Techniques and materials have recently been developed to obtain high dielectric films /K of 300 to 800/. High dielectric barium titanate particles are mixed in a barium titanate glass

Ulrich, D. R.

English

NASA Technical Reports Server

December 1968	 Brief 68-10542 
NASA TECH BRIEF	
A JAL 
 a 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
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from the Clearinghouse for Federal Scientific and Technical Informatiow, Springfield, Virginia 22151. 
High Dielectric Thick Films for Screened Circuit Capacitors 
I	 Schematic	 I 
Transformation 
To Area Layout 
Photoreduction
	
Conductive Paste 
 
To Glass Masks	 MixSet Viscosity 
Screen Patterns
T H	
Prin
ignment 
ting 
	
Alignment	 Al Settings
	
Photodevelop	 Deposition 
	
Screen Assembly	 Substrate 
	
Mesh & Frame	 Select 
	
Impregnate	 Clean 
In the past, screened hybrid microcircuits have used 
low dielectric thick films for capacitors. These consist 
of ceramic dielectric particles mechanically suspended 
in a lead monosilicate glass matrix. Because of the 
small volume of high dielectric particles (35% by 
weight) which can be packed into the low dielectric 
glass, the dielectric constants of such thick films are 
less than 100. The mechanical suspension results in 
low-density structures featuring high-dissipation 
factors. 
Techniques and materials have recently been de-
veloped to obtain high dielectric films (K of 300 to 
800). For these new materials, high dielectric barium 
titanate particles are mixed in a barium titanate glass. 
The final dielectric material thus consists of barium 
titanate particles bound by smaller grained barium 
titanate which has recrystallized out of the glass, giv-
Dielectric Paste 	 I 
Mix	 I 
Set Viscosity 
Alignment 
Printing
Recrystallize Settings 
Deposition 
ing a total barium titanate content of 90 to 95 percent. 
The films are deposited and recrystallized in place on 
alumina substrates for integration into a complete 
circuit. 
Each thick film composition consists of barium ii-
tanate glass and barium titanate microcrystals. Com-
positional ratios for the two mixtures, A and B, are 
shown in Table I, overleaf. Table 2 lists the constit-
uents of the barium titanate glass. 
Reagent grade chemicals are dry blended for 1 hour 
and ball milled in distilled water. The water is re-
moved by filtering and the material is dried under an 
infrared lamp. After calcining in air at 1000°C for I 
hour and comminuting, the composition is melted at 
1450° to 1600°C and quenched to a glass frit in dis-
tilled water. The frit is milled and sifted through a 
325-mesh screen.
(continued overleaf) 
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Table I
Composition of Dielectric Thick Films 
Component
Mixture A
	 Mixture B

(wt.%) 
Barium Titanate Glass	 20	 80 
Barium Titanate Microcrystals
	 80	 20 
Table II

Composition of Barium Titanate Glass
E 
Constituent 
BaO 
Ba F2 
Ti02 
Al203 
Ge02 
Si02 
Barium titanate is then blended with the frit and the 
total composition suspended in a binder and lubri-
cant for screening. The binder-lubricant formulation 
is 200 ml of butyl cellosolve acetate to 21.5 grams of 
Ethoxyl T-10. 
The block diagram shows the integration of the 
dielectric paste into a thick film capacitor. Bottom 
platinum electrodes are screened on alumina sub-
strates and fired at 12600C. Dielectric films with a 
surface area of 0.06 cm 2 are deposited on the elec-
trodes. A 165- or 200-mesh screen gives satisfactory 
depositions. The films are outgassed by drying in a 
vacuum and then heating at 100°C. 
The films are recrystallized according to the follow-
ing schedule: soaked at 425 1 C for 10 minutes to com-
plete burnout of the binder; heated to 1225 0 to 
1275°C in 5 to 10 minutes for recrystallization; soaked 
at temperature for 5 to 15 minutes, and cooled with 
furnace shutdown. To evaluate the capacitors, air-
dried silver is deposited as the top electrode.
Amount (wt. %)

54.7
3.2
24.0
7.9
2.0
8.2 
Notes: 
1. At room temperature and 10 kHz, the dielectric 
constants of materials A and B, when screened as 
thick films, are, respectively, 615 ± 25 and 325 ± 
10. These representca4acitance densities f 12,000 
pf/cm (77,400 pf/in') and 3850 pf/cm (24,800 
pf/in2). Their temperature coefficients are positive 
to 140°C, the dielectric Curie temperature. 
2. Documentation for the invention is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: B68-10542 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: Donald R. Ulrich 
(LA R- 10294) 
Brief 68-10542	 Category 01


High dielectric thick films for screened circuit capacitors

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