JP2005233889A - Sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain defective sensor characteristics from being generated by falling-down impact, in an acceleration sensor having a stacked structure layered with a sensor chip on a circuit chip via a film-like silicone-based adhesive. <P>SOLUTION: In this sensor device S1 provided with the circuit chip 3 having a bonding part 3a, and the sensor chip 5 for detecting an acceleration layered on the bonding part 3a in the circuit chip 3, the circuit chip 3 is bonded to the sensor chip 5 via the film-like silicone adhesive 4, and the thickness of the adhesive 4 is 100 μm or smaller. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sensor device in which a sensor chip is laminated on a circuit chip via a film adhesive.

  Conventionally, this type of sensor device includes a circuit chip having a bonding portion and a sensor chip laminated on the bonding portion of the circuit chip, and the circuit chip and the sensor chip are interposed via a film adhesive. Adhesive acceleration sensors and angular velocity sensors have been proposed (see, for example, Patent Document 1).

Such an acceleration sensor and an angular velocity sensor employ a stack structure in which sensor chips are stacked on a circuit chip as a technique for reducing the mounting area for cost reduction. In particular, in a high-sensitivity acceleration sensor having a low acceleration range used for vehicle control, a silicone-based film adhesive is used for bonding the circuit chip and the sensor chip.
JP 2003-21647 A

  By the way, in the sensor device described above, the reason why the silicone-based film adhesive is used for joining the circuit chip and the sensor chip is to relieve thermal stress from below the chip such as a package.

  However, conventional silicone-based film adhesives have only a thickness of about 175 μm, for example. Thus, when the silicone-based film adhesive is thick, according to the inventor's study, the sensor chip may move and be displaced at the time of a drop impact of the sensor device, resulting in poor sensor characteristics. all right.

  For example, if the sensor chip moves as the sensor device falls, if the bonding wire is connected to the sensor chip, the wire connection part will deteriorate, such as deformation of the wire, and the sensor characteristics will fluctuate. May occur.

  Therefore, in view of the above problems, the present invention suppresses sensor characteristic failure due to a drop impact in a sensor device having a stack structure in which a sensor chip is laminated on a circuit chip via a silicone-based film adhesive. The purpose is to improve the tolerance.

  In order to achieve the above object, according to the first aspect of the present invention, a circuit chip (3) having a bonding portion (3a) and a sensor chip (3) laminated on the bonding portion (3a) in the circuit chip (3). 5), the circuit chip (3) and the sensor chip (5) are bonded via a silicone-based film adhesive (4), and the thickness of the adhesive (4) is , 100 μm or less.

  The present invention has been found experimentally as a result of studies conducted by the present inventors. By making the thickness of the silicone-based film adhesive (4) 100 μm or less, Sufficient drop tolerance can be obtained (see FIG. 2).

  Therefore, according to the present invention, in the sensor device having a stack structure in which the sensor chip (5) is laminated on the circuit chip (3) via the silicone-based film adhesive (4), the sensor characteristics are poor due to the drop impact. In other words, the drop resistance can be improved.

  Here, in the sensor device according to claim 1, when considering the allowance for drop resistance, the thickness of the adhesive (4) may be 50 μm or less as in the invention according to claim 2. preferable.

  According to a third aspect of the present invention, in the sensor device according to the first or second aspect, the bonding wire (6) is electrically connected to the sensor chip (5). Yes.

  Thus, when it is set as the structure by which the bonding wire (6) is electrically connected to the sensor chip (5), by exhibiting the effect of the invention of the above-described claim 1 or claim 2, Defectives such as the sensor chip (5) moving due to the drop impact and the bonding wire (6) being deformed can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an acceleration sensor S1 as a sensor device according to an embodiment of the present invention. This acceleration sensor S1 can be used, for example, for driving control by being mounted on an automobile.

  In FIG. 1, a ceramic package 1 serves as a base part of a sensor S1 and is used to attach the sensor S1 to an appropriate position of a measurement object. A circuit chip 3 is mounted and fixed on the ceramic package 1 via a liquid adhesive 2 made of silicone resin.

  In a preferred embodiment, in this example, the adhesive 2 is mixed with beads 2a made of resin or the like for making the thickness of the adhesive 2 uniform and the height of the circuit chip 3 uniform. That is, this bead 2a functions as a spacer.

  On the upper surface of the circuit chip 3, a bonding portion 3 a which is a region for mounting the sensor chip 5 is provided, and the sensor chip 5 is interposed in the bonding portion 3 a through a silicone-based film adhesive 4. Are stacked.

