DE3224959A1 - IMPROVED CERAMIC CAPACITOR AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Description

Improved Ceramic Capacitor and Process for Its Manufacture

The invention relates to ceramic capacitors and, more particularly, relates to an improved ceramic capacitor and a method for its production. The invention relates in particular to a novel one Method for completing a ceramic fired capacitor and on those resulting therefrom improved capacitor.

The manufacture of ceramic capacitors is generally described in U.S. Patents 3, 00A, 197 and 3,235,939 described.

In general, such a process comprises the manufacture of at least one layer of unfired ceramic, which essentially contains ceramic powder in an organic binder. The layers are screen printed or a similar process is printed with ink that is resistant to decay at high temperatures Contains metal particles. A large number of these layers are stacked on top of one another, the printed ones or the areas forming the electrodes are in conditional simultaneity. The stacked ones Layers are then cut in discontinuous steps along parting lines so that the steps expose mutually offset electrode layers on opposite edge edges.

The stages are next heated for a period of time to a first temperature sufficient to keep the organic Burn off binder. Heating is then continued at a higher temperature around the ceramic to burn and thus form the electrode pressure areas conductive metal electrodes between the ceramic layers.

The resulting ceramic capacitor subcomponents need to be completed now, d. H. A conductive connection must be made between the edges of the different electrode layers exposed on the opposite edges of the capacitor preform, be effected.

Heretofore, such compounds were effected by applying a paste containing silver to the corresponding Edges were applied and the capacitor was heated so that the silver sintered, leaving the electrodes have been connected to each other at the corresponding edges.

In some cases leads are soldered to the silver terminations. However, it is more typical, special in the case of capacitors of low value, the capacitors with a protective insulating layer in all Areas other than the termination and ship them for use in this state.

The cost of such leadless capacitors with silver termination is unmistakable

increased because of the need to use significant amounts of silver for the completion. The ί

Silver-terminated capacitors are still j

disadvantageous in that, if a soldered connection:

bond to the silver termination is established, the

Silver dissolves easily and in the lead-tin!

Alloy of solder flows. When the soldering ι

If not done carefully, the silver of the termination connection can so completely sink into the solder flow that it partially or completely loses electrical contact with the electrode layers.

Another disadvantage of conventionally terminated ceramic capacitors is that the silver termination of little constructive value for the reinforcement of the capacitor against delamination is because the silver is only or essentially on the electrode materials themselves and not on the Ceramic sticks.

To create a level of reinforcement, you can Certain silver finishing pastes contain glass frit material that has a certain connection to the Create ceramics. The use of glass frits, however, creates other difficulties and manufacturing complications including the need to heat the units to a temperature high enough to cause the frying component of the silver paste to melt. In addition to the high energy consumption, the high temperature requirements increase

of the process also increases the possibility of the capacitors being damaged during reheating. Finally, the conductivity of the silver frit finishing paste is worse than that of a purely metallic one Guiding material.

The invention is based on the object of an improved method for producing ceramic capacitors and to propose an improved capacitor made according to this method.

To solve the problem, it is proposed according to the invention that a conventionally fired plate capacitor into a jig or similar covering device to be introduced, which leaves only the edge regions of the capacitor exposed, which the edge parts of the electrodes contains. The covered capacitors are placed in a spray device known per se, wherein heavy gas ions collide against a target material, causing atoms of the target material against the exposed surface of the capacitor are shot. Optionally, but preferably, the exposed surface is the capacitor itself etched by RF spraying prior to spraying, d. H. the heavy gas ions become hurled directly against the exposed surface of the condenser.

In addition to removing the oxides or impurities on the surface, such a spray etch results a wrinkled or corrugated surface for the subsequently applied metal layer by spraying.

According to the method according to the invention, more than one metal layer can be sprayed onto the capacitor surface be applied according to the intended use of the capacitor. For example a satisfactory capacitor termination can be achieved by spraying a Nickel layer, a nickel-vanadium alloy, a copper layer, etc. can be applied. Optional a layer of chrome can be applied first to improve adhesion, followed by a nickel or nickel-vanadium layer applied by spraying. About the subsequent soldering To simplify matters, a very thin layer of silver, e.g. on the order of 0.1 µ, can be placed on top of the nickel layer be attached.

