WO2002004549A1

WO2002004549A1 - Heat-resistant formulation and method for using same

Info

Publication number: WO2002004549A1
Application number: PCT/US2001/040761
Authority: WO
Inventors: Vu V. Lam; Stephen E. Cantor; Andrew G. Bachmann
Original assignee: Dymax Corporation
Priority date: 2000-07-11
Filing date: 2001-05-18
Publication date: 2002-01-17
Also published as: AU2001263505A1

Abstract

A water-soluble, highly washable coating that is especially suitable for use as a solder-resist mask is produced from a polymerizable formulation comprised of polyvinylpyrrolidone, n-vinyl-2-pyrrolidone, polyethylene oxide, glycerol, and a carbohydrate selected from sorbitol, a cyclodextrine compound, fructose, xylose, starch, and mixtures thereof.

Description

Heat-resistant formulation and method for using same

BACKGROUND OF THE INVENTION Resinous coatings are commonly used to provide physical and chemical barrier protection for a wide variety of surfaces, structures, articles, and the like, both during the course of production and also subsequent thereto. The extensive manufacture of printed circuit boards (PCBs) and other such electrical and electronic devices has given rise to a particularly important application for such coatings, that being in the provision of solder resists, or maskants. It is well known in the art that such resist coatings may be of either a permanent or temporary nature, removable in the latter instance by aggressive hot water washing or by use of a chemical solvent; it is also well known that the coatings may be produced from formulations that solidify or cure through a variety of mechanisms, including air-drying, thermal activation and/or photopolymerization.

The properties that a satisfactory coating formulation of this nature must exhibit will vary from case to case, but in general the following will be deemed desirable, if not essential, characteristics: fast cure, good homogeneity and shelf-life (especially with stability against separation), suitable rheological properties (e.g., smooth flow, with maintenance of shape as applied), low volatility, unobjectionable odor, non-toxicity, non-allergenicity, and non-flammability; the cured coating should exhibit, in particular, good adhesion and good resistance to deterioration under prevailing chemical, thermal, and humidity conditions. When the coating is to be a temporary one, moreover, speed, thoroughness, and facility of removal (i.e., good washability) will usually be of primary concern, and the removed deposit (including solid particles, and solute molecules and ions) must not unduly contaminate, clog, or otherwise disable downstream treatment units (e.g. , beds or columns for removing heavy metals and organic materials from the wash water, molecular sieves, etc).

Needless to say, in those instances in which the formulation is intended specifically for use as a solder resist the cured coating must be able to withstand the heat of the molten solder for at least a minimal period of time (e.g., 500° Fahrenheit for five seconds, and preferably at least 550° for ten seconds or longer), without substantial charring or other degradation, swelling, or displacement on or from the substrate; indeed the industry norm for wave solder bath temperatures now defines a preferred range of about 550° to 600°F. A fully satisfactory solder maskant must, in addition, be resistant to solder flux and other chemicals, and must not be wetted significantly by the solder.

Packer et al. U.S. patent No. 4,215,025 discloses water-soluble adhesive coatings for mounting components to printed wiring boards, which consist of a water-soluble alcohol, water, a wetting agent, and a water-soluble, keto group-containing acid of specified structure.

Grosclaude et al. U.S. patent No. 5,225,315 provides a water-soluble solder resist formulation, which preferably contains n-vinyl-2-pyrrolidone, N,N-dimethylacrylamide, and polyvinylpyrrolidone. The U V-curable temporary solder mask taught in Unruh U.S. patent No. 5,420,171 is characterized as containing a reactive diluent monomer, a surfactant, an antioxidant, a water-soluble polymer, a thickener, and a photoinitiator.

SUMMARY OF THE INVENTION Despite the activity in the art exemplified by the foregoing, no formulation described or heretofore available is believed to adequately satisfy the currently applicable criteria for a solder resist, or for a similar material that is suitable for use in producing a high temperature, water-soluble coating or other deposit.

