GB1586275A

GB1586275A - Base material for printed circuits

Info

Publication number: GB1586275A
Application number: GB19125/77A
Authority: GB
Original assignee: AEG Isolier und Kunststoff GmbH; Licentia Patent Verwaltungs GmbH
Current assignee: AEG Isolier und Kunststoff GmbH; Licentia Patent Verwaltungs GmbH
Priority date: 1976-05-06
Filing date: 1977-05-06
Publication date: 1981-03-18
Also published as: SE7705151L; DE2619970A1; IT1084491B

Description

(54) A BASE MATERIAL FOR PRINTED CIRCUITS (71) We, LICENTIA PATENT-VERWAL TUNGS G.m.b.H., of Theodor-Stern-Kai 1, 6000 Frankfurt am Main, Federal Republic of Germany, a German body corporate and AEG ISOLIER-UND KUNSTSTOFF G.m.b.H., of Falderbaumstrasse 15, 3500 Kassel-Waldau, Federal Republic of Germany, a German body corporate, do hereby declare the inven tion, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a surface region of a base material for printed circuits made of an organic polymer bonding means.

It is already known to pre-treat plastics surfaces to be metallised or the surfaces of a base material which is to serve for the manu facture of printed circuits chemically for the purpose of roughening them, particularly by means of surface etching with sulphuric acid containing potassium bichromate or with fluoroboric acid containing an oxidation agent.

Furthermore it is known to carry out sur face treatment with a sulphonating agent, particularly with a gas phase containing sulphur trioxide.

The previously mentioned surface treat ment has the disadvantage that it does not penetrate to very great layer depths which has the result that the bored or punched orifices to be introduced later into the base material exhibit a non-etched surface on their wall which cannot ensure sufficient adhesion.

In addition overetching of the surfaces may occur with the known methods since the control of the etching or oxidation or sul phonating means may only be carried out in some cases with a considerable technical outlay.

However over-etching, as is known, has the result that metal adhesion is affected dis advantageously.

The use of chromic acid-containing etching means is very problematical, - moreover, because of the pollution of the effluent and thus requires considerable effort to overcome it.

Treatment with sulphur trioxide in the gas phase is very expensive too since the control of the concentration of the treatment agent and neutralization of the excess reaction medium requires special apparatus.

Furthermore, it has been proposed to add polymers to a base material-bonding agent or to an adhesion producing agent applied to the base material in order to avoid these disadvantages, these polymers having been modified by chemical preparation and containing in particular sulphonic acid groups as a result of a pre-treatment in a separate process with suitable sulphonating agents, such as sulphuric acid or sulphur trioxide.

This method also has disadvantages since the sulphonating reaction itself does not always lead to products of unambiguous composition and subsidiary reactions occur which lead to oxidation, cross-linking or to decomposition. The reaction mixtures obtained are too hydrophilic during persulphonation so that they cannot adequately be mixed with the organic phase of the resin or adhesion agent solutions and in the case of less strong sulphonation are sufficiently compatible with the organic medium but are not sufficiently hydrophilic or polar for the subsequent processes of the method so that metalization does not in the end have the desired success which may be reproduced.

The present invention seeks to manufacture a substrate material in which the surface and/ or the entire substrate thickness may be provided with active areas for metallization in a simple manner wherein an oxidizing surface treatment for the purpose of roughening the surface may be omitted.

Furthermore, it is desirable that the active -areas should be distributed as uniformly as possible and should be in the desired dose amount over the surface and/or throughout the volume.

According to the invention, there is provided a substance for printed circuits comprising an insulating element of resin impregnated laminate with a surface region of an organic polymer binder, prepared from an organic solution, and a further polymer containing polar salt components formed from acidic groups.

For example polymers made of sulphonated styrene divinyl benzene or sulphonated copolymers made of styrene/acrylic acid or terpolymers made up of the previously mentioned monomers which are present in neutralized form preferably as sodium salts may be used for the binder.

Furthermore, the polymer used may be a salt of a polymerized carboxylic acid for example, a salt of a polymer or a copolymer of acrylic acid. In addition the use of polyesters having salt groups has proved advantageous for the present invention, particularly on the basis of aromatic dicarboxylic acids. Finally, aromatic polymers substituted with reactive groups which contain salt groups may come into use.

Manufacture of the polar salt components which act as active components may be carried out in a separate operation from manufacture of the base layer in a controlled manner and the substances obtained in this way may in a simple and controlled manner in measured quantities be incorporated subsequently into the base material and/or an adhesion-producing layer, which is applied to the base material.

A metallization by the- additive process may be carried out on a base material with the additions in accordance with the invention without the normal oxidizing treatment having to be carried out with strong acidic etching agent.

Problems with the effluent cannot occur in this method. Furthermore, it is advantageous that the additional components may be introduced into the base material or the adhesion-producing layer inherently in any desired volume.

The further polymer may also be added to polymers of the base material which are not accessible normally to the known etching methods.

For example prepregs which are to be pressed are further processed in known manner to form moulded laminated plastics for the manufacture of the base material, said prepregs being manufactured from conventional layers of glass fibre or paper which are impregnated with a dispersion of a resinhardener solution and the further polymer in accordance with the invention.

In a similar manner a resin and/or rubber solution in which the further polymer is dis persed may be applied to the base layer as an adhesion-producing layer. It may be ad visable, depending on the base material or the adhesion-producing layer, for a suitable pretreatment to take place before catalysis and metallization, for example by means of roughening the surfaces mechanically, for example by brushing under wet conditions, or by soaking in a solvent.

The proportion of further polymer in the base layer and/or in the adhesion-producing layer varies within wide limits according to the requirements set in each case.

