FUEL RESISTANCE PACKAGE

Abstract

A fuel resistance package includes a member to be sealed, which is used in a fuel atmosphere including an aromatic compound or ethanol, and a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere. The sealing member is made of resin containing glycidyl amine-based epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less as epoxy resin, an amine-based hardener that ring-opens epoxy groups of the epoxy resin to harden the epoxy resin, and filler made of silica.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on Japanese Patent Application No. 2009-283719 filed on Dec. 15, 2009, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a fuel resistance package having a member to be sealed, which is used in a fuel atmosphere including an aromatic compound or ethanol, and a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere.

BACKGROUND OF THE INVENTION

Environment resistance and, especially, high reliability are required for a package that is directly exposed to fuel or the like. In order to fulfill the reliability, a configuration, in which a member to be sealed is sealed with a sealing member made of inorganic material, has conventionally adopted. As a fuel resistance package having such a configuration, a pressure sensor described in JP-A-7-209115 has proposed, for example.

In the package, a metal diaphragm made of inorganic material and transmitting oil are used as the sealing member, and a sensor element or a wiring part as the member to be sealed is sealed with the metal diaphragm and the transmitting oil, thereby improving the environment resistance.

However, in the package described in JP-A-7-209115, the following problems arise. Since the metal diaphragm is used, material cost may increase. Since control of voids in the enclosed oil is required, labor cost may increase. Since many components are needed, reducing a size of the package may become so difficult.

In view of the above-described problems, the inventors considered using resin material as the sealing member having fuel resistance in place of the conventional inorganic material. However, in the case where resin material is used, components in fuel, such as an aromatic compound or ethanol may penetrate the sealing member, and thereby fuel resistance of the sealing member may be decreased. Therefore, in the case where the resin material is used as the sealing member, prevention of the penetration of the components is needed.

SUMMARY OF THE INVENTION

In view of the above-described difficulty, it is an object of the present invention to provide a fuel resistance package having a member to be sealed, which is used in a fuel atmosphere including an aromatic compound or ethanol, and a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere, and being capable of preventing components in the fuel from penetrating the sealing member.

In order to achieve the above-described object, the inventors considered that molding resin used as a sealing member in a semiconductor device or the like is improved to be a sealing member suitable for a fuel resistance package.

This kind of molding resin includes resin containing epoxy resin as a major component and a hardener that ring-opens epoxy groups of the epoxy resin to harden the epoxy resin, filler made of silica, and a coupling agent for ensuring a binding property between the filler and the epoxy resin.

The inventors analyzed a glass-transition temperature of epoxy resin, and affinity of epoxy resin for components in fuel, such as an aromatic compound or ethanol. It is considered that, when the glass-transition temperature is low, a sealing member is easy to be softened, and it becomes easy to form voids in the sealing member microscopically, and thus, the components in the fuel become easy to penetrate the sealing member.

A relation between the glass-transition temperature of epoxy resin in the sealing member and a penetration degree of the components in the fuel was experimentally analyzed by using NMR. According to the analysis, it was found that, when the glass-transition temperature is 180° C. or more, penetration of the components in the fuel can be limited at a practical level.

Moreover, the inventors thought that it is preferable that a dielectric constant of the epoxy resin in the sealing member is low in order to prevent penetration of ethanol as polar solvent among the components in the fuel. This is because, if the dielectric constant is large, affinity of the epoxy resin for a hydroxyl group (—OH) of ethanol becomes large and ethanol penetrates easily.

A relation between the dielectric constant of the epoxy resin in the sealing member and the penetration degree of the components in the fuel was experimentally analyzed. As shown in FIGS. 3A and 3B, which are described below, it was found that, when the dielectric constant is 3.5 or less, the penetration of ethanol in the fuel can be limited at a practical level.

According to one aspect of the present invention, a fuel resistance package includes a member to be sealed, which is used in a fuel atmosphere including at least one of an aromatic compound and ethanol, and a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere. The sealing member is made of resin containing epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less, and filler made of silica is contained in the resin.

