JPH076623A - Conductive paste additive - Google Patents

Abstract

PURPOSE:To provide conductive paste which prevents drop in insulating resistance or short circuit between conductors caused by migration of silver without sacrifice of conductivity, gives high thixotropy in a screen printing for conductive circuit formation, and forms a conductive pattern with less blotting and dripping. CONSTITUTION:A conductive paste additive consists of inorganic compound powder containing 45-60% SiO2, 10-28% Al2O3, 0.5-10% Li2O3, 2-10% RO (wherein R is at least one alkali earth metal selected from Mg, Ca, Sr, and Ba.), 3% or less Na2O and/or K2O, 0.5-5% F2, 0.5-4% TiO2, 0.5-4% ZrO2, 0.5-4% B2O3, and 0.5-15% at least one oxide of metal selected from Cr, Fe, Co, Ni, and Cu.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste for forming a conductor circuit or the like on a printed wiring board, and more specifically, a conductive metal powder, a thermosetting resin, and an organic solvent vehicle. The present invention relates to an additive composition suitable for a conductive paste containing a main component.

[0002]

2. Description of the Related Art An additive method is one of the methods for forming a conductor circuit on a resinous printed wiring board. This is generally a method of forming a conductor pattern by plating, but instead of plating, a method of forming a conductive paste by screen printing on a substrate has been adopted from the viewpoint of further improving productivity. It was This conductive paste contains a conductive metal powder such as Ag, an epoxy-based or phenol-based thermosetting resin, and an organic solvent vehicle as main components, and is heat-cured at a low temperature of 200 ° C. or lower, for example.

By the way, since the one using Ag as a conductor is inferior in migration resistance, the insulation resistance between the conductors is lowered or a short circuit occurs, and the reliability of the circuit is deteriorated. It becomes an obstacle to obtaining a fine conductor pattern. Conventionally, as a means for preventing the migration of Ag, (1) Au powder is used (2) Cu powder is coated with Ag and metal powder is used (3) Ag-Cu alloy powder is used (4) Ag powder is Cu powder Although the metal powders of (1) to (3) are all expensive, the Cu powder of (4) can be added only in a small amount to the Ag powder. Against Ag
Migration cannot be prevented. Also C
Since the metal powder containing u does not have sufficient oxidation resistance of Cu, it may impair conductivity.

In the screen printing for forming the conductor pattern, the viscosity of the conductive paste is important,
A paste having good thixotropy is desired to form a finer conductor pattern. However,
Low temperature thermosetting conductive paste containing thermosetting resin,
The thixotropy is inferior, bleeding and sagging of the conductor pattern are likely to occur, and it is difficult to form a finer conductor pattern.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to prevent a decrease in insulation resistance between conductors or a short circuit due to migration of Ag without impairing conductivity, and
It is intended to provide a conductive paste additive which gives good thixotropy in screen printing for forming a conductor circuit and can form a conductor pattern with less bleeding and sagging.

[0006]

In order to achieve such an object, the present invention provides the following (1) to (4).

(1) An inorganic composition added to a conductive paste containing a conductive metal powder, a thermosetting resin, and an organic solvent vehicle as main components, the inorganic composition being in terms of oxide weight ratio. , SiO ₂ : 45-60%, Al ₂ O ₃ : 1
_{0~28%, Li 2 O: 0.5~10} %, RO: 2~1
0% (where R is 1 selected from Mg, Ca, Sr and Ba)
Or two or more alkaline earth metals), Na ₂ O and / or
Alternatively, K ₂ O: 3% or less, F ₂ : 0.5 to 5%, Ti
_{O 2: 0.5~4%, ZrO 2} : 0.5~4%, B 2 O
₃ : 0.5 to 4% and 0.5 to 1 of one or more metal oxides selected from Cr, Fe, Co, Ni and Cu.
Conductive paste additive characterized by being made of an inorganic compound powder containing 5%

(2) The conductive paste additive of (1), wherein a part or all of the inorganic compound exists in a glass state.

(3) Conductive metal powder mainly composed of Ag,
As a thermosetting resin, an organic solvent vehicle, and an inorganic composition, in terms of oxide weight conversion ratio, SiO ₂ : 45-60%, A
_{l 2 O 3: 10~28%,} Li 2 O: 0.5~10%,
RO: 2 to 10% (however, R is one or more alkaline earth metals selected from Mg, Ca, Sr, and Ba), N
a ₂ O and / or K ₂ O: 3% or less, F ₂ : 0.5 to 5
%, TiO ₂ : 0.5-4%, ZrO ₂ : 0.5-4
_{%, B 2 O 3: 0.5~4} % and, Cr, Fe, Co, N
Conductive paste containing powder of an inorganic compound containing 0.5 to 15% of one or more metal oxides selected from i and Cu as an essential constituent component

(4) The conductive paste according to (3), in which a part or all of the inorganic compound is present in a glass state.