Although there is effectiveness during metallization with almost 100% proportion of the further polymer it has proved advisable for various reasons to use a proportion of 10 to 30%, for example.

In a particular example, between 10 and 30 % by weight of a powdered polymer substance containing polar salt components formed from acid groups in accordance with the invention on the base of a sulphonated styrene acrylic acid copolymer having at least 5 mol per cent salt groups are added to a surface layer acting as an adhesion-producing agent and having a phenol resin cross linked nitrile rubber as a bonding agent. Adhesion properties of 40 to 80 N/25 mm may be achieved after mechanically roughening the surface, for example by means of a brushing process and after known catalysis and electroless metallization.

The active substance is dispersed in the organically dissolved bonding agent.

Similar results are obtained with a 30% addition of a sodium salt of a weakly crosslinked polyacrylic acid to the same bonding agent.

WHAT WE CLAIM IS:- 1. A substance for printed circuits comprising an insulating element of resin impregnated laminate with a surface region of an organic polymer binder, prepared from an organic solution, and a further polymer containing polar salt components formed from acidic groups.

2. A substrate according to claim 1, wherein the salt components contain sulphonic acid groups.

3. A substrate according to claim 1, wherein the polymer is a salt of a polymerised carboxylic acid.

4. A substrate according to claim 3, wherein the polymerised carboxylic acid is a polyacrylic acid.

5. A substrate according to any one of claims 1 to 4, wherein the polar salt component contain a sodium salt of a styrene-acrylic acid copolymer.

6. A substrate according to any one of claims 1 to 5, wherein the surface region contains from 10 to 30 % by weight of the polymer which contains polar salt components.

7. A substrate according to any one of claims 1 to 4 and 6 wherein the polymer is a sodium salt.

8. A substrate according to claim 7, wherein the polymer is a sodium salt of a sulfonated styrene divinyl benzene polymer.

9. A substrate according to claim 7, wherein the polymer is a sodium salt of a sulfonated styrene-acrylic acid copolymer.

10. A substrate according to claim 7,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. containing polar salt components formed from acidic groups. For example polymers made of sulphonated styrene divinyl benzene or sulphonated copolymers made of styrene/acrylic acid or terpolymers made up of the previously mentioned monomers which are present in neutralized form preferably as sodium salts may be used for the binder. Furthermore, the polymer used may be a salt of a polymerized carboxylic acid for example, a salt of a polymer or a copolymer of acrylic acid. In addition the use of polyesters having salt groups has proved advantageous for the present invention, particularly on the basis of aromatic dicarboxylic acids. Finally, aromatic polymers substituted with reactive groups which contain salt groups may come into use. Manufacture of the polar salt components which act as active components may be carried out in a separate operation from manufacture of the base layer in a controlled manner and the substances obtained in this way may in a simple and controlled manner in measured quantities be incorporated subsequently into the base material and/or an adhesion-producing layer, which is applied to the base material. A metallization by the- additive process may be carried out on a base material with the additions in accordance with the invention without the normal oxidizing treatment having to be carried out with strong acidic etching agent. Problems with the effluent cannot occur in this method. Furthermore, it is advantageous that the additional components may be introduced into the base material or the adhesion-producing layer inherently in any desired volume. The further polymer may also be added to polymers of the base material which are not accessible normally to the known etching methods. For example prepregs which are to be pressed are further processed in known manner to form moulded laminated plastics for the manufacture of the base material, said prepregs being manufactured from conventional layers of glass fibre or paper which are impregnated with a dispersion of a resinhardener solution and the further polymer in accordance with the invention. In a similar manner a resin and/or rubber solution in which the further polymer is dis persed may be applied to the base layer as an adhesion-producing layer. It may be ad visable, depending on the base material or the adhesion-producing layer, for a suitable pretreatment to take place before catalysis and metallization, for example by means of roughening the surfaces mechanically, for example by brushing under wet conditions, or by soaking in a solvent. The proportion of further polymer in the base layer and/or in the adhesion-producing layer varies within wide limits according to the requirements set in each case. Although there is effectiveness during metallization with almost 100% proportion of the further polymer it has proved advisable for various reasons to use a proportion of 10 to 30%, for example. In a particular example, between 10 and 30 % by weight of a powdered polymer substance containing polar salt components formed from acid groups in accordance with the invention on the base of a sulphonated styrene acrylic acid copolymer having at least 5 mol per cent salt groups are added to a surface layer acting as an adhesion-producing agent and having a phenol resin cross linked nitrile rubber as a bonding agent. Adhesion properties of 40 to 80 N/25 mm may be achieved after mechanically roughening the surface, for example by means of a brushing process and after known catalysis and electroless metallization. The active substance is dispersed in the organically dissolved bonding agent. Similar results are obtained with a 30% addition of a sodium salt of a weakly crosslinked polyacrylic acid to the same bonding agent. WHAT WE CLAIM IS:-

1. A substance for printed circuits comprising an insulating element of resin impregnated laminate with a surface region of an organic polymer binder, prepared from an organic solution, and a further polymer containing polar salt components formed from acidic groups.

10. A substrate according to claim 7,

wherein the polar salt components contain a salt of a sulfonated styrene-acrylic acid divinyl benzene terpolymer.

11. A substrate according to any one of claims 1 to 6, wherein the further polymer is an aromatic polyester containing the polar salt components.

12. A substrate according to any one of claims 1 to 11, wherein the impregnating resin for the laminate contains a polymer which contains polar salt components formed from acidic groups.

13. A substrate for printed circuits as claims in claim 1, and substantially as described herein.