NEW DEVELOPMENTS IN BRAZING FLUXES

1. NEW DEVELOPMENTS IN BRAZING FLUXES DR. Y. BASKIN SME BRAZING AND SOLDERING TECHNOLOGIES CONFERENCE ORLANDO, FLORIDA FEBRUARY 7-8, 2002 SME Brazing and Soldering Technologies Conference

2. DEVELOPMENT OF A FLUORIDE-FREE FLUX WAS DRIVEN BY ENVIRONMENTAL AND SAFETY CONCERNS • Cleaner Plant Water Effluents • Better Workplace Air Quality • Improved Safety in Brazing Operations SME Brazing and Soldering Technologies Conference

3. THE PAST DECADES HAVE WITNESSED THE ELIMINATION OF HAZARDOUS METALS AND CHEMICALS • Cadmium from brazing filler metals • Lead from plumbing soft-solders • CFC solvents in all applications • Hydrazine from different formulations • Asbestos from insulation SME Brazing and Soldering Technologies Conference

4. PRIMARY REASONS FOR CONTINUED USE OF FLUORIDE BEARING FLUXES • Fluoride-bearing brazing fluxes perform consistently in many applications, giving little reason for change. • There was an almost universal conviction that it was impossible to develop an acceptable fluoride-free brazing flux, leading to little R&D efforts. • Environmental and health studies concentrated on other sources that exhibited greater dangers, such as CFCs, lead, and other elements. SME Brazing and Soldering Technologies Conference

5. Boric Acid Boron Oxide Elemental Boron Organic Additives Potassium Bifluoride Potassium Fluoborate Potassium Fluoride Potassium Pentaborate Potassium Tetraborate Silicon Dioxide Sodium Tetraborate Water COMMON INGREDIENTS OF CONVENTIONAL BRAZING FLUXES SME Brazing and Soldering Technologies Conference

6. COMPOSITIONAL AREA OF COMMON BRAZING FLUXES SME Brazing and Soldering Technologies Conference

7. FLUX ACTIVATION TEMPERATURE AS A FUNCTION OF B/F RATIO SME Brazing and Soldering Technologies Conference

8. EFFECT OF TIME ON FLUX ACTIVATION TEMPERATURE SME Brazing and Soldering Technologies Conference

9. FLUX EXHAUSTION TEMPERATURE AS A FUNCTION OF B/F RATIO SME Brazing and Soldering Technologies Conference

10. THE HAZARDS ASSOCIATED WITH FLUORIDE-BEARING FLUXES CHANGE DURING DIFFERENT BRAZING OPERATION STAGES • Working with raw flux • Brazing at elevated temperatures when HF and BF3 gases are released • Discharging raw flux and flux residues into plant effluent, and entry into water system SME Brazing and Soldering Technologies Conference

11. EXPOSURE LIMITS AND HAZARD LABELS FOR FIVE FLUORIDES FLUORINE ACGIH OSHA NIOSH OSHA D.O.T COMPOUND TWA-TLV TWA-PEL TWA-REL LABEL LABEL Boron Trifluoride 1ppm 1ppm 1ppm - Poison Hydrogen Fluoride 3ppm 3ppm 3ppm Toxic Corrosive Potassium Bifluoride 2.5 mg/m3 2.5 mg/m3 2.5 mg/m3 Toxic Corrosive Potassium Fluoborate 2.5 mg/m3 2.5 mg/m3 2.5 mg/m3 Toxic - Potassium Fluoride 2.5 mg/m3 2.5 mg/m3 2.5 mg/m3 Toxic - SME Brazing and Soldering Technologies Conference

12. POTENTIAL HEALTH HAZARDS FROM USE OF FLUORIDE-BEARING FLUXES • Irritation to skin and fingernails by the raw flux. • Irritation of the eyes, mucous membranes, and respiratory system by gases and fumes generated during brazing. • Calcium depletion (sclerosis) of the bones and mottled teeth from long-term exposure to fluoride gases and fine fume particles. • Potential health hazards from discharge of untreated flux and flux residues into the water supply. SME Brazing and Soldering Technologies Conference

