Stacked planar transformer

A process for preparing an insulated metallized substrate, wherein a specified metallized substrate is heated from ambient temperature to a peak temperature of at least about 800 degrees centigrade while contacting the substrate with an inert atmosphere containing less than 10 parts per million of oxygen, maintained at such peak temperature for a specified period of time while being contacted with said inert gas, and thereafter heated at a peak temperature of at least about 800 degrees centigrade while being contacted with a gas containing at least 100 parts per million of oxygen.

FIELD OF THE INVENTION 
A process for preparing an insulated multilayer structure in which a 
metallized substrate is patterned with a layer of insulating material. 
BACKGROUND OF THE INVENTION 
Multilayer electronic structures are known to those skilled in the art. 
They are discussed, e.g., in an article by Ananda H. Kumar et al. entitled 
"Glass-Ceramic/Copper Multilayer Substrates for High Performance 
Computers--Materials & Process Challenges," 1991 Proceedings of the 
International Symposium on Microelectronics, (International Society for 
Hybrid Microelectronics, Reston, Va., 1991), at pages 1-5; the authors of 
this article were employed the General Technology Division of I.B.M. 
Corporation, and the article presumably discussed I.B.M. technology. 
The authors of this article teach (at page 1 thereof) that the use of 
copper in the multilayer assembly is desirable because it increases ". . . 
the conductivity of the thick film lines three fold." However, despite 
this substantial advantage of copper, the authors disclose that the use of 
copper presents several distinct problems. 
Thus, at pages 3 of this article, the authors teach that poor adhesion is 
often obtained between the layers of copper and the layers of ceramic 
material, disclosing that "The large difference in the thermal expansion 
coefficients of the glass-ceramic . . . and of copper . . . is a source of 
concern for the integrity of the interface between the two . . . ." 
The authors also teach that, in order to overcome some of the problems 
associated with the use of copper, steps must be taken to insure that the 
copper is not oxidized. Thus, at page 3 of this article, they state that 
"Two important considerations in sintering these substrates are the 
prevention copper oxidation and the complete removal of carbon residue 
from the binder." Furthermore, on the same page 3 of this article, the 
authors disclose the use of a process in which steam mixed with small 
quantities of hydrogen are used during the sintering cycle, stating that 
"The latter prevents the oxidation of copper." 
However, even the use the steam/hydrogen atmosphere during sintering which 
is disclosed by these authors does not provide a finished structure in the 
process described in this article. As is disclosed on page 4 of the 
article, what is further required is "Fabrication of two levels of 
polyimide-copper thin film structure on the substrate surface . . . . " 
Many other authors have recognized and discussed the problems associated 
with the use of copper in multilayer electronic assemblies. Thus, e.g., in 
an article by Satish S. Tamhankar et al. entitled "Optimization of 
Atmosphere Doping for Firing Photoformable Copper Thick Film Materials," 
(1990 Proceedings of the International Symposium on Microelectronics, 
International Society for Hybrid Microelectronics, Reston, Va., 1990, at 
pages 75-83), this issue was also discussed. 
At page 75 of this Tamhankar et al. article, the authors correctly note 
that "In microelectronic packaging, an increasing emphasis on high 
performance applications is evident . . . . Copper thick film systems have 
some unique properties to meet these high performance requirements. 
Compared to precious metals, copper has high electrical conductivity, 
excellent resistance to migration and to solder leach, excellent 
solderability, reworkability, low cost, and stable pricing structure." 
However, the Tamhankar et al. article (at page 75) also correctly notes 
that the use of copper presents many problems, stating that "In spite of 
the many advantages, copper based thick film systems have not gained 
widespread popularity. This has been due to the difficulties experienced 
in processing these materials." 
One of the ". . . difficulties . . ." mentioned by Tamhankar et al. is that 
". . . since copper is prone to oxidation, copper based systems have to be 
fired in a nitrogen atmosphere . . . ." 
Applicants have discovered that, by starting with a specified metallized 
substrate and processing it in a certain sequence, they can overcome many 
of the disadvantages associated with the prior art's use of copper while 
retaining substantially all of the advantages. 
U.S. Pat. Nos. 5,100,714 and 5,058,799 describe a process for preparing a 
metallized ceramic substrate having an enhanced bond strength; the entire 
disclosure of each of these patents is hereby incorporated by reference 
into this specification. The substrate produced by the process of these 
patents may be used to produce the products described and claimed in this 
patent application. 
It is an object of this invention to provide a process for preparing an 
insulated metallized substrate which can be further processed to produce a 
multilayer electronic device which has excellent definition of the 
conductor(s). 
It is another object of this invention to provide a process for preparing 
an insulated metallized substrate which can be further processed to 
produce a multilayer electronic device which has excellent dielectric 
properties and preferably has finely patterned electroformed conductors 
throughout the structure. 
It is another object of this invention to provide a process for preparing 
an insulated metallized substrate which can be further processed to 
produce a multilayer electronic device which has excellent electrical and 
thermal conductivity properties. 
It is another object of this invention to provide a process for preparing 
an insulated metallized substrate which can be further processed to 
produce a multilayer electronic device which does not degrade when exposed 
to high temperature. 
It is another object of this invention to provide a process for preparing 
an insulated metallized substrate which can be further processed to 
produce a multilayer electronic device which is capable of being joined to 
other structures without adversely affecting its properties. 
It is yet another object of this invention to provide multilayer electronic 
devices with finely patterned dielectric layers using finely patterned 
electroformed metal conductor patterns. 
It is yet another object of this invention to produce multilayer electronic 
devices containing vias with high ductility and adhesion in such devices. 
It is yet another object of this invention to provide a process for firing 
a normally air-fireable dielectric material in a nitrogen atmosphere. 
It is another object of this invention to provide an insulated metallized 
substrate which is hermetic. 
It is another object of this invention to provide an insulated metallized 
substrate with excellent physical properties. 
It is another object of this invention to provide an insulated metallized 
substrate to which electrical components may be readily and durably 
affixed in a multiplicity of ways. 
It is another object of this invention to provide a multilayer electronic 
device which has excellent definition of the conductor(s). 
It is another object of this invention to provide a multilayer electronic 
device which has excellent dielectric properties. 
It is another object of this invention to provide multilayer planar motors. 
It is yet another object of this invention to provide a multilayer planar 
commutator. 
It is yet another object of this invention to provide a process for 
preparing a multilayer electronic assembly in which electroformed 
patterning of metal conductor material is included in several layers of a 
cofired structure with the use of a transfer technique. 
It is yet another object of this invention to provide a process in which 
dielectric material is applied to plated via pipes in order to create a 
fine-patterned dielectric structure. 
It is another object of this invention to provide a multilayer electronic 
device which does not degrade when exposed to high temperature. 
It is another object of this invention to provide a planar transformer made 
from a multilayer structure of metal and dielectric material. 
It is another object of this invention to provide a high density multichip 
module package comprised of layers of plated metal and dielectric 
material. 
It is another object of this invention to provide a micro-miniature 
electric motor comprised of layers of metal and dielectric material. 
It is another object of this invention to provide a solenoid comprised of 
alternating planar inductive coils. 
SUMMARY OF THE INVENTION 
In accordance with this invention, there is provided a process for 
preparing an insulated metallized substrate in which the exterior surfaces 
of a metallized substrate are first subjected to a specified heat 
treatment and thereafter contacted with dielectric material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In applicants' preferred process, a metallized substrate is first provided, 
and its surfaces are then treated prior to the time they are contacted 
with a mixture of liquid and ceramic material. 
FIG. 1 is a flow chart illustrating one preferred embodiment of applicants' 
invention. Referring to FIG. 1, in the first step (step 10) of the 
preferred process depicted, a metallized substrate is produced. In 
general, the process of U.S. Pat. Nos. 5,058,799 and 5,100,714, or 
comparable processes, may be used to prepare the metallized substrate. The 
particular metallized substrates which may be advantageously used in the 
process are described elsewhere in this specification. 
Referring again to FIG. 1, the substrate is passed via line 12 to cleaner 
14, wherein it is cleaned to remove contaminants. One preferred high 
temperature cleaning process, which involves exposure of the substrate to 
an inert atmosphere, is described elsewhere in this specification. 
The cleaned substrate is then passed via line 16 to oxidizer 18 in which at 
least a portion of the exterior faces of the substrate is oxidized by 
preferably heating it while exposing it to an inert gas comprised of a 
specified amount of oxygen. This preferred oxidation step also is 
described in more detail elsewhere in this specification, but other means 
of producing the desired degree of oxidation also may be used. 
The oxidized substrate is then passed via line 20 to printer 22 in which a 
patterned layer of dielectric is applied to the exterior faces of the 
substrate. This printing step is also described in more detail elsewhere 
in this specification. 
The printed substrate is then passed via line 24 to dryer 26 in which 
solvent present in the dielectric is removed. The dried substrate is then 
passed via line 28 to binder removal furnace 30 to effect removal of 
organic matter from the dried slurry coating. These steps are described in 
more detail elsewhere in this specification. 
The substrate is then passed via line 32 to sintering furnace 34, in which 
the dried slurry layer is densified. This densified substrate is then 
passed via line 36 to metal oxide remover 38, in which metal oxide on the 
surface of the substrate which was not covered by the dielectric applied 
in printer 22 is removed. These steps are also described in more detail 
elsewhere in this specification. 
The treated substrate from which metal oxide has been removed is then 
passed via line 40 to surface preparer 42, in which the exterior surfaces 
of the substrate are treated in preparation for subsequent deposition of 
metal. The prepared substrate is then passed via line 44 to electroless 
metal deposition step 46, in which a layer of metal is electrolessly 
deposited onto the substrate structure. 
The substrate coated with metal from step 46 is then passed via line 48 to 
step 50, in which a coating of photoresistive material is applied to the 
substrate. The coated substrate from step 50 is then passed via line 52 to 
step 54, in which the photoresistive coating is selectively exposed to 
ultraviolet radiation to selectively harden areas of the coating. These 
steps are described in more detail elsewhere in the specification. 
The exposed substrate from step 54 is then passed via line 56 to developer 
58, in which a portion of the photoresistive coating is removed. The 
substrate from step 58 is then passed via line 60 to metal plater 62, in 
which metal is then plated onto those areas from which the photoresistive 
coating has been removed. 
