Method for diffusion patterning

Method for patterning organic polymer layers comprising the sequential steps: PA1 A. Applying to a substrate an unpatterned layer of acidic polymer dissolved in a plasticizer, PA1 B. Applying to the unpatterned layer a second patterned layer which is a liquid solution of organic base dissolved in a volatile solvent; PA1 C. Heating the patterned layer to effect removal of the volatile solvent from the layer and diffusion of the second layer plasticizer and organic base into the underlying areas of the acidic polymer layer; and PA1 D. Washing the layers with aqueous solution to effect solubilization of the acidic polymer underlying the patterned areas and removal therefrom of the solubilized polymer and plasticizers.

FIELD OF INVENTION 
The invention is directed to a method for diffusion patterning of organic 
polymer films and to polymeric compositions which are especially suitable 
for patterning by that method. 
BACKGROUND OF INVENTION 
Thick film technology has historically been an attractive method of 
producing conductors, dielectrics and resistors that are rugged and 
reliable. The technology is well suited for economical production of short 
production runs. Its ability to be patterned in multilayer configurations 
has allowed fabrication of devices with namely high circuit density. The 
successive levels of conductors in the multilayer structure are separated 
by insulating dielectric layers and are interconnected by vias through the 
dielectric layers. 
The multilayer approach is more expensive than a single layer approach 
because it requires painstaking inspection, realignment between the 
layers, and careful processing to avoid blistering and cracking. 
The most obvious way to reduce these problems associated with multilayer 
production is to reduce line and space dimensions, thereby reducing the 
number of layers in a given structure. The problem with this approach has 
been the limited resolution capability of thick film screen printing, 
which limits the size of vias used to connect layers of circuitry to 10 to 
15 mils diameter. Likewise, conductors are limited to a narrowest line 
width and spacing of 5 to 7 mil lines and spaces in production quantities. 
Many different approaches have been tried to obtain finer pitch lines and 
smaller vias. Extremely fine screen mesh and improved emulsion backing 
have allowed line resolution of as low as four mils line/space to be 
obtained in limited production. Photoformable pastes have been developed 
that allow five mil or finer vias, and two to three mil line/space pitch. 
Thick film metallizations have also been patterned with photoresists and 
etched to produce fine line patterns and thin film conductors have been 
plated up to produce fine line patterns with high conductivity. 
All the above approaches have associated drawbacks. For example, fine mesh 
screens typically lay down thinner conductor and dielectric layers than 
are desirable. Photoformable pastes have a larger amount of organic matter 
that increases shrinkage during firing and can produce dirty burnout that 
may render fired parts useless. Conductors produced with photoformable 
pastes have an undesirable edge curl that can reduce the reliability of 
circuits fabricated with them. The processes that require etch, 
photoresists or plating are lengthy, process-sensitive and expensive. 
Furthermore, some of the processes use solvent that is difficult to 
handle. Accordingly, the need continues for a fast, environmentally safe 
method for making high resolution images in polymer films, and 
particularly in thick films, that avoids the above mentioned problems. 
SUMMARY OF INVENTION 
In a first aspect, the invention is directed to a method for making high 
resolution images on polymer-containing films comprising the sequential 
steps of: 
A. Applying to a substrate an unpatterned first layer comprising a solid 
dispersion of solid acidic organic polymer having an acid number of 20-600 
in a first plasticizer; 
B. Applying to the unpatterned first layer a patterned second layer 
comprising a liquid solution of organic base and volatile solvent; 
C. Heating the patterned second layer to effect removal of the volatile 
solvent from the layer and diffusion of the organic base into the 
underlying areas of the first layer whereby the acidic polymer in the 
underlying areas of the first layer becomes solubilized by reaction with 
the organic base; and 
D. Washing the layers with aqueous solution having a pH of 5-8.5 to remove 
the solubilized acidic polymer and plasticizers from the patterned areas 
of the layers. 
