What flux to get!??!?!?!?!?!?

Using Arduino General Electronics
1

So I am trying to solder a wire to a PSB board.
Here is a image of a different person doing it: http://www.instructables.com/files/deriv/F6G/IBR1/GREPYEFM/F6GIBR1GREPYEFM.LARGE.jpg
But when I try to do it the solder does not stick to the PCB.
What flux would be best for this?
I am fairly new to this and if you could possibly send me a link to where I can buy the one I need, that would help :slight_smile:

So basically I am asking is, what flux would be best for what I am trying to do?
Are all fluxes the same? Are some better than others?

I am new to using flux, and is it also possible I could pick it up from a store like radio shack?

Also if the liquid flux is good for this project, will it be good for other things? Like connecting to wires together?

2

http://www.amazon.com/Solder-Flux-Liquid-2oz-10-4202/dp/B004RIF3BM/ref=pd_sim_hi_12
http://www.radioshack.com/product/index.jsp?productId=12582876

Also if the liquid flux is good for this project, will it be good for other things? Like connecting to wires together?

Yes

3

Is this flux any good?
http://www.ebay.com/itm/NO-CLEAN-LIQUID-FLUX-FOR-BGA-GPU-CPU-REWORK-REFLOW-/140506246517?pt=LH_DefaultDomain_0&hash=item20b6d32d75

4

radio shack has some paste flux and its not as easy to handle as a liquid flux pen, and is messy as all get out, but is usually more agressive than the liquid

typically the flux in your solder should be enough, here are some tips

clean the pads, use a nylon scowering pad (you know those green ones) to clean off oxidation, that is probably most of your problem

tin your wires, tin your pads and just melt the two together

if you get liquid get it in a pen, they have them on digikey and mouser, its much easier to deal with when its in a felt tip marker

I use the kester stuff, its good but could be just a tad bit stronger

5

I was using sand paper for a while but then I realized it started to sand down the copper or the metal.

Is sand paper a bad thing to use?
Also before I sand papered them down, there was a black thing over the copper, What is that?

ALso is this a good pen to get?: http://www.ebay.com/itm/Kester-951-Soldering-Flux-Pen-Low-Solids-No-Clean-10ml-Xbox-360-and-PS3-Reflows-/190780618038?pt=LH_DefaultDomain_0&hash=item2c6b693536

Do you know of any good pens?

6

that is what I have, works fine

sanding, yes, too much of anything is bad, keep in mind this is copper foil glued to a fiberglass board, you can and will sand though it

and no idea what the black thing was without a picture

7

Osgeld:
that is what I have, works fine

sanding, yes, too much of anything is bad, keep in mind this is copper foil glued to a fiberglass board, you can and will sand though it

and no idea what the black thing was without a picture

See the picture linked in the OP. The 'black thing' appears to be a lump of resin protecting the chip. I hope he didn't sand that down.

8

me too

9

You should not be sanding anything. With leaded solder, the rosin flux in the wire should be enough. If you are using lead free solder, then you should also get a no-clean flux meant for it. The No Clean Kester flux pen is just what you need.

Do NOT use paste flux or plumbing flux or acid flux. I try to stay away from Radio Shack solder and fluxes, they tend to be rather strong.

That black thing, as others have said, is covering the chip. That is called COB or Chip On Board. Rather than mount the chip inside an IC package, it is stuck right on the board and tiny wires are connected to the PCB traces. If you sanded that off, it is ruined.

10

Henry_Best:

Osgeld:
that is what I have, works fine

sanding, yes, too much of anything is bad, keep in mind this is copper foil glued to a fiberglass board, you can and will sand though it

and no idea what the black thing was without a picture

See the picture linked in the OP. The 'black thing' appears to be a lump of resin protecting the chip. I hope he didn't sand that down.

I did D:
It still works though. C:
I is this okay?

11

If it works, it works. Why were you sanding the board in the first place? For corroded PCB traces, I use nothing stronger than a pink eraser. And that's only if I'm having problems.

12

A slightly belated response here, but I don't rely on flux to clean corroded or oxidized leads or pads, and wouldn't ever think of using sandpaper or steel wool. Rather I scrape with an Exacto knife till things are shiny and new. I "always" do this to the feet on smt chips, and the legs on TO-220 parts, as a matter of standard practice.

13

blades dig in and cause grooves

most I ever do is a nylon "scotch brite" pad

14

I'd not scrape a trace with an Xacto blade. A bit excessive, too much metal.

A plastic Scotch Brite pad is good. You don't want to scrape any tin plating off.

15

I'd not scrape a trace

It's for smt chip legs [corroded parts leads, and TO-220 component legs], not copper traces. I meant to say "parts", not "pads".

Try it and see. Don't slice. Turn the chip over on its back - dead bug style. Hold the blade at a flatish angle, with the sharp side of the blade away from the direction of travel. And lightly scrape. Anyone who can use diagonal pliers to strip insulation off of wire can easily do the deed.

I've been doing this routinely for about 15-years now, ever since I had some trouble with some parts with oxidized leads, and it works 100% better than any flux. The solder always flows right.