JPS60170316A - Airtightly sealed type crystal oscillator - Google Patents

Abstract

PURPOSE:To prevent occurrence of blowholes in a sealing layer of low-melting point glass, by joining and fixing a crystal oscillator with and to an external supporting body through a heat-curing layer of specific polyimide type conductive paste and airtightly sealing them with the low-melting point glass. CONSTITUTION:Leading-out sections of Ag-Au thin films 2 are formed on both surfaces of the crystal plate 1a of a crystal oscillator 1 in such a way that they are positioned at opposite sides on both sides of the crystal plate 1a, and a pair of lead frames 3 are passed through a glass-made lower case 4a and united with the lower case 4a in one body. The front end part 3a of the frames 3 corresponding to the leading-out section of the thin films 2 are joined with and fixed to the crystal oscillator 1 through a conductive heat-curing layer 5, and the lower case 4a and upper case 4b are sealed with a sealing layer 6 of low-melting point glass. The layer 5 is formed by using polyimide type conductive paste which is formed by using polyimide type conductive paste which is prepared by reacting 1-50mol% diaminosiloxane shown by the formula, 99-50mol diamine which does not contain any silicon atoms in the molecule, and 100mol% aromatic carboxylic acid dianhydride or its drivative simultaneously in a solvent and mixing a conductive filler with the reacted product and, therefore, occurrence of blowholes in the layer 6 can be prevented.

Description

[Detailed Description of the Invention] The present invention relates to a hermetically sealed crystal oscillator.
The purpose is to provide a crystal oscillator as described above that does not cause blow balls that cause hermetic breakdown in the sealing layer of low melting point glass, and that has excellent adhesive strength between the crystal oscillator and the external support. be.

This type of hermetically sealed crystal oscillator has a crystal resonator bonded and fixed to an external support using a conductive bonding agent, and this is hermetically sealed inside a case using low-melting glass. The demand for crystal oscillators has been increasing in recent years because they are more reliable than can-sealed crystal oscillators. However, the epoxy resin-based conductive paste, usually epoxy silver paste, which has traditionally been mainly used for bonding the crystal resonator and the external support, has a thermal decomposition starting temperature of about 300 to 350°C, so it cannot be sealed in an airtight manner. In case of sealing type, it thermally decomposes at the heating temperature (420 to 470"C) during sealing with low melting point glass, resulting in poor conductivity of the joint and a decrease in adhesive strength, as well as thermal decomposition. By creating blowholes (holes that break airtightness) in the low-melting glass layer, which is in a molten state due to outgas, and by extension its hardened sealing layer, or by thinning the layer thickness due to an increase in internal pressure, it becomes impossible to achieve hermetic sealing. I had something to do.

On the other hand, as an alternative to the epoxy resin-based conductive paste, a polyimide-based conductive paste with excellent heat resistance is being considered. This polyimide conductive paste is
It has a high thermal decomposition temperature of 450 to 500°C, and is considered promising because it can withstand the sealing conditions of one hour (approximately 5 to 15 minutes) at the optimum heating temperature for low-melting glass, but on the other hand,
The drawback is that the adhesive force and fixing strength between the crystal resonator and the external support are poor, and the bonded portion easily separates due to impact or the like. Therefore, it has been proposed to improve the adhesion direction by blending a silane coupling agent into the polyimide-based conductive paste, or by applying a silane coupling agent as a primer to the bonding surface in advance. However, depending on the conditions of use, the latter method may actually lead to a decrease in adhesive strength, and the latter method has the problem of increasing the number of steps for manufacturing the crystal oscillator.

As a result of intensive studies in view of the above situation, the inventors discovered that a solution of a specific siloxane-modified polyimide precursor was used to bond the crystal oscillator of a hermetically sealed crystal oscillator to an external support. When a polyimide conductive paste containing a filler is used, thermal decomposition during sealing can be avoided, blowholes do not occur in the sealing layer, and the adhesive strength and fixing strength are high, making it resistant to impact, etc. The inventors discovered that the crystal oscillator and the external support were not easily separated, and came up with the present invention.

