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Wave soldering is a widely used method for producing large quantities of through-hole PCBs, and it is also common in mixed-technology board assembly. Its effectiveness largely depends on the suitability of carriers used for the boards in the process. Wave soldering carriers are critical for protecting sensitive components, controlling heat treatment, and ensuring consistent, reliable connections.
This document provides an overview of the wave soldering process and explains how wave carriers work, helping you decide when to choose wave soldering carriers.
Che cos'è la saldatura a onda?
Saldatura a onda is a mass-soldering technique that reliably connects leads of Through-Hole Technology (THT) components, as well as some mixed-technology components, to a printed circuit board.
- In this process, the mixed-technology board has already gone through Tecnologia di montaggio superficiale (SMT) assembly, and the THT component leads are inserted through the plated holes in the board.
- The underside of the assembly then passes through an automated fluxer to receive a controlled application of flusso across the component leads.
- The flux cleans the metals and helps the solder flow and stick. The circuit board is then glided through a preheat zone to elevate the assembly’s temperature and activate the flux.
- Then the conveyor moves the assembly over a standing wave of molten solder formed by a pump underneath. When the leads and plated barrels meet the wave, capillary action pulls solder up into the holes and forms the joint in a matter of seconds.
- The board exits the wave and cools under ambient and forced air, which allows joints to solidify without disturbance.
What Is a Wave Soldering Carrier?
Custom-built trays used to hold the PCB as it travels through the wave soldering machine are called wave carriers, also referred to as pallets or fixtures. The soldering carriers not only hold the PCB but also protect componenti and areas on the board that are sensitive to high temperatures or do not require soldering in the following ways. Its function involves:
- Selective Masking: Precisely shield areas that do not require soldering, such as gold fingers, connectors, surface-mount, and IC socket holes, preventing solder from entering and causing short circuits and unnecessary contamination.
- Protecting Sensitive Components: LEDs, electrolytic capacitors, and plastic connectors are some components that cannot withstand the high temperature of wave soldering. Carriers provide complete encapsulation and isolation, providing thermal insulation and protection.
- Improving Fabrication Efficiency: Even multiple small PCBs or irregularly shaped boards can be held by carriers such that soldering of multiple boards can be done in a single pass through the solder pot.
Wave Soldering Carrier vs. No Carrier
Whether or not a PCB requires a wave soldering carrier depends on its component layout, board geometry and protection requirements. A PCB with a straightforward design may be able to pass through the solder wave without a carrier, whereas a PCB with bottom-side components or areas that require protection may benefit from a custom carrier. The table below outlines the key differences when running a PCB with and without a wave soldering carrier.
| Fattore | Without Pallet | With Pallet |
| Solder exposure | More areas exposed | Selected areas exposed |
| Bottom-side components | Must be clear of wave | Can be protected |
| PCB support | Conveyor support only | Additional support |
| Irregular boards | May be difficult to handle | Easier to position |
| Setup cost | Più basso | Additional fixture cost |
| Best suited for | Simple, accessible PCB layouts | Mixed or protection-sensitive layouts |
When to Choose Wave Soldering with a Carrier?
The choice between running a board through wave soldering alone or mounting it in a wave carrier depends on two factors: which components populate the board, and how many of them need protection from the wave.
Scegliere Saldatura a onda without a Carrier
Fully THT Boards With No Protected Areas
A stand-alone wave soldering process applies when the board is fully THT, or a mixed technology board whose SMD side has already been reflowed and populated, leaving nothing on the underside that needs shielding.
When Standard Trasportatore Support Is Sufficient
High-volume output for simple PCBs may require wave soldering over selective soldering, and this will also often prove cheaper than selective.
Scegliere Saldatura a onda con un Carrier
Components Cannot Be Exposed to Molten Solder
A wave carrier becomes necessary once the underside carries SMDs, connectors, plastic enclosures, or pre-populated components that cannot withstand contact with molten solder or the wave’s thermal profile.
Il PCB Has an Irregular or Difficult-to-Convey Shape
Oddly shaped boards, boards too small to run safely through the wave, or boards with edge connectors exposed to the wave all call for a carrier, regardless of what the component mix alone would require.
Boards of complicated geometry also need to be transported and held steadily through wave soldering to stop board deformation as the THTs are all being soldered by this one flow along the entire width of the board.
Design Guidelines for Wave Carriers
A wave carrier is only as effective as its design. The following guidelines govern a sound wave soldering pallet design:
● Cutout tolleranza: Cutouts must be sized close to the board outline. Excess clearance allows solder to bleed into masked areas, while insufficient clearance risks board damage during loading or thermal expansion.
● Material heat resistance: The pallet material must withstand repeated exposure to solder pot temperatures of 250–270°C without warping, outgassing, or degrading over successive cycles.
● Thermal mass: The fixture must not excessively block preheat from reaching the cutout areas; otherwise, joints in those zones will be inadequately heated and prone to cold-joint defects.
● Bottom-side autorizzazione: Standoff height must be sufficient to prevent solder from wicking beneath the pallet and reaching masked areas.
● Support and planarità: Support ribs or pins must hold the board securely to prevent sag or bow, which alters wave contact height and produces inconsistent wetting across the panel.
Conclusione
Wave soldering automates the process of soldering through-hole components onto a circuito stampato, resulting in mass production with speed and cost-effectiveness. Things get complicated when the board has surface-mounted devices on the bottom side, since the solder wave can dislodge or damage them during the pass.
Projects that mix through-hole and SMD components, or use non-standard components. Designing and using custom wave carriers would avoid costly rework afterward. Ensuring processes and fixtures are effective, wave soldering can provide maximum yield, minimize assembly defects, and maintain structural integrity of complex printed circuit boards.
Need reliable wave soldering for your PCB assembly?
A ELEPCB, we provide professional PCBA manufacturing services, including wave soldering and custom wave soldering carriers designed to protect sensitive components, support complex board designs and ensure consistent soldering quality.
Contattate il nostro team oggi stesso to discuss your requirements and find the perfect carrier solution for your PCB assembly.
Domande frequenti
A1: Not always; PCBs with only through-hole components can sometimes pass through molten solder waves on conveyor fingers only. Particularly if there is mixed technology, i.e., the presence of SMD with through-hole components, custom carriers become necessary.
A2: Absolutely, many mixed-technology boards are reflowed first and top-side SMD components are soldered first. After which, the board is passed through wave soldering to solder through-hole components. The carriers used for this purpose are specifically designed to protect already soldered SMDs from wave soldering.
A3: If the board is passed through molten wave solder without a proper carrier. The unmasked components on the underside of the board are exposed to the solder wave, which causes unnecessary bridging or heat damage to the units not rated for the exposure. There might be some misalignment in the conveyor leading to missed joints or inconsistent solder fill.
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