KappZapp™ - Silver Solders for Stainless Steel to Stainless Steel and Copper

KappZapp™ solders produce strong and ductile joints on Copper and Stainless Steel. The resulting joints have high tolerance to vibration and stress, with tensile strengths to 33,000 psi on Stainless. KappZapp7™ - 93% Tin - 7% Silver is the best Stainless-to-Copper solder available, with high conductivity, ductility and strength.

Kapp Comet™ Flux is designed specifically to remove the difficult oxide layer on Stainless Steel to allow a strong metallic bond on soldering Stainless Steel and Copper.

KappZapp™ Acid-cored Solders are used in structural applications on Stainless Steel and Copper.

KappFree™ Acid-cored Solder is used in potable water applications on Stainless Steel and Copper


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Benefits and Uses

Low melting temperatures prevent loss of properties and minimize distortion on thin wires and sheets. KappZapp™ Tin-Silver alloys are used for electronics, fabrication, ducting, food containers, storage bins, instruments, Copper plumbing pipe, and cooling coils for refrigerators. In many instances, a stronger overall assembly exists after joining with KappZapp™ Tin-Silver solder than with higher temperature Silver brazing alloys.

The most popular of the low temperature Silver bearing solders are KappZapp3.5™ -96.5% Tin, 3.5% Silver and KappZapp4™ - 96% Tin, 4% Silver. The KappZapp4™ - 4% Silver formula is often preferred for hand soldering Stainless and Copper parts. It has a wider slushy or plastic range to allow users to manipulate parts during cooling.

Kapp Alloy also produces Tin-Silver solders with up to 7% Silver for applications requiring a higher temperature range and/or higher Silver content for superior strength and vibration resistance.

The following chart represents Kapp Alloy’s standard Tin-Silver alloys. Many factors, such as materials, temperature, and method of application determine the solder joint strength and characteristics. Call Kapp for engineering assistance to discuss your specific needs. We recommend testing appropriate alloys in your specific application to ensure suitability. Samples of Kapp alloys are always available upon request.

Composition Temperature
Sn Zn Pb Cd Ag Cu Sb RFQ Wire Ribbon 1/8"x18" Handy Vials Acid Core Rosin Core
96.5       3.5     221-221 430-430 137 X X X X X X
96       4     221-246 430-475 138 X X X X    
95       5     221-254 430-490 139 X X X X    
94       6     221-279 430-535 140 X X X X   X
93       7     221-302 430-575 141 X   X X   X
Sn=Tin, Zn=Zinc, Pb=Lead, Cd=Cadmium, Ag=Silver, Cu=Copper, Sb=Antimony
Physical Properties & Technical Data
Composition 96.5Sn - 3.5Ag 96Sn - 4Ag 95Sn - 5Ag 94Sn - 6Ag 93Sn - 7Ag
Solidus(°F) /(°C) 430°F / 221°C 430°F / 221°C 430°F / 221°C 430°F / 221°C 430°F / 221°C
Liquidus(°F) /(°C) 430°F / 221°C 475°F / 246°C 490°F / 254°C 535°F / 279°C 570°F / 299°C
Tensile Strength (copper) 14,000 psi 14,000 psi 15,000 psi 15,000 psi 15,500 psi
Tensile Strength (stainless) 25,000 psi 28,000 psi 29,000 psi 30,000 psi 31,000 psi
Shear Strength 11,600 psi 12,000 psi 13,000 psi 13,500 psi 14,000 psi
Elongation 48% 49% 49% 49% 49%
Electrical Conductivity (%IACS) 16.4 16.5 16.6 17.1 20.1

All KappZapp™ solid solders are available in bar or wire form. Custom alloys and forms are our specialty.

KappZapp3.5A™ Acid-cored Solder is used in structural applications on Stainless Steel and Copper. This is the same eutectic formulation as KappZapp3.5, but with a 3% Acid core. The flux residue can be removed with warm water or alcohol and a clean rag.

KappFreeA™ Acid-cored Tin-Copper-Silver Solder is used in potable water systems for Stainless Steel to Stainless Steel and Copper. This solder meets ASTM and NSF requirements for Lead-free potable water system soldering. The flux residue can be removed with warm water and a clean rag or simply by flushing with water.