JPH0412501A - Thin film low resistant composite - Google Patents

Abstract

PURPOSE: To provide a thick-film low resistance body composition of relatively high density and low-porosity by comprising silver, palladium, mixture in which an alloy of silver and palladium or its mixture, mixture containing two kinds of glasses, and submicron particle are diffused in an organic medium. CONSTITUTION: A mixture of organic medium in which an alloy of palladium and silver, a mixture of oxides of palladium and silver, or their mixture, a mixture of a glass 0.2-5.0wt.% which is, in melting, wettable to other solids in the composition, while having a softening point 350-500 deg.C with all the solids as the reference and a glass of softening point 550-650 deg.C, and submicron particles 5-20vol.% of RuO2 with all the solids as the reference are diffused, is provided. Thus, a thick-film low resistance body composition of high density and low porosity is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thick film thin film with improved laser trimming stability.
The present invention relates to low-end) resistance compositions, and is particularly suitable for manufacturing chip resistors.

[Background of the invention]

Circuit element (chip) resistors are typically screen printed on large square alumina substrates as a thick film paste with up to 1000 circuit element resistors on a single substrate. The printed resistor is then fired to remove any organic media from the printed pattern and densify the solid. A first encapsulant glass layer is printed on the resistor and fired. At this point, the resistance value has a distribution of 3 to 5%. - an encapsulating material for a resistor that has been encapsulated;
and trimming using a laser beam that passes through the printed resistor layer and directly into the alumina substrate. This laser trimming increases the resistance value by about 50%, but
Reduce the resistance value distribution to about 0.1%.

After laser trimming through the first encapsulant layer and resistor, a second glass cuffing material is printed onto the trimmed resistor and fired at 600°C. After firing the second encapsulation layer, conductive termination is performed by dividing the wide substrate into strips and dipping the ends of the strips into a conductive paste. The thus-terminated pieces were then fired. After this end firing, the piece was divided into separate chips and the terminals of the chips were plated with nickel and solder. Finished circuit element (chip)
The resistor is a large grain about the size of a second. It is usually soldered onto a printed circuit board.

The above-mentioned chip resistor has a resistance of 1 to 1.000,0
Widely manufactured in a wide resistance range of 0.00 Ohm, these must have a resistance change of less than 0.5% even upon encapsulation and trimming. However, it is very difficult to achieve such resistance stability with low-end resistors, ie, resistors with resistance values of only 1 to 100 ohms per unit area.

Low-resistance resistors such as those based on Rub alone, which are used in this technical field, have a resistance change of more than 0.5% in 1000 hours after laser trimming, while higher-resistance resistors have much It is stable. Furthermore, the low resistance resistors conventional in this art have a resistance of ±10% and a temperature coefficient of resistance (TCR) of ±100 ppm.
/ 'C is difficult to manufacture. This is because dense, solid, and unbreakable microstructures are difficult to achieve. The relatively voluminous fraction of the glass binder phase in such compositions makes it difficult to achieve a solid microstructure at this desired density.

[Contents of the invention]

The present invention seeks to overcome the above-mentioned problems by using components that are relatively dense and have low porosity, thus providing a stable microstructure. The low softening point glass and the alloying behavior of Pd and Ag result in microstructural behavior during firing of the resistor, which provides stable resistor properties and consistent properties from lot to lot.

It also has the advantage of being able to transport power as a low resistance capability, which is higher than the 1.5
~2 times as much. The present invention thus overcomes many of the problems of the prior art.

In a first aspect of the present invention, the present invention is directed to a thick film low resistance composition, which includes the following fine powder (a) alloy of palladium and silver, palladium and a mixture of oxides of silver, or a mixture thereof, in which the weight proportions of palladium and silver are 6 to 35% to 45% and 65 to 45%, respectively.
It is 55%.

(b) (1) Softening point 350-500° based on total solids
(2) a mixture of glass having a softening point of 550-650 °C; and (c) 5 to 20% by volume of submicron particles of RuO2 based on total solids; and (d) a mixture of an organic medium in which all of (a) to (c) above are dispersed.

