The ultrasonic probe is characterized by a lead-free soldered alloy including at least 88 wt.% tin which is interposed at least between the first control signal substrate and the piezoelectric element among the adjacent members from the first control signal substrate to the second control signal substrate to join the members. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a medical array type ultrasonic probe and a medical ultrasonic diagnostic apparatus.

  A medical ultrasonic diagnostic apparatus or ultrasonic image inspection apparatus transmits an ultrasonic signal to an object, receives a reflection signal (echo signal) from the object, and images the inside of the object It is. In this medical ultrasonic diagnostic apparatus and ultrasonic image inspection apparatus, an electronically operated array ultrasonic probe having an ultrasonic signal transmission / reception function is mainly used.

  A general ultrasonic probe has a backing material, a piezoelectric element bonded on the backing material and having electrodes formed on both sides of the piezoelectric body, and an acoustic matching layer bonded on the piezoelectric element. In the piezoelectric element and the acoustic matching layer, a plurality of channels are formed by array processing. An acoustic lens is formed on the acoustic matching layer. The electrodes of the piezoelectric elements of each channel are connected to a diagnostic device through a control signal board (flexible printed wiring board (FPC)) or via a cable.

  In such an ultrasonic probe, the backing material absorbs unnecessary ultrasonic waves emitted from the back surface of the piezoelectric element. The piezoelectric element is used as an ultrasonic transmission / reception element. The acoustic matching layer matches the acoustic impedance between the piezoelectric element and the human body, and improves the transmission / reception efficiency of ultrasonic waves. Accordingly, the acoustic impedance of the acoustic matching layer is set to an intermediate value between the piezoelectric body (20 to 38 MRayls) of the piezoelectric element and the human body (1.5 MRayls). When a plurality of acoustic matching layers are used, the acoustic impedance of each layer is set so as to gradually decrease toward the human body. The arrangement pitch of the channels by array processing is about 50 μm to 300 μm. The acoustic lens plays a role of focusing the ultrasonic wave when transmitting and receiving the ultrasonic wave.

  Conventionally, an acoustic matching layer having a one-layer structure, a two-layer structure, or a multilayer gradient structure having three or more layers is known. In particular, three or more acoustic matching layers have recently been suitably used for broadening the bandwidth (see Non-Patent Document 1).

  On the other hand, Patent Document 1 discloses a general method for manufacturing an ultrasonic probe. That is, a first control signal board (for example, a flexible printed wiring board; FPC) on the backing material is bonded. A piezoelectric element having electrodes formed on both sides of a piezoelectric body made of a piezoelectric material such as lead zirconate titanate (PZT) is attached to the FPC. An acoustic matching layer is adhered on the piezoelectric element to form a laminate. In this bonding process, heat treatment may be performed for bonding. Subsequently, the multilayer body is cut from the acoustic matching layer side to the piezoelectric element into an array having a width of about 50 to 300 μm with a dicer to form a plurality of channels. At the time of this cutting, the acoustic matching layer and the adhesive layer are required to have high cutting workability. After cutting the array, the cutting grooves between the channels may be filled with a relatively soft resin such as low acoustic impedance and high damping silicone rubber to maintain mechanical strength. Subsequently, an ultrasonic probe is manufactured by adhering a second control signal substrate (for example, a ground plate) and an acoustic lens in this order on the acoustic matching layers of a plurality of channels.

  In the production of such an ultrasonic probe, a depolarization phenomenon occurs in which the polarization of the piezoelectric element disappears by exceeding the Curie point of the piezoelectric element of the piezoelectric element due to a load such as heating during bonding or heat generated during cutting. . In this case, the repolarization process is performed after the connection of the second control signal board.

  The acoustic matching layer on the piezoelectric element is formed of an acoustic matching layer in which zinc oxide particles are dispersed in an organic resin (see Patent Document 2) and a solid inorganic material in order to efficiently input and output ultrasonic waves to and from the human body. And an acoustic matching layer (see Patent Document 3) formed of a mixture in which an oxide powder is dispersed in an organic resin.

  Conventionally, a thermosetting resin such as an epoxy resin is used to join the control signal substrate, the piezoelectric element, and the acoustic matching layer to each other. In this bonding step, a heat treatment from room temperature to 150 ° C. is performed to cure the thermosetting resin adhesive layer. The heat treatment is performed while applying moderate pressure. This is to realize a thin and uniform adhesive layer in a portion where it is necessary to maintain adhesive strength in the cutting process after bonding and to maintain conductivity such as bonding of a control signal board (FPC) and a piezoelectric element. is there.

  On the other hand, Patent Document 4 describes joining members that need conductivity with a plate-like low melting point indium-based or lead-based solder.

