JP2002310829A - Semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor pressure sensor improved in airtightness holding characteristic. SOLUTION: This semiconductor pressure sensor comprises a semiconductor chip for converting the pressure change of a measuring medium to an electric signal, a resin case for housing the semiconductor chip, a lead terminal drawn out of the resin case and integrally molded therewith, and a connecting member for electrically connecting the semiconductor chip to the lead terminal. The resin case is formed of a thermosetting resin, and the difference between the average linear expansion coefficient from ordinary temperature to post-cure temperature of the thermosetting resin and the linear expansion coefficient of a metal material constituting the lead terminal is set to 3 ppm/ deg.C or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor, and more particularly, to a structure of a resin case for housing a semiconductor chip.

[0002]

2. Description of the Related Art A conventional semiconductor pressure sensor is, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-186104, in a resin case in which flat lead terminals are integrally molded and a concave storage portion is provided at the bottom on the opening side. A semiconductor chip that converts a pressure into an electric signal and a chip chip joined to a glass base are fixed to the recess with a silicone adhesive, the lead terminals and the semiconductor chip are wire-bonded, and the chip and the wire are covered with a silicone gel. What has been known is known.
Further, in a conventional semiconductor pressure sensor, a thermoplastic resin such as polyphenylene-sulfide (PPS) is used as a resin case material.

[0003]

In a conventional semiconductor pressure sensor, when the opening of the resin case is connected to the introduction pipe of the medium to be measured and the pressure is measured accurately, it is important to keep the resin case airtight. When a resin case is molded with a thermoplastic resin such as PPS, the metal lead terminal and the resin do not chemically bond with each other, so they do not adhere to each other, and it is difficult to completely maintain airtightness of the resin case. was there. Also, it is possible to avoid the occurrence of minute gaps between the resin and the lead terminals due to curing shrinkage of the resin during molding and thermal stress between different kinds of members generated when the resin is cooled from the mold temperature to room temperature (20 ° C.). However, there is a problem that it is difficult to completely maintain the airtightness of the resin case.

On the other hand, when a thermosetting resin such as an epoxy resin is used, a resin having a OH group is synthesized by a first-stage reaction between the resin and a curing agent during molding, and a substance having an OH group is synthesized and is present on the lead terminal metal surface. The oxide film reacts with the OH groups to generate hydrogen bonds. Post-curing is performed to promote the second-stage reaction for stably bonding the resin, and hydrogen bonding is promoted during this post-curing. The post-curing temperature is generally around 175 ° C., and the glass transition temperature of the epoxy resin is usually lower than the post-curing temperature. When the temperature exceeds the glass transition temperature, the coefficient of linear expansion of the resin increases, so that the thermal displacement also increases. Therefore, when the temperature of the joint between the metal lead terminal and the resin is larger than the hydrogen bonding force when the temperature is returned to room temperature after the post-curing, interface separation occurs, and it is difficult to completely maintain airtightness. There was a problem. Also, even if it is kept airtight at the beginning, if a thermal shock test or the like is performed, thermal stress repeatedly occurs at the resin and lead terminal interface,
Interfacial peeling sometimes occurred due to fatigue.

An object of the present invention is to provide a semiconductor pressure sensor having improved airtightness.

[0006]

(1) In order to achieve the above object, the present invention provides a semiconductor chip for converting a pressure change of a medium to be measured into an electric signal, a resin case for accommodating the semiconductor chip, In a semiconductor pressure sensor having a lead terminal drawn out of the resin case to the outside and integrally formed, and a connecting member for electrically connecting the semiconductor chip and the lead terminal, the resin case is made of a thermosetting resin. A thermosetting resin in which the difference between the average linear expansion coefficient between the room temperature and the post-curing temperature of the thermosetting resin and the linear expansion coefficient of the metal material constituting the lead terminal is within 3 ppm / ° C. It was made. With this configuration, the airtightness of the semiconductor pressure sensor can be improved.

(2) In the above (1), preferably,
The thermosetting resin has a glass transition temperature lower than the post-curing temperature and a linear expansion coefficient of 8 to 12 ppm / ° C. below the glass transition temperature.

