DE2014881A1 - Glass metallisation materials - Google Patents

Abstract

The metallization material is roasted in air or in an inert atmosphere on a dielectric substrate. This forms an electrically conductive, solderable and adhesive film. The material contains (% by wt.) of fine-particle size precious metal or metals and 2-30% by wt. of fine particle size inorganic binder consisting of a glass of (% by wt.), ZnO 24-34; B2O3 22-30; SiO2 18-25; Na2O 2-10; Al2O3 3-7; ZrO2 2-6; CaO 0-5; Ba0 0-2; PbO 0-1; K2O 0-4.

Description

Metallization Compounds Summary The invention provides metallization compounds based on precious metal (s) and a special, vitreous, zinc borosilicate binder to disposal. these masses, which are burned in air or in an inert atmosphere can, conductive and adhesive films0 The burned-on films can be brazed, without the need for galvanic treatment, with conventional high-temperature solders and low-temperature brazing alloys compatible and with respect to reducing The atmosphere used in high-temperature brazing is stable.

In modern electronic circuits, there is a compactness of the component assemblies in the foreground, for the achievement of which metallization compounds are an important means represent. Small assemblies of electronic components are also made of a ceramic plate or underlay attached and connected to one another by means of electrodes or conductors, the can be printed and fired onto the ceramic base.

Such printed conductors are mechanically strong and resistant to thermal shock and atmospheric pollution resistant. In particular comes the precious metal-containing Metallization masses and electrodes formed with them have a special meaning to. An essential, with the precious metal metallization compound compared to ordinary, The advantage obtained on base metal-based metallizing compounds lies in the accessibility to burning in air at high temperatures without oxidation subject to, creating good electrical conductivity, but also a surface is retained, which is wettable by molten solder or alloy hard solder.

Metallizing compounds usually contain in addition to precious metal an inorganic binder. The inorganic binder mainly has the Function to bind the particulate precious metals to each other and also to adhere to bring about the metals on the ceramic base. Usually the binder is a powdered glass, and the nature of the glass may be suitable for environmental conditions be decisive. Furthermore, the amount of gas must be sufficient for good adhesion, but without To be allowed to be so bare that the burned-on, conductive film can be used prevented by molten metals. The usual uses will be the precious metal-glass metallization masses in air at temperatures in the range of Fired 700 to 10000 C.

It is not uncommon for situations to arise where special component parts of the electronic subsystem one burning in one inert atmosphere (e.g.

Nitrogen or argon). The purpose of the inert atmosphere is exclude atmospheric oxygen and one Oxidation of the through any part of the system that would be damaged by oxidation to prevent the oxygen. The common, commonly available precious metal-glass metallizing compounds are damaged by burning in inert gas; typically show that way burned-on films obtained with them have a high electrical resistance and or poor adhesion to the weight. The surface of the burned-on film has a cracked or roughened appearance.

Most conventional, burned-out precious metal films endure also ii with a view to maintaining good adhesion to the substrate and the Ability to perform their normal functions (e.g. good qualities in the contacting by die and wire bonding) no effect of the reducing Atmospheres that are used in high-temperature brazing (N2-H2 at 800 ° C). In addition, there are only a few, if any, burned-on precious metal films, the low-temperature brazing alloys (e.g.

An-Ge or 1u at 300 to 6000 C) and ate liability to be retained on the substrate without dissolution by the molten alloy brazing alloy capital.

The present invention aims at improved precious metal masses, which overcomes the shortcomings of the prior art in screen printing on ceramics apply and let burn.

The f (ir in the air or in an inert atmosphere on a dielectric base with the formation of fired, electrically conductive, brazeable and adhesive films on these suitable metallization compositions according to the invention characterized by a content of 70 to 98% by weight of finely divided Noble metal or finely divided noble metals and 2 to 30% by weight of finely divided, inorganic Binder, which essentially consists of 24-34% by weight ZnO 22-30% by weight B2O3 18 - 25% by weight SiO2 2 - 10% by weight Na2O 3 - 7% by weight Al2O3 2 - 6% by weight ZrO2 0 - 5% by weight CaO 0-2% by weight BaO 0-1% by weight PbO 0-4% by weight K2O.

It has been found that the use of a glass of the above composition the usual, undesirable ones as the inorganic binder of the metallization compound Avoids the effects of burning in an inert atmosphere and contributes to persistence the conditions of high temperature brazing results.