Patent Document 5 describes that a signal line portion of a control signal board and a piezoelectric element previously processed into a strip shape are connected with a low melting point Sn-based lead-free solder ball, and the piezoelectric elements are arranged in an array. ing.
JP 2005-198261 A JP 2004-104629 A JP 2006-95167 A JP 52-132789 A JP 2008-47971 A T. Inoue et al., IEEE, UFFC, vol.34 No.1, 1987, pp.8-15

  However, when a thermosetting resin such as an epoxy resin is used to join the control signal board (for example, FPC), the piezoelectric element, and the acoustic matching layer to each other, good conduction between the control signal board and the piezoelectric element is ensured. It becomes difficult. In particular, as the channel becomes finer and the area of each divided piezoelectric element becomes smaller, it becomes difficult to ensure conductivity with the control signal substrate by bonding the thermosetting resin.

  On the other hand, when a control signal board (for example, FPC), a piezoelectric element, and an acoustic matching layer are bonded to each other with a plate-shaped solder, there are the following problems with an indium-based or lead-based solder material. That is, the laminate of the piezoelectric element and the acoustic matching layer is cut into an array by a dicer. The array cutting is repeated several tens of times at a narrow pitch (width). Indium-based and lead-based solders are relatively soft and have low mechanical strength characteristics and high elongation. Therefore, the pitch at the time of cutting varies, making it difficult to perform uniform cutting. As a result, the piezoelectric elements are not evenly divided, and capacity variation occurs for each channel. The capacity variation affects the sensitivity variation of the ultrasonic probe, and degrades the quality of the ultrasonic image. In addition, the degradation of cutting performance is caused by smear (dirt due to plastic flow) that indium or lead solder adheres to the cut surface of the laminate, particularly the cut surface including the lower electrode of the piezoelectric element, through the dicing blade. There is a fear. Smear generates a discharge when a high voltage is applied to the piezoelectric element to cause repolarization, thereby destroying the piezoelectric element and reducing the manufacturing yield of the ultrasonic probe.

  Bonding with solder balls does not cause the above problem. However, when the pitch of the channel is narrowed for the purpose of high resolution, it becomes difficult to align and secure the adhesive strength, and the processing work becomes complicated.

  The present invention reduces the pitch fluctuation when the piezoelectric element and two or more acoustic matching layers are cut to form a plurality of channels, and can satisfactorily join the first control signal substrate and the piezoelectric element, and between them. It is an object of the present invention to provide a medical array type ultrasonic probe capable of ensuring good electrical conductivity and a medical ultrasonic diagnostic apparatus including the ultrasonic probe.

According to the first aspect of the present invention, a backing material, a first control signal substrate formed on the backing material, a piezoelectric element and two or more acoustic matching layers are laminated on the first control signal substrate, A medical array ultrasonic probe comprising a plurality of channels formed by dicing from the upper acoustic matching layer to the surface of the first control signal substrate, and a second control signal substrate formed on these channels. There,
The lead-free solder alloy layer containing tin of 88% by weight or more is at least between the first control signal board and the piezoelectric element among the adjacent members from the first control signal board to the second control signal board. A medical array type ultrasonic probe characterized in that the members are joined to each other by being interposed between the members.

  According to a second aspect of the present invention, there is provided a medical ultrasonic diagnostic apparatus comprising a medical array type ultrasonic probe and an ultrasonic probe controller connected to the ultrasonic probe through a cable. Is done.

  According to the present invention, it is possible to provide a medical array type ultrasonic probe with high performance and high reliability.

  According to the present invention, it is possible to provide an ultrasonic diagnostic apparatus that includes the above-described high-performance and high-reliability medical array-type ultrasonic probe and that has improved image quality and sensitivity.

  Hereinafter, a medical array type ultrasonic probe and a medical ultrasonic diagnostic apparatus according to an embodiment of the present invention will be described in detail.

  The medical array type ultrasonic probe according to the embodiment includes a backing on which a first control signal board (for example, a flexible printed wiring board; FPC) is formed on an upper surface. The plurality of channels are formed by stacking a piezoelectric element and two or more acoustic matching layers on the first control signal substrate and dicing from the uppermost acoustic matching layer to the surface of the first control signal substrate. Each of these channels has a piezoelectric element disposed on the first control signal substrate and two or more acoustic matching layers formed on the piezoelectric element. The second control signal board is formed on the uppermost acoustic matching layer of each channel. The acoustic lens is formed on the second control signal substrate directly or via another acoustic matching layer.

  The lead-free solder alloy layer containing tin of 88 wt% or more is interposed between at least the first control signal board and the piezoelectric element among the members from the first control signal board to the second control signal board. Are joined.

  The piezoelectric element includes, for example, a lead zirconate titanate (PZT) piezoelectric ceramic material, a relaxor-based and barium titanate-based ceramic, a piezoelectric body made of a single crystal material, a first control signal substrate side and an acoustic matching layer side of the piezoelectric body. And electrodes formed respectively. In particular, it is preferable to use a piezoelectric body having a Curie point of 300 ° C. or lower, such as a lead zirconate titanate (PZT) piezoelectric ceramic, because ultrasonic waves can be generated with high efficiency.