(3) In the above (1), preferably,
The thermosetting resin constituting the resin case is made of an epoxy resin containing at least spherical fused silica, and the metal material constituting the lead terminal is made of a copper-based alloy.

(4) In the above (1), preferably,
A convex bent portion is provided in a part of the lead terminal buried in the resin layer.

(5) In the above (1), preferably,
A rough surface is provided on a part of the upper and lower portions of the roll processing surface of the buried portion in the resin layer of the lead terminal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a semiconductor pressure sensor according to a first embodiment of the present invention will be described below with reference to FIGS. First, the configuration of the semiconductor pressure sensor according to the present embodiment will be described with reference to FIGS.
FIG. 1 is a sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a first embodiment of the present invention. FIG. 2 is a plan view of FIG.

The semiconductor chip 1 shown in FIGS. 1 and 2 is made of silicon. The semiconductor chip 1 is formed in a concave shape by etching or the like on the lower surface of a central portion, and a thin diaphragm 2 is formed in the central portion.

A pressure detecting circuit (not shown) is formed integrally with the diaphragm 2 on the upper surface of the semiconductor chip 1 by a semiconductor process. The pressure detection circuit is composed of four diffusion resistors formed on the diaphragm 2 and is wired to a bridge with an aluminum conductor.

A characteristic compensation circuit and a protection circuit (not shown) are integrally formed in a peripheral portion other than the diaphragm on the upper surface of the semiconductor chip 1 by a semiconductor process. The characteristic compensation circuit is composed of a digital / analog hybrid circuit that adjusts the relationship between pressure and output to a predetermined transfer function. The digital / analog hybrid circuit stores and holds the characteristic adjustment signal.
A digital section having a PROM and an analog section for amplifying a signal are mainly configured. The characteristic adjustment signal is an adjustment value such as a coefficient value for adjusting each characteristic obtained at the time of zero-span adjustment, sensitivity adjustment, and temperature characteristic adjustment. The protection circuit is a circuit that protects input / output signals provided at input / output stages connected to the outside from electromagnetic noise and the like. The pressure detection circuit, the characteristic adjustment circuit, and the protection circuit are electrically connected to each other by an aluminum conductor or the like.

The semiconductor chip 1 is joined to the glass table 3 by anodic bonding or the like. The semiconductor chip 1 and the glass base 3 constitute a chip box. A vacuum chamber 4 is provided between the lower surface of the diaphragm 2 of the semiconductor chip 1 and the upper surface of the glass base 3. The glass table 3 is made of borosilicate glass glass or the like, and has a coefficient of linear expansion substantially equal to that of the semiconductor chip 1.

The resin case 5 is made of, for example, an epoxy resin (A). The epoxy resin (A) has a spherical silica content of 85%, a glass transition temperature of 156 ° C., a linear expansion coefficient of 11.8 ppm / ° C. below the glass transition temperature, a linear expansion coefficient of 53.3 ppm / ° C. above the glass transition temperature, and the like. Has physical properties. After injection molding or transfer molding, the epoxy resin (A) is post-cured at 175 ° C.
° C).

The lead terminal 6 is made of phosphor bronze and has a physical expansion coefficient of 17 ppm / ° C. Lead terminal 6
Is formed by press-molding a hoop material pre-plated with nickel, and is integrally molded with the resin case 5 by insert-molding with an epoxy resin (A).

At the bottom of the resin case 5 on the side of the opening, a recessed chip receiving portion 7 is provided. One end of the lead terminal 6 is disposed around the portion where the chip comb is provided, and is drawn out through the resin case 5. Semiconductor chip 1
And a glass base 3 are bonded and fixed to the concave portion of the resin case 5 by using a silicone adhesive 8. The electrodes of the semiconductor chip 1 are connected to the lead terminals 6 with aluminum wires 9 by bonding.

Semiconductor chip 1 disposed in resin case 5
And the exposed portions of the lead terminal 6, the silicone adhesive 8, and the aluminum wire 9 are covered by injecting and curing a fluorosilicone-based or fluorine-based silicone gel 10. The silicone gel 10 transmits pressure to the semiconductor chip 1 and prevents a corrosive medium from contacting and damaging the semiconductor chip 1, the lead terminals 6, the silicone adhesive 8, and the aluminum wires 9.

