CA1294991C - Low melting glass composition - Google Patents

Abstract

LOW MELTING GLASS COMPOSITION

Abstract Fluid, stable glasses that are useful for low temperature sealing applications ace made by adding jointly bismuth oxide, zinc oxide, and phosphorus pentoxide to the lead oxide-vanadium oxide binary. The phosphorous pentoxide may be replaced partially or entirely with niobium pentoxide and/or tantalum pentoxide. Additives and fillers may be incorporated into the glass composition to enhance the fluidity or adhesive characteristics of the glass, alter its coefficient of linear thermal expansion or make it suitable for die attach application. Group V metal oxides, particularly niobium pentoxide, are preferred fillers for altering the coefficient of linear thermal expansion. Similarly these Group V metal oxides may also be added as particulate fillers to lead borate, lead borosilicate and zinc borate glasses. Silver metal is a preferred filler for making die attach compositions.

Description

~;~9~

LOW MELTING GLASS COMPOSITION

Description Technical Field This invention relates to novel low temperature sealing glasses. It is particularly concerned with very low melting glasses with or without added ceramic fillers capable of hermetically sealing electronic ceramic parts such as alumina and beryllia in the 300C range.

Background Art This invention addresses the problem of sealing with a glass certain types of semiconductor devices which do not tolerate a sealing cycle above about 300C such as gallium arsenide, many of the other Group III-V co~pounds (i.e., compounds composed of an element from Group III and an element of Group V of the periodic table) and hybrid circuits.

~' ~, .u~ .~a 99~

It i6 well known in the art that commercially available ~older glasses ca~able of sealing ceramic and gla~s component parts such a~ television tube~ and ~emiconductor ceramic eackage~ are p~actical in the 420 to 500C temperature range. The~e ~older gla~6es ars derived from the lead-boron oxide binary which in combination with silica and alumina p~oduces a ~ide glas~ fo~ming region.
The lead oxide-boron oxide euteetic contain~ by weight 13% bo~on oxide and 87~ lead oxide and cepresents the most fluid glas6 in that binary. It ifi the starting point from which most co~mercial ~older gla6ses are derived. The addition of certain ~peci~ic metal oxide&
in the gla~ melt such as silica, alumina, tin and L5 barium oxide renders the cesulting qla~s more complex.
more stable and more resistant to chemicals and hot water.
Lead borate gla~6e~. wi~h the addition o~
particulate low expansion ceramic ~illers to adjust t~e ove~all linear ~he~mal exeansion of ~he sealing gla~.
have been highly succe~6ful during the past two decades in fulfilling the mechanical strength and hermeticity eequirements of the semiconducto~ packaging industry.
There exists, howeve~. with lead borate and lead boro~ilicate gla~se~ a natu~al lower te~perature limitation which precludes any sealing below 400-4Z0C.
With the advent of cer~ain type6 of advanced semiconductor devices (such a~ gallium arsenide~ and related Group I~I V compound multilayer semiconductor devices (6uch a~ la~er diode~, there exists an u~gent need for a ~raz~ical ~ealing gl~s w~ich can b~
~roce6~ed at 300C or le~s and capable o meeting the more de~anding US Mili~ary S~eci~ication~ (MIL-SPECS
883).

9:1 ~ lthough variou~ atte~p~s have been made in the pa~t to develop low tem~e~ature ~ealing gla6ses e~ac~ical ~o~ ~eal~ at 300C o~ lower, these attempts have been seriously limited by the ~aucity of ~otential material selection. Speci~ically what is looked for i8 a unique ~ombination of the following physical characteristics: a metal oxide mixture in the form of a true solution with a low melting point, glas~ ~ormation (supe~cooled liquid), low viscosity in the liquid phase, and glass ~hase stability ac~ompanied with low linear thermal expansion.
One potential candidate i~ the lead-vanadium oxide bina~y which fo~ms a eutectic at a lower tem~erature than the lead-boron oxide euteetic. It tends to form a gla~s during rapid quenching, bu~
recrystallizes too raeidly on reheating to have any pLactical ap~lication.
Dumesnil et al in US 3,408,212 de6cribe the effect of adding large quantities of lead ~luoride to lead-vanadium oxide mixtures. A nar~ow glass forming cegion was found to exist in the center of the PbO-PbF2-V205 ternary diagram with improved glasfi life stability. These soft glasses are cha~acte~ized by very high linear thermal expan~ion (135 to 155 x 10 7~oC) but are not sufficiently stable in the qlass ~orm to be conside~ed a~ eractical glas~ sealants.
Malmendier and Sojka (US 3,837, 866? desc~ibe A~203 and As205 to both 2 5 2 2 5 tics to p~ev~nt early ~ecrystallization and to b~oaden the co~eositional area within which stabl~ glas6es c~n be produced. The addi~ion of arsenic o~ide ~end~, howeve~, ~o increase ~apidly the ~i~co&ity of the resulting glasse~ thus preventing the availability of a ~luid, ~table solder glass at 300C or les~.

