JPS6349174B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to semiconductor pressure transducers. A semiconductor pressure transducer converts the pressure of gas, liquid, etc. into an electrical signal using a semiconductor strain gauge such as a silicon diaphragm. A schematic longitudinal cross-sectional view of the structure is shown in FIG. In FIG. 1, a silicon diaphragm 2 to which a lead wire 1 is connected is fixed to a post 4 via a glass stand 3. The silicon diaphragm 2, the glass stand 3, and the post 4 are each bonded by a method such as an anodic bonding method. The anodic bonding method allows the two to be bonded without using an adhesive. In this case, it is necessary that the thermal expansion coefficients of the members to be joined be similar, that there be no airtight leakage from the joint, that the adhesive strength be high, and that the amount of residual strain after joining is small. . Conventionally, borosilicate glass (for example, Pytx Glass 7740, manufactured by Corning Works), which has a coefficient of thermal expansion similar to that of silicon, has been used for the glass stand, and the post material can be bonded to borosilicate glass using an anodic bonding method. Huani alloy (Fe-42%Ni
(completely annealed) is used. Since this Furni alloy has a transition point around 320°C, anodic bonding is performed at around 300°C. However, as shown in the thermal expansion characteristics of Pyrex glass and Furni alloy shown in FIG. 2, the coefficient of thermal expansion of Furni alloy is considerably larger than that of Pyrex glass at around 300°C. (Example 5 in the figure relates to an example of the present invention, which will be described later.) Therefore, large strains remain in the Pyrex glass after bonding, and not only the characteristics as a pressure transducer cannot be obtained, but also the residual There is a problem that strain acts on the glass as tensile stress, causing Pyrex glass to break. Therefore, this type of bonding has drawbacks such as airtight leakage from the bonded surface and low bonding strength, so it cannot be used with high reliability as a post material for semiconductor pressure transducers that require high precision. I couldn't do it. In addition, when finishing the joint surface before post-joining, the completely annealed Fe-42%Ni alloy is soft and sticky, resulting in sagging on the end face, resulting in poor processing yields and a long time required for finishing. . It is an object of the present invention to solve the problems of the prior art described above, and to provide a semiconductor converter having a post that has a small difference in thermal expansion coefficient from borosilicate glass, is suitable for anodic bonding, and has a high finishing yield. be. The inventors focused on the fact that the expansion coefficient of Fe-Ni alloys changes greatly depending on the amount of Ni, and
In addition to measuring the thermal expansion coefficient of the alloy, we also conducted anodic bonding experiments with Pyrex glass. As a result, the average coefficient of thermal expansion of the post material in the temperature range from room temperature to the bonding temperature with the glass stand is
It has been found that it is sufficient to set the coefficient of thermal expansion to 95 to 105% of the average coefficient of thermal expansion of the glass constituting the glass stand in this temperature range. That is, generally Pyrex glass 7740
The average coefficient of thermal expansion between 30 and 300℃ is 35×10 ^-7 /℃, whereas the average coefficient of thermal expansion between 30 and 300℃ of the post material is 33×10 ^-7 to 37×10 ^-7 /°C was found to cause almost no residual strain in the Pyrex glass. The present invention was made based on such knowledge, and the average coefficient of thermal expansion of the post material constituting the post in the temperature range from room temperature to the bonding temperature is the same as that of the glass constituting the glass stand in the temperature range. The average coefficient of thermal expansion is 95 to 105%. The average thermal expansion coefficient between room temperature and bonding temperature of 30 to 300 degrees Celsius is within the above range, and Ni is 37.5 to 37.5 degrees Celsius.
It is 41.5wt% (weight%). If the amount of Ni deviates from the above composition range, the difference in thermal expansion coefficient between the glass and the glass will increase, resulting in residual strain in the glass after bonding.
Accuracy as a pressure transducer cannot be obtained. Furthermore, the glass may break after bonding, which is inappropriate. Further, in this case, cold working with a working degree of 30% or more is performed, and then stress relief annealing is performed at a temperature of 200 to 600°C. Cold working increases hardness and improves processing accuracy. As a cold working method, rolling, wire drawing, extrusion, swaging, etc. can be adopted, but the working degree is 30
%, as shown in Figure 3, 30~
The average coefficient of thermal expansion at 300°C becomes large, which is undesirable. Considering workability, etc., a processing degree of 40 to 80% is preferable. Note that FIG. 3 relates to a post material having the same composition as the post material according to Example 6, which will be described later. The appropriate stress-relieving annealing temperature after processing is 200 to 600°C. If the temperature is lower than 200°C, the annealing effect will be insufficient and the post material will be deformed during joining, which is unsuitable. Furthermore, if annealing is performed at a temperature higher than the recrystallization temperature of 625°C, the effect of cold working will be lost, so it is preferable to perform annealing at a temperature lower than 600°C. Figure 4 shows annealing (900℃,
1h) (A), and (B) which was further subjected to cold working (working degree 60%) and stress relief annealing (400°C, 330mm) as in the present invention.
This figure shows the relationship between the average coefficient of thermal expansion between room temperature and 300°C and the amount of nickel. There is no correlation between the coefficient of thermal expansion and the amount of nickel, and the coefficient of thermal expansion changes significantly by cold working and stress relief annealing. Further, the following amounts of elements added as deoxidizing and desulfurizing agents and elements mixed during production are preferable. C is necessary as a strong deoxidizing agent to improve the cleanliness of the material, but as its content increases, the coefficient of thermal expansion increases, so it is preferable to keep C at 0.1% or less. Si is also used as a deoxidizing agent, but as its content increases, toughness decreases, so it is preferably kept at 0.5% or less. Mn is used as a desulfurizing agent, but as the content increases, the coefficient of thermal expansion increases, so it is preferably 2.0% or less. P,S
decreases the toughness of the material, so the amount of (P+S)
It is preferable to keep it below 0.01%. Incidentally, when a post using such a post material is bonded to borosilicate glass (Pyrex 7740, manufactured by Corning Works) by an anodic bonding method, the temperature is preferably 280 to 300°C. Figure 2 shows the thermal expansion coefficient (Δl/l) of the post material of Example 5, which will be described later.
However, the post material according to the present invention has a temperature of approximately 300°C.
It has a coefficient of thermal expansion close to that of Pyrex 7740, making it suitable for anodic bonding. Also, the junction temperature is approximately
When the temperature is lower than 270°C, the ability of the glass to behave as an electrolyte decreases, and the bonding time becomes longer and the bonding strength decreases. Examples of the present invention will be described below. Examples 1 to 6, Comparative Examples 1 and 2 28 kg of iron and nickel were melted in a high frequency vacuum melting furnace to obtain alloys having the compositions shown in Examples 1 to 6 and Comparative Examples 1 and 2 in Table 1. After hot forging, we annealed at 900℃ for 1 hour, then cold drawn to a diameter of 5.0mm to create a wire rod with a workability of 60%.
Annealed at 400℃ for 30mm. Table 1 shows the measurement results of the thermal expansion coefficient. A post was fabricated using this alloy, and a glass stand and silicon diaphragm were bonded together to fabricate a semiconductor pressure transducer. Comparative Example 3 An alloy having the composition shown in Comparative Example 3 in Table 1 was produced by melting 28 kg of iron and nickel in a high-frequency melting furnace, and then hot forging and annealing at 900°C for 1 hour. Note that this corresponds to a conventional post material. The measurement results of this thermal expansion coefficient are shown in Table 1. A post was fabricated using this alloy, and a glass stand and silicon diaphragm were further bonded to fabricate a semiconductor pressure transducer.

