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Soldering questions

falter

falter

Veteran Member
Joined
Jan 22, 2011
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Location
Vancouver, BC
Hey guys,

I am trying to master soldering. I am getting better at it, but I'm still having certain things I can't figure out. Hoping others might have advice.

First, I have trouble with the tips. I seem to destroy them pretty quickly... ends break off, etc. I don't think I'm doing anything too wrong.. i turn the iron on.. usually around 45 or more watts.. try to keep it clean, etc.. but in the end in as little as a few minutes the tip is crumbling.

Second thing I worry about is the chips get quite hot. In videos they make it look so quick.. they touch the iron tip to the chip leg.. touch the solder to the leg very quickly and thats it. But on mine, it doesnt do that. It takes forever to heat enough.. if that. And this is with the iron up past 50w. I worry about damaging the chips.. I understand usually its kind of a 3 second rule?
 
What kind of soldering iron are you using, and what are you trying to solder?

A tip shouldn't "crumble", it should be able to withstand the maximum setting of your iron for a reasonable amount of time. Half the battle is getting the right tools for the job. In general for soldering/desoldering digital electronics, a quality variable temperature controlled soldering iron is a must.

Some PCBs, especially modern motherboard, are designed to suck heat away from components. Those are hard to work on, especially when large ground planes are involved. Boards with electronics kits usually aren't like that, so they are just touch, touch, touch, done.

It is very important to keep the tip "tinned". After wiping the tip, immediately apply some fresh solder directly to the tip. That helps prevent the tip from oxidizing, and helps the thermal conductivity when it touches whatever you are trying to solder.

Similarly, when you touch the tip to whatever you are trying to solder (or even desolder), you may need to add some extra solder directly to the tip to increase the surface area in contact with the item.

Don't run the iron hotter than you need to. A good soldering iron shouldn't need to be turned all the way up to solder in a typical component, but you may need to turn it up to deal with components attached to those stubborn thick ground planes. Don't leave it running when you are not using it.

I wouldn't worry too much about chips getting hot, but the real worry is that you will damage PCB traces or burn the PCB. The trick there is a matter of temperature and timing. Your soldering iron needs to be able to provide enough heat fast enough to quickly heat one spot, melt the solder, and get out of there. If it can't then you will wind up slowly heating everything up until it burns to a crisp, while the solder is still not melted.

And yea, the videos always make it look so much more easy than it really is. :p
 
Thanks!

Yes I havent mastered the tinning. But yeah last night, after only about 10 min the tip began to warp or crumble, forblack of a better term. I doubt this iron is of exceptional quality.. its a Radio Shack 60w job. Maybe thats part of the problem. I have beeb keepong contact to 3 seconds or less per pin, but yeah.. last night i found the only way to melt in the new solder was to actually make contact between the solder and the iron. In the videos they say not to do this, and they show the iron pressed against the backside of the pin while the solder goes frontside. This worked brilliantly on my Apple II keyboard keys.. but not on these chips I'm woking on. I'm guessing its as you said.. heat dissipation by design.. maybe the chip legs resist more than the tiny legs of the keyswitches. I'm hopong I can master this before I take on my TV Typewriter project. In that though I think I'm going to use sockets.. safer and easier to swap out chips.
 
The Radio Shack pencil irons aren't great, but they aren't that bad either. That's what I use, only because I can go buy a new one any time. I don't have to mail order.

You could bend the tip while it's hot by putting pressure on it, but I'm guessing you're not doing that. If you didn't tin the tip first thing, and keep it tinned, that could be your problem. If you have a wire wheel or wire brush, you can start over, just make sure to tin it right away. If you fill a small pot with solder and put the tip into that when you aren't soldering, the tip will stay tinned no matter what you do, but you shouldn't need to do that. Just tin it complete the first time, and keep it tinned.

I always use sockets. Any time I replace a chip that wasn't socketed, I install a socket.

You don't need a temperature controlled iron. They are nice, but you can work without. I've never owned one.

