Lead-free reflow oven can be used for lead-free reflow, tin-lead reflow, chip aging, and red glue curing. This reduces the temperature tolerances on the PCB boards and achieves a better soldering effect. The nitrogen gas flows more evenly in the lead-free reflow process than in the tin-lead reflow. Advantages of Lead-Free Reflow SolderingĬompared with the traditional tin-lead PCB reflow soldering, the lead-free reflow soldering has these pros: Lead-free reflow has more difficulty than tin-lead reflow. The lead-free reflow heating rate is higher than that of the lead-tin reflow. Tin-lead reflow allows the reflow temperature fluctuation range of 30☌, but the lead-free reflow allows the reflow temperature fluctuation range of only 5☌. Lead-tin reflow ovens can't assemble lead-free PCBs. Lead-free reflow ovens can handle both lead-free assembly and lead-tin assembly. The lead-free reflow temperatures are about 30☌ higher than the traditional tin-lead reflow temperatures. Lead-free reflow requires using the lead-free solder paste, such as tin-copper alloy solder paste, tin-silver alloy solder paste. Lead-free reflow is different from the traditional tin-lead reflow soldering in: You may need to read the below specifications table to better understand the above lead-free reflow profile. And a lead-free reflow profile using this lead-free solder paste is as below: The commonly seen lead-free solder paste uses the alloy powder Sn96.5Ag3Gu0.5, which has a melting point of 217☌. The lead-free reflow profile specifications depend on the solder paste melting point and the highest temperature that the PCB laminate can bear. Lead-Free Reflow ProfileĪ lead-free reflow soldering profile is made according to the temperature data collected from the reflow oven temperature testing board, which is connected with the DATAPAQ and goes through the reflow oven.Ī lead-free reflow profile reflects the above 4 stages in the reflow process. The cooling slope rate should be about twice the preheat slope rate to avoid PCB parts bending and burrs on the solder joints. The reflow cooling stage is the step where the solder consolidates as the reflow oven zones' temperatures get down from the peak to 75☌, and the components and PCB pads are well soldered. The lead-free reflow stage lasts about 40 seconds to 70 seconds, and the peak temperature lasts for about 10 seconds to 30 seconds.

The reflow oven remains at the peak temperatures for some time so the alloy liquid reflows and the whole PCBA has an even temperature in case of tombstoning. Lead-free reflow temperatures reach about 240☌ to 248☌, and before the temperatures reach the peak, the alloy powder melts and soak the PCB pads and components. The reflow stage is the step when the solder paste completely reflows. The lead-free soak stage lasts about 60 seconds to 120 seconds. Lead-free reflow soaking temperatures reach about 217☌, and the temperature increase slope rate is about 0.5℃/sec to 1℃/sec. The temperatures during the soak stage increase slower than during the preheat stage. And the oxide on the surfaces of components and PCB pads is also removed. The reflow soak stage is the step where the solder paste removes moisture, and the flux activates so it can solder. The lead-free reflow preheat stage lasts about 60 seconds to 120 seconds. Lead-free reflow preheat temperatures reach about 150☌ to 190☌, and the preheat slope rate is about 0.75℃/sec to 2℃/sec. The other reason for this is preparation for reflow to avoid thermal shock and harm to the SMD components, insufficient soldering on PCB pads, solder balls in non-soldering areas, and spattering. When the PCBAs go into the lead-free reflow oven, they are preheated slowly at a uniform rate to remove the moisture and solvent in the solder paste. In the lead-free reflow oven, the PCBAs are transferred by the conveyor belt and undergo four stages: 1. The reflow oven raises the temperatures by heating nitrogen gas. Lead-free reflow is full-automatic and happens in the lead-free reflow oven, which has ten temperature chambers (tin-lead reflow oven has eight). When the PCBAs cool down, the SMD components are soldered on the PCB pads. Lead-free reflow soldering is the process of adjusting reflow oven temperatures to melt and cure lead-free solder paste on the PCB pads. Part 5: Lead-Free Reflow PCB Soldering One-Stop Solution.

Part 4: Advantages of Lead-Free Reflow Soldering.

Solder reflow oven