CH627405A5 - Process for producing basic material for printed circuits - Google Patents

Description

The invention has for its object to avoid the disadvantages of the known designs and to provide a method for producing materials for printed circuits, which are characterized by low price, low and thus the «undercut» avoiding thickness of the metal layer in which the costs of etching are reduced, which do not have to be subjected to dangerous and costly processes as in the known supports made of aluminum or copper, which do not involve any difficulties and do not involve any special operations relating to the connection of the copper layer to the laminate, and in which no material is lost as waste.

35 This object is achieved according to the invention by a method for producing base material for printed circuits, which has the following steps:

a metal layer with a thickness in the range from 0.1 to 100 / im is applied in a continuous process to a film consisting of insulating material;

the composite material formed from the metal layer and the foil is cut to approximately the same size as the core sheet intended to form the laminate;

45 the composite material is placed on one of the outer core arches with its metal layer on the outside; and the composite material and the core sheets are pressed together to form a homogeneous body using pressure and using elevated temperature, and are thus combined with one another.

As can be seen, the method according to the invention allows a very thin layer of copper or other metal to be applied to the laminate, the film of insulating material forming a cover layer of the laminate, 55 with no material being lost as waste, with no difficulties in connecting the metal layer to the Surfacing the laminate and no separate operation is required for connecting the foil carrying the metal layer to a previously compressed laminate.

Further developments and modifications of the invention result from the following description of exemplary embodiments and their illustration in the accompanying drawings and from the dependent patent claims.

In the drawings are:

1 is a perspective of a metal-clad film made of insulating material,

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2 shows a perspective of a base material, on the top or bottom of which a metal-clad film according to FIG. 1 is attached with the film in contact with the base material,

3 shows a perspective of a foil laminated on both sides,

4 shows a perspective of a base material on the upper side of which a metal-clad film is attached and on the underside of which a metal-clad film shown in dashed lines according to FIGS. 1 and 2 can be attached,

5 shows a perspective, partly in section, of a base material covered on both sides with metal-clad foils according to FIG. 1 and a galvanically metal-clad bore extending across the foils and the base material,

6 shows a schematic representation on a larger scale of the arrangement of two metal-clad foils and a plurality of core sheets before they are jointly pressed according to the invention into a block illustrated in FIG. 5, and

Fig. 7 is a schematic representation of an electrochemical coating of a film with metal.

The flexible, sheet-shaped composite material 20 illustrated in Fig. 1 consists of a non-metallic, relatively thin, e.g. plastic film 21 and a metal coating 22 attached to this film. The metal coating or cladding 22, the production of which will be described later in connection with the explanation of FIG. 7, for example, preferably has a thickness of 0.1 to 100 μm, while the thickness of the film is preferably 20 to 200 µm, with specific thicknesses being preferably 5, 10, 20 and 35 mm for the metal deposit and 50 or 100 µm for the film.

The material 20 illustrated in FIG. 1 is, as illustrated in FIG. 2, connected to the side of the film 21 in the manner according to the invention to be described later with a laminate 23. The thickness of the laminate can be 0.2 to 73 mm and is preferably 1.5 mm.

As indicated in FIG. 2, a second metal-clad material 20 can also be attached to the other side of the laminate 23.

Fig. 3 illustrates a double-sided metal-clad thin, flexible composite material 31 with an inner electrically insulating film 32 and outer metal coatings 33 and 34 attached or deposited on the two sides thereof. The composite material 31 is, as shown in Fig. 4, with one of the metal sides united on the surface of a laminate 35. A composite material 20 of the type shown in FIGS. 1 and 2 can be provided on the other side of the laminate 35, or a double-coated composite material according to FIG. 3 can also be attached (not shown) on the other side.

5 shows conductive connections between the metal coatings 22 on both sides of the laminate 23 and the foils 21 attached to them. This cross-connection can be established by using core-catalyzed material both for the foils 21 and for the carrier 23, so that in a chemical metallization bath metal, preferably copper, is deposited on the wall of a hole penetrating both the foils 21 and the laminate 23 as a tubular conductor 36. In the area of the hole which is not protected by an insulating cover, plate-like thickenings 37, which adhere to the metal coatings 22 in a conductive manner, then form at the ends of the tubular conductor 36.

FIG. 6 schematically illustrates how core sheets 36, 37, 38, 39 and composite sheets 20 (consisting of insulating film 21 and metal layer 22 according to FIG. 1) cut to the same size are arranged with respect to one another before using them for a sufficiently long time, and if necessary elevated temperature, to a homogeneous laminate having the metal layers 22 of FIG. 5 on both sides.

The core sheets 36 to 39 are made of resin-impregnated paper or other suitable material. The thickness of the core sheet, before pressing, can be 0.2 to 7.3 mm, but preferably about 1.5 mm. The foils of the cover sheets 20 can advantageously consist of glass fabric impregnated with epoxy resin. The thickness of the cover sheets can be 50 to 300 µm and the full metal cladding 0.1 to 20 µm.

As can be seen, the application of the metal layer or layers fits in one step with the production of the laminate, and there is nothing to remove but waste; on the contrary, the film or films reinforce the laminate and can be planned to achieve its overall thickness.