Accordingly, it is the broad object of the present invention to provide a novel formulation and method for producing a water-soluble deposit upon a substrate, particularly a deposit that is adapted for withstanding high temperatures and for functioning as an effective solder resist maskant. It is also an object of the invention to provide such a formulation and method by which the deposit produced can be readily, thoroughly, and rapidly removed, using relatively mild washing conditions, which formulation produces, upon dissolution, a water stream that does not unduly contaminate, clog, or otherwise disable downstream water-treatment materials or units. Additional objects are to provide such a formulation which is homogeneous and stable against separation and readily applied to a substrate, and which affords fast and complete cure, good adhesion to the underlying surface in the cured state, and excellent resistance to deterioration and displacement.

It has now been found that certain of the foregoing and related objects of the invention are attained by the provision of a formulation broadly comprising, on a weight basis, about

20 to 60 parts of at least one ingredient that is polymerizable to produce a water-soluble solid, preferably n-vinyl-2-pyrrolidone, 2 to 40 parts of a carbohydrate selected from the group consisting of sorbitol, cyclodextrine compounds, fructose, xylose, starch (inclusive of modified starches) and mixtures thereof, and about 25 to 95 (but generally not more than 70) parts of at least one water-soluble ingredient for controlling the rheology and physical stability of the formulation, the formulation being polymerizable to produce a solid deposit.

Three classes of compounds exemplify the rheology-controlling and separation-stabilizing ingredients that are suitable for use herein; i.e. : (1) glycerol, propylene glycol, glyceraldehyde, poly (ethylene glycol), and poly(propylene glycol); (2) polyethylene oxide and polypropylene oxide; and (3) polyvinylpyrrolidone (PVP), poly (2-ethyl-2-oxazoline), poly(methylvinyl ether/maleic anhydride) copolymer, and poly(vinylpyrrolidone/vinyl acetate) copolymer.

Preferably, the formulation will include at least one member selected from each of the three classed defined, and most desirably it will contain 1 to 10 parts of glycerol, 2 to 20 parts of polyethylene oxide, and 20 to 60 parts of polyvinylpyrrolidone; the preferred carbohydrates are sorbitol and the cyclodextrine compounds. The amount of polyvinylpyrrolidone (or equivalent compound) contained in the formulation will preferably be 25 to 40 parts, and most desirably 28 to 35 parts; the amount of n-vinyl-2-pyrrolidone (or equivalent compound) will preferably be 25 to 40 parts, and most desirably 28 to 35 parts; the amount of the selected carbohydrate will preferably be 10 to 30 parts, and most desirably 15 to 25 parts; the amount of polyethylene oxide or polypropylene oxide will preferably be 5 to 12 parts, and most desirably 7 to 10 parts; and the amount of glycerol (or equivalent compound) will preferably be 2 to 8 parts and most desirably 3 to 6 parts. As will be evident to those skilled in the art, although ingredients incorporated into the formulation for controlling rheology, and/or stability against separation, may be available in a wide range of molecular weights, polymers in the lower regions of those ranges will generally be utilized to ensure good solubility.

The formulation of the invention will normally include an effective amount of a free-radical generating thermal catalyst and/or photoinitiator for initiating polymerization of its polymerable ingredient or ingredients, usually along with an effective amount of a stabilizer for preventing premature reaction. The amount of catalyst employed will typically be 1 to 5 parts, preferably 2 to 4 parts, and most desirably 2 to 3 parts, and the amount of stabilizer will typically be 0.01 to 5 parts, preferably 0.05 to 2 parts, and most desirably 0.01 to 1 part. The formulation will advantageously include about 0.01 to 0.1 part by weight of at least one, preferably biodegradable, dye or pigment, and it may contain other ingredients as well, such as supplemental viscosity control agents, thixotropic agents, desiccants, and the like.

Other objects of the invention are attained by the provision of a method for producing an article comprising, as a first step, the application to the surface of a substrate a formulation having the composition and properties herein described. Subsequent steps of the method include effecting curing of the applied formulation to produce a solid deposit on the surface, and washing of the surface to effect removal of the deposit.

