GB1596493A

GB1596493A - Additive method of manufacturing wiring patterns

Info

Publication number: GB1596493A
Application number: GB14736/78A
Authority: GB
Original assignee: Philips Gloeilampenfabrieken NV
Current assignee: Koninklijke Philips NV
Priority date: 1977-04-19
Filing date: 1978-04-14
Publication date: 1981-08-26
Also published as: NL7704238A; FR2388459A1; JPS53129867A; DE2815696A1; FR2388459B1

Description

(54) ADDITIVE METHOD OF MANUFACTURING WIRING PATTERNS (71) We, N. V. PHILIPS' GLOEILAMPENFABRIEKEN, a limited liability Company, organised and established under the laws of the Kingdom of the Netherlands, of Emmasingel 29, Eindhoven, the Netherlands; do hereby declare the invention, 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 invention relates to a method of additively manufacturing wiring patterns, in which method an electrostatic charge image is provided electrographically on a substrate, which charge image is converted into a nuclear metal image which is subsequently intensified.

Such a method is known from the GDR patent specification 94,423, in which method an electrically insulating substrate is provided with a layer of an adhesion intermediary, the desired pattern is printed thereon electrographically by means of a profiled metal electrode, the resulting charge image is converted into a nuclear metal image by contact with a solution of a noble metal salt complex and the nuclear metal image is intensified to the desired conductivity by means of electroless metallization.

As an adhesion intermediary are used as a rule adhesive compositions for example acrylonitrile - butadiene - cresol formaldehyde - adhesive on carriers comprising synthetic resin, for example, glass fibre-reinforced epoxy resin. However, for some professional applications these materials do not have the desired properties.

Therefore, for many applications oxidic substrate material is preferably used, that is to say, ceramic or vitreous material, or an oxide layer which is formed on a metal surface by anodic oxidation. These materials have a better temperature stability and dimensional stability, which is of importance, for example, for hybrid circuits in thick film techniques. Furthermore these support materials have a better heat dissipation and as a rule they are much less sensitive to the action by moisture than are materials comprising synthetic resins.

The invention provides a method of additively manufacturing a wiring pattern on an oxidic substrate (as hereinafter defined), the method comprising the steps of electrophotographically producing an electrostatic charge image on the substrate, converting the charge image into a nuclear metal image by contacting the charge image with a suspension of a metal or metal compound in a dispersion medium, heating the substrate at a temperature of at least 1000C so as to bond the nuclear metal image to the substrate, and intensifying the nuclear metal image by means of an electroless metal-plating solution, wherein the dispersion medium has a resistivity exceeding 108 ohm.cm. Throughout this Specification the expression "oxidic substrate" is understood to mean a ceramic or vitreous oxidic body, an oxide layer formed by anodic oxidation of a metal body and supported by the unoxidized portion of the metal body, or an oxide layer formed by chemical oxidation of a metal or semiconductor body and supported by the unoxidized portion of that body. For a substrate material which consists of glass or ceramic, heating at a temperature above 400"C is necessary. Anodized metals require an aftertreatment temperature between approximately 100 and 1500C.

In addition to the metal or a metal compound, the suspension preferably comprises a powder of a glass-forming binder (as hereinafter defined) and the substrate, after having been contacted with the suspension, is heated above the softening temperature of the glass-forming binder until it is connected to the substrate.

The expression "glass-forming binder" is to be understood to mean that the binder consists of powder of glass of the ultimate composition, or of a mixture of glassforming oxides from which the ultimate glass is formed by heating.

Although it is possible to provide the oxidic substrate material directly with a surface charge, it is recommendable as a rule according to a further embodiment of the method according to the invention to provide the charge on a volatilisable organic dielectric layer carried on a volatilisable organic electrically conductive layer on the oxidic substrate. This is to be preferred in the case of a ceramic substrate; in the case of glass this is also useful, in which case the electrically conductive layer may sometimes be dispensed with. In the case of anodized magnesium, such a combination layer is not necessary. Due to the presence of such a combination of organic layers a higher charge level is possible. This provides a better definition of the charge image as compared with the method in which the charge is provided directly on the oxidic surface.

