JPS62148828A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To avert the stress concn. to a silicon pedestal and to prevent the cracking or breakdown of the silicon pedestal by connecting a metallic stem and can be using a solder brazing filler metal. CONSTITUTION:Lead tin solder 21 is used as the brazing filler metal and the metallic stem 3 is connected to a windowed cap 7 by said solder. More specifically, the lead tin solder is molded to an annular shape and the molded solder is placed on a collar part 3a of the metallic stem 23; further the windowed cap 7 is put thereon. The solder is then melted in a vacuum by using IR rays or is heated to melt in hydrogen or hydrogen forming gas or if a flux is incorporated into the solder, the solder is heated to melt in air or nitrogen, by which the metallic stem 3 and the windowed cap 7 are adhered. The subsequent stages for assembling the sensor after the end of the adhesion are exactly the same as the conventional stages for assembling the sensor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a semiconductor pressure sensor, in which the stem and can are connected not by resistance welding but by lead-tin solder, and the silicon pedestal produced by resistance welding is , which reduces residual stress on silicon chips.

[Conventional technology]

Conventionally, there are various methods of manufacturing semiconductor pressure sensors.
The semiconductor pressure sensor that the present inventors aim to improve has the following structure, and is assembled by the assembly method described below, and has the following assembly problems during the assembly process. Ta.

The gauge-shaped pressure sensor shown in FIG. 2 will be described below as an example.

A silicon diaphragm chip 1, which has a P-type diffusion layer on one side of an N-type single crystal substrate and a thinned portion formed on the other side, is bonded to a silicon pedestal 2 made of silicon single crystal. This silicon pedestal 2 has an extrusion hole for guiding the pressure to be measured to the pressure receiving surface of the silicon diaphragm chip 1, and the silicon pedestal 2 itself, to which this silicon diaphragm chip 1 is attached, is attached to a metal stem 3. The silicon diaphragm chip 1 has a function of not transmitting the thermal stress that sometimes occurs due to the connection of dissimilar materials to the silicon diaphragm chip 1.Next, the silicon pedestal 2 itself is bonded to the metal stem 3 with an adhesive brazing material 12, and then, The lead pin 5 and the bonding pad 6 of the silicon diaphragm chip 1 are connected using a thin gold wire 4. Next, the window opening camp (can) 7 is welded and connected to the metal stem 3 by resistance welding. After this, the window opening cap 7 is welded. A drop of silicone gel 8 is dripped onto the chip surface through the window of the window, and the chip surface is coated and protected with silicone gel 8.Then, the window of the open window camp 7 is covered with a film 9 having ventilation holes 8, and the silicone gel 8 is cured. .

The semiconductor pressure sensor manufactured in this way has a pressure P1 from the pressure introduction pipe IO attached to the metal stem 3.
The gauge pressure P2, which is the pressure difference between the pressure and the atmospheric pressure Pa from the vent hole of the film 9, can be extracted as the electrical output of the silicon diaphragm chip 1, and is used as a gauge pressure type semiconductor pressure sensor mainly for controlling automobile engines. It is used as a sensor.

[Problem that the invention seeks to solve]

Now, in the assembly process of the gauge pressure type semiconductor pressure sensor described above, there is a process that has been problematic in the past.

It is a cap welding process using resistance welding. As is well known, when a cap is connected to a stem by resistance welding, strain during welding remains in the gauge pressure type semiconductor pressure sensor even after the cap is welded. In the gauge pressure type semiconductor pressure sensor, a silicon pedestal 2 is used to prevent this welding strain from being transmitted to the silicon diaphragm chip 1, but this causes the welding strain to concentrate on the silicon pedestal 2.

In addition, the silicon pedestal 2 has a metal stem 3 and a silicon pedestal 2.
Thermal stress generated when bonding is also applied, and in extreme cases, cracks 11 may occur in the silicon pedestal 2.
or the silicon pedestal 2 may be destroyed.

The present invention was made in order to solve the problems of the conventional products as described above, and it avoids sudden stress concentration on the silicon pedestal, thereby preventing cracking or destruction of the silicon pedestal, and improving reliability. The purpose of the present invention is to provide a semiconductor pressure sensor with high performance.

Means for Solving Problem c] A semiconductor pressure sensor according to the present invention connects a metal stem and a can using a brazing material using lead-tin solder.