In a second aspect, the invention is directed to a thick film dielectric 
composition for use as the unpatterned first layer in a diffusion 
patterning process comprising 
A. finely divided particles of inorganic dielectric solids dispersed in 
B. a liquid organic medium comprising a solution of 
(1) film-forming acidic polymer having an acid number of 20-600, 
(2) plasticizer in which the acidic polymer is incompletely soluble; and 
(3) volatile organic solvent, the ratio of polymer to plasticizer being 
such that, when the volatile organic solvent is removed from the organic 
medium, the resulting solvent-free polymer/plasticizer dispersion is 
specularly nonreflective.

DETAILED DESCRIPTION OF THE INVENTION 
A. Definitions 
As used herein the following terms have the indicated meanings: 
The term "eluant" refers to any fluid, either liquid or gaseous, which is 
capable of dissolving or otherwise placing the underlying unpatterned 
layer into a dispersible form. As applied to the invention, the eluant is 
aqueous. 
The term "dispersible" means with respect to a film of given material that 
the material is capable of displacement or removal by physical and/or 
chemical action of a wash liquid. As applied to the invention, the wash 
liquid is aqueous. 
The term "volatile solvent" refers to liquid organic solvents which can be 
removed from the unpatterned first layer by heating to 120 C. or less at 
atmospheric pressure. 
The term "non-crystalline polymer" refers to solid organic polymers having 
no more than about 50% crystallinity. 
The term "acidic polymer" refers to solid organic polymers having an acid 
number of 20-600. 
The term "solvent free" refers to compositions from which volatile solvent 
has been removed substantially completely, i.e. any residual amount of 
solvent is less than about 1% by weight of the remaining composition. 
The terms "acrylate" and "acrylic" as used herein to describe monomers and 
polymers made therefrom include methacrylates as well as acrylates. 
All proportions are by weight unless it is otherwise indicated. 
Detailed Description of the Drawing 
The diffusion patterning process can more easily be appreciated by 
reference to the Drawing, which illustrates schematically the separate 
steps of the process as it is applied to the patterning of thick film 
dielectric paste. 
A layer of thick film dielectric paste 3a is applied by screen printing to 
alumina substrate 1. The thick film paste is comprised of finely divided 
particles of glass dispersed in an organic medium comprising a copolymer 
of an ethylenically unsaturated carboxylic acid and an acrylate having an 
acid number of 50 dissolved in dibutyl phthalate plasticizer and 
terpineol. After printing the layer 3a, the terpineol is removed by 
heating the layer to a temperature of 80 C. for a period of about 10 
minutes. 
A patterned second layer 5a is screen printed over the solvent-free thick 
film layer 3b, the second layer is a viscous liquid comprised of ethyl 
cellulose binder dissolved in triethanolamine (TEA), dibutyl phthalate and 
terpineol. 
Upon forming the patterned layer 5a, the assemblage is heated to 90 C. 
during which the terpineol is evaporated from the layer and the 
triethanolamine and dibutyl phthalate are diffused into the underlying 
areas of thick film dielectric layer 3b where the triethanolamine reacts 
with the acid groups of the polymer to render it water dispersible. 
After diffusion is completed, the patterned layer 5b consists mainly of 
ethyl cellulose and small amounts of residual triethanolamine and dibutyl 
phthalate. It is then washed with water having a pH of 6 to remove the 
remaining components of the layer and to remove the soluble materials in 
the imaged areas of thick film layer 3b. Upon completion of the washing, 
the surface of substrate 1 is exposed in the areas which underlay the 
pattern of layer 3c and a very precise negative image of the pattern 
remains on the surface of substrate 1. 
C. Substrate 
The method of the invention can be used on either inorganic substrates, 
such as Al.sub.2 O.sub.3, SiO.sub.2, silicon, AlN and the like, or organic 
substrates, such as polyimides, phenoxy resins, epoxy resins and the like, 
or composite substrates such as filled organic polymers. When the method 
of the invention is used for making thick film layers, upon completion of 
the washing step, the patterned thick film layer is fired to burn off the 
organic constituents of the layer and to effect densification or sintering 
of the finely divided solid particles. 
