DE1690274A1 - Process for the production of wiring boards with more than two line levels (multilayer circuit boards) - Google Patents

Description

IELEFUNKIN Patent exploitation team

m «b» H * Ulm (Danube), Elisabethenstrasse 3

Ulm (Danube), June 22, 1967 ΪΈ / PT-Ka / Eg - U 81/67

"Method of making more as wiring boards having two line levels (Multilayer circuit boards) "

The invention relates to a method for producing Wiring boards (multilayer circuit boards) which have more than two line unevenness and are made up of one another layered and glued to one another, planar cable runs for the individual conductor levels are composed of supporting plates made of insulating material and which have recesses lined with metal coverings and penetrating the entire wiring board; Cable runs of the conductor levels are in conductive connection with these Metal1 coverings in the recesses and In addition, the components are connected to these metal coverings in the recesses.

Such multiple titre plates are therefore always acceptable more sum use because the connectivity that

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a double-laminated circuit board offers, with today's Technology is often not enough. In multilayer circuit boards of this type, the components are, for example, directly on the surface of the multilayer circuit board applied »with the connections of the components bit electrically connected to the metallized recesses are. Such multi-layer circuit boards can also be used to produce the connections between plug-in cards on which the components are applied. In this case, the metallizations in the recesses are connected to the conductive paths on the Plug-in cards conductively connected.

Se is known, multilayer circuit boards according to the following Manufacturing process: Carrier plates are assumed that only have a metallization on one of their surfaces. By using the usual methods (screen printing or applying the negative line image with phototechnical means and etching) the desired conductor mueter is then produced from the metallizations, however, with the exception of the line patterns, which are on the surface of the finished multi-layer printed circuit board The carrier plates with the conductor pattern for the individual conductor levels are then glued together, which is the case with the previously known method by inserting a

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Ί690274

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Prepreg-SOlie and by heating and pressing the stacked carrier plates in a special tool happens · During this process, the prepreg film softens and glued the support plates lying on top of one another. Then the required recesses z. B. by Drilling introduced. These holes are then copper-plated. Because of this through-copper plating, the the conductor patterns are not yet applied to the surfaces of the multilayer circuit board. Finally will then the line pattern is also applied to the surface of the multilayer circuit board.

The known manufacturing process for such multilayer circuit boards has various disadvantages. So is the tool required for gluing is very expensive because it is necessary to put the multilayer circuit board on a to heat a very specific temperature, and because, in addition, a high pressure must be generated. In addition, at the known method a high percentage of rejects. This high percentage is mainly due to the contact between the conductors and the individual conductor levels the copper coatings of the recesses produced by copper plating is very critical. At the time of the

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Copper surrounds the individual cable suction Drilling only with the very small inner surface of a very thin ring · Finally, it is also disadvantageous that if an imprecise hole occurs, an almost finished and therefore already expensive part becomes scrap.

The object on which the invention is based is to create a manufacturing process for such circuit boards that does not have the disadvantages mentioned above, So in which no very expensive tools are needed, in which the scrap is very low in the production and in the case of an inexact drilling that does not result in a very expensive component, because it is almost finished must be thrown away-

This object is achieved in that of Carrier plates with metallization on both sides are assumed that these carrier plates are preferably carried out simultaneously for all · carrier plates of a wiring «flat θ the recesses be introduced that then these recesses are lined with a first metal layer, and with Exception on the two surfaces of the finished wiring board from the metallizations of the carrier boards in themselves the required line pattern can be generated in a known manner,

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that then the carrier plates are glued together, preferably with an insulating film in between, that after removing glue residue in the recesses and optionally the insulating film parts penetrating the recesses, a second metallization of the through recesses is carried out and that finally the required line patterns are produced on the surface of the wiring board.

Since carrier plates with two-sided metallization are assumed, the thickness is that according to the invention Process produced printed circuit board compared to the printed circuit boards produced by the known method also even less big.

According to one embodiment of the method according to the invention the conductor pattern is applied to one of the later surfaces of the wiring board before the recesses are made jointly in all carrier plates the introduction of the recesses, for example drilling. To facilitate the manufacture of the wiring boards is It is also advantageous to provide parts on the carrier plates that protrude beyond the target plate size. For example, you can

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the carrier plates a circumferential band of z. B, 15 now have. Guide openings are made in these parts protruding beyond the target plate size, e.g. B _- stamped. When the recesses are produced together and, if necessary, also when the plates are glued, these openings are introduced into guide pins of a fistewool. This ensures that the plates to be stacked on top of one another are always exactly on top of one another, so that the holes in the individual plates are aligned with one another when gluing. After gluing, the protruding parts are then separated with the guide openings. If you also make guide openings in the parts with which the line pattern is applied, i.e. the film negatives or »printing screens, which can be made in the carrier plates together with the guide openings, for example, a carrier plate is also ensured during the production of the line nueter, that the film negative or printing screen and the associated circuit board are in the correct position in relation to one another. For this purpose, the guide openings in the carrier plates and the film negatives or printing screens are inserted into guide pins.