After heating the nuclear metal image obtained from the charge image, a good adhesion is obtained and the nuclear metal image as such acts in many cases catalytically for the subsequent metallization by means of an electroless metal plating solution. In cases in which the catalytic effect is lost or has reduced considerably, the nuclear metal image may be reactivated. A nuclear palladium image which has become non-catalytic with vitreous binder may be reactivated, for example, by contact with a SnCl2-HCl solution.

A suitable method of converting a charge image into a nuclear metal image, notably on oxidic substrates, consists in first contacting the charge image with a dispersion of palladium black and then after intermediate rinsing with a solvent is contacted with a dispersion of tin particles and particles of a low-melting-point glass.

The resulting nuclear metal image requires no activation and a copper pattern deposited thereon has a considerable improved adhesion as compared with a copper pattern which is deposited on other nuclear metal images.

For ceramic substrates, the adhesion of a copper pattern formed thereon is improved considerably by heating the assembly, after depositing the pattern, in an inert gas atmosphere at a temperature of at least 400"C. Such heating is carried out, for example, at 850"C in a hydrogen-free nitrogen atmosphere for 10 minutes. As a result of this the solderability is not adversely influenced.

The electrographic printing of the charge according to the desired pattern may be carried out in various manners. An attractive possibility is the use of a copper mould which has the pattern to be transferred in relief. Another possibility is a flat metal electrode having a layer of a synthetic resin in the form of the desired pattern. In these cases a spacer is necessary.

A further possibility is a selective corona discharge via a metallic mask. A profiled conductor-insulator electrode may also be used.

Contactless charge transfer provides a good picture smoothness and has the advantage that detrition of the mould is reduced, which is a great advantage in particular for copper moulds.

The required voltage difference between the substrate and the pattern electrode is obtained by using a flat metal electrode abutting the opposite face of the substrate.

In the case in which the charge image is provided on a dielectric layer, the substrate is previously enveloped in an electrically conductive organic layer.

The method according to the invention may readily be used in hybrid circuit techniques. Copper conductors may be made on glass and ceramic by means of the method according to the invention, which is of great advantage as compared with the gold conductors, silver conductors or silverpalladium conductors hitherto manufactured by means of silk-screening methods. These advantages reside mainly in the absence of silver migration, the very low resistance, the low cost and the excellent solderability.

In this hybrid circuit technique, the resistors are advantageously provided by means of silk-screening. For this purpose conventional metal-metal oxide pastes for example lead ruthenate may be used. This type of resistor has a much larger range of the resistance value than, for example vapour-deposited resistors (nickelchromium) or electrolesely plated resistors (Ni-P). Circuit arrangements with silkscreened copper conductors and silkscreened resistors cannot be made because copper conductors can be heated only in a neutral to reducing atmosphere, while when making resistance materials by silkscreening the assembly must be heated in an oxidizing atmosphere. Hitherto only the combination with carbon resistors on polymer basis was possible for silk-screened copper conductors. However, these resistors have several significant disadvantages, for example, a large contact resistance to the conductors, a high noise level, a large temperature coefficient of resistance, and large moisture sensitivity.

Another embodiment of the method according to the invention may be used to make hybrid circuits; first of all, resistors are manufactured on a substrate by silkscreening a paste containing a metal compound, a vitreous binder, and an organic binder which can be removed by heating, after which the substrate bearing the silk-screened paste pattern is heated in air to remove the organic binder and to melt the vitreous binder, a charge pattern is then provided electrographically corresponding to the desired conductor pattern, said charge pattern is converted in to metal nuclei which finally are intensified to form copper tracks by electroless metallization.

In order to avoid the deposition of copper from the electroless copper-plating solution on the silk-screened resistors, these should be masked except for areas. which contact the conductors. This is preferably done by using a low-melting-point glass, which may be provided by silk-screening electrostatically or electrophoretically.

For making the copper tracks it is necessary to provide a combination layer consisting of an organic electrically conductive layer and an organic dielectric layer. The charge pattern is then produced preferably by means of a selective corona discharge via a mask. After printing and developing the nuclear metal image from which the conductor pattern is to be made, the pattern of the screening glass may be made, likewise by means of a corona discharge, charge image in this case being developed with a dispersion of particles of the relevant low-melting-point glass in a solvent having a low specific conductivity.