~25~91 In US 3,650,778 Dumesnil et al describe lead-free glass composi~ions containing lOS to 60% by weight ZnO, 13~ to 60% V205, 7.5S to 13% B203 and 10~ to 25% P205.
Briti~h Patent No. 1,552,648 describes a blend of PbO-V2o5-p2o5 gla~s mixed with up to 50 zirconium ehosphate (ZrO2.P20~) powder.
Busdiecke~ (US 3,454,4083 describes the addition o ~aO and ZnO ~o lead vanadate to produce a lG high expansion, low tem~erature solder glass. He does not describe the addition of Bi2o3 which i6 a necessary and required component in the present invention. Nor does this patent mention Nb205 or Ta205, both of which are highly desirable com~onents ~5 Qf the ~ealing glass of the present invention.

Disclosure of the Invention The present invention is ba~ad on the discovery that vecy fluid stable glas6es can be prepared by the ~oint addition of (i) bismuth oxide: (ii) zinc, barium, or strontium oxide; and (iii) phosphorus, niobium, or tantalum oxide to the lead-vanadium oxide binary. These three oxide~ when added together to lead and vanadium oxides produce a broad, ~luid and stable glass forming area which makes the resultinq five component glass very practical for low temeerature sealing ap~lications.
The novel low melting glass comeosition of this invention comprises, in weight perc2nt calculated on an oxide basi~:
(a) PbO 30~ to 55~.
(b) V205 30~ to 55%, ~c) Bi2~3 0.1% to 18%, 3~

(d) P205~ Nb205. 0.1% to 10%, Ta205 o~
combinations the~eof ~e) ZnO, BaO, SrO. 0.1~ to 10%
or combinations thereof wherein the combined weight pe~cent of (c)+(d)+(e) is in the ranqe of 0.3~ and 20~, and with the proviso that ~a) may be replaced partially up to 25% by weight with cesium oxide.
This novel glas~ composition has a sealing tem~erature at about 300C, requires a short sealing time, has excellen~ thermal shock resistance and high chemical rasistance in an environment of combined high temperatu~e and elevated hu~idity (85C/85~ ~elative humidity).
Prefer~ed gla~s compositions o this invention consist essentially of in weight percent calculated on an oxide basi~:
(a) PbO 35% to 45~
(b) V205 35~ to 45%
(c) Bi2o3 3% to 8%
(d) ZnO 2% to 7%
(e) P205 0~ to 5~
(f) Nb205 0% to 5%
(g) Ta205 0~ to 8~.
wherein the combined wei~ht percen~ of (a)~f)+(g) is in the range of 0.1 to 19%.
~iYtures of the above-aesc~ibed novel glass compositions with about 1% to about 50% by weight, based on the mixture, G~ a low thermal ex~an~ion ceramic ~a~rticulate filler, pre~erably a G~oup V metal oxide, a~e another aspect of the invention.

Mixture~ of the above-de~cribed novel glass compo6ition6 or gla~ composition-filler mixtures with up to 90% by weight, based on the total mixture of silver or gold powder, are another aspect o~ the s invention.
Solder glasfies mixed with about 1% to about 50%
by weight of a Group V metal oxide filler are yet another aspect of the invention.

Mode~ of Carryinq Out_the Inve~tion Depending upon t~e ~articular ~ealing applica~ion for which the glass is in~ended, additives or ~iller~ may be combined with the fi~e basic components of the gla~s. Examples of such additives ~re copper oxide, silver oxide, and fluorine, which are typically incorporated in~o the gla66 compo~ition in amounts up to 3~ by weight, and WO3 and MoO3, which are typically incorporated into the gla~s composition in amount~ up to 5% by weight.
The addition of ~uch amounts of copper oxide to the glass composi~ion improves the adhe~ion of the glass to metal surface~ 6uch a~ gold. Silver oxide may be added to improve the 1uidity of the glass, if de~ired.
The addition of fluorine to the compo~ition incr~ases the lineac thermal expansion of the resulting gla56, thereby randering the co~posi~ion ~uitable ~or use in ~ealing high coe~ficient of ther~al expanEion metals (the~mal ex~ansion > 115 x 10 /~C~ ~uch a~ 80f t ~teels, copper, copper alloy6, aluminu~, and alu~inum alloy~. To compensate ~or increasing gla~s ins~ability due to the pre6ence o 1uorine, ~he a~ount of bismuth oxide and/o~ niobium pen oxide may be încreafied.
Particulate ceramic ~ille~ may be added to the glas~ powd~r of the invention as a mean~ of controlling 9~