The inorganic compound of the present invention is an inorganic compound that prevents migration represented by conductive metal powder such as Ag and imparts good thixotropy to the conductive paste, and is SiO ₂ --Al ₂ O ₃ -Li ₂ O-RO or the like is added to the basic composition with a metal oxide component effective for preventing migration of Ag or the like, and is substantially crystalline or vitreous, or an inorganic mixture of crystalline and vitreous materials. It is provided as any powder of the composition.

The inorganic compound of the present invention is prepared by uniformly mixing a predetermined oxide, hydroxide, carbonate, metal salt, or natural mineral as a raw material, sintering the mixture at about 1000 ° C to 1500 ° C for several hours, or glass. It can be solidified by melting, and can be obtained as a powder through a generally known pulverization process such as mechanical pulverization, but it is partially or wholly vitrified rather than being crystallized with grain boundaries by sintering. It is more preferable to use a vitreous material having a structure with few grain boundaries or no grain boundaries, which not only facilitates the pulverizing step, but also increases the migration preventing power of Ag and the like.

Next, the specific constitution of the inorganic compound of the present invention will be described in detail. The numerical values hereafter indicate weight% unless otherwise specified.

SiO ₂ is one of the components that form the skeleton of the inorganic compound, and its proportion in the whole is preferably 45 to 60%. If it is less than 45%, not only is the chemical resistance of the inorganic compound poor, but vitrification becomes difficult. If it exceeds 60%, the meltability is poor.

Al ₂ O ₃ is one of the components that form the skeleton of the inorganic compound as described above, and 10 to 28% is preferable. 1
If it is less than 0%, the chemical resistance of the inorganic compound is poor, and if it exceeds 28%, the glass is devitrified and the composition becomes nonuniform.

Li ₂ O is a component that improves the meltability, and is preferably 0.5 to 10%. If it is less than 0.5%, the effect is not obtained, and if it exceeds 10%, the glass is devitrified and the composition becomes nonuniform.

RO is one or more alkaline earth metal components selected from Mg, Ca, Sr and Ba, and 2 to 10% is preferable as a meltability adjusting component. If it is less than 2%, there is no effect, and if it exceeds 10%, the glass tends to devitrify.

Similarly, Na ₂ O and / or K ₂ O is preferably added up to 3% or less as a meltability adjusting component. If it exceeds this range, the chemical resistance is greatly reduced.

F ₂ is a component that improves the meltability,
0.5-5% is preferable. If it is less than 0.5%, its effect is not obtained, and if it exceeds 5%, the volatilization amount of the F2 component at the time of melting becomes large, and it becomes difficult to adjust the component.

In addition to this, TiO ₂ , ZrO ₂ , B ₂ O ₃
A basic composition can be obtained by adding 0.5 to 4% of each component.

Furthermore, the inorganic compound of the present invention has, in addition to the above basic composition, one or more metal components selected from the group consisting of Cr, Fe, Co, Ni and Cu in an amount of 0.
If the inorganic compound is crystalline by sintering, it exists as a solid solution together with other components, or if the inorganic compound is glassy, it exists as a modifying ion. By doing so, the function of preventing migration of Ag or the like is exhibited, but addition of the Cu component is particularly effective in preventing migration. If it is less than 0.5%, the effect is poor,
If it exceeds 15%, it is difficult to vitrify, and a part of the metal components segregates to form a non-homogeneous glass.

Further, another form of the inorganic compound of the present invention can be used as a glass-ceramic body in which a part of it is crystallized by holding it at 600 to 1100 ° C. for a long time after it is made glassy. In this case, TiO ₂ , Z
Since rO ₂ serves as a nucleating agent and precipitates a crystal phase such as β-spodumene, a metal component selected from the group consisting of Cr, Fe, Co, Ni and Cu is concentrated and precipitated on the surface.
An increase in the effect of preventing migration of Ag or the like can be expected. Since the crystal phase obtained has a sufficiently small grain boundary with respect to the crystallinity obtained by sintering, a powder body can be easily obtained in the crushing step, like a glass body.

