CA1203149A

CA1203149A - Solder stripping solution

Info

Publication number: CA1203149A
Application number: CA000437035A
Authority: CA
Inventors: James J. Czaja
Original assignee: Circuit Chemistry Corp
Current assignee: Circuit Chemistry Corp
Priority date: 1982-09-20
Filing date: 1983-09-19
Publication date: 1986-04-15
Also published as: SE8402705L; AT385521B; US4397753A; SE452329B; EP0119262A4; ATA905283A; GB2138448B; JPS59501751A; GB2138448A; WO1984001168A1; GB8412205D0; SE8402705D0; DE3390209T1; EP0119262A1; EP0119262B1; CH661742A5; NL8320311A; DE3390209C2

Abstract

SOLDER STRIPPING SOLUTION

Abstract of the Disclosure Solder stripping solution having an extended life for stripping and removing tin-lead alloy solder or tin deposits from entire circuits or tabs with an insignificant amount of attack on the base epoxy laminate or underlay copper or nickel substrate while leaving a residue-free substrate surface. This solu-tion can be utilized at room temperature or preferably slightly above, and has a prolonged useful life of weeks to months. The composition of the solution includes a hydroxyphenol in an aqueous solution of a nitro-substituted aromatic compound, an inorganic acid, and thiourea.

Description

~2V33l'~

The present invention pertains to a solder strlpping or tin stripper solution for stripping tin and/or tin-lead alloy from a copper or nickel substrate and, more particularly, pertains to a solder stripper solution ~or solder-mask~over-bare copper (SMOBC) type boards or for sub-~e~uent nickel-gold tab plating on printed circuit boards, nickel and/or nickel alloy~, and copper or copper alloys.
II. Backgxound o the Invention:
The prior art solder strippers are divide~ into two types, the ~ir~t type containing peroxide and the second type which is non-peroxide.
The peroxide type of solder strippers all have the same basic chemistry of à ~luoride and a peroxide.
One o~ the majox problems with the peroxide 5ystem is that the reaction is very exothermic in that heat builds up rapidly during the stripping ac~ion. While tab stripping is not a particular problem, the loading factor must be re~uced or cooling coils installed when stripping SMOBC
boards. The peroxide type of solder strippers daxkens the solder at the demarcation line because the mode of solder removal is more of a grain boundary attack than a true dissolving of the solder. Because of this ~actor, the solder turns very black with a white powdery residue. The strippers measle the epoxy since there i5 an immediate attack on the epoxy undercoat and as the solution heats up, the attack becomes even more pronounced. The solutions leave an insoluble whitP

~031~9 residue which becomes progressively thicker as more stripping is undertaken. ~lthough the residue wipes off, it cannot be removed from holes or line overhang without a-secondary treatment. Ventilation is always required in that the peroxide out-gasses_ from the solution emitting a mist of fluoride. As the solution exotherms, the out-gassing becomes more severe. Although the solutions have copper inhibitors, there is still a fair amount of copper attack. The rate of attack rises almost exponentially as the solution heats up. I~ boards with large areas to be stripped are put close together, the solution trapped between the boards can easily reach 135-150F, even though the main body may be at 85F.
This trapped high temperature solution can lead to isolated, excessive copper attack which the stripper is unaware of.
The non-peroxide types have a more diverse chemistry than the peroxide type of solder stripper although most of the non-peroxide types utilize an inorganic acid. The non-peroxid~ strippers have definite advantages over the peroxide type strippers in that the non-peroxide strippers do not measle the epoxy, have controllable stripper rates and are only slightly exothermic, and truly dissolve the solder without simply undercutting the solder.
The present invention overcomes the disadvantages of the prior art by providing a non-peroxide stripper which is a one component system, clear and easily visible while stripping, and does not attack the solder, especially at the demarcation line and has an extended life span after the introduction of tin or solder allov of weeks to months.

~2~

In one approach to overcoming the noted dis-adv~ntages of the prior art, U.S. Patent 3,677,949 discloses a sold~er stripping composition consisting of a nitro-substituted aromatic compound, an inorganic acid selected from the group of fluoboric acid, fluosilicic acid, or sulfamic acid and thiourea.
Additional additives were organic acid acc~lerators and wetting agents. This formulation has suffered since the useful life span is measured in hours after the introduction of tin or alloy thereof into the solution and there is a white powdexy residual left on the surface of the base metal after stripping of the solder which required either scrubbing away or removal by a secondary solution. This patent is par~icularly inef-fective for stripping tin or tin alloy thereof.
The present invention overcomes ~he disadvan-tages of the prior art by providing a non-peroxide solder stripping solution which is a one-component system, clear and visible with a straw-yellow color during stxipping, does not attack the substrate or epoxy board, especially at the demarcation line, and has long shelf life.

