WO1999009794A1

WO1999009794A1 - The production of three-dimensional printed-circuit boards

Info

Publication number: WO1999009794A1
Application number: PCT/EP1998/005014
Authority: WO
Inventors: Gerhard-Dieter Wolf; Friedrich Jonas; Rudolf Winghofer; Stefan Stampfer
Original assignee: Bayer Aktiengesellschaft
Priority date: 1997-08-20
Filing date: 1998-08-07
Publication date: 1999-02-25
Also published as: AU9162098A; TW404152B; DE19736093A1

Abstract

The invention relates to a method for arranging printed conductors on a three-dimensional plastic moulded part, comprising the following steps: the plastic moulded part, which supports the raised conductor layout, is produced by injection moulding; the conductor layout is then coated with an activator-containing primer which is suitable for currentless metallization; the primer is dried; the raised conductor layout is then retreated by injection moulding, during which the lower-lying parts of the plastic moulded piece are filled up so that only the activated printed conductors remain uncovered; the activated printed conductors are chemically metallized and optionally reinforced by electroplating. Such three-dimensional plastic moulded parts with conductor layouts are used in electric or electronic appliances as integrated housings containing the printed-circuit board.

Description

Production of three-dimensional circuit boards

The present invention relates to a method for producing a three-dimensional plastic armature part metallized in the form of conductor tracks and the use thereof as a printed circuit board in the form of the housing of an electrical or electronic

Apparatus.

In electrical engineering, three-dimensional circuit boards, in which, for example, housing parts in the three dimensions of their dimensions can be used directly as circuit carriers, are becoming increasingly important. Such housing parts with integrated circuit boards can be manufactured by various methods. A process that is already used technically is two-component injection molding. Here, a metallizable plastic is injected in a first shot. In a second shot, a plastic that cannot be metallized is injected around the first molded part in such a way that only the desired conductor tracks are exposed.

The molded parts are then metallized using conventional methods known to those skilled in the art, in which case only the exposed structures of the metallizable plastic are metallized. A disadvantage of this method is the fact that the three-dimensional housings thus produced with integrated circuit boards always consist of different plastics and therefore cannot be simply recycled according to type.

Another method uses only one type of plastic. In a first shot, the interconnect pattern is injected as above from a plastic into which a metallization activator, for example based on palladium, has previously been incorporated. Then the same plastic, but without activator, is injected around the first molded part in a second shot in such a way that only the interconnect pattern formed by the activator-containing plastic is exposed; Thereafter, work is also carried out here in conventional metallizing baths known to those skilled in the art. The proportion of plastic used in the activator is not just that

Surface of the molded parts, but evenly distributed in mass in the plastic. The disadvantage of this method is therefore the need for uneconomically high Amounts of catalyst. Both methods are described in the journal Galvanotechnik 85 (1994), p. 1314.

It has now been found that the disadvantages mentioned can be overcome by the process according to the invention described below.

The invention relates to a method for producing a three-dimensional molded plastic part metallized in the form of conductor tracks, which is characterized by the

Process steps:

a) Production of a three-dimensional molded plastic part by injection molding, which carries the conductor track image in raised form in the form of ribs with recesses in between;

b) coating the conductor track image with a primer suitable for electroless metallization and containing an activator;

c) drying the primer;

d) partial or complete leveling of the raised conductor track image in the form of ribs with intervening depressions by filling up the depressions between the ribs of the plastic molded part by renewed injection molding, so that the activated conductor tracks remain exposed;

e) chemical metallization of the activated conductor tracks; and

f) optionally subsequent galvanic reinforcement of the chemically metallized conductor tracks.

The invention further relates to the use of the metallized three-dimensional plastic molded part as a printed circuit board in the form of the housing or inner part of an electrical or electronic apparatus. Plastic molded parts in the sense of the present invention are regularly or irregularly shaped molded parts which represent the housing or housing (inner) parts of an electrical or electronic apparatus. In any case, such housings or housing parts carry conductor tracks in the three dimensions of the dimensions

Housing or housing parts In a rectangular-shaped housing, the conductor tracks can therefore follow the right angle, any other angle can take the place of the right angle.In addition, the conductor tracks can follow any curvature and thus combine any fashionable design and technical applications. Such conductor tracks serve as circuits or parts of circuits of the electrical or electronic apparatus accommodated in such housings or housing parts. Examples of such housings which simultaneously carry conductor tracks are housings of television or radio devices, of computers or, in the case of telephone devices, of both the hand-held device and the telephone base, and further analog possibilities known to those skilled in the art

