Soldering question

[MattM]

Hi everyone. I'm new to these here parts and I was wondering if I could get a little help.

I've never attempted any electronics before and I decided, after some research, to have a go at hacking a USB game pad to make a desktop arcade control panel. Basically, I've run into a problem already, and I'm hoping it's something easily fixed. The gamepad I picked up is the Logitech Precision, discussed on these boards here: http://forum.arcadecontrols.com/index.php?PHPSESSID=48562d17cff18b2ef838228cdbeebddf&topic=78297.msg816690#msg816690.

My issue is with soldering. I was able to tin the wires just fine, I think , but I'm stuck when it comes to the copper traces on the game pad. I place my soldering iron on them, but the solder never even begins to 'melt' onto them. I'm assuming that they aren't heating up for whatever reason. I've read it should only take a few seconds for this to happen.

Needless to say, I'm confused and frustrated, as I've destroyed this gamepad in the process. I can't manage to find any answers on this site, forum, or other sites. Any ideas? Am I doing something obviously wrong? Thanks in advance for any help you can offer.

[HaRuMaN]

Are the copper traces really copper?  Meaning, is there any 'black' paint over them?

In any case, take a Dremel with the wire brush attachment, gently (at the lowest speed) go over the copper points that you want to solder to.  Once that's done, clean the area with some rubbing alcohol and a Q-Tip.  After this, the solder should stick to the copper areas no problem.

[Blanka]

It's common that PCB's have a coating outside the solder-points. That way solder never floats to parts it does not belong directly. If you want to solder to a coated trace, just use a small flat screwdriver to free the copper (hey you know how copper looks when its blank I guess?).
Then solder it fast. It should never take more then 5 seconds to get the copper accept solder. If you heat it too long, the traces can come off, which makes your gamepad FUBAR in no time.

[MattM]

Thanks for the quick replies guys!

There doesn't appear to be any paint or other coating over the points. They actually look just like in the link I posted, which as far as i can tell is fully exposed. I'm rarely right though  .

Nevertheless, other websites spoke of the same thing, so I tried to scrape them back the other day with a screwdriver, and they did become slightly more shiny, but it didn't seem to help. If I used what I read is the incorrect method of tinning the points, namely putting solder on the iron and 'painting' it on the points, it held on them. But as I mentioned, solder wouldn't even melt when doing it the correct way. Would that mean that was still some kind of coating on there?

I'll give the wire brush and rubbing alcohol a go. In the event that I can't get my hands on a Dremel, would steel wool or sandpaper do (according to other sources they can be used)?

Thanks for the advice guys, I'll let you know how it goes.

[BobA]

Looking at pictures of the pad you posted in the other thread there looks to be a coating over all the traces except in the contact area where the button press down.   If this is not removed then you will not be able to get solder to stick to the traces.  Other places you can solder to are the points that are already soldered on the pad.   If a trace goes to a soldered point it is easier to solder there then on the trace that has to have the coating removed.   

You should never put solder on the soldering iron and paint it on the PCB.  The trace and the wire should be heated together or a cold solder joint will result.  You should however tin any wire with solder before trying to attach it to a trace. You can get liquid solder flux that can be painted on the trace.   It must be the electronic type (Rosin) and not the plumbing type (acid).  The liquid flux is only sold in electronics specialty stores.

[MattM]

OK, before I get into it again I just want to say that I really appreciate everyone helping me out!

I've had another little attempt and failed once more. I've tried rubbing the contact points with methylated spirits and that didn't seem to work. I've tried scrapping back the contact point so it's a little more shiny and that didn't seem to work.

It is those uncoated contact points that BobA mentioned that I've been trying to tin, that's why I'm a little surprised that nothing is happening. I must still be doing something obviously wrong.

It's not even that the solder melts but doesn't take to the points, like I've read other people have problems with. It's that the solder doesn't even begin to melt. It just stays in it's original form.

Any other ideas? Are my explanations even making sense, I'm starting to confuse myself, hahaha. 

Thanks again!

[BobA]

Maybe your soldering iron is not working properly.   How many watts is it and can you melt solder on its tip?

[MattM]

The iron is 25W. This is the one I bought: http://www.dse.com.au/cgi-bin/dse.storefront/49fc984a0ba78c06273fc0a87e0106ab/Product/View/T2304

It's working fine as far as I can tell. I can melt solder on the tip and I can fairly easily tin lengths of wire.

[BobA]

Make sure you tin the tip.  It should have a thin coating of solder on it so it can wet properly when put against a solder joint.  Aside from that all I can think of is that you are not holding it against the joint long enough.

[SG Jaycurl]

If you're tinning the tip first, it sounds like you're probably taking the right approach. Have you tried soldering to anything else, just for practice? If not, I might recommend doing that a little bit until you get the feel for it. It could be something as simple as soldering two wires together. Or, if you have some scrap electronics (like an old VCR), take that apart and try to solder some things together or whatever.

