JPS5858804B2 - Denkai capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for constructing a cathode of a capacitor using a conductive paint made of a mixture of conductive particles consisting of a three-component system of silver, palladium, and silver-palladium and a solder heat-resistant resin or glass powder. This invention relates to an integrated circuit board that employs.

The purpose of the present invention is to form inorganic insulating plates such as thin films and thick films (for example, alkali-free glass substrates, alumina porcelain plates, forsterite porcelain plates, terrace glazed alumina porcelain plates) by vapor deposition, sputtering, deposition, and screen printing methods. , a conductor formed using an electrostatic printing method, an optical printing method, etc., and a cathode of a tantalum powder sintered solid, an aluminum foil sintered solid, or an aluminum-tantalum alloy powder sintered solid. Reflow soldering using tin-lead alloy or various alloy-based solder alloy materials to connect capacitors with other metals has disadvantages that occur when soldering by the method, namely melting of the resin component, The object of the present invention is to solve various problems such as the incorporation of silver into tin in solder and the occurrence of electrical short circuits between printed conductors on the substrate surface due to silver migration on the substrate surface.

Prior to explaining the present invention, the prior art will be explained.

In other words, with the development of film circuits over the past ten years, in the field of thin films and thick films, conductors are formed on the surface of glass plates or porcelain plates, and parts without lead wires are sandwiched between solder alloy layers on the conductors. An assembly method has become popular in which an electrode provided on the main body is then soldered to the conductor to which the electrode corresponds via the solder alloy layer.

With this method, there are no lead wires attached to the components mounted on the board, so you can insert the component lead wires into the holes of the printed circuit board using dip or flora soldering. It is not possible to use a soldering method in which the ends of the lead wires are soldered at the bottom of the circuit board.

Therefore, soldering using a one-way reflow solder is being considered.

To explain this method, solder is plated onto the conductor, a solder preform is interposed between the conductor and the component, and then the solder is passed through an infrared furnace, an electric heating furnace, etc. at 250 to 350°C. It is heated to

Then, the solder melts and, with the help of the soldering flux, the solder is joined to the conductor of the board and the component with the oxide removed from the surface, and electrical contact can be established.

In this way, the Florasolder one-sided method can connect the electrodes on the bottom of the component and the conductor of the board, which is difficult to do with human skills, when attaching components without individual lead wires to the membrane circuit. The advantage is that it is possible to simultaneously solder and connect multiple soldering points for one individual component, and it is also possible to efficiently solder and connect many individual components to one board at the same time. There is.

As electrodes for the substrate, plating with gold or copper, three-layer plating with copper, nickel, and gold, and baking with a mixture of silver powder, palladium powder, and glass powder are often used.

On the other hand, the cathode side of individual electrolytic capacitors using solid sintered tantalum powder, tantalum powder-aluminum powder, aluminum foil, or the like as an anode material has conventionally been formed from the following materials.

That is, a manganese dioxide layer was first formed, and then a silver paint layer was formed to form an external solderable surface.

The above silver paint layer is made by applying a paste made by combining 60 to 70 weight percent silver powder with the remainder consisting of cellulose acetate resin and butyl acetate solvent, and then heating it to 60°C to volatilize the solvent. After that, it is baked and cured for 30 minutes at 80°C.

The above-mentioned silver paint conductor layer is heated in a furnace with a maximum holding temperature of 260°C by the above-mentioned or flora soldering method.
When passed for a period of minutes, the cellulose acetate in the components of the silver paint decomposes and the solder evaporates on the surface, and normal soldering cannot achieve the condition.

At the same time, there is a drawback that rapid diffusion of silver into the tin in the solder occurs, destroying a normal conductor layer made of silver paint.

In order to eliminate these drawbacks, it is conceivable to change the resin in the silver paint components to an epoxy resin with high heat resistance.

By doing so, it is possible to prevent the resin from volatilizing under the holding condition of 260° C. for 5 minutes, which is a condition for soldering.

However, it is inevitable that the silver paint conductor layer will be destroyed by the tin in the solder of the silver conductor.

Therefore, as a mitigation measure, it is necessary to incorporate 2 to 3% silver into the tin-lead solder, but this will approximately double the cost of the solder due to the inclusion of silver, and furthermore, it will cause serious problems. It has not been resolved.

Another issue that requires improvement is that when the silver electrode portion of an individual component is in contact with the conductor surface of the substrate, the silver conductor migrates along the insulating surface of the substrate toward the side where the potential is lower than that of the silver conductor. be.

