CA1235049A - Paste vehicle for fusible powdered metal paste - Google Patents

Abstract

IMPROVED FUSIBLE POWDERED METAL PASTE
A B S T R A C T
There is provided a nonaqueous powdered metal paste composition and a vehicle therefor, characterized by resistance to slumping upon heating to the fusion point of the metal, including the powdered metal, and a nonaqueous organic liquid material having a surface tension of from 43 to 65 or higher dynes/cm. at 20°C.

Description

~3~9 IMPROVED FUSIBLE Powdered METAL PASTE

This invention relates to a paste vehicle and a heat-fusible or sinterable metal powder. The vehicle is especially useful for making metalliferous pastes for joining by soft soldering, infiltrating, lacing metal I or for a moldmg purpose.

BACKGROUND OF IRE INVENTION AND Prior PUT

the joining, infiltrating, or coating, or the manufacturing ox many kinds of molded metal parts using a fusible metal powder-containing paste can be done efficiently, (often with automation) provided, however, that upon heating and before fusion of the metal, the metal powder containing paste exhibits controlled hot slump; in other words, the metal powder stays substantially where and as the paste was deposited on the substrate. this primary property has been difficult to obtain with conventional metal pcwder-containlng pastes. The instant vehicles and pastes provide such property.
Restriction of flow of any resulting fused metal that is a lack of general spreading), except Into intended joints or pores, or to form intended joints as in the joining of copper-~ased or iron based metal parts, or in the infiltration of porous metal compacts such as steel compacts, or the adhering of electronic cc~onents to printed circuit boards or hybrid circuit board to avoid bridging in surface mounted devise attachments, are other properties desired 'lye inventive products here can also provide desired restriction of metal flow on remelting. For most electronic soldering purposes at this tin, the composition must be free of corrosive agents such as inorgam c salts.
Brazing can be done with a paste of powdery powdered copper-based ahoy or elemental ocpper-bearing, or with a cupreous so-called "silver solder. Facing applications, erg., to coat, build-up or hard-faoe metal surface s, can be done with pastes containing various metal or alloy Pharisee, e.g., copper, copper-based, cobalt-based or nickel-based alloys, stainless steel, hard facing ~2~35~

alloys, etc. In hard facing, the metal Fodder usually is heated to a wish state Weller liquid phase sistering of the metal occurs.
wherefore hard-facing Fx7wders can be considered here as essentially s:~lter~le. Sometimes -essay pastes can contain particulate refractory neutrals such as alumina or silicon carbide for wear F~lrposes.
Infiltration of porous metal compacts, typically, steel compacts, call for fusion that will fill the pores of the compact with metal.
Such Fetes usually are copper-rich and contain a little iron, erg., .01 to I by weight. Often a bit of refrac*ory-providing material lo is used in them; the refractory material remains as a removable surface residue when the job is done. Molding applications, such as injection molding to make metal parts, can use a variety of metal powers in a paste vehicle. Most molded pastes here are formed of paste, then are heated to leave a sistered object. For efficiency and economy -the vehicle weight proportion ordinarily is minor relative to that of the weight of fusible metal powder.
Soft solder pastes, for example, (melting below 400C., preferably below 330C~ usually contain tin and lead; a little silver often is alloyed with the tin, particularly for electronic 2C work, e.g., for making microelectronic connections. Soft solder pastes new are experiencing wider acceptance in industry, primarily because pastes are more readily adapted to automated manufacture and screen printing on a substrate than are the more conventional and manually effected solder bar, separate flux and iron, or solder wire I (e.g., one containing the flux in a core within the wire) and an iron. I make-up of prior powder metal-containing paste compositions has been largely influenced by the prior practice s particularly in respect of fluxing or surface preparing agents. These haze coursed substantial portions of organic acids, ego, rosin acid, inorganic salt materials, e.g., zinc chloride, ammonium chloride, borax and the like, and recensed fluxes.
Soft solder compositions have not been entirely satisfactory in a number of respects First, because of the presence of inorganic salt fluxes they have tended to be corrosive to the base metal or to introduce water as water of hydration leading to spattering. This problem ads alleviated to a great extent with recensed flux I

vehicles. However the recensed fluxes or vehicles permit excessive r~vement of the solder particles away from the deposition site on heating; they also often give rise to sputtering and "dotting"
which leaves a residue as a halo around the solder joint. Their 5 solder pastes have been prone to exoe suave solder balling, i.e., the font ion of discrete minute kills of soft solder. this is highly undesirable and leads to electrical bridging across what should be electrically isolated connections especially on printed circuit ~xoarcls.
Lo In a preferred embodiment of a soft solder composition an alkali solu~ilized in a polyhydric alcohol, e.g., glycerine, act as a fluxing agent and improves solder ability. For best results herein, in a soft solder metal powder, a slump control system and an inorganic salt-free fluxing system are present. The compositions hereof are practically noncorrosive and easy by formulate and handle. They are readily adaptable to screen printing. Disadvantages attendant prior compositions such as spattering clue to evolution of water vapor, solder balling and bridging, corrosivity, dotting, tenacious residue, failure of the solder to melt due to excessive oxidation, etc., are not observed in the metal-bearing pastes here. "Inorganic Metal Salts are metal or a onlum salts Lange's book of Chemistry, Thea Edition, pp. 209-333.
To better understand the applications of solder pastes, reference nay be had to technology of Electronic Grade Solder Pastes"
Tailor et at, Solid State Technology September 1981, pages 127-135.
One prior paste composition is disclosed by Knot U.S. Patent 1,772,952.
Lois paste comprises a solder metal powder, an amine and a binder or vehicle such as Vaseline m eye compositions do not, however, possess anti slump properties which are currently in demand in the electronics industry. U. S. Patent 2,493,372 to William dated 3 January 1950 discloses a paste composition including a metal powder, eye., tunneled, a salt flu, and a C, H and O compound. Referent ox may also ye had to Us S. Patent 3,954,494 dated 4 May 1976 which discloses a wax-flux composition. U. S. Patent 80~,664 also shows a tin-lead metal powder paste in a Vaseline - glycerine - inorganic salt flux system.

I

Another solder paste composition comprising powdered solder, a resin, a salt of an amino acid ester and a solvent is discussed by Melchiors et at in Patent 3,065,538 dated 27 November 1962.
Another aqueous base solder composition is shown by Johnson in Patent No.: 3,073,270 dated 15 January 1963.
Aye exemplary of prior solder paste compositions is the t~lt~nt to Petersen et at 3,925,112 dated 9 December 1975. according thus invention, where are provided emulsified self-cleaning soldering LIT fluxes having an aqueous phase including from 2 to 30 pow Imparts by weight) of a water soluble hydrazine salt and an oil phase mcluding from 5 to 50 parts of a mixture of petrolatum and wax. Also provided are water solutions ox 2 to 30 pow of the water soluble hydrazine salt, up to 5 parts of a vegetable gum thickener, a wetting agent cud the balance water.
Another prior paste composition is disclosed by Mastrangelo in U. S. Patent 4,273,593 dated 16 June 1981. This paste comprises a solder m tat powder and a vehicle, the latter being 2 hydroxypropyl cellulose blended with glycerine and/or water and further blended with a mixture of poly~lkoxyalkanols.
It has now been found that an improved vehicle for the instant powdered metal pastes is provided as an essentially non aqueous vehicle medium comprising a normally liquid non aqueous organic liquid as an anti slump agent, usually and preferably a polyhydric I alcohol system, characterized in that the liquid has a mimmum surface tension of 43 dynes/cm (20C.), and generally from 43 to 65 or higher dynes/cm. Such system provides a slump control property to the metal bearing paste such that when it is heated toward the melting point of the soft solder metal powder, ego 118C. to I 325C., -the shape of the deposit is substantially maintained until -the metal fuses. Al-though as will be seen from Table I below, and norlaqueous liquid having a surface tension above 43 dynes/om. may be used in the vehicles hereof, polyols are the most practical ankisl~p materials and the invention will be described with reference 35 to polyols for convenience.

