JPS6071662A - Conductive silver paste composition - Google Patents

Abstract

PURPOSE:To obtain titled composition with high adhesivity and heat resistance and good moisture resistance characteristics, useful for die bonding for semiconductor device, by incorporating silver powder in an organic solvent solution of specific cyclohexane-modified polyimide resin or its precursor. CONSTITUTION:The objective composition can be obtained by incorporating ( I ) an organic solvent solution of cyclohexane-modified polyimide resin or its precursor derived from the reaction, in organic solvent, between (A) a diamino compound consisting of (i) 1-40 (pref. 1-15)mol% of diaminocyclohexane of formula I (R is divalent organic group; R' is monovalent organic group; n is integer 1-1,000) and (ii) 60-99 (pref. 85-99)mol% of aromatic diamine containing >=10 (pref. >=50)mol% of 2,5-di(4-aminophenyl)-3,4-diphenyl thiophene (of formula II) and (B) aromatic tetracarboxylic dianhydride or its derivative with (II) 60-95 (pref. 70-90)wt%, on a solid basis for the whole composition, of silver powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive silver paste composition that is useful primarily for so-called "Glue bonding" for adhesively fixing a semiconductor element to a substrate consisting of a stem or a lead frame.

In a semiconductor device, such as a transistor, a semiconductor element is bonded onto an IJ-dead frame using a conductive adhesive material, and a pair of electrodes on the element are electrically connected to the corresponding other lead frame through metal wires. Furthermore, these are integrally sealed with resin. Conventionally, a conductive silver paste composition containing an epoxy resin as a binder component has been used as the conductive adhesive material described above, and after coating a predetermined amount of this on a lead frame and arranging a semiconductor element on the lead frame, A technique has been used in which heat-hardening and die-bonding of recording elements is performed. However, semiconductor devices die-bonded using the conventional conductive silver paste composition have a drawback of poor electrical properties at high temperatures.

To avoid this drawback, a conductive silver paste composition is prepared by kneading silver powder into a solution of a precursor of a general polyimide resin such as polyamic acid, which is composed of pyromellitic anhydride and a normal aromatic diamine. has been proposed,
According to this method, the precursor is ring-closed (imidized) by heat curing during bonding to provide a polyimide resin with extremely excellent heat resistance, and good results are brought about in the electrical properties of the semiconductor device at high temperatures.

However, the precursor of the polyimide resin proposed above has a relatively high moisture absorption rate after ring closure (imidization) and has poor adhesion to semiconductor devices, so it is difficult to bond the substrate and device under high temperature and high humidity. There was a drawback that moisture resistance properties such as a decrease in strength were not obtained.

In view of the above, the object of the present invention is to provide a new and useful conductive adhesive material that can firmly adhesively fix a semiconductor element onto a substrate and has improved heat resistance and moisture resistance.

By the way, the applicant has already developed a polyimide that has good adhesion to semiconductor devices, has a low moisture absorption rate, and is soluble in organic solvents by reacting a specific diamine with an aromatic tetracarboxylic acid or its derivative. We succeeded in obtaining a resin or previous structure.

In subsequent research, this invention involved dissolving the organic solvent-soluble polyimide resin obtained as described above in an organic solvent, or preparing an organic solvent solution of its precursor.
A conductive silver paste composition prepared by further kneading silver powder into these solutions can be used to produce semiconductor devices that meet the above purpose, that is, do not have any of the drawbacks of conventional epoxy thread and polyimide resin precursor silver paste compositions. This was done after discovering that it could be an extremely suitable conductive adhesive material for tie-ponting.

That is, this invention provides the general formula (1);
R is a divalent organic group, R' is a monovalent organic group, n is 1 to 10
an integer of 00] 1 to 40 mol% of diaminosiloxane represented by
・Aromatic diamine 60 to 99 containing at least 5-di(4-aminophenyl)-3,4-diphenylthiophene
Silver powder is kneaded into an organic solvent solution of a siloxane-modified polyimide resin or its precursor obtained by reacting a diamino compound consisting of The present invention relates to a characteristic conductive silver paste composition.