The tool for making the guide openings in the

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Carrier plates and optionally the film negatives or Printing screens is extremely simple. «It consists of two plates, e.g. B. metal plates, one of which is guide pins for the wide plate and this has corresponding holes. These guide pins ensure that the plates at lie on top of each other in the same position for each work step. Between these two plates are stacked Carrier plates and optionally the film negatives or Pressed in pressure screens. The two metal plates point at the points where the guide openings in them Carrier plates are to be introduced, holes through which the guide openings are made with the help of an indented punch. At the. Production of the recesses In the carrier plates, these guide openings are introduced into guide pins in a corresponding tool.

The tool described above can also be used for gluing Metal plate, where the guide openings are in the carrier plates, only be provided with guide pins. Naturally a second tool can also be provided for this operation. Even when gluing, they are piled up Carrier plates pressed together. 2 »To glue a liquid glue, z. B. araldite, applied to the carrier plates, for. B.

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on coated to accelerate the drying of the adhesive, the carrier plates pressed together in the tool described above can be heated.

The liquid adhesive also penetrates the through holes in the multilayer circuit board. aside from that are the holes when using an insulating film to isolate the cable runs of two adjacent ones Carrier plates no longer continuous. According to one embodiment of the method according to the invention, these interfering parts are removed from the through bores by a second drilling process with one in his The diameter of the drill was slightly smaller (e.g. 0.05 && smaller) compared to the previously used drill will. This drilling process ensures that the metalized walls of the through openings are freed from adhesive, and that the disruptive parts of the insulating film are also eliminated. This drilling process is not critical because the Self-centered drill. The second through-copper plating, in turn by electroless deposition of copper and electrolytic After-copper plating produces wisd, reinforces the original copper plating of the carrier plates and connects them Such neighboring through-copper plating by over-copper plating of the hole surrounding the hole through which the hole was drilled

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Isolierstoffolien formed ring. Because of the double copper plating it is ensured that the connections »between the lines and the copper plating are uncritical which means that the reject rate is very low. Finally, you can see the lines on the surfaces the multilayer board is also provided with a tin coating.

The method according to the invention should be based on the drawing as well as the result of the method according to the invention upcoming subject will be explained in more detail.

As already mentioned, the method according to the invention is based on carrier plates that are on both sides are metallized. Such a carrier plate is shown in FIG. 1 a and denoted by 1. The two Metallizations have the reference symbols 2 and 3 »To facilitate the production process, the carrier plates parts protruding beyond their nominal size. In the illustrated embodiment it is assumed that the carrier plates on all sides an excess of z. B. 15 mm exhibit. These parts are above or below the dashed lines in the drawing. They are labeled 1a and 1b. With the help of the

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wrote. Tool are attached to the protruding parts 1a and 1b guide openings introduced, preferably for all carrier plates of a multilayer circuit board at the same time «In addition, guide openings into the printing screens or film negatives required for applying the line pattern. The guide openings can be seen in FIG. 1b and denoted by 4 ·. In the embodiment of the drawing was Assumed that a six-layer printed circuit board is to be produced · For making the recesses in the carrier plates the carrier plates required for a wiring board are threaded with their guide openings into guide pins 6 (see sectional illustration in FIG. 1b). Then the through recesses 5 ζ. Β. introduced through hole. To facilitate the drilling process the conductive pattern can be applied to one of the surfaces of the carrier plates, e.g. B. in a photo-technical way. Then, as shown in Figure 1c (sectional view), the recesses 5 in the individual carrier plates provided in a known manner with a metal coating 6, for. B. by the known process of Durohverkupferung. The strenght the coating introduced into the recesses can, for. B. 35 / um be. The line is then placed on the surfaces of the individual printed circuit boards using the known methods.

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pattern generated, but not on the. Surfaces that are on the outside of the finished multilayer circuit board. The carrier plates of a multilayer printed circuit board are then used glued together. The individual carrier plates with their guide openings can in turn open here Guide pins 7 (see sectional view of Figure 1d) of an auxiliary work can be threaded. Between contiguous Carrier plates 1 are used to isolate the lines of adjacent carrier plates from one another Insulating foils 8 inserted. Before threading of the individual carrier plates 1 on the guide pins 7, the carrier plates on both sides with a Coated with glue. For example, Araldlt can be used as an adhesive. While the glue is drying out are the stacked carrier plates 1 between the plates 9 and 10 clamped in a glue press * Zur The gluing press can accelerate the drying process with the carrier plates stacked on top of one another an oven at a temperature of e.g. B- 100 °. The adhesive layers shown enlarged are denoted by 11 in FIG. 1d.