Summary o~ the Invention The general purpose of the present invention is to provide a non-peroxide solder or tin stripping solu-tion which is clear and easily viewable, is a one-component sys~em, has long shelf life, does not attack the substrate, also does not attack the substrate at the solder demarca-tion line, provides a stripped copper which appears pink and brisht and can be easily activated for subsequent operation, and which does not leave residue on the board.
According to one embodiment of the present invention, there is provided a solder stripping solution of nitro~substituted aromatic compound, an inorganic acid, a thiourea, and a hydroxyphenol in the aqueous solution.
According to another embodiment of the present invention, there is provided solder stripping non-peroxide solution ~or stripping tin/lead alloy from circuit boards particularly solder-mask-over-bar~ copper type circuit boards, the solution including an aqueous solution o a nitro-substituted aromatic compound, fluoboric acid, boric acid, a hydroxyphenol, ammonium nitrate, nitric acid and thiourea where solder or tin is dissolved through chemical reaction ~rom coppex or nickel laminated on the epoxy boards, thereby leaving substrate metal which is oxide free and bright for activation and subse~uent operation.

~31~9 One significant advantage of the non-peroxide solder stripping solution is th~t tho ~oldcr ~lt~Ck mo~
does not leave the solder black at the demarcation line.
The copper appears pink and bright after stripping and can be easily activated for subsequent operation.
~ nother significant aspect and feature of the present invention is a solder stripping solution which is clear and provides for visible viewing during the stripping. The solution is a straw color,that is, a yellow color. After stripping, no residue remains at the bot-tom of the solution until~the stripping solution is near e~austion.
A urther significant aspect and feature o~
the present invention is a solder stripping solution which will strip approximately one-third more tin/lead ~or the same quantity of the prlor art solutions.
An additional significant aspect and feature of the present invention is that the solder stripping solution provides more yield per li~e quantity Wit}l respect to the prior art. While the solder stripping solutiQn is slightly more expensive in cost, the yield makes up the difference. The solder stripping solution will also strip reflowed parts although at a slightly slower rate than that on unreflowed parts.

)31'~

Having thus described one embodiment of the present invention, it is a principal object hereof to provide a solder stripping solution. The solution also strips tin.
One object of the present invention is to pro-vide a solder stripping solution which is particularly useful with solder-mask-over-bare copper (SMOBC) type boards where thPre are large surfaces to be stripped.
Another ob;ect of the present invention is a solder stripping solution which is clear and provides for visibility during the stripping process, and leaves the copper pink and bright for activation and subsequent operation. Also, the stripper solution leaves no residue on the circuit boards.
A further object of the present invention is in th~ manufacture of printed circuit boards where removal of lead-tin solder alloy or tin is a necessary step in the manufacture o the boards. ~nother area of use would be in the removal of defective coatings of tin or solder on electrical components, these components being sensitive to contact with a fluorine containing chemical such as those containing fluoride or fluoborate based compounds.
In such instances, the formulation of the solution of the present invention would not include the use of a fluoborate containing compound.
An additional object of the present invention is the solution of the nitro-substituted aromatic com-pound, an inorganic acid, a thiourea, and a hydroxyphenol which has a stripping life of weeks to months. The composition for stripping lead-tin alloy solder and tin ~rom a copper or nickel substrate includes an extended ~ O;~ 9 life and residue-free substrate surface as provided by the inclusion ol a hydroxyphenol in an aqueous solution of a nitro-substituted aromatic compound, an inorganic acid and thiourea. The hydroxyphenol and/or derivatives thereof negate the life shortening effect once tin is introduced into the solution.
Still another object of the present invention is for use where the application of gold or nickel, or a combination of both, is applied to tab areas of the printed circuit board.