These vehicles also desirably include a low surface energy material such as a hydrocarbon. The hydrocarbon, which is preferably solid or semi-solid (e.g., grease-like) melts, of courser and wets the substrate around the deposit, but carries no significant amount of the metal particles with it. Apparently, the anti slump system remains Burr and provides a cohesive force for the powdered metal.
Althc~1gh hydrocarbons having melting points above 15C. are preferred, in retain embodiments normally likelihood hydrocarbons such as hexane, cyclohexane, Tulane or mixtures thereof, e.g., mineral spirits, may be used. I've high surface energy material ryes as a binder under heat conditions to hold the particles in position. Also the hydrocarbon is easily cleaned, along with any residue that may be left, away from the joint or surrounding area. The hydrocarbon by itself is incapable of imparting slump control properties to a powdered metal contained therein. In the preferred powdered metal compositions especially adapted for screen printing, no dotting is observed.
Surprisingly, even after melting, the fusible metal resists running from the site of application. Of course, in soft solder compositions there is also need for a fluxing agent. Such agent serves -to clean the surfaces of the substrate or joining metal as well as the solder particles, and to inhibit the formation of chide coating on the solder particles as the temperature is elevated toward melting.
The desirable properties of anti slump, anti corrosion and freedc~n Fran spattering in the metal-bearing pastes here are no-t observed in prior compositions known to me. Other additives may desirably be present as will be pointed out below. The instant pasts have no water in them other than insignificant amounts possibly present as an adventitious impurity that might be associated with good Colette technical grade ingredients, No water is added deliberately as such or as a hydrate; so it can be said that the instant pastes end vehicles are nuances as a practical matter. also, it has been found that the high surface tension liquid, i.e., -the polyol, con be a single go onent vehicle or a part of a multi component vehicle, i.e., including also a hydrocarbon. Ire substrate on which the paste its deposited has no significant effect on the hot stump resistance.

- -GRIEF STATEMENT OF TIE; INVASION

refly stated, the present invention is a non aqueous or an hydrous inorganic salt-free, powdered metal paste composition comprising a major amount of a metal powder and a minor amount of a paste vehicle containing an anti slump composition including a non aqueous liquid having a surface tension above 43 dynes/cm. at 20C. and preferably a polyol containing from 2 to 8 carbon atoms and having a surface energy of from 43 to 65 or higher dynes/cm. (20C.). Preferably these pastes also include a paste forming vehicle ingredient which is a hydrocarbon For soft solder compositions a fluxing ingredient is present.
To further extend the utility of the metal or metal alloys, there may key added other ingredients, such as, one or more surfactants, one or more condensed or fused ring aliphatic acids, e.g., colic acid or abietic acid or rosin acids, and one or more plasticizers such as di~n-butyl phthalate. The pastes including a powdered soft solder ally o'er a shiny and coherent it coalesced) solder pool in a controlled area of application.

DETAILED DESCRIPTION OF THE INVASION

20 It has been found that slumping of a paste composition containing a major amount of a powdered metal or metal alloy can be effectively controlled by a unique composition composed of a hydrocarbon or a mixture of hydrocarbons, e.g., petrolatum, and a polyhydric material, e.g., glycerine and sodium hydroxide. me combination of a hydrocarbon having a melting point of at least 15C~ and loss than the melting point of the metal, and a polyhydric alcohol, such as a dip or triethanolamine, or glycerine, or pentaerythritol, ox the like, is however, effective in maintaining quite substantially the profile of the paste as it was initially deposited on the surface or I substrate A solder paste requires, however, a flux. it the fusion point, the metal in the present compositions has not run or spattered or balled up into small discrete byway of molten metal prior to the fusion of the entire mass. A polyhydric alcohol or polyol alone I

also is capable of conferring this property upon a paste composition containing a major amount of a metal or a metal alloy Hoover such a composition while useful with high melting powdered metals, is unsatisfactory as a soft solder position requiring also a Sybil hydrocarbon delineate and a noncorrosive flux.
To form a solder paste, the vehicle portions hereof are blended with a powdered metal to the extent of from 75% to about 93 metal by weight of the paste, and desirably from 80~ to 90%, and rehirable about 85% powdered metal. me particle size of the 10 powdered metal is desirably such that it will not settle out of the vehicle which is quite viscous 120,000 to 200,000 cups., Brook field No. 7 spindle at 20 rum) on standing. In general, for soft solder ccn~ositions the particle size is less than lo mesh (U. SO Standard Sieve Size), desirably 200 400 mesh. A mixture of various sizes 15 and/or shapes of metal powders often is advantageous for achieving desired rheology and other paste properties in these applications.
Solder powder particles are available in two forms, i.e., whose having irregular shape and those having spherical shape. Either shape, or a mixture thereof may be used, although the spherical 20 shape is desired. Where normally liquid hydrocarbon delineates are used, erg., Tulane, the particle size of the solder powder should key less than about lo microns in order to mum mite titling Typically a brazing (or "silver soldering) Foist will contain about 65-75 pow metal powder of -l50 mesh size, an infiltration paste 80-90 pow metal powder of -lo mesh size, a facing paste 60-90 pow metal powder of -lo to -200 mesh size, and a molding paste (as for injection mowing) 85-9Q pow of metal powder of -400 mush size. In each case the balance of lo pow is made up with the vehicles hereof. A mixture of various sizes and/or shapes owe the particles in the metal powders often is advantageous for achieving desired rheology and other paste properties in these Appalachians.
Preparation of the vehicle and paste is achieved with conventional stirring or blending means. Warming can be done, if 35 necessary or desired, to facilitate by dissolving or melting ingredients ~V~3~

together for putting them into very intimately dispersed condition and/or otherwise making a multi phase dispersion with the ingredients in a very fine state of subdivision preparatory to blending with the metalliferous powder to Norm a mass of paste consistency. Preferred c~r~ositions for soft solders include additional fluxing agents, optionally a surfactant, optionally an organic carbcxylic acid, and optionally a delineate; i.e., a plasticizer and/or solvent. Each of eke ~nyredients will be discussed below. Thereafter, the metals or real alloys will be discussed followed by general processing techniques, and specific examples.

THE HYDROCARBON ingredient Hydrocarbons are preferred ingredients for the metal paste compositions hereof. Fluorinated hydrocarbons or chlorofluorinated hydrocarbons may ye used to replate part or all of the hydrocarbon.
me useful materials range in melting point from below about room temperature to normally solid materials, e.g., petroleum hydrocarbon waxes containing from 18 to 60 or more cartons and melting in the range of 28~C. to 100C. The useful hydrocarbons also have a very low ash ox solid residue content and either melt and flow, sublime and/or thermally decompose at a temperature below the melt my point of the solder (i.e., below 330C.). me amount of ash or solid residue from the hydrocarbon remaining at the melt temperature should be less than 0.5% and preferably less than Oily. The useful hydrocarbons may be paraffL~ic, aromatic, or mixed aromatic paraffinic or ~uxtlres of ccmpo~mds of such characteristics, and in use various mixtures of hydrccarbons7 e.g., octadecane, mineral spirits, paraffin wry and petrolatum, e.g., Vaseline. Synthetic hydrocarbons normally solid or semi-solid include commercially available polyethylenest polypropylene, polyethylene propylene polybutenes, polyethylene-styrenes), hydrogenated nonpolar polymeric hydrocarbons having Ring and Ball softening points of from 15C. to 130C., such polymers having a molecular weight less than about 1500 and preferably less than Lowe, hydrogenated polyterpenes, etc. the best material known to me for use grin is petrolatum. Halogen substituted hydrocarbons, eye, fluorocarbons and chlorofluoro carbons may also be used, they also being relatively inert at the temperatures enco~mtered.

