GB2164332A - Porcelainized metal substrates - Google Patents

Porcelainized metal substrates Download PDF

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Publication number
GB2164332A
GB2164332A GB8423141A GB8423141A GB2164332A GB 2164332 A GB2164332 A GB 2164332A GB 8423141 A GB8423141 A GB 8423141A GB 8423141 A GB8423141 A GB 8423141A GB 2164332 A GB2164332 A GB 2164332A
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Prior art keywords
metal substrate
mixture
substrate
layer
porcelainized
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GB8423141A
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GB8423141D0 (en
Inventor
Terry R Bloom
John F Nespor
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CTS Corp
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CTS Corp
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
    • C23D5/00—Coating with enamels or vitreous layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
    • H01L21/4803—Insulating or insulated parts, e.g. mountings, containers, diamond heatsinks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/12—Mountings, e.g. non-detachable insulating substrates
    • H01L23/14—Mountings, e.g. non-detachable insulating substrates characterised by the material or its electrical properties
    • H01L23/142—Metallic substrates having insulating layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/095—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00 with a principal constituent of the material being a combination of two or more materials provided in the groups H01L2924/013 - H01L2924/0715
    • H01L2924/097—Glass-ceramics, e.g. devitrified glass
    • H01L2924/09701—Low temperature co-fired ceramic [LTCC]

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  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Laminated Bodies (AREA)

Abstract

A flexible porcelain tape is manufactured for application to a metal substrate to produce a porcelainized metal substrate. The porcelain tape provides an insulative layer upon which can be applied electrical circuits comprising conductive paths and resistors either before or after the porcelain tape is fired. The porcelain tape comprises glass frit blended with a vehicle, from which volatile gases can be removed to effect a predetermined viscosity. The mixture is applied evenly to a flexible plastics carrier and dried. The tape may be rolled up and stored until needed, whereupon the flexible carrier is peeled away either before or after the porcelain mixture layer is cut to desired size and configuration. Single or multiple layers of the mixture layer can be disposed upon a metal substrate and the combination is laminated, and then fired. The resulting single or multiple layer porcelainized metal substrate provides an insulated aluminum, steel, or other metal substrate for supporting electrical circuits thereon.

