HK1064329B - Partition plate and method for producing a partition plate for a multi-layer pressed stack - Google Patents

Description

Partition plate for a multi-layer plate pressed stack and method for the production thereof

Technical Field

The invention relates to a separator plate for producing one or more multilayer plates, or for producing a stack of multilayer plates according to claim 1. The invention also relates to a method for producing a multi-layer plate press-fit plate stack and to a method for producing a multi-layer plate stack according to claims 28 and 29.

Background

Separators with different structural designs for creating multi-layer board press stacks and various methods for creating multi-layer board press stacks, i.e. methods for pressing multi-layer printed circuit boards, are known from the prior art. Generally, the lamination of multilayer boards (circuit boards) is carried out by a multilayer pressing or vacuum pressing method in which the layers of the multilayer board are pressed against each other at a temperature of about 180 ℃.

For this purpose, a multi-layer laminated plate stack is usually first produced in a corresponding press. Wherein a plurality of multilayer boards, which are separated from each other by a partition or a press plate, are stacked together between two press plates, corresponding press dies and press pads. Each of the multilayer sheets is typically a multilayer structure, i.e., having a plurality of pre-impregnated resin layers separated by laminated plastic layers. Copper foils for establishing corresponding circuits are arranged between the laminated plastic layers or the pre-impregnated resin layers.

Various problems arise in the manufacture of multilayer boards. On the one hand, the thermal expansion of the separator can lead to disadvantageous slippage/displacement of the layers of the multilayer plate, i.e. of the prepreg or laminated plastic layers and/or of the copper foil arranged between the two. On the other hand, it is also important that the pressure in the multi-layer plate laminate is transmitted uniformly by means of the separating plate to the prepreg or plastic layers of the multi-layer plate laminate, so that an optimum bonding of the multi-layer plates is achieved and slipping of the layers is avoided as far as possible.

According to the disclosure of DE3844498a1, warping and unevenness of the copper surfaces of the laminated sheets should be avoided by using vacuum and isostatic pressing processes. Wherein an additional plate is used, which is arranged in a floating manner and serves the function of thermal insulation, which will keep the press plate cool when heating a multi-layer plate press-fit plate stack. However, this method has a disadvantage in that the epoxy resin overflowing during heating adheres to the edges of the multilayer board.

According to the disclosure of DE3507568C2, slip prevention measures are taken to prevent slippage of the prepreg resin layers, but only when the copper foil is selected to be slightly larger in size than the other layers so that the prepreg Zhen resin flows out thereon, is it possible to prevent the prepreg resin from flowing out on the board stack side. However, this method requires a long heating time and the penetration of heat is not uniform, for example, the unevenness is much higher than when an aluminum plate is used as the separator.

DE4116543a1 discloses a partition plate made of alloy steel, which has a characteristic coefficient of expansion close to that of copper. Although surface tension is thus avoided, the heating time for the alloy steel sheet is relatively long.

Therefore, in the past, aluminum sheets of specific alloys have been mainly used, which have good heat conductivity and relatively uniform heat conductivity. In all of the above-mentioned methods, the copper foil and the respective separating sheet must be arranged in a placement space with the other layers in a multi-layer press-fit stack by manual operation by a trained person. Wherein the extremely thin and delicate copper foil is easily broken.

The above-described separator plates and methods of creating multi-layer laminated stacks are not ideal for next generation printed circuit boards (multi-layer boards), especially for UMTS technology. Circuits are becoming narrower and more circuits are being placed on smaller and smaller surfaces at the same time using HDI (high density connection technology) technology. Since, on the one hand, the copper foils to be used are increasingly thinner, thicknesses of less than 12 micrometers or even less than 5 micrometers are known in this connection, with the risk of the inner circuit being pressed against the outer copper foil during lamination of the multilayer board increasing. This automatic adjustment action is called "image transfer". Problems such as uneven thickness etching and inaccurate drilling will occur. In particular, manual laying of such very thin outer copper foils is no longer possible. The outer copper foil preferably has to be produced as a combination with a separating plate or a press plate, as described in DE19831461C 1.

