hey guys this bob was part of fun electronics today I would be showing you how to stencil and Arduino Pro PCB so for this demonstration we're going to assume that you have some experience in both PTH and SMD soldering already some of the reasons you would want to take the next step into sin sling would be for finer pitch components meaning IC is having very small legs hidden connections things such as BGA components and also if you ever want to get into production runs this is exactly how we do it here at smartphone so let's get into the materials needed for stenciling first up you will need some type of frame to hold the PCB steady while you're applying the paste if you don't have a nice frame like this you can use bare PCBs junk PCBs from other projects and you will just need to tape those in place around the PCB that you're stenciling the next material we need is the solder paste itself this is a 500 gram jar solder paste this is exactly what we use it's part fun for our production runs for smaller operations it would be more practical to have a smaller jar this is a 10 gram jar of solder paste the difference between these two jars the one we use here at smartphone is lead-free the smaller jar is a leaded solder the main concern with the leaded solder is when it comes time to reflow you want to make sure that you re flowing in a very well ventilated area the fumes can be harmful so a couple more things about the solder paste when you are storing this you want to store it in a cool dry place such as a fridge for long periods of time if you're going to be using it within a couple weeks it's okay to keep it at room temperature the thing is you want to make sure to keep it in an airtight container and also when you're cleaning it up you want to make sure to scrape up all the excess solder paste it's rather expensive and you don't want to waste it next most importantly you will need the PCB itself these can be single boards or it can be a panelized board like this one here you can see there's two individual boards in this panel the benefit to having a panelized board is a greater efficiency in quicker bill time's this is because you can paste multiple boards at once next is the stencil itself this is a captain plastic stencil from O'Hara RP you can also get stainless steel metal stencils such as this one here the main difference between these two is the durability the plastic stencil will wear out much quicker than the metal stencil for that reason we use the metal stencils here at smartphone for our production runs you can get thousands of uses out of the metal and maybe a few hundred out of the plastic the other difference between these two stencils is the cost the plastic stencil is a much more affordable route and lastly you will need your trusty putty knife let's rock and roll alright so now we're ready to paste if you have a nice frame like this one here all you need to do is take your PCB and place it inside the frame like that and then tape down the edge of the frame so it's nice and secure if you don't have a nice frame like this one here you can use your spare PCBs so what you want to do is set up frame work around the PCB that you're going to be sensing so the next step is getting your putty knife ready for facing so we want to do let's take your solder paste scoop out a good amount like that you're going to want to apply a nice even layer to cross the putty knife somewhat like that now that we have our putty knife ready to go with the paste on it we want to take the stencil and lay it over the PCB you'll want to line up the holes of the stencil exactly with the footprint of the PCB once you have it lined up you want to apply firm pressure with your opposite hand and then you're going to take the putty knife and you're going to apply the paste from side to side like that so when you're applying the paste the first stroke you want to apply a nice even coat of paste to make sure that you're covering the entire PCB and that should be at about a 45 degree angle and then your second stroke you're going to scrape off all the excess paste and you want this one to be a bit steeper upwards of a 90 degree angle and scrape off the paste like that now you want to set down the putty knife and while maintaining pressure with your hand you want to gently lift up the stencil so you don't smear any of the pads now you want to gently remove the PCB from the frame and inspect it and make sure you have the even coverage of paste across the entire thing so our last step is clean up you don't want to waste any of the solder paste and so you want to make sure to clean up your stencil so what you can do is take your putty knife and scrape off all the excess solder paste most paste is water-soluble so you'll want to wash your hands after handling it and if you still feel uncomfortable you can use rubber gloves and some safety glasses so now that we have our board pasted we're ready to populate it with the SMD components a good trick is to start with the smaller components such as caps and resistors and work your way up to the larger components that way you're not reaching over larger ones to populate the small ones things that look out for our polarized components such as this capacitor right here you want to make sure those go on correctly and also when you're putting the components on you want to just gently set them on and if they're a bit crooked you want to just nudge them into place so you don't smear the paste so once the board is fully populated now it's time to reflow you can use anything from a professional reflow oven all the way down to a simple soldering iron today for this demonstration we're gonna be using this hot plate all you want to do set it in and cook it so that's it we hope you found this video useful and good luck in your future stenciling endeavors