The heating of said glass and the nuclear metal image may then be carried out it one operation.

In a similar manner, multi-layer circuits, so called "crossovers" may also be made.

The bottom conductor pattern is made by a method according to the invention, then a glass layer is made, for example by silkscreening, and finally the top conductor layer is made by a method according to the invention. The "crossover" glass is heated in an inert atmosphere (for example nitrogen) and then forms a sealed densely sintered layer.

Methods by which an electrostatic image can be formed on a substrate will now be described with reference to the accompanying drawings, in which: Figures 1 to 4 are shcematic side sectional elevations showing the dispositions of masks, electrodes and substrates used in methods A, B, C, and D respectively.

A) (Figure 1). A substrate 1 is placed on a flat metal counter-electrode 2, while a punctiform electrode 3 is located approximately 10 cm from the substrate 1.A metal auxiliary electrode 4 consisting of a metal mask having etched therein a metal pattern to be deposited is placed at a short distance from the substrate 1 with or without a ceramic spacer 5 disposed between the electrode 4 and the substrate 1.

If the substrate I has an organic dielectric auxiliary layer on one side, said side is, of course, kept facing the electrode 4, and then no spacers are used. A high voltage is applied between the punctiform electrode 4 and the counter-electrode 2 for a short time in such manner that gas discharge occurs, for example, -6 kV is applied for 0.5 seconds.

B) (Figure 2). A substrate 1 surrounded by a conductive organic auxiliary layer 6 is placed between a profiled all-metal electrode 2 and a flat counter-electrode 3, and a dielectric organic auxiliary layer 4 is present on that part of the auxiliary layer 6 facing the profiled electrode 2. A small air gap is maintained between the profiled electrode 2 and the organic auxiliary layer 4 by means of a spacer 5 or by means of surface roughness of the auxiliary layer 4. A high voltage is applied for a short time between the profiled electrode 2 and the counterelectrode 3. The optimum voltage may be determined empirically by developing a series of electrostatic images. As a roughand-ready rule for the voltage Va to be applied may be used for Al203 substrates having auxiliary layers (400+61,) < Va (volts) < {400+6(1,+12)S, 11 being the distance (in microns) from the high points of the profiled electrode to the organic auxiliary layer and 12 being the relief depth (in microns) of the profiled electrode. For example, 1,=50 um; 12=50 ym and Va=1000 volts is chosen.

C) (Figure 3). A substrate 1 enveloped in an electrically conductive organic auxiliary layer 2 is placed between a profiled electrode and a flat counter-electrode 3. A dielectric organic auxiliary layer 4 is present on the side of the layer 2 facing the profiled electrode and rests on spacers 5. The profiled electrode consists of a metal base plate 6 having provided thereon, via adhesive layer 7, a masking pattern consisting of a developed photolacquer 8. A high voltage is applied between the counterelectrode 3 and the profiled electrode for a short time. The optimum voltage can be determined empirically by developing a series of electrostatic images. For profiled electrodes consisting of a steel base plate bearing a 200 Mm thick electrically conductive layer ("Nyloprint" of BASF) in which a pattern is formed by exposure and developing a voltage of 500 to 2000 volts is applied for a few seconds.

D) (Figure 4). A substrate 1 is placed between a profiled conductor-insulator electrode which consists of an insulator plate 2 of glass, ceramic or of a synthetic organic polymer, on which on one side a metal layer 5 is present and on the substrate side a metal layer 3 is present in which the desired pattern is recessed. A counterelectrode 4 is situated on the side of the substrate remote from the metal layer 5. A voltage difference of between 1000 and 3000 V is applied between the counter-electrode 4 and the metal layer 5.

Some embodiments of the invention will now be described with reference to the following examples.

Example 1 A ceramic Al203 substrate 1 without auxiliary layers is provided using the abovedescribed method A with an electrostatic image by applying a voltage of 6 kV between a punctiform electrode 3 and a counterelectrode 2 for 0.5 seconds.

The electrostatic image is developed by contacting the substrate with a liquid developer having the nominal composition 800 ml/l palladium black and 200 mlil lead metasilicate glass particles smaller than 5 ym dispersed in 10-3% by weight of Shell "ASA 3"+0.2% by weight of polymethacrylate in "Shellsol TD" solution.