Thus, DE19831461C1 describes a method for locally joining together copper foils of any type and thickness and aluminum press plates (separator plates) of any alloy and thickness, wherein the aluminum press plates and the copper foils are produced as a composite. The problem here is that it is likewise not possible to achieve a partition or press plate made of aluminum or a corresponding aluminum alloy having the hardness required to avoid the abovementioned "image transfer". The strength of the aluminum alloy heretofore used for the above aluminum press plate is Rm 400 MPa. Pressing at a temperature of about 180 ℃ for a period of about 90 minutes. At this temperature, the strength of the aluminum press plate decreases to about 360 MPa. It is therefore problematic to use the hitherto known splitter plates for next-generation printed circuit boards.

The production of multi-layer laminated plate stacks is also known from the prior art (US-PS 6,130,000), in which carbon steel is used as the separating plate. This method of creating a multi-layer board press stack is not ideal and is associated with high costs.

Disclosure of Invention

The object of the present invention is therefore to propose and further design a separating plate for producing a multilayer plate and for producing a stack of laminated multilayer plates, and a method for producing a multilayer plate and for producing a stack of laminated multilayer plates, on the basis of the above-described separating plate and the above-described method, wherein the problem of the so-called image transfer (Imagetransfer) is avoided for the separating plate in a cost-effective manner.

The above-mentioned object for the partition plate is achieved by: the separating plate (1) is arranged as a press plate in the group of multi-layer laminate stacks (3) to be built and between two multi-layer plates (2), wherein the separating plate (1) is a steel plate, but not an alloy steel plate, wherein the steel plate has a tensile strength at a temperature of 180 ℃ of at least Rm ≥ 500MPa and/or a yield point at a temperature of 180 ℃ of at least Rp0.2 ≥ 470MPa, wherein the steel plate further has an organic coating (8), wherein the organic coating (8) is a coated lubricant and the lubricant is olefin-based. The steel sheet is a non-alloyed steel sheet having a tensile strength at a temperature substantially at 180 ℃ of at least Rm.gtoreq.500 MPa and/or a yield point at a temperature substantially at 180 ℃ of at least Rp0.2.gtoreq.470 MPa.

The idea of the invention is to produce or implement a multilayer board and to create or implement a multilayer board press stack with a separator board having specific mechanical properties. The inventive partition is a steel sheet as a non-alloyed steel sheet, specifically a steel sheet having a tensile strength at a temperature of substantially 180 ℃ of at least Rm.gtoreq.500 MPa and/or a yield point at a temperature of substantially 180 ℃ of at least Rp0.2.gtoreq.470 MPa. As the partition steel sheet, a so-called untreated steel sheet may be used, but a surface-treated steel sheet is preferably used as the partition plate, which will be further described below.

The principle of the invention is that, in the production of multilayer plates or in the production of multilayer plate pressed plate stacks, aluminum press plates or alloy steel plates are likewise not used, but rather steel plates are used which have a thickness of at least 0.3 mm, preferably at least 0.4 mm, i.e. which, in addition, have the stated mechanical strength values and are therefore "thinner" in their structural design than the partition plates which have hitherto been used according to the prior art and have a thickness of approximately 0.5 mm. For example, in the production of such partition panels as steel sheets, in particular in the production by the cold-rolling process, particular attention must be paid to the fact that optimum surface properties are to be achieved, in particular that the corresponding steel sheets produced are crack-free and void-free. In addition, since the thickness of the steel sheet is reduced to "only 0.4 mm" (or less than 0.4 mm), the loading of the press is increased, i.e. the number of multi-layer sheets per stack is correspondingly increased. I.e. at present, only 14 multilayer plates can be loaded per loading/opening of the press, and thus 16 dividing plates are required, while in the present invention the thickness of the dividing plates is reduced from 0.5 mm to 0.4 mm, correspondingly, thus saving 1.6 mm of space. Thus, a place is provided for adding another multilayer board to the multilayer laminated board stack, so that the number of multilayer boards in the multilayer laminated board stack is increased to 15. When the thickness of the steel plate is further reduced to, for example, 0.3 mm, a larger space can be saved. Since more multilayer plates can be produced in one process step, the labor and energy costs are reduced, and the corresponding costs for producing multilayer plates are saved.

