DE69434554T2 - Method for producing solid state capacitors - Google Patents

Description

BACKGROUND AND AREA THE INVENTION

The The present invention is in the field of solid capacitors and is in particular to a method for mass production of attachable to a surface Directed to solid-state capacitors.

DEFINITIONS

Of the Term "solid state capacitor" as used herein is, means a capacitor, which is formed by the method is where a pulverized mass of a solid state capacitor forming material (which will be defined below) is the mass is compressed to form a given shape The compressed mass is sintered to a uniform mass porous To integrate state, the porous Mass z. B. react chemically by anodization of the porous mass is left to a dielectric coating over the surfaces to form within the mass, and then a conductive coating over the dielectric coating is formed (manganization).

In the solid-state capacitor The components that have been anodized define the anode of the capacitor while the conductive or manganized coating over the dielectric the cathode or counter electrode forms.

Of the Term "solids-forming Materials ", like he uses here, defines materials used in manufacturing of solid-state capacitors makes sense are. Solid State Building Materials include at least one of the following: tantalum, niobium, molybdenum, silicon, Aluminum, titanium, tungsten, zirconium and alloys thereof. The main solid-state metals, the present tantalum and, to a lesser extent, niobium are used.

Of the Term "anodization" as used in the present Sign in is used to mean that on the spongy Surfaces above the entire porous, sintered mass of solid-forming Material a dielectric coating, typically by immersion of the sintered solid-forming Materials in an electrolyte, eg. B. a phosphoric acid solution, wherein the solid-forming Material with a positive DC source with respect to a is formed in the bath immersed cathode is formed.

The The term "manganization" is intended to apply generally refer to the step in which a conductive counter electrode coating over the formed from the anodization resulting dielectric. Of the Manganization step is typically done by dipping the Anodized device in a solution of manganese nitrate and heating the impregnated Device in a humid environment to convert the nitrate into a solid, to convert conductive manganese dioxide carried out.

Either the anodization step as well as the manganization step well known in the art of forming solid state capacitors and can depending on the used solid state capacitor and intended end properties of the capacitor vary.

STATE OF THE ART

Solid state capacitors are largely because of that on a relatively limited volumetric Space as a result of the big ones lateral surface within the sintered, porous mass an extremely high capacity can be provided, highly appreciated. It is feasible, for example, To provide a tantalum capacitor, which at working voltages of about 10 V in a capacitor body with a volume of 0.027 c. c. (cubic contents) has a value of 50 to 100 μF having.

So far The advantage of compactness was, as a result of the applied, necessarily extensive encapsulation process severely impaired. In particular, a Appreciation the progress of the present invention best by reference on the conventional Production method of commercial Solid state capacitors be derived.

at such a fabrication becomes the end of a tantalum metal rod pressed on a mass of compressed tantalum powder. Of the Bar is made by co-sintering the bar and powder or by welding of the rod with a pre-sintered mass of the powder with the tantalum powder mass connected. Subsequently the prefabricated units are anodized and manganized, such procedures are typically done by grabbing the tantalum bars and using such bars as "handles" for the subsequent ones Steps are executed.

The Condenser implants need now be packaged in such a way that their use in technical Applications possible is.

Due in large part to the fragility of the connection between the anode rod and the tantalum mass, it is generally necessary to clad the capacitor in a lead frame construction with terminations that allow attachment to a printed circuit board or the like. Typically, the leadframe attachment involves making a cathode connection to the body of the capacitor and making welds between the anode rod and other portions of the leadframe, and then severing connections between protruding portions of the leadframe and the remainder thereof to provide the completed capacitor.

As Those skilled in the art are familiar with manufacturing techniques of solid state capacitors full of difficulties and lead to a housing of the finished capacitor whose volume is the volume of real capacity-generating Components many times over. As has been noted, the connection between the anode rod and the capacitor body fragile, which is why during the Processing of the capacitor preforms during anodization, the Manganization and subsequent steps great care must be applied.

Besides that is the welding of solid-state metals, as is the case with the conventional one Manufacturing is necessary, a difficult procedure.

at the described conventional Process has to be big Care should be taken to ensure that the cathode coating does not shorts with the anode rod, the necessity of spacing these components Total size of the component further increased.

