Separating plate-composite component for producing printed circuit board components and method for producing a composite component of this type

The invention relates to a separating plate composite component for producing printed circuit boards by pressing multilayers stacked with at least one such composite component, which composite component has a separating plate between copper foils.

The invention also relates to a method for producing such a composite component.

For the production of printed circuit boards formed from several layers, so-called multilayer printed circuit boards or multilayers for short, it is known to connect multilayer press packs to one another in corresponding multi-layer or vacuum presses at a temperature of, for example, approx. 180 ° C. The individual multilayer arrangements consist of copper foils, which are necessary for the production of the conductor tracks, as well as synthetic resin layers (prepreg layers, usually epoxy resin layers) or Laminate layers. As a rule, several multilayer packages of this type are arranged one above the other in a press, and these packages are separated from one another by separating or press plates. The main task of these separating plates is to bring about a uniform pressure and temperature distribution when pressing the multilayers in order to achieve high-quality printed circuit board products. The dividing plates usually consist of a steel sheet or aluminum sheet and are therefore also called dividing sheets. Due to the function described, they should be harder than the copper foils.

The separating plates or separating plates are relatively complex and expensive components in the course of the circuit board production described, so that their repeated use is desired. However, this is often counteracted by the fact that when the multilayer is pressed, when the synthetic resin material in the prepreg layers is heated, the synthetic resin material flows over the edges of the separating plates, sometimes also over larger areas of the separating plates, this synthetic resin material after cooling and Solidification can hardly be removed from the partition plates. This applies, for example, to the composite components according to US Pat. No. 5,153,050 A, where an aluminum plate is used as a separating plate, copper foils being glued onto this aluminum plate directly via an adhesive strip on the edge. Although this adhesive strip keeps dust particles of the synthetic resin from penetrating, the liquid synthetic resin cannot avoid soiling of the separating plate at the edges. Another problem here is the different coefficients of thermal expansion of aluminum and copper, so that thermal stresses arise in the Cu-Al-Cu laminate during pressing.

In DE 198 31 461 C a composite component is proposed in which an aluminum partition is enclosed between two comparatively larger copper foils, the copper foils being connected to one another by gluing in a sack-like manner outside the aluminum partition. In this way, the liquid synthetic resin can be kept away from the aluminum separating plate, and the copper foils and the aluminum separating plate can also expand differently according to their different coefficients of thermal expansion if the temperature is increased to approx. 180 ° C during pressing, for example. However, the copper foils of the copper foil sack cannot be coated with resin, since the resin would become liquid during pressing and flow over the edge, which could cause unwanted sticking in the press. In addition, after pressing, the protruding edge areas of the copper foils have to be cut off and removed, with recycling of these copper foils being problematic due to the synthetic resin material that gets onto them during pressing.

It is now the object of the invention to propose a separating plate composite component and an advantageous method for producing such a composite component, with unwanted sticking due to liquid resin when pressing the multilayer can be avoided in a simple manner, and the use of resin-coated copper foils for the Composite component - for the purpose of connecting with the neighboring multilayers - is made possible. Nonetheless, these composite components should be simple and inexpensive to produce3

AT 414 335 Β be adjustable.

To solve this problem, the invention provides a partition plate composite component as in

Claim 1 defined before.

Advantageous embodiments and developments of this composite component are defined in the claims dependent on claim 1.

Furthermore, the invention advantageously provides a method as defined in the independent method claim.

In the technique according to the invention, the resin flowing out of the multilayer package is caught by the non-stick layers on the partition plate, and sticking or soiling of the partition plate is reliably avoided. This also applies if the copper foils, as is preferred, are coated with resin on their sides remote from the anti-stick layers. The copper foils can simply be glued to the non-stick layers, e.g. with the help of a pressure-sensitive adhesive or a hot melt adhesive, in particular a hot melt adhesive, which ensures sufficient adhesion to the non-stick layers for the pressing process, but then enables the copper foils to be detached. The non-stick layers are also referred to as separating layers or separating layers, and they have the function of absorbing the liquid resin and thus preventing this liquid resin from sticking to the separating plate. In this respect, the described gluing of the copper foils to these non-stick layers is also entirely possible, with suitable adhesives being sufficiently known in the prior art. Most of the known pressure-sensitive adhesives or hot-melt adhesives can essentially be used here.