Description

SPECIFICATION Method of producing porcelainized metal substrates This invention relates generally to the production of porcelainized metal substrates and more specifically to a flexible porcelain tape to be utilised in the manufacture of porcelainized metal substrates, providing an insulative surface for supporting thick film circuits thereon.
The prior art has provided numerous methods for manufacturing porcelainized metal substrates. These methods comprise spraying a porcelainized mixture upon the metal substrate, drying the mixture and then firing the combination; utilising electrolytic deposition processes whereby the metal substrate is placed within a tank containing a porcelainized mixture and electric current utilised to deposit the mixture onto the surface of the substrate; or conventional screening methods wherein a porcelain mixture is screen printed onto a metal substrate and followed by drying and firing. These prior art processes have proved to be time consuming, expensive and do not readily lend themselves to multilayering of the porcelain mixtures.Thus, there is a need to develop a method providing a facile manner of handling the porcelain mixture, so that it may be more easily applied to a metal substrate without the use of the time consuming and expensive prior art methods. Also, there is a need for a simplified method of providing for multilayering of porcelain layers whereby selected porcelain mixture layers may support thick film electrical circuits therebetween and the porcelain layers, thick film circuits and metal substrate may be all fired during a single firing step.
Several prior art methods utilising ceramic or glass frit tapes have been developed. U.S. Patent No.
3,293,072 describes a method for providing a self-supporting metallizing film as a sealing tape which may be applied to a ceramic surface for the purpose of sealing the surface to the surface of a metal or ceramic element. U.S. Patent No. 3,371,001 describes the use of a very thin glass layer as a passivation encapsulation, protective and dielectric layer formulation on a semi-conductor wafer. U.S. Patent No.
3,506,473 describes a multilayer transfer tape for transferring a thin glaze, glass or ceramic layer as an insulating layer to a refractory or metal substrate by utilising only pressure to adhere the tape to the substrate, and pulling away the unadhered sections to form the patterns to be fired. U.S. Patent No.
3,518,756 describes the manufacture of multilayer ceramic microelectronic structures having metallized patterns and metallized through holes, the ceramic layers being punched and pressed together before firing. The above patents all deal with the formulation of ceramic or glass tapes for effecting the respective aims specified in the patents, but none of the patents describe a process suitable for utilising a flexible porcelain tape to provide a porcelainized metal substrate, particularly a porcelainized metal substrate suitable for supporting a thick film electrical circuit thereon.
In accordance with the present invention, a flexible porcelain tape is manufactured by first blending together a glass frit and vehicle mixture, the vehicle comprising a combination of solvents and binder material. The fluid glass frit-vehicle mixture may be subjected to a vacuum to remove volatile gases therefrom and effect a desired viscosity. A flexible plastics carrier is stretched over a flat surface and the fluid mixture spread evenly upon the flexible plastics carrier to provide an even, continuous layer of mixture. The glass frit-vehicle mixture is dried, which adheres the mixture to the underlying flexible carrier and form the porcelain tape. If the porcelain tape is not to be used immediately, it may be simply rolled and placed in sealed containers until is to be used.The flexible porcelain tape may be cut to the desired configuration of the substrate to which it is to be applied, with the flexible plastics carrier being removed either prior to or after the cutting or forming operation. Once the flexible plastics carrier is removed, the glass frit-vehicle mixture layer is disposed upon a metal substrate, and the combination placed within a lamination press. After lamination, the laminated mixture layer and substrate are fired to melt and bond the glass frit mixture to the substrate and produce a porcelainized metal substrate. The porcelain layer bonded to the metal substrate provides an insulative layer disposed over the metal substrate which may serve as a heat sink, and thick film circuits comprising conductive and resistive patterns may be applied to the porcelain insulative layer.
The present invention also provides for the manufacture of multilayer porcelain substrates. A single layer or multiple layers of porcelain mixture with the flexible plastics carrier removed therefrom, are disposed on a substrate, the subsequent second and third mixture layers being disposed one upon the other. After the lamination step in which the layer or multiple mixture layers are laminated to the metal substrate, a conductive paint is printed in a conductive pattern on the top porcelain mixture layer and then dried. Next, a resistor paint is screen printed in a pattern overlapping portions of the conductive pattern, and subsequently dried.Then another formed porcelain mixture layer is disposed over the top porcelain mixture layer with the thick film circuit disposed therebetween and laminated to the top layer, followed by the entire combination being fired in a one step firing process. Thus, multiple layers of porcelain mixtures each provided from a flexible porcelain tape, can be stacked one upon another over the subjacent substrate