  The acoustic impedance of the two or more acoustic matching layers gradually decreases toward the acoustic lens. For example, when there are two acoustic matching layers, the first acoustic matching layer (first acoustic matching layer) on the piezoelectric element has an acoustic impedance of 6 to 10 MRayls at 25 ° C., and the second acoustic matching layer on the piezoelectric element The acoustic matching layer (second acoustic matching layer) preferably has an acoustic impedance of 2 to 6 MRayls at 25 ° C. For example, when there are three acoustic matching layers, the first acoustic matching layer (first acoustic matching layer) on the piezoelectric element has an acoustic impedance of 7 to 20 MRayls at 25 ° C., and the second acoustic matching layer on the piezoelectric element The acoustic matching layer (second acoustic matching layer) has an acoustic impedance of 7 to 14 MRayls at 25 ° C., and the third acoustic matching layer (second acoustic matching layer) on the piezoelectric element is 2 to 4 MRayls at 25 ° C. It is preferable to have an acoustic impedance of

  When there are two acoustic matching layers, it is preferable that the first acoustic matching layer is made of, for example, quartz or macor glass, and the second acoustic matching layer is made of, for example, an oxide-containing resin or carbon.

  When there are three acoustic matching layers, the first acoustic matching layer is made of, for example, a flint glass or silicon material, and the second acoustic matching layer is made of, for example, a material of carbon or oxide-containing resin. Is preferably made of, for example, polyethylene, silicone, urethane resin, ethylene vinyl acetate copolymer (EVA).

  The other acoustic matching layer is made of a material that exhibits a smaller acoustic impedance than the uppermost acoustic matching layer constituting the channel.

  Further, the second control signal board may be separated at locations corresponding to the spaces of the plurality of channels.

The lead-free solder alloy containing tin of 88% by weight or more has the general formula Sn _x M1 _y M2 _z , where M1 is at least one metal selected from Ag and Bi, and M2 is from the group consisting of Zn, Cu, Al and In It is preferably represented by at least one metal selected, wherein x is 88% by weight or more and x + y + z is 100% by weight. Specific lead-free solder alloys are Sn-3.5% Ag, Sn-3.5% Ag-0.7% Cu, Sn-3.5% Ag-0.5% Bi-8.0% In. Sn-3.0% Bi-8.0% Bi, Sn-3.0% Bi-8.0% Cu, Sn-3.0% Ag-0.5% Cu can be used. Here,% is% by weight.

  It is preferable that the lead-free solder alloy layer is interposed not only between the first control signal substrate and the piezoelectric element but also between the piezoelectric element and the acoustic matching layer thereon to bond the members. Most preferably, the lead-free solder alloy layer is interposed between all adjacent members from the first control signal board to the second control signal board to join the members. Thus, when joining a some member with a lead-free solder alloy layer, it is preferable that a lead-free solder alloy layer has the same composition. That is, since joining of each member by the lead-free solder alloy layer heats and melts the alloy layer, the heating temperature can be unified by making each alloy layer have the same composition. As a result, for example, all the alloy layers can be joined by heating, melting and cooling at the same temperature after interposing the alloy layers between the members, and the joining operation can be simplified.

  It is desirable that the lead-free solder alloy layer has a thickness of 0.1 to 10 μm, more preferably 0.5 to 5 μm. The lead-free solder alloy layer having such a thickness enables the members from the first control signal board to the second control signal board to be bonded with high strength, and cutting when forming a plurality of channels. Sometimes, it becomes possible to further improve the linearity of cutting. The acoustic impedance of the lead-free solder alloy layer is higher than that of the acoustic matching layer. However, by adjusting the thickness, the influence of transmission / reception efficiency can be reduced.

  Next, the array type ultrasonic probe according to the embodiment will be described in detail with reference to FIG. 1 and FIG. FIG. 1 is a perspective view showing an array-type ultrasonic probe according to the embodiment, and FIG. 2 is a cross-sectional view of the array-type ultrasonic probe of FIG.

The array type ultrasonic probe 1 includes a backing 2. A first control signal board (for example, signal control side flexible printed wiring board: signal control side FPC) 3 is fixed on the backing 2 with, for example, an epoxy resin adhesive layer (not shown). The signal control side FPC 3 has a structure in which, for example, a wiring is formed on a film of polyimide or silicone epoxy resin. The piezoelectric element 4 is joined and fixed on the signal control side FPC 3 by a lead-free solder alloy layer 5 containing 88 wt% or more of tin. The piezoelectric element 4 includes a piezoelectric body 6 made of, for example, a lead zirconate titanate (PZT) piezoelectric ceramic material, and first and second electrodes 7 ₁ and 7 ₂ formed on both surfaces of the piezoelectric body 6. ing. The piezoelectric body 6 may be a composite made of the piezoelectric material and an organic resin. The first acoustic matching layer 8 is joined by a lead-free solder alloy layer 9 containing 88 wt% or more tin on the second electrode 7 ₂ of the piezoelectric element 4, it is fixed. The second acoustic matching layer 10 having a smaller acoustic impedance than the first acoustic matching layer 8 is joined and fixed on the first acoustic matching layer 8 with a lead-free solder alloy layer 11 containing tin of 88 wt% or more. .