That is, the present invention provides a hermetically sealed crystal resonator in which a crystal resonator is bonded and fixed to an external support via a conductive bonding layer, and this is hermetically sealed with low melting point glass. A) General formula; (R1 is a divalent organic group, R' is a monovalent organic group, n is an integer from 1 to I, 000) 1 to 50 mol% of diaminosiloxane and B
) A siloxane-modified polyimide precursor obtained by simultaneously reacting 99 to 50 mol% of a diamine that does not contain a silicon atom in the molecule and C) 100 mol% of an aromatic tetracarboxylic dianhydride or its derivative in a solvent. The present invention relates to a hermetically sealed crystal oscillator comprising a heat-cured layer of a polyimide conductive paste containing a conductive filler in a solution.

In the present invention, in the diaminosiloxane represented by the general formula (1), each R1 and R' in the formula may be the same or different, and a wide variety of conventionally known diaminosiloxanes are included. A typical example is as follows.

The diamine that does not contain a silicon atom in its molecule (hereinafter simply referred to as a silicon-free diamine) used in this invention has the following general formula (2); % formula % (2) (R, does not contain a silicon atom) Aromatic diamines, aliphatic diamines, and alicyclic diamines represented by (which are divalent organic groups) are included, and R2 in the formula may be the same or different from R1 in the general formula (1). It's okay. Particularly preferred are aromatic diamines, representative examples of which include meta-phenylene diamine, para-phenylene diamine, 4,4'-diaminodiphenylmethane, 4-diaminodiphenylmethane,
・4'-diaminodiphenyl ether, 2,2'-bis(4-aminophenyl)propane, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl sulfide, benzidine, benzidine-3,3'-dicarboxylic acid , benzidine-3,3'-disulfonic acid, benzidine-3-monocarboxylic acid, benzidine-3-monosulfonic acid, 3,3'-dimethoxy-benzidine, para-bis(4-aminophenoxy)benzene, meta-bis (4
-aminophenoxy)benzene, metaxylene diamine, baraxylene diamine, and the like.

In this invention, the aromatic tetracarboxylic dianhydride or its derivative to be polymerized with the diamino compound consisting of the diaminosiloxane and silicon-free diamine has the following general formula (3); % formula % (Ar is a tetravalent It is a dianhydride represented by (which is an organic group) or its derivative, and representative examples thereof are as follows.

That is, pyromellitic dianhydride, 3, 3', 4, 4
'-benzophenonetetracarboxylic dianhydride, 3.3
',4,4'-biphenyltetracarboxylic dianhydride,
2,3,3',4'-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)proponic anhydride, bis(3,4-dicarboxyphenyl)sulponic anhydride, bis (3,4-dicarboxyphenyl)ether dianhydride, 2,2'-bis(
2,3-dicarboxyphenyl)propanihydride, 1
・1'-bis(2,3-dicarboxyphenyl)ethane dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride , aromatic tetracarboxylic dianhydrides such as 1,2,7,8-phenanthrenetetracarboxylic dianhydride and their halides, or derivatives such as lower dialkyl ester compounds, which may be used in combination of one or two types. You can use the above.

In this invention, it is necessary to simultaneously polymerize the diaminosiloxane and the silicon-free diamine with an aromatic tetracarboxylic dianhydride or a derivative thereof,
For example, when both diamino compounds are polymerized separately and then mixed, the adhesion of the polyimide-based conductive paste obtained by blending a conductive filler with the diamino compounds and 1li4
Variations in moisture characteristics occur, making it impossible to stabilize quality.

The ratio of the diamino compound consisting of diaminosiloxane and silicon-uncombined diamine to the aromatic tetracarboxylic dianhydride or its WM'A form is usually equimolar, but if necessary, one may be used in a slightly larger amount ( It's okay to do that.

