KR100750331B1 - Thermosetting carbon resistance paste composition - Google Patents

Abstract

Provided is a thermosetting carbon resistance paste composition which is excellent in humidity resistance and heat resistance and is suitable for an embedded board. A composition comprises 20-35 wt% of a cresol novolac epoxy resin represented by a formula 1; 5-15 wt% of a phenolic novolac epoxy resin; 15-30 wt% of a conductive carbon black; 30-45 wt% of an organic solvent; 0.1-5 wt% of a dispersant; and 0.1-2 wt% of a curing accelerator, wherein R is H or an alkyl group. Preferably the organic solvent is at least one selected from cellosolve-based solvents, carbitol-based solvents, terfenol and cyclohexanone.

Description

Thermosetting Carbon Resistance Paste Composition

The present invention relates to a thermosetting carbon resistance paste composition, which is prepared by mixing a conductive carbon powder in a binder prepared by diluting an epoxy resin and a phenol resin with a solvent, wherein the binder is a cresol represented by the following Chemical Formula (1) It comprises a novolak-type epoxy resin.

[Formula 1]

Wherein R is hydrogen or an alkyl group.

The present invention is a thermosetting carbon resistance paste composition for embedded substrates excellent in moisture resistance and heat resistance, and good electrical properties.

In general, most of the current resistor-forming material is a common trend in the embedded PCB industry to implement a built-in resistor using a method of etching or plating a metal thin film to form a resistor.

However, in order to meet the exact pattern and characteristic deviation requirements that are difficult to achieve with current technology, research and development of more stable material development technology is required, and the corrosion or plating method is difficult for mass production and environmental In terms of cotton and cost, it's pretty tough.

Therefore, a thick film method using a low temperature curable polymer has recently been attracting attention. The low temperature curing type method is suitable for mass production, and it is judged to be competitive with other resistors manufactured in other ways in terms of environmental and cost, but the resistance value and tolerance of the embedded characteristics are required. ), TCR and the like, and properties such as moisture resistance and heat resistance of the resistor are also required.

The present invention is to satisfy the above requirements, the object of the present invention is that the heat-cured resistor always implements the same resistance value, the error tolerance is less than 5%, the TCR characteristic is 100ppm It should be within, and to provide a heat-curable carbon resistance paste composition satisfying the moisture resistance and the heat resistance resistance change also k 5%.

In order to achieve the above object, the present invention is 20 to 35% by weight of cresol novolac-type epoxy resin represented by the following formula (1), 5 to 15% by weight of novolak-type phenol resin, 15 to 30% by weight of conductive carbon black %, 30 to 45% by weight of the organic solvent, 0.1 to 5% by weight of the dispersant and 0.1 to 2% by weight of the curing accelerator is characterized.

[Formula 1]

Wherein R is hydrogen or an alkyl group as cresol novolac epoxy resin when R is an alkyl group, especially a methyl group, and a phenol novolac epoxy resin when R is hydrogen.

In the present invention, a binder in which an epoxy resin and a phenol resin are mixed and a conductive carbon black powder are mixed and manufactured by a 3-roll mill method.

The present invention is explained in more detail as follows.

The binder in the present invention is composed of the cresol novolak-type epoxy resin represented by the formula (1) as a main component, the content is 20 to 35% by weight of the cresol novolak-type epoxy resin, novolak-type phenolic resin 5 -15 wt% is preferred.

The binder used in the present invention is made by mixing the cresol novolak-type epoxy resin and novolak-type phenol resin. When mixed in this way and used as a binder, the phenol resin excellent in heat resistance raises the heat resistance of an epoxy resin.

At this time, the binder is made of 50 to 90% by weight of the cresol novolak-type epoxy resin, 10 to 50% by weight of the novolak-type phenol resin. When the mixed resin is out of the above range, the heat resistance is lowered, which is not preferable.

In general, the conductive carbon paste composition is made by mixing 100 to 200 parts by weight of the binder with respect to the total weight of the carbon black powder used. In the present invention, the carbon black powder and the thermosetting resin are mixed in such a conventional mixing ratio. In order to increase the lubricity in the use of the carbon black powder, it may be used in combination with the graphite powder. In the present invention, the tolerance of the carbon powder may be increased, and therefore, it is preferable to use the carbon powder alone.

As carbon black, DBP oil absorption is about 110 ~ 180cc / 100g, particle size is about 20 ~ 50nm and has high purity over 99% (cabot: xc72R, cabot: xc72, columbia carbon: CDX7055U, degussa: Printex L6) It is used, the amount of use is preferably 10 to 40% by weight.

The heat curable carbon resistive paste composition constituted as described above comprises a conductive carbon black powder, a cresol novolac epoxy resin and a novolac phenol resin represented by the formula (1), and then a solvent, a dispersant, a curing accelerator, and the like. Other additives are mixed and then dispersed in a three roll mill method to prepare a paste.

As the organic solvent, one or two or more kinds of general organic solvents such as cellosolve, calbitol, terpenol, cyclohexanone, and isophorone are used. Here, in consideration of workability when printing the composition on a printed circuit board, it is preferable to use a solvent having a boiling point of about 150 to 250 ° C, and such a solvent is used at 30 to 45% by weight.

In addition, the curing accelerator for promoting the curing reaction is preferably 0.1 to 2% by weight, and may be added as a thixotropic agent, antifoaming agent or lubricant as other additives.

It will be described in more detail through the following examples and comparative examples.

