JP2014011751A - Probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a probe such that adhesive agent is adapted not to wrap around the edge of a device substrate such as a semiconductor substrate but to flow into a groove provided on a support substrate.SOLUTION: In a probe, a device substrate 1 on which a plurality of capacitance type cells are arranged and an edge part provided with lead terminals 5 of an external wiring board 4 that is electrically connected to outside are mounted on the same support substrate 2. Electrode pads 7 connected to the cells of the device substrate 1 and the lead terminals 5 of the external wiring board 4 are electrically connected. At least one groove 3 is provided on the surface of the support substrate 2. The device substrate 1 is bonded on the support substrate 2 by adhesive agent. The edge part having the electrode pads 7 of the device substrate 1 is located on the groove 3.

Description

The present invention relates to a probe such as an ultrasonic probe used in an ultrasonic diagnostic apparatus or the like. More specifically, the present invention relates to a probe including a plurality of capacitance type cells.

A capacitive transducer in an ultrasonic probe used in an ultrasonic diagnostic apparatus or the like is formed with a plurality of transducers or cells, and drives the transducer with an electrical signal (drive signal) of an ultrasonic frequency. The signal is converted into an ultrasonic wave, and the ultrasonic wave is transmitted to the subject. Further, a reflected echo of the ultrasonic wave reflected in the subject is received by the vibrator, and the ultrasonic wave is converted into an electric signal.

CMUT (Capacitive) is used as the vibrator constituting the capacitive transducer.
A vibration element called “Micromachined Ultrasound Transducer” has been proposed (see Patent Document 1). The CMUT is a capacitive vibrator, in which one electrode is formed on a film body made of an insulating material, the other electrode is arranged opposite to each other across a space, and a drive signal is applied between the pair of electrodes. As a result, the film body is vibrated to generate ultrasonic waves. Alternatively, when the ultrasonic wave vibrates the film body, a change in the capacitance between the pair of electrodes occurs, and the ultrasonic wave is detected as an electric signal.

When an ultrasonic probe is formed using such a CMUT, usually, one element is formed by a plurality of CMUTs, and a plurality of the elements are arranged in one or two dimensions on the same semiconductor substrate. It is formed. The electrodes on the vibrating membrane side arranged on the ultrasonic wave transmitting / receiving surface side of each CMUT are individually connected to the electrode pads of the elements provided at the end of the semiconductor substrate. Each electrode pad is connected to a lead terminal formed on an external wiring board such as a flexible wiring board by wire bonding, and is configured such that a drive signal is applied to the element from the outside via the lead terminal (Non-Patent Document) 1).

US Patent Publication 2005 / 0203409A1

Omer Oralkan, et. a1. “Volumetric Ultrasound Imaging Using 2-D CMUT Arrays,” IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND CONTROL, VOL. 50, N011, PP. 1581-1594, NOVEMBER 2003

As described above, in order to connect the electrode terminal provided at the end of the semiconductor substrate provided with the element and the lead wire of the flexible wiring board, the semiconductor substrate and the lead terminal of the wiring board are adjacent to each other so that wire bonding can be performed. Be placed. The semiconductor substrate and the wiring substrate are bonded to the same support substrate. In this bonding, it is preferable that the adhesive is applied as uniformly as possible between the semiconductor substrate and the support substrate. That is, if foreign substances such as air are mixed into the adhesive surface or there is a region where the adhesive is not applied partially, the acoustic characteristics at that part will change, affecting the transmission / reception characteristics of the transducer. Because it will end up. Therefore, the area where air is not mixed in or is not applied by applying an adhesive and applying pressure to both the support substrate and the semiconductor substrate, or applying a sufficient amount of adhesive. Adhesion is performed so as not to occur. However, with such a bonding technique, the adhesive sometimes protrudes from the end of the semiconductor substrate. In particular, in an ultrasonic probe in which a plurality of elements are arranged two-dimensionally, the adhesive surface becomes wide, and this becomes remarkable. The adhesive that protrudes to the edge of the semiconductor substrate spreads to the upper surface of the edge of the semiconductor substrate due to its surface tension, and may contaminate the electrode surface to be bonded, and such contamination will cause poor wire bonding connection. Let The same phenomenon tends to occur with respect to the lead terminals of the flexible wiring board, which may cause connection failure in wire bonding.

