NO864089L - PROCEDURE AND DEVICE FOR MANUFACTURING OF METAL COATED BASIC MATERIAL FOR LEADERS. - Google Patents

Description

The present invention relates to a method for the production of prepregs and of metal-coated base material for conductor plates, as stated in the preamble of claim 1, and devices for carrying out the method.

It is known to produce metal-coated base materials for conductor plates by pressing cut-to-size track materials provided with thermosetting resin and metal foils in floor presses. Such a method provides base materials with a quality that varies within the individual plate and from individual plate to individual plate. The pressing process lasts, for example, at 11-stage presses for over two hours, including heating and cooling.

From British patent application 2108427 a method is known where, in a press which has two hot plates, an interrupted pressing is carried out in such a way that a woven web which has been sprinkled with resin powder, and a copper foil which are both introduced into the press are held still during the pressing process and that the pressed product is ejected tactfully.

Here, too, the quality varies within the individual plate, which leads to large amounts of scrap when the consumer wants a homogeneous quality. Moreover, with the known resins it is not possible to achieve an economical working speed.

The use of continuously working double belt presses, such as those known, for example, from the production of decorative laminates, has thus far likewise been unsuccessful because, when using the resins that are common for conductor plate base material, it is not possible to achieve an economically sound working speed.

In the methods known from the literature for the production of conductor plate base material, a long press time is partly due to; over 2 hours required. This long pressing time for the usual multi-stage presses and the usual varra-hardenable resin is partly due to the fact that a faster heating or cooling under pressure must be avoided in order to keep the quality differences between the outer and inner layers and within the individual layers as small as possible. These quality differences are partly conditioned by the shear flow, which leads to different thicknesses between the edge parts and middle parts of the individual plates due to too rapid heating or cooling under pressure. It is also common for the layer structure to use higher quality starting materials for the outer layers of the boards in order to thereby achieve a better surface quality. However, the use of starting materials with different densities leads to a certain inhomogeneity in the layer structure. In addition, extensive stock-keeping and corresponding control during processing is necessary.

The invention aims to avoid the disadvantages of the state of the art and to provide a manufacturing method for prepregs and metal-coated base material for conductor plates, and a means suitable for carrying out the method which is economical, cost-saving and technically easy to handle and which also allows highly to reduce the necessary time and to ensure a complete homogeneity of the team structure. However, this must in no way be at the expense of the quality of the process products, but on the contrary, the properties of the conductor plate base material must be further improved. Further additional and side tasks are also apparent from the benefits listed below.

The invention thus relates to a method for the production of metal-coated conductor plate base material by hot pressing material webs impregnated with heat-curable resin with the metal foil or foils to be applied, in a press device, characterized in that an impregnating agent containing a catalyst-accelerated resin system is used to impregnate the material webs, and that the impregnated material webs are pressed together with the metal foil or

- the foils to be applied.

The invention also relates to a device for carrying out the present method, and the device is characterized by the fact that it comprises a double belt press with rhythmic feeding movement, the press having a heating zone and a cooling zone connected to this, an optionally cooled draw-in-deflection drum pair arranged in front the heating zone, and an extraction-deflection drum pair arranged after the cooling zone.

When carrying out the present method, particularly favorable results are obtained when a resin system with an accelerated epoxy-curing agent-catalyst system is used for the impregnation, namely when pyridine derivatives and/or imidazole, possibly substituted, are present as an accelerator.

Advantageous results are also obtained when phenol-curing agent-catalyst systems are also contained in the resin system used for the impregnation.

With the present method, it is possible by using catalyst-accelerated resin systems to increase the impregnation plant's performance by approx. 20% compared to when using ordinary resins for the production of conductor plate base material. It is particularly advantageous that the present method can be carried out continuously. For this purpose, the material webs which, according to the invention, have been impregnated with the accelerated resin system, can be processed continuously or periodically in double belt presses. Due to the faster initiation of the accelerated resins, it is possible to achieve a faster heating and a faster cooling at the same time that the flow and thus the dreaded push flow is reduced. The thickness tolerance between the edge parts and the middle parts is clearly smaller, which results in increased production reliability, less scrap and a narrower tolerance range for the expected conductor plate base materials. Processing in single- or multi-stage presses where a clear reduction of the thrust flow can be observed,

is, however, not excluded.