the overall thermal expansio~ and contraction of the ~efiulting sealing glass mixture. Increased amounts of a low the~mal exgansion ceramic filler will correspondingly decrease ~he linear ex~ansion of the sealing glass, the decrease being practically a linear function o the gla~s/filler volu~e ratio. Such filler~
a~e commonly used to make glass suitable for sealing lower expansion ce~amics, glasses or me~als. Close matching of thermal expan~ion of the sealing glas~ to the ceramic parts ~e.g. alumina, beryllia or steatite parts) to be joined i6 c~itical to ~ain~ain ze~o stress in the seal joint. Thi~ in~ures ~trength and he~meticity under extrema conditions of thermal cycling and thermal shock. It is also known that the presence in a glass of a crystalline second ~hase i8 beneficial in strengthening a glasfi seal. The addition of a particulate filler ~ini~izes ~rack propagation throughout the gla~s.
While ceramic fillers such as ~he conventional eefractory silicates (e.g., beta-eucryptite, zieconium silicate, willemite, cordierite) and titanates (e.g., lead titanate~ used with lead solder glafises may be used, the low te~p~ature sealing glasses of ~he present invention do not wet the sucfaces of such fillers well.
It ha~ been found, however, that refractory fillers made ~rom Group ~ metal (P, As, Sb, ~, Nb, Ta) oxides are entirely compatible with the glasses sf the invention, exhibit supecior wetting relative to the conventisnal fillers, and provide excellent hermetic seal~. These 3Q new ~roup V metal fille~s are also useful ~ith solder glasse~ o~heL than tho~e of ehis invention. Table 1 belo~ list~ example~ Qf this new class of ~efracto~y fille~, together wi~h linea~ thermal expan~ion value6, whe~e known.

Table 1 ~Linear ~Linear PHOSPHATESExpan~ion NIOBATES Expansion A1203-P205 Nb205 -5 ZrO2~P205 5 A1203-Nb205 26.5 SiO2-Al2030 PbO-Nb205 13 SiO2~B203~ 2PbO-Nb20~ 26 ~1 03-P205 MgO-Nb205 50 ARSENATES ZnO~A1203-Nb205 PbO-As205 SiO2-Alz03~Nbz05 PbO-TiO2~0.1A5205 Pb-Ti2-Nb;~S 0 lS PbO-Bi~03- -15 Tio2 Nb205 ANTI~ONATE5 3PbO^MgO-~b~05 25 PbO-Sb205 PbO~TiO2~ -40 PbO-TiO2 O . lNb205 O.lSb205 TANTALATES
VANAD~TES Ta25 20 ZnO-SiO2- ZnO-Nb205-Ta205 V25 ZnO~A1203 Ta205 zno-Ta20s-v2o5 5io2DAl23-Ta2s Zn-~b2s-v2S 3PbO-4Ta205 65 zrO2-Ta2o5 V205 PbO-2Ta205 40 2~Nb205- 0 2~z05 *Val~es given ar~ x 10-7/C

As exe~ d in Tabl~ 1, the terma "~rou~ V
metal oxide~ d~notes ~om~ounds comprised of a Group V
~etal and oxygen, with or without the inclu~ion of othe~

9~
g metal6. Of this n~w class of fillers, niobium pentoxide i5 preferred (linear thermal ex~ansion approx. zero).
I~ is available commercially with very low levels of ~adioactivity talpha e~i6sion ~ 0.1 count per hr per cm ) which makes ie highly desirable for packaging ~adiation sensitive semiconductor devices such as silicon memory chips. Othe~ niobium-containing oxides such as lead titanium niobate and lead bismuth titanium niobate ace also excellent fillers.
The fillecs, whether of the con~entional type or the new G~oup ~ oxide ty~e, are typically mixed with the glass composieion in amounts in the range of L% to 50S by weight based on thQ mixture. The mixtures are prepared by introducing the glass flakes an~ ~efractory ~owder into a ball mill and milling in a conventional manner to reduce the bulk components to finely divided particle6 that are mixed unifo~mly.
The cesulting glass refractory mixtures may be applied to the work piece a8 such or they may be mixed with an organic vehicle to form a ~aste which is used to coat the wo~k ~iece which is thereafter heated to melt the qlas6 and produce the seal coating. The organic vehicles are synthetic solvents boiling prefecably in the range o~ 150C to 220C such as butyl ca~bitol, carbitol acetate or similar solvents.
A metal powder filler such as ~ilver or gold may be mixed with the glas6 ~owder of the invention in amounts up to 90~ by weight, usually 70~ to 80%, based on the mixture, for die attach application~ in semiconductor chip packaginq. The metal-glass mixture may be formed into a ~asee by focmulation wieh organic vehicles such a~ those described above for applica~ion to ehe die. A refractory filler such as those described above may be added to the metal-glass mix to control the ~2~9:~L

