KR20080107933A - Conductive paste composition and low temperature co-fire cerimic - Google Patents

Abstract

A conductive paste composition having tap density of 3.0 ~ 4.0 g / cm^3 is provided to improve electrical characteristic by improving the adhesion of electrode and a ceramic sheet. A conductive paste composition comprises the conductive powder(32a) and organic vehicle and has a tap density is 3.0 ~ 4.0 g / cm^3. The density after sintering at 800 ~ 950‹C is 4.5 ~ 6.0 g / cm^3. The conductive powder is selected from a group consisting of gold(Au), silver(Ag), palladium(Pd), copper(Cu), nickel(Ni) and their alloy. The specific surface area of the conductive powder particle is 0.29 ~ 1.14 m^2 / g. The organic vehicle comprises solvent and binder.

Description

Conductive Paste Composition and Low-Temperature Simultaneous Ceramic Substrate {CONDUCTIVE PASTE COMPOSITION AND LOW TEMPERATURE CO-FIRE CERIMIC}

1 shows a part of an electrode forming process in a LTCC substrate according to the prior art.

2 is a cross-sectional view showing a gap formed between the electrode and the green sheet in the LTCC substrate according to the prior art.

3 is a cross-sectional view showing a via hole conductor of a low-temperature cofired ceramic substrate formed from a conductive paste composition according to an embodiment of the present invention.

4 is an enlarged view of a via hole conductor in a low temperature co-fired ceramic substrate from which a restraint layer is removed.

5A, 5B and 5C are photographs for explaining the adhesion between the via hole electrode and the green sheet interface in the comparative example.

6A, 6B, and 6C are photographs for explaining the adhesion between the via hole electrode and the green sheet interface in the embodiment.

<Description of the symbols for the main parts of the drawings>

31a, 31b, 31c: green sheet 32a: conductive powder

32b: void 33: circuit pattern

34a, 34b: constraint layer

The present invention relates to a conductive paste composition and a low temperature co-fired ceramic substrate, and more particularly, to a conductive paste capable of improving adhesive strength between an electrode and a ceramic sheet by adjusting a tap density when forming an electrode through firing; A low temperature cofired ceramic substrate having the sintered body.

The electrically conductive paste used for the via electrode of a low temperature co-fired ceramic (LTCC) board | substrate etc. generally contains electroconductive powder, an organic vehicle, etc., and is comprised. After filling such a conductive paste with a via hole of a green sheet or the like and firing at a predetermined temperature range, the electrode of the LTCC substrate can be completed.

1 shows a part of an electrode forming process in a LTCC substrate according to the prior art.

Referring to FIGS. 1A and 1B, in the prior art, first, via holes are formed in the plurality of green sheets 11a, 11b, and 11c, respectively, and then the conductive paste 12 is filled in the via holes. . Thereafter, a predetermined circuit pattern 13 is printed on the green sheets 11a, 11b, and 11c, and the green sheets 11a, 11b, and 11c are laminated to obtain a laminate 10.

Subsequently, as shown in FIG. 1B, restraint layers 14a and 14b which do not sinter at the sintering temperature of the green sheets 11a, 11b and 11c are placed on the upper and lower surfaces of the stacked green sheets 11a, 11b and 11c, respectively. , Heat squeezed. This is to prevent shrinkage of the green sheets 11a, 11b, and 11c.

Finally, by baking at a predetermined sintering temperature (about 800 to 950 ° C.) in the state in which the constraint layers 14a and 14b are pressed, an LTCC substrate having a via electrode (via hole conductor) can be obtained.

However, in the case of the LTCC substrate obtained by the above process, there is a problem that the electrode and the green sheet are not in close contact with each other.

2 is a cross-sectional view showing a gap formed between the electrode and the green sheet in the LTCC substrate according to the prior art.

As shown in Fig. 2, in the prior art, after firing, the electrode 12 and the green sheets 11a, 11b, and 11c are not in close contact with each other, which, when firing, is not horizontally limited by the constraint layer. This is because shrinkage stress is generated at the interface due to the difference in shrinkage between the electrode and the green sheet in the direction.

As such, in the electrode forming process of the LTCC substrate according to the related art, a gap or a gap 15 may be formed between the electrode and the green sheet. Such a gap 15 is generally large enough to cause disconnection between the electrode and the circuit, and therefore, there is a problem in that electrical connection reliability is inferior.

The present invention is to solve the above problems, an object of the present invention is to improve the adhesive strength of the electrode and the ceramic sheet when forming the electrode through the firing, accordingly the conductive paste and improved electrical properties thereof It is providing the low temperature cofired ceramic substrate provided with a sintered compact.