In most embodiments of the method the deposit will be of such nature as to permit immersion of the deposit-bearing substrate in a non-aqueous liquid material at a high temperature for a period of at least five seconds, with the solid deposit remaining securely bonded to the substrate and substantially undegraded in consequence of the immersion step. Preferably, the deposit will be of such character as to allow immersion in such a liquid at a temperature in excess of 500°F., for a period of at least about ten seconds, and most desirably the deposit will withstand a temperature of at least about 550°F. for a period of 15 seconds or longer.

In those instances in which the formulation is composed to function as a solder resist, or for similar masking purposes, the method is carried out by applying it to at least a first portion of the surface of a substrate while leaving at least a second, discrete surface portion uncoated. After effecting curing of the formulation, molten solder is applied and allowed to harden, and the surface is then washed with water to remove the deposit. The substrate used to produce a PCB will of course be a suitable board, and the hardened solder will define electrically conductive paths. The method may include a further step of gradually heating the deposit-bearing substrate, prior to immersion in the hot solder, to temper the deposit so as to reduce cracking and delamination. When the maskant formulation contains a photoinitiator, curing will of course be effected by exposure of the surface to actinic radiation of appropriate wavelength.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Exemplary of the efficacy of the present invention are the following Examples, wherein all parts and percentages specified are on a weight basis: EXAMPLE ONE The ingredients listed in Table One, which follows, were combined in the percentages set forth and thoroughly mixed to provide a series of maskant formulations, A-E. The abbreviations used in the Table have the following meanings: NVP = n-vinyl-2-pyrrolidone; PVP = polyvinylpyrrolidone, of nominal molecular weight 30,000; PEO = polyethylene oxide, of nominal molecular weight 10,000; MD 1024 = IRGANOX MD 1024 antioxidant; CGI 173 = DAROCUR 1173 UV-responsive photoinitiator (both IRGANOX MD 1024 and DAROCUR 1173 are products of Ciba-Geigy Chemical Corporation); PTZ = phenothiazine (10 percent solution); and the pigment is an organic red pigment diluted to four percent in NVP. The viscosity values for the formulations, in centipoise, are set forth in the Table, and in each instance the formulation remained stably homogeneous after standing at room temperature for a period of at least 24 hours.

A 40-mil coating of each of the formulations A-E was applied, by spraying, to discrete areas on the surface of standard fiberglass-reinforced PCBs. The deposits were cured by exposure to UV radiation for a period of about 2 to 25 seconds (depending upon the intensity of the radiation dosage delivered), and the coated substrates were tempered by passage through an oven to gradually heat them to a temperature of 200° to 400°F., in accordance with prevailing industry practices. Each sample was then immersed in solder at about 550°F., contained in a wave bath, for a period of about ten seconds. Upon inspection after removal from the bath, none of the maskant coatings appeared charred or otherwise degraded, nor was there any evidence of separation or displacement from the substrate surface.

The samples thus produced were subjected to moisture absorption tests in which they were exposed to air of 55 and 66 percent absolute humidity and a temperature of 77°F. ; inspections were made after exposures of 24 hours and 120 hours. In all instances (except the most extreme) water uptake was 3 to 4.5 percent (based upon the weight of the coating), and the surface was dry and tack-free. The 120-hour exposure at 66 percent humidity resulted in an uptake of water of about 15 to 16 percent, and produced some surface tackiness.

The coated samples were washed in a domestic dishwashe'rγ using water at 110°F. , thereby effecting complete removal of the cured maskant within a period of six minutes or less. The coatings also showed complete solubility in water. TABLE ONE

Additional tests carried out show that the omission of sorbitol (or a functionally equivalent carbohydrate, as discussed below) results in a formulation that is incapable of producing a cured coating having requisite high-temperature properties, and that also exhibits deficient washing properties. The glycerine, PEO, and PVP contribute, to varying degrees, to the physical uniformity, rheology, and stable homogeneity of the formulations and the cured deposits; at least one of such ingredients, and preferably a representative member of each of the three classes defined, was found to be necessary to avoid undesirable separation of the uncured formulation.