The polymerization reaction may be carried out according to a conventionally known method, and is generally carried out in the presence of an organic solvent in a nitrogen gas stream, while taking into account the exothermic temperature of polymerization, usually at a temperature of 60° C. or lower, and particularly preferably at a temperature of 30° C. or lower. The reaction may be carried out until a high degree of polymerization is reached. This degree of polymerization can be easily detected by examining the intrinsic viscosity [η] of the reactant.

Examples of the organic solvent include N-methyl-2-pyrrolidone, N-N'-dimethylacetamide, N-N'-
Highly polar basic solvents such as dimethylbormamide, N-N'-dimethylsulfoxide, and hexamethylphosphoramide are used. Note that all of these types of solvents are highly hygroscopic, and the absorbed water causes a decrease in molecular weight during polymerization, so it is recommended that they be sufficiently dehydrated with a dehydrating agent before use. In addition to these solvents, there are also general-purpose solvents such as toluene, xylene, benzonitrile, benzene, phenol, and butyl cellosolve. Although a container can be used in combination, the amount used should be within a range that does not reduce the solubility of the polyimide precursor produced.

The siloxane-modified polyimide precursor obtained by the above polymerization reaction is obtained by adding a silicon-free diamine and a diaminosiloxane to an aromatic tetracarboxylic dianhydride via an amide bond, as shown in the following general formula (4). It has a polymer structure in which the bonding units are random, and has a structure in which siloxane bonds are incorporated into the molecular chain of the polyimide precursor.

The siloxane-modified polyimide precursor represented by the general formula (4) is converted into the siloxane-modified polyimide represented by the following general formula (5) by heating and curing.

(R, , R2, R', Ars l, m, and n are as described above) The polyimide-based conductive paste used in this invention is obtained by kneading a conductive filler into a solution of the siloxane-modified polyimide precursor. It is obtained by making it into a paste form. Examples of conductive fillers include Au, Ag, Pd, Pt,
Mn, Cu, Ni.

Metal powder such as AI, Fe, Co, Cr or alloy powder thereof, Ru0z, Cru□, ZnO1SnOx, F
(1203, In203, PdO, Tl20y,
Examples include oxide powders such as Iro, Ph01SbO3, BiO3, and CdO.

One or more of these conductive fillers can be used, and carbon, graphite, carbon black, etc. may also be used in combination with these, but Ag powder and a mixture or alloy powder of Ag and Pd are particularly suitable. It is.

Note that these conductive fillers have various particle shapes such as dendritic, scaly powder, porous material, and acicular powder depending on the manufacturing method, but dendritic and scaly powder are particularly suitable. It is. The particle size of these particles is usually 100 mesh free passes, preferably 325 mesh free passes.

To knead the conductive filler into the solution of the siloxane-modified polyimide precursor, a dispersing machine such as a three-roll mill or a ball mill can be used, but the Miki roll is particularly suitable because it is capable of dispersing high-viscosity paste and has good recovery efficiency. In addition, during this mixing, an appropriate amount of a dispersion aid typified by a surfactant may be used as necessary to improve the properties of the paste. The content of the conductive filler (2) is preferably in a range that accounts for 60 to 95% by weight, preferably 70 to 90% by weight, of the total solid content of the polyimide conductive paste.

The thus obtained polyimide-based conductive paste exhibits excellent adhesion when bonding the crystal resonator and the external support, and after drying to remove the organic solvent,
By heat-treating at about ℃, the polyimide precursor undergoes an intramolecular ring-closing reaction and imidizes, forming a conductive cured layer with a thickness of usually 5 to 100 μm in which a conductive filler is dispersed and bound in a siloxane-modified polyimide resin. Form. This hardened layer has excellent heat resistance, and is usually heated at 420 to 470°C.
It can withstand sealing with low-melting glass that takes about 15 minutes, and almost completely prevents blowhole formation in the glass sealing layer due to outgas. Furthermore, the conductive layer has a high adhesive strength, and there is no fear that it will come off at the joint even if a relatively strong impact is applied to the crystal oscillator.