  The laminate of the lead-free solder alloy layer 5, the piezoelectric element 4, the lead-free solder alloy layer 9, the first acoustic matching layer 8, the lead-free solder alloy layer 11 and the second acoustic matching layer 10 is obtained by cutting using, for example, a dicing blade. A plurality of channels 13 are formed which are divided into a plurality and are arranged one-dimensionally with spaces 12 therebetween. These spaces 12 are allowed to be filled with a relatively soft resin such as low acoustic impedance, high damping silicone rubber.

  The second control signal board (for example, ground side flexible printed wiring board: ground side FPC) 14 is joined to the second acoustic matching layer 10 of the plurality of channels 13 with a lead-free solder alloy layer 15 containing at least 88 wt% tin. It has been fixed.

  The third acoustic matching layer 16 having a smaller acoustic impedance than the second acoustic matching layer 10 which is the uppermost acoustic matching layer is fixed on the ground side FPC 14 with, for example, an epoxy resin adhesive layer (not shown). ing. The acoustic lens 17 is fixed on the third acoustic matching layer 16 by, for example, a rubber adhesive layer (not shown).

The backing 2 is placed on a support base (not shown), and the backing 2, the plurality of channels 13, the third acoustic matching layer 16 and the acoustic lens 17 have an opening at the upper end (not shown). It is stored inside. The case 13 includes a signal processing circuit (not shown) including a control circuit for controlling the driving timing of the piezoelectric element 4 of each channel 13 and an amplifier circuit for amplifying the received signal received by the piezoelectric element 4. Has been. The other end of the control signal side FPC 3 is connected to a control circuit. Ground side FPC14 has one end connected to the first electrode 7 ₁ of the piezoelectric element 4 is connected to the other end signal processing circuitry. The cable (not shown) is inserted from the case part opposite to the acoustic lens 16, and its tip is connected to a signal processing circuit and a control circuit (both not shown).

In the array-type ultrasonic probe 1 having such a configuration, a voltage is applied between the _first and _second electrodes 7 ₁ and 7 ₂ of the piezoelectric element 4 in each channel 13 to resonate the piezoelectric body 6. Sound waves are radiated (transmitted) to the human body through the first and second acoustic matching layers 8, 10, the third acoustic matching layer 16 and the acoustic lens 17 of each channel 13. At the time of reception, the piezoelectric body 6 of the piezoelectric element 4 of each channel 13 is received from the human body through the acoustic lens 17, the third acoustic matching layer 16, and the first and second acoustic matching layers 8, 10 of each channel 13. Is vibrated, and the vibration is electrically converted into a signal to obtain an image. In addition, the acoustic impedance of the first, second acoustic matching layers 8, 10, and the third acoustic matching layer 16 is gradually changed between the piezoelectric body (acoustic impedance: 20 to 38 MRayls) and the human body (acoustic impedance: 1.5 MRayls). By setting so as to approach that of the human body, it is possible to improve the transmission / reception efficiency of ultrasonic waves.

  The acoustic matching layer constituting the channel is not limited to two layers, and may be three or more layers (for example, three layers or four layers). In this case, an acoustic matching layer may be formed on the ground side FPC or may be omitted.

  Next, an example of a method for manufacturing the ultrasonic probe according to the embodiment will be described.

  First, a signal-control-side FPC, a piezoelectric element, a first acoustic matching layer, and a second acoustic matching layer are arranged in this order on the backing material, and a lead-free solder alloy layer containing 88% by weight or more of tin is interposed between these members. Laminate with interposition. Subsequently, the members are fused and fixed with a lead-free solder alloy layer using a thermocompression bonding apparatus such as a bonding apparatus. In addition, in order to raise adhesive strength more, you may apply | coat a surface treating agent like a flux to the joint surface of each member. For the lead-free solder alloy layer, for example, a rolled foil can be used. In addition, a lead-free solder alloy layer may be formed on the bonding surfaces of the members by vapor deposition, sputtering, or plating. It is desirable to form the lead-free solder alloy layer interposed between the members so as to have the same composition and a thickness of 0.1 to 10 μm, more preferably 0.5 to 5 μm at the time of joining.