There are a number of designs and further design options that are useful for the separator plate of the present invention and the method of using the separator plate to create a multi-layer plate press-fit stack. The beneficial design and further design solutions described above include: subjecting the surface of the steel plate to a complete treatment; so that the thickness of the steel plate is 0.3-0.5 mm; so that the steel sheet additionally has an inorganic or metallic coating; so that the coating of metal is made of aluminum or copper; such that the thickness of the coating (8) is at least 2 microns; covering at least one surface of the steel plate with a copper foil (7); so that the tensile strength of the steel plate is at least Rm more than or equal to 690MPa and the yield point thereof is at least Rp0.2 more than or equal to 630 MPa; so that the steel plate (1) is made of a non-alloyed carbon steel; such that the steel sheet contains 0.03 to 1.2 wt% of carbon and 0.2 to 1.5 wt% of manganese; such that the steel sheet contains 0.03 to 0.1 wt% of carbon and 0.2 to 0.5 wt% of manganese; providing the steel sheet with trace amounts of phosphorus, sulfur, aluminum and/or silicon; such that the lubricant is a polyolefin-based polymer; so that the coating is a thin layer of chromium plating; also included is a multi-layer board press-fit board stack (3): wherein the separating plate (1) is arranged as a press plate in a group of multi-layer plate press-fit plate stacks (3), in particular between two multi-layer plates (2); and a multi-layer plate pressed stack (3) for producing single or multiple multi-layer plates (2), in which multi-layer plate pressed stack (3) at least one separating plate (1) is arranged.

Several embodiments of the separator plate according to the invention and of the method according to the invention will be described in detail below with reference to the description and the drawings.

Brief description of the drawings

FIG. 1 is a schematic, diagrammatic illustration of a side view of a multi-layer press stack configuration for building a corresponding multi-layer board (circuit board);

FIG. 2 is a schematic side view of a first embodiment of the separator plate of the present invention, with a table of preferred values of the desired mechanical strength or desired range, and

FIG. 3 is a schematic side view of a separator plate according to a second embodiment, i.e., a surface-treated separator plate.

Detailed Description

Fig. 1 is a schematic view of a multi-layer plate press-fit plate stack 3 having a plurality of partition plates 1 and a plurality of multi-layer plates 2. Fig. 2 shows a separator 1 to which a table of preferred values of the desired mechanical strength or desired range is attached, and finally fig. 3 shows a surface-treated separator 1. The invention relates to a separating plate 1 for laminating a multilayer printed circuit board laminate.

Fig. 1 schematically shows a multi-layer plate press stack 3. As shown, the multi-layer plate press stack 3 is arranged in a corresponding press (not shown in detail in the figures), i.e. between the press platens 4 and the press dies 5 of said press. In order to achieve an optimum arrangement of the multi-layer plate pressed stack 3, a pressure pad 6 is also arranged between the outer separating plates 1.1a, 1.1b in the multi-layer plate pressed stack 3. The multi-layer plate pressed plate stack 3 now comprises a plurality of multi-layer plates 2 and a plurality of separating plates 1, namely an upper outer separating plate 1a, a lower outer separating plate 1b and a plurality of intermediate separating plates 1.1 c. Between the individual separating panels 1, a multilayer panel 2 is accordingly provided, which has the usual construction and is not described in detail here. The multilayer board 2 has a corresponding plurality of layers, namely a corresponding pre-impregnated resin prepreg layer or plastic laminate layer, and a corresponding number of copper foils, not shown in detail in the figures, which are used to realize a corresponding circuit. All relevant details are well known and will not be described in detail herein.

In fig. 1 it is also shown that a corresponding separating film, i.e. a copper foil 7, is also provided between the multilayer plate 2 and the separator plate 1. The separator plate 1 and the copper foil 7 are preferably made in a combined structure, as will be further explained below. Instead of the copper foil 7, the separator 1 may have an adhesion-preventing coating.

In the case of the lamination of multilayer plates 2, i.e. in the case of the lamination of the layers of the multilayer plate shown in fig. 1 into a corresponding assembly, a temperature of about 180 ℃ is preferred in the press. During pressing, the separating plate 1 ensures, on the one hand, an even heat distribution in the multi-layer plate pressed stack 3 and, on the other hand, an even pressure distribution. Otherwise, uneven heat and pressure distribution would occur in the multi-layer plate press stack 3, with the result that some sections of the multi-layer plate 2 would start to flow earlier than others, which would result in air entrapment, thickness distribution exceeding the required tolerance range, eventually causing different distribution of copper in the layers of the stack of multi-layer plates 2 in the cross-section of the multi-layer plates 2 and insufficient lamination in the copper-deficient sections. The design of the partition panel 1 is therefore of great importance in order to produce an optimum multilayer panel 2, in particular in order to avoid possible surface defects of the multilayer panel 2 on the one hand and to avoid such surface defects from being pressed against the adjoining multilayer panel 2 in a multilayer panel press stack on the other hand. For this reason, the design of the partition plates used hitherto according to the prior art is not ideal.