  The sensor chip 5 is configured as a detection element that performs acceleration detection. For example, the sensor chip 5 forms a beam structure having a generally known comb-tooth structure with respect to a silicon substrate or the like, and is movable in accordance with the applied acceleration. The capacitance change (electric signal) between the electrode and the fixed electrode can be detected.

  Further, as the circuit chip 3, a MOS transistor, a bipolar transistor, or the like is formed on a silicon substrate or the like using a known semiconductor process, and functions such as processing and outputting an electric signal of the sensor chip 5. What has is employable.

  The sensor chip 5 and the circuit chip 3 and the circuit chip 3 and the ceramic package 1 are electrically connected through bonding wires 6 and 7 made of gold, aluminum, or the like, respectively.

  Thus, the electrical signal (capacitance change) from the sensor chip 5 is sent to the circuit chip 3 and converted into a voltage signal by a C / V conversion circuit or the like provided in the circuit chip 3 so as to be output as an acceleration signal. It has become.

  Here, the silicone film adhesive 4 for adhering the sensor chip 5 to the circuit chip 3 has a thickness of 100 μm or less, preferably 50 μm or less. In addition, the lower limit of the thickness of the film-like adhesive 4 is preferably about 25 μm or more from the viewpoints of manufacturing restrictions for processing into a film and securing of adhesive strength.

  Such a sensor S1 can be manufactured as follows. First, the adhesive 2 is applied to the ceramic package 1, the circuit chip 3 is assembled through the adhesive 2, and the adhesive 2 is cured. Here, as described above, it is preferable that the adhesive 2 is previously mixed with beads 2a and the like for making the thickness of the adhesive 2 uniform and the height of the circuit chip 3 uniform.

  Next, the sensor chip 5 is assembled, and there are two methods. For example, after a film-like adhesive 4 is attached to a wafer to be a sensor chip, a dicing cut is performed with the film-like adhesive 4 attached, and the divided sensor chip 5 is picked up to obtain a circuit chip. 3 is a method of mounting on top.

  As another method, a wafer to be a sensor chip is diced and cut into sensor chips 5, while the film adhesive 4 is cut to the size of the sensor chip 5. And it is the method of mounting on the circuit chip 3 in order of the film adhesive 4 and the sensor chip 5.

  In this embodiment, since the sensor chip 3 is mounted on the bonding portion 3a of the circuit chip 3 using the film adhesive 4 instead of the liquid adhesive, the liquid adhesive is used. It is possible to prevent contamination of the circuit chip 3 due to bleeding of low molecular weight components (that is, bleeding).

  Specifically, the contamination of the circuit chip 3 due to the bleed is a deterioration in wire bonding connectivity due to contamination of the bonding pad portion around the bonding portion 3a by the low molecular weight component.

  After assembling the sensor chip 5 on the circuit chip 3 with the film-like adhesive 4 on the circuit chip 3 by one of the methods described above, the adhesive force of the film-like adhesive 4 is stabilized by performing the main curing (curing). Make it highly durable.

  Thereafter, bonding wires 6 and 7 are formed by performing wire bonding using a wire such as gold or aluminum. Thus, the acceleration sensor S1 is completed.

  Here, in this embodiment, the basis for the fact that the thickness of the silicone-based film adhesive 4 for adhering the sensor chip 5 to the circuit chip 3 is 100 μm or less, preferably 50 μm or less will be described.

  This is based on the result of the investigation on the relationship between the thickness of the film-like adhesive 4 and the drop resistance, which was performed by the inventor as shown below. FIG. 2 is a diagram illustrating an example of the investigation result.

  In FIG. 2, the horizontal axis indicates the film thickness (unit: μm) as the thickness of the film-like adhesive 4, and the vertical axis indicates the drop resistance (unit: cm). Here, the sensor device S1 in which the thickness of the film adhesive 4 was changed was produced as a sample, and each sample was dropped from a predetermined height onto a hard surface such as concrete. The direction of dropping was a triaxial direction.

  Then, the height of the drop, that is, the drop withstand capability was changed, and the presence or absence of a defect in sensor characteristics such as deformation of the bonding wire 6 due to the movement of the sensor chip 5 accompanying the drop was investigated. In FIG. 2, a case where a sensor characteristic failure occurs is represented by an “X” plot, and a case where the failure does not occur is represented by a “◯” plot.

  Here, if the drop resistance is 60 cm, it is practically sufficient. In other words, if the sensor characteristics do not fail when the drop height is 60 cm, it can be said that a sufficient drop resistance is practically secured.