EXAMPLE TWO .._

The sorbitol contained in Formulation A of Example One is replaced by each of the following carbohydrates: beta-cyclodextrine, fructose, xylose, starch (from corn), mannose, lactose, maltose, sorbose, and sucrose. After being applied, cured, tempered, and subjected to hot solder in the manner and under the conditions described in the foregoing EXAMPLE, the cured deposit produced from the formulation containing beta-cyclodextrine survives without significant degradation or displacement from the substrate; alpha-cyclodextrine and gamma-cyclodextrine are expected to function equivalently, as are mixtures of cyclodextrines with one another and with sorbitol (and perhaps with other carbohydrates as well). The fructose- and xylose-containing formulations also resist displacement from the substrate, but are somewhat charred and deteriorated; each of the other formulations produces a cured deposit that fails to satisfy both criteria by which a satisfactory, very high temperature solder-resist maskant is defined herein. Repeating the foregoing tests, using however solder at about 500°F. , the fructose-, xylose-, and starch-containing formulations functioned substantially equivalently, and were all satisfactory. They resisted displacement and were only somewhat charred and deteriorated after ten-seconds' exposure, and were less so after five seconds.

EXAMPLE THREE Formulations A-E of EXAMPLE ONE are prepared and tested in the manner described, substituting however for the ingredients that are representative of groups (1), (2), and (3), described above, each of the other members of the represented group. In all instances the resultant formulation is found to function satisfactorily as a maskant, in accordance with the invention.

EXAMPLE FOUR

Solder-bearing PCBs, masked with each of formulations A-E of EXAMPLE ONE, are subjected to washing in a closed-loop washing line to effect removal of the maskant and metallurgical and other residual substances. The multiple-effect washing unit consists essentially of prewash, wash, rinse, final rinse, and drying zones, connected in line and adapted for passage of soldered boards moving seriatim, starting at the prewash zone.

The water is introduced into the final rinse zone (ahead of the drying zone) at a temperature of about 140°F. and with a contaminants concentration of about 0.25 to 1.0 ppm; it exits from the prewash zone at about 120°F. and with a contaminants concentration of about 25 to 50 ppm, and it is sprayed upon the boards in each of the several intervening effects, at a pressure of about 40 psi. The water leaving the prewash zone is cleansed and desalted by passage through several beds, including (in sequence) beds for extracting heavy metals, organics, cations, and anions; the water is then reheated as necessary to bring it to its operating temperature. Upon inspection, chemical contamination or depletion, physical clogging or fouling, and general disablement of the several beds (i.e., of activated carbon, molecular sieve materials, etc.) is found to be at relatively low levels and, in at least certain respects, to exceed industry norms. Thus, it is believed that use of the maskant formulations of the instant invention extends significantly the lives of some, if not all, of the water-treatment beds employed (and, perhaps most significantly, the life of the heavy metal-extraction bed), thereby reducing substantially the inconvenience and expense of replacing and/or regenerating those beds.

Although n-vinyl-2-pyrrolidone is deemed to constitute the preferred matrix-forming monomer for use in the instant formulations, other monomers (and/or oligomers) that polymerize to produce water-soluble resins may be found suitable, alone and in combination with one another; possible substitutes for and supplements to NVP include hydroxyethyl(meth)- acrylate, hydroxypropyl(meth)acrylate, methacrylamidopropyltri ethyl ammonium chloride, dimethylaminoalkyl(meth)acrylate and trimethylaminoalkyl(meth)acrylate, and quaternary salts (such as the methane sulfonic acid salts) thereof, N-methylolmethacrylamide, (meth)acrylamide, and derivatives thereof, such as dimethylaminopropylacrylarnide, dimethylacrylamide, 2,4-pentadiene-l-ol, (meth)acrylic acid, itaconic acid, maleic acid, crotonic acid, sodium styrene sulfonate, 2-trimethylammonium ethylacrylate chloride, ammonium sulphaloethyl methacrylate, polyalkyleneglycol(meth)acrylates and di(meth)- acrylates, glycerol(meth)acrylate, etc. The choice of suitable such compounds, and specific combinations thereof, will be apparent to or readily determined by those skilled in the art.