According to the above-mentioned invention, since the conductive adhesive material based on polyimide resin or its precursor is used, electrical properties at high temperatures can be improved, and the diamine component constituting the polyimide resin or its precursor is The use of diaminosiloxane improves the adhesion between the semiconductor element and the substrate, and 2,5-di(4-aminophenyl)-3,4- as another cyamine component.
Since diphenylthiophene is used as an essential component, the moisture absorption rate of the polyimide resin decreases, and these effects can significantly improve moisture resistance, such as improving the adhesive strength between the element and the substrate at high temperatures. .

Further, in this invention, when an organic solvent solution of the polyimide resin itself is used as the vehicle for kneading the silver powder, a paste composition in which the silver powder is kneaded is interposed between the semiconductor element and the substrate, and then the organic solvent is volatilized. Since the conductive cured adhesive layer having the above-mentioned good properties can be formed under mild heating conditions that can be removed, the effect of greatly facilitating the bonding operation is obtained.

In other words, since conventional general polyimide resins are usually infusible and insoluble, it is necessary to prepare an organic solvent solution of the precursor as described above and knead silver powder with it. In order to imidize the above-mentioned precursor, high-temperature heat treatment must be performed, which is disadvantageous in terms of workability.

On the other hand, since the siloxane-modified polyimide resin according to the present invention is soluble in organic solvents, it is possible to use an organic solvent solution of the polyimide resin itself as a vehicle for the silver powder, as described above. This will improve workability.

Of course, the present invention includes not only the use of an organic solvent solution of the polyimide resin itself but also the use of an organic solvent solution of its precursor. That is, if the above-mentioned improvement in workability is not particularly desired, the use of an organic solvent solution of the precursor is not excluded. It can be used satisfactorily depending on the application, and even in this case, at least the drawbacks of the conventional precursor solutions mentioned above can be overcome.

Typical examples of the diaminosiloxane represented by the general formula (1) used as a component of the diamino compound in this invention include the following.

These diaminosiloxanes should be used in a proportion of 1 to 40 mol%, preferably 1 to 15 mol%, based on the total amount of diamino compounds. If it is less than 1 mol %, no effect of improving the adhesion to the semiconductor element can be obtained, and if it exceeds 40 mol %, the properties such as moisture absorption rate and heat resistance of the polyimide will be impaired, which is inappropriate. Furthermore, regarding the practical amount of the above-mentioned diaminosiloxane, it is desirable from the viewpoint of retention characteristics that the silicon atom content in the finally obtained polyimide or its precursor is suppressed to 2% by weight or less.

<Example of Diamino Siloxane> CHa OCH3CH3 111 CHa , CHa 1 CH3CH3 CHa CHa The aromatic cyamine used in combination with the above diamino siloxane accounts for 60 to 99 mol%, preferably 85 to 99 mol% of the total amount of the diamino compound. The essential component of this aromatic diamine is 2,5-di(4
-aminophenyl)-3,4-diphenylthiophene(
(hereinafter referred to as thiophene diamine) is used.

The above-mentioned thiophene diamine is preferably used in an amount of 10 mol % or more, preferably 50 mol % or more in the aromatic diamine, and if the amount used is small, it will be difficult to obtain a polyimide resin with a low moisture absorption rate.

Aromatic cyamines other than thiophene diamines include:
Any conventionally known silicon-uncontained diamine can be used.

Specific examples of such diamines include mekphenylene diamine, paraphenylene diamine, 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, 2,2-his(4-aminophenyl),
3,3'-diaminodiphenylsulfony/, 4,4'
-diaminodiphenylsulfide, benzidine, benzidine-3,3-dicarboxylic acid, benzidine-3,3'-
Disulfonic acid, benzidine-3-monocarphonic acid, benzidine-3-monosulfonic acid, 3,3-dimethoxy-benzidine, para-bis(4-aminophenoxy)benzene, mecubis(4-aminephenoxy)benzene, mexylylenediamine , paraxylylene diamine, and the like.