The sealing member of the present invention is made of resin containing epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less, and filler made of silica is contained in the resin. Therefore, even if a sealing member made of resin material is used, components in fuel can be prevented from penetrating the sealing member.

Furthermore, in order to prevent penetration of an aromatic compound among the components in the fuel, it is preferable that the affinity of the epoxy resin in the sealing member for the aromatic compound is low. A planar space in a molecule is large in naphthalene-based epoxy resin, for example. Thus, the affinity of the naphthalene-based epoxy resin for an aromatic compound having a benzene ring becomes large, and the aromatic compound penetrates easily.

With focusing this point, a relation between a molecular structure of the epoxy resin in the sealing member and the penetration degree of the components in the fuel was experimentally analyzed. As a result, it was found that, when glycidyl amine-based epoxy resin whose planar space is smaller than that of naphthalene-based epoxy resin is used, the penetration of the aromatic compound in the fuel can be limited.

In the case of using the glycidyl amine-based epoxy resin, a hardener that ring-opens epoxy groups of the epoxy resin to harden the epoxy resin was analyzed. In general molding resin, examples of the hardener include an amine-based hardener such as imidazole, a phenol-based hardener and an anhydride-based hardener.

The inventors intended to form the sealing member as follows. Liquid material for the sealing member is applied to the member to be sealed by potting or the like, and then, the applied liquid material is hardened. Since viscosity of a phenol-based hardener becomes high in the step of applying, the inventors decided not to use a phenol-based hardener.

Then, the inventors analyzed an amine-based hardener and an anhydride-based hardener, each of which has a relatively-low viscosity, and focused adhesion force between a sealing member and a member to be sealed in order to select a preferred hardener. It is considered that the adhesion force between the sealing member and the member to be sealed is affected significantly by a hydrogen bond due to the hydroxyl group (—OH) of the resin of the sealing member.

In using the amine-based hardener and the anhydride-based hardener, a ring-opening rate of glycidyl amine-based epoxy resin was experimentally analyzed. As a result, the ring-opening rate is considerably large when the amine-based hardener is used compared to when the anhydride-based hardener is used.

Furthermore, with respect to the sealing member made of the glycidyl amine-based epoxy resin, interfacial strengths with the member to be sealed when the amine-based hardener is used and when the anhydride-based hardener is used were experimentally analyzed. As a result, as shown in FIG. 5, which is described below, it was found that, the adhesion force between the sealing member and the member to be sealed is substantially large when the amine-based hardener is used compared to when the anhydride-based hardener is used.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1 is a schematic cross-sectional view showing a fuel resistance package according to a first embodiment of the present invention;

FIG. 2A is a diagram showing a molecular structure of naphthalene-based epoxy resin;

FIG. 2B is a diagram showing a molecular structure of glycidyl amine-based epoxy resin;

FIG. 3A is a graph showing a relation between immersion time and mass change in the case where naphthalene-based epoxy resin is used;

FIG. 3B is a graph showing a relation between immersion time and mass change in the case where glycidyl amine-based epoxy resin is used;

FIG. 4A is a graph showing a relation between immersion time and mass change in the case where a filler content is 60% by weight;

FIG. 4B is a graph showing a relation between immersion time and mass change in the case where a filler content is 80% by weight;

FIG. 5 is a graph showing a relation between immersion time and interfacial strength in the case where an amine-based hardener is used and in the case where an anhydride-based hardener is used;

FIG. 6 is a graph showing a relation between immersion time and breaking stress of a sealing member;

FIG. 7 is a schematic cross-sectional view showing a substantial part of a fuel resistance package according to a second embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view showing a fuel resistance package according to a third embodiment of the present invention;

FIG. 9 is a schematic cross-sectional view showing a fuel resistance package according to a fourth embodiment of the present invention; and

FIG. 10 is a schematic cross-sectional view showing a fuel resistance package according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to drawings. For the sake of simplicity, similar components in the following embodiments are indicated by the same reference numeral.

First Embodiment

FIG. 1 is a schematic cross-sectional view showing a fuel resistance package S1 according to the first embodiment of the present invention. As shown in FIG. 1, the package S1 is used in a fuel atmosphere 1 containing an aromatic compound or ethanol, and is applied as various sensor devices which are mounted to a vehicle. Examples of the fuel include gasoline containing an aromatic compound or ethanol, that is, deteriorated gasoline.