The plated substrate is then passed via line 64 to photoresist stripper 66, 
in which excess photoresist material is removed. Thereafter, the printed 
substrate is then passed via line 68 to electroless metal removal step 70 
and, thereafter, via line 71 to machiner 73, wherein the printed substrate 
may be cut to the desired size. 
Alternatively, or additionally, the printed substrate may be passed to 
cleaner 14, where the process may be repeated as required to add 
additional layers of ceramic material and/or metal material prior to the 
time the printed substrate is cut to the desired size(s). 
The Substrate Used in Applicants' Process 
Referring to FIG. 1, in the first step of applicants' process, a metallized 
substrate with specified properties is provided. 
The metallized substrate used in applicants' process is a workpiece, such 
as a ceramic workpiece, having a working surface unitary with the 
workpiece and containing a layer of electrically conductive metal on the 
working surface; see, e.g., U.S. Pat. No. 5,100,714 for an illustration of 
the preparation of such a workpiece. 
In the preferred metallized substrate used in applicants' process, a 
heterogeneous juncture band exists between the workpiece and the 
conductive metal layer which is substantially coextensive with the 
conductive metal layer and the working surface. It is preferred, but not 
essential, that this heterogeneous juncture band has a metal-wetted 
surface area which is at least about twice the apparent surface area of 
the metal layer overlying the juncture band, consists essentially of 
workpiece grains unitary with said workpiece and conductive metal unitary 
with said conductive metal layer, and it is constituted by finger-like 
metal protuberances unitary with the metal layer and occupying the space 
between the ceramic grains. 
In addition to having such heterogeneous juncture band, the metallized 
substrate used in applicants' process is preferably capable of 
withstanding repeated firing cycles at a temperature in excess of 400 
degrees centigrade without separation of the metal layer from the working 
surface of the workpiece. In one embodiment, the metallized substrate used 
in applicants' process is capable of withstanding repeated firing cycles 
at a temperature in excess of 600 degrees centigrade without separation of 
the metal layer from the working surface of the workpiece. In another 
preferred embodiment, the metallized substrate used in applicants' process 
is capable of withstanding repeated firing cycles at a temperature in 
excess of 850 degrees centigrade without separation of the metal layer 
from the working surface of the workpiece. 
In one preferred embodiment, the substrate used in step 14 of applicants' 
process is a metallized ceramic substrate. The preparation of such a 
substrate is described in the aforementioned U.S. Pat. Nos. 5,058,799 and 
5,100,714, the entire descriptions of which are hereby incorporated by 
reference into this specification. 
As used herein, the term ceramic refers to a compound or composition which 
(1) is nonmetallic (i.e., does not contain elemental metal), (2) is 
generally subjected to a temperature in excess of 540 degrees centigrade 
during its manufacture and/or use, (3) frequently contains one or more 
metallic oxides, borides, carbides, and/or nitrides, and/or mixtures 
and/or compounds of such materials, and (4) is inorganic (i.e., is not any 
compound which contains carbon such as hydrocarbon!, with the exception 
of carbon oxides, carbon disulfide, and metal carbides). See, e.g., page 
54 of Loran S. O'Bannon's "Dictionary of Ceramic Science and Engineering" 
(Plenum Press, New York, 1984). 
Ceramic substrates, and/or substrates comprised of ceramic material, are 
well known to those skilled in the art. Thus, by way of illustration and 
not limitation, one may use one or more of the ceramic substrates 
described in U.S. Pat. Nos. 5,108,716 (a honeycomb type monolithic ceramic 
substrate), 5,106,654 (porous ceramic substrate), 5,097,246 (glass), 
5,089,881, 5,087,413 (a multilayer ceramic substrate comprised of a 
multiplicity of vias), 5,084,650 (a transparent ceramic substrate.), 
5,082,163 (aluminum nitride metallized with copper), 5,081,563 (a 
multilayer ceramic glass-ceramic substrate formed of a stacked plurality 
of generally parallel signal and insulating layers), 5,081,073 (a 
superconducting ceramic substrate), 5,081,067, 5,080,966 (a multilayer 
ceramic substrate comprised of filled vias), 5,080,958, 5,080,929 (a 
ceramic substrate with through holes), 5,077,091 (a ceramic substrate 
based on nitrides or carbonitrides of at least one metallic element 
selected from Cr, V, Zr, W, Mo, Co, Mn, Ni, Hf and Ta), 5,077,079 (a 
bioadaptable ceramic substrate), 5,075,765, 5,070,602, 5,070,393 (an 
aluminum nitride substrate), 5,070,343 (a ceramic substrate with a 
plurality of U-shaped grooves), 5,068,156, 5,066,620, 5,065,106, 5,063,121 
(sintered nitride ceramic), 5,062,913 (a laminated ceramic substrate), 
5,061,552 (a multi-layer ceramic substrate assembly, 5,057,964, 5,057,376 
(a glass ceramic substrate), 5,057,163 (a conductive ceramic substrate), 
5,056,227 (a polycrystalline ceramic substrate), 5,055,914, 5,053,361 (a 
multilayer ceramic substrate laminate), 5,050,296, 5,047,368, 5,043,223 (a 
multilayer ceramic substrate), 5,041,809 (a glass-ceramic substrate), 
5,041,342, 5,041,016, 5,036,167, 5,035,837, 5,034,850, 5,033,666, 
5,030,396 (a ceramic shaped implant having a porous layer), 5,029,043, 
5,023,407, 5,016,023, 5,014,161, 5,013,607 (a transparent conductive 
ceramic substrate), 5,013,312, 5,011,734 (a ceramic substrate which has on 
its surface a metallized layer made of Au or Cu, or Au-Pt, Au-Pd, Cu-Pt or 
Cu-Pd alloy that is overlaid with a Ni plating layer), 5,011,732 (a glass 
ceramic substrate containing an electrically conductive film formed 
thereon), 5,008,151, 5,008,149 (metallized ceramic substrate), 5,006,673 
(a universal ceramic substrate), 5,004,640, 4,999,731, 4,996,588, 
4,994,302, 4,992,772, 4,990,720, 4,989,117, 4,987,009, 4,986,849, 
4,985,097 (glass), 4,978,452, 4,976,145, 4,973,982, 4,971,738, 4,970,577, 
4,967,315, 4,963,437, 4,960,752 (a polycrystalline superconductor), 
5,959,507, 4,959,255, 4,958,539, and the like. The disclosure of each of 
these United States patents is hereby incorporated by reference into this 
specification. 
In one preferred aspect of this embodiment, the ceramic material used is 
alumina. Thus, e.g., the substrate may consist essentially of alumina 
ceramic (any ceramic whiteware in which alumina is the essential 
crystalline phase). 
In one preferred embodiment, the alumina is a "white alumina" substrate 
which has a density of at least about 3.7 grams per cubic centimeter and 
is comprised of at least about 90 weight percent of aluminum oxide. In 
another preferred embodiment, the alumina used is "black alumina." 
In one embodiment, illustrated in FIG. 2, the ceramic substrate 72 consists 
essentially of alumina and is comprised of a base 74 of relatively low 
density alumina material and, integrally bonded thereto, a layer 76 of 
higher density alumina material. In this embodiment, it is preferred that 
the porosity of layer 76 be less than the porosity of layer 74. In an 
especially preferred embodiment, layer 76 has a porosity such that it is 
substantially impervious to liquid penetration. 
In this embodiment, in general, layer 76 preferably has a thickness of at 
least about 5 times the average grain size of the particles in layer 76. 
In another embodiment, not shown, layer 74 is made from one type of ceramic 
material, and layer 76 comprises or consists essentially of another type 
of ceramic material. 
Referring again to FIG. 1, and by way of further illustration, the ceramic 
substrate used in step 14 may be a porcelain covered metal or metal alloy 
material. Furthermore, the ceramic substrate may be porcelain/ceramic 
covered graphite, porcelain/ceramic covered silicon carbide, and the like. 
Porcelain covered metal materials, and processes for making them, are 
well-known to those skilled in the art. Reference may be had, e.g., to 
U.S. Pat. Nos. 5,053,740, 5,012,182, 5,002,903, 4,957,440, 4,894,609, 
4,620,841, 4,619,810, 4,576,789, 4,556,598, 4,393,438, 4,365,168, 
4,328,614, 4,010,048, 3,585,064, 2,563,502, 4,407,868, and the like. The 
disclosure of each of these patents is hereby incorporated by reference 
into this specification. 
In one preferred embodiment, the ceramic substrate is comprised of or 
consists essentially of a ferromagnetic material, such as a ferrite. 
As is known to those skilled in the art, a ferrite is a ferromagnetic 
compound containing Fe.sub.2 O.sub.3. See, for example, U.S. Pat. No. 
3,576,672 of Harris et al., the entire disclosure of which is hereby 
incorporated by reference into this specification. 
In one embodiment, the ferrite is a garnet. Iron garnet has the formula 
M.sub.3 Fe.sub.5 O.sub.12 ; see, e.g., pages 65-256 of Wilhelm H. Von 
Aulock's "Handbook of Microwave Ferrite Materials" (Academic Press, New 
York, 1965). Garnet ferrites are also described, e.g., in U.S. Pat. No. 
4,721,547, the disclosure of which is hereby incorporated by reference 
into this specification. 
In another embodiment, the ferrite is a spinel ferrite. Spinel ferrites 
usually have the formula MFe.sub.2 O.sub.4, wherein M is a divalent metal 
ion and Fe is a trivalent iron ion. M is typically selected from the group 
consisting of nickel, zinc, magnesium, manganese, and like. These spinel 
ferrites are well known and are described, for example, in U.S. Pat. Nos. 
5,001,014, 5,000,909, 4,966,625, 4,960,582, 4,957,812, 4,880,599, 
4,862,117, 4,855,205, 4,680,130, 4,490,268, 3,822,210, 3,635,898, 
3,542,685, 3,421,933, and the like. The disclosure of each of these 
patents is hereby incorporated by reference into this specification. 
Reference may also be had to pages 269-406 of the Aulock book for a 
discussion of spinel ferrites. 
In yet another embodiment, the ferrite is a lithium ferrite. Lithium 
ferrites are often described by the formula (Li.sub.0.5 Fe.sub.0.5).sup.2+ 
(Fe.sub.2).sup.3+ O.sub.4. Some illustrative lithium ferrites are 
described on pages 407-434 of the aforementioned Aulock book and in U.S. 