d "Petrolatum'` is a well known colloidal system of non straight-chain solid paraffinic hydrocarbons and high boiling Lockwood paraffinic hydrocarbons, in which most of the liquid hydrocarbons are held inside the Melissa. A detailed historical account including the S chemistry of pe-trolatum and modern manufacturing methods is found in Roy and Cosmetic Industry, Vol. 89, 36-37, 76, 78-80, and 82, July 1961. "Petrolatum for Drugs and Cosmetics" Chandler. Petrolatum is typically a yellc~ish to amber or white ser~solid, unctuous mass, practically odorless and tasteless. It has a density at 25C. of LO from 0.820 to 0.865, a melting point of 38 to 54C., and a refractive irks 60t0 of 1.460 - 1~474. It is readily commercially available under the well known proprietary marks Vaseline, Cosmoline, Stanolene, Penreco brand petroleum jelly as well as other convenient trade designations. Petrolat~n may be used in its commercially available form or it may be modified by the addition of petroleum ax or paraffin wax in particulate form, e.g., microcrystalline wax me hydrocarbon mgredient is utilized in an amount which ranges from 10 to 90 pow of the vehicle system, or 0.7% to 22.5% of the solder paste. A nonequals organic liquid having a surface energy in the range of 43 to 65 or higher dynes/cm appears to be essential for the slump control characteristics of the present powdered metal pastes. Although water has a high surface energy as does sulfuric acid, these materials are not satisfactory because of spattering or reactivity at elevated temperatures.

SLUMP CONTROL SYSTEM

As indicated above, the ability of a powdered metal paste to resist hot slump, or running during softening and melting is essential in various applications such as molding, casting, infiltrations, cxkatincJ and in modern microelectronic processing and particularly silk and stencil screening of soft solder pastes. It has been found that a combination of hydrocarbon as above defined and particularly pe-trolatum, and a non aqueous organic liquid having a surface tension at 20C. greater than 43 dynes/cm., and preferably one or more polyhydric alcohols containing 2 to 6 OH groups and having a surface tension ox energy of prom 43 to 65 or higher dynes~om at 20C., is effective in providing a good paste and in preventing slumping of the metal particles. The hydrocarbon alone with powdered metal composition appears incapable of conferring this property to any degree. Non aqueous organic liquid alone gives sufficient anti slump properties but in the case of soft solders, insufficient soldering properties. Soft solder pastes also require a flux and to obtain ale noncorrosiveness required in modern electronic applications the LO flux should not be an inorganic salt, e.g., ZnC12, NH4Cl, or borax, the latter being highly hydrated and thus given to spattering.
the anti lump agents hereof are generally polo cc~Es~lds.
A detailed mechanism of the anti slump properties of this combination is obscure at present.
Table I below gives specific examples of liquids of various kinds useful in inhibiting slump.
The polyols useful herein are aliphatic and normally liquid or ox relatively low melting pollinate it below about 170C~
and mclude ethylene glycol, diethylene glycol, propylene glycol, 20 dipropyle~ glycol, sorbitol, minutely, trimethylolethane, in-methylolpropane, diethanolamine, triethanolamine, pentaerythritol, awl erythritol. These polyols cocci with a hydrocarbon, especially petrolatum in the a Noah of water and in the presence of a finely ~-Lvided metal powder to control slumping on heating and to provide a satisfactory paste medium A fluxing agent either as a separate ingredient, ego, sodium hydroxide, or as a moiety of the polyol (e.g., triethanol~nine or diethanolamine) must be present. me secondary or tertiary amine group appears to be suitable for fluxing.
Thy polyol ivy generally soluble in the hydrocarbon The amount of Lydia polyol constitutes from about 0.5% to 10.0% by weight of the vehicle and powdered solder metal composition.
A comparative study of various agents in 38.9% powdered metal compositions demonstrates the significance of the limitation respecting surface energy or surface tension.

~11-TABLE I
Slump/Resistance Study (For 60% Sun; 40% Pub Powdered Metal)*

Surface Tension Anti slump Slump m) Resistance Remarks 63.4 7% Noah% Glycerine Yes Fluxing occurred 63.4 Glycerine Yes No fluxing 58/2 Formamide Yes Little fluxing occurred 55.1 Cone H2S04 Yes Oxidizing occurred 50.8 Ethylene Iodide Yes P/M binned green 48.4 Triethanolamine Yes Fluxing occurred 48.5 Diethanolamine Yes Fluxing occurred 48.3 Monoethanolamine Yes 47.7 Ethylene Glycol Yes Little fluxing occurred 45.2 Triethylene Glycol Yes i' 44.0 Tetraethylene Glycol Yes "
44.5 Polyethylene Glycol 200 Yes if 44.5 Polyethylene Glycol 600 Yes "
42.9 Aniline No 40,9 Phenol No Solid Chemical 38.0 Pardon JO
36.8 Nitromethane No 32~7 septic Andre No Oxidizing occurred 32.5 Oleic acid No 32.3 Carbon Disulfide No 27.8 Acetic acid No Oxidizing occurred 27.5 n-Octyl alcohol No 2505 Cyclohexane No 24.2 ethyl bromide No 23,0 i-Butyl alcohol no 20~7 t-Butyl alcohol No - -I Vaseline No NOTE: 1. Formula used for slump resistance studies:
88.9% (97.5~ Pub; 1.0% Sun; 1.5% Ago -I 7.8%
Vaseline -I 3.3% Antislw~p agent.
Paste was examined on Cut coupon at designated temperature.

Treble If below shows the hot slump effect on a solder composition using the "anti slump agent" as -the sole vehicle.

liable II
Slu~p/Resistance Study (60~ Sun; 40~, Pb/Sin~le Phase Vehicle System) Surface Tension Antislwmp Slump (UX~n~/~n) Pent Resistant Remarks 63~4 7% Noah Yes Excellent Glycerine Soldering 63.4 Glycerine Yes 55.1 Cone H2SO4 Yes Oxidizing Occurred 50.8 OH I Yes 48.9 rye ~anolamLne Yes 47~7 Ethylene Glycol Yes 40.9 Phenol No Solid Chemical 38.0 Pardon P/M ppt'd quickly 27.5 n-Octyl alcohol ---- PAM Fpt'd quickly Vaseline No __ . __ . . _ _ _ .
Note: 1. Paste was examined on Cut coupon at 235C.

2. Ire Rockwell NaOH/glycerine also provided Good slop resistance for Nordox Ted Cuprcus. (Queue).

Table III below shows the effect of ten~era-ture on hot slwnp resistance with selected polyols and other additives.

Lo 3 TABLE III
Sl~un?/Resistance Stun (Temp. Effect) Surface Tension Anti slump Temp. C) Slump (Oyr~/Cm) Agent at Test Resistance 48~9 Trieth~nolamine 150 Yes 235 Yes 325 Yes 44.5 Polyethylene 150 Yes Glycol 200 235 Yes 325 Yes 42.9 Aniline 150 No 235 No 325 No 38.0 E~rridine 150 No 235 No 325 No ote: 1. Formula used for slump resistance studies:
88.9~ (97.5~ Pub; 1.0% Sun; 1.5% Pug) 7,8%
Vaseline 3.3% Anti slump agent.
Paste was exam mod on Cut coupon a designated t~mperabure.
. When the paste was examined on substrate which has been surface streaked with FC-723* (surface tension 11 dyne/am), the slump resistance behavior was still about the same as that on the Cut coupon.
*Flurried FC-723 is an oleophilic, hydrophobic fluorocarbon in an inert vehicle having a specific gravity of 1.78 produced by EM.