Among others, the following pyridine compounds are suitable as accelerators in the epoxy-resin-curing agent-catalyst system: 2-benzoylpyridine

3- benzoylpyridine

4- benzoylpyridine

2- benzylpyridine

3- benzylpyridine

4- benzylpyridine

2-benzylaminopyridine

4-dimethylaminopyridine

2-Methoxypyridine

4-tert-butylpyridine

3- cyanopyridine

2-hydroxypyridine

6-amino-2-pyridine

2-aminopyridine

3- ethylpyridine

3-ethyl-4-methylpyridine

2- phenylpyridine

2,6-diaminopyridine

3- methylpyridine

2-(aminomethyl)pyridine

2-amino-4-methylpyridine or

2,4-dimethylpyridine

Another advantageous group of accelerators for the purpose indicated here are the per se known substituted imidazole compounds, including imidazole as such, and more specifically

N-methylimidazole

2-methylimidazole

2-phenylimidazole

4- phenylimidazole

4-methylimidazole

2-methylbenzimidazole

5,6-dimethylbenzimidazole

1-methyl-2-phenylbenzimidazole

1,2-dimethylimidazole

4.5-Diphenylimidazole

2-ethyl-4-methylimidazole

carbonyldiimidazole

imidazole

2-undecylimidazole

1- cyanoethyl-2-phenylimidazole or

2- phenylbenzimidazole

Particularly good results were achieved using a combination of the above-mentioned pyridine and imidazole accelerators together with dicyandiamine and benzyldimethylamine, respectively, which are known as curing agents for common hard-

pixies.

With the accelerated resin-curing agent-catalyst systems described here, the curing time is reduced to approx. 2 minutes. Due to the practically complete elimination of the dreaded sliding float, a product of exceptionally smooth and high quality is also obtained.

The accelerated resin-curing agent-catalyst system may contain 0.2-0.8% by weight of the accelerator or of the accelerator mixture, based on solid resin. The pressing process can be carried out under vacuum. A relaxation of the manufactured product has often proved to be beneficial.

In most cases, in order to form a conductor plate base material consisting of several layers, individual webs of material which have been impregnated with the accelerated resin system are unwound from different rolls and fed together with, possibly at the same time, a metal foil web which is unwound from a further roll and which is to be applied to the material web, and the band thus formed is gradually introduced into the press, preferably a double belt press, and hot-pressed. Before the pressing process, the material webs can be cut to final lengths and then, together with the metal foil web, which may have also been cut to final lengths, be fed into the pressure-active zone. It is often the case that unpressed sections of the base material are formed between the compressed sections of the conductor plate base material or that at least a metal foil connection is left between the pressed sections.

Before or after cutting in their relative position

in relation to each other, the material webs can be fixed using clamps, rivets, stapling or the like within the edge

council and then gradually introduced in the press. If two or more conductor plate base materials are to be produced that are coated with metal foil on one or two sides, separating foils are simultaneously introduced into the press during the hot pressing between the webs and sections respectively and pressed with these, and the materials thus obtained are again separated from each other after the pressing process using the separating foils.

It is advantageous to work so that in a first work step the material webs and metal foil webs to be applied are introduced into a hot press zone and then in a second step cooled under pressure in a cooling zone, and finally in a third work step the conductor plate base material is cut along the edge and possibly divided into lengths. It is also possible in the first work cycle to introduce the webs into a press zone and there to heat them using high frequency and then to cool them in this place and then in another work cycle to cut the conductor plate base material along the edge and divide this into lengths.

When joining or cutting the material and metal foil web, clean flow conditions or vacuum must exist. It has also proven beneficial to pre-heat the metal foils to be applied.

Double belt presses have been found to be particularly advantageous for carrying out the present method.

