Brazing & Soldering

Brazing & soldering join metals using filler metal below the base metal’s melting point, enabling low-distortion, leak-tight, and dissimilar-metal joints at moderate temperatures.

Overview

Brazing and soldering are thermal joining processes that use a lower-melting filler metal to bond parts without melting the base materials. Brazing typically runs above 840°F, while soldering is below, but both rely on capillary action to pull molten filler into tight, well-fitted joints. Common methods include torch brazing for flexible, low-to-medium volume work, furnace brazing for high-volume and repeatable assemblies, and wave soldering for PCB production.

These processes shine when you need to join dissimilar metals, protect heat-sensitive components, or minimize distortion on thin sections and precision assemblies. They produce clean, often leak-tight joints with good mechanical strength and excellent electrical conductivity, but joint strength is generally lower than a full-penetration weld and depends heavily on joint design and cleanliness. Brazing and soldering add process steps for fluxing and cleaning and require controlled gaps, but they can simplify machining, reduce fixturing loads, and allow complex multi-joint assemblies to be done in a single thermal cycle.

Common Materials

  • Copper
  • Brass
  • Low carbon steel 1018
  • Stainless steel 304
  • Aluminum 3003
  • Tin-lead and lead-free solder alloys

Tolerances

±0.005" to ±0.010" on assembled joint location; joint gap typically 0.002" to 0.008" for capillary brazed joints

Applications

  • HVAC and refrigeration heat exchanger cores
  • Copper and brass tube manifolds
  • Carbide tool tips brazed to steel shanks
  • Electrical connectors and bus bars
  • PCB assemblies via wave soldering
  • Stainless steel or copper fluid manifolds and fittings

When to Choose Brazing & Soldering

Choose brazing or soldering when you need to join dissimilar or thin metals with minimal distortion, or when joint cleanliness, leak-tightness, and conductivity matter. These processes fit small to very high volumes, from manual torch work to automated furnace or wave solder lines, especially where controlled joint gaps and repeatable thermal cycles are achievable.

vs MIG (GMAW)

Pick brazing or soldering instead of MIG when low heat input, minimal distortion, or joining thin or dissimilar metals is more important than maximum joint strength. They are also better suited for capillary joints, leak-tight tube assemblies, and parts near heat-sensitive components that would be damaged by higher MIG temperatures and spatter.

vs TIG (GTAW)

Choose brazing or soldering over TIG when you need to avoid melting the base metal, reduce residual stresses, or easily join dissimilar alloys such as copper to steel. They are often faster for multi-joint assemblies and can reduce operator skill requirements and fixturing complexity compared to precision TIG welding on thin or intricate parts.

vs Stick (SMAW)

Use brazing or soldering instead of Stick welding when you’re working on thinner sections, small parts, or assemblies that can’t tolerate heavy heat input and weld spatter. They also suit shop or production environments where you want cleaner joints, better appearance, and the ability to join non-ferrous or mixed-metal assemblies that are impractical with Stick.

vs Resistance Welding

Select brazing or soldering when parts can’t be clamped easily between electrodes, when access is limited, or when you need continuous, sealed joints rather than discrete weld nuggets. They are also more forgiving on coatings and plating and work better for complex multi-joint assemblies in one heating cycle.

vs Adhesive Bonding

Choose brazing or soldering when you need metallic joints with higher temperature capability, better electrical or thermal conductivity, and stronger resistance to long-term creep. They avoid cure-time delays and can integrate easily into thermal processes like furnace cycles, especially for fluid or pressure-containing assemblies.

Design Considerations

  • Design lap joints with 3–5 times material thickness overlap where possible to maximize brazed or soldered joint strength
  • Hold joint gaps in the 0.002"–0.008" range for brazing and tighter for soldering to promote capillary flow and consistent fillets
  • Avoid large heat sinks or design for thermal balance, or specify local preheat to prevent cold joints and incomplete wetting
  • Keep joint areas accessible for torch, flux application, and post-braze cleaning; avoid blind crevices that trap flux or fumes
  • Specify compatible base materials, fillers, and plating systems, especially for dissimilar-metal or corrosion-critical joints
  • Call out only critical post-braze dimensions and datums; allow generous non-critical tolerances to reduce fixturing and cycle time costs