FLUXING SYSTEM

As indicated above, -there must be present a noncorrosive an hydrous fluxing system in a soft solder paste composition hereof.
Ire fluxing system may be a single chemical specie dissolved or diapered in the hydrocarbon/polyol system. Alternatively the fluxing system may comprise a plurality of fluxing agents dissolved or dispersed in the hydrocarbon/polyol system. Best results have keen sucker with alkali or basic reacting fluxing agents, and particularly alkali metal hydroxides. muse can be used as solutions in the polyol or as alcoholates of a mandrake or polyhydric alcohol, e.g., methyl, ethyl or isopropyl alcohol, dissolved in the polyol, or the alkali metal salt of the polyol, ego, sodium guy overate.
The alkali metal hydroxide in such component is a preferred noncorrosive fluxing agent and is effective in a proportion of about 0.1-5% by weight of the vehicle, and, advantageously, 0.25-3.5%.
Lowe liquid polyol can constitute from about 0.5 to 75.0% by weight of the vehicle, and, advantageously, about 40%~ On the basis of the entire solder paste, the anoint of polyol ranges from about .3 to 18.8%. me alkali metal hydroxides useful herein include in descending 20 order of preference sodium hydroxide, potassium hydroxide, lithium hydroxide and sesame hydroxide. Such alkali metal hydroxides have a limited volubility in polyhydric alcohols or mixtures of same that are liquid and are conveniently used in concentrations at or near the limit of volubility, i.e., less than about 10% by weight of the 25 polyol. As indicated, they can be present as an alkali metal alcohol ate, e.g., sodium ethyl ate, dissolved or well dispersed in the polyol, the alcohol ate being equivalent to the hydroxide. The polyhydric alcohols include glycerine (which is preferred), ethylene glycol, diethylene glycol, propylene glycol, sorbitol, minutely, pentaerythritol, 30 erythrltol, etc., containing Fran 2 to 6 OH groups. A sodium hydra ~dde/glyerine solution is particularly effective and may be used as the sole fluxing agent, or it may be used in combination with an alkanolamine, e.g., triethanola~QLne or diethanolamine to provide I
-15~
effective fluxing systems for the instant pastes.
A useful fluxing ingredient is also prc~rided as an amine component of the vehicle. Such component is effective in a broad proportion, e.g., about 2-~0~ by weight of the chicle and, advantageously

3~10~. rL'he essential functior~l group of this cc~ponent is an N- _ Al wherein R, Al, and R2 are independently selected from hydrogen, alkyd, alkaline, eyeloalkyl, cyeloalkylene, earboxyalkylene, amino-alkaline, hydroxyalkylene, earbonylalkyl, eta, no more than two of R, Al and R2 being hydrogen. me alkyd and cycloalkyl groups may contain from 1 to 30 earn atoms. me amine component may contain one to three amino groups. A particularly useful group of amine compounds is the water voluble alkanolamine group including one-, dip and trimethanolamines, moo-, do-, and triethanolamines; moo-, I-, and tripropanolamines, and mixtures of the moo-, do-, and trialkanolamines. Alkyd and eyeloalkyl amine, particularly the C2-C18 moo and polyamides, e.g., triethylamine, tri-isopropylarmne, diethylamine, mono-n-butyl amine, propylene Damon eyclohexylamine, eyelopropyl methyl amine, tetramethylene Damon, rosin amine, Swahili-h~ylarnine hyc~oehloride, eyeldlexylene anise, diaminoethylarnine,cli~inopropylc~nine, etc. Thus, the Sunday and configuration of the amino ec~pouncls useful herein are very broad and results among the examples are reasonably equivalent for fluxing. Houdini art guanidino fluxing agents, advantageously aliphatie ones, elm ye considered as I useful amine for the instant purpose. Aromatic amine, while ~unetionall often impart twixt and therefore are not favored.
Similarly, pyric~ne-type materials, such as, pardon or a letdown --16~
give off intensely objectionable odors and are not favored, but could be considered functioning like amine here The preferred anuses are the alkanolamines. Also useful to supplement the base system are the amino acids, particularly the water soluble amino, acids, e.g., arninoacetic acid, beta- arninopropionic acid, (beta-Allen) amirlobutyric acids, epsilon- aminocaproic acid Methyl Gleason, button, alpha-del-ta-diaminovaleric alipnatic carboxylic acids. Issue, urea, propionamide, ~ltanamide, 2,2 dimethylpropion-I to, ~-meth~lpropionamide, N,N-be-ta-trimethylbutyramide, stroll-lo Aryan, etc., can be such base system supplements.

OTHER VEHICLE ING~EDIENIS

Organic carboxylic acids are useful as fluxing and/orsolderability ingredients, particularly in a supplemental role in oombinatiorl with the other ingredients described cibove. Any nigh boiling (above 300C.) aliphatic carboxylic acid may be used. I
prefer, however, to use condensed ring acids such as abietic acid, colic acid, rosin acids, polymerized rosin acids, hydrcger~ted rosin acids rosin esters disproportionate rosin ester gum, wood rosin, gum rosin, tall oil rosin, or fatty acids such as Starkey acid, oleic acid, etc. Fatty amine cud fatty acid compounds are also useful in -this capacity. Examples include N-tallow~1,3-diarnino-propane, 3-diaminoproF~ane dwelt, etch The acids are used in small amounts of Fran 0.5 to 10% by weight of the vehicle composition, or on the basis of the fully forn~lated solder paste, from about .03% to about 2.5%.
It has also been found that a surfactant may be advantageously included in the vehicles hereof. Although such surfactant or wetting event may be amonic, cat ionic, ar~photeric, or non ionic, non ionic events are preferred. Many surEactant materials are known my are used in the present vehicles to help to corrtrol the theological properties, shelf-life stability, air voids, etc. me amount used I

is determined by cut and try and is that amount which is sufficient to impart the desired control. 'muse agents assist in the dispersion of the powdered metal and in carrying the fluxing agent to the surf owes being joined or coated. Generally less than 10'~ by weight each of other ingredients is used and usually Fran .01% to 5% by weight of the vehicle or 0.001% to about 4.5~ of the solder paste.
Specific surfactants include the alkylarylpolyether alcohols, ~r~r~ni~n per fluorinated carboxylates, fluorinated alkali esters of fatty acids, acetylenic glycols (which sometimes can act as a ill d~fo~ner), polyoxye~hylene sorbitan menstruate, etc. Surfactants commonly used in solder pastes may be used herein.
Solvents and/or delineates may also be present in the vehicle compositions hereof For example, when a paste containing powdered solder metal is to he used in a screen printing process, solvents are conveniently used to adjust the viscosity to a satisfactory level. Solvent materials are desirably volatile, at least at the melting point of the solder alloy. Any solvent including low molecular weight alcohols, e.g., ethyl or propel, isopropyl, bottle, Amy, cyclohexyl, terrapin alcohols, etch; kittens, e.g., methyl ethyl kitten, methyl is~butyl kitten; 2-butoxyethanol~l~ ethylene luckily dim ethyl sulfoxide, hydrocarbons, ego, kerosene, terrapin hydrocarbons, hexane, cyclohexane, Hutton, octane, naphthas such as mineral spirits, ethyl acetate, Amy acetate, etch The solvent ingredients may also include higher boiling materials commonly regarded as plasticizers such as dibutyl phthalate/ tricresyl phosphate, etc.
eye selection of the solvent and/or delineate is controlled by the end use, cost, environmental factors, desired plasticity, etc. 'Ire solvent or delineate may be water soluble or substantially water soluble. The solvent or delineate leaves the system after application to a substrate as in screen printing, the residue being the solder paste composition hereof.
Minor omits of known odor ants, bactericide, fungicides, etc., may also be included in the vehicles hereof if desired Amounts of such ingredients usually range from about 0.1 to 2g by weight of the vehicle From -lime to -tinner it is desirable -to include in the compositions of the present invention, particularly in the case of silver solder brazing pastes an inorganic fluxing agent such as a metallic halide, for example, zinc chloride, tin chloride, aluminum chloride, or arnrnonium chloride. Such an agent may be present in an amount ranging from about .5 to 5% by weight of -the vehicle and is u~cful in cleaning the surface to be treated of the metal or metal ally. Such oxidation, unless reproved destroys the integrity of the coating or juncture between the metals involved.
I it the metal fusion temperatures encountered herein all organic ingredients are removed from the system either by volatile-ration or decomposition PREPARATION OF TIE VEX EN