Generally, the package S1 of the present embodiment includes a sensor chip 10, a first substrate 20 that supports the sensor chip 10, a wire 30 that electrically connects the sensor chip 10 and the first substrate 20, and a second substrate 40 that supports the first substrate 20.

Examples of the sensor chip 10 include a pressure sensor, an acceleration sensor, a flow sensor, or a temperature sensor. For example, the sensor chip 10 is a semiconductor chip that is formed by a semiconductor process. Each of the first substrate 20 and the second substrate 40 is a wiring substrate or a lead frame, for example.

The sensor chip 10 is mounted on and fixed to one surface of the first substrate 20 by an adhesive 50 such as solder or Ag paste, and thereby, the sensor chip 10 is supported by the first substrate 20. The sensor chip 10 is placed on one end portion of the first substrate 20 such that a part of the sensor chip 10 protrudes from the one end portion of the first substrate 20.

The sensor chip 10 is wire-connected to the first substrate 20 with the wire 30 made of aluminum, gold or the like at a side of the one end portion of the first substrate 20, and thereby the sensor chip 10 is electrically connected to the first substrate 20. The wire 30 is formed by wire bonding, for example.

The other end portion of the first substrate 20 is mechanically joined to one end portion of the second substrate 40. Although not shown, the joining is performed by using an adhesive such as solder, or a screw, or by caulking, for example. The first and second substrates 20, 40 contact each other through electrodes thereof (not shown). Thus, the first substrate 20 is electrically joined to the second substrate 40.

A resin-molded first resin portion 61 is placed on the one surface of the first substrate 20. The first resin portion 61 covers the one surface of the first substrate 20 other than the sensor chip 10 and the wire 30. A part of the first substrate 20 including the first resin portion 61 and a part of the second substrate 40 are sealed with a resin-molded second resin portion 62.

The second resin portion 62 seals the first and second substrates 20, 40 so as to surround a joined portion between the first and second substrates 20, 40, the first and second substrates 20, 40 which are located adjacent to the joined portion, and a part of the first resin portion 61. The sensor chip 10, the wire 30, a part of the first substrate 20 on which the sensor chip 10 and the wire 30 are placed, and the other end portion of the second substrate 40 protrude from the second resin portion 62.

The first resin portion 61 is made of epoxy resin, and the second resin portion 62 is made of PPS (polyphenylene sulfide), for example. The first and second resin portions 61, 62 are formed by transfer molding with the use of a molding die. After the first resin portion 61 is primary molded, the second resin portion 62 is secondary molded so as to be in contact with the first resin portion 61.

According to the present embodiment, in such a package S1, the sensor chip 10 corresponds to a first member, the first substrate 20 corresponds to a second member, and the wire 30 corresponds to a connecting member that electrically connects the first and second members. As shown in FIG. 1, the wire 30, and the first and second members which are located adjacent to the wire 30 are sealed by a sealing member 70.

In the present embodiment, a boundary portion at which the first resin portion 61 contacts the second resin portion 62 is also sealed with the sealing member 70. Furthermore, the sealing member 70 also seals to cover a boundary portion that becomes a boundary outside the first and second resin portions 61, 62 on an outer peripheral surface of the first and second resin portions 61, 62.

Accordingly, in the package S1, a portion 71 other than the sealing member 70 in the package S1, that is, the portion 71 composed of the sensor chip 10, the first and second substrates 20, 40, the wire 30, the adhesive 50 and the first and second resin portions 61, 62 corresponds to a member 71 to be sealed. When the package S1 is used, the components located in the fuel atmosphere 1 of the member 71 to be sealed, that is, the wire 30, adjacent parts to the wire 30 and the boundary portion are sealed with the sealing member 70.