An object of the present invention is to provide a probe having a configuration in which such an adhesive is prevented from protruding from a semiconductor substrate, a wiring substrate, or the like, and connection failure or the like of wire bonding is unlikely to occur.

In the probe of the present invention, a device substrate on which a plurality of capacitance-type cells are arranged and an end portion having a lead terminal of a wiring substrate that is electrically connected to the outside are mounted on the same support substrate. The electrode pads connected to the cells of the device substrate and the lead terminals of the wiring substrate are electrically connected. At least one groove is provided on the surface of the support substrate, the device substrate is bonded onto the support substrate with an adhesive, and an end portion of the device substrate with the electrode pad is located on the groove. It is characterized by being.

According to the present invention, the adhesive does not flow into the end portion of a device substrate such as a semiconductor substrate, but flows into a groove provided in the support substrate. Similarly, it is possible to prevent the adhesive from entering the end portion of the wiring board where the lead terminal is located. Therefore, it is possible to suppress the contamination of the electrode pad surface of the device substrate and the lead terminal surface of the wiring substrate with the adhesive, thereby enabling good wire bonding and the like.

Sectional drawing of embodiment of the probe by this invention. The top view of FIG. Sectional drawing of another embodiment of a probe. Sectional drawing of the Example of a probe. Sectional drawing of another Example of a probe. The figure explaining the application | coating conditions of DA material, and DA material drawing pattern. The figure explaining the subject at the time of the excess and deficiency state by the application | coating conditions of DA material. The figure which shows the groove processing state of a support substrate. The figure which shows the subject information acquisition apparatus containing the probe of this invention.

In the probe of the present invention, at least one groove is provided on the surface of the support substrate to prevent the adhesive from entering the end of the device substrate such as a semiconductor substrate, and there is an electrode pad of the device substrate. The end is located on the groove.

Hereinafter, embodiments and examples of the probe of the present invention and the manufacturing method thereof will be described.
(Embodiment 1)
FIG. 1 shows a semiconductor substrate 1 which is a device substrate on which CMUTs or capacitive cells are formed and a flexible wiring substrate (FPC) 4 which is an external wiring substrate are mounted on the same supporting substrate according to the first embodiment. The cross section of a probe is shown. FIG. 2 shows an example in which electrode wiring from an element (ultrasonic sensor unit) 8 made of a plurality of CMUTs is arranged for connection as an electrode pad 7 at an end of the semiconductor substrate 1. As the semiconductor substrate 1, a Si crystal substrate is used, and a CMUT is formed by a fine processing technique used in micromachining.

Such a semiconductor substrate 1 is bonded to a support substrate 2 in order to connect to the flexible wiring substrate 4. As the support substrate 2, a normal PCB substrate such as FR4, a glass substrate, or a Si substrate can be used, but is not limited thereto. The support substrate 2 is provided with at least one groove 3. When one groove 3 is provided at a position for wire bonding (indicated by Au wire 6), or as shown in FIG. 3, the end of the semiconductor substrate 1 and the end of the lead terminal 5 of the flexible wiring board 4 are provided. It can also be provided at each incoming location. The size of the groove 3 can be appropriately determined by a wire bonding loop, but is usually in the range of several hundred μm to several millimeters. The cross-sectional shape of the groove 3 is generally rectangular, but is not limited thereto. Even if the side wall portion of the groove 3 is tapered or curved depending on the processing method, there is no problem.

The method of grooving is appropriately selected depending on the material of the substrate. For example, a PCB substrate such as FR4 can be grooved by router or dicing. In the case of a glass substrate, the groove can be formed by half-cutting with a dicer, etching, sandblasting, or the like. FIG. 8 shows an example of the support substrate 2 in a grooved state. An adhesive is applied to the grooved support substrate 2. As the adhesive, an adhesive called a die attach (DA) material is often used, but the adhesive is not limited thereto. Solventless adhesives such as epoxy resins, acrylic resins, and silicon resins can also be used. Among them, adhesives that do not contaminate the bonding pads, such as epoxy resin systems, are preferable.