They allow a continuous or at least partially continuous pre-production. Thereby, compared to a single-stage press used for heating and cooling, the combination of a normal single-stage press as a heating zone and another normal single-stage press as a cooling zone within a pair of steel belts known from the actual double-belt presses and which move rhythmically when the pressure is briefly released has proven to be particularly suitable. When using such a modified double belt press, the application of a pressure of the required order of magnitude up to 80 bar and above requires no special effort, and it is also possible to do this in a precisely controllable manner in terms of pressure uniformity and temperature. In general, presses with pressures up to 100 bar have proven to be suitable.

Regardless of whether heating and cooling takes place

in a zone, generally optionally cooled draw-in-deflection drum pairs are arranged before the press zone. In addition, devices for storing, unrolling and guiding the material webs and material foil webs can be arranged in front of the double-belt press and in the retracting direction. The heating zone is often provided with insulation to avoid excessive heat dissipation radiation. For the metal foil webs, heating

only draw-in deflection drums are used, which can also be equipped with heat shields to reduce or control the radiant heat acting on the material paths.

Within the outlet area of the device, a pair of extraction deflection drums is generally arranged. In addition, edge-cutting devices and possibly length dividing devices can be arranged.

Hitherto, on the one hand, conductor plates of 1.5 mm and on the other hand, conductor plates of 1.6 mm, whose tolerances may amount to ^0.13 mm according to the usual standard, have been marketed. When using the present method, the tolerances are within 1.52 mm along the edge and 1.55 mm in the middle of the individual plates, with the result that a single product is fine because the product produced by the present method is within the tolerance limits for the two products. The production advantages, including an advantageous stock holding etc.

should be ready.

So far, for a 1.5 mm conductor plate, for example, four «■2 2

layers of glass cloth at 230 g/m and three layers at 200 g/m have been used,

and for 1.6 mm thick conductor plates, six layers of 200 g/m 2 and two layers of 230 g/m 2 have been used. With the present method, it is now possible for the unit product to use a single quality of glass fiber cloth which, for example, consists of eight layers of 200 g/m 2. It appears from this that the more expensive quality of 230 g/m 2 no longer is necessary with the consequent logical advantages.

In addition, a complete homogeneity of the layer structure is achieved because only one type of glass fiber cloth is used.

Thanks to the strong acceleration of the curing process achieved according to the invention compared to the use of the known conventional accelerated resin systems, it is now possible in an economical way to carry out a finished production in single-deck presses, whereby a further increase in quality is also made possible because the inevitable differences between the products from the outer and the inner floors when using multi-floor presses are avoided.

Even when processing in a multi-stage press material webs that have been impregnated with the accelerated resin system used according to the invention, for example under vacuum, in addition to high pore-freeness, an improvement in the geometric values is also obtained. This effect is presumably due to the combined effect, i.e. on the one hand due to the use of the accelerated resin system and thus avoiding the dreaded shear flow, and on the other hand due to the vacuum. This results in a narrowing of the tolerances, which is always desired in electronics, whereby interesting production technical aspects are obtained.

The present invention will be explained in more detail below in connection with the embodiment shown in the drawing of a device which is suitable for carrying out the present method.

The device shown in Figure 1 comprises a double belt press 1 with a hot press 2 and a cooling press 3 connected after this. The double belt press 1 works with a rhythmic feeding movement. The heated zone 2 and the cooled zone 3 have the same dimensions. According to a preferred embodiment, a heating zone and a cooling zone each with a length of 3 m and a width of 1.3 m are arranged. The double belt press has a draw-in deflection drum pair which can be cooled, arranged in front of the pressure-active zone 2. After the cooling press 3, a correspondingly designed draw-in deflection drum pair is arranged.

A spindle unwinder with two spindles for prepregs, i.e. glass fiber cloth provided with the resin system, and a further spindle unwinder with two spindles for the metal foils, i.e. in the present case for copper foils, are arranged in front of the double belt press. Guide rollers are arranged between the spindle unrollers for the material web and for the metal foils.

An edge cutting device and then a length dividing device are located after the double belt press in the production direction.

