DE102015201755A1 - Method for applying an insulating layer and electronic component - Google Patents

Abstract

The invention relates to a method for applying an electrically insulating layer (10) to a metallic surface (11), as well as to an electronic component having such a surface. It is provided in a first step (Ia / IIa) a powdered high-temperature polymer (12) having an average particle diameter in the range of 20 to 100 microns applied to the metallic surface (11) and in a second step (Ib / IIb) on the applied High temperature polymer (13) act with thermal radiation, wherein the metallic surface is grounded, so that electric charges flow.

Description

The invention relates to methods for applying an electrically insulating layer to a metallic surface, as well as an electronic component with such.

Electric machines (electromechanical converters), for example electric drive motors for motor vehicles, starters, generators or starter generators, convert electrical energy into mechanical energy (motors) or mechanical energy into electrical energy (generators). This electromechanical transformation is based on electromagnetic induction. Such electrical machines include a fixed stator (also called stator or primary part), which according to a common design comprises a stator core (laminated core) with a plurality of stator poles wound with corresponding wire windings. Electrical machines comprise a movable component (also called rotor or secondary part), which is formed in the most common type as a rotor which is rotatably mounted in or around the annular stator and having a plurality of permanent magnets. In this case, due to the moving magnetic field of the rotor, a current flow in the stator winding is generated (generator) or due to the magnetic field generated by the stator causes the mechanical movement / rotation of the rotor (motor). Reverse construction types in which the rotor comprises a winding and the stator comprises magnets are also known.

The individual windings of the stator or rotor are electrically connected to each other and to the outside by a switching ring (also referred to as Verschaltungsring or contact bridge). The switching ring is usually arranged on the winding head and has a plurality of switching ring elements. Thus, in the case of 3-phase AC machines, the switching ring usually comprises three switching ring elements which electrically connect each third partial winding (coil) to one another. So describes EP 1 505 711 A2 ( DE 10 2004 036 368 A1 ) a switching ring arrangement for a stator of a three-phase AC motor, which consists of three superimposed switching ring elements in the form of copper bars, each of which interconnects every third winding of the stator, and a star point ring. Between the individual switching ring elements and the star point ring, an insulating ring made of an electrically insulating material is arranged in each case. Also DE 10 2008 007 409 A1 describes a three-part switching ring arrangement for a stator, wherein three switching ring elements and a star point ring in a plane adjacent to each other lying in a support ring made of a temperature-resistant plastic, such as polyphenylene sulfide are included. Contact points of the switching ring elements and the star point ring protrude from the carrier ring and are connected to the wire ends of the partial windings of the stator. In the DE 10 2011 115 405 A1 described switching ring assembly has three substantially coaxially arranged switching ring elements, which are embedded in a plastic and thus insulated from each other. The production takes place by injection molding. The switching ring arrangements of DE 10 2008 007 409 A1 and DE 10 2011 115 405 A1 are thus designed as compact components in which the individual switching rings are embedded in solid plastic bodies.

High demands are placed on the electrically insulating material of electronic components, for example between the switching ring elements. It must primarily have a high electrical insulation capacity and in particular a high dielectric strength. In addition, it must have a high resistance especially to temperature fluctuations and peaks. These properties should also be achieved even at low film thicknesses of less than 500 microns to keep the footprint of the electrical component as low as possible.

It is known to provide the individual copper bars before installation with an electrically insulating plastic layer by powder coating. As materials in particular epoxy resins are used. Describes this DE 30 109 82 A1 a typical coating composition consisting of an epoxy resin, rubber elements and inorganic fillers. However, epoxy resins have the disadvantage that they tend to form defects, which in turn can lead to electrical breakdown.

The process of powder coating is fundamentally less expensive than extrusion, injection molding and electrodeposition processes, but can lead to problems in terms of surface quality (homogeneous layer thickness), which is disadvantageous especially for electrical insulation applications.

Also known is the use of high temperature polymers such as polyetheretherketone (PEEK) and polyphenylene sulfide (PPS), which according to the publications DE 10 2006 061 940 A1 . DE10 2005 009 552 A1 and WO 00 2006 0921 26 A1 be applied by means of polymer powder mixtures on a surface.