The adhesive is applied after defoaming by a vacuum stirring defoaming machine or the like before application. Thereby, mixing of bubbles, such as air, into the adhesive can be suppressed. When installing a semiconductor substrate or flexible wiring board on the support substrate, the adhesive is applied to the entire grounding surface of the support substrate, and the application amount or discharge amount and application pattern so that no wetted parts are left. Is set. The application amount is managed as follows. As shown in FIG. 7, there are cases (a-1), (b-1), and (c-1) as the application state. (A-1) is a case where the coating amount is too small, and as shown in (a-2), a gap (gap part due to lack of DA material) 11 is formed under the device substrate. When the air gap 11 is applied to the sensor unit 8, acoustic mismatch occurs, and ultrasonic waves are easily reflected, so that the sensor signal is deteriorated. In addition, when a gap is formed under the bonding pad 7 in the electrode connection portion, ultrasonic energy during wire bonding may be relaxed and bonding may be impossible. This corresponds to the region (A) in FIG. 6A, which shows the discharge amount condition based on the relationship between the discharge pressure and the discharge amount.

Next, in the case of (c-1) in FIG. 7, in contrast to (a-1), a case where the coating amount is too large is shown. In this case, the DA material 12 oozes out to the region Lfpc where the FPC 4 is originally bonded, and the FPC bonding becomes impossible (see (2) of (c-2)). In addition, when the DA material viscosity decreases during the DA material curing process, the DA material 13 crawls up to the surface of the device substrate, that is, the bonding pad, by surface tension, contaminates the electrode, and wire bonding is performed. It may become impossible. This corresponds to the area (C) in FIG.

Although an appropriate amount of DA material is applied in an appropriate pattern as shown in Fig. 7 (b-1), in consideration of process variations, DA material is immersed in the bonding area Lfpc of FPC4. Projection is expected (see (1) in (b-2)). Further, although the amount of oozing is small, the creeping of the adhesive onto the device substrate surface cannot be completely eliminated. Therefore, the groove 3 which is a feature of the present invention is formed in order to absorb the leaching portion. In order to realize the state of (b-1) in FIG. 7, it is necessary to manage the discharge amount of the dispenser, and it is necessary to take characteristic data as shown in the region (B) of FIG. 6 (a).

This data is determined by the dispenser discharge pressure, the ambient temperature, and the DA material viscosity. Although the former two can be controlled, the viscosity of the DA material continues to increase slightly with time even within the shelf life, so it is necessary to correct the characteristic line each time. It is necessary to adjust the discharge amount on the assumption that the slope of the straight line shown in FIG.

As described above, the semiconductor substrate 1 is aligned and grounded so that the end of the electrode pad 7 side is located on the region of the groove 3 of the support substrate with respect to the support substrate 2 to which the adhesive is applied. . In many cases, pressing is performed after grounding, but it is not always necessary to apply pressure. By thermally curing after grounding, the viscosity of the adhesive temporarily decreases, and the entire semiconductor substrate is automatically filled with surface tension, and the semiconductor substrate 1 is bonded. In the semiconductor substrate 1 bonded in this way, since the excess adhesive at the end flows into the groove 3 side, the adhesive extends from the end to the surface side of the semiconductor substrate due to surface tension, and the electrode Contamination of the pad 7 is suppressed. Therefore, the wire 6 is not welded at the time of wire bonding performed thereafter, and it is possible to suppress a connection failure. (D-1) and (d-2) in FIG. 7 show this state, and it can be seen that the leached DA material 14 is absorbed into the groove 3.

The same applies when the flexible wiring board 4 is bonded. In the case of a flexible wiring board, since the grounding position is an end of the support substrate 2, it is difficult to apply an adhesive. Therefore, a B-Stage type epoxy adhesive sheet or the like is used as an adhesive. The adhesive sheet is cut in accordance with the region of the adhesive surface, and is temporarily attached to the adhesive region by applying pressure. Next, the flexible wiring board 4 is grounded on the temporarily bonded adhesive sheet, pressure is applied, and the temperature is raised, whereby the adhesive of the adhesive sheet is melted and thermally cured, so that the flexible wiring board 4 and the supporting substrate are obtained. 2 are bonded. Even in such a process, when the adhesive is melted, the adhesive at the end of the flexible wiring board 4 flows into the groove 3, and the adhesive is prevented from creeping up at the end of the wiring board. In this way, the wire 6 is not welded at the time of wire bonding performed thereafter, and connection failure is suppressed.