The capacitor of the invention thereby provides an extremely desirable structure that the lack of silver at the soldered connection with the capacitor electrodes eliminates the possibility that the Electrode contact is lost during soldering. Significant cost savings are achieved by not using Achieved by silver degrees. As an additional and important benefit, the through Spray applied layer, especially if the edge part of the capacitor is previously etched by spraying has been, a deposit that is on both the electrodes and the intervening ceramic spaces firmly adheres, eliminating any tendency for the capacitor to move along the

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Electrode interfaces split certain cleavage lines, significantly reduced or eliminated will. The mechanical reinforcement effect of the finishes applied by spraying allows the final insulation or any encapsulation coating used, only as electrical insulation and not as mechanical reinforcement of the capacitor to act. The total size or circumference of the capacitor can thus be reduced.

The invention accordingly provides an improved method for manufacturing a ceramic capacitor and in particular, an improved method of terminating a conventional ceramic capacitor to propose. Another object of the invention is to provide a new closure method for ceramic capacitors that require the use of silver or other precious metals on the interface to the capacitor electrodes. Another object of the invention is to propose a process for the production of ceramic capacitors that includes the process step includes spray etching the edge of the capacitor containing the electrode to clean it and then to apply a thin layer of conductive metal by spraying that simultaneously covers the exposed Electrode connects electrically and unifying or mechanically reinforcing Has an effect on the edge of the capacitor.

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Another object of the invention is to propose a ceramic capacitor with terminations at the interfaces with the electrodes are free of silver. Another object of the invention is to provide a capacitor of the described To propose type in which the final layer acts as a mechanical reinforcement against the splitting of the capacitor works. Further refinements of the invention emerge from the following Description of an embodiment shown in the drawing. Show in it:

Fig. 1 is a vertical section in a schematic representation of one for the Completion of prepared ceramic capacitor;

FIG. 2 is a view, similar to that in FIG. 1, showing the capacitor in a covering device shows;

Fig. 3 is a schematic view of the capped capacitor during Spray application;

Figures 4A, 4B and 4C

schematic subsequent views of an untreated capacitor, a Capacitor, which is etched on its upper outer surface by spraying,

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or a capacitor, which is a layer applied by spraying covering the spray-etched surface.

The terms “spray coating”, “spray application” or “spraying” denote the atomization of a cathode target by gas ions and the subsequent precipitation of atoms leached out of the target material as a layer on the capacitor edge with exposed Electrode edges.

The term "spray etching" or "spray etched" means a process in which the cathode and gas ions are directed against the capacitor edges, which are to be terminated in a high-frequency field.

Fig. 1 shows a schematic representation of a conventional one Ceramic capacitor made according to the teaching of US Pat. No. 3,235,939. The condenser 1o contains a plurality of ceramic layers 11 which form the dielectric components of the capacitor form, the layers 11 by intervening Electrode layers 12 and 13 are separated.

The electrode layers 12 and 13 extend as usual over less than the total length of the capacitor, but overlap completely over the largest Part of their expansion. As can be seen from Fig. 1, the electrode layers have 12 edge parts,

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which are exposed at the edge 14 of the capacitor 1o, whereas the electrodes 13 have edge parts that are located on the Edge 15 of the capacitor is exposed.

According to the method according to the invention, a plurality of capacitors 1o is in a die or a Tensioning device 16 (FIG. 2) introduced, the function of which is to remove all outer surfaces of the capacitor the top one, d. H. one of the two edge surfaces 14 or 15 to cover. As shown in Fig. 2, the edge surface 14 of the capacitor lies at the top in the mask of the clamping device 16. Consequently it becomes clear that the edge parts of the electrodes are exposed upward.

Although in the schematic representations of FIGS 3 the capacitors 1o are shown as if they were through individual pockets 17 of the cover device 16 protected, a common covering effect can be achieved that a multitude of capacitors can be stacked next to each other.

The covered capacitors are next subjected to a process in which the top outer surface or the edge 14 is etched by spraying. Although the spray etching step is optional this step is preferred because it - in addition to the usual effect of cleaning the exposed Surface - also a wrinkled or

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grooved or granular application surface for the following applied metal layer forms. The effect of spray etching is illustrated by comparing Fig. AA (unetched) with Fig. AB (etched by spraying) illustrated.