In a first step a) of the method according to the invention, a plastic molded part (housing or housing part) is produced with the aid of injection molding technology, which carries an interconnect image at the intended location in the form of raised ribs with recesses located between them

In a second method step b), these ribs, which represent the conductor track pattern, are covered with a primer suitable for electroless metallization, which contains an activator for electroless metallization. The conductor pattern can be coated with the primer, for example by printing, stamping,

Dipping, painting, knife coating or spraying can be carried out

In a further process step c) the primer is dried

The molded plastic part treated in this way is then through for further treatment d)

Injection molding technology ready, whereby the recesses between the ribs of the molded plastic part are filled up to such an extent that the originally raised conductor pattern is partially or completely leveled, so that the activated ones Conductors remain exposed. This shows an advantage of the method according to the invention, in which very little care must be taken when coating the conductor track image according to method step b), since all the areas of the depressions of the molded plastic part which are coated in the form of the conductor track image are covered in method step d) and are therefore no longer available to the subsequent chemical metallization in the desired sense.

In a further step e), the plastic molded part is then chemically metallized wherever the activated conductor tracks have remained free. This chemical

Finally, if desired, metallization can subsequently be galvanically reinforced in step f).

In principle, all plastics which can be processed by injection molding are suitable as plastics for the plastic parts to be metallized according to the invention. These are, for example: acrylonitrile-butadiene-styrene (ABS) polymers, polycarbonate (PC), their mixtures and flame-retardant types, furthermore polyamide (PA), for example polyamide 6, polyamide 66, polyester types such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aromatic, liquid crystalline polyester, polyvinyl chloride (PVC), polyethylene, polypropylene, polyphenylene sulfide,

Polyphenylene oxide, polyurethanes, polyimides, polyamideimides, polyetherimide, polysulfones, polyacetals, polystyrene and their copolymers or blends.

Preferred plastics for injection molding in the process according to the invention are arylnitrile-butadiene-styrene copolymers, polycarbonate, polyamide, polyetherimide, polysulfones, their copolymers and blends.

These plastics and their processing by injection molding and the machines used for this purpose are known to the person skilled in the art. For injection molding, depending on the softening range and the thermal resistance comes the above

Plastics in the general range of 150 to 400 ° C in question. Many of these plastics can also be used as matrix formers described below; It is now advantageous to match plastics for injection molding and those as matrix formers so that they have comparable thermal resistance.

The width of the ribs on the plastic molded parts is very variable and ranges from about 100 μm to a few centimeters (e.g. 5 cm), preferably from 200 μm to

5 mm. The distance between the ribs is also very variable and ranges from 100 μm to a few centimeters (e.g. 5 cm), preferably from 200 μm to 1 cm, particularly preferably from 400 μm to 0.8 cm. The depressions between the ribs measure from 200 μm to a few centimeters (e.g. 5 cm), preferably from 500 μm to 1 cm, particularly preferably from 1 mm to 0.8 cm. In the second injection molding in step 2), the depressions can be completely filled, so that the ribs from the injection molding a) with the conductor tracks and the plastic from the injection molding d) lie completely in one plane. However, it is equally possible to fill up the depressions only partially, so that the ribs are still shown, but at a lower height than before.

The primer essentially consists of (i) a polymer as film or matrix former, (ii) a metallization catalyst (activator), (iii) optionally organic and / or inorganic fillers, (iv) optionally other constituents and (v) Solvents.

Depending on the solvent system (organic or aqueous), various film or matrix formers can be used. Examples of primers with an organic solvent system are: lacquer systems such as alkyd resins, unsaturated polyester resins, polyurethane resins, epoxy resins, modified fats and oils, polymers or copolymers based on vinyl chloride, vinyl ethers, vinyl esters, styrene, (meth) acrylic acid, acrylonitrile or acrylic esters, Cellulose derivatives or the stoving enamels which crosslink at a higher temperature, such as, for example, polyurethanes from hydroxyl-containing polyethers, polyesters or polyacrylates and masked polyisocyanates, melamine resins from etherified melamine-formaldehyde resins and hydroxyl-containing polyethers, polyesters or polyacrylates, epoxy resins from polyexpoxides and polycarboxylic acid-containing acrylic groups, carboxylates containing carboxylates, carboxylates made of polyesters, polyesterimides, Polyester amide imides, poly amide imides, polyamides, polyhydantoins and polyparabic acids.