  Next, the signal control side FPC of the laminate is heated by pressure bonding to the backing material with an epoxy resin adhesive at 90 ° C. for about 50 minutes, and the adhesive is cured to cure the backing material, the signal control side FPC, the piezoelectric element, A laminated structure composed of one acoustic matching layer and a second acoustic matching layer is produced. Subsequently, from the second acoustic matching layer side toward the backing, the substrate is cut with a dicing blade with a width (pitch) of, for example, 50 to 200 μm, divided into a plurality of arrays, and one-dimensionally arranged with a space. A plurality of channels having a piezoelectric element and first and second acoustic matching layers are formed. Subsequently, if necessary, the space between the channels may be filled with a relatively soft resin such as silicone rubber having a low acoustic impedance and a high damping property to maintain the mechanical strength of each channel. The ground side FPC is joined to the second acoustic matching layer of each channel with a lead-free solder alloy layer containing 88 wt% or more of tin. Thereafter, an acoustic matching layer and an acoustic lens are bonded and fixed on the ground side FPC with an epoxy resin adhesive layer and a silicone rubber adhesive layer, respectively, and housed in a case to manufacture an array-type ultrasonic probe.

  In the production of such an ultrasonic probe, when the piezoelectric body of the piezoelectric element has a Curie point exceeding 300 ° C., it is depolarized by cutting with a dicing blade and heat treatment for joining with a lead-free solder alloy layer. Fear is small. However, when a PZT-based piezoelectric body that generates ultrasonic waves with high efficiency is used, since the Curie point is 130 to 300 ° C., depolarization occurs when affected by heat treatment during cutting and joining. Therefore, repolarization is performed by applying a high voltage between the signal control side FPC and the ground side FPC. This process can guarantee the best characteristics as an ultrasonic probe.

  In addition, when forming a channel by dividing into multiple arrays, it may be performed after a lead-free solder alloy layer is pressure-bonded on the second acoustic matching layer.

  A medical ultrasonic diagnostic apparatus including the ultrasonic probe according to the embodiment will be described with reference to FIG.

  A medical ultrasonic diagnostic apparatus (or a medical ultrasonic image inspection apparatus) that transmits an ultrasonic signal to an object, receives a reflection signal (echo signal) from the object, and images the object. An array type ultrasonic probe having an ultrasonic signal transmission / reception function is provided. This ultrasonic probe has, for example, the one-dimensional array structure shown in FIGS. The ultrasonic probe 1 is connected to an ultrasonic diagnostic apparatus main body 22 through a cable 21. In the ultrasonic diagnostic apparatus main body 22, an ultrasonic probe controller (not shown) that performs transmission and reception processing of ultrasonic signals of the ultrasonic probe, a display 23, and the like are provided.

  The array-type ultrasonic probe according to the embodiment described above includes a backing material, a first control signal board formed on the backing material, a piezoelectric element and two or more acoustic matching layers on the first control signal board. And a plurality of channels having a piezoelectric element and two or more acoustic matching layers formed by dicing from the uppermost acoustic matching layer to the surface of the first control signal substrate, and formed on these channels And a second control signal board. The lead-free solder alloy layer containing tin of 88% by weight or more is at least between the first control signal board and the piezoelectric element among adjacent members from the first control signal board to the second control signal board. The members are joined to each other. The ultrasonic probe having such a configuration has the following effects.

  (1) Since the lead-free solder alloy is excellent in heat resistance and has high adhesiveness, even if heat and mechanical pressure are applied to the acoustic matching layer along with absorption and attenuation of ultrasonic energy, at least the first 1 Separation at the bonding layer made of a lead-free solder alloy layer between the control signal substrate and the piezoelectric element can be prevented. As a result, an array-type ultrasonic probe having high long-term reliability can be provided.

  (2) By bonding the first control signal substrate and the piezoelectric element with the lead-free solder alloy layer, it is possible to ensure good electrical conductivity between them. As a result, a high-performance array-type ultrasonic probe that can efficiently transmit and receive ultrasonic energy can be provided.

  (3) The lead-free solder alloy has high hardness and low extensibility compared with general lead solder. For this reason, when performing array cutting by a dicing blade after joining at least the first control signal substrate and the piezoelectric elements with a lead-free solder alloy layer, the linearity of the cutting is improved and the target width is uniform. It becomes possible to form channels with a pitch. In particular, by joining the members between the first control signal board and the second control signal board all adjacent to each other with a lead-free solder alloy layer interposed therebetween, and then performing array cutting with a dicing blade, further Channels can be formed with a uniform pitch. As a result, since crosstalk between channels can be reduced, a high-resolution array ultrasonic probe can be realized.

  (4) Since the lead-free solder alloy has high hardness and low extensibility, when performing array cutting with a dicing blade after at least the first control signal board and the piezoelectric elements are joined with a lead-free solder alloy layer. The phenomenon that smears (dirt due to plastic flow) adhere to the cut surface of the piezoelectric element (particularly the cut surface including the lower electrode) can be reduced as compared with the case of joining with lead solder. As a result, when repolarization is performed by applying a high voltage from the first and second control signal substrates to the piezoelectric element of the channel, discharge from the vicinity of the lower electrode of the piezoelectric element caused by smear, Breakage can be prevented and the yield of the ultrasonic probe can be improved.