(Embodiment 2)
FIG. 4 shows a second embodiment in which the support substrate has a sound absorbing function. The sound wave that has propagated to the support substrate of the probe may be reflected at the interface behind the support substrate and returned, thereby reducing the quality of the sound image. For this reason, an acoustic backing material is disposed on the back surface of the support substrate of the probe to absorb or scatter sound waves. As an acoustic backing material, a composite material in which metal particles (for example, tungsten) are dispersed in a sound attenuating soft material such as rubber or plastic is known. In the present embodiment, by using the support substrate 9 having the function of the backing material and forming the groove 3 there, the backing material provided on the back surface of the support substrate can be omitted.

Such a support substrate 9 can be formed by, for example, dispersing metal particles (particles such as tungsten and iron oxide) in an epoxy resin, pouring them into a mold, and curing them. The epoxy resin has sufficient rigidity when cured, and its acoustic characteristics can be changed by dispersing metal particles in the resin. As a metal powder to be applied, it is possible to control a wide range of acoustic impedance by applying a material having a high density such as tungsten. The groove 3 can be easily formed by a mold, but is not limited thereto.

Hereinafter, more specific examples will be described.
Example 1
FIG. 1 is a diagram of an ultrasonic probe according to a first embodiment of the present invention. The semiconductor substrate 1 is a 300 μm thick Si single crystal substrate, on which a capacitive transducer is formed, and signal output lines for 600 channels are connected to the wire bonding pad 7 by 300 channels on two sides in the long side direction. ing. The pad 7 is formed at a position 0.2 mm from the edge in the long side direction of the semiconductor substrate 1 and is arranged to be easily affected by scooping up of an adhesive or the like from the end. The support substrate 2 is made of glass epoxy FR-4 and has a thickness of 1.6 mm. The device substrate of the semiconductor substrate 1 is adhered to the support substrate 2 with a die attach material, and the end of the semiconductor substrate 1 is about 0.3 mm on the groove 3 having a width of 500 microns and a depth of 500 microns formed in advance. It sticks out with the protruding amount.

The adhesive is applied to the support substrate 2 by an application method such as dispenser or transfer printing. The viscosity of the adhesive is appropriately adjusted according to the application method of the adhesive. However, if the viscosity is too high, air and the like are difficult to degas. Therefore, it is preferably as low as possible. Desirably, 1 Pa · s to 50 Pa · s is considered suitable. In this example, 40 Pa · s KIDD SI-03LLF-L adhesive was applied.

In this example, a dispenser SHOTMASTER300 manufactured by Musashi Engineering was used, and an adhesive was applied with a general drawing pattern (DA material drawing portion) 10 as shown in FIG. In this example, a support substrate 2 having a size (a, b) as shown in FIG. At this time, as shown in the area (B) of FIG. 6 (a), the state of (b-1) of FIG. 7 can be realized by controlling the discharge amount of the adhesive to 50 mg to 90 mg, and the immersion at that time It was found that the amount of extraction could be completely absorbed by the 500 μm square groove 3. As a result, it was possible to completely avoid bonding pad contamination due to seepage into the FPC bonding region Lfpc and creeping up onto the device substrate surface ((d-1) and (d-2 in FIG. 7). )reference).

FIG. 5 shows a modified example, and the same thing can be said even when the connection is made with such an ACF (anisotropic conductive film). FIG. 5B is an enlarged view of a part of FIG. As shown in FIG. 5B showing the portion corresponding to the ACF edge touch, the bonding pad 5 of the FPC 4 is electrically connected to the bonding pad 7 on the device chip by the ACF 16. In FIG. 5A, reference numeral 17 denotes an insulating film at the edge of the cover lay for edge touch countermeasures when ACF is applied. Here, the end of the FPC 4 floats from the surface of the support substrate 9 by the thickness of the semiconductor substrate 1. However, even in such a structure, the end of the FPC 4 may be positioned on a region near the groove 3.

(Example 2)
In Example 2, Devcon B of ITW Performance Polymers & Fluids Japan Co., Ltd. was applied as the material for forming the support substrate. This is formed of a two-part epoxy resin, to which iron powder is added. Furthermore, tungsten powder C-30 from Allied Material Co., Ltd. was applied, and 70 phr by weight with a particle size of 2.3 μm was added. These materials are sufficiently stirred and finally subjected to centrifugal defoaming treatment and poured into a mold. Curing is carried out at room temperature for about 12 hours. The mold at this time is configured such that the groove 3 having the same size as that of the first embodiment can be formed.