Film or matrix formers based on polyurethane systems that are made up of the following components are particularly well suited:

1. Aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates as described, for example, in Justus Liebigs Analen der Chemie, 362, pp. 75-136. The technically easily accessible polyisocyanates, for example that, are generally particularly preferred

2,4- and 2,6-tolylene diisocyanate and mixtures of these isomers (TDI); Polyphenyl polymethylene polyisocyanates such as those produced by aniline-formaldehyde condensation and subsequent phosgenation (MDI) and carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups containing polyisocyanates.

2. Compounds with at least two isocyanate-reactive hydrogen atoms with a molecular weight of generally from 400 to 10,000, preferably 1,000 to 6,000, particularly preferably 2,000 to 6,000. Reactive hydrogen atoms are those from amino groups, thiol groups, carboxyl groups and preferably hydroxyl groups.

3. If necessary, further compounds with isocyanate-reactive hydrogen atoms, which can serve as chain extenders, and auxiliaries and additives, such as catalysts, surface-active additives and

Response delay. Such polyurethanes are known and are described, for example, in EP-485 839.

In the case of primers with a predominantly or completely aqueous solvent system, in principle all dispersible polymers come, for example

Polyacrylates, polybutadienes, polyesters and melamine resins, in question. Polyurethanes or polyurethane ureas, such as those described in US Pat Angewandte Chemie 82, 1970, pp. 53-63, are described in DE-A 2 314 512 or DE-A 2 314 513. Particularly preferred dispersible polyurethanes have essentially a linear molecular structure and are characterized by a) terminal polyalkylene oxide polyether chains with a content of ethylene oxide units of 0.5 to 10% by weight, based on the total polyurethane, and b) a content of quaternized nitrogen, tertiary sulfur, carboxyl groups or sulfonic acid groups from 0.1 to 15 milliequivalents per 100 g. The composition of such preferred dispersible polyurethanes and their preparation are also known and are described, for example, in DE-A 2 651 506.

Ionic and / or colloidal noble metals or their organometallic covalent compounds or complex compounds with organic ligands are suitable as activators. The precious metals come from subgroups I and VIII of the Periodic Table of the Elements (Mendeleev) and are, for example, Pd, Pt, Au and Ag.

Organic and / or inorganic fillers for such primers are, for example, the oxides of the elements Mn, Ti, Mg, Al, Bi, Cu, Ni, Sn, Cn and Si, and also silicates, bentonites, talc and chalk. Individual examples are furthermore: Powdered high-melting plastics, disperse silica, Russian, other carbon powder,

Clay minerals, titanium oxide.

Solvents for primers which can be used according to the invention are the substances known in printing or coating technology, such as aromatic and aliphatic hydrocarbons, for example toluene, xylene, gasoline; Glycerin; Ketones, for example

Methyl ethyl ketone, cyclohexanone; Esters, for example butyl acetate, dioctyl phthalate, butyl glycolate; Glycol ethers, for example ethylene glycol monomethyl ether, diglyme, propylene glycol monomethyl ether; Esters of glycol ethers, for example ethylene glycol acetate, propylene glycol monomethyl ether acetate; Diacetone alcohol, N-methylpyrrolidone, N-methylcapolactan. Mixtures of these solvents and their blends with other solvents can of course also be used. In the case of water-based primers, water alone or a mixture of water with water-soluble solvents can be used. Water-miscible solvents are, for example, alcohols, such as methanol, ethanol, propanol, butanol; Ketones such as acetone, methyl ethyl ketone, cyclohexanone; Glycol ethers, such as ethylene glycol monomethyl ether, diglyme, propylene glycol monomethyl ether; water-soluble ethers such as tetrahydrofuran, dioxane.

Other constituents for the primers are, for example, surfactants, leveling agents, defoamers and dyes in small concentrations of up to 5% by weight, preferably up to 2% by weight, based on the total amount of primer. Such components are generally known to the person skilled in the art.

Examples of such primer formulations are described in EP-A 48 58 39 and EP-A 50 33 51.

