PH26732A - Dielectric composition having controlled thermal expansion - Google Patents

Description

- ——————————— — — ———— ————————

BACKGROUND OF THE INVENTION

Multilayer thick film Fipcuite are typically ™ fabricated hy Goeaan printing layers oF atterns of dielectric and ronductive materials onto a ceramic substrates and fiving at mlevated bLeaperatuee to fuse the dielectric and conductive materials to the substbrate. In most cases ib ig necessary Lo sequentially print, fire ane cool each layer before the next layer oan he applied. The firing process can involve temperatures as high as 1000" GC, which ran lead bo savers warpage of the substrate glue ina the subsequent cooling © tage. u.S. Fat. id 4,655,864 discloses a dielectric composition comprising a dispersion of finely divided ‘solids comprising: (a) 40-70% volume noncrystallizable glass, (b) 60-30% vol. of . . a mivture refractory ovides, () polymeric binder and (d) wolatile organic solvent. The glass disclosed in the ‘864 patent im oa single glass having a softening point of at least soo” ©. and a viacosity of 110° poises or less at ars”-1025° C.

The mixture of rafractory oxides consists of AlaOx as the primary refractory and a secondary refractory such as quarts, CalrOx or fused silica. 11.5. Fat No. a4, 654,090 discloses a dielectric composition comprising an admixture of finely ee ——————————————————

Co ————————————————— divided solids comprising: (a) SO0-17% wh. noncrystal Lizable glass having a deformation hemp (Tq) of mg0-625" CC. a softening point (Te) of sao”-7o0e, ant . (ToT) 19 50° 75° ©. and; = (ty) 50-20% wi. refractory whieh i substantially insoluble in the glass at ges" - 00” C.

The present invention is an improvement Over the prior art dielectric compositions in that this invention utilizes a Bland or admixture of glasses to tailor the CTE of the glass blend to match that of the suhshrate. This gives great flexibility in preparing alass blends having a wide range of CIE . values and results in significantly reduced warpage . 15 of the substrate.

SUMMARY OF THE INVENTION

} This invention relates to dielectric inl, paste and taps compositions which contain a mixture of glasses wherein (i) at least one glass has Aa copfficient of thermal expansion (CTEY helow the ‘ CTE of the substrate to which the dielectric composition is applied and (ii) at least one glass as a CTE above the OTE of said substrate. The dielectric compositions of this invention

Co ——————————————————— eer significantly Fedure or eliminate warpage of the substrate caused by the Firing process. The dielectric composition is especially useful onan alumina substrate and comprises about 25-60% hy eight of said glass mixture, about 20-69% by weight of a refractory filler and ahput 10-30% by weight of an organic binder based on the total weight of said dielectric composition. Glass (i? and glass (ii) are blended at a weight ratio of 10:90 to 90310 in such a manner that the weight average CTE of the nlended glasses is aqual to or approximately equal to the CTE of the substrate.

DETAILED DESCRIPTION

The present invention relates to dielectric compositions, snitable for casting on A ceramic substrate, comprising in combination, a) ahout 20- 65% hy weight of a refractory filler, (bh) about 10 20% by weight of an organic binder and (c) about | nm 60% hy weight of a mixtures of (i) at least one glass having Aa coefficient of thermal expansion (CTED less than the coefficient of thermal expansion of said substrate and (ii) at least one glass having A coefficient of thermal expasion 20 greater than the coefficient of thermal expansion of said substrate. The dielectric compositions of this invention are useful in an improved process for fabricating electronic circuit hoards and other electronic components, The . novel dielectric compositions result in a significantly reduced warpage of tha substrate and a more uniform firing ] of the dielectric. The glass mixture of this

S invention has a great advantage over the single glass used in prior art dielectric compositions in that the present composition can be prepared having a wide range of CTE values.