Pat. Nos. 4,277,356, 4,238,342, 4,177,438, 4,155,963, 4,093,781, 
4,067,922, 3,998,757, 3,767,581, 3,640,867, and the like. The disclosure 
of each of these patents is hereby incorporated by reference into this 
specification. 
In yet another embodiment, the preferred ferrite is a hexagonal ferrite. 
These ferrites are well known and are disclosed on pages 451-518 of the 
Aulock book and also in U.S. Pat. Nos. 4,816,292, 4,189,521, 5,061,586, 
5,055,322, 5,051,201, 5,047,290, 5,036,629, 5,034,243, 5,032,931, and the 
like. The disclosure of each of these patents is hereby incorporated by 
reference into this specification. 
In one preferred embodiment, the ceramic substrate is comprised of a 
superconductive material. In this embodiment, it is preferred that the 
superconductive material have a critical temperature of greater than about 
77 degrees Kelvin and, more preferably, greater than about 85 degrees 
Kelvin. These superconductive materials are well known to those skilled in 
the art and are described, e.g., in U.S. Pat. No. 5,015,619, the entire 
disclosure of which is hereby incorporated into this specification by 
reference. 
In another embodiment, and by way of further illustration, the ceramic 
material used, in whole or in part, to construct the substrate may be, 
e.g., barium titanate, neodymium nitride, neodymium oxide, and the like. 
In one embodiment, the ceramic substrate is comprised of ceramic 
microspheres. Ceramic microsphere structures are well known to those 
skilled in the art and are described, e.g., in U.S. Pat. Nos. 4,936,384 
and 4,822,422, the entire disclosures of which are hereby incorporated by 
reference into this specification. 
FIG. 3 illustrates one typical laminated structure which may be used as the 
ceramic substrate. Referring to FIG. 3, it will be seen that substrate 78 
is comprised of metal and/or metal alloy base 80 and, bonded thereto, 
porcelain layers 84 and 86. As will be apparent to those skilled in the 
art, base 80 may be a substantially homogeneous material consisting 
essentially of only one metal or metal alloy. Alternatively, base 80 may 
be a laminated structure (such as a laminate of copper/Invar/copper, or 
copper/molybdenum/copper. As is known to those skilled in the art, Invar 
is a trademark for an iron-nickel alloy containing 40-50% nickel and 
characterized by an extremely low coefficient of thermal expansion. Other 
suitable metal- and/or alloy-containing bases 80 will be apparent to those 
skilled in the art. 
As will be apparent to those skilled in the art, the ceramic substrate 
preferably used in step 14 may, but need not, contain ceramic throughout 
its entire structure, as long as the exterior layers of such structure 
consist essentially of one or more ceramic materials. 
It is preferred that the ceramic substrate used, regardless of whether it 
consists essentially of or is only comprised of ceramic material, have a 
volume resistivity of at least about 10.sup.10 ohm-centimeters and, 
additionally, have a thermal conductivity at least about 10 
watts/meter-degrees Centigrade. As is known to those skilled in the art, 
these properties may be measured by A.S.T.M. Standard Test D1829. 
By way of illustration and not limitation, one may use ceramic substrates 
sold by the Coors Ceramics Company of 17750 West 32nd Avenue, Golden, 
Colorado as product numbers ADO-90, AD-94, and AD-96. These products have 
a bulk density (A.S.T.M. C373) of from about 3.7 to about 3.8 grams per 
cubic centimeter, a Rockwell hardness (A.S.T.M. E18) of from about 75 to 
about 80), a coefficient of linear thermal expansion (A.S.T.M. C372) of 
from about 3 to 8.times.10.sup.-6 per degree Centigrade, a flexural 
strength (A.S.T.M. F417 and F394) of from about 40,000 to 60,000 pounds 
per square inch, a water absorption (A.S.T.M. C373) of 0 percent, and a 
compressive strength (A.S.T.M. C773) of from about 300,000 to about 400,00 
pounds per square inch. 
In another embodiment, the substrate used in step 14 either consists 
essentially of graphite or, alternatively, contains a coated structure 
similar to that of FIGS. 2 and/or 3 in which the graphite appears as 
either layer 76 (see FIG. 2) and/or layers 84 and/or 86. In this 
embodiment, the base 74 (see FIG. 2) and/or 80 (see FIG. 3) may be ceramic 
material, inorganic metal oxide material, and the like. 
In another embodiment, the substrate used in step 14 either consists 
essentially of plastic material or, alternatively, contains a coated 
structure similar to that of FIGS. 2 and 3. In this embodiment, one may 
use suitable plastics such as epoxy resin. 
Referring again to FIG. 1, it is preferred that the substrate used in step 
14 contain at least one through hole which extends from its top surface to 
its bottom surface. The preparation of substrates with this configuration 
is well described in U.S. Pat. Nos. 5,058,799 and 5,100,714. 
In one embodiment, the substrate is a ceramic substrate which contains a 
multiplicity of vias extending into the ceramic substrate to a depth of at 
least about one-fifth of its thickness up to about 100 percent of its 
thickness. In one aspect of this embodiment, the extensions are circular 
in cross-section and preferably have a diameter of from about 4 to about 
20 mils. In another aspect of this embodiment, there are at least about 25 
such vias within an area of 0.01 square inches on at least a portion of 
the ceramic substrate. In yet another aspect of this embodiment, there are 
at least about 100 such vias within an area of 0.01 square inches on at 
least a portion of the ceramic substrate. 
In one preferred embodiment, the ceramic substrate contains a through hole 
88 (see FIG. 4). Referring to FIG. 4, it will be seen that, in this 
embodiment, substrate 90 is comprised of ceramic material 92, via 88 which 
extends from top surface 94 to bottom surface 96 of substrate 90, and a 
layer of metal 98 covering the wall of hole 88. The production of such a 
metallized via structure is disclosed, e.g., in the aforementioned 
Zsamboky patents. 
In the remainder of this specification, reference will often be made to the 
processing of a substrate comprised of alumina and copper. It will be 
understood, however, that the comments made with respect to the processing 
of this particular substrate are equally applicable to the processing of 
other substrates which may be used in applicants' process. 
The Cleaning of the Metallized Substrate 
Referring again to FIG. 1, in step 14 the substrate material is preferably 
cleaned. The goal of such cleaning is to remove loose contaminants present 
in the substrate. 
FIG. 5 is a flow diagram illustrating one preferred cleaning process. 
Referring to FIG. 5, and in the preferred embodiment illustrated therein, 
the substrate is preferably charged via line 100 to washer 102, wherein it 
is preferably washed. In general, a soapy mixture of industrial detergent 
is applied to the substrate. Thus, the substrate may be allowed to soak in 
a soapy mixture of the detergent for up to about 20 minutes and thereafter 
may be rinsed with deionized water. 
In one preferred embodiment, illustrated in FIG. 5, prior to the time the 
substrate is washed in washer 102 its surface is etched in texturizer 103. 
As is known to those skilled in the art, this step can be achieved by 
conventional etchants. Thus, e.g., when the metal layer involved is 
copper, one may utilize "ENPLATE" ad-485, which is a mild etchant for 
copper surfaces which is sold by the Enthone-OMI Inc. Company of New 
Haven, Conn. Other comparable etchants also may be used. After such 
etching, the etched device may be passed to washer 102 via line 105 for 
processing as described hereinafter. 
The washed substrate may then be passed via line 104 to dryer 106, wherein 
it is preferably dried to a moisture content of less than about 5 weight 
percent. 
In the next stage of the process, a layer of metal oxide is formed on the 
surface of the metal in the substrate. Applicants have presented one 
preferred means of forming this metal oxide. It is to be understood, 
however, that other such means could be used and still be within the 
spirit and scope of this invention. 
In applicants' preferred process, the dried substrate is passed via line 
108 to inert gas furnace 110, wherein it is preferably fired at a 
temperature of at least 800 degrees centigrade for at least about 5 
minutes while being contacted with an inert atmosphere, which may be 
introduced via line 112. In one preferred embodiment, the inert atmosphere 
consists essentially of nitrogen, which is preferably allowed to flow over 
the substrate. It is preferred that the oxygen content in the furnace 110 
be less than about 10 parts per million. 
In one preferred embodiment, the dried substrate is passed through a 
conveyor furnace (not shown) in which the middle of furnace is at the 
desired peak temperature and the ends of the furnace are each preferably 
at less than about 100 degrees Centigrade. In this embodiment, it is 
preferred to raise the temperature of the dried substrate from about 
ambient to the desired peak temperature over a period of at least about 20 
minutes and, preferably, at least about 40 minutes; and it is preferred to 
utilize a peak temperature of from about 800 to about 950 degrees 
centigrade for from about 5 to about 20 minutes. Thereafter, when the 
substrate is to be transferred to a second furnace for the oxidation heat 
treatment processing, it is preferred to cool the heated substrate to 
ambient over a period of at least about 15 minutes and, more preferably, 
at least from about 15 to about 30 minutes; when the oxidation heat 
processing occurs in the same furnace, however, this cooling step may be 
omitted. During the entire time the substrate is heated at a temperature 
in excess of 100 degrees centigrade, however, it preferably is contacted 
with the inert atmosphere which is comprised of less than 10 parts per 
million of oxygen. 
Conveyor furnaces are well known to those skilled in the art and are 
described, e.g., in U.S. Pat. Nos. 5,096,478, 5,088,920, 5,003,160, 
4,997,364, 4,986,842, and the like; the disclosure of each of these United 
States patents is hereby incorporated by reference into this 
specification. 
When utilizing a conveyor furnace, it is preferred to support the substrate 
by its edges so that the flowing inert gas can contact both the top and 
bottom surfaces of the substrate and the conveyor belt is not contiguous 
with the faces of the substrate. 
In one preferred embodiment, a temperature of at least about 900 degrees 
centigrade is used in furnace 110. 
In the embodiment where two separate furnaces are utilized, the substrate 
passing from furnace 110 is preferably at ambient temperature. Thereafter, 
this substrate is passed via line 114 to oxidizing furnace 116, wherein it 
is subjected to a specified firing profile. 
It will be appreciated by those skilled in the arts that both of the 
heat-treatment cycles could be effected in the same furnace by changing 
the atmosphere used at the appropriate time(s). In this embodiment, 
however, the need to cool the substrate after exposure to inert gas and 
then again raise it to peak temperature priorto exposing it to the mild 
oxidizing atmosphere may be omitted. 
