JP2005114476A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high reliability pressure sensor in which a bonding wire has little risk of breaking. <P>SOLUTION: This pressure sensor 1 comprises by combining a sensor unit 30 and a resin case 40, with the sensor unit 30 comprising a pressure-sensitive element 20 disposed therein and a pressure introduction path 30 formed therein for introducing a pressing medium toward the element 20. The resin case 40 comprises a lead frame 10 disposed therein and electrically connected to the element 20 via a bonding wire 21. The lead frame 10 comprises bonding pad parts 12, each forming a substantially planate pad surface 120 for thereto jointing the bonding wire 21, bent end parts 131 formed by folding down the pad parts 12, and engagement parts 13 disposed in the end parts 131 and structured so as to restrict the movement of the pad surface in the thickness direction by being engaged with the resin case 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure sensor including a pressure sensitive element electrically connected to a lead frame via a bonding wire.

Conventionally, there is a pressure sensor in which a lead frame made of a conductive metal or the like and a pressure sensitive element are electrically connected via a bonding wire (see, for example, Patent Document 1). As a method for bonding a bonding wire to a lead frame or the like, for example, wire bonding in which the lead frame and the bonding wire are welded by ultrasonic vibration of a bonding head positioned so as to sandwich the bonding wire with the lead frame. There is a joining method.
However, the conventional pressure sensor has the following problems. That is, for example, when a resin case in which the lead frame is disposed is manufactured by insert molding, the resin portion undergoes thermal shrinkage due to a temperature difference between the insert molding and the insert molding, and the bonding pad portion at the end of the lead frame is There is a possibility that it is not completely fixed to the resin case. And, when wire bonding is performed by ultrasonic bonding (bonding bonding) to such a bonding pad portion, the ultrasonic wave cannot be satisfactorily applied due to insufficient fixing state of the bonding pad portion, There is a risk of bonding failure of the bonding wire.
Further, for example, when the pressure sensor is used as an automobile part, the bonding pad portion vibrates due to the vibration of the vehicle, and the vibration may be transmitted to the lead frame. When the lead frame vibrates, there is a risk of troubles such as disconnection of the bonding wire even if the initial bonding state is not defective.

JP-A-6-186104 JP 2003-50175 A

  In view of the conventional problems, the present invention is intended to provide a highly reliable pressure sensor that is less likely to cause a bonding wire to break.

The present invention provides a sensor unit in which a pressure sensing element is disposed and a pressure introduction path for introducing a pressure medium toward the pressure sensing element is formed, and the pressure sensing element is electrically connected to the pressure sensing element via a bonding wire. In a pressure sensor that is combined with a resin case formed by insert molding a plate-like lead frame connected to
The lead frame has a bonding pad portion formed with a substantially planar pad surface for bonding the bonding wire;
A bent end portion bent from the bonding pad portion;
And an engaging portion configured to restrict movement in the thickness direction on the pad surface by engaging with the resin case. It exists in a pressure sensor (Claim 1).

The pressure sensor of the present invention includes the lead frame including the engagement portion that engages with the resin case. In the lead frame, the engagement portion is formed at the bent end portion which is bent from the bonding pad portion and is disposed adjacent to the bonding pad portion. Therefore, according to this engagement part, the movement of the thickness direction in the said pad surface which is the surface of the said bonding pad part can be controlled effectively. Therefore, in the pressure sensor, for example, there is little risk of vibration or the like occurring in the bonding pad portion when bonding or using the pressure sensor.
Therefore, according to the bonding pad portion, it is possible to reliably apply ultrasonic waves during bonding and bond the bonding wires with high reliability. Furthermore, according to the bonding pad portion, there is little risk of vibration even when the pressure sensor is vibrated, and troubles such as disconnection of the bonding wire bonded to the bonding pad portion can be prevented in advance. it can.
As described above, the pressure sensor of the present invention is an excellent quality sensor in which the reliability of the bonding wire is improved by suppressing the fear of bonding failure of the bonding wire and disconnection of the bonding wire.

In the present invention, it is preferable that the engaging portion has a first restriction surface facing the front surface side of the pad surface and a second restriction surface facing the back surface side of the pad surface. ).
In this case, a molding surface (appropriately described as a resin molding surface) made of the synthetic resin formed along the first regulation surface and the resin molding surface along the second regulation surface are contacted. In the engaging portion, the movement of the pad surface in the thickness direction is effectively restricted.
Therefore, it is possible to restrict the movement of the bent end formed by the engagement portion and the bonding pad portion adjacent to the bent end, and therefore, in the pad surface which is the surface of the bonding pad portion, The movement in the thickness direction can be suppressed.