FIG. 1 is a schematic sectional view showing an example of a hermetically sealed crystal oscillator according to the present invention, and FIG. 2 is a plan view of the crystal oscillator used in the oscillator.

As shown in the figure, in the crystal resonator 1, a silver-gold thin film 2 is provided on both sides of a disc-shaped crystal plate 1a, except for the peripheral edge, and each silver-gold thin film 2 is provided with a silver-gold thin film 2 on both sides of the crystal plate 1a. The lead-out portions 2a are formed so as to be located on opposite sides in the radial direction. A pair of lead frames 3 pass through the lower case 4a made of glass from both sides, and are integrated into the lower case 4a by being placed in molten glass during molding of the lower case 4a.

The crystal resonator 1 and both lead frames 3 are
Bonding is performed via a conductive heat-cured layer 5 formed by applying a conductive paste and heat-curing it so that electrical conduction is established between the lead-out portion of the gold thin film 2 and the leading end 3a of the lead frame 3. Fixed. Further, like the lower case 4a, the lower case 4a is joined to the upper case 4b made of glass by a low melting point glass sealing layer 6 at the opposing peripheral end face, and the inside of the crystal resonator case 4 is hermetically sealed.

Note that as the material constituting the case 4, ceramic may be used instead of glass. Furthermore, in the above example, the lead frame 3 is arranged so as to pass through the lower case 4a, but it is arranged separately from the lower case 4a so as to pass through the glass sealing layer 5 during glass sealing. Good too.

Next, examples and comparative examples of the present invention will be shown.

The organic tetracarboxylic dianhydride, organic diamine, and organic solvent used below are purified by purification methods such as recrystallization and distillation to eliminate harmful impurities, such as reducing the content of Na'' ions and C1- ions to 5 ppm or less. ingredients are removed.

Example 1 Stirring device, cooling tube. 198 N-methyl-2-pyrrolidone in a flask equipped with a thermometer and nitrogen purging device.
．． 3 g, bis(3-aminopropyl)tetramethyldisiloxane 0.87 g' (0,0035 mol), 4.
4'-diaminodiphenyl ether 19.3g (0,
0965 mol) and stirred until dissolved,
29.4 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was gradually added, and the reaction system was kept below 30°C to form a transparent viscous solution. The reaction system was then maintained at 60° C. for 8 hours to obtain a solution of a siloxane-modified polyimide precursor with a non-volatile solid content of 20.0% by weight and a solution viscosity of 420 voids.

325 to 100 g of the obtained above solution (solid content 20 g)
Mesh free pass scaly silver powder (maximum particle size 32μm,
A conductive paste was prepared by adding 96.6 g of the powder having an average particle size of 5.1 μm and kneading and dispersing it with a three-roll roll. The viscosity of this conductive paste was 870 voids. After applying this conductive paste dropwise onto a 4.2 alloy lead frame and bonding the crystal resonator with the configuration shown in Figure 2,
Drying and imidization were performed by performing stepwise heat treatment at 30 minutes at 200 degrees centigrade, 30 minutes at 200 degrees centigrade, and 90 minutes at 300 degrees centigrade to form a conductive heat-cured layer. Next, the upper and lower cases of the crystal oscillator case were sealed by heating to 430° C. for 15 minutes using low melting point glass to produce a hermetically sealed crystal oscillator as shown in FIG.

Fifty crystal oscillators produced in this way were dropped onto hardwood from a height of 75 cm to test the adhesive strength of the joint between the crystal oscillator and the lead frame. The above-mentioned bonded portion was separated, and no conductivity defects were observed at all. In addition, in order to determine the airtight sealing state, a crystal oscillator 50 with helium gas sealed in the case when sealed with low melting point glass is used.
When a leak test was performed on each of the samples by placing them in a vacuum container, it was found that all of them showed no gas leakage and were completely hermetically sealed.