The function of the double belt press is briefly described below. Four prepreg webs which have been impregnated with the accelerated resin system used according to the invention are unrolled by means of the spindle unrollers and brought together and gradually introduced into the hot press zone. At the same time, copper foils are delivered from two further spindles by the spindle unwinders for the metal foils. In a first work cycle, the material webs are pressed together with the metal foils. The possible pressure is then up to 100 bar.

If a base material is to be produced that is only coated on one side, a heat-resistant separating foil can be wound up on the corresponding spindle and introduced into the double belt press instead of the copper foil. For example, silicone-treated or polytetraethylene-coated aluminum foil can be used as a separating foil. The separation foil can be pulled off from the finished base material web after exiting the double belt press and used again.

After the pressing process, a short-term, almost complete depressurization takes place and, moreover, the rhythmic feeding movement of the pressed section into the cooling zone, whereby the connected base material is cooled under pressure. After completion of the cooling process, the base material is transported further and given the desired dimensions in the subsequent edge cutting device and length dividing device.

The end product is connected via unpressed, i.e. unusable, sections which are separated as waste. The temperature in the heating zone is approx. 190°C. In the subsequent cooling area, the base material web is cooled to approx. 100°C. Between the cooling zone and the edge cutting device, a post-relaxation zone can be arranged to stabilize the shape of the base material.

Although the present method has been described in more detail with reference to a base material with six layers, a base material with a different number of layers can of course also be produced.

When separating foils are used, it is also possible to produce several base material layers at the same time.

The described working conditions primarily depend on the accelerated resin system used and can be varied accordingly.

The present method or the present device can not only be used for coating with copper, but also with other metal foils. They are particularly suitable for coating with combination foils, e.g. Cu/Al, of the type used for fine conductor plates (so-called etchable, strippable plates).

The material losses that occur when carrying out the method described above due to the unpressed sections are of some economic importance. In order to avoid this waste according to a special embodiment, the prepreg webs are already divided to the final final length and thus introduced into the press at a corresponding distance between the metal foil webs. According to a further special embodiment, the metal foils are also divided into lengths before the press. It must

then careful care is taken that no dust is formed or that formed dust is kept away from the prepreg and metal foil rafts by means of suitable precautions, such as a vacuum. It has also proven advantageous to fix the material sections mechanically in relation to each other in their relative position, which can be carried out by means of stapling, clamping or riveting in the edge area which is nevertheless to be cut away. In this way, an almost continuous process is achieved while avoiding material loss.

In principle, it has proven to be advantageous to heat the copper foils. Such a pre-heating is partly achieved more or less forced by the fact that the copper foils on the outside will automatically be heated more strongly than the glass fabric core. According to a special embodiment of the present double-belt press, which is shown in Figure 2, the draw-in drums are arranged at a greater distance from each other, and heated to heat the metal foils which are guided along the draw-in drums. In connection with the retracting-deflection roller pair, support rollers for the steel strips are arranged. In order to avoid heating the parts of the prepreg webs which are located closest to the retracting-deflection drum pair, a pair of heat shields is arranged. This can consist of a cold look. Cooling hoses are used for cooling, which can consist of copper and in which the flow rate of a coolant can be controlled, so that an accurate temperature control is achieved. Instead of the cooling hoses, cooling pockets with forced flow can also be arranged. The heat shields are arranged so that they can be displaced in a horizontal direction, whereby the prepreg webs in this particular embodiment, also in terms of their spatial arrangement, can be protected against temperature effects from the inlet drums which, according to this embodiment, are heated as required.

According to a further special embodiment, the already assembled prepreg webs can in turn be easily preheated over the entire length of the next stroke feed to effect an even faster initiation of the resin in the heating zone.

The press according to the invention can also be used for the production of metal-coated base material for conductor plates when paper is used instead of the fiberglass cloth and a corresponding accelerated resin system based on phenol is used instead of the accelerated resin system based on epoxy according to the invention. The combination of the less expensive starting materials with the almost continuous or short-stroke working press enables a particularly economical production.