It is critical to the practice of this invention that the dielectric composition comprise about 25-60% hy weight (most preferably about 3G 47%) of a mixture of alass (i) and glass (ii). The suitable weight ratio of glass (i) to glass (ii) ranges from about 10:90 to about 90:10, preferably

PETE to TH: 25. The specific ratio of glass (i) to glass (ii) is determined such that the weight average OTE of the glass mixture ia equal to or approximately egual to the CTE of the ceramic substrate. The weight average CTE of the glass mirnture can he calculated using the following formul az , : wt. avg. CTE = [mt % glass (i) times CTE of glass (i)71 + [wt. % glass (ii) times CTE of glass (ii)?

Glass (i) preferably has a CTE of about 6.77 10" 6/2 ©. over the temperature range of 25% 050° GC.

Glass (ii) preferably has a CTE of about BLO 109 6° C, over the temperature range af 259-2509 C. a ee ————— ee ————

Preferably, the difference hetween the CTE of alass (i) and the CTE of glass tii) does not exceed D200 0% 10? — s/c.

The 1] ABBeS suitable for use in this invention can be of any composition. The glasses preferably have a softening point greater than aon" ©. The glasses preferably ate borosilicate gl AGERE. An preferred composition for aqlass (i)? comprises Dy weight aboub 22.8% Gila, 29.0% B-0x, 28.3% RaCOx and 7.9% In0 and 1.5% Copl=x. Another preferred composition for glass (i? comprises Dy weight 100 parts 851i, TH.9 parts Ca, AZ.8 parts Zn, 17.4 parts 01, 10.1 parts Ti, 7.3 partes tH, 14.0 parte Zr, hob parts Fby LH.O parts Mn, 3.7 parts Bn,

X.1 parts FP and 2.4 parts Rb. A preferred composition for glass (1d) comprises by weight about 195.0% Si0x2, 26.7% Baz, 3.0% Al 20x, SO. 2%

BaD, 2.1% Bi-203, and 2.0% TiO. another preferred , composition for glass (ii) comprises by weight about 92.73% Sila, 15.4% B03, 4.1% Alz0x, 4.3%

Na-)0, 5.4% raf, 17.3% Sri and 1.2% ZrDn.

The refractory filler useful in the practice of this invention can he any of those typically used in making dielectric compositions. Suitable fillers include alpha—-quartz, Al 0x, CaZr (=z, forsterite, mullite, cordierite, zirconia ard mixtures thereof, The preferrerl filler is AlaDx. =

Ce ——————————————————————— . The preferred amount of filler used in the dielectric composition is about TR-65% by weight, most preferably about 55%.

The dielectric compositions of this invention comprise about 10-30% hy weight of an organi « binder, preferably about 13-27%, most preferably 15-24%. Suitable organic binders include, for example poly(vinyl hutyral), poly (vinyl acetate), poly (vinyl aloohnl), cellulosic po Lvmers such as 16 mexttiy) cellulose, ethyl cellulose, hyde oy cellulase, methyl hydroxyethyl cellulose, pol ypropy lens, polyethylene, silicon polymers such as poly (mekhy) siloxane), poly (methyl pheny 1 ai lentane) , polystyrene, butadiene / styrene copolymer, polystyrena, paly (vinyl pyrollidane), ) polyamides, high molecular weight polyethers, copolymers of ethylene oxide and propylene orice, polyacrylamides, and various acrylic polymers surh as sodium polyacrylate, poly (lower alkyl acrylates), poly (lower alkyl methacrylates) and various copolymers and acrylates), poly (—lower alkyl methacrylates) and various copolymers ard mul tipolymers orf lower alkyl acrylates and methacryl ates.

The organic binder is preferably dissolved in an organic solvent which can comprise from about g0-90% by weight of the arganic binder component. guitable organic snlvents include for axample, &

ee —————————————————————————— ee ———— acetone, xylene, methanol, ethanol, isopropanol , methyl ethyl ketone, 1,1, 1-tricholoroe thane, tetrachlorosthylene, diethylens glycol monobutyl ether acetate, diethylene alycol morohbutyl mther , amyl acetate, T,R,4-triethyl : pentanediol-1,3- monoisobutyrate, toluens, terpineal methyl ene chloride and fl uneocarbons. The most preferred

Organic salvent is diethylene glycol monobhuty) ether, terpinenl or mixtures thereof.