  The ultrasonic diagnostic apparatus according to the embodiment includes a high-performance, high-reliability array-type ultrasonic probe with low crosstalk, and thus can improve image quality and sensitivity of a tomographic image.

  Hereinafter, embodiments of the present invention will be described in detail.

Example 1
On the element control side FPC, a lead-free solder foil having a length of 25 mm, a width of 10 mm, and a thickness of 5 μm and a composition of Sn-3.5% Ag-0.7% Cu was placed, and this lead-free solder foil was placed on the lead-free solder foil Piezoelectric elements were stacked. The piezoelectric element was fabricated by forming electrodes by sputtering titanium 30 nm / gold 100 nm on both sides of a piezoelectric body made of PZT piezoelectric ceramic having a length of 25 mm, a width of 10 mm, and a thickness of 0.4 mm. The laminate of FPC, lead-free solder foil, and piezoelectric element was heat-pressed for 5 seconds at 250 ° C. under a load of 10 N using a bonding apparatus (FC bonder), thereby joining the FPC and the piezoelectric element with lead-free solder foil. Next, a lead-free solder foil of the same size and composition is placed on the piezoelectric element, and the first acoustic matching made of Macol glass having a length of 25 mm, a width of 10 mm, and a thickness of 0.4 mm is provided on the lead-free solder foil. After the layers were stacked, the piezoelectric element and the first acoustic matching layer were joined with a lead-free solder foil by thermocompression bonding under the same conditions using a bonding apparatus. Subsequently, a lead-free solder foil of the same size and composition is placed on the first acoustic matching layer, and the second sound made of carbon having a length of 25 mm, a width of 10 mm, and a thickness of 0.2 mm is placed on the lead-free solder foil. After the matching layers were stacked, the piezoelectric element and the first acoustic matching layer were joined with a lead-free solder foil by thermocompression bonding under the same conditions using a bonding apparatus. Furthermore, after placing a lead-free solder foil having the same dimensions and composition on the second acoustic matching layer, the lead-free solder foil was pressure-bonded on the second acoustic matching layer. At the time of this crimping, a fluororesin sheet was placed on the lead-free solder foil to prevent the lead-free solder foil from adhering to the bonder pressing surface.

  Subsequently, a silicone resin backing material having a length of 25 mm, a width of 10 mm, and a thickness of 10 mm was bonded to the surface of the signal control side FPC to which the piezoelectric element was not bonded with an organic adhesive. As the organic adhesive, a two-component mixed type epoxy resin (Ecobond 27; manufactured by Emerson & Cumming) was used and thermally cured at 90 ° C. for 50 minutes. Subsequently, a 20 nm chromium layer and a 100 nm gold layer were formed by sputtering on the side surfaces along the longitudinal direction of the first acoustic matching layer and the second acoustic matching layer to form electrode layers. This electrode layer is for establishing electrical connection between the electrode (upper side electrode) of the piezoelectric element on the bonding side with the first acoustic matching layer and an earth side FPC described later.

  By such a process, backing material / epoxy resin / signal control side FPC / lead-free solder foil / piezoelectric body / lead-free solder foil / first acoustic matching layer / lead-free solder foil / second acoustic matching layer / lead-free solder foil After the laminated structure in which the first and second matching layers are integrated, a dicing blade extends from the lead-free solder foil on the second acoustic matching layer side to the lead-free solder foil under the piezoelectric element in the longitudinal direction of the first matching layer and the second matching layer. A plurality of (96) channels were formed by dividing the array so as to be perpendicular to the electrode layer on the side surface along the line. In this step, the piezoelectric element is reliably divided by cutting slightly to the upper surface of the signal control side FPC. The array division width was 200 μm pitch in the longitudinal direction. The thickness of the dicing blade was 50 μm, and the cutting speed was 1 mm / s. At the time of cutting, the problem of pitch fluctuation did not occur, and all the division widths were the same size. Moreover, it was found in the cross-sectional observation after cutting that a good cut surface where smear does not appear was formed.

  Next, the ground-side FPC was heat-pressed to the lead-free solder foil on the second acoustic matching layer after cutting with a bonding apparatus to join the second acoustic matching layer and the ground-side FPC. Next, a third polyethylene acoustic matching layer having a thickness of 0.15 mm is bonded to the ground side FPC by epoxy resin: Ecobond, and an acoustic lens made of silicone resin is bonded to the acoustic matching layer by Ecobond. An ultrasonic probe body was manufactured. Further, an electric field of 1 V per piezoelectric material thickness of 1 μm, that is, a DC voltage of 400 V, was applied for 1 minute between the two FPCs in the constant temperature oven at 40 ° C. with respect to the obtained piezoelectric probe body. The body was repolarized. In the polarization process, no discharge or short circuit occurred. Thereafter, an ultrasonic probe sample was manufactured by casing the ultrasonic probe element body.