Another connection possibility is that the copper foils are connected, for example by means of laser radiation, through the non-stick layers to the metallic separating plate in the manner of a spot weld.

In a manner known per se, the partition plate can consist of a steel sheet or an aluminum sheet, a steel sheet or stainless steel sheet, in particular with a strength of at least 400 MPa, being preferred. However, it can be made of other suitable hard materials (apart from metal), the only important thing being that it is harder than the copper foil to be laminated on, in order to avoid so-called image transfers during the pressing process, ie Pushing the conductor tracks of the inner layers through the outer copper foils.

The composite component according to the invention is characterized in that the non-stick layers are formed by separate separating films which protrude with an edge region over the separating plate and are connected to one another in these protruding edge regions, whereby the separating plate is enclosed in a separating film bag. The partition plate can be freely movable in the interior of the partition foil bag. The separating films can be made of a plastic material, such as made of PET or poly-polymers. Depending on the material of the two separating films, they can be connected to one another via a glued seam with the help of a suitable adhesive. The adhesive seam of the separating film bag can preferably be produced with the aid of a commercially available pressure-sensitive adhesive or a hot-melt adhesive which is applied in the edge region of the separating film in the form of a continuous strip.

On the other hand, a composite component which is particularly favorable in terms of production and cost is made possible if the non-stick layers are formed in a known manner by non-stick coatings applied to the two sides of the separating plate, and if the separating plate together with the non-stick coatings protrudes over the copper foil on all sides. In this embodiment, the partition plate with the non-stick coating applied to it is larger than the copper foils, so that on it or more precisely on the non-stick coatings applied to it

AT 414 335 Β synthetic resin flowing out can be caught. In contrast, in the above-mentioned embodiment of the invention with the partition plate within the partition foil bag, the partition plate and copper foils can be of the same size, since the partition foils then protrude over the edges of the partition plate and the copper foils and can thus serve to catch the outflowing synthetic resin.

The non-stick coatings can be formed from a wide variety of materials, such as Teflon or a polyolefin or also from a lacquer.

The invention is explained in more detail below with reference to the particularly advantageous exemplary embodiment shown in the drawing, to which, however, it is not intended to be restricted. They show in detail:

1 shows, in a schematic view, a structure of a multilayer press pack with a plurality of multilayers and partition plate composite components;

2 shows a schematic view of a separating plate composite component with a separating film sack;

3 shows a schematic plan view of such a composite component according to FIG. 2;

4 shows a schematic view of another embodiment of a partition plate composite component, with a partition plate directly provided with non-stick layers; and FIG. 5 shows a plan view of such a composite component according to FIG. 4.

In Fig. 1, a multilayer press package is shown schematically and in detail, it can be seen that partition plate composite components 1 alternate with multilayer arrangements 2, hereinafter referred to as multilayers 2. The separating plate composite components 1 illustrated with dashed rectangles each have a separating plate 3, also called a pressing plate, separating plate or pressing plate, to which copper foils 5 provided with a resin layer 4 are attached via non-stick layers 6, here in the form of separating foils. The entire unit with resin-coated copper foil 5, 4, separating foil 6, separating sheet 3, again separating foil 6 and copper foil 5 coated with synthetic resin 4 is assembled in advance to form the composite component 1, as shown below with reference to FIGS. 2 and 3 on the one hand and 4 and 5 on the other hand will be explained in more detail in two exemplary embodiments.

The copper foils 4 of the composite components 1 coated with resin 5 belong to the multilayers 2, which furthermore include etched inner layers 7 and synthetic resin layers (prepreg layers) 8.

The fact that such separating plate composite components 1 are provided as units and can be stacked alternately with the multilayer layers when the printed circuit boards are produced, the stacking in the press is considerably simplified, since five components - 4/5; 6; 3; 6; 5/4 - can be laid at once in a single operation. This significantly reduces the handling time. The etched inner layers 7 realize the desired circuit or Conductor structure, and they are glued to one another with the aid of the prepreg layers 8. This connection takes place in a press at elevated temperature and under pressure or else vacuum. In such a press packet, as is partially illustrated schematically in FIG. 1, 20 multilayer arrangements 2 can certainly be layered one on top of the other. The separating sheet composite components 1 are placed between the individual multilayers 2, the separating sheets 3 ensuring a smooth, clean surface of the printed circuit boards produced.