Closing and perhaps most importantly besides the overhead line fabrication effort contradicts the big one Volumetric space through the finished capacitor is evidenced modern manufacturing procedures involving miniaturization a first concern is.

Representative examples for conventional solid state tantalum capacitors and their method of preparation are described in U.S. Patents 4,059,887, 4,520,430, 4,745,769 and 4,945,452 are described and shown.

Representative Examples of conventional solid-state capacitors, which are manufactured using the lead frame method include U.S. Patents 4,107,762, 4,539,623, 4,660,127, 4,899,258 and 4,907,131.

below US patents are listed in connection with a related to the carried out present invention Stand-the-art research have been found.

3117365 discloses ceramic capacitors obtained by depositing U-shaped electrode patterns on a big one Dielectric layer, stacking the layers such that the bases of the U's from the opposite surfaces of the stack, and subsequent cutting to single Capacitors, which are then completed to define, formed become.

3538571 discloses raw ceramic layers that are embossed to discrete, elevated areas that subsequently to create electrodes.

3617834 refers to a ceramic multilayer capacitor by Create a block of capacitors whose edges overlap and disconnect the Blocks in the overlap areas, in order to create graduation areas.

3635759 discloses forming multilayer ceramic capacitors Applying ceramic in a binder to a porous disk, Applying a suction, depositing of liquid metal and repeating this process until a multilayer structure is formed is that, then is fired and cut to form individual capacitors.

3992761 discloses a method of terminating capacitors Embedding a plurality of ceramic capacitors in a plastic block, the ends are exposed. Be on the exposed ends degrees applied, the block is then dissolved to the capacitor body thereof to solve.

4045867 refers to a method for casting a polymer compound around capacitors that performing of termination wires in the upward direction through holes in the bottom of the plastic preforms, attaching the wires on the capacitor, the insertion the capacitors in the preforms, the filling of the preforms with resin and the curing includes.

4574438 shows a pressure-sensitive transducer that is manufactured, by forming a metallic layer on a substrate over which Metal a piezoelectric, dielectric layer is formed, Grooves through the dielectric and the metal in the body of the Substrate are cut, the grooves are filled with plastic, photolithographic Liners over Sections of the device that coincide with the filled grooves, be formed and finally a cover is applied, whose electrodes are aligned perpendicular to the grooves.

4,959,652 shows the formation of an Surface mountable metal-plastic type capacitors made by winding individual capacitors, the terminations by vapor deposition of a metal having a melting point higher than that of the solder used to attach the capacitor to a printed circuit board, coated, the capacitor is coated with resin and then sanded off portions of the resin to expose desired portions of the underlying metal terminating material.

US 3,787,961 discloses a method of manufacturing solid state capacitors in which a solderable metal substrate is provided with a thin layer of a layering metal such as tantalum, titanium, aluminum or niobium. The layer-forming layer of material is etched to leave a pair of discrete islands of the layer-forming metal. The islands form anode electrodes and are oxidized to provide dielectric layers. Then, a metal oxide semiconductor layer is formed on the oxide layer. The cathode layer is then formed on top by spraying a graphite suspension or by means of an electrically conductive paint or other known metallization techniques. The substrate can then be subdivided to form individual capacitors.

US 4,599,788 discloses a method for producing solid state electrolytic capacitors. Valve metal contact surfaces are applied by screen printing on a valve metal substrate, wherein subsequently several formed from a powder with a large lateral surface valve metal balls are applied to the contact surfaces produced by screen printing. The substrate and the beads or pellets are sintered to bond the pellets to the substrate by means of the screen-printed contact surfaces.

SUMMARY THE INVENTION

The The present invention can be summarized to include an improved method for simultaneously producing a plurality from on a surface attachable solid-state capacitors is directed.

According to the present Invention, a method is provided by the features of claim 1 is defined. In short, the preferred method involves which will be explained below, the provision of a substrate, the preferably of the same materials as the solid-forming Material of which the capacitor is made, or one with compatible with it Material exists. There is a compressed wafer on the substrate pulverized, solid-forming Attached material that has a size the size of each Capacitors exceeds many times. The wafer and the substrate are sintered together to form the wafer to connect with the substrate and the powder into a porous mass to integrate.