Shellsol and ASA are trade marks. The dispersion medium which consists of the solutien of 10-3% by weight of "ASA 3"+0.2% by .weight of poly(methyl methacrylate) in "Shellsol TD" has a resistivity between 2x 10" and 5x 10" ohm cm. The resistivity of the developer is approximately 0.5x 1011 Ohm.cm. After developing for 5 seconds, the substrate is rinsed in "Shellsol TD" and is then dried in air at room temperature. The substrate is then fired in air at 800"C for 20 minutes and is then placed for 2--4 hours in an aqueous electroless copper-plating solution at 650C containing per litre: 7.5 gil CuSO4.5H2O 14 gil sodium salt of ethylene diaminetetra-acetic acid 6 gil NaOH 0.5 gil "Carbowax 4000", (which is a polyoxyethylene having a molecular weight of approximately 4000) 25 mlii formaldehyde 35%.

"Carbowax" is a Trade Mark.

A smooth and readily adhering 5 to 10 ym thick copper pattern its obtained on the substrate. "ShelsolTD" is a mixture of isoparaffins having 9 to 12 carbon atoms.

"ASA 3" is a mixture of equal parts of "Ca Aerosol", which is the Ca soap of the didecyl ester of sulphosuccinic acid, the Cr soaps of a mixture of alkyl salicylates (C14- C18), and a copolymer of methacrylate with 2-methyl-5-vinylpyridine.

Example 2 By dipping in a 5% by weight solution of "Calgon" (Chemviron 261 LV), (polyvinyl pyridinium chloride) in a mixture of equal volumes of ethyl alcohol and water, succeeded by drying, a smooth ceramic Al203 substrate is provided with a < 1 pm thick organic conductive layer having a surface resistance smaller than 109 ohms per square ("Calgon" is a Trade Mark). A 2,am thick polystyrene layer having a surface resistance exceeding 1012 ohms per square is deposited on one side of this conductive layer from a 10% solution of polystyrene in chlorobenzene. An electrostatic image is then printed on the substrate bearing the auxiliary layers 6 and 4 using the abovedescribed method B (with '1='2="' 50 microns and Via~1000 volts), which image is then developed for 10 seconds in a liquid developer having the nominal composition: 2 gil palladium black dispersed in a solution of 10-2% by weight of Shell "ASA 3" and 0.2% by weight of poly methyl methacrylate in "Shellsol TD". After developing the assembly is rinsed in "Shellsol TD" and is then dried in air at room temperature. The substrate with the palladium image is heated very rapidly to 7000C and kept at this temperature for a few minutes, so as to remove the polystyrene and the Calgon.

After cooling to room temperature, the substrate is heated at 10000C for 1 hour, the heating and cooling rates being 300 C/hour.

The substrate with the palladium image is placed in an aqueous electroless copperplating solution at 550C for 4 hours. The composition of the solution is the same as that specified in Example 1. A readily adhering copper pattern is obtained.

Example 3 A ceramic Al203 substrate is enveloped, as described in Example 2 with a < I ,um thick "Calgon" layer, and a 2 ,um thick poly(methyl methacrylate) layer is deposited ozone side of the "Calgon" layer by means of a 10% solution in chlorobenzene. An electrostatic image is printed on the poly(methyl methacrylate) layer by method C using a print voltage of 600 volts. The electrostatic image is developed for 5 seconds by means of a liquid developer having the nominal composition 800 mg/l palladium black and 200 mg/l lead borate glass particles having a particle size of < 5 ym dispersed in a solution of 10-3% by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate) in "Shellsol TD". After developing the assembly is rinsed in "Shellsol TD" and dried in air at room temperature. The substrate is then heated in air at 8000C for 15 minutes. After cooling, the nuclea palladium image is activated by placing the substrate for 30 seconds in an activator bath consisting of 10 g of SnCI2 and 10 ml of concentrated HCI per litre of water. After activation the substrate is cleaned in an ultrasonic bath and is then placed for 4 hours at 55"C in the same electroless copper-plating solution specified in Example 1. A 10 ,*4m thick, excellently adhering copper pattern is obtained on the Awl203 substrate. A lead borate glass has the following composition in % by weight PbO 80 B203 16 ZnO 4 Example 4 A ceramic Awl203 substrate is enveloped as described in Example 2 in a < 1 ,am thick "Calgon" layer and a 2,um thick poly(ethyl methacrylate) layer is deposited on one main surface of the "Calgon" layer from a 10% solution in chlorobenzene. An electrostatic image is printed on the "calgon" layer using the above-described method B (with 1,=25 microns, 12=25 microns and Va=800). This electrostatic image is developed for 10 seconds by means of a liquid developer having the nominal composition: 800 mg/l palladium black and 200 mg/l calcium-, barium-, aluminium-, boron oxide glass particles having a particle size of < 10 ym dispersed in solution of 10-3 , by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate) in "Shellsol TD". After developing, the assembly is rinsed in "Shellsol TD" and dried in air at room temperature. The substrate is then heated at 8000C in air for 1 hour and is then placed for 4 hours at 550C in the electroless copper-plating solution specified in Example 1. A readily adhering copper pattern is obtained.

