Wave Soldering vs. Selective Soldering vs. Reflow: Which Is Right for Your Process?
Soldering process selection is one of the decisions that shapes everything downstream — yield, throughput, rework rate, consumable costs, and how well your process handles mixed-technology boards. Get it right and the line runs clean. Get it wrong and you're managing a recurring set of defects that no amount of inspection will solve at the root. For a broader overview of soldering consumables and equipment, see our Soldering, Desoldering & Rework hub.
The three dominant processes in electronics assembly each have a distinct application profile. Here's an honest comparison of where each one belongs — and what that means for the materials your process actually needs.
Wave Soldering: High Throughput, Through-Hole Dominant
Wave soldering moves boards over a molten solder wave, simultaneously soldering all through-hole joints in a single pass. It's fast, consistent at volume, and has been the backbone of through-hole assembly for decades.
Where it fits: high-volume through-hole production, mixed-technology boards where SMT components have already been reflowed on the top side and through-hole components need bottom-side soldering, and any operation where throughput is the primary constraint.
The solder for a wave process is bar solder — fed continuously into the wave solder pot to maintain the bath level as solder is consumed. Alloy selection matters here. Sn63/Pb37 remains the standard for leaded processes because of its eutectic properties — it transitions directly from liquid to solid without a plastic range, which means cleaner joints and less bridging. Lead-free wave soldering typically uses SAC305 or SN100C, both of which run at higher temperatures than leaded and require more careful process control to achieve comparable joint quality. There is a meaningful difference between the two: SAC305 has a liquidus of approximately 217°C, while SN100C melts at around 227°C — but SN100C is often preferred in lead-free wave applications precisely because its processing temperature and joint characteristics more closely approximate leaded Sn63/Pb37 than SAC305 does.
Browse MTE's Bar Solder collection for wave soldering alloys including Indium bar solder in leaded and lead-free formulations.
Flux application before the wave — typically via spray fluxer or foam fluxer — is as important as the solder itself. Browse the Solder Flux & Thinners collection for wave-compatible flux options. See also: Back to the Basics: Flux.
Where wave soldering struggles: fine-pitch SMT components, bottom-side SMT that hasn't been adhesive-bonded, and boards where solder shadowing behind tall components creates bridging or insufficient fill. If your board mix is shifting toward more surface mount content, wave becomes harder to justify.
Reflow Soldering: The Standard for SMT
Reflow is the dominant process for surface mount assembly. Solder paste is applied to the board via stencil, components are placed, and the entire board travels through a reflow oven with a controlled thermal profile — preheat, soak, reflow, and cooling zones — that melts the paste and forms the joints.
Where it fits: any SMT assembly. Fine-pitch components, BGAs, QFNs, and 0201 passives that a wave process can't reliably handle are all standard territory for reflow. The process is repeatable, scalable, and compatible with the component landscape of modern electronics design.
Solder paste selection for reflow centers on three variables: alloy composition, flux chemistry, and particle size (Type number). SAC305 is the most common lead-free alloy. Sn63/Pb37 remains in use where RoHS exemptions apply. Flux chemistry — no-clean versus water-soluble — determines your post-reflow cleaning requirements.
Browse the Solder Paste collection for reflow applications including Indium and Kester options across alloy types and flux chemistries. For guidance on paste selection, see Solder Solutions: Choosing the Right Paste or Wire.
One thing reflow doesn't handle well: through-hole components. Boards with significant through-hole content need either a secondary wave or selective soldering operation after reflow, or hand soldering for low-volume through-hole population.
Selective Soldering: The Answer for Mixed-Technology Boards
Selective soldering is the process most operations reach for when wave soldering isn't precise enough and hand soldering isn't consistent enough. A programmable nozzle applies flux and solder only to defined locations on the board — individual through-hole joints, connectors, or specific areas that can't go through a wave without masking or damage to nearby SMT components.
Where it fits: mixed-technology boards with through-hole components that can't be wave soldered without excessive masking, low-to-medium volume production where board complexity makes wave soldering impractical, and high-reliability applications where joint-by-joint process control matters.
The consumable profile for selective soldering combines elements of both wave and hand soldering processes. Flux is applied locally via a spray or drop-jet fluxer before each soldering sequence. The solder itself is wire-fed into the nozzle from a spool — the same wire solder used in manual operations, but fed and controlled programmatically.
Browse the Wire Solder collection for lead-free and leaded options in SAC305, Sn63/Pb37, and SN100C from Indium, Kester, and Chip Quik.
Hand Soldering: Still Part of Every Operation
No production floor eliminates hand soldering entirely. Rework, repair, prototype builds, low-volume production, and touch-up after automated processes all require it. Wire solder and flux are the consumables, and the same alloy decisions that apply to selective soldering apply here.
Browse the complete Solder, Flux, Paste & Wire collection for the full range across all process types.
Browse Soldering, Desoldering & Rework equipment including Weller and JBC soldering stations.
Making the Call
| Process | Best for | Primary consumable |
|---|---|---|
| Wave soldering | High-volume through-hole | Bar solder + wave flux |
| Reflow | SMT assembly | Solder paste |
| Selective soldering | Mixed-technology boards | Wire solder + selective flux |
| Hand soldering | Rework, low volume, touch-up | Wire solder |
Most operations don't run just one of these. A board with both SMT and through-hole content typically goes through reflow first, then selective soldering or wave for the through-hole joints. Understanding where each process fits — and stocking the right consumables for each — is what keeps the line running without material-driven defects.
MTE Solutions is an exclusive Indium distributor and carries solder consumables across all major process types and alloy compositions. Contact our team to discuss your specific process requirements.