In order to achieve the above object, one aspect of the present invention,

Containing conductive powder and organic vehicle with a tap density of 3.0 to 4.0 g / cm ³ It provides an electrically conductive paste composition characterized by the above-mentioned.

In this case, the tap density is 3.2 to 3.8 g / cm ³ More preferably.

On the other hand, with respect to the conditions for the conductive powder to exist in the powder in the sintered body, the conductive paste composition has a density of 4.5 to 6.0 g / cm ³ after sintering at 800 ~ 950 ℃ Is preferably. In this case, the density after the sintering is 4.8 ~ 5.6 g / cm ³ More preferably.

The conductive powder may be a powder made of a material selected from the group consisting of gold (Au), silver (Ag), palladium (Pd), copper (Cu), nickel (Ni), and alloys thereof, wherein silver ( Ag) powder is most preferred.

In addition, the shape of the conductive powder particles may be spherical.

In this case, it is preferable that the specific surface area of the said electroconductive powder particle is 0.29-1.14 m <^2> / g from a viewpoint for satisfying the tap density conditions mentioned above.

Furthermore, the conductive powder may have a particle group having different diameters.

On the other hand, it is preferable that the conductive paste composition contains no additives other than the above components.

Preferably, the organic vehicle may include a solvent and a binder.

Another aspect of the invention,

In a low temperature cofired ceramic substrate having a wiring conductor,

The wiring conductor provides a low temperature cofired ceramic substrate comprising a sintered body of the conductive paste composition.

In this case, the wiring conductor may include a via hole conductor formed to penetrate the ceramic substrate, and further, the via hole conductor may have a ratio (a / b) of a via diameter (a) and a stack height (b) of 0.025 to 8 Is preferably.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements.

3 is a cross-sectional view showing a via hole conductor of a low-temperature cofired ceramic substrate formed from a conductive paste composition according to an embodiment of the present invention.

As shown in FIG. 3, first, a via hole is formed in each of the plurality of green sheets 31a, 31b, and 31c, and then the conductive hole composition is filled in the via hole. Thereafter, a predetermined circuit pattern 33 is printed on the green sheets 31a, 31b, and 31c, and the plurality of green sheets 31a, 31b, and 31c are stacked.

Subsequently, restraint layers 34a and 34b which do not sinter at the sintering temperature of the green sheets 31a, 31b and 31c are placed on the upper and lower surfaces of the stacked green sheets 31a, 31b and 31c, respectively, and thermally compressed.

Finally, by firing at a predetermined sintering temperature (about 800 to 950 ° C.) in the state where the restraint layers 34a and 34b are pressed, a low temperature co-fired ceramic substrate having the via hole conductor 32 can be obtained.

In the present embodiment, the conductive paste composition used to form the via hole conductor 32 includes the conductive powder 32a and the organic vehicle, in which case the tap density is 3.0 to 4.0 g / cm ^3. It is characterized by that.

The conductive powder is preferably made of a metal, gold (Au), silver (Ag), palladium (Pd), copper (Cu), nickel (Ni), etc. may be employed in consideration of electrical conductivity, alloys thereof It is also possible. In this case, the metal that can be most preferably employed is silver (Ag) in consideration of excellent electrical properties and adhesive properties.

In the present embodiment, when the conductive paste composition is sintered to become the via hole conductor 32 in the low temperature cofired ceramic substrate, the conductive powder 32a is present in the form of powder in the via hole conductor 32. That is, after sintering, the conductive powder 32a is dispersed in the via hole conductor 32, and voids 32b are formed in a region around the conductive powder 32a.

Accordingly, the shrinkage force generated at the interface with the green sheet during sintering, which has been pointed out as a problem of the prior art, is dispersed, thereby suppressing the generation of gaps between the via hole conductor 32 and the green sheet.

In this case, as described above, in order for the conductive powder to exist in the powder form in the via hole conductor 32 after sintering, it is necessary to appropriately adjust the tap density of the conductive paste composition before firing, the specific surface area (BET) of the conductive powder particles, and the like. There is.

In particular, the tap density of the conductive paste composition may be understood as the most important requirement for forming the powdered via hole conductor 32 as shown in FIG. If the tap density is too small, the amount of the conductive powder may be relatively low, and the strength of the via hole conductor 32 may be reduced, and the electrical conductivity may also be reduced. On the contrary, when the tap density is very large, the shrinkage stress acting on the interface between the via hole conductor and the green sheet cannot be dispersed, and there is a problem that voids are formed around the via hole conductor as in the prior art.

Therefore, the above-mentioned tap density range is devised in consideration of all these conditions.

