WO2020111908A1 - Parameter for improvement of printing property of conductive paste, and conductive paste satisfying same - Google Patents

Abstract

The present invention relates to a parameter for a conductive paste comprising metal powder, a solvent, an organic binder, and a glass frit, and a parameter relating to a viscosity for improving the printing property of the conductive paste is provided so that the conductive paste satisfying the parameter has an improved long time printing property.

Description

Parameters for improving the printing properties of conductive pastes and conductive pastes that satisfy them

The present invention relates to a parameter for improving the printing properties of a conductive paste and a conductive paste satisfying the same, and is applied to a conductive paste for forming an electrode in an electronic component such as an electrode for a solar cell, an internal electrode of a multilayer capacitor, or a conductor pattern of a circuit board. It is about possible parameters.

The conductive paste is a fluid composition having a coating ability capable of forming a coating film and electricity flowing through a dried or fired coating film. It is a fluid composition in which a conductive filler (metal filler) alone or glass frit is dispersed in a vehicle made of a resin-based binder and a solvent. It is widely used for forming circuits and forming external electrodes of ceramic capacitors.

In particular, silver paste (Silver Paste) is the most chemically stable and excellent conductivity among composite-based conductive pastes, and its application range is considerably wide in various fields such as conductive adhesion and coating and microcircuit formation. In electronic components that place special emphasis on reliability, such as printed circuit boards (PCBs), the use of silver paste is used as an adhesive or coating material for STH (Silver Through Hole), in multilayer capacitors for internal electrodes, and recently silicon-based solar cells Is widely used as an electrode material.

Rheology of the conductive paste is a major factor in determining the printing characteristics (applicability), and the electronic component is miniaturized and the conductive paste affects the printing characteristics in order to cope with the high density or fine patterning of the electrode pattern. The rheological properties of the conductive paste are important, and especially, the screen printed electrode for solar cells requires a narrow line width and high thickness of the electrode, that is, an increase in the aspect ratio.

In addition, when printed for a long time as an electrode paste for solar cells, the viscosity of the paste changes due to internal friction and heat, solvent absorption, and solvent evaporation due to squeegee and engraving, resulting in disconnection, printing defects, and variations in line width.

On the other hand, most of the existing parameters are for implementing a narrow line width, and research on a solution to problems that may occur when printing for a long time is insufficient.

The present invention provides a viscosity-related parameter of a conductive paste capable of solving the above-mentioned problems when printing for a long time and a conductive paste having improved long-term printability by satisfying the parameters.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention provides a parameter of a conductive paste, which is a parameter for a conductive paste comprising a metal powder, a solvent, an organic binder, and a glass frit, and is a parameter for viscosity to improve printing properties of the conductive paste. do.

In addition, the parameter is characterized in that it is a parameter calculated using a viscosity value measured at different rotational speeds for the conductive paste.

In addition, the parameter is characterized in that it comprises a first parameter subject to the condition that the first viscosity over time change (VC ₁₀ ) value calculated by the following equation 1 is within the range of 0% to 30%.

[Equation 1]

VC ₁₀ (%) = {(B ₁₀ -A ₁₀ )/A ₁₀ }×100

(Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 10rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent has the highest content in the conductive paste Means a solvent included.)

In addition, the parameter is characterized in that it further comprises a second parameter subject to the second viscosity over time change (VC ₁₀₀ ) value calculated by Equation 2 is within the range of 0% to 30%.

[Equation 2]

VC ₁₀₀ (%) = {(B ₁₀₀ -A ₁₀₀ )/A ₁₀₀ }×100

(Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 100rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent is the highest content in the conductive paste Means a solvent included.)

In addition, the parameter is characterized in that it further comprises a third parameter subject to a condition that the _ratio (VC _ratio ) of the first viscosity with time change to the second viscosity with time change calculated by the following equation 3 is within the range of 0.7 to 1.5 .

[Equation 3]

VC _ratio = VC ₁₀ / VC ₁₀₀

(Here, VC ₁₀ is the first viscosity change over time (%) calculated by Equation 1, VC ₁₀₀ is the second viscosity over time change (%) calculated by Equation 2.)

In addition, it characterized in that it further comprises a fourth parameter on the condition that it contains at least one of fatty acids, fatty alcohols and mixtures thereof in the conductive paste.

In addition, the present invention is a conductive paste comprising a metal powder, a solvent, an organic binder, and a glass frit, wherein the first viscosity aging change (VC ₁₀ ) value calculated by Equation 1 is within the range of 0% to 30%. It is characterized in that it satisfies the first parameter to be.

In addition, it is characterized in that it satisfies the second parameter that is the condition that the second viscosity over time change (VC ₁₀₀ ) value calculated by Equation 2 is in the range of 0% to 30%.