During the gluing process, the adhesive also gets into the continuous recesses FIG. 1d denoted by 12. This adhesive mass In the through-

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Extending recesses 5 as well as the parts 13 of the insulating films 3 which penetrate the recesses 5 must now be eliminated. The best way to do this is through a wide hole, with a drill that has a slightly smaller diameter than the drill used for the first hole.If the diameter of the first drill used was 1 mm, then a drill of z B, 0.95 nm · This second drilling process removes the adhesive compound 12 and the foil parts 13 in the bores 5. In the case of a thickness of the metallization in the bores of, for example, 35 μm, this metallization still retains 25 μm in this second drilling process. However, the second drilling process ensures that the metallization is cleaned from the adhesive everywhere. The perforated multilayer circuit board is shown in section in FIG. 1e. A second through-copper plating is now carried out, by means of which the metal covering 6 is reinforced in the individual carrier plates and at the same time the metal covering 6 of adjacent printed circuit boards are connected to one another. In this case, the insulating foils 8 lying between them are bridged by metal in the through bores. The copper-plated bores are shown in FIG. 1f. Now the required line patterns are applied to the surfaces of the multilayer printed circuit board.

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if necessary, can still be tin-plated without current. Thereafter the protruding file, i.e. the parts shown above and below the dashed lines (Figure 1) cut off. The multilayer circuit board is now complete.

FIG. 1f of the drawing shows practically the object produced by the method according to the invention, which is produced from carrier plates with double metallization, these carrier plates being glued to one another
if necessary with the interposition of insulating foils. In addition, the object has through openings with metal coverings. The required line patterns are located in the individual conductor levels

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Claims (10)

U 81/67 Claims 1 Process for the production of wiring boards with more than two line levels (multilayer boards), those made of stacked and glued together, Extensive cable runs for the individual conductor levels load-bearing support plates are composed of insulating material and lined with metal coverings, the entire Have recesses penetrating the wiring board, line runs of the conductor planes with these Metal coverings are in conductive connection and also connected to these metal coverings in the recesses components are, characterized in that it is assumed that the carrier plates are metallized on both sides, that in these carrier plates, preferably at the same time for all carrier plates of a wiring board, the recesses be introduced that then these recesses are lined with a first metal layer, and with the exception The required line patterns are generated on the two surfaces of the finished wiring board from the metallizations of the carrier plates in a manner known per se, that then the carrier plates are glued together, preferably with an insulating film in between, that after - 15 109820/1673 ' - 15 - U 81/67 remove adhesive residues in the recesses and, if necessary the Isollerstoffolienteilteile penetrating the recesses a second metallization of the through recesses is carried out and that finally the required Wiring patterns on the surfaces of the wiring board getting produced. 2. The method according to claim 1, characterized in that before the common introduction of the recesses in all Carrier plates the conductor pattern is applied to one of the surfaces of the wiring board. 3. The method according to claim 1 or 2, characterized in that « that the carrier plates with double-sided metallization to facilitate the production of the wiring boards have parts protruding beyond their nominal plate size that guide openings are made in these parts, ζ. Β · punched, that the plates for the common production of the recesses and / or when gluing with them Openings are inserted in guide pins and that the protruding parts are removed after gluing. 4. The method according to claim 3, characterized in that - 16 109820/1673 - 16 - U 81/67 also in the film negatives "or the printing screens for production the line pattern corresponding guide openings preferably together with the guide openings in the Carrier plates introduced, z. B. punched, and that a carrier plate for the production of the line pattern and a film negative or a printing screen having these guide holes is inserted into guide pins. 5. The method according to any one of claims 1 to 4, characterized in that that the adhesive is hardened by the action of heat. 6. The method according to any one of claims 1 to 5 »characterized in that that araldite is used as an adhesive. 7. The method according to any one of claims 1 to 6, characterized in that that to remove the adhesive residue and possibly from Isolierstoffolientteile from the as holes formed recesses a second drilling process with a slightly smaller drill diameter compared to the first drilling process is carried out. 8. The method according to any one of claims 1 to 7 t, characterized in that that the metal lining the recesses - 17 - 109820/1673 - 17 - U 81/67 layer is generated by electroless copper plating and by electrolytic post-copper plating. 9. The method according to any one of claims 1 to 8, characterized in that that the cable runs are provided with a tin coating on the surfaces. 10. Device for introducing the guide openings in the carrier plates and optionally in the film negatives or printing screens according to claims 3 and 4, characterized in, that two plates, in particular steel plates, with guide pins in one and corresponding openings in the other plate are arranged one above the other, between which the carrier plates to be provided with guide openings etc. are clamped so that these plates at the points where the guide openings on the carrier plates etc. are to be attached, have openings, and that a stamp for introducing the guide openings is provided, the is pressed through these openings. 11 «Device for gluing the guide openings provided carrier plates according to claim 3 *, characterized in that a device according to claim 10 is used is, in which instead of the openings in one plate guide pins are provided for the mounting openings of the carrier plates 109820/1673 Blank page