WO1996018285A1 - Direct and selective process for applying protective layers - Google Patents

Abstract

A process is disclosed for directly and selectively applying a protective layer (4) on a (metal) surface (1) by means of an electronically positionable mechanism that punctually applies a liquid on the surface. The protective layer (4) is formed when the liquid applied so as to punctually wet the (metal) surface (1) dries up. The protective layer (4) protects the surface against a chemical, physical or combined physicochemical treatment, so that only the spots (3) that are not covered by the protective layer (4) are exposed to the surface treatment. The application mechanism is positioned by mechanical means and by a program that reads the information describing which spots (2) of the (metal) surface (1) are to be covered and converts it into positioning data. This process enables a protective layer (4) to be directly and selectively applied on a (metal) surface (1) without intermediate steps such as the photochemical production, exposure and development of a film. This reduces not only the number of operations but also the environmental impact.

Description

Process for the direct and selective application of protective layers

The patent includes an improved method and devices for carrying out the method according to the preamble of claim 1.

Currently, labor-intensive and environmentally damaging processes are used in electroplating and especially in the customized production of electronic circuit boards (= printed circuit before the electronic components are assembled and soldered). Printed circuit boards are manufactured by producing printed circuit board base material (which consists of the insulating carrier layer and the one- or two-sided full-surface copper layer) and subsequent production of the customer-specific printed circuit traces (layout). The process described here is to be used, among other things, starting from the base material for the production of the customer-specific conductor tracks.

In order to apply the template, which is usually created and available in the form of data on a data carrier, to the (metal) surface, a photographic film of this template is first created in the methods currently used. The (metal) surface is coated over the entire surface with a photosensitive coating. With the photographic film, the photosensitive coating on the (metal) surface is exposed and then developed, so that parts of this coating are removed in accordance with the photographic template. This can result in a positive image (the black parts in the template remain as a protective layer on the (metal) surface) or a negative image (the black parts in the template are removed and the (metal) surface is exposed) Template on the (metal) surface.

Another common method of producing the cover layers on the circuit board base material is the use of screen printing techniques. As with the method described above, a photographic film with the desired layout must also be exposed. A photo-sensitive substance is applied to a fine-mesh stainless steel or plastic mesh, exposed with the photographic film and developed. This creates a template for pressing the screen printing lacquer onto the circuit board base material using a doctor blade. The resolution that can be achieved depends on the mesh size of the screen printing fabric used. These currently used processes result on the (metal) surface

Locations that are not covered and locations that are covered with a non-metallic layer that are necessary for the subsequent chemical treatment to achieve the desired different surface properties.

For example, when manufacturing single-sided copper-coated circuit boards using the methods described above, a non-metallic protective layer is applied to those parts of the

Copper surface applied, which should be retained after the etching process, since the etching solution cannot attack on the covered surfaces. After etching the bare

ERSATZBLAH (RULE 26) The etching is stopped and the protective layer is removed, creating the desired conductor pattern.

It is only important that those parts of the (metal) surface (1) that are not to be chemically treated (2) are covered before the chemical treatment and that those areas that are to be subjected to the chemical treatment are uncovered (3). This is exactly what the process described here and patent pending does:

The non-metallic protective layer (4) is applied selectively and directly, so that only those parts of the (metal) surface (1) are coated that are necessary in the subsequent chemical, physical or combined chemical-physical treatment process (2). Those parts of the (metal) surface (1) where the treatment is to take place (3) are not covered. This selective and direct application of a non-metallic protective layer (4) to the (metal) surface (1) is achieved by the use of electronically controlled, positionable axes, which provide a mechanism for the selective application of a substance over the entire (metal) surface (1 ) position. It is possible that the

Application mechanism, the (metal) surface or both are positioned. The application mechanism consists of at least one nozzle which controllably dispenses a substance of variable volume and e.g. forms a grid of dots on the (metal) surface. As the solvent of the substance evaporates, neighboring application points run into a continuous film. After the substance has hardened, a protective layer (4) adheres to the (metal) surface (1).