[Effect]

In this invention, since the metal stem and the aperture cap are connected using a solder spout, the heating temperature when melting the solder is less than 200 degrees Celsius, and the temperature from rising to cooling is low. The time can be very wide, from several minutes to several hours, and as a result, thermal strain during connection can be extremely reduced, stress concentration on the silicon pedestal can be avoided, and cranking or destruction of the silicon pedestal can be prevented.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a semiconductor pressure sensor according to one embodiment of the invention. The basic components of the gauge pressure type semiconductor pressure sensor of this embodiment are the same as the conventional ones except for the lead-tin solder 21, which is a brazing material, so a description thereof will be omitted. Also, since the wire bonding using thin gold wire is exactly the same as the conventional method, explanation of the assembly process will be omitted.

Now, when connecting the window cap 7 to the metal stem 3 by resistance welding, excessive stress is applied to the silicon pedestal 2.
It has already been mentioned that this has a significant effect on the silicon pedestal 2. Therefore, in this embodiment, the metal stem 3 and the aperture cap 7 are connected using lead-tin solder 21 as a brazing material, without using a connection method such as resistance welding that utilizes Joule heat generated by instantaneous application of a large current. I do.

First, lead-tin solder is formed into a ring shape. If necessary, flux may be sandwiched in advance into the molded solder in the form of a sandwich.

Next, this molded solder is placed on the collar portion 3a of the metal stem 23, and the window cap 7 is further placed over it. The flange portion 3a may be processed by forming a solder pool 3b to prevent the solder from spreading to other parts when the solder is melted. This solder is then melted in a vacuum using infrared radiation, or by heating in hydrogen or hydrogen forming gas, or if the solder contains flux, by heating in air or nitrogen. In this manner, the metal stem 3 and the aperture cap 7 are bonded together. Once the adhesion is completed, the subsequent steps are no different from conventional assembly, so a description thereof will be omitted.

If the metal stem 3 and the window cap 7 are connected using a solder joint in this way, ■ the heating temperature when melting the solder is less than 200 degrees Celsius, and the time from temperature rise to cooling is short. This can be done over a very wide range from several minutes to several hours, making it possible to extremely reduce thermal distortion during connection, avoiding stress concentration on the silicon pedestal 2, and thus preventing cranking or destruction of the silicon pedestal 2. .

■ Bonding is done extremely uniformly using the surface tension of melted solder, resulting in better airtightness than connections using conventional resistance welding.

■ If the connection does not go well, you can reheat it and try again.

In addition, although the above embodiment has been explained using a gauge pressure type semiconductor pressure sensor as an example, the present invention can also be applied to the case where a cap is attached to an absolute pressure type semiconductor pressure sensor that maintains the inside of the can in a vacuum. Needless to say.

〔Effect of the invention〕

As described above, according to this invention, since the metal stem and the can are connected using a solder spout, the heating temperature when melting the solder is less than 200 degrees Celsius, and the temperature is lowered by cooling. It is possible to have a very wide range of time from several minutes to several hours, which makes it possible to extremely reduce thermal distortion during connection, and to avoid stress concentration on the silicon pedestal, thereby preventing cranking or breakage of the silicon pedestal. It has a preventive effect.

[Brief explanation of drawings]

Figure 1 is a diagram illustrating a method of manufacturing a semiconductor pressure sensor in which a cap is soldered to a metal stem using lead-tin solder as a brazing material, according to an embodiment of the present invention, and Figure 2 is a diagram illustrating resistance welding. FIG. 3 is a diagram illustrating a conventional method for manufacturing a semiconductor pressure sensor in which a cap is welded to a metal stem. 1... Silicon diaphragm chip, 2... Silicon pedestal, 4... Fine gold wire, 5... Lead pin, 6...
・Silicon diaphragm chip bonding panel,
7...Window cap, 8...Silicone gel, 9.
...Film, 10...Pressure introduction pipe, 12...
Brazing material for bonding the pedestal and metal stem, 23...Metal stem, 3a...Brim of metal stem, 3b--Solder pool provided on the brim of metal stem, 2(... '
I'd 1% solder.

Claims (1)

[Claims] (1) A pressure-sensitive silicon chip having a P-type diffusion layer on one surface of the N-type single crystal substrate and a thin wall portion on the other surface of the substrate, the thin wall portion receiving fluid pressure; It has a function of fixing the chip and preventing stress from the stem described later from being transmitted to the chip, and has a pressure introduction hole for guiding fluid pressure to the pressure-receiving surface of the pressure-sensitive silicon chip, and is made of silicon single crystal. a stem having a lead pin for fixing the silicon pedestal, supplying power to the chip, and taking out an output, and a pressure introduction pipe for guiding fluid pressure to the pressure introduction hole; the pressure-sensitive silicon chip and the silicon pedestal; A semiconductor pressure sensor that has a can that has a function of protecting a base and has a structure that can introduce atmospheric pressure or maintain a vacuum inside, the stem and can being bonded together using lead-tin solder. A semiconductor pressure sensor characterized by: