JPS608372A - Paste for forming conductive material - Google Patents

Abstract

PURPOSE:The titled high-density composition for practical use, having improved long-term stability, screen printing characteristics, etc., comprising an organic binder consisting of ethyl cellulose, etc. and a (meth)acrylic resin-based polyol in a specific ratio, an electrically-conductive metal powder, and a solvent. CONSTITUTION:The desired composition is obtained by blending (A) an organic binder consisting of (i) ethyl cellulose and/or polyvinyl butyral, and (ii) a (meth)acrylic resin-based polyol (e.g., one having 5-200 hydroxyl value, -30- 80 deg.C glass transition temperature, and 1-100 acid value) in a weight atio of (1.0:0.5)-(0.4:1.0) with (B) electrically-conductive metal powder in a weight ratio of (0.5:100)-(5:100), and (C) 10-50wt% solvent (e.g., n-octyl alcohol, etc.).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-temperature firing type conductor-forming paste that has excellent suitability for forming conductor ice such as conductors and resistors for high-density packaging.

Conventionally, conductor-forming pastes used to form conductor circuits such as conductors and resistors for high-density mounting using the metallization method on ceramic substrates, etc., are made of a binder such as ethyl cellulose or nitrocellulose and conductive metal powder. are mixed in a solvent, and in some cases ceramic component powder, glass powder, etc. are mixed in consideration of workability and adhesion to the substrate. This paste for forming a conductor is further applied onto a substrate by a method such as screen printing, and then metalized at high temperature to form a conductor.

In recent years, electronic components have become more high-performance, smaller, and lighter, and the need for high-density mounting boards that include multilayer and composite wiring is increasing, and conventional pastes for forming conductors are no longer sufficient. Therefore, the emergence of a high-performance paste for forming conductors is strongly desired.

Conventional pastes for forming conductors have insufficient paste stability, dimensional accuracy of conductors when applied by screen printing, surface smoothness, and electrical properties after metallization, such as variations in resistance. Occurrences such as

In other words, conductor-forming pastes have traditionally been made of relatively highly viscous organic binders such as ethyl cellulose and nitrocellulose, which tend to settle and separate due to the high specific gravity of the conductive metal particles. However, conductor-forming pastes that use such organic binders have inappropriate dynamic viscosity behavior, so if the viscosity of the paste is increased, unevenness and pattern chipping may occur in the coating film; Lowering the viscosity of the paste not only reduces the stability of the paste itself, but also causes the coating film to sag or bleed, resulting in a significant loss of dimensional accuracy. Also, apply the paste to the substrate and dry and remove the solvent.
The coating film strength of the conductor is insufficient after the conductor has been exposed (hereinafter referred to as the B stage), and due to this lack of strength, the conductor film is chipped due to rubbing during the work process, and furthermore, the fine powder of the conductor generated by the rubbing can be deposited on the board. At present, there are problems such as deposits and poor electrical insulation between patterns.

In order to improve the above-mentioned drawbacks, attempts have been made to optimize the viscosity behavior of the paste by, for example, adding ceramic component powder or glass powder in excess of the required amount, or adding additives such as thixotropy modifiers. However, the electrical properties such as conductor resistance and reproducibility are not sufficient.

Furthermore, JP-A-57-64991 proposes a method using a mutually soluble organic binder made by blending ethyl cellulose and polyisobutyl methacrylate. Under the conditions of use, the paste's storage stability, suitability for screen printing, film strength at B stage, etc. are insufficient.

The essence of the above-mentioned problem is thought to be related to the composition and viscous behavior of the conductor-forming paste, and when paying attention to viscous behavior, a good conductor-forming paste will not pass through the screen when applied by screen printing etc. At the moment when a large shearing force is applied, the viscosity is low, and the viscosity rises immediately after being applied to the substrate, maintaining the pattern shape and maintaining the smoothness of the surface and the desired shape for a long time! It seems to be a paste that can be maintained for a long time.

On the other hand, when focusing on the strength of the conductor coating film in the B stage, it is undesirable to use more binder than necessary, considering the occurrence of cracks and shrinkage during metallization formation and the electrical properties after metallization. It is necessary to strengthen the film strength with the minimum amount of binder.

The present invention focuses on the above-mentioned problems of conventional conductor forming pastes, and significantly improves the long-term stability of the paste, excellent screen printing properties, and film strength at the B stage, thereby eliminating problems in terms of quality control. In addition, as a result of intensive research to obtain a suitable conductor-forming paste that exhibits the desired excellent electrical properties, ethyl cellulose and/or
Alternatively, the present inventors have discovered that this can be significantly improved by maintaining a system consisting of polyvinyl butyral and (meth)acrylic resin polyol in a dispersed state, and have arrived at the present invention.

That is, the present invention provides an organic binder and a conductive metal powder containing ethyl cellulose and/or polyvinyl butyral and (meth)acrylic resin polyol in a weight ratio of t o : o, s to 0.4:1.0. It is a paste for forming a conductor consisting of a solvent and a solvent.

Preferably, the (meth)acrylic resin polyol has a hydroxyl value in the range of 5 to 200, an acid value in the range of 1 to 100, and a T2 of 160°C to 80°C.

The ethylcellulose used in the present invention is, for example, Type 7 to Type 150 described in Paint Handbook (edited by Shinji Iwai, 1958, Sangyo Tosho Co., Ltd. Publishing), p. 508.
It is preferable to select and use one within the range of .

The polyvinyl butyral used in the present invention is a copolymer of vinyl alcohol, vinyl acetate, and vinyl alcohol, and is generally prepared by reacting polyvinyl alcohol obtained by saponifying vinyl poly(M) acid with butyraldehyde. can get. As a reaction method, there are a one-stage method in which saponification and butyralization are carried out simultaneously, and a two-stage method in which saponification and then butyralization are carried out. Regarding its weight average degree of polymerization and butyralization degree! Although there are no restrictions on the polymer, it is preferable to use one having a weight average polymerization degree of 250 or more, particularly preferably 500 or more, and a butylation degree of 50 to 85 mol.

The (meth)acrylic resin polyol used in the present invention refers to a monomer having a hydroxyl group in the molecule (for example, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 1,4-butanediol monomer, although there are no particular restrictions). Methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and these representative hydroxy (meth)acrylates and ethylene oxide, propylene oxide, or ε
- One or two selected from adducts of caprolactone, etc.
monomers) and other monomers copolymerizable with the monomer having a hydroxyl group (for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, grindyl methacrylate) methacrylates such as methacrylate, tetrahydrofurfuryl methacrylate;
A polymer obtained by copolymerizing one or more monomers selected from methacrylic acid, styrene, α-methylstyrene, vinyl acetate, dimethyl maleate, diethyl maleate, acrylamide, N-methylolacrylamide, etc. The hydroxyl value of the polymer is preferably in the range of 5 to 200, particularly preferably in the range of 50 to 200.

However, the hydroxyl value of the polymer is determined by the acetic anhydride-pyridine acetylation method (Ber, 34.3554-335
According to the method of B (1901)). If the hydroxyl value of the (meth)acrylic resin polyol does not exceed 5 or exceeds 200, the viscosity behavior of the resulting paste may be poor, and the coating may sag or bleed, or ethyl cellulose or polyvinyl Compatibility with butyral is insufficient, and the organic binder tends to separate into two layers.

Furthermore, Ty of the (meth)acrylic resin polyol of the present invention
is preferably set in the range of -30°C to 80°C, particularly preferably in the range of -10°C to 50°C.

If Ty exceeds 80°C, the strength of the conductor coating film in the B stage will be weak, and if Tli' does not exceed 130°C, the organic binder will separate into two layers due to poor compatibility with ethyl cellulose and polyvinyl butyral. It's easy to do.

In addition, the acid value of the (meth)acrylic resin polyol is 1 to
It is preferable to use in the range of 100, and if the acid value is 1
When the acid value does not exceed 100 or when the acid value exceeds 100, the viscosity behavior of the resulting paste is inappropriate.

In the present invention, the mixing ratio of ethyl cellulose and/or polyvinyl butyral and (meth)acrylic resin polyol is 1.0:0.5 to 0.4:1.0 by weight.
is preferable, and if the ratio of both is outside this range, the viscosity behavior of the resulting paste will be inappropriate.

The organic binder in the present invention consists of ethyl cellulose and/or polyvinyl butyral and (meth)acrylic resin polyol, but as long as they do not phase separate from each other, one resin can be dispersed in the other resin. good. Rather, it is preferable to use an organic binder in a stably dispersed state because the resulting paste exhibits the effects of the present invention more markedly.

In addition, the solvent used in the present invention has a boiling point range of 150 to 350 °C for the purpose of facilitating quick printability of the conductor forming paste, especially preventing thickening and clogging on screen printing plates. It is best to choose one.

Any good solvent for any of the organic binder resin components of the present invention can be used, and there is no problem in using one type or a mixed solvent of two or more types. The solvent of the present invention also includes what is commonly called a plasticizer.

Specific examples of the solvent include n-octyl alcohol, n-
Alcohols such as decanol, inoctyl alcohol, cyclohexanol, benzyl alcohol, diacetone alcohol, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monoethyl acetate, diethylene glycol monoethyl acetate, diethylene glycol monoethyl acetate, diethylene glycol monomethyl ether acetate, diethylene glycol acetate Monobutyl ether to dimethino maleate
Esters such as dietynope maleate and dibutyl maleate, ethylene glycol motubutyl ether, ethylene glycol diptyle ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether to diethylene glycol monoethyl ether,
Diethylene glycol mono-n-hexyl ether, terpene glycol ether natonoethers, furans such as tetrahydrofurfuryl acetate to tetrahydro 7/L/furyl alcono, ketones such as cyclohexanone, isophorone, acetophenone, dibutyl adipate, isobutyl adipate , diethyl adipate, glycerin monoacetate, glycerin dirotate, glycerin triacetate, glycerin tributyrate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, cyamyl phthalate, dihexyl phthalate, dimethquinethyl phthalate, Plasticizers such as diethoxyethyl phthalate, dibutoxyethyl phthalate, diethoxyethino phthalate, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, diethyl succinate, dibutyl succinate, diethyl tartrate, Examples include α-terpineol and α-tiruvinyl acetate, and one type or a mixture of two or more types may be used. Generally, the proportion of the solvent to the paste for forming a conductor is 10 to 50% by weight [4.%, preferably 15 to 55% by weight].

The conductive metal powder used in the present invention refers to noble metal powder, such as AP+ "L+ Au+ "d+ "r+
A simple substance or alloy such as Rh, with an average particle size of 10
Precious metal fine powder and/or base metal powder of 0 μm or less, preferably 5 μm or less, such as MO+ ”* Mno N
I+ Single substance or alloy such as Cu with an average particle size of 1
00 μm or less, preferably 5 μm or less, one type or a mixture of two or more types of base metal fine powders may be used.

In the present invention, the blending ratio of the organic binder and the conductive metal powder described above is usually such that the weight ratio of the solvent-free organic binder and the conductive metal powder is 0.5=100 to s:1.
It may be used within the range of 00, preferably 1:
100 to s: The range of 100 is 4H.The paste for forming a conductor of the present invention further contains a necessary amount of ceramic component powder, glass powder, and antifoaming agent for the purpose of adhesion between the substrate and m1. , a leveling agent, etc. can also be added.

The paste for forming a conductor of the present invention is applied onto a base material such as glass, ceramics, green sheet, etc. by a method such as screen printing, spraying, inkjet, ), coating, or transfer, and the solvent is dried to transfer it to the B stage. After that, it is fired at high temperature to become metallized. Conditions such as temperature, temperature increase, time, firing atmosphere, etc. during metallization vary depending on the type of conductive metal particles used, particle diameter, etc., and conditions that match the conductive metal particles used may be appropriately selected.

Examples are shown below, and in the examples, parts and parts mean parts by weight and parts by weight, respectively.

In addition, regarding the performance evaluation of the conductor forming paste described below, (A) storage stability of the paste, (B) printing suitability test, (coating film strength at C-B stage, (D) appearance after metallization and The details of the performance evaluation method for items such as electrical characteristics are as follows.

(A) Storage stability of paste): After preparing the paste for forming a conductor, leave it for one week at room temperature and check for sedimentation and separation of the conductor metal particles.