with thick film circuits disposed between laminated adjacent layers of porcelain mixtures, and then the entire combination fired in a single firing step wherein the resulting fired thick film circuits are protectively disposed between two porcelain layers intimately bonded one to another and the substrate.This, of course, protects the printed thick film circuits during firing from oxidation, both during the firing process and afterwards when the overlying fired porcelain mixture layer comprises an insula tive porcelain layer. Alternatively, a printed thick film circuit not subject to the effects of oxidation need not have a porcelain mixture layer disposed thereover and may comprise the topmost layer of the construction. In any of these methods, thick film conductive circuits may be screened onto the overlying porcelain layer or layers after the firing step, and then fired in another step.
The method for producing the flexible porcelain tape provides a porcelain material that is easily handled, formed and applied to a metal substrate whereby the flexible porcelain mixture can be formed to the exact shape of the corresponding metal substrate. Equally important is the ability readily to manufacture multilayer porcelainized metal substrates wherein the thick film electrical circuits may be disposed between protective insulative porcelain layers or upon the top of a plurality of insulative porcelain layers to provide superior insulative separation and high dielectric strength between the circuits and subjacent metal substrate.
In the accompanying drawings: Figure 1 is a schematic representation of the glass frit-vehicle mixture of the present invention being applied in an even layer to a flexible carrier; Figure 2 is an illustration of the flexible porcelain tape comprising the flexible carrier with the layer of glass frit-vehicle mixture disposed thereon; Figure 3 is a flow diagram of a method utilising the present invention to form a porcelainized metal substrate; Figure 4 is a flow diagram of a method utilising the present invention to provide a single or multilayer porcelainized metal substrate supporting a thick film electrical circuit thereon; Figure 5 is an isometric view of a porcelainized metal substrate supporting a thick film electrical circuit and manufactured in accordance with the present invention; and Figure 6 is a schematic representation of a section view of a multilayer porcelainized substrate manufactured in accordance with the present invention.
Referring now to the drawings, and particularly Figures 1 - 4, the porcelainized tape of the present invention is designated generally by reference numeral 10. Flexible porcelain tape 10 is manufactured by first mixing together a vehicle 11 and glass powder 12 to provide a fluid glass frit mixture 14. The glass powder 12 and vehicle 11 may be blended and mixed together in a ball mill as indicated in the first processing step illustrated in Figure 3. The ball mill should be cleaned with acetone or other cleaner in order to ensure that there is no water in the mill because some glass frit mixtures tend to be hygroscopic. Fluid glass frit mixture 14 may be placed in a sealed container and stored until needed, and preferably stored on a rolling storage apparatus which will prevent separation of the glass frit and vehicle.In order to cast fluid frit mixture 14, a flexible plastics film such as polyethylene is disposed over a flat surface. The polyethylene film may be typically three mils thick and comprise any of a number of flexible plastics films suitable for this use. It should be understood that a particular type of film is not critical to the invention described herein. The fluid glass frit mixture 14 is prepared for application to the flexible carrier 16 by effecting a proper viscosity. This may be done by precisely mixing and controlling the constituents of vehicle 11 mixed with glass powder 12 in order to provide the desired viscosity, or the fluid glass frit mixture 14 may be subjected to a vacuum in order to draw off volatile gases and produce the desired viscosity.Typically, it has been found that sixteen ounces (454 gms) of the fluid glass frit mixture 14 may be subjected to a vacuum for approximately two minutes in order to aid in the solidification of the slurry and provide the desired viscosity.
The fluid glass frit mixture 14 is applied to flexible carrier 16 as shown in Figure 1 by means of a "doctor blade" device 20. The doctor blade device 20 includes an adjustable doctor blade 22 located therein whereby glass frit mixture 14 is poured into the front cavity 24 while flexible carrier 16 is advanced in the direction of arrow 30. Doctor blade 22 applies the glass frit mixture 14 evenly to carrier 16 in order to provide a continuous, controlled thickness of mixture 14 on carrier 16. The thickness of applied glass frit mixture 14 is approximately five to seven mils and is allowed to dry on the carrier for several hours.