With this non-metallic protective layer, (metal) surfaces can not only be treated chemically, but also electro-chemically or physically. For example, Metal surfaces are reinforced by means of galvanic methods and other surfaces can be cleaned or removed by sandblasting.

A similar technique is used in the currently used ink jet printers, in which the print head is positioned over a white sheet of paper and ink is applied to the paper according to the electronic information. This results in a selective coating of the paper with ink, which at best results in a paper page printed with letters and / or drawings after the ink has dried.

A (metal) surface (1) can also be coated with a protective layer (4) which is resistant to the subsequent chemical treatment process, using the same method for the selective application of ink to a white sheet of paper.

If you rebuild an inkjet printer in such a way that it can pull in and print cut-out circuit board base material and use, for example, diluted LACOMIT from Canning Ltd., Birmingham, UK, as an ink replacement, a device for the direct and selective application of a non-metallic protective layer is realized. The adapted inkjet printer is controlled by a computer that the Has printed information of the surface coverage in electronic form in a file.

This patent application includes the selective and direct application of a non-metallic protective layer (4) which is resistant to the subsequent chemical, physical or combined chemical-physical treatment onto a (metal) surface (1) with electronically positionable mechanisms, whereby only those parts are covered which should not be subjected to further chemical treatment (2).

In this method proposed here, the production of a photographic film and the exposure and development of the photosensitive layer applied over the entire surface are dispensed with. Not only is there a significant reduction in the number of work steps and thus working hours. Treatment steps (application and development of the photosensitive layer) are also no longer necessary, as a result of which the chemical residues of these processing steps are eliminated and this process contributes to minimizing environmental pollution. Another advantage is the direct use of electronically stored layout information, which is created when using standard layout and routing programs.

The process for which a patent has been applied is primarily intended for applications in the field of galvanic surface treatment and the manufacture of printed circuit boards, although other possible uses are not excluded.

Description of FIG. 1 (schematic cross-sectional representation of a (metal) surface which is selectively covered with a protective layer):

The accompanying FIG. 1 shows a schematic representation of a cross section through a (metal) surface (1), some parts of the (metal) surface (1) being covered by a protective layer (4). In chemical, physical or combined chemical-physical treatment, only those parts of the (metal) surface (3) are

Treatment exposed, which are not covered by this protective layer (4). On the other hand, the parts of the (metal) surface (2) covered by the protective layer (4) are not exposed to the treatment.

Legend:

1. (metal) surface

2. Part of the (metal) surface which is covered by the protective layer and where chemical treatment cannot attack.

3. Part of the (metal) surface that is not covered by the protective layer and where chemical treatment can attack. 4. a protective layer resistant to the chemical treatment, which is placed on the (metal)

Surface adheres firmly.

Claims

PATENT CLAIMS 1) Method for the selective application of thin non-metallic protective layers on (metal) surfaces for the production of electronic components in preparation for a subsequent chemical, physical or combined chemical-physical treatment, characterized in that these layers by means of an electronically controlled and in at least two degrees of freedom Positionable device can be applied directly with at least one nozzle, wherein the application mechanism can be positioned above the (metal) surface, or the (metal) surface below the application mechanism or both. 2) Method according to claim 1, characterized in that the positioning of the Application mechanism and / or the (metal) surface and the application of a substance which forms a layer adhering to the surface is carried out repeatedly until the desired selective coverage of the (metal) surface is achieved. 3) Device for performing the method according to one of claims 1 to 2, characterized in that it consists of an inkjet printer which is electrically controllable and can be positioned in at least 2 degrees of freedom and has at least one nozzle, the nozzle above the surface or the surface below the nozzle or both can be positioned relative to each other. 4) Device according to claim 3, characterized in that the nozzle (s) controllably emits a substance of variable volume.