(B) Printing suitability test: Using a 350-mesh pre-made stainless steel screen, conductor forming paste was applied to conductor patterns with line width, line spacing, and widths of 0.2 and 0.5 on an alumina substrate or green sheet. When printing on top, the printability at that time,
The occurrence of sagging, bleeding, and pattern chipping was observed, and a B stage was formed by drying at 80° C. for 4 hours, and the conductor film was observed for sagging, bleeding, film thickness, and surface smoothness.

(c) Coating film strength at B stage: Place the pad of a finger covered with paper at an angle of 45° at room temperature on the B stage conductor coating created in the printing suitability test.
When rubbed up and down or left and right ~3 times, use a magnifying glass or metallurgical microscope to check whether conductive metal particles are worn and adhered to the surface of the paper, and whether there are deposits of worn metal particles in the conductor pattern and between the patterns. The strength of the film was measured using a

(D) Appearance and electrical property test after metallization: The conductor coating film obtained after metallizing the substrate made into B stage by the same method as the printing suitability test was fired under the conditions shown in each example. Measurement of electrical resistance value and resistance value at intervals We measured the temperature characteristics by changing the environmental temperature and measured the degree of variation in electrical resistance value and the presence of abnormalities such as wire breakage and poor insulation. . Further, the acid value and Tf of the (meth)acrylic resin polyol described in the Examples are values measured using a metallurgical microscope using the method shown below.

Acid value: Jfs, method according to K-5400-8-2-1.

T1: Measured by the Senshiri method of TMA (thermomechanical analyzer).

Comparative Example 1 10 g of ethyl cellulose (type 50) was dissolved in 90 parts of α-terpineol to obtain a polymer solution with a solid content of ions (hereinafter abbreviated as EC-107).

Next, add 20 parts of BC-107 and M. Powder (particle size 0, 4~
3. O/JJn) 52 parts and W powder (particle size 0.2-
3.5/ATT) 18 parts were kneaded using a ceramic pear triple roll, and the viscosity was determined to be SO using an E-type viscometer.
A paste for forming a conductor was prepared by adjusting the paste with α-chillvinyl acetate so as to have an O poise.

Using this paste, various performances were evaluated using the methods described above. The results are shown in Table-1.

Note that an alumina green sheet was used as the evaluation substrate, and the final firing conditions were 1600° C./60 minutes in a reducing atmosphere.

Comparative Example 2 Ethyl cellulose (type 1.00') 10i was dissolved in 90 parts of dibutyl phthalate to obtain a polymer solution (hereinafter abbreviated as EC-10P) with a solid content of ions.

Next, 50 parts of gc-1op, 6 parts of ceramic component powder (main component: silica-based fine powder), and 94 parts of Pt powder (particle size 0.3-4.0 μm) as conductive metal powder were added in the same manner as in Comparative Example 1. Create conductor forming paste by cross-wiring and adjusting viscosity.
Using this paste, various performances were evaluated using the methods described above, and the results are shown in Table 1.

The evaluation substrate was an alumina ceramic substrate, and the metallization conditions were 1400% final firing conditions in air.
It was carried out at ℃/60 minutes.

Rest/2 (B) Evaluation Item Judgment Evaluation was mainly based on resolution and dimensional stability and displayed on a 5-point scale.

5: Best or dimensional stability within ±5%, 4: Relatively good or ±10%, 6° or \Poor or 〃 +
60%〃, 2; Poor or ±3030 copies, 1; Extremely poor or ±50% or more Examples 1 to 6. and comparative example′
5-5 A (meth)acrylic resin polyol obtained by copolymerizing 20 parts of 2-hydroxyethyl methacrylate, 25 parts of methyl methacrylate, 30 parts of ethyl acrylate, 2 parts of methacrylic acid, and 23 parts of tetrahydrofurfuryl methacrylate ( Hydroxyl number 85, enemy side 13, TfI
Φ37℃) was mixed with a mixed solvent of α-terpineol and α-tiruvinyl acetate in a weight ratio of 4:1 to 20% solid content.
A polymer solution (hereinafter abbreviated as PO-2O8) was prepared.

Next, EC-10T and PO-2O8 prepared in Comparative Example 1
60 parts of an organic binder (the actual resin component is 25 parts, and α-terpineol is 30 parts) and Mo powder (particle size 04~
5.0 μm) 95 parts and M. -M11 alloy powder (particle size 0
1 to 2.8 μm) were cross-wired and the viscosity was adjusted in the same manner as in Comparative Example 1 to prepare a paste for forming a conductor. Using the Alumina Green 7-1 substrate, various performance evaluations were performed using the methods described above, and the results are shown in Table 2.