D. Acidic Polymer 
The binder component of the unpatterned first layer, irrespective of the 
manner in which it is applied, must be film forming, non-crystalline and 
must contain a sufficient number of free acid groups that it has an acid 
number of 2--600. So long as the polymer is acidic to that extent, it will 
become dispersible when it is exposed to the action of the diffused 
organic basic compound from the patterned layer. While the molecular 
weight or glass transition temperature (T.sub.g) of the polymer is not of 
itself critical, it is preferred that the T.sub.g be at least 50 C. and 
preferably 70 C. or higher in order that less of the polymer can be used 
in the layer. Non-crystallinity of the acidic polymer is essential in 
order to facilitate diffusion of both the plasticizer and the liquid base 
solution from the patterned layer into the thick film layer. So long as 
they meet the above three criteria, a wide variety of acidic polymers can 
be used as the binder material for the unpatterned first layer of the 
invention. 
A primary function of the unpatterned first layer is to serve as a 
dielectric for multilayer electronic circuits. When the dielectric layers 
of the multilayer are themselves organic, the polymer itself serves the 
dielectric function. But when the layer is a thick film, the polymer 
serves as binder for the dielectric solid particles until the layer is 
fired. 
The purpose of the acid moieties on the polymer molecule is to make the 
areas of the dielectric layer which underlie the pattern dispersible by 
reaction with aqueous basic solutions which are diffused into the polymer 
from the patterned layer. As mentioned hereinabove, it is necessary that 
the number of these acid groups be sufficient to make the polymer 
dispersible in water upon exposure to the basic liquid from the patterned 
layer. It has been found that an acid number of 20 is sufficient for this 
purpose. However, it is essential that the polymer not be water 
dispersible before the base reaction. Therefore, the acid number of the 
polymer should not exceed about 600. It is preferred that the acidic 
polymer have an acid number of 100-300. 
As will be discussed in more detail hereinbelow, it is essential that the 
acidic polymer be substantially soluble in the plasticizer used in the 
unpatterned layer. Nevertheless, it is preferred that the polymer not be 
soluble in all proportions. Though the method of the invention can with 
difficulty be carried out with an homogeneous polymer layer, it is 
nevertheless preferred that the polymer be present with the plasticizer as 
a two-phase system. The interface between the phases serves as a path 
which facilitates diffusion of the basic solution from the patterned layer 
and contact with the acidic polymer. 
The formation of a two-phase system between the polymer and plasticizer 
upon solvent removal can easily be observed from the gloss characteristics 
of the surface of the resultant polymer/plasticizer film. If the film is 
homogeneous, it will be specularly reflective, i.e. it will have a glossy 
appearance. On the other hand, if it is in the desired two-phase state, 
the film will be specularly non-reflective, i.e. it will have a dull, 
satin or matte surface. In order properly to observe specular reflectivity 
it is necessary to remove any plasticizer or other liquid which may have 
migrated to the surface. 
A wide variety of acid-containing polymers and copolymers can be used in 
the invention, such as acrylic polymers, styrene acrylic copolymers, vinyl 
addition polymers, styrene maleic anhydride copolymers, cellulose 
derivatives. Likewise, the exact chemical composition of the acid moiety 
of the acidic polymer is not critical. However, the polymers most 
frequently used will be copolymers of an ethylenically unsaturated acid 
such as acrylic acid, fumaric acid, vinyl sulfonic acid, itaconic acid, 
methacrylic acid, crotonic acid and the like The chemical nature of the 
polymer backbone is not of itself important so long as the polymer is (1) 
non-crystalline, (2) film-forming, (3) contains enough acidic groups so 
that it will undergo ionization upon exposure to basic solutions, and (4) 
is capable of forming a two-phase system with the plasticizer in the 
patterning layer. Within these criteria, the choice of polymers will be 
well within the skill of the known polymer art. 