While polyvinylpyrrolidone, typically having a molecule weight ranging from 15,000 to 90,000, and polyethylene oxide, typically having a molecular weight in the range 10,000 to 200,000, are preferred water-soluble polymeric fillers, alternatives for these ingredients are mentioned above and others may additionally be found, potentially being selected for example from the following: polymers of acrylic and methacrylic acid, sodium carboxymethylcellulose, cellulose ethers such as hydroxyethylcellulose, hydroxypropylcellulo- se, methylcellulose and ethylcellulose, ethyleneimine, and vinyl alcohol. Needless to say, any water-soluble resin produced from one or more of the monomers listed hereinabove will generally also be suitable for use as a polymeric filler in the instant formulations.

The formulation may include drying agents (e.g., sodium and magnesium sulfate, sodium carbonate, sodium bicabonate, and calcium chloride), supplemental viscosity control and thixotropic agents (e.g., silica gel, amoφhous silica, talc, clay), fillers (in addition to the polymers mentioned above) that serve to increase water solubility (e.g., gelatin, pectin, acacia, and other vegetable gums), and organic pigments and colorants. Specific ingredients and amounts will be evident to those skilled in the art based upon the present specification, and need not therefore be discussed in further detail; generally, however, the total amount of water-insoluble ingredients incorporated will not exceed ten weight percent.

The cured deposit will normally be completely removable by washing for a period of five to ten minutes in warm, to hot, water (e.g. , water at 70° to 175° F.). The wash water may be applied by any suitable means, but commercial equipment, employing spraying or other washing techniques, will generally be used to good effect.

The functioning of carbohydrates to increase thermal stability, in accordance with the present invention, is quite suφrising because such compounds tend to decompose readily, or to undergo other alterations, at temperatures much lower than those that are typically maintained in a solder bath, as for example in the making of caramel or molasses. It is notable too that the polyethylene oxides(s), and other oxygenated rheology additives used herein, which would normally decompose at 500° to 600°F., also evidence of a measure of thermal protection in the present system.

It will be understood that, while being especially advantageous for the production of solder-bearing articles, the formulation and method of the invention are not so limited. Rather, they can be utilized for the production of a removable, water-soluble coating or other deposit for virtually any puφose; e.g. , to serve as a water-soluble adhesive such as for the temporary tacking, bonding, or mounting of a component, to serve as a removable marking system, to provide temporary spacers, for potting, to serve as a readily removable protective barrier layer, etc. Finally, it is to be noted that the wafer-soluble formulations described herein need not contain any organic or inorganic substances that are classified as toxic in governmental waste-discharge testings. The dissolved deposits show a neutral pH in concentrations as high as 20 percent, and conventional procedures can be used for waste-water treatment.

Thus, it can be seen that the present invention provides a novel formulation and method for producing a water-soluble deposit upon a substrate, which deposit is particularly adapted for withstanding high temperatures and for functioning as an effective solder resist maskant. The cured deposit can be readily, thoroughly, and rapidly removed, using relatively mild washing conditions, to produce a water stream that does not unduly contaminate, clog, or otherwise disable downstream water-treatment materials or units. The formulation of the invention is homogeneous and stable against separation, and is readily applied to the substrate; it affords fast and complete cure, good adhesion to the underlying surface in the cured state, and excellent resistance to deterioration and displacement.

Claims

THE CLAIMSHaving thus described the invention, what is CLAIMED is:

1. A formulation for producing a highly water-soluble, water-washable, and heat- resistant deposit upon a substrate, comprising, on a weight basis: about 20 to 60 parts of at least one ingredient that is polymerizable to produce a water-soluble solid; about

2 to 40 parts of a carbohydrate selected a first group consisting of sorbitol, cyclodextrine compounds, fructose, xylose, starch, and mixtures thereof; and about 25 to 95 parts of at least one water-soluble ingredient for controlling the rheology and physical stability of said formulation, said formulation being polymerizable to produce a solid deposit.