The invention will be further described using the following examples.

Example 1

A finished glass cloth of the type commonly used for copper-clad fiberglass-epoxy resin laminates for conductor plates and weighing 200 g/m 2 was impregnated with a resin solution consisting of 100 parts of a polymeric partially brominated bisphenol-A glycidyl ether with a proportion of epoxied novolak. of 1-15%, preferably 5-12%, 3.2 parts dicyandiamide, 0.28 parts 3-methylpyridine and 80 parts methylglycol. This prepreg which had been impregnated in this way and which had subsequently been dried at 165°C had a resin content of 42% and a resin flow of 10%. Seven of these prepregs were pressed at a temperature which increased to 195°C and at a pressure of 55 bar with a double-sided 35 µm thick copper foil overlay into a 1.5 mm thick laminate in the device according to the invention. The testing of the laminate gave surprisingly positive results for the dimensional stability which was above average, at the same time with properties which were otherwise similar to the properties of commercially available laminates.

The manufactured laminate had a thickness tolerance of -3/100 mm. By way of comparison, the standards for rigid laminates require a tolerance of -13/100 mm, which has thus far also been fully utilized for the products.

Example 2

A glass cloth, as described in example 1, was impregnated with a resin solution consisting of 100 parts of a polymer, partially brominated bisphenol-A glycidyl ether with one part of epoxidized novolak. of 1-15%, preferably 5-12%, 3.4 parts dicyandiamide, 0.33 parts 4-dimethylaminopyridine and 80 parts methylglycol. The prepreg impregnated in this way and dried at 170°C had a resin content of 44% and a resin flow of 8%. Several of these prepregs were pressed with a double-sided 35 µm copper foil overlay into a 1.5 mm thick laminate in the device according to the present invention at a temperature that increased to 200°C and at a pressure of 50 bar. The test of the laminate also gave, for this embodiment, values that were above the standard in terms of dimensional stability while achieving laminate properties that were otherwise comparable to the properties of commercially available products.

Example 3

With a resin mixture consisting of 100 parts of a polymer, partially brominated bisphenol-A glycidyl ether with a proportion of epoxidized novolak of 1-15%, preferably 5-12%, and with an epoxide equivalent weight between 350 and 520, 3.0 parts of dicyandiamide , 0.40 part 2-amino-4-methylpyridine and 80 parts methylglycol, a 100 g/m<2> heavy glass cloth with the same intended use as described in example 1 was impregnated and then dried at 165°C. The resin content was 44% and the resin flow 20%. Two of these prepregs with < one-sided 35 µm thick copper foil overlay were pressed into a 0.2 mm thick laminate in the device according to the invention using a separating foil and at a temperature which increased to 190°C and at a pressure of 50 bar. The test gave equally good results as the results stated in example 2.

Examples 4-13

The recipes and working conditions for examples 4-13 are indicated in the table below.

Example 14

A cotton paper weighing 110 g/m 2 was impregnated with 33 g of a phenolic resin solution consisting of 40% of an aqueous low molecular weight impregnating resin phenol, 5.2% tetrabromobisphenol-A, 4.8% of a polyalkylated glycol diglycidyl ester and 50% solvent.

The paper which had been impregnated in this way and which had been dried at 120-170°C had a resin content of 23% and a proportion of volatile constituents, measured for 5 minutes at 160°C, of less than 2%.

Then a further impregnation was carried out with 190 g of a resin mixture consisting of 42.6% of a modified diglycidyl ester of a dimer acid, 13.5% tetrabromobisphenol-A, 2.9% antimony trioxide, 1.8% dicyandiamide and 0.7% 2-phenylimidazole with 38.5% methylglycol.

The paper which had been impregnated twice in this way and which had been dried at 110-180°C had a resin flow of 7%.

Six of these prepregs were pressed with a double-sided 35 µm thick Cu foil overlay into a 1.6 mm thick laminate at a temperature that increased to 210°C and at a pressure of 45 bar and using a double belt press.

The test of the laminate surprisingly gave positive results for the stoppability which was above average, with a solder bath resistance which was far above normal for normal FR 2 laminates.