The inorganic compound of the present invention is used by being added to a conductive paste containing a conductive metal powder, a thermosetting resin, and an organic solvent vehicle as main components. The added conductive paste may be an existing conductive paste. The added form is granular, flaky,
Alternatively, it is not limited to any powder form of short fiber, but the particle size is preferably 0.1 to 30 μm,
If it is less than 1 μm, not only the yield in the pulverizing step is low, but also the agglomeration between particles becomes extremely high, and it becomes impossible to uniformly disperse and maintain the individual particles in the conductive paste. If it exceeds 30 μm, not only good thixotropy in screen printing cannot be imparted, but also the printed surface of the conductor pattern becomes rough, which hinders the overcoat treatment in the subsequent step.

The inorganic compound of the present invention is preferably added to the conductive paste in an amount of 0.5 to 15%. 0.5%
If less than 15%, the object of the present invention cannot be achieved, and 15%
If it exceeds, not only the conductivity of the conductive paste is lowered, but also a uniform printed surface in screen printing cannot be obtained.

It is not necessary to use any special conductive metal powder as the conductive metal powder constituting one of the conductive pastes, and a commonly used mixture or alloy of Ag, Ag-Pd, etc. Can be used. The content and particle size of these conductive metal powders in the conductive paste may be similar to those of generally used conductive pastes, but for example, the content is 5
The particle size is preferably 0 to 90% and the particle size is preferably 0.1 to 20 μm.

The thermosetting resin constituting the other one of the conductive pastes is not particularly limited as long as it is a resin which is thermoset at a low temperature by holding it at 200 ° C. or lower for several hours, but is preferably epoxy. Resin, phenolic resin,
It is possible to use one kind or a combination of two or more kinds such as urethane resin. The content of these thermosetting resins in the conductive paste is preferably 5 to 50%.

The organic solvent vehicle that constitutes yet another one of the conductive pastes is not particularly limited as long as it is an organic solvent that has a suitable viscosity and is well compatible with the above-mentioned inorganic compound, conductive metal powder, and thermosetting resin. Although not limited, alcohols, phenols, acetic acid esters, ketones and the like can be preferably used. The content of these organic solvent vehicles in the conductive paste is preferably 5 to 50%.

The above-mentioned conductive metal powder, thermosetting resin, organic solvent vehicle, and the inorganic compound of the present invention are essential constituents, and a dispersant or the like may be added to them as necessary. An arbitrary conductor paste can be obtained by weighing a predetermined amount of each of these components at a mixing ratio that provides an appropriate viscosity and then uniformly mixing them using a mortar, a triple roll, or the like.

[0029]

When a conductive pattern is formed on a printed wiring board by screen printing such a conductive paste and heat-cured at, for example, 200 ° C. or less, the thermosetting resin uniformly fixes the conductive metal powder and the inorganic compound. To do. At this time, the inorganic compound is not softened or crystal-transformed by the thermosetting treatment.

In the conductor film formed by the conductive paste containing the inorganic compound of the present invention, the conductive metal powder such as Ag and the powder body of the inorganic compound are uniformly adhered, so that the Cr contained in the inorganic compound is contained. , A metal oxide component selected from the group consisting of Fe, Co, Ni, and Cu acts to prevent migration of Ag or the like over the entire area of the conductor film.

Further, since the powdery body of the inorganic compound acts as a viscosity adjusting agent for the conductive paste, the conductive paste to which it is added imparts good thixotropy in screen printing.

[0032]

[Effects] According to the present invention, no special conductive metal powder or expensive Pt metal powder is used, and migration of Ag or the like can be prevented without impairing conductivity. It is possible to form a highly reliable circuit by preventing a decrease in insulation resistance and a short circuit.

Further, since a conductive paste having excellent thixotropy can be obtained, it is possible to form a conductor pattern with less bleeding and sagging, and a finer conductor pattern can be formed together with the effect of preventing migration.
We are convinced that we can make a major contribution to the high integration of printed wiring boards.

[0034]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the present invention.