~tre~s in the bonding interface betwesn an el~ctronic component and its metal, gla~s, or ceramic sub~tra~e.
It has also baen found that lead oxide in the glass com~o~ition may be replaced partially up to 25~ by weight with cesium oxide. Such replacemen~ may be made to make the gla~ ~ore ~luid.
Although a erime objective in the use of the~e glasses and glass-filler mixture& of this invention is a low ~ealing gla~ temperature in ~he 300C range, it should be understood that ~here may be special a~lications requiring a higher temperature. Thus no ueper limit in temperature is inherent in the application o~ the glass ~aterials of this invention.
It will be readily under~tood by those of ~kill in the glass ~a~ing art that cupric oxide, cuprou~
oxide, litha~ge (Pb304), lead dioxide (PbO2). o~
any chemical ~recursor6 to the oxides of the compo~itions described in this ap~lication can be used to formulate the gla~ses. Thus, phosphoru6 pentoxide can also be intcoduced in the glass batch in a nonvolatile form such as lead pho~phate, bi6muth ~hosphate or zinc ~hos~hate. Similarly ~luorine can be introduced in the gla~s batch as zinc fluoride or lead fluoride.
Optionally other common glasfi additives may be added in the vi~reou~ glass ~o{~ulation in an amount lower than S% total weight. These are: Tio2, SnOz, 2' ~B203- B203, Sb203, FeO and othe~ transitional metal oxides, ceriu~ oxide and other rare earth oxide~.
The ~ealing gla&~es of the inven~lon are coated onto metal, gla~s. or c~ramic part6 at thicknesses in the range o~ about 100 to 700 microns. The~e metal.
glass, or ceramic parts are usually proauced in the ~orm 9~

of square or rectangular bodies in size~ ranging from about 6 to 25 mm ~er side and 200 to 2500 micron~ thick, flat or with a rece6s. The sealing-gla6~ pattern ~coating) over the entire 6u~face or around the edges i~
S formed by printing and glazing. The6e part~ can be sealed at low tem2erature on cerami~ electronic packages known commarcially as side-brazed package~, chip carriers, and pin grid a~ray~ as well a~ metal packages.
The following exa~les de~cribe the ~reæaration and composition o~ the sealing gla~e~ of the inven~ion. The~e examele~ are not intended to limit the inven~ion in any manner.

ExamPle 1 A bas~ gla~s wa~ pr~pared by mixing 250 gram6 of lead oxide, 250 grams vanadium pentoxide, 24 gram6 of zinc oxide, 61.5 grams of ammonium phosphate and 30 gram~ o~ bismuth trioxide. After heating the mixture in a ceramic crucible at 700C for 20 minute~ the melt was pour~d through cold 6teel rollerfi to facilitate sub6equent cru6hing. The re~ulting glas~ flakes had a composition in weight parcent a~ follow6:

PbO 43,5%
V25 43.s%
ZnO 4.2~
P2O5 3.6%
Bi O3 5.2~

Thi~ glas~ ha~ a linear thermal expan~ion t25C-200C~ =
10~ x 10 7/~C and a DTA (Di~erential The~mal Analysi~) soft~ning poi~t of 225C. Thi~ gla~ forms a chemical bond to alumina at 2aooc a~ ~ee~ under a high power micro~co~e (400~).

ExamPle 2 A base glass was erepared by mixing 250 grams of lead oxide, 250 grams o vanadium oxide, 24 grams of zinc oxide, 61.5 grams of ammoniu~ phosphate, 30 grams of bismuth oxide and 2 grams of cuprous oxide. Ater heating the mixture in a ceramic crucible at 700C for a few minutes, the melt wa~ poured through cold steel rollers to fo~m glass flakes to facilitate subsequent crushing. The ~esulting glas~ flake~ has a composition in weight pe~cent as follows:

PbO 43.3%
V2O~ 43.3%
ZnO 4.2%
P205 3.7~
Bi23 5.2%
Cu2O 0.35%

This glass has a linear the~mal expansion (25C-200C) =
102 x 10 /C and a DTA softening point of 220C.

Additional exameles o~ the sealing glasses of the invention were pre~ared following the procedure described in Exam~le6 1 and 2. These additional exam~le~ ~designated D, E~ F. G and H) are reeo~ted in Table 2 below together with compa~ison glas~
comeositions (designated A, B, and C~ that lack one or moe of the five e~sential co~ponents of the invention glass.

