DE19544480A1 - Simple and rapid circuit board prodn. - by adhesive bonding of pre-structured conductive layer onto substrate - Google Patents

Abstract

A circuit board prodn. process involves structuring an electrically conductive layer according to a layout prior to adhering onto a substrate. The structure may be produced automatically or manually by a mechanical and / or thermal method. Also claimed is a circuit board produced by the above process. Further claimed is an appts. for carrying out the above process, the appts. having: (a) an energetic radiation sources (15) and a support roller (19) for the layer to be structured, the source and the roller being mounted on a fixed base plate (1) for relative motion in four directions; and (b) a plate (18) which supports a substrate (22) on the base plate (1) and which is adjustable parallel to the base plate in two directions roughly matching two directions of relative motion between the source (15) and the roller (10).

Description

The invention relates to a method and an apparatus for Production of printed circuit boards according to the preamble of patent claims 1 and 11, and one produced by the process according to the invention Circuit board.

It is known, for example, from DE 33 35 184 A1, a substrate (epoxy or hard paper) with a thin film of an electrically conductive Material, preferably copper, with the interposition of an adhesive to prove by means. The adhesive ensures after a tempering process a solderable connection between the electrically conductive material and the substrate material. The surface of the electrically conductive Material is provided with a photoresist on which it is applied a photo mask, a corresponding layout, and subsequent Exposure trace structures are fixable. According to the photographic Development and neutralization as well as cleaning in a water bath parts of the electrical material are stripped of the photoresist layer, that were not previously fixed. Preferably by chemical Etching is the electrically conductive that is not required for the conductor routing Material removed. Then the one that has stopped along the ladder fixed photoresist eliminates the now surface of the substrate dried and sealed and the circuit board thus obtained for the Equipped with electronic components. The multitude of the specified operations illustrates the tediousness and Cumbersome procedure. Beyond that arise with this Processes polluting substances in the form of alkalis, acids and solvents, their disposal with a relatively high cost must be operated. Likewise, a considerable effort is required Recovery of the electrically conductive material that is not required required. The base material prepared with photoresist is also closed discard, which are protected with plastic film against UV light must and because of overlay its actual purpose cannot be fed.  

The processing of printed circuit boards with high energy is also known Radiation and releasing the electrically conductive layer to be removed Masks, see DE 36 29 822 A1. The procedure is also in this case cumbersome because first the entire substrate adheres firmly with an elec tric conductive layer and then adhesive layer and Large parts of the conductive layer must be removed again. Also comes it also when removing the previously applied layers to abtra conditions from the surface of the substrate and thus undesirable Material mixing and material loss.

The invention is therefore based on the object of a method for Manufacture of circuit boards to create that in terms of its applications simple, its material consumption economical, its after-treatment development phase is short and its ecological compatibility is favorable. It should be the necessary operations in PCB manufacturing reduce and the formation of environmentally harmful substances or Avoid mixtures of substances.

According to the invention, this object is achieved by the characterizing Features of the first claim solved. So it will only be for them Conductor routing on the substrate required electrically conductive Material in the desired structure from the existing material foil separated, provided with an adhesive material and in one work applied to the substrate. That can be done both by creating Isolation channels in a full-surface used or glued Film as well as by extensive evaporation of the unnecessary Conductor material as well as the combination of these two variants happen. Doing so can dispose of excess material with a vacuum pipette be lifted off. For a good bond between the substrate and the structured film are both the adhesive and the adhesive side the film of importance; they require a certain selection or Pretreatment. Epoxy resins, hardeners and Find accelerators from Ciba Geigy. Using a copper foil, it is advantageous to stick it on its adhesive side Adhesion promoter, e.g. B. a triment layer (zinc layer) for one Epoxy adhesive or a quick-curing contact adhesive.  

Also can be between the conductive layer and the substrate in the PCB industry usual "prepegs" are used with Prepare epoxy resin-treated fabric panels. When warming up 180 ° C over 120 s creates a good connection between the carrier and Foil. If a copper foil is used as the conductive layer, it can For example, have a thickness of 70, 35 or 18 microns.

The desired structure is removed from the film by means of Lasers, preferably infrared lasers, or by means of other high energy Rays; it can also be done with a jet of water or by milling, Sawing, scratching, etc. can be made and is either timed and locally separated from the occupancy process or in one work step with the occupancy, immediately before this. When structuring the Foil made of electrically conductive material preferably adheres to it a cylindrical body (roller, drum) by suction or Glue. It is between the film and the cylinder, for example Glass exists, an intermediate layer supporting the adhesive effect, e.g. B. Tissue paper or scotch tape introduced and the processing by Laser beam made. The material of the liner is u. a. from Foil material, depending on the foil thickness and the laser power. The Excess film material can be separated and removed or vaporized over a large area. But it is also within the scope of Invention, the structuring of the film on a flat table carry out and this in a suitable manner to the substrate transfer. When using one or more lasers for Structuring the metal foil is laser pulse time, feeding the foil and laser energy matched to the film thickness and the film material.