The simplest preparation of the vehicles hereof involves only effective mechanical rnLxing of the ingredients into the petroleum hydrocarbon ingredient, e.g., petrolatum.
The hydrocarbon can, if desired or necessary, be heated to melt it and facilitate the blending operation, and warming of some of the other ingredients also can be of help. It is not necessary that the mixture be a solution. me paste e vehicle can be claldy and contain one or more phases with the disperse phase fine enough so that i-t will no-t separate substantially on standing.
I've materials discussed in de-tail above are considered to be ingredients of the vehicles hereof.

lo THE kettle POWDER

For raking a paste, the metal powder is commented so that it is easily and stably dispersed in the vehicle key grinding, ball milling, paddle blending, ribbon blender, etc. The powder should past through a 20 mesh screen (U. S. Sieve Series) (841 microns).
icily the powder is fmer than 100 mesh (149 microns) beau æ
larger particles are difficult to disperse and maintain in suspension in -the paste. For most applications, a particle size in the range of -150 + 400 mesh (U. S. Sieve Series) is preferred. For rust purposes, from 3 to 20 parts by weight of metal powder is blended with 1 p rut by weight of vehicle. I prefer to use spherically shaped particles, although irregular particles or flakes may be used. The paste compositions hereof generally will have a viscosity in the range of 20,000 cups. to 200,000 cups., Brook field No. 7 spindle at 20 rip The preferred apparent viscosity will depend on the method of dispensing or application of the paste to the materials to be joined. Hand troweling pastes are more satisfactory at the higher apparent viscosities than pastes intended for automatic dispensing such as extruding, flowing or spraying or those which are most suited for application by a screen printing process.
Viscosity can be controlled easily by the amount of solvent or solvent mixture and/or plasticizer employed in the vehicle, or by -the vehicle to power ratio. Pastes often are degassed at reduced pressure.
Solder compositions useful herein as thy metal powder for blending with the above described vehicles to form a paste, or or extrusion ox a hollow wire for making a cored solder wire, are well Icnown. A number of representative compositions useful herein cure given in the Taylor et at article, swooper. In general the solder compositions have a melting point in the range of from akcut 118C.
to about 330C. and comprise tin together with lead and/or silver.
Other metals such as zinc, aluminum, bismuth, cadmium, nickel, indium and cadmium may also be used in the solder compositions.

For making a solder paste, the metal powder is commented so that it is easily and stably dispersed in the vehicle by grinding, ball milling, paddle blending, ribbon blender, etc. The entire powder should pass through a 50 mesh screen (U. S. Sieve Series) (297 microns). Typically, the powder is finer than 100 mesh (149 microns) because larger particles are difficult to disperse cud r~intain in suspension in the paste. A particle size in -the range of --200 400 mesh (U. S. Sieve Series) is preferred. Even smaller particle sizes, i.e., 10 microns or less are desired where normally I Lydia hydrocarbons are used in the vehicle as in silk screening paste compositions. For most E~lrposes, from 3 to 20 parts by weight of solder metal powder is blended with 1 part by weight of vehicle.
me paste compositions hereof generally will have a viscosity in the range of 20,0~0 cups to 200,000 cups. The preferred apparent viscosity will depend on the method of dispensing or application of the solder paste to the materials to be joined. Hand troweling pastes are more satisfactory at the higher apparent viscosities than pastes intended for automatic dispensing such as extruding, flowing or spraying onto a substrate or those which are most suited for application to a substrate, e.g., a printed circuit, my a screen printed process.
Viscosity can be controlled easily by the amount of solvent or solvent mixture andtor plasticizer employed in the vehicle, or by the vehicle to powder ratio. Pastes often are degassed at reduced pressure.
In fcibricating cored solder wire, conventional procedures are used substituting a vehicle of the pro ant invention for a conventional core composition such as a rosin based paste.
Effective control of hot slump in powdered metal pastes is menstruated by the following specific examples. These examples are -Untended to enable those skilled in the art to apply the principles of this Invention in practical embodiments, but are not intended to limit the scope of the invention. In this specification all temperatures are in degrees Celsius unless otherwise stated, all parts, percentages, an ratios are by weight unless otherwise expressly stated, and sieve sizes are for the U. S. Standard Sieve series.

I

Testing for resistance to hot slump of a metal-containing paste was doze by applying a deposit of the paste layout 5 mm diameter by 4-5 mm high) by spatula to a copper coupon, then gradually and automatically warming the coupon with a Browse Corporation reflow instrument (in effect an automated traveling hot plate from room temperature to fusion in about a half-minute to a minute. The thus - heated deposit way observed visually for collapse of the metal prior to its fusing as the vehicle disappeared therefrom.
Significant collapse of particulate metal of the deposit prior to its fusion would indicate hot slump. None of the exemplary pastes given below skewed significant hot slump. In -the case of solder paste the spreading ox molten metal from the deposit area was also observed in the same test. None of the exemplary tin-contaLning solder pastes given below showed significant spreading over the coupon; all had desirably restricted flow. Great spreading away from the locus of application is undesirable for many applications such as soldering in the manufacture of electronic devices.
In the examples toe petrolatum indicated as Petrolatum A
was Vase me brawl petroleum jelly, Vaseline being the trademark of Chesebrough Manufacturing Co., Inc. for US petrolatum sold at retail for household use The other petrolatums used were Yenreco US petrolatums, Penreco being the trademark of Pencil Co.; Petrol-tug B was their Regent grade white petrolatum (Meltmg Point 118-130F.); Petrolatum C was their Royal grade (Melting Point 118-130F.); and Petrolatum D was their Amber grade (Melting Point 122-135F.).

I

In the following examples the following designations have the following identities:

Briton N-60 = alpha-(nonylphenyl)-omega-hydrQ~y-poly(oxy-1,2-ethanediyl), (Aegis-to Jo.: 9016-45-9).
*me trademark of Room & Hays Company .. .. _ . _ . . _ _ Armenia* = bis(hydrogenated tallow alkyl)amine, Amen* ARC = Basque C16 hydrocarbon alkyl)amine, Dune en T = N-tallow trim ethylene Damon, and Damon* 'DO = N-tallow trim ethylene Damon dwelt, respectively.
*'rho trademarks of Akzona, Inc.