Out DE 10 2009 047 856 A1 It is known that when applying plastic particles of polyether ketones should be below a particle size of 10 microns in order to achieve the thinnest possible layers.

As an electrically insulating material, polyimides are used in addition to the materials described, which have more favorable properties in comparison to the above-mentioned to the application as electrical insulation material. However, these have the disadvantage that they are used as a tape or foil or in the form of other semi-finished products.

The invention is based on the object to further improve the insulating effect, the dielectric strength and the resistance of the insulating layer and in particular to provide a favorable process for producing a very high quality insulating layer.

This object is achieved by a method and an electronic component having the features of the independent claims. Thus, a first aspect of the invention relates to a method for applying an electrically insulating layer to a metallic surface, wherein in a first step, a powdered high temperature polymer having an average particle diameter (D ₅₀ ) in the range of 20 to 70 microns is applied to the metallic surface and in a second step acts on the applied high-temperature polymer heat radiation, wherein the metallic surface is grounded, so that electric charges flow off.

The process of powder coating is compared to extrusion, injection molding and electrode position method significantly less expensive. It turns out that the particle diameter of the powder particles used in the powder coating for the homogeneity and the adhesion of the resulting layer has a great importance. So too small particles due to their low mass to Rücksprüheffekten that come especially in materials with very high electrical insulation effect to bear. It has been observed that with increasing coating time or coverage, the rejuvenation effects increase. The reason is that the polymer particles are electrically charged, and are repelled by already deposited on the metallic surface and similarly charged polymer particles. Due to the good electrical insulation of the particles, the deposited particles retain their charge and repel newly arriving, especially small particles with the same charge. Depending on the particle size and the material or the storage effect for electrical charges of the material, these re-heat effects lead to small maximum thicknesses of the insulating layer of significantly less than 50 μm. Furthermore, the deposition by these effects is very irregular and leads to an increased number of points on the workpiece, where hardly any material is reflected. On the other hand, particles which are too large are effectively deposited on the surface due to their mass, but in turn deteriorate the adhesion and promote the formation of inhomogeneities on the coating surface in the form of so-called orange peel since larger particles flow together more poorly.

According to the invention, it has been recognized that there is an optimum particle size of the polymer powder in which neither relevant re-spattering effects nor inhomogeneities due to poor interparticle and / or poor substrate adhesion can be observed.

It was further recognized that after reaching a certain layer thickness, preferably half the final final layer thickness, an annealing step with electrical grounding of the workpiece at a temperature above the glass transition temperature (in amorphous polymers) or the melting temperature (in semicrystalline polymers) of the coating polymer, the layer properties clearly improved. The tempering step is mainly used for the discharge of electrical charges, but also the homogenization of the coating material (more homogeneous layer thickness) and the reduction of possible mechanical stresses. After the annealing step, a powder coating is again carried out under the same parameters as in the first powder coating in order to achieve the final final layer thickness of the polymer layer.

As a result of the improved homogeneity, as well as the choice of material, the method according to the invention leads to electrically insulating layers having a significantly improved insulating effect. Furthermore, in the method according to the invention no pretreatment of the metallic surface and no preheating of the workpiece are necessary, as is the case in the prior art methods, in particular when copper serves as a metallic surface.

In the present case, metallic surfaces are understood to be surfaces which have metallic electrical properties, ie very good electrical conductivity with the lowest possible electrical resistances, and high resistance. Preferably, the method according to the invention is applied to surfaces comprising copper or copper compounds.

On the metallic surface, in the first step of the process according to the invention, the high-temperature polymer is applied to the metallic surface by means of a powder source, for example by means of a spray gun, spray lance or the like. It is not necessary to pretreat the metallic surface, for example, to pickle or preheat. Advantageously, there is a relative movement between the powder source and the metallic surface in order to ensure that the most uniform possible Application of the powder takes place. After reaching a defined layer thickness, preferably half the final layer thickness, the metallic surface coated with the powder is exposed to thermal radiation in the form of an electric ground annealing step above the glass transition temperature (in the case of amorphous polymers) or the melting temperature (in the case of partially crystalline polymers). The action of heat preferably takes place not at points but over a large area, preferably in an oven, in order to allow electrical charges to flow off, to uniform the polymer layer and to reduce mechanical material stresses.

