Insufficient solder paste applied, poor PCB surface finish, component defect, PCB warped.Ĭheck height and volume of paste deposit using 3D SPI before component placement, check PCB solderability, check quality of component, check PCB for bow and twist. Reduce time and/or temperature during preheat and soak stage of profile, consider using nitrogen or higher activity solder paste Reduce time and/or temperature during preheat and soak stage of profileĮxcessive heat during preheat and soak causing flux to become exhausted before entering reflow stage, oxidized solder connections Too much heat applied during preheat and soak causing flux to become exhausted before reflow Reduce heating rate of reflow profile to no more than 2✬/second Heating rate of reflow profile too high causing flux within solder paste to splatter Verify peak temperature and time above liquidus during reflow. Temperature profile incorrect during reflow Store components within humidity cabinet or pre-bake before use, reduce heating rate within reflow profile. Heating rate of reflow profile set too high causing moisture trapped within component to expand during soldering Pre-bake PCB's before use to remove any excess moisture, consider using material with higher Tg rating, store PCB's in moisture cabinet.Ĭomponent flipped over in feeder during index function causing part to be picked and placed upside down.Ĭonsider alternative PCB supplier, pre-bake PCB's before use and consider using material with higher Tg rating, store PCB's in moisture cabinet. Using flat surface finish such as ENIG, check component parameters in placement machine, use enough solder paste or increase thicknessĬontamination under solder mask layer, moisture trapped within FR4 material expanding as PCB is heated. PCB surface finish not flat (HASL), component misplaced, not enough solder paste printed Revise design to either reposition via outside of component footprint or employ plug via Via placed within pad causing solder paste to flow away from pad and through hole during reflow. Contact us today to learn more about working together on your next project. we have over 25 years of experience manufacturing PCBs, PCBAs and providing engineering services to help you meet your quality standards and expectations. 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.Summarized below are some typical reflow / solder defects along with recommended corrections or preventative actions to improve your PCBA process and product quality. 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. 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. Preheating zone: Preheat usually refers to increasing the temperature from normal temperature to 150° C and from 150 ☌ to 180 C.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: 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. Lead-free Reflow Profile: Soaking type vs.
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