CA1042236A - Filler solder - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Filler solder for use on automobile bodies and the like and containing essentially the following constituents within the proportion ranges hereafter set forth:

The arsenic plus antimony in the solder should total at least 3.5%
but not exceed 6%. The solder is free of hard tin-arsenic plate-lets and free of an undesirable grittiness, which is attributed to the elimination of the tin-arsenic platelets. Due to its freedom from grittiness, the filler solder is readily applied to automobile bodies and the like for filling certain crevices and spaces in the sheet metal bodies as a smooth-surfaced deposit.

Description

~Z'~3~
This invention relates to filler solder and more especial-ly to new and improved filler solder especially adapted for use a8 a filler material or automobile bodies and ~he like, such f$11er qolder being readily applicable to the sheet 3teel of automobile bodies and the like as a substantially smooth-surfaced depo~it and without the formation of pits and pops in the subse~uent painting , . . .
and baking operations.
~ ead base iller solder alloy has b~en applied to auto-mobile bodies by partially melting the solder, ~tirring the partl-ally melt~d sold~r slightl~, and then applying the solder to th~heated and tinned automobile body as ~ viscous "mush". The soli-dus temperature, liquidus temperature, and volume fraction of liquid, as a function of temperature, are significant factors ln d~termining ease of application of the solder. For example, a solder alloy with a very narrow free~ing range would be dif~icult to control to a desirable volume raction of liquid to provide the desired fluidity or plasticity for easy application. A lead base filler solder preQently being employed on automobile bodies has the nominal composition of Pb-5%, Sb-1%, Sn-0.5~, As, an~ is about 25% eutectic by volume with a 38C. freezing range. Such a fil~er solder is disclosed in United States Patent 3,197,862 which dis-; closes body filler solders containing about 4.5t to 6% antimony, 0.3% to 0.6% ar~enic, 0.25~ to 3.5~ tin, balance substantially all lead.
~ he aforementioned prior art Pb-Sb-As-8n filler solder alloy has b~en the subject of customer co~plaints over the years in that the solder "mush" or plastic mass was gritty at the appli- -cation temperature and difficult to apply. ~he unde~irable gritti-ness of the filler solder was of su~h nature that one could actual-3~ ly eel the hard grit particles in the soft, semi-soliq mass of - filler solder. The workers applying the filler solder to the auto-mobile bodies complained about the grittiness of the solder, and that the gritty solder wa~ not easily applicable to the automo~ile 1, '.`

~ ~4'~Z;36 bodie~ as a smooth-surfaced deposit. Another customer complaint ~e- -garding the gritty filler solder ha~ been that the gritty solder alloy solidified in such manner on the automobile body as to result in the ormation of pits and pops in the solder in subsequent painting and baking operations. One plausible explanation advanced ; for the formation of the pits an~ pops has heen the dislodging of the grit particles from the solder ~urface ater application of th~
solder, leaving pits or indentations. Air is entrapped or occluded . , ; in the pits by the paint film during the painting, and the expan-sion of the heated occluded air during the baking results in the formation of the pops.
United States Patent 2,370,439 discloses a lead iller alloy for use on automotive vehicles and comprising between about

2 and 7% antimony, between about 0.04 and about 0.1% arsenic, between ahout 0.02% and about 0.07~ copper, between about 1% and about 4% tin, balance subs~antially all lead. United States Patent

3,644,115 relates to solder iller metal alloys comprising abou~
O.OOS to 0.2% aluminum, about 0.2 to 99% tin, remainder lead.
United States Patent 1,807,788 discloses lead base alloys of greater than normal hardness comprising about 1% to about 10% antimony, about 0.2~ to about 2% arsenic, and about 0.1~ to about 2~ tin, the tin content being about one-~ifth of the antimony content.
; United States Patent 2,351,477 discloses a wiping solder allo~ con-taining 61-67% lead, 20-26% bismuth, 10-16% tin, 0.05-.1S% arsenic and 0.1-1% antimony, together with incidental impurities. United ,:
` States Patent 2,439,068 discloses solder compositions consisting ; o about 20% tinr from above 0.005~ to about 0.5~ zinc, from about ' 0.5~ to about 1.1S% antimony, balance substantiall~ all lead.

