DE1208972B - Method of bonding a metal having a copper surface to a layer of polymeric fluorocarbons - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C23f

German class: 48 dl -7/02

Number: 1208 972

File number: 113089 VI b / 48 dl

Filing date: April 11, 1957

Opened on: January 13, 1966

The invention relates to a method for connecting a copper surface having Metal with a layer of polymeric fluorocarbons, in which the copper surface was previously is oxidized.

Solid polymerized trifluorochloroethylene is known to be physical, chemical, and electrical Properties that make it particularly suitable for use in electrical engineering. It is hard and tough, but not brittle. Then it is thermoplastic so it can easily be molded into desired shapes can be brought. It is also chemically stable and remains z. B. more concentrated from prolonged exposure Sulfuric acid, aqueous hydrochloric acid, aqueous fluoric acid, strong pickling solutions, ammonia, aqua regia or other strongly oxidizing substances unaffected. Trifluorochloroethylene is also flexible and elastic, water-repellent and insensitive to strong moisture. Electric has this Material has a relatively low dielectric constant compared to many other thermoplastic materials and low dielectric losses.

This opens up many possible uses for this material. Because of its good mechanical Properties and its chemical stability make it a good insulating substrate for printed circuits. Because of its excellent dielectric properties, it can be used in capacitors of small value or as an insulating material for hermetically sealed connections instead of glass or ceramic Material to be used. Since it repels moisture, it can be used to make a good hermetic one Seal for electrical parts, e.g. B. resistors, capacitors and rectifiers are used. For all of these practical purposes, however, it is necessary to combine the trifluorochloroethylene with a metal associate. However, since it is normally not softenable, it does not adhere well to metals. So far, therefore, was the Use of trifluorochloroethylene or polymeric fluorocarbons is limited to cases in where a firm connection with the metal was not required.

It is known to apply a cover layer made of polytetrafluoroethylene to a copper surface to provide this with an oxide layer. The polytetrafluoroethylene is then molded onto this layer applied to an aqueous suspension, which is then heated and hardened. After another known proposal is the polytetrafluoroethylene in the form of a varnish, but also in liquid form. However, it turns out to be very difficult, if not impossible, to

Method of connecting a one
Metal having a copper surface
a layer of polymer
Fluorocarbons

Applicant:

Hughes Aircraft Company,

Culver City, Calif. (V. St. A.)

Representative:

Dr.-Ing. G. Eichenberg

and Dipl.-Ing. H. Sauerland, patent attorneys,

Düsseldorf, Cecilienallee 76

Named as inventor:
Sidney Jacob Stein, Philadelphia, Pa .;
Louis Bernard Allen, Pennsauken, NJ
(V. St. A.)

Claimed priority:

V. St. v. America April 18, 1956 (579 079)

going pore-free and firmly connected to the metal Prepare a layer of a polymeric fluorocarbon on a metal surface if the fluorocarbon is applied in liquid form, apart from the fact that in this case it is difficult to to create a thicker layer on the metal that still adheres.

The invention is based on the object of creating a method of the type specified at the outset, which is free from these defects, but ensures good adhesion and freedom from pores in the top layer and the application of thicker layers is permitted. According to the invention, this object is achieved by treatment with an aqueous alkaline oxidizing solution on the copper surface

509 778/340

3 4

Both copper oxide and copper oxide increase, especially after the first minute holding layer formed, then a preformed the thickness very quickly. The thickness of the copper oxide solid layer of polymeric fluorocarbon begins to equalize after about 4 minutes. the material applied to the surface oxidized in this way, the fact that the thickness of the copper oxide is essential and under the application of heat and pressure S borrowed remains constant while the copper oxide layer connected to her. Namely, it has been found that continuously increasing, there is a possibility that a polymeric fluorocarbon on copper oxide which oxidizes copper oxide to copper oxide. Adheres equally well, while the copper itself is oxidized to copper oxide early on to copper oxide, badly, but well, adheres to copper oxide and thereby a constant thickness of the copper oxide on the other hand is also obtained between copper oxide and copper io. The copper is not more likely to come out of the oxydul has good adhesion. Removed solution through the layer until it is pitch black; because then from copper oxide and copper oxide there is thus a layer of copper oxide which a solid bond between the fluorocarbon - not only with the metal, but also with the hydrogen and the intermediate layer as well as between copper oxide is firmly connected. This layer can this and the copper surface. These two-sided 15 lightly with polymerized Trifluorchloräthylen Adhesion allows the top layer to be bonded from the. When the copper is out of solution polymeric fluorocarbon is taken out as preformed before it is pitch black, so solid and thus pore-free layer of considerable, there is not enough copper oxide present to be good To apply thickness. to adhere to the said plastic. If that

On the other hand, for a better understanding, the process after 20 copper remains in the solution for too long,

of the invention on the basis of drawn execution, the copper oxide is too thick and flakes off. To the-

examples explained in more detail. It shows accordingly the copper must as soon as it is pitch black

F i g. 1 is a graphical representation of the formation of which is removed from the solution and thoroughly cleaned

Oxide layer, wash to interrupt the reaction.