In the first part of the firing profile in furnace 116, the temperature of 
the furnace is raised from ambient to about at least about 800 degrees 
centigrade over a period of at least about 5 minutes; it is preferred to 
raise the temperature of the substrate to a temperature of at least about 
800 to about 950 degrees centigrade over a period of from about 5 minutes 
to about 20 minutes. During this step, the atmosphere in the furnace is 
preferably substantially inert, containing less than about 10 parts per 
million of elemental oxygen. 
Once the furnace 116 has reached a temperature of at least about 800 
degrees centigrade, however, an oxygen-containing gas (such as, e.g., 
oxygen, air, mixtures thereof, and the like) is introduced via line 118 in 
order to introduce at least about 100 parts per million of oxygen (and, 
preferably from about 100 to about 500 parts per million by total volume 
of the atmosphere in furnace 116! of elemental oxygen). It is preferred to 
contact this "oxidizing atmosphere" with the substrate while the substrate 
is at a temperature above 800 degrees centigrade for at least about 5 
minutes and, preferably, for at least from about 5 to about 20 minutes. 
Thereafter, the substrate is allowed to cool to ambient over a period of at 
least about 15 minutes while the substrate is contacted with an inert 
atmosphere containing less than about 10 parts per million of oxygen. 
The substrate produced via this process is schematically represented in 
FIG. 6, which illustrates a copper/ceramic/copper device. It will be 
apparent to those skilled in the art that, when other substrates are used 
as starting materials and/or when other metals are used for metallizing, 
different, but comparable, devices will be produced. 
Referring to FIG. 6, which is a sectional view of one preferred substrate 
produced in the process, It will be seen that substrate 130 is comprised 
of a ceramic core 132 (such as, e.g., alumina) and, bonded to portions 
thereto, copper patterned layers 134 and 136. The 132/134/136 structures, 
in one preferred embodiment, are produced by the process described in U.S. 
Pat. No. 5,058,799. 
In general, each of copper layers 134 and 136 has a thickness of from about 
10 to about 250 microns and, more preferably, from about 25 to about 125 
microns. By comparison, ceramic layer 132 generally has a thickness of 
from about 250 to about 30,000 microns and, more preferably, from about 
500 to about 1500 microns. 
Formed on top of each of copper layers 134 and 136 is a relatively thin 
layer of cuprous oxide (Cu.sub.2 O). This cuprous oxide is believed to be 
a reddish, crystalline material with a specific gravity of about 6 and a 
melting point of about 1,235 degrees centigrade; it is insoluble in water. 
Referring again to FIG. 6, it will be seen that each of cuprous oxide 
layers 138 and 140 have a thickness of less than 10 microns and preferably 
are from about 1 to about 10 microns thick. 
The aforementioned oxidation step has been described with reference to 
forming a metal oxide (such as cuprous oxide) on the surface of the metal 
layer (such as copper). However, other oxides also may be formed on the 
metal layer, or deposited on such layer, to provide a layer of oxide 
material which is of the desired thickness (from 1 to 10 microns thick) 
and, furthermore, provide an oxidation-resistant layer on top of the 
metal. 
Thus, by way of illustration and not limitation, one may form and/or apply 
to such metal layer(s) one or more of the oxides of silica (in the form of 
glass), tantalum, hafnium, zirconium, titanium, berylium, magnesium, 
barium, and the like. 
Referring again to FIG. 1, after oxidation in oxidizer 18, the oxidized 
substrate is passed via line 20 to printer 22. Printer 22 is preferably a 
screen printing apparatus. 
Any of the screen printing apparatuses well known to those skilled in the 
art may be used as printer 22. Thus, by way of illustration and not 
limitation, one may use the devices, processes, and reagents described in 
U.S. Pat. Nos. 5,107,587, 5,091,221, 5,089,465, 5,089,070, 5,083,058, 
5,036,167, 5,035,965, 5,032,571, 5,028,867, 5,000,090, 4,973,826, 
4,959,256, 4,958,560, and the like. The disclosure of each of these United 
States patents is hereby incorporated by reference into this 
specification. 
At this point in the process, and thereafter, the combined metal/metal 
oxide layers (such as layers 136/140 and 134/138 of FIG. 6) preferably 
provide a resistivity of less than about 1.9.times.10.sup.-6 
ohm-centimeters. In one preferred embodiment, the combined metal/metal 
oxide layers preferably have a melting point of at least 1,000 degrees 
centigrade, Furthermore, it is preferred that the combined metal/metal 
oxide layers adhere to each other well enough to be able to pass A.S.T.M. 
test D3528. 
It is preferred to produce a structure from the substrate that will be 
substantially hermetic, to which or from which helium cannot enter or 
escape at a rate exceeding 10.sup.-8 cubic centimeters per atmosphere 
differential per second at ambient temperature and a metal thickness of at 
least 0.0005". As is known to those skilled in the art, the hermeticity of 
the structure may be tested by standard hermeticity tests (such as, e.g., 
Military Specification 883, method 1014, or A.S.T.M. Standard test F979). 
The desired structure is an insulated metallized substrate which comprises 
a workpiece having a working surface unitary with the workpiece, a layer 
of electrically conductive metal on said working surface, a layer of metal 
oxide on said layer of conductive metal, and a layer of ceramic material 
on said layer of metal oxide, and a heterogeneous juncture band between 
said workpiece and said conductive metal layer, substantially coextensive 
with said conductive metal layer and said working surface, wherein: (1) 
said heterogeneous juncture band consists essentially of grains unitary 
with said workpiece and conductive metal unitary with said conductive 
metal layer and is constituted by finger-like metal protuberances unitary 
with the metal layer and occupying the space between said grains, wherein 
said metallized substrate is capable of withstanding repeated firing 
cycles at a temperature in excess of 400 degrees centigrade without 
separation of the metal layer from the working surface of the workpiece, 
(2) the layer of electrically conductive metal has a thickness of from 
about 10 to about 250 microns, provided that the thickness of said layer 
of electrically conductive metal is at least about ten times as great as 
the thickness of said layer of metal oxide, (3) the layer of metal oxide 
has a thickness of from about 0.1 to about 10 microns, and (4) the layer 
of conductive metal has a resistivity of less than 1.8.times.10 -6 
ohm-centimeters. It is preferred that each of the layer of conductive 
metal and the layer of metal oxide has a melting point of at least about 
1,000 degrees centigrade. 
In the printing process, it is desired to print a patterned layer of 
ceramic/dielectric "ink" over the metal/metal oxide material patterned 
onto the substrate. This printing process is well known to those skilled 
in the art and is described, disclosed, e.g., in U.S. Pat. Nos. 4,152,282 
(silk screening of dielectric paste), 3,864,159, 4,865,875, 4,830,988, and 
4,609,582. The disclosure of each of these patents is hereby incorporated 
by reference into this specification. 
FIG. 7 is sectional view of a ceramic substrate 160 onto which layers of 
copper 134 have been selectively patterned in substantial accordance with 
the procedure of U.S. Pat. No. 5,058,799. In the embodiment depicted, the 
structure is comprised of a through-hole 162 formed by conventional means 
in substrate 160. 
By the procedure described elsewhere in this specification, layers 138 of 
copper oxide are preferably formed over layer 134. Thereafter, layers of 
dielectric "ink" are selectively patterned over the structure. 
As is known to those skilled in the art, in the screen printing process, 
the screen (not shown) is preferably patterned to prevent deposition of 
material in certain areas. Thus, referring to FIGS. 7 and 8, two such 
masked areas are areas 164 and 166. 
Referring again to FIG. 7, it will be seen that a layer 168 of dielectric 
"ink" is selectively patterned onto the structure in the screen printing 
process. Thereafter, after drying, binder removal, and sintering, the 
layer of "ink" so deposited tends to shrink and conform to the shape of 
the surface onto which it was deposited. 
In one embodiment, not shown, at least two layers of the dielectric "ink" 
are separately deposited, dried, processed to remove binder, and then 
sintered. In another embodiment, at least three layers of such dielectric 
"ink" are so deposited. 
The dielectric ink used in the process is preferably deposited as a layer 
with a thickness of at least about 25 microns and, preferably, at least 
about from 25 microns to about 100 microns. 
One may use the dielectric inks commonly used by thick film industry for 
printing printed circuits which are adapted for firing in nitrogen. As is 
known to those skilled in the art, nitrogen fireable dielectrics must 
balance hermeticity with the tendency to blister. This tendency is 
inherent in all dielectrics but is exacerbated by the need to burn out the 
dielectric delivery system with only 5-10 parts per million of oxygen 
present in the predominantly nitrogen atmosphere. 
The dielectric ink used in the process of this invention is preferably a 
mixture of liquid material and solid material which preferably contains at 
least about 80 weight percent of solid material and at least about 10 
weight percent of liquid material. 
In one preferred embodiment, the liquid in the dielectric ink is preferably 
non-aqueous and preferably has a boiling point in excess of 100 degrees 
centigrade. 
The viscosity of the dielectric ink used in the process, when measured with 
a Brookfield RVT viscometer and an ABZ spindle at 10 revolutions per 
minute and room temperature, is preferably less than 500 Pascals. 
The solid material in the dielectric preferably has a particle size 
distribution such that at least about 95 percent (by weight) of such 
particles are smaller than 25 microns. 
One especially preferred dielectric ink is "dielectric composition 4906" 
which is sold by Electro-Science Laboratories, Inc. of 416 East Church 
Road, King of Prussia, Pa. This material has a dielectric constant of from 
about 5 to about 11 and is insoluble in water. It is comprised of at least 
about 5 weight percent of liquid, and at least about 0.5 weight percent of 
organic binder, and at least about 80 weight percent of solid particulate 
matter; the solid particulate matter comprises glass and alumina. 
Substantially all of the particles of such ink are less than about 54 
microns in size. The solid particulate matter liquefies and sinters at a 
temperature in excess of 800 degrees centigrade. 
Yet another suitable dielectric ink is "Fodel 6050 Dielectric Paste," which 
is also sold by the E. I. dupont de Nemours & Company of Wilmington, Del. 