If the substrate is to be coated with several conductive layers one above the other the allocation process takes place several times in succession, if necessary with different structures take place, although between two successive layers of appropriate insulation layer is to be arranged. With automated or partially automated The layout data can be used to structure the electrically conductive layer according to the known methods of data processing in the processing automatic machines can be entered. This makes it possible for the first time with  to design a layout for a corresponding unbundling software, existing data on diskette via the network path or modem to the machine and thus produce the circuit board. It but there is also the possibility of existing layout structures of paper or other material and machine-compatible Generate data using a vectorization program. Also are special for structuring the electrically conductive layers developed machines with high mechanical resolution for Available, the optimization of the structure only when removing, do not position them until the substrate is loaded Control programs for the structuring and transmission units contain and design options in more than one level consider. The structures obtained in this way can be found on the Substrate discrete components are assigned.

The supply and application of the electrically conductive layer, preferably the copper layer, on the substrate or base material takes place with a transport device, which the separated Conductor tracks on a roller or a machining table electro fixed statically, vacuum technology or with other liability options. The transport device itself can be based on mechanical, magnetic, be moved hydraulically or pneumatically. When documenting of the base material with the structured layer or film between the latter and the substrate at the relevant junctions an adhesive is applied that is only at these locations for a solderable Connection between the film and the substrate ensures. The adhesive but can also be applied to the substrate and then the structured layer can be applied if the adhesive layer is the same serves the sealing in time. The transmission of the structured film on the substrate by rolling the roller from one defined beginning, so that deformations of the structured film their occurrence cannot occur. According to the invention The finished printed circuit board is applied to the substrate without chemical post-treatment or further treatment for assembly with construction elements or for installation in a circuit or device supply.  

A Vorrich is used to carry out the method according to the invention suitable for a radiation source on a solid base plate high-energy rays and a roller as a carrier of the to be structured Layer movable in four directions of movement relative to each other has and in which a table as a carrier of the substrate parallel to and on the base plate is arranged adjustable in two directions, which at least at least approximately with two directions of movement of the relative movements match between the radiation source and the roller. The radiation source is advantageously a laser. Between the Radiation source and the roller can be a flexible waveguide be arranged. It is favorable to turn the roller about an axis X-X store and the end of the located near this roller To store waveguide movable in three coordinates.

The invention enables the creation of space in a simple manner structures, the implementation of ultra-fine conductor technology down to 5 µm Width resolution and design options not previously possible skills in PCB manufacturing. It not only leads to reduction Reduction of expenses by avoiding etching processes, but also to save energy, known to produce it Lich polluting combustion processes may be necessary. The quality of the resolution is determined in particular by the material and the Thickness of the foil, the frequency and the power of the laser as well as the Cutting speed determined. Through an exact coordination of all factors determining the cutting quality (resolution) resolutions of <5 µm can be achieved.

In the schematic drawing, a device for carrying out the method according to the invention, preferably controlled by a computer, not shown, is shown in perspective. On a rectangular or square base plate 1 , bearing bodies 2 , 3 , 4 , 5 are fastened at their corners, of which two bearing bodies 2 , 4 and 3 , 5 hold a guide 6 together and on the two larger bearing bodies 4 , 5 bearing 8 , 9 are provided for a roller 10 which is rotatable about an axis XX parallel to the base plate 1 in the direction of a double arrow 7 . A slide 12 is mounted horizontally displaceably along the guides 6 in the direction of a double arrow 11 and in turn has a vertical dovetail guide 13 for a carrier slide 14 of a laser 15 , preferably a YAG laser, which serves as a structuring tool. The laser 15 moves with the carrier slide 14 in the direction of a double arrow 16 . Finally, guides 17 are provided on the base plate 1 at right angles to one another and parallel to the base plate, with the aid of which a table 18 with a carrier material 22 is slidably mounted in the direction of double arrows 19 , 20 at right angles to the laser axis OO. The electrical connections of the laser 15 and the drives of the slides 12 , 14 and the table 18 have been omitted for reasons of clarity. The roller 10 is preferably made of glass and is provided on its surface with a film 21 , which is indicated. If necessary, it can also consist of steel, aluminum or ceramic.

