JPS5820155B2 - thick film conductor - Google Patents

Description

[Detailed description of the invention] The present invention relates to thick film conductors.

Thick film conductors are generally made of conductive powders consisting of Ag, Au, Pd, Pt or mixtures thereof, e.g. PbO, 5i0
2.

B2O3, Bi2O3, Al2O3,'MgOtsuCaO
Amorphous lead bismuth borosilicate glass with the composition 7
It is formed by screen printing a paste in which 3 liters are dispersed in a vehicle on a substrate such as ceramics, and then firing the paste.

Thick film conductors are then used as electrodes in thick film capacitors.

In the above paste, the glass frit serves as a binder between the conductive particles and the ceramic or conductive particles.

Furthermore, Bi2O3 in the glass frit has the role of improving wetting of metal and glass during firing of the conductive paste.

Therefore, the finished thick film conductor is: (I) gold, silver, etc. in the thick film conductor do not dissolve into the solder during soldering;

(9) Oxidation of palladium, etc. in the thick film conductor is prevented during soldering.

Therefore, soldering sometimes has the effect of improving the solder resistance of the conductor and improving the solder wettability.

However, lead bismuth borosilicate glass has a softening temperature of 47
Since the temperature is as low as 9 to 520°C, the firing temperature of the paste is 5°C.
It is necessary to fire at a low temperature of about 00°C.

However, in such low-temperature firing, the conductor component of the paste is not sintered, and the conductivity of the thick film conductor is not stable.

Therefore, the paste was heated to 750 to 1000°C.
It was fired to create a thick film conductor with stable conductivity.

However, when the paste is fired at such high temperatures,
The paste has a very low viscosity and becomes easily flowable.

Therefore, when the above paste is used, for example, as an electrode for a thick film capacitor, the softened glass and conductor components in the paste seep into the pores of the dielectric layer (for example, barium titanate), reducing the withstand voltage of the capacitor. will occur.

A conductive paste using Ag and Pd as conductor components was fired at 850°C, then a thick film resistor layer was created, and a glass paste to protect the resistor layer was applied on top of it.
If the conductor is formed by firing at 0 to 330°C, the lead-bismuth borosilicate glass in the conductive paste will flow out when firing at 850°C, and the glass that wet the silver and noradium surfaces will decrease. ,500~3
When baking at 30°C to form a glass layer, palladium oxidizes, significantly reducing the solderability of the conductor layer.
The disadvantage is that the solder will not stick at all.

In order to improve the solder wettability, it is possible to increase the silver content in the conductor component, but if the silver content increases, the adhesive strength between the conductor layer and the substrate decreases, which is a drawback.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art;
The object of the present invention is to provide a thick film conductor that (1) has high adhesive strength between the conductor layer and the substrate, (9) does not change the characteristics of the dielectric layer, and (2) does not reduce the solderability of the conductor layer.

The above purpose is PbO15~19.4ωt%, CaO3
~4.3ωt%t ZnO1,7~2.2ωt%t
A12032.2~2.8ω is connected B2031.8~
2.3ωt%.

5in210~14ωt% Bi2O350~70ωt
% of zinc-containing lead borosilicate bismuth crystallized glass and Ag70-95ω, a mixture of Pa5-30ωt%, A, 967-92.6ω.

Pd07.4ω ~33ωt% mixture, Ag70~
It is obtained by printing and firing a conductor paste consisting of any one type of A-Pd alloy of 95 ωt%, Pd5 to 30 ωt, and an organic vehicle.

As the binder glass in the conductor paste forming the conductor with the above film thickness, a glass frit having the above composition is used, or PbO15~19.4ωt%+Ca03~4
．． 3 ωt%, ZnO 1.7 to 2.2 ωt%.