This material has a dielectric constant of from about 7 to about 9, a 
breakdown voltage in excess of 1,000 volts per 25 microns of thickness of 
dielectric, and an insulation resistance in excess of 10.sup.11 ohms at 
ambient temperature. When this dielectric is used to coat the substrate, 
it is preferred to fire it in nitrogen atmosphere comprised of water 
vapor; such atmosphere may be readily produced by bubbling an inert or 
relatively inert gas (such as nitrogen) through water maintained at a 
substantially constant temperature prior to flowing the inert gas over the 
heated substrate. 
The aforementioned "Fodel . . ." material, in addition to being comprised 
of glass particles and organic solvent, also contains photosensitive 
plastic binder material which enables a user to expose the dried 
dielectric layer to ultraviolet radiation and to selectively harden 
certain areas thereof. Thereafter, the unexposed areas may be washed away 
prior to the firing of the binder removal step and the sintering step. 
This feature allows the patterning of fine features in the dielectric 
layer. 
Referring again to FIG. 1, after a layer of dielectric material is applied 
to the structure, it is then passed via line 24 to dryer 26, wherein the 
solvent is removed. It is preferred that the temperature in dryer 22 be 
below the boiling point of the organic solvent in the dielectric ink. In 
one preferred embodiment, the structure is subjected to a temperature of 
less than about 150 degrees centigrade (and, more preferably, less than 
about 130 degrees centigrade) until substantially all of the solvent in 
the dielectric layer has evaporated. 
In one embodiment, the steps of printing and drying are repeated at least 
once, and often at least twice, to provide several layers of the dried 
dielectric material. In one aspect of this embodiment, different 
dielectric materials are used in each of the printing/drying sequences to 
provide printed layers with different characteristics. 
In one embodiment, a three-layer dielectric structure is produced with a 
substantially non-porous dielectric material on top, and relatively porous 
dielectric material in the middle, and a lower porosity dielectric 
material on the bottom. 
In another embodiment, one layer of dielectric material is deposited, 
dried, and thereafter fired. Thereafter a second layer of dielectric 
material is deposited upon the first sintered layer, dried, and fired. 
Referring again to FIG. 1, after a suitable number of dried layers of 
dielectric material have been produced, the structure is then passed via 
line 28 to binder removal furnace 30. 
In prior art binder removal processes, it is often recommended that, when 
the structure contains copper, an atmosphere relatively low in oxygen be 
used to avoid the formation of oxides of copper. Applicants have found, 
however, that in their process the use of an oxygen-containing atmosphere 
(such as air, oxygen, mixtures thereof, and the like) effectively removes 
the organic binder without any substantial deleterious effects. 
In applicants' process, thus, it is preferred to heat the structure in 
binder removal furnace 30 to a temperature of at least about 400 degrees 
centigrade (and, preferably, from about 400 to about 500 degrees 
centigrade) for from about 30 minutes to about 60 minutes. In this 
process, one preferably heats the structure from ambient to the 400-500 
degree peak temperature over a period of from about 10 to about 20 
minutes, holds the structure at the peak temperature for at least about 10 
to 20 minutes, and then cools the structure to ambient over a period of 
from about 10-20 minutes. During each of these steps, it is preferred to 
contact the structure with flowing oxygen-containing gas. 
The structure from which binder has been removed is then passed via line 32 
to sintering furnace 34. Thereafter, the temperature of the structure is 
raised from ambient to a peak temperature of from about 800 to about 950 
degrees Centigrade over a period of at least about 20 minutes and 
preferably from about 20 to about 40 minutes; during this portion of the 
firing, the structure is contacted with flowing inert gas containing less 
than about 100 parts per million of oxygen. 
Once the peak temperature has been reached, the structure is maintained at 
this temperature for at least 3 minutes (and, preferably, from about 3 to 
about 15 minutes) while contacting the structure with inert gas containing 
less than about 100 parts per million of oxygen). Thereafter, the 
structure is cooled to ambient over a period of at least about 10 minutes 
(and, preferably, at least about 20 minutes). 
Without wishing to be bound to any particular theory, applicants believe 
that the production of the metal oxide layer in oxidizer 18 affords better 
adhesion between the metal/metal oxide and the glass dielectric; thus, the 
fired dielectric material tends to adhere better to the metal/metal oxide 
structures (see FIG. 8). 
Referring to FIG. 8, the shrinkage which occurred with dielectric 168 may 
be determined by comparing it with the wet-printed dielectric surface (see 
FIG. 7). 
Referring again to FIG. 8, the sintered structure will have certain of its 
copper/copper oxide areas exposed after the sintering. Thus, e.g., areas 
180 and 182 are two of such unmasked areas. 
In the metal oxide removal step 38, the metal oxide layer 138 is removed, 
preferably by chemical means. The structure is preferably dipped into a 
metal oxide etchant which will attack the metal oxide preferentially but 
will not attack the sintered dielectric or the copper or the substrate 160 
to any appreciable extent. 
In one preferred embodiment, the structure is dipped into an aqueous 
solution of hydrochloric acid at a concentration of from about 10 to about 
50 volume percent. It is preferred to use hydrochloric acid at a 
concentration of from about 15 to about 30 volume percent. 
The hydrochloric acid may be used at ambient temperature. Alternatively, it 
may be at a temperature of from about 40 to about 80 degrees centigrade. 
Instead of hydrochloric acid, or in addition thereto, one may use other 
conventional etchants which selectively attack the metal oxide. 
The metal oxide removal is time and temperature dependent. The structure is 
contacted with the removal agent for a time sufficient to remove 
substantially only the metal oxide. 
The structure with the metal oxide removed from it is shown in FIG. 9. See 
areas 184 and 186 which now present bare metal. This bare metal may now be 
treated in a surface preparation step, and thereafter additional metal may 
be added thereto in an electroless metal deposition step. 
In one preferred process, the dielectric ink used is a mixture of the 
aforementioned "dielectric composition 4906" and "Fodel 6050 . . ." 
materials. 
In one preferred embodiment, the dielectric ink is comprised of glass. 
These glass-containing dielectric materials are well known to those 
skilled in the art and are described, e.g., in U.S. Pat. Nos. 4,152,282 
(aluminum oxide and a borosilicate glass), 4,830,988 
(magnesium-barium-aluminum-zirconium-borophosphosilicate glass frit and an 
organic vehicle), 4,865,875 (glass microspheres and a organic vehicle), 
4,861,646 (borosilicate glasses and crystalline fillers), 4,855,266 (a 
high-K dielectric composition containing doped barium titanate and 
glass-forming ions that can be co-fired in a low-oxygen containing 
atmosphere), 4,849,380 (a low K dielectric composition consisting of 
amorphous borosilicate glass containing alumina, a mixture of oxides of 
alkali metals and alkaline earth metals, and a ceramic filler), 4,849,379, 
4,152,282 (aluminum oxide and borosilicate glass), and the like. The 
entire disclosure of each of these patents is hereby incorporated by 
reference into this specification. 
In one preferred embodiment, the dielectric ink is comprised of cordierite 
(2MgO.2Al.sub.2 O.sub.3.5SiO.sub.2), which is a material with a low (about 
3-4) dielectric constant. In another preferred embodiment, the dielectric 
ink is made from glass compositions based on such magnesium oxide, 
alumina, and silica and, additionally, phosphorous pentoxide and boron 
oxide. 
The structure, and its exposed surfaces, are now subjected to the acid 
etching process described in U.S. Pat. Nos. 5,100,714 of 5,058,799; see, 
e.g., columns 11 and 12 of U.S. Pat. No. 5,058,799. In one preferred 
embodiment, a ceramic blank is preheated to a temperature of about 93 
degrees centigrade for approximately five to ten minutes and then dipped 
into a hot, concentrated acid dip to etch the ceramic surface along the 
ceramic grain boundaries thereof. 
The acid etched structure is then passed via line 44 to electroless metal 
deposition step 46 in which electroless metal deposition occurs. This 
electroless deposition may occur by conventional means such as, e.g., by 
one or more of the processes disclosed in U.S. Pat. Nos. 5,102,456 
(copper), 5,075,037 (copper), 5,066,545 (nickel), 5,024,680 (nickel), 
4,971,944 (gold), 4,935,013 (copper/nickel alloy), 3,650,747 (cobalt), and 
the like; the disclosure of each of these patents is hereby incorporated 
by reference into this specification. 
By way of further illustration, and not limitation, one may use the 
electroless deposition process described in U.S. Pat. Nos. 5,100,714 and 
5,058,799. 
The structure produced as a result of this electroless plating is 
illustrated in FIG. 9A. Referring to FIG. 9A, it will be seen that a thin 
layer 187 of electroless copper covers the structure. 
Thereafter, photoresistive coating applied in step 50. One may use any of 
the photoresistive coatings known to those in the art. Thus, by way of 
illustration and not limitation, one may use one or more of the 
photoresistive coatings described in U.S. Pat. Nos. 5,100,508, 5,094,884, 
5,092,968, 5,077,176, 5,069,996, 5,066,561, 5,064,746, 5,057,401, 
5,055,318, 5,055,383, 5,045,485, 5,039,594, 5,037,482, 5,027,062, 
5,021,320, 5,019,488, and the like. The disclosure of each of these United 
States patents is hereby incorporated by reference into this 
specification. 
In one embodiment of this process, a film of photosensitive resist material 
is applied to the exterior surfaces of structure 189 (see FIG. 9A). Thus, 
by way of illustration and not limitation, in step 50, a sheet of 
"DYNACHEM" photoresistive dry film (manufactured by the Thiokol/Dyachem 
Corporation of Tustin, Calif.) may be applied by conventional means. Thus, 
e.g., this film may be applied by means of a "MODEL 300 LAMINATOR" 
manufactured by such Thiokol/Dynachem Corporation. 
FIG. 10 is view of the structure of FIG. 9A to which a layer of 
photoresistive film 190 has been applied. As will be seen from such FIG. 
10, attached to photoresistive film 190 is a removable layer of carrier 
film 192, which is removed prior to development. 
Thereafter, a mask with the desired pattern is placed over film 190 and/or 
over film 192; see FIG. 11. Referring to FIG. 11, mask segments 194 and 
196 will tend to block the transmission of ultraviolet light in dark 
masked areas 198, 200, 202, and 204. 
The masked structure is then exposed to ultraviolet radiation. Thus, e.g., 
one may use a model 39 ultraviolet exposure device manufactured by the 
Hybrid Technology Corporation of Campbell, Calif. As will be apparent to 
those skilled in the art, ultraviolet radiation will be transmitted 
through the masks in every area except for masked segments 198, 200, 202, 
and 204; and, consequently, the areas in which such radiation is 
transmitted will cause the corresponding areas of photoresistive film 
disposed underneath them to polymerize. Such polymerized areas are 
resistant to degradation by the developer subsequently used. 