The sealing member 70 is made of resin material containing filler, and can limit the penetration of components in the fuel as much as possible. Unlike the first and second resin portions 61, 62, the sealing member 70 is not formed by molding with the use of the molding die. The sealing member 70 is formed as follows. Liquid material for the sealing member 70 is applied to the member 71 to be sealed by potting or the like, and then, the applied liquid material is hardened. Portions that are easy to be deteriorated due to the fuel of the member 71 to be sealed are sealed with the sealing member 70, and thereby the member 71 to be sealed is protected from the fuel.

In particular, the sealing member 70 is made of resin containing epoxy resin and filler made of silica contained in the resin. The resin containing epoxy resin includes the epoxy resin as a major component, a hardener that ring-opens epoxy groups of the epoxy resin to harden the epoxy resin, and a coupling agent for ensuring a binding property between the filler and the epoxy resin.

The epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less is used. Examples of the epoxy resin include polycyclic epoxy resin. In particular, it is preferable to use glycidyl amine-based epoxy resin as resin that can achieve the high glass-transition temperature and the low dielectric constant and is easy to limit the penetration of aromatic components in the fuel.

Examples of the hardener include an amine-based hardener. It is preferable to use the amine-based hardener since adhesion force, i.e., interfacial strength between the sealing member 70 and the member 71 to be sealed is increased. Furthermore, an epoxy-based coupling agent which is the same with general molding resin that is used as a sealing member in a semiconductor device, is used as the coupling agent, and the amount thereof is the same with that of the molding resin.

Particulate silica which is the same with that contained in general molding resin is used as the filler. When the whole of the sealing member 70 is assumed to be 100% by weight, it is preferable that the amount of the filler is 60% by weight or more, more preferably, 80% by weight. The above-described configuration of the sealing member 70 is based on an experimental result by the inventors, and the experimental result used as the basis for the configuration will be described below.

As described above, the package S1 of the present embodiment is used in the fuel atmosphere 1 such as the deteriorated gasoline containing an aromatic compound or ethanol. In particular, the package S1 is used as a sensor for measuring a pressure or a temperature in a fuel tank of the vehicle.

According to FIG. 1, the sensor chip 10, the wire 30, the first substrate 20, and the first resin portion 61, and a part of the second resin portion 62 are used in the fuel atmosphere 1. The other end portion of the second substrate 40 protruding from the second resin portion 62 is located outside the fuel atmosphere 1. In this state, a signal from the sensor chip 10 is outputted to the outside from the other end portion of the second substrate 40 through the wire 30 and the first and second substrates 20, 40.

When the package S1 is used, the components in the member 71 to be sealed, which are located in the fuel atmosphere 1 and should be protected from the fuel, are sealed with the sealing member 70. Since the sealing member 70 can limit the penetration of components in the fuel, such as an aromatic compound or ethanol as much as possible, the deterioration of the member 71 to be sealed due to the fuel can be prevented.

In the present embodiment, since the boundary portion between the first and second resin portions 61, 62 is sealed with the sealing member 70, the sealing member 70 fulfills a function to increase joint strength between the first and second resin portions 61, 62.

In the package S1 of the present embodiment, the case where the fuel resistance of the boundary portion between the first and second resin portions 61, 62 is unnecessary depending on composition or a temperature in the fuel atmosphere is assumed. In such a case, the sealing member 70 may not be formed on the boundary portion in the above-described configuration. Next, the effect of the sealing member 70 of the present embodiment and the basis that the sealing member 70 is formed to have the above-described configuration will be specifically described.

First, the reason why the glass-transition temperature of the epoxy resin in the sealing member 70 is set to be 180° C. or more will be described. An immersion test was performed by using epoxy resin having the glass-transition temperature of less than 100° C. and epoxy resin having the glass-transition temperature of 180° C. as the sealing member 70. In the immersion test, the two types of epoxy resins are immersed in the deteriorated gasoline having a temperature of 80° C. for 1000 hours, and NMR measurement of the epoxy resins was performed before and after the immersion. Increase and decrease of peaks due to an aromatic compound and ethanol in the deteriorated gasoline were analyzed based on the NMR spectra.

As a result, in the epoxy resin having the glass-transition temperature of less than 100° C., the peaks due to both the aromatic compound and ethanol were increased after the immersion. In contrast, in the epoxy resin having the glass-transition temperature of 180° C., the peaks due to both the aromatic compound and ethanol were not increased.