~7--(- ~L2V3~

Brief Description of the Drawings Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts thxoughout the figures thereof and where:
FIG. 1 is an operational view o the solder stripping solution;
FIG. 2A-2E is an operational view of steps of a SMOBC board having been stripped o solder or tin in the stripper solution and the subsequent application of a solder mask in selected areas; and, FIG. 3A~3D is an operational view of steps of a printed circuit board and the process necessary for applying the nickel-gold coating in the tab areas.

~ 3~

Description of Preferxed Embodiments The components of the non-peroxide stripping solution of the present invention per liter of ~ater includes the fo:llowing-components in proportions in the following ranges per liter of water for an aqueous solution including:

nitro-substituted aromatic compound-------------~ - 20-lS0 g/l fluoborate compound---------- 0.1-300 g/l 3-hydroxyphenol-------------- 0.1-50 g/l an ammonium compound--------- 0.1-300 g/l ammonium nitrate----- - ~ 0.1-150 g/l inoxganic acid--------------~ 0.1-400 g/l thiourea--------------- - 0.1-30 g/l boric acid---- ---------- 2-60 g/l The solution provides an extended life span for stripping of solder alloys or tin from base metals of copper, nickel or coppe~ alloys including substrates of printed circuit boards.

_9_ (_ ~24~31~9 Sodium meta-nitrobenzene s~fonate is the preferred axomatic nitro compound r but any other water soluble nitro-substituted aromatic compound is suitable. By example for illustrations only but not limiting, o, m, and p-nitrochloroben~enes; r m, and p-nitrobenzene sulfonic acids; and o r m r and p-nitrobenzoic acids and mixtures thereof are suitable. The preferred nitro-substituted aromatic compound used is sodium meta-nitrobenzenesul~onate.
The use o~ nitric acid as the inorganic acid accelerates the reaction speed such that it doubles the stripping rate of previously known stripping compositions of similar formulations. The white residue of tin or lead salts left on the base metal surface is also removed by using nitric acid. ~dditionally r the use of nitric acid instead of fluoboric, fluosilicic, or sulamic greatly increases the stripping rate of the solution, but more importantly removes the white residue let on the copper surface if nitric acid is not used. Nitric acid is the preferred inorganic acid, but other acid such as fluoboric, fluosilicic, or sulamic are suitable i the whi~e residlle left by using these acids alone is removed by a secondary solution. ~s is known by those familiar with fluoborate chemistry, ~oric acid should be present with fluohorate ion so as to negate the effect of free fluoride if the fluoborate ion disassociates.

~)3~

Ammonium fluoborate is the preferred source of ammonium and fluoboxate ion~ Other suitable sources are common ammonium compounds such as ammonium nitrate, ammonium acetate, al~lonium halides, or ammonium hydroxide and sodium fluoborate, potassium fluoborate, or fluoboric acid. Additionally, the introduction of ammonium ion causes the lead-tin alloy solder or tin being attacked to remain in a white and unoxidized condition making it possible for only partial removal of such deposi~s. Heretofore this partial removal and subsequent reactivation has not been possible. T~e addition of ammonium ion as ammonium fluoborate also has the added benefit o increasing the amount of lead and tin that can be dissolved beore precipi-tation occurs.
Thiourea per se is the preferred thiourea, but other alkyl and aromatic thioureas`are also suitable.
The presen~e of 3-hydroxyphenol stops the adverse effect of organo-tin compounds causing premature stoppa~e of a useul strippin~ action thereby extending the life of such a stripping solution to be measured in weeks~
months instead of hours. 3-hydroxyphenol is the preferred hydroxyphenol but other hydroxyphenols and~or their derivatives are suitable for use therein as so determined.