Therefore, in manufacturing the pressure sensor, the ultrasonic wave is reliably applied by suppressing the movement of the pad surface when ultrasonic bonding is performed while pressing the bonding wire toward the bonding pad portion. High bonding can be achieved.
In addition, it is preferable that the said 1st and 2nd control surface is formed with the surface substantially parallel with respect to the said pad surface. In this case, the movement of the pad surface in the thickness direction is effectively suppressed by the contact between the first and second restricting surfaces and the resin molding surface formed along these restricting surfaces. Can do.
Furthermore, the first and second regulating surfaces may be flat or curved. In the case where the first and second regulating surfaces are curved surfaces, the angle formed between the surface formed by the local region of these regulating surfaces and the pad surface may be substantially parallel.

The bent end portion is preferably embedded in the resin case (claim 3).
In this case, the bent end portion embedded in the synthetic resin forming the main body of the resin case functions as an anchor. Therefore, the lead frame and the bonding portion can be more firmly fixed and the movement of the pad surface can be suppressed by the operation effect as the anchor of the bent end portion in addition to the operation effect by the engagement portion.

Further, it is preferable that the engaging portion is an engaging hole drilled in the bent end portion, and the first restricting surface and the second restricting surface are each a part of an inner peripheral surface of the engaging hole ( Claim 4).
In this case, the movement of the bonding pad portion can be reliably suppressed by the engagement between the molding resin filled in the hole and the hole as the engagement portion.

(Example 1)
In this example, as shown in FIG. 1, a pressure sensitive element 20 is arranged, and a sensor unit 30 having a pressure introduction path 300 for introducing a pressure medium toward the pressure sensitive element 20 and a bonding wire are provided. 21 is an example related to a pressure sensor 1 formed by combining a resin case 40 made of a synthetic resin in which a lead frame 10 electrically connected to the pressure sensitive element 20 via 21 is insert-molded. This content will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the lead frame 10 includes a bonding pad portion 12, a bent end portion 131, and an engaging portion 13.
The bonding pad portion 12 is a portion formed by forming a substantially planar pad surface 120 to which the bonding wire 21 is bonded. The bent end portion 131 is a portion bent from the bonding pad portion 12. The engaging portion 13 is a portion that is disposed at the bent end 131 and is configured to restrict movement in the thickness direction of the pad surface 120 by engagement with the resin case 40.
This will be described in detail below.

  As shown in FIGS. 3 and 4, the sensor unit 30 is formed by combining a stem 32 having the through hole 320 and a pedestal portion 31 on which the pressure sensitive element 20 is disposed. The stem 32 is a member including a cylindrical portion 321 having a substantially cylindrical shape and a plate portion 322 having a large-diameter flange shape formed at one end portion of the cylindrical portion 321. The pedestal 31 includes an element layer 311 made of the silicon substrate for forming the pressure sensitive element 20 and a base layer 312 made of a silicon material, and a glass layer (not shown) having excellent electrical insulation. It is the member formed by laminating and joining. On the surface of the base layer 312 corresponding to the end surface in the stacking direction of the pedestal portion 31, an introduction hole drilled so as to penetrate the glass layer and the base layer 312 toward the sensor diaphragm of the pressure-sensitive element 20 formed in the element layer 311. 310 is opened. The sensor unit 20 of this example is formed by joining a pedestal portion 31 to the end surface of the plate portion 322 of the stem 32. In the sensor unit 20, the pressure introduction hole 300 is formed by communication between the through hole 320 of the stem 32 and the introduction hole 310 of the pedestal portion 31.

As shown in the figure, the pressure-sensitive element 20 of this example has a sensor diaphragm (not shown) formed by precisely etching the silicon substrate on the silicon substrate on which the element layer 311 is formed, and a silicon layer. This is an element formed with a strain gauge (not shown). The pressure-sensitive element 20 is configured to measure the pressure generated by measuring the strain generated in the sensor diaphragm by the applied pressure with the strain gauge. The pressure sensitive element 20 has a plurality of electrode pads 210 as electrode terminals, and is configured to be able to supply power and output signals through the electrode pads 210.
The pressure sensitive element 20 is not limited to the pressure sensitive element of this example formed by etching a silicon substrate, and other pressure resistance effect elements whose electrical resistance value changes in accordance with the applied pressure. Etc. can also be used.

  As shown in FIGS. 5 and 6, the resin case 40 is a resin in which a set of seven lead frames 10 cut out from a flat plate member made of a general lead frame material and bent into a predetermined shape is insert-molded. It is a molded product. The resin case 40 is a member having a housing hole 41 having a substantially rectangular cross section for housing the pedestal portion 31 of the stem 30 and a recess 42 in which the plate portion 322 of the stem 30 is disposed. The resin case 40 is configured to fix the plate portion 322 to the concave portion 42 in a state where the pedestal portion 31 is disposed in the accommodation hole 41 (FIG. 1).