Tabl~ 2 (Exa~ple~ in ~eight percent) Component A B C D E F G
_________________________________________________________________ PbO 5447 47 45,5 45.~ 45,5 45,5 45,5 V25 ~6 4747 45.5 45.5 45.5 45.5 45.5 23 ~ 3 3 3 3 3 3 ZnO 3 3 3 3 3 3 3 Nb2S 2 3 U U lt S S S S S
S = stable U = un8table In Table 2, Example A represents the lowest mel~ing combination of lead oxide and vanadium oxide (binary eutectic). This mate~ial in the form of a homogeneous melt when quickly quenched fro~ 700C to room temperature fo~ms an unstable gla~s. On reheating above its 60ftening point it rapidly recry~talli~es which makes thi~ material im~acti~al as a sealing glass.
Glas8es B and C, which lack, res~ectively, bis~uth oxide and~phos~hocu6/niobium~tantalum oxide, were likewise unstable. The increasing addition of zinc, eho~phoru~
and bismuth oxides to the initial lead a~d vanadium oxide melt eenders She resulting glass increasingly more stable to the point that glasses D, ~, F, G and ~ will remain glassy and ~ery fluid for a long ~eriod of time when held at about 320C.
~lass s~ability (or glas~ iifetime) in the above table i6 deined as ~he ability of a glasfi com~o~ition to ~etain its desi~able amorphsu~ and fluid Rhase at or slightly above its sotening ~sint. In Exa~ples ~, E. F, G and H the glaas2~ ~emain fluid at 300C for a ~ini~um time o~ 10 minu~es. ~n contrast 9~

gla68 A recrystallize~ almost in~tantaneously within a few second6. It i~ ~lear that the joint addition of ZnO, Bi2o3 and P205 produce6 the minimum glass lifetime required in a ~ractical sealing gla~.
Similarly as seen from examples E, F, G and H the phosphoroug pentoxide ~ay be partially o~ ~otally ~e~laced with niobium ~entoxide or tantalum pentoxide.
Further example~ (designated I-N) o~ ~table glasses are listed in Table 3 below. It can be seen from Table 3 that stable, sot glasses eminen~ly sui~able for sealing ap~lica~ions can be made by the joint addition of bismuth oxide, zi~c oxide and eho~phoru~tniobium/tantalum pentoxide to a mixture o~
lead oxide and vanadium oxide.
Table~3 ~Examples in weight ~ercent) Component I J K L M N
--- ---_______________________________ PbO 35 40 41 35 35 40 V205~ 40 40 41 44 44 ~o Bi23 10 10 10 4 3 3 7.rl0 3 ~; r~

Nb205 3 3 3 PbF~ 10 10 8 Cu20 DTA Soft. Pt ~C3 230 235236 220 220 230 The~mal Expansion~110 115~10 140 140 136 ~ 10 7/oC

E~am~le 3 The glass flakes ~re~aled according to Example L, Table 3, were ground in a ball mill and the resulting powder scree~ed th~ough a 150 mesh screen. The fine glass powder was mixed with 20% by weight, ba&ed on the mixture, of zirconium silicate powder ana formed into a paste with 10% by weight butyl carbitol solvent. The resulting paste ~as ~creen printed on preoxidized co~per alloy parts (copper alloy containing a small amount of silicon), dried and heated to melt the sealing glas~
materi~l. Th~ thickne~s of the fused gla88 layer was of the order of 200 microns.
The glazed part~ were inverted and held in position by the pres6ure exerted by a metal clip on another copper alloy microelectronic ~ackage. Th~
structure was hea~ed at a rate of 75C pe~ minuta to a peak of 320C for 5 minutes then cooled to room temperature to produce a tight, strong ~itreous seal.
The structu~e wa~ tested in an initial leak test then subjected to a series of thermal shocks as speci~ied by the MIL-SPECS 883, Method 1014, condition C
which requires 15 cycles ~rom 150C to -65C. ~hen 50 te~ted the structu~e indicated a constant hermeticity level o~ les~ than 1 x 10 ~ cc/sec He thus demonstcating the unusually strong nature of the sealing glas~ o~ this învention.

Example 4 Gla~s L of Table 3 wa~ ground into a fine ~owder and blended with 75~ by weigh~ silvec ~etal powde~. About 10~ by weigh~ butyl carbi~ol acatate 501vent wa~ t~en added eo ~he powder mixturs to ~orm a die attac~ pa~te. A~er roll milling of the ~aste tO
produce a well dis~ersed ~uepension, a small quan~ity of ~25~ 91 the silver-gla~ ~a~te wa~ depo~ited on a ceramic ~urface. A silicon semiconductor chip was then imbedded into the ~a~e. After controlled drying the structure was 610wly hea~ed to about 300C to produce a strong S bond between the silicon chip and its substrate.

ExamPle 5 Glas~ L of Table 3 wa~ milled together with 20%
by weight niobium eentoxide powder. Twenty-five gram~
of thi~ blend wa6 then mixed with 75 grams of silver powder. When ~rocessed in the ~ame way as in Example 4 a very strong bond to a copper alloy, sapehire, or glass sub6trate wa~ pcoduced.