The composition of the glass powder in % by weight is: CaO 6.5 Awl202 17.8 BaO 26.7 B203 49.0 Example 5 A substrate in the form of a transparency glass is enveloped as described in Example 2 with a < 1 pm thick "Calgon" layer and a 2,m thick polystyrene layer is formed on one main surface of the "Calgon" layer. An electrostatic image is provided on the polystyrene layer using method B (with 1,=25 cm and 12=30 ym by means of a print voltage of -1000 volts across the substrate and a series resistor of 10 MOhm). Said electrostatic image is developed by means of a liquid developer having the nominal composition 800 mg/l palladium black and 200 mg/l lead borate glass particles of the composition as in Example 3 and a particle size of < 5 ,um dispersed in a solution I 10-30 by weight of Shell "ASA 3" and 0.2 , by weight of poly(methyl methacrylate) in "Shellsol TD". After developing for 10 seconds, the assembly is rinsed in Shellsol TD and then dried in air at room temperature. The substrate is then heated in air at 7500C for 10 minutes and is then placed for a few hours in an electroless copper-plating bath at 650C having the following composition 75 gn CuSO4.5H2O 14 g/l sodium salt of ethylenediaminetetra acetic acid 6 gn NaOH 0.5 g/l "Carbowax 4000" (polyoxyethylene having a molecular weight of 4000).

25 mlii formaldehyde 35%.

During the copper deposition, air is passed through the copper-plating solution.

The result is a beautifully coloured, readily adhering copper pattern on the transparency glass.

Example 6 An electrostatic image is printed on a SiO2 skin, a few microns thick on a silicon slice using a method similar to method B (with 1,=25 ym, 12=20 ,um and an applied voltage of approximately 500 volts). The image is developed for a few seconds by means of a liquid developer having the nominal composition 800 mg/l palladium black and 200 mg/l lead borate dispersed in a solution of 10-3g/o by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate) in "Shellsol TD". After rinsing in "Shellsol TD" and drying in air in room temperature, the substrate is heated in air at 8000C for 10 minutes and is then placed for 4 hours in an electroless copperplating solution 650C having the composition specified in Example 1. The result is a readily adhering copper image.

A comparable product is obtained when a layer of polystyrene is provided on the SiO2 skin. The electrostatic image may be printed according to method C with a print voltage of 600 volts.

Example 7 A ceramic Al203 substrate is enveloped with a < 1 ,um thick "Calgon" layer and a 3 ,um thick polystyrene layer is formed on one main surface of the "Calgon" layer, as described in Example 2. An electrostatic image is printed on the polystyrene layer using method B (with I 112 50 microns and Va -l kV). The electrostatic image is developed for approximately 10 seconds in a liquid developer having the nominal composition 3 gil of tin particles and 3 gil lead borate glass particles smaller than 5 ym dispersed in a solution of 10-3% by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate) in "Shellsol TD". After developing the substrate is rinsed in "Shellsol TD" and ia dried at room temperature, after which the substrate is fired for 5 minutes in air at 8000C. After cooling the image is activated by dipping the substrate in a bath containing 250 mg/l PdCI2 and 4 mlii of concentrated HC1; the substrate is then rinsed in demineralised H2O and is then placed in an electroless copper-plating solution at 650 C. The composition of the copper-plating solution is the same as that used in Example 1. The result is equivalent.

