JPS5968101A - Conductive paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paste that can be baked at low temperatures, can sufficiently withstand electrolytic plating, and has even greater adhesive strength.

Conductive pastes made of silver threads that can be baked at low temperatures are used as electrodes in ceramic electronic components, such as 1-Niramic capacitors, and are also used in hot wire heaters for automobile rear windows.

The conductive coating obtained by C1 baking is sometimes subjected to plating treatment for the purpose of protecting its surface. This is because if soldering is performed on the surface of the conductive film as it is, silver will diffuse into the conductive film and become "C", which is what is called solder eating, and the adhesive strength with the board will deteriorate. Also, the weather resistance of the conductive coating is weak, and properties such as conductivity and adhesive strength may deteriorate due to acid or arsenic or sulfurization, so prevent this. In reality, a Cu electrolytic plating film and an N1 electrolytic plating film are further applied on top of the Cu electrolytic plating film.
Furthermore, an electrolytic plating film of Sn, Pb-8n, etc. is formed thereon.

In addition, when baking silver thread, the specific resistance of the type of conductive coating is 2.
It is difficult to obtain a value of less than 5×10 Ω, ZJl, so for example, an electrolytic plating film of Cu is formed on the surface, and if necessary, an electrolytic plating film of Ni is further formed.

However, when a strongly acidic plating solution is normally used at the stage of forming the electrolytic plating cavity, a phenomenon has been observed in which the glass frit contained in the conductive film is eluted by the acid. In addition, the glass frit will not be reduced by the hydrogen generated during the formation of the electroplated film on the conductive film.
A phenomenon was observed in which the adhesive strength between the substrate and the conductive film was extremely reduced.

As a way to deal with this, it is conceivable that the following measures may be adopted.

■Pt, Pa, Rh, etc., are placed on the side or side.
■Using alloy powders such as Ag and Pt, Pd, Rh, etc.■
The thickness of the conductive film is made to be 15 μm or more. (2) Using Au or an alloy powder of Aq and Au.

However, methods 1, 2, and 2 do not increase the specific resistance of the conductive film, and methods 1, 2, and 3 result in an increase in cost.

In addition, there is a method of increasing the pH of the plating bath to 6 or higher, which is close to neutral, but this method poses a problem in that it is difficult to control the plating bath composition.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional conductive pastes described above.

That is, the gist of the present invention is a conductive paste characterized by being made by kneading silver powder and acid-resistant, low-melting glass frit into an organic paste.

As the main silver powder contained in the conductive paste, those having an average particle size of 10 μm or less and especially those having an average particle size of 5 μm or less are used as a baking paste for floating waist.

In this conductive paste, the mixing ratio (wt%) of silver powder, which is a solid component, and low melting point glass frit, which has acid resistance.
must be in the range of 75,725 to 95:5.

The reason for limiting the mixing ratio to this is as follows.

In other words, if the silver powder content is less than 75% by weight and the glass frit content exceeds 25% by weight, the specific resistance of the conductive film obtained by baking becomes higher than 15Xj O-Ω, /Jl The adhesion strength withstanding this comes to show a saturated value. On the other hand, if the silver powder exceeds 95% by weight and the glass frit exceeds 5% by weight, the variation in the adhesive strength between the baked conductive wave I]φ and the substrate becomes significantly large, making it difficult to obtain stable and sufficient adhesive strength. It disappears.

The mixing ratio (weight %) of the solid component consisting of silver powder and acid-resistant low melting point glass frit and the organic material is selected in the range of 90:10 to 45:55.

The reason for choosing this mixing ratio range is as follows. In other words, it is a paste made of solid components such as organic matter such as cotton, rice cake, etc., so that it can be screen printed.For example, cellulose dissolved in cellosolve is used. - If the amount of jirimata is less than 10-a, it will not be possible to obtain a good α-conducting paste for coating and baking, and if it still exceeds 55% by weight, it will not be possible to obtain a good α-conducting paste for coating and baking.
The genitalia become thin, less than 3 μm, and the conductor 4z1 main and surface 1 sharp inertia become scary.

Furthermore, the conductive paste according to the present invention preferably contains an acid-resistant, low-melting glass frit, or specifically a borosilicate-based glass frit containing alumina.

An embodiment of the 1,1llI silicic acid glass frit containing alumina has the following composition.

PbO50-78% by weight 5io2 15-40% by weight Weight% It is also permissible to mix it into a glass 7 liter composition.

The reason why this borosilicate glass frit containing alumina is limited to the above composition range is as follows.

If the pbo is less than 50% by weight and ridges, the melting point will not allow baking at low temperatures.If it exceeds 78% by weight, it will not be possible to obtain lt1' acidity.

When S10 is less than 15% by weight, acid resistance cannot be obtained, and when S10 exceeds 400% by weight, the melting point cannot be reached to allow baking at low temperatures.

When B,03 is less than 1% by weight, P b O , S i
It prevents the vitrification of O2 and Algos and causes crystallization, and if it exceeds 4% by weight, the acid resistance will be extremely reduced.

If AezOI exceeds 6% by weight, the melting point will not be high enough to allow baking at low temperatures.

In addition, at least one of TiO, Nλ20, I, and O is mixed in an amount of 3% by weight or less, but if TlO2 exceeds 5% by weight, the melting point will not be high.
Moreover, if Na2O exceeds 3% by weight, #f has poor adhesion properties, and if O exceeds 3% by weight, the viscosity will be high, adhesive strength will decrease, and acid resistance will decrease. I will do it.