~ )3~

A preferred composition o~ t~ comp~nents for the solution.10 includes in an aqueous solution to one liter of water the following:
sodium m-nitrobenzene sulfonate ------ 80 g/l fluoboric acid - 48% -----~ ---- 276 g/1 boric acid --------------------------- 8 g/l 3-hydroxyphenol ---------------------- 8 g/l ammonium nitrate --------------------- 36 g/l nitric acid - 42Be -------------~ - 90 ml/l thiourea ----------------------------- 14 g/l water -------------------------- to one liter i (_ ~L2~.)3~L4~ _ Mode of Operation The solder stripping non-peroxide solution of the present invention is utilized to strip tin, or tin/lead alloys for ~he like solder deposits from a copper substrate ` such as that laminated on a printed circuit board or from any like surface particularly, the non-peroxide tin/lead solder removing solution is oriented towards solder-mask-over-bare copper (SMOBC) printed cir-cuit type boards or for subsequent nickel-gold tab stripping. In mass production, the solution can be either sprayed onto the particular se~ment o the printed circuit or, in the alternative, the end of the board can be dipped into a solution such as that illustrated in the drawing. The solution strips the tin/lead alloy from the tabs of the printed circuit board until the copper shows as a pink bright metal. There is no attac~
on the copper itself. The non-peroxide solder stripping solution particularly lends itself to sprayin~ as opposed to a dipping procedure. Upon the room temperature, the solution is recommended for use at 85F. Heating can be accomplished with a 316 stainless steel or teflon type heater and the solution can be utilized in a PVC, polyethylene or polypropylene container. The shel life of the solution is anticipated to be six months when stored at room temperature in a cool dry area. Inherently standard safety e~uipment is utiliæed as the solution contains acids as weli as oxidizers. The appearance of the solution is a straw yellow color with little or no odor.

~2~31~g ~

The yield of the non-peroxi~e solder stripping solution will dissolve 18-22 ounces per gallon of solder from a 0.0008 inch of tin/lead in approximately 90 seconds.
The load factor can be up to one foot squared/gallon.
FIG. 1 illustrates a non-peroxide solder strip-ping solution in a suitable container 12 such as PVC, polyethylene or polypropylene 12. ~ heater 14 such as a 316 stainless steel or te1On type heater or the like is utilized. A printed circuit board 16 having a dielectriC
substrate 18 such as ~-10 glass epoxy or the like includes an etched copper foil 20 thereon having a tin/lead solder plate coating ~2. The one end of the board 24 includes a plurality of circuit traces or tabs 26 which connect to the copper foil circuit.
While the solution lends itself to a dipping operation, the solution also lends itself just as well to a spraying operation. The solution is clear and the work of stripping is easily visible to the naked eye. The solution does not leave the solder black a~ the dem~rca-tion line and provides that on stripping the copper appears pink and bright for the subsequent operation. No residue remains and is particularly useful in the stripping of plated-through holes. Most importantly, there are no of~ensive odors yiven off during the stripping process of the SMOBC. The stripper will dissolve 18-22 ounces per gallon of solder over a 0.0008 inch of tin/lead in approximately 90 seconds with a load factor up to one foot squared per gallon. This is at sligh~ly above room temperature at 85F, but for reflowed solder a tempera-ture range of 95~100 F is suggested. Lower temperatures will result in a corresponding drop in strip rate. The particular advantage is that there is no significant -14~

~ ~3~

attack on the base epoxy laminate or the underlying copper no ma~ter what length of immersion is undertaken.
More importantly, the light powdery residue typically left on the surface of the copper underlay by the prior art peroxide or non-peroxide type strippers is not present and is absent from the non-peroxide solder stripper solution 10.
FIG. 2A-2E is an operational view of steps of a SMOBC process stripped of solder or tin in the stripper solution. FIG. 2A shows the board prior to stripper and FIG. 2B shows the copper etching. FIG. 2C
shows the solution performing solder ox tin stripping.
FIG. 2D shows the selective solder mark applica~ion in selected areas. FIG. 2E shows the areas where the solder mask is not applied and where the areas are then covered with a layer of molten solder in a solder level-ing application step. The solution 10 of the p~esent invention strips in FIG. 2C.
F~G. 3A-3D is an operational view of steps of usin~ the solder stripping solution on a printed circuit board and the process necessary for applying a nickel~
gold oating to the tabs. FIG. 3A shows the PC board, FIG. 3B shows the copper etching, FIG. 3C shows the st~ipping of solder or tin, and FIG. 3D shows the nickel or gold plating.