In view of the present invention, the present invention is directed to a method of manufacturing a low resistance element, comprising the following steps: (a) applying a patterned layer of the thick film composition described above on an inert substrate; and (b) ) The layer is fired at a maximum temperature of 800 to 900°C, and the organic medium is evaporated therefrom to densify the solid.

[Contents of the invention]

A. Conductive Metal The conductive phase of the composition of the present invention may be an alloy of palladium and silver, or a gold powder mixture of palladium and silver.

Mixtures of both can also be used successfully. A specific palladium:silver weight ratio of 40:60 is preferred from the viewpoint of sintering and alloy properties. However, it is also possible to use palladium/silver ratios as low as 35:65 and as high as 45:55.

The particle size of the metal powder is not particularly important as long as it is appropriate for the application method, but is preferably in the range of 0.5 to 5 microns.

B. Inorganic binder The inorganic binder component of the present invention consists of two types of glasses. One of the glasses must have a low melting point and wettability with the other solid surfaces in the composition. This low-melting glass must have a softening point (dilatometer) of 350-500°C and be wettable to the surfaces of the other solids in the composition, namely the second glass, the conductive metal and Ru0z.

The wettability of glass depends on the expected firing temperature (800-900
°C) is easily determined by measuring the contact angle of molten glass on the surface of each other solid. For the present invention, stable wettability is defined as a contact angle of low melting glass on another solid of 3
0° or less, preferably 10° or less.

The softening point of the low melting glass should not exceed about 500° C. to ensure adequate melting of other solid particles so as not to cause insufficient fluidization of the glass during firing. On the other hand, if the softening point of the glass is 350° C. or lower, fluidization of the glass during firing becomes excessive and the distribution of the glass over the entire fired resistor becomes poor. For optimal performance, the softening point of the low melting point glass is in the range of 375-425°C.

The 12 essential components of inorganic binders have a softening point (dilatometer)
It is a high melting point glass having a temperature of 550 to 650°C, preferably 575 to 600°C. It is preferable that the softening point of this glass is not lower than 550°C. This is because the temperature coefficient of expansion (TCE) of these glasses tends to be excessive compared to conventional substrate materials. On the other hand, if the softening point is considerably higher than 650° C., the uniformity of the fine structure of the fired resistor becomes poor and the resistance of the resistor becomes poor.

Provided that the physical properties of the two glasses are appropriate, the composition of the glasses is not critical in itself, except that the composition of both glasses is related to the viscosity and wetting properties of the glass when fired. Thus, a wide variety of oxide glasses containing conventional glass-forming and glass-modifying components can be used, such as aluminoborosilicate, lead borosilicate and lead silicates, such as ship silicates themselves, and bismuth silicates. However, the low softening point glass does not crystallize (is amorphous) at the firing temperature, so it is necessary to obtain a suitable amount of glass fluidity during the firing stage.

The total amount of inorganic binder in the compositions of the present invention is partially a function of the desired resistor performance. For example, a 1 ohm/hole resistor requires on the order of 45% by volume of inorganic binder, a 10 ohm/hole resistor requires about 65% by volume of glass binder, and a 100 ohm/hole resistor requires 5 glass binder darts. Contains % by volume. Therefore, the amount of binder may vary from a low 40% to a high 80% by volume, but is usually within the range of 50 to 65%.

The relative amount of low melting glass in the inorganic binder is a function of the total solids in the composition and the wettability of the low melting glass on other solids. In particular, for adequate wetting of all solids, at least 0.2% by weight of low-melting glass and preferably at least 0.
．． 5% by weight is required. However, if more than about 5% by weight of low melting point glass is used, the composition tends to blister during firing.

There is no particular critical value for the particle size of the inorganic binder. However, glass particles are 0.1 to 10 microns (
The average particle size should be 2-3 microns, preferably in the range 0.5-5 microns. Fine glass of 0.1 micron or less has a very large surface area and requires a large amount of organic medium to obtain adequate fluidity as a printing paste.

On the other hand, particles larger than 10 microns pose an obstacle to screen printing.

C1 Ruthenium Dioxide A small amount of ruthenium dioxide (Rub) is required to lower the TCP of the compositions of the present invention. Required RuO2
The amount of is related to the total volume of the solid composition.

