JPS5829858B2 - pressure sensitive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pressure sensitive device using a pressure sensitive element such as an MO8 type transistor.

Conventionally, an MO8 type transistor chip is fixed to a lever member made of an elastic member, and stress is transferred to the MO8 transistor chip through the lever member.
A pressure-sensitive device has been proposed that applies voltage to an 8-type transistor chip.

In this case, the MO8 type transistor chip is buttoned to the resin layer for the purpose of passivation, but the spring constant of this resin layer (expressed as the product of Young's modulus and the cross-sectional secondary cement) is that of the MO8 type transistor chip. It is usually smaller than the

In such a pressure sensitive device, the stress to be sensed by the MO8 type transistor chip is transmitted from the lever member to the MO8 type transistor chip via the adhesive layer. It is preferable that the adhesive strength between one member be large and uniform in order to achieve highly sensitive and highly accurate pressure sensing.

However, the transistor chip is small (usually 1
71gl13 or less), it is currently difficult to bond uniformly and firmly without variation.For this reason, the pressure-sensitive characteristics of the above-mentioned pressure-sensitive devices are not necessarily good, and their uniformity is not sufficient. I can't say that.

In order to solve this kind of problem, it is possible to make the chip thinner so that the transistor chip can easily follow the deformation of the lever member, but this would require less chip handling during the manufacturing process. Another problem arises in that the manufacturing yield of pressure sensitive devices is significantly reduced.

An object of the present invention is to provide a pressure-sensitive device with good pressure-sensitive characteristics that can be manufactured easily with high yield.

One of the features of this invention is that the pressure sensitive element chip is embedded in a sealed body having a larger spring constant than the pressure sensitive element chip.

For example, an MO8 type transistor chip is embedded as a pressure-sensitive element in a sealed body made of a highly hard epoxy resin, and the sealed body itself is formed into a lever shape.

In a pressure-sensitive device configured in this way, external stress can be effectively transmitted to the pressure-sensitive element chip via the lever-shaped sealing body, so the pressure-sensitive characteristics are greatly improved. Improved.

That is, since the spring constant of the pressure sensitive element chip is smaller than that of the sealed body, it easily deforms following the deformation of the sealed body, making it possible to sense pressure with high sensitivity and precision.

Furthermore, since the pressure-sensitive element chip is not bonded to the lever member as in the conventional method, variations in pressure-sensitive characteristics due to variations in adhesive strength are eliminated.

In this regard, variations in the composition of the sealing material and in the curing conditions can be considered as possible variations in the practice of the present invention, but these can be easily avoided by improving the accuracy of the weighing method and curing conditions.

Furthermore, another advantage of the present invention is that the pressure-sensitive element chip can be made thicker, making it easier to handle the chip.
One point that can be cited is that the manufacturing yield is improved.

Next, preferred embodiments of the invention will be described with reference to the accompanying drawings.

FIGS. 1 and 2 show an MO8 according to an embodiment of the present invention.
2 shows a pressure-sensitive device using type transistors, and the cross section taken along line 1-1 in FIG. 2 corresponds to the cross section in FIG.

In these figures, a pressure sensitive element chip 14 made of an MO8 type transistor is fixed to the surface of an elongated metal support plate 10 by an adhesive layer 12.

The MO8 type transistor constituting the pressure-sensitive element chip 14 is manufactured using, for example, single-crystal silicon as a base material using a known technique.

Adhesive layer 12 for adhering the pressure sensitive element 14 to the support plate 10
As the material, a known organic adhesive, solder, or a brazing material such as gold-silicon alloy can be used.

By the way, as mentioned above, since the chips 14 are generally small, it is extremely difficult to adhere them with uniform adhesive force and with little variation. Even more difficult is the need to consider the uniformity of the image.

MO8 type transistor operates as a pressure sensitive element 1
A stress of 07 (1 yne/cyy!) or more is required, and in the structure shown in FIGS. 1 and 2, a corresponding tensile force or compressive force acts on the chip 14.

Bonding that has a uniform resistance against such a large amount of force is even more difficult because the chip is small.

According to the invention, such difficulties in adhesion are effectively eliminated by the use of a sealing body 16 with a large spring constant.

In other words, in carrying out the present invention, the quality and uniformity of the adhesion between the chip 14 and the support plate 10 are of no importance.

That is, according to the present invention, the chip 14 is placed on the support plate 10.
After adhering to the chip 14 and the support plate 10, the chip 14 and the support plate 10 are embedded in a seal 16 having a higher spring constant than either of them.

Specifically, the chip 14 and the support plate 10 are molded and formed using a highly hard epoxy resin as shown in the figure.

In this case, the wire 20 is connected to the corresponding electrode of the chip 14, and the tip of the wire 18 is also molded.