Of the Sintered wafer is made by cuts passing through the wafer and perpendicular are formed into the substrate into a plurality of subunits divided. Either before or after the subdivision, the wafer and / or the subdivided units anodized and manganized, Of course, the Anodization and manganization are performed before subdivision and the anodization and manganization steps are repeated after subdivision become. The areas between the discrete subunits become preferably treated in a resin injection step to remove the interfaces between to isolate the substrate and the wafer from other areas, so that the manganization steps the substrate, which is the anode of the Make device, not short circuit to the cathode of the capacitor.

Versus the upper surface of the processed wafer becomes an element such as a metal plate pressed into mechanical and electrical contact with the upper surface to to form a counter electrode plate. The cavity areas between the discrete capacitors as a result of the cutting step or the cutting steps that have been previously performed are formed Now by injecting resin into the space between the substrate and the counter electrode plate, in the manner of components of a mold act, is defined, infects, whereby the totality of the spaces defined by the cuts filled with insulating resin material is.

In addition, will the laminated body along cutting lines, which coincide with the previously formed cuts, d. H. by the counterelectrode plate, the resin separating the individual capacitors and the substrate, cut through, resulting in finished capacitors be formed, except at the defined by the counter electrode plate and the substrate Ends are encapsulated, these components being the terminations of the Condenser form, which is an attachment of the capacitor as a surface housing enable the circuit board and wherein the substrate forms the anode of the capacitor and the Counter electrode forms the cathode of the same.

As Professionals using conventional solid-state capacitors and their manufacturing processes are familiar, apparently different from the generally described manufacturing process Advantages.

First elevated by eliminating the conventional Anodendrahts the volumetric efficiency of the capacitor, d. H. the capacity obtained in a given unit volume by one Factor of two to three.

Besides, they are the main ones Manufacturing difficulties such as handling the preform below Using an anode wire and welding the anode wire as well the need to use lead frames has been completely eliminated. The method further eliminates the industry-wide problem of Short circuit between the anode wire and the cathode coating, the conventional one Covering solid state capacitors.

One important advantage of the invention is based on the possibility of a raw body Substrate with a sintered solid-state sintered wafer Provide material. This body can be cut to size be that by simply changing the distance of the cuts formed in the wafer, and consequently the Capacitor size capacitors with the desired capacity be formed.

Important is that by the fact that the counter electrode plate and the substrate indeed as limits of a multiple form for the injection of insulating resin, which separates the individual capacitors, and after sawing the final Form encapsulation of the completed capacitor used the cost of encapsulation is substantially reduced.

It is accordingly an object of the invention, a novel method for the mass production of on a surface attachable solid-state capacitors to accomplish.

A Another object of the invention is to provide a method for the manufacture of attachable to a surface solid-state capacitors, in the elements of the encapsulating materials of the finished Capacitors a function during perform the manufacturing process, namely isolating the anode substrate from the subsequently formed counter electrode components of the capacitor.

A Yet another object of the invention is to provide a method for producing solid state capacitors and a resulting capacitor, that in the prior art occurring problems of a fragile connection between the Anode rod and the tantalum mass and between the anode rod and the Finishing components eliminated to ensure a durable and reliable structure to accomplish.

SUMMARY THE DRAWING

The 1 to 9 The drawings are schematic sectional views illustrating the sequential steps for manufacturing a capacitor according to a first embodiment of the invention.

3a is a perspective view of one in the step 1 to 3 shown subgroup.

10 is an enlarged, fragmentary, perspective view of a according to the method of 1 to 9 finished capacitor according to the invention.

The 11 to 19 Fig. 3 are schematic sectional views showing a variant of the method in progressive stages.

20 is an enlarged, fragmentary, perspective view of a according to the method of 11 to 19 finished capacitor according to the invention.

PRECISE DESCRIPTION THE DRAWING

In the 1 to 9 In the drawing, a series of sectional views is disclosed, illustrating various steps in the manufacture of capacitors according to a first embodiment of the invention.