Though it is not necessary to do so, it will be realized that mixtures of 
acidic and non-acidic polymers can be used as binder for the unpatterned 
layer if it is desired to obtain special properties not otherwise 
obtainable from the acidic polymer by itself. However, the acid content of 
the polymer blend must still be sufficient to render the whole layer 
dispersible upon exposure to the diffused base solution. For example, it 
may in some instances be advantageous to use a mixture of acid-containing 
polymer with another acid-containing polymer or a non-acid containing 
polymer which has limited compatibility with the first acid-containing 
polymer to control the phase structure of the polymer film that is to be 
patterned. As a result, the base solution from the patterned layer can be 
more effectively diffused into the lower layer to attack the regions that 
are rich in acid functions and disperse these regions, thereby causing the 
film structure to collapse rapidly and become readily dispersible within 
the imaged areas. 
A few of the many acidic polymers which can be used in the invention are 
listed in Table 1 below: 
TABLE 1 
______________________________________ 
Composition and Properties of Acidic Polymers 
Composition Acid No. M. Wt. 
______________________________________ 
Poly(vinyl acetate) 26 30,000 
Vinyl acetate/crotonic acid copolymer 
36 30,000 
(95/5) 
Cellulose acetate succinate 
136 30,000 
Ethyl acrylate/methyl methacrylate/ 
76-85 260,000 
acrylic acid copolymer (56/37/7) 
Vinyl acid/crotonic acid/benzophenone 
77 50,000 
copolymer 
Vinyl chloride/vinyl acetate/maleic 
26 -- 
acid copolymer (81/17/2) 
Fumaric acid, modified rosin ester 
110-130 -- 
Styrene/maleic anhydride, 
320 50,000 
partially esterified (50/50) 
Styrene/maleic anhydride, 
480 1,600 
non-esterified (50/50) 
Styrene/maleic anhydride, 
350 1,700 
non-esterified (67/33) 
Methyl methacrylate/methacrylic 
59 70,000 
acid copolymer (92/8) 
Methyl methacrylate/ethyl acrylate/ 
50 100,000 
methacrylic acid copolymer (77/15/8) 
Alkali-soluble thermoplastic resin- 
130 -- 
modified aliphatic polyester resin 
Methyl methacrylate/methacrylic 
119 -- 
acid copolymer (82/7) 
Methyl methacrylate/ethyl acrylate/ 
80 200,000 
acrylic acid copolymer (37/56/7) 
Acrylic acid/alpha methyl styrene/ 
197 2,810 
styrene copolymer 
______________________________________ 
These acid-containing polymers can be prepared by any of the conventional 
polymerization techniques known to those skilled in the art, which include 
solution polymerization, bulk polymerization, bead polymerization, 
emulsion polymerization, etc., in the presence of a free radical 
generating polymerization initiator, such as peroxy compounds. 
E. Plasticizers 
Both the unpatterned layer and the patterned layer preferably contain 
substantial amount of plasticizers in which the polymer component of the 
unpatterned layer is at least partially soluble. The primary function of 
the plasticizer in both layers is to facilitate diffusion of the base 
liquid from the patterning layer into the underlying areas of the 
unpatterned layer. While it is not absolutely necessary to have 
plasticizer in both layers, it is nevertheless preferred because it gives 
greater imaging sensitivity. The plasticizers in the two layers may be the 
same or different so long as they meet the particular criteria for the 
layers. The plasticizer in the lower unpatterned layer must (1) be capable 
of dissolving the polymer in the unpatterned layer, and (2) preferably 
capable of forming a solid two-phase system with the acidic polymer in the 
unpatterned layer. On the other hand, the plasticizer in the patterned 
layer must be a solvent for the binder polymer in the patterned layer, for 
the acidic polymer in the unpatterned layer, and for the organic base. 
The amount of plasticizer used in the layers varies widely depending upon 
the polymer which is used. As was mentioned hereinabove, it is preferred 
to maximize the amount of plasticizer in the unpatterned layer to minimize 
the amount of polymer which must be burned off when the layers are thick 
film pastes. It is preferred that the boiling points of the plasticizers 
be at least 250 C. in order that they remain in the layer as the volatile 
solvent is driven off by heating. Nevertheless, it is further preferred 
that the volatility of the plasticizers be such that they can be removed 
from the system by simple heating if it is desired to reduce the amount of 
plasticizer. In fact this technique may in some instances be preferred 
since the removal of plasticizer in this manner leaves holes in the 
unpatterned film that facilitate diffusion of plasticizer from the 
patterned layer. 