The sensor unit 11 is configured as described above. The epoxy resin (A) used in the present embodiment has an average linear expansion coefficient from room temperature of 20 ° C. to a post cure temperature of 175 ° C. of 16.9 ppm / ° C., and a linear expansion coefficient of phosphor bronze constituting the lead terminal 6. Therefore, unnecessary thermal stress does not occur on the hydrogen bonding surface between the resin and the lead terminal, and peeling does not occur.

In addition, since the coefficient of linear expansion below the glass transition temperature of the epoxy resin (A) is as small as 11.8 ppm / ° C., thermal displacement when the resin shrinks toward the center of the thick portion is small, The hydrogen bonding surface between the lead terminal and the lead terminal does not peel off.

The present inventors evaluated the hermetic sealing performance between the lead terminals 6 of the resin case 5 according to the present embodiment.
After attaching a resin cap having a pressure introducing tube (not shown) to the opening of the resin case 5, the absolute pressure of 1
When 3 KPa was applied and held for 30 seconds, the amount of pressure fluctuation caused by airtight leakage was measured. The initial amount of leakage was zero.

In order to evaluate the durability performance of the hermetic sealing, 1000 cycles of a thermal shock test of −40 ° C. (30 minutes) →→ 130 ° C. (30 minutes) / cycle were performed. The amount of pressure fluctuation due to the leak was similarly zero.

Therefore, the present inventors similarly formed a resin case 5 of the following epoxy resins (B) to (G) shown in Table 1 in addition to the epoxy resin (A) by molding. An airtight leak was evaluated. The epoxy resins (B) to (G) shown in (Table 1) all contain an inorganic filler, and at least 50% or more of the total resin amount is composed of spherical fused silica. . However, since the content of the fused silica is different, there are differences in the physical property values shown in (Table 1). In Table 1, Tg is the glass transition temperature, α1 is the coefficient of linear expansion below the glass transition temperature, α2 is the coefficient of linear expansion above the glass transition temperature, and the average coefficient of linear expansion is between the post-cure temperature of 175 ° C and room temperature of 20 ° C. The average linear expansion coefficient is shown. The average coefficient of linear expansion can be determined using the coefficient of linear expansion at a post cure temperature of 175 ° C and the coefficient of linear expansion at a normal temperature of 20 ° C.

[0025]

[Table 1]

Next, referring to FIG. 3, the epoxy resin (A)
A description will be given of the results of measuring the airtight leakage pressure fluctuation amount of the resin case 5 molded using (G). FIG. 3 is an explanatory diagram of the measurement result of the airtight leakage pressure fluctuation amount of the semiconductor pressure sensor according to the first embodiment of the present invention. In FIG.
The horizontal axis is the average coefficient of linear expansion of the epoxy resin (ppm / ° C)
The vertical axis indicates the airtight leak pressure fluctuation value (KPa).

As shown in FIG. 3, epoxy resin (A),
In (B) and (C), no airtight leakage occurred. On the other hand, epoxy resins (D), (E),
In (F) and (G), an airtight leak has occurred. Therefore, looking at the range in which no airtight leakage occurs, the average linear expansion coefficient of the epoxy resin is 14 to 20.
It turned out that it is enough if it is in the range of ppm / ° C. This range corresponds to a linear expansion coefficient of the lead terminal 6 of 17 ppm / ° C. (phosphor bronze).
It was found to be within 7 ppm / ° C. ± 3 ppm / ° C. That is, the average linear expansion coefficient of the epoxy resin,
Linear expansion coefficient of lead terminal 6 17 ppm / ° C ± 3 ppm /
It can be seen that airtight leakage does not occur when the temperature is within the range of ° C.

As described above, according to the present embodiment, the average coefficient of linear expansion is equal to the coefficient of linear expansion of the lead terminal 6 (1).
By using an epoxy resin within a range of ± 3 ppm / ° C. with respect to (7 ppm / ° C.), airtight leakage does not occur. Therefore, the airtightness can be improved as compared with the related art.

Next, the configuration of the semiconductor pressure sensor according to the second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a second embodiment of the present invention. FIG. 5 is a plan view of FIG. 1 and 2 denote the same parts.