  As shown in FIG. 2, it was found that the relationship between the thickness of the film-like adhesive 4 and the drop resistance is substantially linear. Here, when the thickness of the film adhesive 4 is 175 μm, which is a conventional level, the drop resistance is only about 40 cm.

  And in order to ensure 60 cm which is a target drop tolerance, it turns out that the thickness of the film adhesive 4 should just be 100 micrometers or less. Further, when the thickness of the film-like adhesive 4 is 50 μm, the drop resistance is 80 cm, and considering the margin, the thickness of the film-like adhesive 4 is preferably about 50 μm or less. I can say that.

  Therefore, from the examination results as shown in FIG. 2, in this embodiment, the thickness of the film adhesive 4 in the sensor device S1 is set to 100 μm or less, preferably 50 μm or less.

  As described above, according to this embodiment, in the sensor device S1 including the circuit chip 3 having the bonding portion 3a and the sensor chip 5 stacked on the bonding portion 3a in the circuit chip 3, the circuit chip 3 and the sensor chip 5 are bonded to each other via a silicone-based film adhesive 4, and the thickness of the adhesive 4 is 100 μm or less, thereby providing a sensor device S 1.

  As shown in the examination result of FIG. 2 described above, by setting the thickness of the silicone-based film adhesive 4 to 100 μm or less, a practically sufficient drop resistance can be obtained. Further, as described above, when considering the allowance for drop resistance, the thickness of the adhesive 4 is preferably 50 μm or less.

  Therefore, according to the present embodiment, in the sensor device having a stack structure in which the sensor chip 5 is laminated on the circuit chip 3 via the silicone-based film adhesive 4, the sensor characteristic failure due to the drop impact is suppressed. That is, the drop resistance can be improved.

  In the present embodiment, the bonding wire 6 is electrically connected to the sensor chip 5.

  Thus, when it is set as the structure by which the bonding wire 6 is electrically connected to the sensor chip 5, the sensor chip 5 moves by a drop impact by exhibiting the effect of this embodiment mentioned above appropriately, Thereby, defects such as deformation of the bonding wire 6 can be suppressed.

  In this embodiment, the sensor chip 5 is bonded and fixed on the circuit chip 3 via the silicone film adhesive 4, but this adhesive 4 has a low elasticity and a very soft property. ing.

  Therefore, the thermal stress from the ceramic package 1, the adhesive 2, and the circuit chip 3 can be sufficiently relaxed by the film-like adhesive 4 interposed between the chips 3 and 5. That is, in the present embodiment, it is possible to suppress the characteristic variation of the sensor chip 5 due to the thermal stress from the lower circuit chip 3 as much as possible, which is preferable.

(Other embodiments)
As described above, the acceleration sensor has been described as an example of the sensor device of the present invention. However, the present invention is not limited to the acceleration sensor, and can be applied to an angular velocity sensor, a pressure sensor, a temperature sensor, and an optical sensor. .

  That is, in the sensor device S1 shown in the embodiment, the sensor chip 5 may be an angular velocity detection element, a pressure detection element, a temperature detection element, or a light detection element.

  The circuit chip may be anything such as a circuit using a MOS transistor or a bipolar transistor, a memory circuit, or the like.

  In short, the present invention includes a circuit chip having a bonding part, and a sensor chip as a sensing part laminated on the bonding part in the circuit chip, and the circuit chip and the sensor chip are made of a silicone-based film adhesive. In the sensor device that is bonded via the film, the main part is that the thickness of the film adhesive is regulated to 100 μm or less, and the other parts can be appropriately changed in design.

It is a schematic sectional drawing which shows the acceleration sensor as a sensor apparatus which concerns on embodiment of this invention. It is a figure which shows an example of the investigation result about the relationship between the thickness of the film-form adhesive agent and drop tolerance which the inventor performed.

Explanation of symbols

3 ... Circuit chip, 3a ... Bonding part of circuit chip, 4 ... Film adhesive,
5 ... sensor chip, 6 ... bonding wire.

Claims (3)

A circuit chip (3) having a bonding part (3a);
In the sensor device comprising the sensor chip (5) laminated on the bonding part (3a) in the circuit chip (3),
The circuit chip (3) and the sensor chip (5) are bonded via a silicone-based film adhesive (4),
The thickness of the said adhesive agent (4) is 100 micrometers or less, The sensor apparatus characterized by the above-mentioned. The sensor device according to claim 1, wherein a thickness of the adhesive (4) is 50 μm or less. 3. The sensor device according to claim 1, wherein a bonding wire (6) is electrically connected to the sensor chip (5).

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