Finally got a couple XRE's on stars...now I'm having trouble soldering..help?

[lightime]

Ok guys so I finally got a couple of XRE's to mess around with for a couple projects I have in mind. I have just about zero soldering experience. But I figured I would try to learn this hands on style. I bought a 40watt weller and some solder (96% tin/4% silver). I soldered a set of leads onto the first led pretty much without a hitch and tested it with my driver/battery worked perfect.

I figured the second one would be even easier but NO DICE. I heated up the pad on the star and when I went to touch the solder to it the solder just made a ball and would not stick. I tried a several more times and the same thing would happen over and over so I just gave up as I must be doing something wrong....and that's my question...what am I doing wrong???

As a side note...when I did the first two leads that went well the tip on my soldering iron was nice and shiny. After I let it sit connected for a while and it was real hot the tip now looks dull. Is there any way to make it shiny again? and could this have anything to do with my problem?

Thanks in advance for any guidance!

 

[znomit]

Soldering is a bit of an art, get some junk boards and starts pulling bits off, putting them back on for practice.
You need a sponge to clean your tip.
http://www.kingbass.com/soldering101.html

 

[blasterman]

To make things easier I suggest 'tinning' the wire first before soldering it to the pad. 'Tinning' means you coat the wire end first with solder, let it cool, and then solder the wire to the pad. Things generally work much better that way. To do this simply press the tip of the soldering iron underneath the bare wire and hold the solder against it and coat it as it melts. With brief practice you'll get good at it. Then just tpuch the wire to the top of the pad, and pressing it briefly with the Weller should do the job.

Getting free solder to stick to a high quality star with non-solder pads is like trying to nail jell-o to a wall.

When dealing with stars like this a bit of very fine sandpaper, or a dremmel with a sanding bit helps. Just buff the intended contact pad a bit to scuff it up and solder will stick to it better. Also note after you've re-soldered the same pad a few times burnt up residue makes it tougher to stick. Scuffing it up a bit restores it and makes it easy to solder.

 

[Nos]

You should view some soldering videos on youtube, that will help you learning the basics.

But keep in mind that the pads of the star boards are made of aluminium.........soldering aluminium is complety different league...because you need to brush of the alu-oxid use a deoxid solvent, and special alu-solder.

that alu solder may be agressive to some metals (like contacts on leds).......
ive never seen someone around here who soldered aluminium. I guess we all glue it with artic aluminia

 

[lightime]

Thanks very much for the replies. Guess I will have to practice some more.

Is the solder I have fine or is there a better mix that I should use?

Also, I noticed that I can't leave the soldering iron's tip against the pad long enough to melt the solder because I tried and the led got soo hot that it actually made a crack at the base of it's clear dome. So I held it on the pad a while but then had to touch the solder to the tip which I understand is a no no in soldering??

nos, are you saying you can attach the leads to the pads with artic aluminia?

 

[HarryN]

Hi, there are a couple of schools of thought on soldering.

People that are very experienced and have steady hands can do amazing things. The rest of us really struggle. As a practical matter, nearly all consumer products are made with solder paste (or tanks of solder), not by people fooling around with wire solder.

My suggestions
- Lightly sand your board to expose the copper, then clean with 90% drug store rubbing alcohol.
- Get some "solder it" solder paste in a syringe (fry's electronics)
- Just glob on the paste generously. Even consider to make a continuous line of it from one soldering point to the next.
- Stick a newly cleaned / sanded tip into one end of the solder paste line and just sort of follow the line - not lifing the tip out of the paste between joints
- At each solder point, let it melt, then move on to the next one
- Allow to cool, then clean off the excess with a tooth brush and running water.

 

[bshanahan14rulz]

solder will solidify instead of flow if the part to be soldered isn't hot enough, and aluminum stars' purpose is to remove heat. heat travels quickly through aluminum but "fills" it up pretty quickly. The solder pads on stars are actually solderable, not aluminum. There is a layer of something between the solder pads and the aluminum to keep electricity from moving over but still allowing heat to transfer.

work on a scrap piece of wood or something that won't melt but doesn't conduct heat

Lead-free solder is poop (you with your 40W weller it might not be so bad, I just have a radiohut iron)

tinning leads helps, a lot.

