DE19752586A1 - Attaching metallic surface to thermally softened conducting plastic film - Google Patents

Abstract

A metal film (3) is placed on the surface (4) of a plastic film (5) and wedged into angled indentations by knives or pins. The indentations reach a predetermined depth (t) into the plastic material. Independent claims are also included for the alternatives of pressing and rolling conducting powder grains into the surface and for using a perforated metal film so that the softened plastic flows through the perforations to spread into valleys round the perforations.

Description

The present invention relates to methods of attachment and / or attaching at least one metallic surface a surface of a softened plastic body, in particular a plastic film with electrical conductivity and a PTC characteristic of the electrical resistance.

Such methods are for example from the patent DE 37 07 494 C2 with numerous cross references to other Pa known. The approach of these proposed solutions is that there is always a metallic surface on a ther mix softened plastic body is pressed, the Contact surface of the metallic surface with the polymeric PTC Substance is enlarged by a micro-toothing. To the material of the metallic external contacts is mostly on chemical path at least roughened. So at the same time better anchorage and lower normal resistance of the polymeric PTC element contacted in this way. These procedures are very chemical pretreatment costly and complex.

The object of the present invention is therefore to provide methods for Cost-effective mass production of polymer PTC elements to create with permanently attached external contacts.

According to the invention this object is achieved in that

• - Put a metal foil on the plastic body becomes,
• - an intimate surface contact between the metal foil and the surface of the plastic body is put and
• - The metal foil by knife and / or needles or other tools by at least partial on cut or impress in the plastic body is incorporated.

In a method according to the invention, metallic Surfaces of normal and therefore comparatively inexpensive metal foils on a thermally softened plastic body like this imposed that an intimate surface contact between the Metal foil and the surface of the plastic body is, as is the case, for example, in a rolling process happens. Then the metal foil is cut by knife and / or needles or the like in the softened plastic body by at least partially cutting or impressing ken incorporated. Through this process, the Contact surface between the metal foil and the conditional conductive plastic body enlarged, on the other hand by this measure protrusions in the metal foil or Imprints created in the plastic material that in the form of barbs in the subsequently cooling Anchor the material firmly.

In a further development, the incision or on press the metal foil into the plastic body agreed depth, so that the plastic body is not can be pierced or severed. Especially at Application of two metal foils on a plastic foil according to claim 10, namely on opposite surfaces, this coordination of the depth of penetration must be observed, since other if conductive connections from one metal foil to another can arise as short-circuit connections, whereby the egg generic PTC element would be bridged electrically.

In an essential further development of the method, the Knife and / or the needles inclined at an angle α Surface normals on the metal foil to the plastic body pressed in. By this measure, the depth of penetration can be reduced with the same effect. In addition, one improved clawing of the metal foil in the plastic body reached.  

The knives and / or the needles are advantageously in Groups pressed in opposite directions on the metal foil. At the low to moderate isotropy of the PTC plastic material in the event of thermal expansion, the metal foil causes forces built up, which is a detachment of the metal foil from the Plastic body or shearing the metal foil from the Contrast the surface of the plastic body. The metal foil is thereby anchored even better in the plastic body or clawed.

In a further development of the feature of claim 4, the Knives and / or needles in an x-y plane, the surfaces plane of the plastic body, in groups at an angle β mutually extending and in particular also partially used overlapping. From a vectorial decomposition of the occurring with thermal expansion of the plastic body Forces result from this measure further power compo nents that detach the metal foil from the surface of the Plastic body prevented.

An alternative approach provides that

• - a conductive powder
• - With grains in particular of a predetermined size order
• - At least partially inserted into the plastic body is rolled or pressed.

According to this approach, individual grains become one conductive powder into the thermally softened material of the Plastic body pressed in and so at least subsequently partially enclosed by the plastic material. The grains are also permanently fixed in the plastic body. The Applying and impressing z. B. by pressing or Rolling in made in a large-scale process the. By specifying grains of a predetermined size order or from a predetermined size interval ensure that each grain is treated equally when pressed or pressed into the plastic body  same amount for anchoring in the plastic material and too Lowering the contact resistance. Are there these grains on the surface of the plastic body itself understandable still electrically accessible from the outside, so that through this conductive powder a distributed electrical External contact is formed.

