JPH0740521B2 - Method for forming glass layer for resistor protection - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a glass layer for protecting a resistor.

[Prior Art] A chip resistor as a chip component to be mounted on a thick film circuit has a Ni plating process in manufacturing, and a glass layer provided for the purpose of protecting the resistor also passes the Ni plating process. The nickel plating solution is a strong acid (pH = 1 or less) and is usually processed at a temperature of 50 to 70 ° C. The conventional glass for a chip resistor is altered or removed by this treatment, and its role as a protective layer is not sufficient.

On the other hand, the glass layer provided on the resistor is usually formed by firing at 600 ° C., and it is also known that the rate of change in the resistance value of the resistor during this firing varies greatly depending on the glass composition. It has been required to provide a glass layer having a small rate of change.

That is, conventionally, there has been no satisfactory glass layer having a high acid resistance, a small rate of change in resistance value, no foaming due to a reaction, and a thermal expansion coefficient matching that of an alumina substrate.

[Problems to be Solved by the Invention] The present invention relates to a method of forming a glass layer for the purpose of mechanical and chemical protection of a chip resistor, which can be fired at 600 ° C. and has a reduced resistance change rate. Moreover, it is an object of the present invention to provide a method for forming a glass layer which is excellent in chemical resistance, durability, and particularly acid resistance.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and has a high melting point in the range of 650 to 800 ° C. and 70 to 100% by weight of low-melting glass powder. Melting point glass powder 0-30% by weight
And a layer of a composition comprising 0 to 30% by weight of a refractory filler and 0 to 5% by weight of a refractory pigment on the resistor, followed by firing to form a glass layer for protecting the resistor. wherein the low melting point glass frit is essentially _{PbO 55~65 SiO 2 25~40 Al 2 O} 3 1~5 R 2 O 0.1~5 ( where R ₂ O in weight percentages are _{Li 2 O, Na 2 O,} K _At least one selected from ₂ O and Cs ₂ O) B ₂ O ₃ 0 to 3 ZnO 0 to 3 P ₂ O _{5 to} 5 is provided to provide a method for forming a resistor protecting glass layer.

In the present invention, 70 wt% of low melting point glass powder having a specific composition is contained, and the reason is as follows.

If the low-melting glass powder is less than 70% by weight, the firing temperature of the composition becomes high and the rate of change in resistance value of the resistor due to firing increases, which is not preferable.

Such low-melting glass powder has excellent acid resistance and has a softening point of approximately
Since it is in the range of 550 to 600 ° C, when the content of the refractory filler or the like is 30% by weight or less, the firing can be performed at a temperature of about 600 ° C.

The reasons for limiting the composition of the low melting point glass powder will be described below.

If the PbO content is less than 55%, the softening temperature becomes too high, and under the desired firing conditions, it is not softened and fluidized sufficiently to cause unsintering, which is not preferable. If it exceeds 65%, the glass softening point becomes too low and the coefficient of thermal expansion becomes too large, so that matching with the alumina substrate cannot be achieved, which is not preferable. Desirably 56 ~
64% range.

If the SiO ₂ content is less than 25%, the glass softening point will be too low and the acid resistance will be significantly reduced. On the other hand, if it exceeds 40%, the glass softening point becomes too high, which is not preferable. Preferably 26
~ 39% range.

Al ₂ O ₃ : If it is less than 1%, devitrification may occur in the melting / molding process, which is not preferable. If it exceeds 5%, the softening point becomes too high, which is not preferable. It is preferably in the range of 1.5 to 4.5%.

R ₂ O: An essential component that has the effect of improving the acid resistance of glass. If it is less than 0.1%, the effect is small. On the other hand, 5%
If it exceeds, the softening point becomes too low and the thermal expansion becomes large, which is not preferable. It is preferably in the range of 0.5 to 4.5%.

In addition, B ₂ O ₃ , ZnO or P ₂ O ₅ may be contained in an amount of less than 3% (less than P ₂ O ₅ ) for the purpose of improving the glass solubility. If the content of such a component exceeds the above range, the acid resistance is lowered or the rate of change in resistance value is increased, which is not preferable.

As the low melting point glass powder, the total amount of the above components may be 99% or more, and the remaining 1% may contain Sb ₂ O ₃ , As ₂ O ₃ , F and the like.

The composition of the present invention is 650 to 8 with respect to the above low melting point glass powder.
High melting point glass powder with a softening point in the range of 00 ℃ 0-30
Acid resistance can be improved by making it contain by weight%.

If the content of this high melting point glass powder exceeds 30% by weight or if the softening point thereof exceeds 800 ° C., the sintering temperature of the fired product of the composition becomes too high, which is not preferable. On the other hand, when the softening point of the high melting point glass powder is lower than 650 ° C., the effect of improving the acid resistance is small, which is not preferable.

As such high melting point glass powder, PbO 35-
50, SiO ₂ 35-50, Al ₂ O ₃ 1-5, B ₂ O ₃ 0-15, R ₂ O 0-
5, RO 0~10, ZnO 0~5, ZrO 2 + TiO 2 0~10, those consisting essentially of is preferred.

The reason is as follows.

SiO ₂ : less than 35%, the glass softening point is too low and the effect of improving acid resistance is small, and if it is more than 50%, the glass softening point is too high, which is not preferable. Desirably, it is in the range of 36 to 49%.

If it is less than 35%, the glass softening point becomes too high.
On the other hand, if it exceeds 50%, the softening point becomes too low, which is not preferable. It is preferably in the range of 36 to 49%.