Preferred primers based on organic solvents consist essentially of, for example

a) a film or matrix former in an amount of 3 to 30% by weight,

b) an ionogenic and / or colloidal noble metal or its organometallic covalent compounds or complex compounds with organic ligands in an amount of 0.05-2.5% by weight, calculated as metal,

c) organic and / or inorganic fillers in an amount of

0.5-35% by weight and

d) organic solvents in an amount of 50-90% by weight, all based on the total amount of primer.

In a particularly preferred manner, such primers are based on organic solvents due to an additional content of e) an organic polymeric or prepolymeric additive with a molecular weight of 500-20,000 from the group of polyoxazolines, polymethacrylic acid or their esters, polyacrylates, polyamides, polyesters, polyalcohols and polyamines in an amount of 0.1-15% by weight .-%, based on the total formulation of the primer.

Preferred primers based on aqueous formulations consist essentially of

a) a water-dispersible polymer, preferably a polyurethane, in amounts of 5-60% by weight, preferably 15-45% by weight,

b) a metallization catalyst in the form of an ionic or complex noble metal compound in amounts of 0.02-3.5% by weight, preferably 0.05-0.5% by weight,

c) optionally fillers in amounts of 0-70% by weight, preferably 5-35% by weight,

d) if necessary, other constituents of the type mentioned in quantities of

0 - 5 wt .-%, preferably 0 - 2 wt .-% and

e) water in amounts of 20-88% by weight, preferably 25-50% by weight, in each case based on the total amount of the primer.

Optionally used water-soluble organic solvents of the type mentioned replace a maximum of 1/3, preferably a maximum of 1/4, particularly preferably a maximum of 1/10 of the amount of water mentioned.

The layer thickness of the primer can be varied in a wide range from 0.1 to 200 μm, preferably in the range from 5 to 50 μm. For solvent-based primers, there is a particularly preferred range from 5 to 30 μm; for aqueous primers there is a particularly preferred range of 10-50 μm. After the primer has dried at 0 to 250 ° C, preferably and depending on the plastic used 50 to 200 ° C, the dry layer thickness of the primer is about half the layer thickness of the wet applied primer. Depending on the temperature used, the drying time is between a few minutes and several hours, preferably between 5 and 90 minutes.

After drying, the plastic molded part for leveling the raised conductor tracks is again treated by injection molding with the same plastic as in the first spraying in order to level the rib-shaped raised conductor tracks. This leaves the one applied to the highest points of the ribs

Primer on the surface and is available for subsequent chemical metallization, while primers placed on the flanks of the ribs or the original base of the plastic molded part between the ribs are covered by the second injection molding process and therefore cannot be metallized, which leads to short circuits between them the individual conductor tracks can be reliably prevented. It is advantageous to carefully remove organic solvents or water from the primer by drying before the second injection molding process in order to avoid any bubbles forming in the second injection molding process.

The metallization baths used for electroless metallization are commercially available and known to the person skilled in the art. Metals suitable for producing the conductor tracks are, for example, Cu, Ni, Ag, Au, Pd, preferably Cu.

In the event of a subsequent galvanic reinforcement of the chemically metallized conductor tracks, the metal layer thickness can be increased to up to 500 μm

Question. Examples

example 1

A water-based primer solution I was prepared by combining

26% by weight of a water-dispersible polymer based on a substantially linear aliphatic, polyether group-containing polyurethane with carboxyl groups and sulfonic acid groups, 1% by weight AgN0 ₃ , 30% by weight talc and Ti0 ₂ and 43% by weight Water, all based on the total weight of the aqueous primer.

Example 2

A primer solution II based on organic solvents was prepared by combining 5% by weight of a polyurethane made of poly [(butanediol adipate) -

(neopentylglycol)] and 4,4-diphenylmethane diisocyanate, 0.5% by weight AgN0 ₃ , 10% by weight talc and Ti0 ₂ , 82.85% by weight solvent mixture of diacetone alcohol, i-propanol and Toluene, 1% by weight of a polyamide hot melt adhesive and 0.65% by weight of wetting agents and dyes.