That is, it was found that the epoxy resin having the glass-transition temperature of 180° C. substantially limits the penetration of the aromatic compound and ethanol. Therefore, if the glass-transition temperature of the epoxy resin of the sealing member 70 is 180° C. or more, the sealing member 70 becomes hard, and the penetration of the components in the fuel can be limited.

Next, as epoxy resin having the glass-transition temperature of 180° C. or more, the case where naphthalene-based epoxy resin is used and the case where glycidyl amine-based epoxy resin is used were compared, and hardening thereof due to the difference between the dielectric constants and molecular structures thereof was analyzed. In particular, the sealing member including naphthalene-based epoxy resin and the sealing member including glycidyl amine-based epoxy resin were immersed in the deteriorated gasoline having a temperature of 80° C., and a relation between the immersion time and the mass change of the sealing member was obtained.

FIG. 2A is a diagram showing a molecular structure of naphthalene-based epoxy resin, which is used in the analysis. FIG. 2B is a diagram showing a molecular structure of glycidyl amine-based epoxy resin, which is used in the analysis. The dielectric constant of the naphthalene-based epoxy resin is 3.8, and the dielectric constant of the glycidyl amine-based epoxy resin is 3.5.

FIG. 3A is a graph showing the relation between the immersion time (unit: hour) and the mass change (unit: %) in the case where the naphthalene-based epoxy resin is used. FIG. 3B is a graph showing the relation between the immersion time (unit: hour) and the mass change (unit: %) in the case where the glycidyl amine-based epoxy resin is used. In FIGS. 3A and 3B, the mass change is expressed in percentage based on the immersion time 0, that is, the mass of the sealing member before the immersion.

As shown in FIGS. 3A and 3B, in both cases, the mass of the sealing member increases with immersion time. The mass of the sealing member increases because components of an aromatic compound or ethanol in the deteriorated gasoline penetrate the sealing member and the sealing member swells. That is, it can be said that the lower the degree of the mass increase is, the better the penetration of the components is suppressed.

In particular, as shown in FIGS. 3A and 3B, in the case of using naphthalene-based epoxy resin, the mass increase was 1.5% after the immersion of 1000 hours, and in the case of using glycidyl amine-based epoxy resin, the mass increase was 0.7% after the immersion of 1000 hours. 0.7% is a value that practically realizes sufficient fuel resistance in this kind of package.

According to the analysis, it appears that, if the dielectric constant of the epoxy resin of the sealing member 70 is 3.5 or less, the penetration of the ethanol component in the fuel can be limited at a practical level. The reason is as follows. If the dielectric constant is low, for example, 3.5 or less, it is presumed that affinity of the epoxy resin for a hydroxyl group (—OH) of ethanol as polar solvent becomes small and the penetration of ethanol is drastically suppressed.

Moreover, in the case of using glycidyl amine-based epoxy resin, the penetration of the aromatic component in the fuel is also drastically suppressed compared with the case of using naphthalene-based epoxy resin, which is presumed to be dependent on the difference between the molecular structure of naphthalene-based epoxy resin and the molecular structure of glycidyl amine-based epoxy resin.

As shown in FIGS. 2A and 2B, a planar space of benzene rings in naphthalene-based epoxy resin is large, and a planar space of benzene rings in glycidyl amine-based epoxy resin is small. Thus, the affinity for an aromatic component having a benzene ring in glycidyl amine-based epoxy resin is smaller than that in naphthalene-based epoxy resin, and thereby it is considered that the penetration of the aromatic component does not take place easily in the case of using glycidyl amine-based epoxy resin.

Next, a filler content will be described. If a resin component in the sealing member 70 made of resin is too much, the penetration amount of the components in the fuel may increase. Thus, it is considered that the penetration amount of the components in the fuel can be limited by increasing the filler content to some extent to decrease the resin component in the sealing member 70. A relation between the filler content and the penetration degree of the components in the fuel was experimentally analyzed.