In addition, it is characterized in that it further satisfies the third parameter on the condition that the _ratio (VC _ratio ) of the first viscosity with time change to the second viscosity with time change calculated by Equation 3 is within the range of 0.7 to 1.5.

In addition, it is characterized in that it further satisfies the fourth parameter on the condition that any one or more of fatty acids, fatty alcohols, and mixtures thereof are included in the conductive paste.

When an electrode is formed by using a conductive paste that satisfies the parameters according to the present invention, it is possible to reduce process defects such as disconnection and printing defects that occur during printing for a long time due to a small change in characteristics even during a long process. As a result, the production yield can be increased through stable process progress.

1 to 9 are images after printing 40,000 sheets of conductive pastes according to Examples and Comparative Examples of the present invention.

Before describing the present invention in detail below, it is understood that the terms used herein are only for describing specific embodiments and are not intended to limit the scope of the present invention, which is limited only by the scope of the appended claims. shall. All technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art unless otherwise stated.

Throughout this specification and claims, unless otherwise stated, the terms comprise, comprises, comprising means referring to an article, step or group of articles, and steps, and any other article It is not meant to exclude a step or group of things or a group of steps.

On the other hand, various embodiments of the present invention can be combined with any other embodiments, unless otherwise indicated. Any feature indicated as particularly preferred or advantageous may be combined with any other feature or features indicated as preferred or advantageous. Hereinafter, embodiments and effects according to the present invention will be described with reference to the accompanying drawings.

The conductive paste according to an embodiment of the present invention is a paste composed of a metal powder, a solvent, an organic binder, and a glass frit, and the parameters according to the present invention can be suitably applied to a conductive paste for forming a solar cell electrode.

The parameter for improving the printing properties of the conductive paste according to the present invention is a parameter related to viscosity. In particular, the viscosity of the conductive paste during screen printing correlates with the line width of the pattern. Under the same screen printing conditions, as the viscosity of the conductive paste decreases, the line width increases to decrease the efficiency of the solar cell electrode. Conversely, if the viscosity of the conductive paste becomes too high, the probability of disconnection increases and the line resistance increases to decrease the efficiency of the solar cell electrode. Therefore, it is necessary to have an appropriate viscosity value and to determine the degree to which it is advantageous to maintain it even after a lapse of time.

The present invention presents three parameters that can be the criteria as described above. In order to calculate the parameters according to the present invention, the measured viscosity value of the conductive paste is required, and the viscosity value is measured at each rotation speed (rpm) with a spindle 14 using a rotational viscometer at 25°C. Specific viscosity value measurement conditions are shown in Table 1 below.

division	How to measure
	10 rpm*	Stabilization (0 rpm)	1 rpm	10 rpm	100 rpm
Analysis conditions	30 seconds	(1 minute)	30 seconds	30 seconds	30 seconds

The first parameter is provided that the first viscosity aging change (VC ₁₀ ) value calculated by Equation 1 is within a range of 0% to 30%.

[Equation 1]

VC ₁₀ (%) = {(B ₁₀ -A ₁₀ )/A ₁₀ }×100

(Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 10rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent has the highest content in the conductive paste Means a solvent included.)

The second parameter is subject to the condition that the second viscosity aging change (VC ₁₀₀ ) value measured by the following Equation 2 is within the range of 0% to 30%.

[Equation 2]

VC ₁₀₀ (%) = {(B ₁₀₀ -A ₁₀₀ )/A ₁₀₀ }×100

(Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 100rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent is the highest content in the conductive paste Means a solvent included.)

The third parameter is provided that the ratio (VC _ratio ) of the first viscosity with time change to the second viscosity with time change calculated by Equation 3 is within the range of 0.7 to 1.5.

[Equation 3]

VC _ratio = VC ₁₀ / VC ₁₀₀

(Here, VC ₁₀ is the first viscosity change over time (%) calculated by Equation 1, VC ₁₀₀ is the second viscosity over time change (%) calculated by Equation 2.)

The conductive paste that satisfies the above three parameters has an excellent effect in printing characteristics because disconnection does not occur when printing for a long time.

In addition, the parameter according to the present invention further includes a fourth parameter that is a parameter related to the component in addition to the parameter related to the viscosity.

The fourth parameter is provided that the conductive paste contains at least one of fatty acids, fatty alcohols, and mixtures thereof.

The fatty acids include stearic acid, lauric acid, oleic acid, myristic acid, palmitic acid, behenic acid, and benzoic acid. acid) and mixtures thereof. Preferably it contains at least one selected from stearic acid, lauric acid, oleic acid and mixtures thereof.

The fatty alcohol is cetyl alcohol, stearyl alcohol, lauryl alcohol, octadecyl alcohol, oleyl alcohol, hexadecenol and And at least one selected from mixtures thereof. Preferably it contains at least one selected from stearic acid, lauric acid, oleic acid and mixtures thereof. It is preferable to include at least one selected from cetyl alcohol, stearyl alcohol, lauryl alcohol, and mixtures thereof.