The spray-etched surface 14 is next spray-coated by placing it underneath the target of a spray device is carried out. Optionally, but preferably, an in-line sprayer is used like the device labeled SERIES 9oo SPUTTERING DEVICE, which by Materials Research Corporation of Orangeburgh, New York, is used. A row sprayer is advantageous in that the capacitors continuously below target areas of different Composition can be carried out, making a layer of a first applied by spraying Material directly over surface 14 and then a second spray applied layer over the first layer can be formed. For example, a layer of a nickel-vanadium alloy can first be used be applied by spraying by passing the capacitor below a suitable target material, after which the nickel or Nickel-vanadium layer is coated with a thin layer of silver while it is under a silver target is carried out. In certain circumstances, i. H. to improve adhesion, it is too desirable first to apply a thin

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To bring about a chromium layer and then onto the chromium layer by spraying a nickel or nickel-vanadium layer to be applied, such procedures can easily be carried out in a row sprayer, by continuously running the capacitors under appropriately selected target materials.

The spray application is continued in a manner known per se until the desired layer structure is achieved is. It can be seen from FIG. 4C that the layers 18 applied by spraying are firmly connected Form layer mass, the bottom layer of which firmly adheres to the depressions formed by the spray etching process, Gaps or pores 19 adhered. The layer 18 creates an effective electrical and mechanical connection to it the electrodes 12 and a mechanical connection to the exposed ceramic components of the surface 14. The Layer 18 thus creates a closure and a mechanical reinforcement of the edge 14, whereby they the possibility of Splitting the capacitor along the interface lines between ceramic and electrodes reduced to a minimum.

It will be appreciated that the described spraying and spraying processes would involve the edge portion 15 of the target exposed Capacitor are repeated, with a second finishing layer 2o is formed over the edge 15.

The closed capacitor is now ready for use. Optionally, an insulating layer can be placed over all

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Parts of the condenser, excluding the terminations, are attached.

For example, the following are the process parameters a particular embodiment of the invention described, understood neither the materials nor are the particular details of the description to be regarded as restrictive.

According to the invention, a large number of platelets are placed in a jig, the terminating ends exposed at the top. The loaded clamping device is brought into a vacuum load lock, which is pumped to a pressure of less than 5o χ 1o ~ Torr before the jig is in the Main vacuum spray chamber is introduced. The loaded fixture becomes a high frequency spray etch moves in which the pressure is less than 5 χ 1o ~ Torr. A high purity argon gas becomes Introduced into the etching chamber in order to achieve a pressure of approx. 1o χ 1o ~ Torr. The parts whose upper

2
area is about 311 mm, are etched for 30 seconds at an energy level of 1.4 kW by spraying.

The jig carrying the etched capacitors is then transferred to a point where a 0.12 μ. thick film is applied over the terminal end. The film can be made of pure nickel or an alloy that is 93% nickel by weight

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and contains 7% vanadium. Spraying occurs at a power level of 4.2 kW and a scanning speed of 1o, 2 mm / s over the target area. The spraying is done in an argon gas environment performed at a pressure of Io χ Io 'Torr. The process is repeated to etch and coat the opposite finish surface to effect the capacitors.

If direct nickel or nickel-vanadium layers are applied, a coating thickness in the order of magnitude of 0.12 to 0.5 JX is considered optimal. If a chrome substrate for a high Adhesion is used, layer thicknesses in the order of magnitude of o, o2 - o, o5 u are preferred. As noted above, a very thin coating of silver, e.g. H. on the order of preferably about 0.1 u, added if direct soldering to the termination is intended. It note that such an amount of silver is only a small fraction of what it is normally is used to terminate a capacitor by conventional methods.

From the foregoing it is apparent that according to the present invention thereby a new and novel Process for making ceramic capacitors is provided that the final process step by applying by means of spraying, preferably after etching by means of spraying,

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follows. It can also be seen that the resulting one-time capacitor is economical can be manufactured and is uniquely strong and free from the tendency of silver during the soldering process is extracted, which is characteristic of conventional capacitors with a silver termination.