A wide range of plasticizers can be used to facilitate the penetration of 
the base into the polymer film that is to be patterned and to adjust the 
film properties. A plasticizer would be selected which shows reasonable 
compatibility with the binder and other components of the layers. With 
acrylic binders, for example, plasticizers can include dibutyl phthalate 
and other esters of aromatic acids; esters of aliphatic polyacids such as 
diisooctyl adipate, and nitrate esters; aromatic or aliphatic acid esters 
of glycols, polyoxyalkylene glycols, aliphatic polyols; alkyl and aryl 
phosphates; chlorinated paraffins; and sulfonamide types can be used. 
In general, water insoluble plasticizers are preferred for greater high 
humidity storage stability and environmental operating latitude, but are 
not required. Suitable plasticizers include: triethylene glycol, 
triethylene glycol diacetate, triethylene glycol diproprionate, 
triethylene glycol dicaprylate, triethylene glycol dimethyl ether, 
triethylene glycol bis(2-ethylhexonate), tetraethylene glycol 
diheptanoate, poly(ethylene glycol), poly(ethylene glycol) methyl ether, 
isopropyl naphthalene, diisopropyl naphthalene, poly(propylene glycol), 
glyceryl tributyrate, diethyl adipate, diethyl sebacate, dibutyl suberate, 
tributyl phosphate, tris(2-ethylhexyl) phosphate, t-butylphenyl diphenyl 
phosphate, triacetin, dioctyl phthalate, C.sub.12 H.sub.25 (OCH.sub.2 
CH.sub.2).sub.2 0OH, tris(2-butoxyethyl) phosphate and phthalates such as 
dicyclohexyl phthalate, dioctyl phthalate, diphenyl phthalate, diundecyl 
phthalate, butyl benzyl phthalate, 2-ethylhexyl benzyl phthalate. 
F. Solids Components 
It should be recognized that the method of the invention can be used to 
image organic layers alone as well as thick film and other filled layers. 
When the method is used for thick films, the solids component of the 
unpatterned layer will generally be a dielectric material, such as glass 
or a mixture of glass-forming oxides, which will densify and/or sinter 
when they are fired at, for example, 800-950 C. The chemical composition 
of the solids is not by itself important with respect to application of 
the invention so long as they are inert to the components of the organic 
medium. 
The use of solids in the patterned layer is not always necessary. 
Nevertheless, the use of finely divided solids is a very useful way of 
obtaining appropriate rheological properties of the layer for printing and 
subsequent processing in accordance with the invention. The composition of 
the solids in the patterned layer is not otherwise important since they 
are physically removed from the system by washing after completion of the 
diffusion patterning step. 
The particle size of the solids is also uncritical. However, it should 
ordinarily be in the range of 0.5-20 microns in order to be useful for 
application by screen printing. 
G. Patterned Layer Polymer 
The primary function of the binder polymer in the patterning layer is to 
adjust the rheology of the layer consistent with the way it is applied to 
the unpatterned layer. Therefore, it is not an essential component of the 
patterned layer in every instance. For example, it is not needed when the 
layer is applied by ink jet printing. However, when the patterning layer 
is applied as a thick film paste, the polymer serves both to adjust the 
rheology of the paste and as a binder for the finely divided solids until 
they are removed in the washing step. 
The nature of the binder polymer is not critical within broad limits so 
long as the rheological properties of the patterning layer are appropriate 
for the method of application. However, when the patterned layer is 
applied as a thick film paste, it is strongly preferred to use cellulosic 
polymers such as ethyl cellulose as the binder because of its water 
solubility and its very desirable thixotropic properties. 