If you are using silver solder, that is, the "lead free" kind that everyone is selling these days, don't. It requires too much heat. If you can find 63/37 solder, use that. If not, use 60/40 (lead bearing). You won't die from the lead, just don't rub it on open wounds; and wash your hands when you're done soldering.

If you haven't already, get yourself some perfboard and wire and sockets to practice your technique. Radio Shack hopefully still sells perfboard.
 
Another good way to practice is to take a C64 and socket all of the chips. It takes a while, but the chips are big and have big legs, for the most part. And when you're done, you can use it to test chips from dead C64s.
 
KC9UDX said:
You could bend the tip while it's hot by putting pressure on it, but I'm guessing you're not doing that. If you didn't tin the tip first thing, and keep it tinned, that could be your problem.
Click to expand...

...and that's a reason to use a good iron--tips on those are generally iron-plated, not bare copper, so they last a long, long time. In the long run, they're more economical than bare copper tips. As far as keeping a tip clean, there are cleaners that look like a copper pot-scrubber stuck in a holder that work better than the wet sponge:

tip-cleaner.jpg


I always use sockets. Any time I replace a chip that wasn't socketed, I install a socket.
Click to expand...

So how does that work with QFPs?

You don't need a temperature controlled iron. They are nice, but you can work without. I've never owned one.
Click to expand...

To quote a good friend of mine: "I can't afford cheap tools". The damage that can be done to PCBs with an overheated iron just doesn't justify the saving of a few dollars on an iron. A decent TC iron isn't horribly expensive examples. You want to purchase a tool that will last a lifetime if you're at all serious. I still have my Weller TC station from over 40 years ago--and I can still get parts for it if needed.

If you are using silver solder, that is, the "lead free" kind that everyone is selling these days, don't. It requires too much heat.
Click to expand...

Well, no--LF solders are available with melting points comparable to TL ones. Kester even has parallel product lines between LF and TL alloys. Here's one for the very common Kester 44 solder. My big issue with the LF formulations is that they don't flow or wet as easily as the eutectic TL alloys, but that's a minor quibble. Modern alloys are getting better.

The thing that many novices miss about soldering is that you don't melt the solder on your iron and apply it to the joint (unless you're doing SMT, which is a different discipline and is probably best done with paste-type solder formulations). The idea is to heat the component or joint so that solder and flux applied to it will melt and flow into the spaces between the items being joined. The idea is pretty much universal with all soldering, whether it's plumbing for your house or components for your PC.
 
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Chuck(G) said:
So how does that work with QFPs?
Click to expand...
I don't work on things like that. :)

To quote a good friend of mine: "I can't afford cheap tools".
Click to expand...
Normally, I agree. But, when an expensive tool fails more than the cheap one, I'll go with the cheap one, especially if a new one is minutes away. I used to like Ungar irons, but I've been through three of those and only two of the Radio Shack cheapos.

Well, no--LF solders are available with melting points comparable to TL ones.
Click to expand...
But those aren't the ones everyone is selling these days. Sure, you can buy them online, but good luck buying one in a store. All the ones I can buy around here have very high melting points.
 
Two things:
1. As was already mentioned, copper tips dissolve into the solder. They require constant filing
to maintain shape and need regular replacement.
Iron clad tips last for years and should not be filed. They should only be cleaned with
stainless wool if severely oxidized and normally only need a wet sponge if keep clean
and tinned.
2. You should not be putting so much pressure that your bending the tip.
If your having troubles getting the heat to transfer, make sure there is a light
coat of solder on the tip and that there is flux.
If your not working with separate flux ( recomended ), with the tip on the surface,
apply a small amount of cored solder to the tip as close to the work as possible.
You are not trying to solder yet, your just getting some flux between the work
and the iron tip. Once the joint is up to temperature you can apply solder
to the work ( not the tip ).
Dwight
 
I used the cheap soldering irons from Radio Shack years ago (I was a Radio Shack Manager a long time ago). They work fine and last for years with the slightest care. Even the cheap soldering irons from Radio Shack have plated tips.