United States Patent 2,191,624 relates to wiping solders containing between about 30% and about 40% tint between about 0.02~ and ahout 0.15~ arsenic, remainder lead together with incidental impurities.

United States Patent 2~29Q~237 is concerned with lead base coating alloy consisting o~ 0.2~-3~ antimony~ 0.2~-5% zinc7 1~~10% tin7 :

., bal~nce lead, with the zinc and lead totalling not le~ than 3~.
Oneobiect of the invention i5 to provide a new and im~
proveG filler solder for use on automobile bodies and the like which is free of grittiness, and hence is readil~ applicable to the sheet metal automobile bodies and the like as a smooth sur-faced deposit.
Another ob~ect of the invention is to provide a new and improved filler solder for u e on sheet steel automobile bodies ; and the like, which is free of grittiness due to its being free of an undesirable tin-arsenic phase and, more ~pecifically, free of undesirable hard tin-arsenic platelets.
.... ..
Another object is to provide a new and improved filler solder for use on automobile bodies which eliminates or sub tan-. ~ . , tially eliminates the undesirable pit and pop formation after :;;
painting and baking.
An additional object is to provide a filler solder characterized by possessing a ratio of volume fraction of solid (dendritic lead) to volume fraction of liquid at application temp-eratures such as to possess the desired plasticity or fluidity o~
the filler solder for easy~ trouble-free applica~ion to automobile , ~.. ..
bodies and the like.
A urther object is to provide a filler solder cha~ac-terized by having a wide reezing range which facilitates obtèn-J~ tion of the desired ratio of volume fraction of dendritic lead r~ ~solid) to volume fraction of liquid at the application temperature, such that the filler solder possesse the desired plasticity at the -~ application temperature for easy, ~rouble-free application to i~ automobile bodies and the like.
~ ~ .
~dditional objects and advantages will be readily apparent as the invention is hereinafter described.
We have found that the aforementioned grittiness and --, difficult application problems are minimized or eliminated and all of the aforementioned objects attained by a filler solder alloy ~.

Z3~
containing essentially the following consti~uents and in propor-tion~ within the following critical proportion ranges.
~ b~ ~eiqht -, - .
Antimony................... .1.5 to 5.3 Arsenic.................... Ø7 to 2,5 Tin........................ .maximum 0.20 Lead....................... ~ substantially the balance or remalnder The total of arsenic plus lead in the iller solder is critloally at least 3.5% and not in excess of 6%. The microstructure of the - alloy is free or substantially ree of a tin-arsenic phase and free or substantially free of hard tin-arsenic plateleks, and we attribute the improvements provided by the filler solder of thi~
invention in being free or substantially free o grittiness and hence readily applicable to sheet metal automobile bodies and the like as a smooth ~urfaced deposit to the absence of the tin-arsenic pha~e, and more speci~ically to the absen~e of the hard tin-arsenlc platelet~.
~he freedom or substantial freedom from grittiness and the ease of application to automobile bodies and the like as a smooth surfaced deposlt provided by the body filler ~older of this invention, as well as the elimination or substantial elimination of the pits and also the pOp5 after painting and baking provided by the filler solder herein were unexpected results.
The invention will now be particularly described with --reference ko the accompanying drawings, in which:
Figure 1 i~ a pho~omicrograph of a filler solder alloy o thi3 invention which is free of tin as a constituent, the photomicrograph being at 200X magnification:
Figure 2 is a photomicrograph of a filler solder alloy not of this invention and containing, by weight, 0.25% tin, the photomicrograph being at 200X magnification;
Figure 3 is an electron image of a conventional filler