According to a modified embodiment of this method, the substrate with the charge image is kept in contact for a few seconds with a solution of I gn palladium black which also contains 10-3% by weight of "ASA 3" and 0.2% by weight of poly(methyl methacrylate) in "Shellsol TD". After rinsing in clean "Shellsol TD", it was kept in contact with a dispersion of 5 gil of Sn particles < 10 Nm and 5 gil of lead borate particles (specified in Example 3) having a particle size < 5 Nm. After copper plating as above, a copper pattern having an adhesion of 3.lf1.5 T(g/20 mm2 was obtained. When the substrate with the copper pattern was then heated at 8509C for 10 minutes in a nitrogen atmosphere containing < 10 ppm of oxygen, further improvement in adhesion occurred up to 7.2+1.5 kg/20 mm2. The solderability is excellent in both cases.

Example 8 A ceramix Awl203 substrate is enveloped in a "Calgon" layer having a thickness of < I Nm and a 3 ,um polystyrene layer is formed on one main surface of the "Calgon" layer.

An electrostatic image is printed on the polystyrene layer using method B (with 111250 microns and Va -l kV). The electrostatic image is developed for 5 seconds in a liquid developer having the nominal composition 5 gil cuprous oxide particles (average particles size < 20 Nm and 5 gil lead borate particles having the composition specified in Example 3 and particle size < 5 Clam, dispersed in a solution of 0.025% by weight of chromium (IIE)-Nstearoyl-dihydroxy-anthranilate in "Shellsol TD". This dispersion medium consisting of 0.025% by weight of chromium (III)-Nstearoyl-dihydroxy-anthranilate in "Shelisol TD" has a resistivity of 10" ohm. cm. After developing the assembly is rinsed in "Shellsol TD" and is dried in air at room temperature. The substrate is then heated in air at 7000C for 15 minutes and after cooling is activated for 20 seconds in a bath containing 250 mg/l PdCIz and 4 ml/l concentrated HCI, is then rinsed with demineralised water and is metallized by means of an electroless copper-plating solution at 650C of the same composition as specified in Example 1. The result was a readily adhering copper pattern.

Example 9 A ceramic Awl203 substrate is enveloped in a < I Mm thick "Calgon" layer and a 2 Nm thick poly(methyl methacrylate) layer is formed on one main surface of the "Calgon" layer. An electrostatic image is printed on the poly(methyl methacrylate) layer using method A, by means of a voltage of -6 kV which is applied for a few seconds layer using method A. With vigorous stirring the image is developed for 5 minutes in a liquid developer having the composition 1 gil palladium black and 0.5 gn lead borate glass of the composition specified in Example 3 and a particle size of < 5 Nm dispersed in a mixture of isopropanol and "Shellsol TD" in a volume ratio of 1:6. The conductivity of the developer is approximately 0.6x 10-3Q-'cm-l. After rinsing in isopropanol and drying in air, the substrate is heated in air at 8000C for 20 minutes, is rinsed in demineralised water after cooling, and is then placed for a few hours in an electroless copper-plating solution at 650C having the same composition as in Example 1.

The result is a copper pattern on the Awl203 substrate of a quality which, although slightly less than the other Examples, is still sufficient for practice.

Example 12 A magnesium plate was provided anodically with a 20 pom thick oxide layer in an aqueous electrolyte containing per litre 240 g of ammonium bifluoride (NH4HF2), 100 g of sodium bichromate (Na2Cr2O7 . 2H2O) and 90 ml of 85% orthophosphoric acid. The bath temperature was 80"C, the bath voltage 90 V alternating voltage for 25 minutes and the current density 0.5-5A/dm2. The plate was then provided with a layer of polystyrene by means of dipping in a 5 to 10% by weight solution in toluene or xylene. On the oxide side a charge image was provided by means of a corona discharge according to method A using a metal mask. A nuclear palladium image was produced with a 1 gil solution of palladium black in "Shellsol TD" which also contained 10-3% by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate). After the formation of the nuclear palladium image, the substrate was heated in air to 1000C within 20 minutes. By means of the electroless copper-plating solution specified in Example 1, a 5 to 10 ssm thick copper pattern of good adhesion was obtained.