The flexible porcelain tape 10 produced by this process and illustrated in Figure 2 may be used immediately in further processing applications to provide a porcelainized metal substrate, or simply rolled up and stored in sealed containers until needed. Flexible porcelain tapes 10 are stored in sealed containers in order to prevent the further outgassing of volatile gases from frit vehicle mixture layer 18, such outgassing causing the mixture to become brittle and difficult to handle in later processing steps. As illustrated in Figure 2, the flexible porcelain tape comprises the dried glass frit-vehicle mixture layer 18 and underlying flexible plastics carrier 16. The glass frit-vehicle mixture layer adheres lightly to carrier 16 which may be quite easily peeled away or removed from the mixture 18. It should be clearly understood that flexible porcelain tape 10 may be cut to a desired configuration either prior to or after the removal of flexible carrier 16. In other words, the frit-vehicle mixture layer 18 may be peeled from the carrier 16 and then formed or cut to the desired configuration of the corresponding metal substrate, or tape 10 comprising frit-vehicle mixture layer 18 and carrier 16 may be cut to the desired configuration and then carrier 16 peeled away before mixture layer 18 is applied to the metal substrate. This is illustrated in Figure 3 wherein the processing step of removing the flexible carrier is shown as a step accomplished either prior to or after the cutting or forming of frit-vehicle mixture layer 18.
After flexible frit-vehicle mixture layer 18 is cut or formed and carrier 16 removed, the next step in producing a porcelainized metal substrate is to place the formed flexible mixture layer 18 over the complementarily shaped metal substrate. The metal substrate 50 is placed on the bottom plate of a lamination press, with flexible mixture layer 18 disposed upon the substrate. In order to ensure that the flexible mixture layer 18 does not adhere to the upper portion of the press after the lamination operation, a Teflon (Trade Mark) sheet of approximately five mil thickness may be disposed over layer 18 and a stainless steel plate placed over the Teflon (Trade Mark) sheet. Alternatively, the stainless steel plate may be sprayed with Teflon (Trade Mark) to ensure nonsticking.If the lamination press is a high quality press, then the press surface may be simply sprayed with Teflon (Trade Mark) to ensure that there will be no sticking of mixture layer 18 after lamination. Mixture layer 18 and metal substrate 50 are maintained in the lamination press for several minutes at an approximate press temperature of 100 degrees C and a pressure of approximately 347 - 417 kg/sq.cm (5,000 - 6,000 pounds per square inch).
When the lamination step illustrated in Figure 3 is completed, the metal substrate 50 with laminated layer 18 is removed from the press and placed in a firing kiln. Prior to firing, the edges of laminated layer 18 may be filed or beveled back from the edge of the substrate, which assists in preventing the edges from peeling away from the substrate due to the effects of viscosity. Any firing kiln suitable for a particular application may be utilised, and the firing temperatures will vary according to the specific application and materials used. The firing is at a temperature sufficiently above the softening point of the glass in order to melt the glass and bond it to the underlying metal substrate and produce porcelainized metal substrate 60.Typical firing temperatures are a 520 degrees C peak firing temperature for a porcelainized aluminum substrate and approximately 790 degrees C for a porcelainized steel substrate.
To manufacture a multilayer porcelainized metal substrate comprising multiple layers of mixture layer 18 laminated and fired on metal substrate 50, two or more mixture layers 18 (see Figure 3) are placed one over another on top of the metal substrate. The lamination press may be sprayed with Teflon (Trade Mark) in order to prevent sticking, or the other alternative methods utilised. Metal substrate 50 with multiple mixture layers 18 disposed thereon, is placed in a lamination press for several minutes at approximately 93 degrees C (200 degrees F) and a pressure of approximately 694 kg/sq.cm (10,000 pounds per square inch). After lamination, the firing may be at a temperature appropriate for the particular metal substrate and application, such as approximately 520 degrees C for an aluminum substrate and approximately 790 degrees C for a steel substrate.
The method for producing porcelainized metal substrates with a thick film electrical circuit(s) disposed thereon, follows the steps illustrated in the flow diagram of Figure 4. This process begins with either one or more layers of mixture layer 18 laminated to the metal substrate 50 providing an intermediate laminated metal substrate 55. A conductive paint 70 is printed upon the surface of the lamination layer (see Step A of Figure 4) by screening methods well known in the art, and then the conductive paint 70 is dried, (Step B). Resistor paint 80 is then screen printed in overlapping relationship with the conductive pattern or patterns, thereby forming a resistor pattern located on the lamination with the resistors overlapping portions of the previously printed and dried and conductive patterns.After the printing of the resistor pattern or patterns as illustrated by Step C, the resistor paint is dried (Step D) and then the combination fired to produce a thick film circuit or circuits disposed on the porcelainized metal substrate 90.
This single firing technique obviates further processing steps and reduces the overall energy expenditure of the process, and may be utilised when the conductive and resistive paints are air fireable. It should be understood that Steps A and B and steps C and D are interchangeable, that is, either the conductive pattern or the resistor pattern can be printed before the other.
