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Track and Flux
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PerranOak:
I am composing my first PCB for manufacture. Two questions:

1. What track width should I use? It's a simple microcontroller project that never uses more than about 10mA total.

2. I've seen videos of soldering SMD (I'm an SMD soldering virgin) that use huge amounts of extra flux: can I simply use good quality multicore solder, do I need all that flux?

Thank you.
jancumps:
If you use leadfree solder, I advice to use flux.
SiliconWizard:
1. We'd need to know the finest pitch of the components you're going to use, and the max length of your tracks, but I'd say 8mil to 10 mil is fine for most low-power signal tracks. I'd use a slightly larger width for power supplies. This: http://www.saturnpcb.com/pcb_toolkit/ is a useful tool.

2. Really depends on the kind of components. Additional flux definitely helps for fine-pitch QFPs, QFNs, and also excessively oxydized PCBs, but otherwise it's usually not needed. A flux pen is handy to have anyway, just in case. Also note that if you're using PCBs with a HASL finish, it's often much easier to solder onto for beginners, as the finish is essentially solder.
calexanian:
Good questions. Generally most default to 10 mil track width for just general small stuff like that. I tend to go a bit bigger if the part footprints can support it. The pcb fab house will have minimum specs of both track width and track clearance but you want to stay well above that for a little safety margin. I highly recommend especially on your first design using nothing smaller than soic footprint chips and 0805 parts. It will make hand assembly so much easier especially on a first go around. I would also recommend 15  or even 20 mill tracks if you can fit them. You want also at least 10 mill clearances between tracks. Since you will be hand soldering you will not have to worry so much about heat transfer and such. If you can only fit 10 mill track you should be just fine. The only really worry is possibly lifting the pad and trace up from over heating or physical damage. Get several copies of the board in the event you have an accident.

As for flux, you are really going to need something especially on your first go around. If you can use leaded solder I highly recommend it. Any of the flux types should be fine weather it be RA flux, no clean, or water clean, just make sure you have a matching type flux pen handy as it’s the easiest way to make sure the pad is flowed and to remove bridges that nearly always happen when drag soldering. Also some matching solder wick can be handy as well. Get as fine of solder as you can get. A little goes a very long way on surface mount.
SiliconWizard:
I really second the fine solder advice. The key for SMD soldering (and conversely pitfall for beginners) is using a fine solder diameter, such as 0.2mm-0.3mm. Many beginners try using larger solder wires such as 0.7mm or 0.8mm (because that's what they are used to) and that makes such a mess (even with 0805 components) that you get discouraged quickly.
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