Exam~le 6 A glas6 similar in composition to Example 1 was prepared by replacing the zinc oxide with barium oxide.
A good ~table glass was obtained which, however, did not po~se6s the fluidity of the glas6 of Example 1. A
similar glas6 was preeared using 6trontium oxide instead o~ zinc oxide with essentially similar result~. It can be seen from these example~ that both strontium and barium oxide may ~eplace zinc oxide, but that zinc oxide cemain~ the e~eferred additive.
E_~a~L~
Othe~ ~ealing gla~ses w~thin the scope of the invantion were pre~ared and are reeorted in table 4.
The gla~xes de~ignated T, U, and V have increa~ad replacement o~ lead oxide with cesiu~ oxide and, thus.
increa~ed ~luidity.

~2~

Table 4 (Example~ in weight pe~cent) ComponentO P Q R S T U V
_________________________________________________________________ PbO 43.543.5 40 40 40 35 25 15 Y205 43.543.5 40 43 q3 40 40 40 Bi23 5.2 5.2 6 4 4 6 6 6 ZnO _ _ 7 4 4 7 7 7 P205 3.6 3.6 5 3 3 ~ 5 5 ~aO ~.2 5~0 g.2 Nb205 - - 1 2 2 2 2 2 Cesiu~ oxide 5 15 25 Ag2o ~03 4 DTA Soft. Pt (C) 245242220225 225 205200 185 Linea~ the~mal expansion~ lL5 115112100100 125 135145 * 10 ~C
20 Example ~
A base glass was eeeeared by mixing:
25Q grams lead oxide 250 grams vanadiu~ oxide 2~ grams zinc oxide 30 grams bismuth trioxide ~0 grams ~antalu~ pentoxide After ~ea~ing the mixture in a ceramic crucible at 700C for ~0 minutes the re~ulting molten solution wa~ poueed through cold ~teel~ rollers so facilitate : 30 sub6equent cru6hing. The gla6~y~flake~ are : charac~erized by a linea~ ther~al expansion o~ 106 ~C ~25-200~C) and a DTA softe~ing point of ~225C. The ra~ulting glas~ flaka~ have a co~position in weight eer cent a~ eollows:

~: ~
::

12~

PbO 44.3%
V205 4~.3%
ZnO 4,3~
Bi23 5 3%
Ta205 1.8%

The glas~ flakes were ball milled with ~he addition of 32% by weight ~based on the mixture) o~
niobium pentoxide, also known az columbium pentoxide.
powder for a few hours.
The glassJniobium oxide powder blend was tested by melting a small amount of the ~owder mix on sapphire (single crystal alumina) at about 300C for a fe~
~econds. Examination of the re~ulting glass one hour after cooling ~howed no evidence of glass li~ting, nor any interference colorfi develoeed at the glass/sapphire interface indicating the sealinq glass mixture of this invention to be ~ perfect fit to the thermal expansion of alu~ina cecamic.
Cl06e examination of the surface of the melting glass/niobium oxide powder filler mixtuce indicated tne unusual and rapid wetting tendency of the niobium oxide powder by the melting glasfi. a characteri~tic not readily a~hieved with the t~aditional silicate and titanate powders thu6 greatly facilitating the preglazinq ~roces~ of ~smiconductor ce~a~ic part6.
The sealing glass mix was formed into a ~aste by adding about 10% by weight butyl carbitol sol~ent.
The re~ulting ~aste was screen printed with a masked stainless steel screen on~alumina ~arts. The parts were ~horou~hly dried and heated on a hea~ar block at about 290C to melt and bond the sealing glas~ patter~ to the ceca~ic surface. The thi~kne~s o~ th~ fu~ad gla~
pattecn was on the o~der of 200 to 250 miccons.

:

The ylazed alumina parts were inverted and held in position by th~ pres~ure exerted by a metal clip to a conventional microelectronic base. The structure was heated at a rate o 75-100C per minute to a peak of about ~30C for 5 minutes, then cooled to coom temperature to produce a tight, strong vitreous seal.
The structu~e wa ~ested with an ini~ial leak test then subjected to a series of thermal shocks as s~ecified by the ~IL-SPECS 8~3, Method ~014, condition C
which requires 15 cycles from 150C to -65C. ~hen so tested, the s~ructure showed a constant hecmeticity level o~ less than 1 x 10 8cc/sec He.

Example g The base glas~ of ~xample 8 is blended with 30%
by weigh~ PbO~Nb205 powd~ sintered with 1~ TiO2 at 1150C. This lead niobate material has a negative thermal expansion between 25C to 500C. The resulting glass/filler mixture is applied to alumina ceramic parts with similar strength and hermeticity results as in Example 8.