-4- ~ -. ' 36 ~ :
~ solder allo~ not of this invention and cont~ining, by weight, 1%
,~ tin, the electron image being at 400X magnification and obtained ~; with a Scanning Electron Microscope;
Figure 4 is a photomicrograph showing the large, hard tin-arsenic platelets which had been filtered out of a solder alloy not o~ this invention and containing 2~ by weight tin, the photo-micrograph being at lX magniication;
Figure S is a photomicrograph of a solder alloy not o~
this invention and containing 4.90% by weight arsenic, the photo-~ ,, .
micrograph being at lOOX magnification.
The previously indicated 0.20% maximum of tin in thesolder of the invention is critical for the reasons that with amounts of tin in excess of 0.20% the undesirable tin-arsenic phase and the grittiness occurs in the solder. The 0.7% to 2.5%
range of ars~nic is also critical in the filler solders of this invention for the reasons that with an amount of arsenic in the solder much in excess of 2.5%, there is too great a volume frac-tion of liquid at the application temperature, i.e., ~here is too much li~uid in the filler solder at the application temperature relative to the solid therein. Due to the too great volume fraction of liquid, the filler solder is too liquid and does not have a suitable or proper plasticity for application to automobile bodies.
With an amount of arsenic in the filler solder substantially below 0.7%, there is in general either too great or too little volume fraction of liquid phase at the application temperature, i.e., too much or too little liquid phase is present in the solder at the application temperature relative to the solid therein, or an unde-~irably high liquidus temperature. B~ reason of the excessive or insufficient liquid phase being present, the filler solder is either too li~uid or too solid respectively and is not suitable -~
for application to automobile bodies due to not having a proper plasticity for such application. ~he l.S%-5.3~ of antimon~ is critical in the filler solders of this invention for the reason an --S-- , ,'. ~'' .

- ~4~
amount of antimony much above ~.3% cuts down the freezing range of the solder excessivelv and resul~ in too narrow a freezing range.
With the narrow freezing range, it is more dificult to obtain the ;proper ratio of volume raction of dendritic lead (solid) to volume fraction of liquid such as to attain a suitable or proper :: `
plasticity in the filler solder, at the application temperature, for application to automobile bodies. ~urthermore, an amount of antimony much above 5.3% in the solder results in an excessive volume fraction of liquid in the solder at the application tempera-ture~ i.e., the solder is too li~uid at the application tempera~ureto have the proper plasticity ~or application to automobile bodies.

, A guantity of antimony much below 1.5% in ~he filler solder herein results in an insufficient volume fraction of liquid phase therein~
; and the filler solder is too solid and does not have the desired fluidity or plasticity for ease of application.
It is critical that the total of arsenic plus antimony in tha solder alloys herein be at least 3.5% by weight but not more than 6% by weight for the following reasons: Alloys of this inven-tion containing in excess of a total of 6% of arsenic and antimony aontain too mu~h volume fraction of low-melting secondary phase~s) containing lead, arsenic and antimony. Consequently, excessive volume raction o liquid phase is present in the filler sold~r at ... .
the application temperature in the range of about 24SC. to 285C., and the filler solder is too fluid or liquid and does not have the desired plasticity for application to the automobile body. Alloys of this invention which contain less than a total of 3.5% of `~ arsenic and antimon~ contain insufficient low melting phase(s) con-taining lead, arsenic and antimony, and too much relativel~ high melting phase (dendritic lead). As a result, there is too little volume fraction of liquid phase and too much volume fraction of solid phase tdendritic lead) present at the application temperature in the range o about 245~. to 28SC., and the filler solder does not have sufficient fluidity or li~uidity to possess the desired , .
.~ .~ . .
.~ . , -~ 4;~;~3~i plasticity for application to automobile bodies. Furthermore, the presence of a total of arsenic plus antimony of less than 3.5% in the alloys of this invention results in liquidus temperatures con-siderably higher than 285C. and in excess of 300C., which are higher liquidus temperatures than desixable.
The filler solders herein are characterized by a wide ~ ;
freezing range corresponding to a liquidus of about 285C. and a solidus of about 245C.
The filler solders of this invention are characteriæed ; 10 by containing about 70 to about 80 per cent by volume dendritic ~ lead, which is the solid phase, and about 30 to about 20 par cent .,i ~, ,by volume li~uid phase. By virtue of containing such amounts of solid phase and liquid phase, the filler solders herein possess a desired plasticity at the application temperature for easy, trouble-free application to automobile bcdies and the like. This corresponds to a ratio of volume fraction of solid phase (dendritic lead~ to volume fraction of liquid phase in the filler solder of about 2.33~1 to about 4:1, respectively.
A grain refining agent may, if desired, be added to the ,. . .
solder alloy of this invention. ~he grain refining agent or grain refiner, as the agent is commonly referred to in the alloy art, is ` -added to the solder alloy in small amount which is sufficient to :. .
result in a ~iner grain size in the alloy. Any suitable grain re-fining agent can be utilizable. Sulfur is exemplary of the grain ~-refining agent and, when utilized, is added to the solder alloy heréin in typical amounts of about 0.003% to about 0.004% by weight of the sulfur, based on the total alloy composition. The grain re~iner is added to the solder alloy herein usually by being added to the molten alloy prior to supplying the molten alloy into a mold or molds.
~ he iller solder of this invention is produced by a method involving preparing a molten alloy containing essentially, by weight, 1.5% to 5.3% antimony, 0.7% to 2.5% arsenic, maximum 0.20% tin, the ~-7-..