The dielectric compositions of this invention can be prepared by mixing the glasses with the filler and ball milling. This mis Eure can subsequently be mixed with the arganic binder (which typically is dissolved in organic solvent).

The compositions of this invention can he used in the form of dielectric inks, pastes or dielectric tapes depending upon the particular processing and application. The paste compositions of this invention have a viscosity of about 100, QOO=A400, 00 centipoise and can be diluted with suitable organic sol vent as described earlier to form a flowable dielectric dispersion ink which is suitable for sCreen printing. In fabricating electrical circuit boards and ather multilayer atruohirras, the dielectric paste composition is cast on a rigid ceramic substrate and fired at 2 temperature of ahout goo ® Cc. to about 1000" CC. + or o

EE a sufficient time to volatilize or burnout all the organic material and to sinter the glasses and other inorganic materials. The preferred firing temperature for the paste compositions is about = aso” ©.

The dielectric tape composition of this invention dis a pyrolizable layer of dielectric composition cast on polymeric film or sheabs (referred to in the art as "green tape") which are applied to substrates following a process such as described in U.5. Fat. No. 4,645,550, which 1s herein incorporated by reference.

The dielectric compositions of this invention are suitable for use on Aa variaty of ceramic substrates, such as, for example alumina, aluminum nitride, silicon carbide, beryllia and the like.

The most prefered substrate is 56% by weight alumina which preferably has a CE of about 7.5 x 107° to about 7oon10 ® pet: 9. over a temperature of about 25° - soo C.

The following Examples are presented to demonstrate this invention. The examples are "intended to be illustrative and not limitative.

All parts and percentages are on a weight basis unless otherwise indicated.

Eo er LED I

Dielectric paste compositions falling within a ————————————— the scope of this invention wera prepared hy mixing glass blends with Als filler and ball milling for four hours to give a well-mixed and homogenous power. This powder was then Blended with binder.

The binder component comprised hy weight 3.8% athiyl hydroxy ethyl cellulose, 9.72% ethyl cellulose, 473% 2,2, 4-trimethyl~1,3-pentanediol monoi sobutyrate, and 44% diethylene glycol monobutyl ether acetate.

The compositions were thoroughly mixed on a F-roll mill tr Form the dielectric compositions of this invention. All af these compositions had a formulation of 43% glass, ary filler and 30% organic binder. The glass blends were a mixture of glass (i) and glass (ii) having the composition given below: am 0 22.8% Bil 15.0% 5102

DY, A% Bally 26.7% BaOx 28, 32% Ral 3.0% Al ox ' T.9% In 30.2% Bal 1.5% Coals 2.1% Bins 3.0% Tila em i

The specific glass blends used in the dielectric compositions are given in Table 1 below.

ee ———————————————

Fo Ee Ll. BE xX

Calcul ated CTE

Sample (Glazs i) (Blass ii) of glass blend

A 7H oe TLOTE wu 1070/0.

R HO 50 Ta 305 x 10_,/ Co £5 C es TE so693 x 10 27%.

Ew em rh Xr

Following the procedures of Example I above, dielectric compositions falling outside the scope of this invention were prepared {for comparative

PUrPOSES. Sample D contained 43% of the single glass (i? a= described in Example 1. Sample E contained 43% of the single glass (ii) as described in Example I. The specific glass component 15 given in Table IT below.

TT oe FL. BE TX

Glass Blend (parts by wt.) CTE* of

Sample (Glass i) (Glass ii) glass blend

D 100 0 6.77 x 107%/%.

E 0 100 CB.00 ut 1076. *CTE values are measured and reported by glass manufacturer.

Eo en ELE IITX

The dielectric compositions prepared in

Example [ and Example 11 above were screen printed on 946% alumina substrates having dimensions of ee ———————————————————————— i .. . 120.025 inches. Fach substrate was repeatedly aoreen printed, deied, and fired at a50" Cc. to give a Final dielectric thickness of 10 mils. The warpage of the substrates was then measured and rated as follow: eucessive warpage —-— greater than 15 mils/inch slight warpage -—- 2-1% mils/inch minimal warpage -—- CRmils/inah

The warpage results are presented in Table III hel ow.

