 |
 |
Read
more than 3,700 books online FREE! More than 1900 PDFs now available
for sale |
|
|
|
|
|
|
|
|
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 62
62
CER~.qIC It',TSUl AT=GN
. ~ _ %~ ~
By
J. ~0 Dead`.rick
American Lava Corpor&t~..cn
Cha Toga 9 Tents
The year :~947 reflected a confirming trend of, the cerar.iic ;.ndus-tr~y
toward the development of electrical insulating materials with comer losses at
higher frequencies. Low loss ceramic-to-~.~+~al hermetic serifs play a vital rode fin
the efficient operation of vacuum tubes at m~crow£ve~fr~qu~ncies, consequently a
great deal of at,tent~on was directed to the ~nves'~'gaticin Of sui~ab e sealir~g
materials and techniques.
Scark F~
Using Sakelite as a binder, a]..umi.na spark Slugs are automatically -mod.
by the A. CO Soa.r~ng Plug Company T;td.) The insu7.`to;~s Are stead in a 'fish
temperature furnace to vitr .ficat~ onO Assembly of the insulator and. .rneta7 parts
is accom~list.,ed with Pyrex glass pellets and a copr!;r sealing compound fused +,o-
gether under pres sure at 900°C O
Gainer patentec9.2 a spark plug insulator comprising a fired mixture con-
taining a major proportion of zirconium oxide rails mag~neslum oxide, +,h~ modal
proportion of zirconium oxide to magnesium oxide being began 2 to ~ and 1 to 20
Schaefer patented3 a vitreous alumina base cellar c ns Mating material
containing at least 121: clay and a small amount of a~kaline-earth p~nos-:nate, the
aluminum oxide content being at least 73%. Vitrification temperatures es Jot as
14000c were obtained.
Glass
._
A patent4 tics obtained on ? glass having a pointer factor less tran o.C6!~;9
a dielectric constant of at least 7, and a softening t~mr,ercture below 600°Co It
contains net more than 50% Sigh, less than about 6G; Pro, and the balance of .r.~!ore
than 5% of the alkali met=1 oxides K 0, kayos and Li2O, in the ratio 4 to 1~5
F2Oi1 Na2O and IS to 4(K2O and Na2O)51 TiO2.
Monack5 describes the manufacture of glass-konded mica And discusses the
effect of forming methods on properties of the finished ii~sul&tor. Raw materials,
mixing, preforming, dr>-ing' ~.olding and heating are discussed fit length.
A resort from Ger~nanv6 relates the theol~etic~1 and practical aspects of
bonding glasses and ceramic materials of wnequ=] thermal expansions, inch uding
guiding rifles for the manufacture of bonding g]-asses Loving various thermal ex-
pansion coefficient=.
OCR for page 63
63
c,t,eat ~ te an] Other L2~:i~h Frecue~.c.y Miat,er~ als
~ v-itril~ied ceramic 'cod~,T7 composed primarily of the magnesium orl,h.osili-
cate 2~Dlig0.Si.O¢, is oha~`acter~zed bar very 70~'? dielectric Joss and high electrical
resistance at~6le~r&ted tem?eratu.resO The cLys:.ca].. properties of this material are
l~.~.sted for compar~so:~ with st~atite and zircon porce3~.ainO It is useful for coaxial
].i~.:e spacers, vacu~m-tight me~a]-ceramic seals and other applicati.ons Were CON{
Oslo fa.ctc~r i s of prime - ~nportance.
[~.Cicre~scopic and X-rar e;
OCR for page 64
64
Navias and Greenl3 patented ceram.c comr,os~tions charactc-rized by 'or
power facts and Cow hygrosco,?~cityO These con!positic~ns consist by Height of at
leas+ 70% of ~ refractory titanium compound, the reminder being a mixture of clay
and a fluoride from the alkaline-~-arth fluorides and lead fluoride.
Thurnauer and Deaderic; 4 patented 2 ceramic dielectric com~ositicn
having a dielectric constant of 37 and a. temperature coefficient of di`~.ectr~`c
constant of substantially zero and compris;.ng about 43$ ratios, 55% Tics and
2! CaPC O The electri.c&3 Properties of La.~iC - Tick mixtures are seven.