The tap density of the conductive paste composition is calculated to include both the conductive powder and the organic vehicle included therein. Therefore, the content ratio of the relatively dense conductive powder has the greatest influence on the total tap density, and in this case, the larger the content ratio of the conductive powder is, the larger the tap density is.

In this way, the tap density of the conductive paste composition is to be calculated in view of the conditions for present in the conductive powder in the powder form via-hole conductors after sintering, a range of more preferred tap density is 3.2 ~ 3.8 g / cm ³ to be.

When the tap density condition of the conductive paste composition described above is satisfied, a via hole conductor in which conductive powder is formed in powder form by sintering the conductive paste composition at a general firing temperature (about 800 to 950 ° C.) considering the melting temperature of silver (Ag). (32) can be obtained. In this case, as the conditions for the conductive powder to exist in the powder form, the density of the via hole conductor 32 corresponding to the sintered body of the conductive paste composition may be 4.5 to 6.0 g / cm ³ . This is because the organic vehicle included in the conductive paste composition before sintering is removed, leaving relatively dense materials (conductive powder).

On the other hand, the sintering process is affected by the size or specific surface area of the particles constituting the conductive powder, which also affects the tap density of the conductive paste composition.

If the size of the powder particles is too small, the via hole conductor shrinks earlier than the green sheet upon sintering, so that the via hole conductor pulls the green sheet, thereby generating voids around the via hole conductor. Conversely, when the particle size is too large, the via hole conductor shrinks late, and likewise, voids can be generated around the via hole conductor.

Therefore, in consideration of these matters, when the particles constituting the conductive powder are spherical, it is suitable for the specific surface area of the conductive powder particles to satisfy the tap density condition of 0.29 to 1.14 m ² / g. In this case, in order to more easily satisfy the tap density conditions presented above, the conductive powder may be in the form of particles having different particle diameters.

In addition, the conductive paste composition may change the tap density and the specific surface area of the powder particles, etc., related to the content ratio of the conductive powder, without adding other metal powders or oxides to adjust the stress applied to the via hole conductor. Can be.

That is, by using the conductive paste composition according to the present embodiment, the stress acting on the via hole conductor can be easily adjusted without other additives.

The organic vehicle determines the fluidity and dryness of the conductive paste, and is an element that can influence the dispersibility of the conductive powder. Specifically, the organic vehicle is not particularly limited as long as it dissolves an organic resin having a binder function in a solvent and can provide printability to the conductive paste. The organic resin may be one or more selected from ethyl cellulose resin, nitrocellulose resin, alkyd resin, acrylic resin, styrene resin, phenol resin and the like. In addition, the solvent may be one or more selected from α-terpineol, butyl carbitol, butyl carbitol acetate and the like. On the other hand, the content of the organic vehicle may be appropriately added or reduced in consideration of the content of the conductive powder contained in the conductive paste composition.

4 is an enlarged view of a via hole conductor in a low temperature co-fired ceramic substrate from which a restraint layer is removed.

Referring to FIG. 4, as described above, when the conductive paste composition according to the present embodiment is sintered to form a via hole conductor, the magnitude of shrinkage stress (arrow) acting on an interface with an adjacent green sheet (not shown) and The effect is that the direction is dispersed.

Accordingly, the stability of the interface between the via hole conductor 32 and the green sheet is secured, and thus the via hole conductor 32 can be formed sufficiently high. That is, in the case of the prior art, as described above, large voids are generated between the via hole conductor and the green sheet, so that stability at the interface is reduced, making it difficult to form via hole conductors having the height of the plurality of stacked green sheets. Accordingly, it is common to connect the entire circuit pattern in such a manner that a large number of via hole conductors are formed at a relatively low height, specifically, the height of a single green sheet.

In contrast, in the present embodiment, it is possible to form the via hole conductors 32 as many as the total height of the stacked green sheets at once, and as shown in FIG. 4, the via diameter a and the via hole conductor ( The height b ratio (a / b) of the 32) may satisfy 0.025 to 8.

In addition, in this embodiment, although the via-hole conductor was formed from the electrically conductive paste composition, this invention is not limited to this, Another wiring conductor can also be formed. That is, the conductive paste according to the present invention may be provided in the form of a conductor pattern printed on the substrate in addition to being provided in the form of a via hole conductor through the substrate.

Hereinafter, an experiment was conducted to compare the interfacial properties between the via hole conductor and the conventional via hole conductor by the conductive paste composition according to the present invention through Examples and Comparative Examples.

