![]() ![]() The resulting surface oxide can lead to a number of solder defects such as voiding, beading/balling, graping, and head-in-pillow. that challenges the solder paste’s flux to effectively perform its fluxing action. If the board is simple and there are no complex components such BGAs or big components on the board, the slumping type profile will be the better choice. Figure 2 - Ramp/soak/spike reflow profile. The Soaking type is similar to a trapezoidal shape while the slumping type has a delta shape. There are two different profiles involved in the reflow process – soaking type and slumping type. The maximum allowable cooling down slope needs to be considered in order to avoid any defect from occurring. Profile Length: 3-4.5 minutes from 40☌ to peak 205-235☌ Soak: 130-180☌ for 30-90 seconds Ramp Rate: 1-3☌ per second Time Above Liquidus: 30-90 seconds Cool Down Rate: < 4☌ per second. Cooling zone: In the cooling zone, the temperature is gradually decreasing and makes solid solder joints.A common peak temperature is 20–40 ☌ above liquidus. Reflow zone: The reflow zone, also referred to as the “time above liquidus” (TAL), is the part of the process where the highest temperature is reached.Soaking zone: The preheating period from 150 ° C to the alloy molten point is also known as the soaking period, which means the flux is getting active and is removing the oxidized substitute on the metal surface so it is ready to make a good solder joint between components pins and PCB pads.It also lets big components heat up consistently with other small components. The benefit of the slow warm up is to let solvent and water in the paste vapour come out on time. The temperature ramp from normal to 150° C is less than 5° C /sec (at 1.5 ° C ~ 3 ° C / sec), and the time between 150° C to 180 ° C is around 60 ~ 220 sec. Standard Reflow Profile for Standard and Lead-Free Packages The reflow here in provided is for reference only. Preheating zone: Preheat usually refers to increasing the temperature from normal temperature to 150° C and from 150 ☌ to 180 C.In: 16th international conference on electronic packaging technology, Changsha. Zhou J, Xue F (2015) Investigation of rheology behavior of lead-free solder paste. The typical reflow profile includes four stages: preheating, soaking, reflow, and cooling. There are four steps/zones to this process - preheating, soaking, reflow and cooling.įor the traditional trapezoidal type profile base on lead free solder paste that Bittele uses for SMT assembly process: Their kinetics of reflow soldering were observed by in situ soldering tests. Reflow soldering is a process by which the solder paste is heated and changes to a molten state in order to connect components pins and PCB pads together permanently. A recommended ramp rate would be between 0.75☌/s and 2☌/s. Heating the paste too much before all the solvents evaporate will cause the viscosity to decrease which will then lead to solder slumping. Lead-free Reflow Profile: Soaking type vs. Another defect you may see from a too fast ramp-up is slumping of the solder paste, which can lead to bridging. ![]()
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