7 schematically illustrates an electrochemical coating of a film 67, which is guided from a rotatable roller 68 via deflection rollers 69 to 73 first through an activation container 74 and then via further deflection rollers 75 to 78 through a container 80 containing a chemical metallization bath 79 and finally over others Deflection rollers 81, 82, 83 a rotatable roller 84 receiving the metal-clad film is wound up.

For activation within the container 74, metal solutions, metal colloids (copper colloid), graphite or conductive lacquers can be used, which activate the film 67 on one side or on both sides by means of the line 85 and the devices 86 or 86 and 87 so that the chemical Metallization bath 79 deposits the metal coating (not shown) on the film 67.

After the film 67 has passed through the metallization bath 79, the film 67 and the metallic precipitate in the region between the deflection rollers 81 and 82 are dried, neutralized and hardened by means of devices not shown for this purpose.

Photoforming (copper oxide) on glass fabric impregnated with epoxy resin has proven to be particularly advantageous.

In the following, a few of the numerous special, not graphically illustrated, application and training examples of the invention are briefly mentioned.

The invention can also be used in connection with either the so-called additive or the subtractive method.

When using the additive method, only a thin metal deposit is initially produced, which is then later, either before or after the areas to be left as conductors etched away, brought to the required thickness by electrogalvanic precipitation.

In contrast, in the subtractive method, the metal layer is produced in the required final thickness, and the parts of the coating that are not to be used as conductors are then etched away in the usual way.

When selecting the material for the metal to be coated, it must be taken into account that adhesion with the base carrier can be created, that the material does not give off vapors in high-vacuum coating, or that the material is not inadmissible by the activating agents or the chemical plating bath in electrochemical coating is attacked.

Thermoplastic materials are particularly suitable as films; Insulating films, reinforced, for example, by

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Glass silk fabric; Insulating films that are made adhesive by pressure, heat or a solvent for attachment to the carrier material.

Copper, silver, aluminum, nickel, gold, iron, cobalt, ferromagnetic materials and alloys can be used for metallic lamination of the film.

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Claims (7)

627 405 1. A method for producing base material for printed circuits, in which a metal layer is applied to a laminate consisting of a plurality of core sheets lying one on top of the other, characterized by the following steps: a metal layer with a thickness in the range of 0.1 to 100 mm is applied in a continuous process to a film made of insulating material; the composite material formed from the metal layer and the foil is cut to approximately the same size as the core sheet intended to form the laminate; the composite material is placed on one of the outer core sheets with its metal layer on the outside; and the composite material and the core sheets are pressed together into a homogeneous body using pressure and using an elevated temperature and are combined with one another. 2. The method according to claim 1, characterized in that a metal layer is continuously deposited on both sides of the film of insulating material and the one metal layer is placed on one of the outer core sheets. 2nd PATENT CLAIMS 3. The method according to claim 1 or 2, characterized in that thermoplastic is used as the film. 4. The method according to claim 3, characterized in that a film reinforced by glass silk fabric is used. 5. The method according to any one of the preceding claims, characterized in that the film is made adhesive for the purpose of connecting it to an outer core sheet by pressure, heat or a solvent. 6. The method according to any one of the preceding claims, characterized in that copper, silver, aluminum, gold, iron, cobalt, ferromagnetic materials or alloys are used for the metal layer. 7. The method according to any one of claims 1 to 6, characterized in that foils provided with a metal layer are applied to the two outer core arches, and that metal is galvanically deposited in holes in the foils and the laminate formed by the core elbows, which the mutual metal lamination leading connects. It is known for printed circuits to fasten a metal foil, in particular on an essentially rigid, electrically insulating base material, such foils being produced in a special operation. In the case of laminate materials formed from phenolic paper as the base material, it is essential to use an adhesive for connection to the metal foil. This adhesive coating is not required for laminates based on epoxy. The film must be relatively thick so that it does not develop cracks when pressed together with the so-called core sheet of the laminate. The production of the metal foils in a separate work step represents an enormous cost factor. The foils, which mostly consist of copper, are, as said, necessarily relatively thick, which results in large metal consumption and a correspondingly high weight. In addition, when the thick copper layer is etched under the cover, there is approximately a lateral one corresponding to the thickness Undercutting from both sides, the so-called "under-cutting". The reduction in the thickness of the copper foil is limited by the fact that the manufacturing costs increase to a certain thickness, that the handling becomes more difficult, and finally the foil alone the high pressure required for pressing it together with the core sheet of the laminate couldn't record. In order to reduce the thickness of the copper layer and to produce so-called thinclad materials, it has been proposed to use a thin copper layer, e.g. about 5 to 8 / xm thick, by electrodeposition on an aluminum support and remove the support after combining the film with the core sheet of the laminate. The use of this material is limited due to the price reasons and the problems associated with the removal of the aluminum carrier, which is lost as waste of the aluminum carrier, although the industry for producing printed circuit boards for fine conductor technology is in great demand. The pickling of the aluminum carrier has led to explosions in certain devices, since the chemical decomposition of aluminum produces oxyhydrogen.