JPH0372229A - Manufacture of semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To enable accurate detection of a pressure without use of a pedestal by fluidizing a resin almost radially outward from the center of a carrying position with respect to a carrying surface of a semiconductor pressure sensing element. CONSTITUTION:In the molding of a resin package, a pin gate 3 is provided to inject a resin vertical to a silicon pellet carrying surface 1 and toward the center of position 2 of carrying silicon pellet indicated by the broken line. As a result, the resin is fluidized radially outward from the center of the carrying position 2 as indicated by the arrow. When a resin package 4 undergoes a temperature change, a thermal stress is generated parallel with the carrying surface 1 and outward isotropically way on the center of the carrying position 2. Thus, as the thermal stress is applied to a silicon pellet 5 fastened direct on the resin package 4 isotropically way outward on the center of the silicon pellet, there is no distortion caused by the thermal stress in a diaphragm section of the silicon pellet 5. In other words, this eliminates an undesired output otherwise caused by the thermal stress thereby enabling accurate detection of a pressure.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a method for manufacturing a semiconductor pressure sensor.

(b) Prior Art Generally, a semiconductor pressure-sensitive element of a semiconductor pressure sensor has a structure in which a piezoresistor is bridge-coupled to a diaphragm portion of a silicon pellet having a diaphragm portion. In such a semiconductor pressure sensor, when the diaphragm section is pressurized and deformed, the resistance value of the piezoresistor changes depending on the amount of pressure applied, so by measuring the output of the bridge-coupled resistors, The amount of pressurization is detected. Therefore, in this type of semiconductor pressure sensor, if the diaphragm portion is deformed due to factors other than the pressure to be measured, an undesirable bridge output will occur, making it impossible to accurately detect pressure.

On the other hand, in recent years, resin packages have been increasingly used as packages for housing silicon pellets in order to facilitate the manufacture of semiconductor pressure sensors and reduce costs. However, since the resin package and the silicon pellet have different thermal expansion coefficients, undesired thermal stress is applied to the silicon pellet due to temperature changes, making accurate pressure detection impossible. Therefore, in order to alleviate the thermal stress generated within such silicon pellets, for example, JP-A-63-],
As described in Japanese Patent No. 63248, a pedestal having a thermal expansion coefficient substantially equal to that of the silicon pellet is inserted between the silicon pellet and the resin package.

(c) Problems to be Solved by the Invention However, when using a pedestal as described above, the process of processing such a pedestal, placing and fixing it on a resin package, and the equipment for that process are required when manufacturing a semiconductor pressure sensor. In addition, the cost of the pedestal itself is also required, which poses a problem of increasing the manufacturing cost of the semiconductor pressure sensor.

Therefore, the technical object of the present invention is to manufacture a semiconductor pressure sensor that can accurately detect pressure without using a pedestal.

(d) Means for Solving the Problems The present invention provides a bottom mold for a resin package using a resin whose coefficient of linear expansion is different in the flow direction during molding and in the direction perpendicular to the flow direction, and a semiconductor pressure-sensitive element is placed in the resin package. In order to solve the above problem, in order to solve the above problem, when forming a bottom mold of the resin package, the resin is placed at the center of the mounting position of the semiconductor pressure sensitive element with respect to the mounting surface of the semiconductor pressure sensitive element. It is characterized by flowing approximately radially outward from the base.

Further, the present invention provides a semiconductor pressure sensor in which a circular resin package is made of a resin whose coefficient of linear expansion is different in the flow direction during molding and in the direction perpendicular to the flow direction, and a semiconductor pressure-sensitive element is placed and fixed on the resin package. In order to solve the above problem, the manufacturing method is characterized in that the resin is caused to flow in a substantially spiral shape from the end to the center of the mounting surface.

(E) Function In general, many of the so-called engineering plastics, such as polyphenylene sulfide (PPS) resin and polybutylene terephthalate (PBT) resin used in resin packages for semiconductor pressure sensors, have orientation properties because they contain glass fibers. , the coefficient of linear expansion is small in the flow direction of the resin during injection molding, and the coefficient of linear expansion is large in the direction perpendicular to the flow direction.

In the method of the present invention, when molding the resin package of the semiconductor pressure sensor, the resin is made to flow approximately radially from the center of the mounting position outward toward the mounting surface of the semiconductor pressure-sensitive element. By causing the resin to flow approximately spirally from the surface of the resin package toward its center during molding of the resin package, the thermal stress on the mounting surface is reduced with respect to the center of the mounting position of the semiconductor pressure-sensitive element. Occurs in equal directions.

(f) Example First, as described in the detailed explanation of the present invention, when a silicon pellet is directly fixed to a resin package, stress is applied to the silicon pellet when the temperature changes due to the difference in thermal expansion coefficient between the silicon pellet and the resin package. As a result, an undesired signal is output from the semiconductor pressure sensor. The inventor of the present invention has studied this point in detail and found that stress applied to silicone pellets occurs more often when the resin flows as shown by the arrow in the figure during molding of a resin package, as shown in Figure 6. It has been found. This is thought to be because when the resin orientation of the silicon pellet mounting surface ( ]) is biased, the thermal stress generated at the silicon pellet mounting position (2) indicated by the broken line in the figure is also biased, making the silicon grains more likely to bend.