(1) Preparation of Inorganic Compound Raw materials were prepared so that the composition shown in Table 1 was obtained. As the raw material, a commonly used glass raw material was used. Next, each formulation was put in a crucible and placed in an electric furnace at 1450 ° C-4.
Hr was melted and immediately poured into water to obtain coarse-grained glass. The obtained coarse-grained glass was dried to remove water, then mechanically pulverized and classified to have an average particle diameter of 5 μm.
A glassy powder of The characteristics of this glass were as follows in terms of B composition. Thermal expansion coefficient 58.4 × 10 ^-7 / ° C Transition point 536 ° C Yield point 611 ° C Specific gravity 2.57

[0036]

[Table 1]

(2) Preparation of conductive paste The following paste composition components were prepared with a compounding ratio approximately similar to the commonly used Ag-based conductive paste. Ag metal powder 100 parts by weight Resol type phenolic resin 40 parts by weight Butyl carbitol 45 parts by weight To the total amount of the above component ratio, the glass powder body prepared in (1) is added in a predetermined amount and sufficiently kneaded by a three-roll mill. A conductive paste was obtained.

(3) Formation of Conductor Pattern Using the conductive paste of (2), a test pattern is printed by screen printing on a paper-based phenol resin substrate with through holes, and heat-cured at 150 ° C. for 4 hours. A test piece having a conductor pattern formed thereon was obtained.

(4) Evaluation of migration by humidity resistance load test 60 ° C.-9 while applying DC 50 V between the conductor patterns (hereinafter referred to as gaps) facing each other of each test piece in (3).
After being kept for a predetermined time in a constant temperature and humidity chamber kept at 0 to 95% RH and then left at room temperature for 1 hour, a change in insulation resistance value in the same gap was obtained. As a blank, a test piece made of a conductive paste in which the glass powder body of (2) was not added was added to the evaluation standard. The results are shown in Tables 2 and 3.

[0040]

[Table 2]

[0041]

[Table 3]

With respect to the insulation resistance value between the gaps of the conductors made of the conductive paste to which the glass powder was added as the inorganic compound of the present invention, the resistance value change was smaller than that of the blank, and excellent migration resistance was obtained.

(5) Evaluation of printing characteristics The bleeding, sagging and surface smoothness of the conductor pattern of each test piece in (3) were observed with a microscope, and the quality was judged according to the following evaluation criteria. ◯: Less bleeding, sagging than blank, or good surface smoothness Δ: Similar to blank ×: More bleeding, sagging than blank, or less surface smoothness These results are shown in Table 4. .

[0044]

[Table 4]

The properties of the conductor pattern formed by the conductive paste containing the glass powder as the inorganic compound of the present invention were the same as those of the blank when the glass addition rate was 0.1%, no change was observed, and the addition rate was 20%. The surface smoothness was inferior to that of the blank. However, the test piece of the conductive paste having an appropriate glass addition rate showed less bleeding and sagging than the blank and had good printing characteristics.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H05K 1/09 Z 6921-4E

Claims (4)

[Claims] 1. An inorganic composition to be added to a conductive paste containing a conductive metal powder, a thermosetting resin, and an organic solvent vehicle as main components, wherein the inorganic composition has an oxide weight conversion ratio, SiO ₂ : 45-
_{60%, Al 2 O 3:} 10~28%, Li 2 O: 0.5
-10%, RO: 2-10% (however, R is Mg, Ca, S
one or more alkaline earth metals selected from r and Ba), Na ₂ O and / or K ₂ O: 3% or less, F ₂ :
_{0.5~5%, TiO 2: 0.5~4%} , ZrO 2:
_{0.5~4%, B 2 O 3:} 0.5~4% and, one or selected Cr, Fe, Co, Ni, of Cu
Conductive paste additive characterized by comprising an inorganic compound powder containing 0.5 to 15% of one or more kinds of metal oxides 2. The conductive paste additive according to claim 1, wherein a part or all of the inorganic compound exists in a glass state. 3. A conductive metal powder mainly composed of Ag, a thermosetting resin, an organic solvent vehicle, and an inorganic composition, in terms of oxide weight conversion ratio, SiO ₂ : 45 to 60%, Al _{2
O 3: 10~28%, Li 2} O: 0.5~10%, R
O: 2 to 10% (however, R is one or more alkaline earth metals selected from Mg, Ca, Sr, and Ba), Na
₂ O and / or K ₂ O: 3% or less, F ₂ : 0.5 to 5
%, TiO ₂ : 0.5-4%, ZrO ₂ : 0.5-4
_{%, B 2 O 3: 0.5~4} % and, Cr, Fe, Co, N
Conductive paste containing powder of an inorganic compound containing 0.5 to 15% of one or more metal oxides selected from i and Cu as an essential constituent component 4. The conductive paste according to claim 3, wherein a part or all of the inorganic compound exists in a glass state.