f ~203~9 Specific ~xamples Example 1 A 500 ml stripping solution is prepared by adding sodium m-nitrobenzenesulfonate, fluoboric acid, and thiourea to water, the components being added in an amount to provide the following concentrations:

sod. m-nitrobenzenesulfonate 80 g/l 48% fluoboric acid 276 g/l thiourea 16 g/l The resulting solution is divided into two 250 ml portions. The first of these portions, Solution A, is composed o~ the above formulation. Solution B contains an added amount of 8 ~/1 3-hydroxyphenol. To both solutions tllree pieces of 1" X 5" X .062" copper clad làminate which has been plated with a thickness of 0.0007" of solder alloy are immersed. Both Solutions A and B stripped the solder rom the copper clad laminate in approximately three minutes leaving only a light white residue. After two hours, three more pieces of solder plated copper clad laminate were immersed. The solder on the pieces imMersed in Solution A turned a very deep blac~-yellow color with the solder only being somewhat removed after 15 minu~es~
the pieces immersed in Solution B stripped in approxima~ely three minutes with only the same light white residue being left on the surface of the copper, this residue being easily wiped off.
Solutions A and B were covered and twelve days later more solder plated samples were immersed. The results were exactly the same as described as for two ~lours after the introduction of solder alloy into the solu-tion.

`j )3~
Example 2 ~ lO00 ml stripping solution is prepared by adding sodium m-nitrobenzenesulfonate, fluoboric acid and thiourea to water, the components being added in an amount to provide the following concentrations:

sodium m-nitrobenzenesulfonate 80 g/1 48% fluobirc acid ~76 g/l thiourea 16 g/1 The resulting solution is divided into four 250 ml portions. Solution C is composed of the above formulations with an added 32 ml/l of a 492 g/l solution of a lead fluoborate concentrate. Solution D is composed of the above formulation with an added S0 ml/l o a 328 g/l stannous fluobora;te~concentrate~ Solution E is composed of the above formulation with an added 8 g~1 of 3-hydroxyphenol and 32 ml/l of a lead fluoborate concentrate. Solution F
is com~osed of the above formulation with an added 8 g~l of 3-hydroxyphenol and 50 ~l/l of a 328 g/l stannous fluoborate concentrateO
The four portions, after mixing were allowed to sit for two hours. After two hours a 1" X 5" X .062"
piece of solder plated to a thickness of 0.0007" copper clad laminate was immersed.
Those samples immersed in Solutions C, E and F
were stxipped of their solder coating in approximately three minutes with only a light white residue left on the surface.
The solder on the sample immersed in Solution D turned a very deep black-yeilow color with the solder only being somewhat removed after 15 minutesO

3~

Example 3 A 500 ml stripping solution is prepared by adding sodium m-nitrobenzenesulfonate, fluoboric acid, thiourea, and 3-hydroxyphenol to water, the components being added in an amount to provide the following concentrations:
sodium m-nitrobenzenesulfonate 80 g/l 48% fluoboric acid 276 g/l thiourea 16 g/l 3-hydroxyphenol 8 g/l The resulting solution is divided into two 250 ml portions. The first of these portions, Solution G, is composed of the above formulation. Solution H contains an added 9 percent of a concentrated nitric acid.
To both solutions, three pieces of a 1" X 5" copper clad laminate which was solder plated to a thickness of 0.0007"
was immersed. The pieces immersed in Solution G were solder stripped in approximately three minutes with only a light white residue being left on the copper surEace.
The pieces immersed in Solution H were solder stripped in 1-1/2 minutes with no evidence oE a resi~ue of any kind left on the copper surface.
Example 4 A 300 ml stripping solution is prepared by adding sodium m-nitrobenzenesulfonate, thiourea, nitric acid, and 3-hydroxyphenol to water, the components being added in an amount to provide the following concentrations:
sodium m-nitrobenzenesulfOnate 80 g/l thiourea 16 g/l nitric acid, concentrated 11% by vol.
3-hydroxyphenol 8 g/l The resulting solution is divided into two 150 ml portions.

lZ~3~

The first of these portions, Solution J, is composed of the above formulation. Solution K contains an additional 15n y/l of ammonium fluoborate.
To both solutions three pieces of 1" X 5" X .062"
copper clad lamina~e which have been solder plated to a thickness of 0.0007" are immersed. The samples immersed in Solution J have their solder removed in approximately 1-1/2 minutes with a definite dark discoloration to the solder surface as it dissolves. The samples immersed in Solution K
have their solder removed in approximately i-l/2 minutes with the solder having a definite white and oxide free condition to the surface.
Additional pieces of the 1" X 5" X .062" solder plated laminate were immersed in Solutions J and IC. A
definite precipitation was noticed in Solution J ater eight additional pieces were strippèd. No precipitation was noticed in Solution K until 14 pieces of laminate had their solder stripped.
Example 5 A 300 ml stripping solution is prepared by adding sodium m-nitrobenzenesulfonate, nitxic acid and thiourea to water, the components being added in an amount to provide the following concen~rations:

sodium m-nitrobenzenesulfonate 80 g/l thioureà 16 g/l o 48~ fluoboric acid 276 ~/1 The resulting solution is divided into two 150 ml portions. The first of these portions, Solution L, is composed of the above formulations~ Solution M contains an added amount of 8 g/l 3-hydroxyphenol.