Example 10 The base glasa of Exam~le 8 is blended with 35 zirconium phosphate (Z~02~P205~ which has a linear theL~al ex~ansion of 5 x lO /C. The resulting qlafistfiller ~ix~ure is aeelied to alumina ceramic pa~t6 with ~imilar strength and hecmeticity results a~ in Example a.
Example 11 The ba~e glass of ~xample 8 i6 mixed with ~0%
to 50~ by weight lead ti~anate (PbO-TiO2~ which has a linear expansion equal to -60 x lO 70C sintered at ~Z~9~

600 to 800C with 10% by weight V205 (expansion , 6.3 x 10 7/oC). A~205 and Sb205.
respectively. The6e three powders were tes~ed according to Example 6. These three powders were readily wetted S by the gla~s and sub6tantially lowered the ~hermal expansion of the ~arent glass.

ExamPle LZ
Example 8 was re~eated except that 45~ by weight Ta205 powde~ (expansion ~oe~fi~ient , 20 x 10 7/oC) was added to the glass rather than Nb205. Strength and her~eticity were similar to that obtained in Example 8.

The following Examples 13-17 ~how the suitability of niobium pentoxide~ tantalum oxide and other refractory filler powders der-ived ~rom Group elements with solder glasses other than tho~e of ~he invention.
Example_13 A series of lead borate and lead borosilicate glassefi (Table 5 below) were praeared in a conventional manner by melting the batch components at 900C for 30 minutes in a platinum crucible, exce~t for glass E which required a higher temperature (1100C~. The melts were poured through s~ainless steel rollers to produc~ glass flakes which were then ball milled and screened through a 150 mesh screen.

-Zl-Table 5 ~Examples in weight percent) A B C D E F
S __ ______________________________ PbO 86 85 73 ~4 75 82 a23 ~2 13 12 12 15 ~2 SiO2 - ~ 1 1 5 3 2 3 1 _ 1 5 ZnO 2 - 4 ~ - 3 DT~ soft. Pt320 330 300 320 380 340C

The ~esulting gla~s eowders A to F we~e mixed with niobium pentoxide powder, 325 mesh, ha~ing an al~ha radiation level below 0.1 count~cm /hour. The weight percentages of gla88 and niobium oxide eowders are indicated in Table 6 below. Sealing glass rod samples were prepare~ fo~ thermal ex~ansion measurements (data also listed in Table 6). It can be readily seen that the thermal expansion of each parent glass can be modified to match alumina, or any other substrate in the 50 to 120 x 10 7/oC range with controlled addition of niobium oxide.

Table 6 (Example6 in weight percent) 1 2 3 ~ 5 6 7 _ __ ____ _______________________________ Glass ~ 70 6S
Glass B 75 Glass C 70 Glass D 80 10 Glass E 90 Glass F ao Nb205 30 Z5 30 20 10 20 35 Thermal Ex~ansion x10-7/~ 6Z 72 70 82 70 70 56 Sealing temeerature 450 430 430 420 500 430 460C

Alumina ceramic packages were 6ealed with sealing glas6 comeositions 2, 3, 5 and 6 of Table 6 and subjected to i5 cycles of thermal ~hock from 150C to -65C to 150C without losinq hecmeti~ity.

ExamPle 14 Lead borosilicate gla&~ powdec B (Table 5) wa~
blended with increasing amoun~s of niobium ~entoxide powder. The resulting glas6/filler mixtures were p-e~sed into cylinders and sintered. The resulting linear thermal expan~ions were measured wit~ the re~ult ~hae the expansion decreased nearly linearly from 110 x 10 7/oc foc the pure glas~ ~o 56 x 10 7/oC for a ~ix conlaining 46- by weiqbt niob~u~ oxide.

129~L~?9~

Ex~am~ 15 Lead borosilicate glass powder B (Table 5) was blended with 20% by weight A1203DNb205 and the complex oxide~ listed in Table 1 and sintered a~ in example 14. The linear thermal expansion was decreased as a function of the specific ~hermal expan6ion of each re~pective filler.

ExamPle ~6 A ~e~ies of zinc borate and lead-zinc boLosilicate glasse~ were prepared at 1100C. as in Example 13/ to produce glass flakes ~Table 7 below).

Table _?

G H I J K
_______________________________________________________ zno 50 45 45 35 30 PbO - - 20 15 30 SiO2 - 10 10 10 5 3 ~ ~ - 5 5 ~inear th~rmal expan6ion x10-7/C 52 50 55 4a 56 Soft. pt C 610 650 620 ~30 62~

These flake6 were finely ground in a high eurity alumina ball mill with isopropyl alcohol to produce a powder ~u~pension with a particle ~ize below 5 ~icrons.
Niobium pentoxide (20% by weig~t) was added to each glass su~pen~ion and the resulting slurry applied to the ~ucface of silicon wafer~ with a docto~ blade, dried and fired at 750-B00C in a diffusion tube furnace. The -re6ulting 25 to 50 micron thick glas~ films matched the thermal expansion of the silicon wafers. These films are extremely useful for silicon device surface pas~ivation and for dielectric isolation of high voltage silicon power device~.