F i g. 2 shows a cross-section through a layered 25. The copper thus oxidized is ready for bonding

Structure made according to the invention to the Trifiuorchloräthylen by application of

Fig. 3 shows a printed circuit with the memory heat and pressure in the usual way,

paint the invention, this method of joining copper with

F i g. 4 a partial section through a hermetically trifluorochloroethylene is particularly successful if

sealed connection, 30 it in the case of foils made of electrolytically deposited

F i g. 5 a longitudinal section through a hermetic copper is applied. The copper can be on a

sealed electrical component and carbon plate are electrolytically deposited

F i g. 6 a perspective partial view of a flexible. Then after the precipitation has decreased

seeds of multi-core cable. the one previously in contact with the plate

The invention is based in principle on the knowledge that 35 surface is smooth, while the opposite surface

that copper oxide works well on solid layers of poly- compared to this, it is matt or rough. It was

mer fluorocarbons, e.g. B. polymerisier- found that the trifluorochloroethylene with the

tem trifluorochloroethylene, adheres. matte surface of the copper foil is much better than

First, a layer of copper oxide is applied to the smooth surface, whether or not

Copper is produced, and this layer becomes a something with a 40 equal in the manner described above

Layer of copper oxide to bond with the less effective bond also with the smooth side

Fluorocarbon substantially covered, can be achieved. The bond strength between

which should be relatively thin; because if it can get through to the copper and the trifluorochloroethylene

If it is thick, it will peel or peel off the copper- the weight will be determined which will be required

oxydul. Therefore the formation of the copper oxide 45 is to be a 2.5 cm wide copper strip from that

to remove trifluorochloroethylene by a slow and easily controllable process. Certain types

desirable by having one of copper foils on a copper plate have a smooth surface with

first layer of copper oxide and then a fine, parallel, straight line that runs across the foil

firmly adhering layer of copper oxide is formed. get lost. It has been found that when this

For this purpose, a chemical oxidation surface is used in the manner described above

Medium used, preferably a hot alkali chlorite, trifluorochloroethylene, which copper in

z. B. a solution of a mixture of sodium one direction parallel to the lines with half

hydroxyd and sodium chlorite in water. The copper of the force is deducted from the trifluorochloroethylene

strip or the copper foil will be at a temperature that can be opposed to peeling

of 95 ° C as long as necessary in the direction of the alkali chlorite solution. This shows that the irregular

dives until it is pitch black. This is done in the uneven or rough surface to form a solid

depending on the temperature, the concentration bond between the copper and the trifluorochlorine

and the age of the solution in about 3 to 10 minutes. ethylene supported, possibly by the fact that the

In Fig. 1 is the mode of formation of oxide with crystal structure of copper oxide so that it is in

the data 60 obtained by cathode ray refraction are affected by the irregularities of the copper surface,

graphically represented. The relative thicknesses of the over- to thereby allow the formation of a firm bond

Trains of copper oxide and copper oxide are in support.

dependence on the immersion time. When in practice this can be oxidized copper strip

so the copper is immersed in the oxidation solution and placed on a strip of trifluoroethylene,

the coating of copper oxide is enlarged. 65 This layering is then at a temperature of

in the first minute very quickly, whereupon the thickness about 230 to 280 ⁰ C together. As soon as that

remains constant. Meanwhile, trifluorochloroethylene is gradually forming its reaction temperature

the copper oxide layer over the copper oxide, and area reached, the structure is a pressure of

subjected to about 35 to 70 kg / cm ² until a firm bond between the strips is established. In general, 1 to 3 minutes are sufficient for this. As the layer cools, the shrinkage of the layers differs and the structure can bend or fold with the undesirable result of stressing or breaking the tie layer. To avoid this, the structure is cooled under pressure, advantageously in a cooling press.