~Z~3~
~,.

To bot}l solutions three pieces of 1" X 5" X .062"
copper clad laminate which has been plated with a thickness of 0.0005" of tin are immersed. Both Solutions L and ~5 stripped the tin from the copper clad laminate in approximately 5 minutes leaving only a light white residue. After three hours, three more pieces of tin plated copper clad laminate were immersed in both solutions. The tin on the pieces i~mersed in Solution L turned a deep gray-yellow color with the tin not completely removed after 20 minutes. The tin on the pieces immersed in Solution M stripped in approximately 5 minutes leaving only a light white residue.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Solution for the removal of tin or tin-lead alloy solder from a copper or nickel base, said solution comprising:
a. 20-150 g/l of a m-nitro substituted aromatic compound;
b. 0.5-10 g/l of a thiourea selected from a group of thiourea per se, an alkyl thiourea or an aromatic thiourea;
and, c. 0.1-50 percent by volume of nitric acid.

2. Solution of claim 1 which also contains a fluoborate ion of the formulation RBF4 in the range of 0.1-750 g/l, R
being a cation consisting of either a hydrogen, ammonium, sodium or potassium ion.

3. Solution of claim 2 which also contains boric acid in the range of 2-60 g/l.

4. Solution of claim 3 including 0.1-50 g/l of a hydroxyphenol providing extended life to the stripping solu-tion.

5. Non-peroxide solder stripper solution comprising:
a. nitro-substitute aromatic compound of 20-150 g/l;
b. fluoborate compound of 0.1-750 g/l;
c. nitric acid of 0.1-400 g/l;
d. thiourea of 0.1-30 g/l;
e. boric acid of 2-60 g/l;
f. water to one liter.

6. Solution of claim 5 including hydroxyphenol of 01.-50 g/l.

7. Solution of claim 5 wherein said nitro-substituted aromatic compound is selected from o, m, or p-nitrochloro-benzenes, o, m, or p-nitrobenzenes, sulfonic acids, and o, m, or p-nitrobenzonic acids.

8. Solution of claim 7 comprising sodium metanitroben-zenesulfonate.

9. Solution of claim 6 wherein said hydroxyphenol comprises 3-hydroxyphenol.

10. Solution of claim 5 wherein said thiourea is selected from alkyl and aromatic thiourea.

11. Non-peroxide solder stripping solution comprising:
a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. fluoboric acid of 276 g/l;
c. boric acid of 8 g/l;
d. nitric acid of 90 ml/l;
e. thiourea of 14 g/l;
f. 3-hydroxyphenol of 8 g/l; and, g. to one liter of water.

12. Solution of claim 11 for stripping solder or tin in an SMOBC process.

13. Solution of claim 11 for stripping solder or tin from printed circuit boards in a nickel-gold process.

14. Solution for the removal of tin or tin-lead alloy solder from a copper or nickel base, said solution comprising:
a. 20-150 g/l of a m-nitro substituted aromatic compound;
b. (c.) 0.1-50 percent by volume of an inorgan-ic acid selected from a group including fluobor-ic acid, fluosilicic acid, sulfamic acid, or nitric acid; and, c. (d.) 0.1-50.0 g/l of a hydroxyphenol provid-ing extended life to the stripping solution.

15. Solution of claim 14 where the inorganic acid is nitric acid.

16. Solution of claim 14 which also contains an ammonium ion of the formulation NH4X in the range of 0.1-300 g/l, X
being an ion consisting of either nitrate, fluoborate, ace-tate, halogen, or hydroxide.

17. Solution of claim 14 which also contains a fluoborate ion of the formulation RBF4 in the range of 0.1-750 g/1, R
being a cation consisting of either a hydrogen, ammonium, sodium or potassium ion.