The partition plate 1 is a steel plate, but not an alloy steel plate, wherein the steel plate has a tensile strength at a temperature substantially at 180 ℃ of at least Rm ≥ 500MPa and/or a yield point at a temperature substantially at 180 ℃ of at least Rp0.2 ≥ 470 MPa. In other words, the partition plate 1 is manufactured from a steel plate selected such that the steel plate has a tensile strength Rm ≥ 500MPa substantially at a temperature of 180 ℃ and/or a yield point Rp0.2 ≥ 470MPa substantially at a temperature of 180 ℃ by a method for manufacturing a partition plate 1 for use in a multi-plate press-fit plate stack 3.

Although two variants are listed here, namely a partition 1 or a partition 1 as shown in FIGS. 1 to 3, which on the one hand has a tensile strength of at least Rm.gtoreq.500 MPa or a yield point of at least Rp0.2.gtoreq.470 MPa, it is optimal to achieve both a tensile strength of at least Rm.gtoreq.500 MPa and a yield point of at least Rp0.2.gtoreq.470 MPa (respectively at a temperature of about 180 ℃). The separating panel 1 has proven to be a steel panel and has the best minimum strength values for producing the multilayer panels 2 or for producing the multilayer panel press stack 3. With this separating plate 1, an image transfer (Imagetrnasfer) can be correspondingly avoided, wherein the resulting multilayer plate 2 has an optimum surface and the separating plate 1 according to the invention can also be used several times, which leads to further savings in terms of costs.

Fig. 2 with the attached table shows a partition plate 1, which is a steel plate. The corresponding strength values for the tensile strength Rm and the yield point rp0.2 are listed in the attached table and are each at a temperature of 180 c, i.e. essentially the temperature in the lamination of the multilayer plates 2 in the lamination stack 3 when the respective lamination is performed. As shown in the attached table of fig. 2, the minimum value of the tensile strength Rm is 500MPa or more, and the minimum value of the yield point rp0.2 is 470MPa or more. It has been verified that when the tensile strength Rm is greater than or equal to 690MPa and the yield point Rp0.2 is greater than or equal to 630MPa, a multilayer board 2 having very good properties can be produced and "image transfer" is particularly effectively avoided. According to a preferred embodiment of the separator plate 1 according to the invention, the tensile strength Rm is equal to 789MPa and the yield point rp0.2 is equal to 732 MPa.

Fig. 2 shows an untreated, in particular non-surface-treated steel separator plate 1, while fig. 3 shows a surface-treated or surface-treated, in particular coated, separator plate 1. The partition plate 1 shown in fig. 3 as a steel plate is essentially surface-treated, i.e. coated on both sides. The partition plate 1 shown in fig. 3 also has substantially the mechanical strength values or strength ranges as listed in the attached table of fig. 2. The thickness of the partition plate 1 is 0.3 to 1 mm, and the thickness of the partition plate 1 is preferably 0.3 to 0.5 mm, particularly 0.4 mm. The additional coating 8 of the partition panel 1 shown in fig. 3 can be realized in different ways, for example, it can be an organic, inorganic or metallic coating 8. The coating 8 as metal may be a coating of aluminum or copper. A special plating layer 8 of chromium is also conceivable. Fig. 3 only shows schematically the thickness of the separating plate 1 and the thicknesses of the coating 8 and of the coating 8. The thickness of the coating 8 will be further described below.

The coating 8 can be realized by plating the partition plate 1 with a metal, for example aluminum or copper, which has a better thermal conductivity and thus further improves the thermal conductivity in the multi-plate press stack 3 accordingly.

It is also conceivable for the coating 8 to be an organic or inorganic coating, for example a lubricant applied to the partition plate 1. The lubricant is preferably olefin-based, or may be another organic substance having similar properties to the coating 8. The inorganic coating 8 may also be plastic-based, for example.