If not already heretofore done, the carrier film 192 is removed form the 
photoresistive material 190. Thereafter, the exposed structure is 
contacted with a developer which tends to dissolve those areas of film 190 
which have not polymerized. Thus, e.g., the areas of film 190 underneath 
masks 198, 200, 202, and 204 will be removed by the developer. 
Any conventional developer which selectively removes unpolymerized 
photoresistive film may be used in this process. By way of illustration 
and not limitation, one may use aqueous sodium bicarbonate. 
FIG. 12 shows the product produced after the exposure of the substrate to 
developer 58. Note that, where the masks 198, 200, 202, and 204 had been 
disposed over the structure (see FIG. 11), the photoresistive material has 
been removed. This open areas now can be built up further with the 
deposition of electroplated metal in metal plater 62. 
The electroplating operation is well known to those skilled in the art and 
may be conducted, e.g., in substantial accordance with the procedure of 
one or more of U.S. Pat. Nos. 5,108,554, 5,108,552, 5,106,537, 5,104,563, 
5,103,637, 5,102,521, 5,102,506, 5,101,682, 5,100,524, 5,098,860, 
5,098,544, 5,098,542, 5,096,522, 4,094,726, and the like. The disclosure 
of each of these United States patents is hereby incorporated by reference 
into this specification. 
The product produced is metal plating step 62 is illustrated in FIG. 13. 
Note the presence of the layer 189 of electroplated metal. 
The structure is then passed via line 64 to photoresist stripper 66, 
wherein photoresistive film 190 is removed. The product produced is 
illustrated in FIG. 14. 
Photoresist stripping compositions, and processes and apparatuses for their 
use, are well known to those skilled in the art and are disclosed, e.g., 
in U.S. Pat. Nos. 5,102,777, 5,091,103, 4,992,108, 4,963,342, 4,917,122, 
4,824,763, 4,791,043, 4,744,834, 4,718,974, 4,491,530, 4,483,917, 
4,438,192, and the like. The disclosure of each of these United States 
patents is hereby incorporated by reference into this specification. 
The structure is then passed via line 68 (see FIG. 1) to electroless metal 
removal step 70, wherein the electroless metal is removed by conventional 
means by preferably contacting it with an etchant capable of removing the 
metal. Thus, e.g., one may contact the structure with an aqueous solution 
of potassium persulfate which removes the relatively thin layer of 
electroless metal (such as copper) but leaves the remainder of the 
structure relatively unaffected. Alternatively, or additionally, one may 
use conventional metal etchants well known to those skilled in the art. 
By way of illustration and not limitation, one may use one or more of the 
metal etchants disclosed in U.S. Pat. Nos. 5,064,500, 5,053,105, 
5,034,093, 5,030,323, 5,001,085, 4,996,133, 4,902,607, 4,849,067, 
4,747,907, 4,345,969, 3,520,746, and the like. The disclosure of each of 
these United States patents is hereby incorporated by reference into this 
specification. 
The structure produced after the electroless metal removal step is 
illustrated in FIG. 15. Note that, comparing this structure with FIG. 7, 
an additional layer of sintered dielectric and metal has been added to the 
structure of FIG. 7. As will also be apparent to those skilled in the art, 
this process may be repeated indefinitely to add additional patterned 
layers of dielectric and metal. Alternatively, or additionally, the 
structure may be passed via line 71 to machiner 73, wherein desired 
machining operations may be performed. Thus, for example, end portions 220 
and 222 may be cut at lines 224 and 226 as shown in FIG. 16. 
The following example is presented to illustrate the claimed invention but 
is not to be deemed limitative thereof. Unless otherwise specified, all 
parts are by weight, and all temperatures are in degrees centigrade. 
EXAMPLE 1 
In substantial accordance with the procedure of U.S. Pat. No. 5,058,799, a 
metallized substrate was produced on a 4.5".times.6.5" white alumina blank 
which was 0.025 inches thick and contained patterned copper on each of its 
top and bottom surfaces which was 0.002 inches thick. The copper pattern 
used on the top surface of the substrate is illustrated in FIG. 17. 
The metallized alumina substrate was heat treated in a conveyor furnace, 
model number 14CF-154S, which was manufactured by the Watkins-Johnson 
Company of Scotts Valley, Calif. 
In the first stage of the heat treatment, while the substrate was conveyed 
through the furnace, it was contacted with nitrogen which flowing at a 
rate of 5 cubic feet per minute; during this stage, less than 10 parts per 
million of oxygen were detected in the furnace environment. In this first 
stage, the substrate was heated from ambient to a temperature of 900 
degrees centigrade over a period of 45 minutes. Thereafter, the substrate 
was maintained at the 900 degrees centigrade temperature for ten minutes. 
Thereafter the substrate was cooled to ambient over a period of 30 
minutes. 
The cooled substrate was then run through the same conveyor furnace. It was 
heated from ambient to a temperature of 900 degrees centigrade over a 
period of 45 minutes while being contacted with nitrogen flowing at a rate 
of 5 cubic feet per minute; during this time, the nitrogen contained less 
than ten parts per million of oxygen. 
Once the 900 degree centigrade temperature was reached, the atmosphere was 
changed to a mixture of nitrogen at 200 parts per million of oxygen. The 
substrate was subjected to the 900 degree centigrade temperature for ten 
minutes while being contacted with the flowing gas mixture at a rate of 5 
cubic feet per minute. 
Thereafter, the atmosphere was changed to nitrogen containing less than 10 
parts per million of oxygen and flowing at 5 cubic feet per minute. The 
substrate was cooled from the 900 degree centigrade temperature to ambient 
over a period of 30 minutes. 
A dielectric pattern was screen printed on top of the top surface of 
metallized substrate; the pattern used is depicted in FIG. 18. 
The dielectric ink used was prepared from "Type 4906 dielectric 
composition," which is sold by the Electro-Sciences Laboratories, Inc. of 
416 East Church Road, King of Prussia, Pa. 50 grams of this material were 
diluted with 4 drops of "Type 401 Thinner," which is also sold by such 
Electro-Sciences Laboratories Company. 
3.0 grams of the diluted dielectric ink were used to screen print the 
substrate. The screen printer used was a model CP-885 Screen Printer, 
which is sold by the Presco Division of Affiliated Manufacturers, Inc., 
U.S. Route 22, P.O. Box 5049, North Branch, N.J. 
The substrate to be printed was disposed under a 12".times.12" frame with a 
200 mesh metal stainless steel screen. The dielectric was manually forced 
through the screen pattern with a trailing edge squeegee applied at an 
angle of 20 degrees. Prior to each pass, the screen was covered with 
dielectric in a "flood stroke". One pass in each direction was made with 
the squeegee. 
The substrate was then allowed to stand while in a horizontal position in 
air for 10 minutes in a light-free environment. 
Thereafter the substrate was placed on the bottom heated plate, at a 
temperature of 250 degrees Fahrenheit, which was part of a Dake 
Corporation model 44183 press and maintained on said plate for 20 minutes. 
Thereafter it was removed from the heated plate and allowed to cool. 
The cooled substrate was then returned to the Screen Printer, and an 
intermediate layer of dielectric material was applied to it in the manner 
described above. The intermediate dielectric material, however, was a 
50/50 mixture of Ferro 10-008 "nitrogen fireable dielectric paste" 
(manufactured by the Ferro Corporation of 27 Castillian Drive, Santa 
Barbara, Calif.) and of duPont's Q-Plus QP445 dielectric paste 
(manufactured by the E.I. dupont deNemours and Company of Wilmington, 
Del.). After the intermediate dielectric material was applied in the 
aforementioned matter, it was allowed to stand in a dark atmosphere for 
ten minutes and thereafter dried on the Dake hot plate. 
Thereafter, a third layer of dielectric material was applied and dried in 
exactly the same manner as the first layer, using precisely the same 
composition. 
The dried substrate was then placed into another Watkins-Johnson conveyor 
furnace and, while in air, raised from ambient temperature to a 
temperature of 500 degrees centigrade over a period of 60 minutes, 
maintained at 500 degrees centigrade for 30 minutes, and then cooled to 
ambient over a period of 15 minutes. 
The substrate was then charged to the first Watkins-Johnson conveyor 
furnace and, while being contacted with nitrogen (and less than 10 parts 
per million of oxygen) flowing at a rate of 5 cubic feet per minutes, 
raised from ambient to 900 degrees centigrade over a period of 45 minutes, 
maintained at a temperature of 900 degrees centigrade for 10 minutes, and 
cooled to ambient over a period of 30 minutes. 
The sintered substrate was then treated to remove sintered dielectric from 
the substrate. About 100 tiny (0.007 inch diameter) through holes were 
drilled by a laser through the dielectric to expose the layer of copper 
underneath such dielectric. These through holes were drilled in those 
areas of the structure where connection was to be made to the copper 
pattern. 
The substrate was then rinsed with hot water for five minutes. Thereafter 
it was dipped into methanol for two minutes, and thereafter into acetone 
for 1 minute. 
The substrate was then allowed to air dry for 5 minutes. Thereafter, it was 
dipped into a 50/50 mixture (by volume) of 36.5 volume percent 
hydrochloric acid and water; and it was allowed to stand in this solution 
for 3.0 minutes. 
The substrate was then removed from the solution of hydrochloric acid and 
rinsed with water. Thereafter, the substrate was blown dry with air over a 
period of 30 seconds. 
The dried substrate was then dipped into a solution of "ALCONOX" (a 
detergent sold by Alconox, Inc. of New York, N.Y.) for two minutes. 
Thereafter, the substrate was rinsed with water. 
The substrate was then dipped into an 85 percent solution of phosphoric 
acid (sold by Chemical Distributors, Inc. of Buffalo, N.Y.) for thirty 
seconds. Thereafter, the substrate was rinsed with water. 
38 pounds of ammonium bifluoride flake (sold by the Chemtech Products 
Company of 3500 Missouri Avenue, Alorton, Ill.) were mixed with 5,160 
milliliters of 48 percent fluoroboric acid (sold by the General Chemical 
Company). The substrate was dipped into this mixture for 30 seconds and, 
thereafter, rinsed with water. 