H. Organic Base 
It is preferred that the basic component of the patterning layer be an 
organic base which is compatible with and preferably soluble in the 
plasticizer. The base can be either liquid or solid. When solid bases are 
used it is preferred that the melting points not exceed 120 C. Such 
materials include organic amines such as alkyl amines, aromatic amines 
such as pyridine, morpholine and alkanol amines such as triethanolamine. 
The amount of base in the patterning layer must be sufficient to provide a 
solubilizing effect by diffusion into the underlying first layer. 
The diffusion patterned areas need to be dispersed with an aqueous solution 
in the pH range of 5-8.5. Water is preferred. If necessary, the resulting 
aqueous solution may contain a low level of a base, preferably the same 
base used in the patterning step to help reach the critical concentration 
and make the imaged areas dispersible without deleteriously affecting the 
unimaged areas. It is preferred that the wash solution pH be at least 5 in 
order to avoid excessive neutralization of the diffused base. On the other 
hand, the pH should not be greater than 8.5 in order to avoid 
solubilization of non-imaged areas. Optionally, low levels of water 
soluble surfactants may be present in the wash solution to facilitate the 
interaction between the base and the acidic polymer film. 
I. Formulation and Application 
The method of the invention is intended primarily for use as a functional 
layer in the fabrication of electronic components. Typically the patterned 
layer which contains dispersibility-changing agent (organic base) will 
range from 1 to 30 microns thickness while the first layer can be of much 
greater thickness, from 10 to 100 microns. The thickness of the patterned 
layer is limited chiefly by the method of application, rather than by 
considerations of operability. 
By and large, the individual steps for preparation of the component layers 
for the method of the invention are similar to those which are known by 
those skilled in the art of conventional thick film pastes. 
J. Alternative Patterning Methods 
It is preferred to carry out the diffusion patterning method of the 
invention by screen printing the patterning layer. Nevertheless, that step 
can be carried out by other methods as well. Such methods include thermal 
transfer, electrophotography, pen plotters and ink jet printing. 
Thermal Transfer: The dispersibility changing agents can be formulated with 
polymeric binders and other necessary additives to make a hot melt ink 
composition as practiced by those skilled in the art. The ink composition 
containing the base is precoated on a dimensionally stable thin base, 
e.g., PET film. The ink ribbon is placed in close contact with the thick 
film substrate with the ink facing the thick film composition. Through the 
base side of the ink ribbon, a thermal head similar to those used in 
commercially available computer printers is used to imagewise affect the 
transfer of the ink composition into the thick film substrate. If the 
ribbon formulation and the heating conditions are adjusted properly, the 
heat used to generate the pattern may be adequate to affect the diffusion 
of the active ingredients into the thick film composition and change its 
dispersibility behavior simultaneously. The element is then processed as 
previously described. 
Alternatively, the patterning can be affected by an IR laser if an IR 
absorbing material such as carbon black, graphite or organic dyes which is 
very efficient in converting the IR radiation into heat is added to the 
formulation. The heat generated in this manner will induce the transfer of 
the active ingredients into the thick film substrate. 
Typically, the waxy and water-repelling type of binder materials are used 
in formulating the hot melt inks. If the process is changed slightly, 
instead of diffusing the ink into the thick film composition, the ink is 
overprinted on an aqueously developable organic compound containing 
composition. The water resistant image can be used as a mask or resist for 
the subsequent aqueous processing for a positive mode operation. 
Electrophotography: The dispersibility changing agents can be formulated 
with polymeric binders, charge directors and adjuvants to make toner 
particles which may be dispersed in a liquid carrier medium as practiced 
by those skilled in the art. The toner particles are imagewise applied to 
the thick film substrate through the various mechanisms that are familiar 
to those skilled in the art. At the fusing step, the active ingredients 
are driven into the thick film composition to affect the dispersibility 
change for a predetermined solvent system. 
Pen Plotters: The dispersibility changing agents are formulated with 
additives in a water- or solvent-based liquid vehicle. The pattern is 
generated with a pen through digital commands as in a commercially 
available plotter. The active ingredients are driven into the thick film 
composition to affect the desired solubility change. The aqueous ink 
system is the preferred mode of operation for environmental reasons. 