. .
PEG* 6000 DO = alpha-(l-oxooctadecyl)-omega-[(l-Qxo-octadecyl)oxy] poly(oxy-1,2-ethanediyl3, (Reg. No : 9005-08-07), PEG* 6000 = alpha-hydro-omega-hydroxy-poly(oxy-lt2-ethanediyl), Reg. No.: 25322-68-3, Carbowax* 3350 = a polyoxyethylenic wax, n-llexyl Car-bottle* = diethylene glycol moo n-hexyl ether, and twill Car-bottle* = diethylene glycol monobutyl ether, respectively.
*Lowe trademarks o-f Union Carbide Corp.
.. . .. , __ ___ Flurried*
FC~340 = a liquid fluorocarbon.

*The trademark of EM Company , 5Surfynol*
EYE = 5-decyne-4,7-diol,2,4,7,9-tetramethyl, Reg. No : 126-86-3.
*the traderr~rk of Alp Products and Shekels, Inc.

Donnelly* DO = 2-(2-methoxyethoxy)ethanol, (Reg. No. 111-77-3), art Donnelly* DE = 2-(2-ethoxyethoxy)ethanol, (Reg. No.
111-90-0), respectively.

*me trademarks of Dow Chemical Cc~any . . _ _ " . _ _ . _ . _ _ .
Pastes tabulated below were rude by blending the nicker size flying ingredients, metal powder and other solder ability ingredients with petroleum hydrocarbon in a molten condition, then blending in the other vehicle ingredients when the mass cooled to 32. The specification for -the solder powders was 5% mix ~200 mush, rnax. -325 mesh. me formulations were evaluated according to standards established for electronic grade solder pastes. Act cordir~ly, although some of -the exemplified pastes may not hove met elf -thy electronic grade criteria, -they were operative for other utilization such as for raking a joint using a trowel to apply -the paste. Of the exemplified solder pastes, those preferred for micro-electronics irk slicked no solder balling.
In -the solder tests no spattering was observed dying heating to effect melting, and no significant hot stump or solder it spreading was observed that is, they had good restriction of flow.
E~rrtherrnore, there was no dotting in evidence on the copter substrate, and cleaning of joint easily could be had with a suitable organic solvent, erg., a petroleum naphtha, alcohol, etc.
En Jay of contrast 20 parts of a prior art fluxing comic-session (specifically that of Example 1 of U. S. Patent 3,925,112, itch patent discloses some petrolatum as one of the ingredients in the oily phase of an aqueous soldering flux emulsion) was compounded with 80 parts ox solder alloy powder herein exemplified in the same Lo runner as the pastes herein exerr~lified; resistance to hot slump was not demonstrated nor was restricted flaw (spreading) of melted solder, and there was considerable spattering.

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-Petrolatum A, 95 parts, was blended thoroughly with 5 parts of triethanolamine to make a v2hlcle for a brazing paste.
30 parts of such vehicle was thoroughly blended with 70 parts of elemental copper powder, the opera powder being -150 mesh, to make a soft paste. No significant hot slump was observed upon testing on a copper coupon with the Reflow instnwnent.
A T-bar of an upright piece of steel temporarily wired to rest on and project from a horizontal flat piece of steel was made key applying the brazing paste deposit near one end of the interface between the pieces and heating the resulting assembly in a belt furnace. The assembly was maintained at 1121C. for 10-20 minutes. The result was a good brazed joint between the pieces, with the brazing metal flowing into the joint by couplet and exhibiting no appreciable spreading away from the joint.

Petrolatum A, 95 parts, was blended thoroughly with 5 parts of a clear solution of 7 parts of sodium hydroxide in 93 parts of glycerine to mike a vehicle or a brazing paste. 30 parts of such vehicle was thoroughly blended with 70 parts of elemental copper powder like that of Example 132 to make a soft paste. lye paste was tested for hot slump and brazing effectiveness like the paste of Example 132. No significant hot slump was observed. The resulting brazed joint was a good one, generally resenting that of Example 132.

I

The vehicle of Example 132 us used for Managua an inflator-lion paste. 20 parts of such vehicle was blended thoroughly with 80 parts of a powdered rnetalliferous infiltration composition to rake a grainy paste.
To do this testing a coherent porous "green" (unsintered) compact of steel powder was coated approx~unately 6 run thick all over with the post The rnetalliferous infiltration composition of the paste was a blend of elemental copper powder, a powdered copper-base alloy containing iron, a high green strength copper power (SCM Corporation's HUGS grade), silicon powder, and manganese powder; the infiltration c~nposition had the following approximate nut composition: OWE copper; 1.81% iron; I silicon; 0.32 zinc; and 1.00~ manganese.
No hot slump of the deposit was observed upon testing with the Reflow instrument. me paste-coated compact was heated for three hours at 1232C. to give a very efficient infiltration of the pores; 99~ of the infiltration composition went into the c~npact, and only I residue was left; this easily brushed off from the surface of the resulting infiltrated and sistered compact EX~MPI,E 135 The vehicle of Example 133 was used for matins an infiltration past. 20 parts of such vehicle was blended thoroughly with 80 parts of the powdered metalliferous infiltration compositions of Example 134 to make a grainy paste. The paste was tested for hot slump and infiltration effectiveness like -the paste of Example 134. No significant hot slump was observed. the infiltration of the compact was quite good, but did not reach the dramatically high efficiency obtained in Example 134.

E.~PLE 136 . . _ A soft paste was made by blending thoroughly 20 parts of vehicle with 80 pats of -80 mush 316 L stainless steel powder.
I vehicle was 90 parts of Petrolatum A blended with 10 parts of a solution of 7 ports of sodium hydroxide dissolved in 93 parts of glycerine. me asset was extruded into a fused silica boat as a squat cylindrical shape with a small pointy peak rising about 5 mm. from a position ox ntral to the top (somewhat resembling -the shape of the familiar milk chocolate Casey The boat then was placed into the 600F. zone of a small electrically heated tube fume ox through which hydrogen gas was flowing. The boat then was moved about 2.5 cm -towards the top temperature zone of the furnace at 4-minute intervals until about 20 cm was traversed, then was moved the remaining approximately 5 cm into the top temperature zone (about 1121C.~ and held there for 8 minutes. me brat was removed to a hydrogen-protected tooling zone of the tube for 12 minutes to cool the resulting coherent sistered porous metal part to room t~perature~ The main body of the part retained the original shape of the exudate with no significant hot slump.
Only the pointy peak of the Kiss had blunted a bit and had drooped somewhat.

A vehicle for a powdered metal paste was made by thoroughly blending 75 parts by weight of pe-trolaturn with 5 parts by weight of a cluck solution of 7 parts Noah in 93 parts of glycerine 10 parts I weight of bottle carbitol were coded -to make the vehicle portion.
30 parts by weigh-t of -the foregoing vehicle was blended thoroughly with 70 parts of 316L - stainless steel powder -100 mesh size with 35-50~ ~325 mesh to form a soft paste.
The paste was tested for hot slump by application to a copper coupon and heating on a Browse Corporation reflow instrument at 330C. No significant hot slump was ox æ rued, EXPEL l38 A vehicle for powdered copper metal was made consisting of 82'~ petrolatum and 18% of a I aye- glycerol solution.
90 parts by weight copper shot (-20 80 mesh) was hank blended with 10 parts my weight of -the vehicle. 'the resulting paste was applied to a vertical an a 30 angled surface (steel) in a 1" circular and a l" square preform shape. These panels were heated in a furnace.
The best furnace was run at foe for 30 minutes with 300 cubic meet per hour of dissociated ammonia gas.
Both forms sistered. The leading edges into the belt furnace oxidized and did not Sinatra Both samples held their respective shapes. me leading edges and leading corners of the preforms set at a 30 angle slumped presumably when the vehicle vaporized.
Thus, the vehicle successfully held the shot together up to sistering temperature Any slumping that occurred is attributed to the cxidized/unsintered leading loose shot edge.