As illustrated by Step E, another formed frit-vehicle mixture layer 18 may be disposed over the thick film electrical circuit and laminated layer(s) of intermediate product 55. The additional mixture layer 18 is laminated over the thick film circuit, and then Steps A - E may be repeated if another thick film electrical circuit is to be disposed on the top lamination layer (see Figure 6), and repeated as many times as desired in order to continue the stacking arrangement. Finally, the entire combination is fired in a single firing step whereby the thick film electrical circuit or circuits disposed between adjacent laminated layers of frit-vehicle mixtures are fired simultaneously with the laminated layers.The combination is heated to a temperature in excess of the softening point of the glass frit to effect melting of the glass frit and bonding of one layer to another to form the thick film circuit multilayer porcelainized metal substrate 92.
Referring to Figure 5, there is illustrated in isometric view a multilayered porcelainized metal substrate 100 comprised of metal substrate 105, porcelain layers 102 and 104, and a thick film electrical circuit indicated generally by reference numeral 110. Thick film electrical circuit 110 comprises conductor path 112, conductive pads 114 and resistors 116. Thick film electrical circuit 110 is disposed between porcelain layers 102 and 104.
Figure 6 is a schematic representation of a section view of the multilayer porcelainized metal substrate 92 of Figure 4. Disposed on substrate 120 are two porcelain layers 103, conductor paths 140, resistors 150 and intermediate porcelain layer 160. The topmost thick film circuit also may be covered by a porcelain layer 130 if the circuit requires protection from the effects of oxidation.
A thick film electrical circuit may be disposed on a fired porcelainized metal substrate. After the firing step in which the laminated glass frit-vehicle mixture layer 18 is melted and bonded to the underlying metal substrate, a thick film electrical circuit may be printed upon the porcelainized surface. After printing of the circuit is completed, the combination may be fired. This process is particularly useful where oxida tion is not deleterious to components of the circuit. Of course, the circuit may be fired in a protective atmosphere in order to avoid oxidation, by utilising methods well known in the art.Thus, the process providing a multilayer porcelainized metal substrate having thick film electrical circuits supported on the porcelain layers, either on top of the uppermost porcelain layer or between adjacent porcelain layers, may be modified for specific applications wherein oxidation of the circuit components is to be avoided, oxidation is not critical, or a protective atmosphere is utilised.
Additionally, circuits other than thick film circuits may be utilised with the porcelainized metal substrates of the present invention. Solid metal runs, either cut in pattern form or made by chemical etching techniques well known in the art, have been disposed on the laminated layer prior to firing, and thin film circuits may be disposed on the fired porcelain layer by well known techniques. It should be understood that a number of alternative steps in these processes may be utilised for the particular applications, and each is within the scope of the invention claimed herein.
The following description contains working examples of the invention.
Commercial glass compositions available from Ferro Corporation, Cleveland, Ohio, or another glass composition are suitable for use. Referring to Table I, the three types of glass utilised are glass A having the constituents listed, and glasses B and C identified as EL 50 and EL 2020, respectively, both being commercially available glasses manufactured by Ferro Corporation. Glass A is prepared by mixing the constituents in a twin shell for approximately 30 minutes and then pouring the mixture into a standard clay crucible for firing at approximately 1,100 degrees C. The frit is dripped twice and then ball milled for approximately four hours in acetone to produce glass frit A.
TABLE I Glass Frit Compositions (Percentages by weight) Glass Constituent Glass A Glass B Glass C Pb3O4 31 EL50 EL2020 SiO2 25 Both EL50 and EL2020 available from AL2O3 4 Ferro Corporation, Cleveland, Ohio Na2CO2 15 K2CO3 11 Li2CO3 5 TiO2 9 TABLE II Tape (Glass Frit-Vehicle) Compositions lPercentages by weight) for Aluminum Substrates Mixture Tape A Tape B Tape C Tape D Glass A 57.3 59.6 62.3 Glass B 59.6 Methyl ethyl ketone 5.1 5.4 5.6 5.4 Toluene 11.5 11.9 12.5 11.9 Acetone 7.2 7.5 7.8 7.5 Phthalate Plasticizer 1.4 1.4 1.5 1.4 Silicon Leveling 0.3 2.2 0.3 2.2 Agent Acrylic Binder 17.2 13.9 10.0 13.9 The porcelain tape comprises a glass frit blended with a vehicle, the vehicle comprising solvents and binders.Table II illustrates four tape compositions suitable for manufacturing porcelainized aluminum substrates. The vehicle comprises a combination of the solvent constituents (the methyl ethyl ketone, toluene and acetone) and binder constituents (plasticizer, ination of the solvent constituents (the methyl ethyl ketone, toluen silicon leveling agent and acrylic binder). The phthalate plasticizer may be obtained from Monsanto Corporation and is sold under the product name of Sanicizer 261; the silicon leveling agent is a Dow Corning product identified as DC No. 3: and the acrylic binder is Rohm & Haas Corporation product identified as Acryloid B7. Table II illustrates the proportions of glass frits comprising glass A and glass B mixed with the vehicle to provide porcelain tapes A - D.