In a further development of this method, according to claim 7 those rolled or pressed into the plastic body Grains through a conductive varnish and / or chemical metal deposits formation and / or sputtering of a metal at least in the area the surface of the plastic body with each other and electrically connected. So from distributed outside contacts that z. B. by spring-loaded, flat electrodes with a correspondingly low normal resistance to the PTC material can be connected conductively, flat closed Contacts are made that are permanent in the plastic body are anchored. Because of the large surface area of the individual grains and the dosable number of grains each Area unit will also be one in its effective size adjustable contact surface formed with the plastic body.

Another alternative approach proposes that

• - a metal foil with perforations on the plastic body is placed, whereby
• - The thermally softened plastic at least partially is pressed through the perforations.

In this approach, the viscosity of the thermal soften plastic material or its flowability utilized. Under pressure, the viscous material can have holes in it At least partially penetrate the film. After cooling This creates discrete rivet-shaped holes Anchoring points in the form of small noses.

A profiled Pres se or roller assembly can be used so that the plastic  during the pressing process through the perforations of the metal foil in each case can escape into cavities. The measure of emerging art material is by the hole size, the press force as well as the viscosity or the heating of the plastic materials adjustable. Then the arrangement is made all by gluing the film to the still soft plastic body held together. After cooling, the Ver Anchoring in the perforations made the metal foil tight and good conductive contact with the plastic body. By this ver The contact surface between the plastic body will also drive and metal foil in the area of the perforations enlarged.

In an alternative method, the metal foil with a three-dimensional surface structure from mountains and valleys provided, the metal foil in the valleys on perforations points through which the thermally softened plastic body is at least partially pressed through. The profiling the metal foil together with the perforation directly in front of the Connection with the softened PTC plastic mass. In the pressing process of the metal foil thus prepared with the Plastic body itself can then be a flat press or roller plant can be used because the valleys in the three-dimensional len surface structure of the metal foil itself sufficient hardly to accommodate the small amount required for attachment Provide amount of plastic.

According to all three solution principles disclosed above with the respective further developments can according to claim 10 Plastic body in one process step against two overlying surfaces with a metal foil the. This corresponds to a doubling of the above be written measures, the approaches among themselves can also be combined. In particular, that Plastic material also in viscous form the pressing process be fed.  

Embodiments of the invention are described below with reference to FIG Drawing explained in more detail. The drawing shows:

Figure 1 is a sectional view of a plastic film with contact surfaces produced according to a first embodiment of a method.

Fig. 2 is a sectional view of a plastic film with contact surfaces and produced according to a second embodiment of a method

Fig. 3a, 3b sectional representations of an embodiment of a method according to a third under USAGE dung profiled metal foils produced with two difference union surface profiles plastic film with contact surfaces.

In Fig. 1 shows a sectional view of a manufactured according to a first embodiment of a method plastic film 1 with contact surfaces 2. After placing metal foils 3 on the surface 4 of the plastic body 5 , the metal foil 3 is in each case by pressing with a knife or needles in the plastic body 5 incorporated, which is not shown in Fig. 1. The knives or needles are inclined at an angle α to the surface 4 , so that sufficiently long anchors can be formed in the plastic body 5 at a shallow depth t for permanent anchoring of the metal foils 3 .

The impressions 6 arranged on the top and bottom of the plastic body 5 against the opposite side can also be staggered. Such impressions 6 are preferably combined into groups 7 and applied in pairs with a respective opposite inclination α in a continuous sequence on a metal foil 3 .

In Fig. 2 is a sectional view of a plastic film 1 with contact surfaces 2 is sketched, which has been produced according to a second embodiment of a method. Here, a conductive powder 8 is applied to the surface 4 of the plastic body 5 , the grains 9 are of a size in a narrow interval. The grains 9 are pressed during pressing through the surface 4 into the plastic body 5 with an approximately uniform depth t, with each grain 9 subsequently having a freely accessible surface 10 . On this free surface 10 of each grain 9 of the conductive powder 8 , a largely closed contact surface 11 can be produced in a follow the process step by metallization, as shown in broken lines in FIG. 2. The contact surface 11 then corresponds approximately to a thin metal foil.