Hereinafter, it will be described through a specific example and a comparative example that the printing properties of the conductive paste satisfying the above parameters are improved when printing for a long time.

First, as the conductive paste (A), a silver paste containing silver powder is mixed and dispersed in the composition shown in Table 2, followed by filtration and defoaming.

Category [% by weight]	Example 1A	Example 2A	Example 3A	Example 4A	Example 5A	Comparative Example 1A	Comparative Example 2A	Comparative Example 3A	Comparative Example 4A
Ethyl cellulose resin	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
Diethylene glycol butyl ether acetate	6.1	6.3	6.3	6.1	5.6	6.1	6.1	6.3	6.6
Wax	0.28	0.28	0.28	0.28	0.28	0.28	0.28	0.28	0.28
Silver powder	88.5	88.5	88.5	88.5	88.5	88.5	88.5	88.5	88.2
Glass frit	3.1	3.1	3.1	3.1	3.1	3.1	3.1	3.1	3.1
Additive 1	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
Additive 2	0.92	0.92	0.92	0.92	0.92	0.92	0.92	0.92	0.92
Lauric acid						0.2
Stearic acid							0.2
Oleic acid	0.2
Cetyl alcohol		0.2
Stearyl alcohol			0.2
Lauryl alcohol				0.2	0.7

Next, a conductive paste (B) having a composition except for the main solvent 1% in the corresponding conductive paste (A) is prepared. The composition is prepared with a composition in which the content of diethylene glycol butyl ether acetate, which is the main solvent, is reduced by 1% (total composition 99%), as shown in Table 3 below.

Category [% by weight]	Example 1B	Example 2B	Example 3B	Example 4B	Example 5B	Comparative Example 1B	Comparative Example 2B	Comparative Example 3B	Comparative Example 4B
Ethyl cellulose resin	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
Diethylene glycol butyl ether acetate	5.1	5.3	5.3	5.1	4.6	5.1	5.1	5.3	5.6
Wax	0.28	0.28	0.28	0.28	0.28	0.28	0.28	0.28	0.28
Silver powder	88.5	88.5	88.5	88.5	88.5	88.5	88.5	88.5	88.2
Glass frit	3.1	3.1	3.1	3.1	3.1	3.1	3.1	3.1	3.1
Additive 1	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45	0.45
Additive 2	0.92	0.92	0.92	0.92	0.92	0.92	0.92	0.92	0.92
Lauric acid						0.2
Stearic acid							0.2
Oleic acid	0.2
Cetyl alcohol		0.2
Stearyl alcohol			0.2
Lauryl alcohol				0.2	0.7

Viscosities are measured for the prepared Examples A, B and Comparative Examples A and B, respectively. It is shown in Table 3 below by measuring the viscosity at each rotational speed (rpm) with a spindle 14 using a rotational viscometer at 25°C. In addition, the ratio of the first viscosity aging change value to the first viscosity aging change value with respect to the first viscosity aging change value, which is the viscosity value at 10 rpm, the second viscosity aging change value with the viscosity value at 100 rpm, and the second viscosity aging change value is shown in the table below. It is shown in 4.

	10 rpm viscosity (Pa.s)	100 rpm viscosity (Pa.s)	VC 10 (%)	VC 100 (%)	VC ratio
Example 1A	443000	64000	29.47%	24.41%	1.21
Example 1B	594000	79100
Example 2A	431000	63100	19.53%	24.43%	0.8
Example 2B	683000	78300
Example 3A	380000	59800	29.25%	27.07	1.08
Example 3B	492000	74400
Example 4A	384000	57300	28.53%	28.60%	One
Example 4B	459000	71300
Example 5A	400000	54300	26.65%	24.59%	1.08
Example 5B	517000	69000
Comparative Example 1A	354000	56300	34.09%	23.59%	1.44
Comparative Example 1B	455000	72400
Comparative Example 2A	334000	54900	58.47%	22.34%	2.61
Comparative Example 2B	423000	68400
Comparative Example 3A	362000	55300	72.10%	46.65%	1.54
Comparative Example 3B	623000	81100
Comparative Example 4A	343000	44700	24.28%	38.00%	0.63
Comparative Example 4B	453000	72100

Experimental Example - Measurement of disconnection after printing for a long time Using a conductive paste prepared according to Example A and Comparative Example A, using an ASYS screen printing machine on the alumina substrate, the separation distance 1.5mm, squeegee pressure 75N, printing speed 300mm/ As s, a pattern of a 40 μm line width was screen printed using a 360 mesh screen plate manufactured by Muragami Company, and dried at 100° C. for 30 minutes. The photographed images of whether or not the printed pattern is disconnected after 40000 sheets are shown in Figs. 1 to 9, and the number of disconnected lines is shown in Table 5 below.