After lamination to an aluminum substrate, the tape and substrate are fired at approximately 500 degrees C in a Harrop kiln operating at five inches per minute and with a preheat of approximately 300 degrees C. Tape B was found to be the best and most useful tape for porcelainized aluminum substrates, and Table Ill illustrates the results of a voltage breakdown test applied to one or more layers of porcelain tape B on an aluminum substrate. The voltage breakdown test is conducted by applying a voltage to a conductive patch disposed on the porcelain. Typically, the conductive composition may comprise, by weight, silver (79.5%), a commercial glass (8.2%) sold as XG29 by Drakenfeld Corporation, and a typical screening agent (12.3%). The conductive patch is printed on the porcelain surface and heated in a Harrop kiln at 500 degrees C, the kiln operating at 30 cm (12 inches) per minute.A voltage is applied directly to the conductive patch and increased until the current arcs through the porcelain to the underlying substrate. Excellent results were found by utilising a triple porcelain layered aluminum substrate manufactured from two lower layers of tape D with an overlying layer of tape B, which withstood a voltage surge of 4,000 volts DC.
TABLE Ill Voltage breakdown test for porcelainized aluminum substrate (Tape B) Tape B Number of Porcelain Layers Voltage (DC) 1 2250 2 2800 3 4000 4 > 4000 Triple layered porcelainized aluminum substrates were tested and the results are illustrated in Table IV.
The triple layered porcelainized aluminum substrates were made from three layers of tape B, and from two layers of tape D with one overlying layer of tape B.
TABLE IV Triple layer porcelainized aluminum substrates Test Layers: Three of Two of Tape Tape B D, One of Tape B Result Result 10 day mil. Humidity at 100 VDC Good Good -55 C to + 1 25 C Thermal Shock Good Satisfactory 48 hrs. at 2000C Good 250 hrs. at 2000C & 100 VDC Good 250 hrs. at 2000C & 200 VDC Good 250 hrs. at Room Temperature & 1,000 VDC Good The glass frit and vehicle constituents of tape E utilised for steel substrates are illustrated in Table V.
After lamination of tape E to the steel substrate, the combination was fired at approximately 790 degrees C for 20 minutes to produce a porcelainized steel substrate. Multilayer porcelainized steel substrates are easily produced by the present invention, and the results of tests applied to a porcelainized steel substrate having two layers of tape E, are illustrated in Table Vl.
TABLE V Tape Composition (By Weight) for Steel Substrates Tape E Glass C 59.6 Methyl ethyl ketone 5.4 Toluene 11.9 Acetone 7.5 Phthalate Plasticizer 1.4 Silicon Leveling Agent 0.3 Acrylic Binder 13.9 TABLE Vl Double Layer Porcelainized Steel Substrates Test Two Layers of Tape E Voltage Breakdown > 4000 VDC 10 day mil. Humidity Good -55 C to +125 C Thermal Shock Good 250 hrs. at 300 C Good + 1000 VDC Good One of the important uses of the present invention is the provision of a metal substrate which serves as a heat sink with an insulative porcelain layer disposed thereover for supporting a thick film electrical circuit.It has been found that thick film electrical circuits may be printed on the top layer of laminated porcelain tape and the circuit and tape all fired in a single firing step, or that the thick film electrical circuit may be disposed between adjacent layers of laminated porcelain tape and a single firing step utilised to melt the glass frit mixture and produce the multilayer porcelainized metal substrate as illustrated in Figure 5. This is particularly useful where the thick film electrical circuit is to be protected from oxidation. The present invention may be utilised for producing multilayer porcelainized metal substrates with thick film electrical circuits disposed on the top layer or between adjacent layers of porcelain.
Table VII illustrates a conductive and resistive utilised for providing a thick film electrical circuit on a laminated glass frit-vehicle layer prior to a single firing which produces the porcelainized metal substrate supporting the fired thick film electrical circuit.
TABLE VII Thick film materials for multilayer porcelainized metal substrates Conductive Constituent % By Weight Screening Agent 12.30 Glass Frit with Softening Point of 540 C 6.56 AWL203 1.64 Pd 13.00 Pt 5.00 Ag 61.50 Resistive Screening Agent 69.3 Glass Frit with Softening Point of 5400C 14.2 AWL203 5.7 RuO 10.8 In operation, glass frit powder 12 is first mixed with a vehicle 11 to provide the fluid glass frit mixture 14 which is applied to a flexible carrier 16 and dried. This produces flexible porcelain tape 10 comprising glass frit-vehicle mixture 18 adhered to flexible carrier 16.Flexible carrier 16 is removed from frit-vehicle mixture layer 18, either before or after forming or cutting of mixture layer 18, and then mixture layer 18 is placed over a complementary shaped metal substrate 50 in a lamination press. Mixture layer 18 is laminated to metal substrate 50 and then the combination fired to produce porcelainized metal substrate 60.Multilayer porcelainized metal substrates 90, 92 are produced by laminating a layer or layers or formed frit-vehicle mixture layers 18 onto the metal substrate, printing conductive paint 70 in a pattern on the top laminated mixture layer, drying the conductive pattern, printing resistor paint 80 in a pattern on the top laminated mixture layer so that it overlaps portions of the conductive pattern, drying the resistor paint, and then either firing the combination to provide multilayer porcelain metal substrate 90 or laminating another formed frit-vehicle mixture layer 18 over the thick film electrical circuit and then firing to produce multilayer porcelainized metal substrate 92.
In general, the industrial applicability of the invention is used for producing single or multilayered porcelainized metal substrates.
Although the invention has been illustrated and described in connection with example embodiments, it will be understood that this is illustrative of the invention, and by no means restrictive thereof. Numerous revisions and additions to the embodiments are possible within the scope of the invention as defined by the appended claims.