In the case of a preferred thickness of the partition plate 1 as steel plate of 0.4 mm, the thickness of the cladding 8 is at least 2 micrometers, preferably in the case of a metal cladding 8 in the range of 5 to 25 micrometers. A better surface of the multilayer board 2 can be achieved with the coating 8, in particular damage to the copper foil 7 can be avoided to a large extent.

It is also to be noted that an alloy steel sheet is not used as the steel sheet. Although it is possible to use untreated steel plates, i.e. steel plates which are not surface-treated or coated, as separating sheet 1 or for producing corresponding multi-layer laminated sheet stacks 3, the surface of the separating sheet 1 used must be taken into account, since only a perfect surface prevents damage to the copper foils 7 or the multi-layer sheets 2. In particular, in order to achieve a smoother surface, the steel sheet can also be coated 8 with a lubricant, it being additionally important to take care during cold rolling that the steel sheet has optimum surface properties, i.e. that the surface is crack-free and void-free.

When the partition panel 1 as a steel plate has the above-mentioned strength values, it is very advantageous to use the partition panel 1 as the above-mentioned steel plate. In addition, the thermal expansion coefficient of the separating plate 1, which is a steel plate, is relatively low and is therefore particularly advantageous, so that slipping or sliding or shifting within the layers of the multilayer plate 2 can be avoided during pressing or at corresponding temperatures of substantially 180 ℃.

As described in detail in DE19831461C1, for example, the separator plate 1 shown is preferably produced in combination with a copper foil which is not shown in fig. 2 and 3. The advantage is that a copper foil which is very thin and partially even impossible to lay by hand can be placed in the multi-layer board lamination stack 3 together with the separator board 1 quickly and without special effort, so that the production of the corresponding multi-layer board 2 is achieved.

It is further noted that: hitherto preferred according to the prior art is a partition plate of 0.5 mm thickness. Since the partition plate 1 used in the present invention has the above-described strength values, the thickness of the partition plate 1 can be preferably reduced to 0.4 mm, or even 0.3 mm. Since hitherto according to the prior art a multilayer plate press stack 3 has a total of 14 multilayer plates 2 (only three multilayer plates 2 are schematically shown in fig. 1) per press opening. When the separator 1 of the present invention is used, since the thickness thereof can be preferably reduced to 0.4 mm, 1.6 mm (16 × (0.5-0.4 mm) in total can be saved, so that 16 separators can be used, and thus additional space is provided for another additional multilayer board 2 in one multilayer board press-fit board stack 3, and thus the total number of multilayer boards 2 provided in one multilayer board press-fit board stack 3 can be increased from 14 multilayer boards 2 to 15 multilayer boards 2.

The preferred separating sheet 1 according to the invention has in particular the following composition: 0.04 wt.% carbon, 0.01 wt.% silicon, 0.22 wt.% manganese, 0.012 wt.% phosphorus, 0.005 wt.% sulfur, 0.037 wt.% aluminum, with the remaining weight percent being the iron component. The steel alloy is also known as "ST 2K 70 RP". It is also conceivable to use other steel alloys with corresponding strength values, for example of the type "C75". The divider plate of the present invention is preferably 660 mm long and 580 mm wide.

The partition plate 1 according to the invention or the steel plate according to the invention, which is preferably made of a non-alloyed carbon steel, i.e. of a non-alloyed steel, is placed as a press plate in a multi-plate laminate stack to be built up. The main components of the partition plate 1 of the present invention as a non-alloyed steel sheet are as follows: 0.03-1.2 wt% carbon, 0.2-1.5 wt% manganese. For the corresponding non-alloyed carbon steel or non-alloyed steel sheet, the preferred ranges of the composition are: 0.03-1.0 wt.% carbon and 0.2-0.5 wt.% manganese. The remaining weight percentage is mainly iron content. Wherein the non-alloyed carbon steel, i.e. the steel sheet according to the invention, may contain minor amounts of other elements, such as phosphorus, sulphur, aluminium and/or silicon, which have no influence on the properties of the steel.

In particular, the yield point Rp0.2 is important to avoid the above-mentioned image transfer. When the yield point rp0.2 is very small, the separator plate particularly used according to the prior art is subjected to continuous deformation, and therefore the above-described image transfer phenomenon occurs when such a separator plate is repeatedly used. In the case of the inventive yield point Rp0.2 ≧ 470MPa, it has proved possible to likewise avoid image transfer, since, when the separating plate 1 according to the invention is reused, it is ensured that the separating plate 1 is likewise not subject to a permanent deformation by appropriate design of the yield point, so that the separating plate can be used several times without image transfer occurring.