18. Non-peroxide solder stripper solution comprising:
a. nitro-substituted aromatic compound of 20-150 15 g/l;
b. fluoborate compound of 0.1-750 g/l;
c. hydroxyphenol of 0.1-50 g/l;
d. ammonium compound of 0.1-300 g/l;
e. inorganic acid of 0.1-400 g/l;
f. thiourea of 0.1-30 g/l, g. boric acid of 2-60 g/l; and h. water to one liter.

19. Solution of claim 18 wherein said nitro-substituted aromatic compound is selected from o, m, or p-nitrochloro-benzenes, o, m, or p-nitrobenzenes, sulfonic acids, and o, m, or p-nitrobenzonic acids.

20. Solution of claim 19 comprising sodium metanitro-benzenesulfonate.

21. Solution of claim 18 wherein said ammonium compound is selected from ammonium nitrate, ammonium halides, ammonium acetate, or ammonium hydroxide in combination with sodium fluoborate, potassium fluoborate or fluoboric acid.

22. Solution of claim 21 comprising ammonium fluoborate.

23. Solution of claim 18 wherein said inorganic acid is selected from fluoboric, fluosilic, sulfamic, or nitric acid.

24. Solution of claim 23 comprising nitric acid.

25. Solution of claim 18 wherein said hydroxyphenol comprises 3-hydroxyphenol.

26. Solution of claim 18 wherein said thiourea is selected from alkyl and aromatic thiourea.

27. Non-peroxide solder stripping solution comprising:
a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. fluoboric acid of 276 g/l;
c. boric acid of 8 g/l;
d. 3-hydroxyphenol of 8 g/l;
e. ammonium nitrate of 36 g/l;
f. nitric acid of 90 ml/l;
g. thiourea of 14 g/l; and, h. to one liter of water.

28. Solution of claim 27 for stripping solder or tin in an SMOBC process.

29. Solution of claim 27 for stripping solder or tin from printed circuit boards in a nickel-gold process.

30. Solution of claim 14 comprising 0.5-10 g/l of a thiourea selected from a group of thiourea per se, an alkyl thiourea or an aromatic thiourea.

31. Solution for the removal of tin or tin-lead alloy solder from a copper or nickel base, said solution comprising:
a. 20-150 g/l of a m-nitro substituted aromatic compound;
b. 0.5-10 g/l of a thiourea selected from a group of thiourea per se, and alkyl thiourea or an aromatic thiourea; and, c. 0.1-50 percent by volume of nitric acid.

32. Solution of claim 31 including 0.1-50 g/l of a hydrophenol providing extended life to the stripping solution.

33. Non-peroxide solder stripper solution comprising:
a. nitro-substitute aromatic compound of 20-150 g/l;
b. fluoborate compound of 0.1-750 g/l;
c. nitric acid of 0.1-400 g/l;
d. boric acid of 2-60 g/l; and, e. water to one liter.

34. Solution of claim 33 including hydroxyphenol of 0.1-50 g/l.

35. Solution of claim 33 wherein said nitro-substituted aromatic compound is selected from o, m, or p-nitrochloro-benzenes, o, m, or p-nitrobenzenes, sulfonic acids, and o, m, or p-nitrobenzonic acids.

36. Solution of claim 35 comprising sodium metanitro-benzenesulfonate.

37. Solution of claim 34 wherein said hydroxyphenol comprises 3-hydroxyphenol.

38. Non-peroxide solder stripping solution comprising.
a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. fluoboric acid of 276 g/l;
c. boric acid of 8 g/l;
d. 3-hydroxyphenol of 8 g/l;
e. nitric acid of 90 ml/l; and, f. to one liter of water.

39. Solution of claim 38 for s-tripping solder tin in an SMOBC process.

40. Solution of claim 38 for stripping solder or tin from printed circuit boards in a nickel-gold process.

41. Non-peroxide solder stripping solution comprising:

a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. fluoboric acid of 276 g/l;
c. 3-hydroxyphenol of 89/1; and, d. to one liter of water.

42. Solution of claim 41 further comprising 90 ml/l of nitric acid.

43. Non-peroxide solder stripping solution comprising:
a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. fluoboric acid of 276 g/l;
c. thiourea of 14 g/l;
d. 3-hydroxyphenol of 89/1; and, e. to one liter of water.

44. Non-peroxide solder stripping solution comprising:
a. sodium m-nitrobenzenesulfonate of 80 g/l;
b. nitric acid of 90 ml/l;
c. 3-hydroxyphenol of 89/1; and, d. to one liter of water.