  The impedance characteristic of each channel of the obtained ultrasonic probe sample was measured with an impedance analyzer. As a result, all 96 channels were operated, and the target resonance frequency of 3.5 MHz was achieved. Further, the variation of the impedance curve was 2%.

(Example 2)
An ultrasonic probe sample was manufactured in the same manner as in Example 1 except that a Sn-3.5% Ag foil having a thickness of 5 μm was used as the lead-free solder foil.

  The impedance characteristics of each channel of the obtained ultrasonic probe sample were similarly measured with an impedance analyzer. As a result, all 96 channels were operated, and the target resonance frequency of 3.5 MHz was achieved. Further, the variation of the impedance curve was 2%.

(Example 3)
An ultrasonic probe sample was manufactured in the same manner as in Example 1 except that Sn-3.5% Ag-0.5% Bi-8.0% In foil having a thickness of 5 μm was used as the lead-free solder foil.

  In the obtained ultrasonic probe sample, as in Example 1, all 96 channels were operated, and a target resonance frequency of 3.5 MHz was achieved.

  Moreover, the variation of the impedance curve was 1.5%, and the variation was further reduced as compared with Examples 1 and 2.

  In addition, the observation result of the cut surface confirmed that the cut surface was prepared as compared with Examples 1 and 2. This is because the lead-free solder of Sn-3.5% Ag-0.5% Bi-8.0% In exhibits higher hardness and low extensibility.

Example 4
An ultrasonic probe sample was manufactured in the same manner as in Example 1 except for the following changes.

  The thickness of the PZT-based piezoelectric material is 0.25 mm, the thickness of the first acoustic matching layer is 0.2 mm, the thickness of the second acoustic matching layer is 0.1 mm, and the thickness of the acoustic matching layer on the ground side FPC is Changed to 0.07 mm. Using a dicing blade having a thickness of 30 μm, cutting was performed at a pitch of 70 μm to form 192 channels. In a constant temperature oven at 40 ° C., an electric field of 1 V, ie, a DC voltage of 200 V, was applied for 1 minute per 1 μm thickness of the piezoelectric body of the piezoelectric element between two FPCs to repolarize the piezoelectric body.

  After dicing, the cutting state was observed, and it was confirmed that there was no pitch fluctuation and a good cut surface. No discharge or short circuit occurred during repolarization.

  The impedance characteristics of each channel of the obtained ultrasonic probe sample were measured by the same method as in Example 1. As a result, all 192 channels were operated, and the target resonance frequency of 7 MHz was achieved. The variation of the impedance curve was within 2%.

  In addition, when using a Sn-3.5% Ag foil having a thickness of 5 μm and a Sn-3.5% Ag-0.5% Bi-8.0% In foil having a thickness of 5 μm as the lead-free solder foil, The same result as in Example 4 was obtained.

(Comparative Example 1)
An ultrasonic probe sample was manufactured in the same manner as in Example 1 except that a Sn-37% Pb lead solder foil having a thickness of 5 μm was used instead of the lead-free solder foil.

  In the cutting using the dicing blade in the manufacturing process of the ultrasonic probe sample, the pitch starts to fluctuate as the number of cuttings increases. Therefore, after cutting a certain number of times, the cutting was stopped and the dicing blade was washed (dressing), or the dicing blade was replaced and cut again. When the cut surface was observed, it was confirmed that fine debris resulting from the stretching of the lead solder foil adhered. When a voltage was applied to repolarize after dicing, discharge occurred in a plurality of channels, and the channels became unusable due to a short circuit.

  The impedance characteristic of each channel of the obtained ultrasonic probe sample was measured with an impedance analyzer. As a result, 8 channels out of 96 channels were short-circuited at a resonance frequency of 3.5 MHz.

  Further, in the ultrasonic probe sample manufactured under the same conditions as in Example 4 (using Sn-37Pb lead solder foil), 20 channels out of 192 channels were short-circuited at a resonance frequency of 7 MHz.

  Further, the ultrasonic probe samples having 96 channels and 192 channels all had impedance variations of 5 to 6%.

(Comparative Example 2)
First, the piezoelectric element, the first acoustic matching layer, and the second acoustic matching layer were bonded with an epoxy resin: Ecobond 27, respectively. Subsequently, an element control side FPC was bonded to the piezoelectric element side, and a backing material was bonded to the piezoelectric element side with an epoxy resin: Ecobond 27. Adhesion was performed at 90 ° C. for 50 minutes. Subsequently, a 20 nm chromium layer and a 100 nm gold layer were formed by sputtering on the side surfaces along the longitudinal direction of the first acoustic matching layer and the second acoustic matching layer to form an electrode layer. Further, the ground side FPC and the third acoustic matching layer were bonded on the second matching layer with epoxy resin: Ecobond 27, respectively. The piezoelectric element, the first acoustic matching layer, the second acoustic matching layer, and the third acoustic matching layer were made of the same material as in Example 1.