. , . . : .. . . : ~ ~ .

~:
Z'~3~i balance substantially alL lead, and feeding or supplying the molten alloy into a mold or molds. The constituents can be melted together in a suitable vessel until the molten alloy is obtained or, if de-sired, the lead me~ed first and the remaining consti~uents, either as liquid melt or in solid form, added to or blended with the molten leadO If the remaining constituents are added in solid fo~m to the molten lead, they are melted while together with the molten lead by heat supplied b~ conventional and well known heating means. The , .
; molten alloy is then fed or supplied into a mold or molds, ordin-arily a metal mold or molds, and the alloy cooled to below its solidus temperature. The resulting solidified filler solder cast-ing is removed from the mold, and the microstructure of the solder alloy cas~ing is free or substantially free of the undesirable tin-arsenic phase and of the hard tin-arsenic platelets.
; The cooling of the filler solder alloy in the mold or molds is rapid and at a rate in excess of 20F. per second above the liquidus temperature of the alloy and at a rate in excess of 6F. per second in the temperature range between the liquidus and solidus tamperature of the alloy.
The molten alloy can be cast by any suitable casting procedure including continuous and non-continuous or static cast-ing. For example, the molten alloy can be cast continuously in a `~
wheel mold, such as a vertical wheel mold or a horizontal wheel mold, such as is disclosed in United States Patent 3,197,862 wherein an annular copper mold is formed as an annular groove in the upper surface o a rotable wheel. In the last-mentioned horizontal mold, a cooling water jacke~ is provided within the wheel portion for cooling the solder alloy at a rapid rate hereinbefore disclosed.
In casting in a vertical wheel mold, the molten solder alloy is gravity fed from a vessel to a groove in the metal rim of the wheel, and the solder rapidly cools and rapidly solidifies in the groove.
The solidified solder continuous strip is worked to reduce one of its transvérse dimensions 25% or more after leaving the horizontal .