A12032.2~2.8ω, B2031.8~2
．． 3ω and 5iO210 to 14ω. Bi2O3 powder is added to a crystallized glass frit having a composition such that the total composition is the same as that of the zinc-containing lead-bismuth borosilicate crystallized glass frit, and the zinc-containing borosilicate The amount of BiO in the lead-bismuth crystallized glass was kept small, and Bi2O3 powder was added to it to make the total composition the same as the zinc-containing lead-bismuth borosilicate crystallized glass. It is sufficient to use one type of binder glass.

The conductor powder in the conductive paste is still N170~95ωt%
, Pa5~30ω is the mixture XNl67~92.60
A mixture of Pd07.4ω and 33ω, N1
It is preferable to use one kind of conductor powder selected from Aud alloys with a resistance of 70 to 95ω and an alloy of Pd of 5 to 30ω.

As a vehicle, a conventional organic vehicle (for example, an α-terpineol solution of ethyl cellulose) is used.

The present invention will be explained below with reference to Examples.

Example 1 Lead oxide (pbo), calcium carbonate (CaCO3), zinc oxide (ZnO), alumina (A/l'203χ boric acid (H3BO,), silicon oxide (S A02 ) and bismuth trioxide (B1203) were %1~Nn3 in table 1
The mixture was mixed as in Comparative Example 1.2, placed in a platinum crucible, melted at 1200°C, and then poured into water to be rapidly cooled to produce glass.

Glass with this composition ratio was ground in an agate ball mill to form a powder with an average particle size of 2.5μ, and the softening point and crystallization point (peak temperature) were measured by differential thermal analysis, and the results were as shown in Table 1. .

The crystallized portion of this glass is bismuth silicate (B14 (
The amorphous content was higher than that of lead bismuth borosilicate.

PbO lowers the softening point of glass, contributes to fluidity, and
If it is less than 5%, there is insufficient fluidity, and if it exceeds 19.4%, it is too fluid.

CaO and ZnO help adjust the crystallinity, and CaO3ω
t % t ZnO If less than 1,7 ωt%, crystallization is insufficient;
Ca04.3 ωt % t Zn02.2 If it is larger than ωt %, crystallization progresses too much.

Al2O3 is added to increase water resistance; if it is less than 2.2 ωt%, it is ineffective, and if it exceeds 2.8 ωt%, it inhibits crystallization.

B2O3 and SiO2 are network components of glass, B2031.8ωt01), less than 10% SiO2 has too high fluidity, and B2032.3ωt% tS
When in214ωt% is exceeded, fluidity becomes insufficient.

Bi2O3 is a component that improves the wettability of metal and glass and crystallizes the glass. If it is less than 50 ωt%, the metal wettability is insufficient, and if it is more than 70 ωt%, it will not crystallize.

In addition, as the glass frit in the conductive paste, among the glasses having the above composition, Bi2O3 is used as the glass frit in the conductive paste.
Part or all of.

If Bi2O3 is mixed with the glass frit of the components excluding the above so that the glass composition as a whole becomes the above, after firing the conductor, the same effect as that of crystallized glass and the same effect on wettability with metal can be obtained. .

Next, glass powders of samples N [L4 to 8 in Table 2 were prepared in the same manner as samples K1 to Nl13 in Table 1, and
These were mixed with Bi2O3 as shown in Table 2 to form a mixed frit whose overall composition was the same as %1 in Table 1.

; The glass frits of Samples N111 to %3 in Table 1 and Comparative Example 1.2 and the mixture frits of Samples %4 to N18 in Table 2 were mixed with 70% by weight of silver and 30% by weight of palladium.
3 parts by weight of an α-terpineol solution of ethylcellulose (containing 15% by weight of ethylcellulose) was mixed with 85% by weight of a metal powder consisting of
0 parts by weight was added and kneaded using a three-stage roll to produce a conductive paste.

In addition to these conductive pastes, Dupo
Conductive paste #8151 manufactured by NT Corporation was printed on the alumina substrate 1 shown in FIG. 1 and baked at 900° C. for 10 minutes to form the lower electrode 2 of the thick film capacitor and a 2 mm×2 mm soldering terminal.