FIGS. 3a, 3b show a sectional view of a according to a third embodiment of a method under USAGE dung profiled metal sheets 12 with two different surface profiles fabricated plastic film 1 with outwardly substantially closed contact surfaces 11.

The embodiment of FIG. 3a has a triangular structure in section with a periodic sequence of mountains 13 and valleys 14 . In the valleys 14 there are perforations 15. Through the perforations 15 z. B. in a rolling mill, the at least on its surface 4 thermally softened plastic material of the flat plastic body 5 pressed in the form of lugs 16 . This results in a type of rivet connection between the plastic body 5 and each contact surface 11 to which the surface 4 presses. The formation of the contact surfaces 11 as profiled metal foils 12 increases the rigidity of the contact surfaces 11 in the pressing process and at the same time creates sufficient space for receiving the lugs 16 even when using simple rollers with a flat surface in the region of the valleys 14 .

In Fig. 3b, a profiled metal foil 12 is shown with a periodic rectangular structure, which fulfills the same function as the structure of Fig. 3a.

Claims (10)

1. A method for attaching and / or attaching at least one metallic surface to a surface of a thermally softened plastic body, in particular a plastic film with electrical conductivity and a PTC characteristic of the electrical resistance, characterized in that

• a metal foil ( 3 ) is placed on the plastic body ( 5 ),
• - An intimate surface contact between the metal foil ( 3 ) and the surface ( 4 ) of the plastic body ( 5 ) is made and
• - The metal foil ( 3 ) by knives and / or needles or other tools by at least partially cutting or pressing into the plastic body ( 5 ) is incorporated.

2. The method according to claim 1, characterized in that the partial cutting or pressing in of the metal foil ( 3 ) in the plastic body ( 5 ) to a certain depth (t) is carried out. 3. The method according to one or both of the preceding claims, characterized in that the knives and / or the needles are inclined at an angle α inclined to the surfaces normal to the metal foil ( 3 ) to the plastic body ( 5 ). 4. The method according to one or both of the preceding claims, characterized in that the knives and / or needles in groups ( 7 ) are pressed in opposite directions inclined on the metal foil ( 3 ). 5. The method according to one or more of the preceding claims, characterized in that the knives and / or needles in an xy plane in groups ( 7 ) at an angle β to each other and in particular also partially overlap. 6. Method for applying at least one metallic surface on a surface of a softened plastic body, in particular a plastic film with electrical conductivity with a PTC characteristic,
characterized in that

• - a conductive powder ( 8 )
• - With grains ( 9 ) in particular a predetermined magnitude
• - is at least partially rolled in or pressed in.

7. The method according to the preceding claim, characterized in that

• - The grains ( 9 ) rolled or pressed into the plastic body ( 5 )
• - By a conductive lacquer and / or chemical metal deposition and / or sputtering on a metal
• - At least in the area of the surface ( 4 ) of the plastic body ( 5 ) are connected to one another in a planar and electrically conductive manner.

8. Method for attaching and / or attaching at least one metallic surface to a surface of a softened plastic body, in particular a plastic film with electrical conductivity and a PTC characteristic,
characterized in that

• - A metal foil with holes ( 15 ) is placed on the surface ( 4 ), wherein
• - The thermally softened plastic body ( 5 ) is at least partially pressed through the perforations ( 15 ).

9. The method according to the preceding claim, characterized in that

• - The metal foil ( 3 ) with a three-dimensional structure from mountains ( 13 ) and valleys ( 14 ) on the surface ( 4 ) is provided, wherein
• - The perforations ( 15 ) in the valleys ( 14 ) who arranged.

10. The method according to one or more of claims 1-5 or 6-7 or 8, characterized in that the plastic body ( 5 ) in one process step on two opposite surfaces ( 4 ) is provided with a metal foil ( 3 ).