I recently completed my board based on the P1 (Shown Below). However, i have no experience in SMD soldering. I have however soldering experience with through hole components.
I wanted to set up my work bench to have the capability to be able to solder SMD components. I did some research online and came across the hot air rework station (Link 1), which seem to work fine with the exposed pads, however the pads of the P1 are hidden underneath. How do i go about to solder them, and how do i make sure the pads are soldered properly? I also came across the hot plate [Link 2]. is that better than using the Hot Air?
Moreover, i was planning to use a stencil to place the flux, any recommendations which flux are good?
I do a fair bit of SMD soldering and started out with a simple kit like the ones you linked to.
Here is where I ended up for SMD:
I tried not to use QFN packages when I was hand soldering - it can be done with a hot air gun, pre-tinned pads on the package and board and a lot of tacky flux but, it is not fun.
I tried to use 0805 components and larger SMD packages in my early revisions of a board. It is possible to hand solder 0201 parts, but life is too short.
If you follow the two rules above, you can easily hand solder SMD parts - I would only recommend you get a desk or head-mounted magnifying glass.
For when, QFN or small parts are a must, a friend and I converted a kitchen toaster oven into a reflow over with a Reflowio kit. There are a bunch of these kits out there and they work well. Then, I would get a stainless steel stencil from OSHStencils and apply solder paste, place the parts and bake. I like OSHPark ENIG boards foQFN and small feature parts. Worth the premium over the cheaper HASL boards. Again worked very well.
As your design progresses, you will be able to use the smaller parts and will want to make more boards. That is when I send the boards to MacroFab. These guys are very reasonable, fairly quick and can help you get running quickly.
I hope this helps. Please let me know if you have more questions.
@muneebr1 I’ve built many-a-board with modules. They can be tough to solder. They also fall apart when you’re heating them up (they themselves are typically just a small piece of FR4 with tightly placed components) So you should never move it while heat is being applied. (Unless you’re very very very confident you won’t screw it up. That’s me talking from looooots of experience )
You may think this is funny, but after all the years of doing this I use a skillet I got from Goodwill to reflow my one sided boards. If your board is one sided, I recommend going this direction. I’m using something like this:
Works well, as long as you don’t scorch the boards. (Especially if you’re using lead free solder)
The only way to tell when things are reflowing correctly is to watch the pads around the whole module. Do they look wet? If so, the pads underneath are likely to be as well. Sometimes you can observe the flux underneath bubbling/evaporating away. When the module adheres you may also see it shift into place. I use a good microscope (or magnifying glass) to watch duding the reflow process. That way I can estimate when it’s done.
Generally, a big module like that won’t have issues considering the pads are farther apart. I still recommend you get a stencil for your board. I also use OSH Stencils. I wrote up a tutorial a while back how to build a board using stencils. It may be useful for you.
I do use a hot air gun instead of the hotplate for that example though. (It’s equally a good alternative, but you have to be extremely careful not to roast your components. This is especially important for LEDs)
I used a simple small toaster oven to reflow SMT boards and it’s surprisingly easy to get good results. For smaller fine pitch stuff you just need good solder paste stencils and solder paste.
Just don’t over bake anything plastic because it will melt on you if don’t pay attention.
Don’t be afraid of it, it’s easy unless you have tons of boards to make.
Very helpful feed because I’m making a few boards in the next few weeks.
One question: does anyone have experience soldering flex boards? I’m ordering a flex from Oshpark and it will have some fine pitch resistors (0603). Just wondering if the same process described above would also work with flex boards. I know that getting the flex flat is critical so I’m thinking of securing to a thin metal plate for reflow. Any other tips are much appreciated.
I would recommend having tooling holes in your flex (possibly at the panel level, not the individual final assembly level), and using a fixture that uses these holes during solder stencil and reflow.
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