(Example)

First, a conductive paste composition composed of silver (Ag) powder and an organic vehicle was prepared and filled in via holes previously formed in the green sheet. Specifically, the conductive paste composition of the present embodiment has a tap density of 3.54 g / cm ³ The content ratio of silver powder and organic vehicle was adjusted to be.

Subsequently, the green sheet laminate was fired at 870 ° C. while the conductive paste composition was filled, and the density of the via hole conductor after firing was 5.16 g / cm ^3. Became.

(Comparative example)

In this Comparative Example, a conductive paste composition made of the same material as the above example was prepared, except that the conductive paste composition had a tap density of 4.61 g / cm ^3. The content ratio of silver powder and organic vehicle was adjusted to be. Subsequently, the green sheet laminate was fired at 870 ° C. while the conductive paste composition was filled, and the density of the via hole conductor after firing was 6.61 g / cm ^3. Became. The density of the via hole conductor according to the comparative example is larger than that of the embodiment because the pores formed in the via electrode occupy a large specific gravity in the embodiment.

The degree of adhesion between the via hole electrode and the green sheet interface was investigated with respect to the via hole electrode of the LTCC substrate manufactured through the Examples and Comparative Examples.

First, FIGS. 5A, 5B, and 5C are photographs illustrating a closeness of the interface between the via hole electrode and the green sheet in the comparative example, and FIGS. 5A and 5B are cross-sectional views and FIG. 5C correspond to a plan view.

Referring to FIGS. 5A, 5B, and 5C, in the case of the LTCC substrate according to the comparative example, the adhesion between the via hole and the green sheet may be low and a large gap may be generated in the interface.

On the contrary, referring to the case of the embodiment with reference to FIGS. 6A, 6B, and 6C, it can be seen that the adhesion between the via hole electrode and the green sheet interface is high. That is, in this embodiment, unlike the comparative example, it can be seen that a gap is hardly generated at the interface between the via hole electrode and the green sheet. On the other hand, when the conductive paste composition is fired under the tap density condition of the present embodiment, as shown in FIG. 6B of FIGS. 6A and 6A with higher resolution, the inside of the via hole conductor shown in the center portion is silver (Ag). It can be seen that the particles have a porous structure in which the particles are dispersed.

The present invention is not limited by the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims. Accordingly, various forms of substitution, modification, and alteration may be made by those skilled in the art without departing from the technical spirit of the present invention described in the claims, which are also within the scope of the present invention. something to do.

As described above, according to the present invention, when the electrode is formed through firing, the adhesive strength between the electrode and the ceramic sheet is improved, and thus, a low temperature co-fired ceramic having an electrically conductive paste and its sintered body having improved electrical properties. A substrate can be provided.

Claims (14)

Including conductive powder and organic vehicle, Tap density from 3.0 to 4.0 g / cm ³ The electrically conductive paste composition characterized by the above-mentioned. The method of claim 1, The tap density is between 3.2 and 3.8 g / cm ³ The electrically conductive paste composition characterized by the above-mentioned. The method of claim 1, Density after sintering at 800 ~ 950 ℃ 4.5 ~ 6.0 g / cm ³ The electrically conductive paste composition characterized by the above-mentioned. The method of claim 3, The density after the sintering is 4.8 ~ 5.6 g / cm ³ The electrically conductive paste composition characterized by the above-mentioned. The method of claim 1, The conductive powder is a conductive paste composition, characterized in that the powder consisting of a material selected from the group consisting of gold (Au), silver (Ag), palladium (Pd), copper (Cu), nickel (Ni) and alloys thereof. The method of claim 5, The conductive powder is a silver (Ag) powder, characterized in that the conductive paste composition. The method of claim 1, The form of the said electroconductive powder particle is a spherical form, The electrically conductive paste composition characterized by the above-mentioned. The method of claim 7, wherein The specific surface area of the said electroconductive powder particle is 0.29-1.14 m <^2> / g, The electrically conductive paste composition characterized by the above-mentioned. The method of claim 7, wherein The conductive powder has a particle group having a particle diameter different from each other. The method of claim 1, The conductive paste composition, characterized in that no additives other than the component is included. The method of claim 1, The organic vehicle includes a conductive paste composition comprising a solvent and a binder. In a low temperature cofired ceramic substrate having a wiring conductor, The said wiring conductor consists of a sintered compact of the electrically conductive paste composition in any one of Claims 1-11, The low temperature co-fired ceramic board | substrate characterized by the above-mentioned. The method of claim 12, And the wiring conductor comprises a via hole conductor formed to penetrate the ceramic substrate. The method of claim 13, The via hole conductor is a low-temperature cofired ceramic substrate, characterized in that the ratio (a / b) of the via diameter (a) and the stack height (b) is 0.025 ~ 8.

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