JP2001119039A - Manufacturing method of semiconductor pressure sensor - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent the invasion of air and moisture from the surroundings through a gap between a resin case and a lead terminal, and to prevent the generation of air bubbles in a coating resin layer to improve the use environment resistance and reliability. Improve the method of curing the coating resin so that it can be achieved. A resin case in which a lead terminal is insert-molded. After assembling the pressure-sensitive sensor chip 1 on which a semiconductor strain gauge is formed, the sensor chip and the lead terminal are connected by a bonding wire 5, and the resin case is filled with a gel-like coating resin 6 to form a pressure-sensitive sensor chip. In a semiconductor pressure sensor that covers the area around the bonding wire, the coating resin is injected into the resin case in an uncured state, and the subsequent curing process is divided into the first and second half steps, and the coating is performed at a temperature below the gelation temperature in the first half step. The resin is temporarily cured, and in the latter half of the process, the heating temperature is raised to the gelling temperature to cure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor pressure sensor applied to various fields mainly for automobiles.

[0002]

2. Description of the Related Art First, a surface pressure type semiconductor pressure sensor to which the present invention is applied is shown in FIG. In the figure, reference numeral 1 denotes a pressure-sensitive sensor chip in which a measurement circuit including a semiconductor strain gauge 1b is formed on a thin diaphragm 1a of a silicon chip;
Reference numeral 2 denotes a glass pedestal (spacer) on which the pressure-sensitive sensor chip 1 is mounted and anodically bonded in a vacuum. Reference numeral 3 denotes a resin case formed of a thermoplastic resin such as PPS (polyphenylene sulfide) or PBT (polybutylene terephthalate). A lead terminal (lead frame) for external derivation, which is integrally formed by penetrating the resin case 3 and insert-molded, 5 is a bonding in which a bonding pad formed on a terminal portion of the pressure-sensitive sensor chip 1 and a lead terminal 4 are internally connected. A wire (aluminum wire) 6 is a silicone for transmitting the measured pressure to the pressure-sensitive sensor chip 1 while protecting the surface of the pressure-sensitive sensor chip 1 and the bonding wire 5 from contaminants and moisture contained in the measured pressure medium. Soft gel-like coating resin such as gel or fluorosilicone gel; Shirube圧 is a port with a cap.

The principle of operation of such a semiconductor pressure sensor is well known, and the pressure to be measured applied through the pressure guiding port of the cap 7 is applied to the surface of the pressure-sensitive sensor chip 1 via the gel-like coating resin 6, whereby the pressure-sensitive sensor is Chip 1
Is deformed, the gauge resistance of the semiconductor strain gauge 1b changes, and an electric signal corresponding to the measured pressure is taken out from the lead terminal 4 to an external circuit.

[0004]

By the way, the resin case 3 of the above-mentioned semiconductor type sensor is made of PPS, PPS.
Conventional products molded with a thermoplastic resin such as BT have the following problems in terms of use environment resistance and reliability. That is, the interface between the resin case made of PPS or PBT resin and the lead terminal insert-molded in the case only has an anchor effect due to the uneven surface of the terminal surface. Due to shrinkage and a difference in linear expansion coefficient between the lead terminal 4 and the lead terminal 4, a minute gap g is generated at the interface between the two. For this purpose, for example, 150-
When a sudden negative pressure is applied to the pressure sensor by a cycle test in which pressurization and depressurization are repeated in the range of 13.3 kPa / · abs, a minute gap remaining at the contact interface between the resin case 3 and the lead frame 4 as shown in the figure. Air and moisture are sucked from the outside (atmospheric pressure) through g and enter the resin case to generate air bubbles in the layer of the gel coating resin 6 filled in the resin case. In addition, when a negative pressure is repeatedly applied to the surface of the pressure-sensitive sensor chip 1, the bubble grows, which may cause the pressure-sensitive sensor chip 1 and the bonding wire 5 to be corroded or the bonding wire 5 to be disconnected. However, the pressure to be measured introduced into the pressure sensor is interfered with the air bubbles and is not correctly transmitted to the pressure-sensitive sensor chip 1, which causes a problem that the measurement characteristics of the pressure sensor are adversely affected.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to solve the above-mentioned problems and to reduce the function as a pressure sensor through an interface between a resin case and a lead terminal. To provide a method of manufacturing a semiconductor pressure sensor which is improved so as to prevent the invasion of air and moisture from the surroundings into the resin case and to prevent the generation of bubbles in the coating resin layer, thereby improving the use environment resistance and the reliability. is there.

[0006]

According to the present invention, there is provided a pressure sensitive sensor chip having a semiconductor strain gauge formed in a resin case in which an external lead terminal is insert-molded. The sensor chip and the lead terminal are connected by a bonding wire, and the resin case is filled with a gel coating resin to cover the peripheral area of the pressure-sensitive sensor chip and the bonding wire. Inject the coating resin in an uncured (sol) state, and proceed with the curing process in the first half,
After being divided into the second half step, the coating resin is provisionally cured at a gelation temperature or lower in the first half step, and the heating temperature is raised to the gelation temperature in the second half step for curing (claim 1).

According to the present invention, in the above method, the uncured coating resin can be vacuum-injected into a resin case. According to the above method, even if a gap due to molding shrinkage or the like is generated at the interface between the resin case and the lead terminal insert-molded in the case, the resin is heated to a gelling temperature or lower in the first half of the curing step. As a result, the coating resin becomes a low-viscosity state with high fluidity, so that it enters into a slight gap between the resin case and the lead terminal to fill the gap, and is gelled by heat curing in a subsequent latter curing step. . In particular, by injecting the coating resin into the resin case by vacuum, the coating resin can be filled to every corner in the resin case while preventing air bubbles from being mixed.