High-temperature polymers are polymers which have high continuous use temperatures above 180 ° C, in particular up to 250 ° C. In a particular embodiment of the invention, the high-temperature polymer is a polyimide, in particular polyetherimide, or a polyether ketone, in particular polyether ketone ketone. Advantageously, any inhomogeneities of the layer, in particular its surface, are very easily detectable when polyimide is used, since in particular polyetherimide produces a reflective amber-colored layer which allows inhomogeneities to be detected with the naked eye. This offers the advantage of reliable quality assurance. In addition, polyimides and polyether ketones show very good electrical insulation effect and dielectric strength, especially with relatively thin layers.

In a further preferred embodiment of the invention, it is provided that the particles of the pulverulent high-temperature polymer have an average diameter in the range from 20 to 70 μm, in particular in the range from 20 to 45 μm. Investigations have shown that, in these areas, the homogeneity of the layer is further improved as the maximum layer thickness is increased, since the effects of the rejuvenation are reduced while at the same time the adhesion of the layer to the surface is improved.

In particular, it is preferred that at least 50% of the particles of the pulverulent high-temperature polymer have a diameter in the range from 10 to 40 μm, in particular in the range from 20 to 35 μm. The narrowest possible distribution of the particle diameter has a positive effect on the adhesion of the layer on the metallic surface. Furthermore, it has been shown that an average particle diameter of, in particular, 27 μm, in particular with a D ₅₀ value of the particles of 27 μm, produces an electrically insulating layer optimized in terms of homogeneity, material yield and adhesion.

In a particular embodiment of the invention it is further provided that the heat radiation in an annealing step in the range of 200 to 400 ° C, in particular in the range of 250 to 350 ° C, acts on the applied high-temperature polymer. The annealing step with electrical grounding of the workpiece takes place at a temperature above the glass transition temperature (in the case of amorphous polymers) or the melting temperature (in the case of semicrystalline polymers). The tempering step is mainly used for the discharge of electrical charges, but also the homogenization of the coating material (more homogeneous layer thickness) and the reduction of possible mechanical stresses. After the annealing step, preferably a powder coating is again carried out under the same parameters as in the first powder coating in order to achieve the final layer thickness of the polymer layer.

The preferred temperature ranges are advantageously well above the glass transition temperature of the preferred amorphous high-temperature polymers or above the melting temperature of the preferred semi-crystalline high-temperature polymers. High-temperature polymers, in particular polyimides and polyether ketones, are difficult or impossible to transfer into the melt because they have a melting range and already use charring of the polymer before the entire polymer has been liquefied. In the specified ranges, however, at least one deformation, but preferably a partial melting, of the polymer takes place, so that the particles can form a bond with one another and fill the cavities due to deformation and / or melting and / or wet the metallic surface in the best possible way. In addition, the annealing step leads to a discharge or to a discharge of charges from the polymeric layer, since this is charged electrically or electrostatically due to the deposition of charged particles and / or polarized particles. When using polyimides, in particular polyetherimide and / or polyether ketone, in particular polyether ketone ketone, an annealing step has been found at temperatures in the range from 300 to 325 ° C, in particular 310 ° C, for a period of 10 to 20 minutes, in particular of about 15 minutes particularly favorable for achieving optimum layer properties.

It is furthermore preferred for the insulating layer to have a layer thickness in the range from 80 to 200 μm, and layer thicknesses in the range from 90 to 130 μm are particularly preferred.

When using high-temperature polymers, in particular polyimides and polyether ketone, within these layer thicknesses, a very good compromise between the amount of material and electrical insulation and dielectric strength.

With particular advantage, the first and / or the second step of the method according to the invention are repeated. An at least one repetition serves primarily to fill up existing areas of small material thickness (valleys) under certain circumstances. Thus, the repetition step or the repetition steps in particular increase the surface homogeneity and lead to uniform layer thicknesses over the entire substrate. In addition, since the layer thickness of the insulating layer, particularly in the preferred ranges, is proportional to the breakdown strength and the insulating property, the quality of the insulating layer is significantly improved by the repetitive operation.