In this invention, the aromatic tetracarboxylic dianhydride or its derivative to be reacted with the above diamino f and compound is, for example, pyromellitic dianhydride (hereinafter referred to as PM
DA), 3,4,3',4-benzophenonetetracarboxylic dianhydride (hereinafter referred to as BTDA), 3.
4,3',4-biphenyltetracarphonic dianhydride (
(hereinafter referred to as 5-BPDA), 2,3,3,4-biphenyltetracarboxylic dianhydride (hereinafter referred to as a-BPDA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1・2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propanihydride, Bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,4,9,10-
Examples include perylenetetracarphonic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, and derivatives of these dianhydrides such as chlorides and lower alkyl esters.

Among these, s-B PDA or a combination thereof with other dianhydrides is particularly preferable, and when such dianhydrides are used, pressure shoes at 121° C. and 2 atm. It has excellent electrical characteristics under car test (hereinafter referred to as PCT).
In other words, 1li1. j A polyimide resin with good moisture characteristics can be obtained.

In this invention, the reaction between the diamino compound and the aromatic tetracarboxylic dianhydride or its derivative is generally carried out in a nitrogen gas stream using approximately equal moles of the components in the organic solvent, but a slightly larger amount of one of the components is used. It's okay to do that. In this reaction, the diamino compound used is one or more of the above-mentioned diaminosiloxanes and one or more aromatic cyamines, which essentially include thiophene-based cyamine, and aromatic tetracarphonic dianhydride. As the compound or its derivative, one or more of those listed in Section 11 can be used.

When obtaining a precursor of a siloxane-modified polyimide resin by the above reaction, use a highly polar organic solvent such as N-methyl-2-pyrrolidone, N-N-dimethylacetamide, N-N'-dimethylformamide, or hexamethylphosphoramide. In addition to basic solvents, fluorinated solvents such as m-cresol, para-cresol, xylenol, phenol, and mixed solvents thereof, and low-humidity solvents such as aromatic solvents such as xylene and toluene may be used. I can do it.

The reaction conditions at that time, that is, the reaction conditions for obtaining the precursor, are usually 60°C or lower, particularly preferably 30°C or lower, and the reaction may be carried out at such temperature until a high degree of polymerization is obtained. . This degree of polymerization is the intrinsic viscosity of the reactant [η]
It can be easily detected by examining.

The siloxane-modified polyimide resin precursor thus obtained has an intrinsic viscosity [η] in the range of O14 to 0.8, and a solution viscosity of 1,000 at a nonvolatile content concentration of 25% by weight.
It is about 0 to 20,000 centipoise. If the intrinsic viscosity becomes too low, the film forming ability will be poor and the properties such as insulation properties and heat resistance will be impaired when applied to semiconductor devices.

In this specification, unless otherwise specified, the intrinsic viscosity [η] means a value calculated according to the following formula at a measurement temperature of 30±001° C. using N-methyl-2-pyrrolidone as a solvent.

Jn(t/lo) [η]-□ t: Falling time of polymer solution measured with Ubbelohde viscometer (o: Falling time of solvent measured in the same manner as above C: Polymer concentration (0.5% by weight) Above For example, in the case where only thiophene diamine is used as the aromatic diamine in the precursor of siloxane-modified polyimide resin, the thiophene diamine and diaminosiloxane form an amide bond, as shown in the general formula I2) below. It usually has constituent units that are bonded to aromatic tetracarboxylic dianhydride via random channels. This precursor is made into a paste composition by adding silver powder to the solution, which is applied to a semiconductor element, and then subjected to high-temperature heat treatment to form a siloxane-modified polyimide resin having an imide bond, as shown in the general formula (3) below. becomes.

On the other hand, when directly obtaining a siloxane-modified polyimide resin by the reaction in the organic solvent, the organic solvent may be a phenolic solvent such as mec-cresol, para-cresol, xylenopenophenol, or a mixed solvent thereof, or a xylene-based solvent. , a low hygroscopic solvent with the addition of an aromatic solvent such as toluene is used.

Using such a solvent, the reaction is generally carried out for about 1 to 10 hours while being gradually heated to a temperature in the range of 80 to 200°C. This reaction is a dehydration polycondensation reaction consisting of an amidation reaction and a subsequent imidization reaction, and the water produced as a by-product during the imidization reaction is removed by distillation out of the reaction thread. Removal of this water increases the reaction rate and yields a high molecular weight polyimide. Since the solvent is hardly compatible with water, it facilitates the distillation of by-product water, and also provides good results in preventing hydrolysis due to moisture absorption after the completion of the imidization reaction and the resulting decrease in molecular weight.