Ink Jet, Liquid Ink: The dispersibility changing agent is formulated with 
additives in a water- or solvent-based liquid vehicle as practiced by 
those skilled in the art. The images are generated with an ink jet 
printhead similar to those found in commercially available computer 
printers. The liquid vehicle and/or additives such as plasticizers and 
surfactants can be used to carry the active ingredients into the thick 
film composition to effect the solubility change. The use of water-based 
ink is the preferred mode of operation for environmental reasons. 
Ink Jet, Solid Ink: The dispersibility changing agents can be formulated 
with solid vehicle that melts at an elevated temperature. During printing, 
the ink droplets are ejected in its melted form according to the digital 
commands as in those commercially available computer printers to give high 
resolution images on the thick film composition. Diffusion of the active 
ingredients into the thick film composition changes the dispersibility in 
the imaged areas. 
The waxy ink composition as often used in this type of application can also 
be used as a mask or resist in the same fashion as described in the 
thermal transfer method for an aqueously developable organic compound 
containing composition in a positive mode of operation. 
The invention will be further illustrated by the following examples: 
EXAMPLES 
Example 1 
A dielectric thick film element was prepared using the following 
compositions and procedures: 
______________________________________ 
Dielectric Solids: 
Component % Wt. 
______________________________________ 
Glass A 47.36 
Glass B 31.57 
Alumina 6.55 
Zirconium Silicate 
8.76 
Cobalt Aluminate 3.00 
Titanium Oxide 2.76 
______________________________________ 
Glass A Glass B 
Composition % Wt. % Wt. 
______________________________________ 
BaO 12.56 11.78 
SrO 10.82 10.15 
CaO 6.70 -- 
ZnO 16.0 21.29 
Al.sub.2 O.sub.3 
5.50 6.90 
SiO.sub.2 46.01 47.64 
ZeO.sub.2 2.40 2.42 
______________________________________ 
Paste Composition: 
Amount 
Ingredient % Wt. 
______________________________________ 
Dielectric Solids 60.0 
Elvacite 2010 2.1 
Carboset XPD-1234 6.2 
Butyl Benzyl Phthalate 
11.2 
Tergitol TMN-6 2.1 
Terpineol 18.4 
______________________________________ 
The above paste compositions were prepared in the manner familiar to those 
skilled in formulation of thick film materials and were prepared for 
printing as follows: 
The materials were processed by printing the dielectric optionally one, two 
or three prints, with each print followed by drying 10 to 15 minutes at 80 
to 90 degrees Celsius. A two-phase system was formed upon solvent removal. 
______________________________________ 
Printing Ink: 
Amount 
Ingredient % Wt. 
______________________________________ 
Triethanolamine 30 
(Fisher Scientific Co., Pittsburg PA) 
Butyl Carbitol 10 
(Aldrich Chem. Co., Milwaukee WI) 
Deionized Water 60 
100 
______________________________________ 
The above mentioned components were mixed and stireed to give a homogeneous 
solution. The resulting solution was used as printing ink to generate 
single dot pattern on the dielectric coating using a Hewlett Packard Desk 
Jet ink jet printer (Hewlett Packard, Palo Alto, Calif.). The imaged 
element was baked at 75 C. in an oven for 5 min. It was then immersed in 
warm water at 60 C. with ultrasonic agitation for 1 min. 130 micron wide 
and 26 micron deep vias with perfectly round shape and straight walls were 
obtained. 
Example 2 
A printing ink was prepared using the following procedure: 
______________________________________ 
Printing Ink: 
Amount 
Ingredient % Wt. 
______________________________________ 
Triethanolamine 30 
(Fisher Scientific Co., Pittsburg PA) 
Merpol SH 1.0 
(E. I. du Pont Co., Wilmington DE) 
Deionized Water 69 
100 
______________________________________ 
The above mentioned components were mixed and stirred to give a homogeneous 
solution. The resulting solution was used as printing ink to generate a 
single dot pattern on the dielectric thick film described in Example 1. 