Toy Fe Ll ED TIX aan Rating 4) slight warpage

EB minimal warpage c slight warpage

D (comparative) prceassive warpage

E (comparative) excessive warpage

EM er LLE EN

Following the procedures of Example 1 and

Example 11 dielectric compositions were prepared having glass contents as shown in Table IV. These dielectric compositions were avaluated for warpage as described in Example 111 and the results are presented in Table IV.

The glasses utilized in this example had the following compositions:

— ee ——_——_— (3) ams 1) (Rlass ii) 100 parts Hi 52.3% Si0n

TR. parts Ca 13.4% Bol

HP. parts In A. 1% Al 0x 17.4 parts Al 4, 3% Nao 3 10.1 parts Ti 5.4% Cal

TLR parts KE 17.3% 5r0 14.0 parts Ir 1.2% Zr Qn bob parts Fb &H.0 parts Mn

FLT parts Sn

F.1 parts PF 2.4 parts Fb 35.3 parts Fe

Tos FEL. BE x,

Glass (parts hy wt.) CTE of Warpage

Sample (Glass i) (Blass ii) 31 ass Rating r= — mar Wb 0

F 25 ro FLTRS ow 10 T/C slight warpage : py ; — mh 0 co

G 30 50 FLeT x 10 0/00 minimal warpage pe pe wr pore dy oo .

H 7 29 FLETS ox 10 7/70 slight warpage 1 100 0 TLO0 oN 1076/9 ernCcessive (comparative) warpage . oe ~ - . bo .

J 0 100 7.80 w 10 7/70 excessive (comparative) war page

EX ea LLE VW

Following the procedures of Example 1 a dielectric composition falling within the scope of 2 thie invention was prepared comprising a glass blend containing 10 parts by wh. glass (i) and FO parts by wh. al ams (11) as described in Example T.

The composition was evaluated tor warpage AS in

Frample 111 and Fhe warpans was less than 2 milas/sinch.

Bowl glared FLEE MS a dielectric composition falling within the scope of this invention was prepared by mixing a glass hlend wikh Alay Filler ang organic binder and ball milling for 24 hours to give a well dispersed and homogenous slip composition. This slip composition was then cazt onto polyester mheats (My 1 are Ftoawvaitable from Dod er.) ancl dried to give a film thickness of ahout 4 mils.

The hinder component comprised hy weight Sh.4% 195 acrylic polymer, 39.0% butyl benzyl phthalate plasticizer antl 4. bh sorbitan mleate/sil ane dispersant. The slip composition had a formulation of 39.3% glass mixture, 45.2% refractory filler and 15.5% organic binder. The glass blend was Aa £0 mivctbure of glass (i) and glass (ii) ad described in

Example I in a weight ratio of glass (i) to glass (ii) of Srl.

The dried dielectric bape prepared above was then cut, vi a-punched, and laminated to a 96% alumina substrate (O05 2 4.0 x 0,07% inches) in a hydraulic press at 500-2000 lhs./square inch and about 7a 0, for about I minctes. Nf ter removing

. the Mylar fo polyesbar shes La thre 1 ami nated substrate was fired using a standard thicl: Film furnace profile with a prema i cle e toi ome of approximately G0 ming tes and a peak temperature Of = are” e10” nL for 10 minntes. The warpage was measured as in Frample ITD and wae Temas than 70 mils inch,

We claim: 1. A dielectric composi bion, gui bable fon casting or laminating on for a ceramic substrate, comprising in combination (a) about P0650 by weight of a refractory filler, (hy abooal 1O-30% by wad ght of an organi hinder and G0) aboubk S6-40% by weight of a mixture of (iY atl Veal one ner crystalline glass having a coefficient of ther mal expansion less than the coefficient of th ermal sypansion of said subabrate and (1iY ab least on non-crystalline glass having a coefficient of thermal expansion graaster kb han the coefficient of thermal expansion of said substrate. 2. A composition of claim 1 wherein said substrate is selected from the group cons isting of atumina, aluminum nity ide, beryllia and 5111000 carbide. 32. A composition of claim » wharein said substrate is comprises 96% by we ight alumina. 4, a composition of claim FT wherein said