Thus, even when a negative pressure is applied in accordance with the pressure operation cycle of the semiconductor pressure sensor, air and moisture enter the inside of the case through the interface between the resin case and the lead terminal from the surroundings. It is possible to prevent the generation of bubbles in the coating resin layer, thereby effectively preventing the breakage of the bonding wire due to the generation of bubbles and the fluctuation of the characteristics of the pressure-sensitive sensor chip with respect to the measured pressure.

[0009]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to examples (a) to (d). In the drawings of the embodiment, members corresponding to those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the basic structure of the pressure sensor is the same as that shown in FIG. 2, but the pressure-sensitive sensor chip is attached to the resin case 3 with respect to the resin case 3 in which lead terminals 4 for external lead-out are integrally formed by insert molding. 1 for glass pedestal 2
In the assembled state in which the bonding wires 5 are connected between the pressure-sensitive sensor chip 1 and the lead terminals, when the soft gel-like coating resin 6 is next filled and cured by heating, the following curing is performed. It is assumed that the process is performed in two steps.

First, an uncured (sol) coating resin 6 is injected into a resin case 3 by a dispenser 8 as shown in FIG. The injection amount of the coating resin is controlled so that the layer thickness is 0.8 to 1.5 mm so that the pressure-sensitive sensor chip 1 and the bonding wires 5 are sufficiently covered. Then, as shown in FIG.
Was transferred to a defoaming tank 9 and the inside of the tank was evacuated to sufficiently deaerate the air bubbles mixed in the coating resin 6. Then, the resin case 3 was placed in a curing furnace (constant temperature) shown in FIG. (Tank) 10 to cure the coating resin 6. Here, the curing process is divided into a first half and a second half. In the first half, the coating resin 6 is heated at a gelling temperature or less (for example, at a temperature of 40 to 80 ° C. for about 60 minutes) and temporarily cured.
In the first half of the process, the coating resin 6 has a lower viscosity than in the normal temperature state and exhibits high fluidity, so that the coating resin 6 enters the gap remaining at the interface between the resin case 3 and the lead terminal 4. Fill the gap with. Then, in the subsequent second half step, the curing furnace 10 is heated to a gelation temperature of the coating resin 6 and heated (for example, 120 to 150 ° C.).
For about 30 minutes), and the coating resin 6 is cured by heating and gelled.

As a result, in the assembled product, air and moisture enter from the periphery through the space between the resin case 3 and the lead terminal 4 penetrating the case during the pressurization / decompression operation cycle, and the gel-like coating resin 6 Generation of air bubbles in the layer can be reliably prevented, and disconnection of the bonding wire 5 due to generation of air bubbles and adverse effects on measurement pressure transmission can be prevented. This has been confirmed from the results of a pressure operation cycle test performed by the inventors.

[0012]

As described above, according to the structure of the present invention, the coating resin is poured into the resin case in an uncured state, and the subsequent curing step is divided into the first half and the second half. Temporarily cure the coating resin below the temperature, raise the heating temperature to the gelling temperature in the latter half of the process, and cure by coating shrinkage etc. at the interface between the resin case and the lead terminal inserted in the case. Even if a small gap is generated, in the first half of the curing process of the coating resin injected into the resin case, the coating resin with high fluidity enters the small gap between the resin case and the lead terminal and fills the gap And gelation in the subsequent latter step. In particular, by injecting the coating resin into the resin case by vacuum, it is possible to fill the coating resin to every corner in the case including the gap between the resin case and the lead terminal while preventing air bubbles from being mixed. As a result, even if a sudden negative pressure is applied to the pressure sensor during the pressure operation cycle applied when the semiconductor pressure sensor is used, air and moisture can enter the case from the surroundings through the gap between the resin case and the lead terminal. Also, the generation of bubbles in the coating layer filled in the resin case caused by the intrusion of air is prevented, and the disconnection of the bonding wire caused by the formation of the bubbles and the characteristic fluctuation of the pressure-sensitive sensor chip with respect to the measured pressure are prevented. It is possible to provide a semiconductor pressure sensor having high resistance to use environment and high reliability.

[Brief description of the drawings]

FIGS. 1A to 1D are explanatory diagrams of a method of assembling a semiconductor pressure sensor according to an embodiment of the present invention, wherein FIGS. 1A to 1D sequentially show an injection / defoaming / curing step of a soft coating resin.

FIG. 2 is a sectional view showing an assembly structure of a surface pressure type semiconductor pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure-sensitive sensor chip 3 Resin case 4 Lead terminal 5 Bonding wire 6 Gel coating resin 9 Defoaming tank 10 Cure furnace

Claims (2)

[Claims] A pressure-sensitive sensor chip having a semiconductor strain gauge formed therein is incorporated into a resin case in which an external lead terminal is insert-molded, and the sensor chip and the lead terminal are connected by a bonding wire. In a semiconductor pressure sensor in which a gel-like coating resin is filled to cover the area around the pressure-sensitive sensor chip and bonding wire, the coating resin is injected into the resin case in an uncured state, and the subsequent curing process is performed in the first and second half steps A method for manufacturing a semiconductor pressure sensor, comprising: temporarily curing a coating resin at a temperature lower than a gelling temperature in a first half step, and curing by heating a heating temperature to a gelling temperature in a second half step. 2. The method according to claim 1, wherein the uncured coating resin is vacuum-injected into a resin case.