, ~
4
Metal Ceramic Combinc.tions
}hetal-to -c cramic sea].s15 are prepared b;- the ~pclicati on of tithe nits
hydride to the ceramic and bonding to metals or other similarly prepared cera~.i~s
by brazing or silver soldering at about 1000°C. The bond thus formed is gas tight
a~d suitable for vacuum applications.
During the solar the Germans developed a similar type of metal-~-ce-ram~c
seal employing molybdenum-iron silicates es ~ base- for brazing materials such is
silver, silver alloys and copper. The German seals have been improved for high
frequency use in this country by the use of ceramics with loner electrical losses.
Complete details of the process are described) .
Mcnackl7 classifies glass-to-meta'' seals according to function, geometry,
or type of glass. Properties of sealing glasses mrort~.nt to successful joints
include thermos scous, pLysi¢aI, Electra Cal and ~ho+~o-elas-tic ch£:racteristi:cs.
Metals should hate (] ~ uniform tli~rmQl expansion, (2) stability: during seal making,
(ON good adhesion to g]3S53 (~ i0W cJectr-ical resistance of the oxide films (5)
minimum gas evolution, and (6) lor cost.
In a later publication the same au+hor:8 states that the successful
p,reparation of glass-to-metal seals depends not onl~,T upon agreement of glass ?.n~
metal thermal expansion coefficients but also upon Agreement throughout the entire
elongation curare. Seals are class) fled on Chic basis of facts on9 geometry and
type of glass. I:ata on metals alloys, and corn?os~te Wires is given. ST`o~tcornings
of theoretical considerations are discussed.
The presence of-a metal oxide film is felt to be necessary in metal-to-
g]~ss combinations. If perfectly matching thermal expansion properties arc not
possible, successful seals me.y be formed ~4 tl,o metal is thin and ductile enough
to be deformed by differential expansions .
Met~l-to-ceramic seals developed by Telefunken20 replaced glass ..s the
bonding agent by a sPeci&1 ceramic pc^.st~ composed of the followings 10~20 steatite,
1.44 zettlitz kaolin, 0.48 zirconium and 0~24 kg of potassium feldspar. Fold spar
in the mixture insures tightness, and a rigid ~roo,edure is outlined.
OCR for page 65
65
I.li scel 3 a.neous
A review of the chief c~aracteris'~ics of dielectric materials9 lee.
res~.stivi';.y `?^nd dielectric const;ant9 is presented by Hausner2~.
The same authored discusses in another paper the principles of electrical
conductivity and their a~?plica-bJon to ceramic .se~n--conductors. Studies Were made
on com::'osit.ons consisting mainly of Viol, Fe203, F'e;}O4, ZrO2 and others. The
el:-i'ec+s of ~ompos::ti.ox~s on te.m~erat;ure coeffic~,ienJ~ o' resistance were investigated.
The recl.~ct,ion. of oxides With its effect on conducting properties Was also determined.
Brunetti and Curt~s23 present a. comprehensive treatment of the "field of
pr-.rited circuits. The various methods of app~yi.rlg conducting and resisting .fi]ms
to i.nsu:Lat~ materials are fu1.ly c~.escrited.. Precautions and limitations are
disc. ussed.
A monolithic structure com;~risi.n& alternate layers of vitreous low logy
en~.~e:l: and conductive silver film its described by Bradford' Weller and McNeil
[O't' use as capacitor having electrical characteristics sim-~.~-a~~ to mica. The process
i.5 based on the laying dorsal by spra.y:~g, of layers o. enamel. a].ternati~lg with layers
c.f conc3Luct~ing s~...lver paste 6.~eposil;ed by silk Screen or squeegee r~r..nting. Upon
c:.,rv ng, tile plates are cut to the desired pat~er:Lls and fired for abc:ut 12 hours.
S=~..~7er is exposed at certain Foibles for a.~ta.clling leads. Single Un:LtS may have
ca'~ac..ties of' frown 15 to 50()0 Gruff. and. ccmbinat,ior~s of ca~aci+Jors9 resistc~re, acid
inductances may be contained. ~n a single unit if desired. The c=~aci.tors show a
small :.ncre~ase in cacac:~i,y and dissipation facLo:r vat ;h a rice in temperatures arid
t'~er-: are usable up to 1 25°O Hi Ah no change ire temperature co~f'fi cier~tO
- Borate' Breckenri~ge and Brc~rnJo`~?25 describe a machine for forming thin
ceramic die' ectric sheets for capacitors . ~ ceramic slip is Elutoma+.ical.1.~y deposited
con a sta::r~less Steel belt moving through a Writing tunnel. The dried sheets are
stri,~ped frost the belt and cut to size either before or a.f'cer firings Sheets may
be p~ocuccd Troll, .006 to .030 luck in t'-iic!~less 'loving un' form density after firing
and Story good dielectric st.rength.