When printing using a conductive paste that satisfies the parameters according to the present invention as shown in FIGS. 1 to 9, there is almost no disconnection even after 40,000 sheets of printing, so the printing properties are very excellent when printing for a long time, while the parameters according to the present invention are In the case of printing using an unsatisfactory conductive paste, it can be seen that a large amount of disconnection occurs, so that the printing characteristics are significantly deteriorated when printing for a long time.

	Number of disconnection (pcs)
Example 1A	4
Example 2A	14
Example 3A	6
Example 4A	2
Example 5A	One
Comparative Example 1A	30
Comparative Example 2A	45
Comparative Example 3A	38
Comparative Example 4A	21

Features, structures, effects, and the like exemplified in each of the above-described embodiments may be combined or modified with respect to other embodiments by a person having ordinary knowledge in the field to which the embodiments belong. Therefore, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

Claims (10)

1. As a parameter for a conductive paste comprising a metal powder, a solvent, an organic binder, and a glass frit,

   A parameter of the conductive paste, characterized in that it is a parameter related to viscosity for improving the printing properties of the conductive paste.
2. According to claim 1,

   The parameter is a parameter of the conductive paste, characterized in that the parameter calculated using a viscosity value measured at different rotational speeds for the conductive paste.
3. According to claim 1,

   The parameter is a parameter of the conductive paste, characterized in that it comprises a first parameter subject to the first viscosity over time change (VC ₁₀ ) value calculated by Equation 1 is within the range of 0% to 30%.

   [Equation 1]

   VC ₁₀ (%) = {(B ₁₀ -A ₁₀ )/A ₁₀ }×100

   (Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 10rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent has the highest content in the conductive paste Means a solvent included.)
4. According to claim 3,

   The parameter is a parameter of the conductive paste, characterized in that it further comprises a second parameter subject to the second viscosity over time change (VC ₁₀₀ ) value calculated by Equation 2 is within the range of 0% to 30%.

   [Equation 2]

   VC ₁₀₀ (%) = {(B ₁₀₀ -A ₁₀₀ )/A ₁₀₀ }×100

   (Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 100rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent is the highest content in the conductive paste Means a solvent included.)
5. The method of claim 4,

   The parameter further comprises a third parameter subject to the condition that the _ratio (VC _ratio ) of the first viscosity with time change to the second viscosity with time change calculated by Equation 3 is within the range of 0.7 to 1.5. Paste parameters.

   [Equation 3]

   VC _ratio = VC ₁₀ / VC ₁₀₀

   (Here, VC ₁₀ is the first viscosity change over time (%) calculated by Equation 1, VC ₁₀₀ is the second viscosity over time change (%) calculated by Equation 2.)
6. The method of claim 5,

   A parameter of the conductive paste further comprising a fourth parameter provided that the conductive paste contains at least one of fatty acids, fatty alcohols, and mixtures thereof.
7. A conductive paste comprising a metal powder, a solvent, an organic binder, and a glass frit,

   A conductive paste characterized by satisfying a first parameter provided that the first viscosity aging change (VC ₁₀ ) value calculated by Equation 1 is within a range of 0% to 30%.

   [Equation 1]

   VC ₁₀ (%) = {(B ₁₀ -A ₁₀ )/A ₁₀ }×100

   (Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 10rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent has the highest content in the conductive paste Means a solvent included.)
8. The method of claim 7,

   A conductive paste characterized by further satisfying a second parameter provided that the second viscosity aging change (VC ₁₀₀ ) value calculated by Equation 2 is within a range of 0% to 30%.

   [Equation 2]

   VC ₁₀₀ (%) = {(B ₁₀₀ -A ₁₀₀ )/A ₁₀₀ }×100

   (Wherein, A is the brookfield viscometer 10rpm reference viscosity of the conductive paste, B is the brookfield viscometer 100rpm reference viscosity of the conductive paste having a composition excluding the main solvent 1% from the conductive paste, the main solvent is the highest content in the conductive paste Means a solvent included.)
9. The method of claim 8,

   The conductive paste characterized in that it further satisfies the third parameter provided that the ratio (VC _ratio ) of the first viscosity with time change to the second viscosity with time change calculated by Equation 3 is within the range of 0.7 to 1.5.

   [Equation 3]

   VC _ratio = VC ₁₀ / VC ₁₀₀

   (Here, VC ₁₀ is the first viscosity change over time (%) calculated by Equation 1, VC ₁₀₀ is the second viscosity over time change (%) calculated by Equation 2.)
10. The method of claim 9,

    Conductive paste characterized in that it further satisfies the fourth parameter on the condition that any one or more of fatty acids, fatty alcohols and mixtures thereof in the said conductive paste.

Images