Example 2 In the same manner as in Example 1, N-methyl-2-pyrrolidone 2
2.485 g (0.01 mol) of bis(3-aminopropyl)tetramethyldisiloxane in 10.0 g
, 17.82 g of 4,4'-diaminodiphenylmethane
(0.09 mol) was melted, and 32.2 g (0.09 mol) of 3,3',4,4'-hensiphenotetracarboxylic dianhydride was dissolved.
, 1 mol) to react with a non-volatile solid content of 1948% by weight,
A solution of a siloxane-modified polyimide precursor having a solution viscosity of 143 voids was obtained. This solution long (solid content 19.8
g) 79.2 g of 325 mesh free pass scaly silver powder (maximum particle size 28 μm, average particle size 2.8 μm) and 3
Add 19.8 g of scaly palladium powder (maximum particle size 32 μm, average particle size 3.3 μm) of 25 mesh free pass,
A conductive paste having a viscosity of 280 voids was prepared in the same manner as in Example 1, and a hermetically sealed crystal oscillator was produced in the same manner as in Example 1. When this crystal oscillator was subjected to the same adhesive strength test and leakage test as in Example 1, the number of defective crystal oscillators out of 50 specimens was zero.

Comparative Example N-methyl-2-pyrrolidone 19 was prepared in the same manner as in Example 1.
4,4'-diaminodiphenyl ether 2 in 7.6g
Melt 0.0g (0.1 mol), then 3, 3', 4
・4'-biphenyltetracarboxylic dianhydride 29.4
g (0.1 mol) was reacted to obtain a polyimide precursor solution having a nonvolatile solid content of 20.0% by weight and a solution viscosity of 450 voids. A conductive paste was prepared using this solution in the same manner as in Example 1, and a hermetically sealed crystal oscillator was produced in the same manner as in Example 1. When this crystal oscillator was subjected to an adhesive strength test in the same manner as in Example 1, separation of the bonded portion was observed in 19 out of 50 samples, and 30 out of 50 samples suffered from electrical failure. In addition, in the same leak test as in Example 1, the number of defective pieces out of 50 samples was O.
It was found that there was no problem with the heat resistance of the cured conductive layer.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a hermetically sealed crystal oscillator according to the present invention, and FIG. 2 is a plan view of a crystal oscillator constituting the same crystal oscillator. 1. Crystal resonator, 3. Lead frame (external support), 4. Crystal oscillator case, 5. Heat hardening layer, 6. Low melting point glass sealing layer. Patent Applicant: Nitto Electric Industry Co., Ltd. Figure 1 Figure 2 Procedural Amendment Portal 1, Indication of Case Patent Application No. 1982-26725 2, Name of Invention Hermetically Sealed Crystal Oscillator 3, Percentage of Persons Making Amendments 1 Relationship with Patent applicant ft N+ 1-1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Name 1
$ (396) Nitto Electric Industry Co., Ltd. Representative Kamigata 3rd Department 4, Agent Mail No. 11III 530 7. Contents of amendment A, Specification: (1) Lines 9-8 from the bottom of No. 14; “Carbon, graphite " has been corrected to "Carbon Graftito". (2) Line 7 from the bottom of No. 14; "Mixed" has been corrected to "Mixed powder." Patent applicant Nitto Electric Industry Co., Ltd.

Claims (1)

[Scope of Claims] (1') A hermetically sealed crystal oscillator in which a quartz crystal oscillator is bonded and fixed to an external support via a conductive bonding layer and hermetically sealed with low melting point glass. The conductive bonding layer is A)
General formula; (R, is a divalent organic group, R' is a monovalent organic group, n
is an integer from 1 to t, ooo), B) 99 to 50 mol% of a diamine that does not contain a silicon atom in the molecule, and C) an aromatic tetracarboxylic acid. It consists of a heat-cured layer of a polyimide-based conductive paste in which a conductive filler is blended into a solution of a siloxane-modified polyimide precursor obtained by simultaneously reacting 100 mol% of a dianhydride or its derivative in a solvent. Features a hermetically sealed crystal oscillator.