  As shown in FIG. 6, each lead frame 10 is arranged from the outer peripheral portion of the resin case 40 toward the accommodation hole 41 and has two exposed portions exposed on the surface of the resin case 40. Yes. One exposed portion disposed on the outer peripheral portion of the resin case 40 forms an external terminal 14 for electrical connection with an external device such as an external power source. The other exposed portion arranged along the accommodation hole 41 forms a bonding pad portion 12 that forms a pad surface 120 for bonding and bonding the other end of the bonding wire 21 bonded to the pressure sensitive element 20. ing.

As shown in FIGS. 7 and 8, each lead frame 10 is substantially perpendicular to the pad surface 120 at a portion disposed on the pressure-sensitive element 20 (FIG. 1) side adjacent to the bonding pad portion 12. It has a bent end portion 131 that is bent into a bent shape. The bent end 131 is provided with an engagement hole 130 as the engagement portion 13.
As shown in FIG. 9, the resin case 40 is configured such that a bent end portion 131 is embedded in a synthetic resin constituting the main body. Therefore, in the state where the lead frame 10 is insert-molded, the inside of the engagement hole 130 is filled with synthetic resin. Therefore, in the resin case 40 of the present example, a surface of the inner peripheral surface of the engagement hole 130 that is substantially parallel to the pad surface 120 and faces the surface of the pad surface 120 forms the first restriction surface 135. . A surface of the inner peripheral surface of the engagement hole 130 that is substantially parallel to the pad surface 120 and faces the back surface of the pad surface 120 forms a second restriction surface 136.

  According to the contact between the first restriction surface 135 and the resin molding surface formed along the first restriction surface 135, the movement of the bent end 131 toward the surface side of the pad surface 120 can be restricted. it can. Further, according to the contact between the second restriction surface 136 and the resin molding surface formed along the second restriction surface 136, the movement of the bent end portion 131 toward the back side of the pad surface 120 is restricted. be able to. In the resin case 40 of this example in which the movement of the bent end portion 131 of the lead frame 10 is restricted by the combination of the first restricting surface 135 and the second restricting surface 136, the bonding pad portion 12 adjacent to the bent end portion 131 is used. As for the pad surface 120 forming the surface, the movement in the thickness direction is effectively suppressed.

  As shown in FIGS. 1 and 2, the pressure sensor 1 of this example is configured so that the corresponding bonding pad portion 12 is disposed adjacent to each electrode pad 210 of the pressure-sensitive element 20 of the sensor unit 30. is there. The electrode pad 210 of the pressure sensitive element 20 and the bonding pad portion 12 of the lead frame 10 are electrically connected via the bonding wire 21. The electrode pad 210 and the bonding pad portion 12 are bonded to the end portion of the bonding wire 21 using a well-known wire bonder device (not shown).

As described above, in the resin case 40 constituting the pressure sensor 1 of this example, each lead frame 10 has the bent end portion 131 in which the engagement portion 13 (engagement hole 130) is disposed embedded in the synthetic resin. Has been.
Therefore, in the resin case 40, the movement of the bent end portion 131 in the insertion / extraction direction is caused by the contact between the engagement portion 13 and the resin molding surface formed along the first and second restriction surfaces 135 and 136. It can be effectively suppressed. In the lead frame 10 in which the movement of the bent end portion 131 is restricted, the movement in the thickness direction of the pad surface 120 that forms the surface of the bonding pad portion 12 adjacent to the bent end portion 131 can be reliably suppressed. .

Therefore, when performing the ultrasonic bonding while pressing the bonding wire 21 toward the pad surface 120 of the bonding pad portion 12, the movement of the pad surface 120 such as sinking and lifting is suppressed, and the ultrasonic vibration is good. Can be efficiently applied for bonding. Furthermore, when using the pressure sensor 1 of this example, even if the pressure sensor 1 is vibrated, vibrations generated in the bonding pad portion 12 can be suppressed, and troubles such as disconnection of the bonding wire 21 can be prevented. can do.
As shown in FIG. 10, instead of embedding the bent end portion 131, the shape of the resin case 40 is changed so that the bent end portion 131 is arranged along the outer surface of the resin case 40. You can also According to the resin case 40 molded so that the molding resin is filled in the engagement hole 130 formed in the bent end portion 131, the same operation effect as this example can be obtained.