In the analysis, the sealing member made of resin containing glycidyl amine-based epoxy resin having the glass-transition temperature of 180° C. or more and the dielectric constant of 3.5 or less is used. The amount of filler that is contained in the resin was changed. With respect to the sealing members whose filler contents vary from each other, each sealing member was immersed in the deteriorated gasoline having a temperature of 80° C., and a relation between the immersion time and the mass change of the sealing member was obtained. The result is shown in FIGS. 4A and 4B.

FIG. 4A is a graph showing the relation between the immersion time (unit: hour) and the mass change (unit: %) in the case where the filler content is 60% by weight. FIG. 4B is a graph showing the relation between the immersion time (unit: hour) and the mass change (unit: %) in the case where the filler content is 80% by weight.

As shown in FIG. 4A, in the case where the filler content is 60% by weight, the penetration degree of the components in the fuel slightly exceeds 1%, and the resin having the filler content of 60% by weight can be barely used at a practical level although depending on a fuel atmosphere. Moreover, as shown in FIG. 4B, in the case where the filler content is 80% by weight, the penetration degree of the components in the fuel is drastically improved compared to the case where the filler content is 60% by weight. Accordingly, it is preferable that the filler content is 60% by weight, and more preferably, is 80% by weight.

As the hardener for obtaining moderate low viscosity in the step of applying the sealing member 70, the amine-based hardener and the anhydride-based hardener, which have relatively low viscosity, were selected and compared to each other with focusing the adhesion force between the sealing member 70 and the member 71 to be sealed. It is considered that the adhesion force is affected significantly by a hydrogen bond due to the hydroxyl group (—OH) of the resin of the sealing member 70. In using the respective hardeners, a ring-opening rate of glycidyl amine-based epoxy resin was analyzed.

In the analysis, with respect to the sealing member containing the amine-based hardener as the hardener for the glycidyl amine-based epoxy resin and the sealing member containing the anhydride-based hardener as the hardener for the glycidyl amine-based epoxy resin, NMR measurement was performed before and after hardening. The ring-opening rates of the glycidyl amine-based epoxy resins in the sealing members were measured based on the NMR spectra. As a result, the ring-opening rate when using the amine-based hardener was about 70%. In contrast, the ring-opening rate when using the anhydride-based hardener was about 20%. That is, the ring-opening rate is considerably large when using the amine-based hardener compared to when using the anhydride-based hardener.

Furthermore, in the sealing member 70 in which the resin containing the glycidyl amine-based epoxy resin shown in FIG. 2B and the filler content is 80% by weight, the interfacial strengths with the member 71 to be sealed when the amine-based hardener is used and when the anhydride-based hardener is used were analyzed.

In the analysis, each sealing member 70 was immersed in the deteriorated gasoline having a temperature of 80° C., and a relation between the immersion time and the interfacial strength was obtained. The material for the sealing member 70 was applied to the plate-like member to be sealed and hardened so that the sealing member 70 having a pudding cup shape was formed. The interfacial strength was measured by a test for measuring shear strength with respect to the above sealing member 70, i.e., a pudding cup test. The result is shown in FIG. 5.

FIG. 5 is a graph showing the relation between the immersion time and the interfacial strength in the case where the amine-based hardener is used and in the case where the anhydride-based hardener is used. The white rhombus plots in FIG. 5 show the case where the amine-based hardener is used, and the black rhombus plots in FIG. 5 show the case where the anhydride-based hardener is used.

The plots in FIG. 5 surrounded by broken line circles show shear strength when the member to be sealed itself fractures and a fracture at a boundary portion between the sealing member and the member to be sealed does not occur, i.e., interfacial strength of “cohesion failure of the member to be sealed”. The plots in FIG. 5 surrounded by solid line circles show shear strength when a fracture at the boundary portion occurs, i.e., interfacial strength of “interface failure”.

As shown in FIG. 5, the interfacial strength is drastically decreased when the anhydride-based hardener is used compared to when the amine-based hardener is used. The result directly reflects the difference of the ring-opening rate, and eventually, the difference of the adhesion force with the member to be sealed between the amine-based hardener and the anhydride-based hardener. Accordingly, it was decided to use the amine-based hardener as the hardener.