The substrate was dipped into a 5 volume percent solution of sodium 
hydroxide for three minutes and thereafter rinsed in water. 
A mixture of 1,376 milliliters of "Neoganth B" (a liquid comprised of 
sodium hydrogen sulfate solution and sold by the Atotech Company of Pa.), 
35 milliliters of 98 percent sulfuric acid, and 24 gallons of water was 
prepared. A portion of this mixture was disposed in a small container, and 
the substrate was dipped into this mixture for 12 minutes. 
Thereafter, the substrate was dipped into solution of "Neoganth 834," a 
palladium-ion containing solution sold by such Atotech Company for four 
minutes. The substrate was then rinsed twice in water. 
A solution of 310 grams of boric acid powder, 24 gallons of water, and 275 
milliliters of "AA reduction solution" (sold by such Atotech Company), and 
24 gallons of water, was prepared. A portion of this solution was 
transferred to a beaker, and the substrate was dipped into this for 1 
minute 
A solution of 138 grams of boric acid, 28 grams of said "AA reduction 
solution"), and 24 gallons of water was prepared. A portion of this 
solution was transferred to a beaker, and the substrate was dipped into it 
for 1 minute. 
An "electroless plating solution" for depositing copper was prepared by 
mixing 2,520 milliliters of "NOVIIGANTH HC Makeup Solution" (sold by the 
Chemcut Company of 45 South Street, Hopkinton, Mass.), 36 milliliters of 
"NOVINGANTH HC Stabilizer" (sold by such Chemcut Company), 900 milliliters 
of "rayon grade" liquid caustic soda (sold by the Chemical Distribution, 
Inc. company of Buffalo, N.Y.), and 1,350 milliliters of "Reduction 
Solution Copper" (a formaldehyde preparation sold by the Atotech company 
of Pennsylvania. This mixture was then mixed with 50 gallons of water to 
make up the electroless bath. 
800 milliliters of this bath were transferred to a large beaker and heated 
to a temperature of about 80 degrees centigrade. Thereafter, the substrate 
was dipped into this bath and maintained there for one hour. 
The substrate was then removed from this bath, rinsed with water, and then 
dipped into a citric acid solution which was made from a mixture of 380 
grams of citric acid, 690 milliliters of 98% sulfuric acid, and 24 gallons 
of water. A portion of this solution were transferred to a large beaker, 
and the substrate was dipped into it and maintained therein for four 
minutes. 
Thereafter, a film of photosensitive resist material was applied to the top 
and bottom surfaces of the substrate. A sheet of "DYNACHEM" photoresistive 
dry film (manufactured by the Thiokol/Dyachem Corporation of Tustin, 
Calif.) was applied by means of a "MODEL 300 LAMINATOR" manufactured by 
such Thiokol/Dynachem Corporation to such top and bottom surfaces. 
Thereafter, a mask with the pattern depicted in FIG. 19 was aligned over 
the top surface of the substrate and the photosensitive film. The masked 
structure was then exposed to ultraviolet radiation in a model 39 
ultraviolet exposure device manufactured by the Hybrid Technology 
Corporation of Campbell, Calif. 
Thereafter, the unmasked bottom surface of the substrate was exposed to 
ultraviolet radiation. 
The carrier film was then manually removed from the photoresistive 
material. Thereafter, the exposed substrate was exposed to potassium 
carbonate developer. One part, by volume, of "DEVCONC 11-A" (which is sold 
by the RBP Chemical Corporation) was mixed with 33 parts of water, and 
this developer was used in a "CHEMCUT SYSTEM 547" apparatus run at a speed 
of 2 feet per minute, at temperature of 85 degrees Fahrenheit, and a top 
and bottom pressure of 15 pounds per square inch to spray both sides of 
the substrate and wash out the unexposed photoresistive material in the 
pattern. 
The developed substrate was then rinsed in water and dried. 
A cleaning solution was made up in a rectangular tank (which was 
12".times.36".times.34") containing 5 gallons of "DYNACHEM CLEANER LAC-81" 
(sold by Morton Electronics Materials, 2631 Michelle Drive, Tustin, 
Calif.) and sufficient deionized water to fill such tank. This solution 
was heated to a temperature of 120 degrees Fahrenheit, and the substrate 
was dipped into this solution for 4 minutes. 
The substrate was then dipped into a tank containing hot water at a 
temperature of 85 degrees Fahrenheit and kept there for four minutes. 
Thereafter, the substrate was dipped into a tank of hot running water at 
85 degrees Fahrenheit and maintained there for 5 minutes. 
5 gallons of 98% sulfuric acid were mixed with a sufficient amount of 
deionized water to fill a rectangular tank which was 
12".times.36".times.34". The substrate was then momentarily dipped into 
this solution. 
An electroplating bath was prepared by mixing deionized water, 10 volume 
percent of 98 percent sulfuric acid (obtained from Chemical Distributors 
Inc.), and 10 volume percent of a solution of reagent grade copper 
sulfate, which was made by mixing 2.2 pounds of copper sulfate (obtained 
from Chemical Distributors Inc.) with a gallon of water. 
The substrate was electroplated using the aforementioned bath in an 
electroplating apparatus which moved the substrate back and forth while in 
the bath, bubbled air through the bath, and delivered 0.54 volts and an 
amperage of 10 amperes per square foot of the area of to be plated on the 
substrate. The substrate was plated for one hour, and a layer of copper 
approximately 0.001 inches thick was deposited. 
The substrate was then removed from the bath, rinsed in deionized water, 
and blow dried. Thereafter it was heated to a temperature of 150 degrees 
Fahrenheit in air and maintained under these conditions for one hour. 
The substrate was then dipped into a solution of photoresistive stripping 
solution. One gallon of "DYNACHEM ALKASTRIP SQ-1" was charged into a 
rectangular tank (12".times.36".times.21") with sufficient water to fill 
the tank, and the solution was heated to a temperature of 135 degrees 
Fahrenheit. The substrate was maintained in this hot solution for sixty 
minutes and thereafter removed, rinsed with water, and dried. 
An electroless copper removal solution was then prepared by mixing 55 
pounds of sodium persulfate, 1,750 milliliters of 85 percent phosphoric 
acid, and 35 gallons of water. This solution was heated to a temperature 
of 118 degrees Fahrenheit. The substrate was exposed to this solution in 
the aforementioned CHEMCUT SYSTEM 547 at a pressure of 15 pounds per 
square inch and a rate of 2 feet per minute. 
The substrate was then machined so that areas 250 (see FIG. 20) were cut 
through by a laser machining device. 
A ferrite pot core, manufactured as model number 2123 by the TDK 
Corporation of Japan, was pressed through openings 250. The structure thus 
produced had the appearance illustrated in FIG. 21. 
The device depicted in FIG. 21 contains several transformers and several 
inductors. Referring to FIG. 21, one lead may be attached to coil 254, 
another lead may be attached to coil 256, and these coils maybe used as 
the primary and the secondary of a transformer (or vice versa). The 
ferrite core 260 improves the performance of the planar transformer. 
Another portion of the substrate may be used as a planar inductor, with 
lead 262 and lead 264 being connected to planar inductor 266. 
It is to be understood that the aforementioned description is illustrative 
only and that changes can be made in the apparatus, in the ingredients and 
their proportions, and in the sequence of combinations and process steps, 
as well as in other aspects of the invention discussed herein, without 
departing from the scope of the invention as defined in the following 
claims. 
The Multichip Module of this Invention 
Thus, by way of further illustration, the procedure of Example 1 may be 
substantially repeated to produce the multichip module shown in FIG. 22. 
As will be appreciated by those skilled in the art, the multichip module 
depicted in FIG. 22 is only one of many such modules which may incorporate 
applicant's novel structure. Other such module designs which may be 
modified to incorporate applicants' structure include, e.g., the multichip 
modules described in U.S. Pat. Nos. 5,104,324, 5,091,769, 5,075,765, 
5,072,874, 5,061,988, 5,034,568, 4,964,737, 4,890,156, 4,836,434, 
4,698,662, 4,446,477, 4,103,318, and the like. The disclosure of each of 
these United States patents is hereby incorporated by reference into this 
specification. 
Referring again to FIG. 22, and in the preferred embodiment illustrated 
therein, the substrate 160 is alumina with a thickness of 0.040 inches, 
vias 262 and 264 have been drilled in the substrate to provide connection 
for pins 266 and 268 brazed with solder 270 to copper 134, the first layer 
of dielectric material 168 is a glass-ceramic composition in which blind 
vias 272, 274, and 276 have been cut by laser machining, the next layer of 
copper 189 is formed on top of the dielectric and in the blind vias, the 
second layer of dielectric material 280 is then deposited and processed as 
described in Example 1, blind vias 282, 284, and 286 are formed in this 
second layer of dielectric, a third layer of copper 290 is deposited as 
described in Example 1, and semiconductor integrated circuitry 292, 294, 
and 296 is then attached using conductive adhesive. Wire bonds are then 
made connecting the integrated circuitry to the multilayer ceramic 
substrate. The entire circuit is then enclosed with a protective cover 
298, which is shown in the Figure section attached by solder at points 300 
and 302. 
An Electromechanical Valve 
By way of further illustration, an electromechanical valve may be prepared 
in substantial accordance with the procedure of Example 1 and FIG. 23. 
As will be appreciated by those skilled in the art, the electromechanical 
valve depicted in FIG. 23 is only one of many such valves which may 
incorporate applicant's novel structure. Other such valve designs which 
may be modified to incorporate applicants' structure include, e.g., the 
electromechanical valves U.S. Pat. Nos. 5,094,264, 5,074,379, 5,027,846, 
4,986,445, 4,997,978, 4,974,636, 4,967,781, 4,945,943, 4,907,680, 
4,903,119, 4,779,582, 4,393,921, 3,800,201and the like. The disclosure of 
each of these United States patents is hereby incorporated by reference 
into this specification. 
In the preferred embodiment depicted in FIG. 23, the valve 319 is comprised 
of a hydraulic housing 320 into which hydraulic fluid (not shown) is 
introduced via ports 322 and 324. Disposed within housing 320 is magnet 
326 which cooperates in effecting the movement of assembly 328 in the 
direction of arrows 330 and 332. 
A circuit board 334 comprised of a current controlling device 336 produces 
an electromagnetic field in coils 338 and 340 which inductively couples to 
the coils 342 which are formed in accordance with the procedure of Example 
1. 