It is preferred that the high-temperature polymer applied in the first and / or in the second step, before the first annealing with electrical grounding, has a layer thickness in the range of 30 to 70 μm, in particular in the range of 45 to 55 μm, in particular if a final Layer thickness of 100 microns to be produced. This advantageously leads to the fact that the total layer thickness is not increased beyond the preferred limits even when repeating the individual steps. In addition, in this embodiment, a maximum homogeneity of the insulating layer is achieved by the multi-layer structure. Preferably, after the deposition of the first layer at a layer thickness of 30 to 70 .mu.m, an annealing step with electrical grounding is connected. The tempering step is mainly used for the discharge of electrical charges, but also the homogenization of the coating material (more homogeneous layer thickness) and the reduction of possible mechanical stresses. Particularly in the areas of the layer in which the re-effect of charged particles on the surface leads to a stagnation of the layer growth, the discharge by the annealing step leads to or even in areas where in the first step no or only inhibited layer growth more was possible in a second deposition over the entire substrate, a homogeneous total layer thickness is achieved.

Another aspect of the invention relates to an electronic component comprising a layer stack comprising two metallic surfaces, which are arranged facing each other, wherein an insulating layer is disposed on the metallic surfaces for electrical insulation, which is applied or can be applied by the method according to one of the preceding claims , With particular advantage, the electronic component is a safety coupling, in particular a switching ring, for an electrical machine or a coil.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

1 a schematic structure of a switching ring, and the arrangement of a layer stack arranged therein;

2 a schematic representation of the sequence of the method according to the invention in a preferred embodiment, and

3 a logarithmic plot of a particle diameter distribution according to a preferred embodiment.

The exemplary structure of a switching ring 30 is in 2 shown in the lower part of the 2 an enlarged partial section is shown.

The switching ring shown here 30 for connection to a stator (not shown) has three switching ring elements 32 on, which are concentric with each other and arranged vertically standing in the selected representation. Between the individual switching ring elements 32 is in each case an insulating layer 10 arranged so that the switching ring elements 32 are electrically isolated from each other. Each switching ring element 32 has a variety of contact points 34 on which axially over the individual switching ring elements 32 protrude and are angled radially inward. The contact points 34 serve the electrical interconnection of the partial windings of the stator with each other. For this purpose, the contact points 34 connected to wire ends of the partial windings electrically conductive, for example, materially by welding or soldering. Each switching ring element 32 also has a connection point 36 on, which serve the external connection of the stator, for example, to a high-voltage connection. Each switching ring element 32 together with the contact points 34 and the connection point 36 is preferably in one piece from a metal sheet, for example made of copper.

The switching ring 30 may also have a star point ring, as in this example 38 also here in coaxial arrangement with the three switching ring elements 32 is arranged as an outer ring layer. Between the star point ring 38 and the adjoining switching ring element 32 is also an insulating layer 10 available. The star point ring 38 forms the electrical star point of the electrical wiring for the partial windings. For this purpose, the star point ring 38 Radial inwardly angled Kontaktierungsfortsätze 40 on, which extend in the mounted state on the stator poles of the stator core and are wrapped by the partial windings. The contacting processes 40 serve to contact one end of the wound around the poles of the stator part windings.

The above-described structure of the switching ring 30 is known per se. Other designs may be used in the context of the present inventions.

The lower detail shows a further enlarged section of the switching ring 30 and illustrates the arrangement of the insulating layer 10 between the individual switching ring elements 32 the Schalring 30 , These result in a layer stack 100 , wherein each switching ring element 32 a metallic surface 11 represents, on both sides, but at least on an adjacent metallic surface 11 facing side, the insulating layer 10 is arranged. Between two metallic surfaces 11 are therefore two insulating layers 10 arranged. Depending on the quality and design of the insulating layer 10 as well as with larger tolerances of the switching ring elements 32 can be between the insulating layers 11 column 12 occur.