OCR for page 66
66
BIBLIOGRAPHY
1. Anon., Times Rev. Ind., 1 (2) 26 (1947)
. . .
2. Gainer, Eugene, DO S. Pat. 2~427~034 (1947)
. .
3. Schaefer, C. F.' U. S. Pat. 2~419~290 (1947)
,. . . . .
4.
is.
Armistead, A. H. Jr., U. S. Pate 2,431,98O (1947)
. .
Monack, A. Jig Rapid Insulator Production with Glass-3onded Mica. Ceram. Ind.
48 (2) 59-649 Ibid (3) 76-SO' Ibid (4) 98-10O, Ibid (5) 76-77' 49 (1)
74-76 (1947)
6. Klump and Gohike, Bonding of Glasses and Ceramic Material with Different
Coefficients of Thermal Expansion. Report PB 24~960 (1946) ~
7. - Thurnauer, Hans, Forsterite' a Low Loss Ceramic Dielectric Immaterial.
Tele-Tech, 6 (2) 86-87, 130 (i947)
8. Rigterink, M. D., Microscopic and X-Ray Investigation of Some Steatite
Bodies. Jour. Am. Ceram. Soc. 30 (7) 214-218 (1947)
9. Thiess, [. E., DO S. Pat. 2,419,472 (1947)
10. Bunting, E. N., Shelton, G. R., Creamer, A. S., Properties of Bari~m-
Strontium Titanate Dielectrics. Jour. Am. Ceram. Soc. 30 (4) 105-125 (1947)
11. Rath, A., U. S. Pat. 2~4329250 (1947)
. .,
12. Gainers E.' U. S. Pat. 2,420,692 (1947)
13. Navias, Louisa Green, R. L., U. S. Pat. 2,424,111 (1947)
U. Thurnauer, Hans' Deaderick, James, U. S. Pat. 2,429,5SS (1947)
15. Bondley, R. J., Metal-Ceramic Brazed Seals. Electronics 20 (7) 97-99 (1947)
16. Williams, Neal T., [,etal-Ceramic Vacuum Seals. The Review of Scientific
Instruments 18 (6) 394-397 (1947)
17. Monack, A. it, Theory and Practice of Glass-tetal Seals. Glass Ind.
27 (at 389-94, 408- U. 42O9 (9) 446-49, 464-70, 4769 (10) 502-04, 522-28;
(11) 556-599 576-78, 582 (1946)
18. Monack, A. J ~ Glass-to-Metal Seals in Electronic Components and
Applications. Elec. dig., (39) 96-101, 162-l8O (1947)
19. Partridge, J. H., Glass-to-Metal Joints. Sheet Metal Ind. 24 (237)
119-128 (1947)
OCR for page 67
67
20. Kuh~er9 a., ~eta]-Cera~ic Seals- Stiles 2~7) i94-204 `1947)
210
22 i
. ~;
. .
8.allsn~r ~ ~ o ~.
Die] emetic (calculations. CeramO Age g 49 ~ 4) 165-166 (1947J
Iausner, 7~. ]~99 Semicond.'cting Ceramic 3ff~.teriaDs. Bow. As. Ceram. Scc.
30 <9! 29~-296 `~9,~7) -
23r~me~ti9 CledO' `,ur~i.s, Roger A.,
Ne B . S. ~,i~ cular 468 43 pp., :1947
Printed Circuit Techniques.
Bradford, 5. I., Weller, T3. I. and McNe~gh+9 a. A., Printed Vitreous }enamel
Components. Electronics 20 (12) low] 08 (1947)
Ho-a G. N.g Brecl~enridge, A, -IT. -and Bro~P~lovi, J. .~.:i.' Fabrication of Thin
(,e-ramic Sheets for Capacitors. yours An. reran. Soc. 30 (g) 237-242 (1947)
. . .
Representative terms from entire chapter:
thermal expansion
Items in cart [0]
