this leaved more few space tween the chips and the pins. Nowadays the technology development required put more and more components on a common size PCB, the economical way is to develop the components and make it smaller, So multi functions, system in one chip, 144pins QFP, BGA 0201 01005 components had been invented and used widely in the SMT soldering process. The selected oven needs to be of a suitable size to handle the production rate of the pick and place equipment.
There are various types of reflow soldering machine available depending on the required line speed(output capacity),component size and components polulation of the PCB assemblies to be processed. Good quality PCB, components and solder paste.Repeatable placement of surface mount components.Carefully printed PCB using well designed stencil.The key aspects that lead to an effective SMT reflow soldering process are as follows: and then melting the solder(solder melting temperature 230? to 250?,there are also low temperature solder 140? and high temperature solder above 350?), after the solder cooling down, it will form the stable solder joints between SMC/SMD and PCB. by first pre-heating the components/PCB/solder paste to the soldering temperature, the flux will be activiate and move the oxidated surface of the PCB and SMC/SMD to let the solder easy joint the PCB and joint the SMC/SMD. not a solder joint between PCB and SMC/SMD.Ī reflow oven is the machine used to change the solder paste status from mixture to solder joint. At this status, the solder paste still a mixture with the solder balls and flux.
#Smd reflow full
If use the full automatic SMT stencil printer, then it need a PCB loader to send the PCB to it automaticly.Īfter print the solder paste to the PCB solder pat by stencil printer(manual,semi auto or automatic), then send the PCB to the pick and place machine(chip mounter, surface mounter) to pick and place the surface mount component(SMC/SMD) to the PCB, the solder paste will stick the SMC/SMD to the PCB. There are three method to print the solder paste on PCB, Manually, use semi auto solder printer or use the full automatic online solder paste printer. For reflow soldering normally adopt SnAgCu(Sn 99%, Ag 0.3%, Cu 0.7%) alloy,Make the SnAgCu to the small balls(1#?2#:75-150um?3#:25-45um,4#:20-38um?5#:10-20um) and mixed it with the flux?surface active agent and other things that can be helpful for soldering. Solder paste is a kind mixture of solder alloy and flux. The reflow soldering process normally adopt following steps: The aim of the process is to form acceptable solder joints between SMC and PCB.
SMT Reflow soldering process is the most widely used method of attaching surface mount components(SMC) to printed circuit boards (PCBs).
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