In particular, at least 5% by volume of RuO□ is required, but in some cases up to 20% by volume of RuO2 may be used.

When Ru03 is less than 5% by volume, it is difficult to produce a resistor with good reproducibility, and when it is more than about 20% by volume, the total amount of the conductive phase becomes excessive, resulting in an insufficient amount of glass and a good microstructure. I can't get it. However, the RuO2 particle size must always be less than 1 micron to obtain adequate TCP properties.

Ru5t can be added to the composition in either of two forms. Discrete Rub, Rub added as particles or sintered onto the surface of glass particles.

It can be added in the form of Ru on the glass particle surface
By sintering and introducing 5t, we obtained a more uniform particle distribution, better wetting, and more uniform deposition of Ru01 particles, and reduced the catalysis by the particles when dispersed in organic media. is preferred. In the latter example, the particles are prepared by mixing RuO2 particles with glass particles, heating this mixture above its softening point so that the glass sinters but does not melt or flow, and then crushing this sintered product. Manufactured by

The glass used for the RuO2 addition preferably has an intermediate softening point in the range 400-650 DEG C., which temperature is intermediate to the range of softening points of the main glass component of the inorganic binder. The purpose of this is to obtain good wetting and adhesion of RuO2 without too much glass dislocation during firing. In addition, a small amount of Mn01, Co, O,, Fe=Oi Cub, Ni
, O, etc. or more to further facilitate control of TCP. An effective amount of about 1% by weight is required, but in some cases about 20% by weight may be used. However, to prevent excessive moisture sensitivity, the transition metal oxide should be 15% by weight.
It is preferable to use an amount not exceeding .

D. Organic medium The inorganic particles are mixed with an organic liquid medium (carrier) by mechanical stirring to form a paste-like composition having appropriate softness and fluidity for screen printing. This paste is then printed onto a dielectric or other substrate using "thick film" techniques.

The primary purpose of the organic medium is to act as a carrier for the fine solid dispersion of the composition and to provide a form that can be easily applied to ceramic or other substrates. The organic medium must therefore first of all be dispersible such that the solid has a suitable degree of stability therein. Secondly, the flow properties of the organic medium must be such as to impart good coating properties to the dispersion.

Most thick film compositions are applied onto the substrate by screen printing techniques. Therefore, it must have a suitable viscosity so that it can easily pass through the screen. Furthermore, it must be thixotropic in order to immediately assemble it after screen printing and thereby give good resolution. Although flow properties are of primary importance, organic solvents are important in providing adequate wettability with solids and substrates, good drying rates, dry film strength sufficient to withstand rough handling, and good sintering properties. preferable.

It is also important that the fired composition has a satisfactory appearance.

In all these criteria a wide variety of inert liquids can be used as organic medium. The organic medium for most thick film compositions is typically a solution of a resin in a solvent, usually a solvent containing both a resin and a thixotropic agent. The solvent typically boils within the range of 130-350°C.

The resin most frequently used for this purpose is insulating ethylcellulose. However, resins such as ethyl hydroxyethyl cellulose, wood rosin, mixtures of ethyl cellulose and phenolic resins, polymethacrylates of lower alcohols and monobutyl ethers of ethylene glycol monoacetate can also be used.

The most commonly used solvents for thick film applications are σ or β.
- Terpenes such as terpineol or mixtures thereof with other solvents such as kerosene dibutyl phthalate, butyl carpitol, butyl carpitol acetate, hexylene glycol and high boiling alcohols and alcohol esters. Various combinations of these and other solvents are formulated to obtain the desired viscosity and volatility required for each application.

Commonly used thixotropic agents are hydrogenated castor oil and its derivatives and ethylcellulose. Of course, it is not necessary to always add a thixotropic agent. This is because the solvent/resin properties alone combined with the shear thinning that uncooked rice has in any suspension may be suitable in this regard.

The ratio of organic medium:solids in the dispersion can vary widely. and depends on the method of application of the dispersion and the type of organic medium used. Usually, to obtain good coverage, the dispersion should be supplemented with 60-90% by weight of solids and 40-10% by weight of organic medium.
Contains. Such dispersions usually have a semi-fluid consistency and are commonly referred to as "pastes".