13. EQUIPMENT • Thermolyne 1500 Furnace – Maximum Temperature: 1,200°C • Calibrated Pyrometer with Surface Probe. Maximum Temperature: 1,300°C • 30 Tempilstik Temperature Indicators. Temperature Range: 400-1,200°C • Brookfield Viscometer • Hot Plate • Timer • Balance SME Brazing and Soldering Technologies Conference

14. BASE METALS • Copper • Mild Steel • Brass C-260 (70%Cu/30%Zn) SME Brazing and Soldering Technologies Conference

15. FILLER METALS AWS LIQUIDUS CLASSIFICATION COMPOSITION TEMPERATURE BAg-28 40% Ag 710°C/1,310°F 30%Cu 28%Zn 2%Sn BAg-36 45%Ag 688°C/1,270°F 27%Cu 25%Zn 3%Sn BCuP-4 87.5%Cu 718°C/1,325°F 6%Ag 7.25%P SME Brazing and Soldering Technologies Conference

16. PHYSICAL PROPERTIES OF FLUORIDE-FREE FLUX Form Creamy Paste Color White Specific Gravity 1.4 Viscosity @ 22°C/72°F 225,000 ± 20,000 cps Fluorine Content < 100 ppm Flash Point None Freezing Effects None Heating Effects to 50°C/122°F Minimal Active Temperature Range 670-870°C/1,235-1,600°F SME Brazing and Soldering Technologies Conference

17. TEMPERATURE RANGES FOR FLUXES AND FILLER METALS MAXIMUM ACTIVATION RECOMMEND FLUX TEMPERATURE TEMPERATURE Average Fluoride-Bearing 570°C/1,050°F 870°C/1,600°F Fluoride-Free 670°C/1,235°F 870°C/1,600°F MAXIMUM LIQUIDUS RECOMMENDED FILLER METAL TEMPERATURE TEMPERATURE BAg-28 (40%Ag) 710°C/1,310°F 802°C/1,475°F BAg-36 (45%Ag) 688°C/1,270°F 785°C/1,450°F BCuP-4 (6%Ag) 718°C/1,325°F 785°C/1,450°F SME Brazing and Soldering Technologies Conference

18. FILLER METAL SPREAD AS A FUNCTION OF BASE METAL AND FLUX BASE FILLER METALS METAL FLUX BAg-28 BAg-36 BCuP-4 Brass Fluoride-Free Excellent Excellent Excellent Fluoride-Bearing Excellent Excellent Excellent Copper Fluoride-Free Moderate Moderate Moderate Fluoride-Bearing Excellent Excellent Poor Mild Steel Fluoride-Free Moderate Moderate Poor Fluoride-Bearing Moderate Moderate Poor FURNACE TEMPERATURE: 785°C/1,450°F TIME IN FURNACE: 60 Seconds EXCELLENT SPREAD: > 2.0cm2 MODERATE SPREAD: >0.5cm2<2.0cm2 POOR SPREAD: <0.5cm2 SME Brazing and Soldering Technologies Conference

19. BENEFITS OF USINGFLUORIDE-FREE FLUX • Greater Operator Safety • Better Workplace Air Quality • Cleaner Plant Water Effluents SME Brazing and Soldering Technologies Conference

20. PRIMARY SKIN IRRITATION STUDY FLUORIDE-FREE FLUORIDE-BEARING FLUX FLUX Primary Dermal Irritation Index 2.3 5.9 (PDII) Classification Not a primary irritant. A primary irritant Non-corrosive to skin. Corrosive to skin. SME Brazing and Soldering Technologies Conference

21. COPPER-TO-COPPER COPPER-TO-BRASS COPPER-TO-MILD STEEL BRASS-TO-BRASS BRASS-TO-MILD STEEL MILD STEEL-TO-MILD STEEL APPLICATIONS FOR FLUORIDE-FREE FLUX SME Brazing and Soldering Technologies Conference