3~
.;;., . "
wheel mold, or after leaving the vertical wheel mold. If a grain ~refiner has been added to the solder melt this continuous strip will ordinarily not be worked afker leaving the wheel mold but can be worked, if desired. The working can be effected by cold : ~ .
working such as by compressing in a press, such as a vertical reciprocating press, or by rolling between the rolls of a con-ventional rolling apparatus, whereby the thickness of the solder strip is reduced 25% or more and usually in the range of 2S% to 75%. The solder strip is ~hen cut into the desired length by a conventional cuk~ing blade. Alternatiyely, the liquid molten alloy can be cast by s~atic casting in the form of billets or pigs in a suitable metal mold, for instance a water-cooled copper ~-mold. The billets or pigs are extruded into filler solder bars or strips of the desired cross-sectional dimensions and usually , . ... . ..
to reduce their cross-sectional areas 75% or more, in a conven-tional press-extrusion apparatus. The solder strip is cut into predetermined lengths by means of a conventional cutting blade.
~ he filler solder alloy bars or lengths have a typical cross-section of 1/2" x 1~4".
A plurality of alloys were prepared of the compositions set forth in the table hereinafter set forth. ~he alloys were cast and microstructural analysis conducted on the alloys. The microstructural analysis included light and Scanning Electron Microscopic observation, as well as X-ray analysis. Light optics were used to determined the orm and, with certain alloy, relative amount of the primary phase. Scanning Electron Microscope and microprobe work was employed to determine the components and morphology of the phases. X-ray procedures were employed to de-termine the exact nature o~ the tin-arsenic phase found in the tin-bearing alloys. The liquidus and solidus points were also determined for each alloy. The results are set forth in the table which follows:

'` ~9_ ' ~ .

` ~4~6 .. , . .

~I r~ r~
,~ ~ o o ~, g ~ dY

_~
~ ~ æ~
~i ~ al u ~n 1~ u) u) ~ ,1 ~ u~

_ ~ ~ ~ æ ~ ~ æ ~ æ u, ': / 0~ ` 00 0 0 C~ O 1` ~ ~ ~D 1` 1--1` 1~

... .
, ~.

.~ Or~ oc~a~lnLn~n~u~c~c~ ~

O O U) O
0~o ~ ~ ~i o o o o c~ ~ o o o ~ ~ o o o ,i '" Q~ ::
In oo o o ~ ~ o c~
u~ n o o ~ a~ o o o o ocjo~o~al~t3Ln,1~ ,1 oc~oo .~ ~ 11 11 11 ".
~, ,~ # ~ # ~ ~ # r ~ ~: L ~
'''''. '~

`;.' ' ~342~36 The data of the foregoing table shows that wi~h tin contents of 0.25% and 1.0% in Alloy No.'s 17 and 18, respectively and tin con-tent of 1.5% in each of ALloy No.'s 1, 2 and 3, the tin-arsenic phase, believed to be Sn4As3, which was the undesirable phase, was prese~t. However in Alloy No.'s 15 and 16 of the table, which are filler solder allGys of the present invention and wherein the tin was present therein in amounts of only 0,01% and 0,05%, respective-ly, no tin-arsenic phase was present in the alloy. In Alloy No.'s