Examples 7 to 11 The same conductor forming pastes as in Examples 1 to 6 were prepared except that W powder (particle size: 02 to 65 μm) was used as the conductive metal powder, and the performance was evaluated in the same manner. Similar results were obtained. Obtained.

Example 12 (Meth)acrylic resin polyol (hydroxyl value: 115 ．Acid value 6
2. Solid content 20 using a mixed solvent of glycerin triacetate and diethyl phthalate at a weight ratio of 6:2 at 45°C.
% polymer solution (hereinafter abbreviated as PO-20Q) was prepared. On the other hand, polyvinyl butyral (electrochemical (a) product,
Solid content of product name Denka Butyral (OOK): 1
0% dimethyl phthalate solution (hereinafter abbreviated as FB-10B)
adjusted. The table below shows FB-10B and PO-20Q.
60 parts of an organic binder blended at the weight ratio of the resin components shown in Examples 7 to 11 described in 6 (the actual resin component is 25 parts in total)
60 parts with dimethyl phthalate), 20 parts of Ag powder (particle size 01-25 μm), and Pd powder (02-60 parts).
A paste for forming a conductor was prepared by adding 80 parts of 7 μtn) to the crosstalk 1 and adjusting the viscosity in the same manner as in Comparative Example-1. Using the paste described above, various performance evaluations were performed using the above-described method using an alumina ceramic substrate as a planning board.

The results are shown in Table 6, and the performance evaluation of the paste was satisfactory when the organic binder compounding ratio of polyvinyl butyral and (meth)acrylic resin polyol was in the range of 1:05 to 04:1 by weight. The metallization conditions were air firing, and the final firing conditions were 1450°C/30 minutes.

Example 13 PO-20Q in Example 12 as organic binder
Among the mixed organic binders of and FB-10B, PO-10
A conductor forming paste obtained by replacing the entire amount of B with a composition of PO-10B and EO-10T (ethyl cellulose solution obtained in Comparative Example 1) in a weight ratio of 1:1 and carrying out the same procedure as described in Example 12 below. The results were almost the same as those of Examples 7 to 11 listed in Table 6. In other words, a conductor-forming paste using an organic balancer consisting of three components: ethyl cellulose, polyvinyl butyral, and (meth)acrylic resin polyol was also used. It had sufficiently satisfactory performance.

Comparative Example 6 20 parts of a 100% monopolymer of inobutyl methacrylate was dissolved in 80 parts of a mixed solvent of α-terpineol and α-tyl vinyl acetate in a weight ratio of 4:1 to give a solid content of 2.
A 0% polymer solution (hereinafter abbreviated as PI-20T) was prepared, and then EC-10T and PI-20 prepared in Comparative Example-1 were prepared.
60 parts of a homogeneously dissolved organic binder solution (the actual resin component is 25 parts, and 50 parts of terpineol is mixed with T and T in the weight ratio of each resin component as shown in Experiment No. (A) ~) in Table 4. ) and W powder (particle size 02-65
μm) were kneaded and the viscosity was adjusted in the same manner as in Comparative Example 1 to prepare a paste for forming a conductor. Using the alumina green sheet substrate, various performance evaluations were performed using the methods described above.

The results are shown in Table-4. Note that the metallization conditions were such that the final firing conditions were 1600° C./90 minutes in a reducing atmosphere.

Claims (1)

[Scope of Claims] (1) Ethyl cellulose and/or polyvinyl butyral and (meth)acrylic resin polyol in a weight ratio of t
A conductor-forming paste comprising an organic binder, conductive metal powder, and a solvent containing O: 0.5 to 0.4: 1.0. (2) The hydroxyl value of the (meth)acrylic resin polyol is 5 to 200, and the glass transition temperature is -30°C.
The paste for forming a conductor according to claim 1, wherein the temperature is 80°C. (5) The acid value of the (meth)acrylic resin polyol is 1 to
100. The paste for forming a conductor according to any one of claims 1 and 2, which has a range of 100.