As It will be apparent to those skilled in the art that dimensions are for the sake of clarity and proportions of the various elements exaggerated.

In 1 is a substrate 10 made of solid-forming material, for example tantalum metal. On the upper surface 11 of the substrate 10 is preferably a thin layer of tantalum grains 12 , which are melted onto the substrate, applied to the grains 12 serve to provide a rough surface to bond or bond the wafer 13 , which is described below, multiply. As an alternative to the grains 12 could be the surface 11 be roughened.

On the upper surface 11 of the substrate 10 becomes a wafer 13 pressed, which consists of compressed tantalum powder, to which a binder has been added to form a coherent mass. As is well known, the particles defining the powder forming the wafer may vary in size ranges, such granule size ultimately determining the properties of the resulting capacitors. The wafer 13 and the substrate 10 are then sintered together to burn off the organic binder at the beginning and then the powder of the wafer 13 to transform into an integral porous mass. The sintering also bonds the bottom surface 14 on the upper surface 11 of the substrate 10 and connects the contacting surfaces mechanically and electrically.

By way of example, but not limitation, the thickness of the substrate may vary within an optimum range of 0.127 mm to 0.762 mm (0.005 to 0.003 inches). The granule-forming powder 12 uses larger grains than the wafer powder, whichever is in the wafer 13 vary in size used and can be optimally in the range between about 100 and 800 microns, for example.

Yet always by way of example and assuming that the substrate and The powder consist of tantalum, sintering at 2000 ° C for a duration affects from 5 to 60 minutes, creating the desired bond and porosity wherein the time factor is a function of particle size and Mass of the wafer forming material is. The processing of solids forming Materials including the formation of globules or pellets, the sintering steps and other processing steps (Anodization and manganization), which are required to the porous Converting mass into a capacitor are all known per se, why their description is included here only briefly, since such Processing step does not form part of the present invention.

The substrate 10 and the sintered wafer 13 will be next, as in 2 is shown, cutting through cuts that are perpendicular to the plane of the substrate 10 to be executed in a criss-cross pattern (see 3a ), subjected to the wafer 13 into a plurality of discrete, condenser-forming units 15 to divide. The cuts are preferably to a depth at which the surface 11 of the substrate 10 is exposed, or slightly, so that they penetrate the surface, executed. Optionally, the substrate as a way of handling the out of the substrate 10 and the wafer 13 existing laminate, to be embedded in a resin block (not shown) to a depth exposing the top surface and the wafer.

The divided laminate of the 3 and 3a is then subjected to the processing steps for converting the porous, sintered mass of the wafer, which remains after the sawing, in capacitors. The processing steps are known per se and include an anodization step in which the wafer is immersed in an electrolyte bath, ie, a 1% phosphoric acid solution, the substrate being connected to a positive DC power source with respect to a cathode immersed in the bath. This procedure results in the conversion of the portions of the wafer exposed to the solution and the exposed portions of the substrate into a dielectric material, the metal used being, for example, tantalum or tantalum pentoxide.

The A capacitor forming procedure involves post-formation a counter electrode, wherein the counter electrode forming step, for example by immersing the laminated body in a manganese nitrate solution accomplished will, and the subsequent Heat the device in a humid environment at about 325 ° C to the Convert nitrate into conductive manganese dioxide. The anodization and manganization process can in conventional Be repeated several times to the formation of a desired one dielectric coating and coverage of the counterelectrode, with such a repetition of course because of cracks or breaks in the dielectric due to heating during the preparation of the counter electrode are formed, with such cracks or bridge again need to be anodized to ensure that no short circuit between the anode (defined by the tantalum metal) and the cathode or counter electrode (defined through the manganization process).

The Steps of treatment of the porous tantalum mass for forming a capacitor are disclosed in U.S. Patents 4,059,887 and 4,945,452 closer described.