Therefore, in the first method of the invention, as shown in FIG. 1(a),
When forming the bottom mold of the resin package, place the silicone pellet on the surface (
A bin gate (3) for injecting resin is provided perpendicular to 1) and toward the center of the silicon pellet placement position (2) shown by a broken line. As a result, the resin flows radially outward from the center of the silicon pellet mounting position (2), as shown by the arrows in FIG. 2(b). When such a resin package is subjected to a temperature change, thermal stress is generated parallel to the silicon pellet mounting surface (1) and equally outward from the center of the Zinocom pellet fi2H position (2). This will occur in the direction. Therefore, thermal stress is also applied to the silicon pellet directly fixed to the resin package in the same direction outward from the center of the silicon pellet, so the diaphragm part of the silicon pellet is not distorted and is parallel to its plane. and is pulled in the same direction.

For convenience of explanation, in Figure 1, only the silicon pellet iT&fi side of the resin package is shown. In addition to the side wall (6), the impulse pipe (7)
)have. In order to mold the bottom of a resin package (4) having such a shape according to the method of the present invention, as shown in FIG. Then, a pin gate (3) leading to the center of the silicon pellet placement position is provided, and the resin is injected from there. However, in this case, since the silicon pellet mounting surface is entirely covered with resin, it is necessary to make a hole in the silicon pellet @ lid surface after the bottom mold of the resin package to communicate with the pressure impulse pipe.

Next, the second method of the present invention is applied when the silicon pellet placement surface is circular, and as shown in FIGS. 4(a) and (b), the placement surface ( A pin gate (3') is provided so that the resin is injected from the tangential direction of 1') toward the end thereof. As a result, the resin flows spirally within the circular mounting surface (1) toward the center thereof. FIG. 5 shows an example of a mold (8') used in such a method. Even in this case, the thermal stress generated when the temperature changes is applied parallel to the silicon pellet @lid surface (1) and in the same direction outward from the center of the silicon pellet placement position (2). becomes. Therefore, even in a circular resin package whose bottom is shaped in this manner, the diaphragm portion of the silicon pellet directly fixed onto the mounting surface will not be distorted by thermal stress, and no undesired output will occur due to this.

(G) Effects of the Invention According to the method of the present invention, when producing a resin package, the resin is caused to flow radially or spirally on the semiconductor pressure-sensitive element mounting surface centered on the center of the semiconductor pressure-sensitive element mounting position. As a result, even if the semiconductor pressure-sensitive element is directly fixed to the resin package, distortion due to thermal stress will not occur in the diaphragm portion of the semiconductor pressure-sensitive element. That is, since there is no undesirable output due to thermal stress, accurate pressure detection becomes possible. Therefore, if the method of the present invention is applied, there is no need to provide a pedestal between the resin package and the semiconductor pressure-sensitive element, which has a coefficient of thermal expansion approximately equal to that of the semiconductor pressure-sensitive element, as in the conventional method, and this makes it possible to achieve low-cost and accurate A semiconductor pressure sensor capable of detecting pressure can be manufactured.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are schematic diagrams for explaining an embodiment of the method of the present invention, in which FIG. 1(a) is a perspective view and FIG. 1(b) is a perspective view.
2 is a top view, FIG. 2 is a sectional view of a semiconductor pressure sensor manufactured using the method of the present invention, and FIG. 3 is a folded sectional view showing a mold for a resin package for carrying out the method shown in FIG. 1. , FIGS. 4(a) and 4(b) are schematic diagrams for explaining other embodiments of the method of the present invention, in which FIG. 4(a) is a perspective view and FIG. 4(b) is a perspective view.
5 is a top view, FIG. 5 is a sectional view showing a mold for a resin package for carrying out the method shown in FIG. 4, and FIG. It is a top view explaining a flow direction. (1)... Silicon pellet mounting surface, (2)... Silicon pellet mounting position, (3)... Pin gate, (
4) Resin package, (5) Silicon pellet.

Claims (2)

[Claims] (1) A method for manufacturing a semiconductor pressure sensor, in which a resin package is molded using a resin whose coefficient of linear expansion differs in the flow direction during molding and in the direction perpendicular to the flow direction, and a semiconductor pressure-sensitive element is placed and fixed on the resin package, A semiconductor pressure sensor characterized in that, when molding the resin package, the resin is made to flow approximately radially from the center of the mounting position outward toward the mounting surface of the semiconductor pressure-sensitive element. Production method. (2) A method for manufacturing a semiconductor pressure sensor, in which a circular resin package is molded using a resin whose coefficient of linear expansion differs in the flow direction during molding and in the direction perpendicular to the flow direction, and a semiconductor pressure-sensitive element is placed and fixed on the resin package. A method of manufacturing a semiconductor pressure sensor, characterized in that the resin is caused to flow in a substantially spiral shape from an end toward the center of the mounting surface.