[Table] From Table 1, 30~ of the post materials of Examples 1 to 6
The percentage ratio of the average coefficient of thermal expansion between 300℃ and the average coefficient of thermal expansion between 30 and 300℃ of Pyrex glass is within the range of 95 to 105%, and the Ni content is 37.5 to 41.5wt%. If the coefficient of thermal expansion exceeds the above range, it is recognized that the coefficient of thermal expansion deviates from the above range. Posts for semiconductor pressure transducers were manufactured using the post materials of Examples 1 to 6 and Comparative Examples 1 to 3, and
When bonded to Pyrex glass 7740 at 300°C, the posts of Comparative Examples 1 to 3 often broke the glass, resulting in poor bonding, or had large residual strains, making them unsuitable for use in pressure transducers. On the other hand, the posts according to Examples 1 to 6,
The glass did not break at all, the amount of helium leaked from the joint was less than 10 ¹⁰ atmc.c./S, and complete airtightness was maintained, and the joint was strain-free, making it possible to manufacture a high-precision pressure transducer. . In addition, the adhesive strength of the pressure-receiving part of the semiconductor pressure transducers manufactured using the post materials of Examples 1 to 6 was greater than the breaking strength of the silicon diaphragm, and the rate of non-defective adhesive strength was 90% or more, which was higher than that of conventional materials. The adhesion yield was significantly improved compared to the non-defective rate of 30% or less. Furthermore, in the post manufacturing process, by using the post material of the example, the finishing machining time is reduced by half compared to the conventional method, and the machining accuracy is improved and the machining yield is 99%. Improved. As described in detail above, the semiconductor pressure transducer according to the present invention has excellent bonding properties between the post and the glass stand, high processing accuracy of the post, and high reliability.

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional configuration diagram of a semiconductor pressure transducer, Fig. 2 is a diagram showing the coefficient of thermal expansion of the Fany alloy, Pyrex glass, and the post material according to Example 5, and Fig. 3 is a diagram showing the coefficient of thermal expansion of the post material according to Example 5. 30~300℃ for post material
It is a figure which shows the relationship between the average coefficient of thermal expansion between and the degree of processing. FIG. 4 is a characteristic diagram showing the relationship between the amount of nickel and the coefficient of thermal expansion in an iron-nickel alloy. 2...Diaphragm, 3...Glass stand, 4...
post.

Claims (1)

[Claims] 1. A semiconductor pressure transducer including a semiconductor strain gauge, a post, and a glass stand made of borosilicate gas bonded to the semiconductor strain gauge and the post, wherein the post has a nickel content.
Consisting of 37.5-41.5% by weight iron-nickel alloy,
Moreover, the alloy can be cold-worked with a working degree of 30% or more and 200~
Stress relief annealing is performed at a temperature of 600℃,
The average coefficient of thermal expansion in the temperature range from room temperature to the bonding temperature between the post and the glass stand is 95% of the average coefficient of thermal expansion of the glass in the temperature range.
A semiconductor pressure transducer characterized in that it has ~105%.