The siloxane-modified polyimide resin obtained in this way has an intrinsic viscosity [η] in the range of about 0.3 to 3.0, and has a thiophene-based diamine and The diaminosiloxane is usually randomly bonded to the aromatic tetracarboxylic dianhydride via an imide bond. Note that general formula (3) shows an example in which only thiophene diamine is used as the aromatic diamine.

This siloxane-modified polyimide resin can be prepared overnight by dissolving it in the organic solvent used in the above synthesis, or by isolating the resin from this solution by an appropriate means, and then adding it to another organic solvent (this solvent includes the above-mentioned highly polar basic It is used as a solution dissolved in a solvent (including a solvent).

In addition, in synthesizing the above-mentioned siloxane-modified polyimide resin or its precursor, each organic solvent as a reaction raw material, the above-mentioned tetracarboxylic dianhydride or its derivative, and diamine component are mixed with Na, l<, Ca.
If cationic impurities such as Cl- or anionic impurities such as Cl- are contained, when the obtained siloxane-modified polyimide resin or its precursor solution is applied to the Guiponting of a semiconductor device, the electrical properties and moisture resistance of the device may be affected. may become worse. Therefore, each of the above raw materials should be sufficiently purified in advance by a well-known method before use. For example, the content of Na ions is desirably 5 ppm or less, preferably l'ppm or less.

The conductive silver paste composition of the present invention is made by kneading silver powder into an organic solvent solution of the siloxane-modified polyimide resin or its precursor obtained as described above, and the adhesiveness during bonding is improved upon contact with this cross wire. Add a silane coupling agent or polysiloxane as necessary for purposes such as improving performance.

The silver powder used in this invention has various shapes depending on its manufacturing method, and examples include dendritic powder, scaly powder, granular powder, porous powder, and acicular powder.

Preferably, dendritic powder or scale powder is used.

The particle size of these silver powders is generally 100 mesh free pass, preferably 325 mesh free pass.

For use, it is usually 60 to 95% by weight based on the solid content of the entire composition.
, preferably 70 to 90 iii', 96.

The amount of organic solvent in the paste composition of the present invention is preferably such that the solid content concentration of the composition is usually about 10 to 50% by weight. If the amount of organic solvent used during the synthesis of the polyimide resin or its precursor is insufficient, it may be replenished as appropriate during the preparation of the paste composition.

The conductive silver paste composition of the present invention thus prepared is prepared by a known method such as interposing it between a stem or a lead frame and a semiconductor element, and then using a siloxane-modified polyimide resin. When an organic solvent solution is used, heat treatment is performed at a temperature that allows the solvent to volatilize, for example, 150 to 250° C. for 0.5 to 10 minutes. In the case of using an organic solvent solution of the precursor, the precursor is usually subjected to a high temperature heat treatment at 200 to 250 DEG C. for 120 to 360 minutes to imide the precursor. By doing this, the adhesion to the semiconductor element and the substrate is improved.
It is possible to form a cured adhesive resin layer with low moisture absorption, excellent conductivity and heat regeneration properties.

As described below, the conductive silver paste composition of the present invention can form a cured adhesive resin layer that has not only its original conductive function but also excellent heat resistance, adhesion, and thermal properties. It is extremely useful in a variety of applications that require a high degree of stability, and is especially effective for use in bonding semiconductor devices.

EXAMPLES Below, examples of the present invention will be described in more detail. The silver powder used in the following Examples and Comparative Examples was 325 mesh free pass scale silver powder in Examples 1 to 3 and Comparative Examples 1 to 3, and scaly silver powder of 325 mesh free pass in Examples 4 to 6 and Comparative Example 4.
-5 are dendritic silver powders having similar particle sizes.