Al ₂ O _3: vitrification becomes difficult to occur a devitrification small that during glass melting than 1%. If it exceeds 5%, the softening point becomes too high. It is preferably in the range of 2 to 4%.

Others: R ₂ O (Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O), RO (MgO, CaO, Sr
O, BaO, ZnO) and ZrO ₂ and TiO ₂ components can be contained in their respective limited ranges for the purpose of improving solubility and acid resistance.

On the other hand, although not an essential component, by adding a refractory filler such as Al ₂ O ₃ , ZrSiO ₄ , or ZrO ₂ , the resistance change rate of the resistor during firing can be reduced. However, if the addition amount is more than 30%, sintering may be insufficient, which is not preferable.

The refractory pigment can be added for the purpose of coloring and identification, but if the addition amount exceeds 5%, sintering may be insufficient, which is not preferable. Fe-M as such a pigment
Examples include n-based and Fe-Cr-based black pigments and CoO ₃ -Al ₂ O ₃ -based blue pigments.

Usually, a composition composed of the above components is made into a powder having a size of 1 to 3 μm, and this is mixed with an organic vehicle to form a paste, which is then covered with a RuO ₂ resistor provided on an alumina substrate by a screen printing method at about 600 ° C. Bake for ~ 10 minutes. Here, as the organic vehicle component, generally known ethyl cellulose resin, acrylic resin and the like are used as α-terpineol or trimethylpentadiol monoisobutyrate type solvent, but are not particularly limited.

[Example] Each raw material was blended so as to obtain a target composition, and 1300 was prepared with a platinum crucible.
Dissolve with stirring at ~ 1500 ° C for 1 to 3 hours. Next, the molten glass is crushed into water or flakes and finely crushed by a crusher. Usually, the particle size of the powder is 1 to 3 μm, which is suitable for screen printing. When finely pulverizing, it is permissible to simultaneously pulverize and mix high melting point glass, refractory filler, heat resistant pigment, or the like with low melting point glass as a base, if necessary.

The obtained glass mixed powder is mixed with the vehicle as described above to form a paste. The paste is usually kneaded in a mortar for homogenous dispersion and then passed through a triple roller several times. The paste viscosity was 200,000 ± 50,000 cps (25 ° C.).

On the other hand, an Ag-Pb-based conductor electrode was printed on a 96% alumina substrate as a base, baked at 850 ° C for 10 minutes, a RuO ₂ resistor was screen-printed thereon, and baked at 850 ° C for 10 minutes in the same manner. The glass paste described above was covered by screen printing on the RuO ₂ resistor and baked at 600 ° C. for 10 minutes to form a glass layer. Characteristic evaluation before and after covering with glass
The resistance change rate of the RuO ₂ resistor, the appearance of the glass on the resistor (whether there were foamed pinholes, etc.) and the acid resistance test were conducted.
The acid resistance is judged to be good or bad in combination with the appearance inspection by a scratch test with a razor blade after 1 hour in a 20% HNO ₃ solution (70 ° C) under stricter conditions than the usual Ni plating process. It was

Table 1 shows the results of the above-mentioned tests performed on seven types of glass layers formed according to the present invention and two types of Comparative Examples. As is clear from the table, the glass layer formed according to the present invention has excellent acid resistance and hardly changes the resistance value of the resistor.

The measured values shown in the table are obtained as follows.

b) Acid resistance = 70 ° C, immersed in 20% HNO ₃ solution for 1 hour, washed with water, dried, and then scratched with a razor blade.

Evaluation x: easily peeled off △: part of the glass peeled off ○: the whole surface did not peel off like the untreated state c) visual inspection: RuO ₂ top glass was evaluated for the presence or absence of foam pinholes with a 80x stereoscopic microscope. ×: Large foam or pinholes on the entire surface Δ: Small foams or pinholes partially ○: Foaming, no pinholes [Effect of the invention] According to the present invention, the resistance value change rate of the resistor is extremely small, In addition, it has excellent acid resistance and excellent appearance.

Claims (3)

[Claims] 1. Low melting glass powder 70 to 100% by weight, and 650 to
High melting point glass powder 0 to 30 having a softening point in the range of 800 ° C
% By weight, refractory filler 0-30%, refractory pigment 0
A method of forming a glass layer for protecting a resistor by forming a layer of a composition consisting of 5% by weight on a resistor and firing it to form a glass layer for protecting the resistor, wherein the low melting point glass powder is essentially PbO 55- _{65 SiO 2 25~40 Al 2 O 3} 1~5 R 2 O 0.1~5 ( where R ₂ O is Li ₂ O, Na ₂ O, at least one person selected from K ₂ O and Cs ₂ O) B ₂ A method for forming a resistor-protecting glass layer comprising O ₃ 0 to 3 ZnO 0 to 3 P ₂ O ₅ 0 to ₅ . 2. The high melting point glass powder is essentially expressed in% by weight as PbO 35 to 50 SiO ₂ 35 to 50 Al ₂ O _{31 to} 5 B ₂ O ₃ 0 to 15 R ₂ O 0 to 5 RO 0 to 10 (however, RO is at least one selected from MgO, CaO, SrO and BaO) ZnO 0-5 ZrO ₂ + TiO ₂ 0-10 The glass layer for resistor protection according to claim 1 consisting of Forming method. 3. The method of forming a glass layer for protecting a resistor according to claim 1 or 2, wherein the refractory filler is at least one selected from alumina, zirconia and zircon.