As is obvious to the person skilled in the art, numerous changes, in particular in the choice of Materials, the layer thicknesses and treatment parameters for carrying out the etching and coating be made. Accordingly, the invention is within the scope of the appended claims to be interpreted broadly.

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Claims (1)

HUBERT BAUER PATENT ADVOCATE BUROFBAN PATENT ATTORNEY VNR: 1oo 3o7 H. BAUBR PAT.-ANW. · LOTHRINGER STRASSB B3 / ECKB WimBLMBTRA8SB D-BlOO AACHEN Patent application 'TELEPHONE (0241) 0042 ββ Note: AVX Corporation, a _{mEORAMMRl patentba} „br under the laws of the State of Delaware, ^^^ 6o Cutter Mill Road, Great Neck, _(B lz s7oioobo) New York 11 o22, V. St. A. deutsche bank ao, aachbn asoaesi jot y flOQ 7ΟΟΞΩ1 Bez .: "Improved Ceramic Capacitor and Process for Its Manufacture" IHRB ZBICHBN YOUR MESSAGE MBINB ZBlCHBN AACHSN B / LR (1557) June 28, 1982 Patent claims: / TT) ceramic capacitor (1o), the alternating layers (11) of ceramic, dielectric material and layers (12, 13) of electrode material between the Ceramic layers (11) including alternating layers of the electrode layers (12, 13) have the first edge part that extends to the first or second opposite edges (14, 15) of the capacitor Mo) and is exposed there, the edges of the electrode layers opposite the first edge parts close shortly before the edges (14, 15), characterized in that the first and second edges (14, 15) of the capacitor (1o) with a metal layer (18) applied by spraying are coated, these layers (18) with the exposed ceramic components of these edges (14, and connected to the exposed edge parts of the electrode layers (12, 13), whereby the on layers (12, 13) exposing these edges electrically and the ceramic and electrode components of the edge parts mechanically connected, while the added metal layers (18) for the terminations of the capacitor (1o). 2. Capacitor according to claim 1, characterized in that that the edge parts (14, 15) are etched by spraying to a wrinkled surface before the application of the To create metal layer (18), whereby the material of the layer applied by spraying into the pores (19) which inserts ceramic and electrode materials into it, making it resistant to splitting Connection to the layers (11) and a mechanical one and making electrical connection to the exposed portions of the electrodes (12, 13). 3. Capacitor according to claim 2, characterized in that that the layer (18) contains nickel. 4. Capacitor according to claim 2, characterized in that the layer (18) contains chromium and the combination includes a second spray applied metal layer over the first layer. 5. Capacitor according to claim 4, characterized in that that the second layer contains nickel. 6. Capacitor according to claim 3, characterized by a layer of silver applied by means of spraying the nickel layer. 7. Capacitor according to claim 6, characterized in that that the silver layer has a thickness of approx. 0.1 u. shows. 8. A method for producing a ceramic capacitor, characterized by layers of electrode material between alternating layers of unfired ceramic, alternating layers of electrode layers have a first edge portion extending to the first and second opposite edges, respectively of the capacitor extends with the edges of the electrode layers opposite to the first edge parts finish shortly before the edges, the firing of the unfired ceramic and then the successive one Introducing the first and then the second edge parts of the fired capacitor in a spray zone in the preselected Distances to a metal target cathode, with all the others except for the edge parts to be sprayed Parts are covered, creating an electrically conductive sprayed layer of the target material with the Ceramic and the exposed electrode areas, which determine the edge parts, so as to connect Electrode layers of the treated edge to connect electrically, the sprayed layers the Determine the terminations of the capacitor. 9. The method according to claim 8, characterized in that that the edge parts are etched by spraying before the application of the layer, thereby creating a rough To obtain surface, the pores of which are at least partially filled by the layer material. 1o. Method according to claim 9> characterized in that that nickel is used for the layer. 11. The method according to claim 9, characterized in that the layer contains chromium and this chromium layer is then covered by a second metallic nickel layer applied by means of spraying. 12. The method according to claim 9, characterized in that that a nickel-vanadium alloy is used for the layer. 13. The method according to claim 9, characterized in that a silver layer by spraying over the
Metal layer is applied, the silver layer having a thickness on the order of about
o, 1 u owns.