In the present embodiment, all the terminals are provided with a convex bending portion 12 on the roll-worked surface of the lead terminal 6 buried in the epoxy resin layer. The bent portion 12 is formed by extruding the lead terminal 6 by the thickness of the lead terminal 6. The convex bent portion 12 of the lead terminal 6 increases the contact area with the epoxy resin and at the same time acts as an anchor with respect to the peripheral resin, so that the airtightness is more improved as compared with a lead terminal composed of only a flat surface. improves.

According to this embodiment, the airtightness can be further improved.

Next, the configuration of a semiconductor pressure sensor according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a third embodiment of the present invention. 1 and 2 denote the same parts.

In the present embodiment, an uneven portion 13 having a maximum surface roughness of 20 to 80 μm is provided in the hatched portion of the roll processing surface of the buried portion of the lead terminal 6 in the epoxy resin layer. The uneven portion 13 is formed by a mold transfer method. Similarly, the uneven portion 13 of the lead terminal 6 increases the contact area with the epoxy resin, and at the same time, acts as an anchor to the peripheral resin, so that the airtightness of the lead terminal 6 is lower than that of the lead terminal composed of only a flat surface. Better.

According to the present embodiment, the airtightness can be further improved.

[0035]

According to the present invention, the hermeticity of the semiconductor pressure sensor can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is an explanatory diagram of a measurement result of an airtight leakage pressure fluctuation amount of the semiconductor pressure sensor according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a second embodiment of the present invention.

FIG. 5 is a plan view of FIG. 4;

FIG. 6 is a sectional view showing a configuration of a sensor unit state of a semiconductor pressure sensor according to a third embodiment of the present invention.

[Explanation of Signs] 1 ... Semiconductor chip 2 ... Diaphragm 3 ... Glass table 4 ... Vacuum chamber 5 ... Resin case 6 ... Lead terminal 7 ... Recessed chip storage part 8 ... Silicon adhesive 9 ... Aluminum wire 10 ... Silicone gel 11 ... Sensor Unit 12: Bending part 13: Uneven part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiko Kikuchi, Inventor 2477 Takaba, Hitachinaka-shi, Ibaraki Inside Sawa Service Co., Ltd. (72) Inventor Hoshishi Eguchi 2520, Ojitakaba, Hitachinaka-shi, Ibaraki Hitachi, Ltd. Within the Automotive Equipment Group (72) Inventor Katsumichi Kamiyanagi 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Kazunori Saito 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture No. Fuji Electric Co., Ltd. (72) Inventor Yoshiyasu Ashino 1-1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture F-term (reference) 2F055 AA40 BB01 CC02 DD05 DD11 EE13 FF38 GG12 GG25 4M112 AA01 BA01 CA02 CA08 CA12 CA13 CA28 DA13 DA18 EA02 EA13 EA14 FA06

Claims (5)

[Claims] 1. A semiconductor chip for converting a pressure change of a medium to be measured into an electric signal, a resin case for housing the semiconductor chip, a lead terminal drawn out of the resin case and integrally formed; In a semiconductor pressure sensor having a chip and a connecting member for electrically connecting the lead terminals, the resin case is made of a thermosetting resin, and the average linear expansion coefficient between the room temperature and the post-curing temperature of the thermosetting resin. And a thermosetting resin having a difference between a linear expansion coefficient of a metal material constituting the lead terminal and a linear expansion coefficient of 3 ppm / ° C. or less. 2. The semiconductor pressure sensor according to claim 1, wherein the thermosetting resin has a glass transition temperature lower than a post cure temperature and a linear expansion coefficient of 8 to 12 ppm / ° C. below the glass transition temperature. A semiconductor pressure sensor characterized by the above-mentioned. 3. The semiconductor pressure sensor according to claim 1, wherein the thermosetting resin forming the resin case is made of an epoxy resin containing at least spherical fused silica, and the metal material forming the lead terminal is a copper alloy. A semiconductor pressure sensor, comprising: 4. The semiconductor pressure sensor according to claim 1, wherein a convex bent portion is provided in a part of the lead terminal buried in the resin layer. 5. The semiconductor pressure sensor according to claim 1, wherein a rough surface is provided on a part of the upper and lower portions of the roll processing surface of the buried portion of the lead terminal in the resin layer.