(Example 2)
This example is an example in which the shape of the lead frame 10, in particular, the shape of the bent end 131 embedded in the resin portion is changed based on the pressure sensor of the first embodiment. The contents of this example will be described with reference to FIGS.
As shown in FIG. 11, as the engaging portion 13, a key portion 132 that is folded back so as to be substantially parallel to the pad surface 120 can be formed at the tip of the bent end portion 131. Of the surface of the key part 132, a surface substantially parallel to the pad surface 120 forms the first and second restricting surfaces 135 and 136, and a contact with the resin molding surface formed along these restricting surfaces 135 and 136. By the contact, the movement of the pad surface 120 in the thickness direction can be effectively restricted. Therefore, according to the said key part 132, it can substitute for the engagement hole of Example 1, and also if it combines with the said engagement hole, the effect of Example 1 can further be heightened.

  In addition, as shown in FIG. 12, a thickness changing portion 133 can be formed as a part of the bent end portion 131 as the engaging portion 13. Of the surface of the bent end portion 131, the surface forming the portion where the thickness changes is the first and second restricting surfaces 135 and 136, and the resin molding surface formed along these restricting surfaces 135 and 136; By this contact, the movement of the pad surface 120 in the thickness direction can be effectively restricted. Therefore, according to the thickness changing portion 133, the engagement hole can be substituted, and further, the effect of the first embodiment can be further enhanced by combining with the engagement hole.

Furthermore, as shown in FIG. 13, the bent end portion 131 itself bent so as to form an angle of about 45 degrees (the angle indicated by R in the drawing) with respect to the bonding portion 12 functions as the engaging portion 13. It is also possible to configure. In this case, of the surface of the bent end 131 as the engaging portion 13, a surface that forms approximately 45 degrees with the pad surface 120 forms the first and second restricting surfaces 135 and 136, and these restricting surfaces 135, The movement of the pad surface 120 in the thickness direction can be effectively restricted by the contact with the resin molding surface formed along 136. Therefore, according to the bent end portion 131, the engagement hole can be substituted. Further, when combined with the engagement hole, the function and effect of the first embodiment can be further enhanced.
Other configurations and operational effects are the same as those in the first embodiment.

Sectional drawing which shows the cross-section of the pressure sensor in Example 1. FIG. FIG. 3 is a top view showing a pressure sensor in the first embodiment. FIG. 3 is a cross-sectional view illustrating a cross-sectional structure of the sensor unit in the first embodiment. FIG. 3 is a top view showing the sensor unit in the first embodiment. Sectional drawing which shows the cross-section of the resin case in Example 1. FIG. FIG. 3 is a top view showing a resin case in the first embodiment. FIG. 3 is a front view showing a lead frame in the first embodiment. FIG. 3 is a cross-sectional view taken along line AA showing the cross-sectional shape of the lead frame in Example 1. FIG. 3 is an enlarged view showing the vicinity of the engaging portion of the lead frame in the first embodiment. FIG. 3 is an enlarged view showing the vicinity of the engaging portion of another lead frame in the first embodiment. FIG. 9 is an enlarged view showing the vicinity of an engaging portion of a lead frame 1 in Embodiment 2. FIG. 9 is an enlarged view showing the vicinity of the engaging portion of the lead frame in Example 2. FIG. 9 is an enlarged view showing the periphery of an engaging portion of a lead frame part 3 in Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pressure sensor 10 Lead frame 12 Bonding pad part 120 Pad surface 13 Engagement part 130 Engagement hole 131 Bending end part 135 1st regulation surface 136 2nd regulation surface 132 Key part 133 Thickness change part 20 Pressure sensitive element 21 Bonding wire 30 Sensor unit 40 Resin case

Claims (4)

A sensor unit in which a pressure sensing element is disposed and a pressure introduction path for introducing a pressure medium toward the pressure sensing element is formed, and a plate electrically connected to the pressure sensing element through a bonding wire In a pressure sensor that is combined with a resin case with an insert-shaped lead frame,
The lead frame has a bonding pad portion formed with a substantially planar pad surface for bonding the bonding wire;
A bent end portion bent from the bonding pad portion;
And an engaging portion configured to restrict movement in the thickness direction on the pad surface by engaging with the resin case. Pressure sensor.   2. The pressure sensor according to claim 1, wherein the engaging portion includes a first restricting surface facing the front surface side of the pad surface and a second restricting surface facing the back surface side of the pad surface. .   3. The pressure sensor according to claim 1, wherein the bent end is embedded in the resin case.   The engagement portion according to any one of claims 1 to 3, wherein the engagement portion is an engagement hole perforated in the bent end portion, and the first restriction surface and the second restriction surface are inner circumferences of the engagement holes, respectively. A pressure sensor characterized by being a part of a surface.

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