Next, as a dielectric paste, #8456 manufactured by DuPont, which is mainly composed of barium titanate, was printed and dried on top of the lower electrode, and then the conductive paste was printed on top of that, and after drying, the temperature was increased to 900°C. This was baked for 10 minutes to form a dielectric layer 3 and an upper electrode 4, thereby producing a thick film capacitor.

The thickness of the dielectric layer of the capacitor is 40μ, and the effective electrode area is 9−.

Apply low temperature crystallized glass paste (PbO6) on top of the capacitor.
8ωt%, ZnO20ωt%, B2O33ωt%
, A12035ωt%, 5i022ωt% glass frit 70ωt% ethylcetolose α-terpineol solution (30ωt%) was printed;
A moisture-proof overcoat was applied by baking at 30° C. for 10 minutes.

For each of these capacitors, the capacitance L tan δ and dielectric breakdown voltage were measured, and the terminals were soldered with 60% tin.
Solder wettability when immersed at 230℃ using 40% lead solder, and the relationship between the solder and the board when a copper wire with a diameter of 0.6 m is soldered and the copper wire is pulled perpendicularly to the board and peeled off. Adhesive strength was measured.

The results are shown in Table 3. In addition, these thick film capacitors are
Figure 2 shows the change in dielectric breakdown voltage over time when 100 V DC was applied at 00°C.

In Table 3, Nctl, 2, and 3 (the electric current in the table corresponds to the percentage in Table 1 and Table 2) show good values.

In Comparative Examples 1 and 2 in Table 3, the capacitance and tan δ of the capacitor were slightly larger and the dielectric breakdown voltage was lower than in Experimental Examples 1, 2, and 3.

Furthermore, the solderability of the conductor is rather poor, and the adhesive strength is also low, making it impractical.

In addition, Pb obtained by removing ZnO from the composition of Comparative Example 1 in Table 1
014.5 ωt%, CaO2,9ωt%2 A
120s 1.8ωt%, B2031.6ωt%.

Glass having a composition of 5in29.1ω and Bi2O370.1ω also did not crystallize and the effect of the present invention could not be obtained.
I couldn't.

The reason for this is thought to be that the crystallinity of the glasses in Comparative Examples 1 and 2 in Table 1 was lower than in the other cases, and the glasses fluidized.

This phenomenon is still significant in the case of Comparative Example 3 in Table 3, so that it cannot be put to practical use.

Figure 2 shows the results of the high temperature load test. Curve 5 in FIG. 2 shows the test results of the thick film capacitor of Comparative Example 1 in Table 3, curve 6 shows the test results of Comparative Example 3 of Table 3, curve 6 shows the test results of Comparative Example 3 of Table 3.

In curve 7, the withstand voltage deteriorates significantly as time passes, and it cannot be put to practical use.

Curve 5 shows that the withstand voltage deteriorates over time.

However, curve 6 shows good results with no deterioration at all even after 5000 hours.

Items 4 to 8 in Table 3 use a mixed frit of glass frit and Bi2O3.

After firing, these mixed frits are all %1 in Table 1.
It has the same composition as glass.

Comparing these characteristics with Ntll in Table 1, N114 to 8 in Table 3 are similar to Table 1 for all characteristics.
No difference was observed between Ml and Ml.

From this, whether Bi2O3 is added in advance as a glass component in the conductive paste and exists in a vitrified state or in a mixed state with glass frit, Bi2O3 is a component of crystallized glass in the fired thick film conductor. It can be seen that the composition range of the present invention has exactly the same effect.

Example 2 Glass frit 15ωt of Table 1 %2 in Example 1
%, the content of Ag in the mixture of Ag and Pd is 75.80
．． Ag mixed with 85.90.95ω,
Mixed with Pd powder 85ωt%, this mixed powder 70ωt%
30 ωt% of the same organic vehicle as in Example 1 was added to
The mixture was made into a paste in the same manner as in Example 1, and the same experiment as in Example 1 was conducted.