As in 4 2, a second sequence of saw cuts S2 is formed in alignment with the first sequence of saw cuts S1, the saw cuts S2 penetrating deeper into the substrate and defining channels therein. It should be noted at this point that the process of treating the material of the wafer is not critical to the invention. It is feasible, for example, the entire wafer 13 to anodize and manganize before the saw cuts S1 and S2 are made, or to perform saw cuts prior to the treatment of the wafer. Of course, when the anodizing is carried out before cutting, it is necessary to re-treat the laminated body cut by sawing by anodizing and manganizing. The course of the treatment is best determined empirically and depends on such factors as the size of the individual capacitors, the type (particle size) of powder chosen as the solid-forming material, and the like, which is known per se.

As in 5 shown are the channels 16 up to the level of the surface 11 or something about it with a resinous insulating compound 17 been attacked. Although the resin used is optimal is a liquid epoxy resin, a wide variety of liquid resins that subsequently cure can be used.

To the formation of the second saw cuts S2 and before filling of the channels the device should undergo another anodization step be an anodizing, insulating layer above the through the saw cuts S2 to create exposed metal.

As is apparent from the foregoing description, the resin has 17 (and the subsequent saw cut anodization step) ensures that the only electrical connection between the metallic components of the sintered tantalum powder wafer 13 on the surface 11 representing the interface between the elements forming discrete capacitors 15 and form the substrate.

As in 6 The upper surfaces are shown 18 of the elements 15 in a conventional manner with a first layer 19 made of conductive carbon and a cover layer 20 made of silver to thereby electrically connect to outer (upper) surface portions of the counter electrode formed by manganization.

As in 7 is shown is a cathode plate 21 , z. B. by a conductive adhesive, on the upper surface 22 of the silver plating 20 attached. After applying the adhesive, the voids defined by the initial saw cuts S1 are filled with liquid insulating resin material (eg, epoxy resin) and allowed to cure. The filling of the areas is characterized by the fact that the substrate 10 and the cathode plate 21 together form a cell for receiving injected resin, greatly relieved.

Finally, the in 8th shown composite unit along the sawing lines S3, which coincide with the sawing lines S1 and S2, cut, the sawing steps lead to the formation of completed capacitors C, as in 10 is shown.

As will become apparent, no further processing or encapsulation is required because the saw cuts S3 define completed encapsulated solid state capacitors. The capacitors are attachable to a surface, wherein the anode 10 ' from a segment of the substrate 10 exists while the cathode or counter electrode 21 ' from an increase in the cathode plate 21 consists.

A great advantage of this invention is the ability to make preforms ( 2 ), which consists of a raw material blank of substrate and wafer 13 consist. It is possible, by merely changing the spacing of the saw cuts, to produce capacitors with different final properties in accordance with the requirements of a particular user.

A non-limiting preferred and fulfilling the requirements of the best embodiment preferred manufacturing process for implementing the method according to 1 to 9 in practice is the following:

SEQUENCE OF MANUFACTURE

• 1. Provision of Tantalum Substrate.
• 2. Application of tantalum grains and heating to Bonding the grains on the substrate.
• 3. Press and sintering a tantalum wafer to integrate the powder and Bond the substrate and then anodize.
• 4. Manganize.
• 5. sawing of the wafer (S1).
• 6. Forming a dielectric over the saw cuts.
• 7. Add a first resin barrier ( 17 ).
• 8. Manganize.
• 9. Applying a carbon coating.
• 10. Apply a silver coating.
• 11. Bonding the cathode plate by means of a conductive adhesive.
• 12. Injecting a second resin encapsulation ( 24 ).
• 13 Cutting the wafer into discrete capacitors.

In the 11 to 19 is a modification of in conjunction with the 1 to 9 shown method. The main difference between the methods resides in that the first resin injection step used to add resin components 17 leads, does not apply.

In the description of the in the 11 to 19 The procedures shown are similar to the reference numerals used in the description of 1 to 9 been used.

According to the embodiment ( 11 - 19 ) become the capacitor subcomponents after the formation of the first saw cut (S1) 15 and the exposed surfaces of the substrate 10 with a dielectric coating 30 to cover any exposed metallic components that have been exposed by the saw cuts, and thus an insulating barrier that defines the boundaries between the substrate and the footprint of elements 15 protects, creates. The device is then manganized, followed by a second series of narrower saw cuts (S2), which coincide with the Sägeschnitten S1 is formed. Thereafter, the laminate is subjected to another dielectric-forming step to ensure that the edges exposed by the saw cuts S2 are covered by the dielectric coating ( 16 ). The composite is then manganized to define a counter electrode and as before, ie, by applying a carbon layer 19 and a silver layer 20 and pressing a cathode plate 21 , processed. The cavities between the capacitor elements 15 are then as before with an insulating resin composition 24 and along the sawing lines 53 sawed to the finished capacitor 25 to define how in 20 is shown.