Accordingly, the present invention provides an integrated circuit board on which electrolytic capacitors are integrated without the above-mentioned drawbacks.

An embodiment of the present invention will be described below.

That is, when soldering the cathode part of an individual electrolytic capacitor to the membrane conductor of the board using the electrode arranged on the cathode part, the conductor paint of the electrode is silver, silver-palladium, silver, silver-palladium, etc.
The main idea is to use a mixture of three types of metal powder, palladium, a heat-resistant resin, and its solvent.

Of course, if a high resistance value of the conductor is acceptable, palladium powder, silver-palladium powder, or both may be used as the conductive powder.

If the conductor on the cathode side of an individual electrolytic capacitor is formed as described above, first of all, the combination of heat-resistant resin will provide enough soldering heat resistance to withstand 260℃ for about 5 minutes, and the adoption of a palladium conductor will eliminate silver migration. or can be reduced.

Furthermore, by employing a palladium-silver conductor, the increase in conductor resistance value when using only palladium approaches the conductor resistance value when using only silver powder.

Furthermore, if palladium powder is used, the material cost can be lowered compared to the case where silver is used, which is relatively expensive.

Next, Comparative Examples A, B, and C having conventional compositions and specific Example A of the present invention will be described as follows.

That is, the conductive electrode body of the cathode portion of the electrolytic capacitor is formed from the following.

Comparative Example A Silver powder with an average particle size of 0.5 to 2.5 μm was dispersed in a 70-weight stacking type cellulose acetate weighing 25 weight units and a solvent in a 5-layer stacking type.

Comparative Example B Silver powder having an average particle size of 0.5 to 2.5 μm was dispersed in a 70-weight layer of epoxy resin (25 layers) and a solvent layer (5 layers).

Comparative Example C A type with 20 layers of steel grains with an average particle size of 0.5 to 1.5μ and a type with 45 layers of palladium powder with an average particle size of 1.8 to 2.3μ were combined with 30 layers of epoxy resin. and a five-layered solvent type.

Example A: 10-weight stacking type of silver powder with an average particle size of 0.5-1.5μ; 15-weight stacking type of palladium powder with an average particle size of 1.8-2.3μ; and 15-weight stacking type with an average particle size of 0.7-1 .4 micron palladium-prepared alloy powder with 35 layers is dispersed in a product consisting of 35 layers of epoxy resin and 5 layers of solvent. Calbitol acetate is suitable as the solvent.

Next, Comparative Example A p B ) C and Example A were cured and their performances were compared as shown in the table below.

As shown in the table above, the silver migration time of Example A of the present invention is significantly longer than that of Comparative Examples A and H, which have conventional compositions.

Therefore, the possibility of short-circuit failures between conductors is significantly reduced.

Even under heating conditions equivalent to flora soldering at 260° C. for 30 minutes, the conductor film was not damaged, and the resistance value of Example A was lower than that of Comparative Example C, a silver powder-epoxy resin system.

Furthermore, compared to Comparative Example C, Example A has a lower sheet resistance and is suitable as a conductor.

Therefore, it is particularly effective as a bottom electrode for future membrane circuit components.

As is clear from the above explanation, when the integrated circuit board on which the electrolytic capacitor of the present invention is integrated, the electrolytic capacitor is attached to the conductor portion formed on the circuit board by reflow soldering, the cathode of the electrolytic capacitor is As the conductive electrode body used in this section is made by agglomerating conductive particles consisting of a three-component system of silver, palladium, and silver-palladium together with glass or resin at a temperature that does not cause the resin to scatter, the disadvantage of the conventional example mentioned at the beginning is avoided. Problems such as melting of resin components, incorporation of silver into tin in solder, and occurrence of electrical shorts between printed conductors on the substrate surface due to silver migration on the substrate surface, etc. Does not occur.

Claims (1)

[Claims] 1. When attaching an electrolytic capacitor with a conductor formed on the surface of a porcelain-based thick-film circuit board or a glass-based thin-film circuit board and having a solid electrolyte in the conductor part by reflow soldering, b. An integrated electrolytic capacitor characterized in that conductive particles consisting of a three-component system of silver, palladium, and silver-palladium are agglomerated together with glass or resin at a temperature at which the resin does not scatter as the conductive electrode body of the cathode part. integrated circuit board.