Thereafter, a suitable hardening treatment is performed to obtain a mechanically strong sealing body 16.

Variations in the mechanical strength of the sealing body 16 can be reduced by increasing the accuracy of the resin composition and curing conditions, which is much easier than making the adhesive force uniform.

In order to operate the pressure-sensitive device according to the present invention having the above-described structure, one end of the sealing body 16 is fixed, and a force F is applied to the other end.
is added to make the sealing body 16 stiffer.

Then, the chip 14 and the support plate 10, which have a smaller spring constant than the sealing body, easily deform following the deformation of the sealing body 16.

The channel of the MO8 type transistor in the chip 14 is stressed by this, so its channel resistance (
The drain resistance (drain resistance) changes equilaterally, and an amplified output corresponding to this resistance change is generated.

It is clear that the device layer 12 has essentially no involvement in such an operating mechanism, and it is understood that the quality and uniformity of adhesion is not an issue in this invention.

Therefore, when the chip 14 is face-bonded to the leads 18, the support plate 10 (and the adhesive layer 12) may be omitted.

Note that in the above device, it is clear that the passivation effect on the pressure-sensitive element chip 14 is improved by forming the sealing body 16 thickly.

FIG. 3 shows a pressure-sensitive device according to another embodiment of the present invention, and when buttons are pressed in FIG. 1 or 2, the same reference numerals indicate the same or corresponding parts.

The features of the pressure sensitive device of this example are, firstly, that recesses 22a and 22b are provided on the upper and lower surfaces of the sealing body 16 so that the sealing body 16 is easily deflected near the chip 14;
In order to facilitate the deformation of the elastic member 6, an elastic member 24 is fixed to one main surface of the elastic member 24. Thirdly, in order to facilitate the fixation of the elastic member 24 and the sealing body 16, they are fixed to one end of each. The point is that a fixing hole 26 that passes through is provided.

By firmly fixing one end of the sealing body 16 in this manner and making the sealing body 16 easily deformable in response to the stress F applied to the elastic member 24, the pressure-sensitive element chip 14
The sensitivity and accuracy of detecting the pressure of the transistor inside the chip can be further increased.

As shown in FIG. 3, the elastic member 24 may also be embedded within the sealing body 16, thereby further increasing the effects of the present invention.

Although this invention has been described in detail above, this invention is not limited to the above-mentioned embodiments, and can be implemented in various modified forms.

For example, the pressure sensitive element is not limited to an MO8 type transistor (generally an insulated gate field effect transistor), but other pressure sensitive transistors, pressure sensitive diodes, semiconductor piezoresistive pressure sensitive elements, etc. can be used.

Further, the shape of the sealing body 16 is not limited to a lever shape or an elongated shape, but may be other shapes such as a tire frame shape.

The main advantages of this invention are as follows.

(1) Since the pressure-sensitive element chip is embedded in the sealed body so that stress is applied to the chip by deformation of the sealed body, the pressure-sensitive characteristics are improved and are not affected by the quality or variation of adhesion.

(2) Since thicker semiconductor chips can be used, manufacturing becomes easier and yields are improved.

(3) The thick hermetic body can also be used for the purpose of passivation of the semiconductor chip, thus improving the stability and reliability of the pressure sensitive element.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a pressure-sensitive device according to an embodiment of the present invention, FIG. 2 is a top view of the pressure-sensitive device whose cross section taken along line I-I is shown in FIG. 1, and FIG. FIG. 2 is a sectional view showing a pressure sensitive device according to another embodiment of the invention. Explanation of symbols, 10...Support plate, 12...
・Adhesive layer, 14...Pressure sensitive element chip, 16...
...Sealed body, 18...Lead.

Claims (1)

[Scope of Claims] 1. A pressure-sensitive element chip, and a sealed body that directly surrounds and seals this chip, is formed into a plate shape, and has a spring constant larger than that of the chip, A pressure-sensitive device characterized in that the chip is configured to detect stress according to deflection in the thickness direction. 2. In the pressure-sensitive device according to claim 1, at least one main surface of the sealing body is likely to be bent at a portion corresponding to the buried position of the pressure-sensitive element chip. A pressure-sensitive device characterized by having a recessed portion for 3. In the pressure sensitive device according to claim 1 or 2, on one main surface of the sealing body or inside thereof,
A pressure-sensitive device characterized by being equipped with an auxiliary elastic member for transmitting stress to the sealing body and facilitating deformation of the sealing body due to the stress. 4. In the pressure sensitive device according to claim 3, the fixed end of the sealing body is provided with a mounting hole that penetrates the sealing body and the auxiliary elastic member. Features a pressure-sensitive device.