The present example illustrates -the present invention with a hard surfacing paste queue vehicle was formed in the manner indicated above (as for example in Example 137) by blending -the following ingredients in the amounts indicated.

Petrolatum 65.0 parts Triethanolamine25.0 parts Colic acid 2.0 parts Dibutylphthalate8.0 parts The powdered hard metal nickel alloy had the following elemental analysis:

Carbon 0.64%
Silicon 4.24%
Chromium 14.27 Cobalt 6.01~
Iron ~.65%
Boron OWE%
Nickel Balance The sieve analysis was:
~115 mesh owe%
~150 mesh Trace ~200 mesh 21.8 -~325 mesh 56~3 -325 mesh 21.9 Ten parts by weigh-t of -the vehicle were thoroughly blended with 90 parts by weight of the hard metal powder. The resulting paste was applied to a steel bar:

a on a vertical face, S b) on a flat angled surface (30-45) as it a circle 0.74" X 0.125" thick ii) a square 1" X 1" X 0.312" thick c) on a flat horizontal steel surface in the forms indicated in IBM above.

The preforms were then heated in a traveling belt furnace under the -following conditions.

Belt speed - minute (I- 30 miss. in ho-t zone Preheat - 600F.
Hot Zone - (a) Run 1 - 1800F.
(by Run 2 - 1900F.
(c) Run 3 - 2000F.
Atmosphere - Dissociated ammonia.

Results:
. . . _ Run 1: No melting, no apparent powder oxidation. All forms held their original shape and approximate dimensions. Some cracks developed.

Run 2: Melting started on the vertical sample. No melting on all other samples which held their original shape and dimensions. Cracks developed where powder fell apart when the vehicle vapored.

Run 3; Vertical sample melted and the cmgled sample began to melt, but held shape with some shrinkage. Vertical sample began to run downwards and brazed to steel bars together.

Conclusion:

I've vehicle restrained slumping and allowed the paste to retain its shape up to melting -temperature of the alloy. Not all complies melted, possibly because of the large -thermal mass of the steel bars.

This example is to test stinter a bronze part for application to the Anatoli Michelson hollow core mold process using a thinner porous core mold using a bronze paste.
me paste was made in the manner illustrated in the preceding examples according to the following formulation:

Copper Powder 77 wow Tin Powder 8~5 w/%
No slump Vehicle (Example Al) 14.5 wow The paste WAS hand applied to refractory shapes in a thickness ranging from 0.125 -to 0.?.5". One refractory shape was a graphite triangle and the other an etched alumina rod.
The samples were placed on a thin alumina substrate on a belt Ursa under -the following conditions.

I
~52-Belt Spree Mooney.
Preheat 600F. (nvlO miss.) Hot %one1540F. (I 15 wins.) Atmosphere Dissociated ammonia The parts were sistered. Wren the graphite triangle (spacer) was cut in half, the bronze separated and showed good surface integrity.
Slight slumping was observed It was indicated in this example that the sistering time my temperature were not optimal, kit the concept worked.

The instant vehicles also are useful for swilled "functional"
or "thick film" pastes for mieroeleetronie circuit predation. These pastes often contain very finely-divided noble or non-noble elemental metals and alloys and metal chides such as those of ruthenium, lead, etc., to modify resistivity; glass forming or oeramie-for~ing powder is a fundamental component of such pastes. They usually are screen-printed and fired on a substrate to obtain effective adhesion of the powdered components one to another and to a substrate.
The fired products are used as dielectrics, conductors, resistors, and capacitors. Muir paths for conducting electricity need good line definition. mere fore, lack of significant hot slump and accompanying shape change and thickness change Fran the original paste deposit(s) is essential], and the inventive vehicles can provide that control.
Their firing profile (time and temperature) often is delicate and different for various oempositions and substrates. Typically wiring peacock temperature, for example, with a platinun~silver alloy ox ~llaclL~gold alloy powder-containing paste on an alumina slibs-trate to mice a conductor will be 850-950C.; for soda lime glass substrate such puke is 550-660C.; for porcelain-enameled steel substrates such puke is 625-675C.

he petal or alloy powder in those special pastes usually is smaller -than 10 microns in effective diameter, often being as fine as 2 microns or of sub micron size. Normally such powder is spherical;
sometimes it is in the form of flake. The powder components useful here can include pure gold, silver, copper, etc., as well as an alloy containing same, or can be all glass~Eormers or ceramic-forming go positions without elemental metal content. The vehicle for such paste is in minor proportion relative to that of -the powdered components to be adhered together by the firing. Gold, plating and palladium Lo containing pastes usually cure fired in air, while copper-bearing ones are wired in a protective atmosphere such as nitrogen.
Without the necessary anti slump systems of this inversion, the hydrocarbon itself imparts no significant anti-ho-t slump or molten metal flow restriction effects to pastes containing subject metal powders. However, ale presence of a relatively small proportion of an alkali particularly with a polyol and within the broad ranges herein-before described exerts substantially enhanced anti-hot slump effect and molten metal flow restriction effect than is exerted by the same anti slump system without the alkali and used in a larger proportion within said broad ranges.
Accordingly, it should be evident that one skilled in the art of formulating metal powder-bearing pastes now has a way for:
controlling hot slump to a user's desired specification by formulating for diminishing such slump modestly or even clear down to practically zero; and for imparting, where necessary or desired, restriction of wow of the molten metal anywhere from a modest desired proportion down to insig~Lficance. The combination -in the instant vehicle of hydrocarbon/antislump agent-flux system as defined herein provides such control.

Claims (73)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A nonaqueous noncorrosive inorganic salt free powdered metal soft solder paste composition containing from 75% to 95% by weight of a powdered soft solder metal or powdered soft solder metal alloy having an average particle size finer than 100 mesh (U.S. Standard Sieve Size) and from 5% to 25% by weight of a vehicle comprising a nonaqueous organic liquid having a surface tension of from 43 to 65 or more dynes/cm. at 20°C., and a noncorrosive anhydrous flux.

2. An improved essentially nonaqueous noncorrosive inorganic saltfree paste vehicle for soft solder metal powder, said vehicle comprising petrolatum in which is dispersed in a proportion effective for diminishing hot slump of said metal powder when it is compounded with said vehicle, a nonaqueous organic liquid, having a surface tension of from 43 to 65 or higher dynes/cm. at 20°C., and a noncorrosive anhydrous flux.

3. An improved essentially nonaqueous noncorrosive inorganic salt free paste vehicle for soft solder metal powder, said vehicle comprising petrolatum in which is dispersed in a proportion effective for diminishing hot slump of said metal powder when it is compounded with said vehicle, a base dispersed in a liquid polyol said polyol having a surface tension of from 43 to 65 or higher dynes/cm. at 20°C., and a noncorrosive anhydrous flux.

4. A nonaqueous noncorrosive inorganic salt-free powdered soft solder metal paste composition in accordance with claim 1, wherein the nonaqueous organic liquid is triethanolamine.

5. A nonaqueous noncorrosive inorganic salt-free powdered soft solder metal paste composition in accordance with claim 1, wherein the nonaqueous organic liquid is diethanolamine.

6. The vehicle of claim 3, in which said base is an amino alcohol in a proportion between about 2% and about 40%.

7. The vehicle of claim 6, in which said base is an amino alkane in a proportion between about 2% and about 40%.

8. The vehicle of claim 3, in which the base is sodium hydroxide in a proportion between about 0.05% and about 5%.

9. The paste of claim 1, comprising from about 75-95 parts of powdered tin-containing solder which melts below 330°C. and has a particle size not substantially larger than about 100 mesh.

10. The vehicle of claim 1, which consists essentially of petrolatum, a base and a polyol having a surface tension of from 43 to 65 or more dynes/cm. at 20°C. and is further characterized by the presence therein of a surfactant.