If the tips on your irons are crumbling, you are using too much heat, and pressing too hard. You should not be pressing at all, the weight of the iron should be all that is necessary to make good contact for working when the tip is clean, and "tinned" properly.

I use a temperature controlled station for most soldering now, and I have interchangeable irons with different heat ranges that I can plug in, depending on the work I'm going to perform. For working on circuit boards on ICs, I often use a 20W iron. The iron that I use for general purposes is a 40W. I use 60/40 (lead/tin) solder for most electronic work. It melts and flows easier, making superior electrical connections to the silver based solders that are usually found in stores. You can still find 60/40 at most electronics/computer swapmeets.

I can get a decent used station from a computer swapmeet, or eBay for $40 or so. Weller makes a nice hobbyist/entry level/grade station that sells for around $50 in stores.

Here's how the sequence of events when soldering should go. Plug in iron and let it reach working temperature. Clean tip. Tin tip. Add a little more solder to the tip to ensure good contact. Apply the tip to the work (should be touching the pad on the circuit board and the component lead). Add solder to the circuit board pad, not the tip. When heat is adequate, solder will flow. into the joint and onto the components being joined. Remove the tip from the work. Set the soldering iron on the stand after removing excess solder.

You should not be pressing the soldering tip tip just against the chip lead. If you do that, you will not have adequate heat on the circuit board, and solder will not flow.
 
IMO you need a temperature controlled iron, flux and 60/40 solder.

I use FL22 flux: http://uk.farnell.com/edsyn/fl22/flux-syringe-5ml/dp/3059091 Keep it off your hands!
And one of these stations (I paid about £25 on a local store offer): http://www.web-tronics.com/solomon-soldering-station-sl30.html
And just 60/40 multicore solder, I think 0.5 or maybe 0.7mm: http://www.ebay.co.uk/itm/like/230920661980

Flux is the key - there is flux in the solder, but not enough for re-work usually. Basically you put a (small) blob of flux on whatever you need to unsolder, clean and tin the bit (which literally just means touching the solder on it) then gently hold the tip on the joint in the flux, which turns into a strong acid and cleans off all the tarnish, allowing the solder to then flow nicely and you can then hopefully remove the component. Sometimes components are really difficult to get out though (probably, I'm just not very good at it).

Extra flux can also be useful even when soldering new boards and components. I tend to use a fair bit to be honest, it just helps me get more consistent joints, and often once a joint can gone badly ('dry joint') they can be a pig to fix.

Just my 2p :)
 
If you're really cheap, I've found that you can make an entirely satisfactory flux by dissolving old bits of violin, viola, 'cello, bass, etc. bow rosin in alcohol.

Yeah, I know--:rolleyes:--it's kind of strange, but it works.
 
For electronics, and especially old PCB's, you should be using an iron with controlled temperature in the 650 deg F range. You probably should not be using a soldering iron specified by wattage. Those are meant for arts/crafts and trade applications, and are designed for different kind of solder/flux combinations. The high heat will boil off the flux too fast, making it hard for the solder to stick to the joint, and resulting in your taking too long to try to make a joint. Along with the high heat, this will result in damaged components and PCB traces.

You can get a Hakko clone (such as an Aouye) on Ebay for $50-60, or invest in a Hakko FX-888D for all of $91, and you will have a tool that lasts a long time, and will be much better for your vintage gear.

http://www.amazon.com/Digital-FX888...e=UTF8&qid=1392242631&sr=1-1&keywords=fx+888d

On solder: Use 63/37 Tin/Lead solder. Never use acid core. Don't use lead-free solder on vintage electronics.

