I have a circuit board that no matter what I do, solder wont stick to it. I don’t have much experience in soldering, but I have soldered before, and most recently today. But this one specific circuit board I have has proven to be very difficult. I am using solder with flux core. The pads are clean and show no sign of oxidation. This is the board.
I have tried heating up the pads, The solder just sits on the pads like a ball, it wont stick at all.
Need a more powerful iron at about 350 degrees C
I used a 40w iron at 350c. Didn’t work. I also have a 48w iron. I could try that one. The temp goes up to 450c. Maybe I should try 450, or would that much heat damage the pads?
You could try a bigger tip and more heat, but you’ll need to be pretty confident in your technique. There’s a somewhat inexpensive iron that may yield decent results called the “Pinecil” if you’re willing to wait for it to arrive rather than chancing the higher heat setting and/or changing tips. Also, it may help to use a flux pen instead of relying solely on the flux core.
For soldering battery wires you need at least 420c. Melt solder to the pad, coat the end of the wire with solder then melt the solder on the pad together with the solder on the wire to join them.
You’ve got to time travel back 30 years and get one of these Dick Smith soldering irons 
or something that’s greater than about 60 watts and temperature controlled. You need the power so the tip of the iron doesn’t go cold when you try to solder the very conductive high current pads. That way you don’t need to go to extreme temperatures and damage the circuit board or components.
This is a really good soldering iron for the price. It works as good as as a high end iron. Build quality isn’t fantastic but as long as you don’t abuse it it’s great.
Is there no way to make my 48w iron work for this project? Ordering a new iron will take way too long
You can turn it up to 450c and hope for the best but I don’t recommend it. Try and be quick and you should be ok.
I see. What about Weller 1010? Its a 70w soldering station. Very expensive here, but I can get it today.
That’s certainly a far sight better than what you have. If you choose to buy it, I recommend a large chisel tip for soldering those big pads.
If you can find one that uses an integral heating element in the tip (“Active Tip” as Weller markets it), you’ll be happier overall. It’s newer, better technology.
I would need a WX soldering station right? I checked the price for those, they cost around 1500k USD here. I don’t even know how many times Im going to solder in the future.
Yes, it looks like the WX series uses active tips. Not worth the money at that price. I use a Pace branded station of similar design and paid about 1/4 that for it here, but it’s a US company and may be difficult to source for you.
The station you posted last will do just fine. Try to find an assortment of replacement tips. They aren’t usually expensive.
There’s also this 100w iron from RND lab, it costs the same as the 70w Weller. At this price point, finding easily available replacement tips is a priority. Which one would you recommend, Weller or RND lab? How many mm should the chisel tip be?
My opinion is probably shaded by US availability and familiarity, but I’ve never heard of RND, so would go with Weller.
Look for a 4-6mm chisel tip for the big pads. 1-2mm for soldering pins.
Of course there are no chisel type tips available. I have to order them from overseas. Wont the cone type tip that comes with the iron do the job? This is so frustrating lol.
There are chisel type tips available for the 48w iron though
It’ll work, but you’ll be working harder if using a small tip even on a powerful iron. Many tip brands are interchangeable, so that could work in your favor…
Use as much solder paste as you can.
If you find it, use the best solder paste available: “Amasan Lötfett”.
After applying some paste on the surface, use solder to shine the surface up.
Apply the paste and shine the power wire up with solder, too.
Then solder the wire and surface together.
Get some 63/37 solder if you are using 60/40. It’s a bit easier to work with and generally less chance of a cold solder joint. And as @Mustafa_Gokce says use flux generously. Get some past, liquid and a pen. It can also help to lightly polish the solder pad (I use a pencil eraser) to remove any oxidation before soldering. But 1st a higher wattage iron.
I bought a more powerful iron and solder now sticks to the board without problem. My concern is, the awg 14 wires are very thick and it’s difficult to not make contact between pads. What’s the best way to verify no small particles of solder are touching between pads?
Would it be safe to use awg 16 for soldering esc? Current load will be 25-27 amps. Cables are very short. Around 8cm.
Also, can I skip pads? The board has Ground, B+, B+, Ground. Can I for instance do, Ground, skip first B+, solder second B+? This way there will make it easier to solder thick wires