The imaged element was baked at 75 C. in an oven for 5 minutes. It was 
then immersed in warm water at 60 C. with ultrasonic agitation for 1 
minute. 130 micron wide and 24 micron deep vias with perfectly round shape 
and good edge definition were obtained. 
Example 3 
A dielectric thick coating was prepared using the following procedure: 
______________________________________ 
Amount 
Ingredient % Wt. 
______________________________________ 
Dielectric Solids (as in Example 1) 
58.25 
Elvacite 2051 1.01 
Carboset XPD-1234 9.08 
Butyl Benzyl Phthalate 
16.51 
Terpineol 15.13 
100.0 
______________________________________ 
The above mentioned paste composition was prepared and printed on the 
alumina substrate as described in Example 1. 
A printing ink was prepared using the following procedure: 
______________________________________ 
Amount 
Ingredient % Wt. 
______________________________________ 
Triethanolamine 30.0 
(Fisher Scientific Co., Pittsburg PA) 
Acetic Acid 6.7 
(EM Science, Gibbstown NJ) 
Deionized Water 63.3 
100.0 
______________________________________ 
Triethanolamine was dissolved in deionized water. Acetic acid was slowly 
added with agitation. The resulting solution having a pH of 8.5 was used 
as printing ink to generate the single dot pattern on the dielectric thick 
film using a Hewlett Packard Desk Jet printer (Hewlett Packard, Palo Alto 
Calif.). The imaged element was heated from the back side at about 200 C. 
for 3 sec on, followed by baking at 75 C. in an oven for 5 min. It was 
then immersed in warm water at 60 C. with ultrasonic agitation for 1 min. 
160 micron wide and 29 micron deep vias with very round shape and sharp 
definition were obtained. 
Example 4 
Dielectric paste and patterning paste having the following compositions 
were screen printed on the substrate described in Example 1 using 
techniques known to one skilled in the art. 
The dielectric vehicle had the following composition: 
______________________________________ 
Amount 
Ingredient % Wt. 
______________________________________ 
Poly(methyl methacrylate) 
2 
Methyl Methacrylate/Methacrylic 
18 
Acid Copolymer 
Butyl Benzyl Phthalate 
42 
Terpineol 38 
The dielectric paste had the following composition: 
Inorganic Solids 64 
Dielectric Paste Vehicle 
36 
______________________________________ 
The patterning paste vehicle had the following composition: 
______________________________________ 
Amount 
Ingredient % Wt. 
______________________________________ 
Ethyl Cellulose 4 
Triethanolamine 42 
Terpineol 27 
Butyl Benzyl Phthalate 
27 
The patterning paste had the following composition: 
0.45 Micron Alumina 
63.5 
Patterning Paste Vehicle 
38.5 
______________________________________ 
The patterning layer was then printed by using a via fill screen with 
several sizes of via openings. The patterning paste was then dried at 80 
to 100 C. for 5 to 10 min. Uniform, well defined vias with steep side 
walls were produced. Average size was 4-5 mils, dielectric film thickness 
was in excess of 30 microns. 
GLOSSARY 
Carbitol 
Trademark of Union Carbide Corp., Danbury, Conn. for diethylene glycol 
ethyl ethers. 
Carboset XPD-1234 
Trademark of B. F. Goodrich & Co., Cleveland, Ohio for acidic 
methylmethacrylate copolymers. 
Elvacite 2051 
Trademark of E. I. duPont de Nemours and Co., Wilmington, Del. for methyl 
methacrylate resins. 
Merpol SH 
Trademark of E. I. duPont de Nemours and Co., Wilmington, Del. for 
non-ionic esters of ethylene oxide. 
Santicizer S-160 
Trademark of Monsanto Chemical Co., St. Louis, Mo. for 
N-alkyl-paratoluenesulfonamide plasticizers. 
Tergitol TMN-6 
Trademark of Union Carbide Corp., Danbury, Conn. for non-ionic surfactants.