Example 1 Reflux condenser with calcium chloride filled tube, stirrer,
216 g of N-methylpyrrolidone was placed in a 300 ml sepale flask equipped with a thermometer, and bis(3-aminopropyl)te-1-ramethyldisiloxane (
Said (cyaminosiloxane to formula H) 3.72P(0
, 015 mol), then thiophene diamine 8
5.539 (0,085 mol) was charged and stirred until dissolved. Then 5-BPDA29.4! i' (0,
1 mol) was gradually added and stirred while maintaining the temperature below 30°C until a clear viscous solution was obtained. As a result, a central solution of a siloxane-modified polyimide resin having an intrinsic viscosity of 0.90 was obtained.

Next, silver powder was added to this solution in an amount accounting for 80% by weight of the total solid content, and the mixture was thoroughly kneaded with a three-roll roll, and the solid content concentration was adjusted to 45.5% by weight by adjusting the amount of solvent. A silver paste composition was obtained.

Practical Example 2 The intrinsic viscosity was 0 in the same manner as in Example 1, except that 0.068 mole of thiophene diamine and 0.017 mole of 4,4-cyaminodiphenyl ether were used instead of 0.085 mole of thiophene diamine. A precursor solution of siloxane-modified polyimide resin of .93 was obtained, and using this solution, the following procedure was carried out in the same manner as in Example 1 to obtain a silver powder content (of the total solid content) of 78.
A conductive silver paste composition having a solid content of 41.2% by weight was obtained.

Comparative Example 1 A polyimide resin precursor solution was prepared in the same manner as in Example 1, except that 0.1 mol of 4,4-diaminodiphenyl ether was used instead of 0.015 mol of diaminosiloxane and 0.085 mol of thiophene thread diamine. Using this solution, a conductive silver paste composition having a silver powder content (of the total solid content) of 81% by weight and a solid content of 42.2% by weight was obtained in the same manner as in Example 1.

Comparative Example 2 Instead of 0.085 mol of thiophene diamine, 4.4
-A precursor solution of a siloxane-modified polyimide resin was obtained in the same manner as in Example 1, except that 0.085 mol of diaminodiphenyl ether was used. Using this solution, the silver powder content (total solid content) was ) 79% by weight,
A conductive silver paste composition having a solid content of 402% by weight was obtained.

Example 3 Reflux condenser with calcium chloride filled tube, stirrer,
In a 300 m, e separate flask equipped with a thermometer, 216 g of cresol and 1 (l) of xylene were added, and 3.727 g of bis(3-aminopropyl)tetramethyldisiloxane (diaminosiloxane to the above chemical formula) was added. (
Then, 35.53 g (0,085 mol) of thiophene diamine was added and stirred until dissolved. Then 29.4 g of 5-BPDA (0,1
mol) was gradually added and heated to 180°C for 1 hour while stirring.
The temperature rose to .

During the temperature rise, the reaction system temporarily became solid, but as the temperature was further heated, it became a homogeneous solution. Further, when the temperature of the reaction system reached 80 to 120°C, a dehydration reaction occurred and an imidization reaction began to proceed. The by-produced water was distilled out of the reaction system by azeotroping with xylene while flowing nitrogen gas. In this way, 180-1
The reaction was heated at 90° C. for 8 hours to obtain a transparent and viscous homogeneous solution.

The siloxane-modified polyimide resin solution thus obtained had a solid content concentration (measured by heating at 200°C for 2 hours) of 24.2% by weight and an intrinsic viscosity of 0780. Also, after applying this mW on a glass plate, 0.0 mW was applied at 80°C.
5mmH! When the infrared absorption spectrum of the film obtained by heating and drying under i' for 2 hours was measured, it was found to be 1780c.
Based on the Ikudo group at m and 1720\cm, absorption of C═O was clearly observed.

Using this solution, the silver powder content (
A conductive silver paste composition having a solid content of 41.0% by weight and a solid content of 41.0% by weight was obtained.

Example 4 s-BPDAo, instead of 1 mole, a-B P D
Same as Example 3 except that 0.1 mol of A was used,
A solution of a siloxane-modified polyimide resin having an intrinsic viscosity of 0.600 was obtained, and using this solution, the same procedure as in Example 1 was carried out to obtain a silver powder content (based on the total solid content) of 80% by weight.