11. The vehicle of claim 1, which consists essentially of petrolatum, an alkali metal hydroxide and a polyol having a surface tension of from 43 to 65 or more dynes/cm. at 20°C.
and is further characterized by the presence therein of plasticizer or diluent.

12. The vehicle of claim 11, wherein at least a portion of said diluent is practically water insoluble.

13. The vehicle of claim 12, wherein said diluent comprises a phthalate ester.

14. The vehicle of claim 13, wherein said ester is dibutyl phthalate.

15. The vehicle of claim 11, wherein said diluent com-prises a terpene alcohol.

16. The vehicle of claim 3, compounded for use with soft solder powder wherein said base is an amine and the vehicle also contains carboxylic acid.

17. The vehicle of claim 16, wherein said carboxylic acid is polycyclic.

18. The vehicle of claim 17, wherein said carboxylic acid is cholic acid.

19. The vehicle of claim 17, wherein said carboxylic acid is a rosin acid.

20. The vehicle of claim 19, wherein said rosin acid is principally abietic acid.

21. The vehicle of claim 20, wherein said amine com-prises a water soluble alkanolamine.

22. The vehicle of claim 21, wherein said alkanolamine is triethanolamine.

23. The vehicle of claim 16, wherein said alkali com-prises triethanolamine, said carboxylic acid is cholic acid, and the vehicle is further characterized by the presence of surfactant and di-n-butyl phthalate diluent.

24. The vehicle of claim 2, wherein said liquid polyol comprises glycerine.

25. A nonaqueous noncorrosive inorganic salt free soft solder paste characterized by resistance to slumping during heating to the solder fusion point comprising:
a) from 75 to 95 weight parts per 100 parts of paste composition of a soft solder metal powder composition having a particle size of from -200 to +400 mesh (U.S. Standard Screen), b) from 25 to 5 weight parts heat liquefiable hydro-carbon ranging from semi-solid at room temperature to fugitive from the metal powder at the fusion temperature thereof, c) a nonaqueous organic liquid having a surface tension of from 44 to 65 dynes/cm. at 20°C. dispersed in said hydro-carbon, and, d) an amount of a noncorrosive flux for said soft solder sufficient to form a shiny and coherent residue of solder upon melting and solidifying said powdered soft solder.

26. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 25, wherein the flux is a basic reacting flux.

27. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 26, wherein the basic reacting flux is an amine.

28. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 27, wherein the amine is a trialkylamine in which the alkyl group is selected from the same or different alkyl groups containing from 2 to 6 carbon atoms.

29. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 28, in which the trialkylamine is triethylamine.

30. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 25, in which the flux is an alkali metal hydroxide or an alkali metal alcoholate.

31. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 30, in which the alkali metal hydroxide is dissolved in or reacted with the polyol.

32. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 30, in which the alkali metal hydroxide is sodium hydroxide.

33. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 25, in which the nonaqueous organic liquid is a polyhydric alcohol containing only the elements C, H, and 0.

34. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 33, in which the polyhydric alcohol is glycerine.

35. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 34, wherein the flux is an alkali metal hydroxide or alcoholate.

36. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 25, said paste being further characterized by the presence therein of from 0.5% to 10%
by weight of an alkanolamine.

37. A nonaqueous noncorrosive inorganic salt free soft solder paste as defined in claim 36, wherein the alkanolamine is triethanolamine.

38. The composition of claim 30, in which the alkali is sodium hydroxide in a proportion between about 0.05% and about 5%.

39. The paste of claim 25, comprising from about 75-95 parts of powdered tin-containing solder which melts below 330°C. and has particle size not substantially larger than about 100 mesh.

40. The paste of claim 31, which consists essentially of petrolatum and said alkali and is characterized by the presence therein of surfactant.

41. The paste of claim 31, which consists essentially of petrolatum and said alkali and is characterized by the presence therein of plasticizer or solvent diluent.

42. The paste of claim 41, wherein at least a portion of said diluent is water insoluble.

43. The paste of claim 42, wherein said diluent comprises a phthalate ester.

44. The paste of claim 43, wherein said ester is dibutyl phthalate.

45. The paste of claim 41, wherein said diluent comprises a terpene alcohol.

46. The paste of claim 25, which is further characterized by the presence therein of a carboxylic acid.

47. The paste of claim 46, wherein said carboxylic acid is polycyclic.

48. The paste of claim 46, wherein said carboxylic acid is cholic acid.

49. The paste of claim 46, wherein said carboxylic acid is a resin acid.

50. The paste of claim 46, wherein said resin acid is principally abietic acid.

51. The paste of claim 40, which is further characterized by the presence of an alkanolamine.

52. The paste of claim 51, wherein said alkanolamine is triethanolamine.

53. The paste of claim 39, wherein said alkali comprises sodium hydroxide and glycerine, said carboxylic acid is cholic acid, and the vehicle is further characterized by the presence of surfactant and di-n-butyl phthalate diluent.

54. The paste of claim 25, wherein said polyol is glycerine.

55. The paste of claim 25, wherein the flux/nonaqueous organic liquid system is 7% sodium hydroxide dissolved in 93% glycerine.

56. The paste of claim 51, wherein the alkanolamine is monoethanolamine.

57. The paste of claim 25, wherein the hydrocarbon is a hydrogenated polymeric hydrocarbon having a softening point in the range of 15° to 130°C.

58. A nonaqueous powdered metal paste characterized by resistance to slumping during heating to the fusion point of the metal moiety of the paste comprising from 60 to 90 parts by weight of a powdered metal, powdered metal alloy or a blend of powdered metals having a melting point above 500°C. and having a particle size less than 20 mesh (U.S. Standard Sieve Size), and from 0 to 39 parts by weight of a natural or synthetic hydrocarbon having a melting point above 15°C.
and below the fusion point of the metal or metal alloy powder, and from 0.5 to 40 parts by weight of a nonaqueous organic liquid compound having a surface tension of from 43 to 65 or higher dynes/cm. at 20°C.

59. A nonaqueous powdered metal paste as defined in claim 58, wherein the nonaqueous organic liquid compound is a polyhydric organic compound.

60. A nonaqueous paste as defined in claim 59, wherein the polyhydric organic compound is a polyhydric alcohol.

61. A nonaqueous paste as defined in claim 59, wherein the polyhydric organic compound is selected from diethanolamine and triethanolamine.

62. A nonaqueous paste as defined in claim 60, additional-ly characterized by the presence therein of an alkali metal hydroxide.

63. A nonaqueous paste as defined in claim 62, wherein the alkali metal hydroxide is sodium hydroxide.

64. A nonaqueous paste as defined in claim 62, wherein the polyhydric organic compound is glycerine.

65. A nonaqueous paste as defined in claim 58, wherein the powdered metal paste is a brazing paste and the metal is copper.

66. A nonaqueous paste as defined in claim 58, wherein the metal alloy is a copper alloy.

67. A nonaqueous paste as defined in claim 60, wherein the copper alloy is copper/silver alloy.

68. A nonaqueous paste as defined in claim 66, wherein the copper alloy is copper/iron alloy.

69. A nonaqueous paste as defined in claim 58, wherein the powdered metal blend is a mixture of copper powder and tin powder.

70. A nonaqueous paste as defined in claim 58, wherein the metal alloy is a hard facing nickel alloy.

71. A nonaqueous paste as defined in claim 58, wherein the hydrocarbon is petrolatum.

72. A nonaqueous paste as defined in claim 58, wherein the hydrocarbon is a hydrogenated hydrocarbon polymer.

73. A nonaqueous paste as defined in claim 58, also containing a metal oxide or a ceramic forming powder.