As with the respect to the 1 to 9 described method, the sequence of steps can be changed to a certain degree. With respect to the embodiment of the 11 to 19 the preferred procedure is as follows:

MANUFACTURING PROCESS ( 11 to 19 )

• 1. Roughen the substrate or sinter Metal particles on the substrate.
• 2. Mounting the wafer and sintering together of wafers and Substrate.
• 3. Forming a dielectric.
• 4. sawing at substrate height (S1).
• 5. Further dielectric formation to cover saw-exposed metal.
• 6. Manganize.
• 7. Forming deep cuts (S2) in the substrate.
• 8. Repeat anodizing to in through the S2 sawing step de defined grooves to form a dielectric.
• 9. Manganize.
• 10. Applying carbon and silver to the upper edges of the Capacitors.
• 11. Attach the cathode plate to the silver surfaces by means of a conductive adhesive.
• 12. Inject resin.
• 13 Separation of the individual capacitors by saw cuts (S3).

As From the foregoing description, are novel here Method of forming solid state capacitors disclosed. The method of the invention is the provision of a variety through hollow areas of separate solid-state capacitors between a cathode plate and an anode plate together, wherein the cavities are filled with insulation encapsulating resin and the individual Capacitors are then separated from the matrix after the capacitors completely are formed and encapsulated. The last sawing step leads to the creation of a surface attachable capacitors that are fully encapsulated and completed are, with the separated edges of the substrate define the anode termination and the edges of the the cathode plate define the counter electrode or cathode termination.

Of the represents condenser resulting from the practice of the process a highly efficient use of space that gives a housing, its volume is only about one third of the volume of conventional Solid state capacitors is. Unlike traditional ones Capacitors, due to a displacement of the anode rod from the sintered globules or pellet and due to rupture of the anode rod compound with subject to errors, is the capacitor of the present Invention virtually failsafe.

The Manufacturing methods are further unique in that the Resin components not only for encapsulation of the finished Capacitor, but also as a means of facilitating the manufacturing procedure serve by isolating between the anode and the counter electrode form (method 1) and in both variants described the matrix while stiffen the last sawing operations.

Claims (2)

A method for producing solid-state capacitors, comprising the following steps: providing a substrate ( 10 ), Attaching a lower surface ( 14 ) wafer ( 13 ) of a powdered material for the formation of a solid state capacitor on the substrate, providing an engagement between the substrate ( 10 ) and an upper surface parallel to and spaced from the substrate, sintering the substrate ( 10 ) and the wafer ( 13 ) to the lower surface ( 14 ) of the wafer to the substrate and to integrate the powder of the wafer into a porous mass, dividing the wafer ( 13 ) into several discrete units ( 15 ) passing through channels or cavities ( 23 ) are separated by passing a first series of cuts (S1) through the wafer into the substrate (S1). 10 vertical planes, applying the anodized wafer with an anodization step to form a dielectric coating ( 30 ) over the entire porous mass, forming a counter electrode coating ( 20 ) on the dielectric coating, pressing a counterelectrode plate ( 21 ) against the upper surface of the processed wafer, the plate being in mechanical and electrical contact with the upper surface, and filling the channels or cavities ( 23 ) with an insulating material ( 24 ), the method comprising the further step of cutting individual capacitors by cuts (S3) through the substrate (3). 10 ), the counterelectrode plate ( 21 ) and the insulating material ( 24 ) are separated from each other. Process according to claim 1, which involves the injection of liquid insulating resin ( 24 ) into the channels or cavities ( 23 ) using the substrate and the plate ( 10 . 21 ) as boundaries of a mold, causing the hardening of the resin, and thereafter separating (S3) the plates and the resin along lines corresponding to the channels.