Claims (20)

1. Method for the production of metal-coated base material for conductor plates by hot pressing material webs impregnated with thermosetting resin together with the metal foil or foils to be applied, using a pressing device, characterized in that for impregnation of the material webs an impregnation agent containing a catalyst-accelerated resin system is used, and that the impregnated material webs are pressed together with the metal foil or foils to be applied. 2. Method according to claim 1, characterized in that the impregnating agent used is an impregnating agent which contains an accelerated epoxy-curing agent-catalyst system as a resin system. 3. Method according to claim 1 or 2, characterized in that an impregnating agent containing a phenol-curing agent-catalyst system is used as an accelerated resin system. 4. Method according to claims 1-3, characterized in that a resin system is used which, as an accelerator, contains one or more compounds from the following groups: substituted pyridine compounds, imidazole and/or substituted imidazole. 5. Process according to claims 1-4, characterized in that dicyandiamine and/or benzyldimethylamine are used in addition. 6. Method according to claims 1-5, characterized in that an accelerated resin-curing agent-catalyst system is used which contains 0.2-0.8% by weight of the accelerator or accelerator mixture, based on the solid resin. 7. Method according to claims 1-6, characterized in that the pressing is carried out under vacuum. 8. Method according to claims 1-7, characterized in that in order to form a conductor plate base material consisting of several layers, individual material webs that have been impregnated with the accelerated resin system are rolled off from different rolls and brought together, possibly simultaneously, with at least one metal foil which is rolled off from a further roll and which is to be used for the coating, and that the strip formed in this way is introduced step by step into the press, preferably using a double strip press, and hot pressed. 9. Method according to claims 1-8, characterized in that the material webs are cut to the final length before pressing and then, together with the metal foil web which has possibly also been cut to the final length, are introduced into the pressure-active zone. 10. Method according to claims 1-9, characterized in that no pressed sections of the base material are formed between pressed sections of the conductor plate base material or that a metal foil connection is left behind. 11. Method according to claims 1-10, characterized in that the band-shaped materials are fixed to each other in their relative position before or during the cutting within the edge area using clamps, rivets, staples or the like and are then gradually introduced into the press. 12. Method according to claims 1-11, characterized in that in the first working step the materials and metal foil webs to be applied are introduced into a hot press zone, that in the second step a cooling is carried out under pressure in a cooling zone, and that in the third working step cutting the conductor plate base material along the edge and possibly divided into lengths. 13. Method according to claims 1-11, characterized in that in the first work step the webs are introduced into a press zone and there heated using high-frequency current and then exposed to a cooling, and that in the second work step the conductor plate base material is cut along the edge and possibly divided into lengths. 14. Method according to claims 1-13, characterized in that the metal foil or the metal foils to be applied are preheated. 15. Device for carrying out the method according to claims 1-14, characterized in that it comprises a double-belt press with rhythmic feeding movement, the press having a heating zone and a cooling zone connected to this, an optionally cooled draw-in-deflection drum pair arranged in front of the heating zone and a draw-in-deflection drum pair arranged after the cooling zone. 16. Device for carrying out the method according to claims 1-14, characterized in that it comprises a double-belt press with a rhythmic feeding movement, the press having a first zone in which a capacitive heating using high-frequency current and then a cooling takes place, and that an optionally cooled draw-in-deflection drum pair is arranged in front of the press zone and then a pull-out deflection drum pair. 17. Device according to claim 15 or 16, characterized in that devices for storing, unrolling and guiding the material webs and metal foil webs are arranged in front of the double belt press in the retracting direction. 18. Device according to claim 15 or 16, characterized in that insulations are arranged before and after the heating zone to avoid or limit heat radiation. 19. Device according to claim 15 or 16, characterized in that heatable retracting deflection drums for the metal foil webs and heat shields to protect the material webs from radiant heat are arranged. 20. Device according to claim 15 or 16, characterized in that edge cutting devices and possibly a device for division into lengths are arranged after the extraction-deflection drum pair.