I was a total n00b to soldering until about a month ago myself. This is the process that worked for me when I wanted to solder a wire to a PCB contact point.

1. Tin the iron (melt a small amount of solder on the end of the iron).
2. Tin the wire. I held the wire in a fly-tying vise, heated the exposed end and melted a dab of solder to it.
3. Tin the iron again.
4. Hold the iron on the contact point of the pcb for a couple seconds, then apply solder. It should melt and stick fairly easily.
5. Hold the tinned end of the wire to the tinned contact point and press your iron on it briefly. Should melt together quickly and easily.

The biggest thing I learned (after killing one PCB myself) was the importance of tinning the iron tip. It makes such a huge difference for conducting heat.

Good luck.

[nazerine]

Curious question, what type of solder are you using? If you're not using a rosin core solder, it might be your problem

[HaRuMaN]

Also, if you are using the newer ROHS - compliant solder, that would be a problem as well.

[knohbody]

Take some very fine grade sandpaper, and sand the copper traces. Then put some flux on it, heat up the trace, and apply a small amount of solder to tin the trace. In my experience, the copper pads on joystick pcbs are usually clear coated, so they look shiny, but they won't take solder unless you hit em with something first. The flux just makes it that much easier.

[MattM]

Hey everyone, thanks for the replies!

BobA: I assumed I was holding it on for way to long already (more than 10 seconds). Yeah, I make sure to tin the tip.

SG Jaycurl: that's pretty much what I've been doing but always get stuck at step 4, as the solder never melts on the contact point 

nazerine and HarumaN: this is the solder I'm using: http://www.dse.com.au/cgi-bin/dse.storefront/49ffd59a0a31a0b8273fc0a87e010712/Product/View/N2628 It had rosin printed somewhere on the packaging and it does contain lead.

knohbody: I've tried scraping back the traces with a screwdriver and that makes them a little more shiny but solder still won't melt to it. I have not yet tried the flux, but seeing as it's been recommended to me a few times now, I'll give that a whirl and see what happens.

Thanks all!

[thecheat]

I've often found that brushing on a little dab of flux helps stubborn soldering.

It's also possible that your 25w iron might have a problem soldering to the gold plated contacts. Make sure the metal is copper (orange) and not gold (well, gold).

[richms]

My bet is on a gutless iron just having the heat sucked out of it by the board. IME soldering dirty stuff needs a hotter iron, and a 25 watter will have problems getting up there.

Before you write yourself off as not being able to solder, see if you can borrow a decent iron - chances are all your problems will go away.

[HaRuMaN]

My bet is on a gutless iron just having the heat sucked out of it by the board. IME soldering dirty stuff needs a hotter iron, and a 25 watter will have problems getting up there.

Before you write yourself off as not being able to solder, see if you can borrow a decent iron - chances are all your problems will go away.

I do all my controller hacking with a 15 watt Radio shack iron, I have no problem soldering.

[ChadTower]

PCB "heat sucking" happens on stuff with wide traces or heatsinks nearby... not to pure logic circuits like you'd find on a console controller.  Usually around direct common ground connections.

If he can't melt a joint in ten seconds his tip isn't hot enough.  25W is more than enough for a small job like this so I'm betting his tip is filthy and not getting hot enough on the surface.  If you have a cheap tip, and burned a bunch of crud on the tip, it's not going to work very well until you clean that crud off with some light sandpaper.

[thecheat]

Depending on the iron, the tip might be removable and causing a poor connection. I have an old Weller gun that I'm too cheap to buy a new tip for - I just keep scraping off some oxidized copper each time I use it.

If the tip unscrews (just threaded into the base) or if a set-screw holds it in, remove it and use a wire brush, steel wool, etc.. to brighten up the tip AND ensure the part that contacts the iron's shaft is clean and shiny as well.

If this iron can tin a wire, there shouldn't be any problem tinning a PCB trace.

[ChadTower]

That's not going to work well if he wants to keep soldering with this tip.  Good tips have a coating on them that make them easy to clean and slows the buildup of burned crud.  Once you have sanded that coating off you're guaranteeing the need to sand that tip after nearly every use.  Sandpaper is really only a good route on a trashed tip like you have - I learned this by trashing a couple of good tips myself thinking I was cleaning them.

[thecheat]

That's not going to work well if he wants to keep soldering with this tip.  Good tips have a coating on them that make them easy to clean and slows the buildup of burned crud.  Once you have sanded that coating off you're guaranteeing the need to sand that tip after nearly every use.  Sandpaper is really only a good route on a trashed tip like you have - I learned this by trashing a couple of good tips myself thinking I was cleaning them.

I was more referring to the base of the tip where it contacts the steel shaft of the iron. Of course he should have a properly cleaned and tinned tip but if the base of the tip is oxidized, there won't be good heat transfer at all. Since he has a 25w pencil iron, it is likely that he might have a cheap tip that might need some touching up.