5, 6, 8, 9, 13 and 14 wherein the total of arsenic plus antimony was in excess of 6~ in each alloy, no dendritic lead, which is the relatively high melting phase, was present and the solder is too liquid and does not have the desired plasticity for application to automobile bodies. In Alloy No. 4 wherein the total of -arsenic plus antimony was less than 3.5%, too much relatively high melting phase, i.e., 92~ lead dendrites, is present in the alloy and insufficient low melting phase is present therein, and conse-quently there is too much volume fraction of solid phase and too little volume fraction of liquid phase present in the alloy at the application temperature in the range of about 245C. to about 285C., and the solder is too solid and does not have the desired plasticity for application to automobile bodies at the aforemention-ed application temperatures. Further the liquidus temperature of Alloy No. 4 of ~02C. is undesirably high. In Alloy No.'s 7, 15 and 16, which are alloys of this invention and wherein the total arsenic plus antimony is in the range of 3.5% to 6%, the alloy~
possess a proper ratio of volume fraction of solid phas~ (dendritic lead) to volume fraction of liquid phase at the application tempera-ture in the range of about 245C. to 285C. to have the desired plasticity for easy, trouble-free application to automobile bodies.
Referring to Fig, l which shows the microstructure of a filler solder alloy of the present invention which is free of Sn as a constitùent and contains, by weight 2% As, 2% Sb, balance Pb, the light-colored lead dendrites are shown at 10 and the dark-~42~6 colored low melting phases containing lead, arsenic and antimony at 11. With reference ~o Fig 2 showing the microstructure o~ a prior art filler solder alloy and containing, by weight, 2% As, 2% Sb, 0.25% Sn, balance Pb, the undesirable "islands-like" tin-arsenic phase are shown at 12, the ligh~-colored lead dendrikes at 10, and the daxk-colored low melting phases at 11~ Referring to Fig. 3 showing an electron image o~ the prior art filler solder alloy containing, by weight, 0.5~ As, 5% Sb, 1,5% Sn, balance Pb, a continuous network of the undesirable tin-arsenic phase in the form of hard pla~elets of the tin-arsenic phase, believed to be -~ Sn~As3, is shown a~ 13. We found the hard platelets of the tin-arsenic phase when present in an extruded form or shape of a ;~
rapidly cooled filler solder not oE this invention and containing in excess of 0.20% by weight tin, and also antimony, arsenic, balance substantially all lead, to have a mean largest dimension in excess of 0.001 inch, and a hardness in excess of a 450 Vickers Hardness Number (100 gram load~, as determined by A.S.T.M. designa-tion E-92 which is the Standard Method of Test for Vickers Hardness -of Metallic Materials, In obtaining the photomicrograph of Fig, 4, a solder alloy containing, by weight, 2% tin, 4% arsenic, 2~
antimony, balance lead was melted and then filtered to filter out the large hard tin-arsenic platelets. The separated tin-arsenic platelets, which retained some lead between the platelets, were subsequently remelted and cast in a mold. The hard tin-arsenic platelets are shown at 14. With reference to Fig. 5 showing an alloy containing, by weight, 4.90~ arsenic, 2.13% antimony, balance lead, antimony-arsenic crystals are shown at 15, secondary lead at 16 and other antimony-arsenic phases at 17. Antimony-arsenic -crystals 15 are undesirable, large, hard crystals having typical largest dimension in excess of .001". The presence of the large, hard antimony-arsenic crystals was attributed to the xelatively large amount of arsenic, which was considerably in excess of the 2.5~ upper limit of arsenic, The presence o these large, hard ',''",,:

--\ :
z3~
.~ antimony-arsenic crystals is undesirable as they are believed to contribute to the grittiness problem which is overcome by the filler . solder of the present invention. The alloys of Figs, 1-5 were etched in a mixture of acetic acid and hydrogen peroxide prior to taking the photomicrograph or electron image.
Incidental impurities may be present in the solder alloys : here. The incidental impurities are exemplified by one or more of copper, bismuth, ailver, tellurium, selenium and suliur, , ' '. ' , .

' , ~ .
;, . ' . ' .~ ' ' .

~, , ;., .
: ' :, ': ,'~

, . ~- . - . . ... ..

.,., -

Claims (6)

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

1. A filler solder containing essentially the following constituents in proportions within the proportion ranges hereafter set forth:

the total arsenic plus antimony being at least 3.5% but not more than 6%, the solder being substantially free of hard tin-arsenic platelets and free of an undesirable grittiness due to elimination of the hard tin-arsenic platelets, the solder having a freezing range corresponding to a liquidus of about 285°C. and a solidius of about 245°C., and a plasticity at an application temperature within the about 245°C. to about 285°C. freezing range such as to enable the solder plastic mass to be readily applied to an automobile body.

2. The solder of claim 1, containing, at the application temperature within the about 245°C. to about 285°C. range, about 70% to about 80% by volume of dendritic lead and about 30% to about 20% by volume of liquid phase.

3. The solder of claim 2, wherein the solder is free of tin as a constituent.

4. The solder of claim 2, also containing a grain refining agent.

5. The solder of claim 4, wherein the grain refining agent is sulfur.

6. The filler solder of claim 2,in the form of a bar.