2. The formulation of Claim 1 wherein said polymerizable ingredient is n-vinyl-2- pyrrolidone.

3. The formulation of Claim 1 wherein said carbohydrate is at least one of sorbitol and cyclodextrine compounds.

4. The formulation of Claim 1 wherein said ingredient for controlling rheology and stability is at least one compound selected from at least one of a second group, a third group, and a fourth group; said second group consisting of glycerol, propylene glycol, glyceraldehyde, poly(ethy!ene glycol), and poly ropylene glycol); said third group consisting of polyethylene oxide and polypropylene oxide; and said fourth group consisting of polyvinylpyrrolidone, poly(2-ethyl-2-oxazoline), poly (methyl vinyl ether/maleic anhydride) copolymer, and poly(vinylpyrrolidone/vinyl acetate) copolymer.

5. The formulation of Claim 4 wherein said ingredient for controlling rheology and stability includes at least one member from each of said second, third, and fourth groups.

6. The formulation of Claim 5 wherein said at least one members are 1 to 10 parts of glycerol, 2 to 20 parts of polyethylene oxide, and 20 to 60 parts of polyvinylpyrrolidone.

7. The formulation of Claim 1 additionally including an effective amount of a free- radical generating catalyst for initiating polymerization of said at least one polymerable ingredient, and an effective amount of a stabilizer for preventing premature reaction of said polymerizable ingredient.

8. The formulation of Claim 7 wherein said effective amounts of said catalyst and stabilizer are, on a weight basis, 1 to 5 parts and 0.01 to 5 parts, respectively.

9. The formulation of Claim 7 wherein said catalyst comprises a photoinitiator.

10. The formulation of Claim 8 additionally including about 0.01 to 0.1 part by weight of at least one organic dye or pigment.

11. A formulation for producing a highly water-soluble, water- washable, and heat- resistant deposit upon a substrate, comprising, on a weight basis, 20 to 60 parts of polyvinylpyrrolidone, 20 to 60 parts of n-vinyl-2-pyrrolidone, 2 to 40 parts of a compound selected from a first group consisting of sorbitol, cyclodextrine compounds, fructose, xylose, starch, and mixtures thereof; 2 to 20 parts of polyethylene oxide, and 1 to 10 parts of glycerol, said formulation being polymerizable to produce a solid deposit.

12. The formulation of Claim 11 wherein said amount of polyvinylpyrrolidone is 25 to 40 parts, said amount of n-vinyl-2-pyrrolidone is 25 to 40 parts, said amount of said compound selected from said first group is 10 to 30 parts, said amount of polyethylene oxide is 5 to 12 parts, and said amount of glycerol is 2 to 8 parts.

13. The formulation of Claim 11 wherein said amount of polyvinylpyrrolidone is 28 to 35 parts, said amount of n-vinyl-2-pyrrolidone is 28 to 35 parts, said amount of said compound selected from said first group is 15 to 25 parts, said amount of polyethylene oxide is 7 to 10 parts, and said amount of glycerol is 3 to 6 parts.

14. The formulation of Claim 11 additionally including an effective amount of a free-radical generating catalyst for initiating polymerization of polymerable ingredients of said formulation, and an effective amount of a stabilizer for preventing premature polymerization of said polymerizable ingredients.

15. The formulation of Claim 14 wherein said effective amounts of said catalyst and stabilizer are, on a weight basis, 1 to 5 parts and 0.01 to 5 parts, respectively.

16. The formulation of Claim 14 wherein said catalyst comprises a photoinitiator.

17. The formulation of Claim 16 additionally including about 0.01 to 0.1 part by weight of at least one organic dye or pigment.

18. In a method for producing an article, the steps comprising:

(a) applying to the surface of a substrate a formulation for producing a water-soluble, heat-resistant deposit, comprising, on a weight basis: about 20 to 60 parts of at least one ingredient that is polymerizable to produce a water-soluble solid; about 2 to 40 parts of a carbohydrate selected from a first group consisting of sorbitol, cyclodextrine compounds, fructose, xylose, starch, and mixtures thereof; and about 25 to 90 parts of at least one water-soluble ingredient for controlling the rheology and physical stability of said formulation, said formulation being polymerizable to produce a solid deposit.