Another type of stratification can be made by a continuous process in which a copper strip is passed first through an oxidizing bath and then through a rinsing bath. Thereon strips of trifluoroethylene are placed against both sides of the oxidized copper strip and the stratification thus formed passed through rollers with the application of heat and pressure to the Connect layers. This gives a lamellar structure according to FIG. 2, which consists of a copper layer 12 and cover layers 10 made of trifluorochloroethylene ordered. Copper oxide layers 13 are connected to the copper, while the copper oxide layers 14 bond with the trifluorochloroethylene layers enter. This way you can have any number of alternating layers made of copper and trifluorochloroethylene.

In Fig. 3, a printed circuit 16 is shown. A strip of copper is first described with a strip of trifluorochloroethylene in the Way connected. Then a desired pattern of copper strips 18 with connection points 20 can be obtained, for example, by etching. Various electrical components, such as resistors, Capacitors and rectifiers, can be connected between the connection points 20 to desired Establish electrical circuits. Around the strips 18 and those connected in this way, not shown To isolate and protect components, an additional layer of trifluorochloroethylene can be placed on top and connected to the strips 18 in the same way. This latter layer is made of trifluorochloroethylene can have openings according to the position of the connection points 20 to electrical To be able to establish connections.

F i g. 4 shows a layered, hermetically sealed fitting 22 made according to the described Process is established. The layer 22 contains a disc 24 made of trifluorochloroethylene with a centrally arranged one-sided shoulder26. Copper layers 28 and 30 are with the two sides connected to the disk by copper oxide, and a connecting wire 32 runs centrally through the disk 24 and through the extension 26 and is connected to the copper layer 28 by soldering 34. The connector 22 can be used to interconnect electrical components from a metal housing are enclosed, in which you the approach 26 with the connecting wire 32 through a hole and the housing is soldered to the metal layer 30. The connector 22 can also be in one Sitting trifluorochloroethylene housing containing electrical components, either in a known manner on the circumference of the disk 24 or on the projection 26.

In FIG. 5, a structure is shown in which the bond according to the invention is used for hermetic sealing of a component, e.g. B. a resistor or capacitor is used. It is in one housing 36 made of trifluorochloroethylene of substantially cylindrical shape a component 38, for. B. a Resistor or capacitor, housed with clamping wires 40, which are connected to the component and extending from opposite ends of the housing. The lines 40 protrude by disks 42 made of trifluorochloroethylene, the inner surfaces of which in the manner described with metal disks 44 are connected. The lines 40 are connected to the disks 44 by soldering 46 and the disks 42 made of trifluorochloroethylene in a conventional manner, for. B. by pressure and heat, im Housing 36 molded in. The discs 42 thus form a fixed part of the housing 36, and the hermetic Sealing for the component is provided by the soldered connection 46 between the lines 40 and the Discs 44 completed.

The process described for binding copper to trifluorochloroethylene has proven to be special Proven well in the manufacture of copper wires insulated with trifluorochloroethylene. The wire can be oxidized in the manner described, whereupon trifluorochloroethylene is sprayed around it, to create a tight bond with the wire.

At elevated temperatures, copper has a tendency to attack the trifluorochloroethylene. With the invention However, it is protected against any such effects.

In Fig. 6, the application of the invention to a multi-core, flexible cable 48 is shown. The copper conductors 50 are parallel and spaced between two trifluorochloroethylene strips 52 and 54. The conductors drawn at right angles in cross section can also have other shapes. The cable will manufactured by a continuous process in such a way that first the conductors are passed through an oxidizing bath are passed through, whereupon the oxidized surface is cleaned and the conductors then between strips 52 and 54 are brought from trifluorochloroethylene. The whole thing then runs under the application of pressure and heat from rolling to make the bond.

Claims (4)

Patent claims: 1. A method of joining a metal having a copper surface to a layer from polymeric fluorocarbons, in which the copper surface is oxidized beforehand characterized in that by treatment with an aqueous alkaline oxidizing agent Solution on the copper surface containing both copper oxide and copper oxide Layer formed, then a preformed solid layer of the polymeric fluorocarbon applied to the surface oxidized in this way and with the application of heat and pressure is connected to her. 2. The method according to claim I, characterized in that the copper surface by means of a chemical, oxidizing agent, which consists of a hot alkali chlorite or contains one. 3. The method according to claim 1 or 2, characterized in that the copper is immersed oxidized in a hot, aqueous solution of sodium hydroxide and sodium chlorite will. 4. The method according to any one of claims 1 to 3, characterized in that as polymeric Fluorocarbon a copolymer containing substantial proportions of trifluorochloroethylene is used. Considered publications: British Patent No. 690,031; U.S. Patent No. 2,562,117; "Pitture e Vernici" magazine, 1953, p. 52. 1 sheet of drawings 509 778/340 1.66 © Bundesdruckerei Berlin