Such a glass makes a good one when used in the right amounts Adhesion between the burned-on film and the ceramic base or the ceramic substrate, without a significant loss of electrical conductivity or surface properties, d. H. the ability to accept soft solder and hard solder and to make contact, adjusts.

Preferred embodiments of the invention are described below.

The finely divided, inorganic binder of the metallization compound according to the invention provides a glass composition represent that one has a special combination of metallic oxides in critical proportions as follows: T a b e l l e I General Preferred proportions, proportions,% by weight% by weight ZnO 24 - 34 25 - 30 B2O3 22 - 30 25 - 27 SiO2 18 - 25 20 - 24 Na2O 2 - 10 5 - 10 Al2O3 3 - 7 4 - 6 ZrO2 2 - 6 3 - 5 CaO 0 - 5 0 - 4 BaO 0 - 2 0 - 1 PbO 0 - 1 0 - 1 K2O 0 - 4 0 - 1 TiO2, NiO, Fe2O3 O - 2 (less than O - 1 each 1%) This special Combination of metal oxides in the above proportions is used to form inorganic Binders that are suitable for use in metallization compounds that are exposed to air or are flammable in inert atmospheres and braze themselves or the high temperatures Suspend brazing work (typically several minutes in forming gas (N2-H2 mixture) at 8000 C) necessary.

Without limiting the invention to any particular theory, Apparently, the inorganic binder should only contain small amounts of metal oxides at most contain, which can be "easily" reduced to metal when heated 9n in an inert atmosphere are. For example, ordinary lead oxide glasses cannot be fired in inert atmospheres. It is believed that the lead oxide is at least partially reduced to metallic lead which leads to the formation of a very poor inorganic binder. the always present in the glass of the inorganic binder according to the invention ZnO, B2O3, SiO2, Na2O, Al2O3 and ZrO2 components lead to inorganic ones Binders that hold them well when used in burned-on films and grant solderability. The CaO, BaO, PbO, K2O, Ti2O3, NiO2 and Fe2O3 are components of the glass, which can be used if desired, but if present in give the binder additional stability and the temperature range, in which the glass softens, expand.

The Netall part of the metallization compound consists of a precious metal, a mixture of one or more precious metals, an alloy of two or more Precious metals or mixtures of these components. The precious metals for the purposes of the invention are platinum, palladium, silver, gold, rhodium and iridium. Preferably noble metal mixtures are used, as they are usually used in conductor metallization compounds Use (e.g. palladium-gold, palladium-silver, platinum-gold, platinum-silver). A mixture of precious metals with a content of 75 to 100% gold and 0 to 25% on platinum is particularly suitable for low-temperature brazing.

All precious metal and inorganic binder components should be im generally a finely divided or powdery form, d. H. the shape of powders of sufficient fineness to produce a 325-mesh screen printing stencil (Standard Sieve Scale), d. H. with a clear mesh size of 0.044 mm, with the Powder particles with a size of not contains over about 40 microns. In general, the average particle size of the powder is not greater 20 microns.

The average particle size of the metals is advantageous in the range of 0.1 to 5 microns, while for the inorganic binder an average Particle size in the range of 1 to 15 microns is preferred.

The powders can be made by conventional methods, such as by chemical Precipitation or mechanical comminution. For example, one can use finely divided Generate metal powder by reduction and / or precipitation. The powdery Inorganic binders are generally made using one of the desired metal oxides, or from providing the oxides during melting Compounds formed glass base melts and the melt is poured into water, wherein a coarse frit is obtained, which is then (e.g. on a ball mill with water) grinds to the desired degree of fineness.

The ratio of inorganic binder to metal is dependent on the Conductivity, adhesion and surface properties of the fired films of influence. As the proportion of binding agent decreases, so does the adhesion, however, while the conductivity and surface wettability of the films decrease. There is a balance between conductivity, adhesion and surface properties maintain. The metallization compounds according to the invention oil 70 to 98% by weight of finely divided noble metal and the complementary amount in the range from 2 to Contain 30% by weight of finely divided inorganic binder. The inorganic binder is necessary in an amount of at least 2% to ensure adequate liability of the to give burned-on metallization mass on the base. A use of more than 30% by weight of inorganic binder on the other hand leads to burned-on films, the brazing alloys or lead wires not easily accept.