(b) effecting curing of said applied formulation, to produce a solid deposit on said surface; and (c) washing said surface with water to effect removal of said deposit.

19. The method of Claim 18 including the additional step, effected intermediate said steps (b) and (c), of (d) immersing said deposit-bearing substrate in a non-aqueous liquid material at a high temperature for a period of at least five seconds, said solid deposit remaining securely bonded to said substrate and substantially undegraded in consequence of said step (d).

20. The method of Claim 19 wherein said temperature is in excess of 500°F.

21. The method of Claim 19 wherein said temperature is at least about 550°F. , and wherein said carbohydrate is selected from sorbitol, cyclodextrine compounds fructose, xylose, and mixtures thereof.

22. The method of Claim 21 wherein said period is at least about ten seconds.

23. The method of Claim 18 wherein, in said step (a), said formulation is applied to at least a first portion of the substrate surface while leaving at least a second, discrete portion free thereof.

24. The method of Claim 21 wherein, in said step (a), said formulation is applied to at least a first portion of the substrate surface while leaving at least a second, discrete portion free thereof, and wherein said liquid material is molten solder.

25. The method of Claim 24 wherein said substrate is the substrate for a printed circuit board, and wherein said method includes the further step, effected intermediate said steps (b) and (d), of gradually heating said deposit-bearing substrate to a temperature in the range 200° to 400°F.

26. The method of Claim 18 wherein said formulation contains a free-radical generating photoinitiator for effecting reaction of said at least one polymerizable ingredient thereof, and wherein said step (b) comprises exposing said formulation to actinic radiation to which said photoinitiator is responsive for generating free radicals.

27. In a method for producing an article, the steps comprising: (a) applying to the surface of a substrate a formulation for producing a water-soluble, water-washable, heat-resistant deposit, comprising, on a weight basis, 20 to 60 parts of polyvinylpyrrolidone, 20 to 60 parts of n-vinyl-2-pyrrolidone, 2 to 40 parts of a compound selected from a first group consisting of sorbitol, cyclodextrine compounds, fructose, xylose, starch, and mixtures thereof, 2 to 20 parts of polyethylene oxide, and 1 to 10 parts of glycerol, said formulation being polymerizable to produce a solid deposit. (b) effecting curing of said applied formulation, to produce a solid deposit on said surface; and

(c) washing said surface with water to effect removal of said deposit.

28. The method of Claim 27 including the additional step, effected intermediate said steps (b) and (c), of (d) immersing said deposit-bearing substrate in molten solder at a temperature in excess of 500°F. for a period of at least five seconds, said solid deposit remaining securely bonded to said substrate and substantially undegraded in consequence of said step (d), said formulation being applied to at least a first portion of the substrate surface while leaving at least a second, discrete portion free thereof.

29. The method of Claim 28 wherein said temperature is at least about 550°F., wherein said period is at least about ten seconds, and wherein said carbohydrate is selected from sorbitol, cyclodextrine compounds, fructose, xylose, and mixtures thereof.

30. The method of Claim 27 wherein said formulation additionally includes an effective amount of a free radical generating catalyst for initiating polymerization of said at least one polymerable ingredient of said formulation, and an effective amount of a stabilizer for preventing premature polymerization of said polymerization ingredients; wherein said step (b) comprises exposing said formulation to actinic radiation to which said photoinitiator is responsive for generating free radicals; and wherein, in said formulation, said amount of polyvinylpyrrolidone is 28 to 35 parts, said amount of n-vinyl-2-pyrrolidone is 28 to 35 parts, said amount of said compound selected from said group is 15 to 25 parts, said amount of polyethylene oxide is 7 to 10 parts, and said amount of glycerol is 3 to 6 parts.

31. The method of Claim 28 wherein said substrate is the substrate for a printed circuit board, and wherein said method includes the further step, effected intermediate said steps (b) and (d), of gradually heating said deposit-bearing substrate to a temperature in the range 200° to 400°.