In the above embodiment, laser 15 and roller 10 work together. The film 21 to be structured is held on the roller 10 under vacuum. For structuring, the laser 15 is first brought into the starting position by displacing the slides 12 and 14 along their guides 6 and 13 and the roller 10 along their axis XX between the bearings 8 , 9 and by rotating the roller 10 about this axis. Likewise, the table 18 is suitably assigned to the roller 10 by moving the guide 17 parallel to the base plate 1 . Thereafter, by means of a program-controlled displacement of the roller 10 along the axis XX and by rotation of the roller 10 about this axis, in accordance with a layout, a relative movement takes place between the laser 15 and the roller 10 with the foil 21 , in the course of which the foil 21 with the help of the laser 15 is structured. The parts separated from the film 21 can preferably be removed between the roller 10 and the table 18 , for example by suction. Likewise, the structured parts of the film 21 can be provided with an adhesive layer before they are pressed or rolled onto the carrier material 22 . It is also possible to install the adhesive layer over the entire area of the carrier material 22 and at the same time to use it as a sealing layer. If the carrier material 22 is electrically conductive, preferably metallic, the conductor structure can be applied by means of prepregs or another intermediate layer and an adhesive. Laser energy and feed of the film to be structured are matched to the material and the thickness of the film; For example, with a Cu foil of 18 µm thickness and a laser power of 20 W, the feed rate between the foil and laser can be 50-100 mm / s. Structures down to the micrometer range can be produced by the invention. Instead of the laser 15 and only the end of a can be moved is arranged between laser 15 and roller 10 waveguide as a secondary light source with respect to the roller 10, whereby not only mass problems, but also kinematic problems can be solved more easily. The end of the waveguide near the roller 10 is in this case attached to a cross slide system with three movement coordinates, and the roller 10 only needs to be rotatably supported about its axis XX. The other end of the waveguide is fixed to the laser 15 .

Instead of the roller 10 , a further flat support or only the table 18 can be used, on which the structuring is carried out and the structured film is connected to the substrate. The conductor tracks can be guided around the edges of the circuit board and thus structures on the front and back can be connected to each other. In addition, active and passive electrical components can be assigned to the structures of the circuit board. Worn structures can be regenerated or removed and the substrate can be provided with new structures.

Reference list

1 base plate
2 , 3 , 4 , 5 bearing body
6 , 17 guided tours
7 , 11 , 16 ,
19 , 20 double arrows
8 , 9 bearings
10 roller, cylinder
12 sledges
13 dovetail guide
14 carrier slides
15 lasers (radiation source)
18 table
21 slide
22 substrate (carrier material)
OO laser axis
XX axis of rotation

Claims (13)

1. A process for the production of printed circuit boards, in which at least one layer of an electrically conductive material is adheringly applied to a substrate, characterized in that the layer of electrically conductive material is structured according to a layout prior to its adherent application to the substrate. 2. The method according to claim 1, characterized in that a Adhesive only at the designated connection points between the structured layer and the substrate is arranged. 3. The method according to claim 2, characterized in that at Auf bringing through several structured layers one above the other Insulating layers are separated from each other. 4. The method according to claim 2 or 3, characterized in that the The structure is introduced into the electrically conductive layer done mechanically and / or thermally. 5. The method according to claim 4, characterized in that the Manufacture of the structure automatically or manually follows. 6. The method according to claim 5, characterized in that the structure turured layers are taken from a stack. 7. The method according to claim 5, characterized in that from one Tape to be cut. 8. The method according to claim 6 or 7, characterized in that for transferring the respective structured layer to the substrate a transport device based on adhesive or suction effect is applied.   9. Printed circuit boards, characterized in that they are according to the method have been prepared according to claims 1 to 8. 10. Device for performing the method according to claims 1 to 8, characterized in that on a solid base plate ( 1 ), at least one radiation source ( 15 ) for high-energy rays and a roller ( 19 ) as a carrier of the layer to be structured ( 21 ) are movably mounted in four directions of movement relative to one another, and that a table ( 18 ) is arranged as a support for a substrate ( 22 ) on the base plate ( 1 ) and parallel to it is adjustable in two directions, which at least approximately with two directions of movement of the relative movement between the Radiation source ( 15 ) and the roller ( 10 ) match. 11. The device according to claim 10, characterized in that the radiation source ( 15 ) is a laser. 12. The apparatus according to claim 11, characterized in that a flexible waveguide is arranged between the radiation source ( 15 ) and the roller ( 10 ). 13. The apparatus according to claim 12, characterized in that the roller ( 10 ) rotatable about an axis (XX) and that the near the roller ( 10 ) arranged end of the waveguide is movably mounted in three coordinates.