Claims (23)

1. A method of forming a porcelainized metal substrate, comprising the steps of (a) forming to a desired configuration a flexible porcelain mixture layer comprising a glass frit-vehicle mixture previously dried to a desired consistency, (b) disposing said formed mixture layer and a metal substrate in lamination press means, (c) actuating said lamination press means to heat and press together said mixture layer and metal substrate, and (d) removing the combination mixture layer-metal substrate from said lamination press means and firing said combination to melt and bond said glass frit to said metal substrate and thereby provide a porcelainized metal substrate.
2. The method in accordance with claim 1, further comprising the step of removing flexible carrier means from said flexible porcelain mixture layer either before or after step (a).
3. The method in accordance with claim 1 or claim 2, further comprising the step of beveling the edges of said mixture layer after said mixture layer-metal substrate combination is removed from said lamination press means.
4. The method in accordance with claim 1 or claim 2 or claim 3, wherein said lamination press operates at approximately 1000C for approximately three minutes and at about a pressure of 347 - 417 kg/ sq.cm.
5. The method in accordance with any of claims 1 to 4, further comprising the step of placing at least one more mixture layer upon the mixture layer disposed on said substrate in order to provide multiple porcelain layers supported by said substrate.
6. The method in accordance with claim 5, wherein said lamination press means is operated in the temperature range of approximately 93 to 1000C and a pressure of approximately 694 kg/sq.cm.
7. The method in accordance with any of claims 1 to 6, wherein said metal substrate comprises an aluminum substrate and said firing is at approximately 520 C peak temperature.
8. The method in accordance with any of claims 1 to 6, wherein said metal substrate comprises a steel substrate and the firing is at approximately 790or.
9. The method in accordance with any of claims 1 to 8, further comprising the step of disposing an electrical circuit on the laminated mixture layer prior to firing.
10. The method in accordance with any of claims 1 to 8, further comprising the additional step of disposing an electrical circuit on the surface of the porcelain.
11. The method in accordance with claim 5 or any claim appendant thereto, further comprising the step of disposing an electrical circuit on the topmost mixture layer prior to firing.
12. The method in accordance with claim 5 or any claim appendant thereto, further comprising the step of disposing an electrical circuit on the topmost surface of porcelain.
13. A porcelainized metal substrate, comprising an insulative glass layer bonded to said metal substrate, said insulative glass layer and metal substrate comprising the conjoint product of a mixture of glass frit and vehicle dried on flexible carrier means, the mixture being removed from said carrier means and adhered to said metal substrate by heated pressing, said metal substrate and insulative glass layer being the conjoint reaction product of firing said mixture and substrate to melt and bond said mixture to said substrate subsequently to said pressing.
14. The porcelainized metal substrate in accordance with claim 13, wherein the metal substrate comprises an aluminum substrate and said firing occurs at approximately 520 C.
15. The porcelainized metal substrate in accordance with claim 13, wherein said metal substrate comprises a steel substrate and said firing occurs at approximately 790 C.
16. The porcelainized metal substrate in accordance with any of claims 13 to 15, further comprising another mixture layer wherein said insulative glass layer and substrate comprise the conjoint reaction product of at least two layers of mixture removed from said carrier means and disposed one upon the other, heat pressed with said metal substrate, and the mixture layers and metal substrate being subsequently fired.
17. A method for forming a porcelainized metal substrate with an electrical circuit supported thereon, comprising the steps of (a) forming to desired configuration a flexible porcelain mixture layer comprising a glass frit-vehicle mixture previously dried to a desired consistency, (b) disposing said formed mixture layer and a metal substrate in lamination press means, (c) actuating said lamination press means to heat and press together said mixture layer and metal substrate, (d) removing the combination mixture layermetal substrate from said lamination press means and disposing conductive and resistor patterns on said mixture layer, and (e) firing the electrical circuit and mixture layer-metal substrate to melt and bond said glass frit to said metal substrate and thereby provide said porcelainized metal substrate with electrical circuit supported thereon.
18. A porcelainized metal substrate supporting an electrical circuit thereon, comprising an insulative glass layer bonded to said metal substrate, said insulative glass layer and metal substrate comprising the conjoint product of a mixture of glass frit and vehicle dried on flexible carrier means, the mixture removed from said carrier means and adhered to said metal substrate by heated pressing, said electrical circuit being the product of disposing conductive and resistive patterns on said mixture layer subsequently to said heated pressing, and said metal substrate, insulative glass layer, and electrical circuit being the conjoint reaction product of firing said mixture, substrate, and electrical circuit to melt and bond said mixture to said substrate subsequently to said pressing.
19. The porcelainized metal substrate with electrical circuit in accordance with claim 18, wherein said insulative glass layer comprises the product of at least two layers of mixture adhered to the metal substrate by heated pressing.
20. A porcelainized metal substrate supporting an electrical circuit thereon, comprising an insulative glass layer bonded to said metal substrate, said insulative glass layer and metal substrate comprising the conjoint product of a mixture of glass frit and vehicle dried on flexible carrier means, the mixture being removed from said carrier means and adhered to said metal substrate by heated pressing, said metal substrate and insulative glass layer being the conjoint reaction product of firing to melt and bond said mixture to said substrate subsequently to said pressing, and said electrical circuit being the product of disposing conductive and resistive patterns on said porcelain subsequently to said firing.
21. The porcelainized metal substrate with electrical circuit in accordance with claim 18, wherein said insulative glass layer comprises the product of at least two layers of mixture adhered to the metal substrate by heated pressing.
22. A method of forming a porcelainized metal substrate substantially as hereinbefore described with reference to the tabulated examples.
23. A porcelainized metal substrate substantially as hereinbefore described with reference to the drawings.
GB8423141A 1984-09-13 1984-09-13 Porcelainized metal substrates Withdrawn GB2164332A (en)