[ChadTower]

Yeah, especially if he has a set screw type.  I had one of those and the screw didn't hold it all that flush against the element.  The screw on tips are better about that since the thread provides so much surface area for heat transfer.

The ironic part is that I keep seeing guys start on controller hacks because "it's a small easy job".  The truth is that these controllers are using small logic circuits that are fragile to soldering.  The item iself may be low risk but the job is not a simple one for beginners.  Learning to solder is a lot easier on something older like a VCR motherboard - and who can't get a free dead VCR these days?   

[thecheat]

I thought about doing a keyboard hack, gamepad hack, then I just sucked it up and bought an I-PAC. The money spent on a purpose-built interface was "cheaper" than time spent forcing something to work and continuing to have to mess with it, ultimately doing it over the right way again. When buttons get pushed, and joysticks get moved, I don't want to have to second guess if the ports have swapped, etc... just want it to operate as it should.

Back on topic, there are a ton of soldering kits for sale, check JDR Microdevices and Jameco.. (JDR.com, jameco.com) for pretty cheap.. they teach soldering, schematic reading, troubleshooting, etc. Good way to start out before moving on to more expensive or small (0605 SMT LEDs, anyone?) components.

[MattM]

thecheat, Chadtower and richms: the traces are more of a gold colour than orange, so I guess that might be the issue. Never thought about that. Tinning the wires is no problem at all, so I don't think it's the iron's power or a dodgy tip. Bu then, it's not like I know a lot about these things. Oh, and I chose to do a gamepad hack because I wanted to see if I could make something more so than just having an arcade controller. If I ever make an actual cab though, I'll be thinking about an I-PAC, for the reasons thecheat stated.

As a general update, my uncle came around and helped me out. This kind of stuff, including soldering, was his area of study. To tin the traces (one of the few I hadn't killed ), he laid the iron on them and then touched the solder to the tip of the iron to melt it and then ran the iron along the trace, 'painting' on the solder as it went. I tried it out after him and once I did that, and soldered on the wires, I plugged the PCB into the computer via it's USB cable. I touched the wires from the trace I soldered to together and they registered as button presses.

Now I'm no less confused, as I was under the impression that this was the wrong way to solder and would cause a cold joint that wouldn't work. My uncle reassured me that this was not the case. I've come across a video where it looked as if the guy was using this same method. It's this one:


Needless to say, I don't know what's going on.   

[thecheat]

That method is "cheating" but it works If your solder joints are shiny and flat on traces and are conical shaped on thru-hole joints, all is well. If the solder is a dull bubble, it's a cold joint.

The tricky bit is getting the trace or joint to be at least as hot as the melting point of the solder. That's why lead based solder is easier to work with, lower melting point. If you melt a bit of solder on the tip, it helps the heat transfer and acts like a catalyst.

[MattM]

Ah OK. Thanks for clearing that up thecheat. I was just going to do it like that on a fresh gamepad but I'd still rather work out how to do it correctly.

You mentioned about the gold vs copper traces earlier. This is the pad I'm working with:

(noobofthecentury's picture from an old thread)

Do those contact points look like copper to you? It they are the gold, would brushing on flux as you and others suggested allow me to solder to it?

Sorry if I'm repeating questions or not understanding your answers. I'm just trying my best to grasp this and appreciate everyone's continued assistance. 

[thecheat]

Those are certainly gold, the plating is to keep that area from oxidizing and to ensure good contact with the carbon pad on the rubber button sheet.

An easier way to go about it might be to scrape the solder mask (green part) off the copper traces. That would give you more room to work with. You can start wtih the fat one that goes by SW7 on the top and see how that goes. Just make sure when you scrape off the top, you don't cut the trace.

Extra flux should be a real big help. I have a little tin of it and I'll dip the end of a lead in and scoop out a tiny bit when I'm ready to solder. It makes the solder more "wet" and it flows easier. You get some flux in the core of the (rosin core) solder but usually it's a teensy bit and the solder always melts over the core.

[MattM]

I tried scraping back some of the solder mask on the other areas of the board a few weeks ago, and I had the same problem.

The extra flux is the main thing I haven't attempted yet. I'll see if I can get my hands on some in the next few days and give it a whirl. Fingers crossed.

If it doesn't work, I guess I can always do it the cheating way. 

[ohiojason]

Use flux.

I use to make fun of the new guy at work for insiting we buy Flux. "Why do you need that? Flux core solder has worked fine for the last 20 years for everone else!" I would say. Well I was having problems one afternoon, tried his flux, instantly became a believer, and ate a lot of crow. Is it needed, no, will it make things easier, most definatly.

[Kman-Sweden]

I use a pair of pliers to scrape off the black oxide from the tip of my solder iron from time to time...
When it's nice and copper colored it works nicely. I use the thinest solder I can find... It melts easier than the thick solder.