Example 1

20 g of novolak-type phenolic resin (trade name TD-2131, Gangnam Chemical), 10 g of conductive carbon black powder (brand name xc72R, USA Cabot), butyl carbitol acetate, to 30 g of cresol novolac epoxy resin represented by the above formula (1) 40 g of (diethylene glycol monobutyl ether acetate) and other additives were mixed, stirred, and dispersed to a particle size of about 4 mu m or less. The composition thus obtained was printed on a width of 3 mm, a length of 50 mm and a thickness of about 40 μm, and then cured by heating to obtain a coating film.

The volume resistivity, area resistivity, solder dipping, moisture resistance, and TCR of the coating film obtained in Example 1 were tested in the following manner.

(1) Volume resistance: After measuring the resistance in ohm-meter (ohm-meter) at the point of 30mm of the test piece (thickness 20 ~ 30㎛), it was calculated according to the following formula.

Volume resistance (Ωcm) = (measurement resistance × width of coating film × thickness of coating film) / measuring length of coating film

(2) Surface resistance: It was calculated according to the following formula.

Surface resistance (Ω / □) = (measurement resistance × width of coating) / measuring length of coating

The results of Example 1 were as shown in Table 1 below.

(3) Lead bath dipping: The resistance was measured by an ohm-meter at a point of 30 mm of the test piece (thickness 20 ~ 30㎛), and after dipping in the lead bath was measured according to the following equation.

% Change in resistance = {(initial resistance-resistance after dipping) / initial resistance} × 100

(4) Moisture resistance: Measure the resistance by ohm-meter at the point of 30mm of the test piece (thickness 20 ~ 30㎛) and measure the resistance after 85 ℃, 85%, 168hr in constant temperature and humidity chamber, Calculated accordingly.

% Change in resistance = {(initial resistance-resistance after invasion test) / initial resistance} × 100

(5) TCR: Screen printed 1mm × 1mm on the test substrate made of epoxy resin and then heat-cured to obtain a sample was measured by a TCR measuring instrument and the resistance change rate was calculated according to the following equation.

TCR (ppm / ° C): {(resistance at 125 ° C / resistance at 25 ° C) -1} × {1 / (125-25)} × 10 ⁶

Example 2

To 30 g of phenol novolac epoxy resins represented by the above formula (1), 20 g of novolak-type phenolic resin (trade name TD-2131, Gangnam Chemical), 10 g of carbon black powder (trade name xc72R, U.S. Cabot), butyl carbitol acetate ( 40 g of diethylene glycol monobutyl ether acetate), 0.25 g of a dispersant, and other additives were mixed, and stirred to disperse to a particle size of about 4 μm or less. The composition thus obtained was printed on a width of 3 mm, a length of 50 mm, and a thickness of 40 μm, and then heat-cured to obtain a coating film. In the same manner as in Example 1, the volume resistivity, area resistance, solder dipping, and moisture resistance of the coating film were obtained. , TCR was tested.

Comparative Example 1

50 g of novolac-type phenolic resin (trade name GA1379K, Gangnam Hwaseong), 10 g of carbon black powder (trade name xc72R, Cabot, USA), 40 g of butyl calbitol acetate (diethylene glycol monobutyl ether acetate), 0.25 g of a dispersant, and other additives After stirring, the mixture was dispersed to have a particle size of about 4 μm or less. The composition thus obtained was printed on a width of 3 mm, a length of 50 mm, and a thickness of 40 μm, and then heat-cured to obtain a coating film. In the same manner as in Example 1, the volume resistivity, area resistance, solder dipping, and moisture resistance of the coating film were obtained. , TCR was tested.

Comparative Example 2

To 30 g of modified novolac type epoxy resin (brand name HP7200, Nippon Ink Chemical), 20 g novolak type phenol resin (brand name TD-2131, Gangnam Chemical) 10 g, carbon black powder (brand name xc72R, American Cabot), butyl carbitol acetate ( 40 g of diethylene glycol monobutyl ether acetate), 0.25 g of a dispersant, and other additives were mixed, and stirred to disperse to a particle size of about 4 μm or less. The composition thus obtained was printed on a width of 3 mm, a length of 50 mm, and a thickness of 40 μm, and then heat-cured to obtain a coating film. In the same manner as in Example 1, the volume resistivity, area resistance, solder dipping, moisture resistance of the coating film , TCR was tested.

The results of the Examples and Comparative Examples were as shown in Table 1.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Conductivity Volume resistivity (Ωcm) 0.696 0.448 0.447 0.495 Area resistance (Ω / □) 276 187 205 211 Lead Dipping <3.4% <1.9% <22.5% <11.7% Moisture resistance ± 1.2% ± 1.35% ± 2.64% ± 1.83% TCR -13.15 -27.69 -465.64 -197.13

As described above, according to the present invention, the moisture resistance and the heat resistance are excellent, so that the rate of change of the resistance is almost within ± 5%, and thus the reliability of the resistance characteristics is high. In addition, it is useful as a thermosetting carbon resistance paste that can be applied to an embedded substrate because of its excellent tolerance rate and TCR characteristics.

Claims (3)

20 to 35% by weight of cresol novolac type epoxy resin represented by the following formula (1), 5 to 15% by weight of phenol novolac type epoxy resin, 15 to 30% by weight of conductive carbon black, 30 to 45% by weight of organic solvent, A thermosetting carbon resistance paste composition comprising 0.1 to 5 wt% of a dispersant and 0.1 to 2 wt% of a curing accelerator. [Formula 1]

Wherein R is hydrogen or an alkyl group. The method of claim 1, The cresol novolak-type epoxy resin and phenol novolak-type epoxy resin is a thermosetting carbon resistance paste composition, characterized in that the mixture of 50 to 90% by weight: 10 to 50% by weight The method of claim 1, The organic solvent is a thermosetting carbon resistance paste composition, characterized in that one or two or more of cellosolve, carbitol, terpenol, cyclohexanone or isophorone are used and mixed.