Example 13 Pb-ruthenate resistors were provided on a ceramic substrate by silk-screening. For this purpose a commercially available paste (Dupont 1351) having a vitreous binder was used. In the manner described in Example 4, a layer of "Calgon" and a layer of poly(ethyl methacrylate) were provided on the substrate across the resistors which had been fired for one hour at 850"C. A charge image in the pattern of the desired conductors of a circuit was provided according to method A by means of a metal mask. The charge image was converted into a nuclear image with the Pd-Sn-borate dispersion as described in the modified embodiment of Example 7. Then the assembly was dried. In order to form a screening of the resistors, first a charge image was formed thereon and this was then developed with a dispersion of glass having the composition in % by weight: PbO 71.7 B203 5.0 SiO2 21.0 Awl203 2.3 The assembly was then heated in air at 650"C for 1 minute. Upon developing in an electroless copper-plating solution having the composition described in Example 1, adhering copper tracks are formed, while no copper is deposited on the resistors except at the contact points.

The layer of glass on the resistance members may be provided electrophoretically or by silk-screening.

Due to the thermal treatment at 8500C for 1 hour, the resistance values and the temperature coefficients of the resistors remain at the same values during the subsequent process steps. The contact resistance between the conductors and resistors is negligible.

Example 14 A nuclear image was manufactured on a glass plate in the manner as described in the modified embodiment of Example 7. This was then intensified with a 5 ,um Ni-P layer in a solution which was heated at 900C and contained per litre: 30 g of nickel chloride NiCI2 . 6H2O 30 g of glycine (amino acetic acid) 10 g of sodium hypophosphite.

Said layer was then intensified in a usual electro-plating nickel bath with 15 Mm Ni.

The resulting nickel pattern had a good adhesion to the glass.

WHAT WE CLAIM IS: 1. A method of additively manufacturing a wiring pattern on an oxidic substrate (as hereinbefore defined) the method comprising the steps of electrophotographically producing an electrostatic charge image on the substrate, converting the charge image into a nuclear metal image by contacting the charge image with a suspension of a metal or metal compound in a dispersion medium, heating the substrate at a temperature of at least 100"C so as to bond the nuclear metal image to the substrate, and intensifying the nuclear metal image by means of an electroless metal-plating solution, wherein the

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

Claims

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

layer using method A. With vigorous stirring the image is developed for 5 minutes in a liquid developer having the composition 1 gil palladium black and 0.5 gn lead borate glass of the composition specified in Example 3 and a particle size of < 5 Nm dispersed in a mixture of isopropanol and "Shellsol TD" in a volume ratio of 1:6. The conductivity of the developer is approximately 0.6x 10-3Q-'cm-l. After rinsing in isopropanol and drying in air, the substrate is heated in air at 8000C for 20 minutes, is rinsed in demineralised water after cooling, and is then placed for a few hours in an electroless copper-plating solution at 650C having the same composition as in Example 1.

The result is a copper pattern on the Awl203 substrate of a quality which, although slightly less than the other Examples, is still sufficient for practice.

Example 12 A magnesium plate was provided anodically with a 20 pom thick oxide layer in an aqueous electrolyte containing per litre 240 g of ammonium bifluoride (NH4HF2),

100 g of sodium bichromate (Na2Cr2O7 . 2H2O) and 90 ml of 85% orthophosphoric acid. The bath temperature was 80"C, the bath voltage 90 V alternating voltage for 25 minutes and the current density 0.5-5A/dm2. The plate was then provided with a layer of polystyrene by means of dipping in a 5 to 10% by weight solution in toluene or xylene. On the oxide side a charge image was provided by means of a corona discharge according to method A using a metal mask. A nuclear palladium image was produced with a 1 gil solution of palladium black in "Shellsol TD" which also contained 10-3% by weight of Shell "ASA 3" and 0.2% by weight of poly(methyl methacrylate). After the formation of the nuclear palladium image, the substrate was heated in air to 1000C within 20 minutes. By means of the electroless copper-plating solution specified in Example 1, a 5 to 10 ssm thick copper pattern of good adhesion was obtained.