Thus, the support substrate 9 having both functions as a support substrate and a backing material can be formed by pouring the epoxy resin into the mold and curing at room temperature. Using the support substrate 9 thus obtained, the semiconductor substrate 1 and the flexible wiring substrate 4 can be bonded in the same manner as in Example 1, and the electrode pad 7 and the lead terminal 5 of the flexible wiring substrate can be satisfactorily connected by wire bonding. did it. Further, since the support substrate 9 is formed of a backing material having a sound absorbing effect, a manufacturing process for newly bonding the backing material to the support substrate is not required, and a probe can be easily formed.

(Example 3)
The probe including the capacitive transducer described in the above embodiments and examples can be applied to a subject information acquisition apparatus using acoustic waves. The acoustic wave from the subject is received by the capacitive transducer, and the outputted electrical signal can be used to obtain subject information reflecting the subject's optical characteristic values such as a light absorption coefficient.

FIG. 9 shows an object information acquiring apparatus according to the present embodiment using the photoacoustic effect. The pulsed light 152 generated from the light source 151 that generates light in a pulsed form is irradiated onto the subject 153 via an optical member 154 such as a lens, a mirror, or an optical fiber. The light absorber 155 inside the subject 153 absorbs the energy of the pulsed light and generates a photoacoustic wave 156 that is an acoustic wave. The probe 157 of the present invention receives the photoacoustic wave 156, converts it into an electrical signal, and outputs it to the signal processing unit 159. The signal processing unit 159 performs signal processing such as A / D conversion and amplification on the input electric signal and outputs the signal to the data processing unit 150. The data processing unit 150 acquires subject information (subject information reflecting an optical characteristic value of the subject such as a light absorption coefficient) as image data using the input signal. The display unit 158 displays an image based on the image data input from the data processing unit 150. Note that the probe may be mechanically scanned or may be a handheld type that a user such as a doctor or engineer moves with respect to the subject. Of course, the probe of the present invention can also be used in a subject diagnostic apparatus that detects acoustic waves from a subject to which acoustic waves such as ultrasonic waves are applied. In this case as well, an acoustic wave from the subject is detected by the probe, and the converted signal is processed by the signal processing unit to acquire information inside the subject. Here, an acoustic wave to be transmitted toward the subject can be transmitted from the probe of the present invention.

The probe of the present invention can be applied to an optical imaging apparatus that obtains information in a measurement target such as a living body, a conventional ultrasonic diagnostic apparatus, and the like. Furthermore, it can also be used for other applications such as an ultrasonic flaw detector.

1 .... Semiconductor substrate (device substrate) 2 .... Support substrate (FR-4, resin molding substrate, etc.) 3 .... Groove 4 .... FPC (external wiring board) 5 .... Lead terminal 6 .... Au wire (bonding wire), 7 ... Electrode pad on device substrate, 8 ... Ultrasonic sensor, 9 ... Support substrate with sound absorption function

Claims (6)

A device substrate on which a plurality of capacitance-type cells are arranged and an end portion of the external wiring substrate that is electrically connected to the outside are provided on the same support substrate. A probe in which connected electrode pads and lead terminals of the wiring board are electrically connected,
At least one groove is provided on the surface of the support substrate;
The device substrate is bonded onto the support substrate with an adhesive;
An end of the device substrate having an electrode pad is located on the groove. The probe according to claim 1, wherein the device substrate is a semiconductor substrate, and the external wiring substrate is a flexible wiring substrate. The end portion of the wiring board with the lead terminal is bonded onto the support substrate with an adhesive, and the end portion of the wiring board with the lead terminal is located on any of the grooves. The probe according to 1 or 2. The electrode pad and the lead terminal are electrically connected by wire bonding or anisotropic conductive film (ACF), and the end portion of the wiring board having the lead terminal or the portion corresponding to the ACF edge touch is in the vicinity of the groove. The probe according to claim 1, wherein the probe is located on a region. The probe according to claim 1, wherein the support substrate has a sound absorption function as well as a support function. The probe according to any one of claims 1 to 5,
A light source that generates light;
A signal processing unit for processing a signal output from the probe;
Have
A photoacoustic wave generated by the light emitted from the light source and applied to the subject is received by the probe, and the signal processing unit processes the signal converted into an electrical signal to obtain information on the subject. A subject information acquisition apparatus characterized by acquiring.

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