Example 3

A curved conductor track structure with raised ribs was produced from an acrylonitrile-butadiene-styrene copolymer by injection molding. The metallizable primer solution I from Example 1 was sprayed onto the molded part thus produced. The

The layer was dried at 70 ° C. for 60 minutes and gave a dry layer thickness of about 9 μm. The molded part was then encapsulated with the same copolymer in such a way that only the desired conductor track structure with the metallizable primer layer I was exposed. The mixture was then metallized at 43 ° C. for 1 hour using a chemical copper bath (Shipley, type CP 78). The

Copper thickness of the conductor tracks was 2 μm; after galvanic reinforcement on 35 μm copper, the adhesive strength was 0.8 N / mm. Example 4

A curved conductor track structure with raised ribs was again produced from the copolymer used in Example 3 by injection molding. The metallizable primer solution II was applied to the ribs of the molded part produced in this way

Example 2 sprayed on. After drying for 70 min at 70 ° C, a dry layer thickness of about 18 microns resulted. The sprayed-on primer solution II was also in the recesses between the conductor ribs. The molded part was then encapsulated with the same copolymer in such a way that only the desired conductor track structure with the primer solution II located on the surface was exposed. Thereafter, metallization was carried out for 1.5 hours with the same chemical copper plating bath as in Example 3 at 43 ° C. The thickness of the copper layer was 3 μm; after galvanic reinforcement on 35 μm copper, an adhesive strength of the conductor tracks of 0.8 N / mm was measured.

Claims

claims

1. Method for producing a three-dimensional molded plastic part metallized in the form of conductor tracks, characterized by the method steps:

a) production of a three-dimensional molded plastic part by injection molding, which carries the conductor track image in a raised form in the form of ribs with recesses in between,

c) drying the primer;

d) partial or complete flattening of the raised conductor track image in the form of ribs with intervening depressions by filling up the depressions between the ribs of the plastic molding by renewed injection molding, so that the activated conductor tracks remain exposed;

e) chemical metallization of the activated conductor tracks; and

2. Use of the metallized three-dimensional molded plastic part as

Printed circuit board in the form of the housing or inner part of an electrical or electronic apparatus.

A method according to claim 1, characterized in that as plastics for injection molding acrylonitrile-butadiene-styrene polymers, polycarbonate, polyamide, polyester, polyvinyl chloride, polyethylene, polypropylene, polyphenylene sulfide, Polyphenylene oxide, polyurethanes, polyimides, polyamideimides, polyetherimide, polysulfones, polyacetals, polystyrene, their copolymers or blends, preferably acrylonitrile-butadiene-styrene polymers, polycarbonate, polyamide, polyetherimide, polysulfones, their copolymers or blends are used.

4. The method according to claims 1 and 3, characterized in that the ribs are made in a width of 100 microns to 5 cm, preferably in a width of 200 microns to 5 mm.

5. The method according to claims 1, 3 and 4, characterized in that the

Ribs with a distance of 100 μm to 5 cm, preferably with a distance of 200 μm to 1 cm, particularly preferably 400 μm to 0.8 cm, are produced.

6. The method according to claims 1 and 3 to 5, characterized in that the

Recess between the ribs with a dimension of 200 microns to 5 cm, preferably 500 microns to 1 cm, particularly preferably 1 mm to 0.8 cm.

7. The method according to claims 1 and 3 to 6, characterized in that the

Primer after step b) consists of (i) a polymer as film or matrix former, (ii) a metallization catalyst as activator, (iii) optionally organic or inorganic fillers, (iv) optionally other constituents and (v) solvents.

Process according to Claims 1 and 3 to 7, characterized in that those which essentially consist of are used as primers

a) a film or matrix former in an amount of 3 to 30% by weight,

b) with an ionogenic and / or colloidal noble metal or its organometallic covalent compounds or complex compounds with organic ligands in an amount of 0.05-2.5% by weight, calculated as metal,

c) organic and / or inorganic fillers in an amount of 0.5-35% by weight and

d) organic solvents in an amount of 50-90% by weight, all based on the total amount of primer,

which preferably have an additional content

e) an organic polymeric or prepolymeric additive with a molecular weight of 500-20,000 from the group of polyoxazolines, polymethacrylic acid or their esters, polyacrylates, polyamides, polyesters, polyalcohols and polyamines in an amount of 0.1 -

15% by weight, based on the total formulation of the primer.

9. The method according to claims 1 and 3 to 7, characterized in that those are used as primers based on aqueous formulations, which consist essentially of

c) optionally fillers in amounts of 0-70% by weight, preferably 5-35% by weight, d) if appropriate, other constituents of the type mentioned in amounts of 0-5% by weight, preferably 0-2% by weight, and

10. The method according to claims 8 and 9, characterized in that as a film or. Matrix former a polyurethane is used.