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GB2164332A true GB2164332A (en) 1986-03-19

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2230387A (en) * 1989-04-13 1990-10-17 L S T Lab Ltd Improvements in or relating to automotive electrical systems
EP0501141A1 (en) * 1991-02-21 1992-09-02 Bosch-Siemens Hausgeräte GmbH Process for adding a coating on metal surfaces, especially baking oven or similar apparatus

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1079960A (en) * 1963-12-07 1967-08-16 Burger Elsenwerke Ag Improvements in or relating to enamelling processes
GB2110661A (en) * 1981-12-04 1983-06-22 Cookson Group Plc Improvements relating to the production of vitreous enamelled substrates

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1079960A (en) * 1963-12-07 1967-08-16 Burger Elsenwerke Ag Improvements in or relating to enamelling processes
GB2110661A (en) * 1981-12-04 1983-06-22 Cookson Group Plc Improvements relating to the production of vitreous enamelled substrates

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2230387A (en) * 1989-04-13 1990-10-17 L S T Lab Ltd Improvements in or relating to automotive electrical systems
US5198696A (en) * 1989-04-13 1993-03-30 I.S.T. Laboratories Ltd. Automotive electrical systems
GB2230387B (en) * 1989-04-13 1993-10-06 Ist Lab Ltd Improvements in or relating to automotive electrical systems
EP0501141A1 (en) * 1991-02-21 1992-09-02 Bosch-Siemens Hausgeräte GmbH Process for adding a coating on metal surfaces, especially baking oven or similar apparatus

Also Published As

Publication number Publication date
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