The inventors analyzed mechanical strength of the sealing member 70. The sealing member 70 includes resin containing the glycidyl amine-based epoxy resin having the glass-transition temperature of 180° C. and the dielectric constant of 3.5 as epoxy resin and the amine-based hardener, and the filler. The filler content is 80% by weight.

In the analysis, the sealing member 70 that is hardened to have a dumbbell shape, was immersed in the deteriorated gasoline having a temperature of 80° C., and a relation between the immersion time and the mechanical strength was measured. Here, the mechanical strength was obtained as follows. Tension is applied to the sealing member 70 having the dumbbell shape, and stress when the sealing member 70 is broken, that is, breaking stress was obtained as the mechanical strength. The result is shown in FIG. 6.

FIG. 6 is a graph showing the relation between the immersion time (unit: hour) and the breaking stress (unit: MPa). As shown in FIG. 6, the mechanical strength of the sealing member 70 of the present embodiment hardly changed even if the sealing member 70 was exposed to the fuel atmosphere. That is, the sealing member 70 has a great fuel resistance property.

As described above, according to the present embodiment, the sealing member 70 is made of glycidyl amine-based epoxy resin having the glass-transition temperature of 180° C. or more and the dielectric constant of 3.5 or less, the amine-based hardener that ring-opens epoxy groups of the epoxy resin to harden the glycidyl amine-based epoxy resin, and the filler made of silica. Therefore, even if the sealing member 70 made of resin material is used, components in fuel, such as an aromatic compound or ethanol can be prevented from penetrating the inside of the sealing member 70.

Second Embodiment

FIG. 7 is a schematic cross-sectional view showing a substantial part of a fuel resistance package according to the second embodiment of the present invention. In the present embodiment, an object to be sealed by the sealing member 70 is different from that in the first embodiment, and the different point will be mainly described.

As shown in FIG. 7, the package of the present embodiment has a bump 31 in place of the wire 30 as the connecting member, which electrically connects the sensor chip 10 and the first substrate 20 that supports the sensor chip 10. The bump 31 is a general bump made of gold, copper or the like.

According to the present embodiment, in the configuration shown in FIG. 7, a part 72 other than the sealing member 70, that is, the part 72 composed of the sensor chip 10, the first substrate 20 and the bump 31 corresponds to a member 72 to be sealed. In the member 72 to be sealed, the sealing member 70 is placed between the sensor chip 10 and the first substrate 20, and seals the bump 31.

In this case, the sealing member 70 also has a function as an underfill member below the sensor chip 10, and it is desirable to decrease somewhat the filler content compared to the sealing member 70 of the first embodiment.

Third Embodiment

FIG. 8 is a schematic cross-sectional view showing a fuel resistance package according to the third embodiment of the present invention. As shown in FIG. 8, the package of the present embodiment is different from the package S1 of the first embodiment (refer to FIG. 1) in that the wire 30 and the sensor chip 10 that is located adjacent to the wire 30 are sealed by the first resin portion 61 not the sealing member 70.

Here, a member 73 to be sealed in the present embodiment corresponds to a part other than the sealing member 70 in the configuration shown in FIG. 8. That is, as with the package S1 of the first embodiment, in the present embodiment, the member 73 to be sealed includes the first resin portion 61 that is primary molded and the second resin portion 62 that is secondary molded and located to be in contact with the first resin portion 61, and the boundary portion between the first and second resin portions 61, 62 is sealed by the sealing member 70.

As described above, the sealing member 70 may seal only the boundary portion at which the first resin portion 61 contacts the second resin portion 62. In this case, by using the sealing member 70, the fuel resistance property at the boundary portion and increasing of the joint strength at the boundary portion can be obtained.

Fourth Embodiment

FIG. 9 is a schematic cross-sectional structure showing a fuel resistance package according to the fourth embodiment of the present invention. In the present embodiment, an object to be sealed by the sealing member 70 is different from that in the first embodiment.

As shown in FIG. 9, in the package of the present embodiment, a circuit chip 11 is mounted to the one surface of the first substrate 20 through the adhesive 50, and the circuit chip 11 is connected to the first substrate 20 through the adhesive 50. Furthermore, the circuit chip 11 is wire-connected to the one surface of the first substrate 20 with the wire 30, and thereby the circuit chip 11 is electrically connected to the first substrate 20.