During the defined pressing cycle, the synthetic resin of the prepreg layers 8 begins to flow. The fact that the non-stick layers or separating layers 6 are provided, however, prevents the resin from getting onto the separating plates or generally separating plates 3. In this connection, the resin must also be prevented from flowing to the edges of the partition plates 3.

AT 414 335 Β

In the embodiment according to FIGS. 2 and 3, separate separating films are now provided as non-stick layers 6, and these separating films 6 are larger than the separating plate 3 and also larger than the copper foils 5 with the resin layers 4. As can be seen from FIG If the copper foils 5 and the separating plate 3 are preferably of the same size, even if the copper foils 5 can be slightly smaller than the separating plate 3. It is important, however, that the separating films 6 protrude on all sides over the separating plate 3 in order to collect the liquid resin. So that the resin cannot get between the separating foils 6 to the separating plate 3, the separating foils 6 are connected to one another along an adhesive seam 9 with the aid of a pressure-sensitive adhesive or hot-melt adhesive. As a result, the separating plate 3 is enclosed between the separating foils 6 connected to one another like a sack, that is to say the separating plate 3 is present in a separating foil sack, wherein it is arranged to be freely movable in this separating foil sack.

On the other hand, the copper foils 5 are also glued to the separating foils 6 in the manner of an adhesive seam 10 with the aid of adhesives, for example hot-melt adhesives, in particular hot-melt adhesives.

In the production of such a separating plate composite component 1 according to FIGS. 2 and 3, the separating plate 3 is placed on the lower, larger separating film 6, and the adhesive seam 9 is applied to this lower separating film 6. The upper separating film 6 is then placed over the separating plate 3 and the lower separating film 6, and it is pressed against the adhesive seam 9 on the lower separating film 6. The separating plate 3 is thus protected in the separating film sack formed and it can no longer become soiled. Thereafter, the copper foils 5 coated with resin 4 are glued with the copper side, the so-called shiny side, to the upper or lower separating foil 6, the glued seam 10 being present circumferentially on the edge side. The resin side, ie the resin layers 4, face the adjacent multilayers 2, see FIG. 1, and the resin-coated copper foils 5 can thus form part of the printed circuit boards to be manufactured.

In the variant according to FIGS. 4 and 5, a separating plate 3 is used which is larger than the copper foils 5 and protrudes on all sides over their edges. In this exemplary embodiment according to FIGS. 4 and 5, the separating plate 3 is coated directly with a non-stick coating 16, which in turn serves to catch the resin from the prepreg layers 8 that flows out during the pressing. This collection of resin is possible because the partition plate 3 is larger here than the rest of the laminate structure. The copper foils 5 are again glued onto the non-stick coatings 16 on the separating plate 3 by means of adhesive seams 10. A water-based (poly) olefin, such as the commercially available product TUF-LUBE 3C, a polyolefin emulsion from Tadco Inc., Woodinville, WA, USA, can advantageously be used as the material for the non-stick coatings. Such an olefin is preferred because it is silicone-free and extremely environmentally friendly. The partition plates 3 can consist of any suitable material, such as steel, in particular stainless steel, but also aluminum. A metal, such as steel, with a minimum strength of 400 MPa is preferred in order to avoid a so-called image transfer.

The separating films 6 can consist of any suitable plastic material, such as PET or fluoropolymers.

Conventional pressure-sensitive adhesives or hot-melt adhesives, such as in particular the commercially available adhesive from ATO FINNEY under the name TSP353M, can be used as the adhesive for the adhesive seams 9 and 10, respectively.

With the described application of separating foils 6 or separating layers or non-stick coatings as non-stick layers 6 that catch the synthetic resin during pressing, soiling of the separating plates or separating sheets 3 is reliably avoided. As a result, these separating plates 3 can be used several times without any problems, and in particular the laborious cleaning processes previously required for scraping off synthetic resin can be dispensed with. On the other hand, the use of synthetic resin-coated copper foils 5 is made possible

AT 414 335 Β light, which favors the production of printed circuit boards.

As an alternative, FIG. 4 also schematically illustrates that the copper foils 5 can also be connected to the metallic separating plate 3 via laser welds 10 'that pass through the non-stick coatings 6, instead of via an adhesive seam 10.