Example 13 Pb-ruthenate resistors were provided on a ceramic substrate by silk-screening. For this purpose a commercially available paste (Dupont 1351) having a vitreous binder was used. In the manner described in Example 4, a layer of "Calgon" and a layer of poly(ethyl methacrylate) were provided on the substrate across the resistors which had been fired for one hour at 850"C. A charge image in the pattern of the desired conductors of a circuit was provided according to method A by means of a metal mask. The charge image was converted into a nuclear image with the Pd-Sn-borate dispersion as described in the modified embodiment of Example 7. Then the assembly was dried. In order to form a screening of the resistors, first a charge image was formed thereon and this was then developed with a dispersion of glass having the composition in % by weight: PbO 71.7 B203 5.0 SiO2 21.0 Awl203 2.3 The assembly was then heated in air at 650"C for 1 minute. Upon developing in an electroless copper-plating solution having the composition described in Example 1, adhering copper tracks are formed, while no copper is deposited on the resistors except at the contact points.

The layer of glass on the resistance members may be provided electrophoretically or by silk-screening.

Due to the thermal treatment at 8500C for 1 hour, the resistance values and the temperature coefficients of the resistors remain at the same values during the subsequent process steps. The contact resistance between the conductors and resistors is negligible.

Example 14 A nuclear image was manufactured on a glass plate in the manner as described in the modified embodiment of Example 7. This was then intensified with a 5 ,um Ni-P layer in a solution which was heated at 900C and contained per litre:

30 g of nickel chloride NiCI2 . 6H2O

30 g of glycine (amino acetic acid)

10 g of sodium hypophosphite.

Said layer was then intensified in a usual electro-plating nickel bath with 15 Mm Ni.

The resulting nickel pattern had a good adhesion to the glass.

WHAT WE CLAIM IS: 1. A method of additively manufacturing a wiring pattern on an oxidic substrate (as hereinbefore defined) the method comprising the steps of electrophotographically producing an electrostatic charge image on the substrate, converting the charge image into a nuclear metal image by contacting the charge image with a suspension of a metal or metal compound in a dispersion medium, heating the substrate at a temperature of at least 100"C so as to bond the nuclear metal image to the substrate, and intensifying the nuclear metal image by means of an electroless metal-plating solution, wherein the

dispersion medium has a resistivity exceeding 108 ohm.cm.
2. A method as claimed in Claim 1, wherein the oxidic substrate is a vitreous material or a ceramic material, and the substrate is heated at a temperature of at least 400"C so as to bond the nuclear metal image to the substrate.
3. A method as claimed in Claim 1 or Claim 2, wherein the suspension contains a glass-forming powder (as hereinbefore defined) and after the substrate has been contacted with the suspension, the substrate is heated above the softening-point of the substrate until the softened glass has wetted the substrate, and then the substrate is cooled.
4. A method as claimed in Claim I or Claim 2, wherein the charge image is contacted with a suspension of palladium black, the substrate is rinsed with a solvent, and then the nuclear metal image is contacted with a suspension of tin powder and a glass powder.
5. A method as claimed in any of Claims I to 4, wherein a volatilisable organic electrically conductive layer is deposited on the oxidic substrate, a volatilisable organic dielectric layer is deposited on the organic electrically conductive layer, and the charge image is formed on the volatilisable organic dielectric layer. ~~~~~~~~~~~~~~~~~~~~~
6. A method as claimed in any of Claims I to 5, wherein the oxidic substrate consists of an oxide layer obtained by anodic oxidation of a metal.
7. A method as claimed in Claim 6, wherein the oxidic substrate consists of an oxide layer of anodically oxidised magnesium.
8. A method as claimed in any of Claims I to 7, wherein the nuclear image is reactivated after heating.
9. A method of manufacturing a wiring pattern on an oxidic substrate (as hereinbefore defined), substantially as herein described with reference to any of Examples 1 to 14.
10. An oxidic substrate bearing a wiring pattern manufactured by a method as claimed in any preceding Claim.
11. A method of manufacturing hybrid circuits, wherein the method as claimed in any of Claims 1 to 8, is combined with a known thick-film method of manufacturing resistors and/or while forming insulating glass layers for multilayer circuits.