In this case, a member 74 to be sealed is composed of the components in FIG. 9 other than the sealing member 70, that is, the circuit chip 11, the first substrate 20 and the wire 30. In the present embodiment, the whole circuit chip 11 and the whole wire 30 are used in the fuel atmosphere 1, and the sealing member 70 seals to surround the whole circuit chip 11 and the whole wire 30 at a side of the one surface of the first substrate 20.

When the package is used, the circuit chip 11 and the wire 30 in the member 74 to be sealed, which are located in the fuel atmosphere 1 and need the fuel resistance property, are sealed with the sealing member 70. Therefore, the deterioration of the circuit chip 11 and the wire 30 due to the fuel can be prevented.

Fifth Embodiment

FIG. 10 is a schematic cross-sectional structure showing a fuel resistance package according to the fifth embodiment of the present invention. In the package of the present embodiment, a member 75 to be sealed is composed of the second substrate 40 that is connected to the first substrate 20, the first resin 61 that seals the whole circuit chip 11 and the whole wire 30 on the one surface of the first substrate 20, and the second resin portion 62 that seals a part of the first resin portion 61 and a part of the first and second substrates 20, 40, in addition to the components in FIG. 9 such as the circuit chip 11, the adhesive 50, the first substrate 20 and the wire 30.

The sealing member 70 seals the boundary portion at which the first resin portion 61 contacts the second resin portion 62 in the member 75 to be sealed. According to the present embodiment, by using the sealing member 70, the fuel resistance property at the boundary portion and increasing of the joint strength at the boundary portion can be obtained.

Other Embodiments

Epoxy resin in the sealing member 70 is not limited to the glycidyl amine-based epoxy resin shown in the above embodiments as long as the epoxy resin has the glass-transition temperature of 180° C. or more and the dielectric constant of 3.5 or less. For example, the epoxy resin may be polycyclic epoxy resin other than the glycidyl amine-based epoxy resin.

As long as the member to be sealed includes the first member, the second member and the connecting member that electrically connects the first and second members, and the connecting member is sealed with the sealing member, the above components are not limited to the sensor chip 10, the circuit chip 11, the first substrate 20, the wire 30 and the bump 31. For example, both the first and second members may be chips, circuit boards or the like, and the connecting member may be a tape-like lead member.

While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments and constructions. The invention is intended to cover various modification and equivalent arrangements. In addition, while the various combinations and configurations, which are preferred, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the invention.

Claims

1. A fuel resistance package comprising:

a member to be sealed, which is used in a fuel atmosphere including at least one of an aromatic compound and ethanol; and

a sealing member, which seals the member to be sealed so that the member to be sealed is protected from fuel in the fuel atmosphere, wherein

the sealing member is made of resin containing epoxy resin having a glass-transition temperature of 180° C. or more and a dielectric constant of 3.5 or less, and filler made of silica is contained in the resin.

2. The fuel resistance package according to claim 1, wherein

the epoxy resin is glycidyl amine-based epoxy resin, and

the sealing member further includes an amine-based hardener that ring-opens an epoxy group of the glycidyl amine-based epoxy resin to harden the glycidyl amine-based epoxy resin.

3. The fuel resistance package according to claim 1, wherein

the member to be sealed includes: a first member; a second member; and a connecting member that electrically connects the first member and the second member, and

the connecting member is sealed with the sealing member.

4. The fuel resistance package according to claim 1, wherein

the member to be sealed includes: a first resin portion that is primary molded; and a second resin portion that is secondary molded and located to be in contact with the first resin portion, and a boundary portion between the first resin portion and the second resin portion is sealed with the sealing member.

5. The fuel resistance package according to claim 4, wherein

the member to be sealed further includes: a first member; a second member; and a connecting member that electrically connects the first member and the second member, and

the connecting member is sealed with the first resin portion.

6. The fuel resistance package according to claim 2, wherein

the sealing member further includes a coupling agent that ensures a binding property between the filler and the glycidyl amine-based epoxy resin.