There are plenty of good Youtube videos on soldering. Make sure you watch a video by someone who is IPC certified, and not some hack who taught himself soldering last week. The Curious Inventor on YouTube is pretty good, and has several soldering videos. His introduction is good:

http://www.youtube.com/watch?v=I_NU2ruzyc4

Good luck,

Dave
 
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Chuck(G) said:
If you're really cheap, I've found that you can make an entirely satisfactory flux by dissolving old bits of violin, viola, 'cello, bass, etc. bow rosin in alcohol.

Yeah, I know--:rolleyes:--it's kind of strange, but it works.
Click to expand...

That's fun, but if you care about your electronics, it's better to use flux specifically designed for soldering, so you can control what additives are acting on your joint, and so you know what method, if any, of cleaning is needed. For through-hole, the flux is in the solder, and when you need it, a no-clean or RMA flux pen is very convenient, and not that expensive.
 
Thanks for this thread, guys. I've always been lousy at soldering, and I haven't done any over the past few years, so this will be my starting point for my soldering refresher/improvement course. I sold (or threw away) my crappy old Radio Shack soldering iron awhile ago and have been looking for something better lately. So far I'm leaning toward the Hakko FX-951. Do you think that would be a good choice, or do you have other recommendations?
 
Probably a good choice, I wouldn't know. But, the best iron in the world won't make you a better solderer. Practice makes perfect. And, it doesn't take long to completely master soldering, so long as you take your time and make sure you understand what you're doing. And contrary to popular opinion, soldering is nothing like painting.
 
KC9UDX said:
Probably a good choice, I wouldn't know. But, the best iron in the world won't make you a better solderer. Practice makes perfect. And, it doesn't take long to completely master soldering, so long as you take your time and make sure you understand what you're doing.
Click to expand...
Indeed. FWIW, I've been building and repairing computers and other electronic equipment for > 50 years and have never used a TC iron, just good quality 15 and 25 W fine tip pencils (and a gun for the heavy stuff); as you say, it's mostly practice, preparation and timing, and a certain 'feel' for it. I actually do have a dual mode TC station, but I just use the hot air gun for desoldering.
 
I actually attended a 2-day class on how to solder back in the mid-60's for the navy, and up to a few years ago I've been soldering in my work. I've used pretty much nothing but Kester rosin-core solder, never used any external flux. And pretty much just pencil irons up to about 45w or so.

A couple technique things they taught us were to never melt the solder with the tip of the iron, let the iron heat the joint and let the joint melt the solder.

Be careful not to jiggle the joint for a few seconds, you can visibly see the solder harden. Movement can cause a cold joint, you can see the lack of shinyness in the joint to help identify a suspect soldering. Cold solder joints can cause no end of future problems, from intermittent problems to burnt pcb's.

I always had a tip wiper handy, a moistened paper towel worked in a pinch, and always wiped the tip right after making a connection to clean the flux off the tip. I did field service repair for 20-30 years and seldom had the luxury of a stand handy, so one last tip is don't carelessly set your iron down where it hits the power cord. You can turn the lights off in the room, as I discovered in the Navy's soldering class :)
 
Doug G said:
A couple technique things they taught us were to never melt the solder with the tip of the iron, let the iron heat the joint and let the joint melt the solder.
Click to expand...

I agree with most of your excellent soldering tips. However, with a new tip, I was taught (Navy) to always tin the tip first. FWIW, I've been in the electronics maintenance/engineering arena since about 1960.
 
AO, I don't think Doug said anything about not making sure that the tip wasn't tinned first--that's essential. All Doug was saying (and so was I and others) is that you shouldn't carry the solder to the joint on the tip of the iron--heat the joint and apply the solder to the joint. To do any soldering, a well-tinned tip is essential.

As far as flux goes, I usually wash the board with alcohol or perc using a soft toothbrush to remove residual flux and then inspect the result--it's easier to see the joint quality without a layer of flux over it.

There are times when you have a very large power component to solder down to a large land or ground plane and a 40W iron just isn't going to cut it--the heat radiates away faster than the iron supplies it. You can find this sort of situation in power supplies, for example. That's when I pull out my soldering gun (a 325W Weller) to supply the needed heat.
 
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