JPS597233A - Pressure sensor of semiconductor - Google Patents

Abstract

PURPOSE:To decrease the variation of a zero point due to an outer stress by providing a part having smaller diameter or softer quality than that of a seal part at a stem pedestal part at one part at least of an outside lead of an outer surrounding case. CONSTITUTION:For instance, the stem pedestal 3, the lead 11 are formed with, e.g. ''Kovar'' (Fe: 54%, Ni: 29%, Co: 17%), and a hermetic seal part 3b is made of hard glass. The diameters of the lead 11a at the hermetic seal part and the outer lead 11b of the outer surrounding case are regulated to 0.75mm. and 0.45mm. respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to semiconductor pressure sensors, and more particularly to an improvement in the lead of an envelope in an electric semiconductor pressure sensor.

[Technical background of the invention]

An example of a conventional structure of a semiconductor pressure sensor is shown in FIG.

In the figure, (11 is a silicon single crystal strain body part, N
A pressure-receiving diaphragm part (hereinafter referred to as the diaphragm part from 1bX) on the (ioo) surface formed in a concave manner, leaving the peripheral edge (1a) of one principal surface of the silicon single crystal of the mold (!: Boron is applied to this diaphragm part. Strain gauge part (2) of a P-type diffusion layer formed by partial diffusion.

(2) It is equipped with... The pedestal part of the stem (1, 1 has a coefficient of thermal expansion similar to that of silicon) at the peripheral edge so that the diaphragm part (1b) is not in contact with the rest part (1, 1).
3) is sealed with, for example, a silicone rubber layer (4).

With the above configuration, a space (5) is defined by the concave portion of the diaphragm portion and the pedestal portion, and this space is maintained at a predetermined pressure, for example, atmospheric pressure, by the through hole (3a) formed in the pedestal portion. On the other hand, on the opposite (outward) main surface side of the diaphragm is the pressure introduction pipe (6a) of the cap (6) sealed in the pedestal.
) to apply pressure inside the cap. This applied pressure creates a pressure difference on both sides of the diaphragm, resulting in distortion. Here, the piezoresistance effect causes an increase or decrease in the diffusion resistance, and the value is changed to the lead +71, which passes through the pedestal and is barmetically sealed to the pedestal.
71... (hereinafter shown for each lead) is derived and measured. Note that the leads are hermetically sealed with hard glass (3b).

[Problems with background technology]

When a semiconductor pressure sensor is used, its leads are soldered to other peripheral circuitry or inserted into a socket. However, with the conventional structure, as mentioned above, force is applied to the lead or deformation force is applied to the sensor element, making the offset point (commonly known as the zero point) unstable. There is a serious drawback that there are many.

[Object of the Invention] The present invention was made in order to solve the problems of the structure of the conventional semiconductor pressure sensor described above, and reduces the change in the zero point due to external stress applied to the lead.

[Summary of the invention]

The semiconductor pressure sensor according to the present invention includes a diaphragm portion in which one principal surface of a single crystal silicon plate is formed concave except for its periphery, and has a strain gauge portion on the other principal surface, and a member having an expansion coefficient similar to that of silicon. Diaphragm part 1
A stem pedestal sealed at the periphery of the main surface, a cap sealed to the periphery of the stem pedestal and forming an envelope together with the stem pedestal, a pressure introduction pipe provided in the cap, and a stem pedestal. A hermetic seal is installed through the part.
．． The sensor is characterized in that at least a part of the outer lead of the envelope has a smaller diameter or softer part than the seal part in the stem pedestal part. .

[Embodiments of the invention]

Next, the invention will be explained in detail with reference to the drawings regarding the differences from the conventional one for each embodiment.

The pressure sensor shown in Fig. 2 has an improved lead shape, and the stem pedestal (31, IJ-do old 1 is made of, for example, Kovar (Fe: 54tI), Ni: 29%, Co: 1
7'l), and the hermetic seal portion (3b) is made of hard glass. Then, the hermetic seal lead (
The diameter of the outer lead (ttb) of the envelope is 0.45 mm, and the zero point change rate is lower than that of the conventional 0.75 arm diameter. Reduced to 3/3 or less.

Next, the leads shown in Fig. 3 (121 are the hermetic seal part leads (12a) are the same as those on the diagonal in terms of diameter and material, but the outer leads (12b) of the envelope are made of silver wire with a diameter of 0.45 am. They are joined with solder (12c).Although the lead manufacturing process is slightly longer with the opening method, it is slightly more effective in reducing the rate of zero point change than the diagonal embodiment.

The pressure sensor shown in FIG. 4 has a structure in which a hermetic seal portion (13b) for hermetically sealing the lead (ill) is integrally formed with the stem pedestal (03).

The lead sealed here has the same shape as the lead shown in Figure 2. Further, the same effect can be achieved even if the stem pedestal having the above structure has an external lead portion made of copper wire as shown in FIG.

Furthermore, the lead Q41 shown in FIG. Part (14c) has a diameter of 0.45 mm. It goes without saying that this lead can be applied to the stem pedestal 03) shown in FIG. Furthermore, since the connection part of this lead to the circuit is completely the same as that of a conventional IJ-dead, it is advantageous when used by automatic assembly equipment.

Note that this lead can be freely applied regardless of the type of stem.

〔Effect of the invention〕

According to the present invention, the electrical characteristics of a highly sensitive semiconductor pressure sensor prevents the stress generated in the leads when it is attached to circuit wiring or a socket to have an adverse effect such as changing the seventh point of the strain gauge. can now be reduced to a minimum. That is, when the change in the thousand-point point caused by attachment is generally 500 .mu.V, according to the present invention, it can be reduced to 200 .mu.V or less. This is due to the fact that when the leads are arranged in the conventional manner, stress is generated in the leads, and most of the stress is absorbed and reduced by the small-diameter portions of the leads and the soft portions of the leads. This makes it possible to check the characteristics of pressure sensors, solve the problem of deformation of the leads during packaging, and solve the problem of stress caused by later installation at an angle, and has significant advantages such as improved characteristics and yield. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional semiconductor pressure sensor, and FIGS. 2 to 5 are sectional views each showing an embodiment of the present invention. 1 Silicon single crystal strain body part Ih
Pressure receiving diaphragm part 2.2... Strain gauge part (P-type diffusion layer) 3.13
Pedestal portion 3 h, 1.3 b Hermetic seal portion of stem pedestal portion 11, , 12, ] 4
Leads 11a, 12a,
14a Hermetic lead portions 11b, 12b
External lead 14b Lead external circuit connection area Representative Patent attorney Mr. Inoue Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] a pressure receiving diaphragm portion formed into a concave shape on one principal surface of the single crystal silicon plate except for its periphery and having a strain gauge portion on the other principal surface; a stem pedestal sealed at the periphery of the side main surface, a cap sealed to the periphery of the stem pedestal and forming an envelope together with the stem pedestal, and a pressure introduction pipe provided on the cap; In a semiconductor pressure sensor equipped with a lead extending through a stem pedestal part and hermetically sealed to lead out a strain gauge part, at least a part of the lead outside the envelope has a diameter larger than that of the hermetic seal part in the stem pedestal part. A semiconductor pressure sensor characterized by having a small or soft part.