Claims (1)

1. —_—— EE EE —————EE EE —_— EES substrate has a coefficient of thermal Up Aansl an pr TE ED ge Lely 0 “ from about T.% sw 10 7/00. to ahout 70% x Ta Tn, i capi UY pm on over a temperature of ahooal 2% F000 0 He fr composition of claim 1 hear ei n Ede = weight ratio of said glass (i) bo said glass Of i) pangas From abouk TO:F0 bo about SOx To. ba A composition of claim 1 wherein the we i oi patio of maid alass C0 Loo smal glass (ii? ranges from aboul 250TH Lo about TER To I. A composi Lion af bain len edn wai] glass is a borosilicabe glass, £2, A composition of claim FT wherein Bail glazes (i) has a coefficient of thermal eapansi on of een LE, o abot &. TF 0 10 Ted pee C0, over a temper abors vanae i. are TY apa 0 : Ci 15 orf about pEedEmn (0, and sald glass (ii) has & rrefficient ~f Ehermal espansion of about 8.00 0 Cio pz fh per DL over a btomperaturs eange of about 29 orzo — REO (0.

   5. \ composi tion of claim 3X wherein sad od glass (i) comprises by weiaht about PR.8% Sila, DHLUEY Bala, 1.5% Coals 38.7% Ral and TL9% In. 163, A composition of claim 3 wherein said nl ass (i) comprises by weight 100 pacts S51, Foe parts Ca, 42.8 parts In, 17.4 parts Al, 10.1 parts 2 Ti, F.3 parts Ky, 14.0 parts Ir bof parts Fh, dy, 0 parts Mi, 3.7 packs Sng AL parte Toand 2.40 parla Fh

   11. fo composition of claim 3 wherain mad L5

   . AUT AO ola Car weve omeson bre meant add Gan pe TELA Fe EE a ee Phe, TAT an Ce Cer and LT " } He Syowtraeevorop bio oof oo baim 0 dine in aid v plas CAE vaya een Beg ining vine PEL SR Se CR Ea ful te wl VE Trent Cod Vite ind Tm TE vol 14 po PIE Fo Fabriede ad dae -. pele Dra ey Crit oop it, Pee Caer een vag ge cg oe Fane nt Nha pes Ede ad CY ng boing bin a pede ol any sage Cate ard Ci made) mobs aie at a Peappvor atu oe of mbiond prvi | CL 1 kien} | - Hh LEN sadn bead pers bod vd van Plier cons ao omg Pion of what te Procevinprosd Bion ode badm Lo sbeessin said compres Lion de ow paste beeing oo cimoosi te nf shit I ara ben abel 0 Sith aap hog pera, 1d, Go oeampees iE Lone of claim 1 wherein seid or conn ban bya frementy Far ble abi Vile] it ny WL cola bee ef boneal dee ob pes hor,

   Ty. Soop Bore ed Cain | hero a r Caper Fira do amelie Ei La 41 Scenmpo sd Dian ote Tei LT ale erin anid o creme EE oe Pye beer ape bel opto am pel sen io EA an, Scns doe ode bata CE ere Cd I en] ment TA be foe pet pe) mp bs . oy BAD ORIGINAL Pp

   Le.

   —— er v 2673 26732 EAR fA ocomposi ion of claim LE compe imi ly wag d ht: abrenal mE EY eof mai od ed me voor Boar es ative Ar mer fa iol ped ear Lopes boi and abel POTS vd wad ol on ganda bebe, i] lo ROBERT E.

   SENEALSKI DONALD LL.

   HASEMMAYER Inventor Inventor 18 2 LT BAD OHiGuwwe J