The results are shown in Table 4.

When the mixing ratio of Ag and Pd is up to Ag85ωt%, both the characteristics of the thick film capacitor and the characteristics of the conductor of Example 1, Table 3 rl!
12 (Ag70ωtchi).

When the amount of pAg increases, the capacitance of the capacitor and t
The value of an δ becomes slightly larger, and the dielectric breakdown voltage becomes slightly smaller.

Also, the adhesive strength of the conductor becomes slightly smaller.

However, it is practical with an Ag amount of 95ωt%t, and the Ag amount is 7
If the amount is less than 0 ωt%, the solderability will be poor due to the large amount of Pd, and if the amount of Ag is greater than 95 ωt%, the reliability of the thick film capacitor will be poor, and the adhesive strength of the conductor will be low, both of which are not suitable for practical use. Can not.

Therefore, the content ratio of Ag and Pd in the conductor component is Ag7
It is appropriate to use 0 to 95ω and Pd5 to 30ω.

Example 3 A mixed powder containing 70 ωt% of Ag and 30 ωt of Pd was used, and the glass frit of %2 in Table 1 in Example 1 was used, and the conductor components were 75, 80 and 90 ωt%, respectively, and the glass frit was 25 and 20%, respectively.

Table 5 shows the results of an experiment similar to that of Example 1 performed on a composition having a concentration of 10 ωt%.

Comparing this result with Example 1, Table 3, %2, it can be seen that as the amount of glass frit increases, the capacitance of the thick film capacitor decreases and the adhesive strength of the conductor increases.

The opposite result occurs when the glass frit is reduced.

If the glass frit is more than 25 ωt%, the capacitance of the capacitor will be insufficient and the electrical resistance of the conductor will be too high to be practical.

If the glass frit content is less than 10 ωt%, the adhesive strength of the conductor will be so low that it cannot be put to practical use.

Therefore, the content ratio of the conductive component and the glass frit is 70 to 95 ωt % for the conductive component and 10 to 25 ωt % for the binder.

Example 4 As a conductive component, the ratio of Ag and Pd was Ag70ωt%,
Table 1 Il shown in Example 1 was added to a mixture of Ag powder and circular powder, Ag-Pd alloy powder, and Ag powder and PdO powder each having a pa3oωt% of 85ωt%.
l! Three types of conductive pastes were prepared in the same manner as in Example 1 by mixing 12 glass frits and 15 glass frits.

These three types of conductive pastes were printed on a 96-type alumina substrate and fired at 900° C. for 10 minutes to form a lower electrode of a thick film capacitor.

On top of this, DuPont's dielectric paste #9101 was printed and dried, and then the three types of conductive pastes mentioned above were printed on top of this and baked at 900° C. for 10 minutes to form a thick film capacitor.

The shape is the same as in Example 1.

Table 6 shows the capacitance, tan δ, and dielectric breakdown voltage of these capacitors.

As explained above, the thick film capacitor using the thick film conductor of the present invention has high reliability, has significantly improved soldering properties as a wiring conductor, has satisfactory adhesion strength with a ceramic substrate, and has a high reliability in thick film capacitors. This has a great effect on increasing reliability and lowering costs.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thick film capacitor, and FIG. 2 is experimental data. 2... lower electrode, 3... dielectric layer, 4
...Top electrode.

Claims (1)

[Claims] lAg70~95ωtchitPds~30ωt% AJ-
Pd alloy conductor 75~90ω, pb. 15~19.4ωt%, Ca03~4.3ωt%tZn
01.7~2.2G) t%t A/2032.2~2.
8ωtP coefficient νB2031.8~2.3ωt-coefficient, S 1
0210~14ωt%t Bi2O350~70ωt%
A thick film conductor comprising 10 to 25 ωt% of crystalline glass having a composition.