The present invention will be described in detail below according to Examples.0 Example 1 Silver powder with an average particle size of 2 pm, glass frit, and raw materials for the 1-geometric face were mixed so that the composition ratios shown in Table 1 were obtained. and created a paste.

The glass frits shown in Table 1 had the following compositions A and B.

A, Pbo 67 tori l'4, Sin,
30% by weight, BzOx double is, Altos
1st IB: PL) 065%, Sin, 3
Heavy weight, Btus double membrane%, AI! 20s
0.5% by weight, Tio, 0.5ffit%, Na,
0 1 weight) t%, K2O 1 weight Y]. % This paste was printed on the glass substrate surface, and then 600
Baking was performed at a temperature of C for 5 minutes. After baking, the resistance value of the conductive film was measured. Continue to electrolytically plate the resistor (ii'i! using an acid copper bath so that the resistance is 2Ω,
Furthermore, electrolytic plating of nickel was applied on top of it using a nickel sulfate bath, and the terminal was determined to have a half lf3)'t C adhesion strength IX[dl, and the results are shown in Table 1. .

The resistance value is width 0. ' This value is for an area of 5 gates and length 6001. A practical value for the adhesive strength is 208 Da/d or more.

Incidentally, in Table 1, those marked with * are outside the scope of this invention, and those below 1,000 μm are within the scope of this invention.

Table 1 As is clear from Table 1, the mixing ratio (maximum % in ft) of silver powder and glass frit, which are solid components, is 75:25 to 95:
In the range of 5, the mixing ratio of the solid component and the 1 substance to 2 substances (freeze %) is in the range of 90: 10 to 45: 55,
A conductive film with good conductivity and high adhesive strength even when subjected to electrolytic plating has been obtained.

The adhesive strength of Sample No. 1-1 was 71 or higher than 4oK, which means that if the adhesive strength exceeds 40Ky/cd, the glass substrate would be destroyed and measurement would be impossible.

Example 2 Ganosufurisoto 1, 63 layers of grain with an average particle size of 21tm
Solid component consisting of 2 layers (75 weights) k% and organic varnish 25 weights j? c% were mixed to create a paste.

The glass frit used had a composition adjusted to the ratios shown in Table 2.

Using the substrate binding C ceramic substrate, a conductive film was formed on the ceramic substrate in the same manner as in Example 1, and the RA
After MT plating was applied, the adhesive strength was measured at °C and the results are shown in Table 2 in α. In addition, 41 (the tangent value is 11t t'JE u"21!A -r 12
Q: Is it plated? 2 with Iro. S) c) Since one light was used to match the level, the resistance value (・, (not shown -)) is a famous sample.

41'S 21'j, those marked with a middle * are this origin rj
ll il・Hyakuken outside mo(ri de, so-7L, j;
J outside if1 invention? 1 h'fl! It's a '3'' thing.

Table 2 As is clear from Table 2, a conductive paste with a glass frit within a specified range can produce conductive corrugations with good adhesive strength even when electrolytically plated, similar to JA 1. ing.

Example 5 Sample No. 2-2 and Sample No. 2-7 in Example 2 were used, and cuprous oxide (Cu, 0) was added to each of these pastes.
, adding Zm oxide (GuO) at the ratio shown in Table 6,
Contained.

A conductive film was formed on a glass substrate using the obtained paste in the same manner as in Example 1, and the adhesive strength after electroplating was measured. The results are shown in Table 3.

Table 5 In Table 6, sample number 3-1.3-2.3-5 was prepared by adding Cu, O, and CuO to the paste of sample number 2-2 of Example 2.
(added, test); 1 count, 5 3. =5 4,3 6
History is test 1r2 test f'Filt No. 2-7 paste C
u2O.

This is C1, 1, and 0 with an electric fence. From this ")," 5 * 6-6 is outside the running edge bright range, and 7 is within the invention range Flt except for t-.

From the third stage, Cu2C), Cl0 is further improved to improve its strength by cooling it, X, l
J: I can.

As is clear from each of the above implementation sequences, according to this clarity, n,
';, J:, Conductive f1 with good conductivity, high adhesion, high degree of adhesion, and corrosion resistance even when exposed to lightning and deplating. The paste in which ~ is r[) can be I■(.

! Office, 1'F applicant (°ni Shikisha 1 Sunda Seisakusho

Claims (1)

[Claims] ('') A conductive paste characterized by kneading silver powder and acid-resistant, low-melting-point glass frit into an organic varnish. (2) Claim No. 1, wherein the low melting point glass 7 lit is lead borosilicate glass 7 lit containing alumina.
Conductive paste as described in section. (3) The conductive paste according to claim 11 or (2), wherein the low melting point glass frit has the following composition. pbo so~78wt% 510z 15~40wt skin B2O3L~
4. (4) The conductive paste according to claim 10 or (2), wherein the low melting point glass frit has the following composition. pbo so~78% by weight S1.0. 15-40 heavy Bt Chi Btus 1-4 heavy assault A/iox
Approximately 3% by weight of Tie, MtffiO, and less than 20% of
(5) Mixing ratio (by weight) of solid component silver powder and acid-resistant low melting point glass frit that constitute the conductive paste.
The conductive LIF paste according to claims m to (4), wherein the ratio is in the range of 75:25 to 95:5. (6) Among the conductive paste, a solid component consisting of silver powder and acid-resistant low melting point glass frit, and an organic substance 70%,
The conductive paste according to Claim No. (7) Among the conductive paste, the solid component consisting of silver powder and acid-resistant low melting point glass frit is
The conductive paste according to claim C0, which contains copper or cupric oxide or both in an amount of 3% by weight or less.