Paste viscosity for screen printing is typically Broo
It was measured with a kfield HBT viscometer at high, medium and low shear rates and was within the following range.

Shear rate (sec-wa) Viscosity (Pa, s) 0.2
100-5000 300-2000 Good 600-1500 Best 100-250 Good 140-200 Best 384 7-4010-
25 Good 12-18 Best *HBT Cone and Plate Model B
The amount of carrier utilized as measured by the Rookfield viscometer is determined by the desired final viscosity.

Test Procedure^, Sample Preparation Temperature coefficient of resistance (TCP) test samples were prepared as follows.

10 Alsimag 614 1 x 1'' (2
, 4501 square) screen printing on a ceramic substrate,
The mixture was left to equilibrate to room temperature and then dried at 150°C. The average dry thickness of each set of 10 pieces before firing is Brush.
It should be 22-28 microns as measured by a 5urfanalyzer. The dried printed substrate is then dried for approximately 60 minutes.
Bake for 1 minute, using a heating cycle of heating to 850 °C at 35 °C per minute, holding at 850 °C for 9-10 minutes, and cooling to room temperature at 30 °C per minute.

B9 Measurement and Calculation of Resistance Terminals were attached to the substrate prepared as described above in a small room under temperature control and electrically connected to a digital ohmmeter. The temperature in the small room was adjusted to 25°C and left until equilibrium was reached, after which the resistance of each substrate was measured and recorded.

The temperature of the chamber was then raised to 125°C and allowed to equilibrate, after which the resistance was measured and recorded again.

The temperature of the chamber was then cooled to -55°C and allowed to equilibrate, and the cold resistance was measured and recorded.

The temperature coefficient of resistance (TCP) at high and low temperatures was calculated as follows.

R25'C! and hot and cold TCP values, and R25''C values were standardized to a 25 micron dry print thickness and resistance was reported as ohms/mouth at a 25 micron dry print thickness. The standard value of the test was calculated using the following relational expression.

C8 Laser Trim Stability Laser trimming of thick film resistors is an important technique for the fabrication of hybrid microelectronic circuits. (T
hick Film Hybrid Micro-ci
rcuit Technology, D, W,
Hamer8 and J,V.

Biggers (Wiley, 1972) p-1
73ff]. Its use can be understood by considering that the resistance of a particular resistor printed with the same resistor paste on a group of substrates has a Gaussian (like) distribution. To ensure that all resistors have the same design values for proper circuit characteristics, a laser is used to trim the resistors by removing (vaporizing) a small portion of the resistor material.

The stability of a trimmed resistor is a measure of the fractional change in resistance (drift) that occurs after laser trimming. Resistance drift must be low (high stability) to maintain a value close to the design value suitable for circuit characteristics.

D. Wettability The wettability of low melting glass with other solids is determined by measuring the contact angle of a molten drop of low melting glass on the surface of another solid. The equilibrium shape assumed by a droplet placed on a smooth solid surface under gravity is determined by the mechanical equilibrium forces of three surface tensions: δ (LV) liquid-gas interface; δ (LS) liquid-solid interface. : and δ(SV) solid-gas interface. The contact angle is theoretically independent of droplet volume and depends only on temperature and the respective properties of the solid, liquid, and gas phases at equilibrium in the absence of crystallization and interaction between the substrate and the test liquid. Depends on. Contact angle measurement is an accurate method for characterizing wettability on solid surfaces. This is because the ease with which liquids spread and the "wetting" of solid surfaces increases as the contact angle decreases.

E. Electrostatic Discharge Test This electrostatic discharge (ESD) test meets military standard MIL.
-STD-883C, Method 3015.6. This is an established means of classifying microcircuits (and resistors on them) in terms of their susceptibility to damage or degradation due to exposure to electrostatic discharge.

Electrostatic discharge, as used in this test, is defined as the transfer of electrostatic charge between two objects with different electrostatic potentials, with a rise time of 5 to 10 nanoseconds and a decay time of 150 nanoseconds.
It has ±20 nanoseconds.