Olefin-based lubricants are preferably used as the lubricant. Polyolefin-based polymers or polyolefin emulsifiers, such as suspended polyolefin/water solutions, are also contemplated. This ensures good corrosion protection of the partition plate 1 according to the invention and at the same time achieves a good adhesion-preventing coating, in particular a coating which avoids adhesion to resins.

The thermal conductivity of the partition plate 1 of the present invention is preferably substantially 40 to 60W/mK and/or the thermal expansion coefficient is 9 to 1410^-6K^-1。

Another preferred embodiment of the partition plate 1 of the present invention has the following composition: 0.037 wt.% carbon, 0.003 wt.% silicon, 0.21 wt.% manganese, 0.008 wt.% phosphorus, 0.01 wt.% sulfur, 0.039 wt.% aluminum, 0.020 wt.% chromium, the remaining weight percentages being the iron fraction, and phosphorus, sulfurThe contents of aluminum, chromium and silicon are considered herein as impurities. The composition proposed here is preferably that of a cold-rolled steel strip of the basic type "DC 04", having a thermal conductivity of substantially 57W/mK and a coefficient of thermal expansion of 11.4510^-6K^-1. The coating 8 of the above-mentioned further embodiment is preferably a thin chromium coating and the coating thickness is 70-130mg/m²。

In summary, the inventive separating plate 1 and the inventive method for producing a separating plate 1 achieve the critical advantages and avoid the disadvantages of the prior art.

Claims (16)

1. Separator plate (1) for producing a single multilayer plate or a plurality of multilayer plates (2), or for creating a multilayer plate press stack (3), wherein the separator plate (1) is arranged as a press plate within a group of multilayer plate stacks (3) to be created and between two multilayer plates (2), wherein the separator plate (1) is a steel plate, but not an alloy steel plate, wherein the steel plate has a tensile strength at a temperature of 180 ℃ of at least Rm ≥ 500MPa and/or a yield point at a temperature of 180 ℃ of at least Rp0.2 ≥ 470MPa, wherein the steel plate further has an organic coating (8), wherein the organic coating (8) is a coated lubricant, and wherein the lubricant is olefin-based.

2. The separator plate of claim 1, wherein the surface of the steel plate is completely surface treated.

3. The separator plate according to claim 1 or 2, wherein the thickness of the steel plate is 0.3 to 0.5 mm.

4. The separator plate of claim 1, wherein said steel plate additionally has an inorganic or metallic coating.

5. The separator plate of claim 4, wherein the metallic coating is comprised of aluminum or copper.

6. The separator plate according to claim 1 or 4, wherein the thickness of the coating (8) is at least 2 μm.

7. The separator plate according to claim 4 or 5, wherein at least one surface of the steel plate is coated with a copper foil (7).

8. The separator plate of claim 1, wherein the steel plate has a tensile strength of at least Rm ≥ 690MPa and a yield point of at least Rp0.2 ≥ 630 MPa.

9. The partition plate according to claim 1, characterised in that the steel plate (1) is made of a non-alloyed carbon steel.

10. The separator plate according to claim 1, wherein the steel sheet contains 0.03 to 1.2 wt% of carbon and 0.2 to 1.5 wt% of manganese.

11. The separator plate according to claim 10, wherein the steel sheet contains 0.03 to 0.1 wt% of carbon and 0.2 to 0.5 wt% of manganese.

12. The separator plate of claim 10, wherein the steel plate has trace amounts of phosphorus, sulfur, aluminum, and/or silicon.

13. The separator plate of claim 1, wherein the lubricant is polyolefin-based.

14. The separator plate of claim 4, wherein said coating is a thin layer of chrome plating.

15. A multi-layer plate press stack (3) in which a separator plate (1) is arranged as a press plate within a group of multi-layer plate press stacks (3) and between two multi-layer plates (2), characterized in that between two multi-layer plates (2) a separator plate according to any one of claims 1-14 is arranged.

16. A multi-layer plate press stack (3) for producing single or multiple multi-layer plates (2), characterized in that in the multi-layer plate press stack (3) at least one separating plate (1) according to any one of claims 1 to 14 is provided.