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Soldering. Newbie questions

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alphaai

New Member
Hello,

Im a newbie to soldering.
Just practised some surface mount soldering on a surface mount practise board and my pins weren't soldering properly.
I dont know why. Terrible joint, IC not connected to the board.

I've got a hot air rework/soldering station. I'm not sure if I am using the best solder (60% Tin/40% lead). I also had a kester flux pen 186 of rosin flux type rma
but that dried out and nothing was left to apply to the board before I started soldering. Also hope to make my own pcbs at home.

So I have questions about stenciling, solder paste and solder flux.

1) Do I need to buy a second fridge to hold my solder paste. Apparently it has to be kept at a low temperature before applying.

2) What kind of stencils are best value for money. So many to choose from
I need stencils for QFN chips for starters. Dont know what else.
I like the simplicity of the plastic adhesive stencils but do they last?

3) I have a aoyue 968 and I dont think it was advertised as a lead free soldering iron.
The temp settings for the soldering iron starts from 200 Degrees Celsius
right up to 480 Degrees Celsius and from 100 to 480 Degrees Celisus for Hot Air.
I could use the soldering station to still do lead free work right?

4) Solder Flux, Its so confusing. I don't know which one to choose
Rosin Flux, no-clean high solids tacky flux or others.
Which kind should I be using for SMD?

5) When I watch some youtube videos
it looks like they are just using no clean high solids tacky flux
and no solder paste and just soldering on the pins straightaway.
My take on it is that have applied solder paste earlier on.
Would I be right on this?

Thanks,

Ben
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
If your using leaded solder, use 63/37, not 60/40. These is a big difference how the solder preforms. You should be using a non-lead based solder for ROHS. 63/37 will solidify instantly because it's solidus and liquidus point is the same.

Flux the area. tack one or two pins.

Take the board and solder it upside down. This worked well for me. I just dragged the solder across all of the pins.

Idealy, the way to go is to apply solder paste and heat.

The best way is to modify a toaster oven so that profile heating can be done.

As for storing paste. Put it in a Zip lock bag.
 
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