Test results include the peak voltage and relative resistance change when the resistor is subjected to an electrostatic discharge.

Example 1 4.8 g of silver and 2.3 g of palladium powder and Ru03
A mixture was prepared by mixing with 25.7 g of powder. This conductive powder was further mixed with 32.29 g of manganese alumino lead borosilicate glass having a softening point of 510°C, 7.7 g of alumino lead borosilicate glass having a softening point of 525°C, and 0.79 g of bismuth silicate glass having a softening point of 445°C.
and calcium aluminolead borosilicate having a softening point of 660°C. The total powder has a surface area of 1 to 10
It was ground to a particle size of m''/9.

This powder mixture was dispersed in 38 g of a liquid medium consisting of ethyl cellulose and β-terpineol, and the viscosity was 100 to 100.
A viscous suspension with a pressure of 300 Pa-sec was obtained. In the practice of the present invention, this dispersion is usually screen printed onto an insulating substrate and fired in air at a temperature of 700 to 950°C to produce a fired resistor film.

This resistor with a printed thickness of 25 microns was fired at 850° C. for 10 minutes. The fired resistor had a resistance of 9.8 ohms/output and a temperature coefficient of resistance (TCR) of 35 ppm/''C measured between 25 and 125°C. This resistance drift was reduced after laser trimming and at 85°C. /85% relative humidity environment after storage.This resistance was 0.01±0.01% when a single pulse of 500 V was applied in the electrostatic discharge test. Maximum rated output 8
It had 64mW/sq, m+ml.

Example 2 Ru0220.8ya silver 15.0g and pd7.2g
A further mixture was formed by mixing. These conductors are made of manganese aluminoborosilicate glass 2
6.1g, lead aluminoborosilicate glass 18.19
, 10.59 g of glass with a softening point of 600° C., and 2.3 g of bismuth silicate glass. These powders were dispersed in an organic medium to form a paste, printed with a resistor pattern, and fired as in the previous example. The resistance of this resistor is 3.0 ohm/mouth and TC
R was 50 ppm/·C. This resistance drift is 0.0% after laser trimming and after storage ffi in an 85°C/85% relative humidity environment. O1±0.06%. This resistor has a maximum rated output of 888mW/electrostatic discharge test.
When applying a single pulse of 5000V with "ttrrn" - 0, 0
It changes by 1±0.04%.

Example 3 A fine solid mixture was formed by mixing 19.59 Silver and 16.49 Rung. These conductors are made of the above aluminium borosilicate glass 19.59
, 2.3 g of titania lead aluminoborosilicate glass and 6.3 g of bismuth lead aluminoborosilicate glass.
mixed with. This powder was ground to a surface area of 1-10 m"/y as in Example I. The ground particles were then dispersed in an organic medium and made into a paste. After printing and baking,
The resistance of the fired layer is 32.5 ohms/mouth, and the high temperature TCP is 14
7ppm/'c, and low temperature TCP -99ppm/'c
It was c.

Example 4 Rush 18Ay with 11.09 palladium and 1 silver
9.79 to form a mixture. The Ru02 particles were not sintered onto the surface of the glass particles in this case. This mixture was further mixed with 12.39 g of manganese-lead aluminoborosilicate glass with a softening point of 510°C, 1.99 g of bismuth silicate glass with a softening point of 445°C, 4.12 g of lead-aluminoborosilicate glass with a softening point of 600°C, and 525 g of a lead-aluminoborosilicate glass with a softening point of 600°C.
°C titania lead aluminoborosilicate glass 8.9g
mixed with. Reduce the total glass surface area to 1-10m”
/y.

This powder mixture was dispersed in an ethylcellulose and β-terpinenol liquid medium to form a viscous suspension having the same viscosity range as the previous example. After printing on an insulating substrate and baking at 850°C for 10 minutes, the printed layer has a resistance of 2.8 ohms and a temperature coefficient of resistance of 110 ppm/'
It was O. 0 resistance drift after laser trimming and storage for 500 hours at 85°C/85% relative humidity
．． It was 21%.

