Reflow oven for Soldering is the process of applying heat to solder paste applied PCBs (Printed Circuit Boards) with assembled components. The reason for doing this is to get the electrical and the mechanical connection between components and the PCB. There are three main types of processes used for mass reflow of PBA’s. Later we will discuss how to select the Best Reflow oven for Soldering.
- Convection soldering (with air or nitrogen reflow atmosphere)- Convection ovens using high air/nitrogen turnover provide the greatest possibility of controlling the soldering profile and also provide a fairly even distribution of temperature across the PBA. The disadvantage with convection ovens, when using N2 (nitrogen), is the relatively high gas consumption.
- IR ovens – IR ovens generate the greatest temperature variations across the PBA, amongst other things, this is dependant on component color, and that the temperature difference between the IR element and PBA often is great. This means that there is a risk that certain components overheat. IR ovens are not recommended for lead-free soldering.
- Vapor phase (condensation) ovens) – Vapor phase soldering takes place in an inert environment and uses a liquid as a heat transfer medium. The peak Temperature is limited to the heat transfer liquids boiling temperature and will also provide a very low ΔT across the PBA even for large mass products with uneven mass distribution. Batch systems are highly suitable for prototype manufacturing. The availability of in-line systems on the market is quite limited and soldering cost is higher compared to forced air convection ovens.
Obviously, there are hundreds of options out there, choosing the Best Reflow oven for Soldering can be especially hard because you may not be familiar with all the features, functions, and layout.
Best Reflow oven for Soldering 2021
Happybuy Reflow Oven T962– Benchtop reflow oven
Reflow oven for Soldering has advanced so much in recent years. The layout of the Happybuy Reflow Oven T962 is Ultimate. This is a microprocessor-controlled best DIY reflow oven Arduino, for SMT and surface mount assemblies. It is a perfect complete small engineering model prototype of electronics assembles at home.
Advancement in technology best surface mount reflow oven that works automatically by micro-computer control. This pro best cheap reflow oven has an ergonomic design with an Infrared reflow oven model, best suitable for large welding area for high efficiency.
The Happybuy Reflow Oven T962 Ultimate is one of those benchtop reflow ovens that are good at everything. The temperature is a very accurate reason of that it Adopted fast infrared radiation and circulation the wind for excellent performance. For user interference and inputs, equipment is featured with input keys and an LCD display.
Other than that, This best surface mount reflow oven the LCD Display design is pretty decent. This Happybuy Reflow Oven T962 practical and easily operated a high-efficiency machine.
X-TRONIC 5040-XR3 All-in-One Rework Station
X-Tronic’s All In One Hot Air Rework Soldering Iron Station With Preheater is an amazing advanced technology product. It is a complete multipurpose tool for the soldering of surface mount, SMD, DIY, and Arduino assembly.
This best benchtop reflow oven has featured with Samsung Microcontroller PID technology that gives the the user complete digital experience. All In One Soldering equipped with 70W Soldering Iron, 500W Hot Air Gun and 700W Preheating Station.
All In One Soldering Ultimate is one of those mice that is good at everything,
Double-sided mounting Reflow Soldering Process
There are two alternatives for reflow soldering of double-sided PBA:
Alt 1: On the first side to be soldered, the component bodies are attached with glue to hold them in place during the second reflow. Besides adding the extra subprocess of glue dispensing, there is also a risk of getting adhesive on the soldering surfaces.
Alt 2: When soldering without attaching the component with adhesive, ensure that only components with satisfactory weight per footprint area are used on the side that is being soldered first [5, 20]. Through-hole connectors, components with large mass and/or unsymmetrical weight or lead placement, should be located on the same side of the PCB so that they can be soldered during the second reflow pass.
If done correctly, the bottom side components will be held in place by the solder’s surface tension during liquidus. Reference 20 shows a number of package types not suitable for a 2nd reflow pass. The reflow profile shall be adapted to the board side that will be soldered. When the second soldering operation is carried out, attention should also be taken to the package top temperatures on the underside of the board.
Temperature profiling for lead-free soldering is critical. A minimum solder joint temperature of 235 °C must be achieved; at the same time as the package, top temperatures must not exceed the temperatures specified in To minimize the ΔT, the highest set point temperature in a convection oven should not be in the last peak zone. The recommended reflow profile can be divided into four different sections described more in detail Reflow profile limits are stated
- Preheat zone – Solvent evaporation begins in the preheat zone. The temperature increase shall below in order to avoid the solvent exploding and solder balls forming. A low-temperature increase will also reduce the risk-off “pop-corning” of moisture-sensitive components. Recommendation:- Temperature increase shall be as quick as possible but no greater than 3 °C /s. up to 150 °C.
- Soak zone – In the soak zone (figure 5), flux in the soldering paste is activated. The flux wets both the component leads and the PCB pads to remove oxides. The soak zone is used to even out temperature differences between the PBA’s warmest and coldest areas in order to get a lower ΔT before entering the reflow zone.
Too short time in the soak zone may give unsoldered joints because of oxides remaining on the soldering surfaces. A too long time may exhaust the flux, leaving too little flux Activity for the peak zone.
- Reflow zone (Peak zone) – In the reflow zone (figure 5) the solder melts and the wetting of the metal surfaces begins. The time that the solder is in a liquidus state should be as short as possible in order to reduce the risk of thermal damage to the components.
Recommendation:- Temperature increase <3 °C/s. (200 °C to peak temperature). Time above liquidus 60-90 s. recommended, Required solder joint peak temperature ≥235 °C.
- Cooling zone – In the cooling zone (figure 5), the PBA is cooled to solidify the solder and then to an even lower temperature so that the PBA can be handled outside the reflow oven (e.g. on conveyors, in PBA racks, etc.). Too fast cooling can damage components and PCB. Recommendation:- Ramp-down rate: 2-4 °C/s. (max. 6 °C/s.)
- Process time – Process time (figure 5) is the time taken for the PBA to be transported through the oven. The time should be as short as possible yet fulfilling all temperature ramp rate criteria. Total time will vary depending on the PCB/PBA-mass distribution, -area, component temperature sensitivity, etc. Requirement 25 °C to peak temperature <8 minutes.
The type of solder paste and the solder profile are strongly related. Lead-free soldering shall be performed with ternary Sn/3-4Ag/0.5-0.9Cu solder pastes with an onset (initial melting) temperature of 217 °C and a liquidus (final melting) temperature of a maximum of 221 °C.