The metallization masses according to the figure are generally in an inert carrier to form a spreadable or pasty mass for the coating dispersed on the dielectric ceramic substrate without doing so but is a condition. The proportion of the metalization mass in relation to the carrier'-r can depend on the manner in which the spreadable or pasty mass is to be applied, and the type of carrier used is very different to get voted. In general, one is used to form a spreadable mass or Paste of the desired consistency 1 to 20 parts by weight of metallizing compound (metals and inorganic binder) use per part by weight of the carrier, with one Range of 3 to 10 parts is preferred.

115 Carrier Any liquid can be used, with mm tor preferably works with an inert material. So are water as carriers, or all the different, organic liquids, with or without thickeners and / or stabilizers and / or other conventional additives, can be used. Examples of the organic Liquids are the higher alcohols, such as decanol, esters of the lower alcohols, z. B. the acetates and propionates, the terpenes, such as pine oil, α- and ß-terpineol and the like, and solutions of resins such as the poly methacrylates of lower Alcohols, or solutions of ethyl cellulose, with solvents such as pine oil or the monobutyl ether of ethylene glycol monoacetate (butyl-O-CH2CH2-OOCCH3) use can find. The carrier may contain or of volatile liquids formed to promote rapid setting after application, or waxes, Thermoplastic resins or similar substances contain the thermofluid are so that the Matse at elevated temperature on a relatively cold ceramic base can be applied, on which it solidifies immediately.

The metallization compounds are produced in a conventional manner, by adding the metal or metals and the solids of the inorganic binder in the proportions of 70 to 98 or 2 to 30% by weight, based on their total weight, mixes. In addition, 1 part of inert carrier can be mixed with 1 to 20 parts Mix in the above solids. The metallization compound then becomes the formation a conductive film applied to a dielectric ceramic substrate and burned.

The application of the conductive metallization compound in a brushable or pasty form on the dielectric, ceramic base can be used for each desired purpose, e.g. B. to form conductive circuit elements or connecting elements, and done in any manner desired. In general, however, it is desirable to effect the application in the form of a precise pattern, which is easy to apply the familiar screen printing techniques and methods. The firing takes place usually at temperatures in the range from 750 to 10,000 C in air or in an inert atmosphere Atmosphere using the usual kiln.

Any inert atmosphere can be used for the purposes of the invention. For example, nitrogen, argon, helium, neon, krypton or xenon can be used.

The following examples, in which, as in the rest of the description, all parts, percentages and proportions for the substances or components refer to the weight, serve to further explain the invention.

Using finely divided precious metals and a finely divided inorganic Binder in varying proportions as shown in Table II were different Networking.

mass produced. The finely divided, used in Examples 1 to 5 inorganic binders consisted of one of 27.7% ZnO, 26.7% B2O3, 21.7% SiO2, 8.7% Na2O, 5.8 06 Al2O3, 4.0 0/0 ZrO2, 3.9 O6 CaO, 0.8 06 BaO and 0.7% PbO Glass. The precious metals and the inorganic inhibitor were made in a carrier 8 60 ethyl cellulose and 92% ß-terpineol suspended; the ratio of solids (Metal and glass) to the liquid was 4: 1. The particle sizes of the noble metal powder ranged from 0.01 to 10 microns with the average 8 size being about Was 0.2 microns. The particle sizes of the inorganic binders were in the range from about 1 to 40 ecrons with an average size of about 10 microns. The dispersions of the rel metals and the binder were made on the roller mill treated and passed through a stainless steel screen on 2.54 x 2.54 x 0, G6 cm pads of aluminum oxide (96%) applied and the printed documents at temperatures Fired in air in the range from 850 to 10000 C for 2 to 10 minutes according to the table, the imprint in a pattern consisting of a double row of 0.06 x 0.1 cm rectangles took place.

The metallized alumina left strips 0.04 cm wide 0.015 cm thick made of Fe-Ni-Oo alloy (Kovar metal) by brazing using the conventional, eutectic alloy of 88% Au and 12% Ge (F. 3560 C) as Hard solder or filler metal connected. The parts were made with foil preforms Alloy resin solder assembled and in a forming gas atmosphere (H2-N2 mixture) containing oven from 500 to 600 ° C for 2 min. at the peak temperature. This was followed by the adhesive strength brazing by bending open the strip at right angles with the metallization plane and detachment by means of of a Chatillon type strength tester. Next became the adhesive strength of some metallized aluminum oxide substrates, the 8 min. in formation gas (H2-N2 mixture) had been brazed.