Example 5 Silver/palladium alloy powder 11.19 to palladium 1.39
and Rue, 6-Ly to form a mixture. The value of the silver:palladium ratio of this alloy is 2.6
It is. RuO2 was sintered onto the surface of the manganese aluminolead borosilicate glass. The amount of this glass with a softening point of 510° C. was 18.7 g. This mixture was further mixed with calcium aluminolead borosilicate glass 0.79 with a softening point of 660°C, aluminolead borosilicate glass 1.79 with a softening point of 600°C, and titania aluminolead borosilicate glass 4,739 with a softening point of 525°C. . This powder mixture was dispersed in organic medium 239 containing ethylcellulose and β-terpinenol.

After printing on an insulating substrate and baking for 10 minutes at 850°C, this resistor has a resistance of 8.3 ohms/hole and a temperature coefficient of resistance of -5.
It was 88 ppm/'O at 5°C to 25°C. The resistance drift after laser trimming and storage at 85° C. and 785% relative humidity was 0.12%.

Next is an example of a resistor having a relatively high concentration of Pd. A
The ratio of g/(Pd + Ag) is approximately 6 in most other examples.
It is only 42% compared to 0%.

Example 6 A mixture was formed by mixing Rust 14-69 with 16.85 g of palladium and 12.29 g of silver. The ratio of Ag/(Pd+Ag) in this case was only 42% compared to about 60% in most other examples. This mixture was further mixed with 7.8 g of manganese alumino borosilicate glass having a softening point of 510°C.
Titania alumina lead borosilicate glass 24 at 25℃
．． Mixed with 49.

This powder mixture was dispersed with ethylcellulose and β-terpinenol solution (27.29 g). The fired resistor is 85 ohms and the temperature coefficient of resistance is -257p from -55°C to 25°C.
pm/''O. This negative coefficient can be corrected to a more positive value by balancing the relative amounts of each glass.

Although the present invention has been described in detail as above, the present invention can be more clearly illustrated by the following additional embodiments.

1) The following fine powders: (a) Silver, palladium, alloys of silver and palladium or mixtures thereof; (b) (1) Softening point 350-50 based on total solid content
(2) a mixture of 0.2 to 5.0 wt. c) RuO2 submicron particles 5 based on total solids content
~20% by volume; A thick film low resistance composition comprising a mixture of (a) to (C) all dispersed in (d) an organic medium.

2) The composition according to item 1 above, wherein component (a) is an alloy of palladium and silver.

3) The composition according to item 1 above, wherein component (a) is a mixture of palladium and silver particles in such a proportion that they are alloyed.

4) The composition according to item 3 above, wherein palladium and silver are in the form of an alloy containing 40% silver.

5) Rub, intermediate softening point of particles 400-650℃
The composition according to the preceding item 1, which is sintered onto the surface of the glass particles having the following properties.

6) The intermediate glass contains 1-15% by weight of transition metal oxides.
3. The composition according to item 3 above.

7) The composition according to item 1 above, wherein the low melting point glass has a softening point of 375 to 425°C.

8) The composition according to item 1 above, wherein the high melting point glass has a softening point of 575 to 600°C.

9) The composition according to item 1, wherein the glass has an average particle size of 2 to 3 microns, and substantially all the glass particles have a diameter of 0.1 to 10 microns.

10Xa) Applying a patterned layer of the thick film composition of claim 1 to an inert substrate; (b) Sintering this layer at a maximum temperature of 800-900°C to volatilize the organic medium therefrom to enhance the solid. A method for manufacturing low-resistance elements that involves a continuous process of increasing density.

Claims (1)

[Claims] 1) The following fine powder; (a) silver, palladium, an alloy of silver and palladium, or a mixture thereof; (b) (1) a softening point of 350 to 500 based on the total solid content;
(2) a mixture of 0.2 to 5.0 wt. ) 5 to 20% by volume of submicron particles of RuO_2 based on the total solid content; A thick film low resistance composition comprising a mixture of all of (a) to (c) dispersed in (d) an organic medium. 2) (a) applying a patterned layer of the thick film composition according to claim 1 to an inert substrate; (b) baking this layer at a maximum temperature of 800-900°C to volatilize the organic medium therefrom; A method for manufacturing low-resistance materials that consists of a continuous process that densifies a solid.