In the embodiment depicted, a layer 350 of "TEFLON" and nickel plated 
together (composite) is produced over the copper to facilitate sliding 
motion. 
When the flow channels 351 and 353 register with the channels formed 
between the copper and Teflon plated patterns, fluid is allowed to flow. 
Thus, fluid flow can be controlled by the power fed to the circuit. 
A Resistor Network 
By way of further illustration, a resistor network may be prepared in 
substantial accordance with the procedure of Example 1 and FIG. 24. 
In the preferred embodiment depicted in FIG. 24, the resistor network 360 
is comprised of a substrate 160, a first continuous layer of metal 362 
disposed on the top surface 364 of substrate 160, and a second continuous 
layer of metal 366 disposed on the bottom surface 368 of substrate 160. 
Connection between resistor 362 and resistor 366 may be made by means of, 
e.g., via 370. 
It will be apparent to those skilled in the art that many other resistor 
networks, connected in series and/or parallel and disposed on one or more 
layers of substrate 160 and/or dielectric (not shown), may also be used. 
A Stacked Transformer Assembly 
By way of further illustration, a stacked planar transformer may be 
prepared in substantial accordance with the procedure of Example 1 and 
FIG. 25. 
As will be appreciated by those skilled in the art, the stacked planar 
transformer depicted in FIG. 25 is only one of many such planar 
transformers which may incorporate applicant's novel structure. Other such 
transformer designs which may be modified to incorporate applicants' 
structure include, e.g., the transformers disclosed in U.S. Pat. Nos. 
5,084,958, 5,073,766, 5,069,308, 5,017,902, 5,010,314, 4,993,140, 
4,959,630, 4,953,286, 4,866,344, 4,862,129, and the like; the disclosure 
of each of these United States patents is hereby incorporated by reference 
into this specification. 
In the preferred embodiment depicted in FIG. 25, the planar transformer 380 
is comprised of substrates 160 and, disposed through the center of such 
substrates, a ferrite core 382. A second planar transformer 386, a third 
planar transformer 388, and a fourth planar transformer 390 are formed on 
substrates 160. 
A Refractory Metal Multilayer Substrate 
By way of further illustration, a refractory metal multilayer substrate 
assembly 400 may be prepared in substantial accordance with the procedure 
of Example 1 and FIG. 26. 
Referring to FIG. 26, assembly 400 is comprised of refractory metal 
substrate 402. These type of substrates are well known to those skilled in 
the art and are described, e.g., in U.S. Pat. Nos. 5,082,606, 5,049,164, 
4,984,940, 4,900,257, 4,866,009, 4,835,593, and the like. The disclosure 
of each of these United States patents is hereby incorporated by reference 
into this specification. 
By way of illustration, a refractory multilayer substrate circuit 402 with 
a top surface 404 and a bottom surface 406 may be purchased from Kyocera 
America, Inc., 8611 Balboa Avenue, San Diego, Calif. 92123. 
Referring again to FIG. 26, the refractory metal 406 in substrate 402 
generally extends to said top surface 404 and said bottom surface 406. 
Thereafter, by the use of applicants' process, dielectric material 408 is 
applied to substrate 402, and conductive metal 410 (such as copper) is 
built up from substrate 402. 
A Stacked Capacitor Configuration 
By way of further illustration, one may produce a capacitor in substantial 
accordance with the procedure of Example 1 and FIG. 27. Referring to FIG. 
27, a first layer of conductive metal is separated by a high K dielectric 
material 422 (with a dielectric constant from about 500 to about 3,000) 
from a second layer of conductive metal 424. 
Rotor for a Miniature Electric Motor 
By way of further illustration, and referring to FIG. 28, a rotor 440 is 
comprised of a rotatable shaft 442 and, connected thereto, a rotor 444. 
Disposed on surface 446 of rotor 444 (and also on the opposing surface, 
not shown) is a multiplicity of metal coils 448 which, optionally, may 
contain a ferrite core. Electromagnetic fields may be selectively created 
in metal coils 448 which, through conventional means, can be used to cause 
rotor 444 to rotate. 
A Metallized Graphite Substrate 
By way of yet further illustration, a metallized graphite substrate can be 
made in substantial accordance with Example 1 and FIG. 29. 
Referring to FIG. 29, graphite substrate 161 is bonded to conductive metal 
189 (such as copper), intermediate dielectric layer 168, and top layer 
462. Top layer 462 may be porcelainized copper, and electrical components 
464, 466, and 468 can be built on top of porcelainized layers 467. 
An Electrostatic Planar Motor 
FIG. 30A is a top view of an electrostatic motor 500. Referring to FIG. 
30A, it will be seen that motor 500 is comprised of a rotor 502 rotatably 
mounted on a shaft 504. Disposed beneath rotor 502 is another rotor (shown 
by dotted line outline 506) which is also mounted on shaft 504. It will be 
apparent to those skilled in the art that a multiplicity of such rotors 
can be mounted on one or more shafts. 
In the preferred embodiment illustrated, each of rotors 502 and 506 is a 
substantially planar structure comprised of a dielectric material onto 
which has been deposited conductive metal field-producing elements 508. In 
the preferred embodiment illustrated in FIG. 30A, elements 508 are 
preferably solid bars of copper. In another embodiment, not shown, 
elements 508 may be in the shape of a coil. 
Each of elements 508 is preferably connected to a source of electrical 
power and switching means so that, when power flows through any one or 
more of such elements, an electrostatic field is created in it. Depending 
upon the intensity and polarity of the field created, elements 508 in 
rotor 502 will either be attracted to or repelled by the elements 508 in 
rotor 506. Thus, by appropriate switching of electrical currents to the 
appropriate elements 508 in adjacent rotors 502 and 506, such rotors may 
be caused to rotate. 
Additionally, or alternatively, one may create electromagnetic fields in 
elements 502 and 506 by conventional means. 
It will be apparent to those skilled in the art that each of rotors 502 and 
506 may be multilayer structures made by the process of this invention. In 
this embodiment, one advantage is the superior electrical conductivity 
obtainable with such structures and the microminiaturiziation of such 
structures. When copper or its alloys are used, a conductivity of near 
theoretical bulk resistivity is achieved. 
FIG. 30B is a sectional view taken through lined 30B--30B. 
As will be apparent to those skilled in the art, the motor of FIGS. 30A and 
30B may be used in magnetic disk drives, in optical disk drives, a linear 
induction motor, and the like. As will also be apparent to those skilled 
in the art, applicants' process may be used to make the field-producing 
elements used in other electrostatic motors such as in, e.g., the 
electrostatic motors disclosed in U.S. Pat. Nos. 5,262,695, 5,237,234, 
5,235,225, 5,013,954, 4,754,185, 4,546,292, 4,225,801, 3,951,000, 
3,629,624, 3,535,941, and the like. The disclosure of each of these United 
States patents is hereby incorporated by reference into this 
specification. 
FIG. 31 is a sectional view of a commutator 520 which, in the preferred 
embodiment illustrated, is comprised of a brush in contact with element 
508. For the sake of simplicity, in FIG. 31, only one brush 522 is shown 
in contact with one element 508. As will be apparent to those skilled in 
the art, a multiplicity of brushes 522 may be used. Alternatively, or 
additionally, commutator 520 may move in relation to brush 522, such as in 
the direction of arrow 524, so that brush 522 sequentially contacts 
adjacent element(s) 508. 
Because of the high electrical conductivity of applicants' multilayer 
commutator device, and because the brush 522 contacts ceramic portions 526 
of commutator 520, increased reliability and service life are obtained for 
this device. Similar results are obtained with other commutator designs 
which utilize a ceramic substrate and metal conductive elements 508 such 
as, e.g., the commutator disclosed in U.S. Pat. No. 4,845,395, the entire 
disclosure of which is hereby incorporated by reference into this 
specification. 
Process for Preparing a High-Density Co-Fired Structure 
In the process illustrated in FIGS. 32 to 37, a high density co-fired 
structure is produced. 
In the first step of this process, illustrated in FIG. 32, a pattern of 
conductive metal elements 560 is formed on a carrier 562 by conventional 
means. 
Carrier 562 may be a plastic carrier, a stainless steel carrier, a copper 
carrier, and the like. It is preferred that carrier 562 be reusable. In 
one embodiment, carrier 562 is a stainless steel device from which the 
deposited structure may be removed. 
In one embodiment, onto carrier 562 is deposited a layer of conductive 
metal 564. When the carrier 562 is electrically conductive, then the 
deposition of layer 564 may be omitted. Thus, e.g., when carrier 562 is 
stainless steel, layer 564 need not be used. 
When layer 564 is used, it may be deposited by conventional means such as, 
e. g., electroless deposition. 
Elements 560 may be deposited onto layer 564 or layer 562 by conventional 
means such as, e.g. electroforming into selected areas defined by, e.g., 
photoresistive material. 
FIG. 33 is a structure similar to that of FIG. 32 which, after its 
production, is disposed on the other side of ceramic green body 566 (see 
FIG. 34). Note that, in this embodiment, one of the elements 560 is 
comprised of a projection 568 which, after it is pressed into the green 
body 566, communicates with the opposing element 560 to form a continuous 
electrical path from the top the bottom of the structure. 
Green body 566, illustrated in FIG. 34, may be consist of or be comprised 
of any ceramic material (or precursor material which forms ceramic upon 
firing) such as, e.g., alumina, cordierite, and the like. 
In the embodiment illustrated in FIG. 35, the respective conductive 
structures have been pressed in the directions of arrows 570 and 572 into 
green body 566. 
It is preferred to remove carrier 562 prior to firing the structure. 
Because of a difference in controlled adhesion, this can be accomplished 
by the application of a lifting force (not shown). 
The composite body is then preferably fired to effect sintering. 
Thereafter, as illustrated in FIG. 32E, layers 564 may be removed by 
etching. 
FIG. 37 shows several stacked green structures produced from substrates in 
which the carrier 562 is stainless steel and no layer 564 is produced. As 
will be apparent to those skilled in the art, these green structures can 
be stacked one on the other and cofired. 
It is to be understood that the aforementioned description is illustrative 
only and that changes can be made in the apparatus, in the ingredients and 
their proportions, and in the sequence of combinations and process steps, 
as well as in other aspects of the invention discussed herein, without 
departing from the scope of the invention as defined in the following 
claims.