A conductive silver paste composition having a solid content of 45.2% by weight was obtained.

Example 5 The procedure was repeated in the same manner as in Example 3, except that 0.1 mol of BTDA was used instead of 1 mol of s-BPDAo, so that the intrinsic viscosity was 0.
A solution of a siloxane-modified polyimide resin of 680 was obtained, and this solution was used to prepare a conductive silver paste composition having a silver powder content (of the total solid content) of 80 by weight and a 96° solid content by weight of 44.2 by weight in the same manner as in Example 1. I got it.

Example 6 s -B P D A O, instead of 1 mole, P M
A solution of a siloxane-modified polyimide resin having an intrinsic viscosity of 0.666 was obtained in the same manner as in Example 3, except that 0.1 mol of DA was used. Using this solution, the silver powder content was determined in the same manner as in Example 1. (of total solid content) 80 weight 96° solid content 4
A 3.9% by weight conductive silver paste composition was obtained.

Comparative Example 3 A polyimide resin precursor solution was prepared in the same manner as in Example 3, except that 0.1 mol of thiophene diamine was used instead of 0.015 mol of diaminosiloxane and 0.085 mol of thiophene thread diamine. Using this solution, a conductive silver paste composition having a silver powder content (of the total solid content) of 80% by weight and a solid content of 42.5% by weight was obtained in the same manner as in Example 1.

Comparative Example 4 Epoxy resin (Epicoat #828 manufactured by Shell Chemical Co., Ltd.
) 21', 0.047 g of 2-methylimidazole and 80 g of silver powder were added and thoroughly kneaded with a three-roll mill to obtain a conductive silver paste composition.

Comparative Example 5 To 10 g of epoxy resin (GY250, manufactured by Ciba Corporation), 57.2 g of phenol resin (K P-180, manufactured by Buyo Kagaku Co., Ltd.) was added.
- Phenylimidazole 0.05F and silver powder 857 were added and thoroughly kneaded with a three-roll mill to obtain a conductive silver paste composition.

Using each of the paste compositions according to the above Examples and Comparative Examples, the paste compositions were interposed between the semiconductor element and the lead frame, and then heated and cured, using a measuring machine as shown in the drawings. The shear adhesive strength (h/cm2) was measured at 25°C under normal conditions and after 40 hours of PCTX.
The retention rate of shear adhesive strength after 40 hours of PCTX was calculated according to the following formula. The results were as shown in the table below.

In the figure, 1 is a support, 2 is a lead frame, 3 is a conductive hardened adhesive layer, 4 is a semiconductor element, and 5 is a push-pull gauge for displaying shear adhesive force.

Furthermore, as for the conditions of the heat treatment for curing each composition, for the compositions of Examples 1 and 2 and Comparative Examples 1 and 2, 180°C x 30 minutes, 200°C x 30 minutes, 25°C
0°C x 300 minutes, and Examples 3 to 6 and Comparative Example 3
For the composition, the temperature was 250°C for 10 minutes. Further, the compositions of Comparative Examples 4 and 5 were heated at 180°C for 10 minutes.

As is clear from the above results, the conductive silver paste composition of the present invention can provide a highly reliable semiconductor device with good moisture resistance and no decrease in adhesive strength under high temperature and high humidity conditions. It turns out that.

[Brief explanation of drawings]

The drawing is an explanatory diagram showing a method for measuring adhesive force when a semiconductor element and a substrate are adhesively fixed using a conductive silver paste composition. Patent applicant: Nitto Electric Industry Co., Ltd. Agent: Kunio Negimoto, patent attorney

Claims (1)

[Claims] (1) 1 to 40 mol% of diaminosiloxane represented by the following general formula (1); [wherein, R is a divalent organic group, R' is a monovalent organic group, and n is an integer of 1 to 1000] and 2
・Aromatic diamine 60 to 99 containing at least 5-di(4-aminophenyl)-3,4-diphenylthiophene
Silver powder is kneaded into an organic solvent solution of a siloxane-modified polyimide resin or its precursor obtained by reacting a diamino compound consisting of Characteristic conductive silver paste composition.