  The laminated structure in which the backing material / epoxy resin / signal control side FPC / epoxy resin / piezoelectric material / epoxy resin / first acoustic matching layer / epoxy resin / second acoustic matching layer is integrated is secondly processed by a dicing blade. The array from the acoustic matching layer side to the piezoelectric element was cut to be perpendicular to the side electrode layers along the longitudinal direction of the first matching layer and the second matching layer. The array division width was set at a pitch of 200 μm in the longitudinal direction to form 96 channels. In addition, 192 channels were formed by dividing the array width in the longitudinal direction at a pitch of 70 μm.

  The ultrasonic probe sample of 3.5 MHz with a 200 μm pitch had no problem when cut, but a part of the joint portion was missing in the sample of 7 MHz with a 70 μm pitch. In any frequency sample, no discharge occurred due to repolarization.

  The impedance characteristics of each channel were measured with an impedance analyzer. As a result, there was a channel that was not connected to the ground side FPC. Specifically, in the 3.5 MHz ultrasonic probe sample, 6 channels out of 96 channels were open. In the ultrasonic probe sample of 7 MHz, 13 channels out of 192 channels except for chipping at the time of cutting were open. The variation in impedance was 4 to 5% in all cases.

The evaluation results of the ultrasonic probe samples of these examples and comparative examples are summarized in Table 1 below.

The perspective view of the array type ultrasonic probe concerning the embodiment of the present invention. FIG. 2 is a cross-sectional view of the ultrasonic probe in FIG. 1. 1 is a schematic diagram showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Ultrasonic probe, 2 ... Backing material, 3 ... 1st control signal board (signal control side FPC), 4 ... Piezoelectric element, 5, 9, 11, 15 ... Lead free solder alloy layer, 8 ... 1st acoustic matching Layer 10, second acoustic matching layer, 13 channel, 14 second control signal board (ground side FPC), 17 acoustic lens, 21 cable, 22 ultrasonic probe controller, 23 display.

Claims (9)

A backing material, a first control signal board formed on the backing material, a piezoelectric element and two or more acoustic matching layers are stacked on the first control signal board, and a first control is performed from the uppermost acoustic matching layer. A medical array ultrasonic probe comprising a plurality of channels formed by dicing up to a signal substrate surface and a second control signal substrate formed on these channels,
The lead-free solder alloy layer containing tin of 88% by weight or more is at least between the first control signal board and the piezoelectric element among the adjacent members from the first control signal board to the second control signal board. An array type ultrasonic probe for medical use, wherein the members are joined to each other. The lead-free solder alloy has a general formula Sn _x M1 _y M2 _z , where M1 represents at least one metal selected from Ag and Bi, and M2 represents at least one metal selected from the group consisting of Zn, Cu, Al and In Wherein x is 88% by weight or more and x + y + z is 100% by weight. 2. The medical array ultrasonic probe according to claim 1, wherein   The lead-free solder alloy layer is interposed between the first control signal substrate and the piezoelectric element, and further interposed between the piezoelectric element and the acoustic matching layer on the piezoelectric element, and joins the members together. 3. The medical array ultrasonic probe according to claim 1, wherein the free solder alloy layers have the same composition.   The medical array ultrasonic probe according to any one of claims 1 to 3, wherein the lead-free solder alloy layer has a thickness of 0.5 to 10 µm.   5. The medical array type superstructure according to claim 1, wherein the piezoelectric element includes two electrodes and a piezoelectric body disposed between the electrodes and having a Curie point of 130 to 300 ° C. 6. Acoustic probe.   When there are two acoustic matching layers constituting the channel, the first acoustic matching layer on the piezoelectric element has an acoustic impedance of 6 to 10 MRayls at 25 ° C., and the second acoustic matching layer on the piezoelectric element 6. The medical array ultrasonic probe according to claim 1, which has an acoustic impedance of 2 to 6 MRayls at 25 ° C. 6.   When there are three acoustic matching layers constituting the channel, the first acoustic matching layer on the piezoelectric element has an acoustic impedance of 7 to 20 MRayls at 25 ° C., and the second acoustic matching layer on the piezoelectric element 6 has an acoustic impedance of 7 to 14 MRayls at 25 ° C., and the third acoustic matching layer on the piezoelectric element has an acoustic impedance of 2 to 4 MRayls at 25 ° C. The medical array type ultrasonic probe as described.   In the state where the members from the first control signal board to the second control signal board are joined together by the lead-free solder alloy layer, a voltage is applied from the first and second control signal boards to the piezoelectric element. The medical array ultrasonic probe according to any one of claims 1 to 7, wherein the piezoelectric element is repolarized.   9. A medical ultrasonic diagnostic apparatus comprising: the medical array ultrasonic probe according to claim 1; and an ultrasonic probe controller connected to the ultrasonic probe through a cable.

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