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Kapp Silver Solders in Engine and Automotive Wire Connections, Switches, Controllers, and Sensors

KappZapp™ and KappFree™ for Lead-free, Cadmium-free Electrical Soldering


KappZapp3.5 and KappZapp4 are the most common Lead-free, Cadmium-free alloys used in soldering Copper wire and tabs in automotive switches, sensors and controllers. Whether in solid wire or flux-cored, strength, vibration resistance, and electrical conductivity all go up with an increase in the Silver (Ag) content. The price also increases with the Silver Content. So the challenge is to choose the solder that meets your strength needs without buying more Silver than you need.






96.5Sn - 3.5Ag


96Sn - 4Ag


93Sn - 7Ag

Solidus(°F) /(°C)

440°F / 226°C

430°F / 221°C

430°F / 221°C

430°F / 221°C

Liquidus(°F) /(°C)

500°F / 260°C

430°F / 221°C

475°F / 246°C

570°F / 299°C

Tensile Strength (copper)

10,000 psi

14,000 psi

14,000 psi

15,500 psi

Tensile Strength (stainless)

18,000 psi

25,000 psi

28,000 psi

31,000 psi

Shear Strength

5,000 psi

11,600 psi

12,000 psi

14,000 psi






Electrical Conductivity (%IACS)






KappZapp3.5™ is the most convenient formulation, as it melts at the low eutectic temperature of 430°F / 221°C. For many hand soldering applications, KappZapp4™ is utilized for its wider slushy range of 430 - 475°F / 221 - 246°C. The wider plastic range makes it easier to use in all joint orientations, especially when working in tight locations at odd angles, even upside down.

KappFree™ solder was formulated specifically to provide the flow and bonding characteristics of higher Silver solders without buying more Silver than you need. It behaves similar to KappZapp™, meets NSF requirements as Lead-Free and Cadmium-Free, and actually has a higher electrical conductivity than KappZapp™ solders.


KappZapp™ solders are certified by NSF International to comply with NSF/ANSI Standard 372: Drinking Water System Components – Lead Content. These products are also Certified to NSF/ANSI 61, Annex G and conforms with Lead content requirements for “Lead-free” plumbing as defined by California, Vermont, Maryland, and Louisiana state laws and the U.S. Safe Drinking Water Act in effect as of January 4, 2014. Weighted average lead content < 0.25%; Solder and flux lead content < 0.20%.

These alloys comply with the European RoHS and REACH directives, as well as the EPA Toxic Substance Control Act (TSCA) chemical inventory requirements. No lead, cadmium or mercury used in production. ND = Not Detected


KappEE™ - The Original Automotive Copper to Copper Solder

KappEEElectric Eutectic  Tin-Lead-Silver formula is the original automotive eutectic wiring solder. It is a very cost-effective eutectic electrical/electronic solder where Lead is permissible. The Silver content increases strength and vibration resistance of the joint in higher stress applications. KappEE’s lower application temperature (354°F/179°C) uses less energy and requires less time and post-production cleanup, often requiring only inspection. It also eliminates the effects of high heat used in higher temperature brazing – avoiding electronic material degradation, base metal deformation, discoloration, segregation, annealment, and heat related oxide-scale formation.


KappEE™ is available in both solid wire and as a rosin-core solder for extremely fast electrical/electronic soldering. KappEE™ contains a natural mild rosin core for use on delicate electronic joints. The flux residue can be removed with warm water and a clean rag.

KappEE™ Electric Eutectic Technical Data


62%Tin / 36%Lead / 2%Silver Ag Solid or Rosin Core

Melting Range

Eutectic @ 354°F (179°C)

Tensile Strength

21,000 psi

Shear Strength

10,000 psi



Electrical Conductivity

12.2 (%IACS)

NOTE: Lead is a health hazard. See SDS for precautions and protections. Lead and Cadmium solders should NOT be used for food or potable water applications.             



KappTec™ for High Temperatures and Dissimilar Metals


Finally, in high temperature environments, KappTec™ Cadmium-Silver solder offers superior bonding, strength, vibration resistance, and electrical conductivity. The solder also creates very strong solder joints between all dissimilar metals, except Aluminum. See the chart below for key alloy characteristics.



KappTec™ Composition and Technical Data

Cd (Cadmium):


Ag (Silver):



Technical Data

Melting Range:

640-740°F (338-393°C)


.3153 lbs./in3. / 8.727g/ml

Electrical Conductivity:

22 (% IACS)

Electrical Resistivity:


Shear Strength (Copper):

11,000 psi @ 72°F (22°C)

Shear Strength (1020 Steel):

12,000 psi @ 72°F (22°C)

Tensile Strength:

Up to 25,000 psi

Specific Gravity:


*Shear strength based on double lap joints


NOTE: Cadmium is a health hazard. See SDS for precautions and protections. Lead and Cadmium solders should NOT be used for food or potable water applications.             



For any questions, please fill out the form below and a Kapp representative will contact you shortly.