ExamPle 17 Example 16 wa~ repeated using 25~ by weight tantalum pentoxide powder instead of niobium pentoxide.
Similar result~ were obtained. Tantalum pentoxide lowers the dielectric constant of the glass co~position applied on the silicon surface.

Modiication~ of the above described mode~ of carrying out the invention that are obvious to those in the field~ of glass manufactu~e, semiconductor or other electronic part packaging, and related fields are intended to be within the scope of the following claims.

Claims (46)

1. A low melting glass composition comprising in weight percent calculated on an oxide basis:
(a) PbO 30% to 55%, (b) V2O5 30% to 55%, (c) Bi2O3 0.1% to 18%, (d) P2O5. Nb2O5. 0.1% to 10%.
Ta2O5 or combinations thereof (e) ZnO, BaO, SrO, 0.1% to 10%
or combinations thereof wherein the combined weight percent of (c)+(d)+(e) is in the range of 0.3% and 20%, and with the proviso that (a) may be replaced partially ue to 25% by weight with cesium oxide.

2. The low melting glass of claim 1 wherein the composition includes at least one additive selected from the group consisting of:
up to 3% by weight Cu20 up to 5% by weight Moo3 up to 3% by weight Ag20 up to 5% by weight Wo3 up to 3% by weight F

3. A low melting glass composition comprising in weight percent calculated on an oxide basis (a) PbO 35% to 45%
(b) V2O5 35% to 45%
(c) Bi2O3 3% to 8%
(d) ZnO 2% to 7%
(e) P25 0% to 5%
(f) Nb205 0% to 5%
(g) Ta205 0% to 8%

wherein the combined weight percent of (e)+(f)+(g) is in the range of 0.1 to 10%.

4. The glass of claim 1 mixed with about 1% to about 50% by weight, based on the mixture, of a low thermal expansion ceramic particulate filler that is compatible with the glass.

5. The glass of claim 4 wherein the filler is a Group V metal oxide.

6. The glass of claim 5 wherein the filler is a niobium-containing oxide, zirconium phosphate, or tantalum oxide.

7. The glass of claim 5 wherein the filler is niobium pentoxide.

8. The glass of claim 2 mixed with about 1% to about 50% by weight, based on the mixture, of a low thermal expansion ceramic particulate filler that is compatible with the glass.

9. The glass of claim 8 wherein the filler is a Group V metal oxide.

10. The glass of claim 9 wherein the filler is a niobium-containing oxide, zirconium phosphate, or tantalum oxide.

11. The glass of claim 9 wherein the filler is niobium pentoxide.

12. The glass of claim 3 mixed with about 1% to about 50% by weight, based on the mixture, of a low thermal -26a-expansion ceramic particulate filler that is compatible with the glass.

13. The glass of claim 12 wherein the filler is a Group V metal oxide.

14. The glass of claim 13 wherein the filler is a niobium-containing oxide, zirconium phosphate, aluminum phosphate, or tantalum oxide.

15. The glass of claim 13 wherein the filler is niobium pentoxide.

16. The glass of claim 1 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

17. The glass of claim 2 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

18. The glass of claim 3 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

19. The glass of claim 4 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

20. The glass of claim 5 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

21. The glass of claim 6 mixed with up to 90%
by weight, based of the mixture, of silver or gold powder.

22. The glass of claim 7 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

23. The glass of claim 8 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

24. The glass of claim 9 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

25. The glass of claim 10 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

26. The glass of claim 11 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

27. The glass of claim 12 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

28. The glass of claim 13 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

29. The glass of claim 14 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

30. The glass of claim 15 mixed with up to 90%
by weight, based on the mixture, of silver or gold powder.

31. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 1.

32. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 2.

33. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 3.

34. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 4.

35. An article of manufacture for use in sealing an electronic part comprising a metal, glass. or ceramic body coated with a pattern of the glass composition of claim 5.

36. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 6.

37. An article of manufacture for use in sealing an electronic part comprising a metal, glass. or ceramic body coated with a pattern of the glass composition of claim 7.

38. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 8.

39. An article of manufacture for use in sealing an electronic pact comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 9.

40. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 10.

41. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 11.

42. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 12.

43. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 13.

44. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of the glass composition of claim 14.

45. An article of manufacture for use in sealing an electronic part comprising a metal, glass, or ceramic body coated with a pattern of a glass composition of claim 15.

46. A low melting glass composition consisting essentially of in weight percent calculated on an oxide basis:
(a) PbO: 30% to 55%
(b) V2O5 30% to 55%
(c) Bi2o3: 0.1% to 18%
(d) Nb2O5, Ta2O5 or combinations thereof: 0.1% to 10%
(e) ZnO, BaO, SrO, or combinations thereof. 0.1% to 10%
wherein the combined weight percent of (c)+(d)+(e) is in the range of 0.3% and 20%, and with the proviso that (a) may be replaced partially up to 25% by weight with cesium oxide.