According to the invention now has the switching ring 30 an insulating layer produced by the method according to the invention 10 on.

2 shows a schematic representation of the method according to the invention in a preferred embodiment. In the embodiment shown, the method comprises two repeat units I and II , where in the first unit I in two steps Ia and ib a first layer 14 on a metallic surface 11 is arranged. In the repetition step II gets on the first layer 14 through the same process steps IIa and IIb applied another layer.

At the beginning of the process according to the invention is in a first step Ia a metallic surface 11 , preferably a copper surface or a surface 11 made of copper compounds. The metallic surface 11 no pretreatment has been previously subjected, such as pickling, tempering or the like. On this treated metallic surface 11 is by means of a spray gun 1 or lance a powdered high temperature polymer 12 applied. In order to achieve the most homogeneous possible deposition, there is a relative movement between the metallic surface 11 and spray gun 1 instead of. This can be done either by moving the metallic surface 11 or, as shown, by pivoting the spray gun 1 be achieved. It makes sense that by the pivoting of the spray gun 1 achievable processing area 12 a width or a length of the metallic surface 11 equivalent.

Polyimides, in particular polyetherimides but also polyether ketones, in particular polyether ketone ketone, can be used as the high-temperature polymer. The particles of the powdered high-temperature polymer have the narrowest possible distribution. Particularly advantageous are average particle sizes in the range from 20 to 100 μm, in particular in the range from 20 to 70 μm, particularly preferably in the range from 20 to 45 μm. Particularly suitable is a high-temperature polymer powder having a particle size distribution of D (v; 0.1) = 7 microns, D (v; 0.5) = 27 microns and D (v; 0.9) = 62 microns, ie a powder used with a very narrow particle size distribution and an average diameter of 27 microns.

After achieving a designated layer thickness of 80 to 200 .mu.m, in particular of about 100 .mu.m, preferably half the final layer thickness of the powder application to the metallic surface 11 interrupted. In the subsequent second step ib becomes the applied high temperature polymer 13 a heat radiation (annealing with electrical grounding) 3 exposed.

This can be done, for example, that the metallic surface 11 is introduced in a tempering furnace. The heat radiation 3 has a temperature which is above the glass transition temperature of the high-temperature polymer, ie in particular above 180 ° C., in particular above 250 ° C. At the same time, it is ensured that the temperature is below a critical temperature for the particular high-temperature polymer at which carbonization of the high-temperature polymer would take place. The annealing step is in the range of a few minutes, in particular in the range of 10 to 20 minutes, preferably at about 15 minutes.

The result is a metallic surface with an insulating layer disposed thereon 10 , To the quality of this insulating layer 10 To further improve the process steps Ia and ib in a second repetition step II repeated. The aim is to have a total layer thickness of the insulating layer 10 from 80 to 200 .mu.m, in particular from 90 to 120 .mu.m, preferably of about 100 .mu.m, to achieve. At least three of these are known in most known powder coating processes with high temperature polymers Coating steps required, the choice of particle sizes or the particle size distribution, however, allows in the inventive method, such a layer thickness after two coating steps, interrupted by an annealing step with electrical discharge to achieve.

Preferred embodiment:

In a preferred embodiment, a polyetherimide granules (Ultem 1000) was ground in a liquid nitrogen-filled Pulverisette polyetherimide powder of different particle size distribution and dried in vacuo. The powder was aspirated by means of a rod injector and fluidized to the powder cloud to be expelled over the powder lance. The powder coating was carried out with a total volume flow of 2.5 m ³ / h with a powder output of 100 g / min. In this case, a charge of the powder over a corona system with 30 kV (GEMA system) was achieved. The powder deposition took place on a grounded copper sheet, wherein the distance between the powder lance and copper plate was 125 mm. The dimension of the copper plate was 100 × 100 × 1 mm of Wieland K1 type, Cu-OF R2401. The coating of the copper was carried out in the cold state (at room temperature). A particle size distribution with a mean particle diameter of 27 microns (D (v; 0.5)), wherein for the smallest particles of the particle diameter 7 microns (D (v; 0.1)) and for the largest particles of diameter 62 microns (D (v; 0.9)) achieved the best results. In this case, a deposition layer thickness of 50 μm was deposited per deposition process and then subjected to a 15 minute annealing step at 310 ° C. The result was a very homogeneous and good polyetherimide adhesive layer with a very smooth surface.