On a device of the type Kulicke and Soffa Wire Bonder the wire-bonding contact is carried out according to the thermo-compression method, a gold wire 0.05 mm in diameter with a force at the tip of 120 g 3 seconds using a hot holin (column) temperature of 360 ° C was bound. On a device of the type Kulicke and Soffa Die Bonder the die-bonding contact was carried out at a bar temperature of 3750 C, Table II lists the results.

T a b e l l e II Example 1 2 3 4 5 6 7 8 9 Metallization compound, % By weight gold 70.8 80.5 61.3 0 94.1 94.0 94.0 67.7 92.5 silver 0 0 0 71.6 0 0 0 0 0 Platinum 19.4 9.6 28.8 0 0 0 0 18.5 0 Palladium 0 0 0 17.6 0 0 0 0 0 Inorganic Binder 9.8 9.9 9.9 10.8 5.9 6.0a) 6.0b) 13.8c) 7.5d) Firing conditions time (Min.) - 10-850 10-850 10-850 10-850 10-850 10-900 10-850 2-1000 10-850 temperature (° C) Adhesion, g after 2-minute brazing 317 227 299 263 272 NBf) 163 NB 72 after 8-minute brazing 294 177 281 263 118 NB NB NB NB Contacting Wire good NB NB NB good NB NB good good The acceptable NB NB NB acceptable NB NB bad good In nitrogen yes yes yes yes yes yes yes no no flammable a) Inorganic binder with a content of approximately 26% of B2O3, 67% of SiO2, 3% of Na2O, 2% of K2O and 2% of Al2O3 (Corning 7052 Kovar Sealing Glass) b) Inorganic binder: From 25.2% TiO2, 27.0% SiO2, 22.4% Na2O, 11.1% BaO, 9.2% K2O, 1.7% LiO, 1.7% B2O3 and 1.7% Sb2O3 Glass c) Inorganic binder made from 4 parts of Bi2O3 and 1 part of 63.1% CdO, 16.7% B2O3 12.8% SiO2 and 7.4% Na2O formed glass d) Inorganic binder: Glass formed from 68% PbO, 12.5% B2O3, 9.2% SiO2, 6.9% CdO and 3.4% NaF e) Too weak for quantitative measurement.

f) NB = not determined.

As the table values show, the metallization compounds are suitable from example 1 to 5, i.e. H. Masses within the scope of the invention, good for training electrically conductive films by burning in air or in an inert atmosphere. the Any conductive films that arise can also tolerate the effects of brazing used, reducing atmospheres, while their good adhesion to the substrate and / or their normal functions (e.g. good contact properties) remain. In addition, these conductive films are capable of low temperature brazing alloy to accept without being subject to dissolution. In contrast, the deliver Compositions of example 6 to 9, which contain some common inorganic binders, Fired films having one or more of the above-mentioned desirable properties are deficient.

EXAMPLE 10 In a composition analogous to Example 1, a conventional inorganic binder used in resistance compounds in the form of a glass made of 65 * PbO, 25% SiO2 and 10% B203, whereby the Metallization compounds made of 71.0% gold, 19.1% platinum and 9.9% inorganic binder; passed. The printed base was baked for 2 minutes at 850 ° C. and then brazed. The adhesion values after 2-minute and 8-minute brazing were found to be 231 and 190 g, respectively. A separate base on which this metallization compound is printed and burned been was, a forming gas atmosphere was 2 min. at a Exposed to a peak temperature of 8000 C. The burned-on metallization was after di es he high temperature device of the forming gas for a quantitative measurement too weak. In contrast, samples from Example 1 to 5 were subject to the were subjected to the same treatment, no significant loss of liability.

Claims (3)

1. P a t e n t a n s p r ü c h e For firing in air or in an inert atmosphere on a dielectric Base for the formation of burned-on, electrically conductive, hard-solderable and adhesive ones Films on this suitable metallization compound, characterized by a content from 70 to 98 wt. * of finely divided precious metal or finely divided precious metals and 2 to 30% by weight of finely divided, inorganic binder, which essentially consists of from 24 - 34% by weight ZnO 22 - 30% by weight 3203 18 - 25% by weight SiO2 2 - 10% by weight Na2O 3 - 7% by weight A1203 2 - 6% by weight ZrO2 O - 5% by weight CaO o - 2% by weight BaO 0 - 1% by weight Pb 0 - 4 wt.% K2O formed glass. 2. Mass according to claim 1, characterized in that it is in a inert, liquid carrier is dispersed. 3. Dielectric ceramic base with printed and fired Metallization compound according to claim 1.