Some wire insulation shrinks when heat is applied. If your wire does this, don't expose too much copper before soldering or you might get a short somewhere. (Teflon insulated wire has a more heat-resistant insulator)

Generally speaking, you are supposed to heat up the wire and the solder pad, then apply solder. When the pad and wire are sufficiently hot enough, the solder will just fill in the gaps.

 

[spencer]

Get something with lead in it. A 60/40 tin lead is much better for really cheap. Not the best but readily available and cheap.

 

[lightime]

Thanks very much for all the advice guys. I made a quick trip to radioville and bought 60/40 solder in .032 and a small tub of tip tinner. I sanded/cleaned all of the pads on the led stars until they were nice and shiney...and....drum roll please.............I figured it out!!!!!

The technique that worked for me was holding the iron on the first pad for about 30 seconds then putting a small pool of solder on the pad. Then I would do the second pad and since the led was already pretty warm I waited 20 seconds with the tip touching the pad and then made the pool and so on until all 4 pads had pools. Then I heated the each pool and dipped my wire in the pool..done!


See the pic below I made two led spiders (they are pretty much just artwork because I toasted both those led's hooking them up to a live driver) and I even got fancy and wired two of them in series and they actually worked!! I am VERY happy...wish I had some more stuff to solder. I feel pretty confident now I think I'm getting the hang of it. lovecpf

Thanks guys!!!!!!!!

 

[znomit]

Is that solid wire? Pretty hard to solder.
You shouldn't have to hold the tip on anything for more than a second or two.

 

[lightime]

hmm, if the pad is not hot the solder won't pool and stick to the pad...it just balls up?? 1-2 seconds does not heat the pad up enough. I'd love it if it would stick that fast but I just can't get it to stick that quickly. Could my iron not be powerful enough?

Is that solid wire? Pretty hard to solder.
You shouldn't have to hold the tip on anything for more than a second or two.

 

[znomit]

hmm, if the pad is not hot the solder won't pool and stick to the pad...it just balls up?? 1-2 seconds does not heat the pad up enough. I'd love it if it would stick that fast but I just can't get it to stick that quickly. Could my iron not be powerful enough?

Yes it might not be hot enough. i run around 350C I think.
Check your tip is tight.

Heres what I do.
Wipe tip clean.
Put a little solder onto the tip and tin the wire.
Press tip onto pad, wait 1 second and push solder into where the tip and pad meet. Nice pool of solder. Take the already tinned wire, and place it onto the pad, press down with the tip until solder flows between wire and pad. Done.

 

[kavvika]

I use a 40W weller and 30 seconds is far far too long. That poor LED! Make sure you clean your tip frequently, as even a layer of oxidized solder junk will insulate the tip quite well. I never hold the iron to the star for more than 2-3 seconds. You want to heat the immediate area before the star has a chance to wick the heat away.

But tinning both the star pad and wire is how you start out. Then I reheat the bit of solder on the star, place the wire where I want it, then place the tip of the iron on top, melting both the solder on the wire and star, mating the two together.

 

[lightime]

Ok guys, I will try it like you describe next time. That does sound a lot safer for the led. Thank You

 

[bshanahan14rulz]

40W weller shouldn't take 30 seconds to heat it up enough. hold the solder to the pad while you are heating it and see how long it takes =) glad you are getting better, though!

 

[Calina]

Just to reiterate: make sure the tip is tight. I had a problem some time ago and it took me a while to realize that the tip had somehow partly unscrewed itself.

 

[blasterman]

(1) I have a 30watt Weller. It will liquify thick plumbers solder as fast as a propane torch.

(2) I solder about as well as I bowl when drunk; slow and sloppy (I'm no expert at it)

(3) I've recently worked with some pretty tough industrial stars from Bridgelux, and compared to most of the smooth Cree stars I've played with the Bridgelux are like trying to get solder to stick to a piece of glass.

That said, if you tin the wires before hand, and buff the pad and/or make sure it's clean, it should take more than a couple seconds touch with the Weller to get a tinned wire to stick to the pad.

Anything longer and you are either doing something wrong, the pad surface is dirty, or your iron is defective / tip loose. You risk damaging the LED.

While lead based solders are increasingly politically incorrect, in my experience they are the easiest to use for beginners. I try to use high tin (95%) solders for electrical stuff, but they always seem to require more screwing around than good ol' toxic lead based.

 

[lightime]

I have a couple more xre's coming in tomorrow hopefully and I will get some more practice. I will try all the suggestions and report back. Thanks again to all