In contrast, in the otherwise same process, the use of polyetherimide powder having a particle size distribution with an average particle diameter of 121 μm (D (v; 0.5)), a smallest particle diameter of 12 μm (D (v; 0.1)) and Although a large particle diameter of 204 microns (D (v; 0.9)) hardly rewinding effects but a clearly recognizable uneven distribution, especially the surface. For example, an orange peel on the surface of the layer was particularly evident.

A significant reduction of the average particle diameter to 10 μm (smallest 6 μm, largest 15 μm) showed already with a layer thickness of 50 μm strongly increasing re-heat effects and the associated inhibited layer growth.

3 represents the diameter distribution of the particles used in the preferred embodiment in a logarithmic plot. The particle diameters plotted on the abscissa are most populated in a range of 30 to 40 μm. Due to the distribution results in a D ₅₀ value of 27 microns.

LIST OF REFERENCE NUMBERS

1

spray gun

2

editing area

3

thermal radiation

10

insulating layer

11

metallic surface

12

powdered high-temperature polymer

13

applied high-temperature polymer

14

first shift

30

switching ring

32

Switching ring element

34

contact point

36

connector

38

Star point ring

I

Arranging a first layer

II

repeat step

Ia / IIa

first step

Ib / IIb

second step

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1505711 A2 [0003]
• DE 102004036368 A1 [0003]
• DE 102008007409 A1 [0003, 0003]
• DE 102011115405 A1 [0003, 0003]
• DE 3010982 A1 [0005]
• DE 102006061940 A1 [0007]
• DE 102005009552 A1 [0007]
• WO 002006092126 A1 [0007]
• DE 102009047856 A1 [0008]

Claims (10)

Method for applying an electrically insulating layer ( 10 ) on a metallic surface ( 11 ), in a first step ( Ia / IIa ) a high temperature powdered polymer ( 12 ) having an average particle diameter in the range of 20 to 100 μm on the metallic surface ( 11 ) and in a second step ( I _b / II _b ) on the applied high-temperature polymer ( 13 ) Heat radiation, wherein the metallic surface is grounded, so that electric charges flow off. Process according to claim 1, characterized in that the powdery high-temperature polymer ( 12 ) is a polyimide, in particular polyetherimide or a polyetherketone, in particular polyetherketone ketone. Method according to one of the preceding claims, characterized in that the particles of the powdery high-temperature polymer ( 12 ) have an average diameter in the range of 20 to 70 .mu.m, in particular in the range of 20 to 45 .mu.m. Method according to one of the preceding claims, characterized in that at least 50% of the particles of the powdery high-temperature polymer ( 12 ) have a diameter in the range of 10 to 40 microns, in particular in the range of 20 to 35 microns. Method according to one of the preceding claims, characterized in that the heat radiation in an annealing step with electrical grounding in the range of 200 ° to 400 ° C, in particular in the range of 250 ° to 350 ° C acts on the applied polyimide. Method according to one of the preceding claims, characterized in that the insulating layer ( 10 ) has a layer thickness in the range of 80 to 200 microns. Method according to one of the preceding claims, characterized in that the first step ( Ia / IIa ) and / or the second step ( ib / IIb ) be repeated. Method according to claim 6, characterized in that in the first step ( Ia / IIa ) applied high temperature polymer ( 12 ) has a layer thickness in the range of 30 to 70 .mu.m, in particular in the range of 45 to 55 microns. Electronic component comprising a layer stack ( 100 ) comprising two metallic surfaces ( 11 ), which are arranged facing each other, wherein for electrical insulation on the metallic surfaces ( 11 ) an insulating layer ( 10 ), which is applied or can be applied by